Soleno Therapeutics (SLNO) 10-K 3 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 26, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
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 Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Shell Company	false
Entity Emerging Growth Company	false
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-36593
Entity Tax Identification Number	77-0523891
Entity Address, Address Line One	203 Redwood Shores Parkway
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94065
City Area Code	650
Local Phone Number	213-8444
Entity Incorporation, State or Country Code	DE
Entity Common Stock, Shares Outstanding		79,723,680
Entity Public Float			$ 98.3
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	SLNO
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s Definitive Proxy Statement to be filed with the Commission pursuant to Regulation 14A in connection with the registrant’s 2021 Annual Meeting of Stockholders, to be filed subsequent to the date hereof, are incorporated by reference into Part III of this Report. Such Definitive Proxy Statement will be filed with the Securities and Exchange Commission not later than 120 days after the conclusion of the registrant’s fiscal year ended December 31, 2020. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 49,224	$ 20,733
Prepaid expenses and other current assets	1,019	411
Total current assets	50,243	21,144
Long-term assets
Property and equipment, net	19	22
Operating lease right-of-use assets	124	398
Finance lease right-of-use assets	15	24
Intangible assets, net	14,581	16,525
Other long-term assets		59
Total assets	64,982	38,172
Current liabilities
Accounts payable	3,489	1,995
Accrued compensation	1,005	283
Accrued clinical trial site costs	3,789	1,999
Operating lease liabilities	139	305
Other current liabilities	196	382
Total current liabilities	8,618	4,964
Long-term liabilities
Contingent liability for Essentialis purchase price	10,278	5,938
Other long-term liabilities		147
Total liabilities	19,435	23,225
Commitments and contingencies (Note 8)
Stockholders’ equity
Common stock, $0.001 par value, 250,000,000 and 100,000,000 shares authorized at December 31, 2020 and December 31, 2019, respectively, 79,615,692 and 44,658,054 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively.	80	45
Additional paid-in-capital	227,912	172,708
Accumulated deficit	(182,445)	(157,806)
Total stockholders’ equity	45,547	14,947
Total liabilities and stockholders’ equity	64,982	38,172
2017 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability		10,822
2018 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability	$ 539	$ 1,354

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	250,000,000	100,000,000
Common stock, shares issued	79,615,692	44,658,054
Common stock, shares outstanding	79,615,692	44,658,054

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating expenses
Research and development	$ 23,191	$ 16,267
General and administrative	8,758	6,930
Change in fair value of contingent consideration	4,340	289
Total operating expenses	36,289	23,486
Operating loss	(36,289)	(23,486)
Other income (expense)
Change in fair value of warrants liabilities	11,637	(6,964)
Loss from minority interest investment		(478)
Interest and other income	13	154
Total other income (expense)	11,650	(7,288)
Net loss	$ (24,639)	$ (30,774)
Loss per common share, basic and diluted	$ (0.39)	$ (0.90)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share	62,620,227	34,142,478

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Balances at beginning at Dec. 31, 2018	$ 30,413	$ 32	$ 157,413	$ (127,032)
Balances at beginning (shares) at Dec. 31, 2018		31,755,169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	825		825
Issuance of restricted stock units under equity incentive plans (shares)		61,218
Issuance of common stock	14,483	$ 13	14,470
Issuance of common stock (shares)		12,841,667
Net loss	(30,774)			(30,774)
Balances at ending at Dec. 31, 2019	14,947	$ 45	172,708	(157,806)
Balances at end (shares) at Dec. 31, 2019		44,658,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,500		1,500
Issuance of restricted stock units under equity incentive plan	17		17
Issuance of restricted stock units under equity incentive plans (shares)		109,154
Issuance of common stock	53,722	$ 35	53,687
Issuance of common stock (shares)		34,848,484
Net loss	(24,639)			(24,639)
Balances at ending at Dec. 31, 2020	$ 45,547	$ 80	$ 227,912	$ (182,445)
Balances at end (shares) at Dec. 31, 2020		79,615,692

