This Amendment No. 2 to this registration statement on Form S-1 (Registration No. 333-274863) (the “Registration Statement”) is being filed to, among other things, include our financial statements and certain other information contained in our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the U.S. Securities and Exchange Commission (the “SEC”) on March 21, 2024.

SUBJECT TO COMPLETION, DATED MARCH 21, 2024

Our Common Stock is traded on The Nasdaq Capital Market under the symbol “DNTH.” On March 20, 2024, the last reported sales price for our Common Stock was $27.10 per share.

An investment in our securities involves a high degree of risk. You should carefully consider the information under the heading “Risk Factors” beginning on page 9 of this prospectus and any applicable prospectus supplement.

This prospectus contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), which statements are subject to substantial risks and uncertainties and are based on estimates and assumptions. All statements, other than statements of historical fact, included in this prospectus are forward-looking statements, including, without limitation, statements concerning our plans, objectives, goals, expectations, hopes, beliefs, intentions, assumptions, projections, estimates or strategies and any underlying assumptions regarding the future, our future results of operations and financial position, including the sufficiency of our existing cash resources to fund our operations for as long as anticipated, our liquidity, capital resources, costs and expenses, capital requirements, commitments and contingencies, the development or commercial potential of DNTH103 or any other product candidate, our anticipated preclinical and clinical drug development activities, in particular with respect to DNTH103, and any timelines, developments or results in connection therewith, the efficacy, safety profile, dosing amount or frequency, method of delivery or other potential therapeutic benefits of DNTH103, the receipt or timing of potential regulatory designations, approvals and commercialization of any product candidates, market size or addressable patient population and other statements, including those included under the sections titled “Risk Factors,” “Business,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this prospectus. In some cases, you can identify forward-looking statements by terms such as “aim,” “may,” “might,” “will,” “would,” “shall,” “objective,” “intend,” “target,” “should,” “could,” “can,” “expect,” “anticipate,” “believe,” “design,” “estimate,” “forecast,” “predict,” “project,” “potential,” “possible,” “plan,” “seek,” “contemplate,” “goal,” “likely” or “continue” or the negative of these terms and similar expressions intended to identify forward-looking statements, but the absence of these terms does not mean that a statement is not forward-looking. Forward-looking statements are not historical facts and are based on our current expectations and beliefs with respect to future events and their potential effects and impacts. There can be no assurance that future events affecting us will be those that have been anticipated. Given the significant risks and uncertainties, you should not place undue reliance on these forward-looking statements.

There are a number of risks, uncertainties and other factors that could cause our actual results or outcomes, or the timing of our results or outcomes, to differ materially from the forward-looking statements expressed or implied in this prospectus. Such risks, uncertainties and other factors include, among others, the following risks, uncertainties and factors:

There may be other factors that may cause our actual results or outcomes, or the timing of those results or outcomes, to differ materially from the forward-looking statements expressed or implied in this prospectus, including factors disclosed in the sections titled “Risk Factors,” “Business,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this prospectus. You should evaluate all forward-looking statements made in this prospectus and any prospectus supplement in the context of these risks and uncertainties.

We caution you that the risks, uncertainties and other factors referred to above and elsewhere in this prospectus may not contain all of the risks, uncertainties and other factors that may affect our future results, operations and outcomes. Moreover, new risks emerge from time to time. It is not possible for us to predict all risks. In addition, we cannot assure you that we will realize the results, benefits or developments that we expect or anticipate or, even if substantially realized, that they will result in the consequences or affect us or our business in the way expected. Past performance is not indicative of future performance.

Investing in our securities involves a high degree of risk. You should carefully consider the risk factors set forth below, together with all of the other information included in this prospectus, before deciding whether to purchase our securities. The risks and uncertainties described below are not the only ones we face. Additional risks and uncertainties not presently known to us could adversely affect our business, operating results and financial condition, as well as adversely affect the value of an investment in our securities, and the occurrence of any of these risks might cause you to lose all or part of your investment.

We are a clinical-stage biotechnology company with limited operating history that have incurred significant operating losses and has utilized substantially all of our resources to conduct research and development activities (including with respect to our DNTH103 program) and undertake preclinical studies of product candidates, conducting a clinical trial of our most advanced product candidate and the manufacturing of the product candidates, business planning, developing and maintaining our intellectual property portfolio, hiring personnel, raising capital, and providing general and administrative support for these activities. We have limited experience as a company in initiating, conducting or completing clinical trials. In part because of this lack of experience, we cannot be certain that our current and planned clinical trials will begin or be completed on time, if at all. In addition, while we initiated a Phase 2 clinical trial of DNTH103 in patients with generalized Myasthenia Gravis (“gMG”) in the first quarter of 2024, we have not completed a late-stage clinical trial for any product candidate, have no products approved for commercial sale and have not yet demonstrated our ability to successfully complete late-stage clinical trials (including Phase 3 or other pivotal clinical trials), obtain regulatory or marketing approvals, manufacture a commercial-scale product or arrange for a third party to do so on our behalf, or conduct sales, marketing and distribution activities necessary for successful product commercialization. Additionally, we expect our financial condition and operating results to continue to fluctuate significantly from period to period due to a variety of factors, many of which are beyond our control. Consequently, any predictions made about our future success or viability may not be as accurate as they could be if we had a longer operating history.

Developing biotechnology products is a very long, time-consuming, expensive and uncertain process that takes years to complete. Since our inception in 2019, we have funded our operations primarily through private financings and have incurred significant recurring losses, including net losses of $43.6 million and $28.5 million for the years ended December 31, 2023 and 2022, respectively. We expect our expenses to increase in connection with our ongoing activities, particularly as we prepare to conduct multiple Phase 2 clinical trials, prepare for additional investigational new drug application (“IND”) and other regulatory filings, potentially initiate additional clinical trials, and continue to research, develop and conduct preclinical studies of our other potential product candidates. In addition, if we obtain regulatory approval for any product candidate for commercial sale, including DNTH103, we anticipate incurring significant commercialization expenses related to product

We will also incur additional costs associated with operating as a public company that Former Dianthus did not incur as a private company. Accordingly, we will require substantial additional funding to continue our operations. Based on our current operating plan, we believe that our existing cash, cash equivalents and short-term investments, together with the proceeds from our private placement consummated in January 2024, should be sufficient to fund our operations into the second half of 2027. This estimate is based on assumptions that may prove to be materially wrong, and we could use our available capital resources sooner than we currently expect. Our future capital requirements will depend on many factors, including:

We do not have any committed external sources of funds and adequate additional financing may not be available to us on acceptable terms, or at all. We may be required to seek additional funds sooner than planned through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources. Such financing may dilute our stockholders or the failure to obtain such financing may restrict our operating activities. Any additional fundraising efforts may divert our management from their day-to-day activities, which may adversely affect our business. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms may include liquidation or other preferences and anti-dilution protections that adversely affect your rights as a stockholder. Debt financing may result in imposition of debt covenants, increased fixed payment obligations or other restrictions that may affect our business. For example, on January 24, 2024, we completed the 2024 Private Placement in which we issued 14,500,500 shares of Common Stock and the 2024 Pre-Funded Warrants to purchase up to 4,666,332 shares of Common Stock to certain institutional and accredited investors, which resulted in dilution to our stockholders that did not participate in the 2024 Private Placement, and, to the extent that the 2024 Pre-Funded Warrants are exercised, our stockholders’ ownership interests will be further diluted. If we raise additional funds through upfront payments or milestone payments pursuant to future collaborations with third parties, we may have to relinquish valuable rights to product development programs, or grant licenses on terms that are not favorable to us. Our ability to raise additional capital may be adversely impacted by global macroeconomic conditions and volatility in the credit and financial markets in the United States and worldwide, over which we may have no or little control. Our failure to raise capital as and when needed or on acceptable terms would have a negative impact on our financial condition and our ability to pursue our business strategy, and we may have to delay, reduce the scope of, suspend or eliminate one or more clinical trials, product development programs or future commercialization efforts.

We have incurred significant net losses in each period since inception. Our net losses were $43.6 million and $28.5 million for the years ended December 31, 2023 and 2022, respectively. We expect to continue to incur significant losses for the foreseeable future. Our operating expenses and net losses may fluctuate significantly from quarter to quarter and year to year. We anticipate that our expenses will increase substantially if and as we:

Our failure to become profitable would decrease the value of our company and could impair our ability to raise capital, maintain our research and development efforts, expand our business and/or continue our operations. A decline in the value of our company could also cause you to lose all or part of your investment.

Future reports on our financial statements may include an explanatory paragraph with respect to our ability to continue as a going concern. There is no assurance that adequate additional financing needed to allow us to continue as a going concern will be available to us on acceptable terms, or at all. The perception that we may not be able to continue as a going concern may cause others to choose not to do business with us due to concerns about our ability to meet our contractual obligations.

The development and commercialization of drugs is highly competitive. If approved, DNTH103 or other product candidates will face significant competition and our failure to effectively compete may prevent us from achieving significant market penetration. We compete with a variety of multinational biopharmaceutical companies, specialized biotechnology companies and emerging biotechnology companies, as well as academic institutions, governmental agencies, and public and private research institutions, among others. Many of the companies with which we are currently competing or will compete against in the future have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals, and marketing approved products than we do. Mergers and acquisitions in the pharmaceutical and biotechnology industry may result in even more resources being concentrated among a smaller number of our competitors. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

Our competitors have developed, are developing or may develop programs and processes competitive with DNTH103 or other product candidates and processes. Competitive therapeutic treatments include those that have already been approved and accepted by the medical community and any new treatments. Our success will depend partially on our ability to develop and commercialize products that have a competitive safety, efficacy, dosing and/or presentation profile. Our commercial opportunity and success will be reduced or eliminated if competing products are safer, more effective, have a more attractive dosing profile or presentation or are less expensive than any products we may develop, if any, or if competitors develop competing products or if biosimilars enter the market more quickly than we are able to, if at all, and are able to gain market acceptance. See the section titled “Business—Competition” for a more detailed description of our competitors and the factors that may affect the success of the products that we develop.

We have no products on the market and DNTH103 and our other programs are in the early stages of development. As a result, we expect it will be many years before we commercialize any product candidate, if any. Our ability to achieve and sustain profitability depends on obtaining regulatory approvals for, and successfully commercializing, DNTH103 or other product candidates either alone or with third parties, and we cannot guarantee that we will ever obtain regulatory approval for any product candidates. We have limited experience as a company in conducting and managing the clinical trials necessary to obtain regulatory approvals, including approval by the FDA or comparable foreign regulatory authorities. We have also not yet demonstrated our ability to obtain regulatory approvals, manufacture a commercial scale product or arrange for a third party to do so on our behalf, or conduct sales and marketing activities necessary for successful product commercialization. Before obtaining regulatory approval for the commercial distribution of product candidates, we or an existing or future collaborator must conduct extensive preclinical tests and clinical trials to demonstrate the safety and efficacy in humans of such product candidates.

Commencing clinical trials in the United States is subject to acceptance by the FDA of an IND, a biologics license application (“BLA”) or similar application and finalizing the trial design based on discussions with the FDA and other regulatory authorities. In the event that the FDA requires us to complete additional preclinical studies or we are required to satisfy other FDA requests prior to commencing clinical trials, the start of our clinical trials may be delayed. Even after we receive and incorporate guidance from these regulatory authorities, the FDA or other regulatory authorities could disagree that we have satisfied their requirements to commence any clinical trial or change their position on the acceptability of our trial design or the clinical endpoints selected, which may require us to complete additional preclinical studies or clinical trials, delay the enrollment of our clinical trials or impose stricter approval conditions than we currently expect. There are equivalent processes and risks applicable to clinical trial applications in other countries, including countries in the European Union.

Our future success is substantially dependent on our ability to timely obtain marketing approval for, and then successfully commercialize, our most advanced product candidate, DNTH103. We are investing a majority of our efforts and financial resources into the research and development of this candidate. We initiated a global Phase 2 clinical trial of DNTH103 in gMG in the first quarter of 2024, following receipt of FDA clearance of our IND application. We plan to submit a clinical trial application (“CTA”) in the European Union in the second quarter of 2024. In addition, pending clearance of INDs and/or CTAs that we plan to submit, we anticipate initiating Phase 2 clinical trials of DNTH103 in patients with multifocal motor neuropathy (“MMN”) in the

second quarter of 2024 and chronic inflammatory demyelinating polyneuropathy (“CIDP”) in the second half of 2024. The success of DNTH103 may depend on having a comparable safety and efficacy profile and a more favorable dosing schedule (i.e., less frequent dosing) and more patient-friendly administration (i.e., S.C. self-administration using a pen or other prefilled device) to products currently approved or in development for the indications we plan to pursue.

DNTH103 will require additional clinical development, evaluation of clinical, preclinical and manufacturing activities, marketing approval in multiple jurisdictions, substantial investment and significant marketing efforts before we generate any revenues from product sales, if any. We are not permitted to market or promote this product candidate, or any other product candidates, before we receive marketing approval from the FDA and/or comparable foreign regulatory authorities, and we may never receive such marketing approvals.

The success of DNTH103 will depend on a variety of factors. We do not have complete control over many of these factors, including certain aspects of clinical development and the regulatory submission process, potential threats to our intellectual property rights and the manufacturing, marketing, distribution and sales efforts of any future collaborator. Accordingly, we cannot guarantee that we will ever be able to generate revenue through the sale of this product candidate, even if approved. If we are not successful in commercializing DNTH103, or we are significantly delayed in doing so, our business will be materially harmed.

If we do not achieve our projected development goals in the time frames we announce and expect, the commercialization of DNTH103 or any other product candidates may be delayed and our expenses may increase and, as a result, our stock price may decline.

From time to time, we estimate the timing of the anticipated accomplishment of various scientific, clinical, regulatory and other product development goals, which we sometimes refer to as milestones. These milestones may include the commencement or completion of scientific studies, preclinical studies and clinical trials and the submission of regulatory filings. We have publicly announced and may in the future publicly announce the expected timing of some of these milestones. All of these milestones are and will be based on numerous assumptions. The actual timing of these milestones can vary dramatically compared to our estimates, in some cases for reasons beyond our control. If we do not meet these milestones as publicly announced, or at all, the commercialization of DNTH103 or any other product candidates may be delayed or never achieved and, as a result, our stock price may decline. Additionally, delays relative to our projected timelines are likely to cause overall expenses to increase, which may require us to raise additional capital sooner than expected and prior to achieving targeted development milestones.

We may ultimately discover that our technologies for our specific targets and indications and DNTH103 or any product candidates resulting therefrom do not possess certain properties required for therapeutic effectiveness. We currently have only preclinical and topline data from our Phase 1 clinical trial regarding properties of DNTH103 and the same results may not be seen in patients in our later stage trials. In addition, product candidates using technologies may demonstrate different chemical and pharmacological properties in patients than they do in laboratory studies. This technology and DNTH103 or any product candidates resulting therefrom may not demonstrate the same chemical and pharmacological properties in humans and may interact with human biological systems in unforeseen, ineffective or harmful ways.

Before obtaining marketing approval from regulatory authorities for the sale of any product candidate, we must complete preclinical studies and then conduct extensive clinical trials to demonstrate the safety and efficacy of our product candidate in humans. Our clinical trials may not be conducted as planned or completed on schedule, if at all, and failure can occur at any time during the preclinical study or clinical trial process. For example, we depend on the availability of non-human primates (“NHPs”) to conduct certain preclinical studies that we are required to complete prior to submitting an IND or foreign equivalent and initiating clinical development. There is currently a global shortage of NHPs available for drug development. This could cause the cost of obtaining NHPs for our future preclinical studies to increase significantly and, if the shortage continues, could also result in delays to our development timelines. Furthermore, a failure of one or more clinical trials can occur at any stage of testing. The outcome of preclinical studies and early-stage clinical trials may not be predictive of the success of later clinical trials. Moreover, preclinical and clinical data are often susceptible to varying interpretations and analyses, and many companies that have believed their product candidates performed satisfactorily in preclinical studies and clinical trials have nonetheless failed to obtain marketing approval of their product candidates. In addition, we expect to rely on patients to provide feedback on measures, which are subjective and inherently difficult to evaluate. These measures can be influenced by factors outside of our control and can vary widely from day to day for a particular patient, and from patient to patient and from site to site within a clinical trial.

We could also encounter delays if a clinical trial is placed on clinical hold, suspended or terminated by us, the FDA, the competent authorities of the European Union (“EU”), member states or other regulatory authorities or the IRBs or ethics committees of the institutions in which such trials are being conducted, if a clinical trial is recommended for suspension or termination by the data safety monitoring board or equivalent body for such trial, or on account of changes to federal, state, or local laws. If we are required to conduct additional clinical trials or other testing of DNTH103 or any other product candidates beyond those that we contemplate, if we unable to successfully complete clinical trials of DNTH103 or any other product candidates, if the results of these trials are not positive or are only moderately positive or if there are safety concerns, our business and results of operations may be adversely affected and we may incur significant additional costs.

We have publicly disclosed and may in the future publicly disclose preliminary or topline data from our preclinical studies and clinical trials, which are based on a preliminary analysis of then-available data, and the results and related findings and conclusions are subject to change following a more comprehensive review of the data. We also make assumptions, estimations, calculations and conclusions as part of our analyses of these data without the opportunity to fully and carefully evaluate complete data. As a result, the preliminary or topline results that we report may differ from future results of the same studies, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated or subsequently made subject to audit and verification procedures.

Any preliminary or topline data should be viewed with caution until the final data is available. We have publicly disclosed and may in the future disclose interim data from our preclinical studies and clinical trials. Interim data are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available or as patients from our clinical trials continue other treatments. Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or weigh the importance of data differently, which could impact the value of the particular product candidate, the approvability or commercialization of a particular product candidate and us in general. In addition, the information we choose to publicly disclose regarding a particular preclinical study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is material or otherwise appropriate information to include in our disclosure. If the preliminary, topline or interim data that we report differ from actual results, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and commercialize, DNTH103 or any other product candidate may be harmed, which could harm our business, financial condition, results of operations, cash flows, and prospects.

Results of our clinical trials could reveal a high and unacceptable severity and prevalence of side effects, adverse events or unexpected characteristics. While our completed preclinical studies in NHPs and our Phase 1 clinical trial in humans have not shown any such characteristics, we cannot assure you that such characteristics will not be observed in our future clinical trials. If significant adverse events or other side effects are observed in any of our current or future clinical trials, we may have difficulty recruiting patients to such trials, patients may drop out of our trials, patients may be harmed, or we may be required to abandon the trials or our development efforts of one or more product candidates altogether, including DNTH103. We, the FDA, EU member states, or other applicable regulatory authorities, or an IRB or ethics committee, may suspend any clinical trials of DNTH103 or any other product candidates at any time for various reasons, including a belief that subjects or patients in such trials are being exposed to unacceptable health risks or adverse side effects. Some potential products developed in the biotechnology industry that initially showed therapeutic promise in early-stage studies and trials have later been found to cause side effects that prevented their further development. Other potential products have shown side effects in preclinical studies that do not present themselves in clinical trials in humans. Even if the side effects do not preclude a product candidate from obtaining or maintaining marketing approval, undesirable side effects may inhibit market acceptance of an approved product due to its tolerability versus other therapies. In addition, a half-life extension could prolong the duration of undesirable side effects, which could also inhibit market acceptance. Treatment-emergent adverse events could also affect patient recruitment or the ability of enrolled subjects to complete our clinical trials or could result in potential product liability claims. Potential side effects associated with DNTH103, or any other product candidates, may not be appropriately recognized or managed by the treating medical staff, as toxicities resulting from DNTH103, or any other product

Even if regulatory approval is obtained for DNTH103 or any other product candidates, they may not gain market acceptance among physicians, patients, healthcare payors or the medical community. We may not generate or sustain revenue from sales of the product due to factors such as whether the product can be sold at a competitive cost and whether it will otherwise be accepted in the market. There are several approved products and product candidates in later stages of development for the treatment of gMG, MMN and CIDP. Market participants with significant influence over acceptance of new treatments, such as clinicians and third-party payors, may not adopt a biologic with a target product profile such as that of DNTH103 or for its targeted indications, and we may not be able to convince the medical community and third-party payors to accept and use, or to provide favorable reimbursement for, any product candidates developed by us or our existing or future collaborators. An extended half-life may make it more difficult for patients to change treatments and there is a perception that half-life extension could exacerbate side effects, each of which may adversely affect our ability to gain market acceptance. Market acceptance of DNTH103 or any other product candidates will depend on many factors, including factors that are not within our control.

