Alpine Immune Sciences (ALPN) 10-Q 13 Aug 19 2019 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2019	Aug. 08, 2019
Cover page.
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Document Quarterly Report	true
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		18,587,644
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ALPN
Security Exchange Name	NASDAQ
Entity Central Index Key	0001626199
Current Fiscal Year End Date	--12-31
Entity Ex Transition Period	true
Entity Address, Address Line One	201 Elliott Avenue West, Suite 230
Entity Address, City or Town	Seattle
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98119
City Area Code	206
Local Phone Number	788-4545

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 15,468	$ 10,711
Short-term investments	40,097	41,592
Prepaid expenses and other current assets	1,657	1,242
Total current assets	57,222	53,545
Restricted cash	386	132
Property and equipment, net	1,176	1,196
Operating lease, right-of-use asset	11,303	0
Total assets	70,087	54,873
Current liabilities:
Accounts payable	2,399	1,716
Accrued liabilities	5,518	4,363
Deferred revenue	2,108	0
Operating lease liability, current	452	0
Current portion of long-term debt	2,079	2,048
Total current liabilities	12,556	8,127
Operating lease liability, noncurrent	10,919	0
Long-term debt	1,191	2,155
Total liabilities	24,666	10,282
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value per share; 200,000,000 shares authorized at June 30, 2019 and December 31, 2018; 18,635,197 shares issued and 18,584,730 shares outstanding at June 30, 2019; 13,904,672 shares issued and 13,854,205 shares outstanding at December 31, 2018	19	14
Treasury stock, at cost; 50,467 shares at June 30, 2019 and December 31, 2018	0	0
Additional paid-in capital	115,704	90,664
Accumulated other comprehensive gain (loss)	9	(13)
Accumulated deficit	(70,311)	(46,074)
Total stockholders’ equity	45,421	44,591
Total liabilities and stockholders’ equity	$ 70,087	$ 54,873

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
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)	18,635,197	13,904,672
Common stock, shares outstanding (in shares)	18,584,730	13,854,205
Treasury stock, shares (in shares)	50,467	50,467

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Collaboration revenue	$ 567	$ 390	$ 567	$ 705
Operating expenses:
Research and development	10,166	5,718	20,516	9,510
General and administrative	2,553	1,883	4,898	3,991
Loss on sale of intangible asset	0	1,203	0	1,203
Total operating expenses	12,719	8,804	25,414	14,704
Loss from operations	(12,152)	(8,414)	(24,847)	(13,999)
Other income (expense):
Interest expense	(61)	(83)	(131)	(161)
Interest and other income	357	337	741	642
Loss before taxes	(11,856)	(8,160)	(24,237)	(13,518)
Income tax benefit	0	253	0	305
Net loss	(11,856)	(7,907)	(24,237)	(13,213)
Comprehensive income (loss):
Unrealized gain on investments	17	50	32	4
Unrealized gain (loss) on foreign currency translation	4	0	(10)	0
Comprehensive loss	$ (11,835)	$ (7,857)	$ (24,215)	$ (13,209)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	18,576,199	13,848,974	18,126,556	13,846,865
Basic and diluted net loss per share (in dollars per share)	$ (0.64)	$ (0.57)	$ (1.34)	$ (0.95)

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 Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		13,831,178	50,467
Beginning balance at Dec. 31, 2017	$ 78,917	$ 14	$ 0	$ 88,346	$ (59)	$ (9,384)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		14,906
Exercise of stock options	7			7
Stock-based compensation	511			511
Unrealized gain (loss) on investments	(46)				(46)
Net loss	(5,306)					(5,306)
Ending balance (in shares) at Mar. 31, 2018		13,846,084	50,467
Ending balance at Mar. 31, 2018	73,881	$ 14	$ 0	88,864	(105)	(14,892)
Beginning balance (in shares) at Dec. 31, 2017		13,831,178	50,467
Beginning balance at Dec. 31, 2017	78,917	$ 14	$ 0	88,346	(59)	(9,384)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on investments	4
Unrealized loss on foreign currency translation	0
Net loss	(13,213)
Ending balance (in shares) at Jun. 30, 2018		13,850,762	50,467
Ending balance at Jun. 30, 2018	66,547	$ 14	$ 0	89,387	(55)	(22,799)
Beginning balance (in shares) at Mar. 31, 2018		13,846,084	50,467
Beginning balance at Mar. 31, 2018	73,881	$ 14	$ 0	88,864	(105)	(14,892)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		4,678
Exercise of stock options	0
Stock-based compensation	523			523
Unrealized gain (loss) on investments	50				50
Unrealized loss on foreign currency translation	0
Net loss	(7,907)					(7,907)
Ending balance (in shares) at Jun. 30, 2018		13,850,762	50,467
Ending balance at Jun. 30, 2018	66,547	$ 14	$ 0	89,387	(55)	(22,799)
Beginning balance (in shares) at Dec. 31, 2018		13,854,205	50,467
Beginning balance at Dec. 31, 2018	44,591	$ 14	$ 0	90,664	(13)	(46,074)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Units in Private Placement, net of offering costs (in shares)		4,706,700
Issuance of Units in Private Placement, net of offering costs	23,618	$ 5		23,613
Exercise of stock options (in shares)		124
Exercise of stock options	0
Stock-based compensation	754			754
Unrealized gain (loss) on investments	15				15
Unrealized loss on foreign currency translation	(14)				(14)
Net loss	(12,381)					(12,381)
Ending balance (in shares) at Mar. 31, 2019		18,561,029	50,467
Ending balance at Mar. 31, 2019	56,583	$ 19	$ 0	115,031	(12)	(58,455)
Beginning balance (in shares) at Dec. 31, 2018		13,854,205	50,467
Beginning balance at Dec. 31, 2018	44,591	$ 14	$ 0	90,664	(13)	(46,074)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on investments	32
Unrealized loss on foreign currency translation	(10)
Net loss	(24,237)
Ending balance (in shares) at Jun. 30, 2019		18,584,730	50,467
Ending balance at Jun. 30, 2019	45,421	$ 19	$ 0	115,704	9	(70,311)
Beginning balance (in shares) at Mar. 31, 2019		18,561,029	50,467
Beginning balance at Mar. 31, 2019	56,583	$ 19	$ 0	115,031	(12)	(58,455)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Units in Private Placement, net of offering costs	(20)			(20)
Exercise of stock options (in shares)		23,701
Exercise of stock options	11			11
Stock-based compensation	682			682
Unrealized gain (loss) on investments	17				17
Unrealized loss on foreign currency translation	4				4
Net loss	(11,856)					(11,856)
Ending balance (in shares) at Jun. 30, 2019		18,584,730	50,467
Ending balance at Jun. 30, 2019	$ 45,421	$ 19	$ 0	$ 115,704	$ 9	$ (70,311)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (24,237)	$ (13,213)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on sale of intangible asset	0	1,203
Amortization of right-of-use asset	454	0
Depreciation expense	229	170
Amortization of premium/discount on investments	(185)	(368)
Non-cash interest expense	67	88
Deferred income tax	0	(305)
Stock-based compensation and warrant expense	1,436	1,034
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(415)	(536)
Accounts payable and accrued liabilities	1,829	760
Deferred revenue	2,108	(479)
Lease liabilities	(386)	0
Net cash used in operating activities	(19,100)	(11,646)
Investing activities
Purchases of property and equipment	(200)	(278)
Proceeds from sale of intangible asset	0	250
Purchase of short-term investments	(39,804)	(41,390)
Maturities of short-term investments	40,125	48,626
Proceeds from the sale of short-term investments	1,391	0
Net cash provided by investing activities	1,512	7,208
Financing activities
Proceeds from sale of common stock, net of offering costs	23,598	0
Repayment of debt	(1,000)	0
Proceeds from exercise of stock options	11	7
Net cash provided by financing activities	22,609	7
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(10)	0
Net increase (decrease) in cash and cash equivalents and restricted cash	5,011	(4,431)
Cash and cash equivalents and restricted cash, beginning of period	10,843	8,132
Cash and cash equivalents and restricted cash, end of period	15,854	3,701
Supplemental Information
Recognition of right-of-use asset	11,757	0
Cash paid for interest	$ 67	$ 72