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement Of Stockholders Equity [Abstract]
Less transaction costs	$ 3,778	$ 927

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (24,639)	$ (30,774)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,954	1,958
Noncash lease expense	283	386
Stock-based compensation expense	1,500	825
Change in fair value of stock warrants	(11,637)	6,964
Change in fair value of contingent consideration	4,340	289
Operating loss of minority interest investment		478
Change in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	(549)	10
Due from related party		64
Accounts payable	1,494	1,061
Accrued compensation	722	9
Accrued clinical trial site costs	1,790	1,679
Operating lease liabilities	(305)	(360)
Other liabilities	(177)	36
Net cash used in operating activities	(25,224)	(17,375)
Cash flows from investing activities:
Purchases of property and equipment	(7)	(21)
Security deposit on sublease		(59)
Security deposit received from expired lease		108
Proceeds from sale of minority interest investment in former subsidiary		500
Net cash (used in) provided by investing activities	(7)	528
Cash flows from financing activities:
Proceeds from sale of common stock and common stock warrants, net of costs	53,722	14,483
Proceeds from stock option exercises	17
Principal paid on finance lease liabilities	(17)	(2)
Net cash provided by financing activities	53,722	14,481
Net increase (decrease) in cash and cash equivalents	28,491	(2,366)
Cash and cash equivalents, beginning of period	20,733	23,099
Cash and cash equivalents, end of period	49,224	$ 20,733
Supplemental disclosure of non-cash investing information
Purchases of property and equipment in accounts payable	$ 1

Overview

Overview	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Overview	Note 1. Overview Soleno Therapeutics, Inc. (the Company or Soleno) is focused on the development and commercialization of novel therapeutics for the treatment of rare diseases. Our lead candidate is Diazoxide Choline Controller Release tablets (DCCR), a once-daily oral tablet for the treatment of Prader-Willi Syndrome (PWS). DCCR has orphan designation for the treatment of PWS in the United States (U.S.) as well as in the European Union (E.U.). The Company incorporated in the State of Delaware on August 25, 1999, and is located in Redwood City, California. It initially established its operations as Capnia, a diversified healthcare company that developed and commercialized innovative diagnostics, devices and therapeutics addressing unmet medical needs. In March 2017, the Company m erged with Essentialis, Inc (Essentialis) and subsequently received stockholder approval to amend its Amended and Restated Certificate of Incorporation to change its name from “Capnia, Inc.” to “Soleno Therapeutics, Inc.” Essentialis was a privately held clinical-stage company focused on the development of breakthrough medicines for the treatment of rare diseases where there is increased mortality and risk of cardiovascular and endocrine complications. DCCR has been evaluated in a Phase 3 study (C601 or DESTINY PWS), a 3-month randomized, double-blind placebo-controlled study, which completed enrollment in January 2020, with 127 patients at 29 sites in the U.S. and U.K. Patients who complete treatment in DESTINY PWS are eligible to receive DCCR for up to 36 months in C602, an open-label extension study. Top line results from DESTINY PWS were announced in June 2020. Although the trial did not meet its primary endpoint of change from baseline in hyperphagia, significant improvements were observed in two of three key secondary endpoints. In February 2021 the Company announced analysis limited to data collected before the onset of the COVID-19 pandemic. The analysis of the data through March 1, 2020 showed statistical significance in the primary, all key secondary and several other efficacy endpoints. The Company is evaluating the data and is in communication with the regulatory authorities to determine next steps.

