Atreca Inc - Ordinary Shares (BCEL) 10-K 29 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 29, 2023	Jun. 30, 2022
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2022
Entity File Number	001-38935
Entity Registrant Name	ATRECA, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-3723255
Entity Address, Address Line One	835 Industrial Road, Suite 400
Entity Address, City or Town	San Carlos
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94070
City Area Code	650
Local Phone Number	595-2595
Title of 12(b) Security	Class A Common Stock
Trading Symbol	BCEL
Security Exchange Name	NASDAQ
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	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
Entity Shell Company	false
Entity Public Float			$ 48.8
Auditor Name	WithumSmith+Brown, PC
Auditor Firm ID	100
Auditor Location	San Francisco, California
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0001532346
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		32,441,143
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		6,715,441

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current Assets
Cash and cash equivalents	$ 30,819	$ 94,746
Investments	39,676	22,287
Prepaid expenses and other current assets	7,531	5,337
Total current assets	78,026	122,370
Property and equipment, net	37,972	43,015
Operating lease right-of-use assets	36,056
Long-term investments		31,042
Deposits and other	2,976	3,630
Total assets	155,030	200,057
Current Liabilities
Accounts payable	1,741	3,352
Accrued expenses	9,681	11,555
Operating lease liabilities, current portion	3,544
Other current liabilities	1,327	1,992
Total current liabilities	16,293	16,899
Deferred rent		28,229
Operating lease liabilities, net of current portion	60,331
Total liabilities	76,624	45,128
Commitment and contingencies (Note 9)
Stockholders' equity
Additional paid-in capital	535,592	514,794
Accumulated other comprehensive loss	(266)	(102)
Accumulated deficit	(456,924)	(359,767)
Total stockholders' equity	78,406	154,929
Total liabilities and stockholders' equity	155,030	200,057
Class A common stock
Stockholders' equity
Common stock	3	3
Class B common stock
Stockholders' equity
Common stock	$ 1	$ 1

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Class A common stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	650,000,000	650,000,000
Common stock, shares issued	32,351,950	31,043,356
Common stock, shares outstanding	32,351,950	31,043,356
Class B common stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	6,715,441	6,715,441
Common stock, shares outstanding	6,715,441	6,715,441

Statements of Operations

Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Expenses
Research and development	$ 66,829	$ 78,349
General and administrative	31,466	31,954
Asset impairment	449	0
Total expenses	98,744	110,303
Interest and other income (expense)
Other income	770	851
Interest income	817	207
Interest expense		(3)
Loss on disposal of property and equipment		(77)
Loss before income tax expense	(97,157)	(109,325)
Income tax expense		(1)
Net loss	$ (97,157)	$ (109,326)
Net loss per share, basic	$ (2.52)	$ (2.95)
Net loss per share, diluted	$ (2.52)	$ (2.95)
Weighted-average shares used in computing net loss per share, basic	38,593,894	37,038,195
Weighted-average shares used in computing net loss per share, diluted	38,593,894	37,038,195

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Statements of Operations and Comprehensive Loss
Net loss	$ (97,157)	$ (109,326)
Other comprehensive loss:
Unrealized loss on available-for-sale debt securities	(164)	(160)
Comprehensive loss	$ (97,321)	$ (109,486)

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balances at beginning at Dec. 31, 2020	$ 4	$ 492,436	$ 58	$ (250,441)	$ 242,057
Balances at beginning (in shares) at Dec. 31, 2020	36,804,603
Issuance of common stock through "at-the-market" offering, net of underwriter discount and issuance costs		4,372			4,372
Issuance of common stock through "at-the-market" offering, net of underwriter discount and issuance costs (in shares)	793,361
Issuance of common stock upon exercise of options		273			273
Issuance of common stock upon exercise of options (in shares)	47,061
Issuance of common stock under the Employee Stock Purchase Plan		837			837
Issuance of common stock under the Employee Stock Purchase Plan (shares)	113,772
Stock-based compensation		16,876			16,876
Unrealized loss on available-for-sale debt securities			(160)		(160)
Net loss				(109,326)	(109,326)
Balances at end at Dec. 31, 2021	$ 4	514,794	(102)	(359,767)	154,929
Balances at end (in shares) at Dec. 31, 2021	37,758,797
Issuance of common stock through "at-the-market" offering, net of underwriter discount and issuance costs		3,509			3,509
Issuance of common stock through "at-the-market" offering, net of underwriter discount and issuance costs (in shares)	700,000
Issuance of common stock upon exercise of options		76			76
Issuance of common stock upon exercise of options (in shares)	16,666
Issuance of common stock under the Employee Stock Purchase Plan		322			322
Issuance of common stock under the Employee Stock Purchase Plan (shares)	207,538
Vesting of restricted stock units (shares)	384,390
Stock-based compensation		16,891			16,891
Unrealized loss on available-for-sale debt securities			(164)		(164)
Net loss				(97,157)	(97,157)
Balances at end at Dec. 31, 2022	$ 4	$ 535,592	$ (266)	$ (456,924)	$ 78,406
Balances at end (in shares) at Dec. 31, 2022	39,067,391

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash Flows from Operating Activities
Net loss	$ (97,157)	$ (109,326)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,459	4,550
Asset impairment	449	0
Amortization of operating right-of-use asset	1,622
Loss on disposal of property and equipment		77
Stock-based compensation	16,891	16,876
Amortization of discount or premium on available-for-sale securities	56	1,480
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,441)	2,987
Accounts payable	(1,611)	1,267
Accrued expenses	(1,854)	5,388
Other current liabilities	1,052	(910)
Deferred rent		16,691
Operating lease liabilities	(3,187)
Net cash used in operating activities	(80,721)	(60,920)
Cash Flows from Investing Activities
Purchase of property and equipment	(885)	(35,090)
Purchase of investments	(62,454)	(53,803)
Proceeds from maturities of investments	75,887	178,130
Net cash provided by investing activities	12,548	89,237
Cash Flows from Financing Activities
Proceeds from the issuance of common stock under the Employee Stock Purchase Plan	322	837
Proceeds from exercise of stock options	76	273
Proceeds from issuance of common shares in "at-the-market" equity offering, net of issuance costs	3,509	4,385
Principal payments on capital lease obligations	(4)	(49)
Net cash provided by financing activities	3,903	5,446
Net change in cash, cash equivalents and restricted cash	(64,270)	33,763
Cash, cash equivalents and restricted cash, beginning of period	96,204	62,441
Cash, cash equivalents and restricted cash, end of period	31,934	96,204
Supplemental Disclosure of Cash Flow Information
Cash paid for interest		3
Cash paid for income taxes		1
Supplemental Schedule of Non-Cash Investing and Financing Activities
Costs related to "at-the-market" offering included in accounts payable		13
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 13	$ 33

Business

Business	12 Months Ended
	Dec. 31, 2022
Business
Business	1. Nature of Business Atreca, Inc., or the Company, was incorporated in the State of Delaware on June 11, 2010, or inception date, and is located in San Carlos, California. The Company is a clinical stage biopharmaceutical company utilizing its differentiated platform to discover and develop novel antibody-based immunotherapeutics to treat a range of solid tumor types. The Company's lead product candidate, ATRC-101, is a monoclonal antibody in clinical development with a novel mechanism of action and target derived from an antibody identified using its discovery platform. The Company operates in a single