Description of the Business

Description of the Business	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business Alpine Immune Sciences, Inc. (the “Company”, “Alpine”, “we”, “us”, or “our”), together with its consolidated subsidiaries, is a clinical-stage immunotherapy company committed to leading a new wave of immune therapeutics, creating potentially powerful multifunctional immunotherapies to improve patients’ lives via unique protein engineering technologies. Alpine has two lead programs. The first, ALPN-101 for autoimmune/inflammatory diseases, is a dual selective T-cell costimulation blocker engineered to reduce pathogenic T and B cell immune responses by blocking ICOS and CD28. ALPN-101 is currently enrolling a phase I healthy volunteer trial. The second, ALPN-202 for cancer, is a conditional CD28 costimulator and dual checkpoint inhibitor. Our proprietary scientific platform uses a process known as directed evolution to convert native immune system proteins from the Immunoglobulin Super Family, or IgSF, into multi-targeted therapeutics potentially capable of modulating the human immune system. 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, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation 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 accruals for clinical trial activities and other accruals, 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, 2019 and for the three and six months ended June 30, 2019 and 2018 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 years December 31, 2018 and 2017 included in our Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on March 18, 2019 (“Annual Report”). The results of our operations for the three and six months ended June 30, 2019 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 and our wholly owned operating company and subsidiary, AIS Operating Co., Inc., and Alpine Immune Sciences Australia PTY LTD, respectively. All inter-company balances and transactions have been eliminated in consolidation. Restricted Cash Restricted cash represents cash drawn on lines of credit used to establish collateral to support the security deposit on our leases to rent office and laboratory space in Seattle, Washington. Short-Term Investments Our short-term 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 one year . All investments are classified as available-for-sale securities and are recorded at fair value based on quoted prices in active markets, with unrealized gains and losses excluded from earnings and 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 the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) using the specific-identification method. Leases (effective January 1, 2019) We account for our leases under Accounting Standards Codification (“ASC”) 842, Leases. Under this guidance, arrangements meeting the definition of a lease are classified as operating or financing leases, and are recorded on the condensed consolidated balance sheet as both a right-of-use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or our incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right-of-use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right-of-use asset result in straight-line rent expense over the lease term. For finance leases, interest on the lease liability and the amortization of the right-of-use asset results is front-loaded expense over the lease term. Variable lease expenses are recorded when incurred. In calculating the right-of-use asset and lease liability, we elected to combine lease and non-lease components. We exclude short-term leases having initial terms of 12 months or less from the new guidance as an accounting policy election, and recognize rent expense on a straight-line basis over the lease term. We continue to account for leases in the prior period financial statements under ASC Topic 840. Revenue Recognition Revenue is recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Our steps for recognizing revenue consist of; (1) identifying the contract, (2) identifying the performance obligations as either distinct or bundled goods and services, (3) determining the transaction price associated with each performance obligation for which we expect to be entitled in exchange for transferring such goods and services, (4) allocating the transaction price to the performance obligations in the contract and (5) recognizing revenue upon satisfaction of performance obligations. Our collaboration agreements principally contain multiple performance obligations, which may include (1) grants of, or options to obtain, intellectual property licenses; (2) research and development services; and/or (3) manufacturing or supply services. Payments typically received under these arrangements include one or more of the following: non-refundable upfront license fees, option exercise fees, payment for research and/or development efforts, amounts due upon the achievement of specified objectives, and/or royalties on future product sales. Our revenue is primarily derived from our collaboration agreements with Adaptimmune Therapeutics plc (“Adaptimmune”) and Kite Pharma, a Gilead company (“Kite”). See further discussion of our collaboration agreements in Note 9 . We allocate revenue to each performance obligation based on its relative stand-alone selling price. We generally determine stand-alone selling prices at the inception of the contract based on our best estimate of what the selling price would be if the deliverable was regularly sold by us on a stand-alone basis. Payments received prior to satisfying the relevant revenue recognition criteria are recorded as deferred revenue in the accompanying Condensed Consolidated Balance Sheets and recognized as revenue when the related revenue recognition criteria are met. We recognize revenue under our collaboration agreements based on employee hours contributed to each performance obligation. Our collaboration agreements provide for non-refundable milestone payments. We recognize revenue that is contingent upon the achievement of a substantive milestone in its entirety in the period in which the milestone is achieved. A milestone is considered substantive when the consideration payable to us for such milestone (1) is consistent with our performance necessary to achieve the milestone or the increase in value to the collaboration resulting from our performance; (2) relates solely to our past performance; and (3) is reasonable relative to all of the other deliverables and payments within the arrangement. In making this assessment, we consider all facts and circumstances relevant to the arrangement, including factors such as the scientific, regulatory, commercial, and other risks that must be overcome to achieve the milestone, the level of effort and investment required to achieve the milestone and whether any portion of the milestone consideration is related to future performance or deliverables. We review the contributed employee hours for each performance obligation under our collaboration agreements, and adjust the revenue recognized to reflect changes in assumptions relating to the estimated satisfaction of the performance obligation. We could accelerate revenue recognition in the event of early termination of programs or if our expectations change. Alternatively, we could decelerate revenue recognition if programs are extended or delayed. While such changes to our estimates have no impact on our reported cash flows, the timing of revenue recorded in future periods could be materially impacted. Revenue from Asset Purchase Agreement In June 2018, we entered into an Asset Purchase Agreement (“Purchase Agreement”) with Laurel Venture Capital Ltd. (“Laurel”) and completed the sale of global rights to the indefinite-life GSNOR inhibitor in-process research and development asset acquired as part of the merger with Nivalis in 2017. As consideration under the Purchase Agreement, we received a non-refundable closing payment of $250,000 , which was accounted for as a purchase of our intangible asset. Upon the sale of the GSNOR assets, we derecognized the full carrying value of the intangible asset on our accompanying Condensed Consolidated Balance Sheets and recognized a loss on the sale of the intangible asset of $1.2 million on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) . In June 2019, we recognized as revenue an additional milestone payment of $425,000 , related to the asset purchase. Foreign Currency Translation Our functional currency is the U.S. dollar. All assets and liabilities of our subsidiaries are translated using period-end exchange rates and revenues and expenses are translated at average exchange rates for the year. Translation adjustments are included as components of comprehensive gain (loss) in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) . Recently Issued Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-18, Collaborative Arrangements: Clarifying the Interaction between Topic 808 and Topic 606. This ASU clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. This ASU is effective for public companies for annual reporting periods and interim periods within those annual periods beginning after December 15, 2019. We are currently evaluating the effect, if any, that ASU 2018-18 will have on our consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. This ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any eliminated or modified disclosures. We are evaluating the effect of adopting this new accounting guidance to determine the impact it may have on our financial statements. Recently Adopted Accounting Pronouncements In June 2018, the FASB issued ASU No. 2018-07, which aligns the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees, with certain exceptions. Under the guidance, the measurement of equity-classified nonemployee awards will be fixed at the grant date. Upon transition, nonemployee awards will be required to be measured at fair value as of the adoption date with a cumulative-effect adjustment recognized in retained earnings as of the beginning of the annual period of adoption. ASU 2018-07 is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. We adopted this standard on January 1, 2019 and it did not have a material impact on our financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases. ASU 2016-02 requires a lessee to separate the lease components from the non-lease components in a contract and recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. It also aligns lease accounting for lessors with the revenue recognition guidance in ASU 2014-09. We adopted this ASU effective January 1, 2019 using the additional (optional) approach by recording an operating lease right-of-use asset of $797,000 , a corresponding operating lease liability of $883,000 , and reducing our deferred rent balance by $86,000 to $0 on our accompanying Condensed Consolidated Balance Sheets

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2019
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, 2019 reflects 4,706,700 shares of our common stock issued pursuant to a private placement financing completed in January 2019. The significant number of shares issued has affected 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: June 30, 2019 2018 (unaudited) Warrants to purchase common stock 1,859,733 24,123 Options to purchase common stock 3,266,572 1,990,793 Total 5,126,305 2,014,916

Cash Equivalents and Short-Term

Cash Equivalents and Short-Term Investments	6 Months Ended
	Jun. 30, 2019
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Cash Equivalents and Short-term Investments	Cash Equivalents and Short-Term Investments The amortized cost and fair value of our cash equivalents and short-term investments are as follows (in thousands): June 30, 2019 Assets: (unaudited) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 8,481 $ — $ — $ 8,481 U.S. treasury bills 11,509 6 — 11,515 Corporate debt securities and commercial paper 31,912 13 — 31,925 Total $ 51,902 $ 19 $ — $ 51,921 December 31, 2018 Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 6,405 $ — $ — $ 6,405 U.S. treasury bills 13,966 — (2 ) 13,964 Corporate debt securities and commercial paper 31,331 — (11 ) 31,320 Total $ 51,702 $ — $ (13 ) $ 51,689 All short-term investments held as of June 30, 2019 and December 31, 2018 were classified as available-for-sale securities and had contractual maturities of less than one year. There were no

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Cash and cash equivalents, 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, 2019 , and December 31, 2018 , cash of $3.6 million and $614,000 , respectively, is excluded from the following 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, 2019 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 8,481 $ — $ — $ 8,481 U.S. treasury bills 11,515 — — 11,515 Corporate debt securities and commercial paper — 31,925 — 31,925 Total $ 19,996 $ 31,925 $ — $ 51,921 December 31, 2018 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 6,405 $ — $ — $ 6,405 U.S. treasury bills 13,964 — — 13,964 Corporate debt securities and commercial paper — 31,320 — 31,320 Total $ 20,369 $ 31,320 $ — $ 51,689 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.

Accrued Liabilities

Accrued Liabilities	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 (unaudited) Research and development services $ 3,386 $ 2,457 Employee compensation 1,026 1,009 Legal and professional fees 113 646 Accrued other 993 251 Total $ 5,518 $ 4,363

Long-term Debt

Long-term Debt	6 Months Ended
	Jun. 30, 2019
Debt Instruments [Abstract]
Long-term Debt	Long-term Debt We maintain a long-term financing arrangement with Silicon Valley Bank. On June 30, 2017, we drew down a term loan of $5.0 million . The loan had an interest-only period that expired on July 1, 2018 , at which point we became obligated to make thirty consecutive equal monthly payments of principal (each in an amount that will fully amortize the loan), plus accrued interest. Interest accrues at a floating per annum rate equal to the lender’s prime rate minus 1.75% . As a condition to the loan, we agreed to pay a final payment fee of 7.5% , or $375,000 , upon repayment of the loan. The final payment fee was recorded in long-term debt with an offsetting reduction in long-term debt and was accounted for as a debt discount. Pursuant to the loan agreement we have pledged substantially all of our assets, excluding intellectual property, as collateral. The obligations under the loan agreement are subject to acceleration upon the occurrence of specified events of default, including a material adverse change in our business, operations, financial, or other condition. 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 condition as remote. As such, as of June 30, 2019 , the classification of the loan is split between current and noncurrent based on the timing of payment obligations. The term loan agreement contains customary conditions to borrowings, events of default and negative covenants, including covenants that could limit our ability to, among other things, incur additional indebtedness, liens or other encumbrances; make dividends or other distributions; buy, sell or transfer assets; engage in any new line of business; and enter into certain transactions with affiliates. We were in compliance with our covenants as of June 30, 2019 . Also, in connection with the drawdown of the loan, we granted Silicon Valley Bank 7,069 Series A -1 Preferred Stock warrants at an exercise price of $12.38 per share. The fair value of the warrants on the date of issuance was $53,000 , determined using the Black-Scholes option-pricing model, and was recorded as a discount to the note and as a warrant liability. In connection with the merger and conversion of all outstanding Series A-1 preferred stock, the warrants became exercisable for 7,069 fully vested shares of our common stock. As a result of the change in the underlying shares, the warrants were equity-classified beginning on July 24, 2017 . The debt discount is being amortized to interest expense using the effective interest method over the repayment term of the initial loan amount. Non-cash interest expense associated with the amortization of the discount was $31,000 and $44,000 for the three months ended June 30, 2019 and 2018 , respectively, and $67,000 and $88,000 for the six months ended June 30, 2019 and 2018 , respectively. The unamortized discount was $105,000 as of June 30, 2019

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases We lease office and laboratory space in Seattle, Washington, under an agreement classified as an operating lease that expires on December 31, 2019. This lease has two 12 -month renewal options, which we did not include in the lease term when calculating our right-of-use asset and lease liability, as we are not reasonably certain to renew. This lease does not require any contingent rental payments, impose any financial restrictions, or contain any residual value guarantees. Variable expenses generally represent our share of the landlord’s operating expenses. We do not act as a lessor or have any leases classified as financing leases. In May 2017, as required by the terms of the lease, we entered into a line of credit to establish collateral to support the security deposit in an amount of $132,000 . This is recorded as restricted cash in the accompanying Condensed Consolidated Balance Sheets . In March 2019, we entered into a lease with ARE-Seattle No. 28, LLC (the “Landlord”) for 27,164 square feet of office and laboratory space located at 188 East Blaine Street, Seattle, Washington. The term of the lease is 10.8 years with one option to extend the term by 5 years . The lease term commenced in June 2019. The “Rent Commencement Date” will be nine months after the commencement date. The annual base rent under the lease is $1.7 million for the first year and will increase by 3.0% each year thereafter. We are not required to pay base rent from the Rent Commencement Date through the last day of the ninth month following the Rent Commencement Date. We will receive a maximum tenant improvement allowance of $5.4 million , which is included in our base rent, and a maximum additional tenant improvement allowance of $1.8 million , which will result in additional rent amortized over the term of the lease at an annual rate of 8.0% . The lease also requires us to pay additional amounts for operating and maintenance expenses. In March 2019, in connection with the lease, we provided a $254,000 letter of credit as a security deposit, which is recorded as restricted cash in our accompanying Condensed Consolidated Balance Sheets . At June 30, 2019 , our operating lease right-of-use assets and operating lease liability associated with these leases were $11.3 million and $11.4 million , respectively, which are included in the accompanying Condensed Consolidated Balance Sheets . The components of our lease expense were as follows (in thousands): Three Months Ended Six Months Ended (unaudited) Lease cost: Operating lease cost $ 365 $ 572 Variable lease cost 80 171 Total lease cost $ 445 $ 743 Other information: Cash paid for amounts included in the measurement of lease liabilities $ 452 Right-of-use assets exchanged for new operating lease liabilities $ 11,757 Weighted-average remaining lease term (in years), operating leases 10.3 Weighted-average discount rate, operating leases 10.5 % Maturities of our operating leases as of June 30, 2019 are as follows (in thousands): 2019 (remaining six months) $ 460 2020 228 2021 1,976 2022 2,027 2023 2,079 Thereafter 14,078 Total 20,848 Less: imputed interest (9,477 ) Operating lease liabilities included in the Consolidated Balance Sheets at June 30, 2019 $ 11,371 Rent expense, which is recorded on a straight-line basis, was $206,000 and $398,000 for the three and six months ended June 30, 2018

License and Collaboration Agree

License and Collaboration Agreements	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements Adaptimmune In May 2019, we entered into a collaboration and licensing agreement with Adaptimmune (the “Adaptimmune Collaboration Agreement”) to develop next-generation SPEAR T-cell products. Under the Adaptimmune Collaboration 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, in order to further enhance Adaptimmune’s efforts to design and develop next-generation SPEAR T-cell therapies. In June 2019, under the terms of the Adaptimmune Collaboration Agreement, we received an upfront license payment of $2.0 million and an additional $250,000 in research support payments to fund ongoing programs. These payments were recorded as deferred revenue and will be recognized to revenue based on employee hours contributed to each performance obligation. We recorded revenue of $142,000 for the three months ended June 30, 2019 . In addition, we are eligible for additional research support payments, one-time payments and downstream development and commercialization milestones of up to $288.0 million , if all pre-specified milestones for each program are achieved. We are also eligible to receive low-single digit royalties on worldwide net sales of the applicable products. Kite In October 2015, we entered into a collaboration and licensing agreement (the “Kite Collaboration Agreement”) with Kite to discover and develop protein-based immunotherapies targeting the immune synapse to treat cancer. In May 2019, Kite provided us notice of termination of the Kite Collaboration Agreement following the expiration of the research term. Upon termination, the confidentiality and indemnity obligations of the parties survived and the licenses granted to Kite under the Kite Collaboration Agreement were terminated. Pursuant to the terms of the Kite Collaboration Agreement, the termination was effective in June 2019, thirty days after the effectiveness of Kite’s notice. Under the terms of the Kite Collaboration Agreement, in 2015, Kite made upfront payments to us of $5.5 million , which were initially recorded as deferred revenue. Under the Kite Collaboration Agreement, we recorded revenue of $0 and $390,000 for the three months ended June 30, 2019 and 2018 , respectively, and $0 and $630,000 for the six months ended June 30, 2019 and 2018

Stockholders_ Equity

Stockholders’ Equity	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Securities Offerings In January 2019, we entered into a securities purchase agreement (the “Purchase Agreement”) with a limited number of accredited investors, pursuant to which we sold 4,706,700 units (the “Units”) for an aggregate purchase price of $25.3 million in a private placement (the “Private Placement”). Each Unit has a purchase price of $5.37 and consists of one share of our common stock and a warrant to purchase 0.39 shares of common stock. Pursuant to the terms of the Purchase Agreement, we issued 4,706,700 shares of common stock and warrants to purchase an aggregate of 1,835,610 shares of common stock. The warrants have an exercise price of $12.74 and have a term of five years . The issuance of the securities sold in the Private Placement was not registered under the Securities Act of 1933, as amended, or state securities laws and such securities could not be offered or sold in the United States absent registration with the SEC or an applicable exemption from such registration requirements. In March 2019, we filed a registration statement with the SEC covering the resale of the shares of common stock issuable in connection with the Private Placement and upon exercise of the warrants, which registration was declared effective by the SEC on April 4, 2019. We have incurred legal, accounting and other direct costs related to our efforts to raise capital. These costs have been capitalized as deferred offering costs and are included within prepaid expenses and other current assets in our accompanying Condensed Consolidated Balance Sheets . These were deferred until completion of the Private Placement, at which time $1.7 million were reclassified to additional paid-in capital as a reduction of the proceeds. As of June 30, 2019 , no sales under our Equity Distribution Agreement (as defined below) have occurred. In June 2018, we entered into an equity distribution agreement, (“Equity Distribution Agreement”), with Piper Jaffray & Co., (“Piper Jaffray”), pursuant to which we may sell shares of our common stock through an “at the market” equity offering program for up to $50.0 million , in gross cash proceeds. Piper Jaffray will be entitled to compensation for its services of up to 3.0% of the gross sales price per share of all shares sold through Piper Jaffray under the Equity Distribution Agreement. The Equity Distribution Agreement may be terminated by us upon written notice to Piper Jaffray for any reason or by Piper Jaffray upon written notice to us for any reason or at any time under certain circumstances, including but not limited to if we experience a material adverse change. Under the Equity Distribution Agreement, we will set the parameters for the sale of shares, including the number of shares to be issued, the time period during which sales are requested to be made, limitation on the number of shares that may be sold in any one trading day and any minimum price below which sales may not be made. We have no obligation to sell any shares under the Equity Distribution Agreement, and may at any time suspend solicitation and offers under the Equity Distribution Agreement. In July 2019, our Registration Statement on Form S-3 (File No. 333-212404) expired pursuant to Rule 415(a)(5) under the Securities Act of 1933, as amended. We will be unable to sell shares under the Equity Distribution Agreement until a new Registration Statement on Form S-3 is filed and declared effective by the SEC and a prospectus supplement relating to any sales under the Equity Distribution Agreement is filed with the SEC. Stock-Based Compensation Expense We use the Black-Scholes option pricing model to estimate the fair value of stock options granted at the grant date. 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 and warrant expense is classified in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) as follows (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 (unaudited) Employee: Research and development $ 422 $ 205 $ 762 $ 402 General and administrative 248 247 631 555 Non-Employee: Research and development 11 7 40 8 General and administrative 1 64 3 69 Total stock-based compensation expense $ 682 $ 523 $ 1,436 $ 1,034

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
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 for the three and six -month periods ended June 30, 2019 and 2018 was 0.0% and 0.98% , respectively. The difference between the effective tax rate of 0.00% and the U.S. federal statutory rate of 21% for the three and six -month periods ended June 30, 2019 was primarily due to recognizing a full valuation allowance on deferred tax assets. The difference between the effective tax rate of 0.98% and the U.S. federal statutory rate of 21% for the three and six -month periods ended June 30, 2018 was primarily due to recognizing a full valuation allowance on deferred tax assets, and the estimated annual benefit of the removal of the deferred tax liability of $305,000 recorded as a result of a previously acquired in-process research and development intangible asset. As of June 30, 2019

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation 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 accruals for clinical trial activities and other accruals, 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, 2019 and for the three and six months ended June 30, 2019 and 2018 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 years December 31, 2018 and 2017 included in our Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on March 18, 2019 (“Annual Report”). The results of our operations for the three and six months ended June 30, 2019 are not necessarily indicative of the results to be expected for the full year.
Principles of Consolidation	Principles of Consolidation Our unaudited condensed consolidated financial statements include the financial position and results of operations of Alpine and our wholly owned operating company and subsidiary, AIS Operating Co., Inc., and Alpine Immune Sciences Australia PTY LTD, respectively. All inter-company balances and transactions have been eliminated in consolidation.
Restricted Cash	Restricted Cash Restricted cash represents cash drawn on lines of credit used to establish collateral to support the security deposit on our leases to rent office and laboratory space in Seattle, Washington.
Short-Term Investments	Short-Term Investments Our short-term 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 one year . All investments are classified as available-for-sale securities and are recorded at fair value based on quoted prices in active markets, with unrealized gains and losses excluded from earnings and 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 the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) using the specific-identification method.
Lessees	Leases (effective January 1, 2019) We account for our leases under Accounting Standards Codification (“ASC”) 842, Leases. Under this guidance, arrangements meeting the definition of a lease are classified as operating or financing leases, and are recorded on the condensed consolidated balance sheet as both a right-of-use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or our incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right-of-use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right-of-use asset result in straight-line rent expense over the lease term. For finance leases, interest on the lease liability and the amortization of the right-of-use asset results is front-loaded expense over the lease term. Variable lease expenses are recorded when incurred. In calculating the right-of-use asset and lease liability, we elected to combine lease and non-lease components. We exclude short-term leases having initial terms of 12 months or less from the new guidance as an accounting policy election, and recognize rent expense on a straight-line basis over the lease term. We continue to account for leases in the prior period financial statements under ASC Topic 840.
Revenue Recognition	Revenue Recognition Revenue is recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Our steps for recognizing revenue consist of; (1) identifying the contract, (2) identifying the performance obligations as either distinct or bundled goods and services, (3) determining the transaction price associated with each performance obligation for which we expect to be entitled in exchange for transferring such goods and services, (4) allocating the transaction price to the performance obligations in the contract and (5) recognizing revenue upon satisfaction of performance obligations. Our collaboration agreements principally contain multiple performance obligations, which may include (1) grants of, or options to obtain, intellectual property licenses; (2) research and development services; and/or (3) manufacturing or supply services. Payments typically received under these arrangements include one or more of the following: non-refundable upfront license fees, option exercise fees, payment for research and/or development efforts, amounts due upon the achievement of specified objectives, and/or royalties on future product sales. Our revenue is primarily derived from our collaboration agreements with Adaptimmune Therapeutics plc (“Adaptimmune”) and Kite Pharma, a Gilead company (“Kite”). See further discussion of our collaboration agreements in Note 9 . We allocate revenue to each performance obligation based on its relative stand-alone selling price. We generally determine stand-alone selling prices at the inception of the contract based on our best estimate of what the selling price would be if the deliverable was regularly sold by us on a stand-alone basis. Payments received prior to satisfying the relevant revenue recognition criteria are recorded as deferred revenue in the accompanying Condensed Consolidated Balance Sheets and recognized as revenue when the related revenue recognition criteria are met. We recognize revenue under our collaboration agreements based on employee hours contributed to each performance obligation. Our collaboration agreements provide for non-refundable milestone payments. We recognize revenue that is contingent upon the achievement of a substantive milestone in its entirety in the period in which the milestone is achieved. A milestone is considered substantive when the consideration payable to us for such milestone (1) is consistent with our performance necessary to achieve the milestone or the increase in value to the collaboration resulting from our performance; (2) relates solely to our past performance; and (3) is reasonable relative to all of the other deliverables and payments within the arrangement. In making this assessment, we consider all facts and circumstances relevant to the arrangement, including factors such as the scientific, regulatory, commercial, and other risks that must be overcome to achieve the milestone, the level of effort and investment required to achieve the milestone and whether any portion of the milestone consideration is related to future performance or deliverables.
Revenue from Asset Purchase Agreement	Revenue from Asset Purchase Agreement In June 2018, we entered into an Asset Purchase Agreement (“Purchase Agreement”) with Laurel Venture Capital Ltd. (“Laurel”) and completed the sale of global rights to the indefinite-life GSNOR inhibitor in-process research and development asset acquired as part of the merger with Nivalis in 2017. As consideration under the Purchase Agreement, we received a non-refundable closing payment of $250,000 , which was accounted for as a purchase of our intangible asset. Upon the sale of the GSNOR assets, we derecognized the full carrying value of the intangible asset on our accompanying Condensed Consolidated Balance Sheets and recognized a loss on the sale of the intangible asset of $1.2 million on the accompanying Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) . In June 2019, we recognized as revenue an additional milestone payment of $425,000 , related to the asset purchase.
Foreign Currency Translation	Foreign Currency Translation Our functional currency is the U.S. dollar. All assets and liabilities of our subsidiaries are translated using period-end exchange rates and revenues and expenses are translated at average exchange rates for the year. Translation adjustments are included as components of comprehensive gain (loss) in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) .
Recently Issued and Adopted Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-18, Collaborative Arrangements: Clarifying the Interaction between Topic 808 and Topic 606. This ASU clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. This ASU is effective for public companies for annual reporting periods and interim periods within those annual periods beginning after December 15, 2019. We are currently evaluating the effect, if any, that ASU 2018-18 will have on our consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. This ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any eliminated or modified disclosures. We are evaluating the effect of adopting this new accounting guidance to determine the impact it may have on our financial statements. Recently Adopted Accounting Pronouncements In June 2018, the FASB issued ASU No. 2018-07, which aligns the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees, with certain exceptions. Under the guidance, the measurement of equity-classified nonemployee awards will be fixed at the grant date. Upon transition, nonemployee awards will be required to be measured at fair value as of the adoption date with a cumulative-effect adjustment recognized in retained earnings as of the beginning of the annual period of adoption. ASU 2018-07 is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. We adopted this standard on January 1, 2019 and it did not have a material impact on our financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases. ASU 2016-02 requires a lessee to separate the lease components from the non-lease components in a contract and recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. It also aligns lease accounting for lessors with the revenue recognition guidance in ASU 2014-09. We adopted this ASU effective January 1, 2019 using the additional (optional) approach by recording an operating lease right-of-use asset of $797,000 , a corresponding operating lease liability of $883,000 , and reducing our deferred rent balance by $86,000 to $0 on our accompanying Condensed Consolidated Balance Sheets
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, 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.
Share-Based Compensation Expense	Stock-Based Compensation Expense

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
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: June 30, 2019 2018 (unaudited) Warrants to purchase common stock 1,859,733 24,123 Options to purchase common stock 3,266,572 1,990,793 Total 5,126,305 2,014,916

Cash Equivalents and Short-Te_2

Cash Equivalents and Short-Term Investments (Tables)	6 Months Ended
	Jun. 30, 2019
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Summary of Amortized Cost and Fair Value of Cash Equivalents and Short Term Investments	The amortized cost and fair value of our cash equivalents and short-term investments are as follows (in thousands): June 30, 2019 Assets: (unaudited) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 8,481 $ — $ — $ 8,481 U.S. treasury bills 11,509 6 — 11,515 Corporate debt securities and commercial paper 31,912 13 — 31,925 Total $ 51,902 $ 19 $ — $ 51,921 December 31, 2018 Assets: Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 6,405 $ — $ — $ 6,405 U.S. treasury bills 13,966 — (2 ) 13,964 Corporate debt securities and commercial paper 31,331 — (11 ) 31,320 Total $ 51,702 $ — $ (13 ) $ 51,689

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
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, 2019 (unaudited) Assets: Level 1 Level 2 Level 3 Total Money market funds $ 8,481 $ — $ — $ 8,481 U.S. treasury bills 11,515 — — 11,515 Corporate debt securities and commercial paper — 31,925 — 31,925 Total $ 19,996 $ 31,925 $ — $ 51,921 December 31, 2018 Assets: Level 1 Level 2 Level 3 Total Money market funds $ 6,405 $ — $ — $ 6,405 U.S. treasury bills 13,964 — — 13,964 Corporate debt securities and commercial paper — 31,320 — 31,320 Total $ 20,369 $ 31,320 $ — $ 51,689

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Summary of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 (unaudited) Research and development services $ 3,386 $ 2,457 Employee compensation 1,026 1,009 Legal and professional fees 113 646 Accrued other 993 251 Total $ 5,518 $ 4,363

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Components of Lease Cost	The components of our lease expense were as follows (in thousands): Three Months Ended Six Months Ended (unaudited) Lease cost: Operating lease cost $ 365 $ 572 Variable lease cost 80 171 Total lease cost $ 445 $ 743 Other information: Cash paid for amounts included in the measurement of lease liabilities $ 452 Right-of-use assets exchanged for new operating lease liabilities $ 11,757 Weighted-average remaining lease term (in years), operating leases 10.3 Weighted-average discount rate, operating leases 10.5 %
Lessee, Operating Lease, Liability, Maturity	Maturities of our operating leases as of June 30, 2019 are as follows (in thousands): 2019 (remaining six months) $ 460 2020 228 2021 1,976 2022 2,027 2023 2,079 Thereafter 14,078 Total 20,848 Less: imputed interest (9,477 ) Operating lease liabilities included in the Consolidated Balance Sheets at June 30, 2019 $ 11,371

Stockholders_ Equity (Tables)

Stockholders’ Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Schedule of Stock-based Compensation Expense	Stock-based compensation and warrant expense is classified in the Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) as follows (in thousands): Three Months Ended Six Months Ended 2019 2018 2019 2018 (unaudited) Employee: Research and development $ 422 $ 205 $ 762 $ 402 General and administrative 248 247 631 555 Non-Employee: Research and development 11 7 40 8 General and administrative 1 64 3 69 Total stock-based compensation expense $ 682 $ 523 $ 1,436 $ 1,034

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Significant Accounting Policies
Loss on sale of intangible asset			$ 0	$ 1,203,000	$ 0	$ 1,203,000
Proceeds from sale of intangible asset					0	$ 250,000
Right-of-use asset	$ 11,303,000		11,303,000		11,303,000			$ 0
Operating lease liabilities	11,371,000		11,371,000		$ 11,371,000
Maximum
Significant Accounting Policies
Available for sale securities, contractual maturity period (less than)					1 year
Accounting Standards Update 2016-02
Significant Accounting Policies
Right-of-use asset							$ 797,000
Operating lease liabilities							883,000
Deferred rent	0		$ 0		$ 0		$ 86,000
Laurel Venture Capital Ltd | GSNOR
Significant Accounting Policies
Loss on sale of intangible asset		$ 1,200,000
Milestone payment	$ 425,000
Proceeds from sale of intangible asset		$ 250,000

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Details) - shares	1 Months Ended	3 Months Ended
	Jan. 31, 2019	Mar. 31, 2019
Earnings Per Share [Line Items]
Stock issued during period (in shares)	4,706,700
Common Stock
Earnings Per Share [Line Items]
Stock issued during period (in shares)	4,706,700	4,706,700

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Anti-dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,126,305	2,014,916
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)	1,859,733	24,123
Options 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)	3,266,572	1,990,793

Cash Equivalents and Short-Te_3

Cash Equivalents and Short-Term Investments - Summary of Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 51,902	$ 51,702
Gross unrealized gains	19	0
Gross unrealized losses	0	(13)
Fair market value	51,921	51,689
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,481	6,405
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair market value	8,481	6,405
U.S. treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,509	13,966
Gross unrealized gains	6	0
Gross unrealized losses	0	(2)
Fair market value	11,515	13,964
Corporate debt securities and commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	31,912	31,331
Gross unrealized gains	13	0
Gross unrealized losses	0	(11)
Fair market value	$ 31,925	$ 31,320

Cash Equivalents and Short-Te_4

Cash Equivalents and Short-Term Investments - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Realized gains (losses) on securities	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Cash	$ 3,600	$ 614

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 51,921	$ 51,689
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	19,996	20,369
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	31,925	31,320
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	8,481	6,405
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	8,481	6,405
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	11,515	13,964
U.S. treasury bills | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value assets disclosure	11,515	13,964
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	31,925	31,320
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	31,925	31,320
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

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Research and development services	$ 3,386	$ 2,457
Employee compensation	1,026	1,009
Legal and professional fees	113	646
Accrued other	993	251
Total	$ 5,518	$ 4,363

Long-term Debt (Details)

Long-term Debt (Details) $ / shares in Units, $ in Thousands	Jun. 30, 2017USD ($)installment$ / sharesshares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jan. 31, 2019$ / sharesshares	Jul. 24, 2017shares
Debt Instrument [Line Items]
Warrants exercisable for shares of common stock (in shares) | shares						1,835,610
Warrants issued, exercise price (in dollars per share) | $ / shares						$ 12.74
Amortization of debt discount		$ 31	$ 44	$ 67	$ 88
Unamortized debt discount		$ 105		$ 105
Series A-1 Preferred Stock Warrants
Debt Instrument [Line Items]
Warrants exercisable for shares of common stock (in shares) | shares	7,069
Warrants issued, exercise price (in dollars per share) | $ / shares	$ 12.38
Fair value of warrant liability	$ 53
Common Stock Warrant | Common Stock
Debt Instrument [Line Items]
Warrants exercisable for shares of common stock (in shares) | shares							7,069
Term Loan
Debt Instrument [Line Items]
Proceeds from long term debt	$ 5,000
Number of equal monthly payment | installment	30
Long-term debt final payment fee percentage	7.50%
Long-term debt final payment fee	$ 375
Term Loan | Prime Rate
Debt Instrument [Line Items]
Debt instrument variable interest rate	1.75%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	1 Months Ended	3 Months Ended	6 Months Ended
	Mar. 31, 2019USD ($)ft²term	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)option	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)	May 31, 2017USD ($)
Loss Contingencies [Line Items]
Renewal option | option			2
Renewal term			12 months
Security deposit						$ 132,000
Right-of-use asset			$ 11,303,000		$ 0
Operating lease liabilities			$ 11,371,000
Rent expense		$ 206,000		$ 398,000
ARE
Loss Contingencies [Line Items]
Renewal term	5 years
Security deposit	$ 254,000
Area of office and laboratory space under lease (in sqft) | ft²	27,164
Term of contract	10 years 9 months 18 days
Number of renewal options | term	1
Rent expense due in first year	$ 1,700,000
Percentage increase in lease each year	3.00%
Tenant allowance to be received	$ 5,400,000
Additional tenant allowance to be received	$ 1,800,000
Additional maximum tenant improvement Allowance amortization rate	8.00%

Commitments and Contingencies_2

Commitments and Contingencies - Components of Lease Cost (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Lease cost
Operating lease cost	$ 365	$ 572
Variable lease cost	80	171
Total lease cost	$ 445	743
Other information:
Cash paid for amounts included in the measurement of lease liabilities		452
Right-of-use assets exchanged for new operating lease liabilities		$ 11,757
Weighted-average remaining lease term (in years), operating leases	10 years 3 months 18 days	10 years 3 months 18 days
Weighted-average discount rate, operating leases	10.50%	10.50%

Commitments and Contingencies_3

Commitments and Contingencies - Operating Lease Maturities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019 (remaining six months)	$ 460
2020	228
2021	1,976
2022	2,027
2023	2,079
Thereafter	14,078
Total	20,848
Less: imputed interest	(9,477)
Operating lease liabilities included in the Consolidated Balance Sheets at June 30, 2019	$ 11,371

License and Collaboration Agr_2

License and Collaboration Agreements (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Oct. 31, 2015
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	$ 567,000	$ 390,000	$ 567,000	$ 705,000
Product | Adaptimmune
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	142,000
Product | Adaptimmune | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential future milestones receivable (up to)	288,000,000		288,000,000
Product | Adaptimmune | Upfront License Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments	2,000,000		2,000,000
Product | Adaptimmune | Research Support Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments	250,000		250,000
Product | Kite
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments					$ 5,500,000
Revenue	$ 0	$ 390,000	$ 0	$ 630,000

Stockholders_ Equity - Narrati

Stockholders’ Equity - Narrative (Details)	1 Months Ended		6 Months Ended
	Jan. 31, 2019USD ($)common_stock$ / sharesshares	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Proceeds from issuance of private placement	$ 25,300,000
Purchase agreement aggregate purchase price (in dollars per share) | $ / shares	$ 5.37
Number of shares of common stock (in shares) | common_stock	1
Purchase agreement ratio of common stock to warrants (in shares)	0.39
Stock issued during period (in shares) | shares	4,706,700
Warrants exercisable for shares of common stock (in shares) | shares	1,835,610
Warrants issued, exercise price (in dollars per share) | $ / shares	$ 12.74
Warrants and rights outstanding, term	5 years
Amount reclassified to additional paid-in capital as a reduction of proceeds			$ 1,700,000
Piper Jaffray & Co.
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum amount of common stock eligible to be sold (up to)		$ 50,000,000
Percentage of compensation for services (up to)		3.00%

Stockholders_ Equity - Stock-Ba

Stockholders’ Equity - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Total stock-based compensation expense	$ 682	$ 523	$ 1,436	$ 1,034
Employee: | Research and development
Class of Stock [Line Items]
Total stock-based compensation expense	422	205	762	402
Employee: | General and administrative
Class of Stock [Line Items]
Total stock-based compensation expense	248	247	631	555
Non-Employee: | Research and development
Class of Stock [Line Items]
Total stock-based compensation expense	11	7	40	8
Non-Employee: | General and administrative
Class of Stock [Line Items]
Total stock-based compensation expense	$ 1	$ 64	$ 3	$ 69

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate	0.00%	0.98%
U.S. federal statutory rate	21.00%	21.00%
Deferred tax liability recorded as in-process research and development		$ 305

Uncategorized Items - a10q2019q

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (202,000)