Sienna Biopharmaceuticals (SNNAQ) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 07, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	SNNA
Entity Registrant Name	Sienna Biopharmaceuticals, Inc.
Entity Central Index Key	1,656,328
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		20,538,906

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 88,601,000	$ 9,091,000
Restricted cash	181,000	109,000
Prepaid expenses and other current assets	2,044,000	1,323,000
Total current assets	90,826,000	10,523,000
Property and equipment, net	368,000	291,000
In-process research and development	46,938,000	41,863,000
Goodwill	11,313,000	9,698,000
Other assets	3,000	2,000
Total assets	149,448,000	62,377,000
Current liabilities:
Accounts payable	1,579,000	1,691,000
Accrued personnel costs	1,739,000	959,000
Other accrued expenses	5,275,000	2,097,000
Contingent consideration, current portion	4,675,000	4,764,000
Early exercise liability, current portion	242,000	372,000
Total current liabilities	13,510,000	9,883,000
Contingent consideration-net of current portion	22,625,000	19,346,000
Early exercise liability-net of current portion	311,000	444,000
Success payment liability	5,794,000	1,262,000
Deferred tax liability	10,812,000	9,325,000
Total liabilities	53,052,000	40,260,000
Commitments and contingencies (Note 10)
Stockholders' equity:
Common stock, $0.0001 par value, 300,000,000 and 120,531,000 shares authorized, 20,531,000 and 2,616,000 shares issued and 19,931,000 and 1,719,000 outstanding at September 30, 2017 and December 31, 2016, respectively	3,000	1,000
Additional paid in capital	166,402,000	(1,683,000)
Accumulated other comprehensive income (loss)	4,699,000	(366,000)
Accumulated deficit	(74,708,000)	(35,352,000)
Total stockholders' equity	96,396,000	22,117,000
Total liabilities and stockholders' equity	$ 149,448,000	62,377,000
Series A-1 Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value		328,000
Series A-2 Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value		1,455,000
Series A-3 Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value		$ 57,734,000

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Preferred stock, par value	$ 0.0001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	120,531,000
Common stock, shares issued	20,531,000	2,616,000
Common stock, shares outstanding	19,931,000	1,719,000
Series A-1 Preferred Stock [Member]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	0	2,189,000
Preferred stock, shares issued	0	373,000
Preferred stock, shares outstanding	0	373,000
Series A-2 Preferred Stock [Member]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	0	6,466,000
Preferred stock, shares issued	0	1,102,000
Preferred stock, shares outstanding	0	1,102,000
Series A-3 Preferred Stock [Member]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	0	47,008,000
Preferred stock, shares issued	0	8,008,000
Preferred stock, shares outstanding	0	8,008,000

Condensed Consolidated Statemen

Condensed Consolidated Statement of Operations and Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating expenses:
Research and development	$ 9,398,000	$ 2,746,000	$ 21,020,000	$ 7,165,000
General and administrative	4,924,000	1,581,000	13,562,000	6,125,000
Total operating expenses	14,322,000	4,327,000	34,582,000	13,290,000
Loss from operations	(14,322,000)	(4,327,000)	(34,582,000)	(13,290,000)
Other income	307,000	217,000	318,000	416,000
Interest and other expense	(2,461,000)		(5,304,000)
Net loss before taxes	(16,476,000)	(4,110,000)	(39,568,000)	(12,874,000)
Income tax benefit	85,000		212,000
Net loss	(16,391,000)	(4,110,000)	(39,356,000)	(12,874,000)
Other comprehensive income:
Cumulative translation adjustment	1,588,000		5,065,000
Comprehensive loss	$ (14,803,000)	$ (4,110,000)	$ (34,291,000)	$ (12,874,000)
Per share information:
Net loss, basic and diluted	$ (1.12)	$ (2.42)	$ (6.31)	$ (7.61)
Basic and diluted weighted average shares outstanding	14,674,000	1,697,000	6,233,000	1,692,000

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (39,356,000)	$ (12,874,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	80,000	44,000
Amortization of debt discount	729,000
Stock-based compensation	1,055,000	277,000
Fair value adjustment of success payment liability	4,532,000	(331,000)
Fair value adjustment of contingent consideration	3,190,000
Non-cash interest expense	34,000
Loss on disposal of property and equipment	5,000
Changes in assets and liabilities:
Prepaid expenses and other current assets	(701,000)	(498,000)
Restricted cash	(72,000)	(115,000)
Accounts payable and other accrued liabilities	3,501,000	773,000
Net cash used in operating activities	(27,003,000)	(12,724,000)
Investing activities
Investment in property and equipment	(170,000)	(149,000)
Proceeds from sale of property and equipment	8,000
Net cash used in investing activities	(162,000)	(149,000)
Financing activities
Proceeds from issuance of common stock, net of early exercise liability	188,000	774,000
Proceeds from issuance of convertible promissory notes	3,906,000
Proceeds from initial public offering, net of issuance costs	66,378,000
Net cash provided by financing activities	106,778,000	28,787,000
Effect of exchange rate changes on cash	(103,000)
Net increase in cash and cash equivalents	79,510,000	15,914,000
Cash and cash equivalents at beginning of period	9,091,000	4,962,000
Cash and cash equivalents at end of period	88,601,000	20,876,000
Supplemental disclosures
Preferred stock issued upon conversion of notes payable	3,940,000
Preferred stock issued relating to beneficial conversion feature of notes payable	729,000
Shares issued for services		50,000
Series A-3 Preferred Stock [Member]
Financing activities
Net proceeds from issuance of preferred stock		$ 28,013,000
Series B Preferred Stock [Member]
Financing activities
Net proceeds from issuance of preferred stock	$ 36,306,000

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Organization and Description of Business	1. Organization and Description of Business In these notes to the unaudited condensed consolidated financial statements, the “Company,” “Sienna,” “we,” “us,’” and “our” refers to Sienna Biopharmaceuticals, Inc. (formerly Sienna Labs, Inc.) and its subsidiaries on a consolidated basis. Sienna Biopharmaceuticals, Inc., was incorporated on July 27, 2010, under the laws of the State of Delaware and is headquartered in Westlake Village, California. The Company is a clinical-stage biopharmaceutical company focused on bringing innovations in biotechnology to the discovery, development and commercialization of first-in-class, On July 20, 2017, the Company amended and restated its certificate of incorporation, giving effect to a 1-for-5.87 On August 1, 2017, the Company completed its initial public offering, or IPO, of 4,983,333 shares of common stock, which included the exercise in full by the underwriters of their option to purchase up to 650,000 additional shares of common stock, at an offering price to the public of $15.00 per share. The Company received net proceeds of approximately $66,378,000, after deducting underwriting discounts, commissions and offering related transaction costs. In connection with the IPO, the Company’s outstanding shares of convertible preferred stock were automatically converted into 12,847,000 shares of common stock. As of September 30, 2017, the Company had 19,931,000 shares of common stock outstanding. See Note 12, “Stockholders’ Equity.” In connection with the completion of its IPO, on August 1, 2017, the Company’s certificate of incorporation was amended and restated to provide for 300,000,000 authorized shares of common stock with a par value of $0.0001 per share and 10,000,000 authorized shares of preferred stock with a par value of $0.0001 per share.