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 Basis of Presentation The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP, and pursuant to the accounting and disclosure rules and regulations of the Securities and Exchange Commission, or SEC, include the accounts of the Company. Going Concern In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, we evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of our plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, we evaluate whether the mitigating effect of its plans sufficiently alleviates substantial doubt about our ability to continue as a going concern. The mitigating effect of our plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about our ability to continue as a going concern within one year after the date that the financial statements are issued. In performing this analysis, we excluded certain elements of our operating plan that cannot be considered probable. ​ Our expectation to generate operating losses and negative operating cash flows in the future and the need for additional funding to support our planned operations raise substantial doubt regarding our ability to continue as a going concern for a period of one year after the date that the financial statements are issued. Management intends on completing additional equity financing and reducing spending in fiscal 2023 and 2024. However, due to several factors, including those outside management’s control, there can be no assurance that the Company will be able to complete additional equity financings. If we are unable to complete additional financings, management’s plans include further reducing or delaying operating expenses. We have concluded the likelihood that our plan to successfully reduce expenses to align with our available cash is probable. Accordingly, we believe our plan will be sufficient to alleviate substantial doubt for a period of at least 12 months from the date of issuance of these consolidated financial statements.3 ​ The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of income and expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates in the financial statements include estimated useful lives of property and equipment, impairment of long-lived assets, accrued expenses, valuation of deferred income tax assets, fair value of available-for-sale debt securities, incremental borrowing rate used for lease accounting and fair value of options granted under the Company's stock option plan. Other Income Other income is comprised of amounts earned from services performed under service agreements. The Company follows the provisions of Accounting Standards Update 2014-09 Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers, or Topic 606. In determining the appropriate amount of other income to be recognized as it fulfills its obligations under the agreements, the Company performs the following steps: (i) identifies the promised goods or services in the contract; (ii) determines whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on estimated selling prices; and (v) recognizes other income when (or as) the Company satisfies each performance obligation. The Company generally allocates the transaction price to distinct performance obligations at their stand-alone selling prices, determined by their estimated costs plus some margin. Performance obligations are generally delivered over time and recognized based upon observable inputs as the related research services are performed, which are recorded as research and development expenses. Amounts due under service agreements are generally billed monthly as services are delivered and do not generally result in contract liabilities or assets. In February 2020, the Company entered into an agreement with an external partner for a research project to identify the antigenic targets of select antibodies discovered by the Company with potential utility in oncology. The nonrefundable upfront payment from this agreement was classified as a contract liability and the Company fully recognized the amount as other income over the service period of 18 months. In March 2022, the Company entered into an agreement with a third party for the assignment of certain non-core intellectual property. The initial consideration was classified as other income and recognized upon completion of the assignment. The agreement provides for additional consideration in the event of commercial exploitation of the intellectual property. The term of the agreement extends to the date of expiration of the last to expire of any of the assigned patents. In October, 2022, the Company entered into the Grant Agreement with the Bill & Melinda Gates Foundation under which it was awarded a grant totaling up to $1.2 million for its malaria program. The parties amended the agreement in December 2022 to extend the grant term. During the year ended December 31, 2022, the Company recognized The Company recorded no receivables under service and license agreements as of December 31, 2022 and 2021. The Company recorded $13,000 receivable under service agreement included in prepaid expenses and other current assets as December 31, 2020. The Company recorded 1.2 million contract liabilities as of December 31, 2022. The Company recorded zero and $0.8 million contract liabilities included in other current liabilities, as of December 31, 2021 and 2020, respectively. Collaborations Historically, the Company has entered into a number of discovery collaborations as the Company developed its discovery platform. These collaborations have generally focused on identifying novel antibodies in areas of significant unmet medical need. In July 2020, the Company entered into a Collaboration and License Agreement with Xencor, Inc., or Xencor Agreement, to research, develop and commercialize novel CD3 bispecific antibodies as potential therapeutics in oncology. Under the Xencor Agreement, the Company and Xencor, Inc. will engage in a three-year research program in which the Company will provide antibodies against novel tumor targets through its discovery platform from which Xencor, Inc. will engineer XmAb bispecific antibodies that also bind to the CD3 receptor on T cells. Up to two joint programs are eligible to be mutually selected for further development and commercialization, with each partner sharing 50% of costs and profits. Each company has the option to lead development, regulatory and commercialization activities for one of the joint programs. In addition, the Xencor Agreement allows each partner the option to pursue up to two programs independently, with a mid-to high-single digit percent royalty payable on net sales to the other partner. The Company evaluated the Xencor Agreement under the provisions of ASC 606 and ASU 2018-18, Collaborative Arrangements (Topic 808) Clarifying the Interaction between Topic 808 and Topic 606. The Company concluded that Xencor, Inc. is not a customer as there are no distinct units of account that are reflective of a vendor-customer relationship or exchange of consideration for the research activities. The Company’s share of any collaboration expense is recognized as an research and development expense on the Company’s statements of operations. For the cost-sharing related to the research program, the Company will follow the presentation and disclosure guidance of ASC 808, Collaboration Agreements In-Licensing Arrangements – Development In April 2022 The Company will be required to use commercially reasonable efforts to develop and commercialize at least one licensed product and the Company will pay to Zymeworks an option exercise fee, and lump sum payments upon the achievement of certain development and regulatory milestones and commercial milestones. In addition, with respect to each licensed product, the Company will pay tiered royalties on net sales of licensed products at single-digit royalty rates. The research license fee of $5.0 million was expensed to research and development expense in April 2022 in accordance with the Company's research and development expense policy. Employee Retention Credit The Coronavirus Aid, Relief and Economic Security, or CARES Act, as amended by the further legislation, provides an employee retention credit, or ERC, to eligible employers, which is a refundable tax credit against certain employment taxes. In calendar 2021, the ERC was equal to 70% of qualified wages paid to employees up to $10,000 of qualified wages per employee for each of the first, second and third calendar quarters of 2021. The Company has determined that its aggregate eligible refundable credit for 2021 is $2.9 million. In May 2022, the Company filed the requisite claims for the eligible 2021 ERC. The Company classified the ERC amounts as a reduction to payroll expense. During the year ended December 31, 2022, the Company recorded $2.4 million and $0.5 million related to the ERC within research and development expense and general and administrative expense, respectively, on the Company’s statements of operations. As of December 31, 2022, the Company has a $2.9 million receivable balance from the United States government related to the CARES Act, which is recorded as other receivables in “Prepaid expenses and other current assets” on the Company’s balance sheet. In January 2023, the Company received the entire balance of ERC of Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include all cash balances and highly liquid investments purchased with an original maturity of three months or less. The Company maintained restricted cash of $1.1 million and $1.5 million as of December 31, 2022 and 2021, respectively. These amounts as of December 31, 2022 and 2021 are included in deposits and other in the accompanying balance sheets and is comprised solely of letters of credit required pursuant to leases for Company facilities. The Company’s reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2022 2021 ​ Cash and cash equivalents ​ $ 30,819 ​ $ 94,746 ​ Restricted cash ​ ​ 1,115 ​ ​ 1,458 ​ Cash, cash equivalents and restricted cash shown in the statements of cash flows ​ $ 31,934 ​ $ 96,204 ​ ​ Investments The Company considers securities purchased with original maturities greater than three months to be investments. The Company’s policy is to protect the value of its investment portfolio and minimize principal risk by earning returns based on current interest rates. The Company’s intent is to convert all investments into cash to be used for operations and has classified them as available for sale. For purposes of determining realized gains and losses, the cost of debt securities sold is based on specific identification. Interest and dividends on securities classified as available-for-sale are included in interest income. Leases The Company determines if an arrangement is, or contains, a lease at inception. The Company measures lease liabilities based on the present value of lease payments over the lease term. As the Company’s leases generally do not provide an implicit discount rate, the net present value of future minimum lease payments is determined using the Company’s incremental borrowing rate. Options in the lease terms to extend or terminate the lease are not reflected in the lease liabilities unless it is reasonably certain that any such option will be exercised. The Company measures right-of-use assets at the lease commencement date based on the corresponding lease liabilities adjusted for (i) prepayments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) certain tenant incentives under the lease. The Company evaluates the recoverability of the right-of-use assets for possible impairment in accordance with the long-lived assets policy. The Company has elected not to recognize right-of-use assets or lease liabilities for leases with an initial lease term of twelve months or less. The Company’s lease agreements do not contain residual value guarantees or covenants. Lease expense is recognized on a straight-line basis over the terms of the leases. Incentives granted under the Company’s facilities lease, including rent holidays, are recognized as adjustments to lease expense on a straight-line basis over the terms of the leases. Refer to Recently Adopted Accounting Pronouncements Summary of Significant Accounting Policies Leases Risks and Uncertainties The Company is subject to a number of risks associated with companies at a similar stage, including COVID-19, dependence on key individuals, competition from similar services and larger companies, volatility of the industry, ability to obtain regulatory clearance, ability to obtain adequate financing to support growth, the ability to attract and retain additional qualified personnel to manage the anticipated growth of the Company and general economic conditions. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents, investments and other receivables. Cash and cash equivalents are held at three financial institutions and were in excess of the Federal Deposit Insurance Corporation insurable limit at December 31, 2022 and 2021. Any loss incurred or a lack of access to such funds could have a significant adverse impact on the Company's financial condition, results of operations, and cash flows. Additionally, cash and cash equivalents and investments are maintained at brokerage firms for which amounts are insured by the Securities Investor Protection Corporation subject to legal limits. The Company does not require collateral or other security for other receivables. Property and Equipment, Net Property and equipment are stated at cost less depreciation. Depreciation is computed using the straight-line method with the estimated useful lives of the assets ranging from two Accounting for Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Fair value is estimated based upon internal evaluation of each asset that includes quantitative analyses of cash flows and available market data. Certain factors used for these types of nonrecurring fair value measurements are considered Level 3 inputs. In December 2022, the Company identified certain long-lived assets no longer utilized under current or expected future operations. Accordingly, the Company recognized impairment expense of Intellectual Property Intellectual property-related expenses for the years ended December 31, 2022 and 2021 were $1.1 million and $1.2 million, respectively. As of December 31, 2022, and 2021, the Company has determined that these expenses have not met the criteria to be capitalized. Deferred Rent The Company has entered into lease agreements for its laboratory and office facilities. These leases qualify as and are accounted for as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. Research and Development Costs Research and development costs are expensed as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, stock-based compensation, certain facility costs, legal costs and other costs associated with preclinical and clinical development. A substantial portion of the Company’s ongoing research and development activities are conducted by third-party service providers in connection with preclinical and clinical development activities and contract manufacturing organizations in connection with the production of materials for clinical trials. At the end of the reporting period, the Company compares payments made to third-party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Stock-Based Compensation The Company generally grants stock options to its employees for a fixed number of shares with an exercise price equal to the fair value of the underlying shares at the date of grant. The Company accounts for stock option grants using the fair value method. The fair value of options is calculated using the Black-Scholes option pricing model. For restricted stock units, fair value is based on the closing price of the Company’s Class A common stock on the grant date. Stock-based compensation is recognized as the underlying options vest using the straight-line attribution approach, and forfeitures are recorded as they occur. Emerging Growth Company Status The Company is an “emerging growth company,” or EGC, as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. The Company may take advantage of these exemptions until it is no longer an EGC under Section 107 of the JOBS Act, which provides that an EGC can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards, and as a result of this election, the Company’s financial statements may not be comparable to companies that comply with public company Financial Accounting Standards Board, or FASB, standards’ effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of the IPO or such earlier time that the Company is no longer an EGC. Income Taxes The Company applies the provisions set forth in FASB ASC Topic 740, Income Taxes, to account for the uncertainty in income taxes. In the preparation of income tax returns in federal, foreign and state jurisdictions, the Company asserts certain income tax positions based on its understanding and interpretation of income tax laws. The taxing authorities may challenge such positions, and the resolution of such matters could result in recognition of income tax expense in the Company's financial statements. Management believes it has used reasonable judgments and conclusions in the preparation of its income tax returns. The Company recognizes tax benefits from uncertain tax positions only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company does not anticipate any significant changes within 12 months of this reporting date of its uncertain tax positions. The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the financial statement and income tax basis of existing assets and liabilities. A valuation allowance is provided against the Company's deferred income tax assets when realization is not reasonably assured. Net Loss Per Share Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016 02 and subsequent amendments to the initial guidance under ASU 2017-13, ASU 2018-10, ASU 2018-11, and ASU 2019-01, or collectively, Topic 842, which modifies the accounting by lessees for all leases with a term greater than 12 months. This standard requires lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The Company adopted the new lease accounting standard on January 1, 2022, using the modified retrospective transition method. The Company implemented processes, and internal controls to enable the preparation of financial information. The adoption of this standard had a material impact on the Company’s balance sheet, with the recognition of right-of-use assets and corresponding lease liabilities in the amounts of $37.7 million and $67.1 million respectively, and the derecognition of approximately $10.9 million of deferred rent and $19.1 million of tenant improvement incentives. The adoption of this standard did not have a material impact on the Company’s statements of operations or cash flows. The Company provided detailed right-of-use asset and liability disclosures as required by the new standard in the notes to the Company’s financial statements under Note 8 Leases. The Company adopted the transitional provisions allowed under ASU 2018-11 and as such, the balance sheets and statements of operations for prior periods are not comparable in the year of adoption of ASU 2016-02. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses Topic 326

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2022
Fair Value of Financial Instruments
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments ​ The fair value of the Company's assets and liabilities, which qualify as financial instruments under FASB ASC 820, Fair Value Measurements and Disclosures ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 29,658 ​ $ — ​ $ — ​ $ 29,658 Certificates of deposit ​ ​ 483 ​ ​ — ​ ​ — ​ ​ 483 Corporate debt securities ​ ​ — ​ ​ 1,996 ​ ​ — ​ ​ 1,996 U.S. Treasury securities ​ ​ 37,197 ​ ​ — ​ ​ — ​ ​ 37,197 Total ​ $ 67,338 ​ $ 1,996 ​ $ — ​ $ 69,334 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 90,251 ​ $ — ​ $ — ​ $ 90,251 Certificates of deposit ​ ​ 1,672 ​ ​ — ​ ​ — ​ ​ 1,672 Corporate debt securities ​ ​ — ​ ​ 6,089 ​ ​ — ​ ​ 6,089 U.S. Treasury securities ​ ​ 45,568 ​ ​ — ​ ​ — ​ ​ 45,568 Total ​ $ 137,491 ​ $ 6,089 ​ $ — ​ $ 143,580 ​ ​ The Company utilized the market approach and Level 1 valuation inputs to value its money market funds, certificates of deposit, and U.S. government treasury securities because published fair market values were readily available. The Company measured the fair value of corporate debt securities using Level 2 valuation inputs, which are based on quoted prices and market observable data of similar instruments. As of December 31, 2022 and 2021, gross unrealized gains and unrealized losses for cash equivalents and investments were not material, and the remaining contractual maturity of all marketable securities was less than two years. ​

Cash, Cash Equivalents and Inve

Cash, Cash Equivalents and Investments	12 Months Ended
	Dec. 31, 2022
Cash, Cash Equivalents and Investments
Cash, Cash Equivalents and Investments	4. Cash, Cash Equivalents and Investments The fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ Cash and ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cash ​ Short-term ​ Long-term December 31, 2022 Cost Gains Losses Value Equivalents ​ Investment ​ Investment Cash, cash equivalents and money market funds ​ $ 30,819 ​ $ — ​ $ — ​ $ 30,819 ​ $ 30,819 ​ $ — ​ $ — ​ Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury securities ​ 37,458 ​ ​ — ​ ​ (261) ​ ​ 37,197 ​ ​ — ​ ​ 37,197 ​ ​ — ​ Corporate debt securities ​ ​ 1,999 ​ ​ — ​ ​ (3) ​ ​ 1,996 ​ ​ — ​ ​ 1,996 ​ ​ — ​ Certificates of deposit ​ ​ 485 ​ — ​ (2) ​ 483 ​ — ​ 483 ​ ​ — ​ Total ​ $ 70,761 ​ $ — ​ $ (266) ​ $ 70,495 ​ $ 30,819 ​ $ 39,676 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ Cash and ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cash ​ Short-term ​ Long-term December 31, 2021 Cost Gains Losses Value Equivalents ​ Investment ​ Investment Cash, cash equivalents and money market funds ​ $ 94,746 ​ $ — ​ $ — ​ $ 94,746 ​ $ 94,746 ​ $ — ​ $ — ​ Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury securities ​ 45,665 ​ ​ — ​ ​ (97) ​ ​ 45,568 ​ ​ — ​ ​ 15,014 ​ ​ 30,554 ​ Corporate debt securities ​ ​ 6,093 ​ ​ — ​ ​ (4) ​ ​ 6,089 ​ ​ — ​ ​ 6,089 ​ ​ — ​ Certificates of deposit ​ ​ 1,673 ​ — ​ (1) ​ 1,672 ​ — ​ 1,184 ​ ​ 488 ​ Total ​ $ 148,177 ​ $ — ​ $ (102) ​ $ 148,075 ​ $ 94,746 ​ $ 22,287 ​ $ 31,042 ​ ​ The Company evaluated the securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. It is not more likely than not that the Company will be required to sell the securities, and the Company has no intention to do so prior to the recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2022.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2022
Prepaid Expenses and Other Current Assets.
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Vendor prepayments and deposits ​ $ 2,010 ​ $ 2,681 ​ Prepaid insurance ​ ​ 1,026 ​ ​ 1,531 ​ Prepaid facility maintenance fee ​ 336 ​ 807 ​ Other receivables ​ 3,985 ​ — ​ Interest receivables and other current assets ​ ​ 174 ​ ​ 318 ​ Total prepaid expenses and other current assets ​ $ 7,531 ​ $ 5,337 ​ ​

