Dianthus Therapeutics (DNTH) 10-Q 4 Aug 22 2022 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2022	Jul. 31, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Entity Registrant Name	Magenta Therapeutics, Inc.
Trading Symbol	MGTA
Entity Central Index Key	0001690585
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Ex Transition Period	false
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Shell Company	false
Entity Tax Identification Number	81-0724163
Title of 12(b) Security	Common Stock
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	100 Technology Square
Entity Address, City or Town	Cambridge
Entity Address, Postal Zip Code	02139
Entity Address, State or Province	MA
Entity File Number	001-38541
City Area Code	857
Local Phone Number	242-0170
Entity Common Stock, Shares Outstanding		58,890,486

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 54,832	$ 131,650
Marketable securities	84,593	45,276
Prepaid expenses and other current assets	2,617	3,767
Total current assets	142,042	180,693
Restricted cash	1,780	1,780
Operating lease, right-of-use asset	24,670	0
Property and equipment, net	6,629	7,461
Total assets	175,121	189,934
Current liabilities:
Accounts payable	2,047	3,040
Accrued expenses and other current liabilities	5,786	7,823
Operating lease liability, current portion	3,423	0
Total current liabilities	11,256	10,863
Operating lease liability, net of current portion	28,187	0
Deferred rent	0	6,399
Total liabilities	39,443	17,262
Commitments and contingencies (Note 7)
Stockholders' Equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 150,000,000 shares authorized; 58,848,861 and 58,799,157 shares issued and outstanding as of June 30, 2022 and December 31, 2021, respectively	59	59
Additional paid-in capital	502,009	498,210
Accumulated other comprehensive loss	(602)	(30)
Accumulated deficit	(365,788)	(325,567)
Total stockholders' equity	135,678	172,672
Total liabilities and stockholders' equity	$ 175,121	$ 189,934

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 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	58,848,861	58,848,861
Common stock, Shares outstanding	58,799,157	58,799,157

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses:
Research and development	$ 11,603	$ 11,129	$ 28,150	$ 22,857
General and administrative	6,480	6,481	13,767	13,450
Total operating expenses	18,083	17,610	41,917	36,307
Loss from operations	(18,083)	(17,610)	(41,917)	(36,307)
Interest and other income, net	812	682	1,696	1,890
Net loss	$ (17,271)	$ (16,928)	$ (40,221)	$ (34,417)
Net loss per share, basic	$ (0.29)	$ (0.32)	$ (0.68)	$ (0.67)
Net loss per share, diluted	$ (0.29)	$ (0.32)	$ (0.68)	$ (0.67)
Weighted average common shares outstanding, basic	58,815,543	53,705,289	58,807,395	51,150,391
Weighted average common shares outstanding, diluted	58,815,543	53,705,289	58,807,395	51,150,391
Comprehensive loss:
Net loss	$ (17,271)	$ (16,928)	$ (40,221)	$ (34,417)
Other comprehensive income (loss):
Unrealized gains (losses) on marketable securities	(133)	(7)	(572)	25
Total other comprehensive income (loss)	(133)	(7)	(572)	25
Total comprehensive loss	$ (17,404)	$ (16,935)	$ (40,793)	$ (34,392)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Private Placement [Member]	Common Stock [Member]	Common Stock [Member] Private Placement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Private Placement [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 upon private investment, net of offering costs		$ 86,097		$ 10		$ 86,087
Issuance of common stock upon private investment, net of offering costs, shares				9,599,998
Vesting of restricted stock, shares			8,466
Issuance of common stock upon exercise of stock options	2,869				2,869
Issuance of common stock upon exercise of stock options, shares			353,147
Issuance of common stock under Employee Stock Purchase Plan	86				86
Issuance of common stock under Employee Stock Purchase Plan, shares			13,989
Stock-based compensation expense	4,326				4,326
Unrealized gains (losses) on marketable securities	25						25
Net loss	(34,417)							(34,417)
Ending balance at Jun. 30, 2021	202,892		$ 59		491,679		2	(288,848)
Ending balance, shares at Jun. 30, 2021			58,508,735
Beginning balance at Dec. 31, 2020	143,906		$ 49		398,311		(23)	(254,431)
Beginning balance, shares at Dec. 31, 2020			48,533,135
Net loss	(71,100)
Ending balance at Dec. 31, 2021	172,672		$ 59		498,210		(30)	(325,567)
Ending balance, shares at Dec. 31, 2021			58,799,157
Beginning balance at Mar. 31, 2021	129,059		$ 49		400,921		9	(271,920)
Beginning balance, shares at Mar. 31, 2021			48,603,205
Issuance of common stock upon private investment, net of offering costs		$ 86,097		$ 10		$ 86,087
Issuance of common stock upon private investment, net of offering costs, shares				9,599,998
Issuance of common stock upon exercise of stock options	2,451				2,451
Issuance of common stock upon exercise of stock options, shares			291,543
Issuance of common stock under Employee Stock Purchase Plan	86				86
Issuance of common stock under Employee Stock Purchase Plan, shares			13,989
Stock-based compensation expense	2,134				2,134
Unrealized gains (losses) on marketable securities	(7)						(7)
Net loss	(16,928)							(16,928)
Ending balance at Jun. 30, 2021	202,892		$ 59		491,679		2	(288,848)
Ending balance, shares at Jun. 30, 2021			58,508,735
Beginning balance at Dec. 31, 2021	172,672		$ 59		498,210		(30)	(325,567)
Beginning balance, shares at Dec. 31, 2021			58,799,157
Issuance of common stock under Employee Stock Purchase Plan	49				49
Issuance of common stock under Employee Stock Purchase Plan, shares			49,704
Stock-based compensation expense	3,750				3,750
Unrealized gains (losses) on marketable securities	(572)						(572)
Net loss	(40,221)							(40,221)
Ending balance at Jun. 30, 2022	135,678		$ 59		502,009		(602)	(365,788)
Ending balance, shares at Jun. 30, 2022			58,848,861
Beginning balance at Mar. 31, 2022	151,188		$ 59		500,115		(469)	(348,517)
Beginning balance, shares at Mar. 31, 2022			58,799,157
Issuance of common stock under Employee Stock Purchase Plan	49				49
Issuance of common stock under Employee Stock Purchase Plan, shares			49,704
Stock-based compensation expense	1,845				1,845
Unrealized gains (losses) on marketable securities	(133)						(133)
Net loss	(17,271)							(17,271)
Ending balance at Jun. 30, 2022	$ 135,678		$ 59		$ 502,009		$ (602)	$ (365,788)
Ending balance, shares at Jun. 30, 2022			58,848,861

