0001193125-24-073956 | S-1/A | XBRL Viewer | Dianthus Therapeutics INC DE

Preferred Stock and Convertible Preferred Stock

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Preferred Stock and Convertible Preferred Stock

11. Preferred Stock and Convertible Preferred Stock

Preferred Stock

As of December 31, 2023, the Company was authorized to issue up to 10,000,000 shares of preferred stock at a par value of $0.001. As of December 31, 2023, no shares of preferred stock were issued and outstanding.

Convertible Preferred Stock

On September 11, 2023, the Company completed the Reverse Merger with Former Dianthus in accordance with the Merger Agreement. Under the terms of the Merger Agreement, immediately prior to the effective time of the Reverse Merger, each share of Former Dianthus convertible preferred stock was converted into a share of Former Dianthus common stock. At closing of the Reverse Merger, the Company issued an aggregate of 7,269,183 shares of its common stock to Former Dianthus convertible preferred stockholders, based on the exchange ratio of approximately 0.2181 shares of Company common stock for each share of Former Dianthus common stock outstanding immediately prior to the Reverse Merger.

The authorized, issued and outstanding shares of the convertible preferred stock and liquidation preferences of Former Dianthus as of December 31, 2022 were as follows:


	Issued Dates		Authorized Shares		Shares Issued and Outstanding		Per Share Liquidation Preference		Aggregate Liquidation Amount		Proceeds (Net of Issuance Costs)
Series Seed 1 Convertible Preferred Stock		July 2019, April 2020 and December 2020		6,500,000		6,500,000	$	1.000	$	6,500	$	6,436
Series Seed 2 Convertible Preferred Stock		May 2021		3,829,266		3,829,265	$	3.9172		15,000		14,912
Series A Convertible Preferred Stock		April 2022		23,007,017		23,007,017	$	4.3465		100,000		96,676

Total Convertible Preferred Stock				33,336,283		33,336,282			$	121,500	$	118,024

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,964,472	8,547,949
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	0	7,269,183
Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,749,475	1,273,454
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	0	635
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	214,997	4,677

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of Accrued Expenses

The following table provides a summary of accrued expenses:


	December 31,
	2023		2022
Accrued compensation	$	5,361	$	2,084
Accrued external research and development		456		4,329
Accrued professional fees		422		162
Accrued other expenses		265		33

Accrued expenses	$	6,504	$	6,608

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 132,325	$ 15,365
Short-term investments	41,393	60,125
Receivable from related party	294	4,700
Unbilled receivable from related party	184	938
Prepaid expenses and other current assets	3,255	905
Total current assets	177,451	82,033
Property and equipment, net	185	142
Right-of-use operating lease assets	615	814
Other assets and restricted cash	1,154	121
Total assets	179,405	83,110
Current liabilities:
Accounts payable	2,610	1,167
Accrued expenses	6,504	6,608
Current portion of deferred revenue—related party	100	100
Current portion of operating lease liabilities	417	350
Total current liabilities	9,631	8,225
Deferred revenue—related party	736	791
Long-term operating lease liabilities	168	438
Total liabilities	10,535	9,454
Commitments and contingencies (Note 16)
Convertible preferred stock; $0.0001 par value per share; authorized shares – none and 33,336,283 at December 31, 2023 and 2022, respectively; issued and outstanding – none and 33,336,282 at December 31, 2023 and 2022, respectively; liquidation preference – none and $121,500 at December 31, 2023 and 2022, respectively	0	118,024
Stockholders' equity/(deficit):
Preferred stock; $0.001 par value per share; authorized shares – 10,000,000 and none at December 31, 2023 and 2022, respectively; issued and outstanding – none at December 31, 2023 and 2022	0	0
Common stock, par value per share—$0.001 and $0.0001 at December 31, 2023 and 2022, respectively; authorized shares – 150,000,000 and 8,722,279 at December 31, 2023 and 2022, respectively; issued and outstanding shares – 14,817,696 and 875,279 at December 31, 2023 and 2022, respectively	15	0
Additional paid-in capital	258,231	1,661
Accumulated deficit	(89,423)	(45,868)
Accumulated other comprehensive income/(loss)	47	(161)
Total stockholders' equity/(deficit)	168,870	(44,368)
Total liabilities, convertible preferred stock and stockholders' equity/(deficit)	$ 179,405	$ 83,110

Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity/(Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock issuance cost	$ 4,250
Convertible Preferred Stock [Member]
Stock issuance cost		$ 3,324

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value on Recurring Basis Level 1	$ 0	$ 0
Fair Value on Recurring Basis Level 2	0	0
Fair Value on Recurring Basis Level 3	$ 0	$ 0

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

12. Stock-Based Compensation

Stock Option and Incentive Plan

The Company grants stock-based awards under the Amended and Restated Dianthus Therapeutics, Inc. Stock Option and Incentive Plan (the “Incentive Plan”), which originally became effective on June 19, 2018 as the Magenta Therapeutics, Inc. 2018 Stock Option and Incentive Plan and was amended and restated in September 2023 and renamed the Amended and Restated Dianthus Therapeutics, Inc. Stock Option and Incentive Plan. The Incentive Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards, and dividend equivalent rights. In connection with the Reverse Merger, the Incentive Plan also provided for the assumption of shares remaining available for delivery under the 2019 Stock Plan (as defined below), and such shares will be available for the granting of awards under the Incentive Plan in accordance with applicable stock exchange requirements. The Company also has outstanding stock options under the Magenta Therapeutics, Inc. 2016 Stock Option and Grant Plan, as amended (the “2016 Plan”), but is no longer granting awards under the 2016 Plan.

As of December 31, 2023, the total number of shares reserved under the Incentive Plan was equal to 2,529,070 shares of the Company’s common stock, of which 879,461 shares of the Company’s common stock was available for future issuance. The Incentive Plan provides that the number of shares reserved under the Incentive Plan will automatically increase each January 1 beginning with January 1, 2024 by 4% of the

outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s board of directors or compensation committee of the board of directors. This number is subject to adjustment in the event of a stock split, stock dividend or other change in capitalization. Shares of common stock underlying any awards under the Incentive Plan and the 2016 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without any issuance of stock, expire or are otherwise terminated (other than by exercise) will be available for future awards under the Incentive Plan.

The Incentive Plan is administered by either the board of directors or the compensation committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the administrator, except that the term of stock options and stock appreciation rights may not be greater than ten years (or five years for certain incentive stock options). Awards typically vest over 12 months to four years. The exercise price for stock options granted may not be less than the fair value of common stock as of the date of grant (or 110% of the fair value of common stock for certain incentive stock options). The fair value of common stock is based on quoted market prices.

2019 Stock Plan

In July 2019, Former Dianthus’ Board of Directors adopted, and the Former Dianthus’ stockholders approved, the Dianthus Therapeutics, Inc. 2019 Stock Plan (the “2019 Stock Plan”). In connection with the Reverse Merger, the Company assumed options to purchase shares of Former Dianthus’s common stock that were outstanding under the 2019 Stock Plan immediately prior to the Reverse Merger and such options were converted into options to purchase 1,273,454 shares of Company’s common stock (the “Assumed Options”). No further awards will be made under the 2019 Stock Plan; however, the Assumed Options will remain outstanding under the 2019 Stock Plan in accordance with their terms, as adjusted to reflect the Reverse Merger.

2019 Employee Stock Purchase Plan

Employees may elect to participate in the Dianthus Therapeutics, Inc. 2019 Employee Stock Purchase Plan (the “ESPP”). The purchase price of common stock under the ESPP is equal to 85% of the lower of the fair market value of the common stock on the offering date or the exercise date. The

six-month

offering periods previously began in December and June of each year. Offerings under the ESPP were suspended in May 2023. During the year ended December 31, 2023, there were no shares of common stock purchased under the ESPP. During the year ended December 31, 2022, 7,501 shares of common stock were purchased under the ESPP at a purchase price per share of $15.36. As of December 31, 2023, 37,078 shares remained available for issuance under the ESPP.

The ESPP provides that the number of shares reserved and available for issuance under the ESPP will automatically increase each January 1 through January 1, 2029, by the lesser of (i) 1% of the number of shares issued and outstanding on the immediately preceding December 31, (ii) 62,500 shares and (iii) such number of shares as determined by the Company’s board of directors or its appointed administrator.

Stock Options

The following table summarizes stock option activity for the year ended December 31, 2023:


	Number of stock options outstanding			Weighted average exercise price per share		Weighted average remaining contractual term		Aggregate intrinsic value
						(in years)
Balance at January 1, 2023		529,773		$	94.59		8.2	$	—
Assumption of options in connection with the Reverse Merger		1,273,454			7.95				177
Options granted, fair value of $10.30 per share		610,641			12.09				159
Options exercised		(2,798	)		1.66				46
Options forfeited		(661,595	)		74.14				456

Balance at December 31, 2023		1,749,475		$	10.61		8.4	$	3,181

Exercisable options at December 31, 2023		650,557		$	11.74		7.7	$	1,506
Unvested options at December 31, 2023		1,098,918		$	9.95		8.8	$	1,675

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the common stock for those options that had exercise prices lower than the fair value of the common stock.

The weighted average grant-date fair value per share of stock options granted during the year ended December 31, 2023 was $10.30 per share.

The table below summarizes the assumptions used to determine the grant-date fair value of stock options issued, presented on a weighted average basis during the years ended December 31, 2023 and 2022:


	December 31,
	2023			2022
Risk-free interest rate		4.0	%		2.5	%
Expected term (in years)		6.0			5.9
Expected volatility		87.5	%		81.2	%
Expected dividend yield		0.0	%		0.0	%

Restricted Stock Units

The following table summarizes restricted stock unit activity for the year ended December 31, 2023:


	Number of units outstanding			Weighted average grant date fair value per share
Balance at January 1, 2023		16,084		$	70.09
Restricted stock units granted		7,696			8.80
Restricted stock units vested		(6,495	)		68.96
Restricted stock units forfeited		(17,285	)		43.22

Balance at December 31, 2023		—		$	—

Restricted Stock

In April 2020, Former Dianthus executed a restricted stock award agreement with a consultant to purchase 3,052 shares of common stock at an exercise price of $0.14 per share. The restricted stock award vested over a four-year requisite service period, with 25% vesting on the first anniversary of the vesting commencement date and 2.0833% per month thereafter. The agreement contained restrictions on the ability to sell, assign or pledge the shares awarded. The restricted stock agreement contained a right of repurchase whereby, at the election of the Company, the Company may purchase back all unvested stock should the relationship between the recipient and the Company cease. The fair value of the restricted stock award on the date of the award was $0.14 per share.

Former Dianthus has not issued any restricted stock since April 2020. As of December 31, 2023, the restricted stock award was fully vested.

Stock Warrants

In April 2021, Former Dianthus issued 4,677 warrants for the purchase of common stock at an exercise price of $1.65 per share. The warrants vested on July 30, 2023 and have a grant date fair value of $1.16 per warrant. Former Dianthus has not issued any warrants since April 2021. As of December 31, 2023, the warrants have a weighted average remaining contractual term of 7.3 years.

Stock-based Compensation Expense

The following table provides a summary of stock-based compensation expense related to stock options, restricted stock units, restricted stock, and warrants:


	Year Ended December 31,
	2023		2022
Research and development	$	897	$	416
General and administrative		2,003		1,102

Total stock-based compensation expense	$	2,900	$	1,518

As of December 31, 2023, there was $7.9 million of total unrecognized compensation cost related to granted stock options. The Company expects to recognize that cost over a remaining weighted-average period of 2.6 years.

Income Taxes - Changes in Deferred Tax Asset Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Valuation allowance as of beginning of year	$ 11,566	$ 5,194
Net increases recorded to income tax provision	111,886	6,372
Valuation allowance as of end of year	$ 123,452	$ 11,566

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Line Items]
Unrecognized tax benefits	$ 0	$ 0
State [Member]
Income Tax Disclosure [Line Items]
Operating Loss Carryforward Expiration Year Start	2035
State [Member] \| Research tax credit carryforward and orphan drug tax credit [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforward, amount	$ 3,500
Tax credit carryforward expiration year start	2030
State [Member] \| Expirable [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 299,100
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	320,700
Domestic Tax Authority [Member] \| Research tax credit carryforward and orphan drug tax credit [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforward, amount	$ 14,800
Tax credit carryforward expiration year start	2035

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The financial statements have been prepared in conformity with U.S. GAAP. Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results may differ materially from those estimates.

Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates including the following: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Significant estimates are used in the following areas, among others: the recognition of research and development expense, stock-based compensation expense and revenue recognition.

Cash and Cash Equivalents

All short-term, highly liquid investments with original maturities of 90 days or less are considered to be c

h and cash equivalents. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents are valued at cost, which approximates fair value.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term investments. The Company regularly maintains deposits in accredited financial institutions in excess of federally insured limits. The Company invests its excess cash primarily in money market funds, U.S. treasury securities and U.S. government agency securities in accordance with the Company’s investment policy. The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. The Company has not experienced any realized losses related to its cash, cash equivalents and short-term investments and management believes the Company is not exposed to significant risks of losses.

As of December 31, 2023 and 2022, the Company held cash deposits at Silicon Valley Bank (“SVB”) in excess of government insured limits. On March 10, 2023, SVB was closed by the California Department of Financial Protection and Innovation, and the Federal Deposit Insurance Corporation was appointed as receiver. No losses were incurred by the Company on deposits that were held at SVB. Management believes that the Company is not currently exposed to significant credit risk as the vast majority of the Company’s deposits were either owned directly by the Company and held in custody at a third-party financial institution or, subsequent to March 10, 2023, have been transferred to a third-party financial institution. The Company does not currently have any other significant relationships with SVB.

Short-term Investments

Short-term investments consist of investments in U.S. treasury and U.S. government agency securities. Management of the Company determines the appropriate classification of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its short-term investments as

available-for-sale

pursuant to ASC 320,

Investments – Debt and Equity Securities,

and reports them at fair value in short-term investments with unrealized gains and losses reported as a component of accumulated other comprehensive income loss on the consolidated balance sheet. Realized gains and losses and declines in value judged to be other than temporary are included as a component of interest income based on the specific identification method.

Effective January 1, 2023, when the fair value is below the amortized cost of a marketable security, an estimate of expected credit losses is made in accordance with ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

. The credit-related impairment amount is recognized in the consolidated statements of operations and comprehensive loss. Credit losses are

recognized through the use of an allowance for credit losses account in the consolidated balance sheet and subsequent improvements in expected credit losses are recognized as a reversal of an amount in the allowance account. If the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis, then the allowance for the credit loss is

written-off

and the excess of the amortized cost basis of the asset over its fair value is recorded in the consolidated statements of operations and comprehensive loss. There were no credit losses recorded during the year ended December 31, 2023.

Additional information regarding short-term investments is included in Note 4.

Receivable from Related Party and Unbilled Receivable from Related Party

The receivable from related party and unbilled receivable from related party results from option and license agreements with Zenas BioPharma Limited (“Zenas”), a related party. See Notes 13 and 17 for more information. The receivable represents amounts earned and billed to Zenas but not yet collected while unbilled receivable represents amounts earned but not yet billed to Zenas. The receivable and unbilled receivable are reported at net realizable value. The Company regularly evaluates the creditworthiness of Zenas and their financial condition and does not require collateral from Zenas. As of December 31, 2023 and 2022, no allowance for doubtful accounts was recorded as all accounts were considered collectible.

Property and Equipment

Property and equipment are recorded at cost. Depreciation is provided using the straight-line method over estimated useful lives of three years for computer equipment and five years for furniture and fixtures. Expenditures for major renewals and betterments that extend the useful lives are capitalized. Expenditures for normal maintenance and repairs are expensed as incurred. The cost of assets sold or abandoned, and the related accumulated depreciation are eliminated from the accounts and any gains or losses are recognized in the accompanying consolidated statements of operations and comprehensive loss of the respective period.

Leases

Operating leases are accounted for in accordance with ASU

2016-02,

Leases

, as amended (“ASC 842”).

Right-of-use

lease assets represent the right to use an underlying asset for the lease term and lease liabilities represent an obligation to make lease payments arising from the lease. The measurement of lease liabilities is based on the present value of future lease payments over the lease term. As the Company’s leases do not provide an implicit rate, management used the Company’s incremental borrowing rate based on the information available at the lease commencement date in determining the present value of future lease payments. The

right-of-use

asset is based on the measurement of the lease liability and includes any lease payments made prior to or on lease commencement and excludes lease incentives and initial direct costs incurred, as applicable. Rent expense for operating leases is recognized on a straight-line basis over the lease term. The Company does not have any leases classified as finance leases. Management have elected the practical expedient to exclude short-term leases from

right-of-use

assets and lease liabilities.

The Company’s leases do not have significant rent escalation, holidays, concessions, material residual value guarantees, material restrictive covenants or contingent rent provisions. The Company’s leases include both lease (e.g., fixed payments including rent, taxes, and insurance costs) and

non-lease

components (e.g., common-area or other maintenance costs), which are accounted for as a single lease component as management have elected the practical expedient to group lease and

non-lease

components for all leases.

Additional information and disclosures required under ASC 842 are included in Note 9.

Restricted Cash

In accordance with ASU

2016-18,

Statement of Cash Flows (Topic 230): Restricted Cash

, restricted cash is included as a component of cash, cash equivalents and restricted cash in the accompanying consolidated statements of cash flows. Restricted cash serves as collateral for a letter of credit securing office space. Restricted cash is recorded within other assets and restricted cash line item in the accompanying consolidated balance sheet.

Fair Value Measurements

The Company calculates the fair value of assets and liabilities that qualify as financial instruments and includes additional information in the notes to the consolidated financial statements when the fair value is different than the carrying value of these financial instruments.

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC Topic 820,

Fair Value Measurements and Disclosures

(“ASC 820”), defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. ASC 820 establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available.

Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect management’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality.

The three levels of the fair value hierarchy are described below:

•

Level 1 - Quoted prices in active markets for identical assets or liabilities.

•

Level 2 - Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

•

Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar valuation techniques that use significant unobservable inputs.

To the extent that a valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by management in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Management has segregated all financial assets and liabilities that are measured at fair value on a recurring basis into the most appropriate level within the fair value hierarchy based on the inputs used to determine the fair value at the measurement date in the table below. The Company’s valuation techniques for its Level 2 financial assets included using quoted prices for similar assets in active markets and quoted prices for similar assets in markets that are not active.

The estimated fair value of receivable from related party, unbilled receivable from related party, accounts payable and accrued expenses approximate their carrying amounts due to the relatively short maturity of these instruments.

Additional information regarding fair value measurements is included in Note 7.

Classification of Convertible Preferred Stock

Convertible preferred stock is recorded at its original issuance price, less direct and incremental offering costs, as stipulated by its terms. The Company has applied the guidance in ASC

480-10-S99,

Distinguishing Liabilities from

Equity-Overall-SEC

Materials

, and has therefore classified the convertible preferred stock outside of stockholders’ equity/(deficit) in the accompanying consolidated balance sheet. In September 2023, all outstanding shares of convertible preferred stock were converted into common shares immediately prior to the effective time of the Reverse Merger. Additional information and disclosures are included in Note 11.

Segment Information

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources and in assessing performance. The Company’s CODM is its Chief Executive Officer. The Company operates as a single operating segment and has one reportable segment.

License Revenue—Related Party

To date, the Company’s only revenue has been attributable to an upfront payment and cost reimbursements under the Company’s license agreement with Zenas. The Company has not generated any revenue from product sales and does not expect to generate any revenue from product sales for the foreseeable future.

The Company recognizes revenue pursuant to ASC 606,

Revenue from Contracts with Customers

(“ASC 606”). ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when the performance obligation is satisfied.

The Company evaluates the performance obligations promised in a contract that are based on goods and services that will be transferred to the customer and determine whether those obligations are both (i) capable of being distinct and (ii) distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, the Company applies judgment to determine whether promised goods and services are both capable of being distinct and are distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential transaction price and the likelihood that the transaction price will be received. Variable

consideration is included in the transaction price if, in management’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. The Company then allocates the transaction price to each performance obligation and recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) control is transferred to the customer and the performance obligation is satisfied.

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. If the related performance obligation is expected to be satisfied within the next twelve months this will be classified in current liabilities.

Additional information and disclosures required under ASC 606 are included in Note 13.

Research and Development Costs

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

The Company enters into consulting, research, and other agreements with commercial firms, researchers, and others for the provision of goods and services. Under such agreements, the Company may pay for services on a monthly, quarterly, project or other basis. Such arrangements are generally cancellable upon reasonable notice and payment of costs incurred. Costs are considered incurred based on an evaluation of the progress to completion of specific tasks under each contract using information and data provided by the service providers and vendors, whereas payments are dictated by the terms of each agreement. As such, depending on the timing of payment relative to the receipt of goods or services, management may record either prepaid expenses or accrued services. These costs consist of direct and indirect costs associated with specific projects, as well as fees paid to various entities that perform certain research on behalf of the Company.

Patent Costs

Patent costs are expensed as incurred and recorded within general and administrative expenses.

Income Taxes

Income taxes are recorded in accordance with ASC 740,

Income Taxes (

“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities and for loss and credit carryforwards using enacted tax rates anticipated to be in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if, based upon the weight of available evidence, it is more likely than not that some or all the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position, as well as consideration of the available facts and circumstances. As of December 31, 2023 and 2022, the Company did not have any material uncertain tax positions. The Company recognizes interest and penalties related to uncertain tax positions, if any exist, in income tax expense.

Stock-Based Compensation

The Company accounts 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 the stock-based awards are subject only to service-based vesting conditions. Management estimates the fair value of the stock option awards using the Black-Scholes option pricing model, which requires the input of assumptions, including (a) the fair value of the Company’s 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. Management estimates the fair value of the restricted stock awards using the fair value of the Company’s common stock. Forfeitures are recognized as they are incurred.

Prior to the Reverse Merger, management utilized valuation methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid,

Valuation of Privately Held Company Equity Securities Issued as Compensation

, to estimate the fair value of Former Dianthus common stock. Each valuation methodology included estimates and assumptions that required management’s judgment. These estimates and assumptions included objective and subjective factors, including external market conditions, the prices at which Former Dianthus sold shares of convertible preferred stock, the superior rights and preferences of the convertible preferred stock senior to Former Dianthus common stock at the time, and a probability analysis of various liquidity events, such as a public offering or sale of Former Dianthus, under differing scenarios. Changes to the key assumptions used in the valuations could have resulted in materially different fair values of Former Dianthus common stock at each valuation date. Following the Reverse Merger, the fair value of the Company’s common stock is based on the closing stock price on the date of grant as reported on the Nasdaq Capital Market.

Due to a lack of company-specific historical and implied volatility data, management bases its estimate of expected volatility on the historical volatility of a representative group of companies with similar characteristics to the Company, including stage of product development and life science industry focus. Management believes the group selected has sufficiently similar economic and industry characteristics and includes companies that are most representative of the Company.

Management uses the simplified method, as prescribed by the SEC Staff Accounting Bulletin No. 107,

Share-Based Payment

, to calculate the expected term. The risk-free interest rate is based on observed interest rates appropriate for the term of the awards. The dividend yield assumption is based on history and expectation of paying no dividends.

Compensation expense related to stock-based awards is calculated on a straight-line basis by recognizing the grant date fair value, over the associated service period of the award, which is generally the vesting term.

Additional information regarding share-based compensation is included in Note 12.

Comprehensive Loss

The only component of comprehensive loss other than net loss is change in unrealized losses related to

available-for-sale

debt securities.

Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders are calculated in conformity with the

two-class

method required for participating securities. Convertible preferred stock is a participating security in distributions of the Company. The net loss attributable to common stockholders is not allocated to the convertible preferred shares as the holders of convertible preferred shares do not have a contractual obligation to

share in losses. Under the

two-class

method, basic net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during each period. The weighted-average number of shares of common stock outstanding used in the basic net loss per share calculation does not include unvested restricted common stock as these shares are considered contingently issuable shares until they vest.

Diluted net loss per share of common stock includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options and unvested restricted common stock, which would result in the issuance of incremental shares of common stock. For diluted net loss per share, the weighted-average number of shares of common stock is the same for basic net loss per share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive. For all periods presented, basic and diluted net loss per share were the same, as any additional share equivalents would be anti-dilutive.

Additional information is included in Note 15.

Recently Issued Accounting Pronouncements

On January 1, 2023, the Company adopted ASU

No. 2016-13

using the modified retrospective approach, and no cumulative effect adjustment to accumulated deficit was needed as of the adoption date. Additionally, no prior period amounts were adjusted. The new standard adjusts the accounting for assets held at amortized cost basis, including short-term investments accounted for as

available-for-sale,

and receivables. The standard eliminates the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements and related disclosures.

