Sienna Biopharmaceuticals (SNNAQ) 10-K 14 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 08, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	SNNA
Entity Registrant Name	Sienna Biopharmaceuticals, Inc.
Entity Central Index Key	0001656328
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		30,375,820
Entity Public Float			$ 0
Emerging Growth Company	true
Entity Small Business	true
Entity Shell Company	false
Entity Extended Transition Period	true

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 48,526	$ 74,467
Restricted cash	181	181
Prepaid expenses and other current assets	1,705	2,698
Total current assets	50,412	77,346
Property and equipment, net	311	432
In-process research and development	45,594	47,597
Goodwill	10,989	11,472
Total assets	107,306	136,847
Current liabilities:
Accounts payable	2,792	2,357
Accrued personnel costs	3,057	2,646
Other accrued expenses	4,787	3,007
Contingent consideration, current portion	13,500
Early exercise liability, current portion	213	231
Total current liabilities	24,349	8,241
Contingent consideration-net of current portion	15,700	22,900
Early exercise liability-net of current portion	45	258
Success payment liability	3	3,285
Long-term debt, net	30,125
Deferred tax liability	10,503	10,964
Total liabilities	80,725	45,648
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value, 10,000 shares authorized, no shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively
Common stock, $0.0001 par value, 300,000 shares authorized, 21,177 and 20,740 shares issued and 20,870 and 20,194 outstanding at December 31, 2018 and December 31, 2017, respectively	0	0
Additional paid in capital	182,750	171,726
Accumulated other comprehensive income	3,199	5,370
Accumulated deficit	(159,368)	(85,897)
Total stockholders' equity	26,581	91,199
Total liabilities and stockholders' equity	$ 107,306	$ 136,847

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	21,177,000	20,740,000
Common stock, shares outstanding	20,870,000	20,194,000

Consolidated Statement of Opera

Consolidated Statement of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research and development	$ 51,592	$ 30,484	$ 10,993
General and administrative	24,906	18,087	9,696
Total operating expenses	76,498	48,571	20,689
Loss from operations	(76,498)	(48,571)	(20,689)
Other income (expense), net	3,027	(2,264)	(473)
Net loss before taxes	(73,471)	(50,835)	(21,162)
Income tax benefit		290
Net loss	(73,471)	(50,545)	(21,162)
Other comprehensive income (loss):
Cumulative translation adjustment	(2,171)	5,736	(366)
Comprehensive loss	$ (75,642)	$ (44,809)	$ (21,528)
Per share information:
Net loss, basic and diluted	$ (3.59)	$ (5.19)	$ (12.49)
Basic and diluted weighted average shares outstanding	20,450	9,735	1,694

Consolidated Statements of Stoc

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]	Series A-1 Preferred Stock [Member]	Series A-2 Preferred Stock [Member]	Series A-3 Preferred Stock [Member]	Series B Preferred Stock [Member]
Beginning Balance at Dec. 31, 2015	$ 4,051		$ (2,109)		$ (14,190)	$ 328	$ 1,455	$ 18,567
Beginning Balance, Shares at Dec. 31, 2015		1,690				373	1,102	2,650
Issuance of common stock in connection with exercise of stock options	$ 831		831
Issuance of common stock in connection with exercise of stock options, shares	372	351
Early exercise liability	$ (817)		(817)
Early exercise liability, shares		(343)
Issuance of common stock for services	55		55
Stock-based compensation expense	358		358
Issuance of common stock for services, shares		21
Issuance of new shares	28,012							$ 28,012
Issuance of new shares, shares								3,950
Issuance of Series A-3 shares in connection with the Creabilis Acquisition	11,155							$ 11,155
Foreign currency translation adjustments	(366)			$ (366)
Issuance of Series A-3 shares in connection with the Creabilis Acquisition, shares								1,408
Net loss	(21,162)				(21,162)
Ending Balance at Dec. 31, 2016	22,117		(1,682)	(366)	(35,352)	$ 328	$ 1,455	$ 57,734
Ending Balance, Shares at Dec. 31, 2016		1,719				373	1,102	8,008
Issuance of common stock in connection with exercise of stock options	$ 206		206
Issuance of common stock in connection with exercise of stock options, shares	92	92
Early exercise liability	$ 327		327
Early exercise liability, shares		353
Issuance of common stock for services		$ 6
Stock-based compensation expense	2,112		2,112
Issuance of Series B shares upon conversion of Series B Bridge Notes at $10.40 per share	3,940								$ 3,940
Issuance of Series B shares upon conversion of Series B Bridge Notes, shares									379
Issuance of Series B shares at $12.24 per share	36,306								$ 36,306
Issuance of Series B shares, shares									2,985
Repurchase of common stock	(16)		(16)
Repurchase of common stock, shares		(7)
Issuance of new shares	66,378		66,378
Issuance of new shares, shares		4,983
Convertible notes beneficial conversion feature, net of taxes	439		439
Foreign currency translation adjustments	5,736			5,736
Conversion of preferred stock into common stock			99,763			$ (328)	$ (1,455)	$ (57,734)	$ (40,246)
Conversion of preferred stock into common stock, shares		12,847				(373)	(1,102)	(8,008)	(3,364)
Issuance of common stock in settlement of contingent consideration milestone	4,199		4,199
Issuance of common stock in settlement of contingent consideration milestone, shares		201
Net loss	(50,545)				(50,545)
Ending Balance at Dec. 31, 2017	91,199		171,726	5,370	(85,897)
Ending Balance, Shares at Dec. 31, 2017		20,194
Issuance of common stock in connection with exercise of stock options	$ 407		407
Issuance of common stock in connection with exercise of stock options, shares	37	37
Early exercise liability	$ 231		231
Early exercise liability, shares		239
Stock-based compensation expense	4,700		4,700
Shares issued pursuant to the employee stock purchase plan	707		707
Shares issued pursuant to the employee stock purchase plan, shares		68
Repurchase of common stock	(18)		(18)
Repurchase of common stock, shares		(8)
Issuance of new shares	4,997		4,997
Issuance of new shares, shares		340
Foreign currency translation adjustments	(2,171)			(2,171)
Net loss	(73,471)				(73,471)
Ending Balance at Dec. 31, 2018	$ 26,581		$ 182,750	$ 3,199	$ (159,368)
Ending Balance, Shares at Dec. 31, 2018		20,870

Consolidated Statements of St_2

Consolidated Statements of Stockholders Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Member]
Shares issued, price per share		$ 15
Issuance costs	$ 600	$ 8,367
Series A-3 Preferred Stock [Member]
Shares issued, price per share			$ 1.21
Issuance costs			$ 50
Series B Preferred Stock [Member]
Conversion price per share		$ 10.40
Shares issued, price per share		$ 12.24

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (73,471)	$ (50,545)	$ (21,162)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	157	120	67
Amortization of debt discount and issuance costs	259	729
Stock-based compensation	4,700	2,112	413
Fair value adjustment of success payment liability	(3,282)	2,023	568
Fair value adjustment of contingent consideration	6,300	2,989
Non-cash interest expense	476	34
Loss on disposal of property and equipment	3	5
Changes in assets and liabilities:
Prepaid expenses and other current assets	997	(1,349)	(346)
Accounts payable and other accrued liabilities	2,168	2,870	2,851
Net cash used in operating activities	(61,693)	(41,012)	(17,609)
Investing activities
Investment in property and equipment	(39)	(274)	(238)
Proceeds from sale of property and equipment		8
Acquisition of Creabilis, net of cash received			(6,821)
Net cash used in investing activities	(39)	(266)	(7,059)
Financing activities
Proceeds from issuance of common stock, net of issuance costs, early exercise liability and repurchase of unvested early exercise stock options	5,387	188	831
Net proceeds from issuance of long-term debt	29,866
Proceeds from issuance of common stock for ESPP purchase	707
Proceeds from issuance of convertible promissory notes		3,906
Proceeds from initial public offering, net of issuance costs		66,378
Net cash provided by financing activities	35,960	106,778	28,843
Effect of exchange rate changes on cash	(169)	(52)	28
Net (decrease)/increase in cash, cash equivalents and restricted cash	(25,941)	65,448	4,203
Cash, cash equivalents and restricted cash at beginning of period	74,648	9,200	4,997
Cash, cash equivalents and restricted cash at end of period	48,707	74,648	9,200
Supplemental disclosures
Common stock issued for acquisition			11,155
Fair value of contingent consideration for acquisition			24,110
Fair value of in-process research and development intangible asset			42,254
Fair value of goodwill			9,788
Fair value of deferred tax liability			9,412
Preferred stock issued upon conversion of notes payable		3,940
Preferred stock issued relating to beneficial conversion feature of notes payable		$ 729
Fair value of contingent consideration settled in common stock		4,199
Shares issued for services		$ 126	55
Interest paid in cash	$ 982
Series A-3 Preferred Stock [Member]
Financing activities
Net proceeds from issuance of preferred stock			$ 28,012
Series B Preferred Stock [Member]
Financing activities
Net proceeds from issuance of preferred stock		$ 36,306

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Organization and Description of Business	1. Organization and Description of Business In these notes to the 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 July 20, 2017, the Company amended and restated its certificate of incorporation, giving effect to a 1-for-5.87 On August 1, 2017, the Company completed its initial public offering, or IPO, of 4,983,333 shares of common stock, which included the exercise in full by the underwriters of their option to purchase up to 650,000 additional shares of common stock, at an offering price to the public of $15.00 per share. The Company received net proceeds of approximately $66.4 million after deducting underwriting discounts, commissions and offering related transaction costs. In connection with the IPO, the Company’s outstanding shares of convertible preferred stock were automatically converted into 12.8 million shares of common stock. As of December 31, 2018, the Company had 21.2 million shares of common stock outstanding. See Note 13, “Stockholders’ Equity.” In connection with the completion of its IPO, on August 1, 2017, the Company’s certificate of incorporation was amended and restated to provide for 300.0 million authorized shares of common stock with a par value of $0.0001 per share and 10.0 million authorized shares of preferred stock with a par value of $0.0001 per share. 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, under which the Company’s total access to term loans is now $30.0 million, with additional minimum liquidity requirements. See Note 10, “Long-Term Debt” and Note 16, “Subsequent Events.” 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 closed a follow on offering and completed the sale and issuance of an aggregate of 9,200,000 shares of common stock. The Company received net proceeds from the offering of approximately $21.3 million, after deducting the underwriters’ discounts and commissions and estimated offering expenses payable by the Company. See Note 13, “Stockholders’ Equity” and Note 16, “Subsequent Events.”

