Soleno Therapeutics (SLNO) 10-K 20 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 06, 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	SLNO
Entity Registrant Name	SOLENO THERAPEUTICS INC
Entity Central Index Key	0001484565
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	Non-accelerated Filer
Entity Small Business	true
Entity Shell Company	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		31,755,169
Entity Public Float			$ 27.6

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 23,099	$ 17,100
Restricted cash		35
Prepaid expenses and other current assets	529	343
Due from related party	64
Minority interest investment in former subsidiary	978
Current assets held for sale		516
Total current assets	24,670	17,994
Long-term assets
Property and equipment, net	12	23
Other assets		126
Intangible assets, net	18,469	20,413
Long-term assets held for sale		466
Total assets	43,151	39,022
Current liabilities
Accounts payable	934	633
Accrued compensation and other current liabilities	943	973
Current liabilities held for sale		127
Total current liabilities	1,877	1,733
Long-term liabilities
Contingent liability for Essentialis purchase price	5,649	5,082
Other liabilities		13
Long-term liabilities held for sale		225
Total liabilities	12,738	12,205
Commitments and contingencies (Note 7)
Stockholders’ equity
Common stock	32	19
Additional paid-in-capital	157,413	140,495
Accumulated deficit	(127,032)	(113,697)
Total stockholders’ equity	30,413	26,817
Total liabilities and stockholders’ equity	43,151	39,022
Series B Convertible Preferred Stock [Member]
Stockholders’ equity
Preferred stock
Series A Warrant Liability [Member]
Long-term liabilities
Warrant liability	49	70
Series C Warrant [Member]
Long-term liabilities
Warrant liability	0	6
2017 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability	4,563	$ 5,076
2018 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability	$ 600

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Preferred stock par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock shares authorized	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	31,755,169	19,238,972
Common stock, shares outstanding	31,755,169	19,238,972
Series B Convertible Preferred Stock [Member]
Preferred stock par value (in dollars per share)	$ 0.001
Preferred stock shares authorized	13,780	13,780
Preferred stock, shares issued	0	4,571
Preferred stock, shares outstanding	0	4,571
Preferred stock, aggregate liquidation preference	$ 0	$ 0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating expenses
Research and development	$ 7,178	$ 3,069
Sales and marketing		26
General and administrative	6,556	6,584
Change in fair value of contingent consideration	567	2,492
Total operating expenses	14,301	12,171
Operating loss	(14,301)	(12,171)
Other income (expense)
Cease-use income	6	4
Change in fair value of warrants liabilities	522	(685)
Gain on deconsolidation of former subsidiary	1,994
Interest and other expense, net	(62)	(590)
Total other income (expense)	2,460	(1,271)
Loss from continuing operations before provision for income tax benefit	(11,841)	(13,442)
Provision for income tax benefit from continuing operations	0	1,650
Loss from continuing operations	(11,841)	(11,792)
Loss from discontinued operations:
Operating loss	(1,494)	(3,399)
Other expense		(194)
Total	(1,494)	(3,593)
Net loss	$ (13,335)	$ (15,385)
Loss per common share from continuing operations, basic and diluted	$ (0.56)	$ (1.31)
Loss per common share from discontinued operations, basic and diluted	(0.07)	(0.40)
Net loss per common share, basic and diluted	$ (0.64)	$ (1.71)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share	20,975,479	8,977,795

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	2017 Aspire Purchase Agreement [Member]	2017 PIPE Warrant Liability [Member]	2018 PIPE Warrant Liability [Member]	Essentialis, Inc. [Member]	Series B Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]2017 Aspire Purchase Agreement [Member]	Common Stock [Member]2017 PIPE Warrant Liability [Member]	Common Stock [Member]2018 PIPE Warrant Liability [Member]	Common Stock [Member]Essentialis, Inc. [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]2017 Aspire Purchase Agreement [Member]	Additional Paid-In Capital [Member]2017 PIPE Warrant Liability [Member]	Additional Paid-In Capital [Member]2018 PIPE Warrant Liability [Member]	Additional Paid-In Capital [Member]Essentialis, Inc. [Member]	Accumulated Deficit [Member]
Balances at beginning at Dec. 31, 2016	$ 3,435						$ 3					$ 101,744					$ (98,312)
Balances at beginning (shares) at Dec. 31, 2016						12,780	3,357,387
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,000											1,000
Issuance of common stock on conversion of series B convertible preferred shares							$ 2					(2)
Issuance of common stock on conversion of series B convertible preferred shares (shares)						(8,209)	1,641,800
Issuance of common stock to board members in lieu of cash payments for quarterly board fees	278											278
Issuance of common stock to board members in lieu of cash payments for quarterly board fees (shares)							90,306
Issuance of common stock to acquire Essentialis					$ 17,247						$ 4					$ 17,243
Issuance of common stock to acquire Essentialis (Shares)											3,783,388
Issuance of common stock		$ 10,000	$ 13,827					$ 2	$ 8				$ 9,998	$ 13,819
Issuance of common stock (shares)								2,083,333	8,141,116
Issuance of shares to Aspire Capital in lieu of commitment fees	602											602
Rounding adjustment resulting from 1 for 5 reverse split (Shares)							(24)
Fair value at transaction date of warrants to purchase common stock			$ (4,187)											$ (4,187)
Net loss	(15,385)																(15,385)
Balances at ending at Dec. 31, 2017	26,817						$ 19					140,495					(113,697)
Balances at end (shares) at Dec. 31, 2017						4,571	19,238,972
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares to Aspire Capital in lieu of commitment fees (Shares)							141,666
Stock-based compensation	829											829
Issuance of common stock on conversion of series B convertible preferred shares							$ 1					(1)
Issuance of common stock on conversion of series B convertible preferred shares (shares)						(4,571)	914,200
Issuance of restricted common stock for bonuses	159											159
Issuance of restricted common stock for bonuses (shares)							99,217
Issuance of common stock to board members in lieu of cash payments for quarterly board fees	275											275
Issuance of common stock to board members in lieu of cash payments for quarterly board fees (shares)							146,371
Issuance of common stock to acquire Essentialis											$ 1					$ (1)
Issuance of common stock to acquire Essentialis (Shares)											1,084,034
Issuance of common stock				$ 16,250						$ 11					$ 16,239
Issuance of common stock (shares)										10,272,375
Fair value at transaction date of warrants to purchase common stock				$ (582)											$ (582)
Net loss	(13,335)																(13,335)
Balances at ending at Dec. 31, 2018	$ 30,413						$ 32					$ 157,413					$ (127,032)
Balances at end (shares) at Dec. 31, 2018							31,755,169

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Less transaction costs	$ 250	$ 1,172
Common Stock [Member]
Reverse stock split		0.2

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (13,335)	$ (15,385)
Loss from discontinued operations	(1,494)	(3,593)
Loss from continuing operations	(11,841)	(11,792)
Adjustments to reconcile net loss from continuing operations to net cash used in operating activities:
Depreciation and amortization	1,963	1,611
Stock-based compensation expense	988	880
Income tax benefit		(1,651)
Board fees paid with common stock	275	278
Change in fair value of stock warrants	(522)	685
Change in fair value of contingent consideration	567	2,492
Non-cash expense of issuing shares to Aspire Capital		602
Gain on deconsolidation of former subsidiary	(1,994)
Operating loss of minority interest investment	160
Change in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	(60)	(97)
Due from related party	(64)
Accounts payable	249	191
Accrued compensation and other current liabilities	(43)	(78)
Other long-term liabilities		(40)
Net cash used in continuing operating activities	(10,322)	(6,919)
Net cash used in discontinued operating activities	(1,361)	(3,031)
Net cash used in operating activities	(11,683)	(9,950)
Cash flows from investing activities:
Costs of Essentialis acquisition paid		(573)
Security deposit on sublease		13
Purchases of property and equipment	(8)	(2)
Net cash used in continuing investing activities	(8)	(562)
Net cash (used in) provided by discontinued investing activities	(172)	716
Net cash (used in) provided by investing activities	(180)	154
Cash flows from financing activities:
Proceeds from issuance of common stock		10,000
Proceeds from sale of common stock and common stock warrants	16,500	15,008
Cash paid for the issuance of common stock and common stock warrants	(198)	(1,063)
Net cash provided by continuing financing activities	16,302	23,945
Net cash provided by discontinued financing activities	1,525	225
Net cash provided by financing activities	17,827	24,170
Net increase in cash, cash equivalents and restricted cash	5,964	14,374
Cash, cash equivalents and restricted cash, beginning of period	17,135	2,761
Cash, cash equivalents and restricted cash, end of period	23,099	17,135
Supplemental disclosures of non-cash investing and financing information
Issuance of common stock in Essentialis acquisition		17,246
Contingent consideration of Essentialis acquisition		2,590
Accrued liability for cost of issuing common stock	52
Warrants issued in connection with sale of common stock	582	4,187
Continuing Operations [Member]
Cash flows from financing activities:
Net increase in cash, cash equivalents and restricted cash from continuing operations	5,972	16,464
Discontinued Operations
Cash flows from financing activities:
Net increase in cash, cash equivalents and restricted cash from continuing operations	$ (8)	$ (2,090)

Overview

Overview	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Overview	Note 1. Overview Soleno Therapeutics, Inc. (the “Company” or “Soleno”) was incorporated in the State of Delaware on August 25, 1999, and is located in Redwood City, California. On May 8, 2017, Soleno received stockholder approval to amend its Amended and Restated Certificate of Incorporation to change its name from “Capnia, Inc.” to “Soleno Therapeutics, Inc.” The Company was initially established as a diversified healthcare company that developed and commercialized innovative diagnostics, devices and therapeutics addressing unmet medical needs, which consisted of: precision metering of gas flow technology marketed as Serenz ® ® The Company’s previously wholly-owned subsidiary, NeoForce, Inc. or NFI, through which the Company acquired substantially all of the assets of an unrelated privately-held company, NeoForce Group, Inc., or NeoForce, also marketed innovative pulmonary resuscitation solutions for the inpatient and ambulatory neonatal markets. The Company acquired Essentialis, Inc., or Essentialis, through a merger, or the Merger, on March 7, 2017, pursuant to Agreement and Plan of Merger dated December 22, 2016. Essentialis’s efforts prior to the Merger were focused primarily on developing and testing product candidates that target the ATP-sensitive potassium channel, a metabolically regulated membrane protein whose modulation has the potential to impact a wide range of rare metabolic, cardiovascular, and CNS diseases. Essentialis has tested Diazoxide Choline Controlled Release Tablet, or DCCR, as a treatment for Prader-Willi Syndrome, or PWS, a complex metabolic/neurobehavioral disorder. DCCR has orphan designation for the treatment of PWS in the United States, or U.S., as well as in the European Union, or E.U. Consummation of the Merger was subject to various closing conditions, including the Company’s consummation of a financing of at least $8.0 million at, or substantially contemporaneous with, the closing of the Merger, which occurred on March 7, 2017 and the receipt of stockholder approval of the Merger at a special meeting of its stockholders, which was held on March 6, 2017. Subsequent to the acquisition of Essentialis, the Company determined to divest, sell or otherwise dispose of the CoSense, NFI and Serenz businesses. Accordingly, and pursuant to ASC 205-20-45-10, any assets and liabilities related to the discontinued activities of CoSense, NFI and Serenz have been presented separately in the balance sheet as held for sale items, and the related operations reported herein for the CoSense, NFI and Serenz activities are reported as discontinued operations in the statements of operations. The Company determined to divest, sell or otherwise dispose of the CoSense, NFI and Serenz businesses in order to focus on the development and commercialization of novel therapeutics for the treatment of rare diseases. The Company’s current research and development efforts are primarily focused on advancing its lead candidate, DCCR tablets for the treatment of PWS, into late-stage clinical development. The Company sold its entire interest in NFI in a stock transaction that was completed on July 18, 2017, pursuant to a Stock Purchase Agreement dated July 18, 2017, or the NFI Purchase Agreement, entered into with Neoforce Holdings, Inc., a wholly-owned subsidiary of Flexicare Medical Limited, a privately-held United Kingdom company, for $720,000 and adjustments for inventory and the current cash balances held at NFI. On December 4, 2017, Soleno, and Capnia, Inc., a Delaware corporation, or Capnia, entered into a joint venture with OptAsia Healthcare Limited, or OAHL. The purpose of the joint venture is to develop and commercialize medical monitors, including CoSense, that measure end-tidal carbon monoxide in breath to assist in the detection of excessive hemolysis in neonates, a condition in which red blood cells degrade rapidly and which can lead to adverse neurological outcomes. The Company continues to separately evaluate alternatives for its Serenz portfolio. Restatement of prior periods During the preparation of the condensed consolidated financial statements as of September 30, 2018 and for the related three and nine months then ended, the Company determined that an error had been made in certain previously reported consolidated balance sheets and statements of operations for the valuation and resultant reporting of fair value for the Company’s Series A Warrants, resulting in the value of the warrant liability being overstated. The Company adjusted the prior period information reported in the September 30, 2018 interim condensed consolidated financial statements. The Company determined that the error was not material to any of the previously reported periods in which the error occurred and has not amended any previously issued consolidated financial statements. The following table (in thousands, except share and per share amounts) sets forth the effects of the restatement on affected items within the Company’s previously reported consolidated balance sheets and statements of operations for the periods ended December 31, 2017, March 31, 2018, and June 30, 2018, had the adjustments been made in the corresponding quarters. As of December 31, 2017 As of March 31, 2018 As of June 30, 2018 As of June 30, 2018 As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated Series A Warrant liability $ 352 $ (282 ) $ 70 $ 291 $ (233 ) $ 58 $ 1,015 $ (812 ) $ 203 $ 1,015 $ (812 ) $ 203 Total liabilities 12,487 (282 ) 12,205 13,312 (233 ) 13,079 17,507 (812 ) 16,695 17,507 (812 ) 16,695 Accumulated deficit (113,979 ) 282 (113,697 ) (117,734 ) 233 (117,501 ) (125,371 ) 812 (124,559 ) (125,371 ) 812 (124,559 ) Year Ended December 31, 2017 Quarter Ended March 31, 2018 Quarter Ended June 30, 2018 Six Months Ended June 30, 2018 As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated Change in fair value of warrant liabilities (967 ) 282 (685 ) 212 (49 ) 163 (3,834 ) 579 (3,255 ) (3,622 ) 530 (3,092 ) Total other income (expense) (1,553 ) 282 (1,271 ) 234 (49 ) 185 (3,801 ) 579 (3,222 ) (3,567 ) 530 (3,037 ) Pro Forma net loss per common share $ (1.75 ) $ (0.04 ) $ (1.71 ) $ (0.19 ) $ — $ (0.19 ) $ (0.38 ) $ 0.03 $ (0.35 ) $ (0.57 ) $ 0.03 $ (0.54 )