In November 2023, the FASB issued ASU No.

2023-07,

Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures

. ASU

2023-07

expands annual and interim disclosure requirements for reportable segments, primarily through enhanced disclosures about significant segment expenses. ASU

2023-07

is effective for fiscal years beginning after December 15, 2023, and for interim periods beginning after December 14, 2024, with early adoption permitted. The Company is currently evaluating the guidance and has not determined the impact this standard may have on the consolidated financial statements.

In December 2023, the FASB issued ASU No. 2023-09,

Income Taxes (Topic 740), Improvements to Income Tax Disclosures

, to enhance the transparency and decision usefulness of income tax disclosures. The enhancement will provide information to better assess how an entity’s operations and related tax risks and tax planning and operational opportunities affect its tax rate and prospects for future cash flows. Investors currently rely on the rate reconciliation table and other disclosures, including total income taxes paid, to evaluate income tax risks and opportunities. ASU No. 2023-09 is effective for fiscal years beginning after December 15, 2024 and early adoption is permitted. The Company is currently evaluating the impact ASU No. 2023-09 will have on its consolidated financial statements and related disclosures.

Leases - Summary of the Components of Lease Costs and Rent (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lease, Cost [Abstract]
Operating lease cost	$ 366	$ 198
Variable lease cost	28	4
Short-term lease cost	0	34
Total operating lease costs	$ 394	$ 236

Preferred Stock and Convertible Preferred Stock - Additional Information (Details)	Sep. 11, 2023 shares	Dec. 31, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares
Class of Stock [Line Items]
Preferred stock, Shares authorized		10,000,000	0
Preferred stock, par value \| $ / shares		$ 0.001	$ 0.001
Preferred stock, Shares issued		0	0
Preferred stock, Shares outstanding		0	0
Convertible preferred stock, Terms of conversion	Under the terms of the Merger Agreement, immediately prior to the effective time of the Reverse Merger, each share of Former Dianthus convertible preferred stock was converted into a share of Former Dianthus common stock.
Shares issued upon conversion of convertible preferred stock	7,269,183
Exchange ratio of reverse merger	0.2181

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2023:


	Number of stock options outstanding			Weighted average exercise price per share		Weighted average remaining contractual term		Aggregate intrinsic value
						(in years)
Balance at January 1, 2023		529,773		$	94.59		8.2	$	—
Assumption of options in connection with the Reverse Merger		1,273,454			7.95				177
Options granted, fair value of $10.30 per share		610,641			12.09				159
Options exercised		(2,798	)		1.66				46
Options forfeited		(661,595	)		74.14				456

Balance at December 31, 2023		1,749,475		$	10.61		8.4	$	3,181

Exercisable options at December 31, 2023		650,557		$	11.74		7.7	$	1,506
Unvested options at December 31, 2023		1,098,918		$	9.95		8.8	$	1,675

Schedule of Grant-Date Fair Value of Stock Options Issued, Presented on a Weighted Average Basis


	December 31,
	2023			2022
Risk-free interest rate		4.0	%		2.5	%
Expected term (in years)		6.0			5.9
Expected volatility		87.5	%		81.2	%
Expected dividend yield		0.0	%		0.0	%

Schedule of Activity Relating to Restricted Stock Units

The following table summarizes restricted stock unit activity for the year ended December 31, 2023:


	Number of units outstanding			Weighted average grant date fair value per share
Balance at January 1, 2023		16,084		$	70.09
Restricted stock units granted		7,696			8.80
Restricted stock units vested		(6,495	)		68.96
Restricted stock units forfeited		(17,285	)		43.22

Balance at December 31, 2023		—		$	—

Schedule of Stock Based Compensation Expense

The following table provides a summary of stock-based compensation expense related to stock options, restricted stock units, restricted stock, and warrants:


	Year Ended December 31,
	2023		2022
Research and development	$	897	$	416
General and administrative		2,003		1,102

Total stock-based compensation expense	$	2,900	$	1,518

Reverse Merger (Tables)

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Schedule of Company Obtained Assets and Liabilities

As part of the recapitalization, the Company obtained the assets and liabilities listed below:


Cash and cash equivalents	$	69,738
Other current assets		2,473
Accrued liabilities		(386	)

Net assets acquired	$	71,825

Short-Term Investments - Schedule of Short-term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 41,346	$ 60,286
Gross Unrealized Gain	48	3
Gross Unrealized Loss	(1)	(164)
Fair Value	41,393	60,125
U.S. Treasury Securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	36,370	47,630
Gross Unrealized Gain	48	3
Gross Unrealized Loss	0	(122)
Fair Value	36,418	47,511
U.S. Government Agency Securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	4,976	12,656
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(1)	(42)
Fair Value	$ 4,975	$ 12,614

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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-Topic 320
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+ Details

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	17. Related Party Transactions Zenas BioPharma Limited: The Company is a party to option and license agreements with Zenas, a related party. The Company considers Zenas to be a related party because (i) Tellus BioVentures LLC (“Tellus”), whose sole member is a significant shareholder in the Company and serves as Chairman of the Board of Directors of the Company, is also a significant shareholder in Zenas and serves as Chief Executive Officer and Chairman of the Board of Directors of Zenas and (ii) Fairmount Healthcare Fund LP and Fairmount Healthcare Fund II LP (together, the “Fairmount Funds”), who are significant shareholders in the Company and have a seat on the Board of Directors of the Company, are also significant shareholders in Zenas and have a seat on the Board of Directors of Zenas. As of December 31, 2023, Tellus and affiliated entities owned approximately 10%, and the Fairmount Funds and affiliated entities owned approximately 13% of the Company’s outstanding shares. See Note 13 for more information. In connection with these agreements, the Company recognized $2.8 million and $6.4 million within the license revenue – related party line item in the consolidated statements of operations and comprehensive loss for the years ended December 31, 2023 and 2022, respectively. As of December 31, 2023, the Company recorded a related party receivable of $0.3 million, unbilled related party receivable of $0.2 million, current deferred related party revenue of $0.1 million and noncurrent deferred related party revenue of $0.7 million on its consolidated balance sheet. As of December 31, 2022, the Company recorded a related party receivable of $4.7 million, unbilled related party receivable of $0.9 million, current deferred related party revenue of $0.1 million and noncurrent deferred related party revenue of $0.8 million on its consolidated balance sheet. In 2020, Zenas issued 156,848 common shares to the Company in exchange for the Zenas Option. The Company determined that the fair value on the date of issuance and as of December 31, 2023 and 2022, respectively, was not material to its consolidated financial statements. The Company used the measurement alternative as the measurement attribute for accounting for the Zenas common shares which does not require it to assess the fair value of the common stock at each reporting period as the fair value of the Zenas common shares is not readily determinable nor is there a reliable source for observable transactions from which the Company could determine a fair value. In addition, the Company does not have ready access to significant events occurring at Zenas. If the Company does identify observable price changes in orderly transactions for the identical or similar common shares of Zenas, the Company will measure the common shares at fair value as of the date that the observable transaction occurred. On March 13, 2023, the Fairmount Funds issued promissory notes in the aggregate principal amount of $377 thousand to Former Dianthus at an interest rate of 4.5% per annum. On March 15, 2023, Former Dianthus repaid principal and interest in the amount of $377 thousand to the Fairmount Funds in satisfaction of its obligations under the promissory notes.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

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-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Reverse Merger

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Reverse Merger

3. Reverse Merger

As described in Note 1, Merger Sub merged with and into Former Dianthus, with Former Dianthus surviving as a wholly owned subsidiary of the Company on September 11, 2023. The Reverse Merger was accounted for as a reverse asset acquisition accounted for as a reverse recapitalization in accordance with U.S. GAAP with Former Dianthus as the accounting acquirer of Magenta. At the effective time of the Reverse Merger, substantially all the assets of Magenta consisted of cash and cash equivalents, marketable securities, as well as other nominal

non-operating

assets. Under such reverse recapitalization accounting, the assets and liabilities of Magenta were recorded at their fair value in Magenta’s financial statements at the effective time of the Merger, which approximated book value due to the short-

term nature. No goodwill or intangible assets were recognized. Consequently, the consolidated financial statements of the Company reflect the operations of Former Dianthus for accounting purposes together with a deemed issuance of shares, equivalent to the shares held by the former stockholders of Magenta, the legal acquirer, and a recapitalization of the equity of Former Dianthus, the accounting acquirer.

As part of the recapitalization, the Company obtained the assets and liabilities listed below:


Cash and cash equivalents	$	69,738
Other current assets		2,473
Accrued liabilities		(386	)

Net assets acquired	$	71,825

The Company incurred $0.5 million in stock-based compensation expense, as a result of the acceleration of vesting of stock options and restricted stock units for certain former employees of Magenta at the time of the Reverse Merger. Of this amount, $0.2 million was recorded in the research and development expenses line item and $0.3 million was recorded in the general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss for the year ended December 31, 2023. Additionally, the Company incurred transaction costs of $3.9 million, and this amount was recorded as a reduction to additional

paid-in

capital in the consolidated statements of convertible preferred stock and stockholders’ equity/(deficit) for the year ended December 31, 2023.

With respect to the CVRs issued in connection with the Reverse Merger, the Company believes that the achievement of the milestones outlined in the CVR Agreement are highly susceptible to factors outside the Company’s influence that are not expected to be resolved for a long period of time, if at all. In particular, these amounts are primarily influenced by the actions and judgments of third parties and the buyers of such assets and are based on the buyers of such assets progressing the

in-process

research and development assets into clinical trials, and in the case of one of the agreements, to a regulatory milestone. If the Company were to record a receivable for such contingent payments, it would also record a corresponding liability. As of December 31, 2023, no receivables are recorded on the consolidated balance sheet relating to such contingent payments.

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Summary Of Significant Accounting Policies [Line Items]
Credit losses recorded	$ 0
Allowance for doubtful accounts	0	$ 0
Financial lease liability	0
Unrecognized tax benefits	$ 0	$ 0

Common Stock - Schedule of Common Stock Reserved For Future Issuance (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Equity [Abstract]
Conversion of convertible preferred stock	0	7,269,183
Issuance of common stock upon exercise of stock options	1,749,475	1,273,454
Equity awards available for grant under stock awards	879,461	414,679
Shares available for issuance under the Employee Stock Purchase Plan	37,078	0
Issuance of common stock upon exercise of warrants	214,997	4,677
Total common stock reserved for future issuance	2,881,011	8,961,993

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 67	$ 30

Common Stock - Additional Information (Details)	12 Months Ended
Common Stock - Additional Information (Details)	Dec. 31, 2023 $ / shares shares	Sep. 11, 2023 shares	Dec. 31, 2022 $ / shares shares	Dec. 31, 2021 shares
Common stock, shares authorized	150,000,000		8,722,279
Common stock, Shares issued	14,817,696	11,021,248	875,279
Common stock, Shares outstanding	14,817,696		875,279
Exchange ratio of reverse merger		0.2181
Common stock, Par value \| $ / shares	$ 0.001		$ 0.0001
Common stock, dividends, per share, declared \| $ / shares	$ 0
Common Stock
Common stock, shares authorized	150,000,000		8,722,279
Common stock, Shares issued	14,817,696		875,279
Common stock, Shares outstanding	14,817,696	14,817,696	875,279	875,279
Common stock, Shares outstanding	14,817,696		875,279
Common stock, Par value \| $ / shares	$ 0.001		$ 0.0001

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

16. Commitments and Contingencies

Alloy Therapeutics, LLC:

In August 2019, the Company entered into a license agreement with Alloy Therapeutics, LLC (“Alloy”). The license agreement was amended in October 2022. The license agreement with Alloy grants to the Company the following:

•

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

•

With respect to Alloy antibodies and platform assisted antibodies that are selected by the Company 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.

The Company pays annual license fees and annual partnered antibody program fees totaling $0.1 million to Alloy. The Company is also obligated to pay a $0.1 million fee to Alloy if the Company sublicenses a product

developed with Alloy antibodies or platform assisted antibodies. Upon the achievement, with the first selected antibody for products developed with Alloy, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make additional payments to Alloy of up to $1.8 million and $11.0 million, respectively. Upon the achievement, with the second selected antibody for products developed with Alloy, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make additional payments to Alloy of up to $3.1 million and $15.0 million, respectively. The Company recorded $0.1 million and $0.5 million for amounts owed under the Alloy license agreement within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively.

