VYNE Therapeutics (VYNE) 10-K 28 Mar 18 2017 FY Annual report Financial data

DEI Document

DEI Document - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 28, 2018	Jun. 30, 2017
Entity [Abstract]
Entity Registrant Name	Menlo Therapeutics Inc.
Entity Central Index Key	1,566,044
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		22,977,998
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 0

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 10,206	$ 4,027
Short‑term investments	49,295	26,881
Accounts receivable	786	0
Prepaid expenses and other current assets	3,574	632
Total current assets	63,861	31,540
Long‑term investments	2,978	10,420
Property and equipment, net	28	27
Prepaid and other long‑term assets	0	66
Total assets	66,867	42,053
Current liabilities:
Accounts payable	2,462	1,526
Accrued expenses and other current liabilities	3,559	581
Deferred revenue, current	1,796	1,796
Total current liabilities	7,817	3,903
Deferred revenue, long‑term	6,735	8,531
Other non‑current liabilities	22	57
Total liabilities	14,574	12,491
Commitments and contingencies (see Note 5)
Stockholders’ deficit:
Common stock, $0.0001 par value, 55,000,000 and 36,500,000 shares authorized at December 31, 2017 and 2016, respectively; 5,298,593 and 5,280,058 shares issued and outstanding at December 31, 2017 and 2016, respectively	1	1
Additional paid‑in capital	2,207	699
Accumulated other comprehensive loss	(51)	(26)
Accumulated deficit	(59,191)	(30,115)
Total stockholders’ deficit	(57,034)	(29,441)
Total liabilities, convertible preferred stock and stockholders’ deficit	66,867	42,053
Series A Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	14,183	14,183
Series B Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	44,820	44,820
Series C Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	$ 50,324	$ 0

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, par value per share (in USD per share)	$ 0.001
Preferred stock authorized (shares)	28,322,761	14,120,883
Preferred stock issued (shares)	25,975,346	14,120,883
Preferred stock outstanding (shares)	25,975,346	14,120,883
Preferred stock, liquidation value	$ 109,800	$ 59,300
Common stock, par value per share (in USD per share)	$ 0.0001	$ 0.0001
Common stock authorized (shares)	55,000,000	36,500,000
Common stock issued (shares)	5,298,593	5,280,058
Common stock outstanding (shares)	5,298,593	5,280,058
Series A Convertible Preferred Stock
Preferred stock, par value per share (in USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (shares)	14,300	14,300
Preferred stock issued (shares)	14,300	14,300
Preferred stock outstanding (shares)	14,300	14,300
Preferred stock, liquidation value	$ 14,300	$ 14,300
Series B Convertible Preferred Stock
Preferred stock, par value per share (in USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (shares)	14,106,583	14,106,583
Preferred stock issued (shares)	14,106,583	14,106,583
Preferred stock outstanding (shares)	14,106,583	14,106,583
Preferred stock, liquidation value	$ 45,000	$ 45,000
Series C Convertible Preferred Stock
Preferred stock, par value per share (in USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (shares)	14,201,878	0
Preferred stock issued (shares)	11,854,463	0
Preferred stock outstanding (shares)	11,854,463	0
Preferred stock, liquidation value	$ 50,500	$ 0

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Collaboration and license revenue	$ 4,582	$ 674	$ 0
Operating expenses:
Research and development	29,007	11,255	2,921
General and administrative	5,168	3,751	1,687
Total operating expenses	34,175	15,006	4,608
Loss from operations	(29,593)	(14,332)	(4,608)
Interest income and other expense, net	517	264	0
Net loss attributable to common stockholders	(29,076)	(14,068)	(4,608)
Other comprehensive loss:
Unrealized loss on available‑for‑sale securities	(25)	(26)	0
Comprehensive loss	$ (29,101)	$ (14,094)	$ (4,608)
Net loss attributable to common stockholder per share, basic and diluted (in USD per share)	$ (5.69)	$ (2.82)	$ (0.97)
Weighted‑average number of common shares used to compute basic and diluted net loss per share (in shares)	5,108,121	4,987,133	4,735,148

Statement of Convertible Prefer

Statement of Convertible Preferred Stock and Stockholders' Deficit Statement - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Other Comprehensive Loss
Preferred stock, beginning at Dec. 31, 2014		11,500	0	0
Preferred stock, beginning at Dec. 31, 2014		$ 11,383	$ 0	$ 0
Common stock, beginning (shares) at Dec. 31, 2014					4,962,653
Balance, beginning at Dec. 31, 2014	$ (11,410)				$ 1	$ 28	$ (11,439)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock (shares)		2,800	14,106,583
Issuance of preferred stock	0	$ 2,800	$ 44,820
Exercise of unvested stock options (shares)					317,405
Stock-based compensation	65					65
Unrealized loss on available‑for‑sale securities	0
Net loss	(4,608)						(4,608)
Preferred stock, ending at Dec. 31, 2015		14,300	14,106,583	0
Preferred stock, ending at Dec. 31, 2015		$ 14,183	$ 44,820	$ 0
Common stock, ending (shares) at Dec. 31, 2015					5,280,058
Balance, ending at Dec. 31, 2015	$ (15,953)				$ 1	93	(16,047)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of unvested stock options (shares)	0
Vesting of early exercised stock options	$ 33					33
Stock-based compensation	573					573
Unrealized loss on available‑for‑sale securities	(26)							(26)
Net loss	$ (14,068)						(14,068)
Preferred stock, ending at Dec. 31, 2016	14,120,883	14,300	14,106,583	0
Preferred stock, ending at Dec. 31, 2016		$ 14,183	$ 44,820	$ 0
Common stock, ending (shares) at Dec. 31, 2016	5,280,058				5,280,058
Balance, ending at Dec. 31, 2016	$ (29,441)				$ 1	699	(30,115)	(26)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of preferred stock (shares)				11,854,463
Issuance of preferred stock	0			$ 50,324
Exercise of unvested stock options (shares)					18,535
Issuance of common stock on exercise of stock options	34					34
Vesting of early exercised stock options	22					22
Stock-based compensation	1,452					1,452
Unrealized loss on available‑for‑sale securities	(25)							(25)
Net loss	$ (29,076)						(29,076)
Preferred stock, ending at Dec. 31, 2017	25,975,346	14,300	14,106,583	11,854,463
Preferred stock, ending at Dec. 31, 2017		$ 14,183	$ 44,820	$ 50,324
Common stock, ending (shares) at Dec. 31, 2017	5,298,593				5,298,593
Balance, ending at Dec. 31, 2017	$ (57,034)				$ 1	$ 2,207	$ (59,191)	$ (51)

Statement of Convertible Prefe6

Statement of Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) - Preferred Stock - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Series B Convertible Preferred Stock
Preferred stock issuance costs		$ 179
Series C Convertible Preferred Stock
Preferred stock issuance costs	$ 173

Statement of Cash Flows

Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (29,076)	$ (14,068)	$ (4,608)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8	4	0
Unrealized loss on available‑for‑sale investments	(25)	(26)	0
Amortization of premium on investment securities	66	158	0
Stock‑based compensation expense	1,452	573	65
Gain on disposal of equipment	19	0	0
Accrued interest	31	0	0
Change in operating assets and liabilities:
Accounts receivable	(786)	0	0
Prepaid expenses and other current assets	(1,790)	(555)	(22)
Prepaid and other long‑term assets	66	(66)	0
Accounts payable	620	889	0
Accrued expenses and other current liabilities	2,976	466	346
Deferred revenue	(1,796)	10,327	36
Other non‑current liabilities	(12)	7	0
Net cash used in operating activities	(28,247)	(2,291)	(4,183)
Investing activities
Purchase of property and equipment	(27)	(31)	0
Purchase of investments	(64,148)	(55,309)	0
Proceeds from sales of investments	6,000	3,600	0
Proceeds from maturities of investments	43,110	14,250	0
Net cash used in investing activities	(15,065)	(37,490)	0
Financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs	50,324	0	47,620
Proceeds from the exercise of stock options	34	0	98
Deferred financing costs	(867)	0	0
Net cash provided by financing activities	49,491	0	47,718
Net increase (decrease) in cash and cash equivalents	6,179	(39,781)	43,535
Cash and cash equivalents at beginning of period	4,027	43,808	273
Cash and cash equivalents at end of period	10,206	4,027	43,808
Noncash Investing and Financing Items [Abstract]
Deferred financing costs	$ 316	$ 0	$ 0