We are early in our development efforts and will need to successfully complete later-stage and pivotal clinical trials in order to obtain FDA, European Medical Agency (“EMA”), or comparable foreign regulatory approval to market our product candidates. Carrying out clinical trials and the submission of a successful IND or CTA is a complicated process. As an organization, we have limited experience in preparing, submitting and prosecuting regulatory filings. We initiated a global Phase 2 clinical trial of DNTH103 in gMG in the first quarter of 2024, following receipt of FDA clearance of our IND application. We plan to submit a CTA in the European Union in the second quarter of 2024. In addition, pending clearance of the INDs and/or the CTAs that we plan to submit, we anticipate initiating Phase 2 clinical trials of DNTH103 in patients with MMN in the second quarter of 2024 and CIDP in the second half of 2024. However, we may not be able to file the IND or CTA in accordance with our desired timelines. For example, we may experience manufacturing delays or other delays with IND- or CTA-enabling studies, including with suppliers, study sites, or third-party contractors and vendors on whom we depend. Moreover, we cannot be sure that submission of an IND or a CTA or submission of a trial to an IND or a CTA will result in the FDA or EMA or comparable foreign regulatory authorities allowing further clinical trials to begin, or that, once begun, issues will not arise that lead us to suspend or terminate clinical trials. For example, upon submission of an IND or CTA for a Phase 2 clinical trial of DNTH103, the FDA or EMA may recommend changes to our proposed study designs, including the number and size of registrational clinical trials required to be conducted in such Phase 2 programs. Consequently, we may be unable to successfully and efficiently execute and complete necessary clinical trials in a way that leads to regulatory submission and approval of our product candidates. Additionally, even if regulatory authorities agree with the design and implementation of the clinical trials set forth in an IND or a CTA, such regulatory authorities may change their requirements in the future. The FDA, EMA or comparable foreign regulatory authorities may require the analysis of data from trials assessing different doses of the product candidate alone or in combination with other therapies to justify the selected dose prior to the initiation of large trials in a specific indication. Any delays or failure to file INDs or CTAs, initiate clinical trials, or obtain regulatory approvals for our trials may prevent us from completing our clinical trials or commercializing our products on a timely basis, if at all. We are

In addition, we currently rely on foreign CROs and CDMOs, including WuXi Biologics, and will likely continue to rely on foreign CROs and CDMOs in the future. Foreign CDMOs may be subject to U.S. legislation, including the proposed BIOSECURE Act, sanctions, trade restrictions and other foreign regulatory requirements, which could increase the cost or reduce the supply of material available to us, delay the procurement or supply of such material or have an adverse effect on our ability to secure significant commitments from governments to purchase our potential therapies.

For example, the biopharmaceutical industry in China is strictly regulated by the Chinese government. Changes to Chinese regulations or government policies affecting biopharmaceutical companies are unpredictable and may have a material adverse effect on our collaborators in China which could have an adverse effect on our business, financial condition, results of operations and prospects. Evolving changes in China’s public health, economic, political, and social conditions and the uncertainty around China’s relationship with other governments, such as the United States and the United Kingdom (“UK”), could also negatively impact our ability to manufacture our product candidates for our planned clinical trials or have an adverse effect on our ability to secure government funding, which could adversely affect our financial condition and cause us to delay our clinical development programs.

our preclinical studies and clinical trials, and we control only certain aspects of their activities. As a result, we will have less direct control over the conduct, timing and completion of these preclinical studies and clinical trials and the management of data developed through preclinical studies and clinical trials than would be the case if we were relying entirely upon our own staff. Nevertheless, we are responsible for ensuring that each of our studies and trials is conducted in accordance with the applicable protocol, legal, regulatory and scientific standards, and our reliance on these third parties does not relieve us of our regulatory responsibilities. We and our third-party contractors and CROs are required to comply with GCP regulations, which are guidelines enforced by the FDA and comparable foreign regulatory authorities for any product candidate in clinical development. If we or any of these third parties fail to comply with applicable GCP regulations, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot provide assurance that upon inspection by a given regulatory authority, such regulatory authority will determine that any of our clinical trials comply with GCP regulations. In addition, our clinical trials must be conducted with product generated under cGMP regulations. Our failure to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process. Moreover, our business may be implicated if any of these third parties violates federal or state fraud and abuse or false claims laws and regulations or healthcare privacy and security laws.

Any third parties conducting our clinical trials will not be with our employees and, except for remedies available to us under our agreements with such third parties, we cannot control whether they devote sufficient time and resources to our product candidates. These third parties may be involved in mergers, acquisitions or similar transactions and may have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other product development activities, which could negatively affect their performance on our behalf and the timing thereof and could lead to products that compete directly or indirectly with our current or future product candidates. If these third parties do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols or regulatory requirements or for other reasons, our clinical trials may be extended, delayed or terminated and we may not be able to complete development of, obtain regulatory approval of or successfully commercialize DNTH103 or other product candidates.

We have collaborations with third parties, including our existing license and development collaboration with Zenas BioPharma. If we are unable to maintain these collaborations, or if these collaborations are not successful, our business could be adversely affected.

our executives or other employees. The loss of the services of our executive officers or other key employees could impede the achievement of our research, development and commercialization objectives and seriously harm our ability to successfully implement our business strategy. Furthermore, replacing executive officers and key personnel may be difficult and may take an extended period of time. If we do not succeed in attracting and retaining qualified personnel, it could materially and adversely affect our business, financial condition, cash flows, and results of operations. We could in the future have difficulty attracting and retaining experienced personnel and may be required to expend significant financial resources on our employee recruitment and retention efforts.

We are exposed to the risk that our employees, independent contractors, consultants, commercial collaborators, principal investigators, CROs, CDMOs, suppliers and vendors acting for or on our behalf may engage in misconduct or other improper activities. It is not always possible to identify and deter misconduct by these parties and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with these laws or regulations.

Our internal information technology systems, or those of any of our CROs, CDMOs, other contractors, third party service providers or consultants or potential future collaborators, may fail or suffer security or data privacy breaches or other unauthorized or improper access to, use of, or destruction of proprietary or confidential data, employee data or personal data, which could result in additional costs, loss of revenue, significant liabilities, harm to our brand and material disruption of our operations.

In the ordinary course of our business, we and the third parties upon which we rely collect, receive, store, process, generate, use, transfer, disclose, make accessible, protect, secure, dispose of, transmit, and share (collectively, process) proprietary, confidential, and sensitive data, including personal data, intellectual property, trade secrets, and other sensitive data (collectively, sensitive information).

Some actors now engage and are expected to continue to engage in cyber-attacks, including without limitation nation-state actors for geopolitical reasons and in conjunction with military conflicts and defense activities. During times of war and other major conflicts, we, and the third parties upon which we rely, may be vulnerable to a heightened risk of these attacks, including retaliatory cyber-attacks, that could materially disrupt our systems and operations, supply chain, and ability to produce, sell and distribute our goods and services. In particular, severe ransomware attacks are becoming increasingly prevalent and can lead to significant interruptions in our operations, ability to provide our products or services, loss of sensitive data and income, reputational harm, and diversion of funds. Extortion payments may alleviate the negative impact of a ransomware attack, but we may be unwilling or unable to make such payments due to, for example, applicable laws or regulations prohibiting such payments.

To the extent that any disruption or security breach were to result in a loss, destruction, unavailability, alteration or dissemination of, or damage to, our data or applications, or for it to be believed or reported that any of these occurred, we could incur liability and reputational damage and the development and commercialization of DNTH103, or other product candidates could be delayed. Further, our insurance policies may not be adequate to compensate us for the potential losses arising from any such disruption in, or failure or security breach of, our systems or third-party systems where information important to our business operations or commercial development is stored.

If we (or a third party upon whom we rely) experience a security incident or are perceived to have experienced a security incident, we may experience adverse consequences, such as government enforcement actions (for example, investigations, fines, penalties, audits, and inspections); additional reporting requirements and/or oversight; restrictions on processing sensitive information (including personal data); litigation (including class claims); indemnification obligations; negative publicity; reputational harm; monetary fund diversions; interruptions in our operations (including availability of data); increased investigation and compliance costs; financial loss; and other similar harms. Security incidents and attendant consequences may cause stakeholders (including investors and potential customers) to stop supporting our platform, deter new customers from products, and negatively impact our ability to grow and operate our business.

If not remediated, these material weaknesses could result in material misstatements to our annual or interim financial statements that might not be prevented or detected on a timely basis, or in delayed filing of required

periodic reports. If we are unable to assert that our internal control over financial reporting is effective under Section 404(a) of the Sarbanes-Oxley Act, or, if we become subject to Section 404(b) of the Sarbanes-Oxley Act and our independent registered public accounting firm is unable to express an unqualified opinion as to the effectiveness of the internal control over financial reporting, investors may lose confidence in the accuracy and completeness of our financial reports, the market price of our Common Stock could be adversely affected and we could become subject to litigation or investigations by Nasdaq, the SEC, or other regulatory authorities, all of which could require additional financial and management resources.

Our intellectual property portfolio is at an early stage, and we do not currently own or in-license any issued patents. Our pending and future patent applications may not result in patents being issued. Any issued patents may not afford sufficient protection of our product candidates or their intended uses against competitors, nor can there be any assurance that the patents issued will not be infringed, designed around, invalidated by third parties, or effectively prevent others from commercializing competitive technologies, products or product candidates. Even if these patents are granted, they may be difficult to enforce. Further, any issued patents that we may license or own covering our product candidates could be narrowed or found invalid or unenforceable if challenged in court or before administrative bodies in the United States or abroad, including the United States Patent and Trademark Office (“USPTO”). Further, if we encounter delays in any clinical trials or delays in obtaining regulatory approval, the period of time during which we could market product candidates under patent protection would be reduced. Thus, the patents that we may own or license may not afford any meaningful competitive advantage.

While we may litigate to defend ourselves against these claims, even if we are successful, litigation could result in substantial costs and could be a distraction to management. If our defenses to these claims fail, in addition to requiring us to pay monetary damages, a court could prohibit us from using technologies or features that are essential to our product candidates, if such technologies or features are found to incorporate or be derived from the trade secrets or other proprietary information of the former employers. Moreover, any such litigation or the threat thereof may adversely affect our reputation, our ability to form strategic alliances or sublicense our rights to collaborators, engage with scientific advisors or hire employees or consultants, each of which would have an adverse effect on our business, results of operations, financial condition and prospects. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to management.

In addition, the patent positions of companies in the development and commercialization of biologics and pharmaceuticals are particularly uncertain. U.S. Supreme Court and U.S. Court of Appeals for the Federal Circuit rulings have narrowed the scope of patent protection available in certain circumstances and weakened the rights of patent owners in certain situations, including in the antibody arts. For example, the United States Supreme Court in Amgen, Inc. v. Sanofi (Amgen) recently held that Amgen’s patent claims to a class of antibodies functionally defined by their ability to bind a particular antigen were invalid for lack of enablement where the patent specification provided twenty-six exemplary antibodies, but the claimed class of antibodies covered a “vast number” of additional antibodies not disclosed in the specification. The Court stated that if patent claims are directed to an entire class of compositions of matter, then the patent specification must enable a person skilled in the art to make and use the entire class of compositions. This decision makes it unlikely that we will be granted U.S. patents with composition of matter claims directed to antibodies functionally defined by their ability to bind a particular antigen. Even if we are granted claims directed to functionally defined antibodies, it is possible that a third party may challenge our patents, when issued, relying on the reasoning in Amgen or other recent precedential court decisions. Additionally, there have been proposals for additional changes to the patent laws of the United States and other countries that, if adopted, could impact our ability to enforce our proprietary technology. This combination of events has created uncertainty with respect to the validity and enforceability of patents once obtained. Depending on future actions by the U.S. Congress, the federal courts, the USPTO, and the relevant law-making bodies in other countries, the laws and regulations governing patents could change in unpredictable ways that could have a material adverse effect on our patent rights and weaken our ability to protect, defend and enforce our patent rights in the future.

In addition, a European Unified Patent Court (the “UPC”) came into force June 1, 2023. The UPC is a common patent court to hear patent infringement and revocation proceedings effective for member states of the European Union. This enables third parties to seek revocation of a European patent in a single proceeding at the UPC rather than through multiple proceedings in each of the jurisdictions in which the European patent is validated. Although we do not currently own any European patents or applications, if we obtain such patents and applications in the future, any such revocation and loss of patent protection could have a material adverse impact on our business and our ability to commercialize or license our technology and products. Moreover, the controlling laws and regulations of the UPC will develop over time, and may adversely affect our ability to enforce or defend the validity of any European patents we may obtain. We may decide to opt out from the UPC for any future European patent applications that we may file and any patents we may obtain. If certain formalities and requirements are not met, however, such European patents and patent applications could be challenged for non-compliance and brought under the jurisdiction of the UPC. We cannot be certain that future European patents and patent applications will avoid falling under the jurisdiction of the UPC, if we decide to opt out of the UPC.

The process of obtaining regulatory approvals, both in the United States and abroad, is unpredictable, expensive and typically takes many years following commencement of clinical trials, if approval is obtained at all, and can vary substantially based upon a variety of factors, including the type, complexity and novelty of the product candidates involved. We cannot commercialize product candidates in the United States without first obtaining regulatory approval from the FDA. Similarly, we cannot commercialize product candidates outside of the United States without obtaining regulatory approval from comparable foreign regulatory authorities. Before obtaining regulatory approvals for the commercial sale of our product candidates, including our most advanced product candidate, DNTH103, we must demonstrate through lengthy, complex and expensive preclinical and clinical trials that such product candidates are both safe and effective for each targeted indication. Securing regulatory approval also requires the submission of information about the drug manufacturing process to, and inspection of manufacturing facilities by, the relevant regulatory authority. Further, a product candidate may not be effective, may be only moderately effective or may prove to have undesirable or unintended side effects, toxicities or other characteristics that may preclude our obtaining marketing approval. The FDA and comparable foreign regulatory authorities have substantial discretion in the approval process and may refuse to accept any application or may decide that our data is insufficient for approval and require additional preclinical, clinical or other data. A product candidate could be delayed in receiving, or fail to receive, regulatory approval for many reasons, including: the FDA or comparable foreign regulatory authorities may disagree with the design or implementation of our clinical trials; we may be unable to demonstrate to the satisfaction of the FDA or comparable foreign regulatory authorities that a product candidate is safe and effective for its proposed indication; the results of clinical trials may not meet the level of statistical significance required by the FDA or comparable foreign regulatory authorities for approval; serious and unexpected drug-related side effects may be experienced by participants in our clinical trials or by individuals using drugs similar to a product candidate; we may be unable to demonstrate that a product candidate’s clinical and other benefits outweigh its safety risks; the FDA or comparable foreign regulatory authorities may disagree with our interpretation of data from preclinical studies or clinical trials; the data collected from clinical trials of a product candidate may not be acceptable or sufficient to support the submission of a BLA or other submission or to obtain regulatory approval in the United States or elsewhere, and we may be required to conduct additional clinical trials; the FDA or the applicable foreign regulatory authority may disagree regarding the formulation, labeling and/or the specifications of a product candidate; the FDA or comparable foreign regulatory authorities may fail to approve the manufacturing processes or facilities of third-party manufacturers with which we contract for clinical and commercial supplies; and the approval policies or regulations of the FDA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval.

Of the large number of drugs in development, only a small percentage successfully complete the FDA or foreign regulatory approval processes and are commercialized. The lengthy approval process as well as the unpredictability of future clinical trial results may result in us failing to obtain regulatory approval to market DNTH103 or other product candidates, which would significantly harm our business, results of operations and prospects. If we were to obtain approval, regulatory authorities may approve any such product candidate for fewer or more limited indications than we request, including failing to approve the most commercially promising indications, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. If we are not able to obtain, or if there are delays in obtaining, required regulatory approvals for a product candidate, we will not be able to commercialize, or will be delayed in commercializing, such product candidate and our ability to generate revenue will be materially impaired.

In order to receive approval of our products by the FDA and comparable foreign regulatory authorities, we must show that we and our contract manufacturing partners are able to characterize, control and manufacture our drug products safely and in accordance with regulatory requirements. This includes synthesizing the active ingredient, developing an acceptable formulation, performing tests to adequately characterize the formulated product, documenting a repeatable manufacturing process, meeting facility, process and testing validation requirements, and demonstrating that our drug products meet stability requirements. Meeting these chemistry, manufacturing and control (“CMC”) requirements is a complex task that requires specialized expertise. If we are not able to meet the CMC requirements, we may not be successful in getting our products approved.

We conducted our Phase 1 clinical trial for DNTH103 in New Zealand, and we may in the future choose to conduct more of our clinical trials outside the United States. We currently intend to conduct our Phase 2 clinical trials for DNTH103 in the United States and outside the United States. Although the FDA may accept data from clinical trials conducted outside the United States, acceptance of this data is subject to conditions imposed by the FDA. For example, the clinical trial must be well designed and conducted and performed by qualified investigators in accordance with ethical principles. The trial population must also adequately represent the U.S. population, and the data must be applicable to the U.S. population and U.S. medical practice in ways that the FDA deems clinically meaningful. In addition, while these clinical trials are subject to the applicable local laws, FDA acceptance of the data will depend on its determination that the trials also complied with all applicable U.S. laws and regulations. If the FDA does not accept the data from any trial that we conduct outside the United States, it would likely result in the need for additional trials, which would be costly and time-consuming and would delay or permanently halt our development of the applicable product candidates. Even if the FDA accepted such data, it could require us to modify our planned clinical trials to receive clearance to initiate such trials in the United States or to continue such trials once initiated.

Any regulatory approvals that we may receive for DNTH103 or other product candidates will require the submission of reports to regulatory authorities and surveillance to monitor the safety and efficacy of such product candidates, may contain significant limitations related to use restrictions for specified age groups, warnings, precautions or contraindications, and may include burdensome post-approval study or risk management requirements. For example, the FDA may require a risk evaluation and mitigation strategy (“REMS”) in order to approve a product candidate, which could entail requirements for a medication guide, physician training and communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if the FDA or comparable foreign regulatory authorities approve a product candidate, the products and the activities associated with their development and commercialization, including their design, testing, manufacture, safety, efficacy, recordkeeping, labeling, storage, approval, advertising, promotion, sale, distribution, import and export will be subject to comprehensive regulation by the FDA and other regulatory agencies in the United States and by comparable foreign regulatory authorities. These requirements include submissions of safety and other post-marketing information and reports, registration, as well as ongoing compliance with current cGMPs and GCPs for any clinical trials that we conduct following approval. In addition, manufacturers of drug products and their facilities are subject to continual review and periodic, unannounced inspections by the FDA and other regulatory authorities for compliance with cGMPs.