OmniAb, Inc.:

In September 2022, the Company entered into a commercial platform license agreement and services agreement with two subsidiaries of Ligand Pharmaceuticals Incorporated. In November 2022, Ligand

spun-off

these subsidiaries into a separate legal entity, OmniAb, Inc. (“OmniAb”). The platform license agreement and services agreement with OmniAb grants to the Company the following:

•

A worldwide,

non-exclusive,

non-sublicensable

license under the OmniAb technology to use chicken animals (solely at OmniAb’s facilities and through OmniAb personnel) for generation of OmniAb antibodies for research purposes.

•

A worldwide,

non-exclusive

license under the OmniAb technology to use rodent animals (solely at approved contract research organization (“CRO”) facilities and through approved CRO personnel) for generation of OmniAb antibodies for research purposes. Such license is

non-sublicensable

except to an approved CRO.

Upon the achievement of certain development milestones, the Company is obligated to make additional payments to OmniAb of up to $12.2 million. Upon the achievement of certain commercial milestones, the Company is obligated to make royalty payments in the low to

mid-single

digits. The Company has recorded $0.3 and $0.1 million for amounts owed under the OmniAb license agreement within research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively.

IONTAS Limited:

In July 2020, the Company entered into a collaborative research agreement with IONTAS Limited (“IONTAS”) to perform certain milestone-based research and development activities for the Company under its first development program. This agreement was amended in January 2023 to extend their services to additional development programs. IONTAS provides dedicated resources to perform the research and development activities and receives compensation for those resources as well as success-based milestone payments.

Upon the achievement, with the first development program with IONTAS, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make additional payments to IONTAS of up to £3.1 million and £2.3 million, respectively. Upon the achievement, with the second development program with IONTAS, of certain development milestones, the Company is obligated to make additional payments to IONTAS of up to £2.5 million. The Company has recorded $2.1 million and $1.7 million for amounts owed under the IONTAS collaborative research license agreement within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to employees, consultants, vendors, business partners and other parties with respect to certain matters including, but

not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. To date, the Company has not incurred any material costs as a result of such indemnification agreements. The Company is not aware of any indemnification arrangements that could have a material effect on its financial position, results of operations or cash flows, and has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2023 or 2022.

Litigation

From time to time, the Company may be exposed to litigation relating to potential products and operations. The Company is not currently engaged in any legal proceedings that are expected, individually or in the aggregate, to have a material adverse effect on its financial condition, results of operations or cash flows.

Other

As of December 31, 2023 and 2022, the Company had standing agreements with consultants, contractors or service providers whose terms do not yield material long-term commitments.

License Revenue - Related Party - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2021
Related Party Transaction [Line Items]
License revenue—related party		$ 2,826	$ 6,417
Unbilled receivable from related party		184	938
Deferred revenue current		100	100
Deferred revenue noncurrent		736	791
Zenas BioPharma Limited [Member]
Related Party Transaction [Line Items]
Reimbursement of development costs	$ 1,100
License revenue—related party		2,800	6,400
Related party receivable		300	4,700
Unbilled receivable from related party		200	900
Deferred revenue current		100	100
Deferred revenue noncurrent		700	$ 800
Zenas BioPharma Limited [Member] \| Milestone [Member]
Related Party Transaction [Line Items]
Development milestones	11,000
Zenas BioPharma Limited [Member] \| Royalty [Member]
Related Party Transaction [Line Items]
License revenue—related party		$ 0
Zenas BioPharma Limited [Member] \| Upfront Payment [Member]
Related Party Transaction [Line Items]
Upfront payments	$ 1,000			$ 1,000

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (43,555)	$ (28,476)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	67	30
Stock-based compensation expense	2,900	1,518
Accretion of discount on short-term investments	(1,423)	(606)
Amortization of right-of-use operating lease assets	288	117
Changes in operating assets and liabilities:
Receivable from related party	4,406	(4,231)
Unbilled receivable from related party	754	69
Prepaid expenses and other current assets	123	(631)
Other assets	(1,027)	(31)
Accounts payable, accrued expenses and lease liabilities	661	2,280
Deferred revenue—related party	(55)	891
Net cash used in operating activities	(36,861)	(29,070)
Cash flows from investing activities:
Capital expenditures	(110)	(139)
Purchases of short-term investments	(57,422)	(61,680)
Proceeds from maturities of short-term investments	77,785	2,000
Net cash provided by/(used in) investing activities	20,253	(59,819)
Cash flows from financing activities:
Proceeds from exercise of stock options	5	0
Proceeds from the pre-closing financing	72,000	0
Payment of issuance costs in connection with the pre-closing financing	(4,250)	0
Cash acquired in connection with the reverse recapitalization	69,738	0
Payment of reverse recapitalization transaction costs	(3,919)	0
Proceeds from issuance of promissory notes payable to related party	377	0
Repayment of promissory notes payable to related party	(377)	0
Proceeds from issuance of Series A convertible preferred stock	0	100,000
Payment of issuance costs for Series A convertible preferred stock	0	(3,324)
Net cash provided by financing activities	133,574	96,676
Increase in cash, cash equivalents and restricted cash	116,966	7,787
Cash, cash equivalents and restricted cash, beginning of period	15,425	7,638
Cash, cash equivalents and restricted cash, end of period	132,391	15,425
Supplemental Disclosure
Cash and cash equivalents	132,325	15,365
Restricted cash	66	60
Total cash, cash equivalents and restricted cash	132,391	15,425
Cash paid for interest	0	0
Cash paid for taxes	0	0
Conversion of convertible preferred stock into common stock	118,024	0
Additions to right-of-use lease assets from new operating lease liabilities	$ 89	$ 931

Property and Equipment - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 282	$ 172
Less: accumulated depreciation	(97)	(30)
Property and equipment, net	185	142
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	234	131
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 48	$ 41

Stock-Based Compensation - Schedule of Stock Option Activity (Detail) - Reverse Stock Split Event [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Beginning Balance	529,773
Assumption of options in connection with the reverse merger	1,273,454
Number of Shares, Granted	610,641
Number of Shares, Exercised	(2,798)
Number of Shares, Forfeited	(661,595)
Number of Shares, Ending Balance	1,749,475	529,773
Number of Shares, Options exercisable as of December 31, 2023	650,557
Number of Shares, Options vested and expected to vest as of December 31, 2023	1,098,918
Weighted-Average Exercise Price, Outstanding, Beginning balance	$ 94.59
Assumption of options in connection with the reverse merger	7.95
Weighted-Average Exercise Price, Granted	12.09
Weighted-Average Exercise Price, Exercised	1.66
Weighted-Average Exercise Price, Forfeited	74.14
Weighted-Average Exercise Price, Outstanding, Ending balance	10.61	$ 94.59
Weighted-Average Exercise Price, Options exercisable as of December 31, 2023	11.74
Weighted-Average Exercise Price, Options vested and expected to vest as of December 31, 2023	$ 9.95
Weighted Average Remaining Contractual Term	8 years 4 months 24 days	8 years 2 months 12 days
Weighted Average Remaining Contractual Term, Options exercisable as of December 31, 2023	7 years 8 months 12 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest as of December 31, 2023	8 years 9 months 18 days
Assumption of options in connection with the Reverse Merger	$ 177
Aggregate Intrinsic Value, Granted	159
Aggregate Intrinsic Value, Exercised	46
Aggregate Intrinsic Value, Forfeited	456
Aggregate Intrinsic Value, Ending Balance	3,181
Aggregate Intrinsic Value, Options exercisable as of December 31, 2023	1,506
Aggregate Intrinsic Value, Options vested and expected to vest as of December 31, 2023	$ 1,675

Preferred Stock and Convertible Preferred Stock - Schedule of Preferred Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023
Class of Stock [Line Items]
Authorized Shares	0	10,000,000
Shares Issued	0	0
Shares Outstanding	0	0
Proceeds (Net of Issuance Costs)	$ 0	$ 0
Series Seed 1 Convertible Preferred Stock \| Dianthus
Class of Stock [Line Items]
Authorized Shares	6,500,000
Shares Issued	6,500,000
Shares Outstanding	6,500,000
Per Share Liquidation Preference	$ 1
Aggregate Liquidation Amount	$ 6,500
Proceeds (Net of Issuance Costs)	$ 6,436
Series Seed 1 Convertible Preferred Stock \| Dianthus \| First Issue
Class of Stock [Line Items]
Issued Dates	2019-07
Series Seed 1 Convertible Preferred Stock \| Dianthus \| Second Issue
Class of Stock [Line Items]
Issued Dates	2020-04
Series Seed 1 Convertible Preferred Stock \| Dianthus \| Third issue
Class of Stock [Line Items]
Issued Dates	2020-12
Series Seed 2 Convertible Preferred Stock \| Dianthus
Class of Stock [Line Items]
Issued Dates	2021-05
Authorized Shares	3,829,266
Shares Issued	3,829,265
Shares Outstanding	3,829,265
Per Share Liquidation Preference	$ 3.9172
Aggregate Liquidation Amount	$ 15,000
Proceeds (Net of Issuance Costs)	$ 14,912
Series A Convertible Preferred Stock \| Dianthus
Class of Stock [Line Items]
Issued Dates	2022-04
Authorized Shares	23,007,017
Shares Issued	23,007,017
Shares Outstanding	23,007,017
Per Share Liquidation Preference	$ 4.3465
Aggregate Liquidation Amount	$ 100,000
Proceeds (Net of Issuance Costs)	$ 96,676
Convertible Preferred Stock \| Dianthus
Class of Stock [Line Items]
Authorized Shares	33,336,283
Shares Issued	33,336,282
Shares Outstanding	33,336,282
Aggregate Liquidation Amount	$ 121,500
Proceeds (Net of Issuance Costs)	$ 118,024

Short-Term Investments

12 Months Ended

Dec. 31, 2023

Short-Term Investments [Abstract]

Short-Term Investments

4. Short-Term Investments

The table below provides a summary of short-term investments:


	December 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Available-for-sale, short-term investments:
U.S. treasury securities	$	36,370	$	48	$	—		$	36,418
U.S. government agency securities		4,976		—		(1	)		4,975

Total available-for-sale, short-term investments	$	41,346	$	48	$	(1	)	$	41,393


	December 31, 2022
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Available-for-sale, short-term investments:
U.S. treasury securities	$	47,630	$	3	$	(122	)	$	47,511
U.S. government agency securities		12,656		—		(42	)		12,614

Total available-for-sale, short-term investments	$	60,286	$	3	$	(164	)	$	60,125

Common Stock (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Common Stock Shares Reserved for Future Issuance

The Company had the following shares of Company common stock reserved for future issuance as of December 31, 2023 and 2022:


	December 31,
	2023		2022
Conversion of convertible preferred stock		—		7,269,183
Issuance of common stock upon exercise of stock options		1,749,475		1,273,454
Equity awards available for grant under stock awards		879,461		414,679
Shares available for issuance under the Employee Stock Purchase Plan		37,078		—
Issuance of common stock upon exercise of warrants		214,997		4,677

Total common stock reserved for future issuance		2,881,011		8,961,993

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Financial Assets Measured at Fair Value on Recurring Basis

The following table provides a summary of financial assets measured at fair value on a recurring basis:


Description	Fair Value at December 31, 2023		Level 1		Level 2		Level 3
Recurring Assets:
Cash equivalents:
Money market fund	$	131,193	$	131,193	$	—	$	—
Short-term investments:
U.S. treasury securities		36,418		36,418		—		—
U.S. government agency securities		4,975		—		4,975		—

Total assets measured at fair value	$	172,586	$	167,611	$	4,975	$	—


Description	Fair Value at December 31, 2022		Level 1		Level 2		Level 3
Recurring Assets:
Cash equivalents:
Money market fund	$	11,846	$	11,846	$	—	$	—
U.S. government agency securities		1,999		—		1,999		—
Short-term investments:
U.S. treasury securities		20,775		20,775		—		—
U.S. government agency securities		39,350		26,736		12,614		—

Total assets measured at fair value	$	73,970	$	59,357	$	14,613	$	—

Fair Value of Financial Instruments - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 41,393	$ 60,125
Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	172,586	73,970
Level 1 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	167,611	59,357
Level 2 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	4,975	14,613
Money Market Fund \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	131,193	11,846
Money Market Fund \| Level 1 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	131,193	11,846
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	36,418	47,511
U.S. Treasury Securities \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	36,418	20,775
U.S. Treasury Securities \| Level 1 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	36,418	20,775
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	4,975	12,614
U.S. Government Agency Securities \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1,999
Short-term investments	4,975	39,350
U.S. Government Agency Securities \| Level 1 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		26,736
U.S. Government Agency Securities \| Level 2 \| Fair Value on Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		1,999
Short-term investments	$ 4,975	$ 12,614

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of the Components of Lease Costs and Rent

The following table provides a summary of the components of lease costs and rent:


	Year Ended December 31,
	2023		2022
Operating lease cost	$	366	$	198
Variable lease cost		28		4
Short-term lease cost		—		34

Total operating lease costs	$	394	$	236

Schedule of Maturities of Operating Lease Liabilities

Maturities of operating lease liabilities, which do not include short-term leases, as of December 31, 2023, are as follows:


2024	$	417
2025		222

Total undiscounted operating lease payments	$	639
Less: imputed interest		(54	)

Present value of operating lease liabilities	$	585

Balance sheet classification:
Current portion of lease liabilities	$	417
Long-term lease liabilities		168

Total operating lease liabilities	$	585

Common Stock

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common Stock

10. Common Stock

At the effective time of the Reverse Merger on September 11, 2023, the Company issued an aggregate of 11,021,248 shares of Company common stock to the Former Dianthus stockholders, based on the exchange ratio of approximately 0.2181 shares of Company common stock for each share of Former Dianthus common stock, including those shares of Former Dianthus common stock issued upon the conversion of Former Dianthus preferred stock and those shares of the Former Dianthus common stock issued in the

pre-closing

financing, resulting in 14,817,696 shares of Company common stock being issued and outstanding immediately following the effective time of the Reverse Merger.