Liquidity Risks

Liquidity Risks	12 Months Ended
	Dec. 31, 2018
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 $159.4 million and $85.9 million as of December 31, 2018 and 2017, respectively. The Company had net losses of $73.5 million, $50.5 million and $21.2 million for the years ended December 31, 2018, 2017 and 2016, respectively, and net cash used in operating activities of $61.7 million, $41.0 million and $17.6 million for the years ended December 31, 2018, 2017 and 2016, 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 10 “Long-Term Debt” and Note 16, “Subsequent Events.” The Company had cash and cash equivalents of $48.5 million and $74.5 million at December 31, 2018 and 2017, 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	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	3. Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP. Principles of Consolidation The 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 years ended December 31, 2018, 2017 and 2016, the subsidiaries’ net loss included in the Company’s consolidated statement of operations was $3.3 million, $2.6 million and $0.2 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 consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. The most significant estimates in the Company’s consolidated financial statements relate to equity awards, the success payment liability, clinical trial accruals and the valuation of 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. 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 December 31, 2018, 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 December 31, 2018 and 2017, 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 impairments recognized during the years ended December 31, 2018 and 2017. 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 years ended December 31, 2018 and 2017. Other Income and Expense Other income and expense includes amounts relating to the remeasurement of the success payment liability, interest earned on the Company’s bank accounts, interest expense incurred in connection with the SVB term loan described in Note 10, “Long-Term Debt”, and the amortization of the debt discount in connection with the Series B Bridge Notes described in Note 8, “Convertible Notes”. 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. Stock options issued to 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 December 31, 2018, there have been no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. The Company’s clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations and other third-party vendors. Prepaid expenses and other current assets include no prepaid clinical trial costs as of December 31, 2018 and $1.1 million as of December 31, 2017. Other accrued expenses include accrued clinical trial costs of $2.3 million and $0.9 million as of December 31, 2018 and 2017, 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 years ended December 31, 2018, 2017 and 2016. Shares excluded from the calculation were 2.6 million, 1.7 million and 11.0 million at December 31, 2018, 2017 and 2016, respectively. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred taxes are recognized based on the differences between financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has provided a full valuation allowance on its deferred tax assets. The provision for income taxes represents the current tax payable for the period and the change during the period in deferred tax assets and liabilities. The Company recognizes the effect of an income tax position only if, based on its merits, the position is more likely than not to be sustained on audit by the taxing authorities. Interest and penalties related to uncertain tax positions are recorded as income tax expense. Business combinations Business combinations are accounted for using the acquisition method of accounting. Under the acquisition method, assets acquired, including in-process Other Comprehensive Income (Loss) Included in other comprehensive income (loss) for the years ended December 31, 2018, 2017 and 2016 are an unrealized foreign currency translation loss of $2.2 million, a gain of $5.7 million and a loss of $0.4 million, respectively. This is the Company’s only component of other comprehensive income (loss) for the years ended December 31, 2018, 2017 and 2016. Foreign currency translation The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. These include the entities acquired as part of the Creabilis acquisition. See Note 4, “Creabilis Acquisition”. As part of this transaction, the Company acquired entities in the United Kingdom, denominated in British pounds, and Italy and Luxembourg, denominated in euros. The U.S. dollar effects that arise from translating net assets of these subsidiaries at changing rates are recognized in other comprehensive income (loss) in the 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 March 2018, the FASB issued ASU 2018-05, Income Taxes (Topic 740)—Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118”, No. 115-97, In May 2017, the FASB issued ASU 2017-09, Compensation Stock Compensation (Topic 718): Scope of Modification Accounting In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment”, one-step 2017-04 In January 2017, the FASB issued ASU 2017-01 “Business Combinations (Topic 805): Clarifying the Definition of a Business”, In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). No. 2016-18 beginning-of-period end-of-period 2016-18, In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)” (“ASU 2016-15”), In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09”) ASU 2014-09 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 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 Revenue from Contracts with Customers. 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”, 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 The Company has nearly completed its assessment of ASU 2016-02 right-of-use The Company will adopt the new leasing standards using the modified retrospective transition approach to be applied to leases existing as of, or entered into after, January 1, 2019 and prior periods will not be adjusted. The new standard provides a number of optional practical expedients in transition. The Company has elected the package of practical expedients to not reassess prior conclusions about lease identification under the new standard, lease classification, and initial direct costs. The Company also elected the practical expedient allowing the use of hindsight in determining the lease term and assessing impairment of right-of-use right-of-use, right-of-use non-lease

Creabilis Acquisition

Creabilis Acquisition	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Creabilis Acquisition	4. Creabilis Acquisition In December 2016, the Company entered into a Share Purchase Agreement, or the Purchase Agreement, to acquire the entire issued share capital of Creabilis. Pursuant to the acquisition of Creabilis, the Company obtained SNA-120, SNA-125 SNA-120 first-in-class SNA-125 Upon closing, Creabilis became a direct wholly owned subsidiary in exchange for an upfront payment of approximately $0.2 million in cash, 1,407,679 shares of Series A-3 one-time 20-day The agreement to pay the future milestones and potential one-time On October 19, 2017, the Company achieved the first dosing of a human subject in a phase 2b clinical trial for SNA-120, SNA-120, The Company recorded a deferred tax liability of $9.4 million for the non-deductible in-process For the years ended December 31, 2018, 2017 and 2016, Creabilis’ net loss included in the Company’s consolidated statement of operations was $3.3 million, $2.6 million and $0.2 million, respectively. Additionally, $1.7 million of transaction costs related to the acquisition are included in general and administrative expense for the year ended December 31, 2016.

Identifiable Intangible Assets

Identifiable Intangible Assets	12 Months Ended
	Dec. 31, 2018
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	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consisted of the following as of December 31, 2018 and 2017 (in thousands): Estimated December 31, 2018 2017 Lab equipment 5 $ 307 $ 307 Computer hardware 3 142 116 Capital lease equipment 3 46 46 Furniture and fixtures 5 87 91 Software 3 9 — Leasehold improvements 105 105 Total 696 665 Less accumulated depreciation (385 ) (233 ) Property and equipment, net $ 311 $ 432 Leasehold improvements are depreciated over the shorter of the lease term or the estimated useful life of the related asset. Depreciation expense was $0.2 million, $0.1 million and $0.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 Level 2 Level 3 In certain cases where there is limited activity or less transparency around inputs to valuation, assets are classified as Level 3 within the valuation hierarchy. The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy as of December 31, 2018 and 2017 (in thousands): December 31, 2018 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 48,526 $ — $ — Total $ 48,526 $ — $ — Liabilities: Success payment liability $ — $ — $ 3 Contingent consideration — — 29,200 Total $ — $ — $ 29,203 December 31, 2017 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 74,467 $ — $ — Total $ 74,467 $ — $ — Liabilities: Success payment liability $ — $ — $ 3,285 Contingent consideration — — 22,900 Total $ — $ — $ 26,185 The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Success Payment Contingent Balance at December 31, 2017 $ 3,285 $ 22,900 Change in fair value due to remeasurement (3,282 ) 6,300 Balance at December 31, 2018 $ 3 $ 29,200 Cash equivalents At December 31, 2018, the Company’s cash equivalents are comprised of U.S. Treasury money market funds whose value is based upon quoted market prices in active markets for identical assets or liabilities with no adjustments applied. Accordingly, these investments are classified as Level 1 of the fair value measurements and disclosure guidance. Intangible assets In connection with the acquisition of Creabilis, the Company acquired intangible in-process in-process Contingent consideration 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 7.6% to 16.9%, projected future revenues and expenses based on the cumulative probabilities of multiple scenarios with individual probabilities ranging from 3.8% to 50.1%, 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 consolidated statement of operations. In October 2017, the Company commenced the additional Phase 2b clinical trial for SNA-120, 20-day SNA-120. Success payment liability In October 2015, as a result of an agreement in which the Company agreed to pay certain stockholders success payments if the stock price of the Company’s common stock reached certain thresholds, the Company recorded a success payment liability. The success payment liability was recorded at fair value based on significant unobservable inputs, as discussed in Note 9, “Success Payment Liability”. The change in fair value during the years ended December 31, 2018, 2017 and 2016 resulted in net other income of $3.3 million and net other expense of $2.0 million and $0.6 million, respectively, and was recorded to other income and expense in the consolidated statements of operations. Changes in the fair value is primarily related to the changes in the Company’s stock price and the passage of time. The determination of the fair value of the success payment liability uses assumptions the Company believes would be made by a market participant and the Company assesses these estimates on an on-going There were no transfers of assets or liabilities between the fair value measurement levels during the years ended December 31, 2018 and 2017.