We may seek Fast Track Designation or Orphan Drug Designation for one or more product candidates. If a drug is intended for the treatment of a serious or life-threatening condition and the drug demonstrates the potential to address unmet medical needs for this condition, the product sponsor may apply for Fast Track Designation. The FDA has broad discretion whether or not to grant such designations, so even if we believe a particular product candidate is eligible for such designations, we cannot guarantee that the FDA would decide to grant it. Even if we do receive Fast Track Designation or Orphan Drug Designation, we may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track Designation or Orphan Drug Designation if it believes that the designation is no longer supported by data from a clinical development program. See the section titled “Business—Government Regulation—Expedited Development and Review Programs” located elsewhere in this prospectus for a more detailed description of the process for seeking Fast Track Designation or Orphan Drug Designation.

From time to time, we may be subject to litigation claims through the ordinary course of our business operations regarding, but not limited to, securities litigation, employment matters, security of patient and employee personal information, contractual relations with collaborators and licensors and intellectual property rights. Litigation to defend ourselves against claims by third parties, or to enforce any rights that we may have against third parties, could result in substantial costs and diversion of our resources, causing a material adverse effect on our business, financial condition, results of operations, cash flows, and prospects.

We are subject to the reporting requirements of the Exchange Act, which requires, among other things, that we file with the SEC, annual, quarterly and current reports with respect to our business and financial condition as well as other disclosure and corporate governance requirements. However, we expect to qualify as a “smaller reporting company,” as such term is defined in Rule 12b-2 under the Exchange Act, in at least the near term, which will allow us to take advantage of many of the same exemptions from disclosure requirements, including not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act and reduced disclosure obligations regarding executive compensation in this prospectus and our periodic reports and proxy statements. Once we are no longer a smaller reporting company or otherwise no longer qualify for these exemptions, we will be required to comply with additional legal and regulatory requirements applicable to public companies and will incur significant legal, accounting and other expenses to do so. If we are not able to comply with the requirements in a timely manner or at all, our financial condition or the market price of our Common Stock may be harmed.

If securityholders sell, or indicate an intention to sell, substantial amounts of our Common Stock in the public market, the trading price of our Common Stock could decline. In addition, shares of Common Stock that are subject to outstanding options or warrants of Dianthus are eligible for sale in the public market to the extent permitted by the provisions of various vesting agreements and Rules 144 and 701 under the Securities Act. If any of the foregoing shares of Common Stock are sold, the trading price of our Common Stock could decline.

Our executive officers, directors and principal stockholders, in the aggregate, beneficially own approximately 66% of our outstanding shares of Common Stock as of March 14, 2024. As a result, if these stockholders were to choose to act together, they would be able to control or significantly influence all matters submitted to our stockholders for approval, as well as our management and affairs. For example, these stockholders, if they choose to act together, would control or significantly influence the election of directors and approval of any merger, consolidation or sale of all or substantially all of our assets. This concentration of voting power could delay or prevent an acquisition of us on terms that other stockholders may desire.

We have broad discretion in the use of our cash and cash equivalents and the proceeds from the 2024 Private Placement and may invest or spend the proceeds in ways with which you do not agree and in ways that may not increase the value of your investment.

We have broad discretion over the use of our cash and cash equivalents and the proceeds from the 2024 Private Placement. You may not agree with our decisions, and our use of the proceeds may not yield any return on your investment. Our failure to apply these resources effectively could compromise our ability to pursue our growth strategy and we might not be able to yield a significant return, if any, on our investment of these net proceeds. You will not have the opportunity to influence our decisions on how to use our cash resources.

Changes to tax laws (which changes may have retroactive application) could adversely affect us or our stockholders. We will assess the impact of various tax reform proposals and modifications to existing tax treaties in all jurisdictions where we have operations to determine the potential effect on our business and any assumptions we will make about our future taxable income. We cannot predict whether any specific proposals will be enacted, the terms of any such proposals or what effect, if any, such proposals would have on our business if they were to be enacted. For example, the United States recently enacted the Inflation Reduction Act of 2022 (“IRA”), which implements, among other changes, a 1% excise tax on certain stock buybacks. In addition, beginning in 2022, the Tax Cuts and Jobs Act eliminates the currently available option to deduct research and development expenditures and requires taxpayers to amortize them generally over five years. The U.S. Congress is considering legislation that would restore the current deductibility of research and development expenditures, however, there is no assurance that the provision will be repealed or otherwise modified. Such changes, among others, may adversely affect our effective tax rate, results of operation and general business conditions.

In general, our ability to use our federal and state net operating loss and credits carryforwards to reduce future taxable liabilities is dependent upon our generation of future taxable income, and we cannot predict with certainty when, or whether, we will generate sufficient taxable income or tax liabilities to use all of our carryforwards. Under current law, federal net operating loss carryforwards generated in taxable periods beginning after December 31, 2017, may be carried forward indefinitely, but for taxable years beginning after December 31, 2020 the deductibility of such net operating loss carryforwards is limited to 80% of taxable income. Federal net operating losses generated prior to December 31, 2017, however, have a 20-year carryforward period, but are not subject to the 80% limitation. Similar state law limitations may apply. In addition, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (the “Code”), federal net operating loss and credit carryforwards may become subject to an annual limitation in the event one or more stockholders or groups of stockholders who own at least 5% of a company’s stock increase their ownership by more than 50 percentage points over their lowest ownership percentage within a rolling three-year period (referred to as an “ownership change”). Similar state law limitations may apply. There may also be periods during which the use of net operating loss carryforwards and other tax attributes are suspended or otherwise limited, which could accelerate or permanently increase taxes owed.

As of December 31, 2023, we had federal net operating loss carryforwards of $320.7 million, all of which can be carried forward indefinitely. As of December 31, 2023, Dianthus had state net operating loss carryforwards of $299.1 million, which begin to expire in 2035. As of December 31, 2023, Dianthus also had available research and orphan drug tax credit carryforwards for federal and state income tax purposes of $14.8 million and $3.5 million, respectively, which begin to expire in 2035 and 2030, respectively. We have not conducted a formal study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since inception; however, the Merger is expected to result in an ownership change. For these reasons, we do not expect to be able to utilize a material portion of the net operating losses and research and orphan drug tax credit carryforwards.

On September 11, 2023, we completed our business combination with Dianthus Therapeutics OpCo, Inc. (“OpCo”) in accordance with the terms of the Merger Agreement, pursuant to which, among other matters, Dio Merger Sub, Inc. (“Merger Sub”) merged with and into OpCo, with OpCo surviving as a wholly owned subsidiary of the Company (the “Merger”). In connection with the completion of the Merger, we changed our name from “Magenta Therapeutics, Inc.” to “Dianthus Therapeutics, Inc.” (the “Name Change”), and the business conducted by the Company became primarily the business conducted by OpCo, which is a clinical-stage biotechnology company focused on developing next-generation complement therapeutics for patients living with severe autoimmune and inflammatory diseases. The Merger was intended to qualify for federal income tax purposes as a tax-free reorganization under the provisions of Section 368(a) of the Internal Revenue Code of 1986, as amended.

The foregoing description of the Merger Agreement contained herein does not purport to be complete and is qualified in its entirety by reference to the Merger Agreement, a copy of which is filed as Exhibit 2.1 to the Registration Statement.

As of March 14, 2024, there were approximately 50 stockholders of record of our Common Stock based on information provided by our transfer agent. The actual number of stockholders is greater than this number of record holders, and includes stockholders who are beneficial owners, but whose shares are held in street name by brokers and other nominees. This number of holders of record also does not include stockholders whose shares may be held in trust by other entities.

You should read the following discussion and analysis of our financial condition and results of operations together with our consolidated financial statements and related notes included elsewhere in this prospectus. This discussion contains forward-looking statements that involve risks and uncertainties, including those described in the section titled “Cautionary Statement Concerning Forward-Looking Statements” included elsewhere in this prospectus. Our actual results and the timing of selected events could differ materially from those discussed below. Factors that could cause or contribute to such differences include, but are not limited to, those identified below and those set forth under the section titled “Risk Factors” included elsewhere in this prospectus.

Our most advanced product candidate, DNTH103, is a clinical-stage, highly potent, highly selective and fully human monoclonal immunoglobulin G4 with picomolar binding affinity that is designed to selectively bind only to the active form of the C1s complement protein. The active form of C1s is generated during complement activation by cleavage of the inactive proenzyme C1s. As a validated complement target in the autoimmune and inflammatory field, C1s inhibition prevents further progression of the classical pathway cascade. DNTH103 is engineered with YTE half-life extension technology, a specific three amino acid change in the Fc domain, and has a pharmacokinetic profile designed to support less frequent, lower dose, self-administration as a convenient S.C. injection. Data reported from DNTH103’s Phase 1 clinical trial in 60 healthy volunteers across eight dose cohorts validates the extended half-life and potent classical pathway inhibition and supports a potentially differentiated safety profile of DNTH103. The topline data confirmed its approximately 60-day half-life and highly potent classical pathway inhibition with every two weeks S.C. dosing of 300mg/2mL surpassing the calculated IC90 of 87ug/mL, establishing DNTH103’s best-in-class potential to be the first self-administered subcutaneous injection dosed as infrequently as every two weeks to treat a range of autoimmune disorders. Based on the clinical data available to date, DNTH103 was generally well tolerated with no serious adverse events or complement-related infections. DNTH103 is designed to selectively target the active form of C1s, inhibiting only the classical pathway, while leaving the lectin and alternative pathways intact. As a result, DNTH103 may have a reduced risk of infections from encapsulated bacteria when compared to C5 terminal inhibitors, thus potentially avoiding a U.S. Food and Drug Administration Boxed Warning and associated REMS. We believe that DNTH103 has the potential to yield therapeutic benefit in multiple autoimmune and inflammatory disease indications where inappropriate activation of the classical pathway cascade drives or exacerbates the disease pathology by inhibiting the ability of activated C1s to effect downstream complement activity, ameliorating complement mediated cell death and disruption of normal cellular function.

Securities Purchase Agreement. Pursuant to and subject to the terms and conditions of the Securities Purchase Agreement, we issued and sold, and Selling Stockholders named in the Securities Purchase Agreement purchased, 14,500,500 shares of Common Stock and 4,666,332 2024 Pre-Funded Warrants, exercisable for 4,666,332 shares of Common Stock, at a purchase price of $12.00 per share or $11.999 per 2024 Pre-Funded Warrant, which represents the per share purchase price of the shares of Common Stock less the $0.001 per share exercise price for each 2024 Pre-Funded Warrant, for an aggregate purchase price of approximately $230.0 million.

On September 11, 2023, we completed a business combination with Former Dianthus pursuant to which, among other matters, Former Dianthus became as a wholly owned subsidiary of ours (the “Merger”). In connection with the completion of the Merger, we changed our name from “Magenta Therapeutics, Inc.” to “Dianthus Therapeutics, Inc.,” and the business conducted by us became primarily the business conducted by Former Dianthus.

See Note 1 to our consolidated financial statements for the year ended December 31, 2023 and 2022 included elsewhere in this prospectus for additional information.

To date, we have funded our operations primarily with proceeds from the sale of capital stock and have raised aggregate gross proceeds of $423.5 million from private placements. As of December 31, 2023, we had cash, cash equivalents and short-term investments of $173.7 million. Based on our current operating plan, we believe that our existing cash, cash equivalents and short-term investments, together with the proceeds from our 2024 Private Placement, should be sufficient to fund our operations into the second half of 2027. Until we achieve profitability, we plan to fund our operations and capital expenditures with cash on hand and expect to seek to raise any necessary additional capital through private or public equity or debt financings, loans or other capital sources, which could include income from collaborations, partnerships or other marketing, distribution, licensing or other strategic arrangements with third parties, or from grants. There can be no assurance that we

We have incurred significant recurring losses. We generated net losses of $43.6 million and $28.5 million for the years ended December 31, 2023 and 2022, respectively. As of December 31, 2023, we had an accumulated deficit of $89.4 million. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on a variety of factors, including the timing, scope and results of our research and development activities. We expect our expenses and capital requirements will increase substantially in connection with our ongoing activities, if and as we:

Uncertainty in the global economy presents significant risks to our business. We are subject to continuing risks and uncertainties in connection with the current macroeconomic environment, including increases in inflation, rising interest rates, general economic slowdown or a recession, changes in foreign currency exchange rates, recent bank failures, the prospect of a shutdown of the U.S. federal government, geopolitical factors, including rising tensions between China and Taiwan, the ongoing conflict in Israel and surrounding areas, the attacks on marine vessels traversing the Red Sea and the conflict between Russia and Ukraine and the responses thereto, pandemics or other public health crises, such as the COVID-19 pandemic, and supply chain disruptions. While we are closely monitoring the impact of the current macroeconomic conditions on all aspects of our business, including the impacts on participants in our clinical trials, employees, suppliers, vendors, business partners and regulators, the ultimate extent of the impact on our business remains highly uncertain and will depend on future developments and factors that continue to evolve. Most of these developments and factors are outside of our control and could exist for an extended period of time. We will continue to evaluate the nature and extent of the potential impacts to Dianthus’ business, results of operations, liquidity and capital resources. For additional information, see the section titled “Risk Factors” found elsewhere in this prospectus.

Under the Zenas Agreements, the consideration payable by Zenas Biopharma includes the following: (i) a $1.0 million upfront payment upon execution of the Zenas License Agreement; (ii) an approximate $1.1 million payment representing reimbursement for a portion of development costs previously incurred by us; (iii) reimbursement of a portion of costs related to CMC and expenses for the first antibody sequence through the manufacture of the first two batches of drug product; (iv) reimbursement of a portion of non-CMC-related costs and expenses for the development of the first antibody sequence through the first regulatory approval; (v) development milestones totaling up to $11.0 million; and (vi) royalties on net sales ranging from mid-single digits to low teen percentages.

There is a sales or usage-based royalty exception within ASC 606 that applies when a license of intellectual property is the predominant item to which the royalty relates. In accordance with this royalty exception, we will recognize royalty revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). As of December 31, 2023 and 2022, no royalty revenue has been recognized.

We also determined that the milestone payments of $11.0 million are variable consideration under ASC 606, which need to be added to the transaction price when it is probable that a significant revenue reversal will not occur. Based on the nature of the milestones, such as the regulatory approvals which are generally not within our control, we will not consider achievement of this milestone to be probable until the uncertainty associated with such milestone has been resolved. When it is probable that a significant reversal of revenue will not occur, the milestone payment will be added to the transaction price for which we recognize revenue. As of December 31, 2023 and 2022, no milestones had been achieved.

For the years ended December 31, 2023 and 2022, we recognized related party license revenue totaling $2.8 million and $6.4 million, respectively, associated with the Zenas Agreements.

Research and development expenses account for a significant portion of our operating expenses and consist primarily of external and internal expenses incurred in connection with the discovery and development of DNTH103 or any future product candidates.

Comparison of the Years Ended December 31, 2023 and 2022

The following table summarizes our results of operations and other comprehensive loss for the periods

indicated:

Under the terms of the Zenas Agreements, we recognized related party license revenue of $2.8 million and $6.4 million for the years ended December 31, 2023 and 2022, respectively. The decrease was due to a decreased amount of CMC reimbursement due from Zenas Biopharma during the year ended December 31, 2023 as a result of the substantial completion of the manufacture of the first two batches of drug product for the DNTH103 program in late 2022.

Research and development expenses were $32.8 million for the year ended December 31, 2023, as compared to $29.4 million for the year ended December 31, 2022, an increase of $3.4 million. This increase was due to a $5.3 million increase in internal research and development costs, consisting of personnel and related costs, share-based compensation, and other costs, partially offset by a $1.9 million decrease in external research and development costs, consisting of preclinical study costs, CMC activities, third-party consulting services, clinical operation activities, license and milestone payments and discovery activities.

The $5.3 million increase in internal research and development costs was due to a $4.5 million increase in personnel and related costs, a $0.5 million increase in share-based compensation, and a $0.3 million increase in

other costs. The increases were primarily due to the expansion of our research and development function with additional headcount to support the Phase 1 clinical trial activities of our lead product candidate, DNTH103.

The $1.9 million decrease in external research and development costs was due to a $2.1 million decrease in expenses related to our lead product candidate, DNTH103, partially offset by a $0.2 million increase in discovery activities. The $2.1 million decrease in expenses related to DNTH103 resulted from decreases of $3.9 million in CMC activity costs, $1.3 million in preclinical study costs and $1.2 million in license and milestone payments, partially offset by increases of $4.1 in clinical operations activity costs and $0.2 million in third-party consulting costs. The decreased amount of CMC activities resulted from the substantial completion of the manufacture of the first two batches of drug product for the DNTH103 program in late 2022. The decreased amount of preclinical study costs resulted from the completion of major toxicology studies related to DNTH103 in 2023. The decreased amount of license and milestone payments resulted from the achievement of certain milestones in 2022. The increased amount of clinical operations activity costs resulted from the commencement of the Phase 1 clinical trial in November 2022. The increased consulting costs resulted from the engagement of consultants to assist with regulatory filings and other activities related to DNTH103. The $0.2 million increase in discovery expenses related to development activities of potential molecules beyond DNTH103 in 2023.

General and administrative expenses were $18.2 million for the year ended December 31, 2023, as compared to $6.7 million for the year ended December 31, 2022, an increase of $11.5 million. The increase was primarily due to increases of $4.0 million in severance costs related to former employees of Magenta, $2.5 million in personnel-related costs, $1.7 million in professional services costs, $1.6 million in insurance costs, including director and officer insurance, $0.9 million in share-based compensation, and $0.8 million in other general and administrative expenses.

The provision for income taxes consists primarily of income taxes related to federal and state jurisdictions in which we conduct business. We maintain a full valuation allowance on our federal and state deferred tax assets as we have concluded that it is more likely than not that the deferred assets will not be utilized.

To date, we have funded our operations primarily with proceeds from the sale of capital stock and have raised aggregate gross proceeds of $423.5 million. However, we have incurred significant recurring losses. We had an accumulated deficit of $89.4 million as of December 31, 2023. As of December 31, 2023, we had cash, cash equivalents and short-term investments of $173.7 million. Based on our current operating plan, we believe that our existing cash, cash equivalents and short-term investments, together with the proceeds from our 2024 Private Placement, should be sufficient to fund our operations into the second half of 2027. Until we achieve profitability, we plan to fund our operations and capital expenditures with cash on hand and expect to seek to raise any necessary additional capital through private or public equity or debt financings, loans or other capital sources, which could include income from collaborations, partnerships or other marketing, distribution, licensing or other strategic arrangements with third parties, or from grants. There can be no assurance that we will be successful in raising additional capital or that such capital, if available, will be on terms that are acceptable to us. If we are unable to raise sufficient additional capital, we may be compelled to consider actions such as reducing the scope of our operations and planned capital expenditures or sell certain assets, including intellectual property assets.

The following table summarizes our cash flows for the periods indicated:

For the year ended December 31, 2023, net cash used in operating activities consisted of a net loss of $43.6 million, partially offset by a decrease in net operating assets and liabilities of $4.9 million and net non-cash operating expenses of $1.8 million. The decrease in net operating assets and liabilities was primarily attributable to a decrease in receivable from Zenas BioPharma of $4.4 million, a decrease in unbilled receivable from Zenas

BioPharma of $0.8 million, an increase in accounts payable, accrued expenses and lease liabilities of $0.7 million and a decrease in prepaid expenses and other current assets of $0.1 million, partially offset by an increase in other assets of $1.0 million and a decrease in deferred revenue of $0.1 million. The non-cash operating expenses consisted mainly of stock-based compensation expense of $2.9 million and amortization of right-of-use lease assets of $0.3 million, partially offset by accretion of discount on short-term investments of $1.4 million.

For the year ended December 31, 2023, net cash provided by investing activities consisted of $77.8 million of proceeds from maturities of short-term investments, partially offset by $57.4 million of purchases of short-term investments and $0.1 million of capital expenditures.

