Seres Therapeutics (MCRB) 10-Q 9 May 23 2023 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	May 05, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Trading Symbol	MCRB
Entity Registrant Name	Seres Therapeutics, Inc.
Entity Central Index Key	0001609809
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-37465
Entity Tax Identification Number	27-4326290
Entity Address, Address Line One	200 Sidney Street - 4th Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	945-9626
Entity Common Stock Shares Outstanding		127,901,391
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands		Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents		$ 94,841	$ 163,030
Short term investments		11,703	18,311
Prepaid expenses and other current assets		9,537	13,423
Total current assets		116,081	194,764
Property and equipment, net		24,306	22,985
Operating lease assets		108,914	110,984
Restricted cash		8,185	8,185
Restricted investments		1,401	1,401
Other non-current assets		11,307	10,465
Total assets		270,194	348,784
Current liabilities:
Accounts payable		12,297	17,440
Accrued expenses and other current liabilities	[1]	44,361	59,840
Operating lease liabilities		4,784	3,601
Short term portion of note payable, net of discount		0	456
Deferred revenue - related party		2,376	4,259
Total current liabilities		63,818	85,596
Long term portion of note payable, net of discount		51,234	50,591
Operating lease liabilities, net of current portion		106,692	107,942
Deferred revenue, net of current portion - related party		94,835	92,430
Other long-term liabilities		1,486	1,442
Total liabilities		318,065	338,001
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2023 and December 31, 2022; no shares issued and outstanding at March 31, 2023 and December 31, 2022		0	0
Common stock, $0.001 par value; 200,000,000 shares authorized at March 31, 2023 and December 31, 2022; 126,592,604 and 125,222,273 shares issued and outstanding at March 31, 2023 and December 31, 2022, respectively		127	125
Additional paid-in capital		887,685	875,181
Accumulated other comprehensive loss		2	(12)
Accumulated deficit		(935,685)	(864,511)
Total stockholders' (deficit) equity		(47,871)	10,783
Total liabilities and stockholders' (deficit) equity		$ 270,194	$ 348,784
[1] Includes related party amounts of $ 24,958 and $ 34,770 at March 31, 2023 and December 31, 2022, respectively (see Note 11)

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 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	126,592,604	125,222,273
Common stock, shares outstanding	126,592,604	125,222,273
Related party amounts included in accrued expenses and other current liabilities	$ 24,958	$ 34,770

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenue:
Collaboration revenue - related party	$ (522)	$ 1,493
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Total revenue	$ (522)	$ 1,493
Operating expenses:
Research and development expenses	43,969	39,649
General and administrative expenses	22,470	18,571
Collaboration (profit) loss sharing - related party	3,607	(976)
Total operating expenses	70,046	57,244
Loss from operations	(70,568)	(55,751)
Other (expense) income:
Interest income	1,032	384
Interest expense	(1,948)	(912)
Other income (expense)	310	(345)
Total other expense, net	(606)	(873)
Net loss	$ (71,174)	$ (56,624)
Net loss per share attributable to common stockholders, basic	$ (0.57)	$ (0.61)
Net loss per share attributable to common stockholders, diluted	$ (0.57)	$ (0.61)
Weighted average common shares outstanding, basic	125,862,975	92,164,419
Weighted average common shares outstanding, diluted	125,862,975	92,164,419
Other comprehensive income (loss):
Unrealized gain (loss) on investments, net of tax of $0	$ 12	$ (155)
Currency translation adjustment	2	0
Total other comprehensive income (loss)	14	(155)
Comprehensive loss	$ (71,160)	$ (56,779)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Unrealized gain (loss) on investments, net of tax	$ 0	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss (Income) [Member]
Beginning balance at Dec. 31, 2021	$ 131,507	$ 92	$ 745,829	$ (614,354)	$ (60)
Beginning balance, shares at Dec. 31, 2021		91,889,418
Issuance of common stock upon exercise of stock options, value	257		257
Issuance of common stock upon exercise of stock options, shares		92,478
Issuance of common stock upon vesting of RSUs, net of tax withholdings, shares		69,195
Issuance of common stock under ESPP, value	892		892
Issuance of common stock under ESPP, shares		159,214
Stock-based compensation expense	5,079		5,079
Other comprehensive income loss	(155)				(155)
Net loss	(56,624)			(56,624)
Ending balance at Mar. 31, 2022	80,956	$ 92	752,057	(670,978)	(215)
Ending balance, shares at Mar. 31, 2022		92,210,305
Beginning balance at Dec. 31, 2022	$ 10,783	$ 125	875,181	(864,511)	(12)
Beginning balance, shares at Dec. 31, 2022	125,222,273	125,222,273
Issuance of common stock upon exercise of stock options, value	$ 188		188
Issuance of common stock upon exercise of stock options, shares	56,523	56,523
Issuance of common stock upon vesting of RSUs, net of tax withholdings, shares		259,023
Issuance of common stock under ESPP, value	$ 1,229	$ 1	1,228
Issuance of common stock under ESPP, shares		267,615
Issuance of common stock from at the market equity offering, value	4,239	$ 1	4,238
Issuance of common stock from at the market equity offering, shares		787,170
Stock-based compensation expense	6,850		6,850
Other comprehensive income loss	14				14
Net loss	(71,174)			(71,174)
Ending balance at Mar. 31, 2023	$ (47,871)	$ 127	$ 887,685	$ (935,685)	$ 2
Ending balance, shares at Mar. 31, 2023	126,592,604	126,592,604

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' (Deficit) Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Market Equity Offering [Member]
Issuance costs	$ 225

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss		$ (71,174)	$ (56,624)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense		6,850	5,079
Depreciation and amortization expense		1,400	1,570
Non-cash operating lease cost		2,070	1,058
Net (accretion) amortization of (discounts) premiums on investments		(187)	313
Amortization of debt issuance costs		187	133
Collaboration (profit) loss sharing - related party		3,607	(976)
Changes in operating assets and liabilities:
Prepaid expenses and other current and other non-current assets		3,044	(3,841)
Deferred revenue - related party		522	(1,493)
Accounts payable		(3,806)	(6,464)
Operating lease liabilities		(67)	(1,507)
Accrued expenses and other current and long-term liabilities (3)	[1]	(19,030)	(3,693)
Net cash used in operating activities		(76,584)	(66,445)
Cash flows from investing activities:
Purchases of property and equipment		(4,068)	(2,950)
Purchases of investments		(4,426)	(28,156)
Sales and maturities of investments		11,233	44,078
Net cash provided by investing activities		2,739	12,972
Cash flows from financing activities:
Proceeds from exercise of stock options		188	257
Proceeds from issuance of common stock from at the market equity offering		4,239	0
Issuance of common stock under ESPP		1,229	892
Proceeds from issuance of debt, net of issuance costs		0	27,606
Repayment of notes payable		0	(1,907)
Net cash provided by financing activities		5,656	26,848
Net decrease in cash, cash equivalents, and restricted cash		(68,189)	(26,625)
Cash, cash equivalents and restricted cash at beginning of period		171,215	188,002
Cash, cash equivalents and restricted cash at end of period		103,026	161,377
Supplemental disclosure of cash flow information:
Cash paid for interest		1,737	558
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued expenses		928	622
Prepaid rent reclassified to right-of-use assets		0	4,962
Lease liability arising from obtaining right-of-use assets		$ 0	$ 4,370
[1] Includes related party amoun ts of $ ( 9,812 ) and $ ( 1,107 ) at March 31, 2023 and March 31, 2022, respectively (see Note 11)

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Cash Flows [Abstract]
Accrued Expenses and Other current and Long-term Liabilities Related Party Amounts	$ (9,812)	$ (1,107)

