Alpine Immune Sciences (ALPN) 10-Q 14 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 08, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	ALPN
Entity Registrant Name	Alpine Immune Sciences, Inc.
Entity Central Index Key	1,626,199
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		13,881,645

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 11,982,000	$ 11,819,000
Short-term investments	75,219,000
Prepaid expenses and other current assets	884,000	36,000
Total current assets	88,085,000	11,855,000
Restricted cash	132,000
Property and equipment, net	1,116,000	740,000
Intangible assets	1,453,000
Total assets	90,786,000	12,595,000
Current liabilities:
Accounts payable	1,076,000	127,000
Accrued liabilities	642,000	170,000
Income taxes payable	67,000	66,000
Deferred revenue	405,000	2,008,000
Deferred rent, current portion	44,000	33,000
Current portion of long-term debt	490,000
Total current liabilities	2,724,000	2,404,000
Deferred rent, long-term portion	81,000	113,000
Deferred tax liability	509,000
Long-term debt	4,500,000
Total liabilities	7,814,000	2,517,000
Commitments and contingencies
Convertible preferred stock, $0.0001 par value per share; 10,000,000 and 22,081,852 shares authorized at September 30, 2017 and December 31, 2016, respectively; zero and 4,311,770 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively; aggregate liquidation preference of zero and $11,583 at September 30, 2017 and December 31, 2016, respectively		11,535,000
Stockholders’ deficit:
Common stock, $0.0001 par value per share; 200,000,000 and 46,500,000 shares authorized at September 30, 2017 and December 31, 2016, respectively; 13,881,645 and 608,701 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	1,000
Additional paid-in capital	88,049,000	144,000
Accumulated other comprehensive loss	(12,000)
Accumulated deficit	(5,066,000)	(1,601,000)
Total stockholders’ equity (deficit)	82,972,000	(1,457,000)
Total liabilities, convertible preferred stock, and stockholders’ equity	$ 90,786,000	$ 12,595,000

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	10,000,000	22,081,852
Convertible preferred stock, shares issued	0	4,311,770
Convertible preferred stock, shares outstanding	0	4,311,770
Convertible preferred stock, liquidation preference	$ 0	$ 11,583
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	46,500,000
Common stock, shares issued	13,881,645	608,701
Common stock, shares outstanding	13,881,645	608,701

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Collaboration revenue	$ 128	$ 737	$ 1,603	$ 2,212
Operating expenses:
Research and development	2,750	819	6,916	1,639
General and administrative	1,932	299	4,872	774
Total operating expenses	4,682	1,118	11,788	2,413
Loss from operations	(4,554)	(381)	(10,185)	(201)
Other income (expense):
Bargain purchase gain	6,539		6,539
Interest expense	(75)		(76)
Interest and other income	216	7	261	16
Income (loss) before taxes	2,126	(374)	(3,461)	(185)
Income tax expense	(4)		(4)
Basic and diluted net income (loss) attributable to common stockholders	2,122	(374)	(3,465)	(185)
Comprehensive income (loss):
Unrealized loss on investments	(12)		(12)
Comprehensive income (loss)	$ 2,110	$ (374)	$ (3,477)	$ (185)
Weighted-average shares used to compute basic net income (loss) per share attributable to common stockholders	10,577,772	608,701	3,989,747	550,080
Basic net income (loss) per share attributable to common stockholders	$ 0.20	$ (0.61)	$ (0.87)	$ (0.34)
Weighted-average shares used to compute diluted net income (loss) per share attributable to common stockholders	11,586,795	608,701	3,989,747	550,080
Diluted net income (loss) per share attributable to common stockholders	$ 0.18	$ (0.61)	$ (0.87)	$ (0.34)

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Convertible Preferred Stock and Stockholders' Equity - 9 months ended Sep. 30, 2017 - USD ($)	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Balance, convertible preferred stock at Dec. 31, 2016	$ 11,535,000	$ 11,535,000
Balance, convertible preferred stock, shares at Dec. 31, 2016	4,311,770	4,311,770
Issuance of Series A-1 convertible preferred stock		$ 37,666,000
Issuance of Series A-1 convertible preferred stock		4,989,663
Conversion of convertible preferred stock to common stock		$ (49,201,000)	$ 1,000	$ 49,200,000
Conversion of convertible preferred stock to common stock, shares		(9,301,433)	9,301,433
Balance, convertible preferred stock, shares at Sep. 30, 2017	0
Balance at Dec. 31, 2016	$ 10,078,000			144,000		$ (1,601,000)
Balance, shares at Dec. 31, 2016			608,701
Issuance of Series A-1 convertible preferred stock	37,666,000
Common stock acquired in business combination	38,103,000			38,103,000
Common stock acquired in business combination, shares			3,914,058
Conversion of warrant liability to equity	52,000			52,000
Exercise of stock options and common stock warrants	22,000			22,000
Exercise of stock options and common stock warrants, shares			57,453
Stock-based compensation	528,000			528,000
Unrealized loss on investments	(12,000)				$ (12,000)
Net loss	(3,465,000)					(3,465,000)
Balance at Sep. 30, 2017	$ 82,972,000		$ 1,000	$ 88,049,000	$ (12,000)	$ (5,066,000)
Balance, shares at Sep. 30, 2017			13,881,645

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (3,465)	$ (185)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Bargain purchase gain	(6,539)
Depreciation and amortization	165	30
Non-cash interest expense	43
Stock-based compensation and warrant expense	528	57
Changes in operating assets and liabilities:
Prepaid expenses	(848)	(4)
Accounts payable	924	253
Deferred revenue	(1,603)	(2,212)
Accrued liabilities	82	10
Deferred rent and other	(22)	21
Net cash used in operating activities	(10,735)	(2,030)
Investing activities
Purchases of property and equipment	(509)	(459)
Purchase of short-term investments	(72,239)
Proceeds from the sale of short-term investments	9,960
Cash and cash equivalents acquired in connection with merger	31,130
Net cash used in investing activities	(31,658)	(459)
Financing activities
Proceeds from sale of preferred stock	37,666	10,973
Proceeds from borrowings	5,000
Proceeds from exercise of stock options and common stock warrants	22	49
Net cash provided by financing activities	42,688	11,022
Net increase in cash and cash equivalents and restricted cash	295	8,533
Cash and cash equivalents and restricted cash, beginning of period	11,819	5,423
Cash and cash equivalents and restricted cash, end of period	12,114	$ 13,956
Supplemental Information
Discount in connection with issuance of debt	428
Convertible preferred stock exchanged for common stock	49,201
Reclass of preferred stock warrant liability to equity	$ 52

