Evelo Biosciences (EVLO) 10-Q 9 Nov 23 2023 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2023	Nov. 06, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-38473
Entity Registrant Name	Evelo Biosciences, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5594527
Entity Address, Address Line One	One Kendall Square, 600/700, Suite 7-201
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	577-0300
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	EVLO
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		18,930,960
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001694665

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 17,262	$ 47,940
Prepaid expenses and other current assets	1,674	3,633
Total current assets	18,936	51,573
Property and equipment, net	894	4,842
Right of use asset - operating lease	0	6,868
Other assets	797	1,158
Total assets	20,627	64,441
Current liabilities:
Debt, current portion	33,948	0
Accounts payable	526	1,764
Accrued expenses	4,550	7,945
Operating lease liability, current portion	0	2,259
Other current liabilities	737	427
Total current liabilities	39,761	12,395
Noncurrent liabilities:
Debt, net of current portion	0	43,614
Operating lease liability, net of current portion	0	5,265
Deferred revenue	7,500	7,500
Other noncurrent liabilities	73	659
Total liabilities	47,334	69,433
Commitments and contingencies (Note 9)
Stockholder’s deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding as of September 30, 2023 and December 31, 2022, respectively	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized; 18,853,587 and 5,542,637 shares issued and outstanding as of September 30, 2023 and December 31, 2022, respectively	19	6
Additional paid-in capital	561,304	524,224
Accumulated deficit	(588,030)	(529,222)
Total stockholders’ deficit	(26,707)	(4,992)
Total liabilities and stockholders’ deficit	$ 20,627	$ 64,441

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock shares issued (in shares)	18,853,587	5,542,637
Common stock, shares outstanding (in shares)	18,853,587	5,542,637

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating expenses:
Research and development	$ 6,499	$ 21,928	$ 37,399	$ 62,470
General and administrative	3,891	7,126	15,849	24,909
Loss on disposal and impairment of property and equipment	793	0	2,409	0
Total operating expenses	11,183	29,054	55,657	87,379
Loss from operations	(11,183)	(29,054)	(55,657)	(87,379)
Other income (expense):
Interest expense, net	(1,162)	(788)	(3,642)	(2,835)
Change in fair value of warrants	(9)	0	622	0
Other miscellaneous income (expense), net	(27)	(615)	230	(386)
Total other expenses, net	(1,198)	(1,403)	(2,790)	(3,221)
Loss before income taxes	(12,381)	(30,457)	(58,447)	(90,600)
Income tax benefit (expense)	17	(107)	(361)	(386)
Net loss	$ (12,364)	$ (30,564)	$ (58,808)	$ (90,986)
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.71)	$ (5.66)	$ (6.16)	$ (22.88)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.71)	$ (5.66)	$ (6.16)	$ (22.88)
Weighted average number of common shares outstanding, basic (in shares)	17,384,243	5,402,592	9,546,129	3,976,438
Weighted average number of common shares outstanding, diluted (in shares)	17,384,243	5,402,592	9,546,129	3,976,438

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders’ Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021		2,678,823
Beginning balance at Dec. 31, 2021	$ 8,667	$ 3	$ 423,359	$ (414,695)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)		1,816
Issuance of common stock under Employee Stock Purchase Plan	129		129
Vesting of restricted common stock (in shares)		1,770
Stock-based compensation expense	4,275		4,275
Fees associated with public offering of common stock	(12)		(12)
Net loss	(29,861)			(29,861)
Ending balance (in shares) at Mar. 31, 2022		2,682,409
Ending balance at Mar. 31, 2022	(16,802)	$ 3	427,751	(444,556)
Beginning balance (in shares) at Dec. 31, 2021		2,678,823
Beginning balance at Dec. 31, 2021	8,667	$ 3	423,359	(414,695)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(90,986)
Ending balance (in shares) at Sep. 30, 2022		5,423,654
Ending balance at Sep. 30, 2022	9,334	$ 6	515,009	(505,681)
Beginning balance (in shares) at Mar. 31, 2022		2,682,409
Beginning balance at Mar. 31, 2022	(16,802)	$ 3	427,751	(444,556)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net (in shares)		2,712,318
Issuance of common stock, net	78,982	$ 3	78,979
Vesting of restricted common stock (in shares)		814
Exercise of stock options (in shares)		2,125
Exercise of stock options	30		30
Stock-based compensation expense	3,999		3,999
Net loss	(30,561)			(30,561)
Ending balance (in shares) at Jun. 30, 2022		5,397,666
Ending balance at Jun. 30, 2022	35,648	$ 6	510,759	(475,117)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net (in shares)		23,750
Issuance of common stock, net	712		712
Issuance of common stock under Employee Stock Purchase Plan (in shares)		2,019
Issuance of common stock under Employee Stock Purchase Plan	72		72
Exercise of stock options (in shares)		219
Exercise of stock options	3		3
Stock-based compensation expense	3,463		3,463
Net loss	(30,564)			(30,564)
Ending balance (in shares) at Sep. 30, 2022		5,423,654
Ending balance at Sep. 30, 2022	$ 9,334	$ 6	515,009	(505,681)
Beginning balance (in shares) at Dec. 31, 2022	5,542,637	5,542,637
Beginning balance at Dec. 31, 2022	$ (4,992)	$ 6	524,224	(529,222)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)		2,044
Issuance of common stock under Employee Stock Purchase Plan	36		36
Vesting of restricted common stock (in shares)		1,823
Stock-based compensation expense	2,909		2,909
Net loss	(25,341)			(25,341)
Ending balance (in shares) at Mar. 31, 2023		5,546,504
Ending balance at Mar. 31, 2023	$ (27,388)	$ 6	527,169	(554,563)
Beginning balance (in shares) at Dec. 31, 2022	5,542,637	5,542,637
Beginning balance at Dec. 31, 2022	$ (4,992)	$ 6	524,224	(529,222)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	0
Net loss	$ (58,808)
Ending balance (in shares) at Sep. 30, 2023	18,853,587	18,853,587
Ending balance at Sep. 30, 2023	$ (26,707)	$ 19	561,304	(588,030)
Beginning balance (in shares) at Mar. 31, 2023		5,546,504
Beginning balance at Mar. 31, 2023	(27,388)	$ 6	527,169	(554,563)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)		53,384
Stock-based compensation expense	2,365		2,365
Redemption of fractional shares due to reverse stock split		(51)
Net loss	(21,103)			(21,103)
Ending balance (in shares) at Jun. 30, 2023		5,599,837
Ending balance at Jun. 30, 2023	(46,126)	$ 6	529,534	(575,666)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net (in shares)		13,189,836
Issuance of common stock, net		$ 13	29,293
Issuance of common stock under Employee Stock Purchase Plan (in shares)		124
Issuance of common stock under Employee Stock Purchase Plan			1
Vesting of restricted common stock (in shares)		63,790
Stock-based compensation expense			2,476
Net loss	$ (12,364)
Ending balance (in shares) at Sep. 30, 2023	18,853,587	18,853,587
Ending balance at Sep. 30, 2023	$ (26,707)	$ 19	$ 561,304	$ (588,030)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating activities
Net loss	$ (58,808)	$ (90,986)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,750	11,737
Depreciation expense	1,038	1,537
Loss on disposal and impairment of property and equipment	(2,409)	0
Loss on disposal and impairment of property and equipment		232
Non-cash interest expense	421	188
Non-cash lease expense	3,283	2,175
Decrease in fair value of warrants	(622)	0
Net foreign currency losses	78	1,012
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,958	(799)
Accounts payable	(1,256)	(40)
Accrued expenses and other current liabilities	(3,823)	(814)
Operating lease liabilities	(2,939)	(2,287)
Net cash used in operating activities	(50,511)	(78,045)
Investing activities
Purchases of property and equipment	(59)	(394)
Proceeds from the sale of fixed assets	560	0
Net cash provided by (used in) investing activities	501	(394)
Financing activities
Proceeds from issuance of common stock, net of issuance cost	24,305	79,682
Proceeds from the issuance of common stock under employee stock purchase plan and the exercise of stock options	37	234
Repayments of debt	(5,049)	0
Fees associated with debt issuance	(272)	0
Net cash provided by financing activities	19,021	79,916
Effect of exchange rate changes on cash and cash equivalents	(50)	(1,022)
Net (decrease)/increase in cash, cash equivalents and restricted cash	(31,039)	455
Cash, cash equivalents and restricted cash – beginning of period	49,098	69,754
Cash, cash equivalents and restricted cash – end of period	18,059	70,209
Supplemental disclosure of cash flow information
Cash paid for interest	3,927	2,963
Cash paid for taxes	8	592
Noncash investing and financing activities
Conversion of long-term debt to shares of common stock	5,000	0
Financing and public offering costs in accounts payable and accrued expenses	200	0
Property and equipment additions in accounts payable and accrued expenses	$ 0	$ 128

