Sigilon Therapeutics (SGTX) 10-K 14 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2022	Mar. 01, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity Registrant Name	Sigilon Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity File Number	001-39746
Entity Tax Identification Number	47-4005543
Entity Address, Address Line One	100 Binney Street, Suite 600
Entity Address, City or Town	Cambridge
Entity Address State Or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	336-7540
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	SGTX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 18,238,725
Entity Common Stock, Shares Outstanding		32,466,737
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	238
Auditor Location	Boston, Massachusetts
Entity Central Index Key	0001821323
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 42,066	$ 107,143
Marketable securities	27,560	16,213
Accounts receivable	2,171	59
Unbilled accounts receivable	1,287
Prepaid expenses and other current assets	1,077	2,729
Restricted cash-current	250	250
Total current assets	74,411	126,394
Property and equipment, net	2,854	3,994
Right-of-use assets	8,979	12,863
Restricted cash	1,034	1,118
Total assets	87,278	144,369
Current liabilities:
Accounts payable	936	2,344
Accrued expenses and other current liabilities	6,021	8,998
Lease liabilities, current portion	4,485	4,845
Current portion of long-term debt	6,667	1,667
Deferred revenue from related party, current portion	12,885	17,034
Total current liabilities	30,994	34,888
Deferred revenue from related party, net of current portion		5,333
Lease liability, net of current portion	4,888	8,577
Long-term debt, net of discount and current portion	12,021	18,411
Other liabilities	233
Total liabilities	48,136	67,209
Commitments and contingencies (Note 12)
Stockholders' equity
Common stock, par value $0.001 per share; 175,000,000 shares authorized at December 31, 2022 and December 31, 2021; 32,466,737 and 32,359,895 shares issued and outstanding at December 31, 2022 and December 31, 2021, respectively	32	32
Preferred stock, par value $0.001 per share; 25,000,000 shares authorized at December 31, 2022 and December 31, 2021; no shares issued and outstanding at December 31, 2022 and December 31, 2021
Additional paid-in capital	296,339	290,377
Accumulated other comprehensive loss	(429)	(10)
Accumulated deficit	(256,800)	(213,239)
Total stockholders' equity	39,142	77,160
Total liabilities and stockholders' equity	$ 87,278	$ 144,369

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Consolidated Balance Sheets
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	175,000,000	175,000,000
Common stock, shares issued (in shares)	32,466,737	32,359,895
Common stock, shares outstanding (in shares)	32,466,737	32,359,895
Preferred Stock par value (in dollars per share)	$ 0.001	$ 0.001
Preferred Stock, Shares Authorized	25,000,000	25,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Revenue
Collaboration revenue	$ 12,944	$ 9,599
Operating expenses:
Research and development	37,631	65,069
General and administrative	18,979	20,166
Total operating expenses	56,610	85,235
Loss from operations	(43,666)	(75,636)
Other income (expense), net:
Interest income	946	258
Interest expense	(2,290)	(1,988)
Other income, net	1,449	55
Total other income (expense), net	105	(1,675)
Net loss attributable to ordinary shareholders	$ (43,561)	$ (77,311)
Net loss per share attributable to common stockholders-basic (in dollars per share)	$ (1.34)	$ (2.43)
Net loss per share attributable to common stockholders-diluted (in dollars per share)	$ (1.34)	$ (2.43)
Weighted average common stock outstanding-basic (in shares)	32,405,786	31,860,264
Weighted average common stock outstanding-diluted (in shares)	32,405,786	31,860,264
Other comprehensive loss
Unrealized loss on marketable debt securities	$ (419)	$ (10)
Total other comprehensive loss	(419)	(10)
Total comprehensive loss	$ (43,980)	$ (77,321)

Consolidated Statements of Stoc

Consolidated Statements of Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2020	$ 31	$ 282,053		$ (135,928)	$ 146,156
Beginning balance (in shares) at Dec. 31, 2020	31,464,989
Issuance of common stock upon exercise of stock options	$ 1	2,094			2,095
Issuance of common stock upon exercise of stock options (in shares)	878,015
Issuance of ESPP shares		81			81
Issuance of ESPP shares (in shares)	16,891
Stock-based compensation expense		6,149			6,149
Unrealized loss on marketable debt securities			$ (10)		(10)
Net loss				(77,311)	(77,311)
Ending balance at Dec. 31, 2021	$ 32	290,377	(10)	(213,239)	77,160
Ending balance (in shares) at Dec. 31, 2021	32,359,895
Issuance of common stock upon exercise of stock options		1			$ 1
Issuance of common stock upon exercise of stock options (in shares)	833				833
Issuance of common stock upon vesting of restricted stock units	37,960
Issuance of ESPP shares		60			$ 60
Issuance of ESPP shares (in shares)	68,049
Stock-based compensation expense		5,901			5,901
Unrealized loss on marketable debt securities			(419)		(419)
Net loss				(43,561)	(43,561)
Ending balance at Dec. 31, 2022	$ 32	$ 296,339	$ (429)	$ (256,800)	$ 39,142
Ending balance (in shares) at Dec. 31, 2022	32,466,737

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (43,561)	$ (77,311)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization expense	1,264	1,118
Gain on disposal of fixed assets	(48)
Stock-based compensation expense	5,901	6,149
Non-cash lease expense	3,952	4,785
Non-cash interest expense	277	271
Amortization of premium on marketable securities	8	3
Changes in operating assets and liabilities:
Accounts receivable	(2,112)	118
Unbilled accounts receivable	(1,287)
Prepaid expenses and other current assets	1,652	(1,000)
Accounts payable	(1,236)	713
Accrued expenses and other current liabilities	(2,918)	908
Other liabilities	233
Lease liabilities	(4,117)	(4,749)
Deferred revenue	(9,482)	(9,410)
Net cash used in operating activities	(51,474)	(78,405)
Cash flows from investing activities:
Purchases of marketable securities	(42,524)	(16,226)
Proceeds from maturities of marketable securities	30,750
Purchase of property and equipment	(537)	(1,834)
Proceed from the sale of fixed assets	230
Net cash used in investing activities	(12,081)	(18,060)
Cash flows from financing activities:
Payments of deferred offering costs		(622)
Repayment of debt	(1,667)
Proceeds from the exercise of common stock options and employee equity plans	61	2,176
Net cash (used in) provided by financing activities	(1,606)	1,554
Net decrease in cash, cash equivalents and restricted cash	(65,161)	(94,911)
Cash, cash equivalents and restricted cash at beginning of period	108,511	203,422
Cash, cash equivalents and restricted cash at end of period	43,350	108,511
Supplemental disclosure of cash flow information:
Cash paid for interest	2,004	1,710
Supplemental disclosures of noncash investing and financing activities:
Right-of-use assets obtained in exchange for lease liabilities	68	917
Purchases of property and equipment included in accounts payable and accrued expenses	$ 91	$ 322

