Sienna Biopharmaceuticals (SNNAQ) 10-Q 8 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 06, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	SNNA
Entity Registrant Name	Sienna Biopharmaceuticals, Inc.
Entity Central Index Key	0001656328
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		30,541,978

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 57,169	$ 48,526
Restricted cash	181	181
Prepaid expenses and other current assets	1,319	1,705
Total current assets	58,669	50,412
Property and equipment, net	275	311
Operating lease right-of-use asset	772
In-process research and development	44,591	45,594
Goodwill	10,747	10,989
Total assets	115,054	107,306
Current liabilities:
Accounts payable	2,180	2,792
Accrued personnel costs	1,537	3,057
Other accrued expenses	4,136	5,000
Contingent consideration, current portion	14,600	13,500
Total current liabilities	22,453	24,349
Contingent consideration-net of current portion	19,200	15,700
Operating lease liability-net of current portion	587
Long-term debt, net	29,237	30,125
Deferred tax liability	10,272	10,503
Other long-term liabilities	19	48
Total liabilities	81,768	80,725
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.0001 par value, 10,000 shares authorized, no shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively
Common stock, $0.0001 par value, 300,000 shares authorized, 30,376 and 21,177 shares issued and 30,124 and 20,870 outstanding at March 31, 2019 and December 31, 2018, respectively	0	0
Additional paid in capital	206,886	182,750
Accumulated other comprehensive income	2,186	3,199
Accumulated deficit	(175,786)	(159,368)
Total stockholders' equity	33,286	26,581
Total liabilities and stockholders' equity	$ 115,054	$ 107,306

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
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	300,000,000
Common stock, shares issued	30,376,000	21,177,000
Common stock, shares outstanding	30,124,000	20,870,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating expenses:
Research and development	$ 7,093	$ 12,980
General and administrative	8,746	5,497
Total operating expenses	15,839	18,477
Loss from operations	(15,839)	(18,477)
Other income (expense), net	(543)	1,374
Net loss	(16,382)	(17,103)
Other comprehensive income (loss):
Cumulative translation adjustment	(1,013)	1,374
Comprehensive loss	$ (17,395)	$ (15,729)
Per share information:
Net loss, basic and diluted	$ (0.67)	$ (0.85)
Basic and diluted weighted average shares outstanding	24,606	20,228

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2017	$ 91,199		$ 171,726	$ 5,370	$ (85,897)
Beginning Balance, Shares at Dec. 31, 2017		20,194
Vesting of early exercised shares	70		70
Vesting of early exercised shares, shares		60
Stock-based compensation expense	901		901
Repurchase of early exercised common stock options	(18)		(18)
Repurchase of early exercised common stock options, shares		(8)
Foreign currency translation adjustments	1,374			1,374
Net loss	(17,103)				(17,103)
Ending Balance at Mar. 31, 2018	76,423		172,679	6,744	(103,000)
Ending Balance, Shares at Mar. 31, 2018		20,246
Beginning Balance at Dec. 31, 2017	91,199		171,726	5,370	(85,897)
Beginning Balance, Shares at Dec. 31, 2017		20,194
Ending Balance at Dec. 31, 2018	26,581		182,750	3,199	(159,368)
Ending Balance, Shares at Dec. 31, 2018		20,870
Cumulative effect of adoption of ASU 2016-02	(36)				(36)
Vesting of early exercised shares	56		56
Vesting of early exercised shares, shares		55
Stock-based compensation expense	1,533		1,533
Issuance of new shares	21,445		21,445
Issuance of new shares, shares		9,200
Issuance of warrants to purchase common stock	1,105		1,105
Repurchase of early exercised common stock options	(3)		(3)
Repurchase of early exercised common stock options, shares		(1)
Foreign currency translation adjustments	(1,013)			(1,013)
Net loss	(16,382)				(16,382)
Ending Balance at Mar. 31, 2019	$ 33,286		$ 206,886	$ 2,186	$ (175,786)
Ending Balance, Shares at Mar. 31, 2019		30,124

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Common Stock [Member]
Issuance costs	$ 1,555

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (16,382)	$ (17,103)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	39	39
Amortization of debt discount and issuance costs	233
Stock-based compensation	1,533	901
Fair value adjustment of success payment liability		(1,166)
Fair value adjustment of contingent consideration	4,600	1,500
Non-cash interest expense	214
Loss on disposal of property and equipment	1
Impairment of operating lease - right-of-use asset	13
Changes in assets and liabilities:
Prepaid expenses and other current assets	383	506
Accounts payable and other accrued liabilities	(3,403)	868
Net cash used in operating activities	(12,769)	(14,455)
Investing activities
Investment in property and equipment	(4)	(4)
Net cash used in investing activities	(4)	(4)
Financing activities
Proceeds from issuance of common stock, net of issuance costs, early exercise liability and repurchase of unvested early exercise stock options	21,442	(18)
Debt issuance costs related to long-term debt	(16)
Net cash provided by (used in) financing activities	21,426	(18)
Effect of exchange rate changes on cash	(10)	23
Net increase (decrease) in cash, cash equivalents and restricted cash	8,643	(14,454)
Cash, cash equivalents and restricted cash at beginning of period	48,707	74,648
Cash, cash equivalents and restricted cash at end of period	57,350	$ 60,194
Supplemental Disclosure of Cash Flow Information:
Right-of-use asset obtained in exchange for lease liability	844
Warrants issued	$ 1,105

Organization and Description of

Organization and Description of Business	3 Months Ended
	Mar. 31, 2019
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 unconventional scientific innovations to patients whose lives remain burdened by their disease. On June 29, 2018, the Company entered into a new loan and security agreement (the “SVB Loan Agreement”) with Silicon Valley Bank (“SVB”), pursuant to which SVB agreed to make available to the Company term loans with an aggregate principal amount of up to $40.0 million, $30.0 million of which was funded on June 29, 2018. On January 28, 2019, the Company entered into an amendment to the loan and security agreement, under which the Company’s total access to term loans is now $30.0 million, with additional minimum liquidity requirements. See Note 8, “Long-Term Debt.” On August 3, 2018 the Company entered into a sales agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which the Company may sell from time to time, at its option, up to $75.0 million of the Company’s common stock through an “at-the-market” On August 3, 2018, the Company also filed a Registration Statement on Form S-3 On January 2, 2019, the Company implemented a corporate restructuring to focus resources on its lead product candidate, SNA-120 In February 2019, the Company completed an underwritten public offering of 9,200,000 shares of common stock at a price to the public of $2.50 per share, including 1,200,000 shares of common stock pursuant to the underwriters’ option to purchase additional shares. The Company received net proceeds from the offering of approximately $21.4 million, after deducting the underwriters’ discounts and commissions and offering expenses payable by the Company. See Note 11, “Stockholders’ Equity.”