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Seres Therapeutics, Inc. (the “Company”) was incorporated under the laws of the State of Delaware in October 2010 under the name Newco LS21, Inc. In October 2011, the Company changed its name to Seres Health, Inc., and in May 2015, the Company changed its name to Seres Therapeutics, Inc. The Company is a commercial-stage microbiome therapeutics company focused on the development and commercialization of a novel class of biological drugs, which are designed to treat disease by modulating the microbiome to restore health by repairing the function of a disrupted microbiome to a non-disease state. The Company’s product, VOWST (fecal microbiota spores, live brpk), formerly called SER-109, was approved by the U.S. Food and Drug Administration (“FDA”) on April 26, 2023 and is the first and only orally administered microbiota-based therapeutic. VOWST is indicated to prevent the recurrence of Clostridioides difficile infection (“CDI”) in patients 18 or older following antibacterial treatment for recurrent CDI. The Company plans to launch VOWST in the United States with its collaborator, Nestlé Health Science (“Nestlé”), in June 2023. Building upon VOWST, the Company is developing therapeutic candidates, such as SER-155, to specifically target infections and antimicrobial resistance. SER-155, a microbiome therapeutic candidate consisting of a 16-strain consortium of cultivated bacteria, is designed to prevent enteric-derived infections and resulting blood stream infections, as well as induce immune tolerance responses to reduce the incidence of Graft versus Host Disease ("GvHD") in patients undergoing allogeneic hematopoietic stem cell transplantation (“allo-HSCT”). Gastrointestinal microbiome data from the first 100 days of SER-155 Phase 1b open-label study cohort 1 showed the successful engraftment of SER-155 bacterial strains, and a substantial reduction in the cumulative incidence of pathogen domination, a biomarker associated with the risk of serious enteric infections and resulting bloodstream infections, as well as GvHD. The tolerability profile observed was favorable, with no serious adverse events attributed to SER-155 administration. Enrollment in the placebo-controlled cohort 2 portion of the study is ongoing and 100-day topline results are anticipated in mid-2024. The Company is progressing additional preclinical stage programs to evaluate how microbiome therapeutics may reduce incidence of infection, which the Company refers to as Infection Protection, in indications such as cancer neutropenia, chronic liver disease, solid organ transplant, and antimicrobial resistant infections more broadly in settings of high-risk such as intensive care units. The Company is also continuing its research activities in ulcerative colitis ("UC"), including evaluating the potential to utilize biomarker-based patient selection and stratification for future studies. In addition, the Company continues to leverage microbiome pharmacokinetic and pharmacodynamic data from across its clinical and preclinical portfolios, using its reverse translational microbiome therapeutic development platform to conduct research on various indications, including inflammatory and immune diseases, cancer, and metabolic diseases. The Company has built and deploys a reverse translational platform for the discovery and development of microbiome therapeutics. This platform incorporates high-resolution analysis of human clinical data to identify microbiome biomarkers associated with disease and non-disease states; preclinical screening using human cell-based assays and in vitro/ex vivo and in vivo disease models customized for microbiome therapeutics; and microbiological capabilities and a strain library that spans broad biological and functional breadth to both identify specific microbes and microbial metabolites that are associated with disease and to design consortia of bacteria with specific pharmacological properties. On April 27, 2023, the Company entered into the Credit Agreement and Guaranty (the “Oaktree Credit Agreement”) among the Company, the subsidiary guarantors from time to time party thereto, the lenders from time to time party thereto (the “Lenders”), and Oaktree Fund Administration, LLC, in its capacity as administrative agent for the Lenders (in such capacity, the “Agent”). The Oaktree Credit Agreement establishes a term loan facility of $ 250,000 (the “Term Loan”) consisting of (i) $ 80,000 (“Tranche A-1”) and (ii) $ 30,000 (“Tranche A-2” and collectively, “Tranche A Loan”), funded on the Closing Date. Upon execution of the Oaktree Credit Agreement and funding of Tranche A Loan, the Hercules Loan and Security Agreement was repaid in full, including the prepayment and end of term charges, which totaled $ 53,380 (See Note 14, Subsequent Events ). The Term Loan provides additional liquidity to the Company for its operations, including our share of costs related to commercialization of VOWST. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. The Company's primary focus in recent months has been and will continue to be supporting commercialization, including the manufacture of VOWST, which requires capital and resources. Other than VOWST, the Company’s product candidates are in development, and will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to potential commercialization. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, or maintained, that any product candidate developed will obtain necessary government regulatory approval, or that any approved product will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The accompanying condensed consolidated financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business. For the three months ended March 31, 2023, the Company incurred a net loss of $ 71,174 , and had net operating cash outflows of $ 76,584 . The Company expects that its operating losses and negative cash flows will continue for the foreseeable future. In the Company’s Annual Report on Form 10-K for the year ended December 31, 2022, the Company disclosed that there was substantial doubt about its ability to continue as a going concern as a result of conditions that existed as of the date of issuance of the consolidated financial statements included therein. At that time, primarily as a result of the increased and costly efforts to prepare for potential commercialization of VOWST, in conjunction with the Company's research and development efforts for other preclinical and product candidates, the Company determined that it would need additional funding in early 2024. Because certain elements of management's plans to mitigate the conditions that raised substantial doubt about the Company’s ability to continue as a going concern were contingent upon the approval by the FDA of the Biologics License Application ("BLA") for VOWST, and such approval was outside the Company's control, those elements could not be considered probable according to Accounting Standards Codification (“ASC”) 205-40, Going Concern ("ASC 205-40"), and therefore also could not be considered in the evaluation of mitigating factors. On April 26, 2023, the BLA was approved by the FDA. Accordingly, the Company is entitled to receive a $125,000 milestone payment under its license agreement with Nestlé executed in July 2021 ("2021 License Agreement," see Note 11, Collaboration Revenue ). Additionally, the Company will be eligible to receive payments from Nestlé for the supply of VOWST, and is entitled to share equally in its commercial profits and losses. As of the date of issuance of these condensed consolidated financial statements, management’ s plans to mitigate the conditions that raised substantial doubt about the Company’s ability to continue as a going concern include receipt of the $ 125,000 milestone payment associated with VOWST FDA approval, which is contractually due and payable to the Company from Nestlé, as well as the commercialization of VOWST and receipt of payments from Nestlé for the supply of VOWST, and sharing equally in commercial profits and losses with Nestlé pursuant to the 2021 License Agreement. Management concluded these plans are probable of being effectively implemented and of mitigating the conditions that raised substantial doubt about the Company’s ability to continue as a going concern. The Company expects that its cash, cash equivalents and investments as of March 31, 2023, together with the net proceeds received in April 2023 from the Term Loan and the $ 125,000 milestone payment currently due and payable from Nestlé, will be sufficient to fund its operating expenses, capital expenditure requirements, and debt service obligations for at least the next 12 months from issuance of these condensed consolidated financial statements. The Company may also seek to raise additional capital through financing or other transactions, including the Company’s at the market equity offering. The future viability of the Company beyond 12 months from issuance of these condensed consolidated financial statements is dependent on its ability to raise additional capital to finance its operations. Unaudited Interim Financial Information The accompanying unaudited condensed consolidated financial statements as of March 31, 2023 and for the three months ended March 31, 2023 have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited condensed 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, which was filed with the SEC on March 7, 2023 (the “Annual Report”). The unaudited condensed consolidated interim financial statements have been prepared on the same basis as the audited consolidated financial statements. The condensed consolidated balance sheet at December 31, 2022 was derived from audited annual financial statements, but does not contain all of the footnote disclosures from the annual financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position, results of operations, and cash flows for the periods presented. Such adjustments are of a normal and recurring nature. The results of operations for the three months ended March 31, 2023 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2023 .

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The significant accounting policies and estimates used in preparation of the unaudited condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2022, and the notes thereto, which are included in the Annual Report. There have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2023. 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 unaudited condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. In the unaudited condensed consolidated financial statements, the Company uses estimates and assumptions related to revenue recognition and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from those estimates. Restricted Cash The Company held restricted cash of $ 8,185 as of March 31, 2023 and December 31, 2022, which represents cash held for the benefit of the landlord for the Company's leases. The Company has classified the restricted cash as long-term on its condensed consolidated balance sheets as the underlying leases are greater than 1 year. Cash, cash equivalents and restricted cash were comprised of the following (in thousands): March 31, December 31, 2023 2022 Cash and cash equivalents $ 94,841 $ 163,030 Restricted cash, non-current 8,185 8,185 Total cash, cash equivalents and restricted cash $ 103,026 $ 171,215

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 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 as of March 31, 2023 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 22,646 $ — $ — $ 22,646 Commercial paper — 1,248 — 1,248 Government securities — 2,744 — 2,744 Investments: Commercial paper $ — $ 4,983 $ — $ 4,983 Corporate bonds — 2,249 — 2,249 Government securities — 4,471 — 4,471 $ 22,646 $ 15,695 $ — $ 38,341 Fair Value Measurements as of December 31, 2022 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 47,863 $ — $ — $ 47,863 Commercial paper — 11,691 — 11,691 Government securities — 4,966 — 4,966 Investments: Commercial paper $ — $ 2,465 $ — $ 2,465 Corporate bonds — 2,957 — 2,957 Government securities — 12,889 — 12,889 $ 47,863 $ 34,968 $ — $ 82,831 Money market funds were valued by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. Commercial paper, corporate bonds, and government securities were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy. There were no transfers between Level 1 or Level 2 during the three months ended March 31, 2023. As of both March 31, 2023 and December 31, 2022, the Company held a restricted investment of $ 1,401 , which represents a certificate of deposit that is classified as Level 2 in the fair value hierarchy.

Investments

Investments	3 Months Ended
	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Investments	4. Investments Investments by security type consisted of the following at March 31, 2023 and December 31, 2022 (in thousands): March 31, 2023 Amortized Gross Gross Fair Investments: Commercial paper $ 4,983 $ — $ — $ 4,983 Corporate bonds 2,248 1 — 2,249 Government securities 4,470 1 — 4,471 $ 11,701 $ 2 $ — $ 11,703 December 31, 2022 Amortized Gross Gross Fair Investments: Commercial paper $ 2,465 $ — $ — $ 2,465 Corporate bonds 2,958 — ( 1 ) 2,957 Government securities 12,898 3 ( 12 ) 12,889 $ 18,321 $ 3 $ ( 13 ) $ 18,311 Investments with original maturities of less than 90 days are included in cash and cash equivalents on the condensed consolidated balance sheets and are not included in the table above. Investments with maturities of less than 12 months are considered current assets and those investments with maturities greater than 12 months are considered non-current assets. Excluded from the tables above are restricted investments of $ 1,401 as the cost approximates current fair value as of March 31, 2023 and December 31, 2022, respectively. As of March 31, 2023 and December 31, 2022 , all of the Company's investments are classified as available-for-sale and mature within 12 months of the balance sheet date.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): March 31, 2023 December 31, 2022 Laboratory equipment $ 26,586 $ 24,533 Computer equipment 3,707 3,557 Furniture and office equipment 4,417 3,491 Leasehold improvements 32,811 32,474 Construction in progress 3,225 3,970 70,746 68,025 Less: Accumulated depreciation and amortization ( 46,440 ) ( 45,040 ) $ 24,306 $ 22,985 Depreciation and amortization expense was $ 1,400 and $ 1,570 for the three months ended March 31, 2023 and 2022, respectively. During the three months ended March 31, 2023 the Company disposed of certain fully-depreciated assets with a cost basis of $ 9 .

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Development and manufacturing costs $ 6,043 $ 6,717 Payroll and payroll-related costs 6,877 14,709 Liability related to 2021 License Agreement (Note 11) 24,958 34,770 Facility and other 6,483 3,644 $ 44,361 $ 59,840

Leases

Leases	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Leases	7. Leases The Company leases real estate, primarily laboratory, office and manufacturing space. The Company’s leases have remaining terms ranging from approximately two to ten years . Certain leases include one or more options to renew, exercisable at the Company’s sole discretion, with renewal terms that can extend the lease from approximately one year to five years . The Company evaluated the renewal options in its leases to determine if it was reasonably certain that the renewal option would be exercised, given the Company’s current business structure, uncertainty of future growth, and the associated impact to real estate, the Company concluded that it is not reasonably certain that any renewal options would be exercised. Therefore, the operating lease assets and operating lease liabilities only contemplate the initial lease terms. All the Company’s leases qualify as operating leases. In April 2022, the Company entered into a lease for additional laboratory and office space in Spring House, Pennsylvania, with a lease term of ten years and a renewal option, subject to certain conditions, for an additional five-year term. The undiscounted minimum lease payments are $ 2,980 , net of a tenant improvement allowance of $ 1,223 , over the original ten-year term. The lease commenced in April 2023, and accordingly as of March 31, 2023, the Company has no t recorded a right-of-use asset or a lease liability with respect thereto. The following table summarizes the presentation in the Company’s condensed consolidated balance sheets of its operating leases (in thousands): March 31, 2023 December 31, 2022 Assets: Operating lease assets $ 108,914 $ 110,984 Liabilities: Operating lease liabilities $ 4,784 $ 3,601 Operating lease liabilities, net of current portion 106,692 107,942 Total operating lease liabilities $ 111,476 $ 111,543 Three Months Ended 2023 2022 Operating lease costs $ 5,410 $ 1,672 Short-term lease costs 368 355 Variable lease costs 1,763 1,032 Total lease costs $ 7,541 $ 3,059 During the three months ended March 31, 2023 and 2022, the Company made cash payments for operating leases of $ 3,413 and $ 2,113 , respectively. As of March 31, 2023, future payments of operating lease liabilities are as follows (in thousands): As of 2023 (remaining 9 months) $ 13,403 2024 $ 19,055 2025 $ 21,164 2026 $ 21,754 2027 and thereafter $ 108,383 Total future minimum lease payments $ 183,759 Less: interest ( 72,283 ) Present value of operating lease liabilities $ 111,476 As of March 31, 2023, the weighted average remaining lease term was 8.68 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 13 % . As of March 31, 2022, the weighted average remaining lease term was 4.98 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 10 % .