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Evelo Biosciences, Inc. ("Evelo," "we," "our," "us" or the "Company”) is a biotechnology company incorporated in Delaware on May 6, 2014. We are a clinical-stage biotechnology company focused on discovering and developing a new class of oral medicines that act on immune cells in the small intestine with systemic effects. We are advancing these investigational medicines with the aim of treating a broad range of inflammatory diseases, with an initial focus on psoriasis and atopic dermatitis. Our headquarters is located in Cambridge, Massachusetts. Since inception, we have devoted substantially all of our efforts to research and development and raising capital. We have not generated any product or license revenue related to our primary business purpose to date. We are subject to a number of risks similar to those of other development stage companies, including the inherent uncertainties in drug development, the need to develop commercially viable products, the competition from other companies, many of which are larger and better capitalized, the need to obtain adequate additional financing to fund the development of our product candidates and a dependence on key individuals. We have incurred operating losses since inception and expect such losses and negative operating cash flows to continue for the foreseeable future. As of September 30, 2023, we had cash and cash equivalents of $17.3 million and an accumulated deficit of $588.0 million. Since inception, we have financed operations primarily with the proceeds from the issuance of common stock and since-redeemed preferred stock to equity investors, and from debt financing. In accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), we evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date that these unaudited condensed consolidated statements are issued. The transition to profitability is dependent upon the successful development, approval and commercialization of our product candidates, and the achievement of a level of revenues adequate to support our cost structure. Based on our current operating plan, we believe that our cash and cash equivalents balance as of September 30, 2023 will not be sufficient to fund operations and capital expenditures for at least the twelve months following the filing of this Quarterly Report on Form 10-Q and we will need additional capital if we intend to pursue further development of our candidates. We are exploring strategic alternatives which will inform our future financial and clinical development plans. Management’s belief with respect to our ability to fund operations is based on estimates that are subject to risks and uncertainties, including the outcome of the strategic review process. Actual results may be different from management’s estimates. There can be no assurance that we will be able to obtain additional financial resources on acceptable terms, if at all. If we are unable to obtain sufficient financial resources, we may be required to permanently cease development efforts, which would adversely affect our business prospects. Because of the uncertainty as to the outcome of the strategic review and our ability to secure financial resources and the insufficient amount of cash and cash equivalent resources as of September 30, 2023, management concluded that substantial doubt exists with respect to our ability to continue as a going concern within one year after the date that these unaudited condensed consolidated statements are issued.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification and ASU of the FASB. On June 29, 2023, we effected a 1-for-20 reverse stock split of our common stock. All share and per share amounts in the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split. Use of Estimates The preparation of unaudited condensed consolidated statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the unaudited condensed consolidated financial statements and accompanying notes. Significant estimates and assumptions reflected in these unaudited condensed consolidated financial statements include, but are not limited to, estimates related to the application of Revenue from Contracts with Customers (Topic 606) ("ASC 606") to our collaboration agreement with Meddist Company Limited ("ALJ"), the accrual of research and development expenses, the expected future lives of property and equipment and the valuation of that equipment utilized in impairment analyses, the valuation of stock-based awards, and common stock warrants. We base our estimates on historical experience and market-specific or other relevant assumptions that we believe to be reasonable under the circumstances. Actual results could differ from those estimates. Unaudited Interim Financial Information Our unaudited condensed consolidated financial statements included herein have been prepared pursuant to the rules and regulations of the United States Securities and Exchange Commission (the “SEC”). The unaudited condensed consolidated financial statements include the accounts of our business and our wholly owned and controlled subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. The accompanying unaudited condensed consolidated balance sheet as of September 30, 2023 has been derived from our audited consolidated financial statements for the year ended December 31, 2022. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to rules and regulations. However, we believe that the disclosures are adequate to make the information presented not misleading. These unaudited interim condensed consolidated financial statements should be read in conjunction with the audited annual consolidated financial statements and related notes in our Annual Report on Form 10-K for the fiscal year ended December 31, 2022. These unaudited condensed consolidated financial statements are prepared on the same basis as the audited financial statements. In the opinion of our management, the accompanying unaudited condensed consolidated financial statements contain all adjustments which are necessary to present fairly our financial position as of September 30, 2023, and the results of operations and stockholders' deficit for the three and nine months ended September 30, 2023 and 2022. Such adjustments are of a normal and recurring nature. The results for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be realized for the year ending December 31, 2023, or for any future period. Subsequent Event Considerations We consider events or transactions that occur after the balance sheet date but prior to the issuance of the unaudited condensed consolidated financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. Emerging Growth Company Status We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"), and we may take advantage of reduced reporting requirements that are otherwise applicable to other public companies. We may take advantage of these exemptions until we no longer are an emerging growth company. Section 107 of the JOBS Act provides that an emerging growth company can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. We have elected to use the extended transition period for complying with new or revised accounting standards and, as a result of this election, our unaudited condensed consolidated statements may not be comparable to companies that comply with public company effective dates. We may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of our IPO or such earlier time that we no longer are an emerging growth company. We will remain an emerging growth company until the earlier of (1) the last day of the fiscal year (a) following the fifth anniversary of the completion of the initial public offering of our common stock, or December 31, 2023, (b) in which we have total annual gross revenue of at least $1.235 billion, or (c) in which we are deemed to be a large accelerated filer, which means the market value of our outstanding common stock that are held by non-affiliates exceeds $700 million as of the last business day of our prior second fiscal quarter, and (2) the date on which we have issued more than $1.0 billion in non-convertible debt during the prior three year period. We are also a smaller reporting company, and we will remain a smaller reporting company until the fiscal year following the determination that our voting and non-voting common shares held by non-affiliates is more than $250 million measured on the last business day of our second fiscal quarter, and our annual revenues are more than $100 million during the most recently completed fiscal year and our voting and non-voting common shares held by non-affiliates is more than $700 million measured on the last business day of our second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially expose us to concentrations of credit risk primarily consist of cash and cash equivalents. We placed our operating cash in demand deposit accounts at a single financial institution since February 2022, which have exceeded and are expected to continue to exceed federally insured limits. Our money market funds are held in an investment account at an affiliate institution. As of September 30, 2023 and 2022, we have no off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Comprehensive Loss Comprehensive loss consists of net loss and changes in equity during a period arising from transactions and other equity and circumstances, of which we have none. Our comprehensive loss equals our net loss for all periods presented. Cash, Cash Equivalents and Restricted Cash Cash equivalents are highly liquid investments that are readily convertible into cash with original maturities of three months or less, which consist of cash held in banks and funds held in money market accounts. Cash equivalents are stated at cost, which approximates market value. Our restricted cash consists of the deposits held for the building lease for our office and laboratory premises, for our credit card facility, and for the proceeds from our recent disposition of long-lived assets. As of September 30, 2023 and 2022, we had $0.8 million and $1.2 million in restricted cash balance recorded within other assets The following reconciles cash, cash equivalents and restricted cash as of September 30, 2023 and 2022, as presented on the statements of cash flows, to the related balance sheet accounts (in thousands): September 30, 2023 September 30, 2022 Cash and cash equivalents: Cash $ 1,969 $ 10,363 Money market funds 15,293 58,690 Total cash and cash equivalents 17,262 69,053 Restricted cash 797 1,156 Cash, cash equivalents and restricted cash $ 18,059 $ 70,209 Research and Development Costs Research and development costs are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with the development of our product candidates, such as payroll, consulting, clinical trial costs and manufacturing costs associated with the development of our product candidates. Costs for certain development activities, such as clinical trials and manufacturing development activities, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided to us by our vendors on their actual costs incurred or level of effort expended. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected on the unaudited condensed consolidated balance sheets as prepaid or accrued research and development expenses. Property and Equipment Property and equipment consists of computer hardware and software, furniture and fixtures, office equipment, research and lab equipment, and leasehold improvement recorded at cost. Lab equipment used in research and development activities is only capitalized when it has an alternative future use. These amounts are depreciated using the straight-line method over the estimated useful lives of the assets. Purchased assets that are not yet in service are recorded to construction-in-process and no depreciation expense is recorded. Once they are placed in service they are reclassified to the appropriate asset class. A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 3 - 5 years Computer software 3 years Furniture and fixtures 7 years Research and lab equipment (used/new) 3 - 5 years Leasehold improvements Lesser of asset life or remaining life of lease Repairs and maintenance costs are expensed as incurred. Impairment of Long-Lived Assets We periodically evaluate property and equipment for impairment whenever events or changes in circumstances indicate that a potential impairment may have occurred. If such events or changes in circumstances arise, we compare the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of the long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the long-lived assets. Segments We have one operating segment. Our chief operating decision maker, the Chief Executive Officer, manages our operations on a consolidated basis for the purposes of allocating resources. Accounting Pronouncements Issued and Not Yet Effective as of September 30, 2023 No new accounting pronouncements issued or effective in the period had or are expected to have a material impact on our accompanying unaudited condensed consolidated statements.

ALJ Collaborative Agreement

ALJ Collaborative Agreement	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ALJ Collaborative Agreement	ALJ Collaborative AgreementIn March 2021, we entered into a collaborative commercialization and license agreement (“ALJ Agreement”) with ALJ. Pursuant to the ALJ Agreement, we granted to ALJ an exclusive, non-transferable, sublicensable license to our product candidate EDP1815. In consideration for the rights granted under the ALJ Agreement, ALJ was obligated to pay a one-time, non-refundable upfront fee of $7.5 million. The parties will also share the future operating profits and losses for certain products in certain territories equally (50:50) as well as certain development, regulatory and commercialization costs. We have concluded that the delivery of the license to ALJ shall be accounted for under ASC 606. The development, regulatory and commercialization activities within the territories shall be accounted for under the FASB guidance of Collaborative Arrangements (Topic 808) ("ASC 808"). We have recognized no revenue under the ALJ Agreement to date as we have yet to undertake any of our performance obligations within the agreement. The $7.5 million upfront fee is recorded as deferred revenue as a non-current liability in the accompanying unaudited condensed consolidated balance sheets because the performance obligation is not expected to be completed within the next twelve months. We anticipate payments under the cost-sharing or profit and loss sharing arrangements will be classified in the statement of operations consistent with the guidance of ASC 808. To date, we have neither received nor incurred any such payments. Mayo Foundation for Medical Education and Research In August 2017, we and the Mayo Clinic amended the 2016 Mayo License Agreement. Under the amended agreement, the Mayo Clinic granted us (i) an exclusive, worldwide, sublicensable license under the Mayo Clinic’s rights to certain intellectual property and microbial strains and (ii) a non-exclusive, worldwide, sublicensable license to certain related know-how to develop and commercialize certain microbial strains and licensed products incorporating such strains. As consideration, we paid a nonrefundable upfront fee of $0.3 million and are obligated to pay annual license maintenance fees. The nonrefundable upfront fees were expensed to research and development expense in 2017. Annual maintenance fees are expensed as incurred over the term of the agreement. We may owe the Mayo Clinic milestone payments upon the achievement of certain milestones up to a maximum of $59.1 million in the aggregate, as well as royalties on net sales of licensed products in low single-digit percentages. As of September 30, 2023, we incurred milestone payments since inception of approximately $0.3 million and no amounts are currently due.