Liquidity Risks

Liquidity Risks	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity Risks	2. Liquidity Risks The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had an accumulated deficit of $74,708,000 and $35,352,000 as of September 30, 2017 and December 31, 2016, respectively. The Company had net losses of $16,391,000 and $39,356,000 for the three and nine months ended September 30, 2017 and $4,110,000 and $12,874,000 for the three and nine months ended September 30, 2016, respectively, and net cash used in operating activities of $27,003,000 and $12,724,000 for the nine months ended September 30, 2017 and 2016, respectively. The Company has historically financed its operations primarily through private equity issuances and debt offerings, and more recently through its IPO. The Company had cash and cash equivalents of $88,601,000 and $9,091,000 at September 30, 2017 and December 31, 2016, respectively. This amount will fund operations through at least the next twelve months based on the expected cash burn rate. The Company will be required to raise additional capital to fund future operations through the sale of its equity securities, incurring debt, entering into licensing or collaboration agreements with partners, grants or other sources of financing. If the Company is unable to obtain additional funding from these or other sources when needed, or to the extent needed, it may be necessary to significantly reduce its current rate of spending through reductions in staff and delaying, scaling back, or stopping certain research and development programs. Insufficient liquidity may also require the Company to relinquish rights to product candidates at an earlier stage of development or on less favorable terms to it or its stockholders than the Company would otherwise choose.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	3. Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP, and the applicable rules and regulations of the Securities and Exchange Commission, or the SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted. Unaudited Condensed Consolidated Financial Statements The accompanying financial information for the three and nine months ended September 30, 2017 and 2016, are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of September 30, 2017 and its results of operations for the three and nine months ended September 30, 2017 and 2016 and cash flows for the nine months ended September 30, 2017 and 2016. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other period(s). Principles of Consolidation The unaudited condensed consolidated financial statements include the accounts of Sienna Biopharmaceuticals, Inc. and results of its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. The results of the subsidiaries’ operations were insignificant in the three and nine months ended September 30, 2017 and 2016. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. The most significant estimates in the Company’s consolidated financial statements relate to equity awards, the success payment liability, clinical trial accruals and the valuation of the in-process Cash and Cash Equivalents The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, and obligations issued by U.S. government and U.S. government agencies, and places restrictions on maturities and concentration by type and issuer. The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. As of September 30, 2017, cash and cash equivalents are comprised of funds in cash and U.S. Treasury money market funds. From time to time, the Company maintains cash balances in excess of amounts insured by the Federal Deposit Insurance Corporation. The accounts are monitored by management to mitigate the risk. Fair Value Measurements The Company’s financial instruments, in addition to those presented in Note 7, “Fair Value Measurements”, include cash and cash equivalents, restricted cash, accounts payable, and accrued liabilities. The carrying amount of cash and cash equivalents, restricted cash, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments. In-process Intangible assets acquired in a business combination are recognized separately from goodwill and are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Intangible assets related to in-process Goodwill represents the excess of the purchase price over the estimated fair value of the identifiable assets acquired and liabilities assumed in a business combination. The Company evaluates goodwill for impairment annually and upon the occurrence of triggering events or substantive changes in circumstances that could indicate a potential impairment. An impairment loss is recognized when the fair value of the reporting unit to which the goodwill relates is below its carrying value for the difference between the fair value and its carrying amounts. There was no impairment of goodwill for the nine months ended September 30, 2017 and the year ended December 31, 2016. Research and Development Costs Research and development costs are expensed as incurred. These costs include direct program expenses, which are payments made to third parties that specifically relate to the Company’s research and development, such as payments to clinical research organizations, clinical investigators, manufacturing of clinical material, pre-clinical Stock-Based Compensation The Company measures employee and director stock-based compensation expense for all stock based awards at the grant date based on the fair value measurement of the award. The expense is recorded on a straight-line basis over the requisite service period, which is generally the vesting period, for the entire award. Expense is adjusted for actual forfeitures of unvested awards as they occur. The Company calculates the fair value measurement of stock options using the Black-Scholes valuation model. The Company accounts for stock options issued to non-employees ASC 505-50, Non-employees, re-measuring Clinical Trial Accruals As part of the process of preparing its consolidated financial statements, the Company is required to estimate its expenses resulting from its obligations under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate trial expenses in its consolidated financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials, or the services completed. During the course of a clinical trial, the Company adjusts its rate of clinical expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date in its consolidated financial statements based on the facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through September 30, 2017, there have been no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. The Company’s clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations and other third-party vendors. Prepaid expenses and other current assets include prepaid clinical trial costs of $625,000 and $936,000 as of September 30, 2017 and December 31, 2016, respectively. Other accrued expenses include accrued clinical trial costs of $459,000 as of September 30, 2017. There were no accrued clinical trial costs as of December 31, 2016. Basic and Diluted Net Loss Per Common Share Basic net loss per common share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, excluding the effects of converting preferred stock, stock options and unvested restricted stock outstanding. Diluted net loss per common share is computed by dividing the net loss by the sum of the weighted average number of shares of common stock outstanding during the period plus the potential dilutive effects of convertible preferred stock, convertible notes, stock options and unvested restricted stock outstanding during the period calculated in accordance with the treasury stock method, but are excluded if their impact is anti-dilutive. Because the impact of these items is anti-dilutive during periods of net loss, there was no difference between the weighted average number of shares used to calculate basic and diluted net loss per common share for the three and nine months ended September 30, 2017 and 2016. Shares excluded from the calculation were 1,655,000 and 10,157,000 at September 30, 2017 and 2016, respectively. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred taxes are recognized based on the differences between financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has provided a full valuation allowance on its deferred tax assets. The provision for income taxes represents the current tax payable for the period and the change during the period in deferred tax assets and liabilities. The Company recognizes the effect of an income tax position only if, based on its merits, the position is more likely than not to be sustained on audit by the taxing authorities. Interest and penalties related to uncertain tax positions are recorded as income tax expense. Foreign currency translation The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. These include the entities acquired as part of the Creabilis acquisition. See Note 4, “Creabilis Acquisition”. As part of this transaction, the Company acquired entities in the United Kingdom, denominated in British pounds, and Italy and Luxembourg, denominated in euros. The U.S. dollar effects that arise from translating net assets of these subsidiaries at changing rates are recognized in other comprehensive loss in the condensed consolidated balance sheet. The earnings or loss of these subsidiaries are translated into U.S. dollars using average exchange rates for the periods. Recently Issued Accounting Standards Accounting Pronouncements Adopted In January 2017, the FASB issued ASU 2017-04: “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”), Accounting Pronouncements Being Evaluated In May 2014, the FASB issued ASU 2014-09, ASU 2014-09 In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842), In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)” (“ASU 2016-15”), In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). No. 2016-18 beginning-of-period end-of-period In January 2017, the FASB issued ASU 2017-01 “Business Combinations (Topic 805): Clarifying the Definition of a Business”, In May 2017, the FASB issued ASU 2017-09, Compensation Stock Compensation (Topic 718): Scope of Modification Accounting

Creabilis Acquisition

Creabilis Acquisition	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Creabilis Acquisition	4. Creabilis Acquisition In December 2016, the Company entered into a Share Purchase Agreement, or the Purchase Agreement, to acquire the entire issued share capital of Creabilis. Pursuant to the acquisition of Creabilis, the Company obtained SNA-120, SNA-125 SNA-120 first-in-class SNA-125 Upon closing, Creabilis became a direct wholly owned subsidiary in exchange for an upfront payment of approximately $212,000 in cash, 1,407,679 shares of Series A-3 The Company’s first contingent payment relates to the commencement of a confirmatory Phase 2b trial for SNA-120 SNA-120. The transaction has been accounted for as a business combination under the acquisition method of accounting. Accordingly, the tangible assets and identifiable intangible assets acquired and liabilities assumed have been recorded at fair value, with the remaining purchase price recorded as goodwill. The fair values of current assets and liabilities approximated their book or payoff value. The Company utilized a third-party valuation firm to assist in the determination of the fair values of acquired assets and liabilities, which are based on preliminary cash flow projections and other assumptions. The fair values of acquired intangible assets were determined using several significant unobservable inputs for projected cash flows and discount rates as discussed in Note 5, “Identifiable Intangible Assets”. These inputs are considered Level 3 inputs under the fair value measurements and disclosure guidance. The Company acquired tangible assets consisting of cash of $123,000, prepaid expenses and other current assets of $334,000, property and equipment of $6,000, financial investments of $3,000, and identifiable intangible assets of $42,254,000 related to in-process in-process The agreement to pay the future milestones and potential one-time The Company recorded a deferred tax liability of $9,412,000 for the non-deductible in-process For the three and nine months ended September 30, 2017, Creabilis’ net loss included in the Company’s consolidated statement of operations was $327,000 and $1,449,000, respectively.