Convertible Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Convertible Notes	8. Convertible Notes In January 2017, the Company entered into a note purchase agreement pursuant to which the Company issued, in two tranches, subordinated convertible promissory notes (the “Series B Bridge Notes” and together with the note purchase agreement, the “Series B Bridge Note Agreements”) in an aggregate principal amount of $3.9 million. The Series B Bridge Notes provided for an annual interest rate of 6.0% and a maturity date of January 27, 2018. Under the terms of the Series B Bridge Note Agreements, under certain circumstances, the unpaid principal of the Series B Bridge Notes, including any accrued but unpaid interest thereon, would convert into shares of convertible preferred stock upon the closing of a future preferred stock financing that met specified criteria. Such conversion would be at a 15% discount to the per share price of the convertible preferred stock sold in the financing. In addition, the notes were voluntarily convertible into shares upon the occurrence of a non-qualified The conversion feature included a 15% discount in the convertible notes, which constituted a beneficial conversion feature, that was bifurcated and allocated to additional paid in capital. The intrinsic value of the beneficial conversion feature due to the 15% discount on conversion of the principal and accrued interest was calculated to be $0.7 million. This resulted in a discount of $0.7 million being allocated to the Series B Bridge Notes which was being amortized to interest expense in the consolidated statement of operations on an effective interest method from the date of issuance of each Series B Bridge Notes through the maturity date of January 27, 2018. In April 2017, in connection with the Company’s Series B convertible preferred stock financing, the outstanding principal under the Series B Bridge Notes of $3.9 million, plus $34,000 of accrued interest, converted into an aggregate of 0.4 million shares of Series B convertible preferred stock at a rate of $10.40 per share and the Series B Bridge Notes were cancelled. In connection with the IPO, the Series B convertible preferred stock was automatically converted into 0.4 million shares of common stock. The remaining unamortized discount was recognized in interest expense in the consolidated statement of operations. Included in other income and expense for the year ended December 31, 2017 is amortization of the debt discount of $0.7 million and accrued interest expense of $34,000.

Success Payment Liability

Success Payment Liability	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Success Payment Liability	9. Success Payment Liability In October 2015, the Company entered into a letter agreement with certain stockholders pursuant to which the Company agreed to make success payments to such stockholders (the “Success Payment Agreement”). The agreement ends on its fifth anniversary in October 2020. Success payments are payable in cash or common stock at the Company’s sole discretion and will be owed in the event that the value of its common stock meets or exceeds certain specified share price thresholds on any of the following dates during the success payment period: (1) any date after the 90th day after the date on which the Company completes an initial public offering of its common stock; (2) the date on which the Company sells, leases, transfers, or exclusively licenses all or substantially all of its assets to another company; and (3) the date on which the Company merges or consolidates with or into another entity (other than a merger in which the pre-merger 90-day The amount of the success payment is determined based on whether the value of the common stock of the Company meets or exceeds certain specified share price thresholds, subject to adjustment for any stock dividend, stock split, combination of shares, or other similar events. Each success payment and the associated share price threshold is ascending from $10.0 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 remeasures the liability each reporting period, with changes being recognized in the consolidated statement of operations. 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. The following variables were incorporated in the estimated fair value of the success payment liability: estimated term of the success payments, fair value of common stock, expected volatility, and risk-free interest rate. The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption. During the years ended December 31, 2018, 2017 and 2016, the Company recorded net other income of $3.3 million and net other expense of $2.0 million and $0.6 million, respectively, due to remeasurement of the liability.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	10. Long-Term Debt On June 29, 2018 the Company entered into the SVB Loan Agreement with SVB. Under the SVB Loan Agreement, SVB will provide 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”). See Note 16, “Subsequent Events.” 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 December 31, 2018, the rate was 8.0%. Under the amended SVB Agreement, the Company’s total access to term loans is $30.0 million and, 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. 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. 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, investments and dividends, but no financial covenants), 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 December 31, 2018, the carrying value of the term loan consists of $30.0 million principal outstanding less the debt issuance costs of approximately $0.1 million. The final maturity payment of $1.7 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. Interest expense relating to the term loan for the year ended December 31, 2018 was $1.5 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): December 31, 2018 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 1,650 Total principal and final fee payments 31,650 Unamortized discount and debt issuance costs (1,525 ) Long-term debt, net $ 30,125