Liquidity Risks

Liquidity Risks	3 Months Ended
	Mar. 31, 2019
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 $175.8 million and $159.4 million as of March 31, 2019 and December 31, 2018, respectively. The Company had net losses of $16.4 million and $17.1 million for the three months ended March 31, 2019 and 2018, respectively, and net cash used in operating activities of $12.8 million and $14.5 million for the three months ended March 31, 2019 and 2018, respectively. The Company has historically financed its operations primarily through private and public equity issuances and debt offerings, and more recently through term loans under the SVB Loan Agreement and proceeds from the Company’s ATM Offering Program. See Note 8 “Long-Term Debt.” The Company had cash and cash equivalents of $57.2 million and $48.5 million at March 31, 2019 and December 31, 2018, respectively. The Company believes that its current capital resources will be sufficient to 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 additional debt, entering into licensing or collaboration agreements with partners, grants or other sources of financing. There can be no assurance that sufficient funds will be available to the Company at all or on attractive terms when needed from equity or debt financings. 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	3 Months Ended
	Mar. 31, 2019
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 months ended March 31, 2019 and 2018, are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited 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 March 31, 2019 and its results of operations for the three months ended March 31, 2019 and 2018 and cash flows for the three months ended March 31, 2019 and 2018. 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. For the three months ended March 31, 2019 and 2018, the subsidiaries’ net loss included in the Company’s consolidated statement of operations was $0.4 million and $0.9 million, respectively. 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 condensed 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, warrants, clinical trial accruals and the valuation of contingent consideration obligations and the impairment assessment of the in-process Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and one reportable segment, primarily in the United States. Reclassifications Certain reclassifications have been made to prior year amounts to conform to the current year presentation. The reclassifications were not material to the unaudited condensed consolidated financial statements. 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 March 31, 2019, 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. Restricted Cash At March 31, 2019 and December 31, 2018, the Company held $0.2 million of restricted cash related to cash collateralized standby letters of credit in connection with obligations under the facility lease. Fair Value Measurements The Company’s financial instruments, in addition to those presented in Note 7, “Fair Value Measurements”, include restricted cash, accounts payable, accrued liabilities and long-term debt. The carrying amount of restricted cash, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments. Further, based on the borrowing rates currently available to the Company for loans with similar terms, the Company believes the carrying amount of the long-term debt approximates its fair value. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful lives of the assets which range from three to five years. Maintenance and repairs are expensed as incurred. The Company reviews the carrying values of its property and equipment for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. There were no material impairments recognized during the three months ended March 31, 2019 and the year ended December 31, 2018. 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 acquired 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. There was no impairment of goodwill for the three months ended March 31, 2019 and the year ended December 31, 2018. 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. Prior to the adoption of a new accounting pronouncement on January 1, 2019 related to share-based payments issued to non-employees non-employees 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 March 31, 2019, 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. Other accrued expenses include accrued clinical trial costs of $1.7 million and $2.3 million as of March 31, 2019 and December 31, 2018, respectively. 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 months ended March 31, 2019 and 2018. Shares excluded from the calculation were 4.1 million and 1.7 million at March 31, 2019 and 2018, 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. Other Comprehensive Income (Loss) Included in other comprehensive income (loss) for the three months ended March 31, 2019 and 2018 are an unrealized foreign currency translation loss of $1.0 million and a gain of $1.4 million, respectively. This is the Company’s only component of other comprehensive income (loss) for the three months ended March 31, 2019 and 2018. 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, “Contingent Consideration”. 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 income (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 February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842), right-of-use The FASB subsequently issued the following amendments to ASU 2016-02, • ASU No. 2018-10, Codification Improvements to Topic 842, Leases 2016-02; • ASU No. 2018-11, Leases (Topic 842): Targeted Improvements 2016-02 non-lease On January 1, 2019, the Company adopted ASC 842, which resulted in the recognition of right-of-use right-of-use right-of-use, right-of-use non-lease In June 2018 the FASB issued ASU 2018-07, Compensation —Stock Compensation (Topic 718) —Improvements to Nonemployee Share-Based Payment Accounting” 2018-07”), Compensation—Stock Compensation 2018-07 505-50, Equity—Equity-Based Payments to Non-Employees. 2018-07 In February 2018, the FASB issued ASU 2018-02, “ Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income”, Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement

Contingent Consideration

Contingent Consideration	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Contingent Consideration	4. Contingent Consideration 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. As part of the terms of the acquisition, the Company agreed to make contingent payments up to an aggregate of $58.0 million in a combination of cash and stock upon the achievement of certain development and approval milestones, of which $5.0 million has been previously satisfied. Upon the commencement of the Phase 3 clinical trial of SNA-120, the Company will become obligated to issue $18.0 million in shares of common stock, less certain offsets if applicable, to the former Creabilis shareholders. In addition, the Company is obligated to make certain contingent payments up to an aggregate of $80.0 million in cash upon the achievement of certain annual net sales thresholds and one-time 20-day The agreement to pay the future milestones and potential one-time

Identifiable Intangible Assets

Identifiable Intangible Assets	3 Months Ended
	Mar. 31, 2019
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	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consisted of the following as of March 31, 2019 and December 31, 2018 (in thousands): Estimated Useful Life (in years) March 31, 2019 December 31, 2018 Lab equipment 5 $ 307 $ 307 Computer hardware 3 127 142 Capital lease equipment 3 46 46 Furniture and fixtures 5 87 87 Software 3 9 9 Leasehold improvements 105 105 Total 681 696 Less accumulated depreciation (406 ) (385 ) Property and equipment, net $ 275 $ 311 Leasehold improvements are depreciated over the shorter of the lease term or the estimated useful life of the related asset. Depreciation expense was $39,000 for each of the three months ended March 31, 2019 and 2018.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements The Company determines 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 March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 57,169 $ — $ — Total $ 57,169 $ — $ — Liabilities: Contingent consideration $ — $ — $ 33,800 Total $ — $ — $ 33,800 December 31, 2018 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 48,526 $ — $ — Total $ 48,526 $ — $ — Liabilities: Contingent consideration $ — $ — $ 29,200 Total $ — $ — $ 29,200 The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Contingent Consideration Balance at December 31, 2018 $ 29,200 Change in fair value due to remeasurement 4,600 Balance at March 31, 2019 $ 33,800 Cash equivalents At March 31, 2019, 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 Warrants In connection with the amendment to the SVB Loan Agreement, the Company issued warrants to purchase shares of the Company’s common stock. Based upon the characteristics and provisions of the warrants, they were classified as equity and recorded at their fair value as of the date of issuance. The estimated fair value of the warrants was calculated using the Black-Scholes option pricing model, using a term of 10 years, an estimated volatility of 78.02%, a risk-free interest rate of 2.75% and an expected dividend yield of 0%. The warrants are not measured at fair value on a recurring basis. Contingent consideration In connection with the acquisition of Creabilis, the Company 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 related IPR&D assets using several significant unobservable inputs, including risk adjusted discount rates ranging from 5.8% to 16.8%, projected future revenues and expenses based on the cumulative probabilities of multiple scenarios with individual probabilities ranging from 3.6% to 52.6%, 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. Changes in the fair values of the contingent consideration obligations are recorded in general and administrative expense in the condensed consolidated statement of operations. The increase in value during the three months ended March 31, 2019 and 2018 was $4.6 million and $1.5 million, respectively. For both periods, the increase was primarily related to the passage of time and progress toward milestone dates, as well as changes in external market factors. There were no transfers of assets or liabilities between the fair value measurement levels during the three months ended March 31, 2019 or the year ended December 31, 2018.