Identifiable Intangible Assets

Identifiable Intangible Assets	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Identifiable Intangible Assets	5. Identifiable Intangible Assets The Company’s only identifiable intangible assets were in-process SNA-120 SNA-125 in-process in-process Identifiable intangible assets are initially measured at their respective fair values and will not be amortized until commercialization. If commercialization occurs, intangible assets will be amortized over their estimated useful lives. In-process

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consisted of the following as of September 30, 2017 and December 31, 2016: Estimated September 30, December 31, Lab equipment 5 $ 307,000 $ 236,000 Computer hardware 3 108,000 68,000 Capital lease equipment 3 46,000 46,000 Furniture and fixtures 5 67,000 43,000 Leasehold improvements 33,000 20,000 Total 561,000 413,000 Less accumulated depreciation (193,000 ) (122,000 ) Property and equipment, net $ 368,000 $ 291,000 Leasehold improvements are depreciated over the lease term. Depreciation expense was $27,000 and $80,000, for the three and nine months ended September 30, 2017, and $18,000 and $44,000 for the three and nine months ended September 30, 2016, respectively.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 Level 2 Level 3 In certain cases where there is limited activity or less transparency around inputs to valuation, assets are classified as Level 3 within the valuation hierarchy. The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy as of September 30, 2017 and December 31, 2016: September 30, 2017 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 88,096,000 $ — $ — Total $ 88,096,000 $ — $ — Liabilities: Success payment liability $ — $ — $ 5,794,000 Contingent consideration — — 27,300,000 Total $ — $ — $ 33,094,000 December 31, 2016 Level 1 Level 2 Level 3 Liabilities: Success payment liability $ — $ — $ 1,262,000 Contingent consideration — — 24,110,000 Total $ — $ — $ 25,372,000 The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities: Success Payment Contingent Balance at December 31, 2016 $ 1,262,000 $ 24,110,000 Change in fair value due to re-measurement 4,532,000 3,190,000 Balance at September 30, 2017 $ 5,794,000 $ 27,300,000 Cash and cash equivalents At September 30, 2017, the Company’s cash equivalents are comprised of U.S. Treasury money market funds whose value is based upon quoted market prices in active markets for identical assets or liabilities with no adjustments applied. Accordingly, these investments are classified as Level 1 of the fair value measurements and disclosure guidance. Intangible assets In connection with the acquisition of Creabilis, the Company acquired intangible in-process in-process Contingent consideration The Company also agreed to pay additional amounts based on the achievement of certain development, approval and sales milestones. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going The fair value of the contingent consideration was determined by an independent third-party valuation firm applying the income approach. This approach calculates fair value by estimating future cash flows attributable to the IPR&D assets using several significant unobservable inputs, including risk adjusted discount rates ranging from 4.00% to 18.5%, projected future revenues and expenses based on the cumulative probabilities of multiple scenarios with individual probabilities ranging from 0.1% to 25.0%, and estimates of the timing of the achievement of the various product development, regulatory approval and sales milestones. Significant increases or decreases in any of the probabilities of success and other inputs would result in a significantly higher or lower fair value measurement, respectively. The change in fair value during the three and nine months ended September 30, 2017 was $1,100,000 and $3,190,000, respectively. Increases in the value were related to changes in external market factors and probability adjustments partially offset by decreases in the value related to assumptions regarding milestone payments and is recorded in general and administrative expense in the consolidated statements of operations. There was no change in fair value from the date of acquisition, December 6, 2016 to year end December 31, 2016. Success payment liability In October 2015, as a result of an agreement in which the Company agreed to pay certain stockholders success payments if the stock price of the Company’s common stock reached certain thresholds, the Company recorded a success payment liability. The success payment liability was recorded at fair value based on significant unobservable inputs, as discussed in Note 9, “Success Payment Liability”. The change in fair value during the three and nine months ended September 30, 2017 resulted in expense of $2,459,000 and $4,532,000, respectively, and was recorded to other expense in the consolidated statements of operations. During the three and nine months ended September 30, 2016, the change in fair value resulted in income of $203,000 and $331,000, respectively, and was recorded to other income in the consolidated statements of operations. The valuation of the fair value of the success payment liability uses assumptions the Company believes would be made by a market participant and the Company assesses these estimates on an on-going There were no transfers of assets or liabilities between the fair value measurement levels during the nine months ended September 30, 2017 or the year ended December 31, 2016.

Convertible Notes

Convertible Notes	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Convertible Notes	8. Convertible Notes In January 2017, the Company entered into a note purchase agreement pursuant to which the Company issued, in two tranches, subordinated convertible promissory notes (the “Series B Bridge Notes” and together with the note purchase agreement, the “Series B Bridge Note Agreements”) in an aggregate principal amount of $3,906,000. The Series B Bridge Notes provided for an annual interest rate of 6.0% and a maturity date of January 27, 2018. Under the terms of the Series B Bridge Note Agreements, under certain circumstances, the unpaid principal of the Series B Bridge Notes, including any accrued but unpaid interest thereon, would convert into shares of convertible preferred stock upon the closing of a future preferred stock financing that met specified criteria. Such conversion would be at a 15% discount to the per share price of the convertible preferred stock sold in the financing. In addition, the notes were voluntarily convertible into shares upon the occurrence of a non-qualified The conversion feature included a 15% discount in the convertible notes, which constituted a beneficial conversion feature, that was bifurcated and allocated to additional paid-in In April 2017, in connection with the Company’s Series B convertible preferred stock financing, the outstanding principal under the Series B Bridge Notes of $3,906,000, plus $34,000 of accrued interest, converted into an aggregate of 379,000 shares of Series B convertible preferred stock at a rate of $10.40 per share and the Series B Bridge Notes were cancelled. In connection with the IPO, the Series B convertible preferred stock was automatically converted into 379,000 shares of common stock. The remaining unamortized discount was recognized in interest expense in the consolidated statement of operations. Included in interest and other expense for the three and nine months ended September 30, 2017 is amortization of the debt discount of $0 and $729,000 and accrued interest expense of $0 and $34,000, respectively.

Success Payment Liability

Success Payment Liability	9 Months Ended
	Sep. 30, 2017
Text Block [Abstract]
Success Payment Liability	9. Success Payment Liability In October 2015, the Company entered into a letter agreement with certain stockholders pursuant to which the Company agreed to make success payments to such stockholders (the “Success Payment Agreement”). The agreement ends on its fifth anniversary in October 2020. Success payments are payable in cash or common stock at the Company’s sole discretion and will be owed in the event that the value of its common stock meets or exceeds certain specified share price thresholds on any of the following dates during the success payment period: (1) any date after the 90th day after the date on which the Company completes an initial public offering of its common stock; (2) the date on which the Company sells, leases, transfers, or exclusively licenses all or substantially all of its assets to another company; and (3) the date on which the Company merges or consolidates with or into another entity (other than a merger in which the pre-merger 90-day The amount of the success payment is determined based on whether the value of the common stock of the Company meets or exceeds certain specified share price thresholds, subject to adjustment for any stock dividend, stock split, combination of shares, or other similar events. Each success payment and the associated share price threshold is ascending from $10,000,000 payable at a share price threshold of $53.71 per share to $35,000,000 payable at $71.61 per share and with a maximum payment of $60,000,000 at a share price threshold of $107.42 per share. Each success payment is inclusive of any preceding payments, if previously made, such that the success payments to stockholders will not exceed $60,000,000 in the aggregate. Upon their issuance, the success payments did not require any future service to be provided by the recipients and as such, the success payments were accounted for under ASC 815, Derivatives and Hedging. Accordingly, the Company recorded an initial liability at fair value and re-measures re-measurement