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Operating Lease In May 2016, the Company entered into a 40-month Year ending December 31: 2019 $ 432 2020 74 2021 — 2022 — Thereafter — Total minimum lease payments $ 506 During the years ended December 31, 2018, 2017 and 2016, the Company incurred $0.4 million, $0.5 million and $0.2 million for rent expense, respectively. License and Supply Agreement The Company has an exclusive license and supply agreement with nanoComposix, pursuant to which the Company owes minimum annual royalties of $50,000 or low single digit royalties on net sales of licensed products. Contingencies From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business, including those set forth in Part 1, Item 3 “Legal Proceedings”. As of December 31, 2018, there are no matters where there is at least a reasonable probability that a material loss has been or will be incurred.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	12. 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. The promissory note was considered to be substantively non-recourse non-recourse, 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 “Success Payment Liability” and will receive 25.22% of any related payouts.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Federal Home Loan Banks [Abstract]
Stockholders' Equity	13. Stockholders’ Equity As of December 31, 2018, 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 as of December 31, 2018 and 2017 (in thousands): 2018 2017 Common stock awards outstanding 2,263 1,159 Common stock awards available for grant under employee benefit plans 1,370 1,533 Total shares of common stock reserved for future issuance 3,633 2,692 Convertible Preferred Stock As of December 31, 2018 and 2017, there was no convertible preferred stock outstanding. In connection with the Company’s IPO, all outstanding shares of convertible preferred stock were automatically converted into 12.8 million shares of common stock. In April 2017, the Company issued an aggregate of 3.0 million shares of Series B convertible preferred stock at a price per share of $12.24 for aggregate proceeds of $36.5 million, exclusive of 0.4 million shares of Series B convertible preferred stock issued upon conversion of the Series B Bridge Notes. See Note 8 “Convertible Notes”. All of the Company’s outstanding Series B convertible preferred stock was automatically converted into common stock in connection with the IPO. 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. Stock Awards and Stock-Based Compensation In July 2017, the Company’s board of directors approved the 2017 Incentive Award Plan, or the 2017 Plan, which became effective upon the completion of the IPO on August 1, 2017. The 2017 Plan serves as the successor incentive award plan to the Company’s 2010 Equity Incentive Plan, or the 2010 Plan, and has 1.0 million shares of common stock available for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock-based awards, plus shares of common stock that were reserved for issuance pursuant to future awards under the 2010 Plan at the time the 2017 Plan became effective, plus shares represented by awards outstanding under the 2010 Plan that are forfeited or lapse unexercised and which following the effective date of the 2017 Plan are not issued under the 2010 Plan. In addition, the 2017 Plan reserve will increase on January 1, 2018 and each subsequent anniversary through 2027, by an amount equal to the lesser of (a) four percent of the shares of stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (b) such smaller number of shares of stock as determined by our board of directors; provided, however, that no more than 12.0 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 2018, 2017 and 2016 was estimated on the grant date using the Black-Scholes option-pricing model. The fair value of each non-employee Year Ended December 31, 2018 2017 2016 Expected stock price volatility 65.40–74.21 % 59.13%–64.09 % 46.72%–54.76 % Expected dividend yield — % — % — % Expected term (in years) 5.0–6.1 5.3–10.0 4.0–10.0 Risk-free interest rate 2.55–3.06 % 1.77%–2.60 % 1.12%–2.42 % 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, The table below summarizes the stock option activity for the years ended December 31, 2018, 2017 and 2016: Number Weighted Aggregate Outstanding at December 31, 2015 — — — Granted 1,020 $ 2.35 — Exercised (372 ) 2.35 $ 87 Cancelled (75 ) 2.35 — Outstanding at December 31, 2016 573 $ 2.35 $ 1,412 Granted 686 12.22 — Exercised (92 ) 2.35 260 Cancelled (8 ) 2.35 — Outstanding at December 31, 2017 1,159 $ 8.19 $ 11,795 Granted 1,358 15.95 — Exercised (37 ) 11.04 168 Cancelled (217 ) 12.14 — Outstanding at December 31, 2018 2,263 $ 12.42 $ 18 Exercisable at December 31, 2018 561 $ 7.05 $ 17 The Company granted non-employee non-employee Total compensation cost recorded in the consolidated statements of operations and comprehensive loss, which includes non-cash non-employees non-employees non-cash Year Ended December 31, 2018 2017 2016 Research and development $ 1,519 $ 487 $ 104 General and administrative 3,181 1,625 254 $ 4,700 $ 2,112 $ 358 As of December 31, 2018, there was $13.6 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 3.17 years. As a result of the corporate restructure in January 2019, a portion of this expense will not be recognized. For stock option awards subject to graded vesting, we recognize compensation cost on a straight-line basis over the service period for the entire award. The weighted-average grant date fair value of all stock options granted during the year ended December 31, 2018 was $15.95. The weighted-average remaining contractual life of options outstanding at December 31, 2018 is 8.8 years. The total fair value of the shares vested during the year ended December 31, 2018 was $3.3 million. Additionally, stock compensation expense includes $0.3 million, $0.8 million and $48,000 related to non-employee Prior to its termination in connection with the effectiveness of the 2017 Plan, the 2010 Plan allowed the Company to grant to employees the right to exercise stock options in exchange for cash before the requisite service was provided (e.g., before the award is vested under its original terms); however, such arrangements permit the Company to subsequently repurchase such shares at the exercise price if the employee ceases to be a service provider. Such an exercise is not substantive for accounting purposes. Therefore, the payment received for the exercise price is recognized as an early exercise liability in the consolidated balance sheets and will be transferred to common stock and additional paid in capital as such shares vest. As of December 31, 2018 and 2017, 307,504 and 546,065 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 December 31, 2018 and 2017, of $0.3 million and $0.5 million, respectively, of which $0.2 million and $0.2 million is included in current liabilities, and $0.1 million and $0.3 million is included in non-current 2017 Employee Stock Purchase Plan The Company adopted the 2017 Employee Stock Purchase Plan, or the ESPP, which became effective upon the completion of the IPO on August 1, 2017. The ESPP is designed to allow the Company’s eligible employees to purchase shares of the Company’s common stock, at semi-annual intervals, with their accumulated payroll deductions. Under the ESPP, participants are offered the option to purchase shares of the Company’s common stock at a discount during a series of successive offering periods. The option purchase price will be the lower of 85% of the closing trading price per share of the Company’s common stock on the first trading date of an offering period in which a participant is enrolled or 85% of the closing trading price per share on the purchase date, which will occur on the last trading day of each offering period. The Company 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 0.3 million shares of common stock reserved for future issuance pursuant to the plan. The Company recognized $0.3 million in compensation expense related to the ESPP for the year ended December 31, 2018. During the year ended December 31, 2018, 67,508 shares of common stock were issued under the ESPP.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act, or the Act. The Act amends the Internal Revenue Code of 1986, as amended, or the Code, to reduce tax rates and modify policies, credits and deductions for individuals and businesses. For businesses, the Act reduces the corporate tax rate from a maximum of 35% to a flat 21% rate. The rate reduction became effective on January 1, 2018. A U.S. shareholder of a specified foreign corporation, or SFC, must include in gross income, at the end of the SFC’s last tax year beginning January 1, 2018, the U.S. shareholder’s pro rata share of the SFC’s undistributed and previously untaxed post-1986 foreign earnings and profits. The amount of earnings and profits taken into account is the greater of the amounts determined as of November 2, 2017, or December 31, 2017, unreduced by dividends to other SFCs during the SFC’s last taxable year beginning before January 1, 2018. As of December 31, 2017, the Company’s controlled foreign corporations had negative cumulative earnings and profits; therefore, the Company did not have an income inclusion as a result of the mandatory deemed repatriation. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (SAB 118), which allowed the Company to record provisional amounts for the effects of the TCJA in the period it was enacted for a measurement period not extend beyond one year from the enactment date. Under SAB 118, the Company recorded a provisional reduction in its deferred tax assets and associated valuation allowance of $9.0 million in 2017 for the effects of the TCJA, which was primarily attributable to the reduction in federal tax rates. The Company completed its assessment of the final impact of the TCJA within the required measurement period under SAB 118 and determined that there were no material adjustments to the provisional amounts previously recorded. The amount of loss before taxes (in thousands): Year Ended December 31, 2018 2017 2016 U.S. loss before taxes $ (70,206 ) $ (48,258 ) $ (20,937 ) Foreign loss before taxes (3,265 ) (2,577 ) (225 ) Loss before income taxes $ (73,471 ) $ (50,835 ) $ (21,162 ) Income tax benefit for the years ended December 31, 2018, 2017 and 2016 consists of the following (in thousands): Year Ended December 31, 2018 2017 2016 Current: Federal $ — $ (226 ) $ — State — (64 ) — Foreign — — — Total Current $ — $ (290 ) $ — Deferred: Federal $ — $ — $ — State — — — Foreign — — — Total Deferred — — — Income Tax Benefit $ — $ (290 ) $ — A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Tax computed at federal statutory rate $ (15,429 ) $ (17,284 ) $ (7,407 ) State income taxes, net of federal tax benefit (1,867 ) (1,713 ) (1,058 ) Rate difference on non-US (96 ) 482 33 Research and development credits (1,527 ) (929 ) (359 ) Success based payments (689 ) 688 199 Valuation allowance 18,637 6,222 7,582 Uncertain tax positions — — 379 Transaction costs — — 587 Tax Cut and Jobs Act — 8,960 — Contingent consideration 1,323 1,016 — Return to provision and true-ups (718 ) 2,499 — Permanent items 366 (231 ) 44 Income tax benefit $ — $ (290 ) $ — The components that comprise the Company’s net deferred tax assets at December 31, 2018 and 2017 consist of the following (in thousands): Year Ended December 31, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 19,868 $ 15,815 Amortization 20,754 8,818 Stock-based compensation 1,021 392 R&D credit carryforwards 2,894 1,367 Accrued expenses 648 600 Other 176 168 Total deferred tax assets $ 45,361 $ 27,160 Deferred tax liabilities Foreign intangibles $ (10,503 ) $ (10,964 ) Fixed assets (18 ) (30 ) Total deferred tax liabilities $ (10,521 ) $ (10,994 ) Net deferred tax assets $ 34,840 $ 16,166 Valuation allowance (45,343 ) (27,130 ) Net deferred tax liabilities $ (10,503 ) $ (10,964 ) Realization of the future tax benefits is dependent on the Company’s ability to generate sufficient taxable income within the carryforward period. Management periodically evaluates the recoverability of the deferred tax assets and assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets. Because of the Company’s recent history of operating losses, management believes the future benefits of deferred tax assets are not likely to be realized. Based on the weight of all evidence, including a history of operating losses and the Company’s ability to generate future taxable income to realize these assets, management has determined it is more likely than not that the net deferred tax assets will not be realized and a full valuation allowance has been established to offset the net deferred tax asset. The Company’s valuation allowance increased by $18.2 million from 2017 to 2018. Additionally, the company has a deferred tax liability of $10.5 million related the acquisition of in-process non-taxable As of December 31, 2018, the Company had federal net operating loss carryforwards of approximately $48.8 million, with $25.1 million of net operating losses generated during 2018 carrying forward indefinitely and $23.7 million of net operating losses beginning to expire between 2031 and 2037. There are state net operating loss carryforwards of approximately $11.2 million and foreign net operating loss carryforwards of $41.3 million. The state net operating loss carryforwards will begin to expire in 2031 and the foreign net operating loss carryforwards will begin to expire in 2034. In addition, the Company also has federal credit carryforwards of approximately $2.9 million as of December 31, 2018 which may be available to offset future tax liabilities. These federal credits will expire between 2036 and 2038. Utilization of the net operating loss and research credit carryforwards may be subject to substantial annual limitations due to ownership change limitations that may have occurred or that could occur in the future, as required by Sections 382 and 383 of the Code, as well as similar state provisions. Under Sections 382 and 383 of the Code, if a corporation undergoes an “ownership change,” generally defined as a greater than 50 percentage point change (by value) in its equity ownership by certain stockholders over a three-year period, the corporation’s ability to use its pre-change pre-change The Company has not completed a study to assess whether an ownership change has occurred. If the Company has experienced an ownership change, utilization of the net operating loss and research credit carryforwards would be subject to an annual limitation under Sections 382 and 383 of the Code. Any limitation may result in expiration of a portion of the net operating loss carryforwards before utilization. Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact its effective tax rate. Any carryforwards that will expire prior to utilization as a result of such limitations will be removed from deferred tax assets with a corresponding reduction of the valuation allowance. The following table summarizes the changes in the amount of our unrecognized tax benefits (in thousands): Unrecognized tax benefits at December 31, 2016 984 Increase / (Decrease) for prior year tax positions 4 Increase for current year tax positions — Unrecognized tax benefits at December 31, 2017 $ 988 Increase / (Decrease) for prior year tax positions — Increase for current year tax positions — Unrecognized tax benefits at December 31, 2018 $ 988 Any uncertain tax positions would be related to tax years that remain open and subject to examination by the relevant tax authorities. The Company has no liabilities related to uncertain tax positions, but does have unrecognized tax benefits of $1.0 million which have been recorded as a direct reduction to the deferred tax asset as of the year ended December 31, 2018. At December 31, 2018 and 2017, the Company had unrecognized tax benefits of $1.0 million and $1.0 million, respectively. The Company does not expect any significant increases or decreases to the Company’s unrecognized tax benefits within the next 12 months. If recognized, none of the unrecognized tax benefits would impact the Company’s effective tax rate due to the existence of the valuation allowance. The Company is subject to U.S. federal tax authority examinations and U.S. state tax authority examinations for all years with the net operating loss and credit carryforwards. At December 31, 2018, the Company has not accrued for interest or penalties associated with unrecognized tax liabilities. In subsequent periods, any interest and penalties related to uncertain tax positions will be recognized as a component of income tax expense.