Description of the Business

Description of the Business	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of the Business	1. Description of the Business Alpine Immune Sciences, Inc. (the “Company”, “Alpine”, “we”, “us”, or “our”) is focused on discovering and developing modern, protein-based immunotherapies targeting the immune synapse to treat cancer, inflammation, and other diseases. Our proprietary scientific platform uses a process known as directed evolution, or an iterative scientific engineering process purposefully conducted to “evolve” a protein to create therapeutics potentially capable of modulating immune system interactions. In our pre-clinical animal studies, our platform has proven capable of identifying novel molecules, including single domains capable of modulating multiple targets. We were incorporated on December 30, 2014 under the laws of the State of Delaware and are headquartered in Seattle, Washington. Significant estimates inherent in the preparation of the accompanying financial statements include recoverability and useful lives of intangible assets and the fair value of equity based awards. Reverse Merger and Subscription Agreement On April 18, 2017, we entered into a merger agreement with Nivalis Therapeutics, Inc. (“Nivalis”), a public biotechnology company, and one of its wholly-owned subsidiaries pursuant to which, the subsidiary merged with and into Alpine, with Alpine continuing as a wholly owned subsidiary of Nivalis and the surviving corporation of the merger (the “Merger Agreement”). The merger is intended to qualify for federal income tax purposes as a tax-free reorganization under the provisions of Section 368(a) of the Internal Revenue Code of 1986, as amended. At the closing of the merger, each outstanding share of our capital stock (common stock and preferred stock) was converted into the right to receive shares of Nivalis common stock (subject to the payment of cash in lieu of fractional shares and after giving effect to a 1:4 reverse stock split of Nivalis common stock) such that, immediately following the effective time of the merger, preexisting Nivalis stockholders, optionholders, and warrantholders owned, or held rights to acquire, approximately 26% of the fully-diluted common stock of Nivalis, which changed its name to “Alpine Immune Sciences, Inc.” following the completion of the merger and Alpine’s preexisting stockholders, optionholders, and warrantholders owned, or held rights to acquire approximately 74% of the fully-diluted common stock of Nivalis. The issuance of the shares to our pre-existing stockholders was registered under the Securities Act of 1933, as amended, pursuant to a registration statement on Form S-4 (No. 333-218134) (the “Registration Statement”) declared effective by the Securities and Exchange Commission (the “SEC”) on June 6, 2017. Contemporaneously with the execution and delivery of the Merger Agreement, certain of our pre-existing stockholders entered into a subscription agreement with us pursuant to which such stockholders purchased, immediately prior to the closing of the merger, 1,335,118 shares of our capital stock at a purchase price of $12.74 per share for an aggregate purchase price of approximately $17.0 million. The merger and the subscription described above were consummated on July 24, 2017. Exchange Ratio At the effective time of the merger, each share of Alpine’s common stock and preferred stock was converted into the right to receive 0.4969 shares of Nivalis’ common stock, adjusted to account for the Nivalis reverse stock split. All issued and outstanding stock and per share amounts contained in the financial statements have been retroactively adjusted to reflect this exchange ratio for all periods presented.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying unaudited condensed financial statements have been prepared in accordance with the rules and regulations of the 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 financial statements and accompanying notes. 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 results of our operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the full year. Principles of Consolidation Our condensed consolidated financial statements include the financial position and results of operations of Alpine and AIS Operating Co., Inc., our wholly owned subsidiary and operating company. On July 24, 2017, we closed the merger on the terms described in more detail in Note 1. In connection with the merger, Nivalis effected a 1:4 reverse stock split of its common stock. Upon the closing of the merger, (1) a wholly-owned subsidiary of Nivalis merged with and into Alpine, with Alpine (renamed as “AIS Operating Co., Inc.”) remaining as the surviving entity; and (2) Nivalis was renamed as “Alpine Immune Sciences, Inc.” Unaudited Interim Financial Information The accompanying unaudited condensed consolidated financial statements as of September 30, 2017, and for the three and nine months ended September 30, 2017 and 2016 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 financial statements should be read in conjunction with our audited financial statements and accompanying notes for the years ended December 31, 2016 and 2015, as filed with the SEC in our Registration Statement. Unless indicated otherwise, all amounts presented in financial tables are presented in thousands, except for share, per share and par value amounts. 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. Business Combination We use our best estimates and assumptions to accurately assign fair value to the tangible and intangible assets acquired and liabilities assumed at the acquisition date. Our estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, we may record adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed, with the corresponding offset to bargain purchase gain. In addition, uncertain tax positions and tax-related valuation allowances are initially established in connection with a business combination as of the acquisition date. Our management collects information and reevaluates these estimates and assumptions quarterly and records any adjustments to our preliminary estimates to bargain purchase gain during the measurement period. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to our condensed consolidated statements of operations and comprehensive income (loss). We allocated the preliminary purchase price to the acquired tangible and intangible assets and assumed liabilities of Nivalis based on their estimated fair values as of the acquisition date. The fair value of our identifiable intangible asset is based on detailed valuations using information and assumptions provided by management. Intangible Asset Our intangible asset is our indefinite-life GSNOR inhibitor in-process research and development asset (“IPR&D”) acquired from Nivalis. The IPR&D represents the processes, expertise, and technology employed in the development of S-nitrosoglutathione reductase (“GSNOR”) inhibitors and Nivalis’ lead product candidate, cavosonstat. The IPR&D represents the estimated fair value as of the acquisition date of substantive in-process projects that have not reached technological feasibility. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval. The valuation of IPR&D is determined using a discounted cash flow method. In determining the value of IPR&D, management considers, among other factors, the stage of completion of the projects, the technological feasibility of the projects, whether the projects have an alternative future use, and the estimated residual cash flows that could be generated from the various projects and technologies over their respective projected economic lives. The discount rate used is determined at the time of acquisition and includes a rate of return which accounts for the time value of money, as well as risk factors reflecting the economic risk that the projected cash flows may not be realized We review our IPR&D at least annually for possible impairment. IPR&D is reviewed for possible impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of the IPR&D below their carrying values. We test our IPR&D each year on October 1. Our IPR&D asset totaled $1.5 million at September 30, 2017. Derivative Financial Instruments We evaluate all of our financial instruments, including issued stock purchase warrants, to determine if such instruments are derivatives or contain features qualifying as embedded derivatives. For derivative financial instruments accounted for as liabilities, the derivative instrument is initially recorded at its fair value and is then re-valued at each reporting date, with changes in the fair value reported in the condensed consolidated statement of operations and comprehensive income (loss). We use the Black-Scholes option-pricing model to value the derivative instruments at inception and subsequent valuation dates. The classification of derivative instruments, including whether such instruments should be recorded as liabilities or as equity, is re-assessed at the end of each reporting period. We do not use derivative instruments to hedge exposures to cash flow, market, or foreign currency risks. Revenue Recognition We derive our revenue from collaboration and licensing agreements. We recognize revenue when each of the following four criteria are met: (1) persuasive evidence of an arrangement exists; (2) products have been delivered or services have been rendered; (3) the sales price is fixed or determinable; and (4) collectability is reasonably assured. We recognize revenue under our License and Research Agreement (the “Collaboration Agreement”) with Kite Pharma, Inc. (“Kite”) in accordance with the guidance on multiple element arrangements. Multiple elements or deliverables 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. The evaluation of multiple-element arrangements requires management to make judgments about (1) the identification of deliverables; (2) whether such deliverables are separable from other aspects of the contractual relationship; (3) the estimated selling price of each deliverable; and (4) the expected period of performance for each deliverable. To determine the units of accounting under a multiple-element arrangement, management evaluates certain separation criteria, including whether the deliverables have stand-alone value, based on the relevant facts and circumstances for each arrangement. Management then estimates the selling price for each unit of accounting and allocates the arrangement consideration to each unit using the relative selling price method. The allocated consideration for each unit of accounting is recognized based on the method most appropriate for that unit of account and in accordance with the revenue recognition criteria detailed above. If there are deliverables in an arrangement that are not separable from other aspects of the contractual relationship, they are treated as a combined unit of accounting, with the allocated revenue for the combined unit recognized in a manner consistent with the revenue recognition criteria applicable to the final deliverable in the combined unit. 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. The Collaboration Agreement provides 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 will periodically review the estimated performance periods under the Collaboration Agreement which provides for non-refundable upfront payments and fees. We will adjust the periods over which revenue should be recognized when appropriate to reflect changes in assumptions relating to the estimated performance periods. 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. Comprehensive Income (Loss) Comprehensive income (loss) is comprised of net income (loss) and certain changes in equity excluded from net income (loss). For the three and nine months ended September 30, 2017, other comprehensive loss consists of unrealized losses on our short-term investments. There was no difference between comprehensive income (loss) and net income (loss) for the three and nine months ended September 30, 2016. Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, as amended, which amends the guidance for revenue recognition to replace numerous industry specific requirements. ASU 2014-09, as amended, implements a five-step process for customer contract revenue recognition focusing on transfer of control, as opposed to transfer of risk and rewards. ASU 2014-09, as amended, also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. ASU 2014-09, as amended, is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted, but not before December 15, 2016. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. We are currently expecting to use the modified retrospective method to adopt this standard and are continuing to assess all of the potential impacts of the new standard on our financial statements and related disclosures, although we do not expect the implementation to have a material impact. 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. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and is to be applied at the beginning of the earliest period presented using a modified retrospective approach. We are continuing to evaluate the effect the standard will have on our financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15 which provides new guidance on the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We will be required to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. We are currently assessing the impact the new guidance will have on our condensed consolidated statements of cash flows. In January 2017, the FASB issued an ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business. The amendments in this update clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. We are currently evaluating the impact of adopting this guidance. In May 2017, the FASB issued ASU No. 2017-09 to provide clarity and reduce both diversity in practice and cost and complexity when applying the guidance in Compensation - Stock Compensation ( Recently Adopted Accounting Pronouncements In August 2014, the FASB issued ASU No.2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Under the new guidance, management is required to assess an entity’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. The provisions of this standard are effective for annual periods ending after December 31, 2016, and for annual and interim periods thereafter. We adopted this guidance this year and management believes our existing cash and cash equivalents as of September 30, 2017 are sufficient to fund our operations and do not raise substantial doubt about our ability to continue as a going concern. In March 2016, the FASB issued ASU No. 2016-09-Improvements to Employee Share-Based Payment Accounting, wh ich simplified the accounting for share-based payment transactions, including the income tax consequences, the calculation of diluted earnings per share, the treatment of forfeitures, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. For public business entities, the amendments in this update are effective for annual periods beginning after December 15, 2016 and interim periods within those annual periods. Early adoption is permitted for any entity in any interim or annual period. We adopted ASU 2016-09 with effect from January 1, 2015. The adoption of this standard did not have a material impact on our financial statements. In November 2016, the FASB issued ASU No. 2016-18 relating to restricted cash. The new guidance requires amounts generally described as restricted cash and restricted cash equivalents to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the condensed consolidated statement of cash flows. This guidance is required to be adopted beginning with the first fiscal quarter of 2018; early adoption is permitted. We adopted this guidance effective June 30, 2017, which required us to include restricted cash within the beginning and ending balance of cash and cash equivalents for the nine-month period ended September 30, 2017. We had no restricted cash prior to adopting this guidance, thus we were not required to revise prior period statements of cash flows. The adoption of this guidance does not impact our financial position or results of operations.