Liquidity

Liquidity	12 Months Ended
	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Liquidity	Note 2. Liquidity The Company had a net loss of $24.6 million during 2020 and has an accumulated deficit of $182.4 million at December 31, 2020 resulting from having incurred losses since its inception. The Company had $49.2 million of cash and cash equivalents on hand at December 31, 2020 and used $25.2 million of cash in its operating activities during 2020. The Company has financed its operations principally through issuances of equity securities. On June 26, 2020, the Company sold 34,848,484 shares of common stock in an underwritten public offering at a price of $1.65 per share for net proceeds of $53.7 million. The Company expects to continue incurring losses for the foreseeable future. However, the Company expects that its current cash and cash equivalents balance are sufficient to enable the Company to meet its obligations for at least the next twelve months from the date of this filing.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
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 (GAAP), and the applicable rules and regulations of the Securities and Exchange Commission (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. 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, accrued costs for services rendered in connection with third-party contactor clinical trial activities, 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. Cash and cash equivalents deposited with this commercial bank exceeded the Federal Deposit Insurance Corporation insurable limit at December 31, 2020 and 2019. 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 U.S. 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., the U.K. and Ireland and include deposits in a money market fund which was unrestricted as to withdrawal or use. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of payments primarily related to clinical trials, insurance and short-term deposits. Prepaid expenses are initially recorded upon payment and are expensed as goods or services are received. 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. Leases The Company determines whether an arrangement is a lease at inception. Specifically, it considers whether it controls the underlying asset and has the right to obtain substantially all the economic benefits or outputs from the asset. If the contractual arrangement contains a lease, the Company then determines whether it is an operating or finance lease. Right-of-Use (ROU) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. The Company does not separate lease components from non-lease components, such as common area maintenance charges, and instead accounts for the lease and non-lease components as a single component. The Company does not recognize lease assets and lease liabilities for leases with an original lease term of less than one year. 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 measures equity method investments 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. was sold in September 2019. (See Note 9.) 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 In March 2017, the Company completed the acquisition of Essentialis in accordance with the merger agreement by and between the Company Soleno Therapeutics and Essentialis dated December 22, 2016 (the “Merger Agreement”). The merger transaction was accounted for as an asset acquisition under the acquisition method of accounting and accordingly, the value of $22.0 million was assigned to the identifiable intangible asset relating to the patent for DCCR, which patent expires in June 2028. Intangible assets with finite lives are amortized on a straight-line basis over their estimated useful lives, which for the patent is 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. Research and Development Research and development costs are charged to operations as incurred. Research and development costs consist primarily of salaries, benefits, bonus, share-based compensation, consultant fees, certain facility costs and other costs associated with clinical trials. Clinical trial costs are a significant component of research and development expenses and include costs associated with third-party contractors and other vendors. Invoicing from third-party contractors for services performed can often occur several months later. We accrue the costs of service rendered in connection with third-party contractor activities based on our estimate of fees and costs associate with the contract that were rendered during the period and they are expensed as incurred. 