Selected Quarterly Consolidated

Selected Quarterly Consolidated Financial Data	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Consolidated Financial Data	15. Selected Quarterly Consolidated Financial Data (Unaudited) The following table contains unaudited consolidated financial information on a quarterly basis for 2018 and 2017. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended December 31, 2018 Total operating expenses $ 18,477 $ 21,668 $ 16,584 $ 19,769 Other income (expense), net 1,374 1,429 (210 ) 434 Net loss (17,103 ) (20,239 ) (16,794 ) (19,335 ) Net loss per share, basic and diluted $ (0.85 ) $ (1.00 ) $ (0.82 ) $ (0.93) First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended December 31, 2017 Total operating expenses $ 8,993 $ 11,266 $ 14,322 $ 13,990 Other income (expense), net (1,160 ) (1,672 ) (2,154 ) 2,722 Net loss (10,107 ) (12,857 ) (16,391 ) (11,190 ) Net loss per share, basic and diluted $ (5.30 ) $ (6.50 ) $ (1.12 ) $ (0.56 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events On January 2, 2019, the Company implemented a corporate restructuring to focus resources on its lead product candidate, SNA-120 On January 28, 2019, the Company executed an amendment to the loan and security agreement entered into with Silicon Valley Bank (“SVB”) on June 29, 2018. Under the original agreement, the Company drew down a principal amount of $30.0 million on June 29, 2018, with access to term loans in an aggregate principal amount of up to $40.0 million. Under the amendment, the Company’s total access to term loans is $30.0 million, with additional minimum liquidity requirements. The final payment fee has been increased by 1% to 6.5% of the total term loans advanced. In connection with the amendment, on the amendment effective date, the Company issued to SVB and its affiliate, 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. On February 8, 2019, the Company announced top-line SNA-001 SNA-001 SNA-001. On February 20, 2019, the Company entered into an underwriting agreement with Cowen and Company, LLC and BMO Capital Markets Corp., pursuant to which the Company agreed to issue and sell 8,000,000 shares of its common stock, par value $0.0001 per share to the underwriters. The shares were sold at a public offering price of $2.50 per share, and were purchased by the underwriters from the Company at a price of $2.35 per share. Under the terms of the underwriting agreement, the Company granted the underwriters the option, for 30 days, to purchase up to 1,200,000 additional shares of common stock at the public offering price. The Offering was made under a prospectus supplement and related prospectus filed with the Securities and Exchange Commission pursuant to the Company’s effective shelf registration statement on Form S-3, as No. 333-226595). On February 28, 2019, the underwriters exercised in full their option to purchase 1,200,000 additional shares of the Company’s common stock. The Company received net proceeds from the offering option exercise of approximately $2.8 million, after deducting the underwriters’ discounts and commissions and estimated offering expenses payable by the Company.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP.
Principles of Consolidation	Principles of Consolidation The 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 years ended December 31, 2018, 2017 and 2016, the subsidiaries’ net loss included in the Company’s consolidated statement of operations was $3.3 million, $2.6 million and $0.2 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 consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. The most significant estimates in the Company’s consolidated financial statements relate to equity awards, the success payment liability, clinical trial accruals and the valuation of 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.
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 December 31, 2018, 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 December 31, 2018 and 2017, 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 impairments recognized during the years ended December 31, 2018 and 2017.
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 years ended December 31, 2018 and 2017.
Other Income and Expense	Other Income and Expense Other income and expense includes amounts relating to the remeasurement of the success payment liability, interest earned on the Company’s bank accounts, interest expense incurred in connection with the SVB term loan described in Note 10, “Long-Term Debt”, and the amortization of the debt discount in connection with the Series B Bridge Notes described in Note 8, “Convertible Notes”.
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. Stock options issued to 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 December 31, 2018, there have been no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. The Company’s clinical trial accrual is dependent in part upon the timely and accurate reporting of contract research organizations and other third-party vendors. Prepaid expenses and other current assets include no prepaid clinical trial costs as of December 31, 2018 and $1.1 million as of December 31, 2017. Other accrued expenses include accrued clinical trial costs of $2.3 million and $0.9 million as of December 31, 2018 and 2017, 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 years ended December 31, 2018, 2017 and 2016. Shares excluded from the calculation were 2.6 million, 1.7 million and 11.0 million at December 31, 2018, 2017 and 2016, respectively.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred taxes are recognized based on the differences between financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. The Company has provided a full valuation allowance on its deferred tax assets. The provision for income taxes represents the current tax payable for the period and the change during the period in deferred tax assets and liabilities. The Company recognizes the effect of an income tax position only if, based on its merits, the position is more likely than not to be sustained on audit by the taxing authorities. Interest and penalties related to uncertain tax positions are recorded as income tax expense.
Business combinations	Business combinations Business combinations are accounted for using the acquisition method of accounting. Under the acquisition method, assets acquired, including in-process
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Included in other comprehensive income (loss) for the years ended December 31, 2018, 2017 and 2016 are an unrealized foreign currency translation loss of $2.2 million, a gain of $5.7 million and a loss of $0.4 million, respectively. This is the Company’s only component of other comprehensive income (loss) for the years ended December 31, 2018, 2017 and 2016.
Foreign currency translation	Foreign currency translation The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. These include the entities acquired as part of the Creabilis acquisition. See Note 4, “Creabilis Acquisition”. As part of this transaction, the Company acquired entities in the United Kingdom, denominated in British pounds, and Italy and Luxembourg, denominated in euros. The U.S. dollar effects that arise from translating net assets of these subsidiaries at changing rates are recognized in other comprehensive income (loss) in the 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 March 2018, the FASB issued ASU 2018-05, Income Taxes (Topic 740)—Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118”, No. 115-97, In May 2017, the FASB issued ASU 2017-09, Compensation Stock Compensation (Topic 718): Scope of Modification Accounting In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment”, one-step 2017-04 In January 2017, the FASB issued ASU 2017-01 “Business Combinations (Topic 805): Clarifying the Definition of a Business”, In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” (“ASU 2016-18”). No. 2016-18 beginning-of-period end-of-period 2016-18, In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230)” (“ASU 2016-15”), In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09”) ASU 2014-09 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 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 Revenue from Contracts with Customers. 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”, 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 The Company has nearly completed its assessment of ASU 2016-02 right-of-use The Company will adopt the new leasing standards using the modified retrospective transition approach to be applied to leases existing as of, or entered into after, January 1, 2019 and prior periods will not be adjusted. The new standard provides a number of optional practical expedients in transition. The Company has elected the package of practical expedients to not reassess prior conclusions about lease identification under the new standard, lease classification, and initial direct costs. The Company also elected the practical expedient allowing the use of hindsight in determining the lease term and assessing impairment of right-of-use right-of-use, right-of-use non-lease

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment consisted of the following as of December 31, 2018 and 2017 (in thousands): Estimated December 31, 2018 2017 Lab equipment 5 $ 307 $ 307 Computer hardware 3 142 116 Capital lease equipment 3 46 46 Furniture and fixtures 5 87 91 Software 3 9 — Leasehold improvements 105 105 Total 696 665 Less accumulated depreciation (385 ) (233 ) Property and equipment, net $ 311 $ 432

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
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 December 31, 2018 and 2017 (in thousands): December 31, 2018 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 48,526 $ — $ — Total $ 48,526 $ — $ — Liabilities: Success payment liability $ — $ — $ 3 Contingent consideration — — 29,200 Total $ — $ — $ 29,203 December 31, 2017 Level 1 Level 2 Level 3 Assets: Cash equivalents $ 74,467 $ — $ — Total $ 74,467 $ — $ — Liabilities: Success payment liability $ — $ — $ 3,285 Contingent consideration — — 22,900 Total $ — $ — $ 26,185
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): Success Payment Contingent Balance at December 31, 2017 $ 3,285 $ 22,900 Change in fair value due to remeasurement (3,282 ) 6,300 Balance at December 31, 2018 $ 3 $ 29,200

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
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): December 31, 2018 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 1,650 Total principal and final fee payments 31,650 Unamortized discount and debt issuance costs (1,525 ) Long-term debt, net $ 30,125

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments under Operating Lease Arrangements	The lease contains a renewal option for an additional three-year term. Future minimum rental payments under the lease arrangements as of December 31, 2018, are as follows (in thousands): Year ending December 31: 2019 $ 432 2020 74 2021 — 2022 — Thereafter — Total minimum lease payments $ 506

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
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 as of December 31, 2018 and 2017 (in thousands): 2018 2017 Common stock awards outstanding 2,263 1,159 Common stock awards available for grant under employee benefit plans 1,370 1,533 Total shares of common stock reserved for future issuance 3,633 2,692
Summary of Assumptions Used for Grant Date Fair Value	The following assumptions were used for grant date fair value for the years ended December 31, 2018, 2017 and 2016: Year Ended December 31, 2018 2017 2016 Expected stock price volatility 65.40–74.21 % 59.13%–64.09 % 46.72%–54.76 % Expected dividend yield — % — % — % Expected term (in years) 5.0–6.1 5.3–10.0 4.0–10.0 Risk-free interest rate 2.55–3.06 % 1.77%–2.60 % 1.12%–2.42 %
Summary of Stock Option Activity	The table below summarizes the stock option activity for the years ended December 31, 2018, 2017 and 2016: Number Weighted Aggregate Outstanding at December 31, 2015 — — — Granted 1,020 $ 2.35 — Exercised (372 ) 2.35 $ 87 Cancelled (75 ) 2.35 — Outstanding at December 31, 2016 573 $ 2.35 $ 1,412 Granted 686 12.22 — Exercised (92 ) 2.35 260 Cancelled (8 ) 2.35 — Outstanding at December 31, 2017 1,159 $ 8.19 $ 11,795 Granted 1,358 15.95 — Exercised (37 ) 11.04 168 Cancelled (217 ) 12.14 — Outstanding at December 31, 2018 2,263 $ 12.42 $ 18 Exercisable at December 31, 2018 561 $ 7.05 $ 17
Summary of Non-cash Stock-based Compensation Expense	Total compensation cost recorded in the consolidated statements of operations and comprehensive loss, which includes non-cash non-employees non-employees non-cash Year Ended December 31, 2018 2017 2016 Research and development $ 1,519 $ 487 $ 104 General and administrative 3,181 1,625 254 $ 4,700 $ 2,112 $ 358