Business Combination

Business Combination	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Business Combination	3. Business Combination On July 24, 2017, we closed the merger on the terms described in more detail in Note 1. In connection with the merger, Nivalis effected a 1:4 reverse stock split of its common stock. Upon the closing of the merger, (1) a wholly-owned subsidiary of Nivalis merged with and into Alpine, with Alpine (renamed as “AIS Operating Co., Inc.”) remaining as the surviving entity; and (2) Nivalis was renamed as “Alpine Immune Sciences, Inc.” Under the terms of the Merger Agreement, Nivalis issued shares of its common stock to Alpine’s stockholders, at an exchange rate of 0.4969 shares of Nivalis common stock, after taking into account the 1:4 reverse stock split, for each share of Alpine’s common stock and preferred stock outstanding immediately prior to the merger. The exchange rate was determined through arms’-length negotiations between Nivalis and Alpine. Nivalis also assumed all of the stock options outstanding under Alpine’s Amended and Restated 2015 Stock Plan, as amended (the “Alpine Plan”), and stock warrants for Alpine’s capital stock outstanding immediately prior to the merger, with such stock options and warrants henceforth representing the right to purchase a number of shares of the Nivalis common stock equal to 0.4969 multiplied by the number of shares of Alpine’s common stock or preferred stock previously represented by such options and warrants. Nivalis also assumed the Alpine Plan. Immediately after the merger, there were 13,881,645 shares of Nivalis common stock outstanding. Immediately after the merger, Alpine’s former stockholders, warrantholders, and optionholders owned, or held rights to acquire, approximately 74% of the fully-diluted common stock of Nivalis, which for these purposes is defined as the outstanding common stock of Nivalis, plus “in the money” options and warrants to purchase shares of Nivalis’ common stock, assuming all “in the money” options and warrants of Nivalis outstanding immediately prior to the merger are exercised on a cashless basis immediately prior to the closing of the merger, with Nivalis’ stockholders, optionholders, and warrantholders immediately prior to the merger owning, or holding rights to acquire, approximately 26% of the fully diluted common stock of Nivalis. More than 74% of Nivalis’ common stock outstanding immediately after the merger was held by stockholders party to lock-up agreements, pursuant to which such stockholders have agreed, except in limited circumstances, not to sell, transfer, or engage in swap or similar transactions with respect to shares of Nivalis’ common stock, including, as applicable, shares received in the merger and issuable upon exercise of certain warrants and options, for a period of 180 days following the completion of the merger. The issuance of shares of Nivalis’ common stock to our pre-existing stockholders was registered with the SEC pursuant to the Registration Statement. Immediately prior to the merger, we issued and sold an aggregate of approximately $17.0 million of shares of our common stock to certain existing stockholders. For accounting purposes, our historical financial statements were not adjusted to reflect the merger, other than adjustments to the capital structure to reflect the historical capital structure of Nivalis. No other adjustments to our historical assets and liabilities were made as a result of the merger. In addition to the operating assets and liabilities of Nivalis, we also acquired Nivalis’ tax attributes, which primarily consisted of net operating losses which begin to expire in 2032. Our ability to utilization the tax attributes of Nivalis may be limited under Section 382 of the U.S. Internal Revenue Service and as such, have been reserved. We recorded a deferred tax liability related to future tax benefits arising from IPR&D acquired in the Merger. The combined organization is focusing on the development and commercialization of our innovative immunotherapies. Following the merger, the increased cash resources and increased access to capital of the combined organization will help to support the clinical development of our products. Consideration Transferred The fair value of the consideration transferred was based on the most reliable measure, which was determined to be the market price of Nivalis shares of common stock as of the acquisition date. The fair value of the consideration transferred consisted of the following (in thousands except share and per share amounts): Outstanding Nivalis common stock 3,914,058 Per share fair value of Nivalis common stock $ 9.60 Outstanding Nivalis stock options 421,992 Weighted average per share fair value of Nivalis stock options $ 1.25 Total fair value of consideration (in 000's) $ 38,103 Pursuant to the Merger Agreement, unvested Nivalis stock options immediately vested as of the closing of the business combination and were adjusted to give effect to the recapitalization. Preliminary Purchase Price Allocation As Alpine was the accounting acquirer in the merger, we allocated the preliminary purchase price to the acquired tangible and intangible assets and assumed liabilities of Nivalis based on their estimated fair values as of the acquisition date. The excess of the estimated fair values of net assets acquired over the acquisition consideration paid was recorded as a bargain purchase gain in the condensed consolidated statements of operations and comprehensive income (loss). The determination of the preliminary fair values of the assets acquired and liabilities assumed requires significant judgment, including third party valuation estimates relating to the value of the acquired IPR&D. The allocation of the purchase consideration to the assets acquired and liabilities assumed in our financial statements is preliminary and subject to change as management gathers additional information regarding these items. The initial allocation of the purchase consideration is as follows (in thousands): Preliminary Fair Value Assets: Cash and cash equivalents $ 31,130 Marketable securities 12,952 IPR&D 1,453 Total assets acquired 45,535 Liabilities: Accrued expenses (384 ) Deferred tax liability (509 ) Total liabilities assumed (893 ) Bargain purchase gain (6,539 ) Total $ 38,103 We relied on significant Level 3 unobservable inputs to estimate the fair value of our acquired IPR&D using management’s estimate of future royalties and expected earnings of the assets after taking into account an estimate of future expenses necessary to bring the products to completion. These projected cash flows were then discounted to their present values using a discount rate of 17%, which was considered commensurate with the risks and stages of development of the IPR&D. The bargain purchase gain resulted from expenses incurred by Nivalis between the time the purchase price was negotiated and the close of the transaction, and changes in the Nivalis stock price during that period as the exchange ratio was fixed when the purchase price was negotiated. We recognized acquisition-related costs of $1.3 million for the nine months ended September 30, 2017. These costs are included within general and administrative expense in our condensed consolidated statements operations and of comprehensive income (loss). Pro Forma Financial Information The following pro forma consolidated results of net loss for the nine months ended September 30, 2017 and 2016 assume the business combination was completed as of January 1, 2016 (in thousands, except per share amounts): Nine Months Ended September 30, 2017 2016 Pro forma revenues $ 1,603 $ 2,212 Pro forma net loss (13,634 ) (23,935 ) Pro forma basic and diluted net loss per share $ (0.98 ) $ (1.74 ) For purposes of the pro forma disclosures above, the primary adjustments for the nine months ended September 30, 2017 include the elimination of acquisition related costs and acceleration of stock compensation expense upon the change in control.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	4. Net Income (Loss) Per Share We compute net income (loss) per share attributable to common stockholders using the two-class method required for participating securities. We consider our convertible preferred stock to be participating securities. In accordance with the two-class method, earnings allocated to these participating securities, which include participation rights in undistributed earnings, are subtracted from net income to determine total undistributed earnings to be allocated to common stockholders. Net loss is not allocated to participating securities as there is no contractual obligation to share in net losses. Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding during the period. All participating securities are excluded from basic weighted-average common shares outstanding. In computing both basic net income (loss) per share attributable to common stockholders and diluted net income (loss) per share attributable to common stockholders, undistributed earnings are re-allocated to reflect the potential impact of dilutive securities, including stock options and warrants. Diluted net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted-average number of common equivalent shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders includes any dilutive effect from outstanding stock options and warrants using the treasury stock method. The common stock issuable upon the conversion or exercise of the following dilutive securities has been excluded from the diluted net loss per share attributable to common stockholders calculation because their effect would have been antidilutive for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Convertible preferred stock - 4,311,770 - 4,311,770 Warrants to purchase common stock 7,069 12,422 19,491 12,422 Options to purchase common stock 280,992 520,739 1,791,066 520,739 Total 288,061 4,844,931 1,810,557 4,844,931 The following is a reconciliation of the numerator (net income or loss) and the denominator (number of shares) used in the calculation of basic and diluted net income (loss) per share attributable to common stockholders (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Numerator Basic and diluted net income (loss) attributable to common stockholders $ 2,122 $ (374 ) $ (3,465 ) $ (185 ) Denominator Shares used in computing basic net income (loss) per share attributable to common stockholders 10,577,772 608,701 3,989,747 550,080 Effect of dilutive securities: Options to purchase common stock 1,002,472 — — — Warrants to purchase common stock 6,551 — — — Shares used in computing diluted net income (loss) per share attributable to common stockholders 11,586,795 608,701 3,989,747 550,080 Basic net income (loss) per share attributable to common stockholders $ 0.20 $ (0.61 ) $ (0.87 ) $ (0.34 ) Diluted net income (loss) per share attributable to common stockholders $ 0.18 $ (0.61 ) $ (0.87 ) $ (0.34 )

