Alpine Immune Sciences (ALPN) 10-Q 11 Aug 22 2022 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2022	Aug. 05, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
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		30,400,679
Entity Central Index Key	0001626199
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 24,360	$ 67,907
Short-term investments	143,500	94,396
Accounts receivable	1,317	25,000
Prepaid expenses and other current assets	3,112	4,710
Total current assets	172,289	192,013
Restricted cash, noncurrent	254	254
Property and equipment, net	1,596	1,716
Operating lease, right-of-use asset	8,539	8,837
Long-term investments	33,041	52,866
Deferred tax asset	107	214
Total assets	215,826	255,900
Current liabilities:
Accounts payable	1,812	3,349
Accrued liabilities	12,525	9,417
Deferred revenue, current	42,917	51,773
Operating lease liability, current	682	617
Current portion of long-term debt	4,682	4,622
Total current liabilities	62,618	69,778
Deferred revenue, noncurrent	42,083	50,830
Operating lease liability, noncurrent	10,564	11,009
Long-term debt	1,025	3,380
Total liabilities	116,290	134,997
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized at June 30, 2022 and December 31, 2021; zero shares issued and outstanding at June 30, 2022 and December 31, 2021	0	0
Common stock, $0.001 par value per share; 200,000,000 shares authorized at June 30, 2022 and December 31, 2021; 31,586,629 shares issued and 30,336,162 shares outstanding at June 30, 2022; 31,444,746 shares issued and 30,194,279 shares outstanding at December 31, 2021	30	30
Treasury stock, at cost; 1,250,467 shares at June 30, 2022 and December 31, 2021	0	0
Additional paid-in capital	292,699	287,345
Accumulated other comprehensive loss	(1,369)	(273)
Accumulated deficit	(191,824)	(166,199)
Total stockholders’ equity	99,536	120,903
Total liabilities and stockholders’ equity	$ 215,826	$ 255,900

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021
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)	31,586,629	31,444,746
Common stock, shares outstanding (in shares)	30,336,162	30,194,279
Treasury stock, shares (in shares)	1,250,467	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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Collaboration revenue	$ 5,292	$ 7,193	$ 18,921	$ 10,397
Operating expenses:
Research and development	17,587	14,634	33,898	25,071
General and administrative	4,194	3,290	8,969	6,546
Total operating expenses	21,781	17,924	42,867	31,617
Loss from operations	(16,489)	(10,731)	(23,946)	(21,220)
Other income (expense):
Interest expense	(130)	(218)	(284)	(435)
Interest income	314	51	459	114
Other expense	(15)	0	(72)	0
Loss before taxes	(16,320)	(10,898)	(23,843)	(21,541)
Income tax expense	(1,778)	(131)	(1,782)	(131)
Net loss	(18,098)	(11,029)	(25,625)	(21,672)
Comprehensive income (loss):
Unrealized (loss) gain on investments	(304)	21	(1,078)	16
Unrealized loss on foreign currency translation	(4)	(9)	(18)	(24)
Comprehensive loss	$ (18,406)	$ (11,017)	$ (26,721)	$ (21,680)
Weighted-average shares used to compute basic net loss per share (in shares)	30,324,933	23,908,516	30,311,527	23,888,173
Weighted-average shares used to compute diluted net loss per share (in shares)	30,324,933	23,908,516	30,311,527	23,888,173
Basic net loss per share (in dollars per share)	$ (0.60)	$ (0.46)	$ (0.85)	$ (0.91)
Diluted net loss per share (in dollars per share)	$ (0.60)	$ (0.46)	$ (0.85)	$ (0.91)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Collaboration [Member]	Collaboration [Member]	Collaboration [Member]	Collaboration [Member]