Leases

Leases	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Leases	Leases In January 2018, we entered into an operating sublease arrangement for approximately 40,765 square feet for our office and research and development space at 620 Memorial Drive, Cambridge, MA 02139 from February 2018 extending through September 2025. The lease required a security deposit, which we fulfilled with a standing letter of credit secured by restricted cash on deposit. On July 14, 2023, we entered into a sublease termination and surrender agreement with our landlord Bio-Rad Laboratories, Inc. (“Bio-Rad”) pursuant to which both parties agreed to terminate the sublease agreement, dated as of December 27, 2017, effective as of September 15, 2023. The sublease agreement was previously scheduled to terminate, in accordance with its terms, on September 30, 2025. In exchange for the early termination of the sublease agreement, we agreed to make a one-time termination payment to Bio-Rad in the amount of $0.5 million and Bio-Rad is also entitled to draw on a letter of credit in an amount equal to $0.9 million and retain such proceeds. Further, Bio-Rad may be entitled to an additional payment of up to $2.5 million if the Company realizes specified monetization events. This contingent payment is measured at fair value and recorded within on our unaudited condensed consolidated balance sheets. The carrying value of the liability as of September 30, 2023 was $0.7 million. For the three months ended September 30, 2023 and 2022, we recorded rent expense of $1.8 million and $0.7 million, respectively. For the nine months ended September 30, 2023 and 2022, we recorded rent expenses of $3.3 million and $2.2 million, respectively. Operating cash flows used for operating leases were $2.1 million and $2.3 million for the nine months ended September 30, 2023 and 2022, respectively. The following table presents supplemental balance sheet information related to our operating leases (in thousands): September 30, 2023 December 31, 2022 Assets: Operating lease right-of-use assets $ — $ 6,868 Liabilities: Operating lease liabilities, current — 2,259 Operating lease liabilities, noncurrent — 5,265 Total lease liabilities $ — $ 7,524 Other information: Weighted-average remaining lease term (in years) 0.00 years 2.75 years Weighted-average discount rate — % 9.5 %

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment recorded in our consolidated balance sheet consists of the following (in thousands): September 30, 2023 December 31, 2022 Property and equipment: Lab equipment $ 2,631 $ 9,761 Leasehold improvements — 2,157 Furniture and fixtures — 818 Computers and software 253 253 Office equipment — 66 Construction-in-process 93 1,122 Property and equipment 2,977 14,177 Less: accumulated depreciation (2,083) (9,335) Property and equipment, net $ 894 $ 4,842 We recognized $0.2 million and $0.5 million of depreciation expense for the three months ended September 30, 2023 and 2022, and $1.0 million and $1.5 million for the nine months ended September 30, 2023 and 2022, respectively. In April 2023, a decision was made to cease further development of EDP1815 in atopic dermatitis, which we considered as an impairment triggering event for related lab equipment. Accordingly, we evaluated the recoverability of the asset group associated with the EDP1815 atopic dermatitis program in accordance with ASC 360. Based on this evaluation, we determined that long-lived assets with a carrying amount of $2.1 million were no longer recoverable, and recorded an impairment charge of $1.6 million to write those assets down to their fair value of $0.5 million for the nine months ended September 30, 2023. During the three months ended September 30, 2023, we disposed of the impaired lab equipment for proceeds of $0.5 million. On July 14, 2023, we entered into a sublease termination and surrender agreement with our landlord Bio-Rad pursuant to which we agreed to early terminate our office sublease at 620 Memorial Drive, Cambridge, MA 02139, effective as of September 15, 2023. As a result of this early termination, during the three and nine months ended September 30, 2023, we disposed Furniture and fixtures and Office equipment with a carrying value of $0.3 million for proceeds of $0.1 million, and as a result, recognized a loss on disposal of $0.2 million. We have also written down Leasehold improvements to zero and recognized a loss on disposal of $0.6 million for the three and nine months ended September 30, 2023.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following tables present information about our financial assets and liabilities that have been measured at fair value as of September 30, 2023 and December 31, 2022 (in thousands): Description September 30, 2023 (Level 1) (Level 2) (Level 3) Financial Assets Cash and cash equivalents: Money market funds $ 15,293 $ 15,293 $ — $ — Other assets: Restricted cash held in money market funds 263 263 — — Total $ 15,556 $ 15,556 $ — $ — Financial Liabilities Other noncurrent liabilities: Warrant liabilities $ 37 — — $ 37 Contingent rent liability 711 — — 711 Total $ 748 $ — $ — $ 748 Description December 31, 2022 (Level 1) (Level 2) (Level 3) Financial Assets Cash and cash equivalents: Money market funds $ 46,660 $ 46,660 $ — $ — Other assets: Restricted cash held in money market funds 1,158 1,158 — — Total $ 47,818 $ 47,818 $ — $ — Financial Liabilities Other noncurrent liabilities: Warrant liabilities $ 659 — — $ 659 Total $ 659 $ — $ — $ 659 Our financial assets are reported as cash equivalents and other assets, which are held in money market funds, are classified within Level 1 of the fair value hierarchy because they are valued using quoted prices in active markets as of September 30, 2023 and 2022. The money market funds are invested in a fund comprised of U.S. government securities and instruments. Our financial liability reported as other noncurrent liabilities are common stock warrants issued in connection with the loan arrangement with Horizon Technology Finance Corporation ("Horizon”) (See Note 8), and the contingent rent liability that Bio-Rad, our landlord, may be entitled if we realize specified monetization events (See Note 4). The fair value of the common stock warrants was determined based on the Black-Scholes option-pricing model and classified within Level 3 of the fair value hierarchy. As of September 30, 2023, the expected volatility input of 70% used in the model was deemed unobservable and was determined based on historical share price data of comparable companies for a term equal to the remaining contractual term of the warrants. Other required inputs used in the model were considered observable (Level 1). Significant increases (decreases) in these inputs could result in a significantly lower or higher fair value measurement . The contingent rent liability is measured at an estimated fair value based on probability-weighted estimated cash outflows. The contingent rent liability will be remeasured to fair value at each reporting period with changes recorded in the condensed consolidated statements of operations. The following table shows a reconciliation of the beginning and ending balances for Level 3 financial liabilities measured at fair value on a recurring basis for the three months ended September 30, 2023: Total Level 3 financial liabilities, beginning of period 659 Issuance of contingent rent liability 711 Change in fair value of financial liabilities (622) Level 3 financial liabilities, end of period 748 During the three and nine months ended September 30, 2023, there were no transfers out of Level 3.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses recorded in our unaudited condensed consolidated balance sheet consist of the following (in thousands): September 30, 2023 December 31, 2022 External research and development expenses 2,936 5,389 Employee benefits, compensation and severance $ 693 $ 1,191 Professional and consulting fees 557 883 Other 364 482 Total accrued expenses $ 4,550 $ 7,945