For the year ended December 31, 2023, net cash provided by financing activities primarily consisted of $67.8 million of net proceeds from the sale of shares of Former Dianthus common stock in the pre-closing financing and net cash acquired in connection with the reverse recapitalization of $69.7 million, partially offset by $3.9 million of reverse recapitalization transactions costs.

In August 2019, Former Dianthus entered into a license agreement with Alloy Therapeutics, LLC (“Alloy”) for (i) a worldwide, non-exclusive license to use the Alloy technology solely to generate Alloy antibodies and platform assisted antibodies for internal, non-clinical research purposes, and (ii) with respect to Alloy antibodies and platform assisted antibodies that are selected by us for inclusion into a partnered antibody program, a worldwide, assignable license to make, have made, use, offer for sale, sell, import, develop, manufacture, and commercialize products comprising partnered antibody programs selected from Alloy antibodies and platform assisted antibodies in any field of use. In addition to annual license fees, we are obligated to pay development and commercial milestone payments of up to $12.8 million for the first partnered antibody, which has been selected for the DNTH103 program. The license agreement was amended in October 2022 to extend the agreement to a potential second partnered antibody. In addition to annual license fees, we are obligated to pay development and commercial milestone payments of up to $18.1 million for a second partnered antibody, if and when selected.

In September 2022, Former Dianthus entered into a commercial platform license agreement and services agreement with two subsidiaries of Ligand Pharmaceuticals Incorporated (“Ligand”). In November 2022, Ligand spun-off these subsidiaries into a separate legal entity, OmniAb, Inc. (“OmniAb”), for (i) a worldwide, non-exclusive, non-sublicensable license under the OmniAb technology to use chicken animals for generation of OmniAb antibodies for research purposes and (ii) a worldwide, non-exclusive license under the OmniAb technology to use rodent animals for generation of OmniAb antibodies for research purposes. In addition to annual license fees, we are obligated to pay development milestones payments of up to $12.2 million and to pay royalties in the low to mid-single digits.

In July 2020, Former Dianthus entered into a collaborative research agreement with IONTAS Limited (“IONTAS”) to perform certain milestone-based research and development activities under our first development program. The agreement was amended in January 2023 to extend services to additional development programs. We are obligated to pay development and commercial milestone payments of up to £5.4 million (approximately $6.9 million based on the December 31, 2023 exchange rate) with the first development program and of up to £2.5 million (approximately $3.2 million based on the December 31, 2023 exchange rate) with the second development program.

Critical Accounting Policies and Estimates

Our financial statements are prepared in accordance with generally accepted accounting principles in the United States of America. The preparation of the financial statements and related disclosures requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate estimates and assumptions on a periodic basis. Our actual results may differ materially from these estimates.

We believe that the following accounting policies are critical to understanding our historical and future performance, as the policies relate to the more significant areas involving management’s judgments and estimates used in the preparation of our financial statements.

Research and development expenses are recorded as an expense, as incurred. Research and development expenses consists of (i) costs to engage contractors who specialize in our development activities; (ii) external research and development costs incurred under arrangements with third parties, such as CROs, CDMOs and consultants; and (iii) costs associated with preclinical and clinical activities and regulatory operations.

We make estimates of our accrued expenses as of each balance sheet date in our consolidated financial statements based on facts and circumstances known to us at that time. There may also be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. In accruing expenses, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low in any particular period. To date, there have not been any material adjustments to our prior estimates of accrued research and development expenses.

We account for stock-based compensation awards in accordance with ASC Topic 718, Compensation—Stock Compensation, (“ASC 718”). ASC 718 requires all stock-based payments, including grants of stock options and restricted stock, to be recognized in the consolidated statements of operations and comprehensive loss based on their fair values. All of our stock option awards are subject only to service-based vesting conditions. We estimate the fair value of our stock-based awards using the Black-Scholes option pricing model, which requires the input of assumptions, including (a) the fair value of the common stock, (b) the expected stock price volatility, (c) the calculation of expected term of the award, (d) the risk-free interest rate and (e) expected dividends. We estimate the fair value of the restricted stock awards using the fair value of our Common Stock. Forfeitures are recognized as they are incurred.

We are a clinical-stage biotechnology company. On September 11, 2023, we completed a business combination with Former Dianthus pursuant to which, among other matters, Former Dianthus became as a wholly owned subsidiary of ours. In connection with the completion of the Merger, we changed our name from “Magenta Therapeutics, Inc.” to “Dianthus Therapeutics, Inc.,” and the business conducted by us became primarily the business conducted by Former Dianthus. We were incorporated as a Delaware corporation in June 2015 and Former Dianthus was incorporated as a Delaware corporation in May 2019.

We are focused on developing next-generation complement therapeutics for patients living with severe autoimmune and inflammatory diseases. We believe our lead novel and proprietary monoclonal antibody product candidate, DNTH103, has the potential to address a broad array of complement-dependent diseases as currently available therapies and those in development leave room for improvements in efficacy, safety, and/or dosing convenience. We have purposefully engineered DNTH103 to selectively bind to only the active form of the C1s complement protein and to exhibit improved potency and an extended half-life. By selectively targeting only the active form of C1s, which drives disease pathology and constitutes only a small fraction of the total protein present in circulation, we aim to reduce the amount of drug required for a therapeutic effect. We intend to deliver our product candidate through a lower dose, less frequent, self-administered, convenient subcutaneous injection suitable for a pre-filled pen.

Our most advanced product candidate, DNTH103, is a clinical-stage, highly potent, highly selective and fully human monoclonal immunoglobulin G4 with picomolar binding affinity that is designed to selectively bind only to the active form of the C1s complement protein. The active form of C1s is generated during complement activation by cleavage of the inactive proC1s (as defined below). As a validated complement target in the autoimmune and inflammatory field, C1s inhibition prevents further progression of the classical pathway cascade. DNTH103 is engineered with YTE half-life extension technology, a specific three amino acid change in the Fc domain, and has a pharmacokinetic (“PK”) profile designed to support less frequent, lower dose, self-administration as a convenient S.C. injection.

Clinical Data and Development Plans

Data from DNTH103’s Phase 1 clinical trial in 60 healthy volunteers across eight dose cohorts validates the extended half-life and potent classical pathway inhibition and supports a potentially differentiated safety profile of DNTH103. The topline data confirmed its approximately 60-day half-life and highly potent classical pathway inhibition with every two weeks (“Q2W”) S.C. dosing of 300mg/2mL surpassing the calculated IC90 (as defined below) of 87ug/mL, establishing DNTH103’s best-in-class potential to be the first self-administered subcutaneous injection dosed as infrequently as Q2W to treat a range of autoimmune disorders. Based on the clinical data available to date, DNTH103 was generally well tolerated with no serious adverse events (“SAEs”) or complement-related infections. DNTH103 is designed to selectively target the active form of C1s, inhibiting only the classical pathway, while leaving the lectin and alternative pathways intact. As a result, DNTH103 may have a reduced risk of infections from encapsulated bacteria when compared to C5 terminal inhibitors, thus potentially avoiding an FDA Boxed Warning and REMS. We believe that DNTH103 has the potential to yield therapeutic benefit in multiple autoimmune and inflammatory disease indications where inappropriate activation of the classical pathway cascade drives or exacerbates the disease pathology by inhibiting the ability of activated C1s to effect downstream complement activity, ameliorating complement mediated cell death and disruption of normal cellular function.

We evaluated DNTH103 in a first-in-human Phase 1 single ascending dose (“SAD”) and multiple ascending dose (“MAD”) clinical trial in New Zealand to explore the safety, tolerability, PK, and pharmacodynamics (“PD”) of DNTH103 in healthy volunteers. We reported data from 60 healthy volunteers that have been dosed across eight cohorts, including six SAD cohorts: 1mg/kg intravenous (“I.V.”), 10mg/kg I.V., 30mg/kg I.V., 50mg/kg I.V., 300mg S.C. and 600mg S.C.; and two MAD cohorts: 300mg S.C. and 600mg. S.C. Based on the clinical data available to date, DNTH103 has been generally well-tolerated, demonstrating favorable PK and PD data, supporting its target product profile. Based on data from the 60 healthy volunteers, DNTH103 has a half-life of approximately 60 days. With these data, we conducted a PK simulation that demonstrates the steady state serum concentration of DNTH103, when dosed 300mg S.C. Q2W following an initial I.V. loading dose, exceeds the serum concentration required to surpass 90% classical pathway inhibition in a hemolytic assay (“IC90”) estimated to be 87ug/mL. We believe, based on published scientific literature related to other complement therapies, that the IC90 will be sufficient to achieve clinical activity in patients with gMG.

Overview of Development Plans in Target Indications

MG has an estimated prevalence of approximately 70,000 individuals in the United States. However, given this disease is often underdiagnosed, estimated diagnosed prevalence of MG in the United States has been reported to be as high as approximately 90,000 individuals. The disease affects both men and women, but often presents earlier in women. Approximately 85% of MG patients demonstrate elevated serum levels of acetylcholine receptor (“AChR”) antibodies, which disrupt signal transmission at the neuromuscular junction.

We believe DNTH103 has the potential to meaningfully transform the standard of care in gMG as a potent, lower dose, lower frequency, self-administered S.C. injection that may not have an FDA Boxed Warning or REMS. As a more patient-friendly, predictable, convenient and a less burdensome biologic, DNTH103 has the potential to become a first-line biologic treatment option. Thus, DNTH103 could compete for early treatment of AChR positive gMG patients versus intravenous immune globulin (“IVIG”), terminal complement inhibitors and neonatal fragment crystallizable receptor (“FcRn”) inhibitors, as well as for use in patients that do not adequately respond to other biologics such as IVIG or FcRn inhibitors.

We initiated a global Phase 2 clinical trial of DNTH103 in gMG in the first quarter of 2024, following receipt of FDA clearance of our IND application. We plan to submit a CTA in the European Union in the second quarter of 2024.

Regardless of the activation event, all complement pathways converge at common pathway components, known as C3 and C5. When the C3 and C5 proteins are activated, they enable three principal immune responses: inflammation, opsonization and formation of the MAC, a pore forming structure that leads to the lysis of targeted cells. In a normal immune response, C3b fragments act to mark pathogens for removal from tissues or the bloodstream by phagocytes in a process known as opsonization. C3a or C5a cleaved fragments cause inflammation in the surrounding tissues, attracting phagocytes to ingest opsonized pathogens. Downstream, C5b fragments initiate the formation of the membrane attack complex (“MAC”) on pathogens, causing cell death and elimination. However, under conditions of excessive or uncontrolled activation, the complement system is believed to play a key role in the incidence and progression of several autoimmune and inflammatory diseases. Under these conditions, healthy cells may become part of a trigger for complement activation and/or become opsonized and destroyed.

The acetylcholinesterase inhibitor pyridostigmine has been used to treat neuromuscular symptoms of gMG since the 1950s. However, most patients require additional immunosuppressants such as steroids, azathioprine, mycophenolate, cyclosporine A, or rituximab. Although these therapies have shown some success, many patients continue to have unmet need and experience undesirable side effects, and none of these therapies have been approved for gMG. The treatment landscape for MG has continued to evolve. Plasmapheresis (“PLEX”) and IVIG therapy are therapeutic options, although these are more invasive treatments often reserved for MG crisis.

As such, we believe DNTH103 has the potential to meaningfully transform the standard of care in gMG as a potent, lower dose, lower frequency, self-administered S.C. injection with no FDA Boxed Warning or REMS or requirement for cycling of treatment such as with FcRn inhibitors. As it is designed to be a more patient-friendly, predictable, convenient and a less burdensome biologic, DNTH103 has the potential to become a first-line biologic treatment option. Thus, DNTH103 could compete for early treatment of AChR positive gMG patients versus IVIG, terminal complement inhibitors and FcRn inhibitors, as well as for use in patients that do not adequately respond to other biologics such as IVIG or FcRn inhibitors.

Over 70% of CIDP patients require ongoing treatment with immunosuppressants such as IVIG, subcutaneous immune globulin, PLEX or steroids. Despite treatment, a significant number of patients do not achieve clinical remission and there remains a significant unmet clinical need for this disease. Given the role of complement system in the disease pathology, patients may benefit from a selective C1s inhibitor.

We wholly own the patent portfolio covering our C1s selective antibodies, including three pending U.S. provisional applications, two pending PCT applications, two pending non-provisional applications in the United States and pending foreign patent applications in China, Europe, Japan and Taiwan. The applications are directed to, among other things, antibodies that selectively bind to active C1s and methods of using these antibodies, including methods of treating C1s mediated disorders, and pharmaceutical formulations comprising these antibodies. Patents issuing from these applications covering DNTH103 would be expected to expire no earlier than 2043, subject to any disclaimers or extensions. We continue to develop additional pharmaceutical formulations for DNTH103 and will file patent applications to protect the same as appropriate.

In light of the recently introduced BIOSECURE Act, which would prohibit federal agencies from entering into procurement contracts with an entity that uses biotechnology equipment or services from a biotechnology company of concern, we are considering measures to strengthen our supply chain in the event that WuXi Biologics or one of our other manufacturers is impacted. We will closely monitor the implications of the proposed legislation and how it may impact our future manufacturing strategy, and will implement mitigations and supply chain redundancies, as needed. See the risk factor entitled “We currently rely and expect to rely in the future on the use of manufacturing suites in third-party facilities or on third parties to manufacture DNTH103 and any other product candidates, and we may rely on third parties to produce and process our products, if approved. Our business could be adversely affected if we are unable to use third-party manufacturing suites or if the third-party manufacturers encounter difficulties in production.”

In September 2020, we entered into an option agreement with Zenas BioPharma, under which we agreed to grant Zenas BioPharma an exclusive option for an exclusive license under certain patents and know-how with respect to antibody sequences generated in a research program directed towards the research of monoclonal antibody antagonists targeting the human Complement C1s and C2 proteins, or another human protein (each, a “Research Program”). In consideration for the option grant, we were issued Zenas BioPharma common stock equivalent to one percent of its shares outstanding prior to their Series A financing. On a Research Program-by-Research Program basis, Zenas BioPharma also agreed to pay us a one-time payment of $1 million upon exercising the option to enter into a license agreement with respect to such Research Program. The option may only be exercised for up to two Research Programs.

On June 10, 2022, in connection with Zenas BioPharma’s exercise of the option, we entered into a license agreement with Zenas BioPharma (the “Zenas License Agreement”), under which we granted Zenas BioPharma an exclusive, sublicensable license under certain patents and know-how to research, develop, manufacture, and commercialize monoclonal antibody antagonists targeting the human Complement C1s protein (including the antibody sequence of DNTH103) and, if and when the option is exercised, the human Complement C2 protein, in greater China (the “Territory”). As consideration for the license, we are eligible to receive (i) development milestone payments of up to $11 million, (ii) an approximate $1.1 million payment for reimbursement of a portion of development costs we previously incurred; (iii) reimbursement of a portion of certain CMC-related costs and expenses for the first antibody sequence through the manufacture of the first two batches of drug

product; and (iv) reimbursement of a portion of certain non-CMC-related costs and expenses. Additionally, we are eligible to receive royalty payments based on a percentage of the annual net sales of the Products sold on a region-by-region basis in the Territory. The royalty rate may vary from the mid-single digits to the low double-digits based on different tiers of annual net sales of the licensed products. Zenas BioPharma is obligated to make royalty payments to us for the royalty term of the Zenas License Agreement.

On March 22, 2021, we entered into a cell line license agreement (the “Cell Line License Agreement”) with WuXi Biologics. Under the Cell Line License Agreement, we received a non-exclusive, worldwide, sublicensable license to certain of WuXi Biologics’ know-how, cell line, biological materials and media and feeds to make, have made, use, sell and import certain drug products produced through the use of the cell line licensed by WuXi Biologics under the Cell Line License Agreement (the “WuXi Biologics Licensed Products”).

In the United States, biological products are subject to regulation under the Federal Food, Drug, and Cosmetic Act (“FDCA”), the Public Health Service Act (“PHSA”) and other federal, state, local, and foreign statutes and regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, and local statutes and regulations requires the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process or following approval may subject an applicant to administrative action and judicial sanctions. The process required by the FDA before biologic product candidates may be marketed in the United States generally involves the following:

Prior to beginning any clinical trial with a product candidate in the United States, we must submit an IND to the FDA. An IND is a request for authorization from the FDA to administer an investigational new drug product

In addition to the IND submission process, supervision of human gene transfer trials includes evaluation and assessment by an institutional biosafety committee (“IBC”), a local institutional committee that reviews and oversees research utilizing recombinant or synthetic nucleic acid molecules at that institution. The IBC assesses the safety of the research and identifies any potential risk to public health or the environment and such review may result in some delay before initiation of a clinical trial.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. Furthermore, an independent IRB for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site, and must monitor the study until completed.

Regulatory authorities, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk or that the trial is unlikely to meet its stated objectives. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board, which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. There are also requirements governing the reporting of ongoing preclinical studies and clinical trials and clinical study results to public registries.

A sponsor may choose, but is not required, to conduct a foreign clinical study under an IND. When a foreign clinical study is conducted under an IND, all IND requirements must be met unless waived. When the foreign clinical study is not conducted under an IND, the sponsor must ensure that the study complies with certain FDA regulatory requirements in order to use the study as support for an IND or application for marketing approval or licensure, including that the study was conducted in accordance with GCP, including review and approval by an independent ethics committee and use of proper procedures for obtaining informed consent from subjects, and the FDA is able to validate the data from the study through an onsite inspection if the FDA deems such inspection necessary. The GCP requirements encompass both ethical and data integrity standards for clinical studies.

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, nonclinical studies and clinical trials are submitted to the FDA as part of a BLA requesting approval to market the product for one or more indications. The BLA must include all relevant data available from pertinent preclinical studies and clinical trials, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things. Data can come from company-sponsored clinical studies intended to test the safety and effectiveness of the product, or from a number of alternative sources, including studies initiated and sponsored by investigators. The submission of a BLA requires payment of a substantial application user fee to the FDA, unless a waiver or exemption applies.

In addition, under the Pediatric Research Equity Act (“PREA”), a BLA or supplement to a BLA must contain data to assess the safety and effectiveness of the biological product candidate for the claimed indications in all relevant pediatric subpopulations and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The Food and Drug Administration Safety and Innovation Act requires that a sponsor who is planning to submit a marketing application for a biological product that includes a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration submit an initial pediatric study plan within sixty days after an end-of-Phase 2 meeting or as may be agreed between the sponsor and FDA. Unless otherwise required by regulation, PREA does not apply to any biological product for an indication for which orphan designation has been granted.

Within 60 days following submission of the application, the FDA reviews a BLA submitted to determine if it is substantially complete before the agency accepts it for filing. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the BLA must be resubmitted with the additional information. Once a BLA has been accepted for filing, the FDA’s goal is to review standard applications within 10 months after the filing date, or, if the application qualifies for priority review, six months after the FDA accepts the application for filing. In both standard and priority reviews, the review process may also be extended by FDA requests for additional information or clarification. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facility in which it is manufactured, processed, packed or held meets standards

Before approving a BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCPs. If the FDA determines that the application, manufacturing process or manufacturing facilities are not acceptable, it will outline the deficiencies in the submission and often will request additional testing or information. Notwithstanding the submission of any requested additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval.

After the FDA evaluates a BLA and conducts inspections of manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a Complete Response letter. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A Complete Response letter will describe all of the deficiencies that the FDA has identified in the BLA, except that where the FDA determines that the data supporting the application are inadequate to support approval, the FDA may issue the Complete Response letter without first conducting required inspections, testing submitted product lots and/or reviewing proposed labeling. In issuing the Complete Response letter, the FDA may recommend actions that the applicant might take to place the BLA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor safety or efficacy of a product.