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. 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. 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 and restricted stock units granted to employees, nonemployees and directors are measured at the date of grant based on the estimated fair value of the award. For restricted stock units this fair value is based on the Company’s common stock price on the grant date. The Company estimates the grant date fair value of stock options, 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 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 the Company had made different assumptions, its 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 the volatility of its common stock together with 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 August 2018, the Financial Accounting Standards Board (FASB) Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. In October 2020, the FASB issued ASU 2020-10, “ Codification Improvements”. Recently Issued Accounting Standards During the year ended December 31, 2020, there have been no new, or existing recently issued, accounting pronouncements that are of significance, or potential significance, that impact the Company’s consolidated financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Note 4. Fair Value of Financial Instruments The carrying value of the Company’s 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, 2020 Total Level 1 Level 2 Level 3 Liabilities 2018 PIPE warrant liability $ 539 $ — $ — $ 539 Essentialis purchase price contingency liability 10,278 — — 10,278 Total common stock warrant and contingent consideration liability $ 10,817 $ — $ — $ 10,817 Fair Value Measurements at December 31, 2019 Total Level 1 Level 2 Level 3 Liabilities 2017 PIPE warrant liability $ 10,822 $ — $ — $ 10,822 2018 PIPE warrant liability 1,354 — — 1,354 Essentialis purchase price contingency liability 5,938 — — 5,938 Total common stock warrant and contingent consideration liability $ 18,114 $ — $ — $ 18,114 The Company’s estimated fair value of the 2018 PIPE Warrants was calculated as of December 31, 2020 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 expected term, the expected dividend yield and the risk-free interest rate. The Company used the Monte Carlo simulation of a geometric Brownian motion model to estimate the fair value of the 2017 PIPE Warrants and the 2018 PIPE Warrant as of December 31, 2019 as this model allows for determining path-dependent outcomes. The difference in valuation as a result of using the Black-Scholes pricing model compared to the Monte Carlo simulation model is not significant. 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. 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 its Essentialis purchase price contingent liability. 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 3 liabilities (dollars in thousands). Series A Warrants Series C Warrants 2017 PIPE Warrants 2018 PIPE Warrants Purchase Price Number of Number of Number of Number of Contingent Warrants Liability Warrants Liability Warrants Liability Warrants Liability Liability Balance at January 1, 2019 485,121 $ 49 118,083 $ — 6,024,425 $ 4,563 513,617 $ 600 $ 5,649 Expiration of Series A Warrants (485,121 ) (49 ) — — — — — — — Change in value of 2017 PIPE Warrants — — — — — 6,259 — — — Change in value of 2018 PIPE Warrants — — — — — — — 754 — Change in value of contingent liability — — — — — — — — 289 Balance at December 31, 2019 — — 118,083 — 6,024,425 10,822 513,617 1,354 5,938 Expiration of Series C Warrants — — (118,083 ) — — — — — — Expiration of 2017 PIPE Warrants — — — — (6,024,425 ) (10,822 ) — — — Change in value of 2018 PIPE Warrants — — — — — — — (815 ) — Change in value of contingent liability — — — — — — — — 4,340 Balance at December 31, 2020 — $ — — $ — — $ — 513,617 $ 539 $ 10,278