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2022
Property and Equipment, net
Property and Equipment, net	6. Property and Equipment, net Property and equipment consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 2021 Laboratory equipment ​ $ 13,191 ​ $ 13,128 ​ Furniture and fixtures ​ 1,929 ​ 1,897 ​ Computer hardware and software ​ 1,518 ​ 1,433 ​ Leasehold improvements ​ 37,908 ​ 37,871 ​ Construction in process ​ 178 ​ — ​ ​ ​ 54,724 ​ 54,329 ​ Less accumulated depreciation and amortization ​ (16,752) ​ (11,314) ​ Total property and equipment, net ​ $ 37,972 ​ $ 43,015 ​ ​ Depreciation and amortization expense was $5.5 million and $4.5 million for the years ended December 31, 2022 and 2021, respectively. In December 2022, the Company identified certain long-lived assets no longer utilized under current or expected future operations. Accordingly, the Company recognized impairment expense of $0.4 million in 2022. The Company did not record any impairment of long-lived assets in 2021.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2022
Accrued Expenses
Accrued Expenses	7. Accrued Expenses Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 2021 Compensation and related benefits ​ $ 3,789 ​ $ 4,866 License fees ​ ​ 3,000 ​ ​ — Contract research fees ​ ​ 2,201 ​ ​ 5,521 Professional fees ​ ​ 128 ​ ​ 189 Cease use ​ ​ — ​ ​ 475 Other ​ ​ 563 ​ ​ 504 Total accrued expenses ​ $ 9,681 ​ $ 11,555 ​

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases
Leases	8. Leases The Company leases its office facilities under non-cancellable operating lease agreements that expire at various dates through April 2033. Under the terms of the leases, the Company is responsible for certain insurance, property taxes and maintenance expenses. The office facilities lease agreements contain scheduled increases over the lease term. The Company was not party to any finance leases as of December 31, 2022. The Company vacated its former office space in September 2021, prior to the expiration of the lease in March 2022. The remaining rent payable, deferred rent and associated prepaid rent for the former office space were expensed in full on September 30, 2021 and resulted in a charge of $1.5 million, recorded as a general and administrative operating expense in the Company’s statements of operations. The associated cease-use liability was settled by March 2022 and the lease was terminated. ​ The Company's future lease payments as of December 31, 2022, which are presented as current portion of operating lease liabilities, and operating lease liabilities, net of current portion on the Company's balance sheets (in thousands, except weighted-average data) are as follows: ​ ​ ​ ​ ​ ​ ​ Operating ​ ​ Leases Periods ​ ​ ​ 2023 ​ $ 7,635 2024 ​ 7,846 2025 ​ 8,064 2026 ​ ​ 8,288 2027 ​ ​ 8,519 Thereafter ​ ​ 48,771 Total lease payments ​ $ 89,123 Less: imputed interest ​ (25,248) Present value of lease liabilities ​ $ 63,875 ​ ​ ​ ​ Lease liabilities, current ​ ​ 3,544 Lease liabilities, noncurrent ​ ​ 60,331 Total lease liabilities ​ $ 63,875 ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 10.4 Weighted-average discount rate ​ ​ 6.64% ​ Lease expense under the Company’s operating leases was $5.9 million for the year ended December 31, 2022. Variable lease expense for operating leases was $3.6 million for the year ended December 31, 2022. Rent expense recognized under ASC 840, inclusive of operating and maintenance costs, was $13.2 million during the year ended December 31, 2021. ​ Cash paid for amounts included in the measurement of lease liabilities for the year ended December 31, 2022 was $7.5 million. ​ Practical Expedients ​ Leases with an initial term of 12 months or less are not recorded on the balance sheets. The Company recognizes the lease expense for such leases on a straight-line basis over the lease term. ​ The Company has elected to account for lease (e.g., fixed payments including rent) and non-lease components (e.g., common area maintenance costs) as a single combined lease component under ASC 842 as the lease components are the predominant elements of the combined components. ​ As part of the transition to ASC 842, the Company elected to use the modified retrospective transition method with the new standard being applied as of the January 1, 2022 adoption date. Additionally, the Company has elected, as of the adoption date, not to reassess whether expired or existing contracts contain leases under the new definition of a lease, not to reassess the lease classification for expired or existing leases, and not to reassess whether previously capitalized initial direct costs would qualify for capitalization under ASC 842.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies
Commitments and Contingencies	9. Commitment and Contingencies Litigation The Company is not aware of any asserted or unasserted claims against it where it believes that an unfavorable resolution would have an adverse material impact on the operations or financial position of the Company. ​ Non-executive Severance Plan Under the terms of the Non-executive Severance Plan approved by the Compensation Committee in December 2022, an employee, who is not an employee eligible for individually-negotiated employment agreement, is entitled to severance pay and benefits on a Covered Termination, which is a termination in connection with a Company-initiated reduction-in-force without cause other than due to death or disability that occurs on or prior to June 30, 2024.

Reorganization and Other Charge

Reorganization and Other Charges	12 Months Ended
	Dec. 31, 2022
Reorganization and Other Charges
Reorganization and Other Charges	10. Reorganization and Other Charges On June 1, 2022, the Company implemented and announced a corporate reorganization of its operations. In connection with the reorganization, the Company undertook a workforce reduction and recorded severance and employee benefits charges of $0.7 million to operating expenses in the quarter ending June 30, 2022. As of December 31, 2022, there was no outstanding liability related to severance and employee benefit charges and does not expect to incur any material additional costs related to the reorganization.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2022
Capital Stock
Capital Stock	11. Capital Stock Class A and Class B Common Stock On June 2, 2019 the board of directors of the Company authorized the issuance of 650,000,000 shares of Class A common stock, $0.0001 par value per share, 50,000,000 shares of Class B common stock, $0.0001 par value per share and 300,000,000 shares of preferred stock, $0.0001 par value per share, upon the filing of the Company’s Amended and Restated Certificate of Incorporation. Each holder of Class A common stock is entitled to one vote and each holder of Class B common stock is not entitled to vote except as may be required by law and shall not be entitled to vote on the election of directors at any time. Sales Agreement In August 2020, the Company entered into a sales agreement, or Sales Agreement, with Cowen and Company, LLC, or Cowen, pursuant to which the Company may, upon the terms and subject to the conditions set forth therein, issue and sell through Cowen, acting as the Company’s sales agent and/or principal, shares of the Company’s Class A common stock, having an aggregate offering price of up to $100.0 million, or ATM Shares. The Company has no obligations to sell any ATM Shares under the Sales Agreement. The Sales Agreement provides that Cowen will be entitled to compensation for its services in an amount equal to up to 3.0% of gross proceeds for each time the company issues and sells ATM Shares under the Sales Agreement. The ATM Shares will be sold based on prevailing market prices at the time of the sale, and, as a result, prices may vary. Unless otherwise terminated earlier, the Sales Agreement continues until all shares available under the Sales Agreement have been sold. As of December 31, 2022, the Company issued and sold 1,493,361 shares of our Class A common stock. Net proceeds from the sales was $7.9 million after deducting underwriting fee of $0.3 million and issuance costs of $0.3 million. ​

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2022
Equity Incentive Plans
Equity Incentive Plans	12. Equity Incentive Plans 2019 Equity Incentive Plan The Company’s board of directors adopted and our stockholders approved our 2019 Equity Incentive Plan, or 2019 Plan, on June 2, 2019, and June 7, 2019, respectively. The 2019 Plan became effective on June 19, 2019, and no further grants will be made under the Company’s 2010 Equity Incentive Plan, or 2010 Plan. The purpose of the 2019 Plan, through the grant of stock awards including stock options and other stock-based awards, including restricted stock units, or RSUs,, is to help the Company secure and retain the services of eligible award recipients, provide incentives for such persons to exert maximum efforts for our success and that of the Company’s affiliates, and provide a means by which the eligible recipients may benefit from increases in the value of the Company’s Class A common stock. Stock Option Repricing Effective June 13, 2022, the Company’s board of directors approved a one-time repricing of previously granted and outstanding vested and unvested stock options with exercise prices greater than or equal to $9.00 per share under the 2010 Plan and the 2019 Plan held by eligible employees. As a result, the exercise price for these awards was modified to $1.845 per share, which was the closing price of the Company’s Class A common stock as reported on the Nasdaq Global Select Market on June 13, 2022. No other terms of the repriced stock options were modified, and the repriced stock options will continue to vest according to their original vesting schedules and will retain their original expiration dates. As a result of the repricing, 3,606,163 vested and unvested stock options outstanding as of June 13, 2022 with original exercise prices ranging from $9.87 to $22.10, were repriced. The repricing resulted in incremental stock-based compensation expense of $2.5 million, of which $1.9 million was recognized during the year ended December 31, 2022. The remaining $0.6 million related to unvested stock option awards will be amortized on a straight-line basis over the weighted-average vesting period of those awards of approximately 1.0 years. Stock Options Stock option activity under the 2019 Plan and the 2010 Plan is as follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Weighted- ​ Remaining ​ Intrinsic ​ ​ Number ​ Average ​ Contractual ​ Value ​ of Shares ​ Exercise Price ​ Life (years) ​ (in thousands) Balances, December 31, 2020 4,812,223 ​ $ 13.33 ​ 8.2 ​ $ 21,493 Granted 3,192,470 ​ 8.99 ​ ​ ​ Exercised (47,061) ​ 5.81 ​ ​ ​ Cancelled (794,956) ​ 15.06 ​ ​ ​ Balances, December 31, 2021 7,162,676 ​ $ 11.25 ​ 8.2 ​ $ 21 Granted 446,100 ​ 1.88 ​ ​ ​ Exercised (16,666) ​ 4.56 ​ ​ ​ Cancelled (1,218,576) ​ 7.87 ​ ​ ​ Balances, December 31, 2022 6,373,534 ​ $ 3.56 ​ 7.3 ​ $ 2 Vested and expected to vest at December 31, 2022 6,373,534 ​ $ 3.56 ​ 7.3 ​ $ 2 Exercisable at December 31, 2022 4,178,167 ​ $ 4.02 ​ 6.6 ​ $ 2 Vested at December 31, 2022 4,178,167 ​ $ 4.02 ​ 6.6 ​ $ 2 ​ Additional information regarding the Company’s stock options outstanding and vested and exercisable as of December 31, 2022 is summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Vested and Exercisable ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Remaining ​ Weighted- ​ ​ ​ Average ​ ​ Number of ​ Contractual ​ Average ​ Shares Subject ​ Exercise ​ ​ Stock Options ​ Life ​ Exercise Price ​ to Stock ​ Price per Exercise Prices ​ Outstanding ​ (Years) ​ per Share ​ Options ​ Share Up to $1.83 ​ 254,603 ​ 9.3 ​ $ 1.66 ​ 11,034 ​ $ 0.80 $1.84-$1.89 3,295,250 7.1 ​ $ 1.85 2,414,136 ​ $ 1.85 $1.90-$3.22 ​ 1,270,054 ​ 9.0 ​ $ 3.02 ​ 299,531 ​ $ 3.11 $3.23-$5.40 ​ 990,414 ​ 5.2 ​ $ 5.06 ​ 969,539 ​ $ 5.09 $5.41-$22.07 563,213 7.3 ​ $ 13.01 483,927 ​ $ 13.35 ​ 6,373,534 7.3 ​ $ 3.56 4,178,167 ​ $ 4.02 ​ ​ The weighted-average grant date fair value of options granted to employees and non-employees in the years ended December 31, 2022 and 2021 was $1.26 and $6.66, respectively. The intrinsic value of options exercised for the years ended December 31, 2022 and 2021 was determined to be $8,000 and $519,000, respectively. The fair value of each option is estimated on the date of grant using the Black-Scholes option pricing model, assuming no expected dividends and the following weighted average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 2021 Expected life (in years) 5.89 5.98 ​ ​ Volatility 86.0 % 90.3 % ​ Risk-free interest rate 3.3 % 0.9 % ​ ​ Expected volatility is based on volatilities of public companies operating in the Company’s industry. The expected life of the options is estimated using the simplified method detailed in SEC Staff Accounting Bulletin No. 107. The simplified method calculates the expected term as the mid-point between the weighted-average time to vesting and the contractual maturity. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant. The Company has elected to account for forfeitures as they occur, rather than estimate expected forfeitures. Restricted Stock Units The 2019 Plan provides for the issuance of RSU to employees, directors and consultants. RSUs vest over a period of two years with 50% vesting on the one-year anniversary of the award and the remainder RSU activity for the years ended December 31, 2022 and 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ Number ​ Grant Date ​ of Shares ​ Fair Value per RSU Unvested Balances, December 31, 2020 — ​ $ — RSUs Granted 884,820 ​ 6.15 RSUs Vested ​ — ​ ​ — RSUs Cancelled (17,090) ​ 6.15 Unvested Balances, December 31, 2021 867,730 ​ $ 6.15 RSUs Vested ​ (384,390) ​ ​ 6.15 RSUs Cancelled (152,900) ​ 6.15 Unvested Balances, December 31, 2022 330,440 ​ $ 6.15 ​ 2019 Employee Stock Purchase Plan The Company’s board of directors adopted the 2019 Employee Stock Purchase Plan, or ESPP, on June 2, 2019, and the Company’s stockholders approved the ESPP on June 7, 2019. During the years ended December 31, 2022 and 2021, the expense related to the ESPP were both $0.8 million. The fair value of each ESPP is estimated on the date of grant using the Black-Scholes option pricing model, assuming no expected dividends and the following range of assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 2021 Expected life (in years) 0.5 - 2.0 0.5 - 2.0 ​ ​ Volatility 79.0 - 96.7 % 91.1 - 107.6 % ​ Risk-free interest rate 0.6 - % 0.1 - % ​ ​ The Company recognized $16.9 million of stock-based compensation expense related to options and the ESPP granted to employees and non-employees for each of the years ended December 31, 2022 and 2021. The compensation expense is allocated on a departmental basis, based on the classification of the option holder as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 Research and development ​ $ 7,910 ​ $ 8,571 ​ General and administrative ​ 8,981 ​ 8,305 ​ ​ ​ $ 16,891 ​ $ 16,876 ​ ​ No income tax benefits have been recognized in the statements of operations for stock-based compensation arrangements and no stock-based compensation costs have been capitalized as property and equipment as of December 31, 2022 and 2021. Unrecognized compensation expense as of December 31, 2022, totaled $12.2 million related to non-vested stock options with a remaining weighted-average requisite service period of 1.8 years and $1.3 million related to non-vested RSUs with a remaining weighted-average requisite service period of 0.7 years. ​ Convertible Preferred Stock Warrant Upon the IPO in 2019, t he 49,997 preferred stock warrants were revalued and converted to common stock warrants of Class A common stock shares. In August 2022, 49,997 outstanding warrants expired and there were no warrants outstanding as of December 31, 2022.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2022
401 (k) Plan
401 (k) Plan	13. 401(k) Plan The Company has a 401(k) plan that qualifies as a deferred compensation arrangement under Section 401 of the Internal Revenue Code of 1986, as amended, or the Code. Eligible employees may elect to defer a portion of their pretax earnings subject to certain statutory limits. Beginning January 1, 2021, the Company matches 100% up to the first $5,000 contributed by a participant. All matching contributions are immediately vested. Total matching contributions to the 401(k) Plan were $0.6 million for each of the years ended December 31, 2022 and 2021. ​