The FDA offers a number of expedited development and review programs for qualifying product candidates. The fast track program is intended to expedite or facilitate the process for reviewing new products that meet certain criteria. Specifically, new products are eligible for fast track designation if they are intended to treat a serious or life-threatening disease or condition and data demonstrate the potential to address unmet medical needs for the disease or condition. Fast track designation applies to the combination of the product and the specific indication for which it is being studied. The sponsor of a fast track product has opportunities for more frequent interactions with the review team during product development and, once a BLA is submitted, the product may be eligible for priority review. A fast track product may also be eligible for rolling review, where the FDA may consider for review sections of the BLA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the BLA, the FDA agrees to accept sections of the BLA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the BLA.

Any marketing application for a biologic submitted to the FDA for approval, including a product with a fast track designation and/or breakthrough therapy designation, may be eligible for other types of FDA programs intended to expedite the FDA review and approval process, such as priority review and accelerated approval. A product is eligible for priority review if there is evidence it has the potential to provide a significant improvement in the treatment, diagnosis or prevention of a serious disease or condition. For original BLAs, priority review designation means the FDA’s goal is to take action on the marketing application within six months of the 60-day filing date (as compared to 10 months under standard review).

Additionally, products studied for their safety and effectiveness in treating serious or life-threatening diseases or conditions may receive accelerated approval upon a determination that the product has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. As a condition of accelerated approval, the FDA will generally require the sponsor to perform adequate and well-controlled post-marketing clinical studies to verify and describe the anticipated effect on irreversible morbidity or mortality or other clinical benefit. Under the Food and Drug Omnibus Reform Act of 2022, the FDA may require, as appropriate, that such studies be underway prior to approval or within a specific time period after the date of approval for a product granted accelerated approval. Products receiving accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails to conduct the required post-marketing studies or if such studies fail to verify the predicted clinical benefit. In addition, the FDA currently requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product.

Any products manufactured or distributed by us pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences, periodic reporting, product sampling and distribution, and advertising and promotion of the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing user fee requirements, under which the FDA assesses an annual program fee for each product identified in an approved BLA. Biologic manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMPs, which impose certain procedural and documentation requirements upon us and our third-party manufacturers. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMPs and impose reporting requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMPs and other aspects of regulatory compliance.

The FDA closely regulates the marketing, labeling, advertising and promotion of biologics. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available products for uses that are not described in the product’s labeling and that differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict manufacturer’s communications on the subject of off-label use of their products.

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (collectively, the “ACA”), includes a subtitle called the Biologics Price Competition and Innovation Act of 2009 (“BPCIA”), which created an abbreviated approval pathway for biological products that are highly similar, or “biosimilar,” to or interchangeable with an FDA-approved reference biological product. The FDA has issued several guidance documents outlining an approach to review and approval of biosimilars.

Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first licensed by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a full BLA for the competing product containing that applicant’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of its product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products. At this juncture, it is unclear whether products deemed “interchangeable” by the FDA will, in fact, be readily substituted by pharmacies, which are governed by state pharmacy law.

A reference biologic is granted twelve years of exclusivity from the time of first licensure of the reference product. The first biologic product submitted under the abbreviated approval pathway that is determined to be interchangeable with the reference product has exclusivity against other biologics submitted under the abbreviated approval pathway for the lesser of (i) one year after the first commercial marketing, (ii) 18 months after approval if there is no legal challenge, (iii) 18 months after the resolution in the applicant’s favor of a lawsuit challenging the biologics’ patents if an application has been submitted, or (iv) 42 months after the application has been approved if a lawsuit is ongoing within the 42-month period.

The AKS prohibits, among other things, persons and entities from knowingly and willfully soliciting, receiving, offering or paying remuneration, to induce, or in return for, either the referral of an individual, or the purchase or recommendation of an item or service for which payment may be made under any federal healthcare program. The term remuneration has been interpreted broadly to include anything of value. The AKS has been interpreted to apply to arrangements between pharmaceutical manufacturers on one hand, and prescribers and purchasers on the other. The government often takes the position that to violate the AKS, only one purpose of the remuneration need be to induce referrals, even if there are other legitimate purposes for the remuneration. There are a number of statutory exceptions and regulatory safe harbors protecting some common activities from AKS prosecution, but they are drawn narrowly and practices that involve remuneration, such as consulting agreements, that may be alleged to be intended to induce prescribing, purchasing or recommending may be subject to scrutiny if they do not qualify for an exception or safe harbor. Our practices may not in all cases meet all of the criteria for protection under a statutory exception or regulatory safe harbor. Failure to meet all of the requirements of a particular applicable statutory exception or regulatory safe harbor does not make the conduct per se illegal under the AKS. Instead, the legality of the arrangement will be evaluated on a case-by-case basis based on a cumulative review of all of its facts and circumstances. A person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation.

Civil and criminal false claims laws, including the FCA, and civil monetary penalty laws, which can be enforced through civil whistleblower or qui tam actions, prohibit, among other things, individuals or entities from knowingly presenting, or causing to be presented, claims for payment of federal government funds, including in federal healthcare programs, that are false or fraudulent. Pharmaceutical and other healthcare companies have been prosecuted under these laws for engaging in a variety of different types of conduct that “caused” the submission of false claims to federal healthcare programs. Under the AKS, for example, a claim resulting from a violation of the AKS is deemed to be a false or fraudulent claim for purposes of the FCA.

HIPAA created additional federal criminal statutes that prohibit, among other things, executing a scheme to defraud any healthcare benefit program, including private third-party payors, and making false statements relating to healthcare matters. A person or entity does not need to have actual knowledge of the healthcare fraud statute implemented under HIPAA or specific intent to violate the statute in order to have committed a violation.

The U.S. federal Physician Payments Sunshine Act requires certain manufacturers of drugs, devices, biologics and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program, with specific exceptions, to annually report to the Centers for Medicaid & Medicare Services (“CMS”) information related to payments or other transfers of value made to various healthcare professionals including physicians, physician assistants, nurse practitioners, clinical nurse specialists, certified nurse anesthetists, certified nurse-midwives, and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members. Beginning on January 1, 2023, California Assembly Bill 1278 requires California physicians and surgeons to notify patients of the Open Payments database established under the federal Physician Payments Sunshine Act.

We are also subject to additional similar U.S. state and foreign law equivalents of each of the above federal laws, which, in some cases, differ from each other in significant ways, and may not have the same effect, thus complicating compliance efforts. If our operations are found to be in violation of any of such laws or any other governmental regulations that apply, we may be subject to penalties, including, without limitation, civil, criminal and administrative penalties, damages, fines, exclusion from government-funded healthcare programs, such as Medicare and Medicaid or similar programs in other countries or jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, disgorgement, individual imprisonment, contractual damages, reputational harm, diminished profits and the curtailment or restructuring of our operations.

Numerous state, federal, and foreign laws govern the collection, dissemination, use, access to, confidentiality, and security of personal information, including health-related information. In the United States, numerous federal and state laws and regulations, including state data breach notification laws, state health information privacy laws, and federal and state consumer protection laws and regulations, govern the collection, use, disclosure, and protection of health-related and other personal information could apply to our operations or the operations of our partners. For example, HIPAA, as amended by the Health Information Technology for Economic and Clinical Health (“HITECH”), and their respective implementing regulations imposes data privacy, security, and breach notification obligations on certain health care providers, health plans, and health care clearinghouses, known as covered entities, as well as their business associates and their covered subcontractors that perform certain services that involve using, disclosing, creating, receiving, maintaining, or transmitting individually identifiable protected health information (“PHI”) for or on behalf of such covered entities. These requirements imposed by HIPAA and the HITECH Act on covered entities and business associates include entering into agreements that require business associates protect PHI provided by the covered entity against

improper use or disclosure, among other things; following certain standards for the privacy of PHI, which limit the disclosure of a patient’s past, present, or future physical or mental health or condition or information about a patient’s receipt of health care if the information identifies, or could reasonably be used to identify, the individual; ensuring the confidentiality, integrity, and availability of all PHI created, received, maintained, or transmitted in electronic form, to identify and protect against reasonably anticipated threats or impermissible uses or disclosures to the security and integrity of such PHI; and reporting of breaches of PHI to individuals and regulators.

Entities that are found to be in violation of HIPAA may be subject to significant civil, criminal, and administrative fines and penalties and/or additional reporting and oversight obligations if required to enter into a resolution agreement and corrective action plan with HHS to settle allegations of HIPAA non-compliance. A covered entity or business associate is also liable for civil money penalties for a violation that is based on an act or omission of any of its agents, which may include a downstream business associate, as determined according to the federal common law of agency. HITECH also increased the civil and criminal penalties. applicable to covered entities and business associates and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce HIPAA and seek attorneys’ fees and costs associated with pursuing federal civil actions. To the extent that we submit electronic healthcare claims and payment transactions that do not comply with the electronic data transmission standards established under HIPAA and HITECH, payments to us may be delayed or denied.

In addition, certain state laws, such as the California Consumer Privacy Act of 2018 (“CCPA”), as amended by the California Privacy Rights Act of 2020 (“CPRA”), govern the privacy and security of personal information, including health-related information, in certain circumstances, some of which are more stringent than HIPAA and many of which differ from each other in significant ways and may not have the same effect, thus complicating compliance efforts. The CCPA/CPRA applies to personal data of consumers, business representatives, and employees, and imposes obligations on certain businesses that do business in California, including to provide specific disclosures in privacy notices, rights to California residents in relation to their personal information. Health information falls under the CCPA/CPRA’s definition of personal information where it identifies, relates to, describes, or is reasonably capable of being associated with or could reasonably be linked with a particular consumer or household — unless it is subject to HIPAA — and is included under a new category of personal information, “sensitive personal information,” which is offered greater protection. Failure to comply with these laws, where applicable, can result in the imposition of significant civil and/or criminal penalties and private litigation. Privacy and security laws, regulations, and other obligations are constantly evolving, may conflict with each other to complicate compliance efforts, and can result in investigations, proceedings, or actions that lead to significant civil and/or criminal penalties and restrictions on data processing. Additionally, our use of artificial intelligence and machine learning may be subject to laws and evolving regulations regarding the use of artificial intelligence/machine learning, controlling for data bias, and anti-discrimination.

In addition, the CPRA expands the CCPA’s requirements, including by adding a new right for individuals to correct their personal information and establishing a new regulatory agency to implement and enforce the law. Other states, such as Virginia, Colorado, Connecticut and Utah, have also passed comprehensive privacy laws, and similar laws are being considered in several other states, as well as at the federal and local levels. While the laws in these states, like the CCPA, also exempt some data processed in the context of clinical trials, such developments further complicate compliance efforts, and increase legal risk and compliance costs for us and the third parties upon whom we rely.

Significant uncertainty exists as to the coverage and reimbursement status of any pharmaceutical or biological product for which we obtain regulatory approval. Sales of any product, if approved, depend, in part, on the extent to which such product will be covered by third-party payors, such as federal, state, and foreign government healthcare programs, commercial insurance and managed healthcare organizations, and the level of reimbursement, if any, for such product by third-party payors. Decisions regarding whether to cover any of our product candidates, if approved, the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. Further, no uniform policy for coverage and reimbursement exists in the United States, and coverage and reimbursement can differ significantly from payor to payor. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own reimbursement rates, but also have their own methods and approval process apart from Medicare determinations. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our product candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance.

In addition, the U.S. government, state legislatures and foreign governments have continued implementing cost- containment programs, including price controls, restrictions on coverage and reimbursement and requirements for substitution of generic products. The IRA provides CMS with significant new authorities intended to curb drug costs and to encourage market competition. For the first time, CMS will be able to directly negotiate prescription drug prices and to cap out-of-pocket costs. Each year, CMS will select and negotiate a preset number of high-spend drugs and biologics that are covered under Medicare Part B and Part D that do not have generic or biosimilar competition. On August 29, 2023, HHS announced the list of the first ten drugs that will be subject to price negotiations. These price negotiations will begin in 2023, although the Medicare drug price negotiation program is currently subject to legal challenges. The IRA also provides a new “inflation rebate” covering Medicare patients that will take effect in 2023 and is intended to counter certain price increases in prescriptions drugs. The inflation rebate provision will require drug manufacturers to pay a rebate to the federal government if the price for a drug or biologic under Medicare Part B and Part D increases faster than the rate of inflation. To support biosimilar competition, beginning in October 2022, qualifying biosimilars may receive a Medicare Part B payment increase for a period of five years. Separately, if a biologic drug for which no biosimilar exists delays a biosimilar’s market entry beyond two years, CMS will be authorized to subject the biologics manufacturer to price negotiations intended to ensure fair competition. Notwithstanding these provisions, the IRA’s impact on commercialization and competition remains largely uncertain.

The ACA, which was enacted in March 2010, substantially changed the way healthcare is financed by both governmental and private insurers in the United States, and significantly affected the pharmaceutical industry. The ACA contains a number of provisions of particular import to the pharmaceutical and biotechnology industries, including, but not limited to, those governing enrollment in federal healthcare programs, a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected, and annual fees based on pharmaceutical companies’ share of sales to federal health care programs. Since its enactment, there have been judicial and Congressional challenges to certain aspects of the ACA, and we expect there will be additional challenges and amendments to the ACA in the future. For example, the IRA, among other things, extends enhanced subsidies for individuals purchasing health insurance coverage in ACA marketplaces through plan year 2025. The IRA also eliminates the “donut hole” under the Medicare Part D program beginning in 2025 by significantly lowering the beneficiary maximum out-of-pocket cost and creating a new manufacturer discount program.

Other legislative changes have been proposed and adopted since the ACA was enacted, including automatic aggregate reductions of Medicare payments to providers of on average 2% per fiscal year as part of the federal budget sequestration under the Budget Control Act of 2011. These reductions went into effect in April 2013 and, due to subsequent legislative amendments, will remain in effect until 2032 unless additional action is taken by Congress.

In addition, the Bipartisan Budget Act of 2018, among other things, amended the Medicare Act (as amended by the ACA) to increase the point-of-sale discounts that manufacturers must agree to offer under the Medicare Part D coverage discount program from 50% to 70% off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs being covered under Medicare Part D.

Moreover, there has recently been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries and proposed and enacted federal and state measures designed to, among other things, reduce the cost of prescription drugs, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drug products. For example, in May 2019, CMS adopted a final rule allowing Medicare Advantage Plans the option to use step therapy for Part B drugs, permitting Medicare Part D plans to apply certain utilization controls to new starts of five of the six protected class drugs, and requiring the Explanation of Benefits for Part D beneficiaries to disclose drug price increases and lower cost therapeutic alternatives, which went into effect on January 1, 2021. In response to the Biden administration’s October 2022 executive order, on February 14, 2023, HHS released a report outlining three new models for testing by the CMS Innovation Center which will be evaluated on their ability to lower the cost of drugs, promote accessibility, and improve quality of care. It is unclear whether the models will be utilized in any health reform measures in the future. Further, on December 7, 2023, the Biden administration announced an initiative to control the price of prescription drugs through the use of march-in rights under the Bayh-Dole Act. On December 8, 2023, the National Institute of Standards and Technology published for comment a Draft Interagency Guidance Framework for Considering the Exercise of March-In Rights which for the first time includes the price of a product as one factor an agency can use when deciding to exercise march-in rights. While march-in rights have not previously been exercised, it is uncertain if that will continue under the new framework.

Notwithstanding the IRA, continued legislative and enforcement interest exists in the United States with respect to specialty drug pricing practices. Specifically, we expect regulators to continue pushing for transparency to drug pricing, reducing the cost of prescription drugs under Medicare, reviewing the relationship between pricing and manufacturer patient programs, and reforming government program reimbursement methodologies for drugs.

Whether or not we obtain FDA approval for a product, we must obtain the requisite approvals from regulatory authorities in foreign countries prior to the commencement of clinical trials or marketing of the product in those countries. Certain countries outside of the United States have a similar process that requires the submission of a clinical trial application much like the IND prior to the commencement of human clinical trials.

European Data Laws

The collection and use of personal health data and other personal data in the EU is governed by the provisions of the European General Data Protection Regulation (EU) 2016/679 (“GDPR”), which came into force in May 2018, and related data protection laws in individual EU Member States. The GDPR imposes a number of strict obligations and restrictions on the ability to process, including collecting, analyzing and transferring, personal data of individuals, in particular with respect to health data from clinical trials and adverse event reporting. The GDPR includes requirements relating to the legal basis of the processing (such as consent of the individuals to whom the personal data relates), the information provided to the individuals prior to processing their personal data, the notification obligations to the national data protection authorities, and the security and confidentiality of the personal data. EU Member States may also impose additional requirements in relation to health, genetic and biometric data through their national legislation.

In addition, the GDPR imposes specific restrictions on the transfer of personal data to countries outside of the European Economic Area (“EEA”) that are not considered by the European Commission (“EC”) to provide an adequate level of data protection. Appropriate safeguards are required to enable such transfers. Among the appropriate safeguards that can be used, the data exporter may use the EC approved standard contractual clauses (“SCCs”). With regard to the transfer of data from the EEA to the United States, on July 10, 2023, the EC adopted its adequacy decision for the EU-US Data Privacy Framework. On the basis of the new adequacy decision, personal data can flow from the EEA to U.S. companies participating in the framework.

Failure to comply with the requirements of the GDPR and the related national data protection laws of the EU Member States may result in significant monetary fines for noncompliance of up to €20 million or 4% of the annual global revenues of the noncompliant company, whichever is greater, other administrative penalties and a number of criminal offenses (punishable by uncapped fines) for organizations and, in certain cases, their directors and officers, as well as civil liability claims from individuals whose personal data was processed. Data protection authorities from the different EU Member States may still implement certain variations, enforce the GDPR and national data protection laws differently, and introduce additional national regulations and guidelines, which adds to the complexity of processing personal data subject in the EU data protection regimes. Guidance developed at both the EU level and at the national level in individual EU Member States concerning implementation and compliance practices are often updated or otherwise revised.

Furthermore, there is a growing trend towards the required public disclosure of clinical trial data in the EU, which adds to the complexity of obligations relating to processing health data from clinical trials. Such public disclosure obligations are provided in the new EU Clinical Trials Regulation No. 536/2014 (the “CTR”), EMA disclosure initiatives and voluntary commitments by industry. Failure to comply with these obligations could lead to government enforcement actions and significant penalties against us, harm to our reputation, and adversely impact our business and operating results. The uncertainty regarding the interplay between different regulatory frameworks, such as the CTR and the GDPR, further adds to the complexity that we face with regard to data protection regulation.

With regard to the transfer of personal data from the EEA to the UK, personal data may now freely flow from the EEA to the UK since the UK is deemed to have an adequate data protection level. However, the adequacy decisions include a ‘sunset clause’ which entails that the decisions will automatically expire four years after their entry into force. Additionally, following the UK’s withdrawal from the EU and the EEA, companies also have to comply with the UK’s data protection laws (including the UK GDPR (as defined in section 3(10) (as supplemented by section 205(4)) of the Data Protection Act 2018 (the DPA 2018)), the DPA 2018, and related data protection laws in the UK). Separate from the fines that can be imposed by the GDPR, the UK regime has the ability to fine up to the greater of £17.5 million or 4% of global turnover.