Other Financial Statement Detai

Other Financial Statement Details	12 Months Ended
	Dec. 31, 2020
Other Financial Statement Details Disclosure [Abstract]
Other Financial Statement Details	Note 5. Other Financial Statement Details Property and Equipment, Net Property and equipment are summarized in the following table (in thousands). December 31, 2020 December 31, 2019 Computer hardware $ 53 $ 52 Computer software — — Furniture and fixtures 1 1 Leasehold improvements — — 54 53 Less accumulated depreciation and amortization (35 ) (31 ) Total $ 19 $ 22 Depreciation expense was approximately $11,000 for each of the years ended December 31, 2020 and December 31, 2019. Intangible Assets, Net Intangible assets consist of the following (in thousands). December 31, 2020 December 31, 2019 Amount Accumulated Amortization Net Amount Amount Accumulated Amortization Net Amount Patents and merger costs $ 22,003 $ (7,422 ) $ 14,581 $ 22,003 $ (5,478 ) $ 16,525 Total $ 22,003 $ (7,422 ) $ 14,581 $ 22,003 $ (5,478 ) $ 16,525 Future amortization expense for intangible assets over their remaining useful lives is as follows (in thousands). Year ending December 31 Patents and trademarks 2021 $ 1,944 2022 1,944 2023 1,944 2024 1,944 2025 1,944 2026 and thereafter 4,861 Total $ 14,581 Amortization expense was $1.9 million for the year ended December 31, 2020 and 2019.

