SQZ Biotechnologies (SQZB) 10-Q 8 Nov 23 2023 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 31, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Registrant Name	SQZ BIOTECHNOLOGIES COMPANY
Entity Central Index Key	0001604477
Entity Incorporation, State or Country Code	DE
Current Fiscal Year End Date	--12-31
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	SQZB
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		29,491,125
Entity Address, State or Province	MA
Entity File Number	001-39662
Entity Tax Identification Number	46-2431115
Entity Address, Address Line One	200 Arsenal Yards Blvd
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Watertown
Entity Address, Postal Zip Code	02472
City Area Code	617
Local Phone Number	758-8672

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 10,193	$ 63,709
Prepaid expenses and other current assets	1,894	4,495
Total current assets	12,087	68,204
Property and equipment, net	978	1,959
Restricted cash	2,305	2,305
Operating lease right-of-use assets	14,418	27,432
Total assets	29,788	99,900
Current liabilities:
Accounts payable	1,913	2,511
Accrued expenses	4,352	8,893
Accrued restructuring expenses	170	3,162
Deferred revenue		715
Current portion of operating lease liabilities	2,397	6,562
Total current liabilities	8,832	21,843
Operating lease liabilities, net of current portion	19,075	20,909
Total liabilities	27,907	42,752
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2023 and December 31, 2022; No shares issued or outstanding.
Common stock, $0.001 par value; 200,000,000 shares authorized at June 30, 2023 and December 31, 2022; 29,491,125 shares issued and outstanding at June 30, 2023 and December 31, 2022.	29	29
Additional paid-in capital	334,922	332,093
Accumulated deficit	(333,070)	(274,974)
Total stockholders’ equity	1,881	57,148
Total liabilities and stockholders’ equity	$ 29,788	$ 99,900

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
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	200,000,000	200,000,000
Common stock, shares issued	29,491,125	29,491,125
Common stock, shares outstanding	29,491,125	29,491,125

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenue		$ 3,130	$ 178	$ 9,011
Revenue, Product and Service [Extensible Enumeration]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Grant revenue		$ 322		$ 524
Total revenue		3,452	$ 178	9,535
Operating expenses:
Research and development	$ 10,504	19,631	36,209	55,401
General and administrative	5,614	6,919	15,566	20,789
Restructuring charges	7,683		7,567
Total operating expenses	23,801	26,550	59,342	76,190
Loss from operations	(23,801)	(23,098)	(59,164)	(66,655)
Other income (expense):
Interest income	164	436	1,009	608
Other income (expense), net	(2)	19	59	130
Total other income, net	162	455	1,068	738
Net loss and comprehensive loss	$ (23,639)	$ (22,643)	$ (58,096)	$ (65,917)
Net loss per share, basic	$ (0.8)	$ (0.77)	$ (1.97)	$ (2.3)
Net loss per share, diluted	$ (0.8)	$ (0.77)	$ (1.97)	$ (2.3)
Weighted-average common shares outstanding, basic	29,491,125	29,284,151	29,491,125	28,603,020
Weighted-average common shares outstanding, diluted	29,491,125	29,284,151	29,491,125	28,603,020

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Common Stock [Member] At-the-market Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] At-the-market Offering [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2021	$ 123,976	$ 28		$ 319,458		$ (195,510)
Beginning balance (Shares) at Dec. 31, 2021		28,133,368
Issuance of common stock upon exercise of stock options	29			29
Issuance of common stock upon exercise of stock options (Shares)		14,757
Issuance of common stock under employee stock purchase plan	111			111
Issuance of common stock under employee stock purchase plan (Shares)		41,265
Issuance of common stock under at-the-market offering, net of issuance costs	3,745		$ 1		$ 3,744
Issuance of common stock under at-the-market offering, net of issuance costs (Shares)			1,160,768
Stock-based compensation expense	6,630			6,630
Net loss	(65,917)					(65,917)
Ending balance at Sep. 30, 2022	68,574	$ 29		329,972		(261,427)
Ending balance (Shares) at Sep. 30, 2022		29,350,158
Beginning balance at Jun. 30, 2022	88,188	$ 29		326,943		(238,784)
Beginning balance (Shares) at Jun. 30, 2022		29,148,053
Issuance of common stock under at-the-market offering, net of issuance costs	653				$ 653
Issuance of common stock under at-the-market offering, net of issuance costs (Shares)			202,105
Stock-based compensation expense	2,376			2,376
Net loss	(22,643)					(22,643)
Ending balance at Sep. 30, 2022	68,574	$ 29		329,972		(261,427)
Ending balance (Shares) at Sep. 30, 2022		29,350,158
Beginning balance at Dec. 31, 2022	57,148	$ 29		332,093		(274,974)
Beginning balance (Shares) at Dec. 31, 2022		29,491,125
Stock-based compensation expense	2,829			2,829
Net loss	(58,096)					(58,096)
Ending balance at Sep. 30, 2023	1,881	$ 29		334,922		(333,070)
Ending balance (Shares) at Sep. 30, 2023		29,491,125
Beginning balance at Jun. 30, 2023	24,537	$ 29		333,939		(309,431)
Beginning balance (Shares) at Jun. 30, 2023		29,491,125
Stock-based compensation expense	983			983
Net loss	(23,639)					(23,639)
Ending balance at Sep. 30, 2023	$ 1,881	$ 29		$ 334,922		$ (333,070)
Ending balance (Shares) at Sep. 30, 2023		29,491,125

