0001193125-23-144240 | S-4 | XBRL Viewer | Magenta Therapeutics INC

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Summary of Significant Accounting Policies - Schedule of Estimated Useful Life of Asset (Detail)	12 Months Ended
	Dec. 31, 2022
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	5 years
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	Shorter of life of lease or estimated useful life

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 143,906	$ 49	$ 398,311	$ (23)	$ (254,431)
Beginning balance, shares at Dec. 31, 2020		48,533,135
Issuance of common stock	86,097	$ 10	86,087
Stock Issued During Period, Shares, New Issues		9,599,998
Vesting of restricted stock, shares		218,464
Issuance of common stock upon exercise of stock options	3,363		3,363
Issuance of common stock upon exercise of stock options, shares		421,997
Issuance of common stock under Employee Stock Purchase Plan	141		141
Issuance of common stock under Employee Stock Purchase Plan, shares		25,563
Stock-based compensation expense	10,308		10,308
Unrealized losses on marketable securities	(7)			(7)
Net loss	(71,136)				(71,136)
Ending balance at Dec. 31, 2021	172,672	$ 59	498,210	(30)	(325,567)
Ending balance, shares at Dec. 31, 2021		58,799,157
Issuance of common stock	2,763	$ 2	2,761
Stock Issued During Period, Shares, New Issues		1,644,200
Vesting of restricted stock, shares		76,539
Issuance of common stock upon exercise of stock options	$ 115		115
Issuance of common stock upon exercise of stock options, shares	0	120,013
Stock-based compensation expense	$ 7,021		7,021
Unrealized losses on marketable securities	(151)			(151)
Net loss	(76,462)				(76,462)
Ending balance at Dec. 31, 2022	$ 105,958	$ 61	$ 508,107	$ (181)	$ (402,029)
Ending balance, shares at Dec. 31, 2022		60,639,909

Leases - Schedule of Supplemental Disclosure Of Cash Flow Information Related To The Lease (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 6,567
Operating lease liabilities arising from obtaining right-of-use asset	$ 0

Marketable Securities and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2022

Schedule of Marketable Securities by Security Type

As of December 31, 2022, marketable securities by security type consisted of (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury notes (due within one year)	$	54,596	$	2	$	(183	)	$	54,415

Total	$	54,596	$	2	$	(183	)	$	54,415

As of December 31, 2021, marketable securities by security type consisted of (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury notes (due within one year)	$	30,213	$	—	$	(20	)	$	30,193
U.S. treasury notes (due after one year through two years)		15,093		—		(10	)		15,083

Total	$	45,306	$	—	$	(30	)	$	45,276

Schedule of Financial Assets Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands):


	Fair Value Measurements at December 31, 2022 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	56,663	$	—	$	—	$	56,663
Marketable securities:
U.S. treasury notes		—		54,415		—		54,415

Total	$	56,663	$	54,415	$	—	$	111,078


	Fair Value Measurements at December 31, 2021 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	131,542	$	—	$	—	$	131,542
Marketable securities:
U.S. treasury notes		—		45,276		—		45,276

Total	$	131,542	$	45,276	$	—	$	176,818

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2022

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2022			2021
Laboratory and computer equipment	$	6,954		$	6,397
Furniture and fixtures		826			826
Leasehold improvements		6,905			6,905

		14,685			14,128
Less: Accumulated depreciation and amortization		(8,590	)		(6,667	)

	$	6,095		$	7,461

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Impairment losses on long-lived assets	$ 0	$ 0
Operating lease, right-of-use asset	23,168,000	$ 0
Operating lease, liability	29,962,000
Deferred rent	7,000,000
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset	26,100,000
Operating lease, liability	$ 33,000,000

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 1,925	$ 2,020

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 14,685	$ 14,128
Less: Accumulated depreciation and amortization	(8,590)	(6,667)
Property and equipment, net	6,095	7,461
Laboratory and computer equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,954	6,397
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	826	826
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,905	$ 6,905

Leases (Tables)

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Schedule of Components of the Company's Lease Expense

The components of the Company’s lease expense under ASC 842 were as follows (in thousands):


	Year Ended December 31, 2022
Operating lease cost	$	6,407
Short-term lease cost		—
Variable lease cost		1,406

	$	7,813

Schedule of Supplemental Disclosure Of Cash Flow Information Related To The Lease

Supplemental disclosure of cash flow information related to the lease was as follows (in thousands):


	Year Ended December 31, 2022
Cash paid for amounts included in the measurement of operating lease liabilities	$	6,567
Operating lease liabilities arising from obtaining right-of-use asset	$	—

Schedule of Weighted Average Remaining Lease Term And Discount Rate

The weighted average remaining lease term and discount rate were as follows:


	December 31, 2022
Weighted-average remaining lease term—operating lease (in years)		5.17
Weighted-average discount rate—operating lease		11.00	%

Schedule of Future Minimum Lease Payments Due Under Noncancelable Operating Lease

As of December 31, 2022, the future minimum lease payments due under the noncancelable operating lease was as follows (in thousands):


2023	$	6,936
2024		7,313
2025		7,679
2026		8,062
2027		8,466
Thereafter		1,439

Total future minimum lease payments		39,895
Less: imputed interest		(9,933	)

Total operating lease liabilities	$	29,962

As previously disclosed in the Company’s Annual Report on Form

10-K

and under the previous lease accounting standard, ASC 840,

Leases

, the following table summarizes the future minimum lease payments due under the operating lease as of December 31, 2021 (in thousands):


2022	$	6,375
2023		6,734
2024		7,100
2025		7,455
2026		7,828
Thereafter		9,617

	$	45,109

Schedule of Lease Liabilities

The following table represents the lease liabilities on the consolidated balance sheet (in thousands):


	December 31, 2022
Current operating lease liability	$	3,824
Operating lease liability, net of current portion		26,138

Total operating lease liabilities	$	29,962

Leases - Schedule of Future Minimum Lease Payments Due Under Noncancelable Operating Lease (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2023	$ 6,936
2024	7,313
2025	7,679
2026	8,062
2027	8,466
Thereafter	1,439
Total future minimum lease payments	39,895
Less: imputed interest	(9,933)
Total operating lease liabilities	$ 29,962
2022		$ 6,375
2023		6,734
2024		7,100
2025		7,455
2026		7,828
Thereafter		9,617
Total future minimum lease payments		$ 45,109

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	8,975,671	6,771,227
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	8,475,816	6,248,675
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	427,244	479,918
Employee Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	72,611	42,634

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 7,021	$ 10,308
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	1,877	3,836
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 5,144	$ 6,472

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jan. 01, 2023	Jun. 30, 2019	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of stock options granted			$ 1.48	$ 6.32
Stock based compensation			$ 7,021	$ 10,308
Number of share options exercised			0
Intrinsic value of stock options exercised				1,300
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance restricted stock units vested			0
Fair value of units vested				1,000
Performance Restricted Stock Units [Member] \| Nonprobable Performance Based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense related to unvested share-based awards			$ 1,700
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance restricted stock units vested			76,539
Fair value of units vested			$ 100	$ 300
Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			18 months
Service Based Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense related to unvested share-based awards			$ 13,600
Period for recognition of unrecognized expense			2 years 2 months 12 days
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance under Stock Option and Incentive Plan			3,102,231
2018 Stock Option and Incentive Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for future issuance	2,425,596
2018 Stock Option and Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage applied to the outstanding shares as annual increase in the number of shares authorized for issuance			4.00%
Term of award			10 years
Vesting period			4 years
2018 Stock Option and Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			18 months
2019 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance under Stock Option and Incentive Plan			593,239
Annual Increase In Aggregate Number Of Shares Reserved For Future Issuance		1,000,000
Stock based compensation			$ 100
Percentage of purchase price of common stock under the ESPP			85.00%
Common stock purchased			120,013	25,563
Stock issued, price per shares			$ 0.96	$ 5.53
2019 Employee Stock Purchase Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for future issuance	0
2019 Employee Stock Purchase Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage applied to the outstanding shares as annual increase in the number of shares authorized for issuance		1.00%
Stock based compensation				$ 100