Loan and Security Agreement

Loan and Security Agreement	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Loan and Security Agreement	Loan and Security Agreement Horizon Technology Finance Corporation Loan and Security Agreement In December 2022, we entered into a loan agreement with Horizon (the "Loan Agreement"), as lender and collateral agent (the “Lender”), pursuant to which the Lender agreed to make term loans in an aggregate principal amount of up to $45.0 million, available to us on the closing date and we borrowed $45.0 million. On July 7, 2023, we entered with Horizon into a Waiver and Amendment to the Venture Loan and Security Agreement and Eleventh Extension of Standstill Agreement which amends the Loan Agreement dated as of December 15, 2022. For more information, please see "Note 16. Subsequent Events." December 2022 Loan Agreement Borrowings under the Loan Agreement are collateralized by substantially all of our personal property, excluding intellectual property, and we pledged our equity interests in our subsidiaries, subject to certain limitations with respect to our foreign subsidiaries (the "Collateral"). Interest on the outstanding loan balance accrues at a variable annual rate equal to the greater of (i) 11% and (ii) rate of interest noted in The Wall Street Journal, Money Rates section, as the “Prime Rate” plus the “Loan Rate Spread” as defined in the Loan Agreement. We are required to make interest-only payments on the loans on the stub period date (January 1, 2023) and for the first thirty-six monthly payment dates prior to when the loans are scheduled to begin amortizing on February 1, 2026 (the “Amortization Date”). Beginning on February 1, 2026, we must pay twenty-four equal consecutive monthly installment payments repaying $35.0 million of the principal, plus interest on all outstanding balance until the loans mature on January 1, 2028 (the “Maturity Date”). The remaining $10.0 million of principal is due and payable on the Maturity Date. At our option, we may prepay the loans in whole, subject to a prepayment fee of 3% of the amount prepaid if prepaid on or before the Amortization Date, or if the prepayment occurs after less than 12 months after Amortization Date, 2% of the amount prepaid, and if more than 12 months after the Amortization Date but before the Maturity Date, 1%. A final payment equal to 4.25% of the principal borrowed on the closing date is due on the Maturity Date (or upon repayment in full of principal, if earlier). Upon the entry into the Loan Agreement, we were required to pay Horizon a commitment fee of $0.5 million, as well as other customary fees and expenses. The Loan Agreement contains customary representations, warranties and covenants and also includes customary events of default, including payment defaults, breaches of covenants, change of control and occurrence of a material adverse effect. Upon the occurrence and continuation of an event of default, a default interest rate of an additional 5% per annum may be applied to the outstanding loan balances, and Horizon may declare all outstanding obligations immediately due and payable and exercise all of their rights and remedies as set forth in the Loan Agreement and under applicable law. Our subsidiary, Evelo Biosciences Security Corporation, may maintain cash or cash equivalents so long as we satisfy certain liquidity requirements. In connection with the entry into the Loan Agreement, we also issued to Horizon warrants to purchase up to an aggregate 23,191 shares of our common stock (on a post reverse share split basis), with an exercise price of $38.80 per share (on a post reverse split basis). The warrants are exercisable immediately and expire on December 15, 2032, provided that, under certain circumstances, the warrants may terminate and expire earlier in connection with the closing of certain acquisition transactions involving us. The warrants provide that Horizon may elect to exercise the warrant on a net “cashless” basis at any time prior to the expiration thereof. The fair market value of one share of our common stock in connection with any cashless exercise shall be the closing price or last sale price per share of our common stock on a nationally recognized securities exchange, inter-dealer quotation system or over-the-counter market on which our common stock is traded on the business day immediately prior to the date the holder elects to exercise the warrants on a cashless basis. The warrants were deemed to be a freestanding financial instrument as it is legally detachable and separately exercisable from the debt obligations. We evaluated the terms and conditions of the warrants and concluded it met the criteria to be classified as a liability. As such, we recorded the warrants as a noncurrent liability at its issuance date. On May 10, 2023, we (expressly without conceding that an "Event of Default" (as defined under the Loan Agreement) has occurred) entered with Horizon into a Standstill Agreement (as amended on by that certain First Extension of Standstill Agreement dated as of May 14, 2023 through the Tenth Extension of Standstill Agreement dated as of June 30, 2023, the “Standstill Agreement”) pursuant to which Horizon agreed to forbear from exercising, and not to exercise, any and all remedies available to it under the Loan Agreement, warrants, notes and other Financing Documents (as defined in the Standstill Agreement) during the period commencing on May 10, 2023 and ending on July 7, 2023 (the “Standstill Period”). Waiver and Amendment to Loan Agreement and Eleventh Extension of Standstill Agreement On July 7, 2023, we entered into a Waiver and Amendment to the Venture Loan and Security Agreement and Eleventh Extension of Standstill Agreement (the “First Amendment”) with Horizon. The First Amendment amends the Loan Agreement dated as of December 15, 2022 with Horizon, whereby Horizon agreed to forbear exercising remedies on specified potential defaults (which forbearance will cease to apply if specified conditions as set forth in the First Amendment are not met), we granted a security interest over substantially all of our intellectual property, we paid down on the closing date of the July 10, 2023 private placement (the "Private Placement") $5.0 million of the principal amount of the loans outstanding under the Loan Agreement, and Horizon converted $5.0 million of the principal amount of the loans outstanding under the Loan Agreement into shares of common stock at a price per share equal to the price paid by the Investors in the Private Placement. We also amended the payment schedule and have agreed to prepay up to an additional $10.0 million of the principal amount of the loans outstanding under the Loan Agreement (plus applicable final payments) and Horizon has agreed to convert up to an additional $10.0 million of the principal amount of the loans outstanding under the Loan Agreement into equity, in each case, concurrently with future sales of our equity securities, in amounts equal to 20% of the gross cash proceeds from such equity sales. Horizon further agreed to remove the $5.0 million cash financial covenant previously instituted in connection with an extension of the Standstill Agreement, and we agreed that, upon the failure to achieve specified performance milestones in the future, a $9.0 million cash and cash equivalents covenant would be imposed. We agreed with Horizon to further extend the Standstill Period for a period to permit us to continue operations including advancing our Phase 2a study of EDP2939. Horizon extended the Standstill Period, but only to the extent, and in accordance with, the terms, and subject to the conditions, set forth in the Waiver and Amendment to Loan Agreement and Eleventh Extension of Standstill Agreement. Forbearance and Second Amendment to Loan Agreement and Twelfth Extension of Standstill Agreement On October 17, 2023, we announced that the top-line results from our Part B (Phase 2) clinical study of EDP2939 in moderate psoriasis did not achieve the primary endpoint. Accordingly, the Standstill Period was automatically extended by ten days after this announcement, based on the terms and conditions set forth in the Waiver and Amendment to Loan Agreement and Eleventh Extension of Standstill Agreement, to October 27, 2023 (the “Forbearance Period”). On October 26, 2023, we entered into a Forbearance and Second Amendment to the Venture Loan and Security Agreement and Twelfth Extension of Standstill Agreement with Horizon (the “Second Amendment”). The Second Amendment amends the Loan Agreement, dated as of December 15, 2022, as further amended by the First Amendment, with Horizon, whereby Horizon agreed, among other things, to forbear exercising remedies on specified potential defaults through December 15, 2023. We also paid down $11.0 million in principal. For more information, please see "Note 16. Subsequent Events." Subjective Acceleration Clause The Loan Agreement contains a subjective acceleration clause which allows Horizon to accelerate the maturity of the principal payments under certain circumstances, following expiration of Twelfth Extension of Standstill Agreement with Horizon, pending the results of the strategic review process, Horizon may choose to exercise various remedies available to them. This may include, but is not limited to, demanding the repayment of outstanding loan amounts, advancing the loan maturity date, or taking actions against the collateral that secures our obligations under the Loan Agreement. Additionally, we might be compelled to explore seeking relief through the U.S. Bankruptcy Courts, or winding down our operations. Based upon our significant operating losses, going concern assessment as of September 30, 2023, and conditions of the First Amendment, we determined that we should classify our loan facility with Horizon, which would otherwise be classified as long-term debt, as a current liability on our consolidated balance sheet as of September 30, 2023. We have the following minimum aggregate future loan payments as of September 30, 2023 related to the Loan Agreement, excluding the subsequent Waiver and Amendment to the Venture Loan and Security Agreement impact: (in thousands) 2024 $ — 2025 — 2026 6,875 2027 7,500 Thereafter 20,625 Total minimum payments 35,000 Debt discount (1,052) Total Debt as of September 30, 2023 $ 33,948 For the three months ended September 30, 2023 and 2022, interest expense was approximately $1.3 million and $1.1 million. For the nine months ended September 30, 2023 and 2022, interest expense was approximately $4.4 million and $3.2 million.

In-License Agreements

In-License Agreements	9 Months Ended
	Sep. 30, 2023
Research and Development [Abstract]
In-License Agreements	ALJ Collaborative AgreementIn March 2021, we entered into a collaborative commercialization and license agreement (“ALJ Agreement”) with ALJ. Pursuant to the ALJ Agreement, we granted to ALJ an exclusive, non-transferable, sublicensable license to our product candidate EDP1815. In consideration for the rights granted under the ALJ Agreement, ALJ was obligated to pay a one-time, non-refundable upfront fee of $7.5 million. The parties will also share the future operating profits and losses for certain products in certain territories equally (50:50) as well as certain development, regulatory and commercialization costs. We have concluded that the delivery of the license to ALJ shall be accounted for under ASC 606. The development, regulatory and commercialization activities within the territories shall be accounted for under the FASB guidance of Collaborative Arrangements (Topic 808) ("ASC 808"). We have recognized no revenue under the ALJ Agreement to date as we have yet to undertake any of our performance obligations within the agreement. The $7.5 million upfront fee is recorded as deferred revenue as a non-current liability in the accompanying unaudited condensed consolidated balance sheets because the performance obligation is not expected to be completed within the next twelve months. We anticipate payments under the cost-sharing or profit and loss sharing arrangements will be classified in the statement of operations consistent with the guidance of ASC 808. To date, we have neither received nor incurred any such payments. Mayo Foundation for Medical Education and Research In August 2017, we and the Mayo Clinic amended the 2016 Mayo License Agreement. Under the amended agreement, the Mayo Clinic granted us (i) an exclusive, worldwide, sublicensable license under the Mayo Clinic’s rights to certain intellectual property and microbial strains and (ii) a non-exclusive, worldwide, sublicensable license to certain related know-how to develop and commercialize certain microbial strains and licensed products incorporating such strains. As consideration, we paid a nonrefundable upfront fee of $0.3 million and are obligated to pay annual license maintenance fees. The nonrefundable upfront fees were expensed to research and development expense in 2017. Annual maintenance fees are expensed as incurred over the term of the agreement. We may owe the Mayo Clinic milestone payments upon the achievement of certain milestones up to a maximum of $59.1 million in the aggregate, as well as royalties on net sales of licensed products in low single-digit percentages. As of September 30, 2023, we incurred milestone payments since inception of approximately $0.3 million and no amounts are currently due.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Manufacture and Supply Agreement with Sacco S.r.l. In July 2019, we entered into an agreement with Sacco S.r.l. ("Sacco") pursuant to which Sacco will manufacture and supply single strain, non-genetically modified microbes and extracellular vesicles ("EVs") intended for oral delivery or oral use in pharmaceutical products exclusively for us for a period of five years. Sacco may terminate the agreement if the provision of manufacturing services has been, or is scheduled to be, inactive for a consecutive period of six months. We agreed to pay Sacco an aggregate of €3.0 million, consisting of payments of €0.6 million annually during the exclusivity period. We have incurred annual exclusivity fees since inception of approximately €2.4 million, and no amounts are currently due. In June 2023, we amended our July 2019 agreement with Sacco pursuant to which the 2023 annual exclusivity payment of €0.6 million was deferred from July 2023 to the first quarter of 2024. Additionally, we have a contractual arrangement with an affiliate of Sacco for manufacturing that required us to spend an aggregate minimum amount of €3.9 million, consisting of €1.5 million annually during each of 2023 and 2024 and €0.9 million on or before March 1, 2025. In June 2023, we have also amended this agreement and revised the aggregate minimum spend amount to be nil additional spend in 2023, €1.7 million during 2024 and €2.4 million during 2025. Litigation and Other Proceedings