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
At-the-market Offering [Member]
Payment of issuance costs	$ 3	$ 195

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net loss	$ (58,096)	$ (65,917)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization expense	1,035	833
Amortization of operating lease right-of-use assets	7,024	7,458
Impairment of right-of-use asset	5,991
Stock-based compensation expense	2,829	6,630
(Gain) Loss on disposal of equipment	(113)	43
Changes in operating assets and liabilities:
Accounts receivable		3,000
Prepaid expenses and other current assets	2,601	(1,024)
Accounts payable	(598)	(624)
Accrued expenses	(4,541)	1,013
Accrued restructuring expenses	(2,992)
Deferred revenue	(715)	(9,007)
Operating lease liabilities	(5,999)	(7,242)
Net cash used in operating activities	(53,574)	(62,789)
Cash flows from investing activities:
Purchases of property and equipment	(112)	(421)
Proceeds from disposals of property and equipment	170	34
Net cash provided by (used in) investing activities	58	(387)
Cash flows from financing activities:
Proceeds from issuance of common stock under at-the market offering		3,762
Proceeds from issuance of common stock under employee stock purchase plan		111
Proceeds from exercise of stock options		29
Net cash provided by financing activities		3,902
Net decrease in cash, cash equivalents and restricted cash	(53,516)	(59,274)
Cash, cash equivalents and restricted cash at beginning of period	66,014	145,818
Cash, cash equivalents and restricted cash at end of period	$ 12,498	$ 86,544