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Summary of Loss Before Taxes	The amount of loss before taxes (in thousands): Year Ended December 31, 2018 2017 2016 U.S. loss before taxes $ (70,206 ) $ (48,258 ) $ (20,937 ) Foreign loss before taxes (3,265 ) (2,577 ) (225 ) Loss before income taxes $ (73,471 ) $ (50,835 ) $ (21,162 )
Summary of Income Tax Benefit	Income tax benefit for the years ended December 31, 2018, 2017 and 2016 consists of the following (in thousands): Year Ended December 31, 2018 2017 2016 Current: Federal $ — $ (226 ) $ — State — (64 ) — Foreign — — — Total Current $ — $ (290 ) $ — Deferred: Federal $ — $ — $ — State — — — Foreign — — — Total Deferred — — — Income Tax Benefit $ — $ (290 ) $ —
Summary of Reconciliation of Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate	A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Tax computed at federal statutory rate $ (15,429 ) $ (17,284 ) $ (7,407 ) State income taxes, net of federal tax benefit (1,867 ) (1,713 ) (1,058 ) Rate difference on non-US (96 ) 482 33 Research and development credits (1,527 ) (929 ) (359 ) Success based payments (689 ) 688 199 Valuation allowance 18,637 6,222 7,582 Uncertain tax positions — — 379 Transaction costs — — 587 Tax Cut and Jobs Act — 8,960 — Contingent consideration 1,323 1,016 — Return to provision and true-ups (718 ) 2,499 — Permanent items 366 (231 ) 44 Income tax benefit $ — $ (290 ) $ —
Summary of Net Deferred Tax Assets	The components that comprise the Company’s net deferred tax assets at December 31, 2018 and 2017 consist of the following (in thousands): Year Ended December 31, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 19,868 $ 15,815 Amortization 20,754 8,818 Stock-based compensation 1,021 392 R&D credit carryforwards 2,894 1,367 Accrued expenses 648 600 Other 176 168 Total deferred tax assets $ 45,361 $ 27,160 Deferred tax liabilities Foreign intangibles $ (10,503 ) $ (10,964 ) Fixed assets (18 ) (30 ) Total deferred tax liabilities $ (10,521 ) $ (10,994 ) Net deferred tax assets $ 34,840 $ 16,166 Valuation allowance (45,343 ) (27,130 ) Net deferred tax liabilities $ (10,503 ) $ (10,964 )
Summary of Changes in Unrecognized Tax Benefits	The following table summarizes the changes in the amount of our unrecognized tax benefits (in thousands): Unrecognized tax benefits at December 31, 2016 984 Increase / (Decrease) for prior year tax positions 4 Increase for current year tax positions — Unrecognized tax benefits at December 31, 2017 $ 988 Increase / (Decrease) for prior year tax positions — Increase for current year tax positions — Unrecognized tax benefits at December 31, 2018 $ 988

Selected Quarterly Consolidat_2

Selected Quarterly Consolidated Financial Data (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following table contains unaudited consolidated financial information on a quarterly basis for 2018 and 2017. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended December 31, 2018 Total operating expenses $ 18,477 $ 21,668 $ 16,584 $ 19,769 Other income (expense), net 1,374 1,429 (210 ) 434 Net loss (17,103 ) (20,239 ) (16,794 ) (19,335 ) Net loss per share, basic and diluted $ (0.85 ) $ (1.00 ) $ (0.82 ) $ (0.93) First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended December 31, 2017 Total operating expenses $ 8,993 $ 11,266 $ 14,322 $ 13,990 Other income (expense), net (1,160 ) (1,672 ) (2,154 ) 2,722 Net loss (10,107 ) (12,857 ) (16,391 ) (11,190 ) Net loss per share, basic and diluted $ (5.30 ) $ (6.50 ) $ (1.12 ) $ (0.56 )

Organization and Description _2

Organization and Description of Business - Additional Information (Detail)	Feb. 28, 2019USD ($)shares	Jan. 02, 2019Positions	Aug. 01, 2017USD ($)$ / sharesshares	Jul. 20, 2017	Feb. 28, 2019USD ($)shares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)	Jan. 28, 2019USD ($)	Aug. 31, 2018USD ($)	Aug. 03, 2018USD ($)	Jun. 29, 2018USD ($)
Organization And Description Of Business [Line Items]
Reverse stock split				0.17036
Net proceeds from initial public offering			$ 66,400,000				$ 66,378,000
Common stock, shares outstanding | shares						21,200,000
Common stock, shares authorized | shares			300,000,000			300,000,000	300,000,000
Common stock, par value | $ / shares			$ 0.0001			$ 0.0001	$ 0.0001
Preferred stock, shares authorized | shares			10,000,000			10,000,000	10,000,000
Preferred stock, par value | $ / shares			$ 0.0001			$ 0.0001	$ 0.0001
Principal outstanding						$ 30,000,000
Common stock shares issued | shares						21,177,000	20,740,000
Net proceeds from issuance of common stock						$ 5,387,000	$ 188,000	$ 831,000
Subsequent Event [Member]
Organization And Description Of Business [Line Items]
Net proceeds from initial public offering	$ 2,800,000
Restructuring and related cost, number of positions eliminated | Positions		20
Restructuring and related cost, number of positions eliminated in percent		34.00%
Common stock shares issued | shares	9,200,000				9,200,000
Net proceeds from issuance of common stock					$ 21,300,000
Term Loan [Member] | Subsequent Event [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
Term Loan [Member] | Silicon Valley Bank [Member] | Subsequent Event [Member]
Organization And Description Of Business [Line Items]
Debt instrument aggregate principal amount									$ 30,000,000
Common Stock [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares | shares						340,000	4,983,000
Public offering price per share | $ / shares							$ 15
Convertible preferred stock, as converted into common stock | shares			12,800,000			12,800,000	12,800,000
Common Stock [Member] | Subsequent Event [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares | shares	1,200,000
Initial Public Offering [Member] | Common Stock [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares | shares			4,983,333
Public offering price per share | $ / shares			$ 15
Over-Allotment Option [Member] | Common Stock [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares | shares			650,000
ATM Offering Program [Member]
Organization And Description Of Business [Line Items]
Common stock issued through initial public offering, shares | shares						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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liquidity Risks [Abstract]
Accumulated deficit	$ (159,368)				$ (85,897)				$ (159,368)	$ (85,897)
Net losses	(19,335)	$ (16,794)	$ (20,239)	$ (17,103)	(11,190)	$ (16,391)	$ (12,857)	$ (10,107)	(73,471)	(50,545)	$ (21,162)
Net cash used in operating activities									$ (61,693)	(41,012)	$ (17,609)
Substantial doubt about going concern, within one year									false
Cash and cash equivalents	$ 48,526				$ 74,467				$ 48,526	$ 74,467

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) shares in Millions	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)Segmentshares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares	Jan. 01, 2019USD ($)
Significant Accounting Policies [Line Items]
Net loss			$ (19,335,000)	$ (16,794,000)	$ (20,239,000)	$ (17,103,000)	$ (11,190,000)	$ (16,391,000)	$ (12,857,000)	$ (10,107,000)	$ (73,471,000)	$ (50,545,000)	$ (21,162,000)
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
Prepaid clinical trial costs	$ 0	$ 1,100,000
Accrued clinical trial costs	2,300,000	900,000	2,300,000				900,000				$ 2,300,000	$ 900,000
Shares excluded from calculation of earnings per share | shares											2.6	1.7	11
Unrealized foreign currency translation gains and (losses)											$ 2,200,000	$ (5,700,000)	$ (400,000)
Revenue											0
Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Operating lease liability														$ 1,000,000
Right-of-use assets														$ 800,000
Subsidiaries [Member]
Significant Accounting Policies [Line Items]
Net loss											$ 3,300,000	2,600,000	$ 200,000
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	$ 200,000				$ 200,000				$ 200,000	$ 200,000

Creabilis Acquisition - Additio

Creabilis Acquisition - Additional Information (Detail) - USD ($)	Oct. 19, 2017	Dec. 06, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Deferred tax liability			$ 10,503,000				$ 10,964,000				$ 10,503,000	$ 10,964,000
Goodwill			10,989,000				11,472,000				10,989,000	11,472,000
Goodwill impairment											0	0
Net loss			(19,335,000)	$ (16,794,000)	$ (20,239,000)	$ (17,103,000)	(11,190,000)	$ (16,391,000)	$ (12,857,000)	$ (10,107,000)	(73,471,000)	(50,545,000)	$ (21,162,000)
Creabilis [Member]
Business Acquisition [Line Items]
Upfront cash payment		$ 200,000
Business combination, settlement of liabilities		6,700,000
Potential contingent milestone payments	$ 18,000,000
Acquired tangible assets, deferred tax liability		9,400,000
Deferred tax liability			10,500,000				11,000,000				10,500,000	11,000,000
Deferred tax liability translation adjustments			500,000								500,000
Goodwill		$ 9,800,000	$ 11,000,000				11,500,000				11,000,000	11,500,000
Translation adjustments of goodwill											500,000
Goodwill impairment											0	0
Net loss											$ (3,300,000)	(2,600,000)	(200,000)
Creabilis [Member] | General and Administrative [Member]
Business Acquisition [Line Items]
Business combination, transaction costs													$ 1,700,000
Creabilis [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Shares issued for contingent milestone payment	201,268
Shares issued for contingent milestone payment, value	$ 4,200,000
Shares issued for contingent milestone payment, price per share	$ 20.86
Maximum [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Royalty percentage			1.00%								1.00%
Convertible Preferred Stock Series A Three [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination shares issued		1,407,679
Business combination shares issued, value		$ 11,200,000
Contingent Consideration [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Fair value of contingent consideration in acquisition			$ 29,200,000				$ 22,900,000				$ 29,200,000	$ 22,900,000
Development and Approval Milestones [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration		58,000,000
Net Sales Thresholds and One Time Royalties [Member] | Creabilis [Member]
Business Acquisition [Line Items]
Business combination, aggregate contingent consideration		$ 80,000,000