Stockholders_ Deficit

Stockholders’ Deficit	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Stockholders’ Deficit	Stockholders’ Deficit Preferred Stock We have authorized 10,000,000 shares of Preferred Stock, $0.001 par value, of which the board of directors can set the designation, rights and privileges. No shares of Preferred Stock have been issued or are outstanding. Common Stock We have authorized 200,000,000 shares of Common Stock, $0.001 par value, of which the board of directors can set the designation, rights and privileges. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of our stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors. Reverse Split At our 2023 annual meeting of stockholders, a resolution was passed to effect a reverse stock split of all outstanding shares of our common stock within a certain ratio. On June 29, 2023, we effected a 1-for-20 reverse stock split of our common stock. The reverse stock split had no impact on the number of authorized shares or the par value of preferred and common stock. Trading of our common stock on The Nasdaq Global Select Market commenced on a split-adjusted basis on June 30, 2023. 2023 Private Placement On July 7, 2023, we entered into a purchase agreement with the purchasers named therein, pursuant to which we agreed to issue and sell an aggregate of 11,025,334 shares of our common stock to the purchasers in a private placement, at a purchase price of $2.31 per share, for aggregate gross proceeds of approximately $25.5 million, before deducting private placement expenses. Additionally, on July 11, 2023, Horizon converted $5.0 million of the principal amount of the loans outstanding under the Loan Agreement into 2,164,502 shares of common stock at a conversion price of $2.31 per share, equal to the price paid by the purchasers in the Private Placement. Warrants In connection with our current and prior loan agreements, we issued warrants exercisable for shares of our common stock. The following table summarizes outstanding warrants as of September 30, 2023, reflected on a post split basis: Transactions Number of Shares Issuable Exercise Price Expiration Date K2 HealthVentures warrants 33,187 $ 40.00 June 16, 2031 Horizon Technology warrants 23,191 $ 38.80 December 15, 2032 56,378

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Equity Plans 2021 Inducement Plan In May 2021, our board of directors adopted the Evelo Biosciences, Inc. 2021 Employment Inducement Award Plan (the “Inducement Award Plan”) without stockholder approval pursuant to Rule 5635(c)(4) of the Nasdaq Stock Market LLC listing rules. As of September 30, 2023, 40,500 shares of common stock (on a post reverse split basis) are available for future grant under the Inducement Award Plan. 2018 Incentive Award Plan In April 2018, our board of directors adopted, and our stockholders approved, the 2018 Incentive Award Plan (the "2018 Plan"), effective May 2018, under which we may grant cash and equity-based incentive awards to our employees, officers, directors, consultants and advisors. In June 2023, our board of directors adopted, and our stockholders approved, an amendment and restatement of the 2018 Plan to increase the number of shares of our common stock available for issuance by 200,000 shares. As of September 30, 2023 , 0 shares of common stock were available for the future grant under the 2018 Plan. Stock Options A summary of our stock option activity and related information for the nine months ended September 30, 2023 is as follows: Shares Weighted- Weighted Average - Remaining Contractual Life (years) Aggregate Intrinsic Value (1) (in thousands) Options outstanding as of December 31, 2022 558,565 $ 155.93 6.91 $ 746 Granted 120,943 17.39 Exercised — — Forfeited (94,310) 175.82 Canceled (90,251) 187.31 Options outstanding as of September 30, 2023 494,947 $ 112.56 6.23 $ 15 Exercisable as of September 30, 2023 321,230 $ 138.59 4.85 $ 120 (1) The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of our common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the period. We had 173,717 unvested stock options outstanding as of September 30, 2023. The weighted-average fair value of options granted during the nine months ended September 30, 2023 and 2022 was $7.98 and $57.82, respectively. There were no stock options exercised during the nine months ended September 30, 2023. The aggregate intrinsic value of options exercised during the nine months ended September 30, 2023 and 2022 was zero. The remaining unrecognized compensation expense for outstanding stock options as of September 30, 2023 was $7.5 million and the weighted-average period over which this cost is expected to be recognized is 2.6 years. Restricted Stock Units We issue restricted stock units ("RSUs") under our 2018 Plan and 2021 Inducement Plan. A summary of the RSU activity and related information for the nine months ended September 30, 2023 is as follows: Shares Weighted-Average Unvested balance at December 31, 2022 11,966 $ 145.51 Granted 579,300 11.72 Vested (118,997) 19.86 Forfeited (48,733) 37.09 Unvested balance at September 30, 2023 423,536 $ 10.29 Stock-based compensation expense related to RSUs was $1.2 million and $0.2 million for the three months ended September 30, 2023 and 2022, respectively. Stock-based compensation expense related to RSUs was $2.8 million and $0.9 million for the nine months ended September 30, 2023 and 2022, respectively. The fair value of vested RSUs for the nine months ended September 30, 2023 and 2022 was $0.7 million and $0.6 million, respectively. The remaining unrecognized compensation expense for outstanding restricted stock units as of September 30, 2023 was $3.3 million and the weighted-average period over which this cost is expected to be recognized is 0.91 years. 2018 Employee Stock Purchase Plan In April 2018, our board of directors adopted, and our stockholders approved, the 2018 Employee Stock Purchase Plan (“ESPP”), which became effective in May 2018. As of September 30, 2023, a total of 113,103 shares of common stock were reserved for issuance under the ESPP. The compensation expense recognized related to the ESPP for the three and nine months ended September 30, 2023 and 2022 was immaterial. No shares were purchased under the ESPP during the three months ended September 30, 2023 and 2022, and 2,168 and 3,797 shares were sold during the nine months ended September 30, 2023 and 2022, respectively. Stock-Based Compensation Expense Stock-based compensation expense included in our unaudited condensed consolidated statements of operations is as follows (in thousands): Three Months Ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Research and development $ 1,429 $ 1,694 $ 4,421 $ 5,431 General and administrative 1,047 1,769 3,329 6,306 Total stock-based compensation expense $ 2,476 $ 3,463 $ 7,750 $ 11,737

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic and diluted net loss per common share is determined by dividing the net loss by the weighted-average common shares outstanding during the period, as follows (net loss in thousands): Three Months Ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Numerator Net loss $ (12,364) $ (30,564) $ (58,808) $ (90,986) Denominator Weighted average shares outstanding used in computing net loss per share 17,384,243 5,402,592 9,546,129 3,976,438 Net loss per share, basic and diluted $ (0.71) $ (5.66) $ (6.16) $ (22.88) We compute diluted net loss per common share by giving consideration to all potentially dilutive common shares, except where the effect of including such securities would be anti-dilutive. We have reported net losses since inception and, as such, have determined that all potentially dilutive common shares are anti-dilutive. Consequently, basic and diluted net loss per share of common stock were the same for all periods presented as the impact of all potentially dilutive securities outstanding was anti-dilutive. The following table presents securities excluded from the computation of diluted weighted-average shares outstanding for the periods presented, as they are anti-dilutive: September 30, 2023 2022 Stock options to purchase common stock 494,947 571,606 Warrant 56,378 6,988 RSUs 423,536 15,065 Conversion option — 18,797 Common stock from the ESPP 124 2,009 Total 974,985 614,465

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Weatherden Advisory Services Agreement We receive clinical advisory services from Weatherden Ltd. (“Weatherden”) under agreements that were entered into during 2017 and 2018. Duncan McHale, our Chief Medical Officer, is a part owner of Weatherden. During each of the nine months ended September 30, 2023 and 2022, we paid Weatherden $0.1 million or less. As of September 30, 2023 and 2022, the amounts owed to Weatherden under the supply of service agreement were approximately $0.1 million or less. Securities Purchase Agreement with Related Parties In May 2022, in connection with our registered direct offering, we entered into the Purchase Agreement with a group of purchasers including certain of our executive officers, members of our board of directors and other related parties. Of the 2,712,317 total shares offered, officers and directors purchased an aggregate of 19,691 shares and other related parties purchased an aggregate of 1,412,671 shares of our common stock for $29.20 per share, a price equal to the offering price per share of, and on equal terms as, common stock sold to the public. In July 2023, in connection with the private placement, we entered into a securities purchase agreement with a group of purchasers including two related parties. Of the 11,025,334 total shares offered, related parties purchased an aggregate of 7,778,582 shares of our common stock for $2.31 per share, a price equal to the offering price per share of, and on equal terms as, common stock sold to all purchasers.