Following the UK’s withdrawal from the EU and the EEA, companies are subject to specific transfer rules under the UK regime; personal data may flow freely from the UK to the EEA, since the EEA is deemed to have an adequate data protection level for purposes of the UK regime. These UK international transfer rules broadly mirror the GDPR rules. On February 2, 2022, the UK Secretary of State laid before the UK Parliament the international data transfer agreement (“IDTA”) and the international data transfer addendum to the EC’s standard contractual clauses for international data transfers (Addendum) and a document setting out transitional provisions. The IDTA and Addendum came into force on March 21, 2022 and replaced the old SCCs for the purposes of the UK regime. However, the transitional provisions, adopted with the IDTA and the Addendum, provide that contracts concluded on or before September 21, 2022 on the basis of any old SCCs continue to provide appropriate safeguards for the purpose of the UK regime until March 21, 2024, provided that the processing operations that are the subject matter of the contract remain unchanged and reliance on those clauses ensures that the transfer of personal data is subject to appropriate safeguards.

With regard to the transfer of personal data from the UK to the United States, the UK government has adopted an adequacy decision for the United States, the UK-US Data Bridge, which came into force on October 12, 2023. The UK-US Data Bridge recognizes the United States as offering an adequate level of data protection where the transfer is to a U.S. company participating in the EU-US Data Privacy Framework and the UK Extension.

Regardless of where they are conducted, all clinical trials included in applications for marketing authorization (“MA”) for human medicines in the EU/EEA must have been carried out in accordance with EU

regulations. This means that clinical trials conducted in the EU/EEA have to comply with EU clinical trial legislation but also that clinical trials conducted outside the EU/EEA have to comply with ethical principles equivalent to those set out in the EU/EEA, including adhering to international good clinical practice and the Declaration of Helsinki. The conduct of clinical trials in the EU is governed by the CTR, which entered into force on January 31, 2022. The CTR replaced the Clinical Trials Directive 2001/20/EC, (“Clinical Trials Directive”) and introduced a complete overhaul of the existing regulation of clinical trials for medicinal products in the EU.

Under the former regime, which will expire after a transition period of three years, respectively, as outlined below in more detail, before a clinical trial can be initiated it must be approved in each EU member state where there is a site at which the clinical trial is to be conducted. The approval must be obtained from two separate entities: the National Competent Authority (“NCA”) in the applicable EU member state(s) and one or more Ethics Committees. The NCA of the EU Member States in which the clinical trial will be conducted must authorize the conduct of the trial, and the independent ethics committee must grant a positive opinion in relation to the conduct of the clinical trial in the relevant EU member state before the commencement of the trial. Any substantial changes to the trial protocol or other information submitted with the clinical trial applications must be submitted to or approved by the relevant NCA and Ethics Committees. Under the current regime all suspected unexpected serious adverse reactions to the investigated drug that occur during the clinical trial must be reported to the NCA and to the Ethics Committees of the EU member state where they occur.

A more unified procedure will apply under the new CTR. A sponsor will be able to submit a single application for approval of a clinical trial through a centralized EU clinical trials portal (the “CTIS”). One national regulatory authority (the reporting EU Member State proposed by the applicant) will take the lead in validating and evaluating the application, consult and coordinate with the other concerned EU Member States. If an application is rejected, it may be amended and resubmitted through the EU clinical trials portal. If an approval is issued, the sponsor may start the clinical trial in all concerned EU Member States. However, a concerned EU Member State may in limited circumstances declare an “opt-out” from an approval and prevent the clinical trial from being conducted in such member state. The CTR also aims to streamline and simplify the rules on safety reporting, and introduces enhanced transparency requirements such as mandatory submission of a summary of the clinical trial results to the EU Database. The CTR foresees a three-year transition period. EU Member States will work in CTIS immediately after the system has gone live. Since January 31, 2023, submission of initial clinical trial applications via CTIS is mandatory, and by January 31, 2025, all ongoing trials approved under the former Clinical Trials Directive will need to comply with the CTR and have to be transitioned to CTIS. On July 19, 2023, the EC published guidance concerning the steps to be taken in this transition. This guidance provides, among other things, that (i) documentation which was previously assessed will not be reassessed, (i) templates that were developed and endorsed by the EU Clinical Trials Expert Group to provide compliance with the CTR do not need to be updated and (iii) there is no need to retrospectively create a site suitability form, which are only necessary for new trial sites.

Under both the former regime and the new CTR, national laws, regulations, and the applicable GCP and Good Laboratory Practice standards must also be respected during the conduct of the trials, including the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use guidelines on Good Clinical Practice and the ethical principles that have their origin in the Declaration of Helsinki.

During the development of a medicinal product, the EMA and national regulators within the EU provide the opportunity for dialogue and guidance on the development program. At the EMA level, this is usually done in the form of scientific advice, which is given by the Committee for Medicinal Products for Human Use (“CHMP”) on the recommendation of the Scientific Advice Working Party. A fee is incurred with each scientific advice procedure but is significantly reduced for designated orphan medicines. Advice from the EMA is typically provided based on questions concerning, for example, quality (chemistry, manufacturing and controls testing), nonclinical testing and clinical studies, and pharmacovigilance plans and risk-management programs. Advice is not legally binding with regard to any future Marketing Authorization Application (“MAA”) of the product concerned.

In the EEA, after completion of all required clinical testing, pharmaceutical products may only be placed on the market after obtaining a MA. To obtain an MA of a drug under European Union regulatory systems, an applicant can submit an MAA through, amongst others, a centralized or decentralized procedure. To be used or sold in the UK, a drug must have an effective MA obtained by a centralized application through EMA or a national application. National applications are governed by the Human Medicines Regulations (SI 2012/1916). Applications are made electronically through the Medicines and Healthcare products Regulatory Agency (“MHRA”) Submissions Portal. The process from application to authorizations generally takes up to 210 days, excluding time taken to provide any additional information or data required by the MHRA.

On August 30, 2023, the MHRA published detailed guidance on its recently announced new International Reliance Procedure (“IRP”) for MAAs. The IRP applies since January 1, 2024 and replaces existing EU reliance procedures to apply for authorizations from seven international regulators (e.g. Health Canada, Swiss Medic, FDA, EMA, among others). The IRP allows medicinal products approved in other jurisdictions that meet certain criteria to undergo a fast-tracked MHRA review to obtain and/or update a MA in the UK or Great Britain.

Applicants can submit initial MAAs to the IRP but the procedure can also be used throughout the lifecycle of a product for post-authorization procedures including line extensions, variations and renewals.

The centralized procedure provides for the grant of a single MA that is issued by the EC following the scientific assessment of the application by the EMA that is valid for all EU Member States as well as in the three additional EEA Member States. The centralized procedure is compulsory for specific medicinal products, including for medicines developed by means of certain biotechnological processes, products designated as orphan medicinal products, advanced therapy medicinal products (“ATMP”) and medicinal products with a new active substance indicated for the treatment of certain diseases (AIDS, cancer, neurodegenerative disorders, diabetes, auto-immune and viral diseases). For medicinal products containing a new active substance not yet authorized in EEA before May 20, 2004 and indicated for the treatment of other diseases, medicinal products that constitute significant therapeutic, scientific or technical innovations or for which the grant of a MA through the centralized procedure would be in the interest of public health at EU level, an applicant may voluntarily submit an application for a MA through the centralized procedure.

Under the centralized procedure, the CHMP established at the EMA, is responsible for conducting the initial assessment of a drug. The CHMP is also responsible for several post-authorization and maintenance activities, such as the assessment of modifications or extensions to an existing MA. Under the centralized procedure, the timeframe for the evaluation of an MAA by the EMA’s CHMP is, in principle, 210 days from receipt of a valid MAA. However, this timeline excludes clock stops, when additional written or oral information is to be provided by the applicant in response to questions asked by the CHMP, so the overall process typically takes a year or more, unless the application is eligible for an accelerated assessment. Accelerated evaluation might be granted by the CHMP in exceptional cases, when a medicinal product is expected to be of a major public health interest, particularly from the point of view of therapeutic innovation. Upon request, the CHMP can reduce the time frame to 150 days if the applicant provides sufficient justification for an accelerated assessment. The CHMP will provide a positive opinion regarding the application only if it meets certain quality, safety and efficacy requirements. This opinion is then transmitted to the EC, which has the ultimate authority for granting the MA within 67 days after receipt of the CHMP opinion.

Decentralized Authorization Procedure

Medicines that fall outside the mandatory scope of the centralized procedure have three routes to authorization:(i) they can be authorized under the centralized procedure if they concern a significant therapeutic,

scientific or technical innovation, or if their authorization would be in the interest of public health; (ii) they can be authorized under a decentralized procedure where an applicant applies for simultaneous authorization in more than one EU member state; or (iii) they can be authorized in an EU member state in accordance with that state’s national procedures and then be authorized in other EU countries by a procedure whereby the countries concerned agree to recognize the validity of the original, national MA (mutual recognition procedure).

The decentralized procedure permits companies to file identical MA applications for a medicinal product to the competent authorities in various EU Member States simultaneously if such medicinal product has not received marketing approval in any EU Member State before. This procedure is available for pharmaceutical products not falling within the mandatory scope of the centralized procedure. The competent authority of a single EU Member State, the reference member state, is appointed to review the application and provide an assessment report. The competent authorities of the other EU Member State, the concerned member states, are subsequently required to grant a MA for their territories on the basis of this assessment. The only exception to this is where the competent authority of an EU Member State considers that there are concerns of potential serious risk to public health, the disputed points are subject to a dispute resolution mechanism and may eventually be referred to the EC, whose decision is binding for all EU Member States.

All new MAAs must include a Risk Management Plan (“RMP”) describing the risk management system that the company will put in place and documenting measures to prevent or minimize the risks associated with the product. RMPs are continually modified and updated throughout the lifetime of the medicine as new information becomes available. An updated RMP must be submitted: (i) at the request of EMA or a national competent authority, or (ii) whenever the risk-management system is modified, especially as the result of new information being received that may lead to a significant change to the benefit-risk profile or as a result of an important pharmacovigilance or risk-minimization milestone being reached. The regulatory authorities may also impose specific obligations as a condition of the MA. Since October 20, 2023, all RMPs for centrally authorized products are published by EMA, subject only to limited redactions.

MAs have an initial duration of five years. After these five years, the authorization may subsequently be renewed on the basis of a reevaluation of the risk-benefit balance. Once renewed, the MA is valid for an unlimited period unless the EC or the national competent authority decides, on justified grounds relating to pharmacovigilance, to proceed with only one additional five-year renewal. Applications for renewal must be made to the EMA at least nine months before the five-year period expires.

Additionally, the holder of a MA for an ATMP must put in place and maintain a system to ensure that each individual product and its starting and raw materials, including all substances coming into contact with the cells or tissues it may contain, can be traced through the sourcing, manufacturing, packaging, storage, transport and delivery to the relevant healthcare institution where the product is used. Any authorization which is not followed by the actual placing of the drug on the EU market (in case of centralized procedure) or on the market of the authorizing member state within three years after authorization ceases to be valid.

For the UK, the period of three years during which the drug has not been marketed in Great Britain will be restarted from the date of conversion to a Great Britain MA. Conversion refers to the procedure by which, as of January 1, 2021, MAs granted on the basis of a centralized procedure in the EU are only valid in Norther Ireland but not in Great Britain, whereas, prior EU authorizations have all been automatically converted into UK MAs effective in Great Britain only.

On the other hand, for the EU, in the case the drug has been marketed in the UK, the placing on the UK market before the end of the period starting when the UK left the EU on January 31, 2020 and ending on

December 31, 2020 (the “Brexit Transition Period”) will be taken into account. If, after the end of the Brexit Transition Period, the drug is not placed on any other market of the remaining member states of the EU, the three-year period will start running from the last date the drug was placed on the UK market before the end of the Brexit Transition Period.

Advanced Therapy Medicinal Products

In the EU, medicinal products, including ATMPs are subject to extensive pre- and post-market regulation by regulatory authorities at both the EU and national levels. ATMPs comprise gene therapy products, somatic cell therapy products and tissue engineered products, which are genes, cells or tissues that have undergone substantial manipulation and that are administered to human beings in order to cure, diagnose or prevent diseases or regenerate, repair or replace a human tissue. Pursuant to ATMP regulation, the Committee on Advanced Therapies (“CAT”) is responsible in conjunction with the CHMP for the evaluation of ATMPs. The CHMP and CAT are also responsible for providing guidelines on ATMPs. These guidelines provide additional guidance on the factors that the EMA will consider in relation to the development and evaluation of ATMPs and include, among other things, the preclinical studies required to characterize ATMPs. Although such guidelines are not legally binding, compliance with them is often necessary to gain and maintain approval for product candidates.

In addition to the mandatory RMP, the holder of a MA for an ATMP must put in place and maintain a system to ensure that each individual product and its starting and raw materials, including all substances coming into contact with the cells or tissues it may contain, can be traced through the sourcing, manufacturing, packaging, storage, transport and delivery to the relevant healthcare institution where the product is used.

Similar to accelerated approval regulations in the United States, conditional MAs can be granted in the EU in exceptional circumstances. A conditional MA can be granted for medicinal products where, although comprehensive clinical data referring to the safety and efficacy of the medicinal product have not been supplied, a number of criteria are fulfilled: (i) the benefit/risk balance of the product is positive, (ii) it is likely that the applicant will be in a position to provide the comprehensive clinical data, (iii) unmet medical needs will be fulfilled by the grant of the MA and (iv) the benefit to public health of the immediate availability on the market of the medicinal product concerned outweighs the risk inherent in the fact that additional data are still required. A conditional MA must be renewed annually.

As in the United States, it may be possible to obtain a period of market and / or data exclusivity in the EU that would have the effect of postponing the entry into the marketplace of a competitor’s generic, hybrid or biosimilar product (even if the pharmaceutical product has already received a MA) and prohibiting another applicant from relying on the MA holder’s pharmacological, toxicological and clinical data in support of another MA for the purposes of submitting an application, obtaining an MA or placing the product on the market. New Chemical Entities (“NCE”) approved in the EU qualify for eight years of data exclusivity and 10 years of marketing exclusivity.

An additional non-cumulative one-year period of marketing exclusivity is possible if during the data exclusivity period (the first eight years of the 10-year marketing exclusivity period), the MA holder obtains an authorization for one or more new therapeutic indications that are deemed to bring a significant clinical benefit compared to existing therapies.

The data exclusivity period begins on the date of the product’s first MA in the EU. After eight years, a generic product application may be submitted and generic companies may rely on the MA holder’s data. However, a generic product cannot launch until two years later (or a total of 10 years after the first MA in the EU

of the innovator product), or three years later (or a total of 11 years after the first MA in the EU of the innovator product) if the MA holder obtains MA for a new indication with significant clinical benefit within the eight-year data exclusivity period. Additionally, another noncumulative one-year period of data exclusivity can be added to the eight years of data exclusivity where an application is made for a new indication for a well-established substance, provided that significant pre-clinical or clinical studies were carried out in relation to the new indication. Another year of data exclusivity may be added to the eight years, where a change of classification of a pharmaceutical product has been authorized on the basis of significant pre-trial tests or clinical trials (when examining an application by another applicant for or holder of market authorization for a change of classification of the same substance the competent authority will not refer to the results of those tests or trials for one year after the initial change was authorized).

Products may not be granted data exclusivity since there is no guarantee that a product will be considered by the European Union’s regulatory authorities to include a NCE. Even if a compound is considered to be a NCE and the MA applicant is able to gain the prescribed period of data exclusivity, another company nevertheless could also market another version of the medicinal product if such company can complete a full MAA with their own complete database of pharmaceutical tests, preclinical studies and clinical trials and obtain MA of its product.

On April 26, 2023, the EC submitted a proposal for the reform of the European pharmaceutical legislation. The current draft envisages e.g., a shortening of the periods of data exclusivity, however, there is currently neither a final version of this draft nor a date for its entry into force.

The criteria for designating an orphan medicinal product in the EU are similar in principle to those in the United States. The EMA grants orphan drug designation if the medicinal product is intended for the diagnosis, prevention or treatment of a life-threatening or chronically debilitating condition affecting no more than five in 10,000 persons in the EU (prevalence criterion). In addition, Orphan Drug Designation can be granted if, for economic reasons, the medicinal product would be unlikely to be developed without incentives and if there is no other satisfactory method approved in the EU of diagnosing, preventing, or treating the condition, or if such a method exists, the proposed medicinal product is a significant benefit to patients affected by the condition. An application for orphan drug designation (which is not a MA, as not all orphan-designated medicines reach the authorization application stage) must be submitted first before an application for MA of the medicinal product is submitted. The applicant will receive a fee reduction for the MAA if the orphan drug designation has been granted, but not if the designation is still pending at the time the MAA is submitted, and sponsors must submit an annual report to EMA summarizing the status of development of the medicine. Orphan drug designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process. Designated orphan medicines are eligible for conditional marketing authorization.

The EMA’s Committee for Orphan Medicinal Products reassesses the orphan drug designation of a product in parallel with the review for a MA; for a product to benefit from market exclusivity it must maintain its orphan drug designation at the time of MA review by the EMA and approval by the EC. Additionally, any MA granted for an orphan medicinal product must only cover the therapeutic indication(s) that are covered by the orphan drug designation. Upon the grant of a MA, orphan drug designation provides up to ten years of market exclusivity in the orphan indication.

During the 10-year period of market exclusivity, with a limited number of exceptions, the regulatory authorities of the EU Member States and the EMA may not accept applications for MA, accept an application to extend an existing MA or grant MA for other similar medicinal products for the same therapeutic indication. A similar medicinal product is defined as a medicinal product containing a similar active substance or substances as contained in a currently authorized orphan medicinal product, and which is intended for the same therapeutic indication. An orphan medicinal product can also obtain an additional two years of market exclusivity for an

orphan-designated condition when the results of specific studies are reflected in the Summary of Product Characteristics (“SmPC”) addressing the pediatric population and completed in accordance with a fully compliant Pediatric Investigation Plan (“PIP”). No extension to any supplementary protection certificate can be granted on the basis of pediatric studies for orphan indications.

The 10-year market exclusivity may be reduced to six years if, at the end of the fifth year, it is established that the product no longer meets the criteria for orphan designation, i.e. the condition prevalence or financial returns criteria under Article 3 of Regulation (EC) No. 141/2000 on orphan medicinal products. When the period of orphan market exclusivity for an indication ends, the orphan drug designation for that indication expires as well. Orphan exclusivity runs in parallel with normal rules on data exclusivity and market protection. Additionally, a MA may be granted to a “similar medicinal product” (orphan or not) for the same or overlapping indication subject to certain requirements.

In the EU, companies developing a new medicinal product are obligated to study their product in children and must therefore submit a PIP together with a request for agreement to the EMA. The EMA issues a decision on the PIP based on an opinion of the EMA’s Pediatric Committee. Companies must conduct pediatric clinical trials in accordance with the PIP approved by the EMA, unless a deferral (e.g. until enough information to demonstrate its effectiveness and safety in adults is available) or waiver (e.g. because the relevant disease or condition occurs only in adults) has been granted by the EMA. The MAA for the medicinal product must include the results of all pediatric clinical trials performed and details of all information collected in compliance with the approved PIP, unless a waiver or a deferral has been granted, in which case the pediatric clinical trials may be completed at a later date. Medicinal products that are granted a MA on the basis of the pediatric clinical trials conducted in accordance with the approved PIP are eligible for a six-month extension of the protection under a supplementary protection certificate (if any is in effect at the time of approval), or, in the case of orphan medicinal products, a two year extension of the orphan market exclusivity. This pediatric reward is subject to specific conditions and is not automatically available when data in compliance with the approved PIP are developed and submitted. An approved PIP is also required when a MA holder wants to add a new indication, medicinal form or route of administration for a medicine that is already authorized and covered by intellectual property rights.

In the UK, the MHRA has published guidance on the procedures for UK PIPs which, where possible, mirror the submission format and requirements of the EU system. EU PIPs remain applicable for Northern Ireland and EU PIPs agreed by the EMA prior to January 1, 2021 have been adopted as UK PIPs.