Formation and Business of the C

Formation and Business of the Company	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Business of the Company	Formation and Business of the Company Menlo Therapeutics Inc., or the “Company”, is a late‑stage biopharmaceutical company focused on the development and commercialization of serlopitant for the treatment of pruritus, or itch, associated with dermatologic conditions such as atopic dermatitis, psoriasis and prurigo nodularis. The Company is concurrently evaluating the use of serlopitant for the treatment of refractory chronic cough, a cough that persists for at least eight weeks despite treatment of any identified underlying cause. The Company believes that its product candidate, serlopitant, a highly selective once‑daily, oral small molecule inhibitor of the neurokinin 1 receptor, or NK 1 ‑R, has the potential to significantly alleviate itch and cough symptoms. Pruritus associated with atopic dermatitis, psoriasis and prurigo nodularis, as well as refractory chronic cough, each represents a significant patient need. The Company was incorporated in Delaware in October 2011. Since commencing operations, the Company has devoted substantially all of its resources to developing its product candidate, including conducting clinical trials and providing general and administrative support for these operations. Initial Public Offering In January 2018, the Company completed its initial public offering (“IPO”) of shares of its common stock, pursuant to which the Company issued 8,050,000 shares of common stock, which includes 1,050,000 shares issued pursuant to the over-allotment option granted to its underwriters, and received net proceeds of approximately $125.5 million , after deducting underwriting discounts, commissions and offering expenses. In connection with the completion of the Company's IPO, all shares of convertible preferred stock converted into 9,629,405 shares of common stock. Liquidity and Capital Resources Since inception, the Company has incurred losses and negative cash flows from operations. For the year ended December 31, 2017, the Company incurred a net loss of $ 29.1 million and used $28.2 million of cash in operations. As of December 31, 2017, the Company had cash, cash equivalents and investments of $62.5 million and an accumulated deficit of $59.2 million . Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities. Management plans to finance operations through equity or debt financing arrangements, and/or third‑party collaboration funding. There can be no assurances that, in the event that the Company requires additional financing, such financing will be available on terms which are favorable to the Company, or at all. If the Company is unable to raise additional funding to meet its working capital needs in the future, it will be forced to delay or reduce the scope of its research programs and/or limit or cease its operations. The Company believes that its existing cash, cash equivalents and investments as of December 31, 2017 together with funds available from the January 2018 IPO, will provide sufficient funds to enable it to meet its obligations for at least the next twelve months.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented. Reverse Stock Split On January 8, 2018, the Company effected a reverse split of shares of the Company’s common stock at a ratio of 1-for- 2.6975 pursuant to an amendment to the amended and restated certificate of incorporation approved by the Company’s board of directors and stockholders. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse split. All issued and outstanding common stock share and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse split for all periods presented, and the conversion ratio of the preferred stock was adjusted accordingly. Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting. All long‑lived assets are maintained in the United States of America. Use of Estimates Preparation of financial statements in conformity with U.S. GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting periods covered by the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, stock‑based compensation expense, the resolution of uncertain tax positions and valuation allowance, recovery of long‑lived assets and accruals for research and development costs. Management bases its estimates on historical experience on various assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates. Risk and Uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s potential drug candidate, uncertainty of market acceptance of the Company’s product candidate, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. The Company’s product candidate requires clearances from the U.S. Food and Drug Administration (“FDA”) or other international regulatory agencies prior to commercial sales. There can be no assurance that the product candidate will receive the necessary clearances. If the Company was denied clearance, clearance was delayed or the Company was unable to maintain clearance, it could have a materially adverse impact on the Company. The Company expects to incur substantial operating losses for the next several years and will need to obtain additional financing in order to complete clinical studies and launch and commercialize any product candidates for which it receives regulatory approval. There can be no assurance that such financing will be available or will be at terms acceptable by the Company. Cash and Cash Equivalents Cash and cash equivalents are stated at fair value. Cash equivalents include only securities having an original maturity of three months or less at the time of purchase. The Company limits its credit risk associated with cash and cash equivalents by placing its investments with an institution it believes is highly creditworthy and with highly rated money market funds. As of December 31, 2017 and 2016, cash and cash equivalents consisted of bank deposits, cash and investments in money market funds. Investment Securities The Company classifies its investment securities as available‑for‑sale. Those investments with maturities less than 12 months at the date of purchase are considered short‑term investments. Those investments with maturities greater than 12 months at the date of purchase are considered long‑term investments. The Company’s investment securities classified as available‑for‑sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of comprehensive income or loss. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security as an adjustment to yield using the straight‑line interest method. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Property and Equipment, Net Property and equipment are stated at cost and depreciated using the straight‑line method over the estimated useful lives of the assets, generally between three and five years. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, which include cash, accounts payable and accrued liabilities and other current liabilities, and deferred revenue approximate their fair values due to their short maturities. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist principally of cash, cash equivalents and investments. As of December 31, 2017 and 2016, the majority of our cash, cash equivalents and investments are held by one U.S. financial institution in excess of federally insured limits. We invest cash in excess of our current needs in United States Treasury and government agency securities, highly‑rated short or medium‑term debt securities and money market funds and, by policy, diversify our investments to limit the amount of credit exposure. The Company has an investment policy which limits the Company to investing in highly rated corporate and government notes, and no individual investment may comprise more than 5% of the total portfolio. Income Taxes The Company accounts for income taxes under the asset and liability method which requires, among other things, that deferred income taxes be provided for temporary differences between the tax basis of the Company’s assets and liabilities and their financial statement reported amounts. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes and also for deferred tax assets and liabilities, and any valuation allowances recorded against the Company’s deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and to the extent the Company believes that recovery is not more likely than not, the Company must establish a valuation allowance. The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes, that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits . Research and Development Expenses Research and development costs are expensed as incurred. Substantially all of our research and development expenses consist of expenses incurred in connection with the development of serlopitant. These expenses include certain payroll and personnel expenses including stock‑based compensation expense, consulting costs, contract manufacturing costs, and fees paid to clinical research organizations, or CROs, to conduct research and development. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized and recognized as an expense as the goods are delivered or the related services are performed. The Company estimates non‑clinical study and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage non‑clinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered. Patent Costs The Company has no historical data to support a probable future economic benefit for the arising patent applications, filing and prosecution costs. Therefore, patent costs are expensed as incurred. Operating Leases The Company recognizes rent expense on a straight‑line basis over the non‑cancellable term of the operating lease. Stock-Based Compensation The Company measures and recognizes compensation expense for all stock‑based awards made to employees, directors and non‑employees, based on estimated fair values recognized using the straight‑line method over the requisite service period. The fair value of options to purchase common stock granted to employees is estimated on the grant date using the Black‑Scholes option valuation model. The calculation of stock‑based compensation expense requires that the Company make certain assumptions and judgments about a number of complex and subjective variables used in the Black‑Scholes model, including the expected term, expected volatility of the underlying common stock, risk‑free interest rate, as well as estimating future forfeitures of unvested stock options. To the extent actual forfeiture results differ from the estimates, the difference will be recorded as a cumulative adjustment in the period the estimates are revised. The Company accounts for options issued to non‑employees using the Black‑Scholes option valuation model and is measured and recognized as the stock options are earned. Convertible Preferred Stock The Company recorded the convertible preferred stock at fair value on the dates of issuance, net of issuance costs. The convertible preferred stock is recorded outside of stockholders’ equity because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. All outstanding convertible preferred stock converted into common stock in January 2018 upon the effectiveness of the IPO. Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of the Company during a period from transactions and other events and circumstances excluding transactions resulting from investments and distributions to owners. Comprehensive loss consists of the net loss and changes in accumulated other comprehensive income, which are comprised of unrealized gains (losses) on available‑for‑sale investments. Revenue Recognition To date, the Company’s clinical drug candidates have not been approved for sale by the FDA and the Company has not generated any revenue from product sales. On August 10, 2016, the Company entered into a license and collaboration agreement with Japan Tobacco Inc. and Torii Pharmaceutical Co. Ltd., together referred to as “JT Torii”, which is referred to as the “Collaboration Agreement”. Under the Collaboration Agreement, the Company granted to JT Torii the rights to develop and commercialize products containing serlopitant in Japan for the treatment of diseases and conditions other than nausea or vomiting. In exchange, JT Torii paid an upfront, non‑refundable payment of $11.0 million . In addition, the Company is entitled to receive aggregate payments of up to $28.0 million upon the achievement of specified development and regulatory milestones, and $15.0 million upon the achievement of a commercial milestone, as well as tiered royalties from the mid-single digits up to the mid‑teens on sales of licensed products in Japan. The Company’s performance obligations under the license agreement includes the transfer of intellectual property rights in the form of licenses, obligations to participate on certain development and/or commercialization committees with the collaboration partners and supply manufactured drug product for clinical trials. The Company recognizes revenue pursuant to the Collaboration Agreement in connection with the clinical development and commercialization of products covered by the collaboration, including non-refundable upfront license fees, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. To date, the Company has not generated or recognized revenue from sales of its product candidates. Revenue from the Collaboration Agreement is recognized when (i) persuasive evidence of an arrangement exists, (ii) transfer of technology has been completed, services have been performed or products have been delivered, (iii) the fee is fixed and determinable, and (iv) collection is reasonably assured. The Company evaluates revenue agreements with multiple‑elements in accordance with ASC 605-25 Revenue Recognition - Multiple Element Arrangements . The Company identifies the deliverables included within the agreement and evaluates which deliverables represent separate units of accounting based on the achievement of certain criteria including whether the deliverable has stand‑alone value. Upfront payments for licenses are evaluated to determine if the licensee can obtain standalone value from the license separate from the value of the obligations to participate on certain development and/or commercialization committees with the collaboration partners and supply manufactured drug product for clinical trials in the arrangement to be provided by the Company. The Company is reimbursed by JT Torii for the non-commercial supplies of serlopitant at the same rate as