Warrant Liabilities

Warrant Liabilities	12 Months Ended
	Dec. 31, 2020
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) were determined to be 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 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 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 (the IPO), in November 2014. The Series A Warrants were exercisable prior to the expiration of the five-year term on November 12, 2019. The Series A Warrants contained a fundamental transactions provision that permitted 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 were considered to have a cash settlement feature that precluded their classification as equity instruments. Since their issuance, a total of 4,800 Series A Warrants have been exercised. On November 12, 2019, the remaining Series A Warrants expired. The decrease in fair value of approximately $49,000 from 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 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 expired 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. 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 was exercisable at $31.25 per share prior to their expiration on March 5, 2020. The Series C Warrants contract further provided for the payment of liquidated damages at an amount per month equal to 1% of the aggregate volume weighted average price (VWAP), of the shares into which each Warrant was convertible into in the event that the Company was unable to maintain the effectiveness of a registration statement. The Company evaluated the registration payment arrangement stipulated in the terms of these securities and determined that it was probable that the Company would maintain an effective registration statement and therefore did not allocate any portion of the proceeds related to the warrant financings to the registration payment arrangement. The Warrants also contained a fundamental transactions provision that permitted 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 Series C Warrants were considered to have a cash settlement feature that precluded their classification as equity instruments. The Series C Warrants were exercisable into 118,083 shares of the Company’s common stock prior to their expiration on March 5, 2020. As of December 31, 2019, the fair value of the Series C Warrants was determined to be zero. The Company 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 at December 31, 2019. Volatility 90 % Contractual term (years) 0.17 Expected dividend yield — % Risk-free rate 1.52 % 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 prior to their expiration on December 15, 2020, entitled the holders to purchase 6,024,425 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to certain adjustments. The fair value of the 2017 PIPE Warrants was estimated at $10.8 million as of December 31, 2019, and was zero at December 31, 2020 as the warrants had expired. No warrants were exercised prior to expiration. The $10.8 million decrease and the $6.3 million increase in the fair value of the liability for the 2017 PIPE Warrants during the year ended December 31, 2020 and December 31, 2019, respectively, was recorded as other 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 value as of December 31, 2019. Volatility 99 % Contractual term (years) 1.0 Expected dividend yield — % Risk-free rate 1.60 % 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 to purchase 513,617 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, 2020, the fair value of the 2018 PIPE Warrants was estimated at $0.5 million. The $0.8 million decrease and $0.8 million increase in the fair value of the liability for the 2018 PIPE Warrants during the years ended December 31, 2020 and December 31, 2019, respectively, was recorded as other income (expense) in the consolidated statements of operations. The Company has calculated the fair value of the 2018 PIPE Warrants as of December 31, 2020 using a Black-Scholes pricing model, and the fair value as of December 31, 2019 using a Monte Carlo simulation of a geometric Brownian motion model. The difference in valuation as a result of using the Black-Scholes pricing model compared to the Monte Carlo simulation model is not significant. December 31, 2020 December 31, 2019 Volatility 88 % 99 % Contractual term (years) 3.0 4.0 Expected dividend yield — % — % Risk-free rate 0.17 % 1.56 % The Black-Scholes pricing model and the Monte Carlo simulation of a geometric Brownian motion model require 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 together with the volatility of its own stock. • 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.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Note 7. Leases Leases The Company’s previous operating lease for its headquarters facility office space in Redwood City, California, terminated in August 2019, along with the related subleases. One of the subleases was with Capnia, of which the Company was a joint owner until September 2019. See note 9 for further information. Sublease income received from Capnia during the year ended December 31, 2019 was approximately $65,000. In July 2019, the Company executed a non-cancellable lease agreement for 6,368 square feet of new space in Redwood City, California, which began in September 2019 and expires in May 2021. The lease also provides the Company with the right to use office furniture in the space and allows the purchase of this furniture at the end of the lease term for $1. The lease agreement requires monthly lease payments of approximately $29,000 beginning in November of 2019, with an increase to approximately $30,000 per month in September of 2020. The Company has accounted for the lease as an operating lease for the office space and a finance lease for the office furniture, based on their relative standalone prices. The Company’s operating lease ROU assets, finance ROU assets, and current operating lease liabilities each appear as a separate line within the Company’s consolidated balance sheet. The Company’s current finance lease liabilities were approximately $8,000 and $17,000 as of December 31, 2020 and December 31, 2019, respectively, and are included in other current liabilities on the consolidated balance sheet. As of December 31, 2020 and December 31, 2019, the Company’s long-term operating lease liabilities were zero and $0.1 million, respectively, and the long-term finance lease liabilities were zero and approximately $8,000, respectively. Both the long-term operating lease liabilities and long-term finance lease liabilities are included in other long-term liabilities on the consolidated balance sheet. The components of lease expense were as follows (in thousands): Year Ended December 31, 2020 December 31, 2019 Operating lease cost: Operating lease cost $ 305 $ 418 Sublease income — (173 ) Total operating lease cost $ 305 $ 245 Finance lease cost: Amortization of right-of-use assets $ 9 $ 3 Interest on lease liabilities 2 1 Total finance lease cost $ 11 $ 4 Supplemental cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2020 December 31, 2019 Right-of use assets obtained in exchange for lease obligations (noncash): Operating leases $ — $ 484 Finance leases $ — $ 27 The following is a schedule by year of future maturities of the Company’s lease liabilities as of December 31, 2020 (in thousands): Operating Lease Finance Lease 2021 $ 143 $ 8 Total lease payments 143 8 Less interest (4 ) — Total $ 139 $ 8 The weighted-average remaining lease term was 0.4 and 1.4 years as of December 31, 2020 and December 31, 2019, respectively, for both the operating leases and finance leases. The weighted average discount rate related to the Company’s lease liabilities was 10% as of December 31, 2020 and December 31, 2019 for both the operating leases and finance leases. The Company lease discount rates are based on estimates of its incremental borrowing rate, as the discount rates implicit in the Company’s leases cannot be readily determined. As the Company does not have any outstanding debt the Company estimates the incremental borrowing rate based on its estimated credit rating and available market information.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8. Commitments and 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.