Going Concern and Management's

Going Concern and Management's Plans	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Going Concern and Management's Plans	Note 2. Going Concern and Management’s Plans The Company had a net loss of $13.3 million during 2018 and has an accumulated deficit of $127.0 million at December 31, 2018 resulting from having incurred losses since its inception. The Company had $22.8 million of working capital at December 31, 2018 and used $11.7 million of cash in its operating activities during 2018. The Company has financed its operations principally through issuances of equity securities. The Company has continued to focus on expense control, including reducing its workforce, reducing outside consultants, reducing legal fees and implementing a policy providing for Board members to receive common stock in lieu of cash payments for Board service compensation. On December 19, 2018, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company sold and issued 10,272,375 units at a price per unit of $1.61, for aggregate gross proceeds of $16.5 million. Each unit consisted of one share of common stock and a warrant to purchase 0.05 shares of common stock at an exercise price of $2.00 per share, for an aggregate of 10,272,375 shares of common stock and corresponding warrants to purchase an aggregate of 513,617 shares of common stock, together with the shares of common stock are referred to as the 2018 Resale Shares. The accompanying consolidated financial statements have been prepared under the assumption the Company will continue to operate as a going concern, which contemplates the realization of assets and the settlement of liabilities in the normal course of business. The consolidated financial statements do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts of liabilities that may result from uncertainty related to the Company’s ability to continue as a going concern. The Company expects to continue incurring losses for the foreseeable future and may be required to raise additional capital to complete its clinical trials, pursue product development initiatives and penetrate markets for the sale of its products. Management believes that the Company will continue to have access to capital resources through possible public or private equity offerings, debt financings, corporate collaborations or other means, but the Company’s access to such capital resources is uncertain and is not assured. If the Company is unable to secure additional capital, it may be required to curtail its clinical trials and development of new products and take additional measures to reduce expenses in order to conserve its cash in amounts sufficient to sustain operations and meet its obligations. These measures could cause significant delays in the Company’s efforts to complete its clinical trials and commercialize its products, which is critical to the realization of its business plan and the future operations of the Company. The consolidated financial statements do not include any adjustments relating to the recoverability and classification of asset amounts or the classification of liabilities that might be necessary should it be unable to continue as a going concern. Management believes that the Company does not have sufficient capital resources to sustain operations through at least the next twelve months from the date of this filing. Additionally, in view of the Company’s expectation to incur significant losses for the foreseeable future it will be required to raise additional capital resources in order to fund its operations, although the availability of, and the Company’s access to such resources is not assured. Accordingly, management believes that there is substantial doubt regarding the Company’s ability to continue operating as a going concern within one year from the date of filing these financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 3. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, and the applicable rules and regulations of the Securities and Exchange Commission, or SEC. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Certain amounts from prior periods have been reclassified to conform to the current period presentation, consisting of certain line items within the Consolidated Statements of Cash Flows. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates included in the financial statements include the valuation of deferred income tax assets, the valuation of financial instruments, stock-based compensation, value and life of acquired intangibles, and the valuation of contingent liabilities for the purchase price of assets obtained through acquisition. Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents at one U.S. commercial bank that management believes is of high credit quality. Cash and cash equivalents deposited with these commercial banks exceeded the Federal Deposit Insurance Corporation insurable limit at December 31, 2018 and 2017. The Company expects the maintenance of balances in excess of insurable limits will continue. Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting, making operating decisions, and assessing financial performance. All long-lived assets are maintained in the United States of America. Cash and Cash Equivalents The Company considers all highly liquid investments, including its money market fund, purchased with an original maturity of three months or less to be cash equivalents. The Company’s cash and cash equivalents are held in institutions in the U.S. and the U.K. and include deposits in a money market fund which was unrestricted as to withdrawal or use. Restricted cash was security of the Company credit card. Accounts Receivable Accounts receivable as of December 31, 2017 consist of balances due from customers in the normal course of business and are classified as Assets Held for Sale (See Note 9). The Company did not record an allowance for doubtful accounts as this balance was deemed fully collectible. There were no accounts receivable as of December 31, 2018. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of payments primarily related to insurance and short-term deposits. Prepaid expenses are initially recorded upon payment and are expensed as goods or services are received. Inventory Inventory consists of raw materials to be used in the assembly of the Company’s products, work-in-progress and finished goods. Inventory is stated at the lower of cost or net realizable value under the first-in, first-out (FIFO) method. As of December 31, 2017, the Company’s inventory included approximately $213,000 of raw materials, approximately $30,000 of work-in-progress, and approximately $177,000 of finished goods and was classified as Assets Held for Sale (See Note 9). There was no inventory balance as of December 31, 2018. Patent On May 11, 2010, the Company entered into an Asset Purchase Agreement with BioMedical Drug Development, Inc., or BDDI, pursuant to which BDDI agreed to sell certain technology to us and BDDI received and was entitled to receive, among other consideration, certain royalty payments related to the technology. In June 2015, the Company and BDDI amended the BDDI Asset Purchase Agreement, pursuant to which the Company committed to pay aggregate cash payments of $450,000 and issued 8,000 shares of common stock to an affiliate of BDDI. Under the original Asset Purchase Agreement dated June 11, 2010, the Company purchased a patent for Breath End Tidal Gas Monitor. The patent was issued on June 19, 2003 and expires on August 1, 2027. The Company capitalized the fair value of the patent purchased as an intangible asset on its consolidated balance sheet and amortized the fair value over the remaining useful life of the patent. The BDDI patent is reported as an Intangible Asset and classified as Assets Held for Sale as of December 31, 2017. (See Note 9.) In March 2017, the Company completed the acquisition of Essentialis, Inc., a Delaware corporation, or Essentialis in accordance with the Merger Agreement by and between Soleno Therapeutics and Essentialis dated December 22, 2016. The merger transaction has been accounted for as an asset acquisition under the acquisition method of accounting and accordingly, the value of asset acquired in the amount of $22.0 million was assigned to the identifiable intangible asset relating to the patent for DCCR, which patent expires in June 2028. Business Combinations For business combinations the Company utilizes the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations. The Company recognizes separately from goodwill the fair value of assets acquired and the liabilities assumed. Goodwill as of the acquisition date is measured as the excess of consideration transferred and the acquisition date fair values of the assets acquired, and liabilities assumed. While the Company uses its best estimates and assumptions as a part of the purchase price allocation process to accurately value assets acquired and liabilities assumed at the acquisition date, the Company’s estimates are subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, the Company may retroactively record adjustments to the fair value of the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations. Property and Equipment, Net Property and equipment are stated at cost net of accumulated depreciation and amortization calculated using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or the remaining term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Certain property and equipment were classified as Assets Held for Sale as of December 31, 2017. (See Note 9.) Equity Method Investment Equity method investments are equity securities in investees not controlled by the Company, but over which the Company has the ability to exercise significant influence. The Company’s equity method investment is measured at fair value minus impairment, if any, plus or minus the Company’s share of equity method investee income or loss. The Company’s equity method investment in Capnia, Inc. is classified as Minority interest investment in former subsidiary in the consolidated balance sheet as of December 31, 2018 and was initially measured at fair value. (See Note 9.) The Company expects to divest of its investment within one year of the balance sheet date. Long-Lived Assets The Company reviews its long-lived assets for impairment annually and whenever events or changes in circumstances indicate that the carrying amount of the assets may not be fully recoverable. The Company evaluates assets for potential impairment by comparing estimated future undiscounted net cash flows to the carrying amount of the asset. If the carrying amount of the assets exceeds the estimated future undiscounted cash flows, impairment is measured based on the difference between the carrying amount and the fair value of the assets. Intangible Assets Intangible assets with finite lives are amortized on a straight-line basis over their estimated useful lives of 11 years. The useful life of the intangible asset is evaluated each reporting period to determine whether events and circumstances warrant a revision to the remaining useful life. Intangible Assets in the amount of approximately $447,000 consisting of the patent acquired in the BDDI acquisition were classified as Assets Held for Sale as of December 31, 2017. (See Note 9.) Intangible assets consist of the following at December 31, 2018 (in thousands). Amount Accumulated Amortization Net Amount Useful Lives (years) Patents and merger costs $ 22,003 $ (3,534 ) $ 18,469 11 Total $ 22,003 $ (3,534 ) $ 18,469 Future amortization expense for intangible assets over their remaining useful lives is as follows (in thousands). Year ending December 31 Patents and trademarks 2019 $ 1,944 2020 1,944 2021 1,944 2022 1,944 2023 1,944 2024 and thereafter 8,749 Total $ 18,469 Amortization expense for the years ended December 31, 2018 and 2017, was $1.9 million and $1.7 million, respectively. Research and Development Research and development costs are charged to operations as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, prototype expenses, certain facility costs and other costs associated with clinical trials, net of reimbursed amounts. Costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use are expensed to research and development costs when incurred. Certain Research and Development expenses are reported as Discontinued Operations. (See Note 9.) Change in fair value of contingent consideration The Company recorded the value of contingent future consideration to be paid for the acquisition of Essentialis as a liability in March 2017 at the date of the acquisition. The changes in value of the liability for the contingent consideration since the acquisition date are recorded as operating expense in the consolidated statements of operations. Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the amounts at which assets and liabilities are recorded for financial reporting purposes and the amounts recorded for income tax purposes. A valuation allowance is provided against the Company’s deferred income tax assets when their realization is not reasonably assured. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available. The loss from discontinued operations is reported net of the related effect for income taxes in the statements of operations. Convertible Preferred Stock and other Hybrid Instruments The Company’s convertible preferred stock was classified as permanent equity on its consolidated balance sheet in accordance with authoritative guidance for the classification and measurement of hybrid securities and distinguishing liability from equity instruments. The preferred stock is not redeemable at the option of the holder. Further, the Company evaluated its Series A and Series B Convertible Preferred Stock and determined that it is considered an equity host under ASC 815, Derivatives and Hedging Common Stock Purchase Warrants and Other Derivative Financial Instruments The Company classifies common stock purchase warrants and other free standing derivative financial instruments as equity if the contracts (i) require physical settlement or net-share settlement or (ii) give the Company a choice of net-cash settlement or settlement in its own shares (physical settlement or net-share settlement). The Company classifies any contracts that (i) require net-cash settlement (including a requirement to net cash settle the contract if an event occurs and if that event is outside the control of the Company), (ii) give the counterparty a choice of net-cash settlement or settlement in shares (physical settlement or net-share settlement), or (iii) contain reset provisions as either an asset or a liability. The Company assesses classification of its freestanding derivatives at each reporting date to determine whether a change in classification between equity and liabilities is required. The Company determined that certain freestanding derivatives, which principally consist of Series A, Series C, the 2017 PIPE Warrants and 2018 PIPE Warrants, do not satisfy the criteria for classification as equity instruments due to the existence of certain cash settlement features that are not within the sole control of the Company or variable settlement provision that cause them to not be indexed to the Company’s own stock. Stock-Based Compensation Stock-based compensation costs related to stock options granted to employees and directors are measured at the date of grant based on the estimated fair value of the award. We estimate the grant date fair value, and the resulting stock-based compensation expense, using the Black-Scholes option-pricing model. The grant date fair value of stock-based awards is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the award. Stock options we grant to employees generally vest over four years. The Black-Scholes option-pricing model requires the use of highly subjective assumptions to estimate the fair value of stock-based awards. If we had made different assumptions, our stock-based compensation expense, net loss and net loss per share of common stock could have been significantly different. These assumptions include: • Expected volatility: The Company calculates the estimated volatility rate based on the volatilities of common stock of comparable companies in its industry. • Expected term: The Company does not believe it is able to rely on its historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term for use in estimating the fair value-based measurement of our options. Therefore, the Company has opted to use the “simplified method” for estimating the expected term of options. • Risk-free rate: The risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected time to liquidity. • Expected divided yield: The Company has never declared or paid any cash dividends and do not presently plan to pay cash dividends in the foreseeable future. Consequently, it used an expected dividend yield of zero. The Company accounts for forfeitures as they occur. Recent Accounting Standards Recently Adopted Accounting Standards In November 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or the ASU 2016-18, “ Statement of Cash Flows: Restricted Cash In May 2017, the FASB issued ASU 2017-09, “ Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting In March 2018, the FASB issued ASU 2018-05, “Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118” Tax Cuts and Jobs Act Recently Issued Accounting Standards In February 2016, the FASB issued ASU 2016-02: “ Leases (Topic 842) In July 2017, the FASB issued ASU 2017-11, “ Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features; (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception 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” . The adoption of this ASU is not expected to have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, “ Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting” In August 2018, the FASB issued ASU 2018-13, “ Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. In August 2018, SEC adopted the final rule under SEC Release No. 33-10532, “Disclosure Update and Simplification In October 2018, the FASB issued ASU 2018-17, "Consolidation: Targeted Improvements to Related Party Guidance for Variable Interest Entities

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Note 4. Fair Value of Financial Instruments The carrying value of the Company’s cash, restricted cash, cash equivalents and accounts payable, approximate fair value due to the short-term nature of these items. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: • Level I — • Level II — • Level III — The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands). Fair Value Measurements at December 31, 2018 Total Level 1 Level 2 Level 3 Liabilities Series A warrant liability $ 49 $ 49 $ — $ — Series C warrant liability — — — — 2017 PIPE warrant liability 4,563 — — 4,563 2018 PIPE warrant liability 600 — — 600 Essentialis purchase price contingency liability 5,649 — — 5,649 Total common stock warrant and contingent consideration liability $ 10,861 $ 49 $ - $ 10,812 Fair Value Measurements at December 31, 2017 Total Level 1 Level 2 Level 3 Liabilities Series A warrant liability $ 70 $ 70 $ — $ — Series C warrant liability 6 — — 6 2017 PIPE warrant liability 5,076 — — 5,076 Essentialis purchase price contingency liability 5,082 — — 5,082 Total common stock warrant and contingent consideration liability $ 10,234 $ 70 $ - $ 10,164 The Series A Warrant is a registered security that trades on the open market and the fair value of the Series A Warrant liability is based on the publicly quoted trading price of the warrants which is listed on and obtained from NASDAQ. Accordingly, the fair value of Series A Warrants is a Level 1 measurement. The fair value measurement of the Series C Warrants is based on significant inputs that are unobservable and thus represent Level 3 measurements. The Company’s estimated fair value of the Series C Warrant liability is calculated using the Black-Scholes valuation model, which is equivalent to fair value computed using the Binomial Lattice Option Model. Key assumptions include the volatility of the Company’s stock, the expected warrant term, expected dividend yield and risk-free interest rates. The Company’s estimated fair value of the 2017 PIPE Warrants and the 2018 PIPE Warrants was calculated using a Monte Carlo simulation of a geometric Brownian motion model. The Monte Carlo simulation pricing model requires the input of highly subjective assumptions including the expected stock price volatility, the expected term, the expected dividend yield and the risk-free interest rate. The fair value of the Essentialis purchase price contingent liability is estimated using scenario-based methods based upon the Company’s analysis of the likelihood of obtaining specified approvals from the Federal Drug Administration as well as reaching cumulative revenue milestones (see Note 8). The Level 3 estimates are based, in part, on subjective assumptions. During the periods presented, the Company has not changed the manner in which it values liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the periods presented. The following table sets forth a summary of the changes in the fair value of the Company’s Level 1 and Level 3 warrants, which are treated as liabilities (dollars in thousands). Series A Warrant Series C Warrant 2017 PIPE Warrants 2018 PIPE Warrants Purchase Price Number of Warrants Liability Number of Warrants Liability Number of Warrants Liability Number of Warrants Liability Contingent Liability Balance at January 1, 2018 485,121 $ 70 118,083 $ 6 6,024,425 $ 5,076 — $ — $ 5,082 Change in value of Series A Warrants — (21 ) — — — — — — — Change in value of Series C Warrants — — — (6 ) — — — — — Change in value of 2017 PIPE Warrants — — — — — (513 ) — — — Issuance of 2018 PIPE Warrants — — — — — — 513,617 582 — Change in value of 2018 PIPE Warrants — — — — — — — 18 — Change in value of contingent liability — — — — — — — — 567 Balance at December 31, 2018 485,121 $ 49 118,083 $ — 6,024,425 $ 4,563 513,617 $ 600 $ 5,649

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Note 5. Property and Equipment, Net Property and equipment are summarized in the following table (in thousands). December 31, 2018 December 31, 2017 Computer hardware $ 67 $ 61 Computer software 2 — Furniture and fixtures 23 23 Leasehold improvements 13 13 105 97 Less accumulated depreciation and amortization (93 ) (74 ) Total $ 12 $ 23 Depreciation expense was approximately $19,000 and $44,000 for the years ended December 31, 2018 and December 31, 2017, respectively