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 The Company calculates basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities. The Company considered all series of redeemable convertible preferred stock to have been participating securities as the holders were entitled to receive non-cumulative dividends on a pari passu basis in the event a dividend was paid on common stock. Under the two-class method, the net loss attributable to common stockholders is not allocated to the redeemable convertible preferred stock as the holders of redeemable convertible preferred stock do not have a contractual obligation to share in losses. Under the two-class method, basic net loss per share attributable to common stockholders is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less shares subject to repurchase. Diluted net loss per share attributable to common stockholders is computed by giving effect to all potentially dilutive common stock equivalents outstanding for the period. For purposes of this calculation, redeemable convertible preferred stock, stock options to purchase common stock, early exercised stock options, and warrants to purchase redeemable convertible preferred stock and common stock are considered common shares equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive. Basic and diluted net loss per share was the same for each period presented, as the inclusion of all potential common shares outstanding would have been antidilutive. The rights, including the liquidation and dividend rights, of the holders of Class A and Class B common stock are identical, except with respect to voting. As the liquidation and dividend rights are identical, the undistributed earnings are allocated on a proportionate basis and the resulting net loss per share attributed to common stockholders will, therefore, be the same for both Class A and Class B common stock on an individual or combined basis. The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Numerator: ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders for earnings per share, basic and diluted ​ $ (97,157) ​ $ (109,326) Denominator: ​ ​ ​ ​ ​ ​ Shares used to compute net loss per share, basic and diluted ​ ​ 38,593,894 ​ ​ 37,038,195 Basic and diluted net loss attributable to common stockholders per share ​ $ (2.52) ​ $ (2.95) ​ The following outstanding potentially dilutive common shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because the impact of including them would have been antidilutive: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Common stock options ​ ​ 6,373,534 ​ ​ 7,162,676 Unvested restricted stock units ​ ​ 330,440 ​ ​ 867,730 Common stock warrants ​ — ​ 49,997 ​ ​ ​ 6,703,974 ​ ​ 8,080,403 ​

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Taxes
Income Taxes	15. Income Taxes For the years ended December 31, 2022 and 2021, the Company recorded income tax related to state minimum taxes due. A reconciliation of the federal statutory income tax rate and the Company's effective income tax rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2022 2021 ​ Tax computed at federal statutory rate ​ 21.0 % 21.0 % State income taxes, net of federal benefit ​ (0.7) % 2.3 % Other ​ (4.4) % (1.8) % Change in valuation allowance ​ (15.6) % (24.2) % Credits ​ (0.3) % 2.7 % Effective income tax rate ​ 0.0 % 0.0 % ​ Deferred income taxes result from the tax effect of transactions that are recognized in different periods for financial statement and income tax reporting purposes, as well as operating loss and tax credit carryforwards. Significant components of the Company's deferred income tax assets and liabilities are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 Deferred tax assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforward ​ $ 69,296 ​ $ 63,581 ​ Tax credits ​ 14,862 ​ 15,684 ​ Lease liability ​ ​ 13,414 ​ ​ — ​ Capitalized research and development expenses ​ ​ 11,175 ​ ​ — ​ Intangibles ​ 1,090 ​ 1,211 ​ Fixed assets ​ ​ 410 ​ ​ — ​ Other ​ 4,172 ​ 7,528 ​ Total deferred tax assets ​ 114,419 ​ 88,004 ​ Deferred tax liabilities: ​ ​ ​ Fixed assets ​ — ​ 121 ​ ROU assets ​ 11,289 ​ — ​ Total deferred tax liabilities ​ 11,289 ​ 121 ​ Valuation allowance ​ (103,130) ​ (87,883) ​ Total ​ $ — ​ $ — ​ ​ Beginning January 1, 2022, the Tax Cuts and Jobs Act eliminated the option to deduct research and development expenditures in the current year and requires taxpayers to capitalize such expenses pursuant to Internal Revenue Code, or IRC, Section 174. The capitalized expenses are amortized over a 5-year period for domestic expenses and a 15-year period for foreign expenses. As a result of this provision of the Tax Act, deferred tax assets related to capitalized research and development expenses pursuant to IRC Section 174 increased by $11.2 million. The Company uses the "more likely than not" criterion for recognizing the income tax benefit of uncertain income tax positions and establishing measurement criteria for income tax benefits. The Company has evaluated the impact of these positions and has reserved an unrecognized tax benefit of $4.7 million and $5.0 million as of December 31, 2022 and 2021, respectively. The following table summarizes the changes in the Company’s unrecognized tax benefits during the periods presented (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 ​ ​ ​ ​ ​ ​ ​ Beginning of period ​ $ 4,951 ​ $ 3,378 Current period tax position increases ​ 536 ​ 1,806 Prior period tax position changes ​ (747) ​ (233) End of period ​ $ 4,740 ​ $ 4,951 ​ The decrease in the unrecognized tax benefit in 2022 is primarily reductions based on tax positions related to prior years. In the event the Company should need to recognize interest and penalties related to unrecognized income tax liabilities, this amount will be recorded as an accrued liability and an increase to income tax expense. No amounts of interest or penalties were recognized in the Company's financial statements for 2022 or 2021. The Company is not currently under examination by income tax authorities in federal, state or other foreign jurisdictions. The Company does not anticipate any significant changes within 12 months of this reporting date of its uncertain tax positions. The net increase in the valuation allowance was $15.2 million and $26.5 million in 2022 and 2021, respectively. At December 31, 2022, the Company has federal and state net operating loss carryforwards of $46.5 million and $13.1 million, respectively, which begin to expire in 2030 and $276.1 million of federal net operating loss carryforwards which do not expire but are subject to the 80% taxable income limitation. Additionally, the Company had federal tax credits totaling $13.1 million and $13.2 million at December 31, 2022 and 2021, respectively, and state tax credits totaling $8.9 million and $9.7 million, at December 31, 2022 and 2021, respectively. The federal tax credits begin to expire in 2030. The state tax credits may be carried forward indefinitely. Section 382 of the Internal Revenue Code of 1986, as amended, limits the use of net operating losses and income tax credit carryforwards in certain situations where changes occur in stock ownership of a company. If the Company should have an ownership change of more than 50% of the value of the Company's capital stock, utilization of the carryforwards could be restricted. The Company files income tax returns in the U.S. federal jurisdiction, various state jurisdictions. The U.S. federal and state tax years from 2010 to 2020 remain open to examination due to the carryover of unused net operating loss carryforwards and tax credits. In January 2018, the FASB released guidance on the accounting for tax on the global intangible low-taxed income (GILTI) provisions of the 2017 Tax Act. The GILTI provisions subject certain U.S. entities to current tax on GILTI earned by certain foreign subsidiaries. The Company has considered these new provisions as they are effective for tax years starting after December 31, 2017 and determined that none will likely apply for the years ended December 31, 2022 and 2021. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security, or CARES, Act was enacted and signed into law. GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date. The CARES Act, includes changes to the tax provisions that benefits business entities, and makes certain technical corrections to the 2017 Tax Cuts and Jobs Act. The tax relief measures for businesses include a five-year net operating loss carryback, suspension of annual deduction limitation of 80% of taxable income from net operating losses generated in a tax year beginning after December 31, 2017, changes in the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief, and a technical correction to allow accelerated deductions for qualified improvement property. The CARES Act also provides other non-tax benefits to assist those impacted by the pandemic. The Company has evaluated the impact of the CARES Act and determined there was no material impact to the income tax provision for the year.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2022
Related Party Transactions
Related Party Transactions	16. Related Party Transactions The Company recorded other income of $20,000 and $1,000 for the years ended December 31, 2022 and 2021, respectively, under the Grant Agreement and service contracts with a stockholder. The Company had no receivable from the stockholder as of both December 31, 2022 and 2021. The Company recorded expense of $1.1 million and $1.3 million for the years ended December 31, 2022 and 2021, respectively, related to intellectual property and other legal services performed by a related party. An immediate family member of Tito A. Serafini, one of our directors and our Chief Strategy Officer, is a partner of the legal service provider. The Company has a payable of $172,000 and $203,000 to the related party for the years ended December 31, 2022 and 2021, respectively. The Company recorded expense of $1.0 million and $0.7 million for the years ended December 31, 2022 and 2021, respectively, related to legal services performed by a related party. An immediate family member of Tito A. Serafini, one of our directors and our Chief Strategy Officer, is a partner of the legal service provider. The Company has a payable of $33,000 and $86,000 to the related party at December 31, 2022 and 2021, respectively. The Company recorded research and development expenses of $250,000 for each of the years ended December 31, 2022 and 2021, respectively, under consulting agreements with a member of the Company’s board of directors. The Company has a payable of $74,000 to the member of the Company’s board of directors as of both December 31, 2022 and 2021. ​