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation SQZ Biotechnologies Company (the “Company”) is a clinical-stage biotechnology company developing cell therapies for patients with cancer and other serious medical conditions. The Company uses its proprietary technology, Cell Squeeze, to physically squeeze cells through a microfluidic chip, temporarily opening the cell membrane and enabling biologic material of interest, or cargo, to diffuse into the cell. The Company is using Cell Squeeze technology to create multiple cell therapy platforms focused on directing specific immune responses. As part of the 2023 Restructuring Plan (see Note 12 for further discussion), the Company determined to cease research and clinical activities in the fourth quarter of 2023. The Company was incorporated in March 2013 under the laws of the State of Delaware. The Company is subject to a number of risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, the ability to obtain additional financing, protection of proprietary technology, dependence on key personnel, the ability to attract and retain qualified employees, compliance with government regulations, the impact of overall economic conditions, and the clinical and commercial success of its product candidates. Product candidates currently under development 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 drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. Since inception, the Company has funded its operations primarily with payments received in connection with collaboration agreements, proceeds from equity and debt financing, and most recently, with proceeds from its 2020 initial public offering (“IPO”) and its 2021 follow-on offering (the "Follow-On Offering"), and an Open Market Sales Agreement (the "Sales Agreement"). On November 10, 2021, the Company entered into the Sales Agreement with Jefferies LLC (“Jefferies”) to issue and sell up to $ 75,000,000 in shares of the Company’s common stock from time to time during the term of the Sales Agreement through an “at-the-market” equity offering program under which Jefferies acts as the Company’s sales agent (the “ATM Facility”). The Company did no t sell any shares under the ATM Facility during both the three and nine months ended September 30, 2023. During the three and nine months ended September 30, 2022, the Company sold 1,160,768 shares of common stock under the ATM Facility for net proceeds of approximately $ 3.7 million. Going Concern Assessment Management has assessed the Company’s ability to continue as a going concern in accordance with the requirements of ASC 205-40, taking into consideration its recurring losses from operations incurred since inception, expectation of continuing operating losses for the foreseeable future and the need to raise additional capital to finance future operations. Through September 30, 2023, the Company has funded its operations primarily with proceeds from sales of convertible preferred stock, payments received in connection with collaboration agreements, proceeds from borrowings under a convertible promissory note, which converted into shares of convertible preferred stock, and more recently the proceeds from its IPO, the Follow-On Offering and the ATM Facility. The Company has incurred recurring losses since inception, including a net loss of $ 58.1 million for the nine months ended September 30, 2023. As of September 30, 2023, the Company had an accumulated deficit of $ 333.1 million. Based on its current cash expenditure forecast, the Company expects that its existing cash and cash equivalents will fund its operations into the first quarter of 2024. The Company expects to continue to generate operating losses in the foreseeable future. As of November 8, 2023, the issuance date of the interim condensed consolidated financial statements for the three and nine months ended September 30, 2023, the Company has concluded that there is substantial doubt about its ability to continue as a going concern for a period of one year from the date that these interim condensed consolidated financial statements are issued. The Company will require additional funding through private or public equity financings, debt financings, collaborations, strategic transactions or licensing arrangements to remain in operation. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other strategic transactions. The terms of any financing may adversely affect the holdings or the rights of the Company's stockholders. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. If the Company is unable to obtain funding, the Company will be forced and has already begun to incur additional restructuring costs, or the Company may be unable to continue operations. Although management continues to pursue capital raising activities or strategic transactions there is no assurance that the Company will be successful in obtaining sufficient funding or strategic transactions on terms acceptable to the Company to fund continuing operations, or at all. The Company has announced that it has determined to pursue potential strategic alternatives to support the advancement of its oncology and other programs, including HPV 16 positive tumors, in an effort to allow the Company to partner its clinical and preclinical assets across all disease areas and indications. Potential strategic partnerships may include, but are not limited to, a partnership, acquisition, merger, business combination, or other transaction. There can be no assurance that this process will result in the Company pursuing a transaction or that any transaction, if pursued, will be completed on attractive terms. The Company has not set a timetable for completion of this process and does not intend to comment further unless or until the Board of Directors has approved a definitive course of action, the process is concluded, or it is determined that other disclosure is appropriate. Should a strategic alternative be implemented, the Company anticipates using available net proceeds to discharge its liabilities and outstanding obligations, distribute the remainder, if any, to stockholders and wind down its operations. Should the Company be unable to identify and implement a meaningful strategic alternative in a timely manner, the Company’s Board of Directors is likely to consider bankruptcy or other dissolution proceedings. In connection with the 2023 Restructuring Plan (see Note 12), the Company determined to continue to dose existing patients in its clinical programs through November 2023 and to discontinue enrollment of new patients in its clinical trials and cease remaining research activities. The accompanying interim condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Accordingly, the interim condensed consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. Impact of Macroeconomic Conditions The global economy, including credit and financial markets, has recently experienced extreme volatility and disruptions, including, for example, severely diminished liquidity and credit availability, rising interest and inflation rates, crises involving banking and financial institutions, declines in consumer confidence, declines in economic growth, increases in unemployment rates, uncertainty about economic stability and uncertainty created by geopolitical conflict, war and terrorism. The Company is monitoring the potential impact of general economic conditions on its business and financial statements. On September 29, 2023, the Board of Directors of the Company approved a reduction in the Company’s workforce by approximately 80 % (see Note 12). The decision was based on cost-reduction initiatives intended to reduce the Company’s ongoing operating expenses while it pursues strategic alternatives. In addition the Company completed an evaluation of the impact of the reduction in the workforce on the carrying value of its long-lived assets, including the headquarters facility operating lease asset. This process includes evaluating the estimated remaining lives, significant changes in the use, and potential impairment charges related to its long-lived assets. Based on its evaluation,using market participant assumptions to determine the fair value of the operating lease asset, the Company determined that the facility operating lease asset was impaired and recorded a $ 6.5 million charge as of September 30, 2023. Basis of Presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, SQZ Biotechnologies Security Corporation and SQZ Biotech HK Limited . All intercompany accounts and transactions have been eliminated in consolidation.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Interim Financial Information The accompanying condensed consolidated financial statements as of September 30, 2023 and for the three and nine months ended September 30, 2023 and 2022 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. The accompanying condensed consolidated balance sheet as of December 31, 2022 was derived from audited financial statements but does not include all disclosures required by GAAP. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2022 included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 filed with the SEC on March 22, 2023. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s consolidated financial position as of September 30, 2023, the consolidated results of operations for the three and nine months ended September 30, 2023 and 2022, and the consolidated cash flows for the nine months ended September 30, 2023 and 2022 have been made. The Company’s consolidated results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the full year or any other subsequent interim period. 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 condensed consolidated financial statements, and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses, and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, judgments and methodologies as there are changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions. Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is developing methods of engineering cell function and therapies for the treatment of patients across a range of indications. The Company has determined that its chief operating decision maker is its interim Chief Executive Officer. The Company’s chief operating decision maker reviews the Company’s financial information on a consolidated basis for purposes of allocating resources and assessing financial performance. Recently Issued Accounting Pronouncements The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company will adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and will do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company. The Company may choose to early adopt any new or revised accounting standards whenever such early adoption is permitted for nonpublic companies.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following tables present the Company’s fair value hierarchy for its assets and liabilities that are measured at fair value on a recurring basis (in thousands): FAIR VALUE MEASUREMENTS AT SEPTEMBER 30, 2023 USING: LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Cash equivalents: Money market funds $ 4,360 $ — $ — $ 4,360 $ 4,360 $ — $ — $ 4,360 FAIR VALUE MEASUREMENTS AT LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Cash equivalents: Money market funds $ 62,598 $ — $ — $ 62,598 $ 62,598 $ — $ — $ 62,598 Money market funds were valued by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. There were no changes to the valuation methods during the nine months ended September 30, 2023 .The Company evaluates transfers between levels at the end of each reporting period. There were no transfers between levels during the nine months ended September 30, 2023 .