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, 2020		23,803,183
Beginning balance at Dec. 31, 2020	$ 62,158	$ 24	$ 0	$ 177,947	$ 53	$ (115,866)
Beginning balance, treasury stock (in shares) at Mar. 31, 2021			50,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,597			1,597
Issuance of common stock under equity incentive plans (in shares)		78,955
Issuance of common stock under equity incentive plans	202			202
Unrealized gain (loss) on investments	(5)				(5)
Unrealized loss on foreign currency translation	(15)				(15)
Net loss	(10,643)					(10,643)
Ending balance, common stock (in shares) at Mar. 31, 2021		23,882,138
Ending balance at Mar. 31, 2021	53,294	$ 24	$ 0	179,746	33	(126,509)
Ending balance, treasury stock (in shares) at Dec. 31, 2020			50,467
Beginning balance, common stock (in shares) at Dec. 31, 2020		23,803,183
Beginning balance at Dec. 31, 2020	62,158	$ 24	$ 0	177,947	53	(115,866)
Beginning balance, treasury stock (in shares) at Jun. 30, 2021			50,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on investments	16
Unrealized loss on foreign currency translation	(24)
Net loss	(21,672)
Ending balance, common stock (in shares) at Jun. 30, 2021		23,914,879
Ending balance at Jun. 30, 2021	43,831	$ 24	$ 0	181,300	45	(137,538)
Ending balance, treasury stock (in shares) at Dec. 31, 2020			50,467
Beginning balance, common stock (in shares) at Mar. 31, 2021		23,882,138
Beginning balance at Mar. 31, 2021	53,294	$ 24	$ 0	179,746	33	(126,509)
Beginning balance, treasury stock (in shares) at Jun. 30, 2021			50,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,545			1,545
Issuance of common stock under equity incentive plans (in shares)		32,741
Issuance of common stock under equity incentive plans	9			9
Unrealized gain (loss) on investments	21				21
Unrealized loss on foreign currency translation	(9)				(9)
Net loss	(11,029)					(11,029)
Ending balance, common stock (in shares) at Jun. 30, 2021		23,914,879
Ending balance at Jun. 30, 2021	$ 43,831	$ 24	$ 0	181,300	45	(137,538)
Ending balance, treasury stock (in shares) at Mar. 31, 2021			50,467
Beginning balance, common stock (in shares) at Dec. 31, 2021	31,444,746	30,194,279
Beginning balance at Dec. 31, 2021	$ 120,903	$ 30	$ 0	287,345	(273)	(166,199)
Beginning balance, treasury stock (in shares) at Mar. 31, 2022			1,250,467
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 gain (loss) 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 at Mar. 31, 2022	$ 115,427	$ 30	$ 0	290,184	(1,061)	(173,726)
Ending balance, treasury stock (in shares) at Dec. 31, 2021	1,250,467		1,250,467
Beginning balance, common stock (in shares) at Dec. 31, 2021	31,444,746	30,194,279
Beginning balance at Dec. 31, 2021	$ 120,903	$ 30	$ 0	287,345	(273)	(166,199)
Beginning balance, treasury stock (in shares) at Jun. 30, 2022	1,250,467		1,250,467
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) 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	31,586,629	30,336,162
Ending balance at Jun. 30, 2022	$ 99,536	$ 30	$ 0	292,699	(1,369)	(191,824)
Ending balance, treasury stock (in shares) at Dec. 31, 2021	1,250,467		1,250,467
Beginning balance, common stock (in shares) at Mar. 31, 2022		30,294,434
Beginning balance at Mar. 31, 2022	$ 115,427	$ 30	$ 0	290,184	(1,061)	(173,726)
Beginning balance, treasury stock (in shares) at Jun. 30, 2022	1,250,467		1,250,467
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 gain (loss) 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	31,586,629	30,336,162
Ending balance at Jun. 30, 2022	$ 99,536	$ 30	$ 0	$ 292,699	$ (1,369)	$ (191,824)
Ending balance, treasury stock (in shares) at Mar. 31, 2022			1,250,467

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities
Net loss	$ (25,625)	$ (21,672)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,624	3,142
Amortization of premium/discount on investments	591	410
Depreciation expense	304	327
Non-cash interest expense	105	146
Loss on sale of property and equipment	70	0
Deferred income tax	107	(63)
Changes in operating assets and liabilities:
Accounts receivable	23,683	(39)
Prepaid expenses and other current assets	1,648	(2,096)
Operating lease, right-of-use asset	298	283
Accounts payable and accrued liabilities	1,558	(352)
Deferred revenue	(17,603)	(10,397)
Operating lease liability	(380)	(342)
Net cash used in operating activities	(10,620)	(30,653)
Investing activities
Purchases of property and equipment	(241)	(69)
Purchase of investments	(82,380)	(15,511)
Maturities of investments	51,382	29,900
Net cash (used in) provided by investing activities	(31,239)	14,320
Financing activities
Repayment of debt	(2,400)	0
Proceeds from exercise of stock options	730	211
Net cash (used in) provided by financing activities	(1,670)	211
Effect of exchange rate on cash and cash equivalents	(18)	(24)
Net decrease in cash and cash equivalents and restricted cash	(43,547)	(16,146)
Cash and cash equivalents and restricted cash, beginning of period	68,161	35,213
Cash and cash equivalents and restricted cash, end of period	24,614	19,067
Supplemental Information
Cash paid for interest	$ 192	$ 291

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Alpine 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 cancer and autoimmune and inflammatory diseases. Our approach includes a proprietary scientific platform that converts native immune system proteins into differentiated, multi-targeted therapeutics. We believe our strategies are capable of meaningfully modulating the human immune system and significantly improving outcomes in patients with serious diseases. We were incorporated under the laws of the State of Delaware and are headquartered in Seattle, Washington. As a result of the COVID-19 pandemic, many companies have experienced disruptions in their operations and in markets served. We have implemented temporary precautionary measures to ensure the well-being of our employees and minimize business disruption. We considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts to our results of operations and financial position at June 30, 2022. The full extent of the future impacts of the continuing COVID-19 pandemic on our operations is uncertain and may adversely impact our business, including our clinical trials.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying unaudited 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 unaudited condensed consolidated financial statements and accompanying notes. Significant estimates inherent in the preparation of the accompanying unaudited 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 unaudited condensed consolidated financial statements as of June 30, 2022 and for the three and six months ended June 30, 2022 and 2021 and the related interim information contained within the notes to the condensed consolidated financial statements are unaudited. The unaudited 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 unaudited condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes for the year ended December 31, 2021 included in our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 17, 2022 (“Annual Report”). The results of our operations for the three and six months ended June 30, 2022 are not necessarily indicative of the results to be expected for the full year. Principles of Consolidation Our unaudited 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 securities, 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 securities, commercial paper, and corporate debt securities with a final maturity of each security 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. 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 deemed to be other than temporary 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, 2022
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, 2022 reflects 6,489,357 shares of our common stock issued pursuant to a private placement financing completed in September 2021 and 951,980 shares of our common stock issued in December 2021 pursuant to a private placement financing with Horizon Therapeutics Ireland DAC (“Horizon”). The increased number of shares issued during the 2021 period has impacted the year-over-year comparability of our net loss per share calculations. 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, does not differ from basic net loss per share for the periods presented. June 30, 2022 2021 (unaudited) Warrants to purchase common stock 8,838,694 4,459,629 Stock options and restricted stock units outstanding 7,117,820 5,621,597 Total 15,956,514 10,081,226

Cash Equivalents and Investment

Cash Equivalents and Investments	6 Months Ended
	Jun. 30, 2022
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, 2022 (unaudited) Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 20,314 $ — $ — $ 20,314 U.S. treasury bills 49,131 — (582) 48,549 Corporate debt securities and commercial paper 128,726 — (734) 127,992 Total $ 198,171 $ — $ (1,316) $ 196,855 Classified as: Cash equivalents $ 20,314 Short-term investments 143,500 Long-term investments 33,041 Total $ 196,855 December 31, 2021 Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 50,277 $ — $ — $ 50,277 U.S. treasury bills 30,006 1 (100) 29,907 Corporate debt securities and commercial paper 117,492 2 (139) 117,355 Total $ 197,775 $ 3 $ (239) $ 197,539 Classified as: Cash equivalents $ 50,277 Short-term investments 94,396 Long-term investments 52,866 Total $ 197,539

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2022
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, 2022 and December 31, 2021, cash of $4.3 million and $17.6 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, 2022 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 20,314 $ — $ — $ 20,314 U.S. treasury bills 48,549 — — 48,549 Corporate debt securities and commercial paper — 127,992 — 127,992 Total $ 68,863 $ 127,992 $ — $ 196,855 December 31, 2021 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 50,277 $ — $ — $ 50,277 U.S. treasury bills 29,907 — — 29,907 Corporate debt securities and commercial paper — 117,355 — 117,355 Total $ 80,184 $ 117,355 $ — $ 197,539 Our Level 2 assets consist of commercial paper and corporate debt securities. 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, 2022
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, 2022 December 31, 2021 (unaudited) Prepaid research and development $ 1,811 $ 3,315 Deferred financing 487 352 Prepaid insurance 119 454 Prepaid other 374 266 Other receivables 321 323 Prepaid expenses and other current assets $ 3,112 $ 4,710 Accrued liabilities consist of the following (in thousands): June 30, 2022 December 31, 2021 (unaudited) Research and development services $ 8,068 $ 5,536 Employee compensation 2,207 3,084 Accrued taxes 1,807 127 Accrued other 443 670 Accrued liabilities $ 12,525 $ 9,417

Long-term Debt

Long-term Debt	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt In August 2019 (the “Effective Date”), 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, $3.0 million of which was used to repay amounts owing under our prior loan and security agreement with SVB (the “Original Agreement”). In March 2020, the second tranche of $5.0 million was funded to us. We did not draw down the final tranche of $5.0 million, which expired on July 31, 2020. The Term Loans accrue interest at a floating per annum rate of 0.25% above the prime rate, subject to a floor of 5.75%, which interest is payable monthly commencing in September 2019. Upon the occurrence and during the continuance of an event of default, a default interest rate will apply that is 4.0% above the otherwise applicable interest rate. The Term Loans were interest only until September 30, 2020, however, under the Loan Agreement our interest only period automatically extended to June 30, 2021 if we received aggregate new capital of at least $40.0 million no later than June 30, 2020. We met this milestone in June 2020 in conjunction with the execution of the AbbVie agreement, discussed in detail in Note 9 . As a result of the interest only extension, the Term Loans are payable in 25 equal monthly installments of principal plus interest, with the final installment due and payable on July 1, 2023. We may prepay all, but not less than all, of the Term Loans subject to a prepayment fee equal to $75,000, which represents the deferred portion of the final payment due under the Original Agreement, plus the outstanding principal balance under the Term Loans at the time of such prepayment. Additionally, a final payment in the amount of 5.5% of the funded Term Loans is payable to SVB on the date on which the Term Loans are prepaid, paid or become due and payable in full. The final payment fees are recorded in long-term debt in our accompanying Condensed Consolidated Balance Sheets . The Loan Agreement contains customary representations and warranties, events of default and affirmative and negative covenants, including, among others, covenants that limit or restrict our ability to, among other things, incur additional indebtedness, grant liens, merge or consolidate, make acquisitions, pay dividends or other distributions or repurchase equity, make investments, dispose of assets, engage in any new lines of business, and enter into certain transactions with affiliates, in each case subject to certain exceptions. We assessed the likelihood of the lender accelerating payment of the loan due to a material adverse change in our business, operations, financial, or other conditions as remote. We were in compliance with our covenants as of June 30, 2022. As such, as of June 30, 2022, the classification of the loan is split between current and noncurrent based on the timing of payment obligations. As security for its obligations under the Loan Agreement, we granted SVB a first priority security interest on substantially all of our assets, except intellectual property, and subject to certain other exceptions. In connection with the Loan Agreement, we issued a warrant to SVB to purchase up to 52,083 shares of our common stock at a price of $4.32 per share, 17,361 shares of which became exercisable in August 2019 after we drew down the initial tranche. In March 2020, after we drew down the second tranche of our Term Loan, an additional 17,361 shares became exercisable. The remaining warrants did not vest and expired on July 31, 2020, upon the expiration of the third tranche of our Term Loan. The fair value of the warrants on the date of issuance for the initial tranche and second tranche was $60,000 and $60,000, respectively, determined using the Black-Scholes option-pricing model, and was recorded as a component of equity and as a debt discount in our accompanying Condensed Consolidated Balance Sheets . In connection with the predecessor loan agreement with SVB that we entered into in December 2016, SVB also holds 7,069 fully vested common stock warrants at an exercise price of $12.38 per share. We recorded a total debt discount of $812,000 in connection with the Loan Agreement, which is being amortized to interest expense using the effective interest method over the repayment term of the loan. The unamortized discount included in long-term debt in our accompanying Condensed Consolidated Balance Sheets was $118,000 as of June 30, 2022. Scheduled principal payments on our outstanding debt as of June 30, 2022 under our Loan Agreement, excluding final payment fees, are as follows (in thousands): Total Year ending December 31, (unaudited) 2022 (remainder of year) $ 2,400 2023 2,800 Total future principal payments $ 5,200

Contingencies

Contingencies	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Certain credits received related to our research and development expenditures and previously recorded within other income in our Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) are subject to review by foreign taxing authorities. Upon reaching constructive agreement with the Australian Taxation Office during the quarter ended June 30, 2022, we recorded an estimated current foreign income tax provision of $1.3 million for the expected repayments, which is included within accrued liabilities on our accompanying Condensed Consolidated Balance Sheets .

License and Collaboration Agree

License and Collaboration Agreements	6 Months Ended
	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements 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 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. 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 In May 2019, we entered into a collaboration and licensing agreement with Adaptimmune (the “Adaptimmune Agreement”) to develop next-generation SPEAR T cell products. 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, 2022, 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. In addition, we have recorded $1.8 million in research support payments to fund ongoing programs through June 30, 2022. As of June 30, 2022, $1.1 million for license fee and research support payments related to the additional research program is included within accounts receivable on our Condensed Consolidated Balance Sheets . 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, 2022 December 31, 2021 (unaudited) Contract Assets $ 1,317 $ 25,000 Contract Liabilities $ 85,000 $ 102,603 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 of internal personnel and third-party contract costs. Revenue is recognized based on the level of costs incurred relative to the total estimated costs for the performance obligation. A cost-based input method of revenue recognition requires management to make estimates of 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 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, 2022 2021 2022 2021 (unaudited) AbbVie $ 4,563 $ 7,193 $ 10,523 $ 10,397 Horizon 587 — 8,256 — Adaptimmune 142 — 142 — Total collaboration revenue $ 5,292 $ 7,193 $ 18,921 $ 10,397 Revenue recognized during the period that was included in the opening contract liability balance was $5.1 million and $7.2 million for the three months ended June 30, 2022 and 2021, respectively, and $18.6 million and $10.4 million for the six months ended June 30, 2022 and 2021, respectively.

Stockholders_ Equity

Stockholders’ Equity	6 Months Ended
	Jun. 30, 2022
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Financing Agreements In July 2021, we entered into a sales agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) pursuant to which we may sell shares of our common stock from time to time through an “at the market” equity offering for up to $75.0 million in gross cash proceeds. Cowen will act as the sales agent and will be entitled to compensation for services of up to 3.0% of the gross sales price per share of all shares sold through Cowen under the Sales Agreement. The shares would be issued pursuant to our effective shelf registration statement on Form S-3 (File No. 333-256107). We filed a prospectus supplement, dated July 2, 2021, with the SEC in connection with the offer and sale of the shares pursuant to the Sales Agreement. As of June 30, 2022, no sales have been made under the Sales Agreement. Equity Incentive Plans On January 1, 2022, 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, 2022, we issued stock option grants totaling 1,550,650 shares with a weighted average exercise price of $11.50 per share and 3,750 shares of restricted stock units (“RSUs”) at a grant date fair value of $9.00 per share to eligible employees and board members. 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 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 Six Months Ended 2022 2021 2022 2021 (unaudited) Research and development $ 1,346 $ 852 $ 2,654 $ 1,660 General and administrative 989 693 1,970 1,482 Total stock-based compensation expense $ 2,335 $ 1,545 $ 4,624 $ 3,142

