Alpine Immune Sciences (ALPN) 10-Q 14 Aug 23 2023 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2023	Aug. 04, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Transition Report	false
Entity File Number	001-37449
Entity Registrant Name	ALPINE IMMUNE SCIENCES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8969493
Entity Address, Address Line One	188 East Blaine Street, Suite 200
Entity Address, City or Town	Seattle
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98102
City Area Code	206
Local Phone Number	788-4545
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ALPN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		49,201,547
Entity Central Index Key	0001626199
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 34,076	$ 13,376
Short-term investments	169,724	224,265
Accounts receivable	284	392
Prepaid expenses and other current assets	3,237	2,960
Total current assets	207,321	240,993
Restricted cash, noncurrent	254	254
Property and equipment, net	1,672	1,584
Operating lease, right-of-use asset	7,877	8,219
Long-term investments	35,561	35,481
Deferred tax asset	151	155
Total assets	252,836	286,686
Current liabilities:
Accounts payable	1,645	4,286
Accrued liabilities	13,684	14,003
Deferred revenue, current	37,252	35,571
Operating lease liability, current	829	756
Current portion of long-term debt	0	3,380
Total current liabilities	53,410	57,996
Deferred revenue, noncurrent	20,475	39,185
Operating lease liability, noncurrent	9,563	10,085
Total liabilities	83,448	107,266
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized at June 30, 2023 and December 31, 2022; zero shares issued and outstanding at June 30, 2023 and December 31, 2022	0	0
Common stock, $0.001 par value per share; 200,000,000 shares authorized at June 30, 2023 and December 31, 2022; 49,124,640 shares issued and outstanding at June 30, 2023; 47,234,900 shares issued and 45,984,433 shares outstanding at December 31, 2022	49	46
Treasury stock, at cost; 0 and 1,250,467 shares at June 30, 2023 and December 31, 2022, respectively	0	0
Additional paid-in capital	420,372	404,456
Accumulated other comprehensive loss	(650)	(1,121)
Accumulated deficit	(250,383)	(223,961)
Total stockholders’ equity	169,388	179,420
Total liabilities and stockholders’ equity	$ 252,836	$ 286,686

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	49,124,640	47,234,900
Common stock, shares outstanding (in shares)	49,124,640	45,984,433
Treasury stock, shares (in shares)	0	1,250,467

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Collaboration [Member]	Collaboration [Member]	Collaboration [Member]	Collaboration [Member]
Collaboration revenue	$ 8,593	$ 5,292	$ 17,980	$ 18,921
Operating expenses:
Research and development	19,241	17,587	38,822	33,898
General and administrative	5,007	4,194	10,405	8,969
Total operating expenses	24,248	21,781	49,227	42,867
Loss from operations	(15,655)	(16,489)	(31,247)	(23,946)
Other income (expense):
Interest income	2,528	314	4,946	459
Interest expense	(28)	(130)	(98)	(284)
Other, net	(1)	(15)	(23)	(72)
Loss before taxes	(13,156)	(16,320)	(26,422)	(23,843)
Income tax expense	0	(1,778)	0	(1,782)
Net loss	(13,156)	(18,098)	(26,422)	(25,625)
Comprehensive income (loss):
Unrealized (loss) gain on investments	(238)	(304)	507	(1,078)
Unrealized loss on foreign currency translation	(5)	(4)	(36)	(18)
Comprehensive loss	$ (13,399)	$ (18,406)	$ (25,951)	$ (26,721)
Weighted-average shares used to compute basic net loss per share (in shares)	48,049,936	30,324,933	47,810,374	30,311,527
Weighted-average shares used to compute diluted net loss per share (in shares)	48,049,936	30,324,933	47,810,374	30,311,527
Basic net loss per share (in dollars per share)	$ (0.27)	$ (0.60)	$ (0.55)	$ (0.85)
Diluted net loss per share (in dollars per share)	$ (0.27)	$ (0.60)	$ (0.55)	$ (0.85)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance, common stock (in shares) at Dec. 31, 2021		30,194,279
Beginning balance, treasury stock (in shares) at Mar. 31, 2022			1,250,467
Beginning balance at Dec. 31, 2021	$ 120,903	$ 30		$ 287,345	$ (273)	$ (166,199)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,289			2,289
Issuance of common stock under equity incentive plans (in shares)		100,155
Issuance of common stock under equity incentive plans	550			550
Unrealized (loss) gain on investments	(774)				(774)
Unrealized loss on foreign currency translation	(14)				(14)
Net loss	(7,527)					(7,527)
Ending balance, common stock (in shares) at Mar. 31, 2022		30,294,434
Ending balance, treasury stock (in shares) at Dec. 31, 2021			1,250,467
Ending balance at Mar. 31, 2022	115,427	$ 30		290,184	(1,061)	(173,726)
Beginning balance, common stock (in shares) at Dec. 31, 2021		30,194,279
Beginning balance, treasury stock (in shares) at Jun. 30, 2022			1,250,467
Beginning balance at Dec. 31, 2021	120,903	$ 30		287,345	(273)	(166,199)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized (loss) gain on investments	(1,078)
Unrealized loss on foreign currency translation	(18)
Net loss	(25,625)
Ending balance, common stock (in shares) at Jun. 30, 2022		30,336,162
Ending balance, treasury stock (in shares) at Dec. 31, 2021			1,250,467
Ending balance at Jun. 30, 2022	99,536	$ 30		292,699	(1,369)	(191,824)
Beginning balance, common stock (in shares) at Mar. 31, 2022		30,294,434
Beginning balance, treasury stock (in shares) at Jun. 30, 2022			1,250,467
Beginning balance at Mar. 31, 2022	115,427	$ 30		290,184	(1,061)	(173,726)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,335			2,335
Issuance of common stock under equity incentive plans (in shares)		41,728
Issuance of common stock under equity incentive plans	180			180
Unrealized (loss) gain on investments	(304)				(304)
Unrealized loss on foreign currency translation	(4)				(4)
Net loss	(18,098)					(18,098)
Ending balance, common stock (in shares) at Jun. 30, 2022		30,336,162
Ending balance, treasury stock (in shares) at Mar. 31, 2022			1,250,467
Ending balance at Jun. 30, 2022	$ 99,536	$ 30		292,699	(1,369)	(191,824)
Beginning balance, common stock (in shares) at Dec. 31, 2022	45,984,433	45,984,433
Beginning balance, treasury stock (in shares) at Mar. 31, 2023			1,250,467
Beginning balance at Dec. 31, 2022	$ 179,420	$ 46		404,456	(1,121)	(223,961)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,552			2,552
Issuance of common stock under equity incentive plans (in shares)		65,039
Issuance of common stock under equity incentive plans	113			113
Exercise of warrants ( in shares )		1,708,535
Exercise of warrants	0	$ 2		(2)
Adjustments to offering costs	10			10
Unrealized (loss) gain on investments	745				745
Unrealized loss on foreign currency translation	(31)				(31)
Net loss	$ (13,266)					(13,266)
Ending balance, common stock (in shares) at Mar. 31, 2023		47,758,007
Ending balance, treasury stock (in shares) at Dec. 31, 2022	1,250,467		1,250,467
Ending balance at Mar. 31, 2023	$ 169,543	$ 48		407,129	(407)	(237,227)
Beginning balance, common stock (in shares) at Dec. 31, 2022	45,984,433	45,984,433
Beginning balance, treasury stock (in shares) at Jun. 30, 2023	0		0
Beginning balance at Dec. 31, 2022	$ 179,420	$ 46		404,456	(1,121)	(223,961)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized (loss) gain on investments	507
Unrealized loss on foreign currency translation	(36)
Net loss	$ (26,422)
Ending balance, common stock (in shares) at Jun. 30, 2023	49,124,640	49,124,640
Ending balance, treasury stock (in shares) at Dec. 31, 2022	1,250,467		1,250,467
Ending balance at Jun. 30, 2023	$ 169,388	$ 49		420,372	(650)	(250,383)
Beginning balance, common stock (in shares) at Mar. 31, 2023		47,758,007
Beginning balance, treasury stock (in shares) at Jun. 30, 2023	0		0
Beginning balance at Mar. 31, 2023	$ 169,543	$ 48		407,129	(407)	(237,227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,621			2,621
Issuance of common stock under equity incentive plans (in shares)		210,653
Issuance of common stock under equity incentive plans	928			928
Exercise of warrants ( in shares )		236,567
Issuance of common stock under at the market offering, net of issuance costs (in shares)		919,413
Issuance of common stock under at the market offering, net of issuance costs	9,695	$ 1		9,694
Retirement of treasury stock (in shares)			(1,250,467)
Unrealized (loss) gain on investments	(238)				(238)
Unrealized loss on foreign currency translation	(5)				(5)
Net loss	$ (13,156)					(13,156)
Ending balance, common stock (in shares) at Jun. 30, 2023	49,124,640	49,124,640
Ending balance, treasury stock (in shares) at Mar. 31, 2023			1,250,467
Ending balance at Jun. 30, 2023	$ 169,388	$ 49		$ 420,372	$ (650)	$ (250,383)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Operating activities
Net loss	$ (26,422)	$ (25,625)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,173	4,624
Amortization of premium/discount on investments	(3,397)	591
Depreciation expense	282	304
Non-cash interest expense	45	105
Realized gain on investments	(33)	0
Loss on sale of property and equipment	2	70
Deferred income tax	0	107
Changes in operating assets and liabilities:
Accounts receivable	106	23,683
Prepaid expenses and other current assets	138	1,648
Operating lease, right-of-use asset	342	298
Accounts payable and accrued liabilities	(3,000)	1,558
Deferred revenue	(17,029)	(17,603)
Operating lease liability	(450)	(380)
Net cash used in operating activities	(44,243)	(10,620)
Investing activities
Purchases of property and equipment	(372)	(241)
Purchase of investments	(103,721)	(82,380)
Maturities of investments	161,771	51,382
Net cash provided by (used in) investing activities	57,678	(31,239)
Financing activities
Proceeds from sale of common stock, net of offering costs	9,695	0
Repayment of debt	(3,425)	(2,400)
Proceeds from exercise of stock options	1,041	730
Net cash provided by (used in) financing activities	7,311	(1,670)
Effect of exchange rate on cash and cash equivalents	(46)	(18)
Net increase (decrease) in cash and cash equivalents and restricted cash	20,700	(43,547)
Cash and cash equivalents and restricted cash, beginning of period	13,630	68,161
Cash and cash equivalents and restricted cash, end of period	$ 34,330	$ 24,614