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	4. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): SEPTEMBER 30, DECEMBER 31, 2023 2022 Machinery and equipment $ 6,467 $ 6,840 Leasehold improvements 579 579 Furniture and fixtures 319 319 $ 7,365 $ 7,738 Less: Accumulated depreciation and amortization ( 6,387 ) ( 5,779 ) $ 978 $ 1,959 Depreciation and amortization expense for the three months ended September 30, 2023 and 2022 was $ 0.1 million and $ 0.3 million respectively. Depreciation and amortization expense for the nine months ended September 30, 2023 and 2022 was $ 0.5 million and $ 0.8 million, respectively. In addition to the depreciation and amortization expense recorded during the nine months ended September 30, 2023, the Company recorded restructuring charges of $ 0.5 million (see Note 12).

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): SEPTEMBER 30, DECEMBER 31, 2023 2022 Accrued external research, development and manufacturing costs $ 3,432 $ 5,264 Accrued employee compensation and benefits 68 2,578 Other 852 1,051 $ 4,352 $ 8,893

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	6. Stock-Based Compensation The following table summarizes the Company’s stock option activity since December 31, 2022: NUMBER OF WEIGHTED- WEIGHTED- INTRINSIC (in years) (in thousands) Outstanding at December 31, 2022 5,358,310 $ 8.09 5.26 $ — Granted 3,156,275 0.71 Forfeited or canceled ( 1,103,948 ) 7.62 Outstanding at September 30, 2023 7,410,637 $ 5.02 5.13 $ — Vested and expected to vest at September 30, 2023 7,410,637 $ 5.02 5.13 $ — Options exercisable at September 30, 2023 3,642,551 $ 7.52 3.28 $ — Stock-Based Compensation Expense Stock-based compensation expense related to stock options was classified in the consolidated statements of operations as follows (in thousands): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Research and development expenses $ 294 $ 1,034 $ 1,223 $ 2,563 General and administrative expenses 689 1,342 1,606 4,067 $ 983 $ 2,376 $ 2,829 $ 6,630 As of September 30, 2023 , total unrecognized stock-based compensation expense related to unvested stock-based awards was $ 7.5 million, which is expected to be recognized over a weighted-average period of 2.6 years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes For the three and nine months ended September 30, 2023 and 2022 , the Company recorded no income tax benefits for the net operating losses incurred or for the research and development tax credits generated in each period, due to its uncertainty of realizing a benefit from those items. Substantially all of the Company’s operating losses since inception have been generated in the United States.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Leases The Company’s commitments under its leases are described in Note 9. License and Supply Agreements License Agreement with Massachusetts Institute of Technology In December 2015, the Company entered into an exclusive patent license agreement with the Massachusetts Institute of Technology (“MIT”) (the “MIT Agreement”). The MIT Agreement replaced a May 2013 exclusive agreement with MIT. Under the MIT Agreement, the Company received an exclusive license under the licensed patent rights to develop, manufacture and commercialize any products related to certain intracellular delivery methods that were developed at MIT. As of September 30, 2023 and December 31, 2022 , the Company had no outstanding liabilities related to the MIT Agreement. During each of the three and nine months ended September 30, 2023 and 2022 , the Company recognized less than $ 0.1 million in research and development expense under the sublicense terms of the MIT Agreement. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to its vendors, lessors, contract research organizations, 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 its executive officers and members of its board of directors 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 executive officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnification agreements and is not currently aware of any indemnification claims. Legal Proceedings The Company is not currently 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 as incurred the costs related to such legal proceedings.

Leases

Leases	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Leases	9. Leases As of September 30, 2023, the Company leases its office and laboratory facilities under a non-cancelable operating lease entered into in December 2018, which included lease incentives, payment escalations and rent holidays. The Company had not entered into any financing leases or any short-term operating leases as of September 30, 2023 and December 31, 2022. The components of lease cost were as follows (in thousands): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Lease cost: Operating lease cost $ 2,641 $ 3,347 $ 9,390 $ 10,867 Variable lease cost 298 454 1,118 1,424 $ 2,939 $ 3,801 $ 10,508 $ 12,291 Based on an evaluation, using market participant assumptions to determine the fair value of the operating lease asset, of the remaining useful life of its office and laboratory facilities (see Note 12), the Company determined that the facility operating lease asset was impaired and recorded a $ 6.5 million charge as of September 30, 2023.