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Long-Term Debt	8. Long-Term Debt On June 29, 2018 the Company entered into the SVB Loan Agreement with SVB. Under the SVB Loan Agreement, SVB initially provided the Company with access to term loans in an aggregate principal amount of up to $40.0 million. The first credit extension, of a principal amount of $30.0 million, was funded on June 29, 2018, and is repayable in monthly installments until July 1, 2023, including an initial interest-only period through July 31, 2020. On January 28, 2019, the Company entered into an amendment to the loan and security agreement (as amended, the “SVB Agreement”). Under the amended SVB Agreement, the Company’s total access to term loans is $30.0 million. The Company may prepay the outstanding principal balance of the term loans advanced by SVB in whole but not in part, subject to a prepayment fee ranging from 1.0% to 3.0% of any amount prepaid, depending upon when the prepayment occurs. The Company will also pay a final payment fee equal to 6.50% of the total term loans advanced, due upon the earliest of maturity, acceleration, prepayment or termination of the SVB Agreement. If unrestricted cash at SVB falls below the greater of (i) $30.0 million and (ii) the sum of (x) $15.0 million, plus (y) the Company’s six month cash burn, tested monthly as of the last day of each month, then the Company has the option to either (a) prepay the term loans in denominations of $15.0 million (plus accrued and unpaid interest, the final payment fee in respect to the portion of the terms loans being repaid and the prepayment fee in respect to the pro rata portion of the term loans being prepaid in excess of $15.0 million) or (b) immediately cash secure not less than the lesser of the outstanding balance or $15.0 million of the principal balance of all outstanding indebtedness under the term loans. In addition, the final payment fee has been increased by 1% to 6.5% of the total term loans advanced. Interest on the term loans accrue at a per annum rate of the greater of (i) the Wall Street Journal prime rate plus 2.50% and (ii) 7.25%. On March 31, 2019, the rate was 8.0%. In connection with the amendment, the Company issued to SVB and its affiliate, Life Science Loans II, LLC, warrants to purchase an aggregate of 535,714 shares of the Company’s common stock at an exercise price of $2.80 per share. The warrants are immediately exercisable and have a term of ten years. The Company classified the warrants as equity and their fair value at the time of issuance was determined using a Black-Scholes valuation model and was recorded in the condensed consolidated balance sheets as a debt discount to the debt obligation and will be accreted to interest expense using the effective interest method through the maturity date of the term loan. Under the terms of the SVB Loan Agreement, the Company granted first priority liens and security interests in substantially all of the Company’s assets (excluding all of its intellectual property, which is subject to a negative pledge) and a pledge of the shares of one of its wholly-owned subsidiaries as collateral for the obligations thereunder. The SVB Loan Agreement also contains representations and warranties by the Company and SVB and indemnification provisions in favor of SVB and customary covenants (including limitations on other indebtedness, liens, acquisitions, and investments and dividends), and events of default (including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of SVB’s security interest in the collateral, and events relating to bankruptcy or insolvency). As of March 31, 2019, the carrying value of the term loan consists of $30.0 million principal outstanding less the debt issuance costs of approximately $0.1 million and the warrants of approximately $1.1 million. The final maturity payment of $2.0 million is recognized over the life of the term loan through interest expense using the effective interest method. The debt issuance costs have been recorded as a debt discount which are being accreted to interest expense through the maturity date of the term loan. The amended SVB Agreement was accounted for as a debt modification. Accordingly, issuance costs paid to the lender in connection with the amendment were recorded as a reduction of the carrying amount of the debt liability and were not significant. Issuance costs paid to third parties were recorded as expense and were not significant. The previously deferred fees and costs related to the debt will continue to be amortized over the remaining term. Interest expense relating to the term loan for the three months ended March 31, 2019 was $0.8 million. Interest expense is calculated using the effective interest method, and is inclusive of non-cash Future principal payments for the long-term debt are as follows (in thousands): March 31, 2019 — 2020 4,500 2021 9,586 2022 10,393 2023 5,521 Total principal payments 30,000 Final fee due at maturity in 2023 1,950 Total principal and final fee payments 31,950 Unamortized discount, debt issuance costs and warrants (2,713 ) Long-term debt, net $ 29,237