Identifiable Intangible Assets

Identifiable Intangible Assets - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 06, 2016
Indefinite-lived Intangible Assets [Line Items]
In-process research and development intangible assets, carrying value	$ 45,594,000	$ 47,597,000
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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 696	$ 665
Less accumulated depreciation	(385)	(233)
Property and equipment, net	$ 311	$ 432
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 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	3 years
Property, plant and equipment, gross	$ 142	$ 116
Capital Lease Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years	3 years
Property, plant and equipment, gross	$ 46	$ 46
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	5 years	5 years
Property, plant and equipment, gross	$ 87	$ 91
Software [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)	3 years	3 years
Property, plant and equipment, gross	$ 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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 157	$ 120	$ 67

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	Dec. 31, 2018	Dec. 31, 2017
Level 1 [Member]
Assets:
Cash equivalents	$ 48,526	$ 74,467
Total	48,526	74,467
Level 3 [Member]
Liabilities:
Financial liabilities fair value	29,203	26,185
Success Payment Liabilities [Member] | Level 3 [Member]
Liabilities:
Financial liabilities fair value	3	3,285
Contingent Consideration [Member] | Level 3 [Member]
Liabilities:
Financial liabilities fair value	$ 29,200	$ 22,900

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Success Payment Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 3,285
Change in fair value due to remeasurement	(3,282)
Ending balance	3	$ 3,285
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	22,900
Change in fair value due to remeasurement	6,300	(3,000)
Ending balance	$ 29,200	$ 22,900

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	Oct. 19, 2017USD ($)shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value transfer amount		$ 0	$ 0
Creabilis [Member] | Discount Rate [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input		0.076
Creabilis [Member] | Discount Rate [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration measurement input		0.169
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		0.038
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		0.501
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		$ 6,300,000	(1,200,000)
Fair value of contingent payment settled in stock			4,200,000
Change in fair value due to re-measurement recorded in expense		(6,300,000)	3,000,000
Contingent Consideration [Member] | Creabilis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent milestone payment	$ 5,000,000
Offsets of the contingent consideration	$ 300,000
Success Payment Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded in expense		3,282,000
Other Income [Member] | Success Payment Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded in expense		$ 3,300,000
Other Expense [Member] | Success Payment Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value due to re-measurement recorded in expense			$ 2,000,000	$ 600,000
Common Stock [Member] | Creabilis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares issued for contingent milestone payment | shares	201,268

Convertible Notes - Additional

Convertible Notes - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended		12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Debt Conversion [Line Items]
Accrued interest expense			$ 476,000	$ 34,000
Series B Bridge Notes [Member]
Debt Conversion [Line Items]
Debt instrument face amount	$ 3,900,000	$ 3,900,000
Debt instrument face amount Debt instrument interest percentage		6.00%
Debt instrument maturity date		Jan. 27, 2018
Debt conversion discount percentage		15.00%
Debt discount		$ 700,000
Series B Bridge Notes [Member] | Series B Convertible Preferred Stock [Member]
Debt Conversion [Line Items]
Number of shares issued on conversion of debt	0.4
Per share price of shares issued on conversion of debt	$ 10.40
Amortization of debt discount				700,000
Accrued interest payable	$ 34,000
Accrued interest expense				$ 34,000

Success Payment Liability - Add

Success Payment Liability - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Success Payment Liability [Line Items]
Success payment liability threshold one	$ 10,000,000
Success payment liability threshold one per share	$ 53.71
Success payment liability threshold two	$ 35,000,000
Success payment liability threshold two per share	$ 71.61
Success payment liability threshold maximum	$ 60,000,000
Success payment liability threshold maximum per share	$ 107.42
Success payment liability	$ 60,000,000
Success Payment Liabilities [Member]
Success Payment Liability [Line Items]
Change in fair value due to re-measurement recorded income (expense)	3,282,000
Other Income [Member] | Success Payment Liabilities [Member]
Success Payment Liability [Line Items]
Change in fair value due to re-measurement recorded income (expense)	$ 3,300,000
Other Expense [Member] | Success Payment Liabilities [Member]
Success Payment Liability [Line Items]
Change in fair value due to re-measurement recorded income (expense)		$ 2,000,000	$ 600,000

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Jun. 29, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Principal outstanding	$ 30,000,000		$ 30,000,000
Final maturity payment	1,650,000		1,650,000
Silicon Valley Bank [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan, aggregate principal amount	30,000,000	$ 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
Unrestricted cash threshold amount	$ 30,000,000		$ 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
Warrants issued to purchase common stock	535,714		535,714
Warrant exercise price	$ 2.80		$ 2.80
Warrant term			10 years
Principal outstanding	$ 30,000,000		$ 30,000,000
Debt issuance costs	100,000		100,000
Final maturity payment	$ 1,700,000		1,700,000
Interest expense			$ 1,500,000
Effective interest rate	9.39%		9.39%
Silicon Valley Bank [Member] | Term Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate percentage	7.25%		7.25%
Final payment fee percentage	1.00%		1.00%
Silicon Valley Bank [Member] | Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate percentage	8.00%		8.00%
Final payment fee percentage	6.50%		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) $ in Thousands	Dec. 31, 2018USD ($)
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	1,650
Total principal and final fee payments	31,650
Unamortized discount and debt issuance costs	(1,525)
Long-term debt, net	$ 30,125

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2017USD ($)ft²
Other Commitments [Line Items]
Rent expense		$ 400,000	$ 500,000	$ 200,000
Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
Operating lease obligation period	40 months
Operating lease expiry date	Feb. 29, 2020
Amended Lease Arrangement - Office Space in Westlake Village, California [Member]
Other Commitments [Line Items]
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 Future Minimum Rental Payments under Operating Lease Arrangements (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 432
2020	74
2021	0
2022	0
Thereafter	0
Total minimum lease payments	$ 506

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Dec. 03, 2018	May 17, 2018	Jan. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017	May 31, 2016
Related Party Transaction [Line Items]
Number of nonvested shares				307,504	546,065
Recognized compensation expense				$ 4,700	$ 2,112	$ 413
Notes Receivable [Member]
Related Party Transaction [Line Items]
Principal balance and interest forgiven on promissory note							$ 1,300
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
Recognized compensation expense				$ 300	$ 500	$ 100
Number of shares vested				400,000	200,000
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
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	Dec. 31, 2018	Dec. 31, 2017	Aug. 01, 2017
Class of Stock Disclosures [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000	300,000,000
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001	$ 0.0001

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Shares of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock Disclosures [Abstract]
Common stock awards outstanding	2,263	1,159	573
Common stock awards available for grant under employee benefit plans	1,370	1,533
Total shares of common stock reserved for future issuance	3,633	2,692

Stockholders' Equity - Converti

Stockholders' Equity - Convertible Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Apr. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Aug. 01, 2017
Class of Stock [Line Items]
Preferred stock, shares outstanding		0	0
Common Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, as converted into common stock		12,800,000	12,800,000	12,800,000
Per share price of shares issued on conversion of debt			$ 15
Series B Convertible Preferred Stock Financing [Member]
Class of Stock [Line Items]
Aggregate proceeds from issuance of preferred stock	$ 36.5
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding		0	0
Series B Convertible Preferred Stock [Member] | Series B Convertible Preferred Stock Financing [Member]
Class of Stock [Line Items]
Per share price of shares issued on conversion of debt	$ 12.24
Number of shares issued on conversion of debt	3,000,000
Series B Convertible Preferred Stock [Member] | Series B Bridge Notes [Member]
Class of Stock [Line Items]
Per share price of shares issued on conversion of debt	$ 10.40
Number of shares issued on conversion of debt	400,000

Stockholders' Equity - ATM Offe

Stockholders' Equity - ATM Offering Program - Additional Information (Detail) - ATM Offering Program [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Aug. 31, 2018	Aug. 03, 2018
Class of Stock [Line Items]
Issuance of common stock	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	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2017
Class of Stock [Line Items]
Common stock available for issuance under plan		3,633,000	2,692,000
Number of shares granted to non-employee		1,358,000	686,000	1,020,000
Unrecognized compensation expense related to unvested employee stock award		$ 13,600,000
Unrecognized compensation expense related to unvested employee stock award, recognized period		3 years 2 months 1 day
Weighted-average grant date fair value of stock options granted		$ 15.95
Weighted-average remaining contractual life of options outstanding		8 years 9 months 18 days
Fair value of shares vested		$ 3,300,000
Stock compensation expense related to non-employee option grants		$ 300,000	$ 800,000	$ 48,000
Unvested shares		307,504	546,065
Early exercise liability related to unvested shares		$ 300,000	$ 500,000
Early exercise liability related to unvested shares, current		213,000	231,000
Early exercise liability related to unvested shares, non-current		45,000	258,000
Recognized compensation expense		$ 4,700,000	$ 2,112,000	$ 358,000
2017 Incentive Award Plan [Member]
Class of Stock [Line Items]
Common stock available for issuance under plan					1,000,000
Incentive award plan, description		The 2017 Plan serves as the successor incentive award plan to the Company’s 2010 Equity Incentive Plan, or the 2010 Plan, and has 1.3 million shares of common stock available for issuance pursuant to a variety of stock-based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock-based awards, plus shares of common stock that were reserved for issuance pursuant to future awards under the 2010 Plan at the time the 2017 Plan became effective, plus shares represented by awards outstanding under the 2010 Plan that are forfeited or lapse unexercised and which following the effective date of the 2017 Plan are not issued under the 2010 Plan. In addition, the 2017 Plan reserve will increase on January 1, 2018 and each subsequent anniversary through 2027, by an amount equal to the lesser of (a) four percent of the shares of stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (b) such smaller number of shares of stock as determined by our board of directors; provided, however, that no more than 12.0 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	300,000
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		$ 300,000
Number of shares issued from ESPP		67,508
Non-employee [Member]
Class of Stock [Line Items]
Contractual term		10 years
Number of shares granted to non-employee		0	35,000	65,000
Maximum [Member]
Class of Stock [Line Items]
Fair value of a common stock percentage		110.00%
Maximum [Member] | 2017 Incentive Award Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock under ESPP					12,000,000
Maximum [Member] | 2010 Equity Incentive Plan [Member]
Class of Stock [Line Items]
Stock awards exercisable period		5 years
Maximum [Member] | 2017 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock under ESPP	3,000,000
Minimum [Member]
Class of Stock [Line Items]
Common stock voting rights percentage		10.00%
Minimum [Member] | 2017 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Employee stock purchase price lower of the closing trading price	85.00%