charged by the third party manufacturer, which does not include a significant and incremental discount to JT Torii. The assessment of multiple-element arrangements also requires judgment in order to determine the allocation of revenue to each deliverable and the appropriate period of time over which the revenue should be recognized. Under the Collaboration Agreement, the Company has determined that the license does not have standalone value separate from the research and development services because JT Torii cannot resell such license on a standalone basis or use the license with its available resources to obtain any economic value without the Company’s participation. T he license and the services are combined as one unit of accounting and upfront payments are recorded initially as deferred revenue in the balance sheet. Revenue is then recognized on a straight-line basis over an estimated performance period that is consistent with the term of performance obligations, unless the Company determines there is a discernible pattern of performance other than straight-line, in which case the Company uses a proportionate performance method to recognize the revenue over the estimated performance period. The Company is recognizing the upfront fee on a straight-line basis over the initial period of performance of six years, which represents the estimated development period in the territories based on the initial development plan managed by the joint steering committee. The term of the agreement is through the expiration of the patents associated with serlopitant. The Company periodically reviews its estimated periods of performance based on the progress under each arrangement and accounts for the impact of any changes in estimated periods of performance on a prospective basis. At the inception of each agreement that includes milestone payments, including the Collaboration Agreement, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respective milestone and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. Non‑refundable payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved, assuming all other revenue recognition criteria are met. Other contingent payments in which a portion of the milestone consideration is refundable or adjusts based on future performance or non‑performance (e.g., through a penalty or claw‑back provision) are not considered to relate solely to past performance, and therefore, not considered substantive. Amounts that are not recognized as revenue due to the uncertainty as to whether they will be retained or because they are expected to be refunded are recorded as a liability. The Company recognizes non‑substantive milestone payments over the remaining estimated period of performance once the milestone is achieved. Contingent payments associated with the achievement of specific objectives in certain contracts that are not considered substantive because the Company does not contribute effort to the achievement of such milestones are recognized as revenue upon achievement of the objective, as long as there are no undelivered elements remaining and no continuing performance obligations by the Company, assuming all other revenue recognition criteria are met. Under the Collaboration Agreement, the Company is entitled to receive aggregate payments of up to $28.0 million upon the achievement of specified development and regulatory milestones, and $15.0 million upon the achievement of a commercial milestone. Two of the milestones, which amount to $2 million each, relate to the preparation of an IND for submission to regulatory authorities in the territory are considered substantive given that they are triggered by the Company’s performance relative to the achievement of pre-specified, “at risk” milestone events, including the submission of all completed clinical trials data packages and the validation of the manufacturing process. All other milestones, which amount to an aggregate of $24.0 million , are considered non-substantive because the milestone is dependent upon the performance of the collaboration partner rather than the Company. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Expenses related to the collaboration agreement are recorded as a component of research and development in the statement of operations as incurred, and to date have been immaterial. During the fourth quarter of 2017, the Company achieved a substantive milestone related to the validation of the manufacturing process under the Collaboration Agreement, and recognized revenues of $2.0 million . On September 1, 2017, the Company entered into a separate services agreement with JT Torii to provide research and development services, including regulatory, chemistry and manufacturing support and related materials that is distinct from the original Collaboration Agreement. The Company evaluated the new services agreement and determined that the research and materials delivered to JT Torii represents a separate earnings process that provides standalone value to JT Torii. The fees received under the services agreement will be recognized as and when such services are performed by the Company and JT Torii consumes the benefits of those services. The Company has no obligation to provide services unless requested by JT Torii and agreed to by us. The Company is eligible to receive reimbursement of estimated costs incurred and payment for research services performed directly by the Company at agreed upon rates. During the year ended December 31, 2017, the Company recognized revenue of $0.8 million and recorded expenses of $0.5 million as research and development expense in the statement of operations related to the new services agreement. The services agreement terminates upon the termination of the Collaboration Agreement or by mutual agreement of the parties. Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted‑average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted‑average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock and common stock options are considered to be potentially dilutive securities. Because the Company has reported a net loss for the years ended December 31, 2017, 2016 and 2015, diluted net loss per common share is the same as basic net loss per common share for those periods. Recent Accounting Pronouncements In November 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016‑18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) . The update requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. ASU 2016‑18 is effective for public entities for annual periods beginning after December 15, 2017, and interim periods within those annual periods. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In March 2016, the FASB issued ASU 2016‑09, Improvements to Employee Share‑Based Payment Accounting as part of its simplification initiative, which involves several aspects of accounting for share‑based payment transactions, including the income tax effects, statutory withholding requirements, forfeitures and classification on the statement of cash flows. The standard is effective for companies for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years with early adoption permitted. The Company adopted this standard as of January 1, 2017, and there was no impact to the Company’s financial statements as a result of the adoption. In February 2016, the FASB issued ASU 2016‑02, Leases (ASC 842), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight‑line basis over the term of the lease, respectively. A lessee is also required to record a right‑of‑use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. ASC 842 supersedes the previous leases standard, ASC 840 Leases . The standard is effective on January 1, 2019, with early adoption permitted. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In January 2016, the FASB issued ASU 2016‑01, Recognition and Measurement of Financial Assets and Financial Liabilities , which addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016‑01 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In November 2015, the FASB issued ASU 2015‑17, Balance Sheet Classification of Deferred Taxes to simplify the presentation of deferred income taxes. The amendments in this update require that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. We have elected to early adopt ASU 2015‑17 as of the beginning of our fourth quarter ended December 31, 2015 on a prospective basis. There was no impact to the balance sheet amounts as a result of early adoption. In August 2014, the FASB issued ASU 2014‑15 related to Presentation of Financial Statements ‑ Going Concern (Subtopic 205‑40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern . This update provides guidance about management’s responsibilities in evaluating an entity’s going concern uncertainties, and about the timing and content of related footnote disclosures. Under this amended guidance, an entity’s management should evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. This update is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early application is permitted. The Company adopted this standard in 2016 and there was no impact on the financial position, results of operations or related financial statement disclosures. In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (Topic 606) , which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition . This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, FASB issued ASU No. 2015‑14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which effectively delayed the adoption date by one year, to an effective date for public entities for annual and interim periods beginning after December 15, 2017. In March, April and May 2016, the FASB issued additional updates to the new revenue standard relating to reporting revenue on a gross versus net basis, identifying performance obligations and licensing arrangements, and narrow‑scope improvements and practical expedients, respectively. The effective date of this additional update is the same as that of ASU 2014‑09. The guidance permits the use of either a retrospective or cumulative effect transition method. The Company has not yet selected a transition method. The Company is still finalizing the analysis to quantify the adoption impact of the provisions of the new standard, but it does not currently expect to have a material impact on the financial position or results of operations. Based on the evaluation of its current collaboration agreement and associated revenue streams, most of the revenue will be recorded consistently under both the current and the new standard. The FASB has issued, and may issue in the future, interpretive guidance which may cause the Company’s evaluation to change. The Company believes it is following an appropriate timeline to allow for proper recognition, presentation and disclosure upon adoption effective the beginning of fiscal year 2018. There are no other recently issued accounting standards that apply to the Company or that are expected to have a material impact on results of operations, financial condition, or cash flows.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of our financial instruments reflects the amounts that we estimate we would receive in connection with the sale of an asset or pay in connection with the transfer of a liability in an orderly transaction between market participants at the measurement date (exit price). We disclose and recognize the fair value of our assets and liabilities using a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to valuations based upon unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to valuations based upon unobservable inputs that are significant to the valuation (Level 3 measurements). The guidance establishes three levels of the fair value hierarchy as follows: Level 1 ‑ Inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access at the measurement date; Level 2 ‑ Inputs other than quoted prices that are observable for the assets or liability either directly or indirectly, including inputs in markets that are not considered to be active; Level 3 ‑ Inputs that are unobservable. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. During the years presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the years ended December 31, 2017 and 2016 . A summary of the assets and liabilities carried at fair value in accordance with the hierarchy defined above is as follows (in thousands): Fair Value Measurements Using Total Carrying Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2017 Assets: Money market funds $ 8,685 $ 8,685 $ — $ — Corporate notes 46,098 5,103 40,995 — Government notes 6,175 6,175 — — Total assets $ 60,958 $ 19,963 $ 40,995 $ — Fair Value Measurements Using Total Carrying Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2016 Assets: Money market funds $ 3,808 $ 3,808 $ — $ — Corporate notes 26,108 7,225 18,883 — Government notes 11,193 11,193 — — Total assets $ 41,109 $ 22,226 $ 18,883 $ — The Company uses a market approach for determining the fair value of all its Level 1 and Level 2 money market funds and marketable securities. To value its money market funds, the Company values the funds at $1 stable net asset value, which is the market pricing convention for identical assets that the Company has the ability to access. The investments are classified as available‑for‑sale securities. At December 31, 2017 and 2016, the balance in the Company’s accumulated other comprehensive income was comprised solely of activity related to the Company’s available‑for‑sale securities. There were no realized gains or losses recognized on the sale or maturity of available‑for‑sale securities for the years ended December 31, 2017 and 2016 and as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income for the year. The Company has a limited number of available‑for‑sale securities in insignificant loss positions as of December 31, 2017 and 2016, which the Company does not intend to sell and has concluded it will not be required to sell before recovery of the amortized cost for the investment at maturity. The following table summarizes the available‑for‑sale securities (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2017 Money market funds $ 8,685 $ — $ — $ 8,685 Corporate notes 46,133 — (35 ) 46,098 Government notes 6,191 — (16 ) 6,175 $ 61,009 $ — $ (51 ) $ 60,958 Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Money market funds $ 3,808 $ — $ — $ 3,808 Corporate notes 26,134 — (26 ) 26,108 Government notes 11,193 — — 11,193 $ 41,135 $ — $ (26 ) $ 41,109