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events As of December 31, 2022, the Company had approximately $5.7 million on deposit at Silicon Valley Bank (“SVB”), consisting of $3.9 million of cash and cash equivalents and $1.8 million of restricted cash. SVB was closed on March 10, 2023, by the California Department of Financial Protection and Innovation, which appointed the Federal Deposit Insurance Corporation (“FDIC”) as receiver. Subsequent to the closure of SVB, the FDIC created Silicon Valley Bridge Bank, N.A. (“SVB Bridge Bank”) and the Company’s SVB deposits were transferred to SVB Bridge Bank. As of March 20, 2023, the Company had approximately $36.9 million, including $1.8 million of restricted cash, on deposit at SVB Bridge Bank. On January 31, 2023, the Company received a written notice from the staff of Nasdaq’s Listing Qualifications Department, notifying the Company that, for the 30 consecutive business day period between December 15, 2022 through January 30, 2023, the bid price for its common stock had closed below the $1.00 per share minimum bid price requirement for continued listing on Nasdaq pursuant to Nasdaq Listing Rule 5450(a)(1), or the Minimum Bid Price Requirement. In accordance with Nasdaq Listing Rule 5810(c)(3)(A), the Company has 180 calendar days, or until July 31, 2023, to regain compliance with the Minimum Bid Price Requirement. If the Company fails to satisfy the continued listing requirements of Nasdaq, such as the Minimum Bid Price Requirement, Nasdaq may take steps to delist its common stock. On February 2, 2023, after a review of the Company’s business, programs, resources and capabilities, including anticipated costs and timelines, the Company announced the decision to halt further development of its programs and to conduct a comprehensive review of strategic alternatives. The Company also announced a corporate restructuring on February 7, 2023 that resulted in a reduction in its workforce by 84% that was substantially completed in February 2023 resulting in severance and related costs of approximately $5.4 million. As part of the strategic review process, the Company is exploring potential strategic alternatives that include, without limitation, an acquisition, merger, business combination or other transaction. The Company is also exploring strategic alternatives related to its product candidates and related assets, including, without limitation, licensing transactions and asset sales. There can be no assurance that the strategic review process will result in the Company pursuing a transaction, or that any transaction, if pursued, will be completed on terms favorable to the Company and its stockholders. If the strategic review process is unsuccessful, the Company’s board of directors may decide to pursue a dissolution and liquidation of the Company. On February 6, 2023, the Company entered into an agreement with Wedbush Securities Inc . (“Wedbush”) to act as the Company’s exclusive strategic financial advisor in connection with a potential strategic transaction including but not limited to an acquisition, merger, business combination or other transaction. Upon the consummation of such transaction, the Company agreed to pay Wedbush a success fee of 1.0% of the transaction value with a minimum fee of $1.5 million.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 57,626	$ 131,650
Marketable securities	54,415	45,276
Prepaid expenses and other current assets	3,561	3,767
Total current assets	115,602	180,693
Restricted cash	1,780	1,780
Operating lease, right-of-use asset	23,168	0
Property and equipment, net	6,095	7,461
Total assets	146,645	189,934
Current liabilities:
Accounts payable	2,454	3,040
Accrued expenses and other current liabilities	8,271	7,823
Operating lease liability, current portion	3,824	0
Total current liabilities	14,549	10,863
Operating lease liability, net of current portion	26,138	0
Deferred rent	0	6,399
Total liabilities	40,687	17,262
Commitments and contingencies (Note 9)
Stockholders' Equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.001 par value; 150,000,000 shares authorized; 60,639,909 and 58,799,157 shares issued and outstanding as of December 31, 2022 and 2021, respectively	61	59
Additional paid-in capital	508,107	498,210
Accumulated other comprehensive loss	(181)	(30)
Accumulated deficit	(402,029)	(325,567)
Total stockholders' equity	105,958	172,672
Total liabilities and stockholders' equity	$ 146,645	$ 189,934

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Feb. 07, 2023	Dec. 31, 2022	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Entity incorporation date		Jun. 01, 2015
Entity incorporation state code		DE
Net loss		$ (76,462)	$ (71,136)
Accumulated deficit		$ (402,029)	$ (325,567)
Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Percentage of workforce reduction	84.00%
Severance and related cost	$ 5,400

- Definition

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

+ References

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+ Details

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (76,462)	$ (71,136)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,021	10,308
Depreciation and amortization expense	1,925	2,020
Loss on disposal of property and equipment	0	95
Noncash lease expense	2,920	0
Net amortization of premiums on marketable securities	208	708
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	206	(1,075)
Accounts payable	(801)	(720)
Accrued expenses and other current liabilities	973	153
Operating lease liabilities	(3,080)	0
Deferred rent	0	116
Net cash used in operating activities	(67,090)	(59,531)
Cash flows from investing activities:
Purchases of property and equipment	(314)	(1,264)
Purchases of marketable securities	(69,498)	(45,308)
Maturities of marketable securities	60,000	90,000
Net cash provided by (used in) investing activities	(9,812)	43,428
Cash flows from financing activities:
Proceeds from private investment	0	86,400
Proceeds from issuance of common stock under the ATM Program, net of commissions	2,904	0
Payments of offering costs	(141)	(303)
Proceeds from exercise of common stock options	0	3,363
Proceeds from issuance of common stock under Employee Stock Purchase Plan	115	141
Net cash provided by financing activities	2,878	89,601
Net increase (decrease) in cash, cash equivalents and restricted cash	(74,024)	73,498
Cash, cash equivalents and restricted cash at beginning of period	133,430	59,932
Cash, cash equivalents and restricted cash at end of period	59,406	133,430
Supplemental disclosure of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable and accrued expenses	$ 245	$ 0

Property and Equipment, Net

12 Months Ended

Dec. 31, 2022

Property and Equipment, Net

4. Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2022			2021
Laboratory and computer equipment	$	6,954		$	6,397
Furniture and fixtures		826			826
Leasehold improvements		6,905			6,905

		14,685			14,128
Less: Accumulated depreciation and amortization		(8,590	)		(6,667	)

	$	6,095		$	7,461

Depreciation and amortization expense was $1.9 million and $2.0 million for the years ended December 31, 2022 and 2021, respectively.

Related Parties - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Match Bio Therapies [Member]
Related Party Transaction [Line Items]
Expenses paid to related party	$ 0.3	$ 0.7
Match Bio Therapies [Member] \| Accounts Payable, Accrued Expenses and Other Current Liabilities [Member]
Related Party Transaction [Line Items]
Amounts owed to related party	0.1	0.2
Match Bio Therapies [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Prepaid expense and other current assets related parties		$ 0.1
License Agreement [Member] \| Material Transfer and Evaluation Agreement [Member]
Related Party Transaction [Line Items]
Expenses paid to related party	4.6
License Agreement [Member] \| Material Transfer and Evaluation Agreement [Member] \| Accounts Payable, Accrued Expenses and Other Current Liabilities [Member]
Related Party Transaction [Line Items]
Amounts owed to related party	$ 0.1

Stock-Based Compensation - Schedule of Assumptions Used to Determine the Fair Value of Option Grants (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk-free interest rate	2.50%	0.90%
Expected term (in years)	5 years 10 months 24 days	6 years
Expected volatility	81.20%	80.50%
Expected dividend yield	0.00%	0.00%

Cover Page	12 Months Ended
Cover Page	Dec. 31, 2022
Document Information [Line Items]
Document Type	S-4
Amendment Flag	false
Entity Registrant Name	MAGENTA THERAPEUTICS, INC.
Entity Central Index Key	0001690585
Entity Filer Category	Non-accelerated Filer
Entity Ex Transition Period	false
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Tax Identification Number	85-0724163
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	300 Technology Square, 8th Floor
Entity Address, City or Town	Cambridge
Entity Address, Postal Zip Code	02139
Entity Address, State or Province	MA
City Area Code	857
Local Phone Number	242-0170
Entity Primary SIC Number	2834
Business Contact [Member]
Document Information [Line Items]
Entity Address, Address Line One	300 Technology Square, 8th Floor
Entity Address, City or Town	Cambridge
Entity Address, Postal Zip Code	02139
Entity Address, State or Province	MA
City Area Code	857
Local Phone Number	242-0170
Contact Personnel Name	Stephen Mahoney