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (40,221)	$ (34,417)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,750	4,326
Depreciation and amortization expense	988	953
Loss on disposal of property and equipment		90
Noncash lease expense	1,418
Net amortization of premiums on marketable securities	228	437
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,150	311
Accounts payable	(993)	(1,996)
Accrued expenses and other current liabilities	(1,482)	402
Operating lease liabilities	(1,432)
Deferred rent		120
Net cash used in operating activities	(36,594)	(29,774)
Cash flows from investing activities:
Purchases of property and equipment	(156)	(118)
Purchases of marketable securities	(40,117)
Maturities of marketable securities		37,500
Net cash provided by (used in) investing activities	(40,273)	37,382
Cash flows from financing activities:
Proceeds from private investment		86,400
Payments of offering costs		(81)
Proceeds from exercise of common stock options		2,869
Proceeds from issuance of common stock under Employee Stock Purchase Plan	49	86
Net cash provided by financing activities	49	89,274
Net increase (decrease) in cash, cash equivalents and restricted cash	(76,818)	96,882
Cash, cash equivalents and restricted cash at beginning of period	133,430	59,932
Cash, cash equivalents and restricted cash at end of period	$ 56,612	156,814
Supplemental disclosure of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable and accrued expenses		1,025
Offering costs included in accounts payable and accrued expenses		$ 222

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	6 Months Ended
	Jun. 30, 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 clinical-stage biotechnology company developing novel medicines designed to bring the curative power of stem cell transplants to more patients with blood cancers, genetic diseases and autoimmune diseases. The Company was incorporated under the laws of the State of Delaware in June 2015 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”) The Company has a shelf registration statement on Form S-3 “at-the-market” million available for sale under the ATM Program. The Company has incurred recurring losses since inception, including net losses of $40.2 million for the six months ended June 30, 2022 and $71.1 million the year ended December 31, 2021. As of June 30, 2022, the Company had an accumulated deficit of $365.8 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 its ability to raise additional capital to fund its operations. The Company 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. Although management continues to pursue these plans, 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”).