Cash Equivalents and Short-Term

Cash Equivalents and Short-Term Investments	9 Months Ended
	Sep. 30, 2017
Cash Cash Equivalents And Short Term Investments [Abstract]
Cash Equivalents and Short-term Investments	5. 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): September 30, 2017 Assets: (unaudited) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 4,736 $ — $ — $ 4,736 U.S. treasury bills 17,155 2 — 17,157 Corporate debt securities and commercial paper 63,323 — (14 ) 63,309 Total $ 85,214 $ 2 $ (14 ) $ 85,202 All short-term investments held as of September 30, 2017 were classified as available-for-sale securities and had contractual maturities of less than one year. There were no realized gains and losses on these securities for the periods presented. There were no short-term investments as of December 31, 2016.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	6. Fair Value Measurements 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 : 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. At December 31, 2016, we had cash of $11.8 million and no assets measured using Level 1, Level 2, or Level 3 inputs. As of September 30, 2017, cash of $2.0 million is excluded from the fair value table below. The following table summarizes our financial assets and liabilities measured at fair value on a recurring basis (in thousands): September 30, 2017 Assets: (unaudited) Level 1 Level 2 Level 3 Total Money market funds $ 4,736 $ — $ — $ 4,736 U.S. treasury bills 17,157 — — 17,157 Corporate debt securities and commercial paper — 63,309 — 63,309 Total $ 21,893 $ 63,309 $ — $ 85,202 Our Level 2 assets consist of commercial paper and corporate debt securities. W e 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. On June 30, 2017, we issued Series A-1 preferred stock warrants in connection with long-term debt. The warrant liability was classified as a Level 3 liability and the fair value was determined using the Black-Scholes option-pricing model with the following key assumptions: (1) stock price of $9.64; (2) a risk-free rate of 2.31%; (3) an expected volatility of 78%; and (4) a term of 9.5 years. Both observable and unobservable inputs are used to determine the fair value of the warrant liability. As a result, the unrealized gains and losses of the warrant liability may include changes in fair value attributable to both observable inputs (e.g., changes in market interest rates) and unobservable inputs (e.g., probabilities of the occurrence of an early termination event). In July 2017, in connection with the closing of the merger, our preferred stock warrants converted to common stock warrants. As a result of the change in the underlying shares, the warrants were equity-classified beginning on July 24, 2017. As of the date of conversion, we remeasured the fair value of the warrants, which resulted in a $1,000 decrease in fair value, which was recorded as other income in our accompanying condensed consolidated statements of operations and comprehensive income (loss). See Note 11 for additional discussion of the warrants. The following table shows the reconciliation of the Level 3 warrant liability measured and recorded at fair value on a recurring basis, using significant unobservable inputs (in thousands): Estimated Fair Value Balance as of January 1, 2017 $ — Fair value of warrants at issuance (June 30, 2017) 53,000 Change in fair value of warrant liability in connection with merger (1,000 ) Conversion of warrant liability to equity (52,000 ) Balance as of September 30, 2017 $ —

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2017
Payables And Accruals [Abstract]
Accrued Liabilities	7. Accrued Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 (unaudited) Accrued taxes and licenses $ 354 $ 61 Accrued professional fees 50 5 Deferred compensation — 61 Accrued other 238 43 Total $ 642 $ 170

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2017
Debt Instruments [Abstract]
Long-term Debt	8. Long-term Debt On June 30, 2017, we drew down a term loan of $5.0 million from Silicon Valley Bank with whom we had entered into a long-term financing arrangement on December 16, 2016. The loan has an interest-only period that expires on July 1, 2018, at which point we will be 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. 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 September 30, 2017, 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 September 30, 2017. Also, in connection with the drawdown of the loan, we also granted the financial institution 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 on the accompanying condensed consolidated balance sheets. 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. See Note 11 for further details of these warrants. 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 $43,000 for the three and nine months ended September 30, 2017. The unamortized discount was $385,000 as of September 30, 2017.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Operating Lease On April 1, 2017, we entered into an amendment to our existing lease pursuant to which we agreed to lease additional premises adjacent to our existing leased premises for an annual base rent of $38,000. The amendment is effective on April 12, 2017. The amendment does not alter the December 31, 2019 expiry date of the existing lease. As required by the terms of the lease, in May 2017, 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.

License and Collaboration Agree

License and Collaboration Agreement	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License and Collaboration Agreement	10. License and Collaboration Agreement In October 2015, we entered into the Collaboration Agreement with Kite to discover and develop protein-based immunotherapies targeting the immune synapse to treat cancer. Under our agreement, we are to perform certain research services and grant to Kite an exclusive license to two programs from our TIP technology, which Kite is planning to further engineer into chimeric antigen receptor (“CAR”) and T cell receptor (“TCR”) product candidates. Under the terms of the Collaboration Agreement, Kite made upfront payments to us of $5.5 million, which were initially recorded as deferred revenue. We will also be eligible to receive milestone payments based upon the successful achievement of pre-specified research, clinical, and regulatory milestones totaling up to $530.0 million plus royalty payments on product sales, if any. Kite will receive an exclusive, worldwide license to research, develop, and commercialize engineered autologous T cell therapies incorporating two programs coming from our platform. On October 20, 2017, we entered into an amendment with Kite to extend the research term of the Collaboration Agreement. Under the amended agreement, we are eligible to receive an additional $450,000 research support payment from Kite in two tranches (instead of a single tranche as previously contemplated by the original Collaboration Agreement) (the “Amendment”). The Amendment also amended and restated the original research plan. We adjusted our estimated service period over the extended term and have adjusted the revenue recognition accordingly. We recorded revenue of $128,000 and $737,000 for the three months ended September 30, 2017 and 2016, respectively, and $1.6 million and $2.2 million for the nine months ended September 30, 2017 and 2016, respectively.