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Operating Lease The Company entered into a 26-month 40-month During the three and nine months ended September 30, 2017, the Company incurred $167,000 and $425,000, respectively, for rent expense and $54,000 and $144,000, for the three and nine months ended September 30, 2016, respectively. License and Supply Agreement The Company has an exclusive license and supply agreement with nanoComposix, pursuant to which the Company owes minimum annual royalties of $50,000 or low single digit royalties on net sales of licensed products. Contingencies From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business, including those set forth in Part II, Item 1 “Legal Proceedings”. As of September 30, 2017, there are no matters where there is at least a reasonable probability that a material loss has been or will be incurred.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	11. Related Party Transactions Venvest Biotech, LLC Dr. Beddingfield, the Company’s President and Chief Executive Officer and a member of the Company’s board of directors, is an advisor to Venvest Biotech, LLC, or Venvest, and is considered a non-managing Series A-3 lock-up Stock Purchase Rights In January 2016, in connection with his commencement of employment with the Company, the Company’s board of directors granted Dr. Beddingfield, the Company’s President and Chief Executive Officer, the right to purchase 554,000 shares of the Company’s common stock for a purchase price of $2.35 per share, which the board of directors determined was the fair market value on the date of grant. With respect to 456,000 shares subject to the stock purchase right, 25% of the shares vest on the first anniversary of the grant, and 1/48th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date. With respect to 49,000 shares subject to the stock purchase right, 50% of the shares vest on the first date the volume-weighted average trading price of the Company’s common stock equals or exceeds $71.03 per share, and 1/24th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date. With respect to the remaining 49,000 shares subject to the stock purchase right, 50% of the shares vest upon achievement of a milestone related to clinical development, and 1/24th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date. The Company determined that the stock purchase rights effectively represented an option and the fair value of the option was $558,000, which is being amortized as compensation expense over the performance period of the award with $36,000, $108,000, $31,000 and $88,000, recognized as compensation expense for the three and nine months ended September 30, 2017 and 2016, respectively. In May 2016, Dr. Beddingfield exercised his stock purchase rights in full and purchased restricted stock that vests on the same schedule as the stock purchase rights by providing a promissory note to the Company in the principal amount of $1,300,000, with an interest rate of 1.43% per annum. The promissory note was considered to be substantively non-recourse non-recourse, non-recourse Success Payments Todd Harris, the Company’s Head of Corporate Development and member of the Company’s board of directors, is a beneficiary of the Success Payments Agreement, as described in Note 9 “Success Payment Liability”, and will receive 25.22% of any related payouts.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity As of September 30, 2017, the authorized stock of the Company was 300,000,000 shares of common stock, $0.0001 par value per share, and 10,000,000 shares of preferred stock, $0.0001 par value per share. Common Stock Holders of common stock are entitled to one vote per share and, upon liquidation, dissolution, or winding up of the Company, are entitled to receive all assets available for distribution to stockholders. The holders have no preemptive or other subscription rights and there are no redemption or sinking fund provisions with respect to such shares. Shares of common stock reserved for future issuance were as follows as of September 30, 2017: September 30, 2017 Common stock awards outstanding 1,055,000 Common stock awards available for grant 1,438,000 Total shares of common stock reserved for future issuance 2,493,000 Convertible Preferred Stock As of September 30, 2017, there was no convertible preferred stock outstanding. In connection with the Company’s IPO, all outstanding shares of convertible preferred stock were automatically converted into 12,847,000 shares of common stock. As of December 31, 2016, there were 373,000 shares of Series A-1 Series A-2 Series A-3 In April 2017, the Company issued an aggregate of 2,985,000 shares of Series B convertible preferred stock at a price per share of $12.24 for aggregate proceeds of $36,532,000, exclusive of 379,000 shares of Series B convertible preferred stock issued upon conversion of the Series B Bridge Notes. See Note 8 “Convertible Notes”. All of the Company’s outstanding Series B convertible preferred stock was automatically converted into common stock in connection with the IPO. Stock Awards and Stock-Based Compensation In July 2017, the Company’s board of directors approved the 2017 Incentive Award Plan, or the 2017 Plan, which became effective upon the completion of the IPO on August 1, 2017. The 2017 Plan serves as the successor incentive award plan to the Company’s 2010 Equity Incentive Plan, or the 2010 Plan, and has 1,380,000 shares of common stock available for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock-based awards, plus shares of common stock that were reserved for issuance pursuant to future awards under the 2010 Plan at the time the 2017 Plan became effective, plus shares represented by awards outstanding under the 2010 Plan that are forfeited or lapse unexercised and which following the effective date of the 2017 Plan are not issued under the 2010 Plan. In addition, the 2017 Plan reserve will increase on January 1, 2018 and each subsequent anniversary through 2027, by an amount equal to the lesser of (a) four percent of the shares of stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (b) such smaller number of shares of stock as determined by our board of directors; provided, however, that no more than 12,000,000 shares of stock may be issued upon the exercise of incentive stock options. The terms of awards pursuant to the 2017 Plan are determined by the administrator of the 2017 Plan. The 2017 Plan is administered by the compensation committee of the Company’s board of directors unless the Company’s board of directors assumes authority for administration. In addition, the Company’s board of directors has delegated authority to grant awards to employees other than executive officers and certain senior executives of the Company to a committee consisting of the Company’s chief executive officer. Stock options granted pursuant to the 2017 Plan must have an exercise price of not less than the fair market value of the Company’s common stock on the date of grant, except that incentive stock options granted to an individual who owns (or is deemed to own) at least 10% of the total combined voting power of all classes of the Company’s capital stock (a “10% Holder”), must have an exercise price of at least 110% of the fair market value of a share of common stock on the date of grant. Stock options granted under the 2017 Plan generally expire ten years from the date of the grant, except that incentive stock options granted to a 10% Holder must not be exercisable after five years from the date of grant. The Company’s stock awards under the 2017 Plan vest based on terms in the stock award agreements and generally vest over four years. Following the Company’s IPO and in connection with the effectiveness of the Company’s 2017 Plan, the 2010 Plan terminated and no further awards will be granted under that plan. However, all outstanding awards under the 2010 Plan will continue to be governed by their existing terms. The fair value of each employee award granted during 2016 and during the nine months ended September 30, 2017 was estimated on the grant date using the Black-Scholes option-pricing model. The fair value of each non-employee option granted was estimated on the grant date and subsequently re-measured Nine Months Year Ended Expected stock price volatility 59.61%–64.09% 46.72%–54.76% Expected dividend yield —% —% Expected term (in years) 5.4–10.0 4.0–10.0 Risk-free interest rate 1.77%–2.60% 1.12%–2.42% Due to limited historical data, the Company estimates stock price volatility based on the actual volatility of comparable publicly traded companies over the expected life of the award. The Company has never paid, and does not expect to pay dividends in the foreseeable future. The expected term represents the average time that awards that vest are expected to be outstanding. For employee awards that have an early exercise provision, the Company has sufficient information to utilize four years as an expected term. For awards without an early exercise provision, the Company does not have sufficient history of stock option exercises to estimate the expected term and, thus, calculates expected term using the simplified method, based on the midpoint between the average vesting date and the contractual term. For all non-employees, No. 2016-09, The table below summarizes the stock option activity for the nine months ended September 30, 2017: Number Weighted Aggregate Outstanding at December 31, 2016 573,000 $ 2.35 $ 1,412,000 Granted 582,000 10.81 170,000 Exercised (92,000 ) 2.35 (260,000 ) Cancelled (8,000 ) 2.35 (19,000 ) Outstanding at September 30, 2017 1,055,000 $ 7.02 $ 16,082,000 Exercisable at September 30, 2017 123,000 $ 2.39 $ 2,441,000 The Company granted non-employee Non-cash Three months ended Nine months ended 2017 2016 2017 2016 Research and development $ 201,000 $ 16,000 $ 279,000 $ 72,000 General and administrative 540,000 54,000 776,000 205,000 $ 741,000 $ 70,000 $ 1,055,000 $ 277,000 As of September 30, 2017, there was $5,980,000 of unrecognized compensation expense related to unvested employee stock award agreements, which is expected to be recognized over a weighted-average period of approximately 3.53 years. For stock option awards subject to graded vesting, we recognize compensation cost on a straight-line basis over the service period for the entire award. The weighted-average grant date fair value of all stock options granted during the nine months ended September 30, 2017 was $7.03. The weighted-average remaining contractual life of options outstanding at September 30, 2017 is 9.19 years. The total fair value of the shares vested during the nine months ended September 30, 2017 was $903,000. Additionally, stock compensation expense includes $427,000, $500,000, $8,000 and $21,000, related to non-employee Prior to its termination in connection with the effectiveness of the 2017 Plan, the 2010 Plan allowed the Company to grant to employees the right to exercise stock options in exchange for cash before the requisite service was provided (e.g., before the award is vested under its original terms); however, such arrangements permit the Company to subsequently repurchase such shares at the exercise price if the employee ceases to be a service provider. Such an exercise is not substantive for accounting purposes. Therefore, the payment received for the exercise price is recognized as an early exercise liability in the consolidated balance sheets and will be transferred to common stock and additional paid-in non-current 2017 Employee Stock Purchase Plan The Company adopted the 2017 Employee Stock Purchase Plan, or the ESPP, which became effective upon the completion of the IPO on August 1, 2017. The ESPP is designed to allow the Company’s eligible employees to purchase shares of the Company’s common stock, at semi-annual intervals, with their accumulated payroll deductions. Under the ESPP, participants are offered the option to purchase shares of the Company’s common stock at a discount during a series of successive offering periods. The option purchase price will be the lower of 85% of the closing trading price per share of the Company’s common stock on the first trading date of an offering period in which a participant is enrolled or 85% of the closing trading price per share on the purchase date, which will occur on the last trading day of each offering period. The Company has not yet commenced an offering period. The ESPP is intended to qualify under Section 423 of the U.S. Internal Revenue Service Code of 1986, as amended. The maximum number of the Company’s common stock which will be authorized for sale under the ESPP is equal to the sum of (a) 198,883 shares of common stock and (b) an annual increase on the first day of each year beginning in 2018 and ending in 2027, equal to the lesser of (i) 1% of the shares of common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company’s board of directors; provided, however, no more than 3,000,000 shares of the Company’s common stock may be issued under the ESPP.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes Intraperiod tax allocation rules require the Company to allocate the provision for income taxes between continuing operations and other categories of earnings. As a result, for the nine months ended September 30, 2017 the Company recorded a $212,000 income tax benefit in the consolidated statement of operations. The Company has evaluated the available evidence supporting the realization of its deferred tax assets, including the amount and timing of future taxable income, and has determined that it is more likely than not that its net deferred tax assets will not be realized in the U.S. and certain foreign jurisdictions. Due to uncertainties surrounding the realization of the deferred tax assets, the Company maintains a full valuation allowance against substantially all deferred tax assets. When the Company determines that it will be able to realize some portion or all of its deferred tax assets, an adjustment to its valuation allowance on its deferred tax assets would have the effect of increasing net income in the period such determination is made. As of September 30, 2017, the Company does not have any accrued interest or penalties related to uncertain tax positions. The Company’s policy is to recognize interest and penalties related to uncertain tax positions in income tax expense. The Company is subject to U.S. federal tax authority and U.S. state tax authority examinations for all years with the net operating loss and credit carryforwards.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On October 24, 2017, the Company announced that the first patient had been dosed in the Phase 2b clinical trial of topical product candidate SNA-120 SNA-120 mild-to-moderate 20-day