As of December 31, 2023 and 2022, the Company was authorized to issue up to 150,000,000 shares of $0.001 par value of Company common stock and 8,722,279 shares of $0.0001 par value of Company common stock, respectively. As of December 31, 2023 and 2022, the Company had issued and outstanding shares of 14,817,696 and 875,279, respectively.

Each share of Company common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any. No dividends have been declared or paid by the Company through December 31, 2023.

The Company had the following shares of Company common stock reserved for future issuance as of December 31, 2023 and 2022:


	December 31,
	2023		2022
Conversion of convertible preferred stock		—		7,269,183
Issuance of common stock upon exercise of stock options		1,749,475		1,273,454
Equity awards available for grant under stock awards		879,461		414,679
Shares available for issuance under the Employee Stock Purchase Plan		37,078		—
Issuance of common stock upon exercise of warrants		214,997		4,677

Total common stock reserved for future issuance		2,881,011		8,961,993

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
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-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Subparagraph (a)
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Subparagraph (b)
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Stock-Based Compensation - Schedule of Grant-date Fair Value of Stock Options Issued, Presented on a Weighted Average Basis (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	4.00%	2.50%
Expected term	6 years	5 years 10 months 24 days
Expected volatility	87.50%	81.20%
Expected dividend yield	0.00%	0.00%

Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity/(Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member] Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning balance at Dec. 31, 2021	$ (17,249)	$ 0	$ 21,348	$ 143	$ (17,392)	$ 0
Beginning balance, shares at Dec. 31, 2021		875,279	10,329,265
Issuance of convertible preferred stock, net of issuance costs			$ 96,676
Issuance of convertible preferred stock, net of issuance costs, shares			23,007,017
Stock-based compensation expense	1,518			1,518
Net loss	(28,476)				(28,476)
Other comprehensive income (loss)	(161)					(161)
Ending balance at Dec. 31, 2022	(44,368)	$ 0	$ 118,024	1,661	(45,868)	(161)
Ending balance, shares at Dec. 31, 2022		875,279	33,336,282
Exercise of common stock options	5	$ 1		4
Exercise of common stock options, shares		2,798
Conversion of convertible preferred stock to common stock in connection with the Reverse Merger	118,024	$ 1	$ (118,024)	118,023
Conversion of convertible preferred stock to common stock in connection with the Reverse Merger, shares		7,269,183	(33,336,282)
Issuance of common stock and pre-funded warrants in the pre-closing financing, net of issuance costs	67,750			67,750
Issuance of common stock and pre-funded warrants in the pre-closing financing, net of issuance costs, shares		2,873,988
Issuance of common stock to former stockholders of Magenta Therapeutics, Inc. in connection with the Reverse Merger	71,825			71,825
Issuance of common stock to former stockholders of MagentaTherapeutics, Inc. in connection with the Reverse Merger, shares		3,796,448
Adjustment for change in common stock par value in connection with the Reverse Merger		$ 13		(13)
Reverse recapitalization transaction costs	(3,919)			(3,919)
Stock-based compensation expense	2,900			2,900
Net loss	(43,555)				(43,555)
Other comprehensive income (loss)	208					208
Ending balance at Dec. 31, 2023	$ 168,870	$ 15	$ 0	$ 258,231	$ (89,423)	$ 47
Ending balance, shares at Dec. 31, 2023		14,817,696	0

Stock-Based Compensation - Schedule of Stock Option Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2023 $ / shares
Share-Based Payment Arrangement [Abstract]
Weighted average fair value of stock options granted	$ 10.3

Reverse Merger - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Sep. 11, 2023	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Stock based compensation expense		$ 2,900	$ 1,518
Research and development		32,841	29,379
General and administrative		18,159	$ 6,743
Transaction costs		3,919
Dianthus [Member]
Business Acquisition [Line Items]
Stock based compensation expense	$ 500
Research and development		200
General and administrative		300
Transaction costs		$ 3,900

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

The following table provides a summary of property and equipment:


	December 31,
	2023			2022
Computer equipment	$	234		$	131
Furniture and fixtures		48			41
Subtotal		282			172
Less: accumulated depreciation		(97	)		(30	)

Property and equipment, net	$	185		$	142

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2023

Short-Term Investments [Abstract]

Schedule of short-term investments

The table below provides a summary of short-term investments:


	December 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Available-for-sale, short-term investments:
U.S. treasury securities	$	36,370	$	48	$	—		$	36,418
U.S. government agency securities		4,976		—		(1	)		4,975

Total available-for-sale, short-term investments	$	41,346	$	48	$	(1	)	$	41,393


	December 31, 2022
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Available-for-sale, short-term investments:
U.S. treasury securities	$	47,630	$	3	$	(122	)	$	47,511
U.S. government agency securities		12,656		—		(42	)		12,614

Total available-for-sale, short-term investments	$	60,286	$	3	$	(164	)	$	60,125

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Organization, Description of Business and Liquidity

12 Months Ended

Dec. 31, 2023

Organization, Description of Business and Liquidity

1. Organization, Description of Business and Liquidity

Business

Dianthus Therapeutics, Inc. (formerly Magenta Therapeutics, Inc.) (the “Company” or “Dianthus”) is a clinical-stage biotechnology company focused on developing next-generation complement therapeutics for patients with severe autoimmune and inflammatory diseases. The Company’s corporate headquarters are in New York, New York.

Currently, the Company is devoting substantially all efforts and resources toward product research and development of its product candidates. The Company has incurred losses from operations and negative operating cash flows since its inception. There can be no assurance that its research and development programs will be successful, that products developed, if any, will obtain necessary regulatory approval, or that any approved product, if any, will be commercially viable. In addition, the Company operates in an environment of rapid technological change and is largely dependent on the services of its key employees, consultants, and advisors.

Reverse Merger and

Pre-Closing

Financing

On September 11, 2023, the Company completed its business combination with Dianthus Therapeutics, OpCo Inc. (formerly Dianthus Therapeutics, Inc.) (“Former Dianthus”) in accordance with the terms of the Agreement and Plan of Merger, dated as of May 2, 2023 (the “Merger Agreement”), by and among the Company, Dio Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of the Company (“Merger Sub”), and Former Dianthus, pursuant to which, among other matters, Merger Sub merged with and into Former Dianthus, with Former Dianthus surviving as a wholly owned subsidiary of the Company (the “Reverse Merger”). In connection with the completion of the Reverse Merger, the Company changed its name from “Magenta Therapeutics, Inc.” to “Dianthus Therapeutics, Inc.,” and the business conducted by the Company became primarily the business conducted by Former Dianthus. Unless context otherwise requires, references herein to “Dianthus,” the “Company,” or the “combined company” refer to Dianthus Therapeutics, Inc. (formerly Magenta Therapeutics, Inc.) after completion of the Reverse Merger, the term “Former Dianthus” refers to Dianthus Therapeutics OpCo, Inc. (formerly Dianthus Therapeutics, Inc.), and the term “Magenta” refers to the Company prior to completion of the Reverse Merger. The Company was incorporated in June 2015 and Former Dianthus was incorporated in May 2019.

Immediately prior to the effective time of the Reverse Merger, the Company effected a

1-for-16

reverse stock split of its common stock (the “Reverse Stock Split”). Unless noted otherwise, all references herein to share and per share amounts reflect the Reverse Stock Split.

At the effective time of the Reverse Merger, the Company issued an aggregate of 11,021,248 shares of Company common stock to the Former Dianthus stockholders, based on the exchange ratio of approximately 0.2181 shares of Company common stock for each share of Former Dianthus common stock, including those shares of Former Dianthus common stock issued upon the conversion of Former Dianthus preferred stock and those shares of the Former Dianthus common stock issued in the

pre-closing

financing (as defined below), resulting in 14,817,696 shares of Company common stock being issued and outstanding following the effective time of the Reverse Merger.

At the effective time of the Reverse Merger, the Dianthus Therapeutics, Inc. 2019 Stock Plan (the “2019 Stock Plan”) (as discussed in Note 12) was assumed by the Company, and each outstanding and unexercised option to purchase shares of Former Dianthus common stock immediately prior to the effective time of the

Reverse Merger was assumed by the Company and converted into an option to purchase shares of Company common stock, with necessary adjustments to the number of shares and exercise price to reflect the exchange ratio, and each outstanding and unexercised warrant to purchase shares of Former Dianthus common stock immediately prior to the effective time of the Reverse Merger (including the Former Dianthus

pre-funded

warrants sold in the

pre-closing

financing) was converted into a warrant to purchase shares of Company common stock, with necessary adjustments to the number of shares and exercise price to reflect the exchange ratio.

The Reverse Merger was accounted for as a reverse recapitalization in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). Under this method of accounting, Former Dianthus was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the expectation that, immediately following the Reverse Merger: (i) Former Dianthus’ stockholders own a substantial majority of the voting rights in the combined company; (ii) Former Dianthus’ largest stockholders retain the largest interest in the combined company; (iii) Former Dianthus designated a majority (six of eight) of the initial members of the board of directors of the combined company; and (iv) Former Dianthus’ executive management team became the management team of the combined company. Accordingly, for accounting purposes: (i) the Reverse Merger was treated as the equivalent of Former Dianthus issuing stock to acquire the net assets of Magenta; (ii) the net assets of Magenta are recorded at their acquisition-date fair value in the consolidated financial statements of Former Dianthus and (iii) the reported historical operating results of the combined company prior to the Reverse Merger are those of Former Dianthus. Additional information regarding the Reverse Merger is included in Note 3. Historical common share figures of Former Dianthus have been retroactively restated based on the exchange ratio of approximately 0.2181.

On September 11, 2023, prior to the effective time of the Reverse Merger, the Company entered into a contingent value rights agreement (the “CVR Agreement”) with a rights agent, pursuant to which

pre-Reverse

Merger holders of Magenta common stock received one

non-transferable

contingent value right (each, a “CVR”) for each outstanding share of Magenta common stock held by such stockholder immediately prior to the effective time of the Reverse Merger on September 11, 2023. Subject to, and in accordance with, the terms and conditions of the CVR Agreement, each CVR represents the contractual right to receive a pro rata portion of the proceeds, if any, received by the Company as a result of (i) contingent payments made to the Company, such as milestone, royalty or earnout, when received under any

pre-Reverse

Merger disposition agreements related to Magenta’s

pre-Reverse

Merger assets and (ii) the Company’s sale of assets after the effective date of the Reverse Merger and prior to December 31, 2023, in each case, received within a three-year period following the closing of the Reverse Merger. As of December 31, 2023, no payments have been received under the CVR Agreement.