Balance Sheets Components

Balance Sheets Components	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheets Components	Balance Sheets Components Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2017 2016 Accrued personnel expenses $ 1,108 $ 273 Accrued clinical and development expenses 2,250 245 Other 201 63 Total $ 3,559 $ 581

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Matters The Company’s industry is characterized by frequent claims and litigation, including claims regarding intellectual property. As a result, the Company may be subject to various legal proceedings from time to time. The results of any future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. Management is not aware of any pending or threatened litigation. License Agreement In December 2012, the Company entered into an exclusive worldwide royalty free license agreement with Merck Sharp & Dohme Corp., or “Merck” for exclusive worldwide rights for the development and commercialization of serlopitant and two other NK 1 ‑R antagonists in all human diseases, disorders or conditions, except for the treatment and prevention of nausea or vomiting. The Company paid Merck an upfront non‑refundable, non‑creditable licensing fee of $1.0 million dollars and issued to Merck shares of its common stock. In addition, the Company has agreed to make aggregate payments of up to $25.0 million dollars upon the achievement of specified development and regulatory milestones. Future milestone payments are considered to be contingent consideration and will be accrued when the applicable milestone is achieved. Through December 31, 2017, no milestones have been achieved under the license agreement. Leases The Company conducts its operations using leased office facilities. In September 2017, the Company entered into a lease agreement. The 30 month lease, beginning on October 1, 2017, provides approximately 14,000 square feet of office space in Redwood City, California. Base annual rent is approximately $55,000 per month, with annual increases. The Company recognizes rent expense on a straight‑line basis over the respective lease period. Rent expense for the years ended December 31, 2017, 2016 and 2015 was $400,000 , $208,000 and $7,000 , respectively. As of December 31, 2017, total future minimum lease payments under our operating leases are as follows (in thousands): Year ending December 31: 2018 $ 656 2019 675 2020 173 Total future minimum lease payments $ 1,504 Indemnification As permitted under Delaware law and in accordance with the Company’s bylaws, the Company is required to indemnify its officers and directors for certain events or occurrences while the officer or director is or was serving in such capacity. The Company is also party to indemnification agreements with its directors. The Company believes the fair value of the indemnification rights and agreements is minimal. Accordingly, the Company has not recorded any liabilities for these indemnification rights and agreements as of December 31, 2017. Contingencies From time to time, we may have certain contingent liabilities that arise in the ordinary course of our business activities. We accrue a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Convertible Preferred Stock	Convertible Preferred Stock As of December 31, 2017, the Company’s Certificate of Incorporation, as amended, authorized the Company to issue up to 28,322,761 shares of convertible preferred stock, par value of $0.001 , of which 14,300 were designated Series A convertible preferred stock and 14,106,583 are designated Series B convertible preferred stock, and 14,201,878 shares are designated Series C convertible preferred stock. In July 2017, the Company issued 11,854,463 shares of Series C convertible preferred stock to investors at $4.26 per share with gross proceeds of $50.5 million . In January 2018, the Company completed its initial public offering (“IPO”) of shares of its common stock, pursuant to which the Company issued 8,050,000 shares of common stock, which includes 1,050,000 shares issued pursuant to the over-allotment option granted to its underwriters, and received net proceeds of approximately $125.5 million , after deducting underwriting discounts, commissions and offering expenses. In connection with the completion of the Company's IPO, all shares of convertible preferred stock converted into 9,629,405 shares of common stock. The Company had outstanding convertible preferred stock as of the times set forth below as follows: As of December 31, 2017 Shares Authorized Shares Issued and Outstanding Aggregate Liquidation Preference (in thousands) Series A 14,300 14,300 $ 14,300 Series B 14,106,583 14,106,583 45,000 Series C 14,201,878 11,854,463 50,500 Total 28,322,761 25,975,346 $ 109,800 As of December 31, 2016 Shares Authorized Shares Issued and Outstanding Aggregate Liquidation Preference (in thousands) Series A 14,300 14,300 $ 14,300 Series B 14,106,583 14,106,583 45,000 Total 14,120,883 14,120,883 $ 59,300 Significant terms of the Series A, B and C convertible preferred stock as of December 31, 2017 (collectively, the “Preferred Stock”) are as follows: Liquidation Preference In the event of any liquidation, dissolution, or winding up of the Company, either voluntary or involuntary, the holders of the then outstanding shares of Series A convertible stock and Series B convertible preferred stock and Series C convertible preferred stock are first entitled to receive the amount of $1,000 and $3.19 and $4.26 per share, respectively plus all declared but unpaid dividends for such shares, prior and in preference to any distribution of any assets of the Company to the holders of the common stock. If, upon the occurrence of such event, the proceeds distributed among the holders of the Series A, B and C convertible preferred stock are insufficient to permit the full payment of the aforesaid preferential amounts to each holder the convertible preferred stock, then the entire proceeds legally available for distribution to the convertible preferred stock shall be distributed ratably among the holders of the Series A, B and C convertible preferred stock in proportion to the full preferential amount that each such holder of convertible preferred stock is otherwise entitled to receive. Upon completion of the distributions required by the above‑mentioned liquidation preferences, any remaining proceeds shall be distributed among the holders of Series B and C convertible preferred stock and common stock pro rata based on the number of shares of common stock held by each, assuming full conversion of the Series B and C convertible preferred stock to common stock at the then‑effective conversion price for such shares. Dividends The holders of shares of Series A, B and C convertible preferred stock are entitled to receive non‑cumulative dividends, out of any assets legally available, prior and in preference to any declaration or payment of any dividend on the common stock, at the applicable dividend rate of $80.00 per annum for each share of Series A convertible preferred stock, $0.2552 per annum for each share of Series B convertible preferred stock and $0.3408 per share per annum for each share of Series C convertible preferred stock , all subject to adjustment from time to time for recapitalizations, payable when and if declared by the Company’s board of directors. The Company has never declared any dividends on its convertible preferred stock. Voting The holder of each share of Series B and C convertible preferred stock are entitled to one vote for each share of common stock into which such preferred stock could then be converted and, with respect to such vote, such holder has full voting rights and powers equal to the voting rights and powers of the holders of common stock and is entitled to notice of any stockholders’ meeting in accordance with the Company’s bylaws. The holders of shares of Series A convertible preferred stock do not have a right to vote, other than as required by Delaware law and for certain directors, as set forth below. The holders of shares of Series A convertible preferred stock are entitled to elect two of the Company’s directors. The holders of Series B convertible preferred stock are entitled to elect two of the Company’s directors. The holders of Series C convertible preferred stock are entitled to elect one of the Company’s directors. The holders of outstanding common stock are entitled to elect three of the Company’s directors. The holders of convertible preferred stock and common stock, voting together as a single class, and not as separate series, and on an as converted basis, are entitled to elect any remaining directors of the Company, subject to the approval of the then serving members of the Company’s directors. Conversion The holder of each share of convertible preferred stock has the option to convert each share of convertible preferred stock into such number of fully paid and nonassessable shares of common stock as is determined by dividing the applicable original issue price for such series by the applicable conversion price for such series in effect on the date the certificate is surrendered for conversion. Each share of convertible preferred stock shall automatically be converted into shares of common stock at the conversion rate at the time in effect for such series of convertible preferred stock immediately prior to the earlier of (i) sale of the Company’s common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, with gross proceeds of not less than $40.0 million in the aggregate and an offering price to the public of no less than $17.21 per share, or (ii) upon the receipt by the Corporation of a written request or agreement of the holders of a majority of the outstanding Series A, B and C convertible preferred stock, voting together as a single class and on an as converted basis. The conversion price of the convertible preferred stock was initially set at an amount equal to the issue price. The Series B and C convertible preferred stock conversion price is subject to adjustment for stock dividends, stock splits, re‑capitalization and upon the occurrence of certain triggering events related to anti‑dilution protection rights. In the event that a future preferred stock financing should occur at a price lower than the last preferred financing round, the conversion ratios of the existing preferred stock are changed to protect the ownership position of existing investors.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock	Common Stock As of December 31, 2017, the Company’s Certificate of Incorporation, as amended, authorizes the Company to issue 55,000,000 shares of $0.0001 par value common stock. Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when and if declared by the board of directors, subject to the prior rights of holders of all classes of preferred stock outstanding. The Company has never declared any dividends on common stock. As of December 31, 2017 , there were 12,548,103 shares of common stock reserved available for issuance.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Under the Company’s 2011 Stock Incentive Plan (the “2011 Plan”), the Company may grant options to purchase common stock, restricted stock awards, or directly issue shares of common stock to employees, directors and consultants of the Company. During 2015, the Company’s board of directors and stockholders approved an increase to the shares available under the 2011 Plan to 2,086,600 shares. During 2017, the Company’s board of directors and stockholders approved an increase to the shares available under the 2011 Plan to 3,339,724 shares. As of December 31, 2017 , there were 411,772 shares of common stock available for issuance under the 2011 Plan. Options may be granted at an exercise price per share of not less than 100% of the fair market value at the date of grant. If an incentive stock option is granted to a stockholder holding 10% of the Company’s outstanding capitalization, then the purchase or exercise price per share must not be less than 110% of the fair market value per share of common stock on the grant date. Options granted are exercisable over a maximum term of 10 years from the date of grant and generally vest over a period of four years . Total stock‑based compensation expense for employees and non‑employees recognized in the statements of operations was as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 792 $ 257 $ 1 General and administrative 660 316 64 Total stock‑based compensation expense $ 1,452 $ 573 $ 65 At December 31, 2017, there was approximately $7.3 million of unamortized compensation expense, which was expected to be recognized over a weighted average period of 2.9 years. 2011 Plan The table below summarizes stock option and restricted award activity under the 2011 Plan: Number of Shares Outstanding Weighted-Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balances at January 1, 2015 — Granted 317,405 $ 0.31 Exercised (1) (317,405 ) $ 0.31 Balances at December 31, 2015 — $ — Granted 1,485,132 $ 1.99 Balances at December 31, 2016 1,485,132 $ 1.99 9.32 $ 3,805 Granted 1,040,329 $ 5.56 Exercised (1) (18,535 ) $ 1.83 Balances at December 31, 2017 2,506,926 $ 3.50 8.79 $ 24,033 (1) Includes early exercise of 317,405 options during the year ended December 31, 2015 , of which 138,864 and 218,216 remain unvested as of December 31, 2017 and December 31, 2016 . Upon vesting of restricted shares and exercise of options, the Company issues common stock from its authorized shares. During the years ended December 31, 2017, 2016 and 2015, the Company received $34,000 , $0 and $98,000 upon the exercise of stock options, respectively. There were 139,636 and 222,077 shares of early exercised restricted shares which have not vested at December 31, 2017 and 2016, respectively. As of December 31, 2017 and 2016, the Company had recorded a liability of $43,000 and $68,000 , respectively for the early exercise of stock options, recorded as other current liabilities and other non‑current liabilities. When options are subject to the Company’s repurchase right, the Company may buy back any unvested shares at their original exercise price in the event of an employee’s termination prior to full vesting. The aggregate grant date fair value of employee options vesting during the years ended December 31, 2017, 2016 and 2015 was approximately $539,000 , $182,000 and $1,000 , respectively. The aggregate intrinsic value of shares exercised during the year ended December 31, 2017 and December 31, 2015 was $209,000 and zero , respectively. The weighted average grant date fair value of stock options granted was $5.56 , $1.79 and $0.15 per share during the years ended December 31, 2017, 2016, and 2015, respectively. There were no shares exercised in the year ended December 31, 2016 . Stock Awards Granted to Employees and Directors Stock‑based compensation expense is based on the grant date fair value. The Company recognizes compensation expense for all stock‑based options and restricted awards on a straight‑line basis over the requisite service period of the awards, which is generally the option vesting term of four years. Stock‑ based compensation expense related to awards granted to employees and directors for the years ended December 31, 2017, 2016 and 2015 was approximately $791,000 , $314,000 an $1,000 , respectively. The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model. The Company determines the price volatility based on the historical volatilities of industry peers as it has no trading history for its common stock price. Industry peers consist of several public companies in the biotechnology industry with comparable characteristics, including clinical trials progress and therapeutic indications. The expected term of the options is based on the average period the stock options are expected to remain outstanding. As the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior, the expected term is calculated as the midpoint between the weighted-average vesting term and the contractual expiration period also known as the simplified method. The risk-free rate is based on U.S. Treasury zero coupon issues with remaining terms consistent with the expected terms of the stock options, as determined at the time of grant. To date, the Company has not declared or paid any cash dividends and does not have any plans to do so in the future. Therefore, the Company used an expected divided yield of zero. In addition to the assumptions used in the Black‑Scholes valuation model, the Company must also estimate a forfeiture rate to calculate the stock‑based compensation for its equity awards. The Company will continue to use judgment in evaluating the assumptions related to the Company’s stock‑based compensation on a prospective basis. As the Company continues to accumulate additional data, it may have refinements to its estimates, which could materially impact the Company’s future stock‑based compensation expense. The following assumptions were used to calculate the fair value of awards granted to employees and directors during the years indicated: Year Ended December 31, 2017 2016 2015 Expected term (in years) 6.0 - 6.1 4.6 - 6.1 3.1 Volatility 75% - 100% 68% - 74% 74% Risk‑free interest rate 1.9% - 2.3% 1.3% - 2.1% 1.0% Dividend yield — — — Stock-Based Compensation for Non-employees Stock‑based compensation expense related to stock awards granted to non‑employees is recognized as the awards vest. The Company believes that the fair value of the stock‑based awards granted is more reliably measurable than the fair value of the services received. The fair value of stock awards granted is calculated using the Black‑Scholes option valuation model. Stock‑ based compensation expense related to awards granted to non‑employees for the years ended December 31, 2017, 2016 and 2015 was approximately $661,000 , $259,000 and $64,000 , respectively. The fair values of common stock awards granted to non‑employees were calculated using the following assumptions for the periods presented: Year Ended December 31, 2017 2016 2015 Expected term (in years) 8.3 - 10 9.3 - 10.0 1.0 - 1.8 Volatility 74% - 100% 84% - 86% 62% - 74% Risk‑free interest rate 2.1% - 2.5% 1.6% - 2.5% 0.5% - 0.7% Dividend yield — — —

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Numerator: Net loss attributable to common stockholders, basic and diluted $ (29,076 ) $ (14,068 ) $ (4,608 ) Denominator: Weighted‑average common shares outstanding 5,285,542 5,280,058 5,060,918 Less: weighted‑average common shares subject to repurchase (177,421 ) (292,925 ) (325,770 ) Weighted‑average common shares used to compute basic and diluted net loss per share 5,108,121 4,987,133 4,735,148 Net loss per share attributable to common stockholders: Basic and diluted $ (5.69 ) $ (2.82 ) $ (0.97 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: December 31, 2017 2016 2015 Convertible preferred stock issuable upon conversion to common stock 9,629,405 5,234,800 5,234,800 Outstanding common stock subject to repurchase 139,636 222,077 324,355 Stock options outstanding 2,506,926 1,485,132 — Stock options available for issuance 411,772 198,978 1,684,110 Total 12,687,739 7,140,987 7,243,265