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2022
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 7.48% and 0.61% for the six months ended June 30, 2022 and 2021, respectively. The increase in our effective tax rate was primarily due to recognizing current income tax liabilities of $1.3 million during the quarter ended June 30, 2022, which was a result of a cumulative change to our foreign income tax provision for the activities of our wholly owned subsidiary, Alpine Immune Sciences Australia PTY LTD. Following notification of acceptance received during the quarter ended June 30, 2022 of Alpine Immune Sciences Australia PTY LTD’s tax return filed under a revised transfer pricing model for the six-months period ended December 31, 2019, the tax provisions for each open tax year have been recalculated using the same transfer pricing methodology underlying the accepted return. Additionally, consistent with the change to our transfer pricing methodology, we recorded $0.1 million of deferred tax expense resulting from a reduction to our deferred tax assets during the quarter ended June 30, 2022. The increase in our effective tax rate was also impacted due to recognizing current domestic federal income tax liabilities of $0.4 million during the quarter ended June 30, 2022, which was a result of the mandatory capitalization of research and development expenses under Internal Revenue Code Section 174. As part of the Tax Cuts and Jobs Act of 2017 (TCJA), beginning with the 2022 tax year, expenses that are incurred for research and development in the U.S. will be capitalized and amortized over five years, and expenses that are incurred for research and experimentation outside the U.S. will be capitalized and amortized over 15 years. The differences between the effective tax rates of 7.48% and 0.61% and the U.S. federal statutory rate of 21% for the six months ended June 30, 2022 and 2021, 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, 2022, 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, 2022, 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.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying unaudited 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 unaudited condensed consolidated financial statements and accompanying notes. Significant estimates inherent in the preparation of the accompanying unaudited 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 unaudited condensed consolidated financial statements as of June 30, 2022 and for the three and six months ended June 30, 2022 and 2021 and the related interim information contained within the notes to the condensed consolidated financial statements are unaudited. The unaudited 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 unaudited condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements and accompanying notes for the year ended December 31, 2021 included in our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 17, 2022 (“Annual Report”). The results of our operations for the three and six months ended June 30, 2022 are not necessarily indicative of the results to be expected for the full year.
Principles of Consolidation	Principles of ConsolidationOur unaudited 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 securities, 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 securities, commercial paper, and corporate debt securities with a final maturity of each security 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. 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 deemed to be other than temporary 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, 2022
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, does not differ from basic net loss per share for the periods presented. June 30, 2022 2021 (unaudited) Warrants to purchase common stock 8,838,694 4,459,629 Stock options and restricted stock units outstanding 7,117,820 5,621,597 Total 15,956,514 10,081,226

Cash Equivalents and Investme_2

Cash Equivalents and Investments (Tables)	6 Months Ended
	Jun. 30, 2022
Investments and Cash [Abstract]
Summary 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, 2022 (unaudited) Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 20,314 $ — $ — $ 20,314 U.S. treasury bills 49,131 — (582) 48,549 Corporate debt securities and commercial paper 128,726 — (734) 127,992 Total $ 198,171 $ — $ (1,316) $ 196,855 Classified as: Cash equivalents $ 20,314 Short-term investments 143,500 Long-term investments 33,041 Total $ 196,855 December 31, 2021 Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 50,277 $ — $ — $ 50,277 U.S. treasury bills 30,006 1 (100) 29,907 Corporate debt securities and commercial paper 117,492 2 (139) 117,355 Total $ 197,775 $ 3 $ (239) $ 197,539 Classified as: Cash equivalents $ 50,277 Short-term investments 94,396 Long-term investments 52,866 Total $ 197,539

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
Summary 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, 2022 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 20,314 $ — $ — $ 20,314 U.S. treasury bills 48,549 — — 48,549 Corporate debt securities and commercial paper — 127,992 — 127,992 Total $ 68,863 $ 127,992 $ — $ 196,855 December 31, 2021 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 50,277 $ — $ — $ 50,277 U.S. treasury bills 29,907 — — 29,907 Corporate debt securities and commercial paper — 117,355 — 117,355 Total $ 80,184 $ 117,355 $ — $ 197,539

Additional Balance Sheet Info_2

Additional Balance Sheet Information (Tables)	6 Months Ended
	Jun. 30, 2022
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, 2022 December 31, 2021 (unaudited) Prepaid research and development $ 1,811 $ 3,315 Deferred financing 487 352 Prepaid insurance 119 454 Prepaid other 374 266 Other receivables 321 323 Prepaid expenses and other current assets $ 3,112 $ 4,710
Summary of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, 2022 December 31, 2021 (unaudited) Research and development services $ 8,068 $ 5,536 Employee compensation 2,207 3,084 Accrued taxes 1,807 127 Accrued other 443 670 Accrued liabilities $ 12,525 $ 9,417

Long-term Debt (Tables)

Long-term Debt (Tables)	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	Scheduled principal payments on our outstanding debt as of June 30, 2022 under our Loan Agreement, excluding final payment fees, are as follows (in thousands): Total Year ending December 31, (unaudited) 2022 (remainder of year) $ 2,400 2023 2,800 Total future principal payments $ 5,200

License and Collaboration Agr_2

License and Collaboration Agreements (Tables)	6 Months Ended
	Jun. 30, 2022
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, 2022 December 31, 2021 (unaudited) Contract Assets $ 1,317 $ 25,000 Contract Liabilities $ 85,000 $ 102,603
Schedule of Disaggregation of Revenue	Collaboration revenue 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, 2022 2021 2022 2021 (unaudited) AbbVie $ 4,563 $ 7,193 $ 10,523 $ 10,397 Horizon 587 — 8,256 — Adaptimmune 142 — 142 — Total collaboration revenue $ 5,292 $ 7,193 $ 18,921 $ 10,397