Notes Payable

Notes Payable	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Notes Payables	8. Notes Payable On October 29, 2019 (the “Closing Date”), the Company entered into a Loan and Security Agreement (the “Hercules Loan Agreement”) with Hercules Capital, Inc. (“Hercules”) pursuant to which a term loan in an aggregate principal amount of up to $ 50,000 (the “Original Credit Facility”) was available to the Company in three tranches, subject to certain terms and conditions. Effective as of February 24, 2022 (the “Effective Date”), the Company entered into an Amendment to the Hercules Loan Agreement (the “Amendment”), with the lenders party thereto (the “Hercules Lenders”), and Hercules in its capacity as the administrative agent and the collateral agent for the Hercules Lenders, which amended the Original Credit Facility. Pursuant to the Amendment, term loans in an aggregate principal amount of up to $ 100,000 (the “Hercules Credit Facility”) became available to the Company in five tranches, subject to certain terms and conditions. The first tranche in an aggregate principal amount of $ 25,000 was outstanding as of the Effective Date, after taking into account reborrowing by the Company on the Effective Date of a previously-repaid principal amount of approximately $ 2,900 . The second tranche in an aggregate principal amount of $ 12,500 and the third tranche in an aggregate principal amount of $ 12,500 have been advanced to the Company and were outstanding as of the Effective Date. The fourth tranche in an aggregate principal amount of $ 25,000 was available upon satisfaction of certain conditions, including the approval by the FDA of a biologics license application in respect of SER-109 (the "Regulatory Approval Milestone") by no later than December 15, 2023. The fifth tranche in an aggregate principal amount of up to $ 25,000 was available through the Amortization Date (as defined below) upon satisfaction of certain conditions, including the Hercules Lenders’ investment committee approval. All advances outstanding under the Hercules Credit Facility bore interest at a rate equal to the greater of either (i) the Prime Rate (as reported in The Wall Street Journal) plus 6.40 %, and (ii) 9.65 %. For all advances outstanding under the Hercules Credit Facility, the Company was to make interest only payments through December 31, 2023, extendable to December 31, 2024 upon satisfaction of certain conditions (such applicable date, the “Amortization Date”). The principal balance and interest on the advances was to be repaid in equal monthly installments after the Amortization Date and continuing through October 1, 2024, extendable to October 1, 2025, upon satisfaction of certain conditions (such applicable date, the “Hercules Maturity Date”). The Company had the option to prepay advances under the Hercules Credit Facility, in whole or in part, at any time subject to a prepayment charge equal to: (a) 2.0 % of amounts so prepaid, if such prepayment had occurred during the first year following the Effective Date; (b) 1.5 % of the amount so prepaid, if such prepayment had occurred during the second year following the Effective Date, and (c) 1.0 % of the amount so prepaid, if such prepayment had occurred during the third year following the Effective Date. Prior to the repayment (see Note 14, Subsequent Events ), the Hercules Loan Agreement included an end of term charge of 4.85 % of the aggregate amount of the advances made under the Original Credit Facility, due on the earliest date of (i) November 1, 2023; (ii) the date that the Company prepaid all of the outstanding principal in full, or (iii) the date the loan payments were accelerated due to an event of default. The Hercules Loan Agreement also included an additional end of term charge of 1.75 % of the aggregate amount of the advances under the Hercules Credit Facility (including the first tranche of $ 25,000 ), due on the earliest date of (i) the Hercules Maturity Date; (ii) the date that the Company prepaid all of the outstanding principal in full, or (iii) the date the loan payments were accelerated due to an event of default. Other terms of the Hercules Credit Facility remained generally identical to those under the Original Credit Facility, with certain covenants amended by the Amendment to provide the Company with additional operational flexibility, including the ability for the Company to issue up to $ 350,000 in convertible notes. The Hercules Credit Facility included a conditional liquidity covenant commencing on June 15, 2023, which ceased to apply if certain conditions were satisfied. The Hercules Credit Facility is secured by substantially all of the Company’s assets, other than the Company’s intellectual property. The Company has agreed to not pledge or secure its intellectual property to others. The Company accounted for the Hercules Credit Facility as a modification in accordance with the guidance in ASC 470-50, Debt . Amounts paid to the Hercules Lenders were recorded as debt discount and a new effective interest rate was established. Upon issuance, the Hercules Credit Facility was recorded as a liability with an initial carrying value of $ 50,586 , net of debt issuance costs. The initial carrying value was accreted to the repayment amount, which includes the outstanding principal plus the end of term charge, through interest expense using the effective interest rate method over the term of the debt. The effective interest rate in effect as of March 31, 2023 was 15.48 %. As of March 31, 2023 and December 31, 2022, the carrying value of the debt was $ 51,234 and $ 51,047 , respectively. As of March 31, 2023 the future principal payments due under the arrangement, excluding interest and the end of term charge, were as follows (in thousands): Year Ending December 31, Principal 2023 (remaining 9 months) $ — 2024 50,000 Total $ 50,000 During the three months ended March 31, 2023 and 2022 the Company recognized $ 1,948 and $ 912 , respectively, of interest expense related to the Hercules Loan Agreement, which is reflected in interest expense on the condensed consolidated statements of operations and comprehensive loss. On April 27, 2023, the Company executed the Oaktree Credit Agreement (see Note 14, Subsequent Events ), and accordingly at March 31, 2023, had the intent and ability to refinance the short-term principal obligations of the Hercules Credit Facility, as demonstrated by entering into the Oaktree Credit Agreement. Therefore, the balance of the principal payments on the Hercules Credit Facility is classified as long-term portion of note payable on the accompanying condensed consolidated balance sheets.

Common Stock and Stock-Based Aw

Common Stock and Stock-Based Awards	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Common Stock and Stock-Based Awards	9. Common Stock and Stock-Based Awards On May 21, 2021, the Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, with aggregate gross sales proceeds of up to $ 150,000 , from time to time, through an “at the market” equity offering program under which Cowen acts as sales agent. During the three months ended March 31, 2023, the Company sold 787,170 shares of common stock under the Sales Agreement, at an average price of approximately $ 5.67 per share, raising aggregate net proceeds of approximately $ 4,238 after deducting an aggregate commission of approximately 3 % and other issuance costs. During the three months ended March 31, 2022, the Company did no t sell any shares of common stock under the Sales Agreement. Stock Options The following table summarizes the Company’s stock option activity since December 31, 2022: Number Weighted Weighted Aggregate (in years) Outstanding as of December 31, 2022 14,940,034 $ 10.03 7.25 $ 11,608 Granted 2,118,845 $ 5.50 Exercised ( 56,523 ) $ 3.32 Forfeited ( 176,212 ) $ 10.46 Outstanding as of March 31, 2023 16,826,144 $ 9.48 7.31 $ 12,188 Options exercisable as of March 31, 2023 8,676,217 $ 10.16 5.98 $ 8,764 The weighted average grant-date fair value of stock options granted during the three months ended March 31, 2023 and 2022 was $ 4.56 and $ 5.90 per share, respectively. During the year ended December 31, 2021, the Company granted performance-based stock options to employees for the purchase of an aggregate of approximately 562,000 shares of common stock with a grant date fair value of $ 5.53 per share. These stock options are exercisable only upon achievement of specified performance targets. As of March 31, 2023 , none of these options were exercisable because none of the specified performance targets had been achieved. Because achievement of the specified performance targets was not deemed probable as of March 31, 2023 , the Company did no t record any expense for these stock options from the dates of issuance through March 31, 2023. Restricted Stock Units The following table summarizes the Company’s restricted stock unit activity since December 31, 2022: Number Weighted Unvested restricted stock units as of December 31, 2022 1,549,540 $ 9.37 Granted 3,014,810 $ 5.50 Vested ( 259,023 ) $ 8.91 Forfeited ( 89,493 ) $ 9.50 Unvested restricted stock units as of March 31, 2023 4,215,834 $ 6.63 The Company has granted restricted stock units with service-based vesting conditions ("RSUs") and performance-based vesting conditions ("PSUs"). RSUs and PSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. RSUs and PSUs may not be sold or transferred by the holder and vest according to the service-based or performance-based vesting conditions of the award. During the three months ended March 31, 2023 and 2022, the Company granted 1,692,095 and 989,544 RSUs and 1,322,715 and 0 PSUs, respectively. RSUs generally vest over four years , with 25 % vesting after one year, and the remaining 75 % vesting quarterly over the next 3 years, subject to continued service to the Company through the applicable vesting date. PSUs vest according to the performance requirements of the awards, generally when the Company has determined that the specified performance targets have been achieved. During the year ended December 31, 2021, the Company granted PSUs to two employees for the purchase of an aggregate of 85,000 shares of common stock with a grant date fair value of $ 9.59 per share and 40,000 shares of common stock with a grant date fair value of $ 20.35 per share. These PSUs vest only upon achievement of specified performance targets. In October 2022, 42,500 of the PSUs with a grant date fair value of $ 9.59 , and 20,000 of the PSUs with a grant date fair value of $ 20.35 , vested fully, as the associated performance targets were achieved. Accordingly, the Company recorded $ 815 in compensation expense during the year ended December 31, 2022, with respect to these PSUs. As of March 31, 2023 , the remaining PSUs underlying these awards were not vested because the associated targets had not been achieved. In addition, the performance targets were not deemed probable of achievement. Accordingly, the Company did no t record any expense for these PSUs from the dates of issuance through March 31, 2023. During the three months ended March 31, 2023, the Company granted PSUs to employees for the purchase of an aggregate of 1,322,715 shares of common stock with a grant date fair value of $ 5.50 . These PSUs begin to vest ratably only upon achievement of specified performance targets. As of March 31, 2023 , none of these PSUs had started to vest because the associated targets had not been achieved and were not deemed probable of achievement. Accordingly, the Company did no t record any expense for these PSUs from the date of issuance through March 31, 2023. Stock-based Compensation Expense The Company recorded stock-based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2023 2022 Research and development expenses $ 3,731 $ 2,483 General and administrative expenses 3,119 2,596 $ 6,850 $ 5,079

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Net Loss per Share	10. 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 data): Three Months Ended March 31, 2023 2022 Numerator: Net loss $ ( 71,174 ) $ ( 56,624 ) Loss attributable to common stockholders - basic and diluted $ ( 71,174 ) $ ( 56,624 ) Denominator: Weighted-average shares outstanding 125,862,975 92,164,419 Loss per share applicable to common stockholders - basic and diluted $ ( 0.57 ) $ ( 0.61 ) Anti-dilutive potential common stock equivalents excluded from the calculation of Stock options to purchase common stock 16,826,144 14,820,313 Unvested restricted stock units 4,215,834 1,582,641 Shares issuable under ESPP 68,594 32,355 The anti-dilutive potential common stock equivalents for the three months ended March 31, 2023 and 2022 were excluded from the computation of diluted net income per share attributable to common stockholders because those stock options to purchase common stock and restricted stock units had an anti-dilutive impact due to the assumed proceeds per share using the treasury stock method being greater than the average fair value of the Company’s common shares for those periods.

Collaboration Revenue

Collaboration Revenue	3 Months Ended
	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
Collaboration Revenue	11. Collaboration Revenue License Agreement with NHSc Rx License GmbH (Nestlé) Summary of Agreement In July 2021, the Company entered into the 2021 License Agreement with NHSc Pharma Partners, succeeded by NHSc Rx License GmbH (together with Société des Produits Nestlé S.A., their affiliates, and their subsidiaries, "Nestlé"). Under the terms of the Agreement, the Company granted Nestlé a co-exclusive, sublicensable (under certain circumstances) license to develop, commercialize and conduct medical affairs activities for (i) therapeutic products based on the Company's microbiome technology (including VOWST, previously the Company's SER-109 product candidate) that are developed by the Company or on the Company's behalf for the treatment of CDI and recurrent CDI, as well as any other indications pursued for the products upon mutual agreement of the parties (the “2021 Field”) in the United States and Canada (the “2021 Licensed Territory”), and (ii) VOWST and any improvements and modifications thereto developed pursuant to the terms of the 2021 License Agreement (the "2021 Collaboration Products") for any indications in the 2021 Licensed Territory. The Company was responsible for completing development of VOWST in the 2021 Field in the United States until first regulatory approval, which was obtained on April 26, 2023. Nestlé has the sole right to commercialize the 2021 Collaboration Products in the 2021 Licensed Territory in accordance with a commercialization plan. Both parties will perform medical affairs activities in the 2021 Licensed Territory in accordance with a medical affairs plan. The Company is responsible for the manufacturing and supply for commercialization under a supply agreement that has been executed between the parties. Both parties will perform pre-launch activities of 2021 Collaboration Products prior to the first commercial sale in the United States. The Company is responsible for funding the pre-launch activities until first commercial sale of 2021 Collaboration Products in the 2021 Licensed Territory and in accordance with a pre-launch plan, up to a specified cap. Following first commercial sale of 2021 Collaboration Products, the Company will be entitled to share equally in its commercial profits and losses. In connection with the 2021 License Agreement, the Company received an upfront payment of $ 175,000 . The Company is eligible to receive additional payments of up to $ 360,000 if certain regulatory and sales milestones are achieved. The potential future milestone payments include up to $ 135,000 for the achievement of specified regulatory milestones and up to $ 225,000 for the achievement of specified net sales milestones. The 2021 License Agreement continues in effect until all development and commercialization activities for all 2021 Collaboration Products in the 2021 Licensed Territory have permanently ceased. The 2021 License Agreement may be terminated by either party upon sixty days ’ written notice for the other party’s material breach that remains uncured during such sixty-day period, or immediately upon written notice for the other party’s insolvency. Nestlé may also terminate the 2021 License Agreement at-will (i) with twelve months’ prior written notice, effective only on or after the third anniversary of first commercial sale of the first 2021 Collaboration Product in the 2021 Licensed Territory, or (ii) if first commercial sale of the first 2021 Collaboration Product in the 2021 Licensed Territory has not occurred by the fifth anniversary of the effective date of the 2021 License Agreement, with one hundred eighty days’ prior written notice, which must be provided during a specified period set forth in the 2021 License Agreement. The Company may also terminate the 2021 License Agreement immediately upon written notice if Nestlé challenges any licensed patent in the 2021 Licensed Territory. Upon termination of the 2021 License Agreement, all licenses granted to Nestlé by the Company will terminate. If the Company commits a material breach of the 2021 License Agreement, Nestlé may elect not to terminate the 2021 License Agreement but instead apply specified adjustments to the payment terms and other terms and conditions of the 2021 License Agreement. Accounting Analysis The 2021 License Agreement represents a separate contract between Nestlé and the Company. The 2021 License Agreement is within the scope of Accounting Standard Update 2018-18, Collaborative Arrangements (Topic 808), and has elements that are within the scope of ASC 606 - Revenue From Contracts with Customers (Topic 606) and Topic 808. The Company identified the following promises in the 2021 License Agreement that were evaluated under the scope of Topic 606: (i) delivery of a co-exclusive license for VOWST (previously SER-109) to develop, commercialize and conduct medical affairs in the United States and Canada; (ii) services to be performed in accordance with the development and regulatory activity plan to obtain regulatory approval of VOWST in the United States. The Company also evaluated whether certain options outlined within the 2021 License Agreement represented material rights that would give rise to a performance obligation and concluded that none of the options convey a material right to Nestlé and therefore are not considered separate performance obligations within the 2021 License Agreement. The Company assessed the above promises and determined that the co-exclusive license for VOWST and the services to obtain regulatory approval of VOWST in the United States are reflective of a vendor-customer relationship and therefore represent performance obligations within the scope of Topic 606. The co-exclusive license for VOWST in the United States and Canada is considered functional intellectual property and distinct from other promises under the contract as Nestlé can benefit from the license on its own or together with other readily available resources. The services performed by the Company to obtain regulatory approval of VOWST are not complex or specialized, could be performed by another qualified third party, are not expected to significantly modify or customize the license given that VOWST was late-stage intellectual property that completed clinical development and the services are expected to be performed over a short period of time. Therefore, the license and the services each represents a separate performance obligation within a contract with a customer under the scope of Topic 606 at contract inception. The Company considers the collaborative pre-launch activities and commercialization activities to be separate units of account within the scope of Topic 808 and are not deliverables under Topic 606. The Company and Nestlé are both active participants in the pre-launch activities and commercialization activities and are exposed to significant risks and rewards that are dependent on the commercial success of the activities in the arrangement. The up-front payment of $ 175,000 compensated the Company for: (i) the co-exclusive license for VOWST to develop, commercialize and conduct medical affairs in the United States and Canada, (ii) services performed in accordance with the development and regulatory activity plan to obtain regulatory approval of VOWST in the United States and (iii) pre-launch activities performed by Nestlé and the Company until the first commercial sale of VOWST in the United States. The commercialization activities, which include the commercial manufacturing, participation on joint steering committees and medical affairs work, that occur after regulatory approval of VOWST in the United States, are part of the 50 / 50 sharing of commercial profits. Therefore, the up-front payment of $ 175,000 does not compensate the Company for these activities. The Company allocated the $ 175,000 between the Topic 606 unit of account and the Topic 808 unit of account by determining the standalone selling price (SSP) of each good or service. The selling price of each good or service was determined based on the Company’s SSP with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company determined the transaction price under Topic 606 to be $ 139,500 and the Topic 808 amount to be $ 35,500 at the inception of the 2021 License Agreement. The Company determined that any variable consideration related to regulatory milestones is deemed to be fully constrained and therefore excluded from the transaction price due to the high degree of uncertainty and risk associated with these potential payments, as the Company determined that it could not assert that it was probable that a significant reversal in the amount of cumulative revenue recognized will not occur. The Company also determined that sales milestones relate solely to the license of intellectual property and are therefore excluded from the transaction price under the sales- or usage-based royalty exception of Topic 606. Revenue related to these sales milestones will only be recognized when the associated sales occur, and relevant thresholds are met. The Topic 606 transaction price of $ 139,500 was allocated to the co-exclusive license for VOWST and the services performed in accordance with the development and regulatory activity plan to obtain regulatory approval of VOWST in the United States based on the Company’s SSP. The Company recognized revenue for the license performance obligation at a point in time, that is upon transfer of the license to Nestlé. As control of the license was transferred in July 2021, the Company recognized $ 131,343 of collaboration revenue - related party during the year ended December 31, 2021 pertaining to the license performance obligation. The remaining amount of the Topic 606 transaction price of $ 8,157 was allocated to the services performance obligation and is being recognized over time as the services are performed. During the three months ended March 31, 2023 and 2022 the Company recognized $ 1,122 and $ 768 of collaboration revenue - related party, respectively, related to the services performance obligation under the 2021 License Agreement. The amount allocated to the Topic 808 unit of accounting relates to the pre-launch activities performed prior to the first commercial sale of 2021 Collaboration Products and was determined to be $ 35,500 based on standalone selling price. The Company recorded the $ 35,500 in total liabilities on its condensed consolidated balance sheet at the inception of the arrangement. On a quarterly basis, the Company and Nestlé will provide financial information about the pre-launch activities performed by both parties. The Company reduces the $ 35,500 liability as the pre-launch activities are performed and it makes payments to Nestl é for the pre-launch costs Nestlé incurs. As of March 31, 2023 and December 31, 2022, there was $ 24,958 and $ 34,770 , respectively, included in accrued expenses and other current liabilities which includes Nestlé incurred costs not yet reimbursed. The cost associated with pre-launch activities performed by the Company is recorded within total operating expenses in the Company’s condensed consolidated statements of operations and comprehensive loss. In the three months ended March 31, 2023 and 2022, the Company recognized $ 801 and $ 1,635 , respectively, in research and development expenses and $ 2,703 and $ 2,438 , respectively, in general and administrative expenses associated with pre-launch activities performed. As the Company and Nestlé are both active participants in the pre-launch activities, the sharing of 50 % of the pre-launch costs will be recognized in collaboration (profit) loss sharing - related party in the Company’s condensed consolidated statements of operations and comprehensive loss. The Company recorded $ 3,607 of expense and $ 976 of income in the collaboration (profit) loss sharing line for the three months ended March 31, 2023 and 2022, respectively. Collaboration and License Agreement with Société des Produits Nestlé S.A. (Nestlé) Summary of Agreement In January 2016, the Company entered into a collaboration and license agreement with Nestec Ltd., succeeded by Société des Produits Nestlé S.A. (together with NHSc Rx License GmbH, their affiliates and their subsidiaries, “Nestlé”) (the “2016 License Agreement”) for the development and commercialization of certain product candidates for the treatment and management of CDI and inflammatory bowel disease (“IBD”), including UC and Crohn’s disease. The 2016 License Agreement supports the development of the Company’s portfolio of products for CDI and IBD in markets outside of the United States and Canada (the “2016 Licensed Territory”). Under the 2016 License Agreement, the Company granted to Nestlé an exclusive, royalty-bearing license to develop and commercialize, in the 2016 Licensed Territory, certain products based on its microbiome technology that are being developed or commercialized, as applicable, for the treatment of CDI and IBD, including VOWST, SER-262, SER-287 and SER-301 (collectively, the “2016 Collaboration Products”). The 2016 License Agreement sets forth the Company’s and Nestlé’s respective obligations for development, commercialization, regulatory and manufacturing and supply activities for the 2016 Collaboration Products with respect to the licensed fields and the 2016 Licensed Territory. Under the 2016 License Agreement, Nestlé agreed to pay the Company an upfront cash payment of $ 120,000 , which the Company received in February 2016. The Company is eligible to receive up to $ 285,000 in development milestone payments, $ 375,000 in regulatory payments and up to an aggregate of $ 1,125,000 for the achievement of certain commercial milestones related to the sales of the 2016 Collaboration Products. Nestlé also agreed to pay the Company tiered royalties, at percentages ranging from the high single digits to high teens, of net sales of 2016 Collaboration Products in the 2016 Licensed Territory. Under the 2016 License Agreement, the Company is entitled to receive a $ 20,000 milestone payment from Nestlé following initiation of a SER-287 Phase 2 study and a $ 20,000 milestone payment from Nestlé following the initiation of a SER-287 Phase 3 study. In November 2018, the Company entered into a letter agreement with Nestlé which modified the 2016 License Agreement to address the current clinical plans for SER-287. Pursuant to the letter agreement, the Company and Nestlé agreed that following initiation of the SER-287 Phase 2b study, the Company would be entitled to receive $ 40,000 in milestone payments from Nestlé, which represent the milestone payments due to the Company for the initiation of a SER-287 Phase 2 study and a Phase 3 study. The SER-287 Phase 2b study was initiated and the $ 40,000 of milestone payments were received in December 2018. The letter agreement also provides scenarios under which Nestlé’s reimbursement to the Company for certain Phase 3 development costs would be reduced or delayed depending on the outcomes of the SER-287 Phase 2b study. The 2016 License Agreement continues in effect until terminated by either party on the following bases: (i) Nestlé may terminate the 2016 License Agreement in the event of serious safety issues related to any of the 2016 Collaboration Products; (ii) the Company may terminate the 2016 License Agreement if Nestlé challenges the validity or enforceability of any of the Company’s licensed patents; and (iii) either party may terminate the 2016 License Agreement in the event of the other party’s uncured material breach or insolvency. Upon termination of the 2016 License Agreement, all licenses granted to Nestlé by the Company will terminate, and all rights in and to the 2016 Collaboration Products in the 2016 Licensed Territory will revert to the Company. If the Company commits a material breach of the 2016 License Agreement, Nestlé may elect not to terminate the 2016 License Agreement but instead apply specified adjustments to its payment obligations and other terms and conditions of the 2016 License Agreement. Accounting Analysis The Company assessed the 2016 License Agreement in accordance with Topic 606 and concluded that Nestlé is a customer. The Company identified the following promises under the contract: (i) a license to develop and commercialize the 2016 Collaboration Products in the 2016 Licensed Territory, (ii) obligation to perform research and development services, (iii) participation on a joint steering committee, and (iv) manufacturing services to provide clinical supply to complete future clinical trials. In addition, the Company identified a contingent obligation to perform manufacturing services to provide commercial supply if commercialization occurs, which is contingent upon regulatory approval. This contingent obligation is not a performance obligation at inception and has been excluded from the initial allocation as it represents a separate buying decision at market rates, rather than a material right in the contract. The Company assessed the promised goods and services to determine if they are distinct. Based on this assessment, the Company determined that Nestlé cannot benefit from the promised goods and services separately from the others as they are highly interrelated and therefore not distinct. Accordingly, the promised goods and services represent one combined performance obligation and the entire transaction price will be allocated to that single combined performance obligation. At contract inception, the Company determined that the $ 120,000 non-refundable upfront amount constituted the entirety of the consideration to be included in the transaction price as the development, regulatory, and commercial milestones were fully constrained. During the year ended December 31, 2016, the Company received $ 10,000 from Nestlé in connection with the initiation of the Phase 1b study for SER-262 in CDI. During the year ended December 31, 2017, the Company received $ 20,000 from Nestlé in connection with the initiation of the Phase 3 study for VOWST, then SER-109. During the year ended December 31, 2018, the Company received $ 40,000 from Nestlé in connection with the initiation of the Phase 2b study for SER-287. During the year ended December 31, 2020, the Company received $ 10,000 from Nestlé in connection with the initiation of the Phase 1b SER-301 study. As of March 31, 2023, the aggregate amount of the transaction price allocated to the performance obligation of the 2016 License Agreement was approximately $ 200,000 . During the three months ended March 31, 2023 and 2022, using the cost-to-cost method, which best depicts the transfer of control to the customer, the Company recognized $ ( 1,644 ) and $ 725 of collaboration revenue – related party, respectively. As of March 31, 2023 and December 31, 2022, there was $ 97,211 and $ 96,689 , respectively, of deferred revenue related to the unsatisfied portion of the performance obligations under the Nestlé agreements. As of March 31, 2023 and December 31, 2022, the deferred revenue is classified as current or non-current in the condensed consolidated balance sheets based on the Company’s estimate of revenue that will be recognized within the next 12 months, which is determined by the cost-to-cost method which measures the extent of progress towards completion based on the ratio of actual costs incurred to the total estimated costs expected upon satisfying the performance obligation. All costs associated with the 2016 License Agreement are recorded in research and development expense in the condensed consolidated statements of operations and comprehensive loss. Contract Balances from Contracts with Customers The following table presents changes in the Company’s contract liabilities during the three months ended March 31, 2023 and 2022 (in thousands): Balance as of December 31, 2022 Additions Deductions Balance as of March 31, 2023 Three Months Ended March 31, 2023 Contract liabilities: Deferred revenue - related party $ 96,689 1,644 ( 1,122 ) $ 97,211 Balance as of December 31, 2021 Additions Deductions Balance as of March 31, 2022 Three Months Ended March 31, 2022 Contract liabilities: Deferred revenue - related party $ 103,817 — ( 1,493 ) $ 102,324 During the three months ended March 31, 2023 and 2022 the Company recognized the following revenues as a result of changes in the contract liability balances in the respective periods (in thousands): Three Months Ended 2023 2022 Revenue recognized in the period from: Amounts included in the contract liability at the beginning of the period $ ( 522 ) $ 1,493 When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded. Revenue is recognized from the contract liability over time using the cost-to-cost method. During the three months ended March 31, 2023, the Company's estimate of total costs expected to be incurred increased, resulting in a reversal of revenue based on its cost-to-cost methodology.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies Leases Refer to Note 7, Leases, for discussion of the commitments associated with the Company’s lease portfolio. 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 its officers 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 does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has no t accrued any liabilities related to such obligations in its consolidated financial statements as of March 31, 2023 or December 31, 2022. Legal Contingencies The Company accrues a liability for legal contingencies when it believes that it is both probable that a liability has been incurred and that the Company can reasonably estimate the amount of the loss. The Company reviews these accruals and adjusts them to reflect ongoing negotiations, settlements, rulings, advice of legal counsel and other relevant information. To the extent new information is obtained and the views on the probable outcomes of claims, suits, assessments, investigations or legal proceedings change, changes in the Company’s accrued liabilities would be recorded in the period in which such determination is made. In addition, in accordance with the relevant authoritative guidance, for any matters in which the likelihood of material loss is at least reasonably possible, the Company will provide disclosure of the possible loss or range of loss. If a reasonable estimate cannot be made, however, the Company will provide disclosure to that effect. The Company expenses legal costs as they are incurred. The Company did no t accrue any liabilities related to legal contingencies in its consolidated financial statements as of March 31, 2023 or December 31, 2022 .

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	13. Related Party Transactions As described in Note 11, in July 2021, the Company entered into the 2021 License Agreement with NHSc Pharma Partners, succeeded by NHSc Rx License GmbH (together with Société des Produits Nestlé S.A., their affiliates, and their subsidiaries, “Nestlé”). NHSc Rx License GmbH is an affiliate of one of the Company's significant stockholders, Société des Produits Nestlé S.A. During the three months ended March 31, 2023 and 2022, the Company recognized $ 1,122 and $ 768 , respectively, of related party revenue associated with the 2021 License Agreement. As of March 31, 2023 and December 31, 2022, there was $ 854 and $ 1,976 of deferred revenue related to the 2021 License Agreement, respectively, which is classified as current in the condensed consolidated balance sheets. As of March 31, 2023 and December 31, 2022 there was $ 24,958 and $ 34,770 included in accrued expenses and other liabilities related to the 2021 License Agreement. During the three months ended March 31, 2023 , the Company paid Nestlé $ 13,419 for Nestlé's share of the collaboration expenses pursuant to the 2021 License Agreement. The Company made no payments to Nestlé during the three months ended March 31, 2022 . There is no amount due from Nestlé pursuant to the 2021 License Agreement as of March 31, 2023 or December 31, 2022. As described in Note 11, in January 2016, the Company entered into the 2016 License Agreement with Nestec, Ltd, succeeded by Société des Produits Nestlé S.A. for the development and commercialization of certain product candidates in development for the treatment and management of CDI and IBD, including UC and Crohn’s disease. Société des Produits Nestlé S.A. is one of the Company's significant stockholders. During the three months ended March 31, 2023 and 2022, the Company recognized $ ( 1,644 ) and $ 725 , respectively, of related party revenue associated with the 2016 License Agreement. As of March 31, 2023 and December 31, 2022, there was $ 96,357 and $ 94,713 of deferred revenue related to the 2016 License Agreement, which is classified as current or non-current in the condensed consolidated balance sheets. The Company has made no payments to Nestlé during the three months ended March 31, 2023 and 2022 . There is no amount due from Nestlé pursuant to the 2016 License Agreement as of March 31, 2023 or December 31, 2022 .

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On April 27, 2023, the Company entered into the Oaktree Credit Agreement among the Company, the subsidiary guarantors from time to time party thereto, the Lenders, and the Agent. The Oaktree Credit Agreement establishes the Term Loan consisting of (i) the $ 110,000 Tranche A Loan, (ii) $ 45,000 (the “Tranche B Loan”) that the Company may borrow subject to certain conditions, (iii) $ 45,000 (the “Tranche C Loan”) that the Company may borrow subject to certain conditions, and (iv) $ 50,000 (the “Tranche D Loan”) available in Oaktree’s sole discretion; provided, in the case of the Tranche B Loan and the Tranche C Loan, that the Company and its subsidiaries have achieved certain VOWST net sales targets. The Term Loan has a maturity date of April 27, 2029 (the “Maturity Date”). Of the $ 110,000 Tranche A Loan advanced by the Lenders at closing, approximately $ 53,380 repaid the Company's existing credit facility with Hercules. After deducting other transaction expenses and fees, the Company received net proceeds of approximately $ 50,446 . Borrowings under the Term Loan will bear interest at a rate per annum equal to three-month term Secured Overnight Financing Rate ("SOFR") (subject to a 2.50 % floor and a 5.00 % cap), plus an applicable margin of 7.875 %, payable quarterly in arrears. If certain VOWST net sales targets are met, the applicable margin will be reduced from 7.875 % to 7.50 % through the Maturity Date. The Company is permitted to make quarterly interest-only payments on the Term Loan for the first three years after the Closing Date. Beginning on June 30, 2026, the Company will be required to make quarterly payments of interest, plus repay 7.50 % of the outstanding principal of the Term Loan in quarterly installments until the Maturity Date, unless the interest only period is extended based upon the achievement of certain VOWST net sales targets. The Company is obligated to pay the Lenders an exit fee equal to 1.50 % of the aggregate amount of the Term Loan funded, such exit fee to be due and payable upon the earliest to occur of (1) the Maturity Date, (2) the acceleration of the outstanding Term Loan, and (3) the prepayment of the outstanding Term Loan. The Company may voluntarily prepay the outstanding Term Loan, subject to a customary make-whole for the first two years following the Closing Date plus 4.0 % of the principal amount of the Term Loan prepaid, and thereafter a prepayment premium equal to (i) 4.0 % of the principal amount of the Term Loan prepaid, if prepaid after the second anniversary of the Closing Date through and including the third anniversary of the Closing Date, (ii) 2.0 % of the principal amount of the Term Loan if prepaid after the third anniversary of the Closing Date through and including the fourth anniversary of the Closing Date, (iii) 1.0 % of the principal amount of the Term Loan if prepaid after the fourth anniversary of the Closing Date through and including the fifth anniversary of the Closing Date, with no prepayment premium due after the fifth anniversary of the Closing date through the Maturity Date. The Company’s obligations under the Oaktree Credit Agreement and the other Loan Documents (as defined in the Oaktree Credit Agreement) will be guaranteed by any domestic subsidiaries of the Company that become Guarantors (as defined in the Oaktree Credit Agreement), subject to certain exceptions. The Company’s and the Guarantors’ (collectively, the “Loan Parties”) respective obligations under the Oaktree Credit Agreement and the other Loan Documents are secured by first priority security interests in substantially all assets of the Loan Parties, including intellectual property, subject to certain customary thresholds and exceptions. As of the Closing Date, there are no Guarantors. The Oaktree Credit Agreement contains customary representations, warranties and affirmative and negative covenants, including a financial covenant requiring the Company to maintain certain levels of cash and cash equivalents in accounts subject to a control agreement in favor of the Agent of at least $ 30,000 at all times commencing from 30 days after the Closing Date and decreasing to $25,000 of cash and cash equivalents in such controlled accounts after the Company borrows any Tranche B Loan. In addition, the Oaktree Credit Agreement contains certain events of default that entitle the Agent to cause the Company’s indebtedness under the Oaktree Credit Agreement to become immediately due and payable, and to exercise remedies against the Loan Parties and the collateral securing the Term Loan, including cash. In an event of default and for its duration, as defined in the Oaktree Credit Agreement, an additional default interest rate equal to 2.0 % per annum may apply to all obligations owed under the Oaktree Credit Agreement. On the Closing Date, the Company is required to issue to the Lenders of such Term Loan warrants to purchase 647,589 shares (subject to certain adjustments) of the Company’s common stock (the “Tranche A Warrant”), at an exercise price per share of $ 6.69 . Upon the funding of each of the Tranche B Loan and the Tranche C Loan, the Company is required to issue to the Lenders of the Term Loan additional warrants (together with the Tranche A Warrant, "Warrants") to purchase 264,922 shares (subject to certain adjustments) of the Company’s common stock on each such funding date at an exercise price equal to the trailing volume weighted average price of the Company’s common stock for the 30 trading days prior to the funding date for each tranche. The Warrants are immediately exercisable, and the exercise period will expire seven years from the date of issuance.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
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 unaudited condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. In the unaudited condensed consolidated financial statements, the Company uses estimates and assumptions related to revenue recognition and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from those estimates.
Restricted Cash	Restricted Cash The Company held restricted cash of $ 8,185 as of March 31, 2023 and December 31, 2022, which represents cash held for the benefit of the landlord for the Company's leases. The Company has classified the restricted cash as long-term on its condensed consolidated balance sheets as the underlying leases are greater than 1 year. Cash, cash equivalents and restricted cash were comprised of the following (in thousands): March 31, December 31, 2023 2022 Cash and cash equivalents $ 94,841 $ 163,030 Restricted cash, non-current 8,185 8,185 Total cash, cash equivalents and restricted cash $ 103,026 $ 171,215

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Cash, Cash Equivalents and Restricted Cash	Cash, cash equivalents and restricted cash were comprised of the following (in thousands): March 31, December 31, 2023 2022 Cash and cash equivalents $ 94,841 $ 163,030 Restricted cash, non-current 8,185 8,185 Total cash, cash equivalents and restricted cash $ 103,026 $ 171,215

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis	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 as of March 31, 2023 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 22,646 $ — $ — $ 22,646 Commercial paper — 1,248 — 1,248 Government securities — 2,744 — 2,744 Investments: Commercial paper $ — $ 4,983 $ — $ 4,983 Corporate bonds — 2,249 — 2,249 Government securities — 4,471 — 4,471 $ 22,646 $ 15,695 $ — $ 38,341 Fair Value Measurements as of December 31, 2022 Using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 47,863 $ — $ — $ 47,863 Commercial paper — 11,691 — 11,691 Government securities — 4,966 — 4,966 Investments: Commercial paper $ — $ 2,465 $ — $ 2,465 Corporate bonds — 2,957 — 2,957 Government securities — 12,889 — 12,889 $ 47,863 $ 34,968 $ — $ 82,831

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Schedule of Investments by Security Type	Investments by security type consisted of the following at March 31, 2023 and December 31, 2022 (in thousands): March 31, 2023 Amortized Gross Gross Fair Investments: Commercial paper $ 4,983 $ — $ — $ 4,983 Corporate bonds 2,248 1 — 2,249 Government securities 4,470 1 — 4,471 $ 11,701 $ 2 $ — $ 11,703 December 31, 2022 Amortized Gross Gross Fair Investments: Commercial paper $ 2,465 $ — $ — $ 2,465 Corporate bonds 2,958 — ( 1 ) 2,957 Government securities 12,898 3 ( 12 ) 12,889 $ 18,321 $ 3 $ ( 13 ) $ 18,311

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): March 31, 2023 December 31, 2022 Laboratory equipment $ 26,586 $ 24,533 Computer equipment 3,707 3,557 Furniture and office equipment 4,417 3,491 Leasehold improvements 32,811 32,474 Construction in progress 3,225 3,970 70,746 68,025 Less: Accumulated depreciation and amortization ( 46,440 ) ( 45,040 ) $ 24,306 $ 22,985

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2023
Payables and Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, 2023 December 31, 2022 Development and manufacturing costs $ 6,043 $ 6,717 Payroll and payroll-related costs 6,877 14,709 Liability related to 2021 License Agreement (Note 11) 24,958 34,770 Facility and other 6,483 3,644 $ 44,361 $ 59,840

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Summary of Operating Lease Assets and Liabilities	The following table summarizes the presentation in the Company’s condensed consolidated balance sheets of its operating leases (in thousands): March 31, 2023 December 31, 2022 Assets: Operating lease assets $ 108,914 $ 110,984 Liabilities: Operating lease liabilities $ 4,784 $ 3,601 Operating lease liabilities, net of current portion 106,692 107,942 Total operating lease liabilities $ 111,476 $ 111,543
Summary of Lease Costs	Three Months Ended 2023 2022 Operating lease costs $ 5,410 $ 1,672 Short-term lease costs 368 355 Variable lease costs 1,763 1,032 Total lease costs $ 7,541 $ 3,059
Schedule of Future Payments of Operating Lease Liabilities	As of March 31, 2023, future payments of operating lease liabilities are as follows (in thousands): As of 2023 (remaining 9 months) $ 13,403 2024 $ 19,055 2025 $ 21,164 2026 $ 21,754 2027 and thereafter $ 108,383 Total future minimum lease payments $ 183,759 Less: interest ( 72,283 ) Present value of operating lease liabilities $ 111,476

Notes Payables (Tables)

Notes Payables (Tables)	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Summary of Future Principal Payments Due Under Arrangement, Excluding Interest and End of Term Charge	As of March 31, 2023 the future principal payments due under the arrangement, excluding interest and the end of term charge, were as follows (in thousands): Year Ending December 31, Principal 2023 (remaining 9 months) $ — 2024 50,000 Total $ 50,000

Common Stock and Stock-Based _2

Common Stock and Stock-Based Awards (Tables)	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity since December 31, 2022: Number Weighted Weighted Aggregate (in years) Outstanding as of December 31, 2022 14,940,034 $ 10.03 7.25 $ 11,608 Granted 2,118,845 $ 5.50 Exercised ( 56,523 ) $ 3.32 Forfeited ( 176,212 ) $ 10.46 Outstanding as of March 31, 2023 16,826,144 $ 9.48 7.31 $ 12,188 Options exercisable as of March 31, 2023 8,676,217 $ 10.16 5.98 $ 8,764
Summary of Restricted Stock Unit Activity	The following table summarizes the Company’s restricted stock unit activity since December 31, 2022: Number Weighted Unvested restricted stock units as of December 31, 2022 1,549,540 $ 9.37 Granted 3,014,810 $ 5.50 Vested ( 259,023 ) $ 8.91 Forfeited ( 89,493 ) $ 9.50 Unvested restricted stock units as of March 31, 2023 4,215,834 $ 6.63
Summary of Stock Based Compensation Expense	The Company recorded stock-based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2023 2022 Research and development expenses $ 3,731 $ 2,483 General and administrative expenses 3,119 2,596 $ 6,850 $ 5,079

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
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 data): Three Months Ended March 31, 2023 2022 Numerator: Net loss $ ( 71,174 ) $ ( 56,624 ) Loss attributable to common stockholders - basic and diluted $ ( 71,174 ) $ ( 56,624 ) Denominator: Weighted-average shares outstanding 125,862,975 92,164,419 Loss per share applicable to common stockholders - basic and diluted $ ( 0.57 ) $ ( 0.61 ) Anti-dilutive potential common stock equivalents excluded from the calculation of Stock options to purchase common stock 16,826,144 14,820,313 Unvested restricted stock units 4,215,834 1,582,641 Shares issuable under ESPP 68,594 32,355

Collaboration Revenue (Tables)

Collaboration Revenue (Tables)	3 Months Ended
	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
Changes in Contract Liabilities	The following table presents changes in the Company’s contract liabilities during the three months ended March 31, 2023 and 2022 (in thousands): Balance as of December 31, 2022 Additions Deductions Balance as of March 31, 2023 Three Months Ended March 31, 2023 Contract liabilities: Deferred revenue - related party $ 96,689 1,644 ( 1,122 ) $ 97,211 Balance as of December 31, 2021 Additions Deductions Balance as of March 31, 2022 Three Months Ended March 31, 2022 Contract liabilities: Deferred revenue - related party $ 103,817 — ( 1,493 ) $ 102,324 During the three months ended March 31, 2023 and 2022 the Company recognized the following revenues as a result of changes in the contract liability balances in the respective periods (in thousands): Three Months Ended 2023 2022 Revenue recognized in the period from: Amounts included in the contract liability at the beginning of the period $ ( 522 ) $ 1,493

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Apr. 27, 2023	Apr. 26, 2023	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Nature Of Business And Basis Of Presentation [Line Items]
Entity incorporated month and year			2010-10
Entity incorporation, state or country code			DE
Accumulated deficit			$ 935,685		$ 864,511
Net operating cash outflows			(76,584)	$ (66,445)
Net Income (Loss) Attributable to Parent			$ (71,174)	$ (56,624)
Common stock issued			126,592,604		125,222,273
Common stock at a purchase price			$ 0.001		$ 0.001
Subsequent Event [Member] | Twenty Twenty One License Agreement [Member]
Nature Of Business And Basis Of Presentation [Line Items]
MilestonesPayments		$ 125,000
Subsequent Event [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Credit facility, aggregate principal amount	$ 250,000
Tranche A-1 [Member] | Subsequent Event [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Credit facility, aggregate principal amount	80,000
Tranche A-2 [Member] | Subsequent Event [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Credit facility, aggregate principal amount	30,000
Tranche A Loan [Member] | Subsequent Event [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Credit facility, aggregate principal amount	110,000
Tranche A Loan [Member] | Subsequent Event [Member] | Term Loan Facility [Member] | Hercules Capital Inc [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Repayments of existing credit facility	$ 53,380
Nestle Health Science [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Payment due and payable			$ 125,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Restricted cash	$ 8,185	$ 8,185

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 94,841	$ 163,030
Restricted cash, non-current	8,185	8,185
Total cash, cash equivalents and restricted cash	$ 103,026	$ 171,215	$ 161,377	$ 188,002

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments:
Investments	$ 11,703	$ 18,311
Fair Value, Measurements, Recurring [Member]
Investments:
Investments	38,341	82,831
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash equivalents:
Cash equivalents	22,646	47,863
Commercial Paper [Member]
Investments:
Investments	4,983	2,465
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	1,248	11,691
Investments:
Investments	4,983	2,465
Corporate Bonds [Member]
Investments:
Investments	2,249	2,957
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	2,249	2,957
Government Securities [Member]
Investments:
Investments	4,471	12,889
Government Securities [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	2,744	4,966
Investments:
Investments	4,471	12,889
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	22,646	47,863
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash equivalents:
Cash equivalents	22,646	47,863
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	15,695	34,968
Level 2 [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	1,248	11,691
Investments:
Investments	4,983	2,465
Level 2 [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	2,249	2,957
Level 2 [Member] | Government Securities [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	2,744	4,966
Investments:
Investments	$ 4,471	$ 12,889

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair value, assets transfers from Level 2 to Level 1 measurement	$ 0
Restricted investments	$ 1,401	$ 1,401

Investments - Schedule of Inves

Investments - Schedule of Investments by Security Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 11,701	$ 18,321
Gross Unrealized Gain	2	3
Gross Unrealized Loss	0	(13)
Fair Value	11,703	18,311
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,983	2,465
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	4,983	2,465
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,248	2,958
Gross Unrealized Gain	1	0
Gross Unrealized Loss	0	(1)
Fair Value	2,249	2,957
Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,470	12,898
Gross Unrealized Gain	1	3
Gross Unrealized Loss	0	(12)
Fair Value	$ 4,471	$ 12,889

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Investments [Abstract]
Maximum maturity days for cash equivalents	90 days	90 days
Restricted investments	$ 1,401	$ 1,401

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 70,746	$ 68,025
Less: Accumulated depreciation and amortization	(46,440)	(45,040)
Property and equipment, net	24,306	22,985
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26,586	24,533
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,707	3,557
Furniture and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,417	3,491
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	32,811	32,474
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,225	$ 3,970

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 1,400	$ 1,570
Disposal of fully depreciated assets cost basis	$ 9

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands		Mar. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Development and manufacturing costs		$ 6,043	$ 6,717
Payroll and payroll-related costs		6,877	14,709
Liability related to 2021 License Agreement (Note 11)		24,958	34,770
Facility and other		6,483	3,644
Total accrued expenses and other current liabilities	[1]	$ 44,361	$ 59,840
[1] Includes related party amounts of $ 24,958 and $ 34,770 at March 31, 2023 and December 31, 2022, respectively (see Note 11)

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Apr. 30, 2022	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Apr. 01, 2022
Operating Leased Assets [Line Items]
Existence of option to extend		true
Option to extend, description		Certain leases include one or more options to renew, exercisable at the Company’s sole discretion, with renewal terms that can extend the lease from approximately one year to five years.
Lease renewal term (in years)					5 years
Lease term					10 years
Right-of-use asset		$ 108,914		$ 110,984
Present value of operating lease liabilities		111,476		$ 111,543
Leases Payments		$ 3,413	$ 2,113
Weighted average remaining lease term		8 years 8 months 4 days	4 years 11 months 23 days
Weighted average incremental borrowing rate		13%	10%
Spring House, PA [Member]
Operating Leased Assets [Line Items]
Right-of-use asset		$ 0
Tenant improvement allowance	$ 1,223
Present value of operating lease liabilities		$ 0
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease, remaining term		10 years
Lease renewal term (in years)		5 years
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease, remaining term		2 years
Lease renewal term (in years)		1 year
Minimum [Member] | Spring House, PA [Member]
Operating Leased Assets [Line Items]
Leases Payments	$ 2,980

Leases - Summary of Operating L

Leases - Summary of Operating Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Assets:
Operating lease assets	$ 108,914	$ 110,984
Liabilities:
Operating lease liabilities	4,784	3,601
Operating lease liabilities, net of current portion	106,692	107,942
Total operating lease liabilities	$ 111,476	$ 111,543

Leases - Summary of Lease Costs

Leases - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Leases [Abstract]
Operating lease costs	$ 5,410	$ 1,672
Short-term lease costs	368	355
Variable lease costs	1,763	1,032
Total lease costs	$ 7,541	$ 3,059

Leases - Schedule of Future Pay

Leases - Schedule of Future Payments of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2023 (remaining 9 months)	$ 13,403
2024	19,055
2025	21,164
2026	21,754
2027 and thereafter	108,383
Total future minimum lease payments	183,759
Less: interest	(72,283)
Present value of operating lease liabilities	$ 111,476	$ 111,543

Notes Payables - Additional Inf

Notes Payables - Additional Information (Detail) - USD ($) $ in Thousands			3 Months Ended
	Feb. 24, 2022	Oct. 29, 2019	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Debt Instrument [Line Items]
Interest expense			$ 1,948	$ 912
Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350,000
Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, payment terms			For all advances outstanding under the Hercules Credit Facility, the Company was to make interest only payments through December 31, 2023, extendable to December 31, 2024 upon satisfaction of certain conditions (such applicable date, the “Amortization Date”). The principal balance and interest on the advances was to be repaid in equal monthly installments after the Amortization Date and continuing through October 1, 2024, extendable to October 1, 2025, upon satisfaction of certain conditions (such applicable date, the “Hercules Maturity Date”).
Repayments of Debt	$ 2,900
Additional advance prepayment or repayment percentage	1.75%
Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Interest expense			$ 1,948	$ 912
Loan and Security Agreement [Member] | Original Credit Facility [Member]
Debt Instrument [Line Items]
Percentage of prepayment amount during first year		2%
Percentage of prepayment amount during second year		1.50%
Percentage of prepayment amount during third year		1%
Prepayment or repayment percentage		4.85%
Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, interest rate			9.65%
Debt instrument interest rate			15.48%
Carrying value of debt			$ 51,234		$ 51,047
Loan and Security Agreement [Member] | Hercules Credit Facility [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate			6.40%
Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	$ 100,000
Hercules Capital, Inc. [Member] | Loan and Security Agreement [Member] | Original Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount		$ 50,000
Debt Instrument Tranche Four [Member] | Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	25,000
Debt Instrument Tranche Five [Member] | Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	25,000
First Tranche [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	25,000
First Tranche [Member] | Loan and Security Agreement [Member] | Original Credit Facility [Member]
Debt Instrument [Line Items]
Carrying value of debt			$ 50,586
First Tranche [Member] | Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	25,000
Second Tranche Unavailable to Borrow Due to Not Met Milestone Requirements [Member] | Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	12,500
Third Tranche Available Upon Approval Until June 30, 2021 [Member] | Hercules Lenders [Member] | Second Amendment to Loan and Security Agreement [Member] | Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	$ 12,500

Notes Payable - Summary of Futu

Notes Payable - Summary of Future Principal Payments Due Under Arrangement, Excluding Interest and End of Term Charge (Detail) $ in Thousands	Mar. 31, 2023 USD ($)
Debt Disclosure [Abstract]
2023 (remaining 9 months)	$ 0
2024	50,000
Total	$ 50,000

Common Stock and Stock-Based _3

Common Stock and Stock-Based Awards - Additional Information (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	May 21, 2021 USD ($)	Mar. 31, 2023 USD ($) $ / shares shares	Mar. 31, 2022 shares	Dec. 31, 2022 $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued | shares		126,592,604		125,222,273
Common stock at a purchase price | $ / shares		$ 0.001		$ 0.001
At The Market Equity Offering Program [Member] | Sales Agreement [Member] | Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from sale of common stock | $	$ 150,000,000
Common stock, shares issued | shares		787,170	0
Common stock, share price | $ / shares		$ 5.67
Proceeds from issuance of common stock | $		$ 4,238
Percentage of commission on sale of common stock		3

Common Stock and Stock-Based _4

Common Stock and Stock-Based Awards - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Equity [Abstract]
Number of Shares, Beginning Balance	14,940,034
Number of Shares, Granted	2,118,845
Number of Shares, Exercised	(56,523)
Number of Shares, Forfeited	(176,212)
Number of Shares, Ending Balance	16,826,144	14,940,034
Number of Shares, Options exercisable	8,676,217
Weighted Average Exercise Price, Beginning Balance	$ 10.03
Weighted Average Exercise Price, Granted	5.50
Weighted Average Exercise Price, Exercised	3.32
Weighted Average Exercise Price, Forfeited	10.46
Weighted Average Exercise Price, Ending Balance	9.48	$ 10.03
Weighted Average Exercise Price, Options exercisable	$ 10.16
Weighted Average Remaining Contractual Term, Outstanding	7 years 3 months 21 days	7 years 3 months
Weighted Average Remaining Contractual Term, Options exercisable	5 years 11 months 23 days
Aggregate Intrinsic Value, Outstanding	$ 12,188	$ 11,608
Aggregate Intrinsic Value, Options exercisable	$ 8,764

Common Stock and Stock-Based _5

Common Stock and Stock-Based Awards - Stock Options - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of stock options	$ 4.56	$ 5.90
Performance-based stock options to granted	2,118,845
Stock based compensation expense for stock options	$ 6,850,000	$ 5,079,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of stock options			$ 5.53
Performance-based stock options to granted			562,000
Stock options exercisable	0
Stock based compensation expense for stock options	$ 0

Common Stock and Stock-Based _6

Common Stock and Stock-Based Awards - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units [Member]	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested restricted stock units, Beginning balance | shares	1,549,540
Number of Shares, Granted | shares	3,014,810
Number of Shares, Vested | shares	(259,023)
Number of Shares, Forfeited | shares	(89,493)
Number of Shares, Unvested restricted stock units, Ending balance | shares	4,215,834
Weighted Average Grant Date Fair Value, Unvested restricted stock units, Beginning balance | $ / shares	$ 9.37
Weighted Average Grant Date Fair Value, Granted | $ / shares	5.50
Weighted Average Grant Date Fair Value, Vested | $ / shares	8.91
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	9.50
Weighted Average Grant Date Fair Value, Unvested restricted stock units, Ending balance | $ / shares	$ 6.63

Common Stock and Stock-Based _7

Common Stock and Stock-Based Awards - Restricted Stock Units - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2022 $ / shares shares	Mar. 31, 2023 USD ($) $ / shares shares	Mar. 31, 2022 USD ($) shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 Employee $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense for stock options | $		$ 6,850	$ 5,079
Performance Based Restricted Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee share based compensation expense | $				$ 815
Weighted average grant-date fair value of stock options | $ / shares		$ 5.50
Stock based compensation expense for stock options | $		$ 0
Number of employees granted | Employee					2
Number of shares granted		1,322,715	0
Service Based Restricted Stock Units (RSUs)[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted		1,692,095	989,544
Vesting period		4 years
Service Based Restricted Stock Units (RSUs)[Member] | Vesting After One Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		25%
Service Based Restricted Stock Units (RSUs)[Member] | Vesting Quarterly Over Next 3 Years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		75%
Employee One [Member] | Performance Based Restricted Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of stock options | $ / shares					$ 9.59
Number of shares, vested	42,500
Weighted average grant date fair value, vested | $ / shares	$ 9.59
Number of shares granted					85,000
Employee Two [Member] | Performance Based Restricted Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of stock options | $ / shares					$ 20.35
Number of shares, vested	20,000
Weighted average grant date fair value, vested | $ / shares	$ 20.35
Number of shares granted					40,000

Common Stock and Stock-Based _8

Common Stock and Stock-Based Awards - Summary of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,850	$ 5,079
Research and development expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	3,731	2,483
General and administrative expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 3,119	$ 2,596

Net Loss per Share - Basic and

Net Loss per Share - Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net loss	$ (71,174)	$ (56,624)
Loss attributable to common stockholders - basic	(71,174)	(56,624)
Loss attributable to common stockholders - diluted	$ (71,174)	$ (56,624)
Denominator:
Weighted-average shares outstanding	125,862,975	92,164,419
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Loss per share applicable to common stockholders - basic	$ (0.57)	$ (0.61)
Loss per share applicable to common stockholders - diluted	$ (0.57)	$ (0.61)
Stock Options to Purchase Common Stock [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	16,826,144	14,820,313
Unvested Restricted Stock Units [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	4,215,834	1,582,641
Shares Issuable under ESPP [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	68,594	32,355

Collaboration Revenue - Additio

Collaboration Revenue - Additional Information (Detail) - USD ($)

3 Months Ended

12 Months Ended

Jul. 21, 2021

Jul. 01, 2021

Jan. 31, 2016

Mar. 31, 2023

Mar. 31, 2022

Dec. 31, 2021

Dec. 31, 2020

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2022

Nov. 30, 2018

Feb. 29, 2016

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration (profit) loss sharing - related party

$ (3,607,000)

$ 976,000

Change in collaboration revenue-related party

522,000

1,493,000

Upfront collaboration/license fee

$ 120,000,000

2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration product, percentage of commercial profit

50%

Collaborative arrangement, sharing of pre-launch costs, percentage

50%

Nestle Health Science [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment

96,357,000

$ 94,713,000

$ 120,000,000

Maximum development milestone payments to be received

285,000,000

Maximum regulatory payments to be received

375,000,000

Maximum amount to be received on achievement of certain commercial milestones

1,125,000,000

Proceeds on achievement of development milestone

$ 10,000,000

$ 40,000,000

$ 20,000,000

$ 10,000,000

Transaction price allocated to remaining performance obligations

200,000,000

Collaboration revenue - related party

(1,644,000)

725,000

Deferred revenue

97,211,000

96,689,000

Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration product, percentage of commercial profit

50%

Upfront payment received

$ 175,000,000

Maximum Amount To Be Received On Achievement Of Regulatory and Sales Milestones

$ 360,000,000

Maximum amount to be received on achievement of sales milestones

225,000,000

Collaboration (profit) loss sharing - related party

3,607,000

976,000

Maximum regulatory payments to be received

$ 135,000,000

Transaction price allocated to remaining performance obligations

$ 139,500,000

Termination notice period

60 days

Nestle Health Science [Member] | Phase 2 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront collaboration milestone payments receivable

20,000,000

Nestle Health Science [Member] | Phase 3 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront collaboration milestone payments receivable

$ 20,000,000

Nestle Health Science [Member] | Phase 2b [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront collaboration milestone payments receivable

$ 40,000,000

Proceeds on achievement of development milestone

$ 40,000,000

License [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration revenue - related party

$ 131,343,000

Service [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Transaction price allocated to remaining performance obligations

$ 8,157,000

Collaboration revenue - related party

1,122,000

768,000

Topic 808 [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Transaction price allocated under collaborative arrangement

35,500,000

Topic 808 [Member] | Total Liabilities [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Transaction price allocated under collaborative arrangement

$ 35,500,000

Topic 808 [Member] | Accrued Expenses and Other Current Liabilities [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Transaction price allocated under collaborative arrangement

24,958,000

$ 34,770,000

Research and Development Expense [Member] | Topic 808 [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Cost associated with pre-launch activities

801,000

1,635,000

General and Administrative Expense [Member] | Topic 808 [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Cost associated with pre-launch activities

$ 2,703,000

$ 2,438,000

Collaboration Revenue - Changes

Collaboration Revenue - Changes in Contract Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue - related party, Deductions	$ (522)	$ (1,493)
ASU 2014-09 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue - related party, Balance at beginning of period	96,689	103,817
Deferred revenue - related party, Additions	1,644	0
Deferred revenue - related party, Deductions	(1,122)	(1,493)
Deferred revenue - related party, Balance at end of period	$ 97,211	$ 102,324

Collaboration Revenue - Schedul

Collaboration Revenue - Schedule of Revenue Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenue recognized in the period from:
Amounts included in the contract liability at the beginning of the period	$ 522	$ 1,493

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Indemnification Agreement [Member]
Other Commitments [Line Items]
Obligations accrued	$ 0	$ 0
Legal Contingencies [Member]
Other Commitments [Line Items]
Obligations accrued	$ 0	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Feb. 29, 2016
Related Party Transaction [Line Items]
Common stock at a purchase price	$ 0.001		$ 0.001
Nestle Health Science [Member]
Related Party Transaction [Line Items]
Collaboration revenue - related party	$ (1,644,000)	$ 725,000
Deferred revenue	96,357,000		$ 94,713,000	$ 120,000,000
Payments under agreements with related party	0	0
Due from related party for the reimbursement of development costs	0		0
Nestle Health Science [Member] | 2021 License Agreement [Member]
Related Party Transaction [Line Items]
Collaboration revenue - related party	1,122,000	768,000
Deferred revenue	854,000		1,976,000
Payments under agreements with related party	13,419,000	$ 0
Due from related party for the reimbursement of development costs	0		0
Accrued Expenses and Other Liabilities [Member] | Nestle Health Science [Member] | 2021 License Agreement [Member]
Related Party Transaction [Line Items]
Transaction price allocated under collaborative arrangement	$ 24,958,000		$ 34,770,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Thousands	Jun. 30, 2026	Apr. 27, 2023 USD ($) TradingDays $ / shares shares
Term Loan Facility [Member] | Forecast [Member]
Subsequent Event [Line Items]
Percentage of the outstanding principal amount repaid.	7.50%
Subsequent Event [Member]
Subsequent Event [Line Items]
Net proceeds received from credit facility		$ 50,446
Trading days prior to the funding date | TradingDays		30
Subsequent Event [Member] | Tranche B Warrant [Member]
Subsequent Event [Line Items]
Debt instrument conversion warrants or options issued | shares		264,922
Subsequent Event [Member] | Tranche C Warrant [Member]
Subsequent Event [Line Items]
Debt instrument conversion warrants or options issued | shares		264,922
Subsequent Event [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Additional default interest rate		2%
Subsequent Event [Member] | Term Loan Facility [Member]
Subsequent Event [Line Items]
Debt Instrument maturity date		Apr. 27, 2029
Credit facility, interest rate during period		7.875%
Line of credit facility exit fee percentage		1.50%
Percentage of prepayment amount after the first year		4%
Percentage of prepayment amount after the second year		4%
Percentage of prepayment amount after the third year		2%
Percentage of prepayment amount after the fourth year		1%
Subsequent Event [Member] | Term Loan Facility [Member] | Tranche A Warrant [Member]
Subsequent Event [Line Items]
Debt instrument conversion warrants or options issued | shares		647,589
Warrants exercise price | $ / shares		$ 6.69
Subsequent Event [Member] | Term Loan Facility [Member] | Maximum [Member]
Subsequent Event [Line Items]
Credit facility, interest rate during period		7.875%
Subsequent Event [Member] | Term Loan Facility [Member] | Minimum [Member]
Subsequent Event [Line Items]
Credit facility, interest rate during period		7.50%
Subsequent Event [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Credit facility, aggregate principal amount		$ 250,000
Subsequent Event [Member] | Interest Rate Cap [Member] | SOFR [Member] | Term Loan Facility [Member]
Subsequent Event [Line Items]
Debt instrument, variable interest rate		5%
Subsequent Event [Member] | Interest Rate Floor [Member] | SOFR [Member] | Term Loan Facility [Member]
Subsequent Event [Line Items]
Debt instrument, variable interest rate		2.50%
Subsequent Event [Member] | Tranche A Loan [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Credit facility, aggregate principal amount		$ 110,000
Subsequent Event [Member] | Tranche A Loan [Member] | Term Loan Facility [Member] | Hercules Capital, Inc. [Member]
Subsequent Event [Line Items]
Repayments of existing credit facility		53,380
Subsequent Event [Member] | Tranche B Loan [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Credit facility, aggregate principal amount		45,000
Subsequent Event [Member] | Tranche C Loan [Member] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Credit facility, aggregate principal amount		45,000
Subsequent Event [Member] | Tranche D Loan [Mmeber] | Term Loan Facility [Member] | Oaktree Fund Administration, LLC [Member]
Subsequent Event [Line Items]
Credit facility, aggregate principal amount		$ 50,000

Uncategorized Items - mcrb-2023

Label	Element	Value
Oaktree Fund Administration, LLC [Member] | Term Loan Facility [Member] | Minimum [Member]
Cash	us-gaap_Cash	$ 30,000,000
TrancheB Loan [Member] | Oaktree Fund Administration, LLC [Member] | Term Loan Facility [Member] | Minimum [Member]
Cash	us-gaap_Cash	$ 25,000,000