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Assumptions Used for Grant Date Fair Value (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility, minimum	65.40%	59.13%	46.72%
Expected stock price volatility, maximum	74.21%	64.09%	54.76%
Expected dividend yield	0.00%	0.00%	0.00%
Risk-free interest rate, minimum	2.55%	1.77%	1.12%
Risk-free interest rate, maximum	3.06%	2.60%	2.42%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	5 years	5 years 3 months 18 days	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	6 years 1 month 6 days	10 years	10 years

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Outstanding, beginning balance	1,159	573
Number of Shares, Granted	1,358	686	1,020
Number of Shares, Exercised	(37)	(92)	(372)
Number of Shares, Cancelled	(217)	(8)	(75)
Number of Shares, Outstanding, ending balance	2,263	1,159	573
Number of Shares, Exercisable, ending balance	561
Weighted Average Exercise Price Per Share, Outstanding, beginning balance	$ 8.19	$ 2.35
Weighted Average Exercise Price Per Share, Granted	15.95	12.22	$ 2.35
Weighted Average Exercise Price Per Share, Exercised	11.04	2.35	2.35
Weighted Average Exercise Price Per Share, Cancelled	12.14	2.35	2.35
Weighted Average Exercise Price Per Share, Outstanding, ending balance	$ 12.42	$ 8.19	2.35
Aggregate Intrinsic Value, Outstanding, beginning balance	$ 11,795	$ 1,412
Weighted Average Exercise Price Per Share, Exercisable, ending balance	$ 7.05
Aggregate Intrinsic Value, Granted	$ 0	$ 0	$ 0
Aggregate Intrinsic Value, Exercised	$ 168	$ 260	$ 87
Aggregate Intrinsic Value, Cancelled	0	0	0
Aggregate Intrinsic Value, Outstanding, ending balance	18	$ 11,795	$ 1,412
Aggregate Intrinsic Value, Exercisable, ending balance	$ 17

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Non-cash Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 4,700	$ 2,112	$ 358
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	1,519	487	104
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash stock-based compensation expense	$ 3,181	$ 1,625	$ 254

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Statutory tax rate	21.00%	35.00%
Reduction in deferred tax assets		$ 9,000,000
Increase in valuation allowance	$ 18,200,000
Deferred tax liability	10,503,000	10,964,000
Federal net operating loss carryforwards	48,800,000
Federal net operating loss carryforwards, Not Subject to Expiration	25,100,000
Federal net operating loss carryforwards, Subject to Expiration	$ 23,700,000
Federal and state net operating loss expiry period beginning year	2031
Federal and state net operating loss expiry period ending year	2037
State net operating loss carryforwards	$ 11,200,000
Foreign net operating loss carryforwards	$ 41,300,000
State net operating loss expiry period beginning year	2031
Foreign net operating loss expiry period beginning year	2034
Federal credit carryforwards	$ 2,900,000
Federal credit carryforwards expiry period beginning year	2036
Federal credit carryforwards expiry period ending year	2038
Possible ownership change, evaluation period	3 years
Purchase or sale of stock percentage	0.50%
Unrecognized tax benefits related to direct reduction to the deferred tax asset	$ 1,000,000
Unrecognized tax benefits	988,000	988,000	$ 984,000
Accrual for unrecognized tax benefits and interest	0
Creabilis [Member]
Income Tax Disclosure [Line Items]
Deferred tax liability	$ 10,500,000	$ 11,000,000

Income Taxes - Summary of Loss

Income Taxes - Summary of Loss Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest [Abstract]
U.S. loss before taxes	$ (70,206)	$ (48,258)	$ (20,937)
Foreign loss before taxes	(3,265)	(2,577)	(225)
Net loss before taxes	$ (73,471)	$ (50,835)	$ (21,162)

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal		$ (226)
State		(64)
Foreign	$ 0	0	$ 0
Total Current		(290)
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Total Deferred	$ 0	0	$ 0
Income tax benefit		$ (290)

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax computed at federal statutory rate	$ (15,429)	$ (17,284)	$ (7,407)
State income taxes, net of federal tax benefit	(1,867)	(1,713)	(1,058)
Rate difference on non-USearnings	(96)	482	33
Research and development credits	(1,527)	(929)	(359)
Success based payments	(689)	688	199
Valuation allowance	18,637	6,222	7,582
Uncertain tax positions			379
Transaction costs			587
Tax Cut and Jobs Act		8,960
Contingent consideration	1,323	1,016
Return to provision and true-ups	(718)	2,499
Permanent items	$ 366	(231)	$ 44
Income tax benefit		$ (290)

Income Taxes - Summary of Net D

Income Taxes - Summary of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 19,868	$ 15,815
Amortization	20,754	8,818
Stock-based compensation	1,021	392
R&D credit carryforwards	2,894	1,367
Accrued expenses	648	600
Other	176	168
Total deferred tax assets	45,361	27,160
Deferred tax liabilities
Foreign intangibles	(10,503)	(10,964)
Fixed Assets	(18)	(30)
Total deferred tax liabilities	(10,521)	(10,994)
Net deferred tax assets	34,840	16,166
Valuation allowance	(45,343)	(27,130)
Net deferred tax liabilities	$ (10,503)	$ (10,964)

Income Taxes - Summary of Chang

Income Taxes - Summary of Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Uncertainties [Abstract]
Unrecognized tax benefits, beginning balance	$ 988	$ 984
Increase / (Decrease) for prior year tax positions		4
Increase for current year tax positions	0	0
Unrecognized tax benefits, ending balance	$ 988	$ 988

Selected Quarterly Financial Da

Selected Quarterly Financial Data - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total operating expenses	$ 19,769	$ 16,584	$ 21,668	$ 18,477	$ 13,990	$ 14,322	$ 11,266	$ 8,993	$ 76,498	$ 48,571	$ 20,689
Other income (expense), net	434	(210)	1,429	1,374	2,722	(2,154)	(1,672)	(1,160)	3,027	(2,264)	(473)
Net loss	$ (19,335)	$ (16,794)	$ (20,239)	$ (17,103)	$ (11,190)	$ (16,391)	$ (12,857)	$ (10,107)	$ (73,471)	$ (50,545)	$ (21,162)
Net loss per share, basic and diluted	$ (0.93)	$ (0.82)	$ (1)	$ (0.85)	$ (0.56)	$ (1.12)	$ (6.50)	$ (5.30)	$ (3.59)	$ (5.19)	$ (12.49)

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Thousands	Feb. 28, 2019USD ($)shares	Feb. 22, 2019USD ($)shares	Feb. 20, 2019$ / sharesshares	Jan. 28, 2019USD ($)$ / sharesshares	Jan. 02, 2019Position	Aug. 01, 2017USD ($)$ / shares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Jun. 29, 2018USD ($)
Subsequent Event [Line Items]
Principal outstanding							$ 30,000
Common stock, par value | $ / shares						$ 0.0001	$ 0.0001	$ 0.0001
Net proceeds from initial public offering						$ 66,400		$ 66,378
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of positions eliminated | Position					20
Number of positions eliminated as percentage of total workforce					34.00%
Offering price per share | $ / shares			$ 2.50
Net proceeds from initial public offering	$ 2,800
Common Stock [Member]
Subsequent Event [Line Items]
Issuance of common stock | shares							340,000	4,983,000
Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Issuance of common stock | shares	1,200,000
Cowen and Bmo Capital Markets Corp [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock issued public offering | shares		8,000,000
Net Proceeds from offering		$ 18,500
Cowen and Bmo Capital Markets Corp [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock shares subscribed | shares			8,000,000
Common stock, par value | $ / shares			$ 0.0001
Offering price per share | $ / shares			$ 2.35
Cowen and Bmo Capital Markets Corp [Member] | Maximum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of additional shares authorized to purchase | shares			1,200,000
Option period			30 days
Term Loan [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Debt instrument aggregate principal amount				$ 30,000
Silicon Valley Bank [Member] | Warrant [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Warrants issued to purchase common stock | shares				535,714
Warrant exercise price | $ / shares				$ 2.80
Warrant term				10 years
Silicon Valley Bank [Member] | Term Loan [Member]
Subsequent Event [Line Items]
Principal outstanding									$ 30,000
Debt instrument aggregate principal amount									$ 40,000
Silicon Valley Bank [Member] | Term Loan [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Debt instrument aggregate principal amount				$ 30,000
Final payment fee percentage				6.50%