Warrant Liabilities

Warrant Liabilities	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Warrant Liabilities	Note 6. Warrant Liabilities The Company has issued multiple warrant series, of which the Series A Warrants, Series C Warrants, the 2017 PIPE Warrants and the 2018 PIPE Warrants (the “Warrants”) are considered liabilities pursuant to the guidance established by ASC 815 Derivatives and Hedging. Accounting Treatment The Company accounts for the Warrants in accordance with the guidance in ASC 815 The Company classified the Warrants, with a term greater than one year, as long-term liabilities at their fair value and will re-measure the warrants at each balance sheet date until they are exercised or expire. Any change in the fair value is recognized as other income (expense) in the Company’s consolidated statements of operations. Series A Warrants The Company has issued 489,921 Series A Warrants to purchase shares of its common stock at an exercise price of $32.50 per share in connection with the unit offering offered in the Company’s initial public offering, or the IPO, in November 2014. The Series A Warrants are exercisable at any time prior to the expiration of the five-year term on November 12, 2019. Upon the completion of the IPO, the Series A Warrants started trading on the NASDAQ under the symbol SLNOW. As the Series A Warrants are publicly traded, the Company uses the closing price on the measurement date to determine the fair value of the Series A Warrants. The Series A Warrants contract further provide for the payment of liquidated damages at an amount per month equal to 1% of the aggregate volume weighted average price, or VWAP, of the shares into which each Warrant is convertible into in the event that the Company is unable to maintain the effectiveness of a registration statement as described herein. The Company evaluated the registration payment arrangement stipulated in the terms of these securities and determined that it is probable that the Company will maintain an effective registration statement and has therefore not allocated any portion of the proceeds related to the warrant financings to the registration payment arrangement. The Warrants also contain a fundamental transactions provision that permits their settlement in cash at fair value at the option of the holder upon the occurrence of a change in control. Such change in control events include tender offers or hostile takeovers, which are not within the sole control of the Company as the issuer of these warrants. Accordingly, the Warrants are considered to have a cash settlement feature that precludes their classification as equity instruments. Settlement at fair value upon the occurrence of a fundamental transaction would be computed using the Black Scholes Option Pricing Model, which approximates the binomial lattice model. Since their issuance, a total of 4,800 Series A Warrants have been exercised. As of December 31, 2018, the fair value of the 485,121 outstanding Series A Warrants was approximately $49,000, and the decrease of approximately $21,000 in fair value during the year ended December 31, 2018 was recorded as other income (expense) in the consolidated statements of operations. Series C Warrants On March 5, 2015, the Company entered into separate agreements with certain Series B Warrant holders, who agreed to exercise their Series B Warrants to purchase an aggregate of 117,902 shares of the Company’s common stock at an exercise price of $32.50 per share, resulting in the de-recognition of $6.7 million of the previously issued Series B Warrant liability and gross proceeds to the Company of $3.8 million based on the exercise price of the Series B Warrants. In connection with this exercise of the Series B Warrants, the Company issued to each investor who exercised Series B Warrants, new Series C Warrants for the number of shares of the Company’s common stock underlying the Series B Warrants that were exercised. Each Series C Warrant is exercisable at $31.25 per share and will expire on March 5, 2020. The Series C Warrants contract further provide for the payment of liquidated damages at an amount per month equal to 1% of the aggregate volume weighted average price, or VWAP, of the shares into which each Warrant is convertible into in the event that the Company is unable to maintain the effectiveness of a registration statement as described herein. The Company evaluated the registration payment arrangement stipulated in the terms of these securities and determined that it is probable that the Company will maintain an effective registration statement and has therefore not allocated any portion of the proceeds related to the warrant financings to the registration payment arrangement. The Warrants also contain a fundamental transactions provision that permits their settlement in cash at fair value at the option of the holder upon the occurrence of a change in control. Such change in control events include tender offers or hostile takeovers, which are not within the sole control of the Company as the issuer of these warrants. Accordingly, the Warrants are considered to have a cash settlement feature that precludes their classification as equity instruments. Settlement at fair value upon the occurrence of a fundamental transaction would be computed using the Black Scholes Option Pricing Model, which approximates the binomial lattice model. In April 2015, the Company issued a tender offer to the remaining holders of Series B Warrants to induce the holders to cash exercise the outstanding Series B Warrants in exchange for new Series C Warrants with an exercise price of $31.25 per share that expire on March 5, 2020. The tender offer was extended to Series B Warrant holders under a registration statement filed with the SEC on Form S-4, which was declared effective on June 25, 2015 and expired on July 24, 2015. During July 2015, certain Series B Warrant holder(s) tendered their Series B Warrants under the tender offer, which resulted in the issuance of 181 shares of the Company’s common stock, the issuance of 181 Series C Warrants and proceeds to the Company of approximately $6,000. The Series C Warrants are exercisable into 118,083 shares of the Company’s common stock. As of December 31, 2018, the fair value of the Series C Warrants was determined to be zero. The decline in the fair value of the liability for the Series C Warrants of approximately $6,000 during the year ended December 31, 2018 was recorded as other income (expense) in the consolidated statements of operations. The Company has calculated the fair value of the Series C Warrants using a Black-Scholes pricing model. The Black-Scholes pricing model requires the input of highly subjective assumptions including the expected stock price volatility. The Company used the following inputs. December 31, 2018 December 31, 2017 Volatility 90 % 90 % Contractual term (years) 1.17 2.17 Expected dividend yield — % — % Risk-free rate 2.60 % 1.57 % Warrants Issued as Part of the Units in the 2017 PIPE Offering The 2017 PIPE Warrants were issued on December 15, 2017 in the 2017 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2017 PIPE Offering, and entitle the holder to purchase one share of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2017 PIPE Warrants and terminating at the earlier of December 15, 2020 or 30 days following positive Phase III results for the DCCR tablet in PWS. The exercise price and number of shares of common stock issuable upon exercise of the 2017 PIPE Warrants may be adjusted in certain circumstances, including in the event of a stock split, stock dividend, extraordinary dividend, or recapitalization, reorganization, merger or consolidation. However, the exercise price of the 2017 PIPE Warrants will not be reduced below $1.72. In the event of a change of control of the Company, the holders of unexercised warrants may present their unexercised warrants to the Company, or its successor, to be purchased by the Company, or its successor, in an amount equal to the per share value determined by the Black Scholes methodology. As of December 31, 2018, the fair value of the 2017 PIPE Warrants was estimated at $4.6 million. The decrease in the fair value of the liability for the 2017 PIPE Warrants of approximately $513,000 during the year ended December 31, 2018 was recorded as other income (expense) in the consolidated statements of operations. The Company has calculated the fair value of the 2017 PIPE Warrants using a Monte Carlo simulation of a geometric Brownian motion model. The Monte Carlo simulation pricing model requires the input of highly subjective assumptions including the expected stock price volatility. The following summarizes certain key assumptions used in estimating the fair values. December 31, 2018 December 31, 2017 Volatility 75 % 67 % Contractual term (years) 0.8 0.8 Expected dividend yield — % — % Risk-free rate 2.51 % 1.76 % Warrants Issued as Part of the Units in the 2018 PIPE Offering The 2018 PIPE Warrants were issued on December 19, 2018 in the 2018 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2018 PIPE Offering, and entitle the holders of each of the 10,272,375 units to purchase 0.05 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2018 PIPE Warrants and terminating on December 21, 2023. The exercise price and number of shares of common stock issuable upon exercise of the 2018 PIPE Warrants may be adjusted in certain circumstances, including in the event of a stock split, stock dividend, extraordinary dividend, or recapitalization, reorganization, merger or consolidation. However, the exercise price of the 2018 PIPE Warrants will not be reduced below $2.00. In the event of a change of control of the Company, the holders of unexercised warrants may present their unexercised warrants to the Company, or its successor, to be purchased by the Company, or its successor, in an amount equal to the per share value determined by the Black Scholes methodology. As of December 31, 2018, the fair value of the 2018 PIPE Warrants was estimated at approximately $600,000. The approximate $18,000 increase in the fair value of the liability for the 2018 PIPE Warrants since they were issued was recorded as other income (expense) in the consolidated statements of operations. The Company has calculated the fair value of the 2018 PIPE Warrants using a Monte Carlo simulation of a geometric Brownian motion model. The Monte Carlo simulation pricing model requires the input of highly subjective assumptions including the expected stock price volatility. The following summarizes certain key assumptions used in estimating the fair values. December 31, 2018 December 19, 2018 (date of issue) Volatility 75 % 75 % Contractual term (years) 5.0 5.0 Expected dividend yield — % — % Risk-free rate 2.51 % 2.62 % The Monte Carlo simulation of a geometric Brownian motion model requires the use of highly subjective assumptions to estimate the fair value of stock-based awards. These assumptions include the following estimates. • Volatility: The Company calculates the estimated volatility rate based on the volatilities of common stock of comparable companies in its industry. • Contractual term: The expected life of the warrants, which is based on the contractual term of the warrants. • Expected dividend yield: The Company has never declared or paid any cash dividends and does not currently plan to pay cash dividends in the foreseeable future. Consequently, the Company used an expected dividend yield of zero. • Risk-free rate: The risk-free interest rate is based on the U.S. Treasury rate for similar periods as those of expected volatility.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 7. Commitments and Contingencies Facility Leases On July 1, 2015 the Company executed a new four-year non-cancelable operating lease agreement for 8,171 square feet of office space for its headquarters facility. The lease agreement provides for monthly lease payments of approximately $23,000 beginning in September 2015, with increases in the following three years. An additional 5,265 square feet of office space became part of the new lease agreement on March 1, 2016, and in December 2017 the Company subleased this additional space to a third party through the end of the lease term. The lease and the sublease both expire in August 2019. The Company also leased office space under a non-cancelable operating lease agreement that was set to expire in May 2015, and in February 2015 the Company signed an amendment to its lease agreement, extending the lease through June 2018. The amendment provided for monthly lease payments of approximately $22,000 beginning in June 2015, with increases in the following two years. The Company subleased this facility in January 2016. Minimum rental commitments under all noncancelable leases with an initial term in excess of one year as of December 31, 2018 were approximately $344,000 during 2019 and none thereafter, not including the impact of sublease payments the Company will receive under its existing sublease. Rent expense was approximately $323,000 and $514,000 during the years ended December 31, 2018 and 2017, respectively. Contingencies In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future but have not yet been made. The Company accrues a liability for such matters when it is probable that future expenditures will be made, and such expenditures can be reasonably estimated.

Acquisition of Essentialis Inc.

Acquisition of Essentialis Inc.	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisition of Essentialis Inc.	Note 8. Acquisition of Essentialis Inc. On March 7, 2017, the Company acquired Essentialis through the merger of the Company’s wholly-owned subsidiary Company E Merger Sub, Inc., a Delaware corporation (“Merger Sub”), whereby Merger Sub merged into Essentialis, with Essentialis surviving the merger as a wholly owned subsidiary of the Company. The transaction was accounted for as an asset acquisition under the acquisition method of accounting. The amendments in ASU 2017-01 provide a screen to determine when a set of assets and activities is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set of assets and activities is not a business. In consideration, the Company issued 3,783,388 shares of common stock to stockholders of Essentialis on March 7, 2017. Pursuant to the terms of the Merger Agreement, the Company held back shares of common stock as partial recourse to satisfy indemnification claims. Effective March 7, 2018, on the one-year anniversary of the closing of the merger, the Company issued 180,667 shares for the previously held back amount. In the second quarter of 2018 there were 903,367 additional shares of common stock issued upon the achievement of a development milestone. In total, 4,867,422 shares of common stock were issued to Essentialis stockholders. Additionally, upon the achievement of certain commercial milestones associated with the sale of Essentialis’ product in accordance with the terms of the Merger Agreement, the Company is obligated to make cash earnout payments of up to a maximum of $30.0 million to Essentialis stockholders. The merger consideration described above will be reduced by any such shares of common stock issuable, or cash earnout payments payable, to Essentialis’ management carve-out plan participants and other service providers of Essentialis, in each case, in accordance with the terms of the Merger Agreement. Since the acquisition was determined to be an asset acquisition, the total value of the purchase consideration was allocated to the asset acquired. The fair value of the shares issued on the completion of the merger and of the contingent shares to be issued in the future was based on the stock price of the Company on the date of completion of the merger. In addition, the trading history of the Company was reviewed to assess the reliability of the implied consideration value. The Company trades on the NASDAQ, a major U.S. stock exchange, and has significant average daily trading volume with tight intraday bid-ask spreads. These characteristics indicate Soleno’s shares are actively traded and provide a reliable indication of value. On March 7, 2017, the date of the transaction close, the Company’s stock was trading at $3.85 per common share. Additionally, the average closing price of the stock in the 30 calendar days leading up to the close was also approximately $3.85. Accordingly, the fair value of the shares issued on March 7, 2017 and the estimated fair value of the contingent shares to be issued in the future are based on this stock price. The agreement to pay cash upon the achievement of the commercial milestones results in the recognition of a contingent consideration. The fair value of the contingent cash consideration is based on the Company’s analysis of the likelihood of the drug indication moving from Phase II through approval in the Federal Drug Administration approval process and then reaching the cumulative revenue milestones. In determining the likelihood of this occurring, the analysis relied on 2016 research published by BIO, Biomedtraker, & Amplion titles “Clinical Development Success Rates 2006-2015.” Based on management’s assessment, a 56% probability of achieving each milestone was determined to be reasonable. Additionally, the Company anticipated at the time of the merger that it could reach the commercial milestones of $100.0 million and $200.0 million in applicable revenue in 2023 and 2025, respectively. The Company recorded the acquisition pursuant to the guidance in ASC 805, which provides that not all of the relevant information needed to complete acquisition-date measurements may be obtainable or known at the time of closing the acquisition and in time for issuance of interim or annual financial statements. Therefore, ASC 805 provides for a “measurement period” during which adjustments to the provisional valuation amounts initially recorded can be made in order to reflect information, existing at the acquisition date, but of which management subsequently obtains or becomes aware. ASC 805 provides that the measurement period can extend for up to, but not exceed, one year. Management engaged independent professional assistance and advice in order to assess the fair value of the contingent stock and cash consideration as of March 7 and December 31, 2017. During the process of determining the fair value of the contingent consideration at December 31, 2017, the Company became aware that certain of the subjective assumptions made at the time of the initial valuation should be modified based upon management’s increased understanding of the commercial capabilities of the DCCR drug of which it became aware subsequent to the acquisition. Accordingly, the Company determined that it was appropriate to adjust the provisional valuation amounts recorded for the contingent stock and cash consideration made at the inception in March 2017. As a result, the value of the contingent cash consideration to be paid upon completing successive sales milestones increased and the value of the contingent stock consideration payable upon timing milestones was reduced; the resulting combined change to the total contingent consideration was not material. The initial valuation of the contingent consideration determined the fair value of the contingent stock consideration to be $4.2 million and the fair value of the contingent cash consideration to be $1.1 million, for the combined value of $5.3 million for the total of the stock and cash contingent consideration. The revision of the initial valuation of the contingent consideration, made within the measurement period, determined the fair value of the contingent stock consideration to be $2.7 million and the fair value of the contingent cash consideration to be $2.6 million, for the combined value of $5.3 million for the total of the contingent stock and cash consideration. Also subsequent to March 7, 2017 and prior to reporting the balance sheet and results of operations as of December 31, 2017, and for the year then ended, the Company completed its assessment of the tax effect on the net assets acquired by obtaining the independent study and report regarding the change in control in the previously outstanding stock of Essentialis. As a result of completing the study, the Company determined that, pursuant to Section 382 of the Internal Revenue Code, the utilization of Essentialis’s federal and state operating loss carryforwards were limited, which required the Company to record a net deferred tax liability in the amount of $1.7 million, deferred to future periods, as an element of the assets acquired. As a consequence of recording the net deferred tax liability, the Company’s valuation allowance was reduced by $1.7 million, which resulted in the provision for income tax benefit and an increase in the value of the intangible asset acquired. The probability weighted milestone payments were discounted to determine the present value of future cash payments. The analysis utilized the weighted average cost of capital (WACC) discount rate. The WACC used for the first and second milestones were 30% and 21%, respectively. The aggregate purchase price consideration was as follows (in thousands). Fair value of stock consideration $ 17,246 Fair value of contingent consideration 2,590 Total purchase price consideration $ 19,836 The fair value of the asset acquired is as follows (in thousands). Patents $ 19,836 Net assets acquired $ 19,836 As an asset acquisition, the Company also capitalized approximately $573,000 of total costs incurred to complete the acquisition consisting of legal fees of approximately $469,000, printing fees of approximately $75,000 and accounting and other fees of approximately $29,000. Additionally, the Company recorded as part of the purchase price consideration the value equivalent to the deferred tax liability that resulted from acquiring the assets in the amount of $1.7 million. The total intangible asset of $22.0 million was recorded on the balance sheet and is being amortized ratably over the life of the patents through June 30, 2028. The acquisition of Essentialis assets was completed in March 2017 and the purchase price was established at the date of closing based upon consideration paid at closing and an estimate of the future contingent consideration to be paid. Subsequent to the acquisition date and prior to reporting the balance sheet and results of operations as of December 31, 2017, and for the year then ended, the Company completed and finalized its assessments of the fair value of consideration paid and of the tax effect on the net assets acquired resulting from the change in control in the previously outstanding stock of Essentialis. As a result of completing the study of the fair value of the consideration paid, the Company revised the initial estimate of the fair value paid at closing and of the future contingent consideration to be paid; accordingly, the initial purchase cost of the asset acquired was adjusted as of March 2017 and the change in amortization of the related intangible asset was recorded in the fourth quarter of 2017. As a result of completing the study of the tax effect, the Company determined that, pursuant to Section 382 of the Internal Revenue Code, the utilization of Essentialis’s operating loss carryforwards were limited, which required the Company to record a tax liability in the amount of $1.6 million, deferred to future periods, for the assets acquired for which the cost was recorded as an element of the of assets required. Accordingly, the initial purchase cost of the asset acquired was adjusted as of March 2017 and the increase in amortization of the related intangible asset was recorded in the fourth quarter of 2017. The fair value of the liability for the contingent consideration payable by the Company achieving the commercial sales milestones of $100.0 million and $200.0 million was initially established as $2.6 million at the time of the merger. The fair value of the contingent consideration payable increased to $5.1 million at December 31, 2017 and to $5.6 million at December 31, 2018, based on the Company’s assessment that it could reach the commercial sales milestones of in 2024 and 2026, respectively. The changes in fair value of the contingent consideration payable after the time of the merger are recognized as income or expense in the line titled Change in fair value of contingent consideration in the Company’s consolidated statements of operations.