License and Collaboration Agree

License and Collaboration Agreements	9 Months Ended
	Sep. 30, 2023
Research and Development [Abstract]
License and Collaboration Agreements	10. License and Collaboration Agreements 2018 License and Collaboration Agreement with Roche In October 2018, the Company entered into a license and collaboration agreement (the “2018 Roche Agreement”) with F. Hoffmann-La Roche Ltd (“Roche Basel”) and Hoffmann-La Roche Inc. (“Roche US”, and together with Roche Basel, “Roche”) to jointly develop certain products based on mononuclear antigen presenting cells (“APCs”), including human papillomavirus (“HPV”), using the SQZ APC platform for the treatment of oncology indications. The Company granted Roche a non-exclusive license to its intellectual property, and Roche granted the Company a non-exclusive license to its and its affiliates’ intellectual property for the purpose of performing research activities. In connection with this agreement, the parties terminated an earlier agreement. The 2018 Roche Agreement had a term that extended until all royalty, profit-share and other payment obligations expired or had been satisfied. Roche had the right to terminate the 2018 Roche Agreement, in whole or on a product-by-product basis, upon a specified amount of notice to the Company. The Company or Roche could terminate the agreement if the other party fails to cure its material breach within a specified period after receiving notice of such breach. Under the 2018 Roche Agreement, Roche was granted option rights to obtain an exclusive license to develop APC products or products derived from the collaboration programs on a product-by-product basis and to develop a Tumor Cell Lysate (“TCL”) product. For each of the APC products and TCL product, if Roche exercised its option and paid a specified incremental amount, Roche would have received worldwide, exclusive commercialization rights for the licensed products. On July 25, 2023, the Company announced that Roche determined that it would not exercise its option under the 2018 Roche Agreement to obtain an exclusive license to develop and commercialize the Company’s candidate targeting HPV 16 positive solid tumors under the Company’s SQZ-APC-HPV program. On September 13, 2023, the Company and Roche agreed to terminate the 2018 Roche Agreement, effective immediately. No early termination penalty was incurred by either party. On the effective date, the Company regained full clinical development and future commercialization rights for all its oncology programs, including HPV 16 positive tumors. During the nine months ended September 30, 2023, as a result of the determination by Roche that it would not exercise its option in relation to the first performance obligation the Company concluded that it would incur no further costs to satisfy its performance obligations under the 2018 Roche Agreement and as a result fully recognized the remaining deferred revenue. The Company recognized no revenue and $ 3.5 million during the three months ended September 30, 2023 and 2022 , respectively, under this agreement. The Company recognized $ 0.2 million and $ 9.5 million during the nine months ended September 30, 2023 and 2022, respectively, under this agreement. As of September 30, 2023, the Company had fully recognized all deferred revenue related to the 2018 Roche Agreement.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Net Loss per Share	11. Net Loss per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Numerator: Net loss $ ( 23,639 ) $ ( 22,643 ) $ ( 58,096 ) $ ( 65,917 ) Denominator: Weighted-average common shares outstanding, basic and diluted 29,491,125 29,284,151 29,491,125 28,603,020 Net loss per share attributable to common stockholders, basic and diluted $ ( 0.80 ) $ ( 0.77 ) $ ( 1.97 ) $ ( 2.30 ) The Company’s potential dilutive securities, which consist of common stock options have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: SEPTEMBER 30, 2023 2022 Stock options to purchase common stock 7,410,637 6,606,500 7,410,637 6,606,500

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Restructuring	12. Restructuring On November 30, 2022, the Company’s Board of Directors approved a restructuring plan and strategic prioritization (the “2022 Restructuring Plan”) of its clinical portfolio to concentrate on the development of its second-generation enhanced Antigen Presenting Cells (eAPC) cell therapy program. In connection with the 2022 Restructuring, the Company reprioritized its clinical and development programs, determined to terminate operations in its Hong Kong and China subsidiaries and the Board of Directors approved a workforce reduction of approximately 60 %, including research and development and general and administrative support functions in the United States and China. In the first quarter of 2023, the Company decided to continue to enroll patients in its SQZ-AAC-HPV (AAC) clinical trial. On September 29, 2023, the Company’s Board of Directors approved an additional workforce reduction of approximately 80 % of the remaining employees (the “2023 Restructuring Plan”) and ceased substantially all research and development activities to reduce the Company’s ongoing operating expenses while it pursues strategic alternatives which may include a sale of the Company or some or all of its assets by the end of 2023. In connection with the 2023 Restructuring Plan, the Company determined to continue to dose existing patients in its clinical programs through November 2023 and to discontinue enrollment of new patients in its clinical trials. Also in connection with 2023 Restructuring Plan, each of Howard Bernstein, Ph.D., Interim Chief Executive Officer of the Company, Richard Capasso, Chief Accounting Officer of the Company, Marshelle Smith Warren, M.D., Chief Medical Officer of the Company, and Lawrence Knopf, General Counsel of the Company (collectively, the “Executive Officers”) each entered into transition agreements amending the terms of each of their employment agreements with the Company. The transition agreements provide for an agreed employment termination date for the Executive Officers of November 15, 2023, subject to certain early termination events, and a reduction in their current annual base salaries and expected working time commitments.‌ Following their respective employment termination dates, the Executive Officers are expected to enter into consulting agreements with the Company under which they will perform consulting services on an as-needed basis in return for hourly consulting fees.‌ The following table summarizes the activity for accrued restructuring costs for the nine months ended September 30, 2023 (in thousands): Employee Related Costs Facility Related Costs Total Balance as of December 31, 2022 $ 3,162 $ — $ 3,162 Expenses incurred 1,071 6,496 7,567 Payments ( 2,897 ) ( 69 ) ( 2,966 ) Non-cash charges ( 1,097 ) ( 6,496 ) ( 7,593 ) Balance as of September 30, 2023 $ 239 $ ( 69 ) $ 170 During the nine months ended September 30, 2023, the Company recorded $ 7.6 million of restructuring charges. Employee-related costs of $ 1.1 million were related to the elimination of the requirement for affected employees to provide continued service to retain certain retention payments received in 2023 which were subject to claw back in the event of voluntary termination prior to December 31, 2023, and salary and one-time termination benefits to the affected employees, including healthcare benefits to be paid in the fourth quarter of 2023. The Company completed an evaluation of the impact of the 2023 Restructuring on the carrying value of its long-lived assets, including the headquarters facility operating lease asset. This process includes evaluating the estimated remaining lives, significant changes in the use, and potential impairment charges related to its long-lived assets. The Company used market participant assumptions to determine the fair value of the operating lease asset. Based on its evaluation, the Company determined that the facility operating lease asset was impaired and recorded a $ 6.5 million charge as of September 30, 2023, to reflect the estimated remaining life and reduced anticipated use of the facility. The remaining $ 0.5 million in facility-related charges represent accelerated depreciation on office and laboratory equipment that is no longer in use or recoverable and will be disposed of. The accrued restructuring liability of $ 0.2 million is payable within the next twelve months and has been included as accrued restructuring costs in current liabilities in the consolidated balance sheet. The remaining accrued restructuring charges are subject to assumptions, and actual amounts may differ. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with restructuring activities.‌