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2022
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Sigilon Therapeutics, Inc. (the “Company” or “Sigilon”) is a preclinical stage biotechnology company pioneering a new class of therapeutics and seeking to develop functional cures for patients with acute and chronic diseases by providing stable and durable levels of therapeutic molecules to patients. The Company was incorporated on May 14, 2015 under the laws of the State of Delaware. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, the successful completion of research and development, development by competitors of new technological innovations, dependence on key personnel, protection of technology, compliance with government regulations, and the ability to secure additional capital to fund operations and commercial success of its product candidates. The Company is also subject to additional risks and uncertainties related to the ongoing COVID-19 pandemic and other macroeconomic and geopolitical events, which collectively have caused and may continue to cause major disruptions to businesses and economies worldwide. Since its inception, the Company has devoted substantially all of its efforts to raising capital, obtaining financing, and incurring research and development costs related to advancing its biomedical platform. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. Basis of Presentation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary Sigilon Securities Corporation. All intercompany balances and transactions have been eliminated. The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). Going Concern The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. From its inception through December 31, 2022, the Company has funded its operations primarily with proceeds from its IPO, sales of convertible preferred stock, payments received under its collaboration agreement and proceeds from borrowings under loan and security agreements. The Company has incurred recurring losses since inception, including net losses of $43.6 million and $77.3 million for the years ended December 31, 2022 and 2021, respectively. In addition, as of December 31, 2022, the Company had an accumulated deficit of $256.8 million. The Company expects to generate significant losses and negative cash flows from operations for the foreseeable future. Based on its current operating plans, the Company believes its cash, cash equivalents and marketable securities of $69.6 million as of December 31, 2022 will be sufficient to fund its anticipated level of operations, capital expenditures and satisfy debt repayments for a period of at least 12 months from the issuance date of this Annual Report. The Company expects to generate operating losses for the foreseeable future. Accordingly, the Company will seek additional funding through equity financings, debt financing, or additional collaboration agreements. If the Company is unable to raise additional funds through equity financing, debt financings or additional collaboration agreements the Company may be required to delay, limit, reduce or terminate product development or future commercialization efforts or grant rights to develop and market products or product candidates that the Company would otherwise prefer to develop and market itself.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the period. Estimates and assumptions reflected in these financial statements include, but are not limited to, revenue recognition, research and development expenses and stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions. Concentration of Credit Risk and of Significant Suppliers The financial instruments that potentially subject the Company to concentrations of credit risk are cash, cash equivalents, marketable securities, and accounts receivable. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. As of December 31, 2022, 100% of the Company’s accounts receivable related to one customer and as of December 31, 2021, the Company’s accounts receivable were related to two customers. As of December 31, 2022 and 2021, 100% and 39%, respectively, of the Company’s account receivables were related to the Company’s collaboration agreements with Eli Lilly and Company (Note 9). The Company is dependent on third-party manufacturers to supply certain products for research and development activities in its programs. The Company currently has a supplier of certain raw materials that would be considered a sole supplier. If the Company cannot access additional suppliers or secure sufficient inventory of these raw materials, its programs could be adversely affected by an interruption in the availability of these raw materials. Restricted Cash In connection with the Company’s corporate headquarters and lab space lease agreement entered into in March 2018, the Company is required to maintain a letter of credit of $0.6 million for the benefit of the landlord. On October 16, 2020 the Company took over the lease of office and laboratory space adjacent to its current headquarters, which expires in February 2025. Under the terms of the lease, the Company is required to maintain a letter of credit of $0.5 million. The Company has classified the certificate of deposits collateralizing the letter of credits issued as a security deposit in connection with the Company’s leases of its corporate facility as long-term restricted cash on its balance sheet at December 31, 2022 and 2021. At December 31, 2022 and 2021 the Company classified $0.3 million related to securing the use of corporate credit cards as short-term restricted cash. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset, as follows: ​ ​ ​ ​ ​ Estimated useful life Laboratory equipment ​ 5 Years Leasehold improvements ​ Shorter of the lease term or 10 years Furniture and fixtures ​ 7 Years Computers and software ​ 3 Years ​ Maintenance and repairs are charged to expense as incurred. Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are removed from the accounts and any resulting gains or losses are included in the statement of operations and comprehensive loss in the period of disposal. Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss to be recognized would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. The Company did not recognize any impairment losses on long-lived assets during the years ended December 31, 2022 and 2021. Leases The Company follows the provisions of ASC Topic 842, Leases Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the remaining lease term. The present value of future lease payments are discounted using the interest rate implicit in lease contracts if that rate is readily determinable; otherwise the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis over a similar term, the amount of the lease payments in a similar economic environment. After lease commencement and the establishment of a right-to-use asset and operating lease liability, lease expense is recorded on a straight-line basis over the lease term. The Company enters into contracts that contain both lease and non-lease components. Non-lease components include costs that do not provide a right-to-use a leased asset but instead provide a service, such as maintenance costs. The Company has elected to account for the lease and non-lease components together as a single component for all classes of underlying assets. Variable costs associated with the lease, such as maintenance and utilities, are not included in the measurement of right-to-use assets and lease liabilities but rather are expensed when the events determining the amount of variable consideration to be paid have occurred. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ​ ​ Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. ​ The carrying values of the Company’s accounts receivable, and accounts payable and accrued expenses and other current liabilities approximate their fair value due to the short-term nature of these assets and liabilities. The carrying value of the Company’s long-term debt approximates its fair value at December 31, 2022 because the debt bears interest at a variable market rate and the Company’s credit risk has not materially changed since the inception of the agreement. The Company’s financial instruments consist primarily of cash, cash equivalents and marketable securities (Note 3). Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is developing therapeutic treatments for a wide range of chronic diseases. The Company has determined that its chief operating decision maker is its Chief Executive Officer. The Company’s chief operating decision maker reviews the Company’s financial information on an aggregated basis for purposes of allocating resources and assessing financial performance. All the Company’s tangible assets are located in the United States and all of the Company’s collaboration revenue is derived from its collaboration partners headquartered in the United States. Cash and cash equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of acquisition to be cash equivalents. Marketable securities Marketable securities consist of investments with original maturities greater than ninety days. The Company has classified its investments with maturities beyond one year as short term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. The Company considers its investment portfolio of investments as available-for-sale. Accordingly, these investments are recorded at fair value, which is based on quoted market prices. Unrealized gains and losses are reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses and declines in value judged to be other than temporary are included as a component of other income (expense), net based on the specific identification method. When determining whether a decline in value is other than temporary, the Company considers various factors, including whether the Company has the intent to sell the security, and whether it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis. Fair value is determined based on quoted market prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. Revenue Recognition for License and Collaboration Agreements The Company follows the provisions of ASC Topic 606, Revenue from Contracts with Customers Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The Company enters into licensing arrangements that are within the scope of ASC 606, under which it may exclusively license to third parties’ rights to develop, manufacture and commercialize its product candidates. The terms of these arrangements typically include payment to the Company of one or more of the following: nonrefundable, upfront license fees; reimbursement of research and development costs; development, regulatory and sales milestone payments; and royalties on net sales of licensed products. For costs that were not paid upfront, the payment terms under the Company’s existing licensing arrangements are generally 45 days. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its arrangements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the assessment of the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations, and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. As part of the accounting for arrangements under ASC 606, the Company must use significant judgment to determine: a) the performance obligations based on the determination under step (ii) above; b) the transaction price under step (iii) above; and c) the standalone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above. The Company also uses judgment to determine whether milestones or other variable consideration, except for royalties and sales-based milestones, should be included in the transaction price as described below. The transaction price is allocated to each performance obligation based on the relative stand-alone selling price of each performance obligation in the contract, and the Company recognizes revenue based on those amounts when, or as, the performance obligations under the contract are satisfied. The standalone selling price is the price at which an entity would sell a promised good or service separately to a customer. Management estimates the standalone selling price of each of the identified performance obligations in the Company’s customer contracts, maximizing the use of observable inputs. Because the Company has not sold the same goods or services in its contracts separately to any customers on a standalone basis and there are no similar observable transactions in the marketplace, the Company estimates the standalone selling price of each performance obligation in its customer arrangements based on its estimate of costs to be incurred to fulfil its obligations associated with the performance, plus a reasonable margin. The Company has determined that its only contract liability under ASC 606 is deferred revenue. Amounts received prior to revenue recognition are recorded as deferred revenue in the balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as the current portion of deferred revenue in the balance sheets. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion in the balance sheets. Amounts are recorded as accounts receivable and unbilled accounts receivable when the Company’s right to consideration is unconditional. Exclusive Licenses If the license granted in the arrangement is determined to be distinct from the other promises or performance obligations identified in the arrangement, which generally include research and development services, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a license is distinct from the other promises, the Company considers relevant facts and circumstances of each arrangement, including the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promises, whether the value of the license is dependent on the unsatisfied promises, whether there are other vendors that could provide the remaining promises, and whether it is separately identifiable from the remaining promises. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and the resulting periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the arrangement. Such a change could have a material impact on the amount of revenue the Company records in future periods. Under the Company’s existing license and collaboration agreement, the Company has concluded the research and development services and the license, among other promises are a combined performance obligation (Note 9) and that the transfer of control to the customer occurs over the time period that the research and development services are to be provided by the Company, and this cost-to-cost method is, in management’s judgement, the best measure of progress towards satisfying the performance obligation. Research and Development Services The promises under the Company’s collaboration and license agreements generally include research and development services to be performed by the Company on behalf of the collaboration partner. Payments or reimbursements resulting from the Company’s research and development efforts are estimated at the outset of the arrangement and considered part of the transaction price that is subsequently recognized as revenue because the Company is the principal in the arrangement for such efforts. Customer Options The Company’s arrangements may provide a customer with the right to certain optional purchases, such as the right to license a target either at the inception of the arrangement or within a predefined option period. Under these agreements, fees may be due to the Company at the inception of the arrangement as an upfront fee or payment or upon the exercise of an option to acquire a license. If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the Company evaluates the customer options to determine if they are material rights at the outset of each arrangement. If the goods and services underlying the customer options are not determined to be material rights, these customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon exercise of the option. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative stand-alone selling price, which is determined based on the identified discount, and the probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised or expires. Milestone Payments At the inception of each arrangement that includes research, development or regulatory milestone payments, we evaluate whether the milestones are considered likely to be met and estimate the amount to be considered for inclusion in the transaction price using the most-likely-amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. For milestone payments due upon events that are not within the control of us or the licensee, such as regulatory approvals, we are not able to assert that it is likely that the regulatory approval will be granted and that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur until those approvals are received. In making this assessment, we evaluate factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period we reevaluate the probability of achievement of all milestones subject to constraint and, if necessary, adjust our estimate of the overall transaction price of the arrangement. Any such adjustments are recorded on a cumulative catch-up basis, which would affect the amount of revenue and earnings in the period of adjustment. As of December 31, 2022 and 2021, no milestones under the 2018 Lilly Agreement (Note 9) were included in the transaction price as no milestones had been deemed likely to be achieved or had been achieved. Royalties For arrangements that include sales-based royalties, including milestone payments based on a level of sales, that are the result of a customer-vendor relationship and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied. To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including costs for salaries and bonuses, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered, or the services rendered. Upfront payments under license agreements are expensed as research and development expense upon receipt of the license, and annual maintenance fees under license agreements are expensed in the period in which they are incurred. Milestone payments under license agreements are accrued, with a corresponding expense being recognized, in the period in which the milestone is determined to be probable of achievement and the related amount is reasonably estimable. Research, Development and Manufacturing Contract Costs and Accruals The Company has entered into various research, development and manufacturing contracts with research institutions and other companies. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research, development and manufacturing costs. When billing terms under these contracts do not coincide with the timing of when the work is performed, the Company is required to make estimates of outstanding obligations to those third parties as of period end. Any accrual estimates are based on a number of factors, including the Company’s knowledge of the progress towards completion of the research, development and manufacturing activities, invoicing to date under the contracts, communication from the research institutions and other companies of any actual costs incurred during the period that have not yet been invoiced and the costs included in the contracts. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the estimates made by the Company. The historical accrual estimates made by the Company have not been materially different from the actual costs. Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. Stock-Based Compensation We measure stock-based awards granted to employees, non-employees and directors based on the fair value on the date of the grant and recognize compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. Forfeitures are accounted for as they occur. Generally, we issue stock-based awards in the form of stock options and restricted stock units with only service-based vesting conditions and record the expense for these awards using the straight-line method. We have also issued stock-based awards with performance-based vesting conditions for which the expense is recognized when achievement of such performance conditions becomes probable. The fair value of each share option is estimated on the date of grant using the Black-Scholes option pricing model. Until the completion of our initial public offering in December 2020, we had been a private company and lacked company-specific historical and implied volatility information for our shares. Therefore, we estimate our expected share price volatility based on the historical volatility of publicly traded peer companies and expect to continue to do so until such time as we have adequate historical data regarding the volatility of our own traded share price. The expected term of our share options has been determined utilizing the “simplified method” for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that we have never paid cash dividends on our ordinary shares and do not expect to pay any cash dividends in the future. The Company classifies stock-based compensation expense in its statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Comprehensive Loss Comprehensive loss is composed of net loss and other comprehensive loss. Other comprehensive loss consists of unrealized losses on marketable securities. Net Income (Loss) per Share The Company only has one class of shares outstanding and basic net income (loss) per common share is computed by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) per common share is computed by dividing net income (loss) by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock awards. For periods in which the Company reports a net loss, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements Financial Instruments-Overall In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2022
Fair Value Measurements and marketable securities
Fair Value Measurements and marketable securities	3. Fair Value Measurements Value Measurements The following tables present information about the Company’s financial assets that have been measured at fair value as of December 31, 2022 and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted market prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. During the years ended December 31, 2022 and 2021, there were no transfers between Level 1, Level 2 and Level 3. The following table summarizes the Company’s cash equivalents and marketable securities as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Cash equivalents ​ ​ ​ ​ Money market funds ​ $ 29,310 ​ $ — ​ $ — ​ $ 29,310 Commercial paper ​ ​ — ​ ​ 1,994 ​ ​ — ​ ​ 1,994 U.S. Treasuries ​ ​ — ​ ​ 4,999 ​ ​ — ​ ​ 4,999 Total cash equivalents ​ ​ 29,310 ​ ​ 6,993 ​ ​ — ​ ​ 36,303 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ ​ — ​ ​ 21,594 ​ ​ — ​ ​ 21,594 Commercial paper ​ ​ — ​ ​ 1,738 ​ ​ — ​ ​ 1,738 U.S. Government Agencies ​ ​ — ​ ​ 1,235 ​ ​ — ​ ​ 1,235 U.S. Treasuries ​ ​ — ​ ​ 2,993 ​ ​ — ​ ​ 2,993 Total marketable securities ​ ​ — ​ ​ 27,560 ​ ​ — ​ ​ 27,560 Total ​ $ 29,310 ​ $ 34,553 ​ $ — ​ $ 63,863 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2021 ​ Level 1 Level 2 Level 3 Total Cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 50,847 ​ $ — ​ $ — ​ $ 50,847 Commercial paper ​ ​ — ​ ​ 25,995 ​ ​ — ​ ​ 25,995 Corporate bonds ​ ​ — ​ ​ 1,000 ​ ​ — ​ ​ 1,000 Total cash equivalents ​ ​ 50,847 ​ ​ 26,995 ​ ​ — ​ ​ 77,842 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ ​ — ​ ​ 10,238 ​ ​ — ​ ​ 10,238 Commercial paper ​ — ​ ​ 5,975 ​ ​ — ​ ​ 5,975 Total marketable securities ​ ​ — ​ ​ 16,213 ​ ​ — ​ ​ 16,213 Total ​ $ 50,847 ​ $ 43,208 ​ $ — ​ $ 94,055 ​ ​ Marketable Securities The following tables summarizes the Company’s available-for-sale marketable debt securities as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2022 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Credit ​ ​ ​ ​ Cost Gains Losses Losses Total Corporate bonds ​ $ 21,994 ​ $ — ​ $ (400) ​ $ — ​ $ 21,594 Commercial paper ​ ​ 1,743 ​ ​ — ​ ​ (5) ​ ​ — ​ ​ 1,738 U.S. Treasuries ​ ​ 1,248 ​ ​ — ​ ​ (13) ​ ​ — ​ ​ 1,235 U.S. Government Agencies ​ ​ 2,999 ​ ​ — ​ ​ (6) ​ ​ — ​ ​ 2,993 Total ​ $ 27,984 ​ $ — ​ $ (424) ​ $ — ​ $ 27,560 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2021 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ ​ Cost Gains Losses Total Commercial paper ​ $ 10,244 ​ $ — ​ $ (6) ​ $ 10,238 Corporate bonds ​ ​ 5,977 ​ ​ — ​ ​ (2) ​ ​ 5,975 Total ​ $ 16,221 ​ $ — ​ $ (8) ​ $ 16,213 ​ The unrealized losses at December 31, 2022 were attributed to changes in interest rates and unrealized losses do not represent credit losses. No declines in value were deemed to be other than temporary as of December 31, 2021. The following table summarizes the Company’s available-for-sale marketable debt securities by contractual maturity, as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 ​ 2021 Maturities in one year or less ​ $ 23,231 ​ $ 9,004 Maturities between one and two years ​ 4,329 ​ 7,209 Total ​ $ 27,560 ​ $ 16,213 ​

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2022
Property and Equipment, Net
Property and Equipment, Net	4. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 ​ 2021 Laboratory equipment ​ $ 6,301 ​ $ 6,297 Leasehold improvements ​ 78 ​ 78 Furniture and fixtures ​ 620 ​ 620 Computers and software ​ 177 ​ 163 ​ ​ 7,176 ​ 7,158 Less: Accumulated depreciation and amortization ​ (4,322) ​ (3,164) Total property and equipment, net ​ $ 2,854 ​ $ 3,994 ​ Depreciation and amortization expense for the years ended December 31, 2022 and 2021 was $1.3 million, and $1.1 million, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2022
Accrued Expenses and Other Current Liabilities
Accrued Expenses and Other Current Liabilities	5. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Employee compensation and benefits ​ $ 4,243 ​ $ 3,071 External research and development costs ​ 817 ​ 5,056 Legal and professional fees ​ 714 ​ 656 Other ​ 247 ​ 215 Total accrued expenses and other current liabilities ​ $ 6,021 ​ $ 8,998 ​