Discontinued Operations and Ass

Discontinued Operations and Assets Held for Sale	12 Months Ended
	Dec. 31, 2018
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations and Assets Held for Sale	Note 9. Discontinued Operations and Assets Held for Sale (i) Assets held for sale and discontinued operations Subsequent to the merger with Essentialis described above, the Company explored opportunities divest, sell or dispose of the CoSense, Neo Force, Inc. and Serenz businesses. Under ASC 205-20-45-10, during the period in which a component meets the assets held for sale and discontinued operations criteria, an entity must present the assets and liabilities of the discontinued operation separately in the asset and liability sections of the balance sheet for the comparative reporting periods. The prior period balance sheet should be reclassified for the held for sale items. For income statements, the current and prior periods should report the results of operations of the component in discontinued operations when comparative income statements are presented. The components of the Consolidated Balance Sheet accounts presented as assets and liabilities held for sale as of December 31, 2017 follow (in thousands). There were no assets or liabilities held for sale as of December 31, 2018 after the deconsolidation of Capnia. December 31, 2017 Current assets Accounts receivable $ 50 Inventory 420 Prepaid expenses and other current assets 46 Total current assets held for sale $ 516 Long-term assets Property and equipment, net $ 20 Other intangible assets 446 Total long-term assets held for sale $ 466 Current liabilities Accounts payable $ 51 Accrued compensation and other current liabilities 76 Total current liabilities for sale $ 127 Long-term liabilities Other long-term liabilities $ 225 Total long-term liabilities held for sale $ 225 The components of the Consolidated Statements of Operations presented as discontinued operations follow (in thousands). Year Ended December 31, 2018 2017 Product revenue $ 62 $ 735 Cost of product revenue 32 820 Gross profit (loss) 30 (85 ) Expenses Research and development 1,106 2,427 Sales and marketing 25 218 General and administrative 393 669 Total expenses 1,524 3,314 Operating loss (1,494 ) (3,399 ) Other expense Loss on sale of assets — (186 ) Other expense — (8 ) Total other expense — (194 ) Net loss from discontinued operations $ (1,494 ) $ (3,593 ) Stock-based compensation expense of approximately $76,000 and $120,000 was classified in discontinued operations for the years ended December 31, 2018 and 2017, respectively. (ii) NFI Sale On September 2, 2015, the Company established NeoForce, Inc. (“NFI”), a wholly owned subsidiary of the Company and through NFI, acquired substantially all of the assets of an unrelated privately held company NeoForce Group, Inc.(“NeoForce”). On July 18, 2017, the Company completed the sale of stock of its 100% wholly-owned subsidiary, NFI, primarily related to the Company’s portfolio of neonatology resuscitation business pursuant to a Stock Purchase Agreement (the “Purchase Agreement”), dated as of July 18, 2017, with NeoForce Holdings, Inc. (“Holdings”), a 100% owned subsidiary of Flexicare Medical Limited, a privately held United Kingdom company, for $720,000 and adjustments for inventory and the current cash balances held at NFI. The Company also received the total outstanding accounts receivable and inventory held by NFI at the date of sale, as it was collected or sold, respectively. The transactions contemplated by the Purchase Agreement are a continuation of a process previously disclosed by the Company of evaluating strategic alternatives and focusing on the Company’s rare disease therapeutic business. The Purchase Agreement includes customary terms and conditions, including an adjustment to the purchase price based on inventory and accounts receivables, and provisions that require the Company to indemnify Holdings, to the maximum of $250,000, for certain losses that it incurs as a result of a breach by the Company of its representations and warranties in the Purchase Agreement and certain other matters, which indemnification obligation terminates once the statute of limitations expires. Proceeds from the sale are payable to the Company as follows: (1) a $720,000 payment to the Company in cash on July 18, 2017, (2) the value of outstanding accounts receivable as it is collected by NFI following July 18, 2017, payable on a monthly basis, and (3) the value of inventory as it is sold following July 18, 2017, payable on a monthly basis. The Purchase Agreement contains customary representations and warranties of each of the parties. (iii) CoSense Joint Venture Agreement In December 2017, the Company entered into a joint venture with OAHL with respect to its CoSense product by agreeing to sell shares of Capnia, its wholly-owned subsidiary, to OAHL. CoSense was Soleno’s first Sensalyze Technology Platform product to receive 510(k) clearances from the FDA and CE Mark certification. CoSense measures CO, which can be elevated due to endogenous causes such as excessive breakdown of red blood cells, or hemolysis, or exogenous causes such as CO poisoning and smoke inhalation. The first target market for CoSense is for the use of ETCO measurements to aid in detection of hemolysis in neonates, a disorder in which CO and bilirubin are produced in excess as byproducts of the breakdown of red blood cells. The Company’s entry into the joint venture results from a comprehensive review of strategic alternatives for its legacy products and product candidates following its transition to a primarily therapeutic drug product company. The terms of the Joint Venture Agreement provide that OAHL will invest up to a total of $2.2 million in Capnia’s common shares on an incremental quarterly basis commencing in December 2017. Going forward, OAHL will be responsible for funding a portion of the Capnia operations. The Joint Venture Agreement provided that Capnia would issue shares of common shares to OAHL based on a negotiated price of $1.00 per share when the cumulative investment made by OAHL equaled or exceeded $1.2 million. For financial reporting purposes, Capnia’s assets, liabilities and results of operations have historically been consolidated with those of the Company. During October 2018, the Company and OAHL determined and agreed that the cumulative investment made by OAHL exceeded $1.2 million during the quarter ended September 30, 2018. Accordingly, on October 16, 2018, Capnia issued 1,690,322 shares of its common stock to OAHL, representing 53% of its outstanding shares. After the share issuance the Company no longer holds a controlling interest in Capnia and resulted in the deconsolidation of Capnia’s financial statements with those of the Company and a $2.0 million gain was recognized in the fourth quarter of 2018 as a result of the deconsolidation. Of this amount, $1.2 million relates to the remeasurement of the Company's retained interest in the joint venture to fair value which was measured based on the negotiated price of $1.00 per share for Soleno’s remaining ownership of 1,480,000 shares less a 23% discount for lack of control over Capnia. The total gain is included in other income from continuing operations on the Company's consolidated statements of operations. The remaining 47% investment in Capnia is classified as an equity method investment and presented as a Minority interest investment in former subsidiary in the consolidated balance sheet