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2017
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	11. Convertible Preferred Stock In March 2017, we issued and sold 707,330 shares of Series A convertible preferred stock and received a total of $4.0 million. In April 2017, prior to the execution and delivery of the Merger Agreement certain holders of our Series A-1 convertible preferred stock purchased 2,947,211 shares of Series A-1 preferred stock for $16.7 million in proceeds. Contemporaneously with the execution and delivery of the Merger Agreement certain of our pre-existing stockholders entered into a subscription agreement with us pursuant to which such stockholders purchased immediately prior to the closing of the merger 1,335,118 shares of our convertible preferred stock at a purchase price of $12.74 per share for an aggregate purchase price of approximately $17.0 million. The rights, preferences, and privileges of convertible preferred stock are summarized in our audited financial statements and accompanying notes for the years ended December 31, 2016 and 2015, as filed with the SEC in the Registration Statement. Upon the closing of the merger, all outstanding shares of our convertible preferred stock converted into 9,301,433 shares of common stock. As of September 30, 2017, we do not have any convertible preferred stock outstanding. Preferred Stock Warrants In connection with our draw down of a term loan on June 30, 2017, we granted the lender 7,069 of fully vested Series A-1 preferred stock warrants at an exercise price of $12.38 per share and a term of ten years. The fair value of the warrants on the date of issuance was $53,000 and was recorded as a discount to the note and as a warrant liability within the accompanying condensed consolidated balance sheets. The warrants were initially classified as a liability because the underlying to the warrants were puttable shares. On July 24, 2017, 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. As a result of the equity classification, the warrant liability was remeasured as of July 24, 2017 and the change in fair value was recognized within other (income) expense in our condensed consolidated statements of operations and comprehensive income (loss) and the carrying value of the revised warrant liability was reclassified to additional paid-in capital within stockholders’ deficit.

Stockholders' Deficit

Stockholders' Deficit	9 Months Ended
	Sep. 30, 2017
Stockholders Equity Note [Abstract]
Stockholders’ Deficit	12. Stockholders’ Deficit Stock-Based Compensation Expense We use the Black-Scholes option pricing model to estimate the fair value of stock options granted to employees 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. We also record stock options and other stock-based compensation issued to non-employees at their fair value as of their date of grant using the Black-Scholes option pricing model. Non-employee awards are then periodically remeasured to reflect the current fair value at each reporting period and expense is recognized over the related vesting period. Assumptions used in valuing non-employee stock options are generally consistent with those used for employee stock options with the exception that the expected term is over the contractual life. Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Employee: Research and development $ 38 $ 4 $ 93 $ 5 General and administrative 169 5 386 46 Non-Employee: Research and development 16 1 40 3 General and administrative 6 2 9 3 Total stock-based compensation expense $ 229 $ 12 $ 528 $ 57

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes We are subject to income taxes in the United States 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. Our effective tax rate for the three and nine-month periods ended September 30, 2017 was (0.04) %. The difference between the effective tax rate of (0.04) % and the U.S. federal statutory rate of 35% for the three and nine-month periods ended September 30, 2017 was primarily due to recognizing a full valuation allowance on deferred tax assets. As of September 30, 2017, we determined based on 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 deferred tax assets would be realized and therefore we continued to record a full valuation allowance. No current tax liability or expense associated with our deferred tax assets have been recorded in the financial statements. As part of the merger with Nivalis, we identified $1.5 million of acquired IPR&D. IPR&D acquired in a business combination is an indefinite-lived intangible asset until the completion or abandonment of the associated R&D efforts. Once the research and development efforts are completed or abandoned, the IPR&D will either be impaired or amortized over the asset life as a finite-lived intangible. As the acquired IPR&D is not completed, and has not been abandoned, it is considered indefinite-lived for accounting purposes. Any future reversal of a deferred tax liability resulting from IPR&D costs cannot be scheduled for tax purposes and therefore cannot be considered as a source of future taxable income. Thus, we have recorded a deferred tax liability of $509,000 as a result of the acquired IPR&D having a financial reporting basis of $1.5 million and a tax basis of $0. Under Section 382 of the Internal Revenue Code of 1986, substantial changes in Alpine Immune Sciences’ ownership may limit the amount of net operating loss carryforwards that could be utilized annually in the future to offset taxable income. Any such annual limitation may significantly reduce the utilization of the net operating losses before they expire. Our net operating loss carry forward amounts expire starting in 2032. As of December 31, 2016, we had accumulated approximately $75.7 million of federal tax losses and $0 (tax effected) of state tax losses. Due to our operating loss carryforwards, all tax years remain open to examination by the major taxing jurisdictions to which we are subject. In the event we are assessed interest or penalties at some point in the future, it will be classified in the financial statements as tax expense. Under ASC 740, the benefit of an uncertain tax position that is more likely than not of being sustained upon audit by the relevant taxing authority must be recognized at the largest amount that is more likely than not to be sustained. No portion of the benefit of an uncertain tax position may be recognized if the position has less than a 50% likelihood of being sustained. We do have an uncertain tax position on our research and development credits as of the three and nine-month periods ended September 30, 2017. However, no deferred asset is recorded for the credits due to the full valuation allowance.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	14. Related Party Transactions We have a shared services agreement with Alpine BioVentures GP, LLC, pursuant to which we incurred no costs for the three and nine months ended September 30, 2017 and $3,000 and $12,000 for the three and nine months ended September 30, 2016, respectively. We had an accrual of $5,000 related to the shared services agreement at December 31, 2016, which was paid in April 2017.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	15. Subsequent Events On October 20, 2017, we entered into the Amendment of the Collaboration Agreement with Kite. Pursuant to the terms of the Amendment, the research term of the Collaboration Agreement was extended, providing us additional time to deliver th e