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2022
Subsequent Events
Subsequent Events	17. Subsequent Events The Company has evaluated subsequent events that may require adjustments to or disclosure in the financial statements through March 29, 2023, the date on which the financial statements were available to be issued. ​ 2023 Inducement Plan ​ On February 9, 2023, the 2023 Inducement Plan, or the Inducement Plan, became effective. Subject to adjustment from time to time as provided in the Inducement Plan, 1.0 million shares of Class A common stock are available for issuance under the Inducement Plan. The purpose of the Inducement Plan is to attract, retain and motivate certain new employees of the Company by providing them the opportunity to acquire a proprietary interest in the Company and to align their interests and efforts to the long-term interests of the Company’s stockholders. Each award under the Inducement Plan is intended to qualify as an employment inducement award pursuant to Listing Rule 5635(c) of the corporate governance rules of the Nasdaq Marketplace Rule. The Inducement Plan is administered by the compensation committee of the Company’s board of directors. Under the terms of the Inducement Plan, the compensation committee may grant equity awards, including nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance stock, and other stock awards to new employees of the Company. ​ Silicon Valley Bank Default Silicon Valley Bank, or SVB, was closed on March 10, 2023 by the California Department of Financial Protection and Innovation, which appointed the Federal Deposit Insurance Corporation, or FDIC, as receiver. At the time of closing, the Company maintained less than $5.0 million of its cash in deposit accounts with SVB to manage its operational needs. The vast majority of the Company’s cash, cash equivalents and short-term investments reside in custodial accounts held by J.P. Morgan and Wells Fargo. The Company’s investment portfolio currently does not contain any securities of SVB. On March 12, 2023, the U.S. Treasury, Federal Reserve, and FDIC announced that SVB depositors will have access to all of their money starting March 13, 2023. The Company does not believe it will be impacted by the closure of SVB and will continue to monitor the situation as it evolves. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP, and pursuant to the accounting and disclosure rules and regulations of the Securities and Exchange Commission, or SEC, include the accounts of the Company.
Going Concern	Going Concern In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, we evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of our plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, we evaluate whether the mitigating effect of its plans sufficiently alleviates substantial doubt about our ability to continue as a going concern. The mitigating effect of our plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about our ability to continue as a going concern within one year after the date that the financial statements are issued. In performing this analysis, we excluded certain elements of our operating plan that cannot be considered probable. ​ Our expectation to generate operating losses and negative operating cash flows in the future and the need for additional funding to support our planned operations raise substantial doubt regarding our ability to continue as a going concern for a period of one year after the date that the financial statements are issued. Management intends on completing additional equity financing and reducing spending in fiscal 2023 and 2024. However, due to several factors, including those outside management’s control, there can be no assurance that the Company will be able to complete additional equity financings. If we are unable to complete additional financings, management’s plans include further reducing or delaying operating expenses. We have concluded the likelihood that our plan to successfully reduce expenses to align with our available cash is probable. Accordingly, we believe our plan will be sufficient to alleviate substantial doubt for a period of at least 12 months from the date of issuance of these consolidated financial statements.3 ​ The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of income and expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates in the financial statements include estimated useful lives of property and equipment, impairment of long-lived assets, accrued expenses, valuation of deferred income tax assets, fair value of available-for-sale debt securities, incremental borrowing rate used for lease accounting and fair value of options granted under the Company's stock option plan.
Other Income	Other Income Other income is comprised of amounts earned from services performed under service agreements. The Company follows the provisions of Accounting Standards Update 2014-09 Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers, or Topic 606. In determining the appropriate amount of other income to be recognized as it fulfills its obligations under the agreements, the Company performs the following steps: (i) identifies the promised goods or services in the contract; (ii) determines whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on estimated selling prices; and (v) recognizes other income when (or as) the Company satisfies each performance obligation. The Company generally allocates the transaction price to distinct performance obligations at their stand-alone selling prices, determined by their estimated costs plus some margin. Performance obligations are generally delivered over time and recognized based upon observable inputs as the related research services are performed, which are recorded as research and development expenses. Amounts due under service agreements are generally billed monthly as services are delivered and do not generally result in contract liabilities or assets. In February 2020, the Company entered into an agreement with an external partner for a research project to identify the antigenic targets of select antibodies discovered by the Company with potential utility in oncology. The nonrefundable upfront payment from this agreement was classified as a contract liability and the Company fully recognized the amount as other income over the service period of 18 months. In March 2022, the Company entered into an agreement with a third party for the assignment of certain non-core intellectual property. The initial consideration was classified as other income and recognized upon completion of the assignment. The agreement provides for additional consideration in the event of commercial exploitation of the intellectual property. The term of the agreement extends to the date of expiration of the last to expire of any of the assigned patents. In October, 2022, the Company entered into the Grant Agreement with the Bill & Melinda Gates Foundation under which it was awarded a grant totaling up to $1.2 million for its malaria program. The parties amended the agreement in December 2022 to extend the grant term. During the year ended December 31, 2022, the Company recognized The Company recorded no receivables under service and license agreements as of December 31, 2022 and 2021. The Company recorded $13,000 receivable under service agreement included in prepaid expenses and other current assets as December 31, 2020. The Company recorded 1.2 million contract liabilities as of December 31, 2022. The Company recorded zero and $0.8 million contract liabilities included in other current liabilities, as of December 31, 2021 and 2020, respectively.
Collaborations	Collaborations Historically, the Company has entered into a number of discovery collaborations as the Company developed its discovery platform. These collaborations have generally focused on identifying novel antibodies in areas of significant unmet medical need. In July 2020, the Company entered into a Collaboration and License Agreement with Xencor, Inc., or Xencor Agreement, to research, develop and commercialize novel CD3 bispecific antibodies as potential therapeutics in oncology. Under the Xencor Agreement, the Company and Xencor, Inc. will engage in a three-year research program in which the Company will provide antibodies against novel tumor targets through its discovery platform from which Xencor, Inc. will engineer XmAb bispecific antibodies that also bind to the CD3 receptor on T cells. Up to two joint programs are eligible to be mutually selected for further development and commercialization, with each partner sharing 50% of costs and profits. Each company has the option to lead development, regulatory and commercialization activities for one of the joint programs. In addition, the Xencor Agreement allows each partner the option to pursue up to two programs independently, with a mid-to high-single digit percent royalty payable on net sales to the other partner. The Company evaluated the Xencor Agreement under the provisions of ASC 606 and ASU 2018-18, Collaborative Arrangements (Topic 808) Clarifying the Interaction between Topic 808 and Topic 606. The Company concluded that Xencor, Inc. is not a customer as there are no distinct units of account that are reflective of a vendor-customer relationship or exchange of consideration for the research activities. The Company’s share of any collaboration expense is recognized as an research and development expense on the Company’s statements of operations. For the cost-sharing related to the research program, the Company will follow the presentation and disclosure guidance of ASC 808, Collaboration Agreements
In-Licensing Arrangements - Development	In-Licensing Arrangements – Development In April 2022 The Company will be required to use commercially reasonable efforts to develop and commercialize at least one licensed product and the Company will pay to Zymeworks an option exercise fee, and lump sum payments upon the achievement of certain development and regulatory milestones and commercial milestones. In addition, with respect to each licensed product, the Company will pay tiered royalties on net sales of licensed products at single-digit royalty rates. The research license fee of $5.0 million was expensed to research and development expense in April 2022 in accordance with the Company's research and development expense policy.
Employee Retention Credit	Employee Retention Credit The Coronavirus Aid, Relief and Economic Security, or CARES Act, as amended by the further legislation, provides an employee retention credit, or ERC, to eligible employers, which is a refundable tax credit against certain employment taxes. In calendar 2021, the ERC was equal to 70% of qualified wages paid to employees up to $10,000 of qualified wages per employee for each of the first, second and third calendar quarters of 2021. The Company has determined that its aggregate eligible refundable credit for 2021 is $2.9 million. In May 2022, the Company filed the requisite claims for the eligible 2021 ERC. The Company classified the ERC amounts as a reduction to payroll expense. During the year ended December 31, 2022, the Company recorded $2.4 million and $0.5 million related to the ERC within research and development expense and general and administrative expense, respectively, on the Company’s statements of operations. As of December 31, 2022, the Company has a $2.9 million receivable balance from the United States government related to the CARES Act, which is recorded as other receivables in “Prepaid expenses and other current assets” on the Company’s balance sheet. In January 2023, the Company received the entire balance of ERC of
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include all cash balances and highly liquid investments purchased with an original maturity of three months or less. The Company maintained restricted cash of $1.1 million and $1.5 million as of December 31, 2022 and 2021, respectively. These amounts as of December 31, 2022 and 2021 are included in deposits and other in the accompanying balance sheets and is comprised solely of letters of credit required pursuant to leases for Company facilities. The Company’s reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2022 2021 ​ Cash and cash equivalents ​ $ 30,819 ​ $ 94,746 ​ Restricted cash ​ ​ 1,115 ​ ​ 1,458 ​ Cash, cash equivalents and restricted cash shown in the statements of cash flows ​ $ 31,934 ​ $ 96,204 ​
Investments	​ Investments The Company considers securities purchased with original maturities greater than three months to be investments. The Company’s policy is to protect the value of its investment portfolio and minimize principal risk by earning returns based on current interest rates. The Company’s intent is to convert all investments into cash to be used for operations and has classified them as available for sale. For purposes of determining realized gains and losses, the cost of debt securities sold is based on specific identification. Interest and dividends on securities classified as available-for-sale are included in interest income.
Leases	Leases The Company determines if an arrangement is, or contains, a lease at inception. The Company measures lease liabilities based on the present value of lease payments over the lease term. As the Company’s leases generally do not provide an implicit discount rate, the net present value of future minimum lease payments is determined using the Company’s incremental borrowing rate. Options in the lease terms to extend or terminate the lease are not reflected in the lease liabilities unless it is reasonably certain that any such option will be exercised. The Company measures right-of-use assets at the lease commencement date based on the corresponding lease liabilities adjusted for (i) prepayments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) certain tenant incentives under the lease. The Company evaluates the recoverability of the right-of-use assets for possible impairment in accordance with the long-lived assets policy. The Company has elected not to recognize right-of-use assets or lease liabilities for leases with an initial lease term of twelve months or less. The Company’s lease agreements do not contain residual value guarantees or covenants. Lease expense is recognized on a straight-line basis over the terms of the leases. Incentives granted under the Company’s facilities lease, including rent holidays, are recognized as adjustments to lease expense on a straight-line basis over the terms of the leases. Refer to Recently Adopted Accounting Pronouncements Summary of Significant Accounting Policies Leases
Risks and Uncertainties	Risks and Uncertainties The Company is subject to a number of risks associated with companies at a similar stage, including COVID-19, dependence on key individuals, competition from similar services and larger companies, volatility of the industry, ability to obtain regulatory clearance, ability to obtain adequate financing to support growth, the ability to attract and retain additional qualified personnel to manage the anticipated growth of the Company and general economic conditions.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents, investments and other receivables. Cash and cash equivalents are held at three financial institutions and were in excess of the Federal Deposit Insurance Corporation insurable limit at December 31, 2022 and 2021. Any loss incurred or a lack of access to such funds could have a significant adverse impact on the Company's financial condition, results of operations, and cash flows. Additionally, cash and cash equivalents and investments are maintained at brokerage firms for which amounts are insured by the Securities Investor Protection Corporation subject to legal limits. The Company does not require collateral or other security for other receivables.
Property and Equipment	Property and Equipment, Net Property and equipment are stated at cost less depreciation. Depreciation is computed using the straight-line method with the estimated useful lives of the assets ranging from two
Accounting for Impairment of Long-Lived Assets	Accounting for Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Fair value is estimated based upon internal evaluation of each asset that includes quantitative analyses of cash flows and available market data. Certain factors used for these types of nonrecurring fair value measurements are considered Level 3 inputs. In December 2022, the Company identified certain long-lived assets no longer utilized under current or expected future operations. Accordingly, the Company recognized impairment expense of
Intellectual Property	Intellectual Property Intellectual property-related expenses for the years ended December 31, 2022 and 2021 were $1.1 million and $1.2 million, respectively. As of December 31, 2022, and 2021, the Company has determined that these expenses have not met the criteria to be capitalized.
Deferred Rent	Deferred Rent The Company has entered into lease agreements for its laboratory and office facilities. These leases qualify as and are accounted for as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, stock-based compensation, certain facility costs, legal costs and other costs associated with preclinical and clinical development. A substantial portion of the Company’s ongoing research and development activities are conducted by third-party service providers in connection with preclinical and clinical development activities and contract manufacturing organizations in connection with the production of materials for clinical trials. At the end of the reporting period, the Company compares payments made to third-party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs.
Stock-Based Compensation	Stock-Based Compensation The Company generally grants stock options to its employees for a fixed number of shares with an exercise price equal to the fair value of the underlying shares at the date of grant. The Company accounts for stock option grants using the fair value method. The fair value of options is calculated using the Black-Scholes option pricing model. For restricted stock units, fair value is based on the closing price of the Company’s Class A common stock on the grant date. Stock-based compensation is recognized as the underlying options vest using the straight-line attribution approach, and forfeitures are recorded as they occur.
Emerging Growth Company Status	Emerging Growth Company Status The Company is an “emerging growth company,” or EGC, as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. The Company may take advantage of these exemptions until it is no longer an EGC under Section 107 of the JOBS Act, which provides that an EGC can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards, and as a result of this election, the Company’s financial statements may not be comparable to companies that comply with public company Financial Accounting Standards Board, or FASB, standards’ effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of the IPO or such earlier time that the Company is no longer an EGC.
Income Taxes	Income Taxes The Company applies the provisions set forth in FASB ASC Topic 740, Income Taxes, to account for the uncertainty in income taxes. In the preparation of income tax returns in federal, foreign and state jurisdictions, the Company asserts certain income tax positions based on its understanding and interpretation of income tax laws. The taxing authorities may challenge such positions, and the resolution of such matters could result in recognition of income tax expense in the Company's financial statements. Management believes it has used reasonable judgments and conclusions in the preparation of its income tax returns. The Company recognizes tax benefits from uncertain tax positions only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company does not anticipate any significant changes within 12 months of this reporting date of its uncertain tax positions. The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the financial statement and income tax basis of existing assets and liabilities. A valuation allowance is provided against the Company's deferred income tax assets when realization is not reasonably assured.
Net Loss Per Share	Net Loss Per Share
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016 02 and subsequent amendments to the initial guidance under ASU 2017-13, ASU 2018-10, ASU 2018-11, and ASU 2019-01, or collectively, Topic 842, which modifies the accounting by lessees for all leases with a term greater than 12 months. This standard requires lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The Company adopted the new lease accounting standard on January 1, 2022, using the modified retrospective transition method. The Company implemented processes, and internal controls to enable the preparation of financial information. The adoption of this standard had a material impact on the Company’s balance sheet, with the recognition of right-of-use assets and corresponding lease liabilities in the amounts of $37.7 million and $67.1 million respectively, and the derecognition of approximately $10.9 million of deferred rent and $19.1 million of tenant improvement incentives. The adoption of this standard did not have a material impact on the Company’s statements of operations or cash flows. The Company provided detailed right-of-use asset and liability disclosures as required by the new standard in the notes to the Company’s financial statements under Note 8 Leases. The Company adopted the transitional provisions allowed under ASU 2018-11 and as such, the balance sheets and statements of operations for prior periods are not comparable in the year of adoption of ASU 2016-02. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses Topic 326