Concurrently with the execution and delivery of the Merger Agreement, and in order to provide Former Dianthus with additional capital for its development programs, Former Dianthus entered into a subscription agreement, as amended (the “Subscription Agreement”), with certain investors named therein (the “Investors”), pursuant to which, subject to the terms and conditions of the Subscription Agreement, immediately prior to the effective time of the Reverse Merger, Former Dianthus issued and sold, and the Investors purchased, (i) 2,873,988 shares of Former Dianthus common stock and (ii) 210,320

pre-funded

warrants, exercisable for 210,320 shares of Former Dianthus common stock, at a purchase price of approximately $23.34 per share or $23.34 per warrant, for an aggregate purchase price of approximately $72.0 million (the

“pre-closing

financing”).

Risks and Uncertainties

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on its key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing and compliance with government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability.

The Company’s lead product candidate that is in development and any future product candidates will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure, and extensive compliance-reporting capabilities. Even if its product development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales.

Liquidity

In accordance with Accounting Standards Update

No. 2014-15,

Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern

(Subtopic

205-40),

the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the accompanying consolidated financial statements were issued (the “issuance date”):

•

Since its inception, the Company has funded its operations primarily with outside capital and has 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. In addition, the Company had an accumulated deficit of $89.4 million as of December 31, 2023;

•

The Company expects to continue to incur significant recurring losses and rely on outside capital to fund its operations for the foreseeable future; and

•

As of the issuance date, the Company expects that its existing cash, cash equivalents and short-term investments on hand as of the issuance date will be sufficient to fund its obligations as they become due for at least twelve months beyond the issuance date. The Company expects that its research and development and general and administrative costs will continue to increase significantly, including in connection with conducting clinical trials and manufacturing for its existing product candidate and any future product candidates to support commercialization and providing general and administrative support for its operations, including the costs associated with operating as a public company.

In the event the Company is unable to secure additional outside capital, management will be required to seek other alternatives which may include, among others, a delay or termination of clinical trials or the development of its product candidates, temporary or permanent curtailment of the Company’s operations, a sale of assets, or other alternatives with strategic or financial partners.

The accompanying consolidated financial statements do not include any adjustments that might result from the outcome of these uncertainties. Accordingly, the consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business.

Stock-Based Compensation - Schedule of Activity Relating to Restricted Stock Units (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of units outstanding, Beginning Balance \| shares	16,084
Number of units outstanding, Granted \| shares	7,696
Number of units outstanding, Vested \| shares	(6,495)
Number of units outstanding, Forfeited \| shares	(17,285)
Number of units outstanding, Ending Balance \| shares	0
Weighted average grant date fair value per share, Beginning Balance \| $ / shares	$ 70.09
Weighted average grant date fair value per share, Granted \| $ / shares	8.8
Weighted average grant date fair value per share, Vested \| $ / shares	68.96
Weighted average grant date fair value per share, Forfeited \| $ / shares	43.22
Weighted average grant date fair value per share, Ending Balance \| $ / shares	$ 0

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2023

Prepaid Expense and Other Assets, Current [Abstract]

Summary of Prepaid Expenses and Other Current Assets

The following table provides a summary of prepaid expenses and other current assets:


	December 31,
	2023		2022
Prepaid materials, supplies and research and development services	$	2,155	$	820
Prepaid insurance		596		32
Prepaid subscriptions, software and other administrative services		504		53

Prepaid expenses and other current assets	$	3,255	$	905

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

For the years ended December 31, 2023 and 2022, the Company recorded no current or deferred income tax expenses or

enefits as it has incurred losses since inception and has provided a full valuation allowance against its deferred tax assets.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023			2022
Federal statutory income tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		2.1	%		2.2	%
Research tax credits		34.5	%		2.2	%
Tax attributes acquired as part of reverse merger		201.1	%		—
Other		(1.7	)%		(3.0	)%
Increase in deferred tax asset valuation allowance		(257.0	)%		(22.4	)%

Effective income tax rate		0.0	%		0.0	%

The following table provides a summary of net deferred tax assets:


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	73,580		$	5,383
Capitalized research and development costs		22,446			4,315
Tax credit carryforwards		16,147			1,120
Lease liabilities		14,063			183
Share-based compensation		6,462			273
Amortization of license fees		3,209			—
Accrued expenses		795			484
Other		59			4

Gross deferred tax assets		136,761			11,762
Valuation allowance		(123,452	)		(11,566	)

Total deferred tax assets		13,309			196
Deferred tax liabilities:
Right-of-use lease assets		(12,499	)		(189	)
Depreciation and amortization		(810	)		—
Other		—			(7	)

Total deferred tax liabilities		(13,309	)		(196	)

Net deferred tax assets	$	—		$	—

As of December 31, 2023, the Company had federal net operating loss carryforwards of approximately $320.7 million, all of which can be carried forward indefinitely. As of December 31, 2023, the Company had state tax net operating loss carryforwards of approximately $299.1 million, which begin to expire in 2035. As of December 31, 2023, the Company 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.

In assessing the realizability of the net deferred tax assets, management considers all relevant positive and negative evidence in determining whether it is more likely than not that some portion or all the deferred income tax assets will not be realized. The realization of the gross deferred tax assets is dependent on several factors, including the generation of sufficient taxable income prior to the expiration of the net operating loss carryforwards. Management believes that it is more likely than not that the Company’s deferred income tax assets will not be realized.

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2023 and 2022 related primarily to the increase in net operating loss carryforwards, capitalized research and development expenses and research tax credit carryforwards. During the years ended December 31, 2023 and 2022, capitalized research and development expenses increased pursuant to Section 174 of the Internal Revenue Code of 1986, as amended (the “Code”). The changes in the valuation allowance for the years ended December 31, 2023 and 2022 were as follows:


	Year Ended December 31,
	2023		2022
Valuation allowance as of beginning of year	$	11,566	$	5,194
Net increases recorded to income tax provision		111,886		6,372

Valuation allowance as of end of year	$	123,452	$	11,566

Net operating loss carryforwards are subject to review and possible adjustment by the Internal Revenue Service and may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50% as defined under Sections 382 and 383 in the Code, which could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the Company’s value immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has not yet conducted a study to determine if any such changes have occurred that could limit the ability to use the net operating loss carryforwards. However, the Reverse Merger is expected to result in an ownership change. Therefore, the Company does not expect to be able to utilize a material portion of the net operating losses and research and orphan drug tax credit carryforwards.

The Company has not recorded any liabilities for unrecognized tax benefits as of December 31, 2023 or 2022. The Company will recognize interest and penalties related to uncertain tax positions, if any, in income tax expense. As of December 31, 2023 and 2022, the Company had no accrued interest or penalties related to uncertain tax positions.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
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+ Details

License Revenue - Related Party	12 Months Ended
License Revenue - Related Party	Dec. 31, 2023
Related Party Transactions [Abstract]
License Revenue - Related Party	13. License Revenue—Related Party In September 2020, the Company entered into an Option Agreement with Zenas (“Zenas Option”), a related party (See Note 17). Through the Zenas Option, the Company provided Zenas an option to enter into an exclusive license agreement for the development and commercialization of products arising from its research of monoclonal antibody antagonists targeting certain specific complement proteins. In September 2021, the Company notified Zenas that it had elected the first antibody sequence as a clinical candidate. In October 2021, Zenas notified the Company that it was exercising its option for such clinical candidate. The Zenas Option provided that upon the exercise of the option, the Company would negotiate in good faith a license agreement with Zenas pursuant to which it would grant Zenas the exclusive license with respect to the antibody sequences for the Zenas territory, which includes People’s Republic of China, including Hong Kong, Macau, and Taiwan. In accordance with Zenas Option, within 60 days following the execution of a license agreement, Zenas agreed to pay the Company a one-time payment of $1.0 million for the exercise of the corresponding option. In addition, in connection with the exercise of the Zenas Option, Zenas was required to reimburse the Company for a portion of chemistry, manufacturing, and controls-related (“CMC”) costs and expenses from the date of delivery of its option exercise notice through the execution of a license agreement. In June 2022, the Company and Zenas executed the license agreement (“Zenas License”). The Zenas Option and Zenas License are collectively referred to as the “Zenas Agreements”. The Zenas License provides Zenas with a license in the People’s Republic of China, including Hong Kong, Macau, and Taiwan, for the development and commercialization of sequences and products under the first antibody sequence. The Company is also obligated to perform certain research and development and CMC services, and will also participate in a joint steering committee (“JSC”). Under the Zenas License, Zenas also has the right to exercise an option with respect to a second antibody sequence. If Zenas exercises the option and pays the Company the option exercise fee related to the second antibody sequence, the Company will grant Zenas an exclusive license to the sequences and products under this second antibody sequence. Since the Zenas Agreements were negotiated with a single commercial objective, they are treated as a combined contract for accounting purposes. The Company assessed the Zenas Agreements in accordance with ASC 606 and concluded that it represents a contract with a customer and is within the scope of ASC 606. The Company determined that there is one combined performance obligation that consists of the license and data transfer, the research and development and CMC services, and the participation in the JSC. The Company determined that Zenas’ right to exercise an option with respect to a second antibody sequence does not represent a material right. The consideration under the Zenas Agreements includes the following payments by Zenas to the Company: (i) a $1 million upfront payment upon execution of the Zenas License; (ii) an approximate $1.1 million payment representing reimbursement for a portion of development costs previously incurred by the Company; (iii) reimbursement of a portion of all CMC-related costs and expenses for the first antibody sequence through the manufacture of the first two batches of drug product; (iv) reimbursement of a portion of all 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 the mid-single digits to the low teens. The Company determined that the combined performance obligation is satisfied over time; therefore, the Company will recognize the transaction price from the license agreement over the Company’s estimated period to complete its activities. The Company concluded that it will utilize a cost-based input method to measure its progress toward completion of its performance obligation and to calculate the corresponding amount of revenue to recognize each period. The Company believes this is the best measure of progress because other measures do not reflect how the Company transfers its performance obligation to Zenas. In applying the cost-based input method of revenue recognition, the Company uses actual costs incurred relative to budgeted costs expected to be incurred for the combined performance obligation. These costs consist primarily of third-party contract costs. Revenue will be recognized based on the level of costs incurred relative to the total budgeted costs for the combined performance obligation. A cost-based input method of revenue recognition requires management to make estimates of costs to complete the Company’s performance obligation. In making such estimates, judgment is required to evaluate assumptions related to cost estimates. The Company 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 the Company’s control, the Company 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 the Company recognizes revenue. As of December 31, 2023, no milestones had been achieved. 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, the Company 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). We have not recorded any royalty revenue to date. For the years ended December 31, 2023 and 2022, the Company recognized related party license revenue totaling $2.8 million and $6.4 million, respectively, associated with the Zenas Agreements. As of December 31, 2023, the Company recorded a related party receivable of $0.3 million, unbilled related party receivable of $0.2 million, current deferred related party revenue of $0.1 million and noncurrent deferred related party revenue of $0.7 million on its consolidated balance sheet. As of December 31, 2022, the Company recorded a related party receivable of $4.7 million, unbilled related party receivable of $0.9 million, current deferred related party revenue of $0.1 million and noncurrent deferred related party revenue of $0.8 million on its consolidated balance sheet.