Workforce Reduction

Workforce Reduction	9 Months Ended
	Sep. 30, 2023
Restructuring Charges [Abstract]
Workforce Reduction	Workforce ReductionOn January 31, 2023, our board of directors approved a plan to reduce the Company's workforce by 48 employees, or approximately 45% of our total headcount as of January 31, 2023, and further reductions in the workforce were made in the second quarter of 2023, in order to preserve cash and prioritize investment in our core clinical programs. During the three and nine months ended September 30, 2023, we recognized less than $0.1 million and $3.1 million of charges in the condensed consolidated statement of operations related to this workforce reduction. These charges primarily consisted of severance costs.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On October 26, 2023, we entered into the Second Amendment with Horizon, whereby Horizon agreed, among other things, to forbear exercising remedies on specified potential defaults through December 15, 2023, and we paid down $11.0 million of the principal amount of the loans outstanding under the Loan Agreement. Horizon further agreed to remove from the Loan Agreement certain covenants relating to our obligations (i) to maintain ongoing clinical trials, (ii) to maintain a minimum amount of cash or cash equivalents on deposit in controlled accounts, and (iii) to repay the loans outstanding under the Loan Agreement with a percentage of the proceeds of future equity sales. The Second Amendment also provides that no cash interest-only payments are required to be paid to Horizon effective as of October 1, 2023 and that such interest payments shall be treated as payments-in-kind and added to the outstanding principal balance of the loans. The Second Amendment amends the mandatory prepayment provision in the Loan Agreement to require us to prepay a portion of the loans outstanding under the Loan Agreement in an amount equal to 70% of any net proceeds received by us from equity sales, licensing or sale of our assets. Finally, the Second Amendment waives all prepayment fees and eliminates or defers the final payment fees related to the $11.0 million in principal paid in connection with the Second Amendment, depending upon repayment of principal.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification and ASU of the FASB. On June 29, 2023, we effected a 1-for-20 reverse stock split of our common stock. All share and per share amounts in the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the unaudited condensed consolidated financial statements and accompanying notes. Significant estimates and assumptions reflected in these unaudited condensed consolidated financial statements include, but are not limited to, estimates related to the application of Revenue from Contracts with Customers (Topic 606) ("ASC 606") to our collaboration agreement with Meddist Company Limited ("ALJ"), the accrual of research and development expenses, the expected future lives of property and equipment and the valuation of that equipment utilized in impairment analyses, the valuation of stock-based awards, and common stock warrants. We base our estimates on historical experience and market-specific or other relevant assumptions that we believe to be reasonable under the circumstances. Actual results could differ from those estimates.
Principles of Consolidation	All intercompany transactions and balances have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Subsequent Event Considerations	Subsequent Event Considerations We consider events or transactions that occur after the balance sheet date but prior to the issuance of the unaudited condensed consolidated financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially expose us to concentrations of credit risk primarily consist of cash and cash equivalents. We placed our operating cash in demand deposit accounts at a single financial institution since February 2022, which have exceeded and are expected to continue to exceed federally insured limits. Our money market funds are held in an investment account at an affiliate institution. As of September 30, 2023 and 2022, we have no off-balance sheet risk such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.
Comprehensive Loss	Comprehensive Loss Comprehensive loss consists of net loss and changes in equity during a period arising from transactions and other equity and circumstances, of which we have none. Our comprehensive loss equals our net loss for all periods presented.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted CashCash equivalents are highly liquid investments that are readily convertible into cash with original maturities of three months or less, which consist of cash held in banks and funds held in money market accounts. Cash equivalents are stated at cost, which approximates market value. Our restricted cash consists of the deposits held for the building lease for our office and laboratory premises, for our credit card facility, and for the proceeds from our recent disposition of long-lived assets.
Research and Development Costs	Research and Development Costs Research and development costs are expensed in the period incurred. Research and development expenses consist of both internal and external costs associated with the development of our product candidates, such as payroll, consulting, clinical trial costs and manufacturing costs associated with the development of our product candidates. Costs for certain development activities, such as clinical trials and manufacturing development activities, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided to us by our vendors on their actual costs incurred or level of effort expended. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected on the unaudited condensed consolidated balance sheets as prepaid or accrued research and development expenses.
Property and Equipment	Property and Equipment Property and equipment consists of computer hardware and software, furniture and fixtures, office equipment, research and lab equipment, and leasehold improvement recorded at cost. Lab equipment used in research and development activities is only capitalized when it has an alternative future use. These amounts are depreciated using the straight-line method over the estimated useful lives of the assets. Purchased assets that are not yet in service are recorded to construction-in-process and no depreciation expense is recorded. Once they are placed in service they are reclassified to the appropriate asset class. A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 3 - 5 years Computer software 3 years Furniture and fixtures 7 years Research and lab equipment (used/new) 3 - 5 years Leasehold improvements Lesser of asset life or remaining life of lease Repairs and maintenance costs are expensed as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We periodically evaluate property and equipment for impairment whenever events or changes in circumstances indicate that a potential impairment may have occurred. If such events or changes in circumstances arise, we compare the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of the long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the long-lived assets.
Segments	Segments We have one operating segment. Our chief operating decision maker, the Chief Executive Officer, manages our operations on a consolidated basis for the purposes of allocating resources.
Accounting Pronouncements Issued and Not Yet Effective	Accounting Pronouncements Issued and Not Yet Effective as of September 30, 2023 No new accounting pronouncements issued or effective in the period had or are expected to have a material impact on our accompanying unaudited condensed consolidated statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following reconciles cash, cash equivalents and restricted cash as of September 30, 2023 and 2022, as presented on the statements of cash flows, to the related balance sheet accounts (in thousands): September 30, 2023 September 30, 2022 Cash and cash equivalents: Cash $ 1,969 $ 10,363 Money market funds 15,293 58,690 Total cash and cash equivalents 17,262 69,053 Restricted cash 797 1,156 Cash, cash equivalents and restricted cash $ 18,059 $ 70,209
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following reconciles cash, cash equivalents and restricted cash as of September 30, 2023 and 2022, as presented on the statements of cash flows, to the related balance sheet accounts (in thousands): September 30, 2023 September 30, 2022 Cash and cash equivalents: Cash $ 1,969 $ 10,363 Money market funds 15,293 58,690 Total cash and cash equivalents 17,262 69,053 Restricted cash 797 1,156 Cash, cash equivalents and restricted cash $ 18,059 $ 70,209
Schedule of Estimated Useful Lives of Property and Equipment	A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 3 - 5 years Computer software 3 years Furniture and fixtures 7 years Research and lab equipment (used/new) 3 - 5 years Leasehold improvements Lesser of asset life or remaining life of lease Repairs and maintenance costs are expensed as incurred. Property and equipment recorded in our consolidated balance sheet consists of the following (in thousands): September 30, 2023 December 31, 2022 Property and equipment: Lab equipment $ 2,631 $ 9,761 Leasehold improvements — 2,157 Furniture and fixtures — 818 Computers and software 253 253 Office equipment — 66 Construction-in-process 93 1,122 Property and equipment 2,977 14,177 Less: accumulated depreciation (2,083) (9,335) Property and equipment, net $ 894 $ 4,842

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Schedule of Consolidated Balance Sheets and Lease Term	The following table presents supplemental balance sheet information related to our operating leases (in thousands): September 30, 2023 December 31, 2022 Assets: Operating lease right-of-use assets $ — $ 6,868 Liabilities: Operating lease liabilities, current — 2,259 Operating lease liabilities, noncurrent — 5,265 Total lease liabilities $ — $ 7,524 Other information: Weighted-average remaining lease term (in years) 0.00 years 2.75 years Weighted-average discount rate — % 9.5 %

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 3 - 5 years Computer software 3 years Furniture and fixtures 7 years Research and lab equipment (used/new) 3 - 5 years Leasehold improvements Lesser of asset life or remaining life of lease Repairs and maintenance costs are expensed as incurred. Property and equipment recorded in our consolidated balance sheet consists of the following (in thousands): September 30, 2023 December 31, 2022 Property and equipment: Lab equipment $ 2,631 $ 9,761 Leasehold improvements — 2,157 Furniture and fixtures — 818 Computers and software 253 253 Office equipment — 66 Construction-in-process 93 1,122 Property and equipment 2,977 14,177 Less: accumulated depreciation (2,083) (9,335) Property and equipment, net $ 894 $ 4,842

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following tables present information about our financial assets and liabilities that have been measured at fair value as of September 30, 2023 and December 31, 2022 (in thousands): Description September 30, 2023 (Level 1) (Level 2) (Level 3) Financial Assets Cash and cash equivalents: Money market funds $ 15,293 $ 15,293 $ — $ — Other assets: Restricted cash held in money market funds 263 263 — — Total $ 15,556 $ 15,556 $ — $ — Financial Liabilities Other noncurrent liabilities: Warrant liabilities $ 37 — — $ 37 Contingent rent liability 711 — — 711 Total $ 748 $ — $ — $ 748 Description December 31, 2022 (Level 1) (Level 2) (Level 3) Financial Assets Cash and cash equivalents: Money market funds $ 46,660 $ 46,660 $ — $ — Other assets: Restricted cash held in money market funds 1,158 1,158 — — Total $ 47,818 $ 47,818 $ — $ — Financial Liabilities Other noncurrent liabilities: Warrant liabilities $ 659 — — $ 659 Total $ 659 $ — $ — $ 659
Schedule of Level 3 Financial Liabilities Measured at Fair Value on a Recurring Basis	The following table shows a reconciliation of the beginning and ending balances for Level 3 financial liabilities measured at fair value on a recurring basis for the three months ended September 30, 2023: Total Level 3 financial liabilities, beginning of period 659 Issuance of contingent rent liability 711 Change in fair value of financial liabilities (622) Level 3 financial liabilities, end of period 748

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses recorded in our unaudited condensed consolidated balance sheet consist of the following (in thousands): September 30, 2023 December 31, 2022 External research and development expenses 2,936 5,389 Employee benefits, compensation and severance $ 693 $ 1,191 Professional and consulting fees 557 883 Other 364 482 Total accrued expenses $ 4,550 $ 7,945

Loan and Security Agreement (Ta

Loan and Security Agreement (Tables)	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Schedule of Minimum Aggregate Future Loan Payments	We have the following minimum aggregate future loan payments as of September 30, 2023 related to the Loan Agreement, excluding the subsequent Waiver and Amendment to the Venture Loan and Security Agreement impact: (in thousands) 2024 $ — 2025 — 2026 6,875 2027 7,500 Thereafter 20,625 Total minimum payments 35,000 Debt discount (1,052) Total Debt as of September 30, 2023 $ 33,948

Stockholders_ Deficit (Tables)

Stockholders’ Deficit (Tables)	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Schedule of Warrants Exercisable	In connection with our current and prior loan agreements, we issued warrants exercisable for shares of our common stock. The following table summarizes outstanding warrants as of September 30, 2023, reflected on a post split basis: Transactions Number of Shares Issuable Exercise Price Expiration Date K2 HealthVentures warrants 33,187 $ 40.00 June 16, 2031 Horizon Technology warrants 23,191 $ 38.80 December 15, 2032 56,378