CoSense Joint Venture Agreement

CoSense Joint Venture Agreement	12 Months Ended
	Dec. 31, 2020
Equity Method Investments And Joint Ventures [Abstract]
CoSense Joint Venture Agreement	Note 9. CoSense Joint Venture Agreement In December 2017, the Company entered into a joint venture with OptAsia Healthcare Limited (OAHL), with respect to its CoSense product by agreeing to sell shares of Capnia, its then wholly-owned subsidiary, to OAHL. CoSense was based on the Company’s Sensalyze Technology Platform and received 510(k) clearances from the FDA and CE Mark certification in the E.U 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 held a controlling interest in Capnia and resulted in the deconsolidation of Capnia’s financial statements from 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 related 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 was included in other income from continuing operations on the Company’s consolidated statements of operations. The remaining 47% investment in Capnia was classified as an equity method investment and presented as a Minority interest investment in former subsidiary in the consolidated balance sheet. During September 2019, the Company sold its remaining 47% investment in Capnia to Sinon for a total purchase price of $0.5 million. As of the sale date, the Company had a minority interest investment in former subsidiary balance of $0.5 million, after recording $0.5 million for its share of Capnia’s losses during 2019 up until the date of sale, which is included in the line titled “Loss from minority interest investment” in the Company’s consolidated statements of operations. A gain of approximately $33,000 was recognized upon the sale and is presented, together with the Company’s share of Capnia’s net losses during the period, in the consolidated statements of operations in the line titled “Loss from minority interest investment”. Following the transaction, the Company has no interest remaining in Capnia and the previous joint venture agreement with OAHL has been terminated.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	Note 10. Stockholders’ Equity Convertible Preferred Stock The Company is authorized to issue 10,000,000 shares of Preferred Stock. Common Stock On March 7, 2017, the Company completed its merger with Essentialis and issued 4,867,422 shares of common stock to stockholders of Essentialis. 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 the former Essentialis stockholders. On December 11, 2017, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company issued warrant to purchase 6,024,425 of the Company’s common stock at an exercise price of $2.00 per share which expired December 15 th 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 prepared and filed a registration statement with the SEC to register for resale the 2018 Resale Shares. The registration statement was declared effective in April 2019. On October 25, 2019, the Company sold 12,841,667 shares of its common stock, including 1,675,000 shares sold upon full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $1.20 per share. The net proceeds of the offering were $14.5 million, after deducting the underwriting discount and other offering expenses. On June 26, 2020, the Company sold 34,848,484 shares of its common stock, including 4,545,454 Equity Incentive Plans The Company has the 2014 Equity Incentive Plan (the 2014 Plan). 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, 2020, a total of 1,432,229 shares are available for future grant under the 2014 Plan. On September 28, 2020, the Board of Directors adopted the 2020 Inducement Equity Incentive Plan (the Inducement Plan), and reserved 1,500,000 shares of the Company’s common stock for issuance to equity awards granted under the Inducement Plan. The Inducement Plan provides for the grant of equity-based awards, including nonqualified stock options, restricted stock units, restricted stock, stock appreciation rights, performance shares and performance units, and its terms are substantially similar to the Company’s 2014 Equity Incentive 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, 2020 and 2019 of $1.5 million and $0.8 million, 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, 2020 and December 31, 2019. Stock compensation expense was allocated between departments as follows (in thousands). Year ended December 31, 2020 December 31, 2019 Research and development $ 348 $ 158 General and administrative 1,152 667 Total $ 1,500 $ 825 Stock Options The Company granted options to purchase 824,150 and 658,285 of the Company’s common stock during the years ended December 31, 2020 and 2019, 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, 2020 December 31, 2019 Expected life (years) 5.5-6.1 5.5-6.1 Risk-free interest rate 0.4%-0.5% 1.6%-2.6% Volatility 64%-96% 70%-75% 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 the Company’s common stock together with 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 and restricted stock unit transactions for the years ended December 31, 2020 and 2019 as issued under the 2014 Plan. Number of Options Weighted- Average Exercise Price per Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding Share (in years) (in thousands) Balance at January 1, 2019 1,667,153 $ 6.03 8.27 Options granted 658,285 $ 1.77 Options canceled/forfeited (202,321 ) $ 6.99 — Balance at December 31, 2019 2,123,117 $ 4.62 7.87 Options granted 824,150 $ 2.79 Options exercised (8,518 ) $ 1.96 Options canceled/forfeited (101,010 ) $ 2.34 Balance at December 31, 2020 2,837,739 $ 4.18 7.62 $ 347 Options vested at December 31, 2020 1,577,255 $ 5.64 6.62 $ 205 Options vested and expected to vest at December 31, 2020 2,837,739 $ 4.18 7.62 $ 347 The weighted-average grant date fair value of employee options granted was $1.76 and $1.14 per share for the years ended December 31, 2020 and December 31, 2019, respectively. At December 31, 2020 total unrecognized employee stock-based compensation was $1.8 