Subsequent Events - Additional Information (Details) - Subsequent Event [Member] - Private Placement [Member] $ / shares in Units, $ in Millions	Jan. 22, 2024 USD ($) $ / shares shares
Subsequent Event [Line Items]
Sold and issued of shares \| shares	14,500,500
Stock issued, price per share	$ 12
Pre-funded Warrants [Member]
Subsequent Event [Line Items]
Stock issued, price per share	$ 11.999
Pre-funded warrants to purchase \| shares	4,666,332
Exercise price (in USD per share)	$ 0.001
Aggregate purchase price of pre-funded warrant \| $	$ 230
Class of warrant or right maximum beneficial ownership percent	9.99%
Pre-funded warrants increase or decrease percentage	19.99%

Commitments and Contingencies - Additional Information (Details) $ in Thousands, £ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 GBP (£)
Other Commitments [Line Items]
Research and development expense	$ 32,841	$ 29,379
Alloy Therapeutics Llc [Member]
Other Commitments [Line Items]
Payment of annual license fees and program fees	100
Research and development expense	100	500
Alloy Therapeutics Llc [Member] \| Development Milestone [Member] \| First Selected Antibody [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due	1,800
Alloy Therapeutics Llc [Member] \| Development Milestone [Member] \| Second Selected Antibody [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due	3,100
Alloy Therapeutics Llc [Member] \| Commercial Milestone [Member] \| First Selected Antibody [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due	11,000
Alloy Therapeutics Llc [Member] \| Commercial Milestone [Member] \| Second Selected Antibody [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due	15,000
OmniAb, Inc [Member]
Other Commitments [Line Items]
Research and development expense	300	100
Ligand Pharmaceuticals Incorporated [Member] \| Development Milestone [Member]
Other Commitments [Line Items]
Potential milestone payments due	12,200
IONTAS Limited [Member]
Other Commitments [Line Items]
Research and development expense	$ 2,100	$ 1,700
IONTAS Limited [Member] \| Development Milestone [Member] \| First Development Program [Member]
Other Commitments [Line Items]
Potential milestone payments due \| £			£ 3.1
IONTAS Limited [Member] \| Development Milestone [Member] \| Second Development Program [Member]
Other Commitments [Line Items]
Potential milestone payments due \| £			2.5
IONTAS Limited [Member] \| Commercial Milestone [Member] \| First Development Program [Member]
Other Commitments [Line Items]
Potential milestone payments due \| £			£ 2.3

Net Loss Per Share - Schedule of Basic and diluted net loss per share of common stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net loss	$ (43,555)	$ (28,476)
Denominator:
Weighted-average shares of common stock outstanding	5,153,711	875,279
Less: weighted-average unvested restricted shares of common stock	(288)	(1,045)
Weighted average number of shares outstanding, basic	5,153,423	874,234
Weighted average number of shares outstanding, diluted	5,153,423	874,234
Net loss per share attributable to common stockholders, basic	$ (8.45)	$ (32.57)
Net loss per share attributable to common stockholders, diluted	$ (8.45)	$ (32.57)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Cover Page	12 Months Ended
Cover Page	Dec. 31, 2023
Document Type	S-1/A
Amendment Flag	false
Entity Registrant Name	Dianthus Therapeutics, Inc.
Entity Central Index Key	0001690585
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Tax Identification Number	81-0724163
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	7 Times Square, 43rd Floor,
Entity Address, City or Town	New York
Entity Address, Postal Zip Code	10036
Entity Address, State or Province	NY
City Area Code	929
Local Phone Number	999-4055
Business Contact [Member]
Entity Address, Address Line One	7 Times Square, 43rd Floor,
Entity Address, City or Town	New York
Entity Address, Postal Zip Code	10036
Entity Address, State or Province	NY
City Area Code	929
Local Phone Number	999-4055

Organization, Description of Business and Liquidity - Additional Information (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 11, 2023 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 shares
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Reverse stock split description	Immediately prior to the effective time of the Reverse Merger, the Company effected a 1-for-16 reverse stock split of its common stock (the “Reverse Stock Split”). Unless noted otherwise, all references herein to share and per share amounts reflect the Reverse Stock Split.
Net loss \| $		$ (43,555)	$ (28,476)
Accumulated deficit \| $		$ (89,423)	$ (45,868)
Common stock, Shares issued	11,021,248	14,817,696	875,279
Exchange ratio of reverse merger	0.2181
Shares of common stock issued in pre-closing financing	2,873,988
Shares pre-funded warrants to purchase	210,320
Pre-funded warrants exercisable	210,320
Prefunded warrants price per share \| $ / shares	$ 23.34
Common stock price per share \| $ / shares	$ 23.34
Proceeds from pre-closing financing \| $	$ 72,000
Common Stock [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Common stock, Shares issued		14,817,696	875,279
Common stock, Shares outstanding	14,817,696	14,817,696	875,279	875,279

Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, Shares authorized	0	33,336,283
Convertible preferred stock, Share issued	0	33,336,282
Convertible preferred stock, Shares Outstanding	0	33,336,282
Convertible preferred stock, Liquidation Preference	$ 0	$ 121,500,000
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, Shares authorized	10,000,000	0
Preferred stock, Shares issued	0	0
Preferred stock, Shares outstanding	0	0
Common stock, Par value	$ 0.001	$ 0.0001
Common stock, shares authorized	150,000,000	8,722,279
Common stock, Shares issued	14,817,696	875,279
Common stock, Shares outstanding	14,817,696	875,279

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid materials, supplies and research and development services	$ 2,155	$ 820
Prepaid Insurance	596	32
Prepaid subscriptions, software and other administrative services	504	53
Prepaid expenses and other current assets	$ 3,255	$ 905

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenues:
License revenue—related party	$ 2,826	$ 6,417
Operating expenses:
Research and development	32,841	29,379
General and administrative	18,159	6,743
Total operating expenses	51,000	36,122
Loss from operations	(48,174)	(29,705)
Other income/(expense):
Interest income	4,764	1,145
(Loss)/gain on currency exchange, net	(85)	136
Other expense	(60)	(52)
Total other income	4,619	1,229
Net loss	$ (43,555)	$ (28,476)
Net loss per share attributable to common stockholders, basic	$ (8.45)	$ (32.57)
Net loss per share attributable to common stockholders, diluted	$ (8.45)	$ (32.57)
Weighted-average number of share of common stock outstanding, used in computing net loss per share of commonstock, basic	5,153,423	874,234
Weighted-average number of share of common stock outstanding, used in computing net loss per share of commonstock, diluted	5,153,423	874,234
Comprehensive loss:
Net loss	$ (43,555)	$ (28,476)
Other comprehensive income/(loss):
Change in unrealized gains/(losses) related to available-for-sale debt securities	208	(161)
Total other comprehensive income/(loss)	208	(161)
Total comprehensive loss	$ (43,347)	$ (28,637)

Leases - Additional Information (Details) - USD ($)	12 Months Ended
Leases - Additional Information (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Leases [Line Items]
Property sublease, description	The Company leases space under operating leases for administrative offices in New York, New York, and Waltham, Massachusetts and wet laboratory space in Watertown, Massachusetts. The Company also leased office space under operating leases, which had a non-cancelable lease term of less than one year and, therefore, management elected the practical expedient to exclude these short-term leases from right-of-use assets and lease liabilities.
Operating lease costs	$ 394,000	$ 236,000
Weighted-Average remaining lease term	19 months
Weighted-average discount rate - operating lease	10.60%
General and Administrative Expenses [Member]
Leases [Line Items]
Operating lease costs	$ 400,000	200,000
Research and Development Expenses [Member]
Leases [Line Items]
Operating lease costs	$ 17	$ 0

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Mar. 15, 2023	Mar. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Sep. 11, 2023	Dec. 31, 2020
Related Party Transaction [Line Items]
Common stock, Shares issued			14,817,696	875,279	11,021,248
Unbilled receivable from related party			$ 184	$ 938
Deferred revenue current			100	100
Deferred revenue noncurrent			736	791
Aggregate principal amount			377	0
Principal and interest repaid			377	0
Zenas BioPharma Limited [Member]
Related Party Transaction [Line Items]
Common stock, Shares issued						156,848
Related party receivable			300	4,700
Unbilled receivable from related party			200	900
Deferred revenue current			100	100
Deferred revenue noncurrent			$ 700	800
Zenas BioPharma Limited [Member] \| Dianthus [Member]
Related Party Transaction [Line Items]
Aggregate principal amount		$ 377
Interest rate		4.50%
Zenas BioPharma Limited [Member] \| Tellus Bioventures Llc [Member]
Related Party Transaction [Line Items]
Percentage of outstanding shares			10.00%
Zenas BioPharma Limited [Member] \| Fairmount Funds [Member]
Related Party Transaction [Line Items]
Percentage of outstanding shares			13.00%
Principal and interest repaid	$ 377
License Revenue [Member] \| Zenas BioPharma Limited [Member]
Related Party Transaction [Line Items]
Revenues			$ 2,800	$ 6,400

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2023

Prepaid Expense and Other Assets, Current [Abstract]

Prepaid Expenses and Other Current Assets

5. Prepaid Expenses and Other Current Assets

The following table provides a summary of prepaid expenses and other current assets:


	December 31,
	2023		2022
Prepaid materials, supplies and research and development services	$	2,155	$	820
Prepaid insurance		596		32
Prepaid subscriptions, software and other administrative services		504		53

Prepaid expenses and other current assets	$	3,255	$	905

Leases - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 417
2025	222
Total undiscounted operating lease payments	639
Less: imputed interest	(54)
Present value of operating lease liabilities	585
Current portion of lease liabilities	417	$ 350
Long-term lease liabilities	168	$ 438
Total operating lease liabilities	$ 585

Income Taxes - Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 73,580	$ 5,383
Capitalized research and development costs	22,446	4,315
Tax credit carryforwards	16,147	1,120
Lease liabilities	14,063	183
Share-based compensation	6,462	273
Amortization of license fees	3,209	0
Accrued expense	795	484
Other	59	4
Gross deferred tax assets	136,761	11,762
Valuation allowance	(123,452)	(11,566)	$ (5,194)
Total deferred tax assets	13,309	196
Deferred tax liabilities:
Right-of-use lease assets	(12,499)	(189)
Depreciation and amortization	(810)	0
Other	0	(7)
Total deferred tax liabilities	(13,309)	(196)
Net deferred tax assets	$ 0	$ 0

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

9. Leases

The Company leases space under operating leases for administrative offices in New York, New York, and Waltham, Massachusetts and wet laboratory space in Watertown, Massachusetts. The Company also leased office space under operating leases, which had a

non-cancelable

lease term of less than one year and, therefore, management elected the practical expedient to exclude these short-term leases from

right-of-use

assets and lease liabilities.

The following table provides a summary of the components of lease costs and rent:


	Year Ended December 31,
	2023		2022
Operating lease cost	$	366	$	198
Variable lease cost		28		4
Short-term lease cost		—		34

Total operating lease costs	$	394	$	236

The Company recorded the operating lease costs of $0.4 million and $0.2 million within the general and administrative expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively. The Company recorded the operating lease costs of $17 and nil within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively.

Maturities of operating lease liabilities, which do not include short-term leases, as of December 31, 2023, are as follows:


2024	$	417
2025		222

Total undiscounted operating lease payments	$	639
Less: imputed interest		(54	)

Present value of operating lease liabilities	$	585

Balance sheet classification:
Current portion of lease liabilities	$	417
Long-term lease liabilities		168

Total operating lease liabilities	$	585

The weighted-average remaining term of operating leases was 19 months and the weighted-average discount rate used to measure the present value of operating lease liabilities was 10.6% as of December 31, 2023.

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Dec. 31, 2023	Dec. 31, 2022	Jul. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of stock options granted			$ 10.3
Warrant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock exercise price	$ 1.65
Share based compensation arrangement , requisite service period		4 years
Vesting period			7 years 3 months 18 days
Warrants issued	4,677
Warrant per grant date fair value	$ 1.16
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock Purchased		3,052
Common stock exercise price		$ 0.14
Sharebased compensation arrangement by share based payment vested commencement percentage		2.0833%
Restricted stock award vested percentage		25.00%
Grant Weighted Average Grant Date Fair Value Per Share		0.14%
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized			2,529,070
Share-Based Compensation Arrangement by Share-Based Payment Award, Terms of Award			The Incentive Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards, and dividend equivalent rights. In connection with the Reverse Merger, the Incentive Plan also provided for the assumption of shares remaining available for delivery under the 2019 Stock Plan (as defined below), and such shares will be available for the granting of awards under the Incentive Plan in accordance with applicable stock exchange requirements. The Company also has outstanding stock options under the Magenta Therapeutics, Inc. 2016 Stock Option and Grant Plan, as amended (the “2016 Plan”), but is no longer granting awards under the 2016 Plan.
Shares available for issuance			879,461
Total unrecognized stock-based compensation expense related to unvested share-based awards			$ 7.9
Period for recognition of unrecognized expense			2 years 7 months 6 days
Percentage of purchase price of common stock under the ESPP			110.00%
Number of shares reserved and available for issuance increment percentage			4.00%
2018 Stock Option and Incentive Plan [Member] \| Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			12 months
2018 Stock Option and Incentive Plan [Member] \| Restricted Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
2018 Stock Option and Incentive Plan [Member] \| Stock Options and Stock Appreciation Rights [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of award			10 years
2018 Stock Option and Incentive Plan [Member] \| Certain Incentive Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of award			5 years
2019 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Terms of Award			The ESPP provides that the number of shares reserved and available for issuance under the ESPP will automatically increase each January 1 through January 1, 2029, by the lesser of (i) 1% of the number of shares issued and outstanding on the immediately preceding December 31, (ii) 62,500 shares and (iii) such number of shares as determined by the Company’s board of directors or its appointed administrator.
Shares available for issuance			37,078
Percentage of purchase price of common stock under the ESPP			85.00%
Common stock purchased			0	7,501
Stock issued, price per share				$ 15.36
2019 Employee Stock Purchase Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved and available for issuance increment percentage			1.00%
Additional number of shares reserved and available for issuance			62,500
2019 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options vested and expected to vest as of September 30, 2023					1,273,454

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 2,900	$ 1,518
Stock-based Compensation Expense \| Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	897	416
Stock-based Compensation Expense \| General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 2,003	$ 1,102

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Basis of Presentation

Use of Estimates

Cash and Cash Equivalents

All short-term, highly liquid investments with original maturities of 90 days or less are considered to be c

h and cash equivalents. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents are valued at cost, which approximates fair value.