Stockholders_ Equity (Tables)

Stockholders’ Equity (Tables)	6 Months Ended
	Jun. 30, 2022
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 Six Months Ended 2022 2021 2022 2021 (unaudited) Research and development $ 1,346 $ 852 $ 2,654 $ 1,660 General and administrative 989 693 1,970 1,482 Total stock-based compensation expense $ 2,335 $ 1,545 $ 4,624 $ 3,142

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	Jun. 30, 2022	Dec. 31, 2021
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	1 Months Ended
	Dec. 31, 2021	Sep. 30, 2021
2021 PIPE
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Issuance of units/common stock, net of offering costs (in shares)		6,489,357
Horizon
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Issuance of units/common stock, net of offering costs (in shares)	951,980

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Anti-dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	15,956,514	10,081,226
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)	8,838,694	4,459,629
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)	7,117,820	5,621,597

Cash Equivalents and Investme_3

Cash Equivalents and Investments - Summary of Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 198,171	$ 197,775
Gross unrealized gains	0	3
Gross unrealized losses	(1,316)	(239)
Fair market value	196,855	197,539
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Fair market value	20,314	50,277
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	143,500	94,396
Long-term investments
Debt Securities, Available-for-sale [Line Items]
Fair market value	33,041	52,866
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,314	50,277
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair market value	20,314	50,277
U.S. treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	49,131	30,006
Gross unrealized gains	0	1
Gross unrealized losses	(582)	(100)
Fair market value	48,549	29,907
Corporate debt securities and commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	128,726	117,492
Gross unrealized gains	0	2
Gross unrealized losses	(734)	(139)
Fair market value	$ 127,992	$ 117,355

Cash Equivalents and Investme_4

Cash Equivalents and Investments - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Investments and Cash [Abstract]
Debt securities, available-for-sale, term (less than)	2 years		2 years
Realized gains (losses) on securities	$ 0	$ 0
Available-for-sale debt securities in unrealized loss position	$ 124,800,000		$ 83,000,000

Fair Value Measurements- Narrat

Fair Value Measurements- Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Cash	$ 4.3	$ 17.6

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 196,855	$ 197,539
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	68,863	80,184
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	127,992	117,355
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	20,314	50,277
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	20,314	50,277
Money market funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Money market funds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
U.S. treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	48,549	29,907
U.S. treasury bills | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	48,549	29,907
U.S. treasury bills | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
U.S. treasury bills | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Corporate debt securities and commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	127,992	117,355
Corporate debt securities and commercial paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	0	0
Corporate debt securities and commercial paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	127,992	117,355
Corporate debt securities and commercial paper | Level 3
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, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid research and development	$ 1,811	$ 3,315
Deferred financing	487	352
Prepaid insurance	119	454
Prepaid other	374	266
Other receivables	321	323
Prepaid expenses and other current assets	$ 3,112	$ 4,710

Additional Balance Sheet Info_4

Additional Balance Sheet Information - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Research and development services	$ 8,068	$ 5,536
Employee compensation	2,207	3,084
Accrued taxes	1,807	127
Accrued other	443	670
Accrued liabilities	$ 12,525	$ 9,417