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Schedule of reconciliation of cash and cash equivalents and restricted cash	The Company’s reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same amounts shown in the statements of cash flows were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2022 2021 ​ Cash and cash equivalents ​ $ 30,819 ​ $ 94,746 ​ Restricted cash ​ ​ 1,115 ​ ​ 1,458 ​ Cash, cash equivalents and restricted cash shown in the statements of cash flows ​ $ 31,934 ​ $ 96,204 ​

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value of Financial Instruments
Summary of financial assets and liabilities subject to fair value measurements on a recurring basis	The fair value of the Company's assets and liabilities, which qualify as financial instruments under FASB ASC 820, Fair Value Measurements and Disclosures ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 29,658 ​ $ — ​ $ — ​ $ 29,658 Certificates of deposit ​ ​ 483 ​ ​ — ​ ​ — ​ ​ 483 Corporate debt securities ​ ​ — ​ ​ 1,996 ​ ​ — ​ ​ 1,996 U.S. Treasury securities ​ ​ 37,197 ​ ​ — ​ ​ — ​ ​ 37,197 Total ​ $ 67,338 ​ $ 1,996 ​ $ — ​ $ 69,334 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ Level 1 Level 2 Level 3 Total Assets ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 90,251 ​ $ — ​ $ — ​ $ 90,251 Certificates of deposit ​ ​ 1,672 ​ ​ — ​ ​ — ​ ​ 1,672 Corporate debt securities ​ ​ — ​ ​ 6,089 ​ ​ — ​ ​ 6,089 U.S. Treasury securities ​ ​ 45,568 ​ ​ — ​ ​ — ​ ​ 45,568 Total ​ $ 137,491 ​ $ 6,089 ​ $ — ​ $ 143,580 ​

Cash, Cash Equivalents and In_2

Cash, Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2022
Cash, Cash Equivalents and Investments
Summary of fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type	The fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ Cash and ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cash ​ Short-term ​ Long-term December 31, 2022 Cost Gains Losses Value Equivalents ​ Investment ​ Investment Cash, cash equivalents and money market funds ​ $ 30,819 ​ $ — ​ $ — ​ $ 30,819 ​ $ 30,819 ​ $ — ​ $ — ​ Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury securities ​ 37,458 ​ ​ — ​ ​ (261) ​ ​ 37,197 ​ ​ — ​ ​ 37,197 ​ ​ — ​ Corporate debt securities ​ ​ 1,999 ​ ​ — ​ ​ (3) ​ ​ 1,996 ​ ​ — ​ ​ 1,996 ​ ​ — ​ Certificates of deposit ​ ​ 485 ​ — ​ (2) ​ 483 ​ — ​ 483 ​ ​ — ​ Total ​ $ 70,761 ​ $ — ​ $ (266) ​ $ 70,495 ​ $ 30,819 ​ $ 39,676 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ Cash and ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cash ​ Short-term ​ Long-term December 31, 2021 Cost Gains Losses Value Equivalents ​ Investment ​ Investment Cash, cash equivalents and money market funds ​ $ 94,746 ​ $ — ​ $ — ​ $ 94,746 ​ $ 94,746 ​ $ — ​ $ — ​ Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury securities ​ 45,665 ​ ​ — ​ ​ (97) ​ ​ 45,568 ​ ​ — ​ ​ 15,014 ​ ​ 30,554 ​ Corporate debt securities ​ ​ 6,093 ​ ​ — ​ ​ (4) ​ ​ 6,089 ​ ​ — ​ ​ 6,089 ​ ​ — ​ Certificates of deposit ​ ​ 1,673 ​ — ​ (1) ​ 1,672 ​ — ​ 1,184 ​ ​ 488 ​ Total ​ $ 148,177 ​ $ — ​ $ (102) ​ $ 148,075 ​ $ 94,746 ​ $ 22,287 ​ $ 31,042 ​ ​

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2022
Prepaid Expenses and Other Current Assets.
Summary of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2022 2021 Vendor prepayments and deposits ​ $ 2,010 ​ $ 2,681 ​ Prepaid insurance ​ ​ 1,026 ​ ​ 1,531 ​ Prepaid facility maintenance fee ​ 336 ​ 807 ​ Other receivables ​ 3,985 ​ — ​ Interest receivables and other current assets ​ ​ 174 ​ ​ 318 ​ Total prepaid expenses and other current assets ​ $ 7,531 ​ $ 5,337 ​

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2022
Property and Equipment, net
Summary of property and equipment	Property and equipment consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 2021 Laboratory equipment ​ $ 13,191 ​ $ 13,128 ​ Furniture and fixtures ​ 1,929 ​ 1,897 ​ Computer hardware and software ​ 1,518 ​ 1,433 ​ Leasehold improvements ​ 37,908 ​ 37,871 ​ Construction in process ​ 178 ​ — ​ ​ ​ 54,724 ​ 54,329 ​ Less accumulated depreciation and amortization ​ (16,752) ​ (11,314) ​ Total property and equipment, net ​ $ 37,972 ​ $ 43,015 ​ ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2022
Accrued Expenses
Summary of accrued expenses	Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 2021 Compensation and related benefits ​ $ 3,789 ​ $ 4,866 License fees ​ ​ 3,000 ​ ​ — Contract research fees ​ ​ 2,201 ​ ​ 5,521 Professional fees ​ ​ 128 ​ ​ 189 Cease use ​ ​ — ​ ​ 475 Other ​ ​ 563 ​ ​ 504 Total accrued expenses ​ $ 9,681 ​ $ 11,555

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases
Schedule of future lease payments	The Company's future lease payments as of December 31, 2022, which are presented as current portion of operating lease liabilities, and operating lease liabilities, net of current portion on the Company's balance sheets (in thousands, except weighted-average data) are as follows: ​ ​ ​ ​ ​ ​ ​ Operating ​ ​ Leases Periods ​ ​ ​ 2023 ​ $ 7,635 2024 ​ 7,846 2025 ​ 8,064 2026 ​ ​ 8,288 2027 ​ ​ 8,519 Thereafter ​ ​ 48,771 Total lease payments ​ $ 89,123 Less: imputed interest ​ (25,248) Present value of lease liabilities ​ $ 63,875 ​ ​ ​ ​ Lease liabilities, current ​ ​ 3,544 Lease liabilities, noncurrent ​ ​ 60,331 Total lease liabilities ​ $ 63,875 ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 10.4 Weighted-average discount rate ​ ​ 6.64% ​

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	Stock option activity under the 2019 Plan and the 2010 Plan is as follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ Aggregate ​ ​ ​ ​ Weighted- ​ Remaining ​ Intrinsic ​ ​ Number ​ Average ​ Contractual ​ Value ​ of Shares ​ Exercise Price ​ Life (years) ​ (in thousands) Balances, December 31, 2020 4,812,223 ​ $ 13.33 ​ 8.2 ​ $ 21,493 Granted 3,192,470 ​ 8.99 ​ ​ ​ Exercised (47,061) ​ 5.81 ​ ​ ​ Cancelled (794,956) ​ 15.06 ​ ​ ​ Balances, December 31, 2021 7,162,676 ​ $ 11.25 ​ 8.2 ​ $ 21 Granted 446,100 ​ 1.88 ​ ​ ​ Exercised (16,666) ​ 4.56 ​ ​ ​ Cancelled (1,218,576) ​ 7.87 ​ ​ ​ Balances, December 31, 2022 6,373,534 ​ $ 3.56 ​ 7.3 ​ $ 2 Vested and expected to vest at December 31, 2022 6,373,534 ​ $ 3.56 ​ 7.3 ​ $ 2 Exercisable at December 31, 2022 4,178,167 ​ $ 4.02 ​ 6.6 ​ $ 2 Vested at December 31, 2022 4,178,167 ​ $ 4.02 ​ 6.6 ​ $ 2 ​
Schedule of share-based payment arrangement, option, exercise price range	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Vested and Exercisable ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ Remaining ​ Weighted- ​ ​ ​ Average ​ ​ Number of ​ Contractual ​ Average ​ Shares Subject ​ Exercise ​ ​ Stock Options ​ Life ​ Exercise Price ​ to Stock ​ Price per Exercise Prices ​ Outstanding ​ (Years) ​ per Share ​ Options ​ Share Up to $1.83 ​ 254,603 ​ 9.3 ​ $ 1.66 ​ 11,034 ​ $ 0.80 $1.84-$1.89 3,295,250 7.1 ​ $ 1.85 2,414,136 ​ $ 1.85 $1.90-$3.22 ​ 1,270,054 ​ 9.0 ​ $ 3.02 ​ 299,531 ​ $ 3.11 $3.23-$5.40 ​ 990,414 ​ 5.2 ​ $ 5.06 ​ 969,539 ​ $ 5.09 $5.41-$22.07 563,213 7.3 ​ $ 13.01 483,927 ​ $ 13.35 ​ 6,373,534 7.3 ​ $ 3.56 4,178,167 ​ $ 4.02
Schedule of summarizes RSU activity	RSU activity for the years ended December 31, 2022 and 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ Number ​ Grant Date ​ of Shares ​ Fair Value per RSU Unvested Balances, December 31, 2020 — ​ $ — RSUs Granted 884,820 ​ 6.15 RSUs Vested ​ — ​ ​ — RSUs Cancelled (17,090) ​ 6.15 Unvested Balances, December 31, 2021 867,730 ​ $ 6.15 RSUs Vested ​ (384,390) ​ ​ 6.15 RSUs Cancelled (152,900) ​ 6.15 Unvested Balances, December 31, 2022 330,440 ​ $ 6.15
Schedule of stock-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 Research and development ​ $ 7,910 ​ $ 8,571 ​ General and administrative ​ 8,981 ​ 8,305 ​ ​ ​ $ 16,891 ​ $ 16,876 ​ ​
2019 Plan and 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of share-based payment award, stock options, valuation assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 2021 Expected life (in years) 5.89 5.98 ​ ​ Volatility 86.0 % 90.3 % ​ Risk-free interest rate 3.3 % 0.9 % ​ ​
2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of share-based payment award, stock options, valuation assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2022 2021 Expected life (in years) 0.5 - 2.0 0.5 - 2.0 ​ ​ Volatility 79.0 - 96.7 % 91.1 - 107.6 % ​ Risk-free interest rate 0.6 - % 0.1 - % ​ ​