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Operating Lease In May 2016, the Company entered into a 40-month 2016-02 In June 2017, the Company amended the lease agreement to include an additional 5,973 square feet (“Suite 215”) and an allowance for leasehold improvements of up to $0.1 million. In March 2019, the Company subleased Suite 215 and received an upfront payment of $0.1 million for rental income on the sublease. The lease and sublease terminate concurrently on February 29, 2020. The Company does not plan on exercising a renewal option for Suite 215. On January 1, 2019, the Company adopted ASC 842, which resulted in the recognition of right-of-use In March 2019, in connection with the sublease of Suite 215, the Company evaluated the ROU asset for impairment. Because the lease payments for Suite 215 exceeded the sublease income over the remaining lease term, the Company recorded an impairment charge of $13,000 to write-down the ROU asset to the fair value of the sublease income over the remaining term. As of March 31, 2019 the balance of the ROU asset was $0.8 million and the balance of the lease liability was $0.9 million, of which $0.6 million is considered long-term and $0.3 million is considered short-term and is included in other accrued expenses. Also included in other accrued expenses is a prepaid rent liability of $0.1 million for the upfront payment received in connection with the sublease of Suite 215. Total operating lease expense for the three months ended March 31, 2019 was $0.1 million. Total sublease income for the three months ended March 31, 2019 was $9,000. Supplemental cash flow information for the three months ended March 31, 2019 related to operating leases was as follows (in thousands): Three Months Ended Cash paid for amounts included in the measurement of operating lease liabilities $ 107 Right-of-use $ 844 As of March 31, 2019, the maturities of the Company’s operating lease liabilities were as follows (in thousands): 2019 (remaining nine months) $ 324 2020 272 2021 239 2022 239 2023 40 Total operating lease payments 1,114 Less: imputed interest (200 ) Total operating lease liabilities $ 914 As of March 31, 2019, the weighted average remaining lease term for the company’s operating leases was 3.3 years. 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. 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 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 certain specified dates during the success payment period. Each success payment and the associated share price threshold is ascending from $10.0 million payable at a share price threshold of $53.71 per share to $35.0 million payable at $71.61 per share and with a maximum payment of $60.0 million 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 $60.0 million 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 accounting guidance for derivatives and hedging. Accordingly, the Company recorded an initial liability at fair value and remeasured the liability each reporting period, with changes being recognized in the consolidated statement of operations in other income and expense. The fair value of the success payments liability was estimated based on a third-party valuation using a model which simulates the future movement of stock prices based on several key variables. As of March 31, 2019 and December 31, 2018, the success payment liability was immaterial. During the three months ended March 31, 2018, the Company recorded other income of $1.2 million, due to remeasurement of the liability. There was no change in the liability during the three months ended March 31, 2019. Indemnifications The Company has indemnification obligations to its directors and executive officers for specified events or occurrences, subject to certain limits, while the directors and executive officers are serving at the Company’s request in such capacities. There have been no claims to date and the Company did not accrue any liabilities related to these agreements as of March 31, 2019 and December 31, 2018. 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 March 31, 2019, there are no matters where there is at least a reasonable possibility that a material loss has been or will be incurred.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	10. 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 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 553,652 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 454,912 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 49,370 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 49,370 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. On December 3, 2018, 50% of these shares vested as a result of achieving the clinical development milestone relating to the top-line results of SNA-120 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 $1.3 million, with an interest rate of 1.43% per annum. In June 2017, the Company forgave all outstanding principal and accrued interest under the related party non-recourse Success Payments Todd Harris, a member of the Company’s board of directors, is a beneficiary of the Success Payments Agreement, as described in Note 9 “Commitments and Contingencies—Success Payment Liability” and will receive 25.22% of any related payouts.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2019
Federal Home Loan Banks [Abstract]
Stockholders' Equity	11. Stockholders’ Equity As of March 31, 2019, the authorized stock of the Company was 300.0 million shares of common stock, $0.0001 par value per share, and 10.0 million 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 (in thousands): March 31, Common stock awards outstanding 3,029 Restricted stock units outstanding 772 Common stock awards available for grant under employee benefit plans 892 Common stock warrants outstanding 536 Total shares of common stock reserved for future issuance 5,229 Convertible Preferred Stock As of March 31, 2019 and December 31, 2018, there was no convertible preferred stock outstanding. ATM Offering Program In August 2018, the Company entered into a sales agreement with Cowen pursuant to which the Company may sell from time to time, at its option, up to $75.0 million of the Company’s common stock through ATM Offering Program, under which Cowen will act as sales agent. The aggregate compensation payable to Cowen shall be 3% of the gross sales price of the common stock sold by Cowen pursuant to the Sales Agreement. During the year ended December 31, 2018, the Company issued 340,307 shares of its common stock through its ATM Offering Program and received net proceeds of approximately $5.0 million, after deducting commissions of $0.2 million and other offering expenses of $0.4 million. During the quarter ended March 31, 2019, the Company did not issue any shares of its common stock through the ATM Offering Program. 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 0.3 million shares of common stock available at March 31, 2019 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 increased on January 1, 2018 and 2019 and will increase further on 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 12.0 million 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 2019 and 2018 was estimated on the grant date using the Black-Scholes option-pricing model. Prior to the adoption of a new accounting pronouncement on January 1, 2019 related to share-based payments issued to non-employees non-employee In determining the fair value of stock options granted, the following weighted average assumptions were used in the Black-Scholes option-pricing model for awards granted for the three months ended March 31, 2019 and the year ended December 31, 2018. Three Months Ended March 31, 2019 Year Ended December 31, 2018 Expected stock price volatility 69.91–73.62% 65.40–74.21% Expected dividend yield — % — % Expected term (in years) 2.0–5.6 5.0–6.1 Risk-free interest rate 2.46%–2.52% 2.55–3.06% Due to limited historical data, the Company estimates stock price volatility based on a combined weighted average of the Company’s historical average volatility and that of a selected peer group 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, Stock Options The table below summarizes the stock option activity for the three months ended March 31, 2019: Number of Shares (in thousands) Weighted Average Exercise Price Per Share Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 2,263 $ 12.42 $ — Granted 962 2.32 Exercised — — — Cancelled (196 ) 15.38 Outstanding at March 31, 2019 3,029 $ 9.02 $ — Exercisable at March 31, 2019 799 $ 6.90 $ — Restricted Stock Units (RSUs) The table below summarizes the RSU activity for the three months ended March 31, 2019: Number of RSUs Weighted Unvested at December 31, 2018 — $ — Granted 772 2.32 Vested — — Cancelled — — Unvested balance at March 31, 2019 772 $ 2.32 The Company did not grant any non-employee Total compensation cost recorded in the condensed consolidated statements of operations and comprehensive loss, which includes non-cash non-employees non-employees non-cash Three Months Ended March 31, 2019 2018 Research and development $ 414 $ 443 General and administrative 1,119 458 $ 1,533 $ 901 As of March 31, 2019, there was $13.2 million of unrecognized compensation expense related to unvested employee stock award agreements, which is expected to be recognized over a weighted-average period of approximately 2.83 years. As a result of the corporate restructuring in January 2019, the Company recorded a $0.2 million reduction in stock-based compensation expense relating to the forfeiture of the unvested awards. For stock option awards subject to graded vesting, the Company recognizes 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 three months ended March 31, 2019 was $1.73. The weighted-average remaining contractual life of options outstanding at March 31, 2019 is 9.1 years. The total fair value of the shares vested during the three months ended March 31, 2019 was $1.1 million. Additionally, stock-based compensation expense includes $42,000 and $0.1 million 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 capital as such shares vest. As of March 31, 2019 and December 31, 2018, 251,888 and 307,504 unvested shares, respectively, were legally issued but are not considered outstanding for accounting purposes and are therefore excluded from basic and diluted net loss per share until the repurchase right lapses and the shares are no longer subject to the repurchase feature. In connection with these unvested shares, the Company has recorded an early exercise liability as of March 31, 2019 and December 31, 2018, of $0.2 million and $0.3 million, respectively of which $0.2 million and $0.2 million is included in other accrued expenses, and $16,000 and $0.1 million is included in other long-term liabilities in the condensed consolidated balance sheets at March 31, 2019 and December 31, 2018, respectively. Warrants In January 2019, in connection with the amendment to the SVB Loan Agreement, the Company issued warrants to purchase an aggregate of 535,714 shares of the Company’s common stock at an exercise price of $2.80 per share. Based upon the characteristics and provisions of the warrants, they were classified as equity and recorded at their fair value as of the date of issuance of $1.1 million to additional paid in capital, with no further adjustments to their valuation. The estimated fair value of the warrants was calculated using the Black-Scholes option pricing model, using assumptions that are based on the individual characteristics of the warrants on the valuation date, as well as assumptions for expected volatility, expected life, yield and risk-free interest rate. 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 began the first offering period on December 31, 2017. 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 3.0 million shares of the Company’s common stock may be issued under the ESPP. The ESPP has 0.6 million shares of common stock reserved for future issuance pursuant to the plan. The Company recognized $44,000 and $0.1 million in compensation expense related to the ESPP for the three months ended March 31, 2019 and 2018, respectively. As of December 31, 2018, 67,508 shares of common stock were issued under the ESPP, and no additional shares were issued during the three months ended March 31, 2019.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes There is no provision for income taxes for the three months ended March 31, 2019 as the Company has incurred operating losses since inception. 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 March 31, 2019, 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.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
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 months ended March 31, 2019 and 2018, are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited 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 March 31, 2019 and its results of operations for the three months ended March 31, 2019 and 2018 and cash flows for the three months ended March 31, 2019 and 2018. 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. For the three months ended March 31, 2019 and 2018, the subsidiaries’ net loss included in the Company’s consolidated statement of operations was $0.4 million and $0.9 million, respectively.
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 condensed 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, warrants, clinical trial accruals and the valuation of contingent consideration obligations and the impairment assessment of the in-process
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and one reportable segment, primarily in the United States.
Reclassifications	Reclassifications Certain reclassifications have been made to prior year amounts to conform to the current year presentation. The reclassifications were not material to the unaudited condensed consolidated financial statements.
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 March 31, 2019, 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.
Restricted Cash	Restricted Cash At March 31, 2019 and December 31, 2018, the Company held $0.2 million of restricted cash related to cash collateralized standby letters of credit in connection with obligations under the facility lease.
Fair Value Measurements	Fair Value Measurements The Company’s financial instruments, in addition to those presented in Note 7, “Fair Value Measurements”, include restricted cash, accounts payable, accrued liabilities and long-term debt. The carrying amount of restricted cash, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments. Further, based on the borrowing rates currently available to the Company for loans with similar terms, the Company believes the carrying amount of the long-term debt approximates its fair value.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation on property and equipment is calculated using the straight-line method over the estimated useful lives of the assets which range from three to five years. Maintenance and repairs are expensed as incurred. The Company reviews the carrying values of its property and equipment for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. There were no material impairments recognized during the three months ended March 31, 2019 and the year ended December 31, 2018.
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 acquired 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. There was no impairment of goodwill for the three months ended March 31, 2019 and the year ended December 31, 2018.
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. Prior to the adoption of a new accounting pronouncement on January 1, 2019 related to share-based payments issued to non-employees non-employees
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 March 31, 2019, 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. Other accrued expenses include accrued clinical trial costs of $1.7 million and $2.3 million as of March 31, 2019 and December 31, 2018, respectively.
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 months ended March 31, 2019 and 2018. Shares excluded from the calculation were 4.1 million and 1.7 million at March 31, 2019 and 2018, 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.
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Included in other comprehensive income (loss) for the three months ended March 31, 2019 and 2018 are an unrealized foreign currency translation loss of $1.0 million and a gain of $1.4 million, respectively. This is the Company’s only component of other comprehensive income (loss) for the three months ended March 31, 2019 and 2018.
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, “Contingent Consideration”. 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 income (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 February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842), right-of-use The FASB subsequently issued the following amendments to ASU 2016-02, • ASU No. 2018-10, Codification Improvements to Topic 842, Leases 2016-02; • ASU No. 2018-11, Leases (Topic 842): Targeted Improvements 2016-02 non-lease On January 1, 2019, the Company adopted ASC 842, which resulted in the recognition of right-of-use right-of-use right-of-use, right-of-use non-lease In June 2018 the FASB issued ASU 2018-07, Compensation —Stock Compensation (Topic 718) —Improvements to Nonemployee Share-Based Payment Accounting” 2018-07”), Compensation—Stock Compensation 2018-07 505-50, Equity—Equity-Based Payments to Non-Employees. 2018-07 In February 2018, the FASB issued ASU 2018-02, “ Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income”, Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment consisted of the following as of March 31, 2019 and December 31, 2018 (in thousands): Estimated Useful Life (in years) March 31, 2019 December 31, 2018 Lab equipment 5 $ 307 $ 307 Computer hardware 3 127 142 Capital lease equipment 3 46 46 Furniture and fixtures 5 87 87 Software 3 9 9 Leasehold improvements 105 105 Total 681 696 Less accumulated depreciation (406 ) (385 ) Property and equipment, net $ 275 $ 311