Long-term Debt - Narrative (Det

Long-term Debt - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended
	Mar. 31, 2020 USD ($)	Aug. 31, 2019 USD ($) installment tranche $ / shares shares	Jun. 30, 2022 USD ($)	Jul. 31, 2020 USD ($)	Mar. 30, 2020 USD ($) shares	Dec. 31, 2016 $ / shares shares
Debt Instrument [Line Items]
Unamortized debt discount			$ 118
Term Loans
Debt Instrument [Line Items]
Debt instrument, total discount recorded					$ 812
Term Loans | Term Loans, Tranche One | Common Stock Warrant
Debt Instrument [Line Items]
Fair value of warrant		$ 60
Term Loans | Term Loans, Tranche Two | Common Stock Warrant
Debt Instrument [Line Items]
Fair value of warrant					$ 60
Silicon Valley Bank | Original Agreement
Debt Instrument [Line Items]
Repayments of debt		3,000
Prepayment fee (equal to)		75
Silicon Valley Bank | Original Agreement | Common Stock Warrant
Debt Instrument [Line Items]
Warrants issued (in shares) | shares						7,069
Warrants issued, exercise price (in dollars per share) | $ / shares						$ 12.38
Silicon Valley Bank | Term Loans
Debt Instrument [Line Items]
Maximum borrowing capacity, amount		$ 15,000
Number of tranches (up to) | tranche		3
Debt instrument variable interest rate (as a percent)		0.25%
Percentage of default interest rate (as a percent)		4%
New capital milestone for continuation of interest only payment period		$ 40,000
Number of equal monthly installments payable | installment		25
Final payment percentage (as a percent)		5.50%
Silicon Valley Bank | Term Loans | Common Stock Warrant
Debt Instrument [Line Items]
Warrants issued (in shares) | shares		52,083
Warrants issued, exercise price (in dollars per share) | $ / shares		$ 4.32
Number of shares exercisable (in shares) | shares		17,361			17,361
Silicon Valley Bank | Term Loans | Base Rate
Debt Instrument [Line Items]
Debt instrument, interest rate floor (as a percent)		5.75%
Silicon Valley Bank | Term Loans | Term Loans, Tranche One
Debt Instrument [Line Items]
Proceeds from borrowings, net of issuance costs		$ 5,000
Silicon Valley Bank | Term Loans | Term Loans, Tranche Two
Debt Instrument [Line Items]
Proceeds from borrowings, net of issuance costs	$ 5,000
Silicon Valley Bank | Term Loans | Term Loans, Tranche Three
Debt Instrument [Line Items]
Unused borrowing capacity, expired amount				$ 5,000

Long-term Debt - Schedule of Ma

Long-term Debt - Schedule of Maturities of Long-term Debt (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2022 (remainder of year)	$ 2,400
2023	2,800
Total future principal payments	$ 5,200

Contingencies (Details)

Contingencies (Details) $ in Millions	3 Months Ended
	Jun. 30, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Current tax expense	$ 1.3

License and Collaboration Agr_3

License and Collaboration Agreements - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		38 Months Ended
	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) candidate program $ / shares shares	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 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	$ 85,000	$ 102,603	$ 85,000		$ 85,000		$ 85,000
Revenue recognized from contract with customer			5,100	$ 7,200	18,600	$ 10,400
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 | Premium Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities		$ 3,100
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 | Research Support Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from contract with customer							1,800
Adaptimmune | Product | License Fee and Research Support Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License fee	1,000
License fee and research support payments	$ 1,100		$ 1,100		$ 1,100		$ 1,100

License and Collaboration Agr_4

License and Collaboration Agreements - Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Contract Assets	$ 1,317	$ 25,000
Contract Liabilities	$ 85,000	$ 102,603

License and Collaboration Agr_5

License and Collaboration Agreements - Collaboration Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	$ 5,292	$ 7,193	$ 18,921	$ 10,397
AbbVie
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	4,563	7,193	10,523	10,397
Horizon
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	587	0	8,256	0
Adaptimmune
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue	$ 142	$ 0	$ 142	$ 0

Stockholders_ Equity - Narrativ

Stockholders’ Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	6 Months Ended
	Jan. 01, 2022	Jul. 31, 2021	Jun. 30, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options, grants in period (in shares)			1,550,650
Grants in period, weighted average exercise price (in dollars per share)			$ 11.50
Restricted Stock Units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Awards granted during period (in shares)			3,750
Weighted average grant date fair value of awards granted during period (in dollars per share)			$ 9
Financing Agreements | Cowen
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum amount of common stock eligible to be sold (up to)		$ 75
Percentage of compensation for services		3%
Number of shares issued in transaction (in shares)			0
2018 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of additional shares authorized (in shares)	1,500,000

Stockholders_ Equity - Stock-Ba

Stockholders’ Equity - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Class of Stock [Line Items]
Total stock-based compensation expense	$ 2,335	$ 1,545	$ 4,624	$ 3,142
Research and development
Class of Stock [Line Items]
Total stock-based compensation expense	1,346	852	2,654	1,660
General and administrative
Class of Stock [Line Items]
Total stock-based compensation expense	$ 989	$ 693	$ 1,970	$ 1,482

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Effective tax rate (as a percent)		7.48%	0.61%
Current tax expense	$ 1,300
Deferred tax expense	100	$ 107	$ (63)
Current domestic federal income tax liabilities	$ 400