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2022
Net Loss Per Share
Schedule of earnings per share, basic and diluted	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Numerator: ​ ​ ​ ​ ​ ​ Net loss attributable to common stockholders for earnings per share, basic and diluted ​ $ (97,157) ​ $ (109,326) Denominator: ​ ​ ​ ​ ​ ​ Shares used to compute net loss per share, basic and diluted ​ ​ 38,593,894 ​ ​ 37,038,195 Basic and diluted net loss attributable to common stockholders per share ​ $ (2.52) ​ $ (2.95) ​
Schedule of antidilutive securities excluded from computation of earnings per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Common stock options ​ ​ 6,373,534 ​ ​ 7,162,676 Unvested restricted stock units ​ ​ 330,440 ​ ​ 867,730 Common stock warrants ​ — ​ 49,997 ​ ​ ​ 6,703,974 ​ ​ 8,080,403

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Taxes
Schedule of effective income tax rate reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2022 2021 ​ Tax computed at federal statutory rate ​ 21.0 % 21.0 % State income taxes, net of federal benefit ​ (0.7) % 2.3 % Other ​ (4.4) % (1.8) % Change in valuation allowance ​ (15.6) % (24.2) % Credits ​ (0.3) % 2.7 % Effective income tax rate ​ 0.0 % 0.0 % ​
Schedule of deferred tax assets and liabilities	Significant components of the Company's deferred income tax assets and liabilities are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2022 2021 Deferred tax assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforward ​ $ 69,296 ​ $ 63,581 ​ Tax credits ​ 14,862 ​ 15,684 ​ Lease liability ​ ​ 13,414 ​ ​ — ​ Capitalized research and development expenses ​ ​ 11,175 ​ ​ — ​ Intangibles ​ 1,090 ​ 1,211 ​ Fixed assets ​ ​ 410 ​ ​ — ​ Other ​ 4,172 ​ 7,528 ​ Total deferred tax assets ​ 114,419 ​ 88,004 ​ Deferred tax liabilities: ​ ​ ​ Fixed assets ​ — ​ 121 ​ ROU assets ​ 11,289 ​ — ​ Total deferred tax liabilities ​ 11,289 ​ 121 ​ Valuation allowance ​ (103,130) ​ (87,883) ​ Total ​ $ — ​ $ — ​ ​
Schedule of unrecognized tax benefits roll forward	The following table summarizes the changes in the Company’s unrecognized tax benefits during the periods presented (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2022 2021 ​ ​ ​ ​ ​ ​ ​ Beginning of period ​ $ 4,951 ​ $ 3,378 Current period tax position increases ​ 536 ​ 1,806 Prior period tax position changes ​ (747) ​ (233) End of period ​ $ 4,740 ​ $ 4,951

Business (Details)

Business (Details)	12 Months Ended
	Dec. 31, 2022 segment
Business
Number of operating segments	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) Institution shares	Dec. 31, 2021 USD ($) Institution	Dec. 31, 2020 USD ($)
Other Income
Expected service period	18 months
Contract liabilities	$ 1,200,000	$ 0	$ 800,000
Convertible Preferred Stock Warrants
Warrants outstanding | shares	0
Concentration of credit risk
Number of financial institutions holding cash and cash and cash equivalents | Institution	3	3
Assignment and License Agreement | Prepaid expenses and other current assets
Other Income
Receivables under agreements	$ 0	$ 0	$ 13,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Collaboration and Service Arrangements (Details)	1 Months Ended	12 Months Ended
	Jul. 31, 2020 Program	Dec. 31, 2022 USD ($)	Oct. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research cost sharing provision payable		$ 12,000		$ 12,000
Research cost sharing provision receivable		25,000		$ 25,000
Collaboration And License Agreement | Xencor Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Term of the research program (in years)	3 years
Maximum number of joint programs eligible for further development and commercialization | Program	2
Percentage of costs and profit shared by partners	50%
Maximum number of independent programs each partner may pursue | Program	2
Grant Agreement | Bill & Melinda Gates Foundation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amount of grant awarded			$ 1,200,000
Income related to Grant Agreement		20,000
Unused funds received recorded as deferred revenue		$ 1,200,000

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - In-Licensing Arrangements - Development (Details) - Option and license agreement - Zymeworks Inc $ in Millions	1 Months Ended
	Apr. 30, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Commercial option to extend research license	2 years
Upfront consideration for purchase of license	$ 5
Term of the research license	2 years
Research and development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront consideration for purchase of license	$ 5

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Employee Retention Credit (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Unusual or Infrequent Item, or Both [Line Items]
Eligible refundable credit			$ 2.9
Employee retention credit amount received from Internal revenue service	$ 2.9
Prepaid expenses and other current assets
Unusual or Infrequent Item, or Both [Line Items]
Amount receivable from government		$ 2.9
Research and development
Unusual or Infrequent Item, or Both [Line Items]
Employee retention tax credit		2.4
General and administrative
Unusual or Infrequent Item, or Both [Line Items]
Employee retention tax credit		$ 0.5

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash and cash equivalents and restricted cash reported within the condensed balance sheets
Cash and cash equivalents	$ 30,819	$ 94,746
Restricted cash	$ 1,115	$ 1,458
Restricted Cash, Asset, Statement of Financial Position [Extensible List]	Deposits and Others	Deposits and Others
Cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 31,934	$ 96,204	$ 62,441

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment
Asset impairment	$ 449	$ 0
Minimum
Property and Equipment
Estimated useful lives	2 years
Maximum
Property and Equipment
Estimated useful lives	5 years

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Intellectual Property (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Summary of Significant Accounting Policies
Intellectual property-related expenses	$ 1.1	$ 1.2

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	6,703,974	8,080,403
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	0	0

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Recent Accounting Pronouncements Not Yet Adopted (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Jan. 01, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 36,056
Operating lease liabilities	$ 63,875
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 37,700
Operating lease liabilities		67,100
Deferred rent derecognized		10,900
Tenant improvement derecognized		$ 19,100

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Maximum
Company's financial assets and liabilities subject to fair value measurements on a recurring basis
Remaining contractual maturity of marketable securities (in years)	2 years	2 years
Recurring basis
Assets
Total assets	$ 69,334	$ 143,580
Recurring basis | Money market funds
Assets
Total assets	29,658	90,251
Recurring basis | Certificates of deposit
Assets
Total assets	483	1,672
Recurring basis | Corporate debt securities
Assets
Total assets	1,996	6,089
Recurring basis | U.S. Treasury securities
Assets
Total assets	37,197	45,568
Recurring basis | Level 1
Assets
Total assets	67,338	137,491
Recurring basis | Level 1 | Money market funds
Assets
Total assets	29,658	90,251
Recurring basis | Level 1 | Certificates of deposit
Assets
Total assets	483	1,672
Recurring basis | Level 1 | U.S. Treasury securities
Assets
Total assets	37,197	45,568
Recurring basis | Level 2
Assets
Total assets	1,996	6,089
Recurring basis | Level 2 | Corporate debt securities
Assets
Total assets	$ 1,996	$ 6,089

Cash, Cash Equivalents and In_3

Cash, Cash Equivalents and Investments - Fair value and Amortized cost (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	$ 30,819	$ 94,746
Short-term Investment	39,676	22,287
Long-term Investment		31,042
Cash, cash equivalents and money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	30,819	94,746
Available-for-sale:
Amortized Cost	30,819	94,746
Estimated Fair Value	30,819	94,746
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Short-term Investment	37,197	15,014
Long-term Investment		30,554
Available-for-sale:
Amortized Cost	37,458	45,665
Gross Unrealized Losses	(261)	(97)
Estimated Fair Value	37,197	45,568
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Short-term Investment	1,996	6,089
Available-for-sale:
Amortized Cost	1,999	6,093
Gross Unrealized Losses	(3)	(4)
Estimated Fair Value	1,996	6,089
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Short-term Investment	483	1,184
Long-term Investment		488
Available-for-sale:
Amortized Cost	485	1,673
Gross Unrealized Losses	(2)	(1)
Estimated Fair Value	483	1,672
Total
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	30,819	94,746
Short-term Investment	39,676	22,287
Long-term Investment		31,042
Available-for-sale:
Amortized Cost	70,761	148,177
Gross Unrealized Losses	(266)	(102)
Estimated Fair Value	$ 70,495	$ 148,075

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expenses and Other Current Assets.
Vendor prepayments and deposits	$ 2,010	$ 2,681
Prepaid insurance	1,026	1,531
Prepaid facility maintenance fee	336	807
Other receivables	3,985
Interest receivables and other current assets	174	318
Total prepaid expenses and other current assets	$ 7,531	$ 5,337

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	$ 54,724	$ 54,329
Less accumulated depreciation and amortization	(16,752)	(11,314)
Total property and equipment, net	37,972	43,015
Depreciation and amortization expense	5,500	4,500
Asset impairment	449	0
Laboratory equipment
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	13,191	13,128
Furniture and fixtures
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	1,929	1,897
Computer hardware and software
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	1,518	1,433
Leasehold improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	37,908	$ 37,871
Construction-in-process
Property, Plant and Equipment, Net, by Type [Abstract]
Property, plant and equipment, gross	$ 178

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued Expenses
Compensation and related benefits	$ 3,789	$ 4,866
License fees	3,000
Contract research fees	2,201	5,521
Professional fees	128	189
Cease use		475
Other	563	504
Total accrued expenses	$ 9,681	$ 11,555

Leases (Details)

Leases (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2022	Dec. 31, 2021
Leases
Gain (loss) on termination of lease	$ 1.5
Lease expense		$ 5.9
Variable lease expense		3.6
Rent expenses			$ 13.2
Cash paid for operating lease liabilities		$ 7.5

Leases - Future lease payments

Leases - Future lease payments (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Leases
2023	$ 7,635
2024	7,846
2025	8,064
2026	8,288
2027	8,519
Thereafter	48,771
Total lease payments	89,123
Less: imputed interest	(25,248)
Present value of lease liabilities	63,875
Lease liabilities, current	3,544
Lease liabilities, noncurrent	$ 60,331
Weighted-average remaining lease term (in years)	10 years 4 months 24 days
Weighted-average discount rate	6.64%