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Note 10. Stockholders’ Equity Convertible Preferred Stock The Company is authorized to issue 10,000,000 shares of Preferred Stock. The Company had issued a total of 13,780 shares of Series B Convertible Preferred Stock pursuant to the Securities Purchase Agreement entered into on June 29, 2016 with Sabby Management, LLC. As of December 31, 2018, there were no shares of Series B Convertible Preferred Stock outstanding as all such previously issued shares had been converted to common shares. Common Stock On December 22, 2016, the Company entered into the Merger Agreement with Essentialis. Consummation of the Merger was subject to various closing conditions, including the Company’s consummation of a financing of at least $8.0 million at, or substantially contemporaneous with, the closing of the Merger, which occurred on March 7, 2017 and the receipt of stockholder approval of the Merger at a special meeting of stockholders, which the Company received on March 6, 2017. On March 7, 2017, the Company completed the Merger with Essentialis and issued 3,783,388 shares of common stock to shareholders of Essentialis. Pursuant to the terms of the Merger Agreement, the Company held back shares of common stock as partial recourse to satisfy indemnification claims. Effective March 7, 2018, on the one-year anniversary of the closing of the merger, the Company issued 180,667 shares for the previously held back amount. In the second quarter of 2018 there were 903,367 additional shares of common stock issued upon the achievement of a development milestone. In total, 4,867,422 shares of common stock were issued to Essentialis stockholders. Additionally, upon the achievement of certain commercial milestones associated with the sale of Essentialis’ product in accordance with the terms of the Merger Agreement, the Company is obligated to make cash earnout payments of up to a maximum of $30.0 million to Essentialis stockholders. The merger consideration described above will be reduced by any such shares of common stock issuable, or cash earnout payments payable, to Essentialis’ management carve-out plan participants and other service providers of Essentialis, in each case, in accordance with the terms of the Merger Agreement. On January 27, 2017, the Company entered into the 2017 Aspire Purchase Agreement with Aspire Capital, which provided that, upon the terms and subject to the conditions and limitations set forth therein, Aspire Capital was committed to purchase up to an aggregate of $17.0 million in value of shares of the Company’s common stock over the 30-month term of the purchase agreement. Additionally, on the date of the closing of the financing, as defined in the Merger Agreement, the Company issued to Aspire Capital, and Aspire Capital purchased from the Company an aggregate of $2.0 million of the Company’s common stock. On December 11, 2017, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company sold and issued 8,141,116 immediately separable units at a price per unit of $1.84 for aggregate gross proceeds of $15.0 million. Each unit consisted of one share of the Company’s common stock and a warrant to purchase 0.74 shares of the Company’s common stock at an exercise price of $2.00 per share, for an aggregate of 8,141,116 shares of common stock and corresponding warrants to purchase an aggregate of 6,024,425 shares of common stock, together the shares of common stock are referred to as the 2017 Resale Shares. The Company also granted certain registration rights to these stockholders, pursuant to which, among other things, the Company prepared and filed a registration statement with the SEC to register for resale the 2017 Resale Shares. The registration statement was declared effective in February 2018. On December 19, 2018, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company sold and issued 10,272,375 units at a price per unit of $1.61, for aggregate gross proceeds of $16.5 million. Each unit consisted of one share of the Company’s common stock and a warrant to purchase 0.05 shares of the Company’s common stock at an exercise price of $2.00 per share, for an aggregate of 10,272,375 shares of common stock and corresponding warrants to purchase an aggregate of 513,617 shares of common stock, together with the shares of common stock are referred to as the 2018 Resale Shares. The Company also granted certain registration rights to these stockholders, pursuant to which, among other things, the Company will prepare and file with the SEC a registration statement to register for resale the 2018 Resale Shares prior to March 31, 2019. Equity Incentive Plans The Company has adopted the 1999 Incentive Stock Plan, the 2010 Equity Incentive Plan, and the 2014 Equity Incentive Plan, or the 2014 Plan, and together, the Plans. The 1999 Incentive Stock Plan expired in 2009, and the 2010 Equity Incentive Plan has been closed to new issuances. Under the 2014 Plan the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units, performance units or performance shares to employees, directors, advisors, and consultants. Options granted under the 2014 Plan may be incentive stock options (“ISOs”) or nonqualified stock options (“NSOs”). ISOs may be granted only to Company employees, including officers and directors. The Board of Directors has the authority to determine to whom stock options will be granted, the number of options, the term, and the exercise price. Options are to be granted at an exercise price not less than fair value. For individuals holding more than 10% of the voting rights of all classes of stock, the exercise price of an option will not be less than 110% of fair value. The vesting period is normally monthly over a period of 4 years from the vesting date. The contractual term of an option is no longer than five years for ISOs for which the grantee owns greater than 10% of the voting power of all classes of stock and no longer than ten years for all other options. The terms and conditions governing restricted stock units is at the sole discretion of the Board. As of December 31, 2018, a total of 1,150,961 shares are available for future grant under the 2014 Plan. The Company recognized stock-based compensation expense related to options and restricted stock units granted to employees, directors and consultants for the years ended December 31, 2018 and 2017 of approximately $988,000 and $1.0 million, respectively, of which approximately $76,000 and $120,000 and was recorded in discontinued operations in 2018 and 2017, respectively. The compensation expense is allocated on a departmental basis, based on the classification of the option holder. No income tax benefits have been recognized in the statements of operations for stock-based compensation arrangements during the year ended December 31, 2018 and December 31, 2017. Stock compensation expense was allocated between departments in continuing operations as follows (in thousands). Year ended December 31, 2018 December 31, 2017 Research and development $ 205 $ 93 General and administrative 707 787 Total $ 912 $ 880 Stock Options The Company granted options to purchase 756,086 and 622,755 of the Company’s common stock in 2018 and 2017, respectively. The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions. Year Ended December 31, 2018 December 31, 2017 Expected life (years) 5.5-6.0 5.5-6.1 Risk-free interest rate 2.7%-2.8% 1.9%-2.2% Volatility 70%-71% 61%-69% Dividend rate — % — % The Black-Scholes option-pricing model requires the use of highly subjective assumptions to estimate the fair value of stock-based awards. These assumptions include the following estimates: • Expected life: The expected life of stock options represents the average of the contractual term of the options and the weighted-average vesting period, as permitted under the simplified method. The Company does not believe it is able to rely on historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term for use in estimating the fair value-based measurement of stock options. Therefore, it has opted to use the “simplified method” for estimating the expected term of options. • Risk-free interest rate: The risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected time to liquidity. • Volatility: The estimated volatility rate based on the volatilities of common stock of comparable companies in the Company’s industry. • Dividend rate: The Company has never declared or paid any cash dividends and does not presently plan to pay cash dividends in the foreseeable future. Consequently, the Company used an expected dividend yield of zero The following table summarizes stock option transactions for the years ended December 31, 2018 and 2017 as issued under the Plans. Shares Available Number of Options Weighted- Average Exercise Price per Weighted Average Remaining Contractual Term for Grant Outstanding Share (in years) Balance at January 1, 2017 191,770 581,687 $ 17.10 8.48 Additional shares authorized 134,295 Amendment to plan to authorize additional shares 1,785,837 Options granted (622,755 ) 622,755 $ 3.04 Options exercised — — — — Options canceled/forfeited 177,455 (177,455 ) $ 8.84 — Balance at December 31, 2017 1,666,602 1,026,987 $ 9.99 7.94 Additional shares authorized 223,742 Shares allocated to grants of restricted stock units (99,217 ) Options granted (756,086 ) 756,086 $ 1.68 Options exercised — — — — Options canceled/forfeited 115,920 (115,920 ) $ 12.72 — Balance at December 31, 2018 1,150,961 1,667,153 $ 6.03 8.27 Options vested at December 31, 2018 820,422 $ 9.85 7.64 Options vested and expected to vest at December 31, 2018 1,667,153 $ 6.03 8.27 The weighted-average grant date fair value of employee options granted was $1.08 and $1.88 per share for the year ended December 31, 2018 and December 31, 2017, respectively. At December 31, 2018 total unrecognized employee stock-based compensation was $1.2 million, which is expected to be recognized over the weighted-average remaining vesting period of 2.5 years. As of December 31, 2018, the outstanding stock options had an intrinsic value of approximately $71,000. The fair value of an equity award granted to a nonemployee generally is determined in the same manner as an equity award granted to an employee. In most cases, the fair value of the equity securities granted is more reliably determinable than the fair value of the goods or services received. Stock-based compensation related to its grant of options to non-employees has not been material to date. Restricted Stock Units There were 99,217 restricted stock units granted by the Company during the year ended December 31, 2018 to employees and nonemployees. The shares were 100% vested on the grant date and were valued based on the Company’s common stock price on the grant date, with approximately $159,000 of the related stock-based compensation expense recognized at that time. 2014 Employee Stock Purchase Plan The Company’s board of directors and stockholders have adopted the 2014 Employee Stock Purchase Plan, or the ESPP. The ESPP has become effective, and the board of directors will implement commencement of offers thereunder in its discretion. A total of 27,967 shares of the Company’s common stock has been made available for sale under the ESPP. In addition, the ESPP provides for annual increases in the number of shares available for issuance under the plan on the first day of each year beginning in the year following the initial date that the board of directors authorizes commencement, equal to the least of: • 1.0% of the outstanding shares of the Company’s common stock on the first day of such year; • 55,936 shares; or • such amount as determined by the board of directors. As of December 31, 2018, there were no purchases by employees under this plan. Series D Warrants The Company issued 256,064 Series D Warrants in October 2015, which are exercisable into 586,182 shares of the Company’s common stock, with an exercise price of $12.30 and a term of five years expiring on October 15, 2020. The Company’s Series D Warrants contain standard anti-dilution provisions for stock dividends, stock splits, subdivisions, combinations and similar types of recapitalization events. They also contain a cashless exercise feature that provides for their net share settlement at the option of the holder in the event that there is no effective registration statement covering the continuous offer and sale of the warrants and underlying shares. The Company is required to comply with certain requirements to cause or maintain the effectiveness of a registration statement for the offer and sale of these securities. The Series D Warrant agreement further provides for the payment of liquidated damages at an amount per month equal to 1% of the aggregate VWAP of the shares into which each Series D Warrant is convertible into in the event that the Company is unable to maintain the effectiveness of a registration statement as described herein. The Company evaluated the registration payment arrangement stipulated in the terms of this securities agreement and determined that it is probable that the Company will maintain an effective registration statement and has therefore not allocated any portion of the proceeds to the registration payment arrangement. The Series D Warrant agreement specifically provides that under no circumstances will the Company be required to settle any Series D Warrant exercise for cash, whether by net settlement or otherwise. Accounting Treatment The Company accounts for the Series D Warrants in accordance with the guidance in ASC 815 Derivatives and Hedging. Other Common Stock Warrants As of December 31, 2018, the Company had 102,070 common stock warrants outstanding from the 2010/2012 convertible notes, with an exercise price of $24.35 and a term of 10 years expiring in November 2024. The Company also had outstanding 1,851 common stock warrants issued in 2009, with an exercise price of $108.00 and a term of 10 years, which expired in January 2019 and 16,500 common stock warrants issued to the underwriter in the Company’s IPO, with an exercise price of $35.70 and a term of 10 years, expiring in November 2024.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Note 11. Income Taxes The geographical distribution of loss before income taxes are summarized below (in thousands). December 31, 2018 2017 United States $ (11,830 ) $ (13,707 ) Foreign (11 ) (17 ) Income (loss) before income taxes $ (11,841 ) $ (13,724 ) Income (loss) resulting from discontinued operations $ (1,494 ) $ (3,593 ) Taxes allocated to discontinued operations — — The components of the provision for income tax benefit follows (in thousands). December 31, 2018 2017 Current: Federal $ — $ — State — 1 Foreign — — — 1 Deferred Federal — (1,578 ) State — (73 ) Foreign — — — (1,651 ) Total provision for income taxes benefit $ — $ (1,650 ) The provision for income tax benefit differs from the amount estimated by applying the statutory federal income tax rate to the operating loss from continuing operations due to the following (in thousands). December 31, 2018 2017 Tax on the loss before income tax expense computed at the federal statutory rate $ (2,486 ) $ (4,666 ) State tax (benefit) at statutory rate, net of federal benefit (187 ) (67 ) Tax reform — 10,613 Foreign rate differential 2 3 Change in valuation allowance 4,143 (8,485 ) Change in research and development credits (99 ) (121 ) Stock based compensation—ISOs 143 295 Change in fair value of warrants (110 ) 343 Change in fair value of contingent consideration 119 — Gain on deconsolidation (4 ) — Disallowance of loss on discontinued operations (426 ) — Acquisition costs — 203 Change in NOL true up (590 ) — Change in temporary difference true up (456 ) — Loss on sale of NFI — (677 ) Other (49 ) 909 Provision for income tax benefit $ — $ (1,650 ) Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities are as follows at December 31, 2018 and 2017 (in thousands). December 31, 2018 2017 Non-Current Deferred Tax Assets: Federal and state net operating loss carryforwards $ 28,532 $ 25,486 Research and other credits 2,037 1,807 Reserves and accruals 52 145 Assets held for sale 15 17 Fixed assets 67 — Capital loss carryover 425 459 Stock based compensation 70 36 Other deferred tax assets 542 — Gross non-current deferred tax assets 31,740 27,950 Intangible Assets (4,062 ) (4,414 ) Fixed Assets — (3 ) Total non-current deferred tax liabilities (4,062 ) (4,417 ) Total deferred tax assets 27,678 23,533 Valuation allowance (27,678 ) (23,533 ) Net deferred tax assets $ — $ — The Company has recorded a full valuation allowance against its net deferred tax assets due to the uncertainty as to whether such assets will be realized. The valuation allowance increased by $4.1 million from December 31, 2017 to December 31, 2018 primarily due to the generation of current year net operating losses and research and development credits claimed. As of December 31, 2018, the Company had $129.8 million of federal, $51.4 million of state and approximately $264,000 of foreign net operating losses available to offset future taxable income. The federal net operating loss carryforwards begins to expire in 2019, the state net operating loss carryforwards will begin to expire in 2028 and the foreign net operating loss carryforward can be carried forward indefinitely, if not utilized. As of December 31, 2018, the Company also had $1.2 million of federal and approximately $798,000 of state research and development credit carryforwards. The federal research and development credit carryforward begin to expire in 2024 and the state research and development credit can be carried forward indefinitely. Utilization of the net operating loss and tax credit carry forwards are subject to an annual limitation due to the ownership percentage change limitations provided by the Internal Revenue Code of 1986 and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization. The Company completed Section 382 analysis through December 2016 and determined that an ownership change, as defined under Section 382 of the Internal Revenue Code, occurred in June 2016. The Company’s tax attributes are subject to an annual limitation of $0.5 million per year for federal purposes. For years ended after December 31, 2016, the utilization of net operating losses and tax credit carryforwards are subject to further limitation in the event an additional ownership change were to occur for tax purposes. The Company is in process of completing an analysis of whether there was an ownership change, as defined under Section 382 of the Internal Revenue Code, resulting from the issuance of new shares during 2018 and, as such, is not able at this time to determine the impact on the NOL carryforwards, if any, as of the date of these consolidated financial statements as result of the 2018 share issuances. Once the analysis is completed, the Company will make any appropriate adjustments to the balances of NOLs to be carried forward and thus adjust the NOL deferred tax asset accordingly, if required. United States taxes and foreign withholding taxes have not been provided on undistributed earnings for certain non-United States subsidiaries as of December 31, 2018, as the earnings, if any, are intended to be indefinitely reinvested. The following tables summarize the activities of gross unrecognized tax benefits (in thousands). December 31, 2018 2017 Beginning balance $ 854 $ 795 Increases (decreases) related to prior year tax positions 23 (4 ) Increase related to current year tax positions 87 63 Ending Balance $ 964 $ 854 There were no unrecognized tax benefits that would impact the effective tax rate as of December 31, 2018 and December 31, 2017. As of December 31, 2018, unrecognized tax benefits of approximately $964,000 would be offset by a change in valuation allowance. The Company files income tax returns in the U.S. federal jurisdiction, certain state jurisdictions and United Kingdom. In the normal course of business, the Company is subject to examination by federal, state, local and foreign jurisdictions, where applicable. In the U.S federal jurisdiction, tax years 1999 forward remain open to examination, in the state tax jurisdiction, years 2008 forward remain open to examination and in the foreign jurisdiction, years 2015 forward remain open to examination. The Company is currently not under audit by any federal, state, local or foreign jurisdiction. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), which allowed us to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. As a result, we previously provided provisional estimates of the effect of the Tax Act in our financial statements. In the fourth quarter of 2018, we completed our analysis to determine the effect of the Tax Act and determined that no further adjustments were needed. The Jobs Act also establishes global intangible low-taxed income, or “GILTI,” provisions that impose a tax on foreign income in excess of a deemed return on intangible assets of foreign corporations. The Company’s accounting policy for the income tax effects of GILTI will be to recognize those taxes as expenses in the period incurred. In 2018, the Company’s foreign subsidiary realized a tested loss for the period and therefore, the Company did not have a GILTI inclusion for the year. The Company uses the “more likely than not” criterion for recognizing the tax benefit of uncertain tax positions and to establish measurement criteria for income tax benefits. The Company has determined it has no material unrecognized assets or liabilities related to uncertain tax positions as of December 31, 2018. The Company does not anticipate any significant changes in such uncertainties and judgments during the next 12 months. In the event the Company should need to recognize interest and penalties related to unrecognized tax liabilities, this amount will be recorded as a component of other expense.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss per share	Note 12. Net loss per share Basic net loss per share is computed by dividing net loss by the weighted-average number of common stock actually outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock outstanding and dilutive potential common stock that would be issued upon the exercise of common stock warrants and options. For the years ended December 31, 2018 and 2017, the effect of issuing the potential common stock is anti-dilutive due to the net losses in those periods and the number of shares used to compute basic and diluted earnings per share are the same in each of those periods. The following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported (in common stock equivalent shares). As of December 31, 2018 2017 Convertible preferred stock — 914,200 Warrants issued to 2010/2012 convertible note holders to purchase common stock 102,070 102,070 Options to purchase common stock 1,667,153 1,026,987 Warrants issued in 2009 to purchase common stock 1,851 1,851 Warrants issued to underwriter to purchase common stock 16,500 16,500 Series A warrants to purchase common stock 485,121 485,121 Series C warrants to purchase common stock 118,083 118,083 Series D warrants to purchase common stock 586,162 586,162 2017 PIPE warrants 6,024,425 6,024,425 2018 PIPE warrants 513,617 — Total 9,514,982 9,275,399

Compensation Plan for Board Mem

Compensation Plan for Board Members	12 Months Ended
	Dec. 31, 2018
Compensation Related Costs [Abstract]
Compensation Plan for Board Members	Note 13. Compensation Plan for Board Members In 2017, the Compensation Committee of the Board of Directors recommended, and the Board approved a revised compensation plan pursuant to which all board fees are paid in common stock of the Company. Payment to the Board of Directors in shares of the Company’s common stock is made after the close of the quarter in which the compensation is earned. During 2018 and 2017, the Company and 90,306 shares, respectively, of common stock to its Board members for fees earned