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying unaudited condensed financial statements have been prepared in accordance with the rules and regulations of the 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 financial statements and accompanying notes. 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 results of our operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results to be expected for the full year.
Principles of Consolidation	Principles of Consolidation Our condensed consolidated financial statements include the financial position and results of operations of Alpine and AIS Operating Co., Inc., our wholly owned subsidiary and operating company. On July 24, 2017, we closed the merger on the terms described in more detail in Note 1. In connection with the merger, Nivalis effected a 1:4 reverse stock split of its common stock. Upon the closing of the merger, (1) a wholly-owned subsidiary of Nivalis merged with and into Alpine, with Alpine (renamed as “AIS Operating Co., Inc.”) remaining as the surviving entity; and (2) Nivalis was renamed as “Alpine Immune Sciences, Inc.”
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying unaudited condensed consolidated financial statements as of September 30, 2017, and for the three and nine months ended September 30, 2017 and 2016 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 financial statements should be read in conjunction with our audited financial statements and accompanying notes for the years ended December 31, 2016 and 2015, as filed with the SEC in our Registration Statement. Unless indicated otherwise, all amounts presented in financial tables are presented in thousands, except for share, per share and par value amounts.
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.
Business Combination	Business Combination We use our best estimates and assumptions to accurately assign fair value to the tangible and intangible assets acquired and liabilities assumed at the acquisition date. Our estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, we may record adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed, with the corresponding offset to bargain purchase gain. In addition, uncertain tax positions and tax-related valuation allowances are initially established in connection with a business combination as of the acquisition date. Our management collects information and reevaluates these estimates and assumptions quarterly and records any adjustments to our preliminary estimates to bargain purchase gain during the measurement period. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to our condensed consolidated statements of operations and comprehensive income (loss). We allocated the preliminary purchase price to the acquired tangible and intangible assets and assumed liabilities of Nivalis based on their estimated fair values as of the acquisition date. The fair value of our identifiable intangible asset is based on detailed valuations using information and assumptions provided by management.
Intangible Asset	Intangible Asset Our intangible asset is our indefinite-life GSNOR inhibitor in-process research and development asset (“IPR&D”) acquired from Nivalis. The IPR&D represents the processes, expertise, and technology employed in the development of S-nitrosoglutathione reductase (“GSNOR”) inhibitors and Nivalis’ lead product candidate, cavosonstat. The IPR&D represents the estimated fair value as of the acquisition date of substantive in-process projects that have not reached technological feasibility. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval. The valuation of IPR&D is determined using a discounted cash flow method. In determining the value of IPR&D, management considers, among other factors, the stage of completion of the projects, the technological feasibility of the projects, whether the projects have an alternative future use, and the estimated residual cash flows that could be generated from the various projects and technologies over their respective projected economic lives. The discount rate used is determined at the time of acquisition and includes a rate of return which accounts for the time value of money, as well as risk factors reflecting the economic risk that the projected cash flows may not be realized We review our IPR&D at least annually for possible impairment. IPR&D is reviewed for possible impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of the IPR&D below their carrying values. We test our IPR&D each year on October 1. Our IPR&D asset totaled $1.5 million at September 30, 2017.
Derivative Financial Instruments	Derivative Financial Instruments We evaluate all of our financial instruments, including issued stock purchase warrants, to determine if such instruments are derivatives or contain features qualifying as embedded derivatives. For derivative financial instruments accounted for as liabilities, the derivative instrument is initially recorded at its fair value and is then re-valued at each reporting date, with changes in the fair value reported in the condensed consolidated statement of operations and comprehensive income (loss). We use the Black-Scholes option-pricing model to value the derivative instruments at inception and subsequent valuation dates. The classification of derivative instruments, including whether such instruments should be recorded as liabilities or as equity, is re-assessed at the end of each reporting period. We do not use derivative instruments to hedge exposures to cash flow, market, or foreign currency risks.
Revenue Recognition	Revenue Recognition We derive our revenue from collaboration and licensing agreements. We recognize revenue when each of the following four criteria are met: (1) persuasive evidence of an arrangement exists; (2) products have been delivered or services have been rendered; (3) the sales price is fixed or determinable; and (4) collectability is reasonably assured. We recognize revenue under our License and Research Agreement (the “Collaboration Agreement”) with Kite Pharma, Inc. (“Kite”) in accordance with the guidance on multiple element arrangements. Multiple elements or deliverables 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. The evaluation of multiple-element arrangements requires management to make judgments about (1) the identification of deliverables; (2) whether such deliverables are separable from other aspects of the contractual relationship; (3) the estimated selling price of each deliverable; and (4) the expected period of performance for each deliverable. To determine the units of accounting under a multiple-element arrangement, management evaluates certain separation criteria, including whether the deliverables have stand-alone value, based on the relevant facts and circumstances for each arrangement. Management then estimates the selling price for each unit of accounting and allocates the arrangement consideration to each unit using the relative selling price method. The allocated consideration for each unit of accounting is recognized based on the method most appropriate for that unit of account and in accordance with the revenue recognition criteria detailed above. If there are deliverables in an arrangement that are not separable from other aspects of the contractual relationship, they are treated as a combined unit of accounting, with the allocated revenue for the combined unit recognized in a manner consistent with the revenue recognition criteria applicable to the final deliverable in the combined unit. 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. The Collaboration Agreement provides 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 will periodically review the estimated performance periods under the Collaboration Agreement which provides for non-refundable upfront payments and fees. We will adjust the periods over which revenue should be recognized when appropriate to reflect changes in assumptions relating to the estimated performance periods. 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.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is comprised of net income (loss) and certain changes in equity excluded from net income (loss). For the three and nine months ended September 30, 2017, other comprehensive loss consists of unrealized losses on our short-term investments. There was no difference between comprehensive income (loss) and net income (loss) for the three and nine months ended September 30, 2016.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, as amended, which amends the guidance for revenue recognition to replace numerous industry specific requirements. ASU 2014-09, as amended, implements a five-step process for customer contract revenue recognition focusing on transfer of control, as opposed to transfer of risk and rewards. ASU 2014-09, as amended, also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. ASU 2014-09, as amended, is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted, but not before December 15, 2016. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. We are currently expecting to use the modified retrospective method to adopt this standard and are continuing to assess all of the potential impacts of the new standard on our financial statements and related disclosures, although we do not expect the implementation to have a material impact. 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. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and is to be applied at the beginning of the earliest period presented using a modified retrospective approach. We are continuing to evaluate the effect the standard will have on our financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15 which provides new guidance on the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We will be required to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. We are currently assessing the impact the new guidance will have on our condensed consolidated statements of cash flows. In January 2017, the FASB issued an ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business. The amendments in this update clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. We are currently evaluating the impact of adopting this guidance. In May 2017, the FASB issued ASU No. 2017-09 to provide clarity and reduce both diversity in practice and cost and complexity when applying the guidance in Compensation - Stock Compensation (
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2014, the FASB issued ASU No.2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Under the new guidance, management is required to assess an entity’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. The provisions of this standard are effective for annual periods ending after December 31, 2016, and for annual and interim periods thereafter. We adopted this guidance this year and management believes our existing cash and cash equivalents as of September 30, 2017 are sufficient to fund our operations and do not raise substantial doubt about our ability to continue as a going concern. In March 2016, the FASB issued ASU No. 2016-09-Improvements to Employee Share-Based Payment Accounting, wh ich simplified the accounting for share-based payment transactions, including the income tax consequences, the calculation of diluted earnings per share, the treatment of forfeitures, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. For public business entities, the amendments in this update are effective for annual periods beginning after December 15, 2016 and interim periods within those annual periods. Early adoption is permitted for any entity in any interim or annual period. We adopted ASU 2016-09 with effect from January 1, 2015. The adoption of this standard did not have a material impact on our financial statements. In November 2016, the FASB issued ASU No. 2016-18 relating to restricted cash. The new guidance requires amounts generally described as restricted cash and restricted cash equivalents to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the condensed consolidated statement of cash flows. This guidance is required to be adopted beginning with the first fiscal quarter of 2018; early adoption is permitted. We adopted this guidance effective June 30, 2017, which required us to include restricted cash within the beginning and ending balance of cash and cash equivalents for the nine-month period ended September 30, 2017. We had no restricted cash prior to adopting this guidance, thus we were not required to revise prior period statements of cash flows. The adoption of this guidance does not impact our financial position or results of operations.

Business Combination (Tables)

Business Combination (Tables) - Nivalis Therapeutics, Inc.	9 Months Ended
	Sep. 30, 2017
Business Acquisition [Line Items]
Schedule of Fair Value of Consideration Transferred	The fair value of the consideration transferred was based on the most reliable measure, which was determined to be the market price of Nivalis shares of common stock as of the acquisition date. The fair value of the consideration transferred consisted of the following (in thousands except share and per share amounts): Outstanding Nivalis common stock 3,914,058 Per share fair value of Nivalis common stock $ 9.60 Outstanding Nivalis stock options 421,992 Weighted average per share fair value of Nivalis stock options $ 1.25 Total fair value of consideration (in 000's) $ 38,103
Schedule of Initial Allocation of Purchase Consideration	The initial allocation of the purchase consideration is as follows (in thousands): Preliminary Fair Value Assets: Cash and cash equivalents $ 31,130 Marketable securities 12,952 IPR&D 1,453 Total assets acquired 45,535 Liabilities: Accrued expenses (384 ) Deferred tax liability (509 ) Total liabilities assumed (893 ) Bargain purchase gain (6,539 ) Total $ 38,103
Schedule of Pro Forma Financial Information	The following pro forma consolidated results of net loss for the nine months ended September 30, 2017 and 2016 assume the business combination was completed as of January 1, 2016 (in thousands, except per share amounts): Nine Months Ended September 30, 2017 2016 Pro forma revenues $ 1,603 $ 2,212 Pro forma net loss (13,634 ) (23,935 ) Pro forma basic and diluted net loss per share $ (0.98 ) $ (1.74 )

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule of Anti-dilutive Securities Excluded from Diluted Net Loss Per Share Attributable to Common Stockholders Calculation	The common stock issuable upon the conversion or exercise of the following dilutive securities has been excluded from the diluted net loss per share attributable to common stockholders calculation because their effect would have been antidilutive for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Convertible preferred stock - 4,311,770 - 4,311,770 Warrants to purchase common stock 7,069 12,422 19,491 12,422 Options to purchase common stock 280,992 520,739 1,791,066 520,739 Total 288,061 4,844,931 1,810,557 4,844,931
Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Income (Loss) Per Share Attributable to Common Stockholders	The following is a reconciliation of the numerator (net income or loss) and the denominator (number of shares) used in the calculation of basic and diluted net income (loss) per share attributable to common stockholders (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Numerator Basic and diluted net income (loss) attributable to common stockholders $ 2,122 $ (374 ) $ (3,465 ) $ (185 ) Denominator Shares used in computing basic net income (loss) per share attributable to common stockholders 10,577,772 608,701 3,989,747 550,080 Effect of dilutive securities: Options to purchase common stock 1,002,472 — — — Warrants to purchase common stock 6,551 — — — Shares used in computing diluted net income (loss) per share attributable to common stockholders 11,586,795 608,701 3,989,747 550,080 Basic net income (loss) per share attributable to common stockholders $ 0.20 $ (0.61 ) $ (0.87 ) $ (0.34 ) Diluted net income (loss) per share attributable to common stockholders $ 0.18 $ (0.61 ) $ (0.87 ) $ (0.34 )