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company did not record a provision or benefit for income taxes during the years ended December 31, 2017, 2016 and 2015. The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate: Year Ended December 31, 2017 2016 2015 Statutory Rate 34 % 34 % 34 % State Tax 1 % — % 6 % Permanent Differences (3 )% — % — % Other (1 )% — % — % General Business Credits 4 % 2 % 1 % Change in Valuation Allowance (11 )% (36 )% (41 )% Tax Reform - Tax Rate Change (24 )% — — Total — % — % — % The tax effect of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands): Year Ended December 31, 2017 2016 2015 Deferred Tax Assets NOLs $ 10,404 $ 10,458 $ 5,992 Depreciation and Amortization 226 328 362 Stock‑Based Compensation 274 161 34 Research & Development Credits 2,063 586 233 Deferred Revenue 1,791 — — Other Accruals 235 98 — Total Deferred Tax Assets $ 14,993 $ 11,631 $ 6,621 Valuation Allowance (14,993 ) (11,631 ) (6,621 ) Net Deferred Tax Assets $ — $ — $ — Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The net change in the total valuation allowance for the years ended December 31, 2017, 2016 and 2015 was an increase of approximately $3.4 million , $5.0 million , and $1.9 million , respectively. As of December 31, 2017 and 2016, the Company had net operating loss carryforwards for federal income tax purposes of $44.3 million and $28.2 million , respectively which expire beginning in the year 2031 and federal research and development tax credits of $2.1 million and $0.5 million , respectively which expire beginning in the year 2031. As of December 31, 2017 and 2016, the Company had net operating loss carryforwards for state income tax purposes of $15.0 million and $15.0 million , respectively which expire beginning in the year 2031 and state research and development tax credits of $0.9 million and $0.4 million , respectively which do not expire. Federal and state tax laws impose substantial restrictions on the utilization of the net operating loss and credit carryforwards in the event of an ownership change as defined in Section 382 of the Internal Revenue Code. Accordingly, the Company’s ability to utilize these carryforwards may be limited as a result of such ownership change. Such a limitation could result in the expiration of carryforwards before they are utilized. The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes , that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. To the extent accrued interest and penalties do not ultimately become payable, amounts accrued will be reduced and reflected as a reduction of the provision for income taxes in the period that such determination is made. As of December 31, 2017 the Company had no accrued interest and penalties related to uncertain tax positions. The Company filed US and California tax returns with varying statues of limitations. The federal and California tax years from 2011 to 2017 remain open to examination due to the carryover of unused net operating losses and tax credits. The Company does not expect any material changes to the estimated amount of liability associated with its uncertain tax positions within the next 12 months. Uncertain Tax Positions The following table summarizes the activity related to unrecognized tax benefits (in thousands): For the year ended December 31, 2017 2016 2015 Tax Benefits: Unrecognized Benefit ‑ beginning of period $ 229 $ 93 $ 73 Gross Increases(Decreases) ‑ prior period tax positions 59 — — Gross Increases(Decreases) ‑ current period tax positions 515 136 20 Total Unrecognized Benefit ‑ end of period $ 803 $ 229 $ 93 Tax Reform On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a corporate tax rate decrease from 34% to 21% (the “Rate Reduction”) effective for tax years beginning after December 31, 2017. The Company reduced deferred tax assets at December 31, 2017 for the effect of the Rate Reduction. The Rate Reduction did not impact the Company's provision for income taxes for 2017 due to the full valuation allowance on deferred tax assets. Staff Accounting Bulletin No. 118 ("SAB 118") was issued to address the application of US GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Act. The Company determined that $7.0 million of the reduction in deferred tax assets resulting from Rate Reduction was both provisional and a reasonable estimate at December 31, 2017. Additionally, the Company is still in the process of analyzing certain provisions of the Act including the application of new executive compensation limitation provisions under Internal Revenue Section 162(m). These items are subject to revisions from further analysis of the Tax Act and interpretation of any additional guidance issued by the U.S. Treasury Department, IRS, FASB, and other standard-setting and regulatory bodies.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions From 2011 through 2016, the Company has operated with significant consulting and management services provided by Velocity Pharmaceutical Development, LLC (“VPD”). Development services fees paid to VPD under the Development Services Agreement were $1.0 million and $0.8 million for the years ended December 31, 2016 and 2015, respectively. The Company also reimbursed VPD for consulting, travel and other expenses incurred on our behalf. As of December 31, 2017 and 2016, the Company did not have any outstanding liabilities to VPD. Several managing directors of VPD have served as officers and directors of the Company. David Collier, M.D., a former member of the Company’s board of directors, is the Chief Executive Officer of VPD, and Xiaoming Zhang, Ph.D., our Senior Vice President, Non‑Clinical and Pharmaceutical Development, is a Venture Partner of VPD.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 8, 2018, the Company effected a reverse split of shares of the Company’s common stock at a ratio of 1-for- 2.6975 pursuant to an amendment to the amended and restated certificate of incorporation approved by the Company’s board of directors and stockholders. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse split. All issued and outstanding common stock share and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse split for all periods presented, and the conversion ratio of the preferred stock was adjusted accordingly. The Company adopted a 2018 Omnibus Incentive Plan, or 2018 Plan, effective on January 23, 2018. The 2018 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock, restricted stock units, dividend equivalent rights and other stock and cash-based awards (including annual cash incentives and long-term cash incentives). The Company has reserved for issuance pursuant to awards under the 2018 Plan, 3,000,000 shares of our common stock. The Company adopted a 2018 Employee Stock Purchase Plan, or ESPP, effective on January 23, 2018. The ESPP will enable eligible employees of the Company and designated affiliates to purchase shares of common stock at a discount following its effectiveness. The Company has reserved 325,000 shares of common stock for issuance under the ESPP. In January 2018, the Company completed its initial public offering (“IPO”) of shares of its common stock, pursuant to which the Company issued 8,050,000 shares of common stock and received net proceeds of approximately $125.5 million , after deducting underwriting discounts, commissions and offering expenses. In connection with the completion of the Company's IPO, all shares of convertible preferred stock converted into 9,629,405 shares of common stock.

Selected Unaudited Quarterly Fi

Selected Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Unaudited Quarterly Financial Data	Selected Unaudited Quarterly Financial Data The following tables show a summary of the Company’s unaudited quarterly financial data for each of the four quarters of 2017 and 2016 (in thousands, except per share amounts): Three Months Ended December 31, 2017 September 30, 2017 June 30, 2017 March 31, 2017 Collaboration and service revenue $ 2,775 $ 909 $ 449 $ 449 Operating expenses 12,252 9,244 6,675 6,004 Other income (expense), net 200 163 73 81 Net loss (9,277 ) (8,172 ) (6,153 ) (5,474 ) Basic and diluted net loss per common share (1) $ (1.80 ) $ (1.59 ) $ (1.21 ) $ (1.05 ) Three Months Ended December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Collaboration and service revenue $ 450 $ 224 $ — $ — Operating expenses 5,374 3,699 3,636 2,297 Other income (expense), net 88 77 74 25 Net loss (4,836 ) (3,398 ) (3,562 ) (2,272 ) Basic and diluted net loss per common share (1) $ (0.96 ) $ (0.68 ) $ (0.72 ) $ (0.43 ) (1) Basic and diluted net loss per common share are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share information may not equal annual basic and diluted net loss per common share.