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Event On November 6, 2023, as a result of the impact of the 2023 Restructuring including the reduction in force and anticipated cessation of remaining research and clinical activities in the fourth quarter of 2023, the Company executed an agreement with the landlord of the Company’s headquarters facility. In exchange for a commitment for the Company to vacate the facility by mid-November, payment of one-quarter of the November 2023 Base Rent, as defined, and certain common area maintenance and utility fees, release of a $ 2.3 million letter of credit securing the Company’s performance under the lease and a lump sum payment of $ 1.0 million, by a certain date, following the closing of a strategic transaction, the landlord has agreed to discharge the lease and release the Company from any remaining payment obligations under the lease. In the event the lump sum is not paid when due, outstanding obligations under the lease will remain in full force. Upon vacating the headquarters facility in mid-November, the Company will record an impairment charge of approximately $ 14.4 million, the remaining carrying value of the facility lease right of use asset.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying condensed consolidated financial statements as of September 30, 2023 and for the three and nine months ended September 30, 2023 and 2022 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. The accompanying condensed consolidated balance sheet as of December 31, 2022 was derived from audited financial statements but does not include all disclosures required by GAAP. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These interim condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2022 included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 filed with the SEC on March 22, 2023. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s consolidated financial position as of September 30, 2023, the consolidated results of operations for the three and nine months ended September 30, 2023 and 2022, and the consolidated cash flows for the nine months ended September 30, 2023 and 2022 have been made. The Company’s consolidated results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results of operations that may be expected for the full year or any other subsequent interim period.
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 condensed consolidated financial statements, and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses, and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, judgments and methodologies as there are changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions.
Segment Information	Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is developing methods of engineering cell function and therapies for the treatment of patients across a range of indications. The Company has determined that its chief operating decision maker is its interim Chief Executive Officer. The Company’s chief operating decision maker reviews the Company’s financial information on a consolidated basis for purposes of allocating resources and assessing financial performance.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company will adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and will do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company. The Company may choose to early adopt any new or revised accounting standards whenever such early adoption is permitted for nonpublic companies.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Summary of fair value hierarchy for assets and liabilities	The following tables present the Company’s fair value hierarchy for its assets and liabilities that are measured at fair value on a recurring basis (in thousands): FAIR VALUE MEASUREMENTS AT SEPTEMBER 30, 2023 USING: LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Cash equivalents: Money market funds $ 4,360 $ — $ — $ 4,360 $ 4,360 $ — $ — $ 4,360 FAIR VALUE MEASUREMENTS AT LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Cash equivalents: Money market funds $ 62,598 $ — $ — $ 62,598 $ 62,598 $ — $ — $ 62,598

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2023
Property, Plant and Equipment, Net [Abstract]
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): SEPTEMBER 30, DECEMBER 31, 2023 2022 Machinery and equipment $ 6,467 $ 6,840 Leasehold improvements 579 579 Furniture and fixtures 319 319 $ 7,365 $ 7,738 Less: Accumulated depreciation and amortization ( 6,387 ) ( 5,779 ) $ 978 $ 1,959

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Summary of accrued expenses	Accrued expenses consisted of the following (in thousands): SEPTEMBER 30, DECEMBER 31, 2023 2022 Accrued external research, development and manufacturing costs $ 3,432 $ 5,264 Accrued employee compensation and benefits 68 2,578 Other 852 1,051 $ 4,352 $ 8,893