Cash Equivalents and Short-Te25

Cash Equivalents and Short-Term Investments (Tables)	9 Months Ended
	Sep. 30, 2017
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): September 30, 2017 Assets: (unaudited) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value Money market funds $ 4,736 $ — $ — $ 4,736 U.S. treasury bills 17,155 2 — 17,157 Corporate debt securities and commercial paper 63,323 — (14 ) 63,309 Total $ 85,214 $ 2 $ (14 ) $ 85,202

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes our financial assets and liabilities measured at fair value on a recurring basis (in thousands): September 30, 2017 Assets: (unaudited) Level 1 Level 2 Level 3 Total Money market funds $ 4,736 $ — $ — $ 4,736 U.S. treasury bills 17,157 — — 17,157 Corporate debt securities and commercial paper — 63,309 — 63,309 Total $ 21,893 $ 63,309 $ — $ 85,202
Reconciliation of Level 3 Warrant Liability Measured and Recorded at Fair Value on Recurring Basis, Using Significant Unobservable Inputs	The following table shows the reconciliation of the Level 3 warrant liability measured and recorded at fair value on a recurring basis, using significant unobservable inputs (in thousands): Estimated Fair Value Balance as of January 1, 2017 $ — Fair value of warrants at issuance (June 30, 2017) 53,000 Change in fair value of warrant liability in connection with merger (1,000 ) Conversion of warrant liability to equity (52,000 ) Balance as of September 30, 2017 $ —

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 (unaudited) Accrued taxes and licenses $ 354 $ 61 Accrued professional fees 50 5 Deferred compensation — 61 Accrued other 238 43 Total $ 642 $ 170

Stockholders' Deficit (Tables)

Stockholders' Deficit (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders Equity Note [Abstract]
Schedule of Stock-based Compensation Expense	Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 (unaudited) Employee: Research and development $ 38 $ 4 $ 93 $ 5 General and administrative 169 5 386 46 Non-Employee: Research and development 16 1 40 3 General and administrative 6 2 9 3 Total stock-based compensation expense $ 229 $ 12 $ 528 $ 57

Description of the Business - A

Description of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Jul. 24, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2016USD ($)	Dec. 31, 2016$ / sharesshares
Description Of Business [Line Items]
Convertible preferred stock, shares issued | shares		0		4,311,770
Convertible preferred stock, purchase price per share | $ / shares		$ 0.0001		$ 0.0001
Aggregate purchase price | $		$ 37,666	$ 10,973
Convertible Preferred Stock
Description Of Business [Line Items]
Convertible preferred stock, shares issued | shares	1,335,118			4,311,770
Convertible preferred stock, purchase price per share | $ / shares	$ 12.74
Aggregate purchase price | $	$ 17,000
Nivalis Therapeutics, Inc.
Description Of Business [Line Items]
Stock split conversion ratio	0.25
Expected ownership percentage immediately following merger consummation	26.00%
Effective date of merger	Jul. 24, 2017
Alpine’s Preexisting Stockholders, Optionholders, and Warrantholders
Description Of Business [Line Items]
Expected ownership percentage immediately following merger consummation	74.00%
Alpine’s Preexisting Stockholders, Optionholders, and Warrantholders | Common Stock
Description Of Business [Line Items]
Stock split conversion ratio	0.4969

Summary of Significant Accoun30

Summary of Significant Accounting Policies - Additional Information (Details)	Jul. 24, 2017	Sep. 30, 2017USD ($)	Jun. 29, 2017USD ($)
Significant Accounting Policies
Intangible assets		$ 1,453,000
Restricted cash		$ 132,000	$ 0
Accounting Standards Update 2017-09
Significant Accounting Policies
Modifications to terms or conditions of share-based payment award, description		For the quarter ended September 30, 2017, there were no modifications to the terms or conditions of a share-based payment award.
IPR&D
Significant Accounting Policies
Intangible assets		$ 1,500,000
Maximum
Significant Accounting Policies
Business combination, fair value measurement period		1 year
Nivalis Therapeutics, Inc.
Significant Accounting Policies
Effective date of merger	Jul. 24, 2017
Description of Reverse stock split		1:4 reverse stock split
Stock split conversion ratio	0.25

Business Combination - Addition

Business Combination - Additional Information (Details) $ in Thousands	Jul. 24, 2017USD ($)shares	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Jul. 25, 2017shares	Dec. 31, 2016shares
Business Acquisition [Line Items]
Common stock, shares outstanding | shares		13,881,645			608,701
Aggregate purchase price		$ 37,666	$ 10,973
Net operating loss carryforward expiration beginning year		2,032
Percenatge of projected cash flows discounted to their present value using discount rate		17.00%
Acquisition-related costs		$ 1,300
Convertible Preferred Stock
Business Acquisition [Line Items]
Aggregate purchase price	$ 17,000
Minimum
Business Acquisition [Line Items]
Percentage of shares outstanding after merger		74.00%
Common Stock
Business Acquisition [Line Items]
Lock out period of shares issued in merger		180 days
Alpine’s Preexisting Stockholders, Optionholders, and Warrantholders
Business Acquisition [Line Items]
Expected ownership percentage immediately following merger consummation	74.00%
Alpine’s Preexisting Stockholders, Optionholders, and Warrantholders | Common Stock
Business Acquisition [Line Items]
Stock split conversion ratio	0.4969
Nivalis Therapeutics, Inc.
Business Acquisition [Line Items]
Effective date of merger	Jul. 24, 2017
Description of Reverse stock split		1:4 reverse stock split
Stock split conversion ratio	0.25
Common stock, shares outstanding | shares	3,914,058			13,881,645
Expected ownership percentage immediately following merger consummation	26.00%

Business Combination - Schedule

Business Combination - Schedule of Fair Value of Consideration Transferred (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 24, 2017	Sep. 30, 2017	Jul. 25, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Outstanding Nivalis common stock		13,881,645		608,701
Nivalis Therapeutics, Inc.
Business Acquisition [Line Items]
Outstanding Nivalis common stock	3,914,058		13,881,645
Per share fair value of Nivalis common stock	$ 9.60
Outstanding Nivalis stock options	421,992
Weighted average per share fair value of Nivalis stock options	$ 1.25
Total fair value of consideration (in 000's)	$ 38,103

Business Combination - Schedu33

Business Combination - Schedule of Initial Allocation of Purchase Consideration (Detail) - USD ($)	Jul. 24, 2017	Sep. 30, 2017	Sep. 30, 2017
Liabilities:
Bargain purchase gain		$ (6,539,000)	$ (6,539,000)
Nivalis Therapeutics, Inc.
Assets:
Cash and cash equivalents	$ 31,130,000
Marketable securities	12,952,000
IPR&D	1,453,000
Total assets acquired	45,535,000
Liabilities:
Accrued expenses	(384,000)
Deferred tax liability	(509,000)
Total liabilities assumed	(893,000)
Bargain purchase gain	(6,539,000)
Total	$ 38,103,000

Business Combination - Schedu34

Business Combination - Schedule of Pro Forma Financial Information (Details) - Nivalis Therapeutics, Inc. - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Pro forma revenues	$ 1,603	$ 2,212
Pro forma net loss	$ (13,634)	$ (23,935)
Pro forma basic and diluted net loss per share	$ (0.98)	$ (1.74)

Net Income (Loss) Per Share - S

Net Income (Loss) Per Share - Schedule of Anti-dilutive Securities Excluded from Diluted Net Loss Per Share Attributable to Common Stockholders Calculation (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	288,061	4,844,931	1,810,557	4,844,931
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		4,311,770		4,311,770
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)	7,069	12,422	19,491	12,422
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)	280,992	520,739	1,791,066	520,739