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 57,169 $ — $ — Total $ 57,169 $ — $ — Liabilities: Contingent consideration $ — $ — $ 33,800 Total $ — $ — $ 33,800 December 31, 2018 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 48,526 $ — $ — Total $ 48,526 $ — $ — Liabilities: Contingent consideration $ — $ — $ 29,200 Total $ — $ — $ 29,200
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 (in thousands): Contingent Consideration Balance at December 31, 2018 $ 29,200 Change in fair value due to remeasurement 4,600 Balance at March 31, 2019 $ 33,800

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Future Principal Payments for Long-term Debt	Future principal payments for the long-term debt are as follows (in thousands): March 31, 2019 — 2020 4,500 2021 9,586 2022 10,393 2023 5,521 Total principal payments 30,000 Final fee due at maturity in 2023 1,950 Total principal and final fee payments 31,950 Unamortized discount, debt issuance costs and warrants (2,713 ) Long-term debt, net $ 29,237

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Operating Leases	Supplemental cash flow information for the three months ended March 31, 2019 related to operating leases was as follows (in thousands): Three Months Ended Cash paid for amounts included in the measurement of operating lease liabilities $ 107 Right-of-use $ 844
Schedule of Maturities of Operating Lease Liabilities	As of March 31, 2019, the maturities of the Company’s operating lease liabilities were as follows (in thousands): 2019 (remaining nine months) $ 324 2020 272 2021 239 2022 239 2023 40 Total operating lease payments 1,114 Less: imputed interest (200 ) Total operating lease liabilities $ 914

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2019
Federal Home Loan Banks [Abstract]
Summary of Shares of Common Stock Reserved for Future Issuance	Shares of common stock reserved for future issuance were as follows (in thousands): March 31, Common stock awards outstanding 3,029 Restricted stock units outstanding 772 Common stock awards available for grant under employee benefit plans 892 Common stock warrants outstanding 536 Total shares of common stock reserved for future issuance 5,229
Summary of Assumptions Used for Grant Date Fair Value	In determining the fair value of stock options granted, the following weighted average assumptions were used in the Black-Scholes option-pricing model for awards granted for the three months ended March 31, 2019 and the year ended December 31, 2018. Three Months Ended March 31, 2019 Year Ended December 31, 2018 Expected stock price volatility 69.91–73.62% 65.40–74.21% Expected dividend yield — % — % Expected term (in years) 2.0–5.6 5.0–6.1 Risk-free interest rate 2.46%–2.52% 2.55–3.06%
Summary of Stock Option Activity	The table below summarizes the stock option activity for the three months ended March 31, 2019: Number of Shares (in thousands) Weighted Average Exercise Price Per Share Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 2,263 $ 12.42 $ — Granted 962 2.32 Exercised — — — Cancelled (196 ) 15.38 Outstanding at March 31, 2019 3,029 $ 9.02 $ — Exercisable at March 31, 2019 799 $ 6.90 $ —
Schedule of Nonvested Restricted Stock Units Activity	The table below summarizes the RSU activity for the three months ended March 31, 2019: Number of RSUs Weighted Unvested at December 31, 2018 — $ — Granted 772 2.32 Vested — — Cancelled — — Unvested balance at March 31, 2019 772 $ 2.32
Summary of Non-cash Stock-based Compensation Expense	Total compensation cost recorded in the condensed consolidated statements of operations and comprehensive loss, which includes non-cash non-employees non-employees non-cash Three Months Ended March 31, 2019 2018 Research and development $ 414 $ 443 General and administrative 1,119 458 $ 1,533 $ 901

Organization and Description _2

Organization and Description of Business - Additional Information (Detail)	Jan. 02, 2019Positions	Feb. 28, 2019USD ($)$ / sharesshares	Mar. 31, 2019USD ($)shares	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)shares	Jan. 28, 2019USD ($)	Aug. 31, 2018USD ($)	Aug. 03, 2018USD ($)	Jun. 29, 2018USD ($)
Organization And Description Of Business [Line Items]
Principal outstanding			$ 30,000,000
Restructuring and related cost, number of positions eliminated | Positions	20
Net proceeds from offering after deducting the underwriters' discounts and commissions and offering expenses			$ 21,442,000	$ (18,000)
Term Loan [Member]
Organization And Description Of Business [Line Items]
Debt instrument aggregate principal amount						$ 30,000,000
Term Loan [Member] | Silicon Valley Bank [Member]
Organization And Description Of Business [Line Items]
Debt instrument aggregate principal amount									$ 40,000,000
Principal outstanding									$ 30,000,000
Underwritten Public Offering [Member]
Organization And Description Of Business [Line Items]
Common stock shares issued | shares		9,200,000
Common stock price per share | $ / shares		$ 2.50
Over-Allotment Option [Member]
Organization And Description Of Business [Line Items]
Common stock shares issued | shares		1,200,000
Net proceeds from offering after deducting the underwriters' discounts and commissions and offering expenses		$ 21,400,000
ATM Offering Program [Member]
Organization And Description Of Business [Line Items]
Common stock shares issued | shares			0		340,307
Proceeds from issuance of common stock, net					$ 5,000,000
Issuance of common stock, commissions paid					200,000
Issuance of common stock, other offering expenses					$ 400,000
ATM Offering Program [Member] | Cowen [Member]
Organization And Description Of Business [Line Items]
Amount which can be raised under ATM offering program							$ 75,000,000	$ 75,000,000
Shelf Registration Statement [Member] | Maximum [Member]
Organization And Description Of Business [Line Items]
Aggregate registered amount								$ 250,000,000

Liquidity Risks - Additional In

Liquidity Risks - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Liquidity Risks [Abstract]
Accumulated deficit	$ (175,786)		$ (159,368)
Net losses	(16,382)	$ (17,103)
Net cash used in operating activities	$ (12,769)	$ (14,455)
Substantial doubt about going concern, within one year	false
Cash and cash equivalents	$ 57,169		$ 48,526

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) shares in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)Segmentshares	Mar. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)	Jan. 01, 2019USD ($)
Significant Accounting Policies [Line Items]
Net loss	$ (16,382,000)	$ (17,103,000)
Number of operating segment | Segment	1
Number of reportable segment | Segment	1
Impairments charge	$ 0		$ 0
Impairments of intangible assets	0		0
Impairment of goodwill	0		0
Accrued clinical trial costs	$ 1,700,000	$ 2,300,000
Shares excluded from calculation of earnings per share | shares	4.1	1.7
Unrealized foreign currency translation gains and (losses)	$ 1,000,000	$ 1,400,000
Operating lease liability	914,000			$ 1,000,000
Right-of-use assets	772,000			$ 800,000
Subsidiaries [Member]
Significant Accounting Policies [Line Items]
Net loss	$ 400,000	$ 900,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of asset	3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of asset	5 years
Standby Letters of Credit [Member]
Significant Accounting Policies [Line Items]
Cash collateral for borrowed securities	$ 200,000		$ 200,000

Contingent Consideration - Addi

Contingent Consideration - Additional Information (Detail) - Creabilis [Member] - USD ($) $ in Millions	Dec. 06, 2016	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Potential contingent milestone payments	$ 18
Payment for contingent consideration	5
Maximum [Member]
Business Acquisition [Line Items]
Royalty percentage		1.00%
Contingent Consideration [Member]
Business Acquisition [Line Items]
Fair value of contingent consideration in acquisition		$ 33.8	$ 29.2
Development and Approval Milestones [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration	58
Net Sales Thresholds and One Time Royalties [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration	$ 80

Identifiable Intangible Assets

Identifiable Intangible Assets - Additional Information (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Dec. 06, 2016
Indefinite-lived Intangible Assets [Line Items]
In-process research and development intangible assets, carrying value	$ 44,591,000	$ 45,594,000
In-process Research and Development Intangible Assets [Member]
Indefinite-lived Intangible Assets [Line Items]
Impairment recognized on identifiable intangible assets	$ 0	$ 0
In-process Research and Development Intangible Assets [Member]
Indefinite-lived Intangible Assets [Line Items]
Identifiable intangible assets, initial value recorded			$ 42,300,000

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 681	$ 696
Less accumulated depreciation	(406)	(385)
Property and equipment, net	$ 275	311
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years
Property, plant and equipment, gross	$ 307	307
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years
Property, plant and equipment, gross	$ 127	142
Capital Lease Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years
Property, plant and equipment, gross	$ 46	46
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years
Property, plant and equipment, gross	$ 87	87
Software [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years
Property, plant and equipment, gross	$ 9	9
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 105	$ 105

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 39	$ 39

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 ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Level 1 [Member]
Assets:
Cash equivalents	$ 57,169	$ 48,526
Total	57,169	48,526
Level 3 [Member]
Liabilities:
Financial liabilities fair value	33,800	29,200
Contingent Consideration [Member] | Level 3 [Member]
Liabilities:
Financial liabilities fair value	$ 33,800	$ 29,200

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - Contingent Consideration [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 29,200
Change in fair value due to remeasurement	4,600	$ 1,500
Ending balance	$ 33,800

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value transfer amount	$ 0		$ 0
Measurement Input, Option Volatility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant	0.7802
Measurement Input, Risk Free Interest Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant	0.275
Measurement Input, Expected Dividend Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant	0
Measurement Input, Expected Term [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant,term	10 years
Creabilis [Member] | Discount Rate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input	0.058
Creabilis [Member] | Discount Rate [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input	0.168
Creabilis [Member] | Probability of Multiple Scenarios [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input	0.036
Creabilis [Member] | Probability of Multiple Scenarios [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input	0.526
In-process Research and Development Intangible Assets [Member] | Creabilis [Member] | Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible asset measurement input	0.205
In-process Research and Development Intangible Assets [Member] | Creabilis [Member] | Probability of Multiple Scenarios [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible asset measurement input	0.001
In-process Research and Development Intangible Assets [Member] | Creabilis [Member] | Probability of Multiple Scenarios [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible asset measurement input	0.225
Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value	$ 4,600,000	$ 1,500,000

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Detail) - USD ($)	Jun. 29, 2018	Mar. 31, 2019	Jan. 28, 2019
Debt Instrument [Line Items]
Principal outstanding		$ 30,000,000
Silicon Valley Bank [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan, aggregate principal amount	$ 40,000,000		$ 30,000,000
Term loan, first credit extension	$ 30,000,000
Term loan, initiation date		Jun. 29, 2018
Term loan, maturity date		Jul. 1, 2023
Term loan, interest-only period end date		Jul. 31, 2020
Final payment in percentage		6.50%
Unrestricted cash threshold amount		$ 30,000,000
Term loan, covenant description		If unrestricted cash at SVB falls below the greater of (i) $30.0 million and (ii) the sum of (x) $15.0 million, plus (y) the Company’s six month cash burn, tested monthly as of the last day of each month, then the Company has the option to either (a) prepay the term loans in denominations of $15.0 million (plus accrued and unpaid interest, the final payment fee in respect to the portion of the terms loans being repaid and the prepayment fee in respect to the pro rata portion of the term loans being prepaid in excess of $15.0 million) or (b) immediately cash secure not less than the lesser of the outstanding balance or $15.0 million of the principal balance of all outstanding indebtedness under the term loans.
Prepayment of term loans		$ 15,000,000
Amount of cash secured of the principal balance of outstanding loans		$ 15,000,000
Final payment fee percentage description		The final payment fee has been increased by 1% to 6.5% of the total term loans advanced.
Interest rate percentage		8.00%
Warrants issued to purchase common stock		535,714
Warrant exercise price		$ 2.80
Warrant term		10 years
Principal outstanding		$ 30,000,000
Debt issuance costs		100,000
Final maturity payment		2,000,000
Warrants and right outstanding		1,100,000
Interest expense		$ 800,000
Effective interest rate		10.89%
Silicon Valley Bank [Member] | Term Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Prepayment fee in percentage		1.00%
Interest rate percentage		7.25%
Silicon Valley Bank [Member] | Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Prepayment fee in percentage		3.00%
Final payment fee percentage		6.50%
Silicon Valley Bank [Member] | Term Loan [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Interest rate percentage, spread on variable rate		2.50%

Long-Term Debt - Schedule of Fu

Long-Term Debt - Schedule of Future Principal Payments for Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Long-term Debt, Fiscal Year Maturity [Abstract]
2019	$ 0
2020	4,500
2021	9,586
2022	10,393
2023	5,521
Total principal payments	30,000
Final fee due at maturity in 2023	1,950
Total principal and final fee payments	31,950
Unamortized discount, debt issuance costs and warrant	(2,713)
Long-term debt, net	$ 29,237	$ 30,125

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended
	May 31, 2016	Mar. 31, 2019USD ($)$ / shares	Mar. 31, 2018USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Jun. 30, 2017USD ($)ft²
Other Commitments [Line Items]
Operating lease expiry date		Feb. 29, 2020
Upfront payment received		$ 100,000
Right of use asset		772,000		$ 800,000
Operating lease liability		914,000		$ 1,000,000
Discount rate used to present value lease payments				12.50%
Operating lease impairment charges		13,000
Long-term		587,000
Short-term		300,000
Prepaid rent liability		100,000
Operating lease expense		100,000
Sublease income		$ 9,000
Weighted-average remaining operating lease term		3 years 3 months 18 days
Success payment liability threshold one		$ 10,000,000
Success payment liability threshold one per share | $ / shares		$ 53.71
Success payment liability threshold two		$ 35,000,000
Success payment liability threshold two per share | $ / shares		$ 71.61
Success payment liability threshold maximum		$ 60,000,000
Success payment liability threshold maximum per share | $ / shares		$ 107.42
Aggregate success payment maximum		$ 60,000,000
Other Income [Member] | Success Payment Liabilities [Member]
Other Commitments [Line Items]
Change in fair value due to re-measurement recorded income (expense)		0	$ 1,200,000
Directors And Officers Liability Insurance [Member]
Other Commitments [Line Items]
Indemnification claims		0
Accrued indemnification liabilities		$ 0			$ 0
Accounting Standards Update 2016-02 [Member]
Other Commitments [Line Items]
Cumulative effect of adoption of ASU 2016-02				$ 36,000
Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Operating lease obligation period	40 months
Operating lease renewal term	3 years
Operating lease expiry date	Feb. 29, 2020
Amended Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Additional area of office space leased | ft²						5,973
Minimum [Member]
Other Commitments [Line Items]
Annual royalties			$ 50,000
Maximum [Member] | Amended Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Additional allowance for leasehold improvements						$ 100,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Operating Leases (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 107
Right-of-use assets obtained in exchange for lease liabilities - operating leases	$ 844

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Leases [Abstract]
2019 (remaining nine months)	$ 324
2020	272
2021	239
2022	239
2023	40
Total operating lease payments	1,114
Less: imputed interest	(200)
Total operating lease liabilities	914	$ 1,000
Total operating lease payments	$ 1,114

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	Dec. 03, 2018	May 17, 2018	Jan. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jun. 30, 2017	May 31, 2016
Related Party Transaction [Line Items]
Number of nonvested shares				251,888	307,504
Recognized compensation expense				$ 1,533,000	$ 901,000
Notes Receivable [Member]
Related Party Transaction [Line Items]
Principal balance and interest forgiven on promissory note							$ 1,300,000
Dr.Beddingfield [Member]
Related Party Transaction [Line Items]
Stock issued during period shares acquisitions		47,594
President and Chief Executive Officer [Member] | Stock Purchase Rights [Member]
Related Party Transaction [Line Items]
Number of shares granted under stock purchase rights			553,652
Purchase price of common stock			$ 2.35
Fair value of the option granted			$ 1,300,000
Recognized compensation expense				$ 100,000	$ 56,000
Number of shares vested				31,518		400,000
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			454,912
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			2.00%
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			49,370
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			4.00%
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			49,370
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			4.00%
Percentage of shares vesting	50.00%		50.00%
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	Mar. 31, 2019	Dec. 31, 2018
Class of Stock Disclosures [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Preferred stock, shares authorized	10,000,000	10,000,000
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 shares in Thousands	Mar. 31, 2019	Dec. 31, 2018
Class of Stock Disclosures [Abstract]
Common stock awards outstanding	3,029	2,263
Restricted stock units outstanding	772
Common stock awards available for grant under employee benefit plans	892
Common stock warrants outstanding	536
Total shares of common stock reserved for future issuance	5,229

Stockholders' Equity - Converti

Stockholders' Equity - Convertible Preferred Stock - Additional Information (Detail) - shares	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Class of Stock [Line Items]
Preferred stock, shares outstanding	0	0
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding	0		0

Stockholders' Equity - ATM Offe

Stockholders' Equity - ATM Offering Program - Additional Information (Detail) - ATM Offering Program [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Aug. 31, 2018	Aug. 03, 2018
Class of Stock [Line Items]
Issuance of common stock	0	340,307
Proceeds from issuance of common stock, net		$ 5
Issuance of common stock, commissions paid		0.2
Issuance of common stock, other offering expenses		$ 0.4
Cowen [Member]
Class of Stock [Line Items]
Amount which can be raised under ATM offering program			$ 75	$ 75
Stock issuance costs under sales agreement as a percent of gross proceeds			3.00%

Stockholders' Equity - Stock Aw

Stockholders' Equity - Stock Awards and Stock-Based Compensation - Additional Information (Detail) - USD ($)	Aug. 01, 2017	Jan. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jul. 31, 2017
Class of Stock [Line Items]
Common stock available for issuance under plan			5,229,000
Number of shares granted to non-employee			962,000
Unrecognized compensation expense related to unvested employee stock award			$ 13,200,000
Unrecognized compensation expense related to unvested employee stock award, recognized period			2 years 9 months 30 days
Reduction in allocation of stock-based compensation expense			$ 200,000
Weighted-average grant date fair value of stock options granted			$ 1.73
Weighted-average remaining contractual life of options outstanding			9 years 1 month 6 days
Fair value of shares vested			$ 1,100,000
Stock compensation expense related to non-employee option grants			$ 42,000	$ 100,000
Unvested shares			251,888	307,504
Early exercise liability related to unvested shares			$ 200,000		$ 300,000
Early exercise liability related to unvested shares, current			200,000		200,000
Early exercise liability related to unvested shares, non-current			16,000		$ 100,000
Adjustments to additional paid in capital warrant issued			1,105,000
Recognized compensation expense			$ 1,533,000	$ 901,000
Silicon Valley Bank [Member] | Warrant [Member]
Class of Stock [Line Items]
Warrants issued to purchase common stock		535,714
Warrant exercise price		$ 2.80
Adjustments to additional paid in capital warrant issued		$ 1,100,000
2017 Incentive Award Plan [Member]
Class of Stock [Line Items]
Common stock available for issuance under plan						300,000
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 0.3 million shares of common stock available at March 31, 2019 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 increased on January 1, 2018 and 2019 and will increase further on 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 12.0 million 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]
Common stock available for issuance under plan	600,000
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 3.0 million shares of the Company’s common stock may be issued under the ESPP.
Recognized compensation expense			$ 44,000	$ 100,000
Number of shares issued from ESPP			0		67,508
Non-employee [Member]
Class of Stock [Line Items]
Contractual term			10 years
Number of shares granted to non-employee			0	0
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 - Summar_2

Stockholders' Equity - Summary of Assumptions Used for Grant Date Fair Value (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility, minimum	69.91%	65.40%
Expected stock price volatility, maximum	73.62%	74.21%
Expected dividend yield	0.00%	0.00%
Risk-free interest rate, minimum	2.46%	2.55%
Risk-free interest rate, maximum	2.52%	3.06%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Expected term (in years)	2 years	5 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Expected term (in years)	5 years 7 months 6 days	6 years 1 month 6 days

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding, beginning balance | shares	2,263
Number of Shares, Granted | shares	962
Number of Shares, Exercised | shares	0
Number of Shares, Cancelled | shares	(196)
Number of Shares, Outstanding, ending balance | shares	3,029
Number of Shares, Exercisable, ending balance | shares	799
Weighted Average Exercise Price Per Share, Outstanding, beginning balance	$ 12.42
Weighted Average Exercise Price Per Share, Granted	2.32
Weighted Average Exercise Price Per Share, Exercised	0
Weighted Average Exercise Price Per Share, Cancelled	15.38
Weighted Average Exercise Price Per Share, Outstanding, ending balance	9.02
Weighted Average Exercise Price Per Share, Exercisable, ending balance	$ 6.90
Aggregate Intrinsic Value, Outstanding, beginning balance | $	$ 0
Aggregate Intrinsic Value, Granted	$ 0
Aggregate Intrinsic Value, Exercised | $	$ 0
Aggregate Intrinsic Value, Cancelled | $	0
Aggregate Intrinsic Value, Outstanding, ending balance | $	0
Aggregate Intrinsic Value, Exercisable, ending balance | $	$ 0

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Nonvested Restricted Stock Units Activity (Detail) - Restricted Stock Units (RSUs) [Member] shares in Thousands	3 Months Ended
	Mar. 31, 2019$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Granted | shares	772
Number of unvested shares, Vested | shares	0
Number of unvested shares, Cancelled | shares	0
Ending Balance, Unvested | shares	772
Weighted Average Grant Date Fair Value, Granted | $ / shares	$ 2.32
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Cancelled | $ / shares	0
Ending Balance, Unvested | $ / shares	$ 2.32

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Non-cash Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 1,533	$ 901
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	414	443
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 1,119	$ 458

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Income Tax Disclosure [Abstract]
Provision for income tax	$ 0