Reorganization and Other Char_2

Reorganization and Other Charges (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Dec. 31, 2022
Reorganization and Other Charges
Severance and employee benefits charges	$ 0.7
Outstanding liability		$ 0

Capital Stock (Details)

Capital Stock (Details) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jun. 02, 2019 Vote $ / shares shares	Aug. 31, 2020 USD ($)	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares
Class of Stock [Line Items]
Preferred stock, shares authorized | shares	300,000,000
Preferred stock par value | $ / shares	$ 0.0001
Net proceeds from sales			$ 3,509	$ 4,385
At The Market Offering [Member]
Class of Stock [Line Items]
Percentage of gross proceeds as compensation for services		3%
Class A common stock
Class of Stock [Line Items]
Common stock, shares authorized | shares	650,000,000		650,000,000	650,000,000
Common stock, par value | $ / shares	$ 0.0001		$ 0.0001	$ 0.0001
Number of votes entitled per share | Vote	1
Class A common stock | At The Market Offering [Member]
Class of Stock [Line Items]
Share offering price		$ 100,000
Shares sold | shares			1,493,361
Net proceeds from sales			$ 7,900
Underwriting fees			300
Issuance costs deduction amount from gross proceeds			$ 300
Class B common stock
Class of Stock [Line Items]
Common stock, shares authorized | shares	50,000,000		50,000,000	50,000,000
Common stock, par value | $ / shares	$ 0.0001		$ 0.0001	$ 0.0001

Equity Incentive Plans - Stock

Equity Incentive Plans - Stock Option Repricing (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jun. 13, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense, vested		$ 16,891	$ 16,876
2019 Plan and 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price	$ 9
Modified exercise price	$ 1.845
Number of Stock options outstanding	3,606,163	6,373,534	7,162,676	4,812,223
Exercise price, lower range limit	$ 9.87
Exercise price, upper range limit	$ 22.10
Incremental stock based compensation expense	$ 2,500
Stock-based compensation expense, vested		$ 1,900
Stock-based compensation expense, unvested	$ 600
Remaining weighted-average vesting period	1 year

Equity Incentive Plans - Stoc_2

Equity Incentive Plans - Stock option (Details) - 2019 Plan and 2010 Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Balance at beginning of period (in shares)	7,162,676	4,812,223
Granted (in shares)	446,100	3,192,470
Exercised (in shares)	(16,666)	(47,061)
Cancelled (in shares)	(1,218,576)	(794,956)
Balance at end of period (in shares)	6,373,534	7,162,676	4,812,223
Vested and expected to vest at end of period (in shares)	6,373,534
Exercisable at end of period (in shares)	4,178,167
Vested at end of period (in shares)	4,178,167
Weighted-Average Exercise Price
Balance at beginning of period (in dollars per share)	$ 11.25	$ 13.33
Granted (in dollars per share)	1.88	8.99
Exercised (in dollars per share)	4.56	5.81
Cancelled (in dollars per share)	7.87	15.06
Balance at end of period (in dollars per share)	3.56	$ 11.25	$ 13.33
Vested and expected to vest at end of period (in dollars per share)	3.56
Exercisable at end of period (in dollars per share)	4.02
Vested at end of period (in dollars per share)	$ 4.02
Weighted-Average Remaining Contractual Life
Weighted-average remaining contractual life of options (years)	7 years 3 months 18 days	8 years 2 months 12 days	8 years 2 months 12 days
Vested and expected to vest at end of period (in years)	7 years 3 months 18 days
Exercisable at end of period (in years)	6 years 7 months 6 days
Vested at end of period (in years)	6 years 7 months 6 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options	$ 2	$ 21	$ 21,493
Vested and expected to vest at end of period	2
Exercisable at end of period	2
Vested at end of period	$ 2

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional information regarding stock option (Details) - 2019 Plan and 2010 Plan - $ / shares		12 Months Ended
	Jun. 13, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, lower range limit	$ 9.87
Exercise price, upper range limit	$ 22.10
Number of Shares
Number of Stock options outstanding	3,606,163	6,373,534	7,162,676	4,812,223
Shares subject to stock options		4,178,167
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 3.56	$ 11.25	$ 13.33
Options Vested and Exercisable, weighted-average exercise Price per share		$ 4.02
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		7 years 3 months 18 days	8 years 2 months 12 days	8 years 2 months 12 days
Up to $1.83
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, upper range limit		$ 1.83
Number of Shares
Number of Stock options outstanding		254,603
Shares subject to stock options		11,034
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 1.66
Options Vested and Exercisable, weighted-average exercise Price per share		$ 0.80
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		9 years 3 months 18 days
$1.84-$1.89
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, lower range limit		$ 1.84
Exercise price, upper range limit		$ 1.89
Number of Shares
Number of Stock options outstanding		3,295,250
Shares subject to stock options		2,414,136
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 1.85
Options Vested and Exercisable, weighted-average exercise Price per share		$ 1.85
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		7 years 1 month 6 days
$1.90-$3.22
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, lower range limit		$ 1.90
Exercise price, upper range limit		$ 3.22
Number of Shares
Number of Stock options outstanding		1,270,054
Shares subject to stock options		299,531
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 3.02
Options Vested and Exercisable, weighted-average exercise Price per share		$ 3.11
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		9 years
$3.23-$5.40
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, lower range limit		$ 3.23
Exercise price, upper range limit		$ 5.40
Number of Shares
Number of Stock options outstanding		990,414
Shares subject to stock options		969,539
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 5.06
Options Vested and Exercisable, weighted-average exercise Price per share		$ 5.09
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		5 years 2 months 12 days
$5.41-$22.07
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, lower range limit		$ 5.41
Exercise price, upper range limit		$ 22.07
Number of Shares
Number of Stock options outstanding		563,213
Shares subject to stock options		483,927
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share		$ 13.01
Options Vested and Exercisable, weighted-average exercise Price per share		$ 13.35
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding		7 years 3 months 18 days

Equity Incentive Plans - Weight

Equity Incentive Plans - Weighted-average grant date fair value (Details) - 2019 Plan - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value (in dollars per share)	$ 1.26	$ 6.66
Intrinsic value of options exercised	$ 8,000	$ 519,000
Expected dividend	0%	0%

Equity Incentive Plans - Weig_2

Equity Incentive Plans - Weighted average assumptions (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
2019 Plan and 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	5 years 10 months 20 days	5 years 11 months 23 days
Volatility	86%	90.30%
Risk-free interest rate	3.30%	0.90%
2019 Employee Stock Purchase Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	6 months	6 months
Volatility	79%	91.10%
Risk-free interest rate	0.60%	0.10%
2019 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	2 years	2 years
Volatility	96.70%	107.60%
Risk-free interest rate	3.50%	0.20%

Equity Incentive Plans - Restri

Equity Incentive Plans - Restricted Stock Units (Details) - Unvested restricted stock units - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of Shares
Unvested balance, at beginning of period (in shares)	867,730
RSUs Granted (in shares)		884,820
RSUs Vested (in shares)	(384,390)
RSUs Cancelled (in shares)	(152,900)	(17,090)
Unvested balance, at end of period (in shares)	330,440	867,730
Weighted-Average Grant Date Fair Value per RSU
Weighted-Average Grant Date Fair Value per RSU Unvested balance, at beginning of period (in dollars per share)	$ 6.15
RSUs Granted (in dollars per share)		$ 6.15
RSUs Vested (in dollars per share)	6.15
RSUs Cancelled (in dollars per share)	6.15	6.15
Weighted-Average Grant Date Fair Value per RSU Unvested balance, at end of period (in dollars per share)	$ 6.15	$ 6.15
2019 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Vesting on the one year anniversary | 2019 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50%
Vesting on the two year anniversary | 2019 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50%

Equity Incentive Plans - 2019 E

Equity Incentive Plans - 2019 Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 16,891	$ 16,876
Class A common stock | 2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 800	$ 800
Expected dividend	0%	0%

Equity Incentive Plans - Stock-

Equity Incentive Plans - Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 16,891	$ 16,876
Income tax benefits for stock-based compensation	0	0
Stock-based compensation costs capitalized	0	0
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	7,910	8,571
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 8,981	$ 8,305

Equity Incentive Plans - Unreco

Equity Incentive Plans - Unrecognized compensation (Details) - 2019 Plan $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Common stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 12.2
Remaining weighted-average requisite service period	1 year 9 months 18 days
Unvested restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 1.3
Remaining weighted-average requisite service period	8 months 12 days

Equity Incentive Plans - Conver

Equity Incentive Plans - Convertible Preferred Stock Warrant (Details) - shares	1 Months Ended	12 Months Ended
	Aug. 31, 2022	Dec. 31, 2019	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding warrants expired	49,997
Warrants outstanding			0
Convertible preferred stock warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of convertible preferred stock (in shares)		49,997

401(k) Plan (Details)

401(k) Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
401 (k) Plan
Employer contribution (as a percent)	100%
Amount up to which the employer matches 100 percent contribution	$ 5,000
Total matching contributions	$ 600,000	$ 600,000

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 attributable to common stockholders for earnings per share, basic and diluted	$ (97,157)	$ (109,326)
Denominator:
Shares used to compute net loss per share, basic	38,593,894	37,038,195
Shares used to compute net loss per share, diluted	38,593,894	37,038,195
Basic net loss attributable to common stockholders per share	$ (2.52)	$ (2.95)
Diluted net loss attributable to common stockholders per share	$ (2.52)	$ (2.95)

Net Loss Per Share - Antidiluti

Net Loss Per Share - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	6,703,974	8,080,403
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	6,373,534	7,162,676
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	330,440	867,730
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation		49,997

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands		12 Months Ended
	Mar. 27, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Period of operating loss carryback	5 years
Percentage of taxable income limitation of net operating loss carryforwards	80%
Amount of increase in deferred tax assets		$ 11,200
Unrecognized tax benefits		4,740	$ 4,951	$ 3,378
Interest or penalties		0	0
Net increase in valuation allowance		$ 15,200	26,500
Federal
Operating Loss Carryforwards [Line Items]
Percentage of taxable income limitation of net operating loss carryforwards		80%
Operating loss carryforwards		$ 46,500
Operating loss carryforwards, not subject to expiration		276,100
Tax credit carryforward		13,100	13,200
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		13,100
Tax credit carryforward		$ 8,900	$ 9,700

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the federal statutory income tax rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of the federal statutory income tax rate
Tax computed at federal statutory rate	21%	21%
State income taxes, net of federal benefit	(0.70%)	2.30%
Other	(4.40%)	(1.80%)
Change in valuation allowance	(15.60%)	(24.20%)
Credits	(0.30%)	2.70%
Effective income tax rate	0%	0%

Income Taxes - Deferred income

Income Taxes - Deferred income tax assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforward	$ 69,296	$ 63,581
Tax credits	14,862	15,684
Lease Liability	13,414
Capitalized research and development expenses	11,175
Intangibles	1,090	1,211
Fixed assets	410
Other	4,172	7,528
Total deferred tax assets	114,419	88,004
Fixed assets		121
ROU assets	11,289
Total deferred tax liabilities	11,289	121
Valuation allowance	(103,130)	(87,883)
Unrecognized Tax Benefits
Unrecognized benefit - beginning of period	4,951	3,378
Current period tax position increases	536	1,806
Prior period tax position changes	(747)	(233)
Unrecognized benefit - end of period	$ 4,740	$ 4,951

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Due to related party	$ 74,000	$ 74,000
Research and development expense	250,000	250,000
Other income	20,000	1,000
Receivable from stockholders	0	0
Intellectual property related legal fees
Related Party Transaction [Line Items]
Expense	1,100,000	1,300,000
Due to related party	172,000	203,000
Other legal fees
Related Party Transaction [Line Items]
Expense	1,000,000	700,000
Due to related party	$ 33,000	$ 86,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands, shares in Millions	Mar. 10, 2023	Feb. 09, 2023	Dec. 31, 2022	Dec. 31, 2021
Subsequent Event [Line Items]
Cash and Cash Equivalents			$ 30,819	$ 94,746
Subsequent event | Maximum | Silicon Valley Bank
Subsequent Event [Line Items]
Cash and Cash Equivalents	$ 5,000
Subsequent event | Class A common stock | Inducement Plan 2023
Subsequent Event [Line Items]
Shares available for issuance		1