Significant Accounting Polici21

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented.
Reverse Stock Split	Reverse Stock Split On January 8, 2018, the Company effected a reverse split of shares of the Company’s common stock at a ratio of 1-for- 2.6975 pursuant to an amendment to the amended and restated certificate of incorporation approved by the Company’s board of directors and stockholders. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse split. All issued and outstanding common stock share and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse split for all periods presented, and the conversion ratio of the preferred stock was adjusted accordingly.
Segments	Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting. All long‑lived assets are maintained in the United States of America.
Use of Estimates	Use of Estimates Preparation of financial statements in conformity with U.S. GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting periods covered by the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, stock‑based compensation expense, the resolution of uncertain tax positions and valuation allowance, recovery of long‑lived assets and accruals for research and development costs. Management bases its estimates on historical experience on various assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are stated at fair value. Cash equivalents include only securities having an original maturity of three months or less at the time of purchase. The Company limits its credit risk associated with cash and cash equivalents by placing its investments with an institution it believes is highly creditworthy and with highly rated money market funds. As of December 31, 2017 and 2016, cash and cash equivalents consisted of bank deposits, cash and investments in money market funds.
Investment Securities	Investment Securities The Company classifies its investment securities as available‑for‑sale. Those investments with maturities less than 12 months at the date of purchase are considered short‑term investments. Those investments with maturities greater than 12 months at the date of purchase are considered long‑term investments. The Company’s investment securities classified as available‑for‑sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of comprehensive income or loss. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security as an adjustment to yield using the straight‑line interest method. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost and depreciated using the straight‑line method over the estimated useful lives of the assets, generally between three and five years. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, which include cash, accounts payable and accrued liabilities and other current liabilities, and deferred revenue approximate their fair values due to their short maturities.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist principally of cash, cash equivalents and investments. As of December 31, 2017 and 2016, the majority of our cash, cash equivalents and investments are held by one U.S. financial institution in excess of federally insured limits. We invest cash in excess of our current needs in United States Treasury and government agency securities, highly‑rated short or medium‑term debt securities and money market funds and, by policy, diversify our investments to limit the amount of credit exposure. The Company has an investment policy which limits the Company to investing in highly rated corporate and government notes, and no individual investment may comprise more than 5% of the total portfolio
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method which requires, among other things, that deferred income taxes be provided for temporary differences between the tax basis of the Company’s assets and liabilities and their financial statement reported amounts. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes and also for deferred tax assets and liabilities, and any valuation allowances recorded against the Company’s deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and to the extent the Company believes that recovery is not more likely than not, the Company must establish a valuation allowance. The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes, that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits .
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as incurred. Substantially all of our research and development expenses consist of expenses incurred in connection with the development of serlopitant. These expenses include certain payroll and personnel expenses including stock‑based compensation expense, consulting costs, contract manufacturing costs, and fees paid to clinical research organizations, or CROs, to conduct research and development. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized and recognized as an expense as the goods are delivered or the related services are performed. The Company estimates non‑clinical study and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage non‑clinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered.
Patent Costs	Patent Costs The Company has no historical data to support a probable future economic benefit for the arising patent applications, filing and prosecution costs. Therefore, patent costs are expensed as incurred.
Operating Leases	Operating Leases The Company recognizes rent expense on a straight‑line basis over the non‑cancellable term of the operating lease.
Share-Based Compensation	Stock-Based Compensation The Company measures and recognizes compensation expense for all stock‑based awards made to employees, directors and non‑employees, based on estimated fair values recognized using the straight‑line method over the requisite service period. The fair value of options to purchase common stock granted to employees is estimated on the grant date using the Black‑Scholes option valuation model. The calculation of stock‑based compensation expense requires that the Company make certain assumptions and judgments about a number of complex and subjective variables used in the Black‑Scholes model, including the expected term, expected volatility of the underlying common stock, risk‑free interest rate, as well as estimating future forfeitures of unvested stock options. To the extent actual forfeiture results differ from the estimates, the difference will be recorded as a cumulative adjustment in the period the estimates are revised. The Company accounts for options issued to non‑employees using the Black‑Scholes option valuation model and is measured and recognized as the stock options are earned.
Convertible Preferred Stock	Convertible Preferred Stock The Company recorded the convertible preferred stock at fair value on the dates of issuance, net of issuance costs. The convertible preferred stock is recorded outside of stockholders’ equity because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. All outstanding convertible preferred stock converted into common stock in January 2018 upon the effectiveness of the IPO.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of the Company during a period from transactions and other events and circumstances excluding transactions resulting from investments and distributions to owners. Comprehensive loss consists of the net loss and changes in accumulated other comprehensive income, which are comprised of unrealized gains (losses) on available‑for‑sale investments.
Revenue Recognition	Revenue Recognition To date, the Company’s clinical drug candidates have not been approved for sale by the FDA and the Company has not generated any revenue from product sales. On August 10, 2016, the Company entered into a license and collaboration agreement with Japan Tobacco Inc. and Torii Pharmaceutical Co. Ltd., together referred to as “JT Torii”, which is referred to as the “Collaboration Agreement”. Under the Collaboration Agreement, the Company granted to JT Torii the rights to develop and commercialize products containing serlopitant in Japan for the treatment of diseases and conditions other than nausea or vomiting. In exchange, JT Torii paid an upfront, non‑refundable payment of $11.0 million . In addition, the Company is entitled to receive aggregate payments of up to $28.0 million upon the achievement of specified development and regulatory milestones, and $15.0 million upon the achievement of a commercial milestone, as well as tiered royalties from the mid-single digits up to the mid‑teens on sales of licensed products in Japan. The Company’s performance obligations under the license agreement includes the transfer of intellectual property rights in the form of licenses, obligations to participate on certain development and/or commercialization committees with the collaboration partners and supply manufactured drug product for clinical trials. The Company recognizes revenue pursuant to the Collaboration Agreement in connection with the clinical development and commercialization of products covered by the collaboration, including non-refundable upfront license fees, contingent consideration payments based on the achievement of defined collaboration objectives and royalties on sales of commercialized products. To date, the Company has not generated or recognized revenue from sales of its product candidates. Revenue from the Collaboration Agreement is recognized when (i) persuasive evidence of an arrangement exists, (ii) transfer of technology has been completed, services have been performed or products have been delivered, (iii) the fee is fixed and determinable, and (iv) collection is reasonably assured. The Company evaluates revenue agreements with multiple‑elements in accordance with ASC 605-25 Revenue Recognition - Multiple Element Arrangements . The Company identifies the deliverables included within the agreement and evaluates which deliverables represent separate units of accounting based on the achievement of certain criteria including whether the deliverable has stand‑alone value. Upfront payments for licenses are evaluated to determine if the licensee can obtain standalone value from the license separate from the value of the obligations to participate on certain development and/or commercialization committees with the collaboration partners and supply manufactured drug product for clinical trials in the arrangement to be provided by the Company. The Company is reimbursed by JT Torii for the non-commercial supplies of serlopitant at the same rate as charged by the third party manufacturer, which does not include a significant and incremental discount to JT Torii. The assessment of multiple-element arrangements also requires judgment in order to determine the allocation of revenue to each deliverable and the appropriate period of time over which the revenue should be recognized. Under the Collaboration Agreement, the Company has determined that the license does not have standalone value separate from the research and development services because JT Torii cannot resell such license on a standalone basis or use the license with its available resources to obtain any economic value without the Company’s participation. T he license and the services are combined as one unit of accounting and upfront payments are recorded initially as deferred revenue in the balance sheet. Revenue is then recognized on a straight-line basis over an estimated performance period that is consistent with the term of performance obligations, unless the Company determines there is a discernible pattern of performance other than straight-line, in which case the Company uses a proportionate performance method to recognize the revenue over the estimated performance period. The Company is recognizing the upfront fee on a straight-line basis over the initial period of performance of six years, which represents the estimated development period in the territories based on the initial development plan managed by the joint steering committee. The term of the agreement is through the expiration of the patents associated with serlopitant. The Company periodically reviews its estimated periods of performance based on the progress under each arrangement and accounts for the impact of any changes in estimated periods of performance on a prospective basis. At the inception of each agreement that includes milestone payments, including the Collaboration Agreement, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respective milestone and whether the milestone consideration is reasonable relative to all deliverables and payment terms in the arrangement in making this assessment. Non‑refundable payments that are contingent upon achievement of a substantive milestone are recognized in their entirety in the period in which the milestone is achieved, assuming all other revenue recognition criteria are met. Other contingent payments in which a portion of the milestone consideration is refundable or adjusts based on future performance or non‑performance (e.g., through a penalty or claw‑back provision) are not considered to relate solely to past performance, and therefore, not considered substantive. Amounts that are not recognized as revenue due to the uncertainty as to whether they will be retained or because they are expected to be refunded are recorded as a liability. The Company recognizes non‑substantive milestone payments over the remaining estimated period of performance once the milestone is achieved. Contingent payments associated with the achievement of specific objectives in certain contracts that are not considered substantive because the Company does not contribute effort to the achievement of such milestones are recognized as revenue upon achievement of the objective, as long as there are no undelivered elements remaining and no continuing performance obligations by the Company, assuming all other revenue recognition criteria are met. Under the Collaboration Agreement, the Company is entitled to receive aggregate payments of up to $28.0 million upon the achievement of specified development and regulatory milestones, and $15.0 million upon the achievement of a commercial milestone. Two of the milestones, which amount to $2 million each, relate to the preparation of an IND for submission to regulatory authorities in the territory are considered substantive given that they are triggered by the Company’s performance relative to the achievement of pre-specified, “at risk” milestone events, including the submission of all completed clinical trials data packages and the validation of the manufacturing process. All other milestones, which amount to an aggregate of $24.0 million , are considered non-substantive because the milestone is dependent upon the performance of the collaboration partner rather than the Company. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Expenses related to the collaboration agreement are recorded as a component of research and development in the statement of operations as incurred, and to date have been immaterial. During the fourth quarter of 2017, the Company achieved a substantive milestone related to the validation of the manufacturing process under the Collaboration Agreement, and recognized revenues of $2.0 million . On September 1, 2017, the Company entered into a separate services agreement with JT Torii to provide research and development services, including regulatory, chemistry and manufacturing support and related materials that is distinct from the original Collaboration Agreement. The Company evaluated the new services agreement and determined that the research and materials delivered to JT Torii represents a separate earnings process that provides standalone value to JT Torii. The fees received under the services agreement will be recognized as and when such services are performed by the Company and JT Torii consumes the benefits of those services. The Company has no obligation to provide services unless requested by JT Torii and agreed to by us. The Company is eligible to receive reimbursement of estimated costs incurred and payment for research services performed directly by the Company at agreed upon rates. During the year ended December 31, 2017, the Company recognized revenue of $0.8 million and recorded expenses of $0.5 million as research and development expense in the statement of operations related to the new services agreement. The services agreement terminates upon the termination of the Collaboration Agreement or by mutual agreement of the parties.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted‑average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted‑average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock and common stock options are considered to be potentially dilutive securities. Because the Company has reported a net loss for the years ended December 31, 2017, 2016 and 2015, diluted net loss per common share is the same as basic net loss per common share for those periods.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016‑18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) . The update requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. ASU 2016‑18 is effective for public entities for annual periods beginning after December 15, 2017, and interim periods within those annual periods. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In March 2016, the FASB issued ASU 2016‑09, Improvements to Employee Share‑Based Payment Accounting as part of its simplification initiative, which involves several aspects of accounting for share‑based payment transactions, including the income tax effects, statutory withholding requirements, forfeitures and classification on the statement of cash flows. The standard is effective for companies for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years with early adoption permitted. The Company adopted this standard as of January 1, 2017, and there was no impact to the Company’s financial statements as a result of the adoption. In February 2016, the FASB issued ASU 2016‑02, Leases (ASC 842), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight‑line basis over the term of the lease, respectively. A lessee is also required to record a right‑of‑use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. ASC 842 supersedes the previous leases standard, ASC 840 Leases . The standard is effective on January 1, 2019, with early adoption permitted. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In January 2016, the FASB issued ASU 2016‑01, Recognition and Measurement of Financial Assets and Financial Liabilities , which addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016‑01 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The Company is currently evaluating the effects, if any, that the adoption of this guidance will have on its financial statements. In November 2015, the FASB issued ASU 2015‑17, Balance Sheet Classification of Deferred Taxes to simplify the presentation of deferred income taxes. The amendments in this update require that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. We have elected to early adopt ASU 2015‑17 as of the beginning of our fourth quarter ended December 31, 2015 on a prospective basis. There was no impact to the balance sheet amounts as a result of early adoption. In August 2014, the FASB issued ASU 2014‑15 related to Presentation of Financial Statements ‑ Going Concern (Subtopic 205‑40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern . This update provides guidance about management’s responsibilities in evaluating an entity’s going concern uncertainties, and about the timing and content of related footnote disclosures. Under this amended guidance, an entity’s management should evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. This update is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early application is permitted. The Company adopted this standard in 2016 and there was no impact on the financial position, results of operations or related financial statement disclosures. In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (Topic 606) , which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition . This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, FASB issued ASU No. 2015‑14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which effectively delayed the adoption date by one year, to an effective date for public entities for annual and interim periods beginning after December 15, 2017. In March, April and May 2016, the FASB issued additional updates to the new revenue standard relating to reporting revenue on a gross versus net basis, identifying performance obligations and licensing arrangements, and narrow‑scope improvements and practical expedients, respectively. The effective date of this additional update is the same as that of ASU 2014‑09. The guidance permits the use of either a retrospective or cumulative effect transition method. The Company has not yet selected a transition method. The Company is still finalizing the analysis to quantify the adoption impact of the provisions of the new standard, but it does not currently expect to have a material impact on the financial position or results of operations. Based on the evaluation of its current collaboration agreement and associated revenue streams, most of the revenue will be recorded consistently under both the current and the new standard. The FASB has issued, and may issue in the future, interpretive guidance which may cause the Company’s evaluation to change. The Company believes it is following an appropriate timeline to allow for proper recognition, presentation and disclosure upon adoption effective the beginning of fiscal year 2018. There are no other recently issued accounting standards that apply to the Company or that are expected to have a material impact on results of operations, financial condition, or cash flows.
Fair Value Measurements	Fair Value Measurements The fair value of our financial instruments reflects the amounts that we estimate we would receive in connection with the sale of an asset or pay in connection with the transfer of a liability in an orderly transaction between market participants at the measurement date (exit price). We disclose and recognize the fair value of our assets and liabilities using a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to valuations based upon unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to valuations based upon unobservable inputs that are significant to the valuation (Level 3 measurements). The guidance establishes three levels of the fair value hierarchy as follows: Level 1 ‑ Inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access at the measurement date; Level 2 ‑ Inputs other than quoted prices that are observable for the assets or liability either directly or indirectly, including inputs in markets that are not considered to be active; Level 3 ‑ Inputs that are unobservable. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. During the years presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Carried at Fair Value	A summary of the assets and liabilities carried at fair value in accordance with the hierarchy defined above is as follows (in thousands): Fair Value Measurements Using Total Carrying Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2017 Assets: Money market funds $ 8,685 $ 8,685 $ — $ — Corporate notes 46,098 5,103 40,995 — Government notes 6,175 6,175 — — Total assets $ 60,958 $ 19,963 $ 40,995 $ — Fair Value Measurements Using Total Carrying Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2016 Assets: Money market funds $ 3,808 $ 3,808 $ — $ — Corporate notes 26,108 7,225 18,883 — Government notes 11,193 11,193 — — Total assets $ 41,109 $ 22,226 $ 18,883 $ —
Summary of Available-for-sale Securities	The following table summarizes the available‑for‑sale securities (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2017 Money market funds $ 8,685 $ — $ — $ 8,685 Corporate notes 46,133 — (35 ) 46,098 Government notes 6,191 — (16 ) 6,175 $ 61,009 $ — $ (51 ) $ 60,958 Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Money market funds $ 3,808 $ — $ — $ 3,808 Corporate notes 26,134 — (26 ) 26,108 Government notes 11,193 — — 11,193 $ 41,135 $ — $ (26 ) $ 41,109

Balance Sheets Components (Tabl

Balance Sheets Components (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2017 2016 Accrued personnel expenses $ 1,108 $ 273 Accrued clinical and development expenses 2,250 245 Other 201 63 Total $ 3,559 $ 581

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Operating Lease Payments	As of December 31, 2017, total future minimum lease payments under our operating leases are as follows (in thousands): Year ending December 31: 2018 $ 656 2019 675 2020 173 Total future minimum lease payments $ 1,504

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Convertible Preferred Stock	The Company had outstanding convertible preferred stock as of the times set forth below as follows: As of December 31, 2017 Shares Authorized Shares Issued and Outstanding Aggregate Liquidation Preference (in thousands) Series A 14,300 14,300 $ 14,300 Series B 14,106,583 14,106,583 45,000 Series C 14,201,878 11,854,463 50,500 Total 28,322,761 25,975,346 $ 109,800 As of December 31, 2016 Shares Authorized Shares Issued and Outstanding Aggregate Liquidation Preference (in thousands) Series A 14,300 14,300 $ 14,300 Series B 14,106,583 14,106,583 45,000 Total 14,120,883 14,120,883 $ 59,300

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Allocation of Recognized Period Costs	Total stock‑based compensation expense for employees and non‑employees recognized in the statements of operations was as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 792 $ 257 $ 1 General and administrative 660 316 64 Total stock‑based compensation expense $ 1,452 $ 573 $ 65
Schedule of Stock Option Activity	The table below summarizes stock option and restricted award activity under the 2011 Plan: Number of Shares Outstanding Weighted-Average Exercise Price Weighted- Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balances at January 1, 2015 — Granted 317,405 $ 0.31 Exercised (1) (317,405 ) $ 0.31 Balances at December 31, 2015 — $ — Granted 1,485,132 $ 1.99 Balances at December 31, 2016 1,485,132 $ 1.99 9.32 $ 3,805 Granted 1,040,329 $ 5.56 Exercised (1) (18,535 ) $ 1.83 Balances at December 31, 2017 2,506,926 $ 3.50 8.79 $ 24,033 (1) Includes early exercise of 317,405 options during the year ended December 31, 2015 , of which 138,864 and 218,216 remain unvested as of December 31, 2017 and December 31, 2016 .
Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following assumptions were used to calculate the fair value of awards granted to employees and directors during the years indicated: Year Ended December 31, 2017 2016 2015 Expected term (in years) 6.0 - 6.1 4.6 - 6.1 3.1 Volatility 75% - 100% 68% - 74% 74% Risk‑free interest rate 1.9% - 2.3% 1.3% - 2.1% 1.0% Dividend yield — — —
Non-employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Fair Value Assumptions	The fair values of common stock awards granted to non‑employees were calculated using the following assumptions for the periods presented: Year Ended December 31, 2017 2016 2015 Expected term (in years) 8.3 - 10 9.3 - 10.0 1.0 - 1.8 Volatility 74% - 100% 84% - 86% 62% - 74% Risk‑free interest rate 2.1% - 2.5% 1.6% - 2.5% 0.5% - 0.7% Dividend yield — — —