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity since December 31, 2022: NUMBER OF WEIGHTED- WEIGHTED- INTRINSIC (in years) (in thousands) Outstanding at December 31, 2022 5,358,310 $ 8.09 5.26 $ — Granted 3,156,275 0.71 Forfeited or canceled ( 1,103,948 ) 7.62 Outstanding at September 30, 2023 7,410,637 $ 5.02 5.13 $ — Vested and expected to vest at September 30, 2023 7,410,637 $ 5.02 5.13 $ — Options exercisable at September 30, 2023 3,642,551 $ 7.52 3.28 $ —
Summary of Stock-Based Compensation Expense	Stock-based compensation expense related to stock options was classified in the consolidated statements of operations as follows (in thousands): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Research and development expenses $ 294 $ 1,034 $ 1,223 $ 2,563 General and administrative expenses 689 1,342 1,606 4,067 $ 983 $ 2,376 $ 2,829 $ 6,630

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Summary of Components of Lease Cost	The components of lease cost were as follows (in thousands): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Lease cost: Operating lease cost $ 2,641 $ 3,347 $ 9,390 $ 10,867 Variable lease cost 298 454 1,118 1,424 $ 2,939 $ 3,801 $ 10,508 $ 12,291

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Summary of basic and diluted net loss per share attributable to common stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): THREE MONTHS ENDED NINE MONTHS ENDED 2023 2022 2023 2022 Numerator: Net loss $ ( 23,639 ) $ ( 22,643 ) $ ( 58,096 ) $ ( 65,917 ) Denominator: Weighted-average common shares outstanding, basic and diluted 29,491,125 29,284,151 29,491,125 28,603,020 Net loss per share attributable to common stockholders, basic and diluted $ ( 0.80 ) $ ( 0.77 ) $ ( 1.97 ) $ ( 2.30 )
Summary of potentially dilutive shares excluded from the calculation of diluted net loss	The Company’s potential dilutive securities, which consist of common stock options have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: SEPTEMBER 30, 2023 2022 Stock options to purchase common stock 7,410,637 6,606,500 7,410,637 6,606,500

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Summary of Accrued Restructuring Costs	The following table summarizes the activity for accrued restructuring costs for the nine months ended September 30, 2023 (in thousands): Employee Related Costs Facility Related Costs Total Balance as of December 31, 2022 $ 3,162 $ — $ 3,162 Expenses incurred 1,071 6,496 7,567 Payments ( 2,897 ) ( 69 ) ( 2,966 ) Non-cash charges ( 1,097 ) ( 6,496 ) ( 7,593 ) Balance as of September 30, 2023 $ 239 $ ( 69 ) $ 170

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 29, 2023	Nov. 10, 2021	Nov. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Proceeds from issuance of common stock under at-the market offering							$ 3,762,000
Income (loss) from continuing operations						$ 58,100,000
Accumulated deficit				$ 333,070,000		333,070,000		$ 274,974,000
Percentage of reduction in workforce	80%		60%
Operating lease asset impaired charges						$ 6,500,000
Follow-on Offering [Member]
Number of shares sold at-the-market offering facility				0	1,160,768	0	1,160,768
Proceeds from follow on public offer net of underwriting discounts and before payment of offering costs					$ 3,700,000		$ 3,700,000
Follow-on Offering [Member] | Maximum [Member]
Proceeds from issuance of common stock under at-the market offering		$ 75,000,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities (Detail) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Assets:
Assets, fair value disclosure	$ 4,360	$ 62,598
Level 1 [Member]
Assets:
Assets, fair value disclosure	4,360	62,598
Money Market Funds [Member] | Cash equivalents [Member]
Assets:
Assets, fair value disclosure	4,360	62,598
Money Market Funds [Member] | Cash equivalents [Member] | Level 1 [Member]
Assets:
Assets, fair value disclosure	$ 4,360	$ 62,598

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Sep. 30, 2023 USD ($)
Fair Value Disclosures [Abstract]
Fair value, assets, level 1 to level 2 transfers, amount	$ 0
Fair value, assets, level 2 to level 1 transfers, amount	0
Fair value, liabilities, level 1 to level 2 transfers, amount	0
Fair value, liabilities, level 2 to level 1 transfers, amount	0
Fair value, assets, level 1 to level 3 transfers, amount	0
Fair value, assets, level 2 to level 3 transfers, amount	0
Fair value, assets, level 3 to level 1 transfers, amount	0
Fair value, assets, level 3 to level 2 transfers, amount	0
Fair value, liabilities, level 1 to level 3 transfers, amount	0
Fair value, liabilities, level 2 to level 3 transfers, amount	0
Fair value, liabilities, level 3 to level 1 transfers, amount	0
Fair value, liabilities, level 3 to level 2 transfers, amount	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment, Net [Abstract]
Machinery and equipment	$ 6,467	$ 6,840
Leasehold improvements	579	579
Furniture and fixtures	319	319
Total property and equipment, gross	7,365	7,738
Less: Accumulated depreciation and amortization	(6,387)	(5,779)
Total property and equipment, net	$ 978	$ 1,959

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 0.1	$ 0.3	$ 0.5	$ 0.8
Restructuring charges			$ 0.5

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued external research, development and manufacturing costs	$ 3,432	$ 5,264
Accrued employee compensation and benefits	68	2,578
Other	852	1,051
Total accrued expenses	$ 4,352	$ 8,893