In March 2016, the EMA launched an initiative to facilitate development of product candidates in indications, often rare, for which few or no therapies currently exist. The Priority Medicines (“PRIME”) scheme is intended to encourage drug development in areas of unmet medical need and provides accelerated assessment of products representing substantial innovation reviewed under the centralized procedure. Products from small- and medium-sized enterprises may qualify for earlier entry into the PRIME scheme than larger companies on the basis of compelling non-clinical data and tolerability data from initial clinical trials. Many benefits accrue to sponsors of product candidates with PRIME designation, including but not limited to, early and proactive regulatory dialogue with the EMA, frequent discussions on clinical trial designs and other development program elements, and potentially accelerated MAA assessment once a dossier has been submitted. Importantly, once a candidate medicine has been selected for the PRIME scheme, a dedicated contact point and rapporteur from the CHMP or from CAT are appointed facilitating increased understanding of the product at EMA’s Committee level. A kick-off meeting with the CHMP/CAT rapporteur initiates these relationships and includes a team of multidisciplinary experts to provide guidance on the overall development plan and regulatory strategy. PRIME eligibility does not change the standards for product approval, and there is no assurance that any such designation or eligibility will result in expedited review or approval.

Similar to the United States, both MA holders and manufacturers of medicinal products are subject to comprehensive regulatory oversight by the EMA, the EC and/or the competent regulatory authorities of the EU Member States. This oversight applies both before and after grant of manufacturing licenses and MAs. It includes control of compliance with EU good manufacturing practices rules, manufacturing authorizations, pharmacovigilance rules and requirements governing advertising, promotion, sale, and distribution, recordkeeping, importing and exporting of medicinal products.

Failure by us or by any of our third-party partners, including suppliers, manufacturers and distributors to comply with EU laws and the related national laws of individual EU Member States governing the conduct of clinical trials, manufacturing approval, MA of medicinal products and marketing of such products, both before and after grant of MA, statutory health insurance, bribery and anti-corruption or other applicable regulatory requirements may result in administrative, civil or criminal penalties. These penalties could include delays or refusal to authorize the conduct of clinical trials or to grant an MA, product withdrawals and recalls, product seizures, suspension, withdrawal or variation of the MA, total or partial suspension of production, distribution, manufacturing or clinical trials, operating restrictions, injunctions, suspension of licenses, fines and criminal penalties.

These pharmacovigilance rules can impose on holders of MAs the obligation to conduct a labor intensive collection of data regarding the risks and benefits of marketed medicinal products and to engage in ongoing assessments of those risks and benefits, including the possible requirement to conduct additional clinical studies or post-authorization safety studies to obtain further information on a medicine’s safety, or to measure the effectiveness of risk- management measures, which may be time consuming and expensive and could impact our profitability. MA holders must establish and maintain a pharmacovigilance system and appoint an individual qualified person for pharmacovigilance, who is responsible for oversight of that system. Key obligations include expedited reporting of suspected serious adverse reactions and submission of periodic safety update reports (“PSURs”) in relation to medicinal products for which they hold MAs. The EMA reviews PSURs for medicinal products authorized through the centralized procedure. If the EMA has concerns that the risk benefit profile of a product has varied, it can adopt an opinion advising that the existing MA for the product be suspended, withdrawn or varied. The agency can advise that the MA holder be obliged to conduct post-authorization Phase IV safety studies. If the EC agrees with the opinion, it can adopt a decision varying the existing MA. Failure by the MA holder to fulfill the obligations for which the EC’s decision provides can undermine the ongoing validity of the MA.

The manufacturing process for pharmaceutical products in the EU is highly regulated and regulators may shut down manufacturing facilities that they believe do not comply with regulations. Manufacturing requires a manufacturing authorization, and the manufacturing authorization holder must comply with various requirements set out in the applicable EU laws, regulations and guidance, including Directive 2001/83/EC, Directive 2003/94/EC, Regulation (EC) No 726/2004 and the European Commission Guidelines for Good Manufacturing Practice (“GMP”). These requirements include compliance with EU GMP standards when manufacturing pharmaceutical products and active pharmaceutical ingredients, including the manufacture of active pharmaceutical ingredients outside of the EU with the intention to import the active pharmaceutical ingredients into the European Union. Similarly, the distribution of pharmaceutical products into and within the EU is subject to compliance with the applicable EU laws, regulations and guidelines, including the requirement to hold appropriate authorizations for distribution granted by the competent authorities of the EU Member States. The

The advertising and promotion of our products is also subject to EU laws concerning promotion of medicinal products, interactions with physicians, misleading and comparative advertising and unfair commercial practices. In addition, other national legislation of individual EU Member States may apply to the advertising and promotion of medicinal products and may differ from one country to another. These laws require that promotional materials and advertising in relation to medicinal products comply with the product’s SmPC as approved by the competent regulatory authorities. The SmPC is the document that provides information to physicians concerning the safe and effective use of the medicinal product. It forms an intrinsic and integral part of the MA granted for the medicinal product. Promotion of a medicinal product that does not comply with the SmPC is considered to constitute off-label promotion. All advertising and promotional activities for the product must be consistent with the approved SmPC and therefore all off-label promotion is prohibited. Direct-to-consumer advertising of prescription-only medicines is also prohibited in the EU. Violations of the rules governing the promotion of medicinal products in the EU could be penalized by administrative measures, fines and imprisonment. These laws may further limit or restrict the advertising and promotion of our products to the general public and may also impose limitations on its promotional activities with healthcare professionals.

EU regulation with regards to dispensing, sale and purchase of medicines has generally been preserved in the UK following Brexit, through the HMRs. However, organizations wishing to sell medicines online need to register with the MHRA. Following Brexit, the requirements to display the common logo no longer apply to UK- based online sellers, except for those established in Northern Ireland.

In the EU, interactions between pharmaceutical companies and physicians are also governed by strict laws, regulations, industry self-regulation codes of conduct and physicians’ codes of professional conduct both at EU level and in the individual EU Member States. The provision of benefits or advantages to physicians to induce or encourage the prescription, recommendation, endorsement, purchase, supply, order or use of medicinal products is prohibited in the European Union. The provision of benefits or advantages to physicians is also governed by the national anti-bribery laws of the EU Member States. Violation of these laws could result in substantial fines and imprisonment. Payments made to physicians in certain EU Member States also must be publicly disclosed. Moreover, agreements with physicians must often be the subject of prior notification and approval by the physician’s employer, his/her regulatory professional organization, and/or the competent authorities of the individual EU Member States. These requirements are provided in the national laws, industry codes, or professional codes of conduct, applicable in the individual EU Member States. Failure to comply with these requirements could result in reputational risk, public reprimands, administrative penalties, fines or imprisonment.

In the UK, the pharmaceutical sector is recognized as being particularly vulnerable to corrupt practices, some of which fall within the scope of the Bribery Act 2010. Due to the Bribery Act 2010’s far-reaching territorial application, the potential penalized act does not have to occur in the UK to become within its scope. If the act or omission does not take place in the UK, but the person’s act or omission would constitute an offense if carried out there and the person has a close connection with the UK, an offense will still have been committed. The Bribery Act 2010 is comprised of four offenses that cover (i) individuals, companies and partnerships that give, promise or offer bribes, (ii) individuals, companies and partnerships that request, agree to receive or accept bribes, (iii) individuals, companies and partnerships that bribe foreign public officials and (iv) companies and partnerships that fail to prevent persons acting on their behalf from paying bribes. The penalties imposed under the Bribery Act 2010 depend on the offence committed, harm and culpability and penalties range from unlimited fines to imprisonment for a maximum term of ten years and in some cases both.

Regulations in the UK and Other Markets

The UK formally left the EU on January 31, 2020 and EU laws now only apply to the UK in respect of Northern Ireland as laid out in the Protocol on Ireland and Northern Ireland and as amended by the Windsor Framework sets out a long-term set of arrangements for the supply of medicines into Northern Ireland. The EU and the UK agreed on a trade and cooperation agreement (“TCA”), which includes provisions affecting the life sciences sector (including on customs and tariffs). There are some specific provisions concerning pharmaceuticals, including the mutual recognition of GMP, inspections of manufacturing facilities for medicinal products and GMP issued documents. The TCA does not, however, contain wholesale mutual recognition of UK and EU pharmaceutical regulations and product standards.

The UK government has adopted the Medicines and Medical Devices Act 2021 (the “MMDA”) to enable the UK’s regulatory frameworks to be updated following the UK’s departure from the EU. The MMDA introduces regulation-making, delegated powers covering the fields of human medicines, clinical trials of human medicines, veterinary medicines and medical devices. The MHRA has since been consulting on future regulations for medicines and medical devices in the UK.

If we fail to comply with applicable foreign regulatory requirements, it may be subject to, among other things, fines, suspension of clinical trials, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

As of March 14, 2024, we had 53 employees, all of whom were employed full time and 37 of whom were engaged in research and development activities. 14 of our employees hold Ph.D. or M.D. degrees. None of our employees are represented by a labor union or covered under a collective bargaining agreement. We consider our relationship with our employees to be good.

We are currently a remote-based company, and a majority of our employees work remotely. We currently lease space for administrative offices in Waltham, Massachusetts and New York, New York and wet laboratory space in Watertown, Massachusetts. Our space in Waltham is approximately 2,750 square feet under a lease that expires in January 2025, our space in New York is approximately 3,367 square feet under a lease that expires in August 2025 and our space in Watertown varies monthly based on our needs but does not exceed 1,000 square feet under a lease that expires in August 2025. Our New York office is our corporate headquarters. As the company expands, we believe suitable additional, or substitute space will be available as and when needed.

From time to time, we may be involved in litigation and other legal proceedings arising in the ordinary course of our business. We are not currently a party to or aware of any legal proceedings that we believe will have, individually or in the aggregate, a material adverse effect on our business, financial condition, results of operations or cash flows. The outcome of any claims or litigation, regardless of the merits, is inherently uncertain. Regardless of the outcome, litigation and other legal proceedings can have a material adverse impact on us, our business, financial condition, results of operations or cash flows because of defense and settlement costs, diversion of management resources, in the case of intellectual property claims, requirements to change our product candidates, change our business practices, pay monetary damages or enter into short- or long-term royalty or licensing agreements, and other factors.

Pursuant to the Merger Agreement, Magenta was entitled to designate two directors to the Board of Directors (the “Magenta Designees”) and Former Dianthus was entitled to designate six directors to the Board of Directors (the “Former Dianthus Designees”). Effective as of September 11, 2023, the following individuals continued to serve as members of the Board of Directors as the Magenta Designees: Alison F. Lawton and Anne McGeorge, and the following individuals were appointed as members of the Board of Directors as Former Dianthus Designees: Marino Garcia, Leon O. Moulder, Jr., Tomas Kiselak, Lei Meng, Paula Soteropoulos and Jonathan Violin, Ph.D.

In accordance with the terms of our Certificate of Incorporation and By-laws, our Board of Directors is divided into three classes, Class I, Class II and Class III, with members of each class serving staggered three-year terms. The members of the classes are divided as follows:

The following table sets forth the name, age and position of each of our current directors and executive officers as of March 14, 2024:

Marino Garcia. Mr. Garcia has served as our President and Chief Executive Officer and as a member of our Board of Directors since September 2023, and as President and Chief Executive Officer and a director of Former Dianthus since November 2021. Prior to joining Former Dianthus, Mr. Garcia served as Senior Vice President, Corporate and Business Development at Zealand Pharma A/S, a biotechnology company, from October 2018 to October 2021. Mr. Garcia previously served as Executive Vice President, Chief Strategy Officer at Synergy Pharmaceuticals from March 2016 to September 2018 and was the Senior Vice President for Corporate Development for the two preceding years. Prior to Synergy, Mr. Garcia served as Vice President, US Commercial Operations and Global New Product Development at Aspreva Pharmaceuticals Corporation, a company collaborating with Roche to develop CellCept (myocophenolate mofetil) for a range of autoimmune diseases, including Lupus Nephritis, Myasthenia Gravis, and Pemphigus Vulgaris. Prior to joining Aspreva, Mr. Garcia served in various roles at large multinational biopharmaceutical companies, including Merck & Co., Pfizer Inc. and Eli Lilly and Co. Mr. Garcia received his M.B.A. from the Ivey Business School at Western University in London, Ontario and his Bachelor of Commerce from Concordia University in Montreal, Quebec. We believe that Mr. Garcia is qualified to serve on the Board of Directors because of his significant operational and senior management experience in the biopharmaceutical industry.

Ryan Savitz. Mr. Savitz has served as our Chief Financial Officer since September 2023, and was promoted to add Chief Business Officer to his title in February 2024. Mr. Savitz has served as Chief Financial Officer of Former Dianthus since June 2022. Mr. Savitz was recently promoted to Chief Financial and Business Officer on February 7, 2024. He most recently served as Managing Director in Citigroup’s Healthcare Investment Banking division where he was employed from June 2010 to June 2022 and focused on advising biopharma companies on private and public capital raising, partnering, and mergers and acquisitions. Prior to becoming Managing Director, he held positions of increasing responsibility, all within the Healthcare Investment Banking division at Citigroup. Mr. Savitz received his Bachelor of Science in Finance from the Pennsylvania State University.

Simrat Randhawa, M.D. Dr. Randhawa has served as our Chief Medical Officer since September 2023 and as Chief Medical Officer of Former Dianthus since April 2022. Dr. Randhawa most recently served as Senior Vice President of Clinical and Medical Affairs at Aurinia Pharmaceuticals Inc. (Nasdaq: AUPH), an autoimmune-focused company, from February 2017 to April 2022, where he supported the clinical development of voclosporin. Dr. Randhawa has held a number of senior commercial and medical leadership roles in the autoimmune and rare disease spaces within large pharma and biotech companies such as Novartis AG and BioMarin Pharmaceutical Inc. Previously, he supported business development opportunities and integration needs in the health care sector while at McKinsey Consulting. Dr. Randhawa completed his M.D. at Drexel University and received his M.B.A. from Columbia University.

Adam Veness, Esq. Mr. Veness has served as our Senior Vice President, General Counsel and Secretary since September 2023, and Senior Vice President, General Counsel and Secretary of Former Dianthus since June 2023. Prior to joining Former Dianthus, Mr. Veness served as General Counsel and Secretary at Cyteir Therapeutics, Inc. (Nasdaq: CYT), a clinical-stage oncology company, from April 2022 until June 2023. Prior to Cyteir, Mr. Veness served as General Counsel and Secretary at Acceleron Pharma Inc., a biopharmaceutical

company, from 2019 until Acceleron’s acquisition by Merck & Co. in November 2021. Mr. Veness served in various roles at Acceleron from July 2014 until his appointment as General Counsel in 2019. During his tenure at Acceleron, Mr. Veness gained experience in roles of increasing responsibility where he served on the Executive Committee responsible for company strategy, and he led the global legal and compliance functions, including capital markets and SEC reporting obligations, corporate governance, contracts, intellectual property, employment matters, and data privacy. Prior to Acceleron, Mr. Veness was a corporate and securities attorney at the law firm, Mintz Levin, where he represented and counseled public and private companies in the biopharmaceutical, technology, and healthcare industries. Mr. Veness earned a B.A. in Political Science and Philosophy from Tulane University, and a J.D. from Boston University School of Law.

Edward Carr. Mr. Carr has served as our Chief Accounting Officer since September 2023, and as Chief Accounting Officer of Former Dianthus since April 2022. Prior to joining Former Dianthus, Mr. Carr served as Chief Financial Officer of Abeona Therapeutics (Nasdaq: ABEO), a clinical stage biotechnology company, from August 2021 to March 2022 and as Chief Accounting Officer from November 2018 to August 2021. Prior to Abeona, Mr. Carr served as Assistant Controller at Coty Inc. (NYSE: COTY), a manufacturing company, from October 2017 to November 2018 and as Chief Accounting Officer at Foster Wheeler AG (Nasdaq: FWLT), an engineering and construction company, from April 2007 to March 2017. Mr. Carr, who is a Certified Public Accountant, began his career at Ernst & Young LLP. He received his Master of Professional Accountancy and Bachelor of Business Administration from West Virginia University.

Leon O. Moulder, Jr. Mr. Moulder has served as Chair and a member of our Board of Directors since September 2023, and as Chair and a member of the board of directors of Former Dianthus since July 2019. Mr. Moulder is the sole Managing Member of Tellus BioVentures, a life science investment fund he founded in March 2019. Mr. Moulder also founded Zenas BioPharma, a biopharmaceutical company, in December 2019 and has served as Chairman of its board of directors since its inception and its Chief Executive Officer from its inception to April 2021 and from July 2023. From May 2010 to January 2019, Mr. Moulder was the co-founder, Chief Executive Officer and a member of the board of directors of TESARO, Inc., a formerly public biopharmaceutical company that was acquired by GlaxoSmithKline plc. From April 2009 to January 2010, Mr. Moulder served as Vice Chairman of the board of directors, President and Chief Executive Officer of Abraxis BioScience, Inc., a biotechnology company. Before that, Mr. Moulder served as Vice Chairman of Eisai Corporation of North America, a pharmaceutical company and wholly owned subsidiary of Eisai Co., Ltd., from January 2008 until January 2009, following Eisai Co., Ltd.’s acquisition of MGI PHARMA, Inc., in January 2008. Mr. Moulder served as President and Chief Executive Officer and as a member of the board of directors of MGI PHARMA, Inc. from May 2003 to January 2008. Mr. Moulder currently serves as a director for Zai Lab Ltd. (Nasdaq: ZLAB) and several privately held Tellus BioVentures portfolio companies, and he previously served on the board of Trevena, Inc. (Nasdaq: TRVN) from November 2011 until December 2023. Mr. Moulder earned a B.S. in Pharmacy from Temple University and an M.B.A. from the University of Chicago. Mr. Moulder is a Trustee of Temple University and a council member for the University of Chicago Booth School of Business. We believe that Mr. Moulder is qualified to serve on the Board of Directors because of his significant operational and senior management experience in the biopharmaceutical industry, as well as his extensive experience as a director on public and private boards in the industry.

Mr. Moulder may be deemed to have sole voting and dispositive power over the shares held by Tellus BioVentures. A summary of transactions between the Company and Tellus BioVentures is included under the section titled “Certain Related Person Transactions—Dianthus and Former Dianthus Transactions” located elsewhere in this prospectus, and Tellus BioVentures is also party to the Registration Rights Agreement.

Tomas Kiselak. Mr. Kiselak has served as a member of our Board of Directors since September 2023, and as a member of the board of directors of Former Dianthus since May 2021. Mr. Kiselak is a Managing Member at Fairmount Funds Management LLC, a healthcare investment firm he co-founded in April 2016. Prior to

Fairmount, Mr. Kiselak was a managing director at RA Capital Management, LLC, a healthcare and life science investment firm. Mr. Kiselak has served as the Chairman of the board of Viridian Therapeutics, Inc. (“Viridian”) (Nasdaq: VRDN) since June 2021 and a member of the Viridian board of directors since October 2020, and as a director for Apogee Therapeutics, Inc. (Nasdaq: APGE) since June 2023, Spyre Therapeutics Inc. (Nasdaq: SYRE) since June 2023 and several private companies. He received a bachelor’s degree in Neuroscience and Economics from Amherst College. We believe that Mr. Kiselak is qualified to serve on the Board of Directors because of his experience advising biotechnology companies and as a manager of funds specializing in the area of life sciences.