Net Loss per Share Attributab27

Net Loss per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Numerator: Net loss attributable to common stockholders, basic and diluted $ (29,076 ) $ (14,068 ) $ (4,608 ) Denominator: Weighted‑average common shares outstanding 5,285,542 5,280,058 5,060,918 Less: weighted‑average common shares subject to repurchase (177,421 ) (292,925 ) (325,770 ) Weighted‑average common shares used to compute basic and diluted net loss per share 5,108,121 4,987,133 4,735,148 Net loss per share attributable to common stockholders: Basic and diluted $ (5.69 ) $ (2.82 ) $ (0.97 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: December 31, 2017 2016 2015 Convertible preferred stock issuable upon conversion to common stock 9,629,405 5,234,800 5,234,800 Outstanding common stock subject to repurchase 139,636 222,077 324,355 Stock options outstanding 2,506,926 1,485,132 — Stock options available for issuance 411,772 198,978 1,684,110 Total 12,687,739 7,140,987 7,243,265

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate: Year Ended December 31, 2017 2016 2015 Statutory Rate 34 % 34 % 34 % State Tax 1 % — % 6 % Permanent Differences (3 )% — % — % Other (1 )% — % — % General Business Credits 4 % 2 % 1 % Change in Valuation Allowance (11 )% (36 )% (41 )% Tax Reform - Tax Rate Change (24 )% — — Total — % — % — %
Schedule of Deferred Tax Assets and Liabilities	The tax effect of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands): Year Ended December 31, 2017 2016 2015 Deferred Tax Assets NOLs $ 10,404 $ 10,458 $ 5,992 Depreciation and Amortization 226 328 362 Stock‑Based Compensation 274 161 34 Research & Development Credits 2,063 586 233 Deferred Revenue 1,791 — — Other Accruals 235 98 — Total Deferred Tax Assets $ 14,993 $ 11,631 $ 6,621 Valuation Allowance (14,993 ) (11,631 ) (6,621 ) Net Deferred Tax Assets $ — $ — $ —
Summary of Unrecognized Tax Benefits	The following table summarizes the activity related to unrecognized tax benefits (in thousands): For the year ended December 31, 2017 2016 2015 Tax Benefits: Unrecognized Benefit ‑ beginning of period $ 229 $ 93 $ 73 Gross Increases(Decreases) ‑ prior period tax positions 59 — — Gross Increases(Decreases) ‑ current period tax positions 515 136 20 Total Unrecognized Benefit ‑ end of period $ 803 $ 229 $ 93

Selected Unaudited Quarterly 29

Selected Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Unaudited Quarterly Financial Data	The following tables show a summary of the Company’s unaudited quarterly financial data for each of the four quarters of 2017 and 2016 (in thousands, except per share amounts): Three Months Ended December 31, 2017 September 30, 2017 June 30, 2017 March 31, 2017 Collaboration and service revenue $ 2,775 $ 909 $ 449 $ 449 Operating expenses 12,252 9,244 6,675 6,004 Other income (expense), net 200 163 73 81 Net loss (9,277 ) (8,172 ) (6,153 ) (5,474 ) Basic and diluted net loss per common share (1) $ (1.80 ) $ (1.59 ) $ (1.21 ) $ (1.05 ) Three Months Ended December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Collaboration and service revenue $ 450 $ 224 $ — $ — Operating expenses 5,374 3,699 3,636 2,297 Other income (expense), net 88 77 74 25 Net loss (4,836 ) (3,398 ) (3,562 ) (2,272 ) Basic and diluted net loss per common share (1) $ (0.96 ) $ (0.68 ) $ (0.72 ) $ (0.43 ) (1) Basic and diluted net loss per common share are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share information may not equal annual basic and diluted net loss per common share.

Formation and Business of the30

Formation and Business of the Company (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Capitalization, Equity [Line Items]
Net loss		$ (9,277)	$ (8,172)	$ (6,153)	$ (5,474)	$ (4,836)	$ (3,398)	$ (3,562)	$ (2,272)	$ (29,076)	$ (14,068)	$ (4,608)
Net cash used in operating activities										(28,247)	(2,291)	$ (4,183)
Cash, cash equivalents and investments		62,500								62,500
Accumulated deficit		$ (59,191)				$ (30,115)				$ (59,191)	$ (30,115)
IPO | Subsequent Event
Schedule of Capitalization, Equity [Line Items]
Shares issued (shares)	8,050,000
Proceeds from issuance initial public offering, net	$ 125,500
Over-Allotment Option | Subsequent Event
Schedule of Capitalization, Equity [Line Items]
Shares issued (shares)	1,050,000
Convertible Stock Converted into Shares of Common Stock | Subsequent Event
Schedule of Capitalization, Equity [Line Items]
Common shares issued upon conversion of convertible stock (shares)	9,629,405

Significant Accounting Polici31

Significant Accounting Policies - Reverse Stock Split (Details)	Jan. 08, 2018
Subsequent Event | Common Stock
Class of Stock [Line Items]
Number of shares issued for every share converted in reverse stock split	0.3707

Significant Accounting Polici32

Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017segmentfinancial_institution	Dec. 31, 2016financial_institution
Accounting Policies [Abstract]
Number of operating segments | segment	1
Number of financial institutions holding majority of Company cash and cash equivalents and investments in excess of federally insured limits | financial_institution	1	1
Individual investment limit as a percentage of the total investment portfolio (percent)	5.00%

Significant Accounting Polici33

Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of plant and equipment	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of plant and equipment	5 years

Significant Accounting Polici34

Significant Accounting Policies - Revenue Recognition (Details) - JT Torii - USD ($) $ in Millions	Aug. 10, 2016	Dec. 31, 2017	Sep. 30, 2017
Collaboration Agreement
Revenue Recognition, Milestone Method [Line Items]
Collaborative agreement, upfront payment received	$ 11
Collaborative arrangements, revenue recognition, initial performance period	6 years
Development and Regulatory Milestones
Revenue Recognition, Milestone Method [Line Items]
Collaborative arrangements, potential milestone proceeds	$ 28
Amount of revenue recognized for each milestone		$ 2
Commercial Milestone
Revenue Recognition, Milestone Method [Line Items]
Collaborative arrangements, potential milestone proceeds	15
Development and Regulatory Milestone, Preparation of Investigational New Drug Submission, Milestone One
Revenue Recognition, Milestone Method [Line Items]
Collaborative arrangements, potential milestone proceeds	2
Development and Regulatory Milestone, Preparation of Investigational New Drug Submission, Milestone Two
Revenue Recognition, Milestone Method [Line Items]
Collaborative arrangements, potential milestone proceeds	2
Non-substantive Milestones
Revenue Recognition, Milestone Method [Line Items]
Collaborative arrangements, potential milestone proceeds	$ 24
Research and Development Arrangement
Revenue Recognition, Milestone Method [Line Items]
Research and development arrangement, contract to perform for others, compensation earned			$ 0.8
Research and development expense			$ 0.5

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 60,958	$ 41,109
Fair Value Measurements | Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	19,963	22,226
Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	40,995	18,883
Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Corporate notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	46,098	26,108
Corporate notes | Fair Value Measurements | Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	5,103	7,225
Corporate notes | Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	40,995	18,883
Corporate notes | Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Government notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	6,175	11,193
Government notes | Fair Value Measurements | Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	6,175	11,193
Government notes | Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Government notes | Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	8,685	3,808
Money market funds | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	8,685	3,808
Money market funds | Fair Value Measurements | Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	8,685	3,808
Money market funds | Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	0	0
Money market funds | Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	$ 0	$ 0

Fair Value Measurements (Availa

Fair Value Measurements (Available-for-Sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Money market funds, amortized cost	$ 10,206	$ 4,027	$ 43,808	$ 273
Amortized cost	61,009	41,135
Unrealized gains	0	0
Unrealized losses	(51)	(26)
Fair value	60,958	41,109
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	46,133	26,134
Available-for-sale securities, unrealized gains	0	0
Available-for-sale securities, unrealized losses	(35)	(26)
Available-for-sale securities, fair value	46,098	26,108
Government notes
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, amortized cost	6,191	11,193
Available-for-sale securities, unrealized gains	0	0
Available-for-sale securities, unrealized losses	(16)	0
Available-for-sale securities, fair value	6,175	11,193
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Money market funds, amortized cost	8,685	3,808
Money market funds, unrealized gains	0	0
Money market funds, unrealized losses	0	0
Money market funds, fair value	$ 8,685	$ 3,808

Balance Sheets Components (Deta

Balance Sheets Components (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued personnel expenses	$ 1,108	$ 273
Accrued clinical and development expenses	2,250	245
Other	201	63
Total	$ 3,559	$ 581

Commitments and Contingencies38

Commitments and Contingencies (Details)	Oct. 01, 2017USD ($)ft²	Dec. 31, 2012USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Acquired Indefinite-lived Intangible Assets [Line Items]
Operating lease, term of contract	30 months
Operating lease, monthly expense	$ 55,000
Operating lease, rent expense			$ 400,000	$ 208,000	$ 7,000
Merck
Acquired Indefinite-lived Intangible Assets [Line Items]
Licensing fee		$ 1,000,000
Development and Regulatory Milestones | Merck
Acquired Indefinite-lived Intangible Assets [Line Items]
Collaborative arrangements, potential milestone payments		$ 25,000,000
CALIFORNIA
Acquired Indefinite-lived Intangible Assets [Line Items]
Leased office space, square footage | ft²	14,000

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Operating Lease Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Year ending December 31:
2,018	$ 656
2,019	675
2,020	173
Total future minimum lease payments	$ 1,504