Significant Accounting Polici20

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP, and the applicable rules and regulations of the Securities and Exchange Commission, or the SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted.
Unaudited Condensed Consolidated Financial Statements	Unaudited Condensed Consolidated Financial Statements The accompanying financial information for the three and nine months ended September 30, 2017 and 2016, are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position as of September 30, 2017 and its results of operations for the three and nine months ended September 30, 2017 and 2016 and cash flows for the nine months ended September 30, 2017 and 2016. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other period(s).
Principles of Consolidation	Principles of Consolidation The unaudited condensed consolidated financial statements include the accounts of Sienna Biopharmaceuticals, Inc. and results of its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. The results of the subsidiaries’ operations were insignificant in the three and nine months ended September 30, 2017 and 2016.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. The most significant estimates in the Company’s consolidated financial statements relate to equity awards, the success payment liability, clinical trial accruals and the valuation of the in-process
Cash and Cash Equivalents	Cash and Cash Equivalents The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, and obligations issued by U.S. government and U.S. government agencies, and places restrictions on maturities and concentration by type and issuer. The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. As of September 30, 2017, cash and cash equivalents are comprised of funds in cash and U.S. Treasury money market funds. From time to time, the Company maintains cash balances in excess of amounts insured by the Federal Deposit Insurance Corporation. The accounts are monitored by management to mitigate the risk.
Fair Value Measurements	Fair Value Measurements The Company’s financial instruments, in addition to those presented in Note 7, “Fair Value Measurements”, include cash and cash equivalents, restricted cash, accounts payable, and accrued liabilities. The carrying amount of cash and cash equivalents, restricted cash, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments.
In-process Research and Development and Goodwill	In-process Intangible assets acquired in a business combination are recognized separately from goodwill and are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Intangible assets related to in-process Goodwill represents the excess of the purchase price over the estimated fair value of the identifiable assets acquired and liabilities assumed in a business combination. The Company evaluates goodwill for impairment annually and upon the occurrence of triggering events or substantive changes in circumstances that could indicate a potential impairment. An impairment loss is recognized when the fair value of the reporting unit to which the goodwill relates is below its carrying value for the difference between the fair value and its carrying amounts. There was no impairment of goodwill for the nine months ended September 30, 2017 and the year ended December 31, 2016.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. These costs include direct program expenses, which are payments made to third parties that specifically relate to the Company’s research and development, such as payments to clinical research organizations, clinical investigators, manufacturing of clinical material, pre-clinical
Stock-Based Compensation	Stock-Based Compensation The Company measures employee and director stock-based compensation expense for all stock based awards at the grant date based on the fair value measurement of the award. The expense is recorded on a straight-line basis over the requisite service period, which is generally the vesting period, for the entire award. Expense is adjusted for actual forfeitures of unvested awards as they occur. The Company calculates the fair value measurement of stock options using the Black-Scholes valuation model. The Company accounts for stock options issued to non-employees ASC 505-50, Non-employees, re-measuring
Clinical Trial Accruals	Clinical Trial Accruals As part of the process of preparing its consolidated financial statements, the Company is required to estimate its expenses resulting from its obligations under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate trial expenses in its consolidated financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of consummation of trials, or the services completed. During the course of a clinical trial, the Company adjusts its rate of clinical expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date in its consolidated financial statements based on the facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through September 30, 2017, there have been no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. The Company’s clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations and other third-party vendors. Prepaid expenses and other current assets include prepaid clinical trial costs of $625,000 and $936,000 as of September 30, 2017 and December 31, 2016, respectively. Other accrued expenses include accrued clinical trial costs of $459,000 as of September 30, 2017. There were no accrued clinical trial costs as of December 31, 2016.
Basic and Diluted Net Loss Per Common Share	Basic and Diluted Net Loss Per Common Share Basic net loss per common share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, excluding the effects of converting preferred stock, stock options and unvested restricted stock outstanding. Diluted net loss per common share is computed by dividing the net loss by the sum of the weighted average number of shares of common stock outstanding during the period plus the potential dilutive effects of convertible preferred stock, convertible notes, stock options and unvested restricted stock outstanding during the period calculated in accordance with the treasury stock method, but are excluded if their impact is anti-dilutive. Because the impact of these items is anti-dilutive during periods of net loss, there was no difference between the weighted average number of shares used to calculate basic and diluted net loss per common share for the three and nine months ended September 30, 2017 and 2016. Shares excluded from the calculation were 1,655,000 and 10,157,000 at September 30, 2017 and 2016, respectively.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred taxes are recognized based on the differences between financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has provided a full valuation allowance on its deferred tax assets. The provision for income taxes represents the current tax payable for the period and the change during the period in deferred tax assets and liabilities. The Company recognizes the effect of an income tax position only if, based on its merits, the position is more likely than not to be sustained on audit by the taxing authorities. Interest and penalties related to uncertain tax positions are recorded as income tax expense.
Foreign currency translation	Foreign currency translation The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. These include the entities acquired as part of the Creabilis acquisition. See Note 4, “Creabilis Acquisition”. As part of this transaction, the Company acquired entities in the United Kingdom, denominated in British pounds, and Italy and Luxembourg, denominated in euros. The U.S. dollar effects that arise from translating net assets of these subsidiaries at changing rates are recognized in other comprehensive loss in the condensed consolidated balance sheet. The earnings or loss of these subsidiaries are translated into U.S. dollars using average exchange rates for the periods.
Recently Issued Accounting Standards	Recently Issued Accounting Standards Accounting Pronouncements Adopted In January 2017, the FASB issued ASU 2017-04: “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”), Accounting Pronouncements Being Evaluated In May 2014, the FASB issued ASU 2014-09, ASU 2014-09 In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842), In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)” (“ASU 2016-15”), In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). No. 2016-18 beginning-of-period end-of-period In January 2017, the FASB issued ASU 2017-01 “Business Combinations (Topic 805): Clarifying the Definition of a Business”, In May 2017, the FASB issued ASU 2017-09, Compensation Stock Compensation (Topic 718): Scope of Modification Accounting