Leases - Additional Information (Detail) $ in Thousands	12 Months Ended
Leases - Additional Information (Detail) $ in Thousands	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 ft² Sublease	Apr. 01, 2022 ft²	Mar. 31, 2022 ft²
Leases [Line Items]
Restricted cash	$ 1,780	$ 1,780
Long-term deferred rent	$ 0	6,399
Deferred rent, current portion		555
Property sublease, description	The Company has a sublease, as amended, for up to approximately 69,000 square feet of office and laboratory space in Cambridge, Massachusetts. The sublease is subject and subordinate to a prime lease between the sublandlord and the prime landlord. The term of the sublease commenced in June 2018 and expires in February 2028. The sublandlord has the right to terminate the sublease after five years.
Sublease termination period	5 years
Sublease expiration period	2028-02
Sublease commencement period	2018-06
Rent expense		6,200
Sub Sublease [Member]
Leases [Line Items]
Square feet of property subject to sublease \| ft²				27,000	26,114	13,643
Number of Sub-sublease \| Sublease				2
Rental payments receivable	$ 3,600
Other income from sub-sublease	3,100	$ 3,500
Office and Lab Sublease [Member] \| Letter of Credit [Member]
Leases [Line Items]
Restricted cash	$ 1,800
Office and Lab Sublease [Member] \| Paid By Sublandlord [Member]
Leases [Line Items]
Payments for tenant improvements			$ 5,200

401(k) Savings Plan

12 Months Ended

Dec. 31, 2022

401(k) Savings Plan

10. 401(k) Savings Plan

The Company has a 401(k) available for participating employees who meet certain eligibility requirements. Eligible employees may defer a portion of their salary as defined by the plan. Company contributions to the plan may be made at the discretion of the board of directors of the Company. Effective August 2021, the Company began making matching contributions of up to 2% of eligible wages. During the years ended December 31, 2022 and 2021, the Company recorded $0.2 million and $0.1 million, respectively, of expense related to this matching contribution.

- Definition

The entire disclosure for retirement benefits.

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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax

11. Income Taxes

During the years ended December 31, 2022 and 2021, the Company recorded no income tax benefits for the net operating losses incurred or for the research and orphan drug tax credits generated in each year, due to its uncertainty of realizing a benefit from those items.

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,
	2022			2021
Federal statutory income tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		5.9			5.8
Research and orphan drug tax credits		4.1			3.3
Other		(1.1	)		0.5
Increase in deferred tax asset valuation allowance		(29.9	)		(30.6	)

Effective income tax rate		—	%		—	%

Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands):


	December 31,
	2022			2021
Deferred tax assets:
Net operating loss carryforwards	$	73,843		$	67,236
Capitalized research and development expenses		20,137			8,665
Research and orphan drug tax credit carryforwards		15,550			12,370
Operating lease liability		8,110			—
Stock compensation expense		6,683			5,430
Accrued expense		1,112			936
Other		—			1,891

Total deferred tax assets		125,435			96,528
Valuation allowance		(118,215	)		(95,367	)

Net deferred tax assets		7,220			1,161

Deferred tax liabilities:
Operating lease, right-of-use asset		(6,271	)		—
Depreciation and amortization		(949	)		(1,161	)

Total deferred tax liabilities		(7,220	)		(1,161	)

Net deferred tax assets and liabilities	$	—		$	—

As of December 31, 2022, the Company had net operating loss carryforwards for federal income tax purposes of $272.9 million, of which $17.5 million begin to expire in 2035 and $255.4 million can be carried forward indefinitely. As of December 31, 2022, the Company had net operating loss carryforwards for state income tax purposes of $272.6 million which begin to expire in 2035. As of December 31, 2022, the Company also had available research and orphan drug tax credit carryforwards for federal and state income tax purposes of $12.9 million and $3.4 million, respectively, which begin to expire in 2035 and 2030, respectively. Utilization of the net operating loss carryforwards and research and orphan drug tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”) due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. The Company has not conducted a formal study to assess whether a change of control has occurred or whether there have been multiple changes of control since inception due to the significant complexity and cost associated with such a study. If the Company has experienced a change of control, as defined by Section 382 and 383 of the Code, at any time since inception, utilization of the net operating loss carryforwards or research and orphan drug tax credit carryforwards may be subject to an annual limitation under Section 382 and 383 of the Code, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term

tax-exempt

rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and orphan drug tax credit carryforwards before utilization.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. The Company considered its history of cumulative net losses incurred since inception and its lack of commercialization of any products since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2022 and 2021. The Company reevaluates the positive and negative evidence at each reporting period.

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022 and 2021 related primarily to the increase in net operating loss carryforwards, capitalized research and development expenses and research and orphan drug tax credit carryforwards. During the year ended December 31, 2022, capitalized research and development expenses increased pursuant to Section 174 of the Code. The changes in the valuation allowance for the years ended December 31, 2022 and 2021 and were as follows (in thousands):


	Year Ended December 31,
	2022		2021
Valuation allowance as of beginning of year	$	95,367	$	73,600
Net increases recorded to income tax provision		22,848		21,767

Valuation allowance as of end of year	$	118,215	$	95,367

The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2022 or 2021.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are open under statute from 2019 to the

presen

t. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision.

- 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.

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+ Details

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, Shares authorized	10,000,000	10,000,000
Preferred stock, Shares issued	0	0
Preferred stock, Shares outstanding	0	0
Common stock, Par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, Shares issued	60,639,909	58,799,157
Common stock, Shares outstanding	60,639,909	58,799,157

Common Stock

12 Months Ended

Dec. 31, 2022

Common Stock

6. Common Stock

The Company has a shelf registration statement on Form

S-3

(the “Shelf”) on file with the SEC, which covers the offering, issuance and sale of up to an aggregate of $250.0 million of common stock, preferred stock, debt securities, warrants and/or units of any combination thereof. The Company also entered into a sales agreement, as amended, with Cowen and Company, LLC, as sales agent to provide for the issuance and sale by the Company of up to $50.0 million of common stock from time to time in

“at-the-market”

offerings under the Shelf (the “ATM Program”). The Shelf was declared effective by the SEC on August 12, 2022.

During the year ended December 31, 2022, the Company sold 1,644,200 shares of its common stock under the ATM Program at a weighted average price per share of $1.82 resulting in net proceeds of $2.8 million after commissions and offering costs. As of December 31, 2022, $247.0 million remained available under the Shelf, including up to $47.0 million available for sale under the ATM Program.

In May 2021, the Company issued and sold 9,599,998 shares of its common stock in a private placement at a purchase price of $9.00 per share, resulting in net proceeds of $86.1 million, after deducting offering expenses. In connection with the private placement, the Company filed a resale registration statement with the SEC in June 2021 to register the resale of these shares by the purchasers in the private placement.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends unless declared by the board of directors.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies

9. Commitments and Contingencies

Leases

The Company’s commitments under its leases are described in Note 8.

Collaboration Agreement

In March 2018, the Company entered into a collaboration agreement with Heidelberg Pharma Research GmbH (“HDPR”) whereby the parties agreed to combine the Company’s stem cell platform with proprietary antibodies across up to four exclusive targets with HDPR’s proprietary Antibody Targeted Amanitin Conjugates platform. Under the agreement, the Company may pay upfront technology access fees, research exclusivity fees and payment for research support. Additionally, upon the exercise of certain license rights, the Company may be obligated to pay HDPR development, regulatory and commercial milestone payments of up to $83.5 million per target as well as royalties on net sales of products licensed under the agreement. During each of the years ended December 31, 2022 and 2021, the Company recorded $0.4 million of research and development expense related to this agreement for upfront technology access fees, research exclusivity fees and research support. During the year ended December 31, 2022, the Company recorded $2.0 million of research and development expense related to the achievement of a development milestone. During the year ended December 31, 2021, the Company did not incur any expense related to the achievement of these milestones.

Intellectual Property Licenses

The Company has a license agreement with the President and Fellows of Harvard College (“Harvard”), entered into in November 2016, for an exclusive, worldwide, royalty-bearing license for certain technologies related to conditioning and mobilization. The Company is obligated to pay Harvard maintenance fees of $0.1 million annually and to reimburse qualified expenses related to the patents. The Company is also obligated to pay milestone payments of up to $7.4 million for the first two licensed products upon the achievement of certain development and regulatory milestones and to pay royalties on a

product-by-product

and

country-by-country

basis on net sales of products licensed under the agreement. During the year ended December 31, 2022, the Company did not incur any expense related to the achievement of these milestones. During the year ended December 31, 2021, the Company recorded $0.1 million of expense related to the achievement of one of these milestones.

In November 2022, the Company entered into a license agreement with ImmunoGen, Inc. (“ImmunoGen”), for an exclusive, worldwide, royalty-bearing license for certain technology related to one of the Company’s conditioning programs. Upon execution of the agreement, the Company made a nonrefundable payment of $4.4 million in partial consideration for the license. The Company is also obligated to pay milestone payments of up to $125.0 million in the aggregate upon the achievement of certain development, regulatory and sales-based milestones and to pay single-digit royalties on a

product-by-product

and

country-by-country

basis on net sales of products licensed under the agreement. During the year ended December 31, 2022, the Company did not incur any expense related to the achievement of these milestones. Effective December 29, 2022, Michael Vasconcelles, a member of the Company’s board of directors, became ImmunoGen’s Executive Vice President of Research, Development, and Medical Affairs (see Note 12).

The Company has agreements with third parties in the normal course of business, under which it can license certain developed technologies. If the Company exercises its rights to license the respective technologies, it may be subject to additional fees and milestone payments. During the year ended December 31, 2022, the Company recorded research and development expense of $0.1 million related to the license of certain developed technologies under these agreements. During the year ended December 31, 2021, the Company did not incur any expense related to these licenses.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, 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. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2022.

Legal Proceedings

The Company is not currently a party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred.

Leases - Schedule of Weighted Average Remaining Lease Term And Discount Rate (Detail)	Dec. 31, 2022
Leases [Abstract]
Weighted-average remaining lease term - operating lease (in years)	5 years 2 months 1 day
Weighted-average discount rate - operating lease	11.00%

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 0	$ 0
Unrecognized tax benefits	$ 0	$ 0
Earliest tax year [Member]
Income Tax Disclosure [Line Items]
Open Tax Year	2019
State [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforward, amount	$ 3,400
Tax credit carryforward expiration year start	2030
Operating loss carryforward expiration year start	2035
State [Member] \| Expirable [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 272,600
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	272,900
Tax credit carryforward, amount	$ 12,900
Tax credit carryforward expiration year start	2035
Operating loss carryforward expiration year start	2035
Domestic Tax Authority [Member] \| Expirable [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 17,500
Domestic Tax Authority [Member] \| Non-expirable [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 255,400

Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Aug. 12, 2022	May 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Net proceeds from common stock			$ 2,904	$ 0
Common stock, voting rights			Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders.
ATM Program [Member]
Class of Stock [Line Items]
Stock issued, shares			1,644,200
Net proceeds from common stock			$ 2,800
Shelf [Member]
Class of Stock [Line Items]
Remaining value of securities available under the shelf			$ 247,000
Common Stock [Member]
Class of Stock [Line Items]
Stock issued, shares			1,644,200	9,599,998
Common Stock [Member] \| Private Placement [Member]
Class of Stock [Line Items]
Stock issued, shares		9,599,998
Stock issued, price per shares		$ 9
Net proceeds from common stock		$ 86,100
Maximum [Member]
Class of Stock [Line Items]
Shelf offering value	$ 250,000
Weighted Average [Member] \| ATM Program [Member]
Class of Stock [Line Items]
Stock issued, price per shares			$ 1.82
Cowen and Company LLC [Member] \| Maximum [Member]
Class of Stock [Line Items]
Common stock reserved for future issuance	$ 50,000
Cowen and Company LLC [Member] \| Maximum [Member] \| ATM Program [Member]
Class of Stock [Line Items]
Remaining value of securities available under the shelf			$ 47,000

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Feb. 07, 2023	Feb. 06, 2023	Jan. 31, 2023	Mar. 20, 2023	Dec. 31, 2022
Silicon Valley Bank [Member]
Subsequent Event [Line Items]
Deposit					$ 5.7
Cash and Cash Equivalents [Member] \| Silicon Valley Bank [Member]
Subsequent Event [Line Items]
Deposit					3.9
Restricted Cash [Member] \| Silicon Valley Bank [Member]
Subsequent Event [Line Items]
Deposit					$ 1.8
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of consecutive business day below closing minimum bid requirement			30 days
Minimum bid price requirement			$ 1
Minimum bid price requirements description			the Company has 180 calendar days, or until July 31, 2023, to regain compliance with the Minimum Bid Price Requirement. If the Company fails to satisfy the continued listing requirements of Nasdaq, such as the Minimum Bid Price Requirement, Nasdaq may take steps to delist its common stock.
Period granted to regain compliance with minimum bid requirement			180 days
Percentage of workforce reduction	84.00%
Severance and related cost	$ 5.4
Minimum fee payable under agreement		$ 1.5
Percentage of success fee of transaction value		1.00%
Subsequent Event [Member] \| SVB Bridge Bank [Member]
Subsequent Event [Line Items]
Deposit				$ 36.9
Subsequent Event [Member] \| Restricted Cash [Member] \| SVB Bridge Bank [Member]
Subsequent Event [Line Items]
Deposit				$ 1.8

Nature of the Business and Basis of Presentation

12 Months Ended

Dec. 31, 2022

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Magenta Therapeutics, Inc. (the “Company”) is a biotechnology company focused on improving stem cell transplantation. The Company was incorporated under the laws of the State of Delaware in June 2015 as HSCTCo Therapeutics, Inc. In February 2016, the Company changed its name to Magenta Therapeutics, Inc. and in June 2018 the Company completed an initial public offering of its common stock.

On February 2, 2023, after a review of the Company’s business, programs, resources and capabilities, including anticipated costs and timelines, the Company announced the decision to halt further development of its programs and to conduct a comprehensive review of strategic alternatives. The Company also announced a corporate restructuring on February 7, 2023 that resulted in a reduction in its workforce by 84% that was substantially completed in February 2023 resulting in severance and related costs of approximately $5.4 million (see Note 13).

As part of the strategic review process, the Company is exploring potential strategic alternatives that include, without limitation, an acquisition, merger, business combination or other transactions. The Company is also exploring strategic alternatives related to its product candidates and related assets, including, without limitation, licensing transactions and asset sales. There can be no assurance that the strategic review process will result in the Company pursuing a transaction, or that any transaction, if pursued, will be completed on terms favorable to the Company and its stockholders. If the strategic review process is unsuccessful, the Company may decide to pursue a dissolution and liquidation of the Company.

In addition, the Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, the continuing impact of the ongoing coronavirus

(“COVID-19”)

pandemic and the ability to secure additional capital to fund operations. 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 the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The Company has incurred recurring losses since inception, including net losses of $76.5 million and $71.1 million for the years ended December 31, 2022 and 2021, respectively. As of December 31, 2022, the Company had an accumulated deficit of $402.0 million. The Company expects to continue to generate operating losses for the foreseeable future. The Company expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the issuance date of these consolidated financial statements. The future viability of the Company beyond that point is dependent on the results of the strategic review process and its ability to raise additional capital to fund its operations.

The Company expects to continue to incur costs and expenditures in connection with the process of evaluating strategic alternatives. There can be no assurance, however, that the Company will be able to successfully consummate any particular strategic transaction. The process of continuing to evaluate these strategic options may be very costly, time-consuming and complex and the Company has incurred, and may in the future incur, significant costs related to this continued evaluation, such as legal, accounting and advisory fees and expenses and other related charges. Should the Company resume the development of its programs, it will need to obtain substantial additional funding in connection with continuing operations, particularly as the Company advances its preclinical activities and clinical trials for its product candidates in development. If the

Company is unable to raise capital when needed, or on attractive terms, it could be forced to delay, reduce or eliminate its research or drug development programs or any future commercialization efforts. There is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Stock-Based Compensation - Schedule of Activity Relating to Restricted Stock Units (Detail)	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance \| shares	289,918
Number of Shares, Granted \| shares	185,871
Number of Shares, Vested \| shares	(76,539)
Number of Shares, Forfeited \| shares	(142,006)
Number of Shares Outstanding, Ending Balance \| shares	257,244
Weighted Average Grant Date Fair Value Outstanding, Beginning Balance \| $ / shares	$ 7.79
Weighted Average Grant Date Fair Value, Granted \| $ / shares	1.9
Weighted Average Grant Date Fair Value, Vested \| $ / shares	6.46
Weighted Average Grant Date Fair Value,Forfeited \| $ / shares	6.97
Weighted Average Grant Date Fair Value Outstanding, Ending Balance \| $ / shares	$ 4.38
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance \| shares	190,000
Number of Shares, Granted \| shares	0
Number of Shares, Vested \| shares	0
Number of Shares, Forfeited \| shares	(20,000)
Number of Shares Outstanding, Ending Balance \| shares	170,000
Weighted Average Grant Date Fair Value Outstanding, Beginning Balance \| $ / shares	$ 9.91
Weighted Average Grant Date Fair Value, Granted \| $ / shares	0
Weighted Average Grant Date Fair Value, Vested \| $ / shares	0
Weighted Average Grant Date Fair Value,Forfeited \| $ / shares	7.51
Weighted Average Grant Date Fair Value Outstanding, Ending Balance \| $ / shares	$ 10.19