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of BusinessAlpine Immune Sciences, Inc. (the “Company”, “Alpine”, “we”, “us”, or “our”), together with its consolidated subsidiaries, is a clinical-stage biopharmaceutical company dedicated to discovering and developing innovative, protein-based immunotherapies to treat autoimmune and inflammatory diseases. Our approach includes a proprietary scientific platform that converts native immune system proteins into differentiated, multi-targeted therapeutics. We are seeking to create first- or best-in-class multifunctional immunotherapies via our unique protein engineering technologies to improve outcomes in patients with serious diseases. We were incorporated under the laws of the State of Delaware and are headquartered in Seattle, Washington.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and generally accepted accounting principles in the United States of America (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Significant estimates inherent in the preparation of the accompanying condensed consolidated financial statements include those used for revenue recognition, accruals for clinical trial activities and other accruals, the potential outcome of uncertain tax positions that have been recognized in our condensed consolidated financial statements or tax returns, and the estimated fair value of equity-based awards. We base our estimates and assumptions on historical experience when available and on various factors we believe to be reasonable under the circumstances. Actual results could differ materially from those estimates. The accompanying condensed consolidated financial statements as of June 30, 2023 and for the three and six months ended June 30, 2023 and 2022 and the related interim information contained within the notes to the condensed consolidated financial statements are unaudited. The interim financial statements have been prepared on the same basis as the audited financial statements and in the opinion of management, reflect all normal recurring adjustments necessary for a fair statement of our financial position for the interim periods presented. The accompanying condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on March 23, 2023. The results of our operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the full year. Principles of Consolidation Our condensed consolidated financial statements include the financial position and results of operations of Alpine Immune Sciences, Inc. and our wholly owned operating company and subsidiary, AIS Operating Co., Inc., and our wholly-owned subsidiary, Alpine Immune Sciences Australia PTY LTD. All inter-company balances and transactions have been eliminated in consolidation. Cash and Cash Equivalents and Restricted Cash We consider all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking and interest-bearing accounts, and highly liquid money market funds. Restricted cash represents cash drawn on our line of credit used to establish collateral to support the security deposit on our operating lease to rent office and laboratory space in Seattle, Washington. Periodically, we maintain deposits in financial institutions in excess of government insured limits. We believe we are not exposed to significant credit risk as our deposits, which are held at financial institutions, are high credit quality securities such as money market funds, U.S. Treasury bills, and commercial paper. To date, we have not realized any losses on these deposits. Investments Our investments include funds invested in highly liquid money market funds, U.S. Treasury bills, U.S. agency securities, non-U.S. government securities, and corporate debt and commercial paper with contractual maturities of less than two years. These investments are classified as available-for-sale debt securities, which are recorded at fair value based on quoted prices in active markets for Level 1 assets and based on market pricing and other observable market inputs for similar securities for Level 2 assets. We classify our investments maturing within one year of the reporting date as short-term investments. If the estimated fair value of a debt security is below its amortized cost basis, we evaluate whether it is more likely than not that we will sell the security before its anticipated recovery in market value and whether credit losses exist for the related securities. A credit loss exists if the present value of expected cash flows is less than the amortized cost basis of the security. Credit-related losses are recognized as an allowance for credit losses on the balance sheet with a corresponding adjustment to earnings. Unrealized gains and losses that are unrelated to credit deterioration are reported in other comprehensive income (loss). Purchase premiums and discounts are recognized as interest income using the interest method over the terms of the securities. Realized gains and losses and declines in fair value for these investments deemed to be expected credit losses are reflected in our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) using the specific-identification method.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. The net loss per share for the three and six months ended June 30, 2023 reflects the issuance of 15,509,282 shares of common stock sold in our underwritten public offering in September 2022, including the subsequent partial exercise of the underwriters’ over-allotment option in October 2022. The increase in the number of shares outstanding impacts the comparability of our net loss per share for each period. The common stock issuable upon the conversion or exercise of the following dilutive securities has been excluded from the diluted net loss per share calculation because their effect would have been anti-dilutive. Diluted net loss per share, therefore, is the same as basic net loss per share for the periods presented. June 30, 2023 2022 (unaudited) Warrants to purchase common stock 6,893,321 8,838,694 Stock options and restricted stock units outstanding 8,288,540 7,117,820 Total 15,181,861 15,956,514