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2022
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies 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. Unaudited Interim Financial Information The consolidated balance sheet at December 31, 2021 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited consolidated financial statements as of June 30, 2022 and for the three and six months ended June 30, 2022 and 2021 have been prepared by the Company pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes, however, that the disclosures are adequate to make the information presented not misleading. These consolidated financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2021 included in the Company’s Annual Report on Form 10-K, 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. 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 more-likely-than-not 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 and for the three and six months ended June 30 2021, the Company’s consolidated financial statements continue to be presented in accordance with ASC 840, the accounting standard originally in effect for such periods. As of and for the three and six months ended June 30, 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 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 non-lease non-lease right-of-use 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 three and six months ended June 30, 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 effect is anti-dilutive. The Company reported a net loss for the three and six months ended June 30, 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 June 30, 2022 2021 Stock options to purchase common stock 6,115,903 Unvested restricted common stock units 454,122 510,000 Shares of common stock issuable under Employee Stock Purchase Plan 81,868 11,238 8,870,622 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) 2016-02”), right-of-use 2016-02, right-of-use 2018-10, Codification Improvements to Topic 842 Leases 2018-11, Targeted Improvements to Topic 842 Leases 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, right-of-use right-of-use

Fair Value of Financial Assets

Fair Value of Financial Assets	6 Months Ended
	Jun. 30, 2022
Fair Value of Financial Assets	3. Fair Value of Financial Assets As of June 30, 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) $ 85,195 $ — $ (602 ) $ 84,593 Total $ $ $ ) $ 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 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 June 30, 2022 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 54,825 $ — $ — $ 54,825 Marketable securities: U.S. treasury notes — 84,593 — 84,593 Total $ 54,825 $ 84,593 $ — $ 139,418 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

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2022
Accrued Expenses and Other Current Liabilities	4. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, 2022 December 31, 2021 Accrued external research and development expenses $ 2,806 $ 2,813 Accrued payroll and related expenses 2,209 3,346 Deferred rent, current portion — 555 Accrued other 771 1,109 $ 5,786 $ 7,823

Stock-Based Awards

Stock-Based Awards	6 Months Ended
	Jun. 30, 2022
Stock-Based Awards	5. Stock-Based Awards 2018 Stock Option and Incentive Plan The Company grants stock-based awards under the Magenta Therapeutics, Inc. 2018 Stock Option and Incentive Plan (the “2018 Plan”). The Company also has outstanding stock options under the Magenta Therapeutics, Inc. 2016 Stock Option and Grant Plan, as amended (the “2016 Plan”), but is no longer granting awards under the 2016 Plan. As of June 30, 2022, 3,293,076 shares of common stock were available for issuance under the 2018 Plan. Grant of Stock Options During the six months ended June 30, 2022, the Company granted options to certain employees and consultants with service-based vesting conditions for the purchase of 3,086,485 shares of common stock with a weighted average grant date fair value of $1.66 per share. Stock-based compensation expense is being recognized over the requisite service period of 18 months to four years. Grant of Restricted Stock Units During the six months ended June 30, 2022, the Company granted 102,276 restricted stock units to certain employees with a weighted average grant date fair value of $2.23 per share. Stock-based compensation expense is being recognized over the requisite service period of 18 months to four years. 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 Stock-Based Compensation Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 Research and development expenses $ 462 $ 996 $ 989 $ 1,941 General and administrative expenses 1,383 1,138 2,761 2,385 $ $ $ $ As of June 30, 2022, unrecognized compensation expense related to unvested share-based awards with service-based vesting conditions was $17.5 million, which is expected to be recognized over a weighted average period of 2.6 years. Additionally, the Company had unrecognized compensation cost of $1.9 million related to the unvested performance restricted stock units for which the performance conditions were not considered probable of achievement as of June 30, 2022.