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Number Of Shares - Outstanding at December 31, 2022	5,358,310
Granted	3,156,275
Forfeited or canceled	(1,103,948)
Number Of Shares - Outstanding at June 30, 2023	7,410,637	5,358,310
Number Of Shares - Vested and expected to vest at June 30, 2023	7,410,637
Number Of Shares - Options exercisable at June 30, 2023	3,642,551
Weighted Average Exercise Price - Outstanding at December 31, 2022	$ 8.09
Granted	0.71
Forfeited or canceled	7.62
Weighted Average Exercise Price - Outstanding at June 30, 2023	5.02	$ 8.09
Weighted Average Exercise Price - Vested and expected to vest at June 30, 2023	5.02
Weighted Average Exercise Price - Options exercisable at June 30, 2023	$ 7.52
Weighted-Average Remaining Contractual Term	5 years 1 month 17 days	5 years 3 months 3 days
Weighted-Average Remaining Contractual Term - Vested and expected to vest	5 years 1 month 17 days
Weighted-Average Remaining Contractual Term - Options exercisable	3 years 3 months 10 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 983	$ 2,376	$ 2,829	$ 6,630
Research and Development Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	294	1,034	1,223	2,563
General and Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 689	$ 1,342	$ 1,606	$ 4,067

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($)
Stockbased Compensation [Line Items]
Unrecognized compensation expense related to unvested stock based awards	$ 7.5
Unrecognized compensation expense expected period for recognition	2 years 7 months 6 days

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income tax benefits	$ 0	$ 0	$ 0	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Other Commitments [Line Items]
Commitments and contingencies (Note 8)
Research and development	10,504,000	$ 19,631,000	36,209,000	$ 55,401,000
Sublicense Agreement [Member] | Maximum [Member]
Other Commitments [Line Items]
Research and development	100,000	$ 100,000	100,000	$ 100,000
Massachusetts Institute Of Technology
Other Commitments [Line Items]
Commitments and contingencies (Note 8)	$ 0		$ 0		$ 0

Leases - Summary of Components

Leases - Summary of Components of Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lease cost:
Operating lease cost	$ 2,641	$ 3,347	$ 9,390	$ 10,867
Variable lease cost	298	454	1,118	1,424
Lease Cost	$ 2,939	$ 3,801	$ 10,508	$ 12,291

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($)
Leases [Abstract]
Operating lease asset impaired charges	$ 6.5

License and Collaboration Agr_2

License and Collaboration Agreements - Additional Information (Detail) - 2018 License and Collaboration Agreement With Roche [Member] - Roche [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
License And Collaboration Agreements [Line Items]
Estimated costs to be incurred to satisfy performance obligation			$ 0
Performance obligation revenue recognized	$ 0	$ 3,500,000	$ 200,000	$ 9,500,000

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of basic and diluted net loss per share attributable to common stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Net loss	$ (23,639)	$ (22,643)	$ (58,096)	$ (65,917)
Weighted-average common shares outstanding, basic	29,491,125	29,284,151	29,491,125	28,603,020
Weighted-average common shares outstanding, diluted	29,491,125	29,284,151	29,491,125	28,603,020
Net loss per share attributable to common stockholders, basic	$ (0.8)	$ (0.77)	$ (1.97)	$ (2.3)
Net loss per share attributable to common stockholders, diluted	$ (0.8)	$ (0.77)	$ (1.97)	$ (2.3)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of potentially dilutive shares excluded from the calculation of diluted net loss (Detail) - shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	7,410,637	6,606,500
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	7,410,637	6,606,500

Restructuring - Additional Info

Restructuring - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 29, 2023	Nov. 30, 2022	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Percentage of reduction in workforce	80%	60%
Restructuring charges			$ 7,683	$ 7,567
Accrued restructuring liability			$ 170	170	$ 3,162
Employee Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				1,071
Forgiveness of The Obligation to Repay Certain Retention Payments Received [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				1,100
Salary And One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Lease asset impairment charge				6,500
Accelerated Depreciation On Office And Laboratory Equipment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 500

Restructuring - Summary of Accr

Restructuring - Summary of Accrued Restructuring Costs (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		$ 3,162
Expenses incurred	$ 7,683	7,567
Payments		(2,966)
Non-cash charges		(7,593)
Restructuring Reserve, Ending Balance	170	170
Employee Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		3,162
Expenses incurred		1,071
Payments		(2,897)
Non-cash charges		(1,097)
Restructuring Reserve, Ending Balance	$ 239	239
Facility Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Expenses incurred		6,496
Payments		(69)
Non-cash charges		(6,496)
Payments, balance		$ (69)

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Millions		9 Months Ended
	Nov. 06, 2023	Sep. 30, 2023
Subsequent Event [Line Items]
Operating lease asset impaired charges		$ 6.5
Subsequent Event [Member]
Subsequent Event [Line Items]
Letter of credit outstanding	$ 2.3
Lump sum payment	1
Operating lease asset impaired charges	$ 14.4