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	Note 14. Defined Contribution Plan The Company sponsors a 401(k) Plan, which stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations of eligible compensation. The Company may match employee contributions in amounts to be determined at the Company’s sole discretion. To date, the Company has not made any matching contributions.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Note 15. Subsequent Events On February 4, 2019 the Company formed a new wholly owned subsidiary in Ireland named Soleno Therapeutics Europe Limited.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, and the applicable rules and regulations of the Securities and Exchange Commission, or SEC. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Certain amounts from prior periods have been reclassified to conform to the current period presentation, consisting of certain line items within the Consolidated Statements of Cash Flows.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates included in the financial statements include the valuation of deferred income tax assets, the valuation of financial instruments, stock-based compensation, value and life of acquired intangibles, and the valuation of contingent liabilities for the purchase price of assets obtained through acquisition.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents at one U.S. commercial bank that management believes is of high credit quality. Cash and cash equivalents deposited with these commercial banks exceeded the Federal Deposit Insurance Corporation insurable limit at December 31, 2018 and 2017. The Company expects the maintenance of balances in excess of insurable limits will continue.
Segments	Segments The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting, making operating decisions, and assessing financial performance. All long-lived assets are maintained in the United States of America.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments, including its money market fund, purchased with an original maturity of three months or less to be cash equivalents. The Company’s cash and cash equivalents are held in institutions in the U.S. and the U.K. and include deposits in a money market fund which was unrestricted as to withdrawal or use. Restricted cash was security of the Company credit card.
Accounts Receivable	Accounts Receivable Accounts receivable as of December 31, 2017 consist of balances due from customers in the normal course of business and are classified as Assets Held for Sale (See Note 9). The Company did not record an allowance for doubtful accounts as this balance was deemed fully collectible. There were no accounts receivable as of December 31, 2018.
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of payments primarily related to insurance and short-term deposits. Prepaid expenses are initially recorded upon payment and are expensed as goods or services are received.
Inventory	Inventory Inventory consists of raw materials to be used in the assembly of the Company’s products, work-in-progress and finished goods. Inventory is stated at the lower of cost or net realizable value under the first-in, first-out (FIFO) method. As of December 31, 2017, the Company’s inventory included approximately $213,000 of raw materials, approximately $30,000 of work-in-progress, and approximately $177,000 of finished goods and was classified as Assets Held for Sale (See Note 9). There was no inventory balance as of December 31, 2018.
Intangible Assets	Intangible Assets Intangible assets with finite lives are amortized on a straight-line basis over their estimated useful lives of 11 years. The useful life of the intangible asset is evaluated each reporting period to determine whether events and circumstances warrant a revision to the remaining useful life. Intangible Assets in the amount of approximately $447,000 consisting of the patent acquired in the BDDI acquisition were classified as Assets Held for Sale as of December 31, 2017. (See Note 9.) Intangible assets consist of the following at December 31, 2018 (in thousands). Amount Accumulated Amortization Net Amount Useful Lives (years) Patents and merger costs $ 22,003 $ (3,534 ) $ 18,469 11 Total $ 22,003 $ (3,534 ) $ 18,469 Future amortization expense for intangible assets over their remaining useful lives is as follows (in thousands). Year ending December 31 Patents and trademarks 2019 $ 1,944 2020 1,944 2021 1,944 2022 1,944 2023 1,944 2024 and thereafter 8,749 Total $ 18,469 Amortization expense for the years ended December 31, 2018 and 2017, was $1.9 million and $1.7 million, respectively.
Business Combinations	Business Combinations For business combinations the Company utilizes the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations. The Company recognizes separately from goodwill the fair value of assets acquired and the liabilities assumed. Goodwill as of the acquisition date is measured as the excess of consideration transferred and the acquisition date fair values of the assets acquired, and liabilities assumed. While the Company uses its best estimates and assumptions as a part of the purchase price allocation process to accurately value assets acquired and liabilities assumed at the acquisition date, the Company’s estimates are subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, the Company may retroactively record adjustments to the fair value of the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to the Company’s consolidated statements of operations.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost net of accumulated depreciation and amortization calculated using the straight-line method over the estimated useful lives of the assets, generally between three and five years. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or the remaining term of the lease. Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Certain property and equipment were classified as Assets Held for Sale as of December 31, 2017. (See Note 9.)
Equity Method Investment	Equity Method Investment Equity method investments are equity securities in investees not controlled by the Company, but over which the Company has the ability to exercise significant influence. The Company’s equity method investment is measured at fair value minus impairment, if any, plus or minus the Company’s share of equity method investee income or loss. The Company’s equity method investment in Capnia, Inc. is classified as Minority interest investment in former subsidiary in the consolidated balance sheet as of December 31, 2018 and was initially measured at fair value. (See Note 9.) The Company expects to divest of its investment within one year of the balance sheet date.
Long-Lived Assets	Long-Lived Assets The Company reviews its long-lived assets for impairment annually and whenever events or changes in circumstances indicate that the carrying amount of the assets may not be fully recoverable. The Company evaluates assets for potential impairment by comparing estimated future undiscounted net cash flows to the carrying amount of the asset. If the carrying amount of the assets exceeds the estimated future undiscounted cash flows, impairment is measured based on the difference between the carrying amount and the fair value of the assets.
Research and Development	Research and Development Research and development costs are charged to operations as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, prototype expenses, certain facility costs and other costs associated with clinical trials, net of reimbursed amounts. Costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use are expensed to research and development costs when incurred. Certain Research and Development expenses are reported as Discontinued Operations. (See Note 9.)
Change in Fair Value of Contingent Consideration	Change in fair value of contingent consideration The Company recorded the value of contingent future consideration to be paid for the acquisition of Essentialis as a liability in March 2017 at the date of the acquisition. The changes in value of the liability for the contingent consideration since the acquisition date are recorded as operating expense in the consolidated statements of operations.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the amounts at which assets and liabilities are recorded for financial reporting purposes and the amounts recorded for income tax purposes. A valuation allowance is provided against the Company’s deferred income tax assets when their realization is not reasonably assured. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available. The loss from discontinued operations is reported net of the related effect for income taxes in the statements of operations.
Convertible Preferred Stock and Other Hybrid Instruments	Convertible Preferred Stock and other Hybrid Instruments The Company’s convertible preferred stock was classified as permanent equity on its consolidated balance sheet in accordance with authoritative guidance for the classification and measurement of hybrid securities and distinguishing liability from equity instruments. The preferred stock is not redeemable at the option of the holder. Further, the Company evaluated its Series A and Series B Convertible Preferred Stock and determined that it is considered an equity host under ASC 815, Derivatives and Hedging
Common Stock Purchase Warrants and Other Derivative Financial Instruments	Common Stock Purchase Warrants and Other Derivative Financial Instruments The Company classifies common stock purchase warrants and other free standing derivative financial instruments as equity if the contracts (i) require physical settlement or net-share settlement or (ii) give the Company a choice of net-cash settlement or settlement in its own shares (physical settlement or net-share settlement). The Company classifies any contracts that (i) require net-cash settlement (including a requirement to net cash settle the contract if an event occurs and if that event is outside the control of the Company), (ii) give the counterparty a choice of net-cash settlement or settlement in shares (physical settlement or net-share settlement), or (iii) contain reset provisions as either an asset or a liability. The Company assesses classification of its freestanding derivatives at each reporting date to determine whether a change in classification between equity and liabilities is required. The Company determined that certain freestanding derivatives, which principally consist of Series A, Series C, the 2017 PIPE Warrants and 2018 PIPE Warrants, do not satisfy the criteria for classification as equity instruments due to the existence of certain cash settlement features that are not within the sole control of the Company or variable settlement provision that cause them to not be indexed to the Company’s own stock.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation costs related to stock options granted to employees and directors are measured at the date of grant based on the estimated fair value of the award. We estimate the grant date fair value, and the resulting stock-based compensation expense, using the Black-Scholes option-pricing model. The grant date fair value of stock-based awards is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the award. Stock options we grant to employees generally vest over four years. The Black-Scholes option-pricing model requires the use of highly subjective assumptions to estimate the fair value of stock-based awards. If we had made different assumptions, our stock-based compensation expense, net loss and net loss per share of common stock could have been significantly different. These assumptions include: • Expected volatility: The Company calculates the estimated volatility rate based on the volatilities of common stock of comparable companies in its industry. • Expected term: The Company does not believe it is able to rely on its historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term for use in estimating the fair value-based measurement of our options. Therefore, the Company has opted to use the “simplified method” for estimating the expected term of options. • Risk-free rate: The risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected time to liquidity. • Expected divided yield: The Company has never declared or paid any cash dividends and do not presently plan to pay cash dividends in the foreseeable future. Consequently, it used an expected dividend yield of zero. The Company accounts for forfeitures as they occur.
Recent Accounting Standards	Recent Accounting Standards Recently Adopted Accounting Standards In November 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or the ASU 2016-18, “ Statement of Cash Flows: Restricted Cash In May 2017, the FASB issued ASU 2017-09, “ Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting In March 2018, the FASB issued ASU 2018-05, “Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118” Tax Cuts and Jobs Act Recently Issued Accounting Standards In February 2016, the FASB issued ASU 2016-02: “ Leases (Topic 842) In July 2017, the FASB issued ASU 2017-11, “ Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features; (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception 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” . The adoption of this ASU is not expected to have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, “ Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting” In August 2018, the FASB issued ASU 2018-13, “ Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. In August 2018, SEC adopted the final rule under SEC Release No. 33-10532, “Disclosure Update and Simplification In October 2018, the FASB issued ASU 2018-17, "Consolidation: Targeted Improvements to Related Party Guidance for Variable Interest Entities
Patents [Member]
Intangible Assets	Patent On May 11, 2010, the Company entered into an Asset Purchase Agreement with BioMedical Drug Development, Inc., or BDDI, pursuant to which BDDI agreed to sell certain technology to us and BDDI received and was entitled to receive, among other consideration, certain royalty payments related to the technology. In June 2015, the Company and BDDI amended the BDDI Asset Purchase Agreement, pursuant to which the Company committed to pay aggregate cash payments of $450,000 and issued 8,000 shares of common stock to an affiliate of BDDI. Under the original Asset Purchase Agreement dated June 11, 2010, the Company purchased a patent for Breath End Tidal Gas Monitor. The patent was issued on June 19, 2003 and expires on August 1, 2027. The Company capitalized the fair value of the patent purchased as an intangible asset on its consolidated balance sheet and amortized the fair value over the remaining useful life of the patent. The BDDI patent is reported as an Intangible Asset and classified as Assets Held for Sale as of December 31, 2017. (See Note 9.) In March 2017, the Company completed the acquisition of Essentialis, Inc., a Delaware corporation, or Essentialis in accordance with the Merger Agreement by and between Soleno Therapeutics and Essentialis dated December 22, 2016. The merger transaction has been accounted for as an asset acquisition under the acquisition method of accounting and accordingly, the value of asset acquired in the amount of $22.0 million was assigned to the identifiable intangible asset relating to the patent for DCCR, which patent expires in June 2028.

Overview (Tables)

Overview (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Effects of Restatement on Affected Items within Company's Previously Reported Consolidated Balance Sheets and Statements of Operations	The following table (in thousands, except share and per share amounts) sets forth the effects of the restatement on affected items within the Company’s previously reported consolidated balance sheets and statements of operations for the periods ended December 31, 2017, March 31, 2018, and June 30, 2018, had the adjustments been made in the corresponding quarters. As of December 31, 2017 As of March 31, 2018 As of June 30, 2018 As of June 30, 2018 As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated Series A Warrant liability $ 352 $ (282 ) $ 70 $ 291 $ (233 ) $ 58 $ 1,015 $ (812 ) $ 203 $ 1,015 $ (812 ) $ 203 Total liabilities 12,487 (282 ) 12,205 13,312 (233 ) 13,079 17,507 (812 ) 16,695 17,507 (812 ) 16,695 Accumulated deficit (113,979 ) 282 (113,697 ) (117,734 ) 233 (117,501 ) (125,371 ) 812 (124,559 ) (125,371 ) 812 (124,559 ) Year Ended December 31, 2017 Quarter Ended March 31, 2018 Quarter Ended June 30, 2018 Six Months Ended June 30, 2018 As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated As Previously Reported Correction of error As Restated Change in fair value of warrant liabilities (967 ) 282 (685 ) 212 (49 ) 163 (3,834 ) 579 (3,255 ) (3,622 ) 530 (3,092 ) Total other income (expense) (1,553 ) 282 (1,271 ) 234 (49 ) 185 (3,801 ) 579 (3,222 ) (3,567 ) 530 (3,037 ) Pro Forma net loss per common share $ (1.75 ) $ (0.04 ) $ (1.71 ) $ (0.19 ) $ — $ (0.19 ) $ (0.38 ) $ 0.03 $ (0.35 ) $ (0.57 ) $ 0.03 $ (0.54 )

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Intangible Assets	Intangible assets consist of the following at December 31, 2018 (in thousands). Amount Accumulated Amortization Net Amount Useful Lives (years) Patents and merger costs $ 22,003 $ (3,534 ) $ 18,469 11 Total $ 22,003 $ (3,534 ) $ 18,469
Schedule of Future Amortization Expense	Future amortization expense for intangible assets over their remaining useful lives is as follows (in thousands). Year ending December 31 Patents and trademarks 2019 $ 1,944 2020 1,944 2021 1,944 2022 1,944 2023 1,944 2024 and thereafter 8,749 Total $ 18,469

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Summary of Financial Instruments Measured at Fair Value on Recurring Basis	The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands). Fair Value Measurements at December 31, 2018 Total Level 1 Level 2 Level 3 Liabilities Series A warrant liability $ 49 $ 49 $ — $ — Series C warrant liability — — — — 2017 PIPE warrant liability 4,563 — — 4,563 2018 PIPE warrant liability 600 — — 600 Essentialis purchase price contingency liability 5,649 — — 5,649 Total common stock warrant and contingent consideration liability $ 10,861 $ 49 $ - $ 10,812 Fair Value Measurements at December 31, 2017 Total Level 1 Level 2 Level 3 Liabilities Series A warrant liability $ 70 $ 70 $ — $ — Series C warrant liability 6 — — 6 2017 PIPE warrant liability 5,076 — — 5,076 Essentialis purchase price contingency liability 5,082 — — 5,082 Total common stock warrant and contingent consideration liability $ 10,234 $ 70 $ - $ 10,164
Summary of Changes in Fair Value of Level1 and Level 3 Financial Instruments	The following table sets forth a summary of the changes in the fair value of the Company’s Level 1 and Level 3 warrants, which are treated as liabilities (dollars in thousands). Series A Warrant Series C Warrant 2017 PIPE Warrants 2018 PIPE Warrants Purchase Price Number of Warrants Liability Number of Warrants Liability Number of Warrants Liability Number of Warrants Liability Contingent Liability Balance at January 1, 2018 485,121 $ 70 118,083 $ 6 6,024,425 $ 5,076 — $ — $ 5,082 Change in value of Series A Warrants — (21 ) — — — — — — — Change in value of Series C Warrants — — — (6 ) — — — — — Change in value of 2017 PIPE Warrants — — — — — (513 ) — — — Issuance of 2018 PIPE Warrants — — — — — — 513,617 582 — Change in value of 2018 PIPE Warrants — — — — — — — 18 — Change in value of contingent liability — — — — — — — — 567 Balance at December 31, 2018 485,121 $ 49 118,083 $ — 6,024,425 $ 4,563 513,617 $ 600 $ 5,649

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment are summarized in the following table (in thousands). December 31, 2018 December 31, 2017 Computer hardware $ 67 $ 61 Computer software 2 — Furniture and fixtures 23 23 Leasehold improvements 13 13 105 97 Less accumulated depreciation and amortization (93 ) (74 ) Total $ 12 $ 23

Warrant Liabilities (Tables)

Warrant Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Series C Warrant [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	The Company used the following inputs. December 31, 2018 December 31, 2017 Volatility 90 % 90 % Contractual term (years) 1.17 2.17 Expected dividend yield — % — % Risk-free rate 2.60 % 1.57 %
2017 PIPE Warrant Liability [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	The following summarizes certain key assumptions used in estimating the fair values. December 31, 2018 December 31, 2017 Volatility 75 % 67 % Contractual term (years) 0.8 0.8 Expected dividend yield — % — % Risk-free rate 2.51 % 1.76 %
2018 PIPE Warrant Liability [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	The following summarizes certain key assumptions used in estimating the fair values. December 31, 2018 December 19, 2018 (date of issue) Volatility 75 % 75 % Contractual term (years) 5.0 5.0 Expected dividend yield — % — % Risk-free rate 2.51 % 2.62 %

Acquisition of Essentialis In_2

Acquisition of Essentialis Inc. (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Purchase Price Consideration	The aggregate purchase price consideration was as follows (in thousands). Fair value of stock consideration $ 17,246 Fair value of contingent consideration 2,590 Total purchase price consideration $ 19,836
Fair Values of Assets Acquired	The fair value of the asset acquired is as follows (in thousands). Patents $ 19,836 Net assets acquired $ 19,836

Discontinued Operations and A_2

Discontinued Operations and Assets Held for Sale (Tables)	12 Months Ended
	Dec. 31, 2018
Discontinued Operations And Disposal Groups [Abstract]
Components of Discontinued Operations	The components of the Consolidated Balance Sheet accounts presented as assets and liabilities held for sale as of December 31, 2017 follow (in thousands). There were no assets or liabilities held for sale as of December 31, 2018 after the deconsolidation of Capnia. December 31, 2017 Current assets Accounts receivable $ 50 Inventory 420 Prepaid expenses and other current assets 46 Total current assets held for sale $ 516 Long-term assets Property and equipment, net $ 20 Other intangible assets 446 Total long-term assets held for sale $ 466 Current liabilities Accounts payable $ 51 Accrued compensation and other current liabilities 76 Total current liabilities for sale $ 127 Long-term liabilities Other long-term liabilities $ 225 Total long-term liabilities held for sale $ 225 The components of the Consolidated Statements of Operations presented as discontinued operations follow (in thousands). Year Ended December 31, 2018 2017 Product revenue $ 62 $ 735 Cost of product revenue 32 820 Gross profit (loss) 30 (85 ) Expenses Research and development 1,106 2,427 Sales and marketing 25 218 General and administrative 393 669 Total expenses 1,524 3,314 Operating loss (1,494 ) (3,399 ) Other expense Loss on sale of assets — (186 ) Other expense — (8 ) Total other expense — (194 ) Net loss from discontinued operations $ (1,494 ) $ (3,593 )

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Summary of Stock Based Compensation Expense	Stock compensation expense was allocated between departments in continuing operations as follows (in thousands). Year ended December 31, 2018 December 31, 2017 Research and development $ 205 $ 93 General and administrative 707 787 Total $ 912 $ 880
Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model	The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions. Year Ended December 31, 2018 December 31, 2017 Expected life (years) 5.5-6.0 5.5-6.1 Risk-free interest rate 2.7%-2.8% 1.9%-2.2% Volatility 70%-71% 61%-69% Dividend rate — % — %
Summary of Stock Option Transactions	The following table summarizes stock option transactions for the years ended December 31, 2018 and 2017 as issued under the Plans. Shares Available Number of Options Weighted- Average Exercise Price per Weighted Average Remaining Contractual Term for Grant Outstanding Share (in years) Balance at January 1, 2017 191,770 581,687 $ 17.10 8.48 Additional shares authorized 134,295 Amendment to plan to authorize additional shares 1,785,837 Options granted (622,755 ) 622,755 $ 3.04 Options exercised — — — — Options canceled/forfeited 177,455 (177,455 ) $ 8.84 — Balance at December 31, 2017 1,666,602 1,026,987 $ 9.99 7.94 Additional shares authorized 223,742 Shares allocated to grants of restricted stock units (99,217 ) Options granted (756,086 ) 756,086 $ 1.68 Options exercised — — — — Options canceled/forfeited 115,920 (115,920 ) $ 12.72 — Balance at December 31, 2018 1,150,961 1,667,153 $ 6.03 8.27 Options vested at December 31, 2018 820,422 $ 9.85 7.64 Options vested and expected to vest at December 31, 2018 1,667,153 $ 6.03 8.27