Convertible Preferred Stock (De

Convertible Preferred Stock (Details)	1 Months Ended		12 Months Ended
	Jan. 31, 2018USD ($)shares	Jul. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2017USD ($)director$ / sharesshares	Dec. 31, 2015shares	Dec. 31, 2016$ / sharesshares
Class of Stock [Line Items]
Preferred stock authorized (shares) | shares			28,322,761		14,120,883
Preferred stock, par value per share (in USD per share)			$ 0.001
Number of directors common shareholders are entitled to elect | director			3
Threshold proceeds of public stock offering of Company common shares that triggers automatic conversion of preferred convertible shares into common shares | $			$ 40,000,000
Threshold price per share in public stock offering of Company common shares that triggers automatic conversion of preferred convertible shares into common shares (in USD per share)			$ 17.21
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized (shares) | shares			14,300		14,300
Issuance of preferred stock (shares) | shares				2,800
Preferred stock, par value per share (in USD per share)			$ 0.001		$ 0.001
Preferred stock, liquiditiy preference per share (in USD per share)			1,000
Preferred stock, dividend per annum (in USD per share)			$ 80
Number of directors preferred shareholders are entitled to elect | director			2
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized (shares) | shares			14,106,583		14,106,583
Issuance of preferred stock (shares) | shares				14,106,583
Preferred stock, par value per share (in USD per share)			$ 0.001		$ 0.001
Preferred stock, liquiditiy preference per share (in USD per share)			3.19
Preferred stock, dividend per annum (in USD per share)			$ 0.2552
Number of directors preferred shareholders are entitled to elect | director			2
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized (shares) | shares			14,201,878		0
Issuance of preferred stock (shares) | shares		11,854,463	11,854,463
Preferred stock, par value per share (in USD per share)			$ 0.001		$ 0.001
Preferred shares issued, price per share (in USD per share)		$ 4.26
Proceeds from issuance initial public offering, net | $		$ 50,500,000
Preferred stock, liquiditiy preference per share (in USD per share)			4.26
Preferred stock, dividend per annum (in USD per share)			$ 0.3408
Number of directors preferred shareholders are entitled to elect | director			1
IPO | Subsequent Event
Class of Stock [Line Items]
Shares issued (shares) | shares	8,050,000
Proceeds from issuance initial public offering, net | $	$ 125,500,000
Common shares issued upon conversion of convertible stock (shares) | shares	9,629,405
Over-Allotment Option | Subsequent Event
Class of Stock [Line Items]
Shares issued (shares) | shares	1,050,000

Convertible Preferred Stock - C

Convertible Preferred Stock - Convertible Preferred Stock Outstanding (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Preferred stock outstanding (shares)	25,975,346	14,120,883
Preferred stock, liquidation value	$ 109,800	$ 59,300
Preferred stock authorized (shares)	28,322,761	14,120,883
Preferred stock issued (shares)	25,975,346	14,120,883
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock outstanding (shares)	14,300	14,300	14,300	11,500
Preferred stock, liquidation value	$ 14,300	$ 14,300
Preferred stock authorized (shares)	14,300	14,300
Preferred stock issued (shares)	14,300	14,300
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock outstanding (shares)	14,106,583	14,106,583	14,106,583	0
Preferred stock, liquidation value	$ 45,000	$ 45,000
Preferred stock authorized (shares)	14,106,583	14,106,583
Preferred stock issued (shares)	14,106,583	14,106,583
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock outstanding (shares)	11,854,463	0	0	0
Preferred stock, liquidation value	$ 50,500	$ 0
Preferred stock authorized (shares)	14,201,878	0
Preferred stock issued (shares)	11,854,463	0

Common Stock (Details)

Common Stock (Details) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Common stock authorized (shares)	55,000,000	36,500,000
Common stock, par value per share (in USD per share)	$ 0.0001	$ 0.0001
Common stock reserved for issuance (shares)	12,548,103

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available under the Plan (shares)	12,548,103
Total stock‑based compensation expense	$ 1,452	$ 573	$ 65
Unamortized compensation expense	$ 7,300
Unamortized compensation expense, recognition period	2 years 10 months 24 days
Proceeds from the exercise of stock options	$ 34	0	98
Liability for early exercise of stock options	43	68
Aggregate grant date fair value of options vested during the year	539	$ 182	1
Aggregate instrinsic value of shares exercised during the year	$ 209		$ 0
Weighted average grant date fair value of options granted (in USD per share)	$ 5.56	$ 1.79	$ 0.15
Options exercised during the year (shares)		0
Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock‑based compensation expense	$ 791	$ 314	$ 1
Non-employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock‑based compensation expense	$ 661	$ 259	$ 64
2011 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available under the Plan (shares)	3,339,724		2,086,600
Shares available for issuenace under the Plan (shares)	411,772
Option vesting period	4 years
Options exercised during the year (shares)	18,535		317,405
2011 Stock Incentive Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option exercise price as a percent of fair value on grant date (percent)	100.00%
Option expiration period	10 years
Option vesting period	4 years
2011 Stock Incentive Plan | Incentive Stock Option Granted to Stockholder Holding 10% of the Company's Outstanding Capitalization
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option exercise price as a percent of fair value on grant date (percent)	110.00%
2011 Stock Incentive Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Early exercised restricted shares that had not vested	139,636	222,077
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock‑based compensation expense	$ 792	$ 257	$ 1
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock‑based compensation expense	$ 660	$ 316	$ 64

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option and Restricted Stock Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised (shares)		0
2011 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balances, beginning (shares)	1,485,132	0	0
Granted (shares)	1,040,329	1,485,132	317,405
Exercised (shares)	(18,535)		(317,405)
Balances, ending (shares)	2,506,926	1,485,132	0
Outstanding, exercise price per share (in USD per share)	$ 3.50	$ 1.99
Granted, exercise price per share (in USD per share)	5.56	$ 1.99	$ 0.31
Exercised, exercise price per share (in USD per share)	$ 1.83		$ 0.31
Options outstanding, weighted average remaining contractual term	8 years 9 months 15 days	9 years 3 months 26 days
Options outstanding, aggregate intrinsic value	$ 24,033,000	$ 3,805,000	$ 0
Early Exercised Stock Options | 2011 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised (shares)			(317,405)
Unvested options included in early exercise (shares)	138,864	218,216

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value Assumptions for Director, Employee and Non-Employee Grants (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			3 years 1 month 6 days
Volatility (percent)			74.00%
Volatility, minimum (percent)	75.00%	68.00%
Volatility, maximum (percent)	100.00%	74.00%
Risk-free interest rate, minimum (percent)	1.90%	1.30%
Risk-free interest rate, maximum (percent)	2.30%	2.10%
Risk-free interest rate (percent)			1.00%
Dividend yield (percent)	0.00%	0.00%	0.00%
Employees and Directors | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years	4 years 7 months 6 days
Employees and Directors | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Non-employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum (percent)	74.00%	84.00%	62.00%
Volatility, maximum (percent)	100.00%	86.00%	74.00%
Risk-free interest rate, minimum (percent)	2.10%	1.60%	0.50%
Risk-free interest rate, maximum (percent)	2.50%	2.50%	0.70%
Dividend yield (percent)	0.00%	0.00%	0.00%
Non-employees | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	8 years 3 months 18 days	9 years 3 months 18 days	1 year
Non-employees | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	10 years	10 years	1 year 9 months 18 days

Net Loss per Share Attributab46

Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss attributable to common stockholders, basic									$ (29,076)	$ (14,068)	$ (4,608)
Net loss attributable to common stockholders, diluted									$ (29,076)	$ (14,068)	$ (4,608)
Denominator:
Weighted‑average common shares outstanding (shares)									5,285,542	5,280,058	5,060,918
Less: weighted‑average common shares subject to repurchase (shares)									(177,421)	(292,925)	(325,770)
Weighted‑average number of common shares used to compute basic and diluted net loss per share (in shares)									5,108,121	4,987,133	4,735,148
Net loss per share attributable to common stockholders:
Basic and diluted (in USD per share)	$ (1.80)	$ (1.59)	$ (1.21)	$ (1.05)	$ (0.96)	$ (0.68)	$ (0.72)	$ (0.43)	$ (5.69)	$ (2.82)	$ (0.97)

Net Loss per Share Attributab47

Net Loss per Share Attributable to Common Stockholders - Antidilutive Shares (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of EPS	12,687,739	7,140,987	7,243,265
Convertible preferred stock issuable upon conversion to common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of EPS	9,629,405	5,234,800	5,234,800
Outstanding common stock subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of EPS	139,636	222,077	324,355
Stock options outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of EPS	2,506,926	1,485,132	0
Stock options available for issuance
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of EPS	411,772	198,978	1,684,110

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory Rate	34.00%	34.00%	34.00%
State Tax	1.00%	0.00%	6.00%
Permanent Differences	(3.00%)	0.00%	0.00%
Other	(1.00%)	0.00%	0.00%
General Business Credits	4.00%	2.00%	1.00%
Change in Valuation Allowance	(11.00%)	(36.00%)	(41.00%)
Tax Reform - Tax Rate Change	(24.00%)	0.00%	0.00%
Total	0.00%	0.00%	0.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
NOLs	$ 10,404	$ 10,458	$ 5,992
Depreciation and Amortization	226	328	362
Stock‑Based Compensation	274	161	34
Research & Development Credits	2,063	586	233
Deferred Revenue	1,791	0	0
Other Accruals	235	98	0
Total Deferred Tax Assets	14,993	11,631	6,621
Valuation Allowance	(14,993)	(11,631)	(6,621)
Net Deferred Tax Assets	$ 0	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Increase in valuation allowance	$ 3,400,000	$ 5,000,000	$ 1,900,000
Reduction in deferred tax assets resulting from the rate reduction	7,000,000
Accrued interest and penalties related to uncertain tax positions	0
Federal Tax
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	44,300,000	28,200,000
State Tax
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	15,000,000	15,000,000
Research Development Tax Credit | Federal Tax
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	2,100,000	500,000
Research Development Tax Credit | State Tax
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	$ 900,000	$ 400,000

Income Taxes - Uncertain Tax Po

Income Taxes - Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized Benefit - beginning of period	$ 229	$ 93	$ 73
Gross Increases(Decreases) ‑ prior period tax positions	59	0	0
Gross Increases(Decreases) ‑ current period tax positions	515	136	20
Unrecognized Benefit - end of period	$ 803	$ 229	$ 93

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Related Party Transaction [Line Items]
Accounts payable	$ 0		$ 0
Velocity Pharmaceutical Development, LLC | Development Services Fees
Related Party Transaction [Line Items]
Related party expenses	$ 1,000,000	$ 800,000

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	Jan. 08, 2018	Jan. 31, 2018USD ($)shares	Jan. 23, 2018shares	Dec. 31, 2017shares
Subsequent Event [Line Items]
Common stock reserved for issuance (shares)				12,548,103
Common Stock | Subsequent Event
Subsequent Event [Line Items]
Number of shares issued for every share converted in reverse stock split	0.3707
IPO | Subsequent Event
Subsequent Event [Line Items]
Shares issued (shares)		8,050,000
Proceeds from issuance initial public offering, net | $		$ 125.5
Common shares issued upon conversion of convertible stock (shares)		9,629,405
2018 Omnibus Incentive Plan | Subsequent Event
Subsequent Event [Line Items]
Common stock reserved for issuance (shares)			3,000,000
2018 Employee Stock Purchase Plan | Subsequent Event
Subsequent Event [Line Items]
Common stock reserved for issuance (shares)			325,000

Selected Unaudited Quarterly 54

Selected Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Collaboration and license revenue	$ 2,775	$ 909	$ 449	$ 449	$ 450	$ 224	$ 0	$ 0	$ 4,582	$ 674	$ 0
Operating expenses	12,252	9,244	6,675	6,004	5,374	3,699	3,636	2,297	34,175	15,006	4,608
Other income (expense), net	200	163	73	81	88	77	74	25	517	264	0
Net loss	$ (9,277)	$ (8,172)	$ (6,153)	$ (5,474)	$ (4,836)	$ (3,398)	$ (3,562)	$ (2,272)	$ (29,076)	$ (14,068)	$ (4,608)
Basic and diluted net loss per common share (in USD per share)	$ (1.80)	$ (1.59)	$ (1.21)	$ (1.05)	$ (0.96)	$ (0.68)	$ (0.72)	$ (0.43)	$ (5.69)	$ (2.82)	$ (0.97)