Cash Equivalents and Investment

Cash Equivalents and Investments	6 Months Ended
	Jun. 30, 2023
Investments and Cash [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments The amortized cost and fair value of our cash equivalents and investments are as follows (in thousands): June 30, 2023 (unaudited) Assets: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Money market funds $ 31,353 $ — $ — $ 31,353 U.S. treasury bills 105,571 3 (326) 105,248 U.S. agency securities 34,985 — (247) 34,738 Corporate debt securities and commercial paper 65,361 — (62) 65,299 Total $ 237,270 $ 3 $ (635) $ 236,638 Classified as: Cash equivalents $ 31,353 Short-term investments 169,724 Long-term investments 35,561 Total $ 236,638 December 31, 2022 Assets: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Money market funds $ 11,004 $ — $ — $ 11,004 U.S. treasury bills 113,964 5 (721) 113,248 U.S. agency securities 10,921 5 (11) 10,915 Non-U.S. government securities 6,060 — (22) 6,038 Corporate debt securities and commercial paper 129,940 4 (399) 129,545 Total $ 271,889 $ 14 $ (1,153) $ 270,750 Classified as: Cash equivalents $ 11,004 Short-term investments 224,265 Long-term investments 35,481 Total $ 270,750 All investments held as of June 30, 2023 and December 31, 2022 were classified as available-for-sale debt securities and consist of highly liquid funds with high credit ratings that, on their date of purchase, had a contractual maturity of two years or less. Realized gains on investments were $28,000 and $33,000 for the three and six months ended June 30, 2023, respectively, and zero for the three and six months ended June 30, 2022. There were no realized losses on investments for the three and six months ended June 30, 2023 and 2022. The following table summarizes the fair value and gross unrealized losses by category, disaggregated by the length of time that individual debt securities have been in a continuous unrealized loss position (in thousands): June 30, 2023 (unaudited) Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury bills $ 85,011 $ (303) $ 5,980 $ (23) $ 90,991 $ (326) U.S. agency securities 34,738 (247) — — 34,738 (247) Corporate debt securities and commercial paper 15,296 (54) 6,061 (8) 21,357 (62) Total $ 135,045 $ (604) $ 12,041 $ (31) $ 147,086 $ (635) December 31, 2022 (unaudited) Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury bills $ 82,694 $ (368) $ 17,648 $ (353) $ 100,342 $ (721) U.S. agency securities 7,552 (11) — — 7,552 (11) Non-U.S. government securities 3,012 (16) 3,026 (6) 6,038 (22) Corporate debt securities and commercial paper 27,839 (195) 22,171 (204) 50,010 (399) Total $ 121,097 $ (590) $ 42,845 $ (563) $ 163,942 $ (1,153)

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Cash and cash equivalents, restricted cash, receivables, accounts payable and accrued liabilities, which are recorded at invoiced amount or cost, approximate fair value based on the short-term nature of these financial instruments. Fair value is defined as the exchange price received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs supported by little or no market activity and significant to the fair value of the assets or liabilities. As of June 30, 2023 and December 31, 2022, cash of $2.7 million and $2.4 million, respectively, is excluded from the fair value table below. The following tables summarize our financial assets and liabilities measured at fair value on a recurring basis (in thousands): June 30, 2023 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 31,353 $ — $ — $ 31,353 U.S. treasury bills 105,248 — — 105,248 U.S. agency securities — 34,738 — 34,738 Corporate debt securities and commercial paper — 65,299 — 65,299 Total $ 136,601 $ 100,037 $ — $ 236,638 December 31, 2022 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 11,004 $ — $ — $ 11,004 U.S. treasury bills 113,248 — — 113,248 U.S. agency securities — 10,915 — 10,915 Non-U.S. government securities — 6,038 — 6,038 Corporate debt securities and commercial paper — 129,545 — 129,545 Total $ 124,252 $ 146,498 $ — $ 270,750 Our Level 2 assets consist of U.S. agency securities, non-U.S. government securities, corporate debt securities, and commercial paper. We review trading activity and pricing for our available-for-sale securities as of the measurement date. When sufficient quoted pricing for identical securities is not available, we use market pricing and other observable market inputs for similar securities obtained from various third-party data providers. These inputs either represent quoted prices for similar assets in active markets or have been derived from observable market data.

Additional Balance Sheet Inform

Additional Balance Sheet Information	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Additional Balance Sheet Information	Additional Balance Sheet Information Prepaid expenses and other current assets consist of the following (in thousands): June 30, 2023 December 31, 2022 (unaudited) Prepaid research and development $ 2,245 $ 1,881 Prepaid insurance 175 368 Prepaid other 413 394 Other receivables 404 317 Prepaid expenses and other current assets $ 3,237 $ 2,960 Accrued liabilities consist of the following (in thousands): June 30, 2023 December 31, 2022 (unaudited) Research and development services $ 9,460 $ 7,657 Employee compensation 2,933 4,110 Accrued taxes 820 1,847 Legal and professional fees 445 334 Accrued other 26 55 Accrued liabilities $ 13,684 $ 14,003

Long-term Debt

Long-term Debt	6 Months Ended
	Jun. 30, 2023
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt In August 2019, we entered into an Amended and Restated Loan and Security Agreement (the “Loan Agreement”) with Silicon Valley Bank (“SVB”), pursuant to which SVB agreed to extend term loans to us with an aggregate principal amount of up to $15.0 million (the “Term Loans”). Borrowings under the Loan Agreement consisted of up to three separate tranches. The initial tranche of $5.0 million was funded in August 2019, the second tranche of $5.0 million was funded in March 2020, and we did not draw down the final tranche of $5.0 million, which expired in July 2020. In May 2023, we voluntarily repaid in full the remaining outstanding carrying value of $1.4 million of our Term Loans, which consisted of $800,000 in principal and final payments of $625,000, plus prorated accrued interest. In connection with the debt payoff, we wrote-off the remaining unamortized debt discount. As of June 30, 2023, we had no remaining balance outstanding under our Loan Agreement with SVB.