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax	The geographical distribution of loss before income taxes are summarized below (in thousands). December 31, 2018 2017 United States $ (11,830 ) $ (13,707 ) Foreign (11 ) (17 ) Income (loss) before income taxes $ (11,841 ) $ (13,724 ) Income (loss) resulting from discontinued operations $ (1,494 ) $ (3,593 ) Taxes allocated to discontinued operations — —
Summary of Provision for Income Tax Benefit	The components of the provision for income tax benefit follows (in thousands). December 31, 2018 2017 Current: Federal $ — $ — State — 1 Foreign — — — 1 Deferred Federal — (1,578 ) State — (73 ) Foreign — — — (1,651 ) Total provision for income taxes benefit $ — $ (1,650 )
Provision for Income Tax Benefit by Applying Statutory Federal Income Tax Rate to Operating Loss from Continuing Operations	The provision for income tax benefit differs from the amount estimated by applying the statutory federal income tax rate to the operating loss from continuing operations due to the following (in thousands). December 31, 2018 2017 Tax on the loss before income tax expense computed at the federal statutory rate $ (2,486 ) $ (4,666 ) State tax (benefit) at statutory rate, net of federal benefit (187 ) (67 ) Tax reform — 10,613 Foreign rate differential 2 3 Change in valuation allowance 4,143 (8,485 ) Change in research and development credits (99 ) (121 ) Stock based compensation—ISOs 143 295 Change in fair value of warrants (110 ) 343 Change in fair value of contingent consideration 119 — Gain on deconsolidation (4 ) — Disallowance of loss on discontinued operations (426 ) — Acquisition costs — 203 Change in NOL true up (590 ) — Change in temporary difference true up (456 ) — Loss on sale of NFI — (677 ) Other (49 ) 909 Provision for income tax benefit $ — $ (1,650 )
Significant Components of Company's Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows at December 31, 2018 and 2017 (in thousands). December 31, 2018 2017 Non-Current Deferred Tax Assets: Federal and state net operating loss carryforwards $ 28,532 $ 25,486 Research and other credits 2,037 1,807 Reserves and accruals 52 145 Assets held for sale 15 17 Fixed assets 67 — Capital loss carryover 425 459 Stock based compensation 70 36 Other deferred tax assets 542 — Gross non-current deferred tax assets 31,740 27,950 Intangible Assets (4,062 ) (4,414 ) Fixed Assets — (3 ) Total non-current deferred tax liabilities (4,062 ) (4,417 ) Total deferred tax assets 27,678 23,533 Valuation allowance (27,678 ) (23,533 ) Net deferred tax assets $ — $ —
Summary of Gross Unrecognized Tax Benefits	The following tables summarize the activities of gross unrecognized tax benefits (in thousands). December 31, 2018 2017 Beginning balance $ 854 $ 795 Increases (decreases) related to prior year tax positions 23 (4 ) Increase related to current year tax positions 87 63 Ending Balance $ 964 $ 854

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities Outstanding Excluded from Computations of Diluted Weighted-Average Shares Outstanding	The following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported (in common stock equivalent shares). As of December 31, 2018 2017 Convertible preferred stock — 914,200 Warrants issued to 2010/2012 convertible note holders to purchase common stock 102,070 102,070 Options to purchase common stock 1,667,153 1,026,987 Warrants issued in 2009 to purchase common stock 1,851 1,851 Warrants issued to underwriter to purchase common stock 16,500 16,500 Series A warrants to purchase common stock 485,121 485,121 Series C warrants to purchase common stock 118,083 118,083 Series D warrants to purchase common stock 586,162 586,162 2017 PIPE warrants 6,024,425 6,024,425 2018 PIPE warrants 513,617 — Total 9,514,982 9,275,399

Overview - Additional Informati

Overview - Additional Information (Detail) - USD ($)	Jul. 18, 2017	Dec. 22, 2016
NeoForce Holdings Inc. [Member]
Class of Stock [Line Items]
Proceeds from the sale of business	$ 720,000
Essentialis, Inc. [Member]
Class of Stock [Line Items]
Amount of financing needed		$ 8,000,000

Overview - Effects of Restateme

Overview - Effects of Restatement on Affected Items within Company's Previously Reported Consolidated Balance Sheets and Statements of Operations (Detail) - USD ($)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total liabilities	$ 16,695,000	$ 13,079,000	$ 16,695,000	$ 12,738,000	$ 12,205,000
Accumulated deficit	(124,559,000)	(117,501,000)	(124,559,000)	(127,032,000)	(113,697,000)
Change in fair value of warrants liabilities	(3,255,000)	163,000	(3,092,000)	522,000	(685,000)
Total other income (expense)	$ (3,222,000)	$ 185,000	$ (3,037,000)	$ 2,460,000	$ (1,271,000)
Pro Forma net loss per common share	$ (0.35)	$ (0.19)	$ (0.54)	$ (0.64)	$ (1.71)
Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total liabilities	$ 17,507,000	$ 13,312,000	$ 17,507,000		$ 12,487,000
Accumulated deficit	(125,371,000)	(117,734,000)	(125,371,000)		(113,979,000)
Change in fair value of warrants liabilities	(3,834,000)	212,000	(3,622,000)		(967,000)
Total other income (expense)	$ (3,801,000)	$ 234,000	$ (3,567,000)		$ (1,553,000)
Pro Forma net loss per common share	$ (0.38)	$ (0.19)	$ (0.57)		$ (1.75)
Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total liabilities	$ (812,000)	$ (233,000)	$ (812,000)		$ (282,000)
Accumulated deficit	812,000	233,000	812,000		282,000
Change in fair value of warrants liabilities	579,000	(49,000)	530,000		282,000
Total other income (expense)	$ 579,000	(49,000)	$ 530,000		$ 282,000
Pro Forma net loss per common share	$ 0.03		$ 0.03		$ (0.04)
Series A Warrant Liability [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Series A Warrant liability	$ 203,000	58,000	$ 203,000	$ 49,000	$ 70,000
Change in fair value of warrants liabilities				$ 21,000
Series A Warrant Liability [Member] | Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Series A Warrant liability	1,015,000	291,000	1,015,000		352,000
Series A Warrant Liability [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Series A Warrant liability	$ (812,000)	$ (233,000)	$ (812,000)		$ (282,000)

Going Concern and Management'_2

Going Concern and Management's Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Dec. 19, 2018	Dec. 11, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Mar. 31, 2018
Liquidity And Managements Plans [Line Items]
Net loss			$ (13,335)	$ (15,385)
Accumulated deficit			(127,032)	(113,697)	$ (124,559)	$ (117,501)
Positive (deficit) in working capital			22,800
Net cash used in operating activities			$ (11,683)	$ (9,950)
Equity Unit Purchase Agreements [Member]
Liquidity And Managements Plans [Line Items]
Number of newly issued	10,272,375	8,141,116
Price per unit	$ 1.61	$ 1.84
Gross Proceeds from issuance of units	$ 16,500	$ 15,000
Common Stock [Member] | Equity Unit Purchase Agreements [Member]
Liquidity And Managements Plans [Line Items]
Warrant to call common stock	0.05	0.74
Warrant exercise price	$ 2	$ 2
Warrants, to purchase shares of common stock	513,617	6,024,425

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	May 11, 2010USD ($)shares	Dec. 31, 2018USD ($)BankSegment	Dec. 31, 2017USD ($)
Schedule Of Significant Accounting Policies [Line Items]
Number of commercial banks | Bank		1
Number of operating segments | Segment		1
Accounts receivable		$ 0
Raw materials			$ 213,000
Work-in-process			30,000
Finished goods			177,000
Inventory, Net		$ 0
Aggregate cash payments	$ 450,000
Shares issued during period | shares	8,000
Estimated useful life		11 years
Amortization		$ 1,900,000	$ 1,700,000
Expected dividend yield		0.00%	0.00%
Stock Options [Member]
Schedule Of Significant Accounting Policies [Line Items]
Vesting period		4 years
Expected dividend yield		0.00%
Assets Held for Sale [Member]
Schedule Of Significant Accounting Policies [Line Items]
Intangible assets classified as assets held for sale		$ 447,000
Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment		3 years
Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment		5 years
Essentialis, Inc. [Member]
Schedule Of Significant Accounting Policies [Line Items]
Net intangible assets acquired		$ 22,000,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Intangible Assets (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Finite-Lived Intangible Assets [Line Items]
Amount	$ 22,003
Accumulated Amortization	(3,534)
Total	$ 18,469
Useful life	11 years
Patents and Merger Costs [Member]
Finite-Lived Intangible Assets [Line Items]
Amount	$ 22,003
Accumulated Amortization	(3,534)
Total	$ 18,469
Useful life	11 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Future Amortization Expense (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Finite-Lived Intangible Assets [Line Items]
Total	$ 18,469
Patents And Trademark [Member]
Finite-Lived Intangible Assets [Line Items]
2019	1,944
2020	1,944
2021	1,944
2022	1,944
2023	1,944
2024 and thereafter	8,749
Total	$ 18,469

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 07, 2017
Liabilities
Contingent liability for Essentialis purchase price	$ 5,649			$ 5,082
Series A Warrant Liability [Member]
Liabilities
Warrant liability	49	$ 203	$ 58	70
Series C Warrant [Member]
Liabilities
Warrant liability	0			6
2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,563			5,076
2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	600
Convertible preferred stock warrant liability [Member] | Series A Warrant Liability [Member]
Liabilities
Warrant liability	49
Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	10,861			10,234
Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | Series A Warrant Liability [Member]
Liabilities
Warrant liability	49			70
Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | Series C Warrant [Member]
Liabilities
Warrant liability				6
Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,563			5,076
Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	600
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	49			70
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | Series A Warrant Liability [Member]
Liabilities
Warrant liability	49			70
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	10,812			10,164
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | Series C Warrant [Member]
Liabilities
Warrant liability				6
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,563			5,076
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Convertible preferred stock warrant liability [Member] | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	600
Essentialis, Inc. [Member]
Liabilities
Contingent liability for Essentialis purchase price					$ 2,590
Essentialis, Inc. [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	5,649			5,082
Essentialis, Inc. [Member] | Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	$ 5,649			$ 5,082

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 1 and Level 3 Financial Instruments (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)shares
Purchase price contingent liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 5,082
Change in value of liabilities	567
Balance at end of period	$ 5,649
Series A Warrant Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the end of period, in shares | shares	485,121
Series A Warrant Liability [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 70
Balance at the beginning of period, in shares | shares	485,121
Change in value of liabilities	$ (21)
Balance at end of period	$ 49
Balance at the end of period, in shares | shares	485,121
Series C Warrant [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 6
Balance at the beginning of period, in shares | shares	118,083
Change in value of liabilities	$ (6)
Balance at the end of period, in shares | shares	118,083
2017 PIPE Warrant Liability [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 5,076
Balance at the beginning of period, in shares | shares	6,024,425
Change in value of liabilities	$ (513)
Balance at end of period	$ 4,563
Balance at the end of period, in shares | shares	6,024,425
2018 PIPE Warrant Liability [Member] | Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in value of liabilities	$ 18
Issuance of 2018 PIPE Warrants	$ 582
Issuance of 2018 PIPE Warrants | shares	513,617
Balance at end of period	$ 600
Balance at the end of period, in shares | shares	513,617

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 105	$ 97
Less accumulated depreciation and amortization	(93)	(74)
Total	12	23
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	67	61
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	23	23
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 13	$ 13

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 19,000	$ 44,000

Warrant Liabilities - Additiona

Warrant Liabilities - Additional Information (Detail)	Mar. 05, 2015USD ($)$ / sharesshares	Jul. 31, 2015USD ($)shares	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Dec. 19, 2018$ / sharesshares	Dec. 15, 2017$ / shares	Apr. 30, 2015$ / shares
Class Of Warrant Or Right [Line Items]
Change in fair value of stock warrants			$ 3,255,000	$ (163,000)	$ 3,092,000	$ (522,000)	$ 685,000
Proceeds from issuance of common stock under tender offer							10,000,000
Expected Dividend Yield [Member]
Class Of Warrant Or Right [Line Items]
Measurement input						0
Series A Warrants to Purchase Shares of Common Stock [Member] | IPO [Member]
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon issuance of warrants | shares						489,921
Exercise price of warrants exercised | $ / shares						$ 32.50
Warrants term						5 years
Series A Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Aggregate VWAP (percent)						1.00%
Warrants exercised (in shares) | shares						4,800
Warrants outstanding (in shares) | shares						485,121
Warrant liability			$ 203,000	$ 58,000	$ 203,000	$ 49,000	70,000
Change in fair value of stock warrants						(21,000)
Series A Warrant Liability [Member] | Convertible preferred stock warrant liability [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability						$ 49,000
Series B Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares	$ 32.50
Warrants exercised (in shares) | shares	117,902
De-recognition of warrant liability	$ 6,700,000
Proceeds from exercise of warrants	$ 3,800,000
Series C Warrant [Member]
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon issuance of warrants | shares						118,083
Exercise price of warrants exercised | $ / shares	$ 31.25									$ 31.25
Aggregate VWAP (percent)						1.00%
Warrant liability						$ 0	6,000
Change in fair value of stock warrants						(6,000)
Proceeds from issuance of common stock under tender offer		$ 6,000
Warrants cashless exercised (in shares) | shares		181
Series C Warrant [Member] | Common Stock [Member]
Class Of Warrant Or Right [Line Items]
Issuance of shares upon cashless exercise warrants (in shares) | shares		181
2017 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares									$ 2
Warrant liability						4,563,000	$ 5,076,000
Change in fair value of stock warrants						$ (513,000)
Warrant issuance description						The 2017 PIPE Warrants were issued on December 15, 2017 in the 2017 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2017 PIPE Offering, and entitle the holder to purchase one share of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2017 PIPE Warrants and terminating at the earlier of December 15, 2020 or 30 days following positive Phase III results for the DCCR tablet in PWS.
Fair value of estimated warrants						$ 4,600,000
2017 PIPE Warrant Liability to Purchase Common Stock [Member] | Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares						$ 1.72
2018 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon issuance of warrants | shares								10,272,375
Exercise price of warrants exercised | $ / shares								$ 2
Warrant liability						$ 600,000
Change in fair value of stock warrants						$ 18,000
Warrant issuance description						The 2018 PIPE Warrants were issued on December 19, 2018 in the 2018 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2018 PIPE Offering, and entitle the holders of each of the 10,272,375 units to purchase 0.05 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2018 PIPE Warrants and terminating on December 21, 2023.
Fair value of estimated warrants						$ 600,000
Warrant to call common stock | shares								0.05
2018 PIPE Warrant Liability [Member] | Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares						$ 2

Warrant Liabilities - Fair Valu

Warrant Liabilities - Fair Value of Convertible Preferred Stock Warrant Liability (Detail)	Dec. 31, 2018	Dec. 19, 2018	Dec. 31, 2017
Series C Warrant [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.90		0.90
Series C Warrant [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	1 year 2 months 1 day		2 years 2 months 1 day
Series C Warrant [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0260		0.0157
2017 PIPE Warrant Liability [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.75		0.67
2017 PIPE Warrant Liability [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	9 months 18 days		9 months 18 days
2017 PIPE Warrant Liability [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0251		0.0176
2018 PIPE Warrant Liability [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.75	0.75
2018 PIPE Warrant Liability [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	5 years	5 years
2018 PIPE Warrant Liability [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0251	0.0262

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Mar. 01, 2016ft²	Jul. 01, 2015USD ($)ft²	Feb. 28, 2015USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
Non-cancelable operating lease agreement term		4 years
Area of real estate property (in sqft) | ft²		8,171
Future minimum commitment under non-cancelable operating lease		$ 23,000	$ 22,000
Period of increases to monthly payments		3 years	2 years
Additional area of office space for headquarters facility | ft²	5,265
Lease expiration period		2019-08
Sublease expiration period		2019-08
Future minimum commitment under non-cancelable operating lease during 2019				$ 344,000
Future minimum commitment under non-cancelable operating lease due in two years and thereafter				0
Rent expense				$ 323,000	$ 514,000