Lei Meng. Ms. Meng has served as a member of our Board of Directors since September 2023, and as a member of the board of directors of Former Dianthus since April 2022 and as Senior Therapeutics Analyst on the private investment team of Avidity Partners since January 2021. Prior to Avidity, Ms. Meng was the Vice President of Marketing Analytics and Business Development and Licensing Commercial Assessments at Allergan from February 2017 to May 2020. Prior to becoming Vice President, she held positions of increasing responsibility at Allergan from March 2012 to January 2017. Prior to Allergan, Ms. Meng was a therapeutics analyst investing in public life science companies at Samlyn Capital. Prior to Samlyn, Ms. Meng had worked as a management consultant at McKinsey & Co., serving life sciences clients, and as a researcher in Medicinal Chemistry and Clinical Research at Merck & Co. Ms. Meng has been a Director of Prellis Biologics, an antibody discovery platform company, since August 2022. She received her M.B.A. from INSEAD, a Masters in Organic Chemistry from Harvard University and her Bachelors in Biochemistry from Barnard College. We believe that Ms. Meng is qualified to serve on the Board of Directors because of her extensive experience as an operator in the pharmaceutical and biotechnology industry and as an investor in life science companies.

Paula Soteropoulos. Ms. Soteropoulos has served as a member of our Board of Directors since September 2023, and as a member of the board of directors of Former Dianthus since April 2022. Ms. Soteropoulos currently serves as the Chairman of the board of Ensoma, Inc., a private venture-backed company, where she began as founding Executive Chairman in March 2020. Since January 2024, she has also served as interim CEO for Ensoma. Since November 2020, she has served on the board of directors of Rallybio Corporation (Nasdaq: RLYB). Since July 2013, she has served on the board of directors of uniQure N.V. Since January 2023, she also has served as a Venture Partner to 5AM Ventures, an investment firm. From January 2015 through September 2019, she served as President and Chief Executive Officer of Akcea Therapeutics Inc. (Nasdaq: AKCA), a biopharmaceutical company. From July 2013 to December 2014, she served as Senior Vice President and General Manager, Cardiometabolic Business and Strategic Alliances at Moderna Therapeutics Inc. Prior to this, Ms. Soteropoulos worked at Genzyme Corporation, a biotechnology company, from 1992 to 2013, most recently as Vice President and General Manager, Cardiovascular, Rare Diseases. Ms. Soteropoulos holds a Bachelor of Science degree in chemical engineering and a Master of Science degree in chemical and biochemical engineering, both from Tufts University, and holds an executive management certificate from the University of Virginia, Darden Graduate School of Business Administration. Ms. Soteropoulos serves on the Advisory Board for the Chemical and Biological Engineering Department of Tufts University. We believe that Ms. Soteropoulos is qualified to serve on the Board of Directors because of her experience advising biotechnology companies in the areas of drug development, global commercialization and manufacturing.

Jonathan Violin, Ph.D. Dr. Violin has served as a member of our Board of Directors since September 2023, and he co-founded Former Dianthus in July 2019 and has served on its board of directors since inception. Dr. Violin has served as a Venture Partner at Fairmount Funds Management LLC, a healthcare investment firm, since June 2023. Prior to joining Fairmount, Dr. Violin served as President, Chief Executive Officer and member of the Board of Viridian Therapeutics, Inc. (Nasdaq: VRDN), a biopharmaceutical company, from January 2021 to February 2023, and he previously served as President and Chief Operating Officer of Viridian from October 2020 until January 2021. He was the Co-Founder of Viridian’s predecessor and led its operations from April 2020 to its acquisition. Dr. Violin also co-founded Quellis Biosciences, Inc., a biotechnology company (acquired by Astria Therapeutics, Inc. (Nasdaq: ATXS), formerly Catabasis Pharmaceuticals, Inc.), in 2018 and, since January 2021, has served on the Astria Therapeutics board of directors. Prior to that, he co-founded and helped lead Trevena Inc. (Nasdaq: TRVN), a biotechnology company, in various roles from 2008 until November 2018,

including most recently as Senior Vice President, Scientific Affairs and Investor Relations Officer. Dr. Violin received a Ph.D. from the Department of Pharmacology in the Biomedical Sciences Program at the University of California, San Diego, a M.B.A. with a concentration in Health Sector Management from the Fuqua School of Business at Duke University, and a B.S. in Chemical Pharmacology from Duke University. We believe that Dr. Violin is qualified to serve on the Board of Directors because of his extensive experience and innovations in the field of biotechnology and his academic expertise and accomplishments.

Alison F. Lawton. Ms. Lawton has served as a member of our Board of Directors since December 2020 and the Chair of our Board of Directors from August 2021 through the completion of the Merger. Ms. Lawton is an executive leader with more than 30 years of experience in biopharma. She served as President and Chief Executive Officer of Kaleido Biosciences, Inc., a pharmaceutical company, from August 2018 to June 2020, and served as President and Chief Operating Officer from December 2017 to August 2018. Prior to joining Kaleido, Ms. Lawton served as Chief Operating Officer at Aura Biosciences, Inc., an oncology therapeutics company, from January 2015 until December 2017, and, prior to joining Aura, served as a consultant to Aura from March 2014 to December 2014. From January 2013 to January 2014, Ms. Lawton served as Chief Operating Officer at OvaScience Inc., a life sciences company. From 2014 to 2017, Ms. Lawton also served as a biotech consultant for various companies, including as Chief Operating Officer consultant at X4 Pharmaceuticals Inc. (Nasdaq: XFOR). Prior to that, Ms. Lawton spent more than 20 years in various positions of increasing responsibility, including as Senior Vice President and General Manager of Genzyme Biosurgery, a division of Genzyme Corporation which is a global pharmaceutical company, and prior to that, Senior Vice President of Market Access at Genzyme, and subsequently at Sanofi S.A., also a global biopharmaceutical company, following the acquisition of Genzyme by Sanofi in 2011. Additionally, Ms. Lawton previously served two terms as the industry representative on the U.S. Food & Drug Administration’s Cell & Gene Therapy Advisory Committee and as Chairman of the Board of the Regulatory Affairs Professional Society. Ms. Lawton has served on the board of directors of ProQR Therapeutics N.V. (Nasdaq: PRQR) since September 2014 and X4 Pharmaceuticals since October 2020 and the private companies SwanBio Therapeutics, Inc., BlueRock Therapeutics LP and AgBiome, LLC. Ms. Lawton previously served on the boards of directors of Spyre Therapeutics Inc. (Nasdaq: SYRE) (formerly known as Aeglea BioTherapeutics, Inc.) from December 2020 to January 2024, Kaleido from August 2018 to October 2020, Verastem, Inc. (Nasdaq: VSTM) from November 2012 to May 2020, CoLucid Pharmaceuticals, Inc., a formerly public biotechnology company from March 2016 until its acquisition by Eli Lilly and Company in March 2017, and Cubist Pharmaceuticals, Inc., a formerly public biopharmaceutical company, from February 2012 to December 2014 prior to its acquisition by Merck & Co. in January 2015. Ms. Lawton holds a B.Sc. in Pharmacology from Kings College, University of London. We believe that Ms. Lawton is qualified to serve on the Board of Directors based on her roles on public and private boards of directors as well as her extensive experience in the life sciences industry.

Anne McGeorge. Ms. McGeorge has been a member of our Board of Directors since June 2019. Ms. McGeorge has over 35 years of experience providing strategic guidance and operational oversight to health care organizations. Ms. McGeorge has been on the adjunct faculty at the University of North Carolina at Chapel Hill since August 2005. Ms. McGeorge currently serves on the board of directors of The Oncology Institute, Inc. (Nasdaq: TOI). She also serves on the board of directors of the private companies CitiusTech, a health care technology company, Nimbus Therapeutics, LLC, a biotech company, CLEAR Insurance, a Cayman based captive insurance company, and the National Marrow Donor Program (Be The Match), a 501(c)(3) organization, and is on the advisory board at FCA Healthcare Innovations (formerly Dioko Ventures). Additionally, Ms. McGeorge previously served on the board of directors of SOC Telemed, Inc. (Nasdaq: TLMD) from October 2020 until it was acquired by Patient Square Capital, Inc. in April 2022. Prior to her retirement in July 2017, Ms. McGeorge worked at Grant Thornton LLP where she routinely advised clients on audit and financial matters relating to the healthcare industry. During her time at Grant Thornton LLP, Ms. McGeorge was Managing Partner of Grant Thornton LLP’s Health Care Industry Practice from January 2006 to July 2017 as well as Global Managing Partner for Grant Thornton International’s Health Care Industry Practice from August 2015 to July 2017. Ms. McGeorge was formerly a Partner at Deloitte & Touche LLP from 2002 to 2005 and at Arthur Andersen LLP from 1997 to 2002. Ms. McGeorge received a B.B.A., Business, Accounting from the College of

William and Mary, and an M.S., Accounting/Taxation from the University of Virginia. We believe that Ms. McGeorge is qualified to serve on the Board of Directors based on her extensive experience providing auditing and financial services for the healthcare industry.

Our Board of Directors has established an audit committee (the “Audit Committee”), a compensation committee (the “Compensation Committee”), a nominating and corporate governance committee (the “Nominating and Corporate Governance Committee”) and science and technology committee (the “Science and Technology Committee”), each of which operates pursuant to a charter adopted by the Board of Directors. We believe the functioning and composition of these committees comply with the requirements of the Sarbanes-Oxley Act of 2002, Nasdaq listing rules and SEC rules and regulations. The Board of Directors may also establish other committees from time to time to assist the Company and its Board of Directors. Each of the Audit Committee, Compensation Committee, Nominating and Corporate Governance Committee and Science and Technology Committee has the responsibilities described below.

Alison F. Lawton, Anne McGeorge, and Paula Soteropoulos serve on the Audit Committee, and each qualifies as an independent director, as defined under applicable Nasdaq listing rules, meets the additional, heightened independence criteria applicable to members of the audit committee under the rules of the SEC and the applicable Nasdaq listing rules, and has sufficient knowledge in financial and auditing matters to serve on the Audit Committee. Ms. McGeorge serves as chair of the Audit Committee. Ms. McGeorge is an “audit committee financial expert” as defined in Item 407(d)(5)(ii) of Regulation S-K promulgated under the Securities Act.

The primary responsibilities of the Audit Committee are to oversee the Company’s accounting and financial reporting processes, including the audits of the financial statements, and the internal and external audit processes. The Audit Committee also oversees the system of internal controls established by management and our compliance with legal and regulatory requirements. The Audit Committee is also responsible for the review, consideration and approval or ratification of related party transactions as well as the oversight of the Company’s practices with respect to risk assessment and risk management. The Audit Committee oversees the independent auditors, including their independence and objectivity. The Audit Committee is empowered to retain outside legal counsel and other advisors as it deems necessary or appropriate to assist it in fulfilling its responsibilities and to approve the fees and other retention terms of the advisors.

Paula Soteropoulos, Leon O. Moulder, Jr. and Tomas Kiselak serve on the Compensation Committee, and each qualifies as an independent director, as defined under applicable Nasdaq listing rules and also meets the additional, heightened independence criteria applicable to members of the compensation committee. Ms. Soteropoulos serves as the chair of the Compensation Committee.

Alison F. Lawton, Lei Meng and Leon O. Moulder, Jr. serve on the Nominating and Corporate Governance Committee, and each qualifies as an independent director, as defined under applicable Nasdaq listing rules. Ms. Lawton serves as chair of the Nominating and Corporate Governance Committee.

Tomas Kiselak, Lei Meng and Jonathan Violin serve on the Science and Technology Committee. Mr. Kiselak serves as chair of the Science and Technology Committee. The primary responsibilities of the Science and Technology Committee are to assist the Board of Directors in overseeing the Company’s innovation, new product development and research and development activities.

to assess independence of our directors. Nasdaq listing rules have objective tests and a subjective test for determining who is an “independent director.” The subjective test states that an independent director must be a person who lacks a relationship that, in the opinion of the Board of Directors, would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. The Board of Directors has not established categorical standards or guidelines to make these subjective determinations, but considers all relevant facts and circumstances. After considering the foregoing factors, the Board of Directors has determined each of our directors other than Marino Garcia and Jonathan Violin meets the Nasdaq independence requirements. Mr. Garcia and Dr. Violin are not considered independent due to their role as an executive officer of Dianthus and receipt of compensation for the provision of consulting services, respectively.

Former directors Drs. Bruce Booth, Thomas O. Daniel, Michael Vasconcelles, Jeffrey W. Albers and Amy Lynn Ronneberg were considered independent during the period they served on the Board. Former directors Drs. Jason Gardner and David T. Scadden were not considered independent during the period they served on the Board due to their role as an executive officer of Magenta and due to his service as chair of the Scientific Advisory Board, respectively.

EXECUTIVE COMPENSATION

This section discusses the material elements of compensation awarded to, earned by or paid to each principal executive officer of the Company during 2023, the two next most highly compensated executive officers of the Company and two additional former executive officers of the Company. The following individuals are referred to as the “Named Executive Officers” or “NEOs.”

2023 Summary Compensation Table

The following table presents the compensation awarded to, earned by or paid to each of the NEOs for the fiscal years ended December 31, 2023 and December 31, 2022.

Narrative Disclosure to Summary Compensation Table

Compensation Philosophy and Process

The Company’s Board of Directors and Compensation Committee review compensation annually for all employees, including the NEOs. In setting executive base salaries and annual incentives and granting equity incentive awards, the Compensation Committee considers compensation for comparable positions in the market, the historical compensation levels of the Company’s executives, internal equity, individual performance as compared to the Company’s expectations and objectives, the Company’s desire to motivate the Company’s employees to achieve short- and long-term results that are in the best interests of the Company’s stockholders and a long-term commitment to the Company. The Company targets a general competitive position, based on independent third-party benchmark analytics to inform the mix of compensation of base salary, annual incentives or long-term incentives.

The Compensation Committee is responsible for determining the compensation of the NEOs; however, the Board of Directors, upon recommendation of the Compensation Committee, is responsible for determining the Compensation of the Chief Executive Officer. The Compensation Committee typically reviews and discusses each NEO’s proposed compensation with the Chief Executive Officer (other than his own compensation). Based on those discussions and its discretion, taking into account the factors noted above, the Compensation Committee then sets the compensation for each NEO, other than the Chief Executive Officer, and recommends the compensation for the Chief Executive Officer to the Board of Directors for approval. The Chief Executive Officer is not present for discussions regarding his own compensation.

In 2023, the Compensation Committee retained the services of Alpine Rewards, LLC (“Alpine Rewards”) as its external independent compensation consultant. In this role, Alpine Rewards served as an advisor to the Compensation Committee on topics primarily related to the Company’s broader compensation structure, executive new hire compensation packages, executive compensation structure, peer group review, benchmarking of executive positions and equity share usage and dilution. The Board of Directors and Compensation Committee considered Alpine Rewards’ input on certain compensation matters as they deemed appropriate. The Compensation Committee requires that its compensation consultants be independent of management and performs an annual assessment of the compensation consultants’ independence to determine whether the consultants are independent. After review of the independence factors set forth by Nasdaq and the SEC, the Compensation Committee determined that the engagement of Alpine Rewards does not raise any conflict of interest.

Employment Agreements

Each of Messrs. Garcia and Savitz and Dr. Randhawa entered into an employment agreement in connection with his appointment as an executive officer of Former Dianthus, each of which was amended in connection with the Merger and his appointments as an officer of the Company. The employment agreements generally set forth the initial base salary, target annual bonus opportunity, one-time signing bonus in consideration for certain restrictive covenants (including standard confidentiality and nondisclosure, assignment of intellectual property work product and post-termination noncompetition and non-solicitation of employees, consultants and customers covenants), and eligibility for employee benefit plans. In addition, the employment agreements set forth the terms of initial stock option grants. Each employment agreement also provides for severance benefits in connection with certain terminations of employment, as described under “Additional Narrative Disclosure—Potential Payments Upon Termination or Change in Control” below.

Base Salary

Each NEO’s base salary is a fixed component of annual compensation for performing specific duties and functions and has been established by the Compensation Committee or Board of Directors, as applicable, taking into account each individual’s role, responsibilities, skills, and experience. Base salaries for the NEOs are reviewed annually by the Compensation Committee or Board of Directors, as applicable, typically in connection with the Company’s annual performance review process, and adjusted from time to time to realign salaries with market levels after taking into account individual responsibilities, internal equity, performance, and experience.

Base salaries are intended to provide a level of compensation sufficient to attract and retain an effective management team, when considered in combination with the other components of our executive compensation program. The relative levels of base salary are designed to reflect each NEO’s scope of responsibility and accountability. Effective with the closing of the Merger on September 11, 2023, the base salaries for Messrs. Garcia and Savitz and Dr. Randhawa were set forth below:

2023 Annual Cash Incentives

The Company’s cash annual incentive program is intended to reward the NEOs for meeting specified performance goals during the fiscal year. For 2023, each NEO was eligible for a target annual incentive based on a specific percentage of their earned base salaries for 2023, which are set forth below for those NEOs who were employed as of December 31, 2023 and eligible to receive a 2023 annual incentive:

The 2023 annual incentive program for Messrs. Garcia and Savitz and Dr. Randhawa was based upon achievement of corporate performance goals related to: (i) execution towards organizational readiness to initiate a phase 2 clinical trial of DNTH103 in generalized Myasthenia Gravis, (ii) strengthening the data package for DNTH103 and expanding its use in potential indications and other life cycle developments, (iii) building a pipeline of additional targets beyond DNTH103 and (iv) building an optimal high-performance organization required to achieve financial and development milestones. Following the end of 2023, the Compensation Committee recommended, and the Board of Directors approved, achievement of corporate performance and resulting annual incentive payouts at 115% of target.

Retention Incentive Bonuses

On February 23, 2023, the Compensation Committee approved retention incentive bonuses to Messrs. Mahoney and Beetham and Dr. Olson pursuant to the Company’s Senior Executive Cash Incentive Bonus Plan. Each retention incentive bonus was equal to the pro-rata amount of: (i) 125% of the NEOs’ 2023 base salary, plus (ii) 125% of the NEO’s 2023 target bonus, in each case, subject to a maximum of 75% of such amount. The retention incentive bonuses provided for payment upon the earliest of (a) the completion of a merger or similar change of control of Company, (b) the completion of a liquidation of the Company,(c) the date of the NEO’s termination by the Company not for cause (as defined in the NEO’s employment agreement) or (d) any other date determined by the Compensation Committee. As a result, Dr. Olson received a retention incentive bonus of $277,027 in connection with her termination and Messrs. Mahoney and Beetham received retention incentive bonuses of $539,134 and $523,490, respectively, in connection with the Merger.

Equity Awards

The Company’s equity grant program is intended to align the interests of the NEOs with those of the Company’s stockholders and to motivate them to make important contributions to the Company’s performance. During 2023, in light of the ongoing strategic process, the Company did not make any grants of equity awards to the NEOs.

In connection with the Merger, outstanding stock options originally granted by Former Dianthus were assumed and converted into Company stock options based on the exchange ratio, subject to the same vesting terms as in effect prior to the Merger. The assumed options are described in more detail under “Outstanding Equity Awards at 2023 Fiscal Year End” below.

Modification of Stock Options

In connection with the Merger and pursuant to the terms of the Merger Agreement, all outstanding stock options held by Messrs. Mahoney and Beetham and Dr. Olson that had an exercise price that was equal to or less than $2.00 (prior to giving effect to the 1-for-16 reverse stock split) were modified to provide that they

will remain outstanding and exercisable until the third anniversary of the Merger (or if earlier, the original expiration date of such stock option).

Outstanding Equity Awards at 2023 Fiscal Year End

The following table presents information regarding all outstanding stock options held by each of the NEOs on December 31, 2023, after giving effect to the 1-for-16 reverse stock split. None of the NEOs held any outstanding stock awards as of December 31, 2023.