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment consisted of the following as of September 30, 2017 and December 31, 2016: Estimated September 30, December 31, Lab equipment 5 $ 307,000 $ 236,000 Computer hardware 3 108,000 68,000 Capital lease equipment 3 46,000 46,000 Furniture and fixtures 5 67,000 43,000 Leasehold improvements 33,000 20,000 Total 561,000 413,000 Less accumulated depreciation (193,000 ) (122,000 ) Property and equipment, net $ 368,000 $ 291,000

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy as of September 30, 2017 and December 31, 2016: September 30, 2017 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 88,096,000 $ — $ — Total $ 88,096,000 $ — $ — Liabilities: Success payment liability $ — $ — $ 5,794,000 Contingent consideration — — 27,300,000 Total $ — $ — $ 33,094,000 December 31, 2016 Level 1 Level 2 Level 3 Liabilities: Success payment liability $ — $ — $ 1,262,000 Contingent consideration — — 24,110,000 Total $ — $ — $ 25,372,000
Summary of Changes in Fair Value of Level 3 Financial Liabilities	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities: Success Payment Contingent Balance at December 31, 2016 $ 1,262,000 $ 24,110,000 Change in fair value due to re-measurement 4,532,000 3,190,000 Balance at September 30, 2017 $ 5,794,000 $ 27,300,000

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Summary of Shares of Common Stock Reserved for Future Issuance	Shares of common stock reserved for future issuance were as follows as of September 30, 2017: September 30, 2017 Common stock awards outstanding 1,055,000 Common stock awards available for grant 1,438,000 Total shares of common stock reserved for future issuance 2,493,000
Summary of Assumptions Used for Grant Date Fair Value	The following assumptions were used for grant date fair value for the period ended September 30, 2017 and December 31, 2016: Nine Months Year Ended Expected stock price volatility 59.61%–64.09% 46.72%–54.76% Expected dividend yield —% —% Expected term (in years) 5.4–10.0 4.0–10.0 Risk-free interest rate 1.77%–2.60% 1.12%–2.42%
Summary of Stock Option Activity	The table below summarizes the stock option activity for the nine months ended September 30, 2017: Number Weighted Aggregate Outstanding at December 31, 2016 573,000 $ 2.35 $ 1,412,000 Granted 582,000 10.81 170,000 Exercised (92,000 ) 2.35 (260,000 ) Cancelled (8,000 ) 2.35 (19,000 ) Outstanding at September 30, 2017 1,055,000 $ 7.02 $ 16,082,000 Exercisable at September 30, 2017 123,000 $ 2.39 $ 2,441,000
Summary of Non-cash Stock-based Compensation Expense	Non-cash Three months ended Nine months ended 2017 2016 2017 2016 Research and development $ 201,000 $ 16,000 $ 279,000 $ 72,000 General and administrative 540,000 54,000 776,000 205,000 $ 741,000 $ 70,000 $ 1,055,000 $ 277,000

Organization and Description 24

Organization and Description of Business - Additional Information (Detail)	Aug. 01, 2017USD ($)$ / sharesshares	Jul. 20, 2017	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2016$ / sharesshares
Organization And Description Of Business [Line Items]
Reverse stock split		0.17036
Net proceeds from initial public offering | $	$ 66,378,000		$ 66,378,000
Common stock, shares outstanding	19,931,000		19,931,000	1,719,000
Common stock, shares authorized	300,000,000		300,000,000	120,531,000
Common stock, par value | $ / shares	$ 0.0001		$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000		10,000,000	0
Preferred stock, par value | $ / shares	$ 0.0001		$ 0.0001
Common Stock [Member]
Organization And Description Of Business [Line Items]
Convertible preferred stock, as converted into common stock	12,847,000		12,847,000
Initial Public Offering [Member] | Common Stock [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares	4,983,333
Public offering price per share | $ / shares	$ 15
Over-Allotment Option [Member] | Common Stock [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares	650,000

Liquidity Risks - Additional In

Liquidity Risks - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Liquidity Risks [Abstract]
Accumulated deficit	$ (74,708,000)		$ (74,708,000)		$ (35,352,000)
Net losses	(16,391,000)	$ (4,110,000)	(39,356,000)	$ (12,874,000)
Net cash used in operating activities			$ (27,003,000)	(12,724,000)
Substantial doubt about going concern, within One year			false
Cash and cash equivalents	$ 88,601,000	$ 20,876,000	$ 88,601,000	$ 20,876,000	$ 9,091,000	$ 4,962,000

Significant Accounting Polici26

Significant Accounting Policies - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Impairments of intangible assets				$ 0	$ 0
Impairment of goodwill				0	0
Prepaid clinical trial costs	$ 625,000	$ 936,000
Accrued clinical trial costs	$ 459,000	$ 0		$ 459,000	$ 0
Shares excluded from calculation of earnings per share	1,655,000		10,157,000

Creabilis Acquisition - Additio

Creabilis Acquisition - Additional Information (Detail) - USD ($)	Dec. 06, 2016	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Deferred tax liability			$ 10,812,000		$ 10,812,000		$ 9,325,000
Goodwill			11,313,000		11,313,000		9,698,000
Goodwill impairment					0		0
Net loss			(16,391,000)	$ (4,110,000)	(39,356,000)	$ (12,874,000)
Creabilis [Member]
Business Acquisition [Line Items]
Upfront cash payment	$ 212,000
Business combination, settlement of liabilities	6,732,000
Business combination net working capital adjustment			236,000		236,000
Acquired tangible assets, cash	123,000
Acquired tangible assets, prepaid expenses and other current assets	334,000
Acquired tangible assets, property and equipment	6,000
Acquired tangible assets, financial investments	3,000
Acquired tangible assets, identifiable intangible assets	42,254,000
Acquired tangible assets, accounts payable	201,000
Acquired tangible assets, accrued expenses	494,000
Acquired tangible assets, accrued compensation	266,000
Acquired tangible assets, deferred tax liability	9,412,000
Net assets acquired	$ 32,347,000
Deferred tax liability			10,812,000		10,812,000		9,325,000
Deferred tax liability tax adjustments			321,000		321,000
Deferred tax liability translation adjustments			1,166,000		1,166,000
Goodwill			11,313,000		11,313,000		9,698,000
Change in fair value of goodwill					395,000
Translation adjustments of goodwill					(1,220,000)
Goodwill impairment					0		0
Net loss			(327,000)		(1,449,000)
Creabilis [Member] | Scenario, Forecast [Member]
Business Acquisition [Line Items]
Trading period preceding the commencement of the trial		20 days
Creabilis [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Business combination contingent consideration payable			$ 5,000,000		$ 5,000,000
Maximum [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Royalty percentage			1.00%		1.00%
Convertible Preferred Stock Series A Three [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination shares issued	1,407,679
Business combination shares issued, value	$ 11,155,000
Contingent Consideration [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Fair value of contingent consideration in acquisition	24,110,000		$ 27,300,000		$ 27,300,000		$ 24,110,000
Development and Approval Milestones [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration	58,000,000
Net Sales Thresholds and One Time Royalties [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration	80,000,000
In-process Research and Development Intangible Assets [Member]
Business Acquisition [Line Items]
Acquired tangible assets, identifiable intangible assets	42,254,000
In-process Research and Development Intangible Assets [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Goodwill	$ 9,788,000

Identifiable Intangible Assets

Identifiable Intangible Assets - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Dec. 06, 2016
Finite-Lived Intangible Assets [Line Items]
In-process research and development intangible assets, carrying value	$ 46,938,000	$ 41,863,000
In-process Research and Development Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets, initial value recorded			$ 42,254,000
Impairment recognized on identifiable intangible assets	$ 0	$ 0

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 561,000	$ 413,000
Less accumulated depreciation	(193,000)	(122,000)
Property and equipment, net	$ 368,000	$ 291,000
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years	5 years
Property, plant and equipment, gross	$ 307,000	$ 236,000
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years	3 years
Property, plant and equipment, gross	$ 108,000	$ 68,000
Capital Lease Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years	3 years
Property, plant and equipment, gross	$ 46,000	$ 46,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years	5 years
Property, plant and equipment, gross	$ 67,000	$ 43,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 33,000	$ 20,000

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense			$ 80,000	$ 44,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 27,000	$ 18,000	$ 80,000	$ 44,000

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Level 1 [Member]
Assets:
Cash equivalents	$ 88,096,000
Total	88,096,000
Level 3 [Member]
Liabilities:
Financial liabilities fair value	33,094,000	$ 25,372,000
Success Payment Liabilities [Member] | Level 3 [Member]
Liabilities:
Financial liabilities fair value	5,794,000	1,262,000
Contingent Consideration [Member] | Level 3 [Member]
Liabilities:
Financial liabilities fair value	$ 27,300,000	$ 24,110,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail)	9 Months Ended
	Sep. 30, 2017USD ($)
Success Payment Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1,262,000
Change in fair value due to re-measurement recorded in expense	4,532,000
Ending balance	5,794,000
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	24,110,000
Change in fair value due to re-measurement recorded in expense	3,190,000
Ending balance	$ 27,300,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value transfer amount				$ 0		$ 0
General and Administrative [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded income (expense)	$ 0	$ 1,100,000		3,190,000
Other Income [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded income (expense)			$ 203,000		$ 331,000
Other Expense [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded income (expense)		$ (2,459,000)		$ (4,532,000)
Creabilis [Member] | In-process Research and Development Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration				20.50%
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration				4.00%
Minimum [Member] | Creabilis [Member] | In-process Research and Development Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration				0.10%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration				18.50%
Maximum [Member] | Creabilis [Member] | In-process Research and Development Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration				22.50%

Convertible Notes - Additional

Convertible Notes - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Sep. 30, 2017	Sep. 30, 2017
Debt Conversion [Line Items]
Amortization of debt discount				$ 729,000
Series B Bridge Notes [Member]
Debt Conversion [Line Items]
Debt instrument face amount	$ 3,906,000	$ 3,906,000
Debt instrument face amount Debt instrument interest percentage		6.00%
Debt instrument maturity date		Jan. 27, 2018
Debt conversion discount percentage		15.00%
Debt principal and accrued interest				729,000
Amortization of debt discount		$ 729,000
Series B Bridge Notes [Member] | Series B Convertible Preferred Stock [Member]
Debt Conversion [Line Items]
Amortization of debt discount			$ 0	729,000
Number of shares issued on conversion of debt	379,000
Per share price of shares issued on conversion of debt	$ 10.40
Accrued interest expense	$ 34,000		$ 0	$ 34,000

Success Payment Liability - Add

Success Payment Liability - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2015
Success Payment Liability [Line Items]
Success payment liability threshold one			$ 10,000,000
Success payment liability threshold one per share			$ 53.71
Success payment liability threshold two			$ 35,000,000
Success payment liability threshold two per share			$ 71.61
Success payment liability threshold maximum			$ 60,000,000
Success payment liability threshold maximum per share			$ 107.42
Success payment liability	$ 60,000,000		$ 60,000,000		$ 694,000
Other Income [Member]
Success Payment Liability [Line Items]
Change in fair value due to re-measurement recorded income (expense)		$ 203,000		$ 331,000
Other Expense [Member]
Success Payment Liability [Line Items]
Change in fair value due to re-measurement recorded income (expense)	$ (2,459,000)		$ (4,532,000)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	May 01, 2015	May 31, 2016	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2017USD ($)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Other Commitments [Line Items]
Rent expense			$ 167,000	$ 54,000		$ 425,000	$ 144,000
Lease Arrangement - Office Space in Carlsbad, California [Member]
Other Commitments [Line Items]
Operating lease obligation period	26 months
Operating lease expiry date	Jun. 30, 2017
Operating lease renewal option term	3 years
Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Operating lease obligation period		40 months
Operating lease expiry date		Feb. 29, 2020
Amended Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Operating lease renewal option term					3 years
Additional area of office space leased | ft²					5,973
Maximum [Member] | Amended Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Additional allowance for leasehold improvements					$ 108,000
Minimum [Member]
Other Commitments [Line Items]
Annual royalties			$ 50,000			$ 50,000

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	May 31, 2016
Related Party Transaction [Line Items]
Number of nonvested shares		600,000		600,000			897,000
Recognized compensation expense				$ 1,055,000	$ 277,000
Notes Receivable [Member]
Related Party Transaction [Line Items]
Principal balance and interest forgiven on promissory note						$ 1,321,000
President and Chief Executive Officer [Member] | Stock Purchase Rights [Member]
Related Party Transaction [Line Items]
Number of shares granted under stock purchase rights	554,000
Purchase price of common stock	$ 2.35
Fair value of the option granted	$ 558,000
Recognized compensation expense		$ 36,000	$ 31,000	$ 108,000	$ 88,000
Number of shares vested				190,000
President and Chief Executive Officer [Member] | Stock Purchase Rights [Member] | Notes Receivable [Member]
Related Party Transaction [Line Items]
Principal amount of promissory note								$ 1,300,000
Interest rate percentage								1.43%
President and Chief Executive Officer [Member] | Share-based Compensation Award, Tranche One [Member] | Stock Purchase Rights [Member]
Related Party Transaction [Line Items]
Number of nonvested shares	456,000
Vesting condition description				25% of the shares vest on the first anniversary of the grant, and 1/48th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date.
Percentage of shares vest on first anniversary	25.00%
Percentage of shares vest monthly thereafter	0.02%
President and Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Two [Member] | Stock Purchase Rights [Member]
Related Party Transaction [Line Items]
Number of nonvested shares	49,000
Vesting condition description				50% of the shares vest on the first date the volume-weighted average trading price of the Company's common stock equals or exceeds $71.03 per share, and 1/24th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date.
Percentage of shares vest monthly thereafter	0.04%
Percentage of shares vesting	50.00%
Minimum vesting share price	$ 71.03
President and Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Three [Member] | Stock Purchase Rights [Member]
Related Party Transaction [Line Items]
Number of nonvested shares	49,000
Vesting condition description				50% of the shares vest upon achievement of a milestone related to clinical development, and 1/24th of the shares vest monthly thereafter, subject to Dr. Beddingfield continuing to provide services to the Company through each such vesting date.
Percentage of shares vest monthly thereafter	0.04%
Percentage of shares vesting	50.00%
President and Chief Executive Officer [Member] | Venvest Biotech LLC [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Distribution percentage based on gains on shares of capital stock				20.00%
Todd Harris [Member]
Related Party Transaction [Line Items]
Success payments liability related payouts percentage				25.22%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - $ / shares	Sep. 30, 2017	Aug. 01, 2017	Dec. 31, 2016
Class of Stock Disclosures [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000	120,531,000
Preferred stock, shares authorized	10,000,000	10,000,000	0
Preferred stock, par value	$ 0.0001	$ 0.0001

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Shares of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2017	Dec. 31, 2016
Class of Stock Disclosures [Abstract]
Common stock awards outstanding	1,055,000	573,000
Common stock awards available for grant	1,438,000
Total shares of common stock reserved for future issuance	2,493,000

Stockholders' Equity - Converti

Stockholders' Equity - Convertible Preferred Stock - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Apr. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Aug. 01, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred stock, shares outstanding			0		0
Common Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, as converted into common stock			12,847,000	12,847,000
Series B Convertible Preferred Stock Financing [Member]
Class of Stock [Line Items]
Aggregate proceeds from issuance of preferred stock	$ 36,532,000
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding			0
Series A-1 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding			0		373,000
Series A-2 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding			0		1,102,000
Series A-3 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding			0		8,008,000
Aggregate proceeds from issuance of preferred stock		$ 28,013,000
Series B Convertible Preferred Stock [Member] | Series B Convertible Preferred Stock Financing [Member]
Class of Stock [Line Items]
Per share price of shares issued on conversion of debt	$ 12.24
Number of shares issued on conversion of debt	2,985,000
Series B Convertible Preferred Stock [Member] | Series B Bridge Notes [Member]
Class of Stock [Line Items]
Per share price of shares issued on conversion of debt	$ 10.40
Number of shares issued on conversion of debt	379,000

Stockholders' Equity - Stock Aw

Stockholders' Equity - Stock Awards and Stock-Based Compensation - Additional Information (Detail) - USD ($)	Aug. 01, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jul. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common stock available for issuance under plan		2,493,000		2,493,000
Number of shares available to non-employee				582,000
Unrecognized compensation expense related to unvested employee stock award		$ 5,980,000		$ 5,980,000
Unrecognized compensation expense related to unvested employee stock award, recognized period				3 years 6 months 10 days
Weighted-average grant date fair value of stock options granted				$ 7.03
Weighted-average remaining contractual life of options outstanding				9 years 2 months 8 days
Fair value of shares vested				$ 903,000
Stock compensation expense related to non-employee option grants		$ 427,000	$ 8,000	$ 500,000	$ 21,000
Unvested shares		600,000		600,000			897,000
Early exercise liability related to unvested shares		$ 553,000		$ 553,000			$ 816,000
Early exercise liability related to unvested shares, current		242,000		242,000			372,000
Early exercise liability related to unvested shares, non-current		$ 311,000		$ 311,000			$ 444,000
2017 Incentive Award Plan [Member]
Class of Stock [Line Items]
Common stock available for issuance under plan						1,380,000
Incentive award plan, description				The 2017 Plan serves as the successor incentive award plan to the Company’s 2010 Equity Incentive Plan, or the 2010 Plan, and has 1,380,000 shares of common stock available for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock-based awards, plus shares of common stock that were reserved for issuance pursuant to future awards under the 2010 Plan at the time the 2017 Plan became effective, plus shares represented by awards outstanding under the 2010 Plan that are forfeited or lapse unexercised and which following the effective date of the 2017 Plan are not issued under the 2010 Plan. In addition, the 2017 Plan reserve will increase on January 1, 2018 and each subsequent anniversary through 2027, by an amount equal to the lesser of (a) four percent of the shares of stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (b) such smaller number of shares of stock as determined by our board of directors; provided, however, that no more than 12,000,000 shares of stock may be issued upon the exercise of incentive stock options.
2010 Equity Incentive Plan [Member]
Class of Stock [Line Items]
Stock awards expiration period				10 years
Stock awards vesting period				4 years
2017 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock under ESPP	198,883
Common stock shares outstanding percentage	1.00%
Employee stock purchase price closing trading price	85.00%
Employee stock purchase plan, description				The maximum number of the Company’s common stock which will be authorized for sale under the ESPP is equal to the sum of (a) 198,883 shares of common stock and (b) an annual increase on the first day of each year beginning in 2018 and ending in 2027, equal to the lesser of (i) 1% of the shares of common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company’s board of directors; provided, however, no more than 3,000,000 shares of the Company’s common stock may be issued under the ESPP.
Non-employee [Member]
Class of Stock [Line Items]
Contractual term				10 years
Number of shares available to non-employee				32,000
Maximum [Member]
Class of Stock [Line Items]
Fair value of a common stock percentage				110.00%
Maximum [Member] | 2017 Incentive Award Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock under ESPP						12,000,000
Maximum [Member] | 2010 Equity Incentive Plan [Member]
Class of Stock [Line Items]
Stock awards exercisable period				5 years
Maximum [Member] | 2017 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock under ESPP	3,000,000
Minimum [Member]
Class of Stock [Line Items]
Common stock voting rights percentage				10.00%
Minimum [Member] | 2017 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Employee stock purchase price lower of the closing trading price	85.00%

Stockholders' Equity - Summar42

Stockholders' Equity - Summary of Assumptions Used for Grant Date Fair Value (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility, minimum	59.61%	46.72%
Expected stock price volatility, maximum	64.09%	54.76%
Expected dividend yield	0.00%	0.00%
Risk-free interest rate, minimum	1.77%	1.12%
Risk-free interest rate, maximum	2.60%	2.42%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 4 months 24 days	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	10 years	10 years

Stockholders' Equity - Summar43

Stockholders' Equity - Summary of Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding, beginning balance | shares	573,000
Number of Shares, Granted | shares	582,000
Number of Shares, Exercised | shares	(92,000)
Number of Shares, Cancelled | shares	(8,000)
Number of Shares, Outstanding, ending balance | shares	1,055,000
Number of Shares, Exercisable, ending balance | shares	123,000
Weighted Average Exercise Price Per Share, Outstanding, beginning balance	$ 2.35
Weighted Average Exercise Price Per Share, Granted	10.81
Weighted Average Exercise Price Per Share, Exercised	2.35
Weighted Average Exercise Price Per Share, Cancelled	2.35
Weighted Average Exercise Price Per Share, Outstanding, ending balance	7.02
Weighted Average Exercise Price Per Share, Exercisable, ending balance	$ 2.39
Aggregate Intrinsic Value, Outstanding, beginning balance | $	$ 1,412,000
Aggregate Intrinsic Value, Granted	$ 170,000
Aggregate Intrinsic Value, Exercised | $	$ (260,000)
Aggregate Intrinsic Value, Cancelled | $	(19,000)
Aggregate Intrinsic Value, Outstanding, ending balance | $	16,082,000
Aggregate Intrinsic Value, Exercisable, ending balance | $	$ 2,441,000

Stockholders' Equity - Summar44

Stockholders' Equity - Summary of Non-cash Stock-based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 741,000	$ 70,000	$ 1,055,000	$ 277,000
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	201,000	16,000	279,000	72,000
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 540,000	$ 54,000	$ 776,000	$ 205,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income tax benefit	$ 85,000	$ 212,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member]	Oct. 24, 2017USD ($)Patient
Phase 2b Clinical Trial [Member]
Subsequent Event [Line Items]
Number of patients with moderate pruritus and mild-to-moderate psoriasis | Patient	190
Creabilis [Member]
Subsequent Event [Line Items]
Trading period preceding the commencement of the trial	20 days
Common Stock [Member] | Creabilis [Member]
Subsequent Event [Line Items]
Milestone payment | $	$ 5,000,000