Leases

Leases	6 Months Ended
	Jun. 30, 2022
Leases [Abstract]
Leases	6. 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 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 The components of the Company’s lease expense under ASC 842 were as follows (in thousands): Three Months Ended Six Months Ended June 30, 2022 June 30, 2022 Operating lease cost $ 1,601 $ 3,203 Short-term lease cost — — Variable lease cost 4 510 $ $ Supplemental disclosure of cash flow information related to the lease was as follows (in thousands): Three Months Ended Six Months Ended June 30, 2022 June 30, 2022 Cash paid for amounts included in the measurement of operating $ 1,622 $ 3,217 Operating lease liabilities arising from obtaining right-of-use asset $ — $ — The weighted average remaining lease term and discount rate were as follows: June 30, 2022 Weighted-average remaining lease term - operating lease (in years) 5.67 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 June 30, 2022, the future minimum lease payments due under the noncancelable operating lease was as follows (in thousands): 2022 (six months) $ 3,350 2023 6,936 2024 7,313 2025 7,679 2026 8,062 Thereafter 9,904 Total future minimum lease payments 43,244 Less: imputed interest (11,634 ) Total operating lease liabilities $ 31,610 The following table represents the lease liabilities on the consolidated balance sheet (in thousands): June 30, 2022 Current operating lease liability $ 3,423 Operating lease liability, net of current portion 28,187 Total operating lease liabilities $ As previously disclosed in the Company’s Annual Report on Form 10-K ASC 840, Leases, 2022 $ 6,375 2023 6,734 2024 7,100 2025 7,455 2026 7,828 Thereafter 9,617 $ 45,109 In 2018, the Company entered into two sub-subleases sub-subleases, sub-sublease, sub-sublease sub-subleases. sub-subleases.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies	7. Commitments and Contingencies Leases The Company’s commitments under its leases are described in Note 6. 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 the three months ended June 30, 2022, the Company did not incur any research and development expenses related to this agreement. During the three months ended June 30, 2021, the Company recorded less than $0.1 million of research and development expense related to this agreement for upfront technology access fees, research exclusivity fees and research support. During each of the six months ended June 30, 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 six months ended June 30, 2022, the Company recorded $2.0 million of research and development expense related to the achievement of a development milestone. During the three and six months ended June 30, 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 country-by-country . 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 three and six months ended June 30, 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 three and six months ended June 30, 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 June 30, 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.

401(k) Savings Plan

401(k) Savings Plan	6 Months Ended
	Jun. 30, 2022
401(k) Savings Plan	8. 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 three and six months ended June 30, 2022, the Company recorded $0.1 million of expense related to this matching contribution.

Related Parties

Related Parties	6 Months Ended
	Jun. 30, 2022
Related Parties	9. Related Parties 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 the three months ended June 30, 2022 and 2021, the Company recorded expense of less than $0.1 million and $0.2 million, respectively, related to these agreements. For the six months ended June 30, 2022 and 2021, the Company recorded expense of $0.1 million and $0.3 million, respectively, related to these agreements. As of June 30, 2022 and December 31, 2021, amounts on the consolidated balance sheets related to these agreements were less than $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 which amounts were included in prepaid expenses and other current assets.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2022
Use of Estimates	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.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The consolidated balance sheet at December 31, 2021 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited consolidated financial statements as of June 30, 2022 and for the three and six months ended June 30, 2022 and 2021 have been prepared by the Company pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes, however, that the disclosures are adequate to make the information presented not misleading. These consolidated financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2021 included in the Company’s Annual Report on Form 10-K,
Fair Value Measurements	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.
Income Taxes	Unaudited Interim Financial Information The consolidated balance sheet at December 31, 2021 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited consolidated financial statements as of June 30, 2022 and for the three and six months ended June 30, 2022 and 2021 have been prepared by the Company pursuant to the rules and regulations of the SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes, however, that the disclosures are adequate to make the information presented not misleading. These consolidated financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2021 included in the Company’s Annual Report on Form 10-K, 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. 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 more-likely-than-not
Leases	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 and for the three and six months ended June 30 2021, the Company’s consolidated financial statements continue to be presented in accordance with ASC 840, the accounting standard originally in effect for such periods. As of and for the three and six months ended June 30, 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 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 non-lease non-lease right-of-use
Comprehensive Loss	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 three and six months ended June 30, 2022 and 2021, the Company’s only element of other comprehensive income (loss) was unrealized gains (losses) on marketable securities.
Net Loss per Share	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 effect is anti-dilutive. The Company reported a net loss for the three and six months ended June 30, 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 June 30, 2022 2021 Stock options to purchase common stock 6,115,903 Unvested restricted common stock units 454,122 510,000 Shares of common stock issuable under Employee Stock Purchase Plan 81,868 11,238 8,870,622
Recently Issued Accounting Pronouncements	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	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02”), right-of-use 2016-02, right-of-use 2018-10, Codification Improvements to Topic 842 Leases 2018-11, Targeted Improvements to Topic 842 Leases 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, right-of-use right-of-use