Leases

12 Months Ended

Dec. 31, 2022

Leases of Lessee Disclosure

8. Leases

The Company has a sublease, as amended, for up to approximately 69,000 square feet of office and laboratory space in Cambridge, Massachusetts. The sublease is subject and subordinate to a prime lease between the sublandlord and the prime landlord. The term of the sublease commenced in June 2018 and expires in February 2028. The sublandlord has the right to terminate the sublease after five years. The Company classified this sublease as an operating lease under ASC 842. The Company is obligated to pay real estate taxes and other costs related to the premises, including costs of operations and management of the leased premises. To the extent these costs are variable, they were not included in the measurement of the

right-of-use

asset and lease liability. In connection with the sublease, as amended, the sublandlord funded $5.2 million in tenant improvements to the leased facility during 2019. The Company is required to maintain a cash balance of $1.8 million to secure a letter of credit associated with the sublease. This amount was classified as noncurrent restricted cash in the consolidated balance sheets at December 31, 2022 and 2021.

As of December 31, 2021, the Company had long-term deferred rent of $6.4 million related to lease incentives and payment escalations. As of December 31, 2021, the short-term portion of deferred rent of $0.6 million was included in accrued expenses and other current liabilities. In connection with the adoption of ASC 842 on January 1, 2022, these amounts were recorded as a reduction to the operating lease,

right-of-use

asset.

The components of the Company’s lease expense under ASC 842 were as follows (in thousands):


	Year Ended December 31, 2022
Operating lease cost	$	6,407
Short-term lease cost		—
Variable lease cost		1,406

	$	7,813

Supplemental disclosure of cash flow information related to the lease was as follows (in thousands):


	Year Ended December 31, 2022
Cash paid for amounts included in the measurement of operating lease liabilities	$	6,567
Operating lease liabilities arising from obtaining right-of-use asset	$	—

The weighted average remaining lease term and discount rate were as follows:


	December 31, 2022
Weighted-average remaining lease term—operating lease (in years)		5.17
Weighted-average discount rate—operating lease		11.00	%

Because the interest rate implicit in the lease was not readily determinable, the Company’s estimated incremental borrowing rate was used to calculate the present value of the lease.

As of December 31, 2022, the future minimum lease payments due under the noncancelable operating lease was as follows (in thousands):


2023	$	6,936
2024		7,313
2025		7,679
2026		8,062
2027		8,466
Thereafter		1,439

Total future minimum lease payments		39,895
Less: imputed interest		(9,933	)

Total operating lease liabilities	$	29,962

The following table represents the lease liabilities on the consolidated balance sheet (in thousands):


	December 31, 2022
Current operating lease liability	$	3,824
Operating lease liability, net of current portion		26,138

Total operating lease liabilities	$	29,962

As previously disclosed in the Company’s Annual Report on Form

10-K

and under the previous lease accounting standard, ASC 840,

Leases

, the following table summarizes the future minimum lease payments due under the operating lease as of December 31, 2021 (in thousands):


2022	$	6,375
2023		6,734
2024		7,100
2025		7,455
2026		7,828
Thereafter		9,617

	$	45,109

Rent expense for the year ended December 31, 2021 was $6.2 million.

In 2018, the Company entered into two

sub-subleases

of approximately 27,000 square feet of office space in Cambridge, Massachusetts. One of the

sub-subleases,

as amended, expired in December 2021. The remaining

sub-sublease,

as amended, was set to expire in April 2022 but was further amended to increase the square footage from 13,643 square feet to 26,114 square feet and to extend the expiration to April 2024. As of December 31, 2022, the remaining base rent payments due to the Company under the amended

sub-sublease

was $3.6 million. The Company recorded other income of $3.1 million and $3.5 million during the years ended December 31, 2022 and 2021, respectively, related to these

sub-subleases.

Income Taxes - Schedule of Reconciliation of U.S. Federal Statutory Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Federal statutory income tax rate	21.00%	21.00%
State taxes, net of federal benefit	5.90%	5.80%
Research and orphan drug tax credits	(4.10%)	3.30%
Other	1.10%	0.50%
Increase in deferred tax asset valuation allowance	29.90%	(30.60%)
Effective income tax rate	0.00%	0.00%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

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,
	2022			2021
Federal statutory income tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		5.9			5.8
Research and orphan drug tax credits		4.1			3.3
Other		(1.1	)		0.5
Increase in deferred tax asset valuation allowance		(29.9	)		(30.6	)

Effective income tax rate		—	%		—	%

Company's Deferred Tax Assets

Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands):


	December 31,
	2022			2021
Deferred tax assets:
Net operating loss carryforwards	$	73,843		$	67,236
Capitalized research and development expenses		20,137			8,665
Research and orphan drug tax credit carryforwards		15,550			12,370
Operating lease liability		8,110			—
Stock compensation expense		6,683			5,430
Accrued expense		1,112			936
Other		—			1,891

Total deferred tax assets		125,435			96,528
Valuation allowance		(118,215	)		(95,367	)

Net deferred tax assets		7,220			1,161

Deferred tax liabilities:
Operating lease, right-of-use asset		(6,271	)		—
Depreciation and amortization		(949	)		(1,161	)

Total deferred tax liabilities		(7,220	)		(1,161	)

Net deferred tax assets and liabilities	$	—		$	—

Changes in Deferred Tax Asset Valuation Allowance

During the year ended December 31, 2022, capitalized research and development expenses increased pursuant to Section 174 of the Code. The changes in the valuation allowance for the years ended December 31, 2022 and 2021 and were as follows (in thousands):


	Year Ended December 31,
	2022		2021
Valuation allowance as of beginning of year	$	95,367	$	73,600
Net increases recorded to income tax provision		22,848		21,767

Valuation allowance as of end of year	$	118,215	$	95,367

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Nov. 30, 2022	Mar. 31, 2018	Nov. 30, 2016
Other Commitments [Line Items]
Research and development expense	$ 55,141	$ 46,766
Achievement of Development Milestone [Member]
Other Commitments [Line Items]
Research and development expense	2,000
Collaboration Agreement [Member]
Other Commitments [Line Items]
Research and development expense	400	400
Collaboration Agreement [Member] \| Development, Regulatory and Commercial Milestone [Member] \| Per Target [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due				$ 83,500
License Agreement With Harvard [Member] \| Maintenance [Member] \| Annual [Member]
Other Commitments [Line Items]
Payment obligation					$ 100
License Agreement With Harvard [Member] \| Achievement of Development and Regulatory Milestones [Member]
Other Commitments [Line Items]
Research and development expense	0	100
License Agreement With Harvard [Member] \| Achievement of Development and Regulatory Milestones [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due	7,400
License Agreement With Third Parties [Member] \| License [Member]
Other Commitments [Line Items]
Research and development expense	$ 100	$ 0
License Agreement [Member]
Other Commitments [Line Items]
Upfront nonrefundable payment			$ 4,400
License Agreement [Member] \| Achievement of Development and Regulatory Milestones [Member] \| Maximum [Member]
Other Commitments [Line Items]
Potential milestone payments due			$ 125,000

Stock-Based Compensation - Schedule of Common Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning Balance	6,248,675
Number of Shares, Granted	4,509,673
Number of Shares, Exercised	0
Number of Shares, Forfeited	(2,282,532)
Number of Shares, Ending Balance	8,475,816	6,248,675
Number of Shares, Options vested and expected to vest as of December 31, 2022	8,475,816
Number of Shares, Options exercisable as of December 31, 2020	3,641,107
Weighted-Average Exercise Price, Outstanding, Beginning balance	$ 9.15
Weighted-Average Exercise Price, Granted	2.13
Weighted-Average Exercise Price, Exercised	0
Weighted-Average Exercise Price, Forfeited	7.31
Weighted-Average Exercise Price, Outstanding, Ending balance	5.91	$ 9.15
Weighted-Average Exercise Price, Options vested and expected to vest as of December 31, 2022	5.91
Weighted-Average Exercise Price, Options exercisable as of December 31, 2022	$ 8.27
Weighted Average Remaining Contractual Term	8 years 2 months 12 days	8 years 2 months 12 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest as of December 31, 2022	8 years 2 months 12 days
Weighted Average Remaining Contractual Term, Options exercisable as of December 31, 2022	7 years 1 month 6 days
Aggregate Intrinsic Value, Beginning Balance	$ 0

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 55,141	$ 46,766
General and administrative	25,761	27,926
Total operating expenses	80,902	74,692
Loss from operations	(80,902)	(74,692)
Interest and other income, net	4,440	3,556
Net loss	$ (76,462)	$ (71,136)
Net loss per share, basic	$ (1.29)	$ (1.29)
Net loss per share, diluted	$ (1.29)	$ (1.29)
Weighted average common shares outstanding, basic	59,372,357	54,948,808
Weighted average common shares outstanding, diluted	59,372,357	54,948,808
Comprehensive loss:
Net loss	$ (76,462)	$ (71,136)
Other comprehensive loss:
Unrealized losses on marketable securities	(151)	(7)
Total other comprehensive loss	(151)	(7)
Total comprehensive loss	$ (76,613)	$ (71,143)

Income Taxes - Changes in Deferred Tax Asset Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Valuation allowance as of beginning of year	$ 95,367	$ 73,600
Net increases recorded to income tax provision	22,848	21,767
Valuation allowance as of end of year	$ 118,215	$ 95,367

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2022

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2022		2021
Accrued payroll and related expenses	$	4,162	$	3,346
Accrued external research and development expenses		3,091		2,813
Deferred rent, current portion		—		555
Accrued other		1,018		1,109

	$	8,271	$	7,823

401(k) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Defined contribution plan, Employer matching contribution, percent of employees' gross pay	2.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.2	$ 0.1

Accrued Expenses

12 Months Ended

Dec. 31, 2022

Accrued Expenses

5. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2022		2021
Accrued payroll and related expenses	$	4,162	$	3,346
Accrued external research and development expenses		3,091		2,813
Deferred rent, current portion		—		555
Accrued other		1,018		1,109

	$	8,271	$	7,823

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2022

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Concentrations of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains all cash, cash equivalents and marketable securities at two accredited financial institutions in amounts that exceed federally insured limits (see Note 13).

The Company has been dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company has historically relied on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.

Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Marketable Securities

The Company’s marketable securities are classified as

available-for-sale

and are carried at fair value with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Realized gains and losses and declines in value judged to be other than temporary are included as a component of interest and other income, net based on the specific identification method. The Company classifies its marketable securities with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities are available for current operations.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


		Estimated Useful Life
Lab equipment		5 years
Computer equipment		3 years
Furniture and fixtures		5 years
Leasehold improvements		Shorter of life of lease or estimated useful life

Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment and

right-of-use

assets. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2022 or 2021.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined 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 on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

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

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, 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 determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

Leases

Prior to January 1, 2022, the Company accounted for leases under ASC 840,

Leases

(“ASC 840”). Effective January 1, 2022, the Company accounts for leases under ASC 842,

Leases

(“ASC 842”). Therefore, as of December 31, 2021, the Company’s consolidated financial statements continue to be presented in accordance with ASC 840, the accounting standard originally in effect for such period. As of and for the year ended December 31, 2022, the Company’s consolidated financial statements are presented in accordance with ASC 842.

In accordance with ASC 842, the Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset’s economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its

right-of-use

asset and lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. The Company’s policy is to not record leases with an original term of twelve months or less on its consolidated balance sheets and recognizes those lease payments in the income statement on a straight-line basis over the lease term. The Company’s existing leases are for office and laboratory space.

In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as

non-lease

components. The Company has elected to not separate lease and

non-lease

components. Only the fixed costs for lease components and their associated

non-lease

components are accounted for as a single lease component and recognized as part of a

right-of-use

asset and lease liability. Rent expense for operating leases is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expense in the consolidated statements of operations and comprehensive loss.

Deferred Rent

The Company’s lease agreements include payment escalations and lease incentives, which, prior to the adoption of ASC 842

on January 1, 2022, were accrued or deferred as appropriate such that rent expense for each lease was recognized on a straight-line basis over the respective lease term. Adjustments for such items, consisting primarily of tenant improvement allowances and payment escalations, were recorded as deferred rent and amortized over the lease term.

Segment Information

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. All of the Company’s tangible assets are held in the United States.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits, facilities costs, depreciation, manufacturing expenses and external costs of outside vendors engaged to conduct preclinical development activities and clinical trials as well as the cost of licensing technology.

Upfront payments and milestone payments made for the licensing of technology are expensed as research and development in the period in which they are incurred. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Research, Development and Manufacturing Contract Costs Accruals

The Company has entered into various research, development and manufacturing contracts with research institutions and other companies both inside and outside of the United States. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research, development and manufacturing costs. When evaluating the adequacy of any accrual estimate, the Company analyzes a number of factors, including the Company’s knowledge of the progress of the studies or trials, including the phase or completion of events; invoices received to date under the contracts; communication from the third parties of any actual costs incurred during the period that have not yet been invoiced; and the costs included in the contracts. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock-Based Compensation

The Company measures compensation expense for all stock options and other stock-based awards granted to employees, directors and

non-employees

based on the fair value on the date of grant and recognizes such compensation expense over the requisite service period, which is generally the vesting period of the respective award. Generally, the Company issues awards with either service-only vesting conditions and records the expense using the straight-line method or service and performance vesting conditions and records the expense when achievement of the performance condition becomes probable using the graded-vesting method. The Company accounts for forfeitures as they occur.

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, the Company estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies along with the volatility of its own stock and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in

effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in its consolidated financial statements by applying a

two-step

process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed

more-likely-than-not

to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2022 and 2021, the Company’s only element of other comprehensive income (loss) was unrealized gains (losses) on marketable securities.

Net Loss per Share

Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) per share is computed by dividing net income (loss) by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock options. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their affect is anti-dilutive.

The Company reported a net loss for the years ended December 31, 2022 and 2021. The following potential dilutive securities, presented based on amounts outstanding at each period end, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact:


	As of December 31,
	2022		2021
Stock options to purchase common stock		8,475,816		6,248,675
Unvested restricted common stock units		427,244		479,918
Shares of common stock issuable under Employee Stock Purchase Plan		72,611		42,634

		8,975,671		6,771,227

Recently Issued Accounting Pronouncements

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326)

. The new standard adjusts the accounting for assets held at amortized costs basis, including marketable securities accounted for as available for sale. 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. For public entities, the guidance was effective for annual reporting periods beginning after December 15, 2019 and for interim periods within those fiscal years. For nonpublic entities and emerging growth companies that choose to take advantage of the extended transition period, the guidance is effective for annual reporting periods beginning after December 15, 2020. Early adoption is permitted for all entities. In November 2019, the FASB issued ASU

No. 2019-10,

which deferred the effective date for nonpublic entities and emerging growth companies to annual reporting periods beginning after December 15, 2022, including interim periods within those fiscal years. The Company does not believe the guidance will have a material impact on its consolidated financial statements.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU

No. 2016-02,

Leases (Topic 842)

(“ASU

2016-02”),

which require lessees to recognize most leases on their balance sheet as a

right-of-use

asset and a lease liability. In general, lease arrangements exceeding a twelve-month term must be recognized as assets and liabilities on the balance sheet. Under ASU

2016-02,

right-of-use

asset and lease obligation is recorded for all leases, whether operating or financing, while the income statement reflects lease expense for operating leases and amortization and interest expense for financing leases. The FASB also issued ASU

2018-10,

Codification Improvements to Topic 842

Leases

, and ASU

2018-11,

Targeted Improvements to Topic 842 Leases

, which allows the new lease standard to be applied as of the adoption date with a cumulative-effect adjustment to the opening balance of retained earnings rather than retroactive restatement of all periods presented. The Company adopted the new leasing standards on January 1, 2022 using a modified retrospective approach applied at the beginning of the period of adoption.

The Company elected the “package of practical expedients,” which permits the Company not to reassess under the new standards for prior conclusions about lease identification, lease classification and initial direct costs. The Company did not apply the hindsight practical expedient when determining the lease term for existing leases and assessing impairment of expired or existing leases. The Company elected to utilize its incremental borrowing rate based on the remaining lease term as of the date of adoption. In connection with the adoption of ASU

2016-02,

the Company recognized a

right-of-use

asset of $26.1 million and lease liabilities of $33.0 million on its consolidated balance sheet. The deferred rent balance of $7.0 million as of January 1, 2022 was recorded as an offset to the Company’s

right-of-use

asset. The adoption of the standard did not have a material impact on the Company’s results of operations or cash flows.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2022

Stock-Based Compensation

7. Stock-Based Compensation

2018 Stock Option and Incentive Plan

The Magenta Therapeutics, Inc. 2018 Stock Option and Incentive Plan (the “2018 Plan”) provides for the grant of incentive stock options,

non-statutory

stock options, restricted stock, restricted stock units, stock appreciation rights, performance units and performance shares to employees, directors and consultants. Shares of common stock underlying any awards under the 2018 Plan and the Magenta Therapeutics, Inc. 2016 Stock Option and Grant Plan (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 2018 Plan. As of December 31, 2022, 3,102,231 shares remained available for future grants under the 2018 Plan.

The 2018 Plan provides that the number of shares reserved and available for issuance under the 2018 Plan will automatically increase each January 1 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 compensation committee. This number is subject to adjustment in the event of a stock split, stock dividend or other change in capitalization. The number of shares reserved for issuance under the 2018 Plan was increased by 2,425,596 shares effective January 1, 2023.

2016 Stock Option and Grant Plan

The Company also has outstanding stock options and restricted stock awards under the 2016 Plan, but is no longer granting awards under this plan.

The 2018 Plan is administered by the board of directors, or at the discretion of the board of directors, by a committee of the board. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or their committee if so delegated, except that the term of awards may not be greater than ten years. Vesting periods are determined at the discretion of the board of directors. Awards typically vest over eighteen 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. The fair value of common stock is based on quoted market prices.

2019 Employee Stock Purchase Plan

Employees may elect to participate in the Magenta 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 begin in December and June of each year. During the year ended December 31, 2022, 120,013 shares of common stock were purchased under the ESPP at a purchase price per share of $0.96. During the year ended December 31, 2021, 25,563 shares of common stock were purchased under the ESPP at a weighted average purchase price of $5.53 per share. The Company recognized $0.1 million and less than $0.1 million of stock-based compensation during the years ended December 31, 2022 and 2021, respectively, related to the ESPP. As of December 31, 2022, 593,239 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) 1,000,000 shares and (iii) such number of shares as determined by the compensation committee of the Company’s board of directors. The number of shares reserved for issuance under the ESPP did not increase on January 1, 2023.

Common Stock Option Valuation

The assumptions that the Company used to determine the fair value of options granted were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2022			2021
Risk-free interest rate		2.5	%		0.9	%
Expected term (in years)		5.9			6.0
Expected volatility		81.2	%		80.5	%
Expected dividend yield		0	%		0	%

Common Stock Option Activity

The following table summarizes the Company’s option activity since December 31, 2021:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2021		6,248,675		$	9.15		8.2	$	—
Granted		4,509,673		$	2.13
Exercised		—		$	—
Forfeited		(2,282,532	)	$	7.31

Outstanding as of December 31, 2022		8,475,816		$	5.91		8.2	$	—

Options vested and expected to vest as of December 31, 2022		8,475,816		$	5.91		8.2	$	—

Options exercisable as of December 31, 2022		3,641,107		$	8.27		7.1	$	—

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

the fair value of the Company’s common stock. There were no option exercises during the year ended December 31, 2022. The aggregate intrinsic value of options exercised during the year ended December 31, 2021 was $1.3 million.

The weighted average grant-date fair value per share of stock options granted during the years ended December 31, 2022 and 2021 was $1.48 and $6.32, respectively.

Restricted Stock Units

The Company granted service-based restricted stock units to certain employees which vests over eighteen months to four years. Upon vesting, each restricted stock unit entitles the holder to a specified number of shares of common stock.

The table below summarizes the Company’s restricted stock unit activity since December 31, 2021:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		289,918		$	7.79
Granted		185,871		$	1.90
Vested		(76,539	)	$	6.46
Forfeited		(142,006	)	$	6.97

Outstanding as of December 31, 2022		257,244		$	4.38

The total fair value of restricted stock units vested during the years ended December 31, 2022 and 2021 was $0.1 million and $0.3 million, respectively.

Performance Restricted Stock Units

The Company grants performance-based restricted stock units to certain senior employees which vest upon the occurrence of certain operational and financial events. At the achievement of the performance-based vesting criteria, each performance-based restricted stock unit entitles the holder to a specified number of shares of common stock.

The table below summarizes the Company’s performance restricted stock unit activity since December 31, 2021:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		190,000		$	9.91
Granted		—		$	—
Vested		—		$	—
Forfeited		(20,000	)	$	7.51

Outstanding as of December 31, 2022		170,000		$	10.19

There was no performance restricted stock units vested during the year ended December 31, 2022. The total fair value of performance restricted stock units vested during the year ended December 31, 2021 was $1.0 million.

Stock-Based Compensation

Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows (in thousands):


	Year Ended December 31,
	2022		2021
Research and development expenses	$	1,877	$	3,836
General and administrative expenses		5,144		6,472

	$	7,021	$	10,308

As of December 31, 2022, unrecognized compensation expense related to unvested share-based awards with service-based vesting conditions was $13.6 million, which is expected to be recognized over a weighted average period of 2.2 years. Additionally, the Company had unrecognized compensation cost of $1.7 million related to the unvested performance restricted stock units for which the performance conditions were not considered probable of achievement as of December 31, 2022.

Marketable Securities and Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 54,415	$ 45,276
Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	111,078	176,818
Level 1 [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	56,663	131,542
Level 2 [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	54,415	45,276
Money Market Funds [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	56,663	131,542
Money Market Funds [Member] \| Level 1 [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	56,663	131,542
US Treasury Notes [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	54,415	45,276
US Treasury Notes [Member] \| Level 1 [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
US Treasury Notes [Member] \| Level 2 [Member] \| Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 54,415	$ 45,276

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2022

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

Concentrations of Credit Risk and of Significant Suppliers

Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Marketable Securities

The Company’s marketable securities are classified as

available-for-sale

Property and Equipment


		Estimated Useful Life
Lab equipment		5 years
Computer equipment		3 years
Furniture and fixtures		5 years
Leasehold improvements		Shorter of life of lease or estimated useful life

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment and

right-of-use

Fair Value Measurements

•

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

•

Leases

Prior to January 1, 2022, the Company accounted for leases under ASC 840,

Leases

(“ASC 840”). Effective January 1, 2022, the Company accounts for leases under ASC 842,

Leases

right-of-use

In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as

non-lease

components. The Company has elected to not separate lease and

non-lease

components. Only the fixed costs for lease components and their associated

non-lease

components are accounted for as a single lease component and recognized as part of a

right-of-use

Deferred Rent

The Company’s lease agreements include payment escalations and lease incentives, which, prior to the adoption of ASC 842

Segment Information

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. All of the Company’s tangible assets are held in the United States.

Research and Development Costs

Research, Development and Manufacturing Contract Costs Accruals

Patent Costs

Stock-Based Compensation

The Company measures compensation expense for all stock options and other stock-based awards granted to employees, directors and

non-employees

Income Taxes

The Company accounts for uncertainty in income taxes recognized in its consolidated financial statements by applying a

two-step

more-likely-than-not

Comprehensive Loss

Net Loss per Share


	As of December 31,
	2022		2021
Stock options to purchase common stock		8,475,816		6,248,675
Unvested restricted common stock units		427,244		479,918
Shares of common stock issuable under Employee Stock Purchase Plan		72,611		42,634

		8,975,671		6,771,227

Recently Issued Accounting Pronouncements

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326)

No. 2019-10,

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU

No. 2016-02,

Leases (Topic 842)

(“ASU

2016-02”),

which require lessees to recognize most leases on their balance sheet as a

right-of-use

asset and a lease liability. In general, lease arrangements exceeding a twelve-month term must be recognized as assets and liabilities on the balance sheet. Under ASU

2016-02,

right-of-use

2018-10,

Codification Improvements to Topic 842

Leases

, and ASU

2018-11,

Targeted Improvements to Topic 842 Leases

2016-02,

the Company recognized a

right-of-use

asset. The adoption of the standard did not have a material impact on the Company’s results of operations or cash flows.

Marketable Securities and Fair Value Measurements - Schedule of Marketable Securities by Security Type (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Amortized Cost	$ 54,596	$ 45,306
Gross Unrealized Gains	2
Gross Unrealized Losses	(183)	(30)
Estimated Fair Value	54,415	45,276
US Treasury Notes [Member] \| Due With In One Year [Member]
Marketable Securities [Line Items]
Amortized Cost	54,596	30,213
Gross Unrealized Gains	2
Gross Unrealized Losses	(183)	(20)
Estimated Fair Value	$ 54,415	30,193
US Treasury Notes [Member] \| Due After One Year Through Two Years [Member]
Marketable Securities [Line Items]
Amortized Cost		15,093
Gross Unrealized Losses		(10)
Estimated Fair Value		$ 15,083

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Schedule of Estimated Useful Life of Asset

Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


		Estimated Useful Life
Lab equipment		5 years
Computer equipment		3 years
Furniture and fixtures		5 years
Leasehold improvements		Shorter of life of lease or estimated useful life

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following potential dilutive securities, presented based on amounts outstanding at each period end, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact:


	As of December 31,
	2022		2021
Stock options to purchase common stock		8,475,816		6,248,675
Unvested restricted common stock units		427,244		479,918
Shares of common stock issuable under Employee Stock Purchase Plan		72,611		42,634

		8,975,671		6,771,227

Marketable Securities and Fair Value Measurements

12 Months Ended

Dec. 31, 2022

Marketable Securities And Fair Value Measurements

3. Marketable Securities and Fair Value Measurements

As of December 31, 2022, marketable securities by security type consisted of (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury notes (due within one year)	$	54,596	$	2	$	(183	)	$	54,415

Total	$	54,596	$	2	$	(183	)	$	54,415

As of December 31, 2021, marketable securities by security type consisted of (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury notes (due within one year)	$	30,213	$	—	$	(20	)	$	30,193
U.S. treasury notes (due after one year through two years)		15,093		—		(10	)		15,083

Total	$	45,306	$	—	$	(30	)	$	45,276


	Fair Value Measurements at December 31, 2022 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	56,663	$	—	$	—	$	56,663
Marketable securities:
U.S. treasury notes		—		54,415		—		54,415

Total	$	56,663	$	54,415	$	—	$	111,078


	Fair Value Measurements at December 31, 2021 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	131,542	$	—	$	—	$	131,542
Marketable securities:
U.S. treasury notes		—		45,276		—		45,276

Total	$	131,542	$	45,276	$	—	$	176,818

Income Taxes - Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 73,843	$ 67,236
Capitalized research and development expenses	20,137	8,665
Research and orphan drug tax credit carryforwards	15,550	12,370
Operating Lease Liability	8,110	0
Stock compensation expense	6,683	5,430
Accrued expense	1,112	936
Other	0	1,891
Total deferred tax assets	125,435	96,528
Valuation allowance	(118,215)	(95,367)	$ (73,600)
Net deferred tax assets	7,220	1,161
Deferred tax liabilities:
Operating lease, right-of-use asset	6,271	0
Depreciation and amortization	(949)	(1,161)
Total deferred tax liabilities	(7,220)	(1,161)
Net deferred tax assets and liabilities	$ 0	$ 0

Leases - Schedule of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Current operating lease liability	$ 3,824	$ 0
Operating lease liability, net of current portion	26,138	$ 0
Total operating lease liabilities	$ 29,962

Related Parties

12 Months Ended

Dec. 31, 2022

Related Parties

12. Related Parties

Effective December 29, 2022, Michael Vasconcelles, a member of t

he Com

pany’s board of directors, became ImmunoGen’s Executive Vice President of Research, Development, and Medical Affairs. The Company and ImmunoGen entered into a license agreement in November 2022 (see Note 9) and a Material Transfer and Evaluation Agreement, as amended, in August 2020. For the year ended December 31, 2022, the Company recorded expense of $4.6 million related to these agreements. As of December 31, 2022, amounts on the consolidated balance sheet related to these agreements was $0.1 million which was included in accounts payable and accrued expenses.

Effective March 2018, Amy Lynn Ronneberg, the then serving President of Be The Match BioTherapies, LLC, became a member of the Company’s board of directors and subsequently was appointed Chief Executive Officer of the National Marrow Donor Program/Be The Match, or NMDP/Be The Match, organization in June 2020. The Company has collaboration agreements with the National Marrow Donor Program (as successor in interest to Be The Match BioTherapies Collection Services, LLC (formerly known as Be The Match BioTherapies, LLC)) and a research agreement with an affiliated organization, Center for International Blood and Marrow Transplant Research. In addition, in June 2020, the Company entered into a clinical collaboration agreement with NMDP/Be The Match to evaluate the potential utility of

MGTA-145

for mobilizing and collecting hematopoietic stem cells from donors in a single day and then using them for allogeneic transplant in patients. Under the terms of this agreement, the Company shall fund up to fifty percent of NMDP/Be The Match clinical trial costs and provide the trial drugs which will be incl

uded i

n research and development expense. For the years ended December 31, 2022 and 2021, the Company recorded expense of $0.3 million and $0.7 million, respectively, related to these agreements. As of December 31, 2022 and 2021, amounts on the consolidated balance sheets related to these agreements were $0.1 million and $0.2 million, respectively, which amounts were included in accounts payable and accrued expenses and other current liabilities and less than $0.1 million as of December 31, 2021, which amount was included in prepaid expenses and other current assets.

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued payroll and related expenses	$ 4,162	$ 3,346
Accrued external research and development expenses	3,091	2,813
Deferred rent, current portion		555
Accrued other	1,018	1,109
Total	$ 8,271	$ 7,823

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Schedule of Assumptions Used to Determine the Fair Value of Option Grants

The assumptions that the Company used to determine the fair value of options granted were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2022			2021
Risk-free interest rate		2.5	%		0.9	%
Expected term (in years)		5.9			6.0
Expected volatility		81.2	%		80.5	%
Expected dividend yield		0	%		0	%

Schedule of Common Stock Option Activity

The following table summarizes the Company’s option activity since December 31, 2021:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2021		6,248,675		$	9.15		8.2	$	—
Granted		4,509,673		$	2.13
Exercised		—		$	—
Forfeited		(2,282,532	)	$	7.31

Outstanding as of December 31, 2022		8,475,816		$	5.91		8.2	$	—

Options vested and expected to vest as of December 31, 2022		8,475,816		$	5.91		8.2	$	—

Options exercisable as of December 31, 2022		3,641,107		$	8.27		7.1	$	—

Schedule of Stock Based Compensation Expense

Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows (in thousands):


	Year Ended December 31,
	2022		2021
Research and development expenses	$	1,877	$	3,836
General and administrative expenses		5,144		6,472

	$	7,021	$	10,308

Restricted Stock Units (RSUs) [Member]

Schedule of Activity Relating to Restricted Stock Units

The table below summarizes the Company’s restricted stock unit activity since December 31, 2021:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		289,918		$	7.79
Granted		185,871		$	1.90
Vested		(76,539	)	$	6.46
Forfeited		(142,006	)	$	6.97

Outstanding as of December 31, 2022		257,244		$	4.38

Performance Restricted Stock Units [Member]

Schedule of Activity Relating to Restricted Stock Units

The table below summarizes the Company’s performance restricted stock unit activity since December 31, 2021:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		190,000		$	9.91
Granted		—		$	—
Vested		—		$	—
Forfeited		(20,000	)	$	7.51

Outstanding as of December 31, 2022		170,000		$	10.19

Leases - Schedule of Components of the Company's Lease Expense (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Lease, Cost [Abstract]
Operating lease cost	$ 6,407
Short-term lease cost	0
Variable lease cost	1,406
Lease cost	$ 7,813