Acquisition of Essentialis Inc

Acquisition of Essentialis Inc - Additional Information (Detail)	Mar. 07, 2018shares	Mar. 07, 2017USD ($)$ / sharesshares	Jun. 30, 2018shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Share price (in usd per share) | $ / shares		$ 3.85
Fair value of stock consideration				$ 4,200,000
Fair value of cash consideration				1,100,000
Total purchase price consideration				5,300,000
Increase (decrease) in valuation allowance				4,100,000
First commercial sales milestone				100,000,000
Second commercial sales milestone				200,000,000
Contingent liability payment on achievement of sales milestone		$ 2,600,000		5,600,000	$ 5,100,000
Changes Measurement [Member]
Business Acquisition [Line Items]
Fair value of stock consideration				2,700,000
Fair value of cash consideration				2,600,000
Total purchase price consideration				5,300,000
Essentialis, Inc. [Member]
Business Acquisition [Line Items]
Common stock shares issued in acquisition (shares) | shares		3,783,388
Contingent consideration potential additional shares issuable if milestones are reached (shares) | shares			903,367
Maximum total common stock issuable in acquisition (in shares) | shares		4,867,422
Fair value of stock consideration		$ 17,246,000
Total purchase price consideration		19,836,000
Value of deferred tax liability assumed		1,700,000		1,700,000
Increase (decrease) in valuation allowance				(1,700,000)
Tax liability recorded				1,600,000
Essentialis, Inc. [Member] | Patents [Member]
Business Acquisition [Line Items]
Capitalized costs		573,000
Legal fees		469,000
Printing fees		75,000
Accounting and other fees		29,000
Total intangible asset		$ 22,000,000
Essentialis, Inc. [Member] | Indemnification Claims [Member]
Business Acquisition [Line Items]
Common stock shares issued in acquisition (shares) | shares	180,667	180,667
Essentialis, Inc. [Member] | Earnout Payments [Member]
Business Acquisition [Line Items]
Maximum potential cash earnout payments		$ 30,000,000
Essentialis, Inc. [Member] | Development Milestone [Member]
Business Acquisition [Line Items]
Probability of development success rate (percent)		56.00%
Revenue milestone in 2023				100,000,000
Revenue milestone in 2025				$ 200,000,000
Essentialis, Inc. [Member] | Revenue Milestone One [Member] | Measurement Input, Discount Rate [Member]
Business Acquisition [Line Items]
Fair value inputs, discount rate (percent)		0.30
Essentialis, Inc. [Member] | Revenue Milestone Two [Member] | Measurement Input, Discount Rate [Member]
Business Acquisition [Line Items]
Fair value inputs, discount rate (percent)		0.21

Acquisition of Essentialis In_3

Acquisition of Essentialis Inc - Purchase Price Consideration (Detail) - USD ($) $ in Thousands	Mar. 07, 2017	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Fair value of stock consideration		$ 4,200
Fair value of contingent consideration		5,649	$ 5,082
Total purchase price consideration		$ 5,300
Essentialis, Inc. [Member]
Business Acquisition [Line Items]
Fair value of stock consideration	$ 17,246
Fair value of contingent consideration	2,590
Total purchase price consideration	19,836
Net assets acquired	19,836
Essentialis, Inc. [Member] | Patents [Member]
Business Acquisition [Line Items]
Patents	$ 19,836

Discontinued Operations and A_3

Discontinued Operations and Assets Held for Sale - Additional Information (Detail)	Oct. 16, 2018shares	Jul. 18, 2017USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / shares	Sep. 30, 2018USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, current					$ 516,000
Assets held for sale, long-term					466,000
Liabilities held for sale, current					127,000
Liabilities held for sale, long-term					225,000
Stock-based compensation expense				$ 988,000	1,000,000
Current period gain recognized			$ 2,000,000
Capnia Inc Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Negotiated price per share | $ / shares			$ 1	$ 1
Percentage of ownership interest				47.00%
Number of shares owned | shares			1,480,000	1,480,000
Percentage of discount for lack of control				0.23
NeoForce, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage of wholly-owned subsidiary		100.00%
Flexicare Medical Limited [Member] | NeoForce Holdings Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage of wholly-owned subsidiary		100.00%
OAHL [Member] | Capnia Inc Joint Venture [Member] | Corporate Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment threshold requirement			$ 1,200,000	$ 1,200,000	$ 2,200,000	$ 1,200,000
Negotiated price per share | $ / shares					$ 1
Investment threshold requirement stock issuance					$ 1,200,000
Issuance of common stock (shares) | shares	1,690,322
Percentage of ownership interest	53.00%
Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock-based compensation expense				76,000	120,000
CoSense, NFI and Serenz [Member] | Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, current			0	0	516,000
Assets held for sale, long-term			0	0	466,000
Liabilities held for sale, current			0	0	127,000
Liabilities held for sale, long-term			$ 0	$ 0	$ 225,000
NeoForce, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum indemnification obligation for certain losses		$ 250,000
Proceeds from the sale of business		$ 720,000

Discontinued Operations and A_4

Discontinued Operations and Assets Held for Sale - Consolidated Balance Sheet Components of Discontinued Operations (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Current assets
Total current assets held for sale		$ 516,000
Long-term assets
Total long-term assets held for sale		466,000
Current liabilities
Total current liabilities for sale		127,000
Long-term liabilities
Total long-term liabilities held for sale		225,000
CoSense, NFI and Serenz [Member] | Discontinued Operations, Held-for-sale [Member]
Current assets
Accounts receivable		50,000
Inventory		420,000
Prepaid expenses and other current assets		46,000
Total current assets held for sale	$ 0	516,000
Long-term assets
Property and equipment, net		20,000
Other intangible assets		446,000
Total long-term assets held for sale	0	466,000
Current liabilities
Accounts payable		51,000
Accrued compensation and other current liabilities		76,000
Total current liabilities for sale	0	127,000
Long-term liabilities
Other long-term liabilities		225,000
Total long-term liabilities held for sale	$ 0	$ 225,000

Discontinued Operations and A_5

Discontinued Operations and Assets Held for Sale - Components of Income of Discontinued Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other expense
Total	$ (1,494)	$ (3,593)
CoSense, NFI and Serenz [Member] | Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Product revenue	62	735
Cost of product revenue	32	820
Gross profit (loss)	30	(85)
Expenses
Research and development	1,106	2,427
Sales and marketing	25	218
General and administrative	393	669
Total expenses	1,524	3,314
Operating loss	(1,494)	(3,399)
Other expense
Loss on sale of assets		(186)
Other expense		(8)
Total other expense		(194)
Total	$ (1,494)	$ (3,593)

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)

Dec. 19, 2018

Mar. 07, 2018

Dec. 11, 2017

Mar. 07, 2017

Jan. 27, 2017

Dec. 22, 2016

Oct. 31, 2015

Jun. 30, 2018

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Jun. 29, 2016

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Convertible preferred stock, shares authorized

10,000,000

10,000,000

Proceeds from issuance of common stock

$ 10,000,000

Stock-based compensation expense

$ 988,000

$ 1,000,000

Expected dividend yield

0.00%

0.00%

Weighted average grant date fair value per option granted (in dollars per share)

$ 1.08

$ 1.88

Future stock-based compensation for unvested employee options granted and outstanding

$ 1,200,000

Stock options outstanding, intrinsic value

$ 71,000

Number of shares available for issuance under the plan on the first day of each year

31,755,169

19,238,972

Series D Warrants [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Exercise price of warrants (in dollars per share)

$ 12.30

Number of common stock purchased upon issuance of warrants

586,182

Warrants outstanding (in shares)

256,064

Warrants term

5 years

Warrants expiration date

Oct. 15, 2020

Liquidated damages amount percent of VWAP (percent)

1.00%

Warrants to Purchase Stock [Member] | 2010 and 2012 Convertible Promissory Notes [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Exercise price of warrants (in dollars per share)

$ 24.35

Warrants outstanding (in shares)

102,070

Warrants term

10 years

Warrants expiration period

2024-11

Underwriter [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Exercise price of warrants (in dollars per share)

$ 35.70

Warrants outstanding (in shares)

16,500

Warrants term

10 years

Warrants expiration period

2024-11

Employee Stock Purchase Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of shares available for grant

27,967

Percentage of outstanding stock maximum

1.00%

Number of shares available for issuance under the plan on the first day of each year

55,936

Discontinued Operations, Held-for-sale [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation expense

$ 76,000

$ 120,000

Minimum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Ownership interest of voting rights of all classes of stock (percent)

10.00%

Stock Options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

4 years

Number of shares available for grant

1,150,961

1,666,602

191,770

Income tax benefits recognized from stock-based compensation

$ 0

$ 0

Number of options granted

756,086

622,755

Expected dividend yield

0.00%

Future stock-based compensation, requisite service period

2 years 6 months

Stock Options [Member] | Minimum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of fair market value

110.00%

Stock Options [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Contractual term of option

10 years

ISOs [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Contractual term of option

5 years

Restricted Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation expense

$ 159,000

Stock units granted

99,217

Vesting percentage

100.00%

Equity Unit Purchase Agreements [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of newly issued

10,272,375

8,141,116

Price per unit

$ 1.61

$ 1.84

Gross Proceeds from issuance of units

$ 16,500,000

$ 15,000,000

Common Stock [Member] | Equity Unit Purchase Agreements [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Warrant to call common stock

0.05

0.74

Exercise price of warrants (in dollars per share)

$ 2

$ 2

Number of common stock purchased upon issuance of warrants

513,617

6,024,425

Warrants Issued in 2009 to Purchase Common Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Exercise price of warrants (in dollars per share)

$ 108

Warrants outstanding (in shares)

1,851

Warrants term

10 years

Warrants expiration period

2019-01

Aspire Capital Fund, LLC [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Maximum commitment under stock purchase agreement

$ 17,000,000

Purchase agreement term

30 months

Proceeds from issuance of common stock

$ 2,000,000

Essentialis, Inc. [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Amount of financing needed

$ 8,000,000

Common stock shares issued in acquisition (shares)

3,783,388

Indemnification claims period

1 year

Contingent consideration potential additional shares issuable if milestones are reached (shares)

903,367

Maximum total common stock issuable in acquisition (in shares)

4,867,422

Essentialis, Inc. [Member] | Indemnification Claims [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock shares issued in acquisition (shares)

180,667

180,667

Essentialis, Inc. [Member] | Earnout Payments [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Maximum potential cash earnout payments

$ 30,000,000

Series B Convertible Preferred Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Convertible preferred stock, shares authorized

13,780

13,780

Preferred stock shares issued

0

4,571

13,780

Preferred stock, shares outstanding

0

4,571

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Based Compensation Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	$ 988,000	$ 1,000,000
Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	912,000	880,000
Research and Development [Member] | Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	205,000	93,000
General and Administrative [Member] | Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	$ 707,000	$ 787,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, Minimum	2.70%	1.90%
Risk-free interest rate, Maximum	2.80%	2.20%
Volatility, Minimum	70.00%	61.00%
Volatility, Maximum	71.00%	69.00%
Dividend rate	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (years)	5 years 6 months	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (years)	6 years	6 years 1 month 6 days

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Stock Option Transactions (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Options [Member]
Shares Available for Grant
Options Available, Beginning balance	1,666,602	191,770
Options Available, Additional shares authorized	223,742	134,295
Options Available, Amendment to plan to authorize additional shares		1,785,837
Options Available, Granted	(756,086)	(622,755)
Options Available, Exercised		0
Options Available, Canceled/Forfeited	115,920	177,455
Options Available, Ending balance	1,150,961	1,666,602	191,770
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance	1,026,987	581,687
Options granted	756,086	622,755
Options exercised	0	0
Options canceled/forfeited	(115,920)	(177,455)
Ending balance	1,667,153	1,026,987	581,687
Options vested at end of period (shares)	820,422
Options vested and expected to vest at end of period (shares)	1,667,153
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 9.99	$ 17.10
Options granted (in dollars per share)	1.68	3.04
Options exercised (in dollars per share)	0
Options canceled/forfeited (in dollars per share)	12.72	8.84
Ending balance (in dollars per share)	6.03	$ 9.99	$ 17.10
Options vested at end of period (in dollars per share)	9.85
Options vested and expected to vest at end of period (in dollars per share)	$ 6.03
Weighted Average Remaining Contractual Term
Options outstanding at end of period	8 years 3 months 7 days	7 years 11 months 8 days	8 years 5 months 23 days
Options vested at end of period	7 years 7 months 20 days
Options vested and expected to vest at end of period	8 years 3 months 7 days
Restricted Stock Units [Member]
Shares Available for Grant
Options Available, Shares allocated to grants of restricted stock units	(99,217)

Income Taxes - Geographical Dis

Income Taxes - Geographical Distribution of Income (Loss) before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
United States	$ (11,830)	$ (13,707)
Foreign	(11)	(17)
Income (loss) before income taxes	(11,841)	(13,724)
Income (loss) resulting from discontinued operations	$ (1,494)	$ (3,593)

Income Taxes - Summary of Provi

Income Taxes - Summary of Provision for Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0	$ 0
State	0	1
Foreign	0	0
Current Income Tax Expense (Benefit)	0	1
Deferred
Federal	0	(1,578)
State	0	(73)
Foreign	0	0
Deferred Income Tax Expense (Benefit), Total	0	(1,651)
Total provision for income taxes benefit	$ 0	$ (1,650)

Income Taxes - Provision for In

Income Taxes - Provision for Income Tax Benefit by Applying Statutory Federal Income Tax Rate to Operating Loss from Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Tax on the loss before income tax expense computed at the federal statutory rate	$ (2,486)	$ (4,666)
State tax (benefit) at statutory rate, net of federal benefit	(187)	(67)
Tax reform		10,613
Foreign rate differential	2	3
Change in valuation allowance	4,143	(8,485)
Change in research and development credits	(99)	(121)
Stock based compensation—ISOs	143	295
Change in fair value of warrants	(110)	343
Change in fair value of contingent consideration	119
Gain on deconsolidation	(4)
Disallowance of loss on discontinued operations	(426)
Acquisition costs		203
Change in NOL true up	(590)
Change in temporary difference true up	(456)
Loss on sale of NFI		(677)
Other	(49)	909
Total provision for income taxes benefit	$ 0	$ (1,650)

Income Taxes - Significant Comp

Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Non-Current Deferred Tax Assets:
Federal and state net operating loss carryforwards	$ 28,532	$ 25,486
Research and other credits	2,037	1,807
Reserves and accruals	52	145
Assets held for sale	15	17
Fixed assets	67
Capital loss carryover	425	459
Stock based compensation	70	36
Other deferred tax assets	542
Gross non-current deferred tax assets	31,740	27,950
Intangible Assets	(4,062)	(4,414)
Fixed Assets		(3)
Total non-current deferred tax liabilities	(4,062)	(4,417)
Total deferred tax assets	27,678	23,533
Valuation allowance	$ (27,678)	$ (23,533)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance	$ 4,100,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0	$ 0
Unrecognized tax benefit offset by change in valuation allowance	964,000
Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	500,000
U.S. Federal Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	129,800,000
U.S. Federal Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	1,200,000
State Tax Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	51,400,000
State Tax Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	798,000
Foreign Tax Authority [Member] | Her Majesty's Revenue and Customs (HMRC) [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 264,000

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Beginning balance	$ 854	$ 795
Increases (decreases) related to prior year tax positions	23	(4)
Increase related to current year tax positions	87	63
Ending Balance	$ 964	$ 854

Net loss per share - Schedule o

Net loss per share - Schedule of Potentially Dilutive Securities Outstanding Excluded from Computations of Diluted Weighted-Average Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	9,514,982	9,275,399
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding		914,200
Underwriter [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	16,500	16,500
Series A Warrants to Purchase Shares of Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	485,121	485,121
Series C Warrant to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	118,083	118,083
Series D Warrant To Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	586,162	586,162
2017 PIPE Warrant Liability [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	6,024,425	6,024,425
2018 PIPE Warrant Liability [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	513,617
Warrants Issued to 2010/2012 Convertible Note Holders to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	102,070	102,070
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	1,667,153	1,026,987
Warrants Issued in 2009 to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	1,851	1,851

Compensation Plan for Board M_2

Compensation Plan for Board Members - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Board of Directors [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Issuance of common stock to board members in lieu of cash payments for quarterly board fees (shares)	146,371	90,306

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail)	Feb. 04, 2019
Subsequent Event [Member] | Soleno Therapeutics Europe Limited [Member] | Ireland [Member]
Subsequent Event [Line Items]
Wholly owned subsidiary formation date	Feb. 4, 2019