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2022
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 June 30, 2022 2021 Stock options to purchase common stock 6,115,903 Unvested restricted common stock units 454,122 510,000 Shares of common stock issuable under Employee Stock Purchase Plan 81,868 11,238 8,870,622

Fair Value of Financial Assets

Fair Value of Financial Assets (Tables)	6 Months Ended
	Jun. 30, 2022
Schedule of Marketable Securities by Security Type	As of June 30, 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) $ 85,195 $ — $ (602 ) $ 84,593 Total $ $ $ ) $ 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 June 30, 2022 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 54,825 $ — $ — $ 54,825 Marketable securities: U.S. treasury notes — 84,593 — 84,593 Total $ 54,825 $ 84,593 $ — $ 139,418 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

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2022
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): June 30, 2022 December 31, 2021 Accrued external research and development expenses $ 2,806 $ 2,813 Accrued payroll and related expenses 2,209 3,346 Deferred rent, current portion — 555 Accrued other 771 1,109 $ 5,786 $ 7,823

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	6 Months Ended
	Jun. 30, 2022
Schedule of Stock Based Compensation Expense	Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 Research and development expenses $ 462 $ 996 $ 989 $ 1,941 General and administrative expenses 1,383 1,138 2,761 2,385 $ $ $ $

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 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): Three Months Ended Six Months Ended June 30, 2022 June 30, 2022 Operating lease cost $ 1,601 $ 3,203 Short-term lease cost — — Variable lease cost 4 510 $ $
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): Three Months Ended Six Months Ended June 30, 2022 June 30, 2022 Cash paid for amounts included in the measurement of operating $ 1,622 $ 3,217 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: June 30, 2022 Weighted-average remaining lease term - operating lease (in years) 5.67 Weighted-average discount rate - operating lease 11.00 %
Schedule of Future Minimum Lease Payments Due Under Noncancelable Operating Lease	As of June 30, 2022, the future minimum lease payments due under the noncancelable operating lease was as follows (in thousands): 2022 (six months) $ 3,350 2023 6,936 2024 7,313 2025 7,679 2026 8,062 Thereafter 9,904 Total future minimum lease payments 43,244 Less: imputed interest (11,634 ) Total operating lease liabilities $ 31,610 As previously disclosed in the Company’s Annual Report on Form 10-K ASC 840, Leases, 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): June 30, 2022 Current operating lease liability $ 3,423 Operating lease liability, net of current portion 28,187 Total operating lease liabilities $

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 08, 2019	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	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		$ (17,271)	$ (16,928)	$ (40,221)	$ (34,417)	$ (71,100)
Accumulated deficit		(365,788)		(365,788)		$ (325,567)
Aggregate value of available securities		$ 281,000		$ 281,000
Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shelf offering value	$ 350,000
Cowen and Company LLC [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
ATM offering value	$ 100,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	8,870,622	6,637,141
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	8,334,632	6,115,903
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	454,122	510,000
Shares of common stock issuable under Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, amount	81,868	11,238

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Jan. 01, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset	$ 24,670		$ 0
Operating Lease, Liability	31,610
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset	26,100
Operating Lease, Liability	$ 33,000
Deferred rent balance		$ 7,000

Fair Value of Financial Asset_2

Fair Value of Financial Assets - Schedule of Marketable Securities by Security Type (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Amortized Cost	$ 85,195	$ 45,306
Gross Unrealized Gains
Gross Unrealized Losses	(602)	(30)
Estimated Fair Value	84,593	45,276
US Treasury Notes [Member] | Due With In One Year [Member]
Marketable Securities [Line Items]
Amortized Cost	85,195	30,213
Gross Unrealized Gains
Gross Unrealized Losses	(602)	(20)
Estimated Fair Value	$ 84,593	30,193
US Treasury Notes [Member] | Due After One Year Through Two Years [Member]
Marketable Securities [Line Items]
Amortized Cost		15,093
Gross Unrealized Gains
Gross Unrealized Losses		(10)
Estimated Fair Value		$ 15,083

Fair Value of Financial Asset_3

Fair Value of Financial Assets - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 84,593	$ 45,276
Fair Value on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	139,418	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	54,825	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	84,593	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	54,825	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	54,825	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	84,593	45,276
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	$ 84,593	$ 45,276

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued external research and development expenses	$ 2,806	$ 2,813
Accrued payroll and related expenses	2,209	3,346
Deferred rent, current portion		555
Accrued other	771	1,109
Total	$ 5,786	$ 7,823

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	$ 17.5
Period for recognition of unrecognized expense	2 years 7 months 6 days
Employees And Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, grants in period, gross	3,086,485
Weighted average fair value of stock options granted	$ 1.66
Minimum [Member] | Employees And Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement , requisite service period	18 months
Maximum [Member] | Employees And Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement , requisite service period	4 years
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	$ 1.9
Restricted Stock Units (RSUs) [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant of restricted stock	102,276
Grant weighted average grant date fair value per share	$ 2.23
Restricted Stock Units (RSUs) [Member] | Minimum [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement , requisite service period	18 months
Restricted Stock Units (RSUs) [Member] | Maximum [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement , requisite service period	4 years
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance	3,293,076
2019 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance	663,548
Percentage of purchase price of common stock under the ESPP	85%
Common stock purchased	49,704	13,989
Stock issued, price per shares	$ 0.99	$ 6.15

Stock-Based Awards - Schedule o

Stock-Based Awards - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 1,845	$ 2,134	$ 3,750	$ 4,326
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	462	996	989	1,941
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 1,383	$ 1,138	$ 2,761	$ 2,385

Leases - Schedule of Components

Leases - Schedule of Components of the Company's Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Lease, Cost [Abstract]
Operating lease cost	$ 1,601	$ 3,203
Short-term lease cost	0	0
Variable lease cost	4	510
Lease cost	$ 1,605	$ 3,713

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Disclosure Of Cash Flow Information Related To The Lease (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 1,622	$ 3,217
Operating lease liabilities arising from obtaining right-of-use asset	$ 0	$ 0

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Remaining Lease Term And Discount Rate (Detail)	Jun. 30, 2022
Leases [Abstract]
Weighted-average remaining lease term - operating lease (in years)	5 years 8 months 1 day
Weighted-average discount rate - operating lease	11%

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments Due Under Noncancelable Operating Lease (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Leases [Abstract]
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
2022 (six months)	$ 3,350
2023	6,936
2024	7,313
2025	7,679
2026	8,062
Thereafter	9,904
Total future minimum lease payments	43,244
Less: imputed interest	(11,634)
Total operating lease liabilities	$ 31,610

Leases - Schedule of Lease Liab

Leases - Schedule of Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Operating Lease Liabilities, Gross Difference, Amount [Abstract]
Current operating lease liability	$ 3,423	$ 0
Operating lease liability, net of current portion	28,187	$ 0
Total operating lease liabilities	$ 31,610

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 ft² Sublease	Jan. 01, 2022 ft²	Dec. 31, 2021 USD ($) ft²
Leases [Line Items]
Restricted cash	$ 1,780		$ 1,780					$ 1,780
Long-term deferred rent	0		$ 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
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	2,100		$ 2,100
Other income from sub-sublease	600	$ 700	1,400	$ 1,900
Office and Lab Sublease [Member] | Letter of Credit [Member]
Leases [Line Items]
Restricted cash	$ 1,800		$ 1,800
Office and Lab Sublease [Member] | Paid By Sublandlord [Member]
Leases [Line Items]
Payments for tenant improvements					$ 5,200

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2018	Nov. 30, 2016
Other Commitments [Line Items]
Research and development expense	$ 11,603	$ 11,129	$ 28,150	$ 22,857
Research and Development Expenses [Member]
Other Commitments [Line Items]
Research and development expense				100
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	0	$ 100	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] | Maximum [Member]
Other Commitments [Line Items]
Payment obligation						$ 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		$ 100

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Retirement Benefits [Abstract]
Defined contribution plan,Employers matching contributions subject to time based vesting requirements		2%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.1	$ 0.1

Related Parties - Additional In

Related Parties - Additional Information (Detail) - Match Bio Therapies [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Expenses paid to related party	$ 0.1	$ 0.2	$ 0.1	$ 0.3
Accounts Payable, Accrued Expenses and Other Current Liabilities [Member]
Related Party Transaction [Line Items]
Amounts owed to related party	0.1		0.1		$ 0.2
Prepaid Expenses and Other Current Assets [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Prepaid expense and other current assets related parties	$ 0.1		$ 0.1