million, which is expected to be recognized over the weighted-average remaining vesting period of 2.7 years. The intrinsic value of options exercised during the year ended December 31, 2020 was approximately $10,000. Restricted Stock Units There were 751,633 and 61,218 restricted stock units granted by the Company during the years ended December 31, 2020 and December 31, 2019, respectively, to employees and directors. The shares granted to directors were 100% vested on the grant date and represent compensation for past board services. The shares granted to employees typically vest annually over a period of four years. The shares were valued based on the Company’s common stock price on the grant date. The following table summarizes restricted stock unit transactions for the years ended December 31, 2020 and 2019 as issued under the 2014 Plan: Number of Restricted Stock Units Weighted- Average Grant-Date Fair Value per Share Outstanding at January 1, 2019 — Restricted stock units granted 61,218 $ 2.17 Restricted stock units vested (61,218 ) $ 2.17 Outstanding at December 31, 2019 — Restricted stock units granted 751,633 $ 3.68 Restricted stock units vested (103,133 ) $ 2.60 Restricted stock units cancelled (67,500 ) $ 3.85 Outstanding at December 31, 2020 581,000 $ 3.85 The fair value of all restricted stock units vested during the year ended December 31, 2020 and 2019 was $0.3 million and $0.1 million, respectively. At December 31, 2020 total unrecognized employee stock-based compensation related to restricted stock units was $1.7 million, which is expected to be recognized over the weighted-average remaining vesting period of 3.1 years. 2014 Employee Stock Purchase Plan The Company’s board of directors and stockholders have adopted the 2014 Employee Stock Purchase Plan (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, 2020, there were no purchases by employees under this plan. Series D Warrants The Company issued 256,064 Series D Warrants in October 2015, which were exercisable into 586,182 shares of the Company’s common stock, with an exercise price of $12.30. The warrants expired on October 15, 2020 and no warrants were exercised. Accounting Treatment The Company has accounted for the Series D Warrants in accordance with the guidance in ASC 815 Derivatives and Hedging. Other Common Stock Warrants As of December 31, 2020, 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 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, 2020
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, 2020 2019 United States $ (22,197 ) $ (30,729 ) Foreign (2,442 ) (45 ) Loss before income taxes $ (24,639 ) $ (30,774 ) The provision for income tax benefit differs from the amount estimated by applying the statutory federal income tax rate to the operating loss due to the following (in thousands). December 31, 2020 2019 Tax on the loss before income tax expense computed at the federal statutory rate $ (5,174 ) $ (6,463 ) State tax (benefit) at statutory rate, net of federal benefit (2,293 ) (1,691 ) Foreign rate differential 51 10 Change in valuation allowance 8,231 6,696 Change in research and development credits (303 ) (200 ) Stock based compensation—ISOs 71 149 Change in fair value of warrants (2,444 ) 1,461 Change in fair value of contingent consideration 911 61 Change in net operating loss true up 846 (725 ) Change in state rate true up — 701 Change in temporary difference true up — — Other 104 1 Provision for income tax benefit $ — $ — 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, 2020 and 2019 (in thousands). December 31, 2020 2019 Non-current deferred tax assets: Federal and state net operating loss carryforwards $ 41,999 $ 35,091 Research and other credits 2,803 2,349 Reserves and accruals 236 77 Fixed assets 63 71 Capital loss carryover 1,115 1,115 Stock based compensation 337 85 Lease liability 41 131 Other deferred tax assets 129 196 Gross non-current deferred tax assets 46,723 39,115 Intangible assets (4,080 ) (4,623 ) Right-of-use assets (39 ) (118 ) Total non-current deferred tax liabilities (4,119 ) (4,741 ) Total deferred tax assets 42,604 34,374 Valuation allowance (42,604 ) (34,374 ) 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 $8.2 million from December 31, 2019 to December 31, 2020 primarily due to the generation of current year net operating losses, capital losses and research and development credits claimed. As of December 31, 2020, the Company had $164.7 million of federal, $98.6 million of state and $2.2 million of foreign net operating losses available to offset future taxable income. The federal net operating loss carryforwards began to expire in 2019, the federal net operating loss carryforwards of $57.4 million may be carried forward indefinitely, 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, 2020, the Company also had $1.7 million of federal and $1.1 million 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 currently in the process of analyzing 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 through 2020 and expects that analysis to completed during 2021. As such, as of the date of these consolidated financial statements the Company is not able to determine the impact on the net operating loss (NOL) carryforwards, if any. U.S. taxes and foreign withholding taxes have not been provided on undistributed earnings for certain non-U.S. subsidiaries as of December 31, 2020, 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, 2020 2019 Beginning balance $ 1,111 $ 964 Increase related to prior year tax positions — 7 Decrease related to prior year tax positions (4 ) (4 ) Increase related to current year tax positions 216 144 Ending balance $ 1,323 $ 1,111 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 $1.3 million of unrecognized assets and liabilities related to uncertain tax positions as of December 31, 2020. Changes in the unrecognized tax benefits within the next 12 months are expected to be similar to prior years and should not significantly increase or decrease. