Sigilon Therapeutics (SGTX) 10-Q 10 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	001-39746
Entity Registrant Name	Sigilon Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4005543
Entity Address State Or Province	MA
Entity Address, Address Line One	100 Binney Street, Suite 600
Entity Address, City or Town	Cambridge
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		31,529,653
Entity Central Index Key	0001821323
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash	$ 178,789	$ 202,229
Accounts receivable (inclusive of $83 and $63 from a related party at March 31, 2021 and December 31, 2020, respectively)	140	177
Prepaid expenses and other current assets	4,058	1,729
Restricted cash-current	75	75
Total current assets	183,062	204,210
Property and equipment, net	3,107	2,991
Right-of-use assets	16,098	16,731
Restricted cash	1,118	1,118
Total assets	203,385	225,050
Current liabilities:
Accounts payable	2,006	1,988
Accrued expenses and other current liabilities	6,912	7,892
Lease liabilities, current portion	5,427	5,361
Deferred revenue from related party, current portion	20,134	31,777
Total current liabilities	34,479	47,018
Deferred revenue from related party, net of current portion	8,725
Lease liability, net of current portion	11,099	11,893
Long-term debt, net of discount	19,874	19,807
Other liabilities	176	176
Total liabilities	74,353	78,894
Commitments and contingencies (Note 9)
Stockholders? equity
Common stock, par value $0.001 per share; 175,000,000 shares authorized at March 31, 2021 and December 31, 2020; 31,501,952 and 31,464,989 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	32	31
Preferred stock, par value $0.001 per share; 25,000,000 shares authorized at March 31, 2021 and December 31, 2020; no shares issued and outstanding at March 31, 2021 and December 31, 2020
Additional paid-in capital	283,901	282,053
Accumulated deficit	(154,901)	(135,928)
Total stockholders' equity	129,032	146,156
Total liabilities, convertible preferred stock and stockholders? equity	$ 203,385	$ 225,050

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Condensed Consolidated Balance Sheets
Accounts receivable from a related party	$ 83	$ 63
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)	31,501,952	31,464,989
Common stock, shares outstanding (in shares)	31,501,952	31,464,989
Preferred Stock par value (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

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue
Collaboration revenue (inclusive of $2,932 and $3,466 from a related party for the three months ended March 31, 2021 and 2020, respectively)	$ 2,958	$ 3,466
Operating expenses:
Research and development (inclusive of related party payments to MIT of $66 and $220 for the three months ended March 31, 2021 and 2020, respectively)	15,985	13,274
General and administrative	5,540	2,871
Total operating expenses	21,525	16,145
Loss from operations	(18,567)	(12,679)
Other income (expense), net:
Interest income	86	203
Interest expense	(488)	(208)
Other expense	(4)	(16)
Change in fair value of preferred stock warrant liability		(35)
Total other expense, net	(406)	(56)
Net loss and comprehensive loss	$ (18,973)	$ (12,735)
Net loss per share attributable to common stockholders-basic and diluted	$ (0.60)	$ (2.55)
Weighted average common stock outstanding-basic and diluted	31,487,710	4,984,527

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from related party	$ 2,932	$ 3,466
MIT
Payments to related party	$ 66	$ 220

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2019	$ 90,206	$ 5	$ 3,553	$ (81,320)	$ (77,762)
Beginning balance (in shares) at Dec. 31, 2019	31,836,001	5,221,628
Issuance of convertible preferred stock, net of issuance costs	$ 26,946
Issuance of convertible preferred stock, net of issuance costs (in shares)	4,500,000
Issuance of common stock upon exercise of stock options			121		121
Issuance of common stock upon exercise of stock options (in shares)		93,109
Stock-based compensation expense			667		667
Net loss				(12,735)	(12,735)
Ending balance at Mar. 31, 2020	$ 117,152	$ 5	4,341	(94,055)	(89,709)
Ending balance (in shares) at Mar. 31, 2020	36,336,001	5,314,737
Beginning balance at Dec. 31, 2019	$ 90,206	$ 5	3,553	(81,320)	(77,762)
Beginning balance (in shares) at Dec. 31, 2019	31,836,001	5,221,628
Net loss					(54,600)
Ending balance at Dec. 31, 2020		$ 31	282,053	(135,928)	146,156
Ending balance (in shares) at Dec. 31, 2020		31,464,989
Issuance of common stock upon exercise of stock options		$ 1	144		$ 145
Issuance of common stock upon exercise of stock options (in shares)		36,963			36,963
Stock-based compensation expense			1,704		$ 1,704
Net loss				(18,973)	(18,973)
Ending balance at Mar. 31, 2021		$ 32	$ 283,901	$ (154,901)	$ 129,032
Ending balance (in shares) at Mar. 31, 2021		31,501,952

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Stock issuance costs	$ 1
Convertible Preferred Stock
Stock issuance costs	$ 54

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (18,973)	$ (12,735)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization expense	247	202
Stock-based compensation expense	1,704	667
Non-cash lease expense	1,197	745
Non-cash interest expense	67	5
Change in fair value of preferred stock warrant liability		35
Changes in operating assets and liabilities:
Accounts receivable	37	(168)
Prepaid expenses and other current assets	(2,329)	(1,043)
Accounts payable	578	2,355
Accrued expenses and other current liabilities	(991)	(1,029)
Lease liabilities	(1,292)	(938)
Deferred revenue	(2,918)	(3,298)
Net cash used in operating activities	(22,673)	(15,202)
Cash flows from investing activities:
Purchase of property and equipment	(290)	(190)
Net cash used in investing activities	(290)	(190)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, including deemed dividend, net of issuance costs		26,946
Payments of deferred offering costs	(622)	(1)
Proceeds from the exercise of common stock options	145	121
Net cash (used in) provided by financing activities	(477)	27,066
Net increase in cash and restricted cash	(23,440)	11,674
Cash and restricted cash at beginning of period	203,422	76,645
Cash and restricted cash at end of period	179,982	88,319
Supplemental disclosure of cash flow information:
Cash paid for interest	420	209
Supplemental disclosures of noncash investing and financing activities:
Lease assets obtained in exchange for lease liabilities	564	1,078
Deferred offering costs included in accounts payable		$ 18
Purchases of property and equipment included in accounts payable and accrued expenses	$ 108

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	Sigilon Therapeutics, Inc. Notes to the Condensed Consolidated Financial Statements (Unaudited) ​ 1. Nature of the Business and Basis of Presentation Sigilon Therapeutics, Inc. (the “Company” or “Sigilon”) is a biopharmaceutical company with a platform of biomedical technologies and cell therapies created to avoid host detection and foreign body responses with a goal of providing functional cures to patients with chronic diseases. The Company was incorporated on May 14, 2015 under the laws of the State of Delaware. On December 8, 2020, the Company closed its initial public offering (“IPO”) of 8,050,000 shares of its common stock, including the exercise in full by the underwriters of their option to purchase up to 1,050,000 additional shares of common stock, at a public offering price of $18.00 per share. The aggregate net proceeds to the Company from the offering was $131.8 million. 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. 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 accompanying Unaudited Condensed Financial Statements have been prepared in accordance with (i) U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and (ii) the instructions to Form 10-Q and Article 8 of Regulation S-X. Accordingly, such financial statements do not include all the information and footnotes required by U.S. GAAP for a complete set of financial statements. In the opinion of management, the Unaudited Condensed Financial Statements include all adjustments, consisting of normal recurring accruals and other adjustments, considered necessary for a fair statement of the Company’s financial position, results of operations, stockholders’ equity (deficit) and cash flows as of and for the periods presented. The accompanying Condensed Balance Sheet as of December 31, 2020 was derived from the Company’s audited financial statements at that date but does not include all of the footnote disclosures required by U.S. GAAP. The Unaudited Condensed Financial Statements should be read in conjunction with the Company’s audited financial statements and related notes included in its Annual Report on Form 10-K for the year ended December 31, 2020 (the “2020 Form 10-K”). The Company’s significant accounting policies are described in Note 2 to the Notes to Financial Statements in the 2020 Form 10-K and are updated, as necessary, in subsequent Form 10-Q filings. Reverse Stock Split 1 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 March 31, 2021, 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 $19.0 million for the three months ended March 31, 2021 and $54.6 million for the year ended December 31, 2020. In addition, as of March 31, 2021, the Company had an accumulated deficit of $154.9 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 of $178.8 million as of March 31, 2021 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 Quarterly 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. Impact of COVID-19 In December 2019, a novel strain of coronavirus, which causes the disease known as COVID-19, was reported to have surfaced in Wuhan, China. Since then, COVID-19 coronavirus has spread globally. In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic and the U.S. government imposed travel restrictions on travel between the United States, Europe and certain other countries. The outbreak and government measures taken in response have had a significant impact, both direct and indirect, on businesses and commerce, as certain worker shortages have occurred, supply chains have been disrupted, and facilities and production have been suspended. The future progression of the pandemic and its effects on the Company’s business and operations are uncertain. The COVID-19 pandemic has impacted and may continue to impact the clinical sites and startup activities for the Company’s Phase 1/2 clinical trial, including third-party manufacturing and logistics providers, which would disrupt its clinical supply chain or the availability or cost of materials, and it may affect the Company’s ability to timely complete our clinical trials and delay the initiation and/or enrollment of any future clinical trials, disrupt regulatory activities or have other adverse effects on its business and operations. The Company is monitoring the potential impact of COVID-19 on its business and financial statements. The effects of the public health directives and the Company’s work-from-home policies may negatively impact productivity, disrupt its business and delay clinical programs and timelines and future clinical trials, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on its ability to conduct business in the ordinary course. These and similar, and perhaps more severe, disruptions in the Company’s operations could negatively impact business, results of operations and financial condition, including its ability to obtain financing. To date, the Company has not incurred impairment losses in the carrying values of its assets as a result of the pandemic and are not aware of any specific related event or circumstance that would require the Company to revise its estimates reflected in financial statements. The Company cannot be certain what the overall impact of the COVID-19 pandemic will be on its business and prospects. The extent to which the COVID-19 pandemic will directly or indirectly impact its business, results of operations, financial condition and liquidity, including planned and future clinical trials and research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19, the actions taken to contain or treat it, and the duration and intensity of the related effects.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
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, the valuations of common stock, stock-based awards and the preferred stock warrant liability. 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 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 March 31, 2021 and December 31, 2020, all of the Company’s accounts receivable were related to three and two customers, respectively. One of these receivables, which represented 36% of the Company’s total receivables as of March 31, 2021 and December 31, 2020, is related to the Company’s collaboration agreements with Eli Lilly and Company (Note 8) 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, its programs could be adversely affected by an interruption in the availability of these raw materials. Net Income (Loss) per Share The Company follows the two-class method when computing net income (loss) per share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. For purposes of this calculation, outstanding stock options, unvested restricted common stock, and convertible preferred stock are considered potential dilutive common stock and are excluded from the computation of diluted net income (loss) per share attributable to common stockholders if their effect is anti-dilutive. The Company’s convertible preferred stock contractually entitles the holders of such shares to participate in dividends but do not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the three months ended March 31, 2021 and 2020. 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 In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements As of March 31, 2021 and December 31, 2020 the Company did not have any financial assets and liabilities that were measured at fair value on a recurring basis. The carrying value of the Company’s long-term debt approximates its fair value at March, 31 2021 and December 31, 2020 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. ​

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2021
Property and Equipment, Net
Property and Equipment, Net	4. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 4,670 ​ $ 4,325 Leasehold improvements ​ 60 ​ 60 Furniture and fixtures ​ 620 ​ 620 Computers and software ​ 48 ​ 30 ​ ​ 5,398 ​ 5,035 Less: Accumulated depreciation and amortization ​ (2,291) ​ (2,044) Total property and equipment, net ​ $ 3,107 ​ $ 2,991 ​ Depreciation and amortization expense for the three months ended March 31, 2021 and 2020 was $0.2 million and $0.2 million, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2021
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): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 ​ 2020 Employee compensation and benefits ​ $ 1,622 ​ $ 2,910 External research and development costs ​ 4,194 ​ 3,584 Legal and professional fees ​ 750 ​ 1,155 Other ​ 346 ​ 243 Total accrued expenses and other current liabilities ​ $ 6,912 ​ $ 7,892 ​

Debt

Debt	3 Months Ended
	Mar. 31, 2021
Debt
Debt	6. Debt The following discussion of the Company’s debt should be read in conjunction with Note 8 to the Notes to the Consolidated Financial Statements in the 2020 Form 10-K. As of March 31, 2021 and December 31, 2020, long-term debt consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Principal amount of long‑term debt ​ $ 20,000 ​ $ 20,000 Less: Current portion of long‑term debt ​ ​ — ​ — Long‑term debt, net of current portion ​ 20,000 ​ 20,000 Final debt payment liability ​ ​ 700 ​ ​ 700 Debt discount, net of accretion ​ (826) ​ (893) Long‑term debt, net of discount and current portion ​ $ 19,874 ​ $ 19,807 ​ As of March 31, 2021 and December 31, 2020, the interest rate applicable to borrowings under the 2020 Credit Facility was 8.40%. During the three months ended March 31, 2021 and 2020, the weighted average effective interest rate on outstanding borrowings was approximately 9.8% and 5.3%, respectively. The estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ March 31, ​ 2021 2021 (Remaining nine months) ​ $ — 2022 ​ 1,666 2023 ​ 6,667 2024 ​ ​ 6,667 2025 ​ ​ 5,000 ​ ​ $ 20,000 ​ As of March 31, 2021, the Company was in full compliance with all financial covenants of the Loan Agreement.

Stock Based Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2021
Stock Based Compensation
Stock Based Compensation	7. Stock Based Compensation The Company uses stock options to provide long-term incentives to its employees, non-employee directors and certain consultants. The Company has three equity compensation plans under which awards are currently authorized for issuance: the 2020 Employee Stock Purchase Plan, the 2020 Equity Incentive Plan and the 2016 Equity Incentive Plan. As of March 31, 2021 there were 614,649 shares available for issuance under the 2020 Employee Stock Purchase Plan, 1,860,215 shares available for issuance under the 2020 Equity Incentive Plan and no shares available for issuance under the 2016 Equity Incentive Plan. 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 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 Risk-free interest rate ​ 0.66 % 1.16 % Expected dividend yield ​ 0.00 % 0.00 % Expected term (in years) ​ 6.1 ​ 6.0 ​ Expected volatility ​ 78.39 % 82.60 % ​ Stock Option Activity The following table summarizes the Company’s stock option activity since December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ ​ ​ ​ ​ ​ ​ Weighted ​ remaining ​ Aggregate ​ ​ Number of ​ average ​ contractual term ​ intrinsic value ​ ​ options ​ exercise price ​ (in years) ​ (in thousands) Balances at December 31, 2020 3,872,457 ​ $ 4.98 7.5 ​ $ 166,728 Options granted 964,981 ​ 39.55 ​ ​ ​ Options cancelled (162,076) ​ 9.39 ​ ​ ​ Options exercised (36,963) ​ 3.90 ​ ​ ​ ​ Balances at March 31, 2021 ​ 4,638,399 ​ ​ 12.02 ​ 7.7 ​ ​ 64,482 Vested and expected to vest at March 31, 2021 4,638,399 ​ $ 12.02 7.7 ​ $ 64,482 Exercisable at March 31, 2021 2,120,779 ​ $ 3.58 6.4 ​ $ 39,811 ​ 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 three months ended March 31, 2021 and 2020 were $1.0 million and $0.7 million, respectively. The weighted average grant date fair value of stock options during the three months ended March 31, 2021 and 2020 was $26.64 and $6.54, respectively. Restricted Stock In February 2016, the Company issued and sold 4,633,331 shares of restricted stock to its nonemployee and employee founders for $0.0003 per share. The shares vested 25% upon the first anniversary of the issuance of shares of Series A Preferred Stock and then 6.25% per quarter through the fourth anniversary of the vesting commencement date of February 5, 2016. The unvested shares were subject to repurchase by the Company, at the holder’s original purchase price in the event the holder’s service with the Company voluntarily or involuntarily terminates. Proceeds from the issuance and sale of restricted common stock are recorded as a liability within accrued expenses and other current liabilities for those restricted shares expected to vest in the next 12 months and other liabilities for those restricted shares expected to vest in greater than 12 months on the balance sheet. The liability for unvested common stock subject to repurchase is then reclassified to additional paid-in capital as the Company’s repurchase right lapses. As of March 31, 2021 and December 31, 2020, there were no shares of unvested restricted stock. The aggregate intrinsic value of restricted stock awards that vested during the three ended March 31, 2020 was $2.6 million. The aggregate intrinsic value of restricted stock awards is calculated as the positive difference between the prices paid, if any, of the restricted stock awards and the fair value of the Company’s common stock. Stock-based Compensation Expense Stock-based compensation expense related to stock options and restricted stock awards was classified in the statement of operations and comprehensive loss as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ 2021 2020 Research and development ​ $ 839 ​ $ 246 General and administrative ​ 865 ​ 421 ​ ​ $ 1,704 ​ $ 667 ​ As of March 31, 2021, total unrecognized stock-based compensation expense related to unvested stock-based awards was $31.0 million, which is expected to be recognized over a weighted average period of 3.5

License and Collaboration Agree

License and Collaboration Agreement	3 Months Ended
	Mar. 31, 2021
License and Collaboration Agreement
License and Collaboration Agreement	8. 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 March 31, 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, 2020, 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. This resulted in an increase to total estimated costs expected to be incurred of $23.0 million for the year ended December 31, 2020. This 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, 2020, the transaction price for the Combined Performance Obligation increased by $17.9 million 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. Additionally, the transaction price for the Phase 1 supply performance obligation increased by $1.9 million. During the three months ended March 31, 2021, consistent with the Company’s presentation to the JRC, the Company revised the estimated timeline for the completion of certain activities under the 2018 Lilly Agreement. During the three months ended March 31, 2021 and 2020, the Company recognized $2.9 million and $3.1 million, respectively, of collaboration revenue. As of March 31, 2021 and December 31, 2020, the Company recorded as a contract liability deferred revenue of $28.9 million and $31.8 million, respectively, of which, $20.1 million and $31.8 million, respectively, were current liabilities in the accompanying balance sheet. As of March 31, 2021 and December 31, 2020 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 and 1.5 years, respectively. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Deferred revenues at beginning of period ​ $ 31,777 ​ $ 44,690 Revenues deferred during the period ​ — ​ — Revenues recognized during the period ​ (2,918) ​ (3,298) Deferred revenues at end of period ​ $ 28,859 ​ $ 41,392 ​

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies.
Commitments and Contingencies	9. Commitments and Contingencies 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.

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2021
Net Loss per Share
Net Loss per Share	10. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Numerator: ​ ​ Net loss ​ $ (18,973) ​ $ (12,735) Net loss attributable to common stockholders ​ $ (18,973) ​ $ (12,735) Denominator: ​ ​ ​ ​ Weighted average common stock outstanding—basic and diluted ​ 31,487,710 ​ 4,984,527 Net loss per share attributable to common stockholders—basic and diluted ​ $ (0.60) ​ $ (2.55) ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Series A Convertible preferred stock (as converted to common stock) — ​ 10,201,185 Series B Convertible preferred stock (as converted to common stock) — ​ 5,948,143 Warrants to purchase Series A‑1 convertible preferred stock (as converted to common stock) — ​ 37,036 Warrants to purchase Series B convertible preferred stock (as converted to common stock) — ​ 11,111 Warrants to purchase common stock ​ 19,044 ​ — Stock options to purchase common stock 4,638,399 ​ 4,040,556 ​ 4,657,443 20,238,031 ​

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2021
Related Party Transactions
Related Party Transactions	11. Related Party Transactions As described in Note 11 of the Company’s 2020 Form 10-K, 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. Through the completion of the Company’s initial public offering in December 2020, two members of the Company’s board of directors were employed by MIT and subsequent to the initial public offering one member of the Company’s board of directors was employed by MIT. The Company incurs charges for the use of certain MIT equipment and facilities. For the three months ended March 31, 2021 and 2020, the Company incurred expenses of $0.1 million and $0.2 million related to business with MIT, respectively. The Company paid five of its co-founders, two of whom were members of the board of directors employed by MIT, $0.1 million for the three months ended March 31, 2020 for ongoing consulting services. As of March 31, 2021 and December 31, 2020, there was $0 and less than $0.1 million recorded in accounts payable as due to these related parties, respectively. As described in Note 8 above, the Company entered into the 2018 Lilly Agreement with Lilly in April 2018. During the three months ended March 31, 2021 and 2020, the Company recognized $2.9 million and $3.5 million, respectively, of related party revenue associated with the Lilly collaboration agreements. As of March 31, 2021 and December 31, 2020, the Company had deferred revenue related to the collaboration agreements with Lilly of $28.9 million and $31.8 million, respectively. At March 31, 2021 and December 31, 2020, the Company had $0.1 million of outstanding receivables with Lilly. 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 the initial term ends on December 31, 2021 and shall automatically renew for successive one-month periods until either party terminates the agreement. Under this agreement, the Company recorded other income of $0.1 million during the three months ended March 31, 2021. The Company received cash payments of less than $0.1 million during the three months ended March 31, 2021.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
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, the valuations of common stock, stock-based awards and the preferred stock warrant liability. 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 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 March 31, 2021 and December 31, 2020, all of the Company’s accounts receivable were related to three and two customers, respectively. One of these receivables, which represented 36% of the Company’s total receivables as of March 31, 2021 and December 31, 2020, is related to the Company’s collaboration agreements with Eli Lilly and Company (Note 8) 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, its programs could be adversely affected by an interruption in the availability of these raw materials.
Net Income (Loss) per Share	Net Income (Loss) per Share The Company follows the two-class method when computing net income (loss) per share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. For purposes of this calculation, outstanding stock options, unvested restricted common stock, and convertible preferred stock are considered potential dilutive common stock and are excluded from the computation of diluted net income (loss) per share attributable to common stockholders if their effect is anti-dilutive. The Company’s convertible preferred stock contractually entitles the holders of such shares to participate in dividends but do not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the three months ended March 31, 2021 and 2020.
Recently Adopted 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 In December 2019, the FASB issued ASU 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2021
Property and Equipment, Net
Schedule of Property And Equipment	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Laboratory equipment ​ $ 4,670 ​ $ 4,325 Leasehold improvements ​ 60 ​ 60 Furniture and fixtures ​ 620 ​ 620 Computers and software ​ 48 ​ 30 ​ ​ 5,398 ​ 5,035 Less: Accumulated depreciation and amortization ​ (2,291) ​ (2,044) Total property and equipment, net ​ $ 3,107 ​ $ 2,991

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
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): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 ​ 2020 Employee compensation and benefits ​ $ 1,622 ​ $ 2,910 External research and development costs ​ 4,194 ​ 3,584 Legal and professional fees ​ 750 ​ 1,155 Other ​ 346 ​ 243 Total accrued expenses and other current liabilities ​ $ 6,912 ​ $ 7,892

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2021
Debt
Schedule of long-term debt	As of March 31, 2021 and December 31, 2020, long-term debt consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Principal amount of long‑term debt ​ $ 20,000 ​ $ 20,000 Less: Current portion of long‑term debt ​ ​ — ​ — Long‑term debt, net of current portion ​ 20,000 ​ 20,000 Final debt payment liability ​ ​ 700 ​ ​ 700 Debt discount, net of accretion ​ (826) ​ (893) Long‑term debt, net of discount and current portion ​ $ 19,874 ​ $ 19,807
Schedule of estimated future principal payments	The estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ March 31, ​ 2021 2021 (Remaining nine months) ​ $ — 2022 ​ 1,666 2023 ​ 6,667 2024 ​ ​ 6,667 2025 ​ ​ 5,000 ​ ​ $ 20,000

Stock Based Compensation (Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Stock Based Compensation
Schedule of weighted average assumption for grant date fair value of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 Risk-free interest rate ​ 0.66 % 1.16 % Expected dividend yield ​ 0.00 % 0.00 % Expected term (in years) ​ 6.1 ​ 6.0 ​ Expected volatility ​ 78.39 % 82.60 %
Schedule of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ ​ ​ ​ ​ ​ ​ Weighted ​ remaining ​ Aggregate ​ ​ Number of ​ average ​ contractual term ​ intrinsic value ​ ​ options ​ exercise price ​ (in years) ​ (in thousands) Balances at December 31, 2020 3,872,457 ​ $ 4.98 7.5 ​ $ 166,728 Options granted 964,981 ​ 39.55 ​ ​ ​ Options cancelled (162,076) ​ 9.39 ​ ​ ​ Options exercised (36,963) ​ 3.90 ​ ​ ​ ​ Balances at March 31, 2021 ​ 4,638,399 ​ ​ 12.02 ​ 7.7 ​ ​ 64,482 Vested and expected to vest at March 31, 2021 4,638,399 ​ $ 12.02 7.7 ​ $ 64,482 Exercisable at March 31, 2021 2,120,779 ​ $ 3.58 6.4 ​ $ 39,811
Schedule of stock based compensation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ 2021 2020 Research and development ​ $ 839 ​ $ 246 General and administrative ​ 865 ​ 421 ​ ​ $ 1,704 ​ $ 667

License and Collaboration Agr_2

License and Collaboration Agreement (Tables)	3 Months Ended
	Mar. 31, 2021
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): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Deferred revenues at beginning of period ​ $ 31,777 ​ $ 44,690 Revenues deferred during the period ​ — ​ — Revenues recognized during the period ​ (2,918) ​ (3,298) Deferred revenues at end of period ​ $ 28,859 ​ $ 41,392

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2021
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): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Numerator: ​ ​ Net loss ​ $ (18,973) ​ $ (12,735) Net loss attributable to common stockholders ​ $ (18,973) ​ $ (12,735) Denominator: ​ ​ ​ ​ Weighted average common stock outstanding—basic and diluted ​ 31,487,710 ​ 4,984,527 Net loss per share attributable to common stockholders—basic and diluted ​ $ (0.60) ​ $ (2.55)
Schedule of potential dilutive securities excluded from the computation of diluted net loss per share	​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Series A Convertible preferred stock (as converted to common stock) — ​ 10,201,185 Series B Convertible preferred stock (as converted to common stock) — ​ 5,948,143 Warrants to purchase Series A‑1 convertible preferred stock (as converted to common stock) — ​ 37,036 Warrants to purchase Series B convertible preferred stock (as converted to common stock) — ​ 11,111 Warrants to purchase common stock ​ 19,044 ​ — Stock options to purchase common stock 4,638,399 ​ 4,040,556 ​ 4,657,443 20,238,031

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details) $ / shares in Units, $ in Thousands	Dec. 08, 2020USD ($)$ / sharesshares	Nov. 25, 2020	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Nature of the Business and Basis of Presentation
Reverse stock split		0.44
Net loss			$ 18,973	$ 12,735	$ 54,600
Accumulated deficit			154,901		135,928
Cash			$ 178,789		$ 202,229
IPO
Nature of the Business and Basis of Presentation
Shares issued | shares	8,050,000
Offering price | $ / shares	$ 18
Aggregate net proceeds	$ 131,800
Over-Allotment Option
Nature of the Business and Basis of Presentation
Shares issued | shares	1,050,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - Accounts receivable - Customer Concentration Risk - customer	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies
Number of customers	3	2
Lilly
Summary of Significant Accounting Policies
Concentrations of credit risk	36.00%	36.00%

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property and Equipment, Net
Property, Plant and Equipment, Gross	$ 5,398		$ 5,035
Less: Accumulated depreciation and amortization	(2,291)		(2,044)
Total property and equipment, net	3,107		2,991
Depreciation and amortization expense	247	$ 202
Laboratory equipment
Property and Equipment, Net
Property, Plant and Equipment, Gross	4,670		4,325
Leasehold improvements
Property and Equipment, Net
Property, Plant and Equipment, Gross	60		60
Furniture and fixtures
Property and Equipment, Net
Property, Plant and Equipment, Gross	620		620
Computers and software
Property and Equipment, Net
Property, Plant and Equipment, Gross	$ 48		$ 30

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued Expenses and Other Current Liabilities
Employee compensation and benefits	$ 1,622	$ 2,910
External research and development costs	4,194	3,584
Legal and professional fees	750	1,155
Other	346	243
Total accrued expenses and other current liabilities	$ 6,912	$ 7,892

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt
Principal amount of long-term debt	$ 20,000	$ 20,000
Total estimated future principal payments	20,000	20,000
Final debt payment liability	700	700
Debt discount, net of accretion	(826)	(893)
Long-term debt, net of discount and current portion	$ 19,874	$ 19,807

Debt - Narrative (Details)

Debt - Narrative (Details) - 2020 Credit Facility	Mar. 31, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Interest rate	8.40%
Weighted average effective interest rate on outstanding borrowings	9.80%	5.30%

Debt - Maturities (Details)

Debt - Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Long-term Debt, Fiscal Year Maturity [Abstract]
2022	$ 1,666
2023	6,667
2024	6,667
2025	5,000
Total estimated future principal payments	$ 20,000	$ 20,000

Stock Based Compensation - Equi

Stock Based Compensation - Equity Incentive Plans (Details)	Mar. 31, 2021shares
2020 Employee Stock Purchase Plan
Stock Based Compensation
Number of shares available for grant	614,649
2020 Equity Incentive Plan
Stock Based Compensation
Number of shares available for grant	1,860,215
2016 Equity Incentive Plan
Stock Based Compensation
Number of shares available for grant	0

Stock Based Compensation - Stoc

Stock Based Compensation - Stock Option Valuation (Details)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Assumptions used
Expected dividend yield	0.00%
Employee and directors
Assumptions used
Risk free interest rate	0.66%	1.16%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6 years 1 month 6 days	6 years
Expected volatility	78.39%	82.60%

Stock Based Compensation - St_2

Stock Based Compensation - Stock Option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Number of options
Balances	3,872,457
Options granted	964,981
Options cancelled	(162,076)
Options exercised	(36,963)
Balances	4,638,399		3,872,457
Vested and expected to vest	4,638,399
Exercisable	2,120,779
Weighted average exercise price
Balances	$ 4.98
Options granted	39.55
Options cancelled	9.39
Options exercised	3.90
Balances	12.02		$ 4.98
Vested and expected to vest	12.02
Exercisable	$ 3.58
Weighted average remaining contractual term
Balances	7 years 8 months 12 days		7 years 6 months
Vested and expected to vest	7 years 8 months 12 days
Exercisable	6 years 4 months 24 days
Aggregate intrinsic value
Balances	$ 64,482		$ 166,728
Vested and expected to vest	64,482
Exercisable	39,811
Aggregate intrinsic value of stock options exercised	$ 1,000	$ 700
Weighted average grant date fair value of stock options	$ 26.64	$ 6.54

Stock Based Compensation - Rest

Stock Based Compensation - Restricted Stock (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Feb. 29, 2016	Mar. 31, 2020	Mar. 31, 2021	Dec. 31, 2020
Stock Based Compensation
Unvested shares			0	0
Nonemployee and employee founders
Stock Based Compensation
Restricted stock issued, shares	4,633,331
Share Price	$ 0.0003
Aggregate intrinsic value, vested		$ 2.6
25% Vesting | Nonemployee and employee founders
Stock Based Compensation
Vesting percentage	25.00%
6.25% Vesting | Nonemployee and employee founders
Stock Based Compensation
Vesting percentage	6.25%

Stock Based Compensation - St_3

Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock Based Compensation
Stock based compensation	$ 1,704	$ 667
Unrecognized stock-based compensation expense	$ 31,000
Period of unrecognized stock-based compensation expense	3 years 6 months
Research and development
Stock Based Compensation
Stock based compensation	$ 839	246
General and administrative
Stock Based Compensation
Stock based compensation	$ 865	$ 421

License and Collaboration Agr_3

License and Collaboration Agreement - Lilly License and Collaboration Agreement (Details) - USD ($) $ in Thousands	Apr. 02, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
License and Collaboration Agreement
Collaboration revenue		$ 2,958	$ 3,466
Current liabilities		34,479		$ 47,018
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
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			17,900
Allocation of transaction price to Phase I supply	5,900			1,900
Increase in total estimated costs expected to be incurred				23,000
Collaboration revenue		2,900	$ 3,100
Contract with customer liability current		28,900		31,800
Current liabilities		$ 20,100		$ 31,800
Research and development services performance obligation period		2 years		1 year 6 months
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
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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
License and Collaboration Agreement
Deferred revenues at beginning of period	$ 31,777	$ 44,690
Revenues recognized during the period	(2,918)	(3,298)
Deferred revenues at end of period	$ 28,859	$ 41,392

Net Loss per Share - Basic and

Net Loss per Share - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Numerator:
Net loss	$ (18,973)	$ (12,735)	$ (54,600)
Net loss attributable to common stockholders	$ (18,973)	$ (12,735)
Denominator:
Weighted average common stock outstanding-basic and diluted	31,487,710	4,984,527
Net loss per share attributable to common stockholders-basic and diluted	$ (0.60)	$ (2.55)

Net Loss per Share - Potential

Net Loss per Share - Potential dilutive securities excluded from the computation of diluted net loss per share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net loss per share
Warrants to purchase convertible preferred stock (as converted to common stock)	19,044
Stock options to purchase common stock	4,638,399	4,040,556
Total diluted shares	4,657,443	20,238,031
Series A Preferred Stock
Net loss per share
Convertible preferred stock (as converted to common stock)		10,201,185
Series B Convertible Preferred Stock
Net loss per share
Convertible preferred stock (as converted to common stock)		5,948,143
Warrants to purchase convertible preferred stock (as converted to common stock)		11,111
Series A-1 Convertible preferred stock
Net loss per share
Warrants to purchase convertible preferred stock (as converted to common stock)		37,036

Related Party Transactions (Det

Related Party Transactions (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)shares	Mar. 31, 2020USD ($)item	Dec. 31, 2020USD ($)	Dec. 09, 2020item	Dec. 08, 2020item
Related Party Transactions
Number of co-cofounders | item		5
Accounts payable to related party	$ 0
Revenue from related party	2,932	$ 3,466
Maximum
Related Party Transactions
Accounts payable to related party			$ 100
Lilly License and Collaboration Agreement
Related Party Transactions
Revenue from related party	2,900	$ 3,500
Deferred revenue from related party	28,900		31,800
Accounts receivable	100		$ 100
Flagship Pioneering Inc.
Related Party Transactions
Other income	100
Flagship Pioneering Inc. | Maximum
Related Party Transactions
Cash payments received	$ 100
MIT
Related Party Transactions
Shares issued | shares	333,333
Number Of Board Of Directors | item		2
Number of board of directors employed by related party | item					2
Related Party Transaction, Expenses from Transactions with Related Party	$ 100	$ 200
Amount of transaction		$ 100
MIT | Private Placement
Related Party Transactions
Number of board of directors employed by related party | item				1