Debt

Debt	12 Months Ended
	Dec. 31, 2022
Debt
Debt	6. Debt As of December 31, 2022 and 2021, long-term debt consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 ​ 2021 Principal amount of long‑term debt ​ $ 18,333 ​ $ 20,000 Less: Current portion of long‑term debt ​ ​ (6,667) ​ (1,667) Long‑term debt, net of current portion ​ 11,666 ​ 18,333 Final debt payment liability ​ ​ 700 ​ ​ 700 Debt discount, net of accretion ​ (345) ​ (622) Long‑term debt, net of discount and current portion ​ $ 12,021 ​ $ 18,411 ​ In September 2020, the Company entered into a loan and security agreement (the “2020 Credit Facility”), with Oxford Finance LLC (“Oxford”). Effective as of September 2020, the Company paid off in full its borrowings under our prior debt facility using part of the proceeds from the 2020 Credit Facility and accounted for this as a debt extinguishment. The 2020 Credit Facility initially provided for borrowings of up to $20.0 million under one term loan (“Term A Loan”), as well as additional borrowings of up to an aggregate maximum of $5.0 million, under one additional term loan (“Term B Loan”) (collectively the “Term Loans”). Under the 2020 Credit Facility, the Company borrowed $20.0 million in September 2020. The Company did not elect to borrow the additional $5.0 million under the Term B Loan and the option to borrow under the Term B Loan has expired. Borrowings under the 2020 Credit Facility bear interest at an annual rate equal to greater of 8.40% and the sum of the thirty day U.S. Dollar LIBOR rate report in the Wall Street Journal Borrowings under the 2020 Credit Facility are collateralized by substantially all of the Company’s personal property, other than its intellectual property. The Company is subject to certain affirmative and negative covenants restricting the Company’s activities, including limitations on dispositions, mergers or acquisitions; encumbering its intellectual property; incurring indebtedness or liens; paying dividends; making certain investments; and engaging in certain other business transactions. In addition, the Company is required, on an annual basis, to deliver to Oxford annual audited financial statements with an audit opinion from its independent registered public accounting firm. The obligations under the 2020 Credit Facility are subject to acceleration upon the occurrence of specified events of default, including a material adverse change in the Company’s business, operations or financial or other condition. As of December 31, 2022 and 2021, the interest rate applicable to borrowings under the 2020 Credit Facility was 12.4% and 8.40%, respectively, and the weighted average effective interest rate on outstanding borrowings was approximately 13.8% and 9.80%, respectively. The estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2023 ​ $ 6,666 2024 ​ 6,667 2025 ​ ​ 5,000 2026 ​ ​ — 2027 ​ ​ — ​ ​ $ 18,333 ​ In connection with the 2020 Credit Facility, the Company issued to Oxford warrants to purchase up to 50,000 shares of Series B, convertible preferred stock, at an exercise price of $6.00 per share, which were immediately exercisable upon issuance. Following the issuance of the Series B-1 convertible preferred stock, the Series B warrants converted into Series B-1 warrants. Further, in conjunction with the completion of the IPO all warrants converted into warrants to acquire common stock. Following the Company’s reverse stock split and the IPO there were 19,044 warrants to purchase Common Stock at an exercise price of $15.75. As of December 31, 2022 and 2021, 19,044 warrants to purchase Common Stock were outstanding and were classified as equity.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2022
Common Stock.
Common Stock	7. Common Stock As of December 31, 2022 and 2021, the Company’s Certificate of Incorporation, as amended and restated at such time, authorized the Company to issue 175,000,000 shares, of $0.001 par value common stock. Under the Company’s certificate of incorporation, each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any, subject to the preferential dividend rights of the Preferred Stock. As of December 31, 2022 and 2021, no dividends had been declared. At-the-Market Offering On April 14, 2022, the Company entered into an Equity Distribution Agreement with Canaccord Genuity LLC, or Canaccord, pursuant to which the Company may issue and sell shares of common stock, from time to time, having an aggregate offering price of up to $10.0 million. Sales of common stock through Canaccord may be made by any method that is deemed an “at the market” offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended. The Company is not obligated to make any sales of its common stock under the Equity Distribution Agreement. Any sales under the Equity Distribution Agreement will be made pursuant to the registration statement on Form S-3 (File No 333- 264296)

Stock Based Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2022
Stock Based Compensation
Stock Based Compensation	8. Stock Based Compensation Summary of Plans In November 2020 the Company adopted the 2020 Incentive Plan (the “2020 Plan”) and the 2020 Employee Stock Purchase Plan (the “2020 ESPP”). In 2016, the Company adopted the 2016 Equity Incentive Plan (the “2016 Plan”). These plans are administered by the Board of Directors or, at the discretion of the Board of Directors, by a committee of the Board of Directors. 2020 Incentive Plan The 2020 Plan provides for the grant of stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, performance-share awards, cash-based awards and dividend equivalent rights to employees, members of the board of directors and consultants of the Company. The number of shares initially reserved for issuance under the 2020 Plan was 1,500,000 shares of common stock. The number of shares reserved for issuance may be increased by the number of shares under the previously authorized 2016 Stock Option Plan that are not needed to fulfill the Company’s obligations for awards issued under the 2016 Stock Option Plan as a result of forfeiture, expiration, cancellation, termination or net issuances of awards thereunder. The number of shares of common stock that may be issued under the 2020 Plan is also subject to increase on the first day of each fiscal year by the lesser of (i) four percent of the Company’s outstanding shares of common stock as of that date, or (ii) an amount determined by the board of directors. As of December 31, 2022, 1,850,378 shares were available for grant under the 2020 Plan. The terms of stock awards agreements, including type of stock award to be granted, the provisions of each stock award, including the number of shares, vesting requirements and exercise prices, are determined by the board of directors and are subject to the provisions of the Plan. Option awards generally vest over a four-year period and expire after ten years. Certain options provide for accelerated vesting in the event of a change in control, as defined. The exercise price per share for stock options granted may not be less than the fair market value of the common stock at the date of grant. 2020 Employee Stock Purchase Plan The 2020 ESPP provides participating employees with the opportunity to purchase shares of the Company’s common stock at defined purchase prices over six-month offering periods. A total of 300,000 shares of common stock were initially reserved for issuance under this plan. The number of shares of common stock that may be issued under the 2020 ESPP will automatically increase on the first day of each calendar year, beginning on January 1, 2021 and ending on and including January 1, 2030, equal to the lesser of (i) 1% of the shares of common stock outstanding on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as determined by the board of directors, provided that not more than 3,200,000 shares of common stock may be issued under the 2020 ESPP. As of December 31, 2022, 853,307 shares were available for grant under the 2020 Plan. For the years ended December 31, 2022 and 2021, 68,049 and 16,891 shares of common stock were issued under the 2020 ESPP, respectively. 2016 Equity Incentive Plan The 2016 Plan provided for the Company to grant incentive stock options and nonqualified stock options or other awards including restricted stock awards, unrestricted stock awards, and restricted stock units to the Company’s employees, officers, directors, advisors, and consultants of the Company. No additional shares are to be granted under the 2016 Plan. Shares that are expired, terminated, surrendered, or canceled without having been fully exercised will be available for future awards under the 2020 Plan. The terms of stock awards agreements, including type of stock award to be granted, the provisions of each stock award, including the number of shares, vesting requirements and exercise prices, were determined by the board of directors and are subject to the provisions of the Plan. Option awards generally vest over a four-year period and expire after ten years. Certain options provide for accelerated vesting in the event of a change in control, as defined. The exercise price per share for stock options granted may not be less than the fair market value of the common stock at the date of grant. Stock Option Valuation The fair value of each option is estimated on the date of grant using the Black-Scholes option-pricing model. The Company was a private company prior to the initial public offering and lacked company-specific historical and implied volatility information for its stock. Therefore, it estimates its expected stock price volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield of 0% is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future. The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees and directors: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ ​ 2022 ​ 2021 Risk-free interest rate ​ 1.75 % 0.80 % Expected dividend yield ​ 0.00 % 0.00 % Expected term (in years) ​ 6.0 ​ 6.1 ​ Expected volatility ​ 84.28 % 78.31 % ​ Stock Option Activity The following table summarizes the Company’s stock option activity since December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ ​ ​ ​ ​ ​ ​ Weighted ​ remaining ​ Aggregate ​ ​ Number of ​ average ​ contractual term ​ intrinsic value ​ ​ options ​ exercise price ​ (in years) ​ (in thousands) Balances at December 31, 2021 3,138,646 ​ $ 10.74 ​ 7.6 ​ $ 328 Options granted 2,564,140 ​ 2.23 ​ ​ ​ ​ Options cancelled (789,567) ​ 8.64 ​ ​ ​ ​ Options exercised (833) ​ 0.57 ​ ​ ​ ​ ​ Outstanding and expected to vest at December 31, 2022 ​ 4,912,386 ​ ​ 6.63 ​ 7.8 ​ ​ — Exercisable at December 31, 2022 2,045,196 ​ $ 7.81 6.1 ​ $ — ​ The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised during the twelve months ended December 31, 2022 and 2021 were less than $0.1 million and $6.0 million, respectively. The weighted average grant date fair value of stock options during the years ended December 31, 2022 and 2021 was $1.58 and $19.00, respectively. Restricted Stock Units The Company has granted restricted stock units with time-based vesting conditions to employees. The restricted stock units primarily vest over 3 years from the grant date. The Company values restricted stock units on the grant-date using the market price of the Company’s common stock. The following table summarizes restricted stock unit activity since December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ average grant ​ ​ Shares ​ date fair value Unvested shares as of December 31, 2021 275,400 ​ $ 5.57 Vested ​ (37,960) ​ ​ 5.55 Forfeited (87,040) ​ 5.62 Unvested shares as of December 31, 2022 ​ 150,400 ​ $ 5.54 ​ Stock-based Compensation Expense Stock-based compensation expense related to stock options and restricted stock units was classified in the statement of operations and comprehensive loss as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Research and development ​ $ 1,883 ​ $ 2,230 General and administrative ​ 4,018 ​ 3,920 ​ ​ $ 5,901 ​ $ 6,150 ​ As of December 31, 2022, total unrecognized stock-based compensation expense related to unvested stock-based awards was $10.4 million, which is expected to be recognized over a weighted average period of 2.0 years.

License and Collaboration Agree

License and Collaboration Agreement	12 Months Ended
	Dec. 31, 2022
License and Collaboration Agreement
License and Collaboration Agreement	9. License and Collaboration Agreement Lilly License and Collaboration Agreement On April 2, 2018, the Company entered into a License and Collaboration Agreement with Lilly (the “2018 Lilly Agreement”). Under the 2018 Lilly Agreement, the Company granted Lilly an exclusive worldwide, royalty-bearing license, including the right to grant sublicenses, to the Company’s encapsulation technology applied to islet cells. The Company is responsible for research and development activities, including supply and manufacturing activities, through investigational new drug (“IND”) filing readiness for the first product candidate, including costs up to $47.5 million and certain supply and manufacturing of products and materials in Phase 1 clinical trials and for clinical and commercial use following Phase 1 clinical trials. Lilly will be responsible for development and commercialization of any licensed product post-IND filing readiness and research and development costs for the IND product candidate above the $47.5 million cost threshold. Lilly is also responsible for all research, development and commercialization related to any subsequent product candidate. The parties are collaborating with the intent of developing encapsulated cell therapies for the potential treatment of type 1 diabetes. The activities under the agreement are governed by a joint research committee (“JRC”), which meets quarterly and consists of at least three members each from the Company and Lilly. Under the 2018 Lilly Agreement, Lilly was obligated to pay the Company a one-time, non-refundable and non-creditable license issuance fee of $62.5 million. Lilly is also obligated to make aggregate milestone payments to the Company of up to $165.0 million upon achievement of certain regulatory milestones for the first licensed product and regulatory milestones up to $160.0 million for additional licensed products. Lilly is also obligated to pay the company sales-based milestones of up to $250.0 million for each licensed product and tiered (from mid-single-to-low-double digit) sales-based royalties for each licensed product. The 2018 Lilly Agreement will expire upon the expiration of the last royalty term, on a product-by-product and country-for country basis. The royalty term, by product and country, commences upon the first commercial sale and ends upon the later to occur of (i) the expiration of the Company’s patent rights of a product candidate developed under the Lilly Agreement, (ii) the expiration of any data exclusivity period in a country or (iii) 10 years after the first commercial sale. The Company will have the right, and the obligation, to supply Lilly’s requirements for the material to be used in the manufacture of licensed products for clinical and commercial use. In connection with the supply responsibilities, the parties may enter into supply and quality agreements for both clinical and commercial supply. The Company evaluated the 2018 Lilly Agreement under ASC 606 as the transactions underlying the agreement were considered transactions with a customer. The Company identified the following material promises under the arrangement: (i) exclusive license to research, develop, manufacture and commercialize licensed products, (ii) initial technology transfer, (iii) research activities (including pre-IND supply), (iv) cell line development and supply, (v) product trademark election, (vi) requirement to supply Lilly with the licensed product related to Phase 1 clinical trial (“Phase 1 Supply”) and (vii) participation in the JRC. The Company determined that the exclusive license to research, develop, manufacture and commercialize the licensed product was not distinct from the related research and manufacturing activities to be provided by the Company as a result of Lilly being unable to benefit on its own or with other resources reasonably available in the marketplace because the license to the Company’s intellectual property requires significant specialized capabilities in order to be further developed, the research services necessary to develop the product are highly specialized and the Company’s proprietary technology is a key capability of that development. The cell line development and supply and research activities were determined not to be distinct because they are performed in conjunction with the research activities to further develop the underlying technology. The product trademark was determined not to be distinct because the benefit that Lilly receives from the Company’s trademark license only exists when combined with the right to commercialize the licensed product. In addition, the Company determined that the impact of the participation in the JRC was insignificant and had an immaterial impact on the accounting model. Therefore, the Company determined that the first five promises should be combined into a single performance obligation (the “Combined Performance Obligation”). The Company determined the sixth promise, the Phase 1 Supply promise, is distinct in the contract. As this is at no cost to Lilly, the right to receive this supply represents a material right and a distinct performance obligation. As such, the Company determined there were two distinct performance obligations at the outset of the 2018 Lilly Agreement. The Company determined that the $62.5 million upfront payment represents the entirety of the consideration to be included in the transaction price as of the outset of the arrangement. The potential milestone payments that the Company may have been eligible to receive were initially excluded from the transaction price at the outset of the arrangement because (i) all development and regulatory milestone payments did not meet the criteria for inclusion using the most-likely-amount method and (ii) the Company recognizes as revenue sales-based milestones and royalties when the related sales occur. As of December 31, 2022 and 2021 no milestones or royalties have been deemed likely to be achieved or have been achieved. The Company recognizes revenue for the Combined Performance Obligation as the research, development and manufacturing services are provided using an input method, based on the cumulative costs incurred compared to the total estimated costs expected to be incurred to satisfy the Combined Performance Obligation. The transfer of control to the customer occurs over the time period that the research and development services are to be provided by the Company, and this cost-to-cost method is, in management’s judgement, the best measure of progress toward satisfying this performance obligation. The Company allocated $56.6 million of the transaction price to the Combined Performance Obligation at the outset of the arrangement. The Phase 1 Supply was determined to be a material right, and the standalone selling price was estimated using the expected cost-plus margin approach. The Company allocated $5.9 million of the transaction price to the Phase 1 Supply at the outset of the arrangement. The Company has determined that the Phase 1 Supply will be satisfied at a point in time when the customer obtains control of each unit of product. Therefore, the Company will recognize revenue as shipments of the Phase 1 Supply are made to Lilly. The Company reevaluates the transaction price and the total estimated costs expected to be incurred to satisfy the performance obligations at the end of each reporting period and as uncertain events, such as changes to the expected timing and cost of certain research, development and manufacturing activities that the Company is responsible for, are resolved or other changes in circumstances occur, and, if necessary, the Company will adjust its estimate of the transaction price and total estimated costs expected to be incurred. During the year ended December 31, 2022, consistent with the Company’s presentation to the JRC, the Company revised its estimate of total costs to complete the activities under the 2018 Lilly Agreement to reflect the Company’s experiences to date and the impact this has on its expected future research and development activities to satisfy the Combined Performance Obligation. During the year ended December 31, 2022, there has been an increase to the total estimated costs expected to be incurred of $13.5 million verse the estimate as of December 31, 2021. The increase in total estimated costs impacted both the Company’s estimated transaction price for the 2018 Lilly Agreement, as Lilly is obligated to reimburse the Company if the costs exceed $47.5 million to complete the services, and the Company’s input method used to recognize revenue, as this measure compares the Company’s cumulative costs incurred to the Company’s total estimated costs expected to be incurred. During the year ended December 31, 2022, based on the allocation of total transaction price to each performance obligation using the relative stand-alone selling price of each performance obligation under the 2018 Lilly Agreement, the transaction price for the Combined Performance Obligation increased by $12.7 million and the Phase 1 supply performance obligation increased by $1.3 million. During the years ended December 31, 2022 and 2021, the Company recognized $12.9 million and $9.6 million, respectively, of collaboration revenue. As of December 31, 2022 and 2021, the Company recorded as a contract liability deferred revenue of $12.9 million and $22.4 million, respectively, of which, $12.9 million and $17.0 million, respectively, were current liabilities in the accompanying balance sheet. As of both December 31, 2022 and 2021 the research and development services related to the Combined Performance Obligation were expected to be performed over a remaining period of approximately 2.0 years. Contract Liability The changes in the total contract liability (deferred revenue) balances related to the Company’s license and collaboration agreements with Lilly were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Deferred revenues at beginning of period ​ $ 22,367 ​ $ 31,777 Revenues deferred during the period ​ 3,458 ​ — Revenues recognized during the period ​ (12,940) ​ (9,410) Deferred revenues at end of period ​ $ 12,885 ​ $ 22,367 ​ During the years ended December 31, 2022 and 2021, the Company recognized revenue of $12.9 million and $9.4 million, respectively, related to deferred revenue that was recorded as a contract liability at the beginning of each respective year, respectively.

Patent License Agreement

Patent License Agreement	12 Months Ended
	Dec. 31, 2022
Patent License Agreement
Patent License Agreement	10. Patent License Agreement On February 8, 2016, the Company entered into an exclusive patent license agreement with the Massachusetts Institute of Technology (“MIT”) whereby MIT granted an exclusive royalty bearing license to the Company to develop, manufacture and commercialize products covered by certain patent rights owned by MIT The Company also has various rights to grant sublicenses. Under the terms of the agreement, the Company paid an upfront license issuance fee of $0.1 million and is also obligated to pay annual maintenance fees to MIT, all of which are recognized as research and development expense in the statement of operations. All annual minimum payments are fully creditable against royalties subsequently due on net sales of licensed products earned in the same calendar year. The Company also must pay MIT a royalty percentage in the low single digits on all net sales of licensed products and a royalty percentage in the low to mid double digits on any sublicensing revenue. In addition, the Company is obligated to make aggregate milestone payments to MIT of up to $2.1 million upon achievement of specified milestones related to the initiation and execution of clinical trials and first commercial sale of a product. The term of the license agreement will continue until the later of (i) the expiration of the last valid claim within the patent rights covering the product in such country, (ii) the consequence of certain patent challenges or (iii) default. Under terms of the agreement. MIT may terminate the agreement in the event (i) the Company fails to pay any amount due when required to be made and fails to cure such failure within thirty (30) days after receipt of notice from MIT, (ii) is in material breach of its diligence obligations under the agreement and fails to remedy within ninety (90) days after receipt of notice, (iii) is in any other material breach under the agreement and fails to remedy within sixty (60) days after receipt of notice, (iv) declares insolvency or bankruptcy or (v) the Company or a sublicensee brings a patent challenge. The Company may terminate the agreement at any time on written notice to MIT at least ninety (90) days prior to the termination date specified in the notice. Upon expiration or termination of the agreement, all rights revert to MIT.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Taxes
Income Taxes	11. Income Taxes For the years ended December 31, 2022 and 2021, the Company recorded no income tax benefits for the net operating losses incurred or for the research and development tax credits generated in each period in U.S Federal and Massachusetts, due to its uncertainty of realizing a benefit from those items. All the Company’s operating losses since inception have been generated in the United States. A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.0 6.3 Federal and state tax credits 7.3 6.3 Stock‑based compensation (1.0) 0.1 Other (0.1) — Change in deferred tax asset valuation allowance (33.2) (33.7) Effective income tax rate 0.0 % 0.0 % ​ Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Deferred tax assets: ​ ​ Net operating loss carryforwards ​ $ 53,823 ​ $ 49,145 Research and development tax credit carryforwards ​ 17,645 ​ 14,446 Lease liabilities ​ 2,566 ​ 3,670 Deferred revenue ​ 3,525 ​ 6,115 Accrued expense and other liabilities ​ 1,066 ​ 585 Capitalized R&E expenses ​ ​ 7,688 ​ ​ — Other ​ 2,658 ​ 1,627 Total deferred tax assets ​ 88,971 ​ 75,588 Less: Valuation Allowance ​ (86,276) ​ (71,818) Total net deferred tax assets ​ 2,695 ​ 3,770 Deferred tax liabilities: ​ ​ Lease right‑of‑use assets ​ (2,457) ​ (3,517) Fixed assets ​ (238) ​ (253) Total deferred tax liabilities ​ (2,695) ​ (3,770) Net deferred tax assets ​ $ — ​ $ — ​ As of December 31, 2022, the Company had U.S. federal net operating loss carryforwards of $197.7 million, which may be available to offset future taxable income, of which $10.5 million of the total net operating loss carryforwards expire at various dates beginning in 2036, while the remaining $187.2 million do not expire but are limited in their usage to 80% of annual taxable income. In addition, as of December 31, 2022, the Company had state net operating loss carryforwards of $193.4 million, which may be available to offset future taxable income and expire at various dates beginning in 2037. As of December 31, 2022, the Company also had federal and state research and development tax credit carryforwards of $9.2 million and $5.0 million, respectively, which may be available to reduce future tax liabilities and expire at various dates beginning in 2037 and 2032, respectively. In addition, the Company had Orphan Drug Designations granted by the Food and Drug Administration (“FDA”) for SIG-001, SIG-005 and SIG-007, but withdrew their designations for SIG-001 and SIG-005 during the year. The Company generated an orphan drug credit in the amount of $4.5 million which may be available to reduce future tax liabilities and begin to expire in 2039. Utilization of the net operating loss and research and development credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, and corresponding provisions of state law, due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss and research and development credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company completed a Section 382 study for the tax period from the Company’s inception through December 31, 2019 and concluded that $0.4 million of net operating losses generated before February 10, 2016 is more likely than not subject to restrictive limitation and reduced the net operating loss carryforward balance. There could also be additional ownership changes in the future which may result in additional limitations on the utilization of net operating loss carryforwards and credits. The Company has evaluated the positive and negative evidence bearing upon its ability to realize its deferred tax assets, which are composed principally of net operating loss carryforwards. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of its federal and state net deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 2022 and 2021. The Company reevaluates the positive and negative evidence at each reporting period. The changes in the valuation allowance for deferred tax assets during the years ended December 31, 2022 and 2021 related primarily to the increases in net operating loss carryforwards, research and development tax credits generated and the deferred tax assets related to deferred revenue. The changes in the valuation allowance for 2022 and 2021 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Valuation allowance at beginning of year ​ $ 71,818 ​ $ 45,735 Increases recorded to income tax provision ​ 14,458 ​ 26,083 Valuation allowance at end of year ​ $ 86,276 ​ $ 71,818 ​ The Company assesses the uncertainty in its income tax positions to determine whether a tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals of litigation processes, based on the technical merits of the position. For the tax position meeting the more-likely-than-not threshold, the tax amount recognized in the financial statements is reduced by the largest benefit that has a greater than 50% likelihood of being realized upon the ultimate settlement with the relevant taxing authority. As of December 31, 2022 and 2021, the Company had not recorded any reserves for uncertain tax positions or related interest and penalties. The Company files income tax returns as prescribed by the tax law of the jurisdiction in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdiction, where applicable. As of December 31, 2022 and 2021, there were no pending tax examinations. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies
Commitments and Contingencies	12. Commitments and Contingencies 401(k) Plan In January 2017, and as amended in January 2019, the Company established a defined-contribution plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Starting in 2020, the Company makes matching contributions at a rate of 100% of each employee’s contribution up to a maximum employee contribution of 3% of eligible plan compensation. For each of the years ended December 31, 2022 and 2021, the Company made matching contributions of $0.3 million and $0.4 million, respectively. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and certain of its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Legal Proceedings The Company is not a party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings.

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases
Leases	13. Leases Corporate headquarters In August 2017, the Company entered into an operating lease agreement for its corporate headquarters located at 100 Binney Street, Cambridge, Massachusetts. The term of the lease commenced in February 2018 and is scheduled to expire in February 2025. Under the terms of the lease, the Company provided a security deposit of $0.6 million, which is included in restricted cash in the accompanying balance sheets. The lease provides for annual rent escalations. The Company pays for its proportionate share of building operating costs such as maintenance, utilities, and insurance that are treated as variable costs and excluded from the measurement of the lease. The Company is entitled to one option to extend the lease term for an additional three years. The option to extend the lease term was not included in the right-of-use asset and lease liability as it was not reasonably certain of being exercised. In October 2019, the Company entered into an assignment agreement in which it agreed to take over a lease of office and laboratory space adjacent to its current headquarters at 100 Binney Street in Cambridge, Massachusetts. The lease commenced on October 16, 2020, the date in which the space was delivered to the Company, and expires in February 2025. Under the terms of the lease, the Company provided a security deposit of $0.5 million, which is included in restricted cash in the accompanying balance sheets. The lease provides for annual rent escalations. The Company pays for its proportionate share of building operating costs such as maintenance, utilities, and insurance that are treated as variable costs and excluded from the measurement of the lease. The Company does not have an option to extend the lease term. Manufacturing Services Agreement In June 2019, the Company entered into a development and manufacturing services agreement for the commercial production of its Encapsulated Cell Product. The Company was required to pay an up-front suite reservation fee of $0.3 million and is required to pay a $0.1 million per month suite fee as well as certain labor, raw materials, testing and shipping costs for manufacturing services through September 2020, the initial term of the agreement. The Company concluded that this agreement contains an operating lease as the suite is designated for its exclusive use during the term of the agreement. Upon commencement in September 2019, the Company recorded a right-of-use asset of $1.7 million, inclusive of prepaid rent and a lease liability of $1.4 million. The Company recognizes lease expense on a straight-line basis over the term of the lease. In March 2020, the Company elected to extend its use of the designated suite through June 30, 2021 resulting in the remeasurement of the operating lease. Accordingly, the operating lease liability December 2021 Finance leases The Company does not have any material finance leases as of December 31, 2022 and 2021. Summary of lease costs The components of lease cost under ASC 842 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ Lease costs 2022 2021 Operating lease cost ​ $ 4,827 ​ ​ 6,029 ​ Short term lease cost ​ 679 ​ ​ 679 ​ Variable lease cost ​ 724 ​ ​ 1,101 ​ Total lease cost ​ $ 6,230 ​ $ 7,809 ​ ​ Supplemental disclosure of cash flow information related to leases was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities (operating cash flows) ​ $ 4,844 ​ $ 5,965 ​ Lease assets obtained in exchange for new operating lease liabilities ​ $ 68 ​ $ 917 ​ ​ The weighted-average remaining lease term and discount rate were as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2022 ​ 2021 Weighted‑average remaining lease term (in years) ​ 2.2 years 3.1 years Weighted‑average discount rate ​ 8.4 % 8.4 % ​ The following table presents the maturity of the Company’s operating lease liabilities as of December 31, 2022 (in thousands): ​ ​ ​ ​ Year Ending December 31, ​ 2023 ​ $ 4,599 2024 ​ 4,734 2025 ​ 802 2026 ​ — 2027 ​ — Thereafter ​ — Total future minimum lease payments ​ 10,135 Less: imputed interest ​ (842) Present value of operating lease liability ​ $ 9,293 ​

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2022
Net Loss per Share
Net Loss per Share	14. Net Loss per Share Net Loss per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Numerator: ​ ​ Net loss ​ $ (43,561) ​ $ (77,311) Net loss attributable to common stockholders ​ $ (43,561) ​ $ (77,311) Denominator: ​ ​ ​ ​ Weighted average common stock outstanding—basic and diluted ​ 32,405,786 ​ 31,860,264 Net loss per share attributable to common stockholders—basic and diluted ​ $ (1.34) ​ $ (2.43) ​ The Company’s potential dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Warrants to purchase common stock ​ 19,044 ​ 19,044 Future issuable shares under the employee stock purchase plan ​ 56,720 ​ 33,650 Unvested restricted stock units ​ 150,400 ​ 275,400 Stock options to purchase common stock 4,912,386 ​ 3,138,646 ​ 5,138,550 3,466,740 ​

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2022
Related Party Transactions
Related Party Transactions	15. Related Party Transactions The Company has a patent license agreement with MIT and issued 333,333 shares of its common stock to MIT as part of the consideration for this patent license (Note 10). Additionally, through the completion of the Company’s IPO two members of the Company’s board of directors were employed by MIT and subsequent to the IPO one member of the Company’s board of directors is employed by MIT. The Company incurs charges for the use of certain MIT equipment and facilities. For the years ended December 31, 2022 and 2021, the Company incurred expenses of $0.4 million and $0.1 million, respectively, related to business with MIT. As of December 31, 2022 and 2021, there was less than $0.1 million and $0 recorded in accounts payable due to this related party. As described in Note 9 above, the Company entered into the 2018 Lilly Agreement with Lilly, a shareholder of the Company, in April 2018. During the years ended December 31, 2022 and 2021, the Company recognized $12.9 million and $9.5 million, respectively, of related party revenue associated with the Lilly collaboration agreements. As of December 31, 2022 and 2021, the Company had deferred revenue related to the collaboration agreements with Lilly of $12.9 million and $22.4 million, respectively. As of December 31, 2022 and 2021, we had $2.2 million and $0.1 million in accounts receivable with Lilly, respectively. As of December 31, 2022 we had $1.3 million in unbilled accounts receivable with Lilly and as of December 31, 2021 we did not have unbilled accounts receivable. On February 1, 2022, the Company entered into a shared space arrangement with a portfolio company of Flagship Pioneering, to sublease a portion of its office and laboratory space in Cambridge, Massachusetts. The term of the shared space arrangement commenced on February 1, 2022 and continues for an initial term ending on July 31, 2023. The agreement may be renewed for six successive one-month periods. The Company will be paid a fee based on the portfolio company’s occupancy of the office and laboratory space. Under this agreement, the Company recorded other income, net, of $0.2 million during the year ended December 31, 2022. The Company received $3.0 million of cash payments during the year ended December 31, 2022, and as of December 31, 2022, the Company had no outstanding receivables under this agreement. In January 2021, the Company entered into a shared space arrangement with a portfolio company of Flagship Pioneering, one of the Company’s significant stockholders, to sublease a portion of its office and laboratory space in Cambridge, Massachusetts. The term of the shared space arrangement commenced in January 2021 and ended on December 31, 2021. Under this agreement, the Company recorded other income of $0.4 million during the year ended December 31, 2021. The Company received cash payments of $0.4 million during the year ended December 31, 2021.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the period. Estimates and assumptions reflected in these financial statements include, but are not limited to, revenue recognition, research and development expenses and stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions.
Concentration of Credit Risk and of Significant Suppliers	Concentration of Credit Risk and of Significant Suppliers The financial instruments that potentially subject the Company to concentrations of credit risk are cash, cash equivalents, marketable securities, and accounts receivable. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. As of December 31, 2022, 100% of the Company’s accounts receivable related to one customer and as of December 31, 2021, the Company’s accounts receivable were related to two customers. As of December 31, 2022 and 2021, 100% and 39%, respectively, of the Company’s account receivables were related to the Company’s collaboration agreements with Eli Lilly and Company (Note 9). The Company is dependent on third-party manufacturers to supply certain products for research and development activities in its programs. The Company currently has a supplier of certain raw materials that would be considered a sole supplier. If the Company cannot access additional suppliers or secure sufficient inventory of these raw materials, its programs could be adversely affected by an interruption in the availability of these raw materials.
Restricted Cash	Restricted Cash In connection with the Company’s corporate headquarters and lab space lease agreement entered into in March 2018, the Company is required to maintain a letter of credit of $0.6 million for the benefit of the landlord. On October 16, 2020 the Company took over the lease of office and laboratory space adjacent to its current headquarters, which expires in February 2025. Under the terms of the lease, the Company is required to maintain a letter of credit of $0.5 million. The Company has classified the certificate of deposits collateralizing the letter of credits issued as a security deposit in connection with the Company’s leases of its corporate facility as long-term restricted cash on its balance sheet at December 31, 2022 and 2021. At December 31, 2022 and 2021 the Company classified $0.3 million related to securing the use of corporate credit cards as short-term restricted cash.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset, as follows: ​ ​ ​ ​ ​ Estimated useful life Laboratory equipment ​ 5 Years Leasehold improvements ​ Shorter of the lease term or 10 years Furniture and fixtures ​ 7 Years Computers and software ​ 3 Years ​ Maintenance and repairs are charged to expense as incurred. Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are removed from the accounts and any resulting gains or losses are included in the statement of operations and comprehensive loss in the period of disposal.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss to be recognized would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. The Company did not recognize any impairment losses on long-lived assets during the years ended December 31, 2022 and 2021.
Leases	Leases The Company follows the provisions of ASC Topic 842, Leases Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the remaining lease term. The present value of future lease payments are discounted using the interest rate implicit in lease contracts if that rate is readily determinable; otherwise the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis over a similar term, the amount of the lease payments in a similar economic environment. After lease commencement and the establishment of a right-to-use asset and operating lease liability, lease expense is recorded on a straight-line basis over the lease term. The Company enters into contracts that contain both lease and non-lease components. Non-lease components include costs that do not provide a right-to-use a leased asset but instead provide a service, such as maintenance costs. The Company has elected to account for the lease and non-lease components together as a single component for all classes of underlying assets. Variable costs associated with the lease, such as maintenance and utilities, are not included in the measurement of right-to-use assets and lease liabilities but rather are expensed when the events determining the amount of variable consideration to be paid have occurred.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ​ ​ ​ Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. ​ The carrying values of the Company’s accounts receivable, and accounts payable and accrued expenses and other current liabilities approximate their fair value due to the short-term nature of these assets and liabilities. The carrying value of the Company’s long-term debt approximates its fair value at December 31, 2022 because the debt bears interest at a variable market rate and the Company’s credit risk has not materially changed since the inception of the agreement. The Company’s financial instruments consist primarily of cash, cash equivalents and marketable securities (Note 3).
Segment Information	Segment Information The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is developing therapeutic treatments for a wide range of chronic diseases. The Company has determined that its chief operating decision maker is its Chief Executive Officer. The Company’s chief operating decision maker reviews the Company’s financial information on an aggregated basis for purposes of allocating resources and assessing financial performance. All the Company’s tangible assets are located in the United States and all of the Company’s collaboration revenue is derived from its collaboration partners headquartered in the United States.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of acquisition to be cash equivalents.
Marketable securities	Marketable securities Marketable securities consist of investments with original maturities greater than ninety days. The Company has classified its investments with maturities beyond one year as short term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. The Company considers its investment portfolio of investments as available-for-sale. Accordingly, these investments are recorded at fair value, which is based on quoted market prices. Unrealized gains and losses are reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses and declines in value judged to be other than temporary are included as a component of other income (expense), net based on the specific identification method. When determining whether a decline in value is other than temporary, the Company considers various factors, including whether the Company has the intent to sell the security, and whether it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis. Fair value is determined based on quoted market prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.
Revenue Recognition for License and Collaboration Agreements	Revenue Recognition for License and Collaboration Agreements The Company follows the provisions of ASC Topic 606, Revenue from Contracts with Customers Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The Company enters into licensing arrangements that are within the scope of ASC 606, under which it may exclusively license to third parties’ rights to develop, manufacture and commercialize its product candidates. The terms of these arrangements typically include payment to the Company of one or more of the following: nonrefundable, upfront license fees; reimbursement of research and development costs; development, regulatory and sales milestone payments; and royalties on net sales of licensed products. For costs that were not paid upfront, the payment terms under the Company’s existing licensing arrangements are generally 45 days. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its arrangements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the assessment of the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations, and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. As part of the accounting for arrangements under ASC 606, the Company must use significant judgment to determine: a) the performance obligations based on the determination under step (ii) above; b) the transaction price under step (iii) above; and c) the standalone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above. The Company also uses judgment to determine whether milestones or other variable consideration, except for royalties and sales-based milestones, should be included in the transaction price as described below. The transaction price is allocated to each performance obligation based on the relative stand-alone selling price of each performance obligation in the contract, and the Company recognizes revenue based on those amounts when, or as, the performance obligations under the contract are satisfied. The standalone selling price is the price at which an entity would sell a promised good or service separately to a customer. Management estimates the standalone selling price of each of the identified performance obligations in the Company’s customer contracts, maximizing the use of observable inputs. Because the Company has not sold the same goods or services in its contracts separately to any customers on a standalone basis and there are no similar observable transactions in the marketplace, the Company estimates the standalone selling price of each performance obligation in its customer arrangements based on its estimate of costs to be incurred to fulfil its obligations associated with the performance, plus a reasonable margin. The Company has determined that its only contract liability under ASC 606 is deferred revenue. Amounts received prior to revenue recognition are recorded as deferred revenue in the balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as the current portion of deferred revenue in the balance sheets. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion in the balance sheets. Amounts are recorded as accounts receivable and unbilled accounts receivable when the Company’s right to consideration is unconditional. Exclusive Licenses If the license granted in the arrangement is determined to be distinct from the other promises or performance obligations identified in the arrangement, which generally include research and development services, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a license is distinct from the other promises, the Company considers relevant facts and circumstances of each arrangement, including the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promises, whether the value of the license is dependent on the unsatisfied promises, whether there are other vendors that could provide the remaining promises, and whether it is separately identifiable from the remaining promises. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and the resulting periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the arrangement. Such a change could have a material impact on the amount of revenue the Company records in future periods. Under the Company’s existing license and collaboration agreement, the Company has concluded the research and development services and the license, among other promises are a combined performance obligation (Note 9) and that the transfer of control to the customer occurs over the time period that the research and development services are to be provided by the Company, and this cost-to-cost method is, in management’s judgement, the best measure of progress towards satisfying the performance obligation. Research and Development Services The promises under the Company’s collaboration and license agreements generally include research and development services to be performed by the Company on behalf of the collaboration partner. Payments or reimbursements resulting from the Company’s research and development efforts are estimated at the outset of the arrangement and considered part of the transaction price that is subsequently recognized as revenue because the Company is the principal in the arrangement for such efforts. Customer Options The Company’s arrangements may provide a customer with the right to certain optional purchases, such as the right to license a target either at the inception of the arrangement or within a predefined option period. Under these agreements, fees may be due to the Company at the inception of the arrangement as an upfront fee or payment or upon the exercise of an option to acquire a license. If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the Company evaluates the customer options to determine if they are material rights at the outset of each arrangement. If the goods and services underlying the customer options are not determined to be material rights, these customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon exercise of the option. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative stand-alone selling price, which is determined based on the identified discount, and the probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised or expires. Milestone Payments At the inception of each arrangement that includes research, development or regulatory milestone payments, we evaluate whether the milestones are considered likely to be met and estimate the amount to be considered for inclusion in the transaction price using the most-likely-amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. For milestone payments due upon events that are not within the control of us or the licensee, such as regulatory approvals, we are not able to assert that it is likely that the regulatory approval will be granted and that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur until those approvals are received. In making this assessment, we evaluate factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period we reevaluate the probability of achievement of all milestones subject to constraint and, if necessary, adjust our estimate of the overall transaction price of the arrangement. Any such adjustments are recorded on a cumulative catch-up basis, which would affect the amount of revenue and earnings in the period of adjustment. As of December 31, 2022 and 2021, no milestones under the 2018 Lilly Agreement (Note 9) were included in the transaction price as no milestones had been deemed likely to be achieved or had been achieved. Royalties For arrangements that include sales-based royalties, including milestone payments based on a level of sales, that are the result of a customer-vendor relationship and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied. To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including costs for salaries and bonuses, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered, or the services rendered. Upfront payments under license agreements are expensed as research and development expense upon receipt of the license, and annual maintenance fees under license agreements are expensed in the period in which they are incurred. Milestone payments under license agreements are accrued, with a corresponding expense being recognized, in the period in which the milestone is determined to be probable of achievement and the related amount is reasonably estimable.
Research, Development and Manufacturing Contract Costs and Accruals	Research, Development and Manufacturing Contract Costs and Accruals The Company has entered into various research, development and manufacturing contracts with research institutions and other companies. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research, development and manufacturing costs. When billing terms under these contracts do not coincide with the timing of when the work is performed, the Company is required to make estimates of outstanding obligations to those third parties as of period end. Any accrual estimates are based on a number of factors, including the Company’s knowledge of the progress towards completion of the research, development and manufacturing activities, invoicing to date under the contracts, communication from the research institutions and other companies of any actual costs incurred during the period that have not yet been invoiced and the costs included in the contracts. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the estimates made by the Company. The historical accrual estimates made by the Company have not been materially different from the actual costs.
Patent Costs	Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.
Stock-Based Compensation	Stock-Based Compensation We measure stock-based awards granted to employees, non-employees and directors based on the fair value on the date of the grant and recognize compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. Forfeitures are accounted for as they occur. Generally, we issue stock-based awards in the form of stock options and restricted stock units with only service-based vesting conditions and record the expense for these awards using the straight-line method. We have also issued stock-based awards with performance-based vesting conditions for which the expense is recognized when achievement of such performance conditions becomes probable. The fair value of each share option is estimated on the date of grant using the Black-Scholes option pricing model. Until the completion of our initial public offering in December 2020, we had been a private company and lacked company-specific historical and implied volatility information for our shares. Therefore, we estimate our expected share price volatility based on the historical volatility of publicly traded peer companies and expect to continue to do so until such time as we have adequate historical data regarding the volatility of our own traded share price. The expected term of our share options has been determined utilizing the “simplified method” for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that we have never paid cash dividends on our ordinary shares and do not expect to pay any cash dividends in the future. The Company classifies stock-based compensation expense in its statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is composed of net loss and other comprehensive loss. Other comprehensive loss consists of unrealized losses on marketable securities.
Net Income (Loss) per Share	Net Income (Loss) per Share The Company only has one class of shares outstanding and basic net income (loss) per common share is computed by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) per common share is computed by dividing net income (loss) by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock awards. For periods in which the Company reports a net loss, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements Financial Instruments-Overall In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Schedule of property and equipment estimated useful life	​ ​ ​ ​ ​ Estimated useful life Laboratory equipment ​ 5 Years Leasehold improvements ​ Shorter of the lease term or 10 years Furniture and fixtures ​ 7 Years Computers and software ​ 3 Years ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value Measurements and marketable securities
Schedule of financial assets and liabilities measured at fair value on a recurring basis	The following table summarizes the Company’s cash equivalents and marketable securities as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Cash equivalents ​ ​ ​ ​ Money market funds ​ $ 29,310 ​ $ — ​ $ — ​ $ 29,310 Commercial paper ​ ​ — ​ ​ 1,994 ​ ​ — ​ ​ 1,994 U.S. Treasuries ​ ​ — ​ ​ 4,999 ​ ​ — ​ ​ 4,999 Total cash equivalents ​ ​ 29,310 ​ ​ 6,993 ​ ​ — ​ ​ 36,303 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ ​ — ​ ​ 21,594 ​ ​ — ​ ​ 21,594 Commercial paper ​ ​ — ​ ​ 1,738 ​ ​ — ​ ​ 1,738 U.S. Government Agencies ​ ​ — ​ ​ 1,235 ​ ​ — ​ ​ 1,235 U.S. Treasuries ​ ​ — ​ ​ 2,993 ​ ​ — ​ ​ 2,993 Total marketable securities ​ ​ — ​ ​ 27,560 ​ ​ — ​ ​ 27,560 Total ​ $ 29,310 ​ $ 34,553 ​ $ — ​ $ 63,863 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2021 ​ Level 1 Level 2 Level 3 Total Cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 50,847 ​ $ — ​ $ — ​ $ 50,847 Commercial paper ​ ​ — ​ ​ 25,995 ​ ​ — ​ ​ 25,995 Corporate bonds ​ ​ — ​ ​ 1,000 ​ ​ — ​ ​ 1,000 Total cash equivalents ​ ​ 50,847 ​ ​ 26,995 ​ ​ — ​ ​ 77,842 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ ​ — ​ ​ 10,238 ​ ​ — ​ ​ 10,238 Commercial paper ​ — ​ ​ 5,975 ​ ​ — ​ ​ 5,975 Total marketable securities ​ ​ — ​ ​ 16,213 ​ ​ — ​ ​ 16,213 Total ​ $ 50,847 ​ $ 43,208 ​ $ — ​ $ 94,055 ​
Schedule of marketable securities	The following tables summarizes the Company’s available-for-sale marketable debt securities as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2022 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Credit ​ ​ ​ ​ Cost Gains Losses Losses Total Corporate bonds ​ $ 21,994 ​ $ — ​ $ (400) ​ $ — ​ $ 21,594 Commercial paper ​ ​ 1,743 ​ ​ — ​ ​ (5) ​ ​ — ​ ​ 1,738 U.S. Treasuries ​ ​ 1,248 ​ ​ — ​ ​ (13) ​ ​ — ​ ​ 1,235 U.S. Government Agencies ​ ​ 2,999 ​ ​ — ​ ​ (6) ​ ​ — ​ ​ 2,993 Total ​ $ 27,984 ​ $ — ​ $ (424) ​ $ — ​ $ 27,560 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements as of ​ ​ December 31, 2021 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ ​ Cost Gains Losses Total Commercial paper ​ $ 10,244 ​ $ — ​ $ (6) ​ $ 10,238 Corporate bonds ​ ​ 5,977 ​ ​ — ​ ​ (2) ​ ​ 5,975 Total ​ $ 16,221 ​ $ — ​ $ (8) ​ $ 16,213 ​
Schedule of available-for-sale marketable debt securities by contractual maturity	The following table summarizes the Company’s available-for-sale marketable debt securities by contractual maturity, as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 ​ 2021 Maturities in one year or less ​ $ 23,231 ​ $ 9,004 Maturities between one and two years ​ 4,329 ​ 7,209 Total ​ $ 27,560 ​ $ 16,213

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2022
Property and Equipment, Net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 ​ 2021 Laboratory equipment ​ $ 6,301 ​ $ 6,297 Leasehold improvements ​ 78 ​ 78 Furniture and fixtures ​ 620 ​ 620 Computers and software ​ 177 ​ 163 ​ ​ 7,176 ​ 7,158 Less: Accumulated depreciation and amortization ​ (4,322) ​ (3,164) Total property and equipment, net ​ $ 2,854 ​ $ 3,994 ​

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2022
Accrued Expenses and Other Current Liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Employee compensation and benefits ​ $ 4,243 ​ $ 3,071 External research and development costs ​ 817 ​ 5,056 Legal and professional fees ​ 714 ​ 656 Other ​ 247 ​ 215 Total accrued expenses and other current liabilities ​ $ 6,021 ​ $ 8,998

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2022
Debt
Schedule of long-term debt	As of December 31, 2022 and 2021, long-term debt consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 ​ 2021 Principal amount of long‑term debt ​ $ 18,333 ​ $ 20,000 Less: Current portion of long‑term debt ​ ​ (6,667) ​ (1,667) Long‑term debt, net of current portion ​ 11,666 ​ 18,333 Final debt payment liability ​ ​ 700 ​ ​ 700 Debt discount, net of accretion ​ (345) ​ (622) Long‑term debt, net of discount and current portion ​ $ 12,021 ​ $ 18,411 ​
Schedule of estimated future principal payments	The estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2023 ​ $ 6,666 2024 ​ 6,667 2025 ​ ​ 5,000 2026 ​ ​ — 2027 ​ ​ — ​ ​ $ 18,333 ​

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Stock Based Compensation
Schedule of weighted average assumption for grant date fair value of stock options	The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees and directors: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ ​ 2022 ​ 2021 Risk-free interest rate ​ 1.75 % 0.80 % Expected dividend yield ​ 0.00 % 0.00 % Expected term (in years) ​ 6.0 ​ 6.1 ​ Expected volatility ​ 84.28 % 78.31 % ​
Schedule of stock option activity	The following table summarizes the Company’s stock option activity since December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ ​ ​ ​ ​ ​ ​ Weighted ​ remaining ​ Aggregate ​ ​ Number of ​ average ​ contractual term ​ intrinsic value ​ ​ options ​ exercise price ​ (in years) ​ (in thousands) Balances at December 31, 2021 3,138,646 ​ $ 10.74 ​ 7.6 ​ $ 328 Options granted 2,564,140 ​ 2.23 ​ ​ ​ ​ Options cancelled (789,567) ​ 8.64 ​ ​ ​ ​ Options exercised (833) ​ 0.57 ​ ​ ​ ​ ​ Outstanding and expected to vest at December 31, 2022 ​ 4,912,386 ​ ​ 6.63 ​ 7.8 ​ ​ — Exercisable at December 31, 2022 2,045,196 ​ $ 7.81 6.1 ​ $ — ​
Schedule of restricted stock activity	The following table summarizes restricted stock unit activity since December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ average grant ​ ​ Shares ​ date fair value Unvested shares as of December 31, 2021 275,400 ​ $ 5.57 Vested ​ (37,960) ​ ​ 5.55 Forfeited (87,040) ​ 5.62 Unvested shares as of December 31, 2022 ​ 150,400 ​ $ 5.54 ​
Schedule of stock-based compensation expense	Stock-based compensation expense related to stock options and restricted stock units was classified in the statement of operations and comprehensive loss as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ 2022 2021 Research and development ​ $ 1,883 ​ $ 2,230 General and administrative ​ 4,018 ​ 3,920 ​ ​ $ 5,901 ​ $ 6,150 ​

License and Collaboration Agr_2

License and Collaboration Agreement (Tables)	12 Months Ended
	Dec. 31, 2022
Lilly License and Collaboration Agreement
License and Collaboration Agreement
Schedule of the changes in the total contract liability (deferred revenue) balances related to the Company's license and collaboration agreements	The changes in the total contract liability (deferred revenue) balances related to the Company’s license and collaboration agreements with Lilly were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Deferred revenues at beginning of period ​ $ 22,367 ​ $ 31,777 Revenues deferred during the period ​ 3,458 ​ — Revenues recognized during the period ​ (12,940) ​ (9,410) Deferred revenues at end of period ​ $ 12,885 ​ $ 22,367 ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Taxes
Schedule of reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.0 6.3 Federal and state tax credits 7.3 6.3 Stock‑based compensation (1.0) 0.1 Other (0.1) — Change in deferred tax asset valuation allowance (33.2) (33.7) Effective income tax rate 0.0 % 0.0 % ​
Schedule of deferred tax assets and liabilities	Net deferred tax assets as of December 31, 2022 and 2021 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Deferred tax assets: ​ ​ Net operating loss carryforwards ​ $ 53,823 ​ $ 49,145 Research and development tax credit carryforwards ​ 17,645 ​ 14,446 Lease liabilities ​ 2,566 ​ 3,670 Deferred revenue ​ 3,525 ​ 6,115 Accrued expense and other liabilities ​ 1,066 ​ 585 Capitalized R&E expenses ​ ​ 7,688 ​ ​ — Other ​ 2,658 ​ 1,627 Total deferred tax assets ​ 88,971 ​ 75,588 Less: Valuation Allowance ​ (86,276) ​ (71,818) Total net deferred tax assets ​ 2,695 ​ 3,770 Deferred tax liabilities: ​ ​ Lease right‑of‑use assets ​ (2,457) ​ (3,517) Fixed assets ​ (238) ​ (253) Total deferred tax liabilities ​ (2,695) ​ (3,770) Net deferred tax assets ​ $ — ​ $ — ​
Schedule of changes in valuation allowances	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31, ​ 2022 2021 Valuation allowance at beginning of year ​ $ 71,818 ​ $ 45,735 Increases recorded to income tax provision ​ 14,458 ​ 26,083 Valuation allowance at end of year ​ $ 86,276 ​ $ 71,818

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases
Schedule of components of lease cost	The components of lease cost under ASC 842 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ Lease costs 2022 2021 Operating lease cost ​ $ 4,827 ​ ​ 6,029 ​ Short term lease cost ​ 679 ​ ​ 679 ​ Variable lease cost ​ 724 ​ ​ 1,101 ​ Total lease cost ​ $ 6,230 ​ $ 7,809 ​ ​
Schedule of supplemental disclosure of cash flow information	Supplemental disclosure of cash flow information related to leases was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities (operating cash flows) ​ $ 4,844 ​ $ 5,965 ​ Lease assets obtained in exchange for new operating lease liabilities ​ $ 68 ​ $ 917 ​ ​
Schedule of weighted average remaining lease term and discount rate	The weighted-average remaining lease term and discount rate were as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ ​ December 31, ​ ​ ​ 2022 ​ 2021 Weighted‑average remaining lease term (in years) ​ 2.2 years 3.1 years Weighted‑average discount rate ​ 8.4 % 8.4 % ​
Schedule of maturity of operating lease liabilities	The following table presents the maturity of the Company’s operating lease liabilities as of December 31, 2022 (in thousands): ​ ​ ​ ​ Year Ending December 31, ​ 2023 ​ $ 4,599 2024 ​ 4,734 2025 ​ 802 2026 ​ — 2027 ​ — Thereafter ​ — Total future minimum lease payments ​ 10,135 Less: imputed interest ​ (842) Present value of operating lease liability ​ $ 9,293

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2022
Net Loss per Share
Schedule of Basic and diluted net loss per share attributable to common stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Numerator: ​ ​ Net loss ​ $ (43,561) ​ $ (77,311) Net loss attributable to common stockholders ​ $ (43,561) ​ $ (77,311) Denominator: ​ ​ ​ ​ Weighted average common stock outstanding—basic and diluted ​ 32,405,786 ​ 31,860,264 Net loss per share attributable to common stockholders—basic and diluted ​ $ (1.34) ​ $ (2.43) ​
Schedule of potential dilutive securities excluded from the computation of diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Warrants to purchase common stock ​ 19,044 ​ 19,044 Future issuable shares under the employee stock purchase plan ​ 56,720 ​ 33,650 Unvested restricted stock units ​ 150,400 ​ 275,400 Stock options to purchase common stock 4,912,386 ​ 3,138,646 ​ 5,138,550 3,466,740

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Nature of the Business and Basis of Presentation
Net loss	$ 43,561	$ 77,311
Accumulated deficit	256,800	$ 213,239
Cash, cash equivalents and marketable securities	$ 69,600

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2022 USD ($) customer	Dec. 31, 2021 USD ($) customer	Oct. 16, 2020 USD ($)	Mar. 31, 2018 USD ($)
Summary of Significant Accounting Policies
Restricted cash		$ 250	$ 250
Payment terms of licensing arrangements	45 days
Letter of Credit
Summary of Significant Accounting Policies
Restricted cash				$ 500	$ 600
Asset Pledged as Collateral
Summary of Significant Accounting Policies
Restricted cash		$ 300	$ 300
Accounts receivable | Customer Concentration Risk
Summary of Significant Accounting Policies
Number of customers | customer		1	2
Concentrations of credit risk		100%
Accounts receivable | Customer Concentration Risk | Lilly
Summary of Significant Accounting Policies
Concentrations of credit risk		100%	39%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2022
Laboratory equipment
Property and Equipment, Net
Property, Plant and Equipment, Useful Life	5 years
Leasehold improvements
Property and Equipment, Net
Property, Plant and Equipment, Useful Life	10 years
Furniture and fixtures
Property and Equipment, Net
Property, Plant and Equipment, Useful Life	7 years
Computers and software
Property and Equipment, Net
Property, Plant and Equipment, Useful Life	3 years

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurements
Total cash equivalents	$ 36,303	$ 77,842
Total marketable securities	27,560	16,213
Total	63,863	94,055
Money market funds
Fair Value Measurements
Total cash equivalents	29,310	50,847
Commercial paper
Fair Value Measurements
Total cash equivalents	1,994	25,995
Total marketable securities	1,738	5,975
Corporate bonds
Fair Value Measurements
Total cash equivalents		1,000
Total marketable securities	21,594	10,238
U.S. Government Agencies
Fair Value Measurements
Total marketable securities	1,235
U.S. Treasuries
Fair Value Measurements
Total cash equivalents	4,999
Total marketable securities	2,993
Level 1
Fair Value Measurements
Total cash equivalents	29,310	50,847
Total	29,310	50,847
Level 1 | Money market funds
Fair Value Measurements
Total cash equivalents	29,310	50,847
Level 2
Fair Value Measurements
Total cash equivalents	6,993	26,995
Total marketable securities	27,560	16,213
Total	34,553	43,208
Level 2 | Commercial paper
Fair Value Measurements
Total cash equivalents	1,994	25,995
Total marketable securities	1,738	5,975
Level 2 | Corporate bonds
Fair Value Measurements
Total cash equivalents		1,000
Total marketable securities	21,594	$ 10,238
Level 2 | U.S. Government Agencies
Fair Value Measurements
Total marketable securities	1,235
Level 2 | U.S. Treasuries
Fair Value Measurements
Total cash equivalents	4,999
Total marketable securities	$ 2,993

Fair Value Measurements - Cash

Fair Value Measurements - Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Cash Equivalents and Marketable Securities
Amortized Cost	$ 27,984	$ 16,221
Gross Unrealized Losses	(424)	(8)
Total	27,560	16,213
Commercial paper
Cash Equivalents and Marketable Securities
Amortized Cost	1,743	10,244
Gross Unrealized Losses	(5)	(6)
Total	1,738	10,238
Corporate bonds
Cash Equivalents and Marketable Securities
Amortized Cost	21,994	5,977
Gross Unrealized Losses	(400)	(2)
Total	21,594	$ 5,975
U.S. Treasuries
Cash Equivalents and Marketable Securities
Amortized Cost	1,248
Gross Unrealized Losses	(13)
Total	1,235
U.S. Government Agencies
Cash Equivalents and Marketable Securities
Amortized Cost	2,999
Gross Unrealized Losses	(6)
Total	$ 2,993

Fair Value Measurements - Avail

Fair Value Measurements - Available-for-sale marketable debt securities by contractual maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
available-for-sale marketable debt securities contractual maturity
Maturities in one year or less	$ 23,231	$ 9,004
Maturities between one and two years	4,329	7,209
Total	$ 27,560	$ 16,213

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment, Net
Property and equipment, gross	$ 7,176	$ 7,158
Less: Accumulated depreciation and amortization	(4,322)	(3,164)
Total property and equipment, net	2,854	3,994
Depreciation and amortization expense	1,264	1,118
Laboratory equipment
Property and Equipment, Net
Property and equipment, gross	6,301	6,297
Leasehold improvements
Property and Equipment, Net
Property and equipment, gross	78	78
Furniture and fixtures
Property and Equipment, Net
Property and equipment, gross	620	620
Computers and software
Property and Equipment, Net
Property and equipment, gross	$ 177	$ 163

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued Expenses and Other Current Liabilities
Employee compensation and benefits	$ 4,243	$ 3,071
External research and development costs	817	5,056
Legal and professional fees	714	656
Other	247	215
Total accrued expenses and other current liabilities	$ 6,021	$ 8,998

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt
Principal amount of long-term debt	$ 18,333	$ 20,000
Less: Current portion of long-term debt	(6,667)	(1,667)
Longterm debt, net of current portion	11,666	18,333
Final debt payment liability	700	700
Debt discount, net of accretion	(345)	(622)
Longterm debt, net of discount and current portion	$ 12,021	$ 18,411

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended
	Sep. 30, 2020	Dec. 31, 2022	Dec. 31, 2021
Debt
Debt discount		$ 345	$ 622
2020 Credit Facility
Debt
Initial debt issuance costs	$ 300
Debt discount	$ 700
Amortization of debt issuance costs		$ 300	$ 300
Effective interest rate (as a percent)	8.40%	12.40%	8.40%
Weighted average effective interest rate on outstanding borrowings		13.80%	9.80%
2020 Credit Facility | LIBOR
Debt
Variable spread rate	8.23%
2020 Credit Facility | Term A Loan
Debt
Proceeds from Lines of Credit	$ 20,000
Maximum borrowing capacity	20,000
2020 Credit Facility | Term B Loan
Debt
Maximum borrowing capacity	$ 5,000
Term Loan
Debt
Percentage of original principal amount	3.50%

Debt - Maturities (Details)

Debt - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Estimated future principal payments due
2023	$ 6,666
2024	6,667
2025	5,000
Total principal	$ 18,333	$ 20,000

Debt - Warrants (Details)

Debt - Warrants (Details) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Series B Convertible Preferred Stock | 2020 Credit Facility
Warrants
Warrants issued to purchase shares	50,000
Exercise price per share	$ 6
Common Stock
Warrants
Warrants issued to purchase shares	19,044
Exercise price per share	$ 15.75
Outstanding warrants	19,044	19,044

Common Stock (Details)

Common Stock (Details)	12 Months Ended
	Dec. 31, 2022 Vote $ / shares shares	Dec. 31, 2021 Vote $ / shares shares
Common Stock.
Common stock, shares authorized (in shares) | shares	175,000,000	175,000,000
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Dividend declared	$ 0	$ 0
Number of votes | Vote	1	1

Common Stock - At-the-Market Of

Common Stock - At-the-Market Offering (Details) $ in Millions	Apr. 14, 2022 USD ($)
At the market offering
Common Stock
Maximum amount of shares offered	$ 10

Stock Based Compensation - Equi

Stock Based Compensation - Equity Incentive Plans (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock Based Compensation
Expected dividend yield	0%	0%
2020 Employee Stock Purchase Plan
Stock Based Compensation
Number of shares authorized			300,000
Percent of the Company outstanding shares	1%
Number of shares available for grant	853,307
Purchase prices offering periods	6 months
Number of shares issued	68,049	16,891
2020 Employee Stock Purchase Plan | Maximum
Stock Based Compensation
Number of shares issued	3,200,000
2020 Equity Incentive Plan
Stock Based Compensation
Number of shares authorized			1,500,000
Percent of the Company outstanding shares	4%
Number of shares available for grant	1,850,378
Vesting period	4 years
Expiration period	10 years
2016 plan
Stock Based Compensation
Vesting period	4 years
Expiration period	10 years
Number of additional shares granted	0

Stock Based Compensation - Stoc

Stock Based Compensation - Stock Option Valuation (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Assumptions used
Risk free interest rate	1.75%	0.80%
Expected dividend yield	0%	0%
Expected term (in years)	6 years	6 years 1 month 6 days
Expected volatility	84.28%	78.31%

Stock Based Compensation - St_2

Stock Based Compensation - Stock Option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of options
Beginning balances	3,138,646
Options granted	2,564,140
Options cancelled	(789,567)
Options exercised	(833)
Ending balances	4,912,386	3,138,646
Exercisable	2,045,196
Weighted average exercise price
Beginning balances	$ 10.74
Options granted	2.23
Options cancelled	8.64
Options exercised	0.57
Ending balances	6.63	$ 10.74
Exercisable	$ 7.81
Weighted average remaining contractual term
Weighted average remaining contractual term (in years)	7 years 9 months 18 days	7 years 7 months 6 days
Exercisable	6 years 1 month 6 days
Aggregate intrinsic value
Beginning balances	$ 328
Ending balances		$ 328
Aggregate intrinsic value of stock options exercised	$ 100	$ 6,000
Weighted average grant date fair value of stock options (in dollars per share)	$ 1.58	$ 19

Stock Based Compensation - Rest

Stock Based Compensation - Restricted Stock Units (Details) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Stock Based Compensation
Vesting period	3 years
Shares
Unvested shares beginning balance | shares	275,400
Unvested shares, Vested | shares	(37,960)
Unvested shares, Forfeited | shares	(87,040)
Unvested shares ending balance | shares	150,400
Weighted average grant date fair value
Weighted average grant date fair value, beginning balance | $ / shares	$ 5.57
Weighted average grant date fair value, Vested | $ / shares	5.55
Weighted average grant date fair value, forfeited | $ / shares	5.62
Weighted average grant date fair value, ending balance | $ / shares	$ 5.54

Stock Based Compensation - St_3

Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock Based Compensation
Stock based compensation	$ 5,901	$ 6,150
Unrecognized stock-based compensation expense	$ 10,400
Period of unrecognized stock-based compensation expense	2 years
Research and development
Stock Based Compensation
Stock based compensation	$ 1,883	2,230
General and administrative
Stock Based Compensation
Stock based compensation	$ 4,018	$ 3,920

License and Collaboration Agr_3

License and Collaboration Agreement - Lilly License and Collaboration Agreement (Details) $ in Thousands		12 Months Ended
	Apr. 02, 2018 USD ($) item	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
License and Collaboration Agreement
Collaboration revenue		$ 12,944	$ 9,599
Current liabilities		30,994	34,888
Lilly License and Collaboration Agreement
License and Collaboration Agreement
Amount of research and development costs the Company is responsible to cover	$ 47,500
Threshold amount of research and development costs above which the collaboration partner is responsible for	$ 47,500	47,500
Minimum number of members from the Company and partner on joint research committee | item	3
Non-refundable, non-creditable upfront payment received	$ 62,500
Sales based milestone payments receivable	$ 250,000
Term of the license and collaboration agreement	10 years
Upfront payment	$ 62,500
Allocation of transaction price to combined performance obligation	56,600	12,700
Allocation of transaction price to Phase I supply	5,900	1,300
Increase in total estimated costs expected to be incurred		13,500
Collaboration revenue		12,900	9,600
Current liabilities		12,900	17,000
Contract with customer liability, deferred revenue		$ 12,885	$ 22,367	$ 31,777
Research and development services performance obligation period		2 years
Lilly License and Collaboration Agreement | First Licensed Product | Maximum
License and Collaboration Agreement
Maximum payments to be received from collaboration partner if milestones are met	165,000
Lilly License and Collaboration Agreement | Additional Licensed Product | Maximum
License and Collaboration Agreement
Maximum payments to be received from collaboration partner if milestones are met	$ 160,000

License and Collaboration Agr_4

License and Collaboration Agreement - Contract Liability (Details) - Lilly License and Collaboration Agreement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
License and Collaboration Agreement
Deferred revenues at beginning of period	$ 22,367	$ 31,777
Revenues deferred during the period	3,458
Revenues recognized during the period	(12,940)	(9,410)
Deferred revenues at end of period	$ 12,885	$ 22,367

Patent License Agreement (Detai

Patent License Agreement (Details) - MIT $ in Millions	Feb. 08, 2016 USD ($)
Patent License Agreement
Upfront license issuance fee	$ 0.1
Aggregate license fee payable	$ 2.1
Notice period for default in payment	30 days
Notice period to cure material breach of diligence obligation	90 days
Notice period to cure any other material breach of obligation	60 days
Notice period to terminate the agreement	90 days

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Income tax benefits	$ 0	$ 0
Income tax rate reconciliation
Federal statutory income tax rate	21%	21%
State income taxes, net of federal benefit	6%	6.30%
Federal and state tax credits	7.30%	6.30%
Stock-based compensation	(1.00%)	0.10%
Other	(0.10%)
Change in deferred tax asset valuation allowance	(33.20%)	(33.70%)
Effective income tax rate	0%	0%

Income Taxes - Deferred tax ass

Income Taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 53,823	$ 49,145
Research and development tax credit carryforwards	17,645	14,446
Lease liabilities	2,566	3,670
Deferred revenue	3,525	6,115
Accrued expense and other liabilities	1,066	585
Section 174 capitalized R&E expenses	7,688
Other	2,658	1,627
Total deferred tax assets	88,971	75,588
Less: Valuation Allowance	(86,276)	(71,818)	$ (45,735)
Total net deferred tax assets	2,695	3,770
Deferred tax liabilities:
Lease right-of-use assets	(2,457)	(3,517)
Fixed assets	(238)	(253)
Total deferred tax liabilities	$ (2,695)	$ (3,770)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2019
Tax carryforwards
Operating loss carryforwards		$ 0.4
Orphan tax credit carryforward	$ 4.5
State and Local Jurisdiction
Tax carryforwards
Operating loss carryforwards	193.4
State and Local Jurisdiction | Research and development tax credit
Tax carryforwards
Tax credit carryforwards	5
Federal
Tax carryforwards
Operating loss carryforwards	197.7
Operating loss carryforwards, subject to expiration	10.5
Operating loss carryforwards, not subject to expiration	187.2
Federal | Research and development tax credit
Tax carryforwards
Tax credit carryforwards	$ 9.2

Income Taxes - Changes in valua

Income Taxes - Changes in valuation allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Valuation allowance at beginning of year	$ 71,818	$ 45,735
Increases recorded to income tax provision	14,458	26,083
Valuation allowance at end of year	$ 86,276	$ 71,818

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies
Matching contribution rate (as a percent)	100%
Maximum employee contribution (as a percent)	3%
Company matching contributions	$ 0.3	$ 0.4

Leases - Narratives (Details)

Leases - Narratives (Details) $ in Thousands	1 Months Ended					12 Months Ended
	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2022 USD ($)	Oct. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Aug. 31, 2017 USD ($) Option
Leases
Operating lease renewal term									3 years
Number of options to extend | Option									1
Option to extend						true
Right of use assets	$ 12,863					$ 8,979		$ 1,700
Operating lease liabilities						$ 9,293		$ 1,400
Increase (decrease) in right-of-use asset due to remeasurement	(500)	$ 1,400	$ 1,400	$ 1,100
Increase (decrease) in operating lease, liability due to remeasurement	$ (500)			$ 1,100
Manufacturing Services Agreement
Leases
Up-front suite reservation fee					$ 300
Suite fee					$ 100
Restricted Cash
Leases
Security deposit							$ 500		$ 600

Leases - Leases Cost (Details)

Leases - Leases Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Leases
Operating lease cost:	$ 4,827	$ 6,029
Short term lease cost	679	679
Variable lease cost	724	1,101
Total lease cost	$ 6,230	$ 7,809

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Leases
Cash paid for amounts included in the measurement of operating lease liabilities (operating cash flows)	$ 4,844	$ 5,965
Lease assets obtained in exchange for new operating lease liabilities	$ 68	$ 917
Weighted-average remaining lease term (in years)	2 years 2 months 12 days	3 years 1 month 6 days
Weighted-average discount rate	8.40%	8.40%

Leases - Maturities (Details)

Leases - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2019
Leases
2023	$ 4,599
2024	4,734
2025	802
Total future minimum lease payments	10,135
Less: imputed interest	(842)
Present value of operating lease liability	$ 9,293	$ 1,400

Net Loss per Share - Basic and

Net Loss per Share - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss	$ (43,561)	$ (77,311)
Net loss attributable to common stockholders	$ (43,561)	$ (77,311)
Denominator:
Weighted average common stock outstanding-basic (in shares)	32,405,786	31,860,264
Weighted average common stock outstanding-diluted (in shares)	32,405,786	31,860,264
Net loss per share attributable to common stockholders-basic (in dollars per share)	$ (1.34)	$ (2.43)
Net loss per share attributable to common stockholders-diluted (in dollars per share)	$ (1.34)	$ (2.43)

Net Loss per Share - Potential

Net Loss per Share - Potential dilutive securities excluded from the computation of diluted net loss per share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Net Loss per Share
Warrants to purchase common stock	19,044	19,044
Future issuable shares under the employee stock purchase plan	56,720	33,650
Unvested restricted stock	150,400	275,400
Stock options to purchase common stock	4,912,386	3,138,646
Total	5,138,550	3,466,740

Related Party Transactions (Det

Related Party Transactions (Details) $ in Millions		12 Months Ended
	Feb. 01, 2022 item	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($)	Dec. 09, 2020 item	Dec. 08, 2020 item
Lilly License and Collaboration Agreement
Related Party Transactions
Revenue from related party		$ 12.9	$ 9.5
Deferred revenue from related party		12.9	22.4
Shared Space Agreement
Related Party Transactions
Number of successive periods for renewal of sublease | item	6
Sublease renewal term	1 month
Flagship Pioneering Inc.
Related Party Transactions
Other income			0.4
Cash payments received		3	0.4
Outstanding receivables related to other current assets		0
Flagship Pioneering Inc. | Shared Space Agreement
Related Party Transactions
Other income		$ 0.2
MIT.
Related Party Transactions
Shares issued | shares		333,333
Number of board of directors employed by related party | item				1	2
Expenses with related party		$ 0.4	0.1
Accounts payable to related party			0
MIT. | Maximum
Related Party Transactions
Accounts payable to related party		0.1
Lilly
Related Party Transactions
Accounts receivable from related party		2.2	0.1
Unbilled accounts receivable from related party		$ 1.3	$ 0