Net Income (Loss) Per Share -36

Net Income (Loss) Per Share - Schedule of Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Income (Loss) Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator
Basic and diluted net income (loss) attributable to common stockholders	$ 2,122	$ (374)	$ (3,465)	$ (185)
Denominator
Shares used in computing basic net income (loss) per share attributable to common stockholders	10,577,772	608,701	3,989,747	550,080
Effect of dilutive securities:
Options to purchase common stock	1,002,472
Warrants to purchase common stock	6,551
Shares used in computing diluted net income (loss) per share attributable to common stockholders	11,586,795	608,701	3,989,747	550,080
Basic net income (loss) per share attributable to common stockholders	$ 0.20	$ (0.61)	$ (0.87)	$ (0.34)
Diluted net income (loss) per share attributable to common stockholders	$ 0.18	$ (0.61)	$ (0.87)	$ (0.34)

Cash Equivalents and Short-Te37

Cash Equivalents and Short-Term Investments - Summary of Amortized Cost and Fair Value of CashEquivalents and Short Term Investments (Details) $ in Thousands	Sep. 30, 2017USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 85,214
Gross unrealized gains	2
Gross unrealized losses	(14)
Fair market value	85,202
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,736
Fair market value	4,736
U.S. Treasury Bills
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	17,155
Gross unrealized gains	2
Fair market value	17,157
Corporate Debt Securities and Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	63,323
Gross unrealized losses	(14)
Fair market value	$ 63,309

Cash Equivalents and Short-Te38

Cash Equivalents and Short-Term Investments - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Realized gains and losses on securities	$ 0
Short-term investments		$ 0
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, contractual maturity period	1 year

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 24, 2017	Jun. 30, 2017	Jul. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash				$ 2,000	$ 11,800
Series A-1 Preferred Stock Warrants | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Date of conversion of preferred stock warrants to common stock warrants	Jul. 24, 2017
Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Stock price		$ 9.64
Risk-free rate		2.31%
Expected volatility		78.00%
Term		9 years 6 months
Decrease in fair value of warrant			$ (1,000)	$ (1,000)

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) $ in Thousands	Sep. 30, 2017USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 85,202
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	4,736
Corporate Debt Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	63,309
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	85,202
Fair Value, Measurements, Recurring | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	4,736
Fair Value, Measurements, Recurring | U.S. Treasury Bills
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	17,157
Fair Value, Measurements, Recurring | Corporate Debt Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	63,309
Fair Value, Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	21,893
Fair Value, Measurements, Recurring | Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	4,736
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury Bills
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	17,157
Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	63,309
Fair Value, Measurements, Recurring | Level 2 | Corporate Debt Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets disclosure	$ 63,309

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Level 3 Warrant Liability Measured and Recorded at Fair Value on Recurring Basis, Using Significant Unobservable Inputs (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Jul. 31, 2017	Sep. 30, 2017
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Conversion of warrant liability to equity		$ 52
Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of warrants at issuance (June 30, 2017)		53,000
Change in fair value of warrant liability in connection with merger	$ (1,000)	(1,000)
Conversion of warrant liability to equity		$ (52,000)

Accrued Liabilities - Summary o

Accrued Liabilities - Summary of Accrued Expenses and Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued taxes and licenses	$ 354	$ 61
Accrued professional fees	50	5
Deferred compensation		61
Accrued other	238	43
Total	$ 642	$ 170

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Details) - USD ($)	Jul. 24, 2017	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Amortization of debt discount			$ 43,000,000	$ 43,000,000
Unamortized debt discount			$ 385,000,000	$ 385,000,000
Series A-1 Preferred Stock Warrants
Debt Instrument [Line Items]
Class of warrant or rights, granted		7,069
Warrants issued, exercise price		$ 12.38
Fair value of warrant liability		$ 53,000
Series A-1 Preferred Stock Warrants | Common Stock
Debt Instrument [Line Items]
Warrants exercisable for shares of common stock			7,069	7,069
Date of conversion of preferred stock warrants to common stock warrants	Jul. 24, 2017
Term Loan
Debt Instrument [Line Items]
Term loan debt		$ 5,000,000
Interest-only period expiration date				Jul. 1, 2018
Long-term debt final payment fee percentage				7.50%
Long-term debt final payment fee			$ 375,000	$ 375,000
Term Loan | Prime Rate
Debt Instrument [Line Items]
Debt instrument variable interest rate				1.75%

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	Apr. 01, 2017	Sep. 30, 2017	May 31, 2017
Operating Leased Assets [Line Items]
Operating lease, annual base rent	$ 38,000
Operating lease amendment effective date		Apr. 12, 2017
Operating lease, Expiry date		Dec. 31, 2019
Line of Credit
Operating Leased Assets [Line Items]
Security deposit			$ 132,000

License and Collaboration Agr45

License and Collaboration Agreement - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Oct. 20, 2017USD ($)Tranche	Oct. 31, 2015USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	$ 128,000	$ 737,000	$ 1,603,000	$ 2,212,000
Kite | Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue						$ 5,500,000
Revenue recognized	$ 128,000	$ 737,000	$ 1,600,000	$ 2,200,000
Kite | Collaboration Agreement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables						$ 530,000,000
Kite | Amended Agreement | Subsequent Event
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible to receive additional research support payment					$ 450,000
Number of tranches | Tranche					2

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - USD ($)	Jul. 24, 2017	Jun. 30, 2017	Apr. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Temporary Equity [Line Items]
Convertible preferred stock, shares issued					0		4,311,770
Proceeds from issuance of convertible preferred stock					$ 37,666,000	$ 10,973,000
Convertible preferred stock, purchase price per share					$ 0.0001		$ 0.0001
Convertible preferred stock outstanding					0		4,311,770
Series A-1 Preferred Stock Warrants
Temporary Equity [Line Items]
Class of warrant or rights, granted		7,069
Warrants issued, exercise price		$ 12.38
Warrants issued, term for exercise		10 years
Fair value of warrant liability		$ 53,000
Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock to common stock, shares	9,301,433				9,301,433
Common Stock | Series A-1 Preferred Stock Warrants
Temporary Equity [Line Items]
Date of conversion of preferred stock warrants to common stock warrants	Jul. 24, 2017
Warrants exercisable for shares of common stock					7,069
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued				707,330
Proceeds from issuance of convertible preferred stock				$ 4,000,000
Series A-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued			2,947,211
Proceeds from issuance of convertible preferred stock			$ 16,700,000
Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued	1,335,118						4,311,770
Proceeds from issuance of convertible preferred stock	$ 17,000,000
Convertible preferred stock, purchase price per share	$ 12.74
Conversion of convertible preferred stock to common stock, shares					(9,301,433)
Convertible preferred stock outstanding					0

Stockholders' Deficit - Schedul

Stockholders' Deficit - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 229	$ 12	$ 528	$ 57
Employee | Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	38	4	93	5
Employee | General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	169	5	386	46
Non-Employee | Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	16	1	40	3
Non-Employee | General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6	$ 2	$ 9	$ 3

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	Jul. 24, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Effective tax rate		(0.04%)	(0.04%)
U.S. federal statutory rate		35.00%	35.00%
Net operating loss carryforward expiration beginning year			2,032
Description of the likelihood that an uncertainty in income taxes will not be sustained upon audit by taxing authority			less than a 50% likelihood
Federal
Income Taxes [Line Items]
Net operating loss carryforward expiration beginning year			2,032
Net operating loss carryforward				$ 75,700,000
State
Income Taxes [Line Items]
Net operating loss carryforward				$ 0
Nivalis Therapeutics, Inc.
Income Taxes [Line Items]
IPR&D acquired in business combination	$ 1,453,000
Deferred tax liability, IPR&D	509,000
IPR&D acquired in business combination, tax basis	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Alpine BioVentures GP, LLC - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Expenses related to shared services agreement		$ 0	$ 3,000	$ 0	$ 12,000
Accrued expenses related to shared services agreement						$ 5,000
Payment of accumulated expenses related to shared services agreement	$ 5,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Kite - Amended Agreement	Oct. 20, 2017USD ($)Tranche	Oct. 31, 2015USD ($)
Subsequent Event [Line Items]
Research support payment received		$ 450,000
Subsequent Event
Subsequent Event [Line Items]
Eligible to receive additional research support payment	$ 450,000
Number of tranches | Tranche	2