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Stock Option Activity	A summary of our stock option activity and related information for the nine months ended September 30, 2023 is as follows: Shares Weighted- Weighted Average - Remaining Contractual Life (years) Aggregate Intrinsic Value (1) (in thousands) Options outstanding as of December 31, 2022 558,565 $ 155.93 6.91 $ 746 Granted 120,943 17.39 Exercised — — Forfeited (94,310) 175.82 Canceled (90,251) 187.31 Options outstanding as of September 30, 2023 494,947 $ 112.56 6.23 $ 15 Exercisable as of September 30, 2023 321,230 $ 138.59 4.85 $ 120 (1) The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of our common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the period.
Schedule of Restricted Stock Unit Activity	A summary of the RSU activity and related information for the nine months ended September 30, 2023 is as follows: Shares Weighted-Average Unvested balance at December 31, 2022 11,966 $ 145.51 Granted 579,300 11.72 Vested (118,997) 19.86 Forfeited (48,733) 37.09 Unvested balance at September 30, 2023 423,536 $ 10.29
Schedule of Stock-based Compensation Expense	Stock-based compensation expense included in our unaudited condensed consolidated statements of operations is as follows (in thousands): Three Months Ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Research and development $ 1,429 $ 1,694 $ 4,421 $ 5,431 General and administrative 1,047 1,769 3,329 6,306 Total stock-based compensation expense $ 2,476 $ 3,463 $ 7,750 $ 11,737

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Basic and diluted net loss per common share is determined by dividing the net loss by the weighted-average common shares outstanding during the period, as follows (net loss in thousands): Three Months Ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Numerator Net loss $ (12,364) $ (30,564) $ (58,808) $ (90,986) Denominator Weighted average shares outstanding used in computing net loss per share 17,384,243 5,402,592 9,546,129 3,976,438 Net loss per share, basic and diluted $ (0.71) $ (5.66) $ (6.16) $ (22.88)
Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding	The following table presents securities excluded from the computation of diluted weighted-average shares outstanding for the periods presented, as they are anti-dilutive: September 30, 2023 2022 Stock options to purchase common stock 494,947 571,606 Warrant 56,378 6,988 RSUs 423,536 15,065 Conversion option — 18,797 Common stock from the ESPP 124 2,009 Total 974,985 614,465

Organization and Basis of Pre_2

Organization and Basis of Presentation (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 17,262	$ 47,940	$ 69,053
Accumulated deficit	$ (588,030)	$ (529,222)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details) $ in Millions		9 Months Ended
	Jun. 29, 2023	Sep. 30, 2023 USD ($) segment	Dec. 31, 2022	Sep. 30, 2022 USD ($)
Accounting Policies [Abstract]
Reverse stock split ratio	0.05
Noncurrent restricted cash | $		$ 0.8		$ 1.2
Restricted Cash, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Other assets	Other assets
Number of operating segments | segment		1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted cash (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Cash and cash equivalents:
Cash	$ 1,969		$ 10,363
Money market funds	15,293		58,690
Total cash and cash equivalents	17,262	$ 47,940	69,053
Restricted cash	797		1,156
Cash, cash equivalents and restricted cash	$ 18,059	$ 49,098	$ 70,209	$ 69,754

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Details)	Sep. 30, 2023
Computer hardware | Minimum
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	3 years
Computer hardware | Maximum
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	5 years
Computer software
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	7 years
Research and lab equipment (used/new) | Minimum
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	3 years
Research and lab equipment (used/new) | Maximum
Property, Plant and Equipment [Line Items]
Useful life of property and equipment (in years)	5 years

ALJ Collaborative Agreement (De

ALJ Collaborative Agreement (Details) - USD ($) $ in Thousands	1 Months Ended
	Mar. 31, 2021	Sep. 30, 2023	Dec. 31, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue recognized		$ 7,500	$ 7,500
ALJ | Transaction with party to collaborative arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue recognized	$ 7,500	$ 7,500
Share of operating profits and losses and development, regulatory and commercialization costs (as percent)	50%

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jul. 14, 2023 USD ($)	Jan. 31, 2018 ft²
Leases [Abstract]
Area of leased office and research development space (in square feet) | ft²						40,765
Early termination of sublease, one-time termination payment					$ 0.5
Early termination of sublease, amount lessor entitled to draw on letter of credit					0.9
Early termination of sublease, contingent payment to lessor					$ 2.5
Early termination of sublease, contingent liability	$ 0.7		$ 0.7
Rent expense	$ 1.8	$ 0.7	3.3	$ 2.2
Operating lease payments			$ 2.1	$ 2.3

Leases - Schedule of Consolidat

Leases - Schedule of Consolidated Balance Sheets and Lease Term (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Assets:
Operating lease right-of-use assets	$ 0	$ 6,868
Liabilities:
Operating lease liabilities, current	0	2,259
Operating lease liabilities, noncurrent	0	5,265
Total lease liabilities	$ 0	$ 7,524
Weighted-average remaining lease term (in years)	0 years	2 years 9 months
Weighted-average discount rate	0%	9.50%

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($)	Sep. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Property and equipment:
Property and equipment	$ 2,977,000		$ 14,177,000
Less: accumulated depreciation	(2,083,000)		(9,335,000)
Property and equipment, net	894,000		4,842,000
Lab equipment
Property and equipment:
Property and equipment	2,631,000		9,761,000
Property and equipment, net		$ 2,100,000
Leasehold improvements
Property and equipment:
Property and equipment	0		2,157,000
Property and equipment, net	0
Furniture and fixtures
Property and equipment:
Property and equipment	0		818,000
Computers and software
Property and equipment:
Property and equipment	253,000		253,000
Office equipment
Property and equipment:
Property and equipment	0		66,000
Construction-in-process
Property and equipment:
Property and equipment	$ 93,000		$ 1,122,000

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 200,000	$ 500,000	$ 1,038,000	$ 1,537,000
Property and equipment, net	894,000		894,000			$ 4,842,000
Impairment of disposed assets	(600,000)		(600,000)
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, net					$ 2,100,000
Tangible asset impairment			1,600,000
Property and equipment, fair value	500,000		500,000
Proceeds from disposition of property and equipment	500,000		500,000
Furniture And Fixtures And Office Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, net	300,000		300,000
Proceeds from disposition of property and equipment	100,000		100,000
Impairment of disposed assets	200,000		200,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 0		$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial Assets
Total	$ 15,556	$ 47,818
Other noncurrent liabilities:
Warrant liabilities	37	659
Contingent rent liability	711
Total	748	659
Money market funds
Financial Assets
Money market funds	15,293	46,660
Restricted cash held in money market funds	263	1,158
(Level 1)
Financial Assets
Total	15,556	47,818
Other noncurrent liabilities:
Warrant liabilities	0	0
Contingent rent liability	0
Total	0	0
(Level 1) | Money market funds
Financial Assets
Money market funds	15,293	46,660
Restricted cash held in money market funds	263	1,158
(Level 2)
Financial Assets
Total	0	0
Other noncurrent liabilities:
Warrant liabilities	0	0
Contingent rent liability	0
Total	0	0
(Level 2) | Money market funds
Financial Assets
Money market funds	0	0
Restricted cash held in money market funds	0	0
(Level 3)
Financial Assets
Total	0	0
Other noncurrent liabilities:
Warrant liabilities	37	659
Contingent rent liability	711
Total	748	659
(Level 3) | Money market funds
Financial Assets
Money market funds	0	0
Restricted cash held in money market funds	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details)	Sep. 30, 2023
Measurement Input, Price Volatility | Horizon Technology warrants | (Level 3) | Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.70

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Level 3 Financial Liabilities Measured At Fair Value on a Recurring Basis (Details) - (Level 3) $ in Thousands	3 Months Ended
	Sep. 30, 2023 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 financial liabilities, beginning of period	$ 659
Change in fair value of financial liabilities	(622)
Level 3 financial liabilities, end of period	$ 748

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
External research and development expenses	$ 2,936	$ 5,389
Employee benefits, compensation and severance	693	1,191
Professional and consulting fees	557	883
Other	364	482
Total accrued expenses	$ 4,550	$ 7,945

Loan and Security Agreement - N

Loan and Security Agreement - Narrative (Details)					1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 26, 2023 USD ($)	Oct. 17, 2023	Jul. 11, 2023 USD ($)	Jul. 10, 2023 USD ($)	Dec. 31, 2022 USD ($) payment $ / shares shares	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)
Line of Credit Facility [Line Items]
Number of shares called by warrants (in shares) (up to) | shares						56,378		56,378
Interest expense						$ 1,300,000	$ 1,100,000	$ 4,400,000	$ 3,200,000
Horizon Technology warrants
Line of Credit Facility [Line Items]
Number of shares called by warrants (in shares) (up to) | shares					23,191	23,191		23,191
Common stock exercise prices (in dollars per share) | $ / shares					$ 38.80	$ 38.80		$ 38.80
Horizon Technology Finance Corporation Loan and Security Agreement | Secured Debt
Line of Credit Facility [Line Items]
Borrowing, face amount					$ 45,000,000
Loan and security agreement, interest rate					11%
Interest only payment period | payment					36
Principal and interest payment period | payment					24
Periodic payment					$ 35,000,000
Final payment amount					$ 10,000,000
Final payment fee, percent					4.25%
Line of credit facility, commitment fee amount					$ 500,000
Debt default interest rate per annum					5%
Horizon Technology Finance Corporation Loan and Security Agreement | Secured Debt | On or before Amortization Date
Line of Credit Facility [Line Items]
Early repayment fee					3%
Early repayment fee, threshold period					12 months
Horizon Technology Finance Corporation Loan and Security Agreement | Secured Debt | After less than 12 months after Amortization Date
Line of Credit Facility [Line Items]
Early repayment fee					2%
Early repayment fee, threshold period					12 months
Horizon Technology Finance Corporation Loan and Security Agreement | Secured Debt | More than 12 months after the Amortization Date
Line of Credit Facility [Line Items]
Early repayment fee					1%
First Amendment Of Loan Agreement
Line of Credit Facility [Line Items]
Repayments of debt				$ 5,000,000
Debt converted amount			$ 5,000,000
Conversion, additional amount of equity component				$ 10,000,000
Proceeds from equity sales of percentage				0.20
Debt instrument, covenant, cash				$ 5,000,000
Debt instrument, covenant, cash and cash equivalents				$ 9,000,000
Second Amendment Of Loan Agreement | Secured Debt | Subsequent Event
Line of Credit Facility [Line Items]
Repayments of debt	$ 11,000,000
Debt, standstill period extension		10 days

Loan and Security Agreement - S

Loan and Security Agreement - Schedule of Minimum Aggregate Future Loan Payments (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Debt Disclosure [Abstract]
2024	$ 0
2025	0
2026	6,875
2027	7,500
Thereafter	20,625
Total minimum payments	35,000
Debt discount	(1,052)
Total Debt as of September 30, 2023	$ 33,948

In-License Agreements (Details)

In-License Agreements (Details) - USD ($)	1 Months Ended	74 Months Ended
	Aug. 31, 2017	Sep. 30, 2023
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Amount due under license agreement		$ 0
Mayo Clinic
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront fee	$ 300,000
Milestone payments upon achievement of certain development, regulatory, and commercial events (up to)		$ 300,000
Mayo Clinic | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments upon achievement of certain development, regulatory, and commercial events (up to)	$ 59,100,000

Commitments and Contingencies (

Commitments and Contingencies (Details) - Collaborative Arrangement € in Millions	1 Months Ended	51 Months Ended
	Jul. 31, 2019 EUR (€)	Sep. 30, 2023 EUR (€)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 EUR (€)
Sacco
Commitment And Contingencies [Line Items]
Term of collaboration arrangement	5 years
Period of inactive manufacturing services causing termination under collaborative agreement	6 months
Aggregate amount due under collaborative arrangement	€ 3
Annual amount due under collaborative arrangement	0.6			€ 0.6
Fee incurred under collaborative arrangement		€ 2.4
Amount due | $			$ 0
Affiliate Of Sacco
Commitment And Contingencies [Line Items]
Aggregate amount due under collaborative arrangement	€ 3.9
Collaborative arrangement, aggregate minimum amount, year one		1.5
Collaborative arrangement, aggregate minimum amount, year two		1.5
Collaborative arrangement, aggregate minimum amount, thereafter		0.9
Collaborative arrangement, revised, aggregate minimum amount, year one		1.7
Collaborative arrangement, revised, aggregate minimum amount, year two		€ 2.4

Stockholders_ Deficit - Narrati

Stockholders’ Deficit - Narrative (Details) $ / shares in Units, $ in Millions				9 Months Ended
	Jul. 11, 2023 shares	Jul. 07, 2023 USD ($) $ / shares shares	Jun. 29, 2023	Sep. 30, 2023 vote $ / shares shares	Dec. 31, 2022 $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Preferred stock, authorized (in shares)				10,000,000	10,000,000
Preferred stock par value per share (in dollars per share) | $ / shares				$ 0.001	$ 0.001
Preferred stock, issued (in shares)				0	0
Preferred stock, outstanding (in shares)				0	0
Common stock, shares authorized (in shares)				200,000,000	200,000,000
Common stock, par value (in dollars per share) | $ / shares				$ 0.001	$ 0.001
Common stock, voting rights, votes per share | vote				1
Reverse stock split ratio			0.05
Debt conversion shares issued (in shares)	2,164,502
Private placement
Subsidiary, Sale of Stock [Line Items]
Number of shares sold in public offering (in shares)		11,025,334
Offering price per share (in dollars per share) | $ / shares		$ 2.31
Proceeds from issuance of private placement | $		$ 25.5

Stockholders_ Deficit - Schedul

Stockholders’ Deficit - Schedule of Warrants Exercisable (Details) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Class of Warrant or Right [Line Items]
Number of Shares Issuable (in shares)	56,378
K2 HealthVentures warrants
Class of Warrant or Right [Line Items]
Number of Shares Issuable (in shares)	33,187
Exercise price (in dollars per share)	$ 40
Horizon Technology warrants
Class of Warrant or Right [Line Items]
Number of Shares Issuable (in shares)	23,191	23,191
Exercise price (in dollars per share)	$ 38.80	$ 38.80

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested stock options outstanding (in shares)	173,717		173,717
Weighted average fair value of options granted (in dollars per share)			$ 7.98	$ 57.82
Exercise of stock options (in shares)			0
Aggregate intrinsic value of options exercised			$ 0	$ 0
Unrecognized stock based compensation expense, stock options	$ 7,500,000		$ 7,500,000
Compensation cost not yet recognized, period for recognition			2 years 7 months 6 days
Stock-based compensation expense			$ 7,750,000	11,737,000
Stock-based compensation expense	2,476,000	$ 3,463,000	7,750,000	11,737,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of options exercised			$ 700,000	600,000
Compensation cost not yet recognized, period for recognition			10 months 28 days
Stock-based compensation expense	1,200,000	200,000	$ 2,800,000	900,000
Unrecognized stock based compensation expense, stock options	$ 3,300,000		$ 3,300,000
2021 Stock Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock available for future grant (in shares)	40,500		40,500
2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares of common stock reserved for issuance (in shares)			200,000
2018 Employee Stock Purchase Plan | Employee stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares of common stock reserved for issuance (in shares)			113,103
Stock-based compensation expense	$ 0	$ 0	$ 0	$ 0
Number of shares issued for purchase (in shares)	0	0	2,168	3,797

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Shares
Options outstanding, beginning balance (in shares)	558,565
Granted (in shares)	120,943
Exercised (in shares)	0
Forfeited (in shares)	(94,310)
Canceled (in shares)	(90,251)
Options outstanding, ending balance (in shares)	494,947	558,565
Exercisable as of period end (in shares)	321,230
Weighted- Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 155.93
Granted (in dollars per share)	17.39
Exercised (in dollars per share)	0
Forfeited (in dollars per share)	175.82
Canceled (in dollars per share)	187.31
Options outstanding, ending balance (in dollars per share)	112.56	$ 155.93
Weighted - Average Exercise Price, Exercisable at end of period (in dollars per share)	$ 138.59
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract]
Options, outstanding, Weighted Average - Remaining Contractual Life (in years)	6 years 2 months 23 days	6 years 10 months 28 days
Options, exercisable, Weighted Average - Remaining Contractual Life (in years)	4 years 10 months 6 days
Options, outstanding, Aggregate Intrinsic Value	$ 15	$ 746
Options, exercisable, Aggregate Intrinsic Value	$ 120

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) - RSUs	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Shares
Unvested beginning balance (in shares) | shares	11,966
Granted (in shares) | shares	579,300
Vested (in shares) | shares	(118,997)
Forfeited (in shares) | shares	(48,733)
Unvested ending balance (in shares) | shares	423,536
Weighted-Average Grant Date Fair Value
Unvested beginning balance (in dollars per share) | $ / shares	$ 145.51
Granted (in dollars per share) | $ / shares	11.72
Vested (in dollars per share) | $ / shares	19.86
Forfeited (in dollars per share) | $ / shares	37.09
Unvested ending balance (in dollars per share) | $ / shares	$ 10.29

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,476	$ 3,463	$ 7,750	$ 11,737
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,429	1,694	4,421	5,431
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,047	$ 1,769	$ 3,329	$ 6,306

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator
Net loss	$ (12,364)	$ (21,103)	$ (25,341)	$ (30,564)	$ (30,561)	$ (29,861)	$ (58,808)	$ (90,986)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic (in shares)	17,384,243			5,402,592			9,546,129	3,976,438
Weighted average shares outstanding used in computing net loss per share, diluted (in shares)	17,384,243			5,402,592			9,546,129	3,976,438
Net loss per share, basic ( in dollars per share)	$ (0.71)			$ (5.66)			$ (6.16)	$ (22.88)
Net loss per share, diluted (in dollars per share)	$ (0.71)			$ (5.66)			$ (6.16)	$ (22.88)

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding (Details) - shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	974,985	614,465
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	494,947	571,606
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	56,378	6,988
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	423,536	15,065
Conversion option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	0	18,797
Common stock from the ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted weighted-average shares outstanding (in shares)	124	2,009

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	Jul. 31, 2023	May 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Related Party Transaction [Line Items]
Amounts due to related party			$ 737		$ 427
Purchase Agreement
Related Party Transaction [Line Items]
Issuance of common stock shares on reserved for split basis (in shares)		2,712,317
Offering price per share (in dollars per share)	$ 2.31	$ 29.20
Number of shares sold in public offering (in shares)	11,025,334
Purchase Agreement | Other Related Parties
Related Party Transaction [Line Items]
Number of shares sold in public offering (in shares)	7,778,582
Weatherden Advisory Services Agreement
Related Party Transaction [Line Items]
Payment to related party			100	$ 100
Related Party
Related Party Transaction [Line Items]
Amounts due to related party			$ 100	$ 100
Management | Purchase Agreement
Related Party Transaction [Line Items]
Issuance of common stock shares on reserved for split basis (in shares)		19,691
Other Affiliates | Purchase Agreement
Related Party Transaction [Line Items]
Issuance of common stock shares on reserved for split basis (in shares)		1,412,671

Workforce Reduction (Details)

Workforce Reduction (Details) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2023 employee	Sep. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Restructuring Charges [Abstract]
Number of employees reduced | employee	48
Percentage of employees reduced	45%
Restructuring charges | $		$ 0.1	$ 3.1

Subsequent Events (Details)

Subsequent Events (Details) - Second Amendment Of Loan Agreement - Secured Debt - Subsequent Event $ in Millions	Oct. 26, 2023 USD ($)
Subsequent Event [Line Items]
Repayments of debt	$ 11
Debt covenant, prepayment portion as percentage of net proceeds from equity sales, licensing or assets sale	70%