Contingencies

Contingencies	6 Months Ended
	Jun. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Certain tax credits received related to our research and development expenditures, which were recorded in previous years within other income within our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) , were subject to review by foreign taxing authorities. During 2022, we reached constructive agreement with the Australian Taxation Office and recorded an estimated current foreign income tax provision for the expected repayments of $1.3 million. As of June 30, 2023, accrued estimated remaining tax liabilities of $828,000, net of amounts paid in 2022, are recorded within accrued liabilities on our accompanying Condensed Consolidated Balance Sheets .

License and Collaboration Agree

License and Collaboration Agreements	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements AbbVie Ireland Unlimited Company (“AbbVie”) In June 2020, we entered into an option and license agreement with AbbVie (the “AbbVie Agreement”) for the development of ALPN-101 (“acazicolcept”). The AbbVie Agreement grants AbbVie the exclusive option to purchase an exclusive worldwide license to acazicolcept (the “License Option”). The License Option is exercisable by AbbVie at any time and will expire 90 days from the achievement of certain development milestones. If AbbVie exercises the License Option, AbbVie will take over the future development and commercialization. Prior to the exercise of the License Option, we will perform research and development services, including conducting our Phase 2 study in systemic lupus erythematosus, based on an agreed-upon development plan (the “Development Plan”). We will be fully responsible for all costs incurred to conduct the activities under the Development Plan, provided that, AbbVie may be responsible for increased costs under the Development Plan in connection with certain material amendments proposed by AbbVie. We will also be solely responsible, at our sole cost and expense, for manufacturing and regulatory filings for acazicolcept necessary to complete activities under the Development Plan. In June 2020, in connection with the execution of the AbbVie Agreement, AbbVie paid us a nonrefundable upfront payment of $60.0 million. Prior to the exercise of the License Option, AbbVie has agreed to make cash payments upon our achievement of certain predefined pre-option development milestones (the “Alpine Development Milestones”) up to an aggregate amount of $75.0 million. In 2021, we received $45.0 million of the Alpine Development Milestones. If AbbVie exercises the License Option, they will pay a one-time cash payment of $75.0 million. Following the exercise of the License Option, AbbVie has also agreed to make aggregate cash payments of up to $205.0 million upon AbbVie’s achievement of certain development and commercial milestones and additional aggregate cash payments of up to $450.0 million upon AbbVie’s achievement of certain sales-based cash milestones, collectively referred to as (the “AbbVie Milestones”). Subsequent to commercialization, we are also eligible to receive high single-digit to low double-digit percentage royalties on worldwide net sales of licensed products. For revenue recognition purposes, we determined that our contractual promises in the AbbVie Agreement are not distinct and are interdependent with our performance obligation to provide research and development services under the Development Plan. Thus, all contractual promises related to the upfront payment and Alpine’s Development Milestones were combined into a single performance obligation. We determined the Alpine Development Milestone payments are probable of significant revenue reversal as the achievement is highly dependent on factors outside our control. Therefore, these milestone payments were fully constrained and were not initially included in the transaction price. In June 2021, we re-evaluated and updated the transaction price to include the achieved portion of the Alpine Development Milestones. We will continue to re-evaluate the transaction price each reporting period and update as uncertain events are resolved or other changes in circumstances occur. We expect to recognize the remaining deferred revenue over the remaining life of the Development Plan, which began in June 2020 and ends upon the later of the exercise or expiration of the option. The License Option and the AbbVie Milestones were determined not to be performance obligations at the inception of the contract as they did not represent material rights. If exercised, the License Option and AbbVie Milestones will be accounted for as a separate contract and will be recognized as revenue if and when triggered. Any consideration related to sales-based royalties and profit-sharing payments will be recognized when the related sales occur. Horizon Therapeutics Ireland DAC (“Horizon”) In December 2021, we entered into an exclusive license and collaboration agreement with Horizon (the “Horizon Agreement”) for the development and commercialization of up to four preclinical candidates generated from our unique discovery platform. The agreement includes licensing of one of our existing preclinical biologic therapeutic programs (the “Existing Program”), as well as a research partnership to jointly develop candidates for up to three additional autoimmune and inflammatory disease programs for other designated biological targets (the “Research Programs”). These candidates include previously undisclosed multi-specific fusion protein-based therapeutic candidates for autoimmune and inflammatory diseases. We will advance candidate molecules to predefined preclinical milestones while Horizon will be responsible for the respective costs and, ultimately, Horizon will assume responsibility for development and commercialization activities and costs. In connection with the execution of the Horizon Agreement in December 2021, we entered into a stock purchase agreement under which Horizon purchased 951,980 shares of our common stock in a private placement for approximately $15.76 per share and aggregate proceeds of $15.0 million. The shares were sold at a 25% premium to the volume-weighted average share price of our common stock for a specified 30-day period prior to entering into the agreement. The fair value of the common stock issued to Horizon of $11.9 million was recorded to equity, based on the closing price of common stock on the effective date of the Horizon Agreement. For accounting purposes, the $3.1 million difference between the cash proceeds and the fair value of the common stock was treated as additional consideration attributable to the Horizon Agreement. Under the terms of the agreements, Horizon also paid us a non-refundable upfront payment of $25.0 million in the first quarter of 2022. In addition, we are eligible to receive up to $381.0 million per program, or up to approximately $1.5 billion in total, in future success-based payments related to development, regulatory and commercial milestones. Furthermore, we are eligible to receive tiered royalties from a mid-single digit percentage to a low double-digit percentage on global net sales. In addition to proceeds from the non-refundable upfront payment, we have recognized $1.7 million from research and development support provided by us through June 30, 2023. For revenue recognition purposes, we determined the transaction price at inception was $28.1 million, which consists of the upfront payment of $25.0 million and the $3.1 million premium on the stock purchase, and that the Existing Program and each Research Program are distinct performance obligations. We allocated revenue to each performance obligation based on its relative stand-alone selling price. The future success-based payments related to development and regulatory milestones are probable of significant revenue reversal as the achievement is highly dependent on factors outside our control. Therefore, these milestone payments are fully constrained and are not initially included in the transaction price. We will continue to re-evaluate the transaction price each reporting period and update as uncertain events are resolved or other changes in circumstances occur. Any consideration related to commercial milestones and royalties will be recognized when the related sales occur. Adaptimmune Therapeutics plc (“Adaptimmune”) In May 2019, we entered into a collaboration and licensing agreement with Adaptimmune to develop next-generation SPEAR T cell products (the “Adaptimmune Agreement”). Under the Adaptimmune Agreement, we are to perform certain research services and grant Adaptimmune an exclusive license to programs from our secreted immunomodulatory protein (“SIP”) and transmembrane immunomodulatory protein (“TIP”) technologies. Through June 30, 2023, we have recorded a total of $3.0 million in license payments under the terms of the Adaptimmune Agreement consisting of a $2.0 million upfront license payment received in June 2019 and an additional $1.0 million license fee upon Adaptimmune’s selection of an additional research program in June 2022. We have also recognized $2.1 million in research support payments to fund ongoing programs through June 30, 2023. In addition, we are eligible for research support payments, one-time payments and downstream development and commercialization milestones of up to $288.0 million, if respective pre-specified milestones for each program are achieved. We are also eligible to receive low-single digit percentage royalties on worldwide net sales of the applicable products. For revenue recognition purposes, licensing and research support fees billed under the agreement are being recorded as deferred revenue and recognized to revenue based on employee hours contributed to each performance obligation. Contract balances and revenue recognition We report contract assets resulting from unconditional rights to consideration related to upfront payments, and for completed but unpaid research and development services within accounts receivable in our accompanying Condensed Consolidated Balance Sheets . Contract liabilities, representing advance consideration for licensing rights bundled with research and development services and other promises for which the underlying performance obligations have not yet been satisfied, are reported as deferred revenue in our accompanying Condensed Consolidated Balance Sheets . Contract liabilities are presented as current and noncurrent based on estimated timing of when the underlying performance obligations will be met. Respective balances are as follows (in thousands): June 30, 2023 December 31, 2022 (unaudited) Contract Assets $ 284 $ 392 Contract Liabilities $ 57,727 $ 74,756 We use cost-based input methods to measure progress towards completion of our performance obligations and to calculate the corresponding revenue to recognize under our contracts with customers each period. In applying the cost-based input, we use actual costs incurred relative to budgeted costs for each combined performance obligation. Actual costs consist primarily of labor related to internal personnel and third-party contracts. Revenue is recognized based on the percentage of costs incurred relative to the total estimated costs for the performance obligation. A cost-based input method of revenue recognition requires management to estimate the costs to complete our performance obligations. In making such estimates, significant judgment is required to evaluate assumptions related to cost estimates. The cumulative effect of revisions to estimated costs to complete our performance obligations will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods. Collaboration revenue recognized in our accompanying Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) , disaggregated by customer, is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2023 2022 2023 2022 (unaudited) AbbVie $ 6,748 $ 4,563 $ 12,346 $ 10,523 Horizon 1,715 587 5,170 8,256 Adaptimmune 130 142 464 142 Total collaboration revenue $ 8,593 $ 5,292 $ 17,980 $ 18,921 Revenue recognized during the period that was included in the opening contract liability balance was $17.0 million and $18.6 million for the six months ended June 30, 2023 and 2022, respectively.

Stockholders_ Equity

Stockholders’ Equity	6 Months Ended
	Jun. 30, 2023
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Securities Offering In April 2023, we entered into a sales agreement (the “Sales Agreement”) with Cowen and Company, LLC (“TD Cowen”) to sell shares of our common stock, from time to time, through an “at the market” equity offering for up to $100.0 million in aggregate gross proceeds. TD Cowen will act as the sales agent and will be entitled to compensation for services of up to 3.0% of the gross sales proceeds from shares sold through TD Cowen under the Sales Agreement. The shares will be issued pursuant to our shelf registration statement on Form S-3 (File No. 333-271517), which was filed with the SEC on April 28, 2023 and declared effective on May 9, 2023. On May 11, 2023, we filed a final prospectus supplement with the SEC relating to the offer and sale of the shares pursuant to the Sales Agreement. As of June 30, 2023, we have sold 919,413 shares of common stock under the Sales Agreement for a price of $10.93 per share. The associated gross proceeds of $10.0 million were recorded net of directly related financing costs of $354,000 within additional-paid-in-capital on our accompanying Condensed Consolidated Balance Sheets . Treasury Shares In June 2023, we retired 1,250,467 shares of treasury stock, and returned the shares of common stock to the status of authorized but unissued shares. Common Stock Warrants In connection with the exercise of certain prefunded warrants during the six months ended June 30, 2023, we issued 1,945,102 shares of common stock. Equity Incentive Plans On January 1, 2023, in connection with our 2018 Equity Incentive Plan (the “2018 Plan”) annual increase provision, a total of 1,500,000 additional shares were automatically added to the shares authorized under the 2018 Plan. During the six months ended June 30, 2023, we issued stock option grants totaling 1,779,970 shares with a weighted average exercise price of $7.68 per share under our 2018 Plan. Stock-Based Compensation Expense We use the Black-Scholes option pricing model to estimate the fair value of stock options at the grant date. The fair value of restricted stock units (“RSUs”) is equal to the closing stock price on the date of grant. We recognize the fair value of stock-based compensation as compensation expense over the requisite service period, which is the vesting period. Stock-based compensation is classified in our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2023 2022 2023 2022 (unaudited) Research and development $ 1,531 $ 1,346 $ 3,012 $ 2,654 General and administrative 1,090 989 2,161 1,970 Total stock-based compensation expense $ 2,621 $ 2,335 $ 5,173 $ 4,624

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We are subject to income taxes in the United States and Australia and our effective tax rate is calculated quarterly based upon current assumptions relating to the full year’s estimated operating results and various tax-related items. Each quarter an estimate of the annual effective tax rate is updated should we revise our forecast of earnings based upon our operating results. If there is a change in the estimated effective annual tax rate, a cumulative adjustment is made. Our effective tax rate was 0% and 7.5% for the six months ended June 30, 2023 and 2022, respectively. Our effective tax rate of 7.5% for the six months ended June 30, 2022 was primarily due to the recognition of current foreign tax liabilities of $1.3 million as a result of a cumulative change to our income tax provision and a $0.1 million reduction to our deferred tax assets as a result of a change to our transfer pricing methodology for the activities of our wholly owned subsidiary, Alpine Immune Sciences Australia PTY, LTD, and $0.4 million in domestic federal income tax expense resulting from the mandatory capitalization of research and development expenses beginning with the 2022 tax year. The differences between the effective tax rates of 0% and 7.5% and the U.S. federal statutory rate of 21% for the six months ended June 30, 2023 and 2022, respectively, were primarily due to recognizing a full valuation allowance on deferred tax assets, and partial valuation allowance on our foreign deferred tax assets, tax expense resulting from the acceptance of a voluntary disclosure agreement with the Australian Taxation Office, and tax benefits relating to research and development tax credits. As of June 30, 2023, we determined that, based on an evaluation of our sources of income and all available evidence, both positive and negative, including our latest forecasts and cumulative losses in recent years, it was more likely than not that none of our domestic deferred tax assets would be realized and, therefore, we continued to record a full domestic valuation allowance. As of June 30, 2023, we determined that it was more likely than not that only a portion of our foreign deferred tax assets would be realized and have recorded a partial foreign valuation allowance. We did not record significant current tax liabilities or expense during the six months ended June 30, 2023.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and generally accepted accounting principles in the United States of America (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Significant estimates inherent in the preparation of the accompanying condensed consolidated financial statements include those used for revenue recognition, accruals for clinical trial activities and other accruals, the potential outcome of uncertain tax positions that have been recognized in our condensed consolidated financial statements or tax returns, and the estimated fair value of equity-based awards. We base our estimates and assumptions on historical experience when available and on various factors we believe to be reasonable under the circumstances. Actual results could differ materially from those estimates. The accompanying condensed consolidated financial statements as of June 30, 2023 and for the three and six months ended June 30, 2023 and 2022 and the related interim information contained within the notes to the condensed consolidated financial statements are unaudited. The interim financial statements have been prepared on the same basis as the audited financial statements and in the opinion of management, reflect all normal recurring adjustments necessary for a fair statement of our financial position for the interim periods presented. The accompanying condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on March 23, 2023. The results of our operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the full year.
Principles of Consolidation	Principles of ConsolidationOur condensed consolidated financial statements include the financial position and results of operations of Alpine Immune Sciences, Inc. and our wholly owned operating company and subsidiary, AIS Operating Co., Inc., and our wholly-owned subsidiary, Alpine Immune Sciences Australia PTY LTD. All inter-company balances and transactions have been eliminated in consolidation.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash We consider all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking and interest-bearing accounts, and highly liquid money market funds. Restricted cash represents cash drawn on our line of credit used to establish collateral to support the security deposit on our operating lease to rent office and laboratory space in Seattle, Washington. Periodically, we maintain deposits in financial institutions in excess of government insured limits. We believe we are not exposed to significant credit risk as our deposits, which are held at financial institutions, are high credit quality securities such as money market funds, U.S. Treasury bills, and commercial paper. To date, we have not realized any losses on these deposits.
Investments	Investments Our investments include funds invested in highly liquid money market funds, U.S. Treasury bills, U.S. agency securities, non-U.S. government securities, and corporate debt and commercial paper with contractual maturities of less than two years. These investments are classified as available-for-sale debt securities, which are recorded at fair value based on quoted prices in active markets for Level 1 assets and based on market pricing and other observable market inputs for similar securities for Level 2 assets. We classify our investments maturing within one year of the reporting date as short-term investments. If the estimated fair value of a debt security is below its amortized cost basis, we evaluate whether it is more likely than not that we will sell the security before its anticipated recovery in market value and whether credit losses exist for the related securities. A credit loss exists if the present value of expected cash flows is less than the amortized cost basis of the security. Credit-related losses are recognized as an allowance for credit losses on the balance sheet with a corresponding adjustment to earnings. Unrealized gains and losses that are unrelated to credit deterioration are reported in other comprehensive income (loss). Purchase premiums and discounts are recognized as interest income using the interest method over the terms of the securities. Realized gains and losses and declines in fair value for these investments deemed to be expected credit losses are reflected in our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) using the specific-identification method.
Net Loss Per Share	Net Loss Per ShareBasic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period.
Fair Value Measurements	Fair Value Measurements Cash and cash equivalents, restricted cash, receivables, accounts payable and accrued liabilities, which are recorded at invoiced amount or cost, approximate fair value based on the short-term nature of these financial instruments. Fair value is defined as the exchange price received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs supported by little or no market activity and significant to the fair value of the assets or liabilities.
Stock-Based Compensation Expense	Stock-Based Compensation Expense

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Diluted Net Loss Per Share Attributable to Common Stockholders	The common stock issuable upon the conversion or exercise of the following dilutive securities has been excluded from the diluted net loss per share calculation because their effect would have been anti-dilutive. Diluted net loss per share, therefore, is the same as basic net loss per share for the periods presented. June 30, 2023 2022 (unaudited) Warrants to purchase common stock 6,893,321 8,838,694 Stock options and restricted stock units outstanding 8,288,540 7,117,820 Total 15,181,861 15,956,514

Cash Equivalents and Investme_2

Cash Equivalents and Investments (Tables)	6 Months Ended
	Jun. 30, 2023
Investments and Cash [Abstract]
Schedule of Amortized Cost and Fair Value of Cash Equivalents and Investments	The amortized cost and fair value of our cash equivalents and investments are as follows (in thousands): June 30, 2023 (unaudited) Assets: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Money market funds $ 31,353 $ — $ — $ 31,353 U.S. treasury bills 105,571 3 (326) 105,248 U.S. agency securities 34,985 — (247) 34,738 Corporate debt securities and commercial paper 65,361 — (62) 65,299 Total $ 237,270 $ 3 $ (635) $ 236,638 Classified as: Cash equivalents $ 31,353 Short-term investments 169,724 Long-term investments 35,561 Total $ 236,638 December 31, 2022 Assets: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Money market funds $ 11,004 $ — $ — $ 11,004 U.S. treasury bills 113,964 5 (721) 113,248 U.S. agency securities 10,921 5 (11) 10,915 Non-U.S. government securities 6,060 — (22) 6,038 Corporate debt securities and commercial paper 129,940 4 (399) 129,545 Total $ 271,889 $ 14 $ (1,153) $ 270,750 Classified as: Cash equivalents $ 11,004 Short-term investments 224,265 Long-term investments 35,481 Total $ 270,750
Schedule of Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value	The following table summarizes the fair value and gross unrealized losses by category, disaggregated by the length of time that individual debt securities have been in a continuous unrealized loss position (in thousands): June 30, 2023 (unaudited) Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury bills $ 85,011 $ (303) $ 5,980 $ (23) $ 90,991 $ (326) U.S. agency securities 34,738 (247) — — 34,738 (247) Corporate debt securities and commercial paper 15,296 (54) 6,061 (8) 21,357 (62) Total $ 135,045 $ (604) $ 12,041 $ (31) $ 147,086 $ (635) December 31, 2022 (unaudited) Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury bills $ 82,694 $ (368) $ 17,648 $ (353) $ 100,342 $ (721) U.S. agency securities 7,552 (11) — — 7,552 (11) Non-U.S. government securities 3,012 (16) 3,026 (6) 6,038 (22) Corporate debt securities and commercial paper 27,839 (195) 22,171 (204) 50,010 (399) Total $ 121,097 $ (590) $ 42,845 $ (563) $ 163,942 $ (1,153)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured at Fair Value on Recurring Basis	The following tables summarize our financial assets and liabilities measured at fair value on a recurring basis (in thousands): June 30, 2023 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 31,353 $ — $ — $ 31,353 U.S. treasury bills 105,248 — — 105,248 U.S. agency securities — 34,738 — 34,738 Corporate debt securities and commercial paper — 65,299 — 65,299 Total $ 136,601 $ 100,037 $ — $ 236,638 December 31, 2022 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 11,004 $ — $ — $ 11,004 U.S. treasury bills 113,248 — — 113,248 U.S. agency securities — 10,915 — 10,915 Non-U.S. government securities — 6,038 — 6,038 Corporate debt securities and commercial paper — 129,545 — 129,545 Total $ 124,252 $ 146,498 $ — $ 270,750

Additional Balance Sheet Info_2

Additional Balance Sheet Information (Tables)	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): June 30, 2023 December 31, 2022 (unaudited) Prepaid research and development $ 2,245 $ 1,881 Prepaid insurance 175 368 Prepaid other 413 394 Other receivables 404 317 Prepaid expenses and other current assets $ 3,237 $ 2,960
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, 2023 December 31, 2022 (unaudited) Research and development services $ 9,460 $ 7,657 Employee compensation 2,933 4,110 Accrued taxes 820 1,847 Legal and professional fees 445 334 Accrued other 26 55 Accrued liabilities $ 13,684 $ 14,003

License and Collaboration Agr_2

License and Collaboration Agreements (Tables)	6 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Contract Balances	Contract liabilities are presented as current and noncurrent based on estimated timing of when the underlying performance obligations will be met. Respective balances are as follows (in thousands): June 30, 2023 December 31, 2022 (unaudited) Contract Assets $ 284 $ 392 Contract Liabilities $ 57,727 $ 74,756
Schedule of Disaggregation of Revenue	Collaboration revenue recognized in our accompanying Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) , disaggregated by customer, is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2023 2022 2023 2022 (unaudited) AbbVie $ 6,748 $ 4,563 $ 12,346 $ 10,523 Horizon 1,715 587 5,170 8,256 Adaptimmune 130 142 464 142 Total collaboration revenue $ 8,593 $ 5,292 $ 17,980 $ 18,921

Stockholders_ Equity (Tables)

Stockholders’ Equity (Tables)	6 Months Ended
	Jun. 30, 2023
Stockholders' Equity Note [Abstract]
Schedule of Stock-based Compensation Expense	Stock-based compensation is classified in our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2023 2022 2023 2022 (unaudited) Research and development $ 1,531 $ 1,346 $ 3,012 $ 2,654 General and administrative 1,090 989 2,161 1,970 Total stock-based compensation expense $ 2,621 $ 2,335 $ 5,173 $ 4,624

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	Jun. 30, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Debt securities, available-for-sale, term (less than)	2 years	2 years

Net Loss Per Share - Narrative

Net Loss Per Share - Narrative (Details) - shares	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023
Common Stock
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Stock issued (in shares)	15,509,282	15,509,282

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Anti-dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	15,181,861	15,956,514
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,893,321	8,838,694
Stock options and restricted stock units outstanding
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	8,288,540	7,117,820

Cash Equivalents and Investme_3

Cash Equivalents and Investments - Summary of Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 237,270	$ 271,889
Gross Unrealized Gains	3	14
Gross Unrealized Losses	(635)	(1,153)
Fair Market Value	236,638	270,750
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Fair Market Value	31,353	11,004
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Fair Market Value	169,724	224,265
Long-term investments
Debt Securities, Available-for-sale [Line Items]
Fair Market Value	35,561	35,481
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	31,353	11,004
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	31,353	11,004
U.S. treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	105,571	113,964
Gross Unrealized Gains	3	5
Gross Unrealized Losses	(326)	(721)
Fair Market Value	105,248	113,248
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	34,985	10,921
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(247)	(11)
Fair Market Value	34,738	10,915
Non-U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		6,060
Gross Unrealized Gains		0
Gross Unrealized Losses		(22)
Fair Market Value		6,038
Corporate debt securities and commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	65,361	129,940
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(62)	(399)
Fair Market Value	$ 65,299	$ 129,545

Cash Equivalents and Investme_4

Cash Equivalents and Investments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Investments and Cash [Abstract]
Debt securities, available-for-sale, term (less than)	2 years		2 years		2 years
Realized gains on investments	$ 28	$ 0	$ 33	$ 0
Realized losses on securities	$ 0	$ 0	$ 0	$ 0

Cash Equivalents and Investme_5

Cash Equivalents and Investments - Schedule of Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt securities, less than 12 months, fair value	$ 135,045	$ 121,097
Debt securities, less than 12 months, unrealized losses	(604)	(590)
Debt securities, 12 months or greater, fair value	12,041	42,845
Debt securities, 12 months or greater, unrealized losses	(31)	(563)
Debt securities, total, fair value	147,086	163,942
Debt securities, total, unrealized losses	(635)	(1,153)
U.S. treasury bills
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt securities, less than 12 months, fair value	85,011	82,694
Debt securities, less than 12 months, unrealized losses	(303)	(368)
Debt securities, 12 months or greater, fair value	5,980	17,648
Debt securities, 12 months or greater, unrealized losses	(23)	(353)
Debt securities, total, fair value	90,991	100,342
Debt securities, total, unrealized losses	(326)	(721)
U.S. agency securities
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt securities, less than 12 months, fair value	34,738	7,552
Debt securities, less than 12 months, unrealized losses	(247)	(11)
Debt securities, 12 months or greater, fair value	0	0
Debt securities, 12 months or greater, unrealized losses	0	0
Debt securities, total, fair value	34,738	7,552
Debt securities, total, unrealized losses	(247)	(11)
Corporate debt securities and commercial paper
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt securities, less than 12 months, fair value	15,296	27,839
Debt securities, less than 12 months, unrealized losses	(54)	(195)
Debt securities, 12 months or greater, fair value	6,061	22,171
Debt securities, 12 months or greater, unrealized losses	(8)	(204)
Debt securities, total, fair value	21,357	50,010
Debt securities, total, unrealized losses	$ (62)	(399)
Non-U.S. government securities
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt securities, less than 12 months, fair value		3,012
Debt securities, less than 12 months, unrealized losses		(16)
Debt securities, 12 months or greater, fair value		3,026
Debt securities, 12 months or greater, unrealized losses		(6)
Debt securities, total, fair value		6,038
Debt securities, total, unrealized losses		$ (22)

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Cash	$ 2.7	$ 2.4

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 236,638	$ 270,750
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	31,353	11,004
U.S. treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	105,248	113,248
U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	34,738	10,915
Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure		6,038
Corporate debt securities and commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	65,299	129,545
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	136,601	124,252
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	31,353	11,004
Level 1 | U.S. treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	105,248	113,248
Level 1 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 1 | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure		0
Level 1 | Corporate debt securities and commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	100,037	146,498
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 2 | U.S. treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 2 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	34,738	10,915
Level 2 | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure		6,038
Level 2 | Corporate debt securities and commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	65,299	129,545
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 3 | U.S. treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 3 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Level 3 | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure		0
Level 3 | Corporate debt securities and commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 0	$ 0

Additional Balance Sheet Info_3

Additional Balance Sheet Information - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid research and development	$ 2,245	$ 1,881
Prepaid insurance	175	368
Prepaid other	413	394
Other receivables	404	317
Prepaid expenses and other current assets	$ 3,237	$ 2,960

Additional Balance Sheet Info_4

Additional Balance Sheet Information - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Research and development services	$ 9,460	$ 7,657
Employee compensation	2,933	4,110
Accrued taxes	820	1,847
Legal and professional fees	445	334
Accrued other	26	55
Accrued liabilities	$ 13,684	$ 14,003

Long-term Debt (Details)

Long-term Debt (Details)	1 Months Ended
	Mar. 31, 2020 USD ($)	Aug. 31, 2019 USD ($) tranche	Jun. 30, 2023 USD ($)	May 31, 2023 USD ($)	Jul. 31, 2020 USD ($)
SVB Term Loan
Debt Instrument [Line Items]
Long-term debt, gross			$ 0	$ 1,400,000
Debt instrument, face amount				800,000
Prepayment fee				$ 625,000
Silicon Valley Bank | Term Loans
Debt Instrument [Line Items]
Maximum borrowing capacity, amount		$ 15,000,000
Number of tranches (up to) | tranche		3
Silicon Valley Bank | Term Loans | Term Loans, Tranche One
Debt Instrument [Line Items]
Proceeds from borrowings, net of issuance costs		$ 5,000,000
Silicon Valley Bank | Term Loans | Term Loans, Tranche Two
Debt Instrument [Line Items]
Proceeds from borrowings, net of issuance costs	$ 5,000,000
Silicon Valley Bank | Term Loans | Term Loans, Tranche Three
Debt Instrument [Line Items]
Unused borrowing capacity, expired amount					$ 5,000,000

Contingencies (Details)

Contingencies (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Current tax expense	$ 0	$ 1,300	$ 1,300
Accrued estimated remaining tax liabilities	$ 828

License and Collaboration Agr_3

License and Collaboration Agreements - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended		18 Months Ended	49 Months Ended	50 Months Ended
	Dec. 31, 2021 USD ($) program candidate $ / shares shares	Jun. 30, 2023 USD ($) payment	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) payment	Jun. 30, 2023 USD ($) payment	Jun. 30, 2023 USD ($) payment	Dec. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2020 USD ($) payment	Jun. 30, 2019 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities		$ 57,727		$ 57,727	$ 57,727	$ 57,727	$ 74,756
Revenue recognized from contract with customer		$ 17,000	$ 18,600
AbbVie | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential future revenue recognition, milestone method, number of payments | payment									1
Potential cash payment upon exercising license option									$ 75,000
Potential cash payment upon achievement of certain development and commercial milestones									205,000
Potential cash payment upon achievement of certain sales-based cash milestones									450,000
AbbVie | Product | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential future revenue recognition milestones receivable									75,000
AbbVie | Product | Upfront License Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities									$ 60,000
AbbVie | Product | Achieved Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities	$ 45,000
Horizon
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of preclinical candidates | candidate	4
Number of existing programs | program	1
Number of additional programs | program	3
Horizon | Common Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, premium on price per share, stock price period	30 days
Horizon | Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares issued in transaction (in shares) | shares	951,980
Purchase price per share (in dollars per share) | $ / shares	$ 15.76
Sale of stock, consideration received on transaction	$ 15,000
Sale of stock, premium on price per share, stock price period	25%
Sale of stock, consideration received on transaction, fair value portion	$ 11,900
Sale of stock, consideration received on transaction, additional consideration portion	3,100
Horizon | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities	28,100
Potential future revenue recognition milestones receivable	1,500,000
Potential future revenue recognition milestones receivable, per program	381,000
Horizon | Product | Upfront Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities	25,000							$ 25,000
Horizon | Product | Research and Development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from contract with customer				$ 1,700
Horizon | Product | Premium Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities	$ 3,100
Adaptimmune | Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential future revenue recognition, milestone method, number of payments | payment		1		1	1	1
Adaptimmune | Product | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential future milestones receivable (up to)		$ 288,000		$ 288,000	$ 288,000	$ 288,000
Adaptimmune | Product | Upfront License Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities										$ 2,000
Adaptimmune | Product | License Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from contract with customer					$ 3,000
Adaptimmune | Product | License Fee and Research Support Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities			$ 1,000
Adaptimmune | Product | Research Support Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from contract with customer						$ 2,100

License and Collaboration Agr_4

License and Collaboration Agreements - Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Contract Assets	$ 284	$ 392
Contract Liabilities	$ 57,727	$ 74,756

License and Collaboration Agr_5

License and Collaboration Agreements - Collaboration Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	$ 8,593	$ 5,292	$ 17,980	$ 18,921
AbbVie
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	6,748	4,563	12,346	10,523
Horizon
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	1,715	587	5,170	8,256
Adaptimmune
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	$ 130	$ 142	$ 464	$ 142

Stockholders_ Equity - Narrativ

Stockholders’ Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		6 Months Ended
	Jan. 01, 2023	Jun. 30, 2023	Apr. 30, 2023	Jun. 30, 2023	Jun. 30, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Proceeds from sale of common stock, net of offering costs				$ 9,695	$ 0
Retirement of treasury stock (in shares)		1,250,467
Prefunded Warrants
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Warrants issued (in shares)		1,945,102		1,945,102
2018 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of additional shares authorized (in shares)	1,500,000
Options, grants in period (in shares)				1,779,970
Grants in period, weighted average exercise price (in dollars per share)				$ 7.68
Public Stock Offering
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum amount of common stock eligible to be sold (up to)			$ 100,000
Public Stock Offering | Sales Agreement
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares issued in transaction (in shares)				919,413
Purchase price per share (in dollars per share)		$ 10.93		$ 10.93
Proceeds from sale of common stock, net of offering costs				$ 10,000
Payments of stock issuance costs				$ 354
Public Stock Offering | Sales Agreement | TD Cowen
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Percentage of compensation for services			3%

Stockholders_ Equity - Stock-Ba

Stockholders’ Equity - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Class of Stock [Line Items]
Total stock-based compensation expense	$ 2,621	$ 2,335	$ 5,173	$ 4,624
Research and development
Class of Stock [Line Items]
Total stock-based compensation expense	1,531	1,346	3,012	2,654
General and administrative
Class of Stock [Line Items]
Total stock-based compensation expense	$ 1,090	$ 989	$ 2,161	$ 1,970

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Effective tax rate (as a percent)	0%	7.50%
Current tax expense	$ 0	$ 1,300	$ 1,300
Deferred income tax	$ 0	107
Domestic federal income tax expense		$ 400