Concentration of Credit Risk

Short-term Investments

available-for-sale

pursuant to ASC 320,

Investments – Debt and Equity Securities,

Effective January 1, 2023, when the fair value is below the amortized cost of a marketable security, an estimate of expected credit losses is made in accordance with ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

. The credit-related impairment amount is recognized in the consolidated statements of operations and comprehensive loss. Credit losses are

written-off

Additional information regarding short-term investments is included in Note 4.

Receivable from Related Party and Unbilled Receivable from Related Party

Property and Equipment

Leases

Operating leases are accounted for in accordance with ASU

2016-02,

Leases

, as amended (“ASC 842”).

Right-of-use

right-of-use

assets and lease liabilities.

non-lease

components (e.g., common-area or other maintenance costs), which are accounted for as a single lease component as management have elected the practical expedient to group lease and

non-lease

components for all leases.

Additional information and disclosures required under ASC 842 are included in Note 9.

Restricted Cash

In accordance with ASU

2016-18,

Statement of Cash Flows (Topic 230): Restricted Cash

Fair Value Measurements

Fair Value Measurements and Disclosures

The three levels of the fair value hierarchy are described below:

•

Level 1 - Quoted prices in active markets for identical assets or liabilities.

•

Additional information regarding fair value measurements is included in Note 7.

Classification of Convertible Preferred Stock

Convertible preferred stock is recorded at its original issuance price, less direct and incremental offering costs, as stipulated by its terms. The Company has applied the guidance in ASC

480-10-S99,

Distinguishing Liabilities from

Equity-Overall-SEC

Materials

Segment Information

License Revenue—Related Party

The Company recognizes revenue pursuant to ASC 606,

Revenue from Contracts with Customers

Additional information and disclosures required under ASC 606 are included in Note 13.

Research and Development Costs

Patent Costs

Patent costs are expensed as incurred and recorded within general and administrative expenses.

Income Taxes

Income taxes are recorded in accordance with ASC 740,

Income Taxes (

Stock-Based Compensation

The Company accounts for stock-based compensation awards in accordance with ASC Topic 718,

Compensation – Stock Compensation

Prior to the Reverse Merger, management utilized valuation methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid,

Valuation of Privately Held Company Equity Securities Issued as Compensation

Management uses the simplified method, as prescribed by the SEC Staff Accounting Bulletin No. 107,

Share-Based Payment

Additional information regarding share-based compensation is included in Note 12.

Comprehensive Loss

The only component of comprehensive loss other than net loss is change in unrealized losses related to

available-for-sale

debt securities.

Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders are calculated in conformity with the

two-class

share in losses. Under the

two-class

Additional information is included in Note 15.

Recently Issued Accounting Pronouncements

On January 1, 2023, the Company adopted ASU

No. 2016-13

available-for-sale,

In November 2023, the FASB issued ASU No.

2023-07,

Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures

. ASU

2023-07

expands annual and interim disclosure requirements for reportable segments, primarily through enhanced disclosures about significant segment expenses. ASU

2023-07

In December 2023, the FASB issued ASU No. 2023-09,

Income Taxes (Topic 740), Improvements to Income Tax Disclosures

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of U.S. Federal Statutory Rate to Effective Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023			2022
Federal statutory income tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		2.1	%		2.2	%
Research tax credits		34.5	%		2.2	%
Tax attributes acquired as part of reverse merger		201.1	%		—
Other		(1.7	)%		(3.0	)%
Increase in deferred tax asset valuation allowance		(257.0	)%		(22.4	)%

Effective income tax rate		0.0	%		0.0	%

Company's Deferred Tax Assets

The following table provides a summary of net deferred tax assets:


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	73,580		$	5,383
Capitalized research and development costs		22,446			4,315
Tax credit carryforwards		16,147			1,120
Lease liabilities		14,063			183
Share-based compensation		6,462			273
Amortization of license fees		3,209			—
Accrued expenses		795			484
Other		59			4

Gross deferred tax assets		136,761			11,762
Valuation allowance		(123,452	)		(11,566	)

Total deferred tax assets		13,309			196
Deferred tax liabilities:
Right-of-use lease assets		(12,499	)		(189	)
Depreciation and amortization		(810	)		—
Other		—			(7	)

Total deferred tax liabilities		(13,309	)		(196	)

Net deferred tax assets	$	—		$	—

Changes in Deferred Tax Asset Valuation Allowance

During the years ended December 31, 2023 and 2022, capitalized research and development expenses increased pursuant to Section 174 of the Internal Revenue Code of 1986, as amended (the “Code”). The changes in the valuation allowance for the years ended December 31, 2023 and 2022 were as follows:


	Year Ended December 31,
	2023		2022
Valuation allowance as of beginning of year	$	11,566	$	5,194
Net increases recorded to income tax provision		111,886		6,372

Valuation allowance as of end of year	$	123,452	$	11,566

Property and Equipment

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment

6. Property and Equipment

The following table provides a summary of property and equipment:


	December 31,
	2023			2022
Computer equipment	$	234		$	131
Furniture and fixtures		48			41
Subtotal		282			172
Less: accumulated depreciation		(97	)		(30	)

Property and equipment, net	$	185		$	142

Depreciation expense was $67 and $30 for the years ended December 31, 2023 and 2022, respectively.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

7. Fair Value of Financial Instruments

The following table provides a summary of financial assets measured at fair value on a recurring basis:


Description	Fair Value at December 31, 2023		Level 1		Level 2		Level 3
Recurring Assets:
Cash equivalents:
Money market fund	$	131,193	$	131,193	$	—	$	—
Short-term investments:
U.S. treasury securities		36,418		36,418		—		—
U.S. government agency securities		4,975		—		4,975		—

Total assets measured at fair value	$	172,586	$	167,611	$	4,975	$	—


Description	Fair Value at December 31, 2022		Level 1		Level 2		Level 3
Recurring Assets:
Cash equivalents:
Money market fund	$	11,846	$	11,846	$	—	$	—
U.S. government agency securities		1,999		—		1,999		—
Short-term investments:
U.S. treasury securities		20,775		20,775		—		—
U.S. government agency securities		39,350		26,736		12,614		—

Total assets measured at fair value	$	73,970	$	59,357	$	14,613	$	—

There were no transfers between levels for the years ended December

31,

2023 or 2022.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Earnings Per Share [Text Block]

15. Net Loss Per Share

Basic and diluted net loss per share of common stock were calculated as follows:


	Year Ended December 31,
	2023			2022
Numerator:
Net loss	$	(43,555	)	$	(28,476	)
Denominator:
Weighted-average shares of common stock outstanding		5,153,711			875,279
Less: weighted-average unvested restricted shares of common stock		(288	)		(1,045	)
Weighted-average shares used to compute net loss per share of common stock, basic and diluted		5,153,423			874,234

Net loss per share attributable to common stockholders, basic and diluted	$	(8.45	)	$	(32.57	)

The Company’s potential dilutive securities, which include convertible preferred stock, stock options, unvested restricted shares of common stock, and warrants for the purchase of common stock, have been excluded from the computation of diluted net loss per share as the effect would be antidilutive. Therefore, the weighted-average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share is the same. The following potential dilutive securities, presented on an as converted basis, were excluded from the calculation of net loss per share due to their anti-dilutive effect:


	Year Ended December 31,
	2023		2022
Convertible preferred stock (as converted)		—		7,269,183
Stock options outstanding		1,749,475		1,273,454
Unvested restricted shares of common stock		—		635
Warrants for the purchase of common stock		214,997		4,677

Total		1,964,472		8,547,949

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued compensation	$ 5,361	$ 2,084
Accrued external research and development	456	4,329
Accrued professional fees	422	162
Accrued other expenses	265	33
Accrued expenses	$ 6,504	$ 6,608

Income Taxes - Schedule of Reconciliation of U.S. Federal Statutory Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%
State taxes, net of federal benefit	2.10%	2.20%
Research tax credits	34.50%	2.20%
Tax attributes acquired as part of reverse merger	201.10%	0.00%
Other	(1.70%)	(3.00%)
Increase in deferred tax asset valuation allowance	(257.00%)	(22.40%)
Effective income tax rate	0.00%	0.00%

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	18. Subsequent Events The Company evaluated subsequent events from December 31, 2023, the date of these consolidated financial statements, through March 21, 2024, which represents the date the consolidated financial statements were issued, for events requiring recording or disclosure in the consolidated financial statements for the year ended December 31, 2023. The Company concluded that no events have occurred that would require recognition or disclosure in the consolidated financial statements except as noted below. On January 22, 2024, the Company entered into a securities purchase agreement for a private placement with certain institutional and accredited investors. At the closing of the private placement on January 24, 2024, the Company sold and issued 14,500,500 shares of common stock at a price per share of $12.00, and pre-funded warrants to purchase 4,666,332 shares of common stock at a purchase price of $11.999 per pre-funded warrant, which represents the per share purchase price of the common stock less the $0.001 per share exercise price for each pre-funded warrant, for an aggregate purchase price of approximately $230 million. The pre-funded warrants are exercisable at any time after the date of issuance. A holder of pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise. A holder of pre-funded warrants may increase or decrease this percentage to a percentage not in excess of 19.99% by providing at least 61 days’ prior notice to the Company.

Reverse Merger - Schedule of Company Obtained Assets and Liabilities (Detail) $ in Thousands	Sep. 11, 2023 USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 69,738
Other current assets	2,473
Accrued liabilities	(386)
Net assets acquired	$ 71,825

Preferred Stock and Convertible Preferred Stock (Tables)

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Schedule of Preferred Stock Activity

The authorized, issued and outstanding shares of the convertible preferred stock and liquidation preferences of Former Dianthus as of December 31, 2022 were as follows:


	Issued Dates		Authorized Shares		Shares Issued and Outstanding		Per Share Liquidation Preference		Aggregate Liquidation Amount		Proceeds (Net of Issuance Costs)
Series Seed 1 Convertible Preferred Stock		July 2019, April 2020 and December 2020		6,500,000		6,500,000	$	1.000	$	6,500	$	6,436
Series Seed 2 Convertible Preferred Stock		May 2021		3,829,266		3,829,265	$	3.9172		15,000		14,912
Series A Convertible Preferred Stock		April 2022		23,007,017		23,007,017	$	4.3465		100,000		96,676

Total Convertible Preferred Stock				33,336,283		33,336,282			$	121,500	$	118,024

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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+ Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of Basic and diluted net loss per share of common stock

Basic and diluted net loss per share of common stock were calculated as follows:


	Year Ended December 31,
	2023			2022
Numerator:
Net loss	$	(43,555	)	$	(28,476	)
Denominator:
Weighted-average shares of common stock outstanding		5,153,711			875,279
Less: weighted-average unvested restricted shares of common stock		(288	)		(1,045	)
Weighted-average shares used to compute net loss per share of common stock, basic and diluted		5,153,423			874,234

Net loss per share attributable to common stockholders, basic and diluted	$	(8.45	)	$	(32.57	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following potential dilutive securities, presented on an as converted basis, were excluded from the calculation of net loss per share due to their anti-dilutive effect:


	Year Ended December 31,
	2023		2022
Convertible preferred stock (as converted)		—		7,269,183
Stock options outstanding		1,749,475		1,273,454
Unvested restricted shares of common stock		—		635
Warrants for the purchase of common stock		214,997		4,677

Total		1,964,472		8,547,949

Accrued Expenses

12 Months Ended

Dec. 31, 2023

Accrued Expenses

8. Accrued Expenses

The following table provides a summary of accrued expenses:


	December 31,
	2023		2022
Accrued compensation	$	5,361	$	2,084
Accrued external research and development		456		4,329
Accrued professional fees		422		162
Accrued other expenses		265		33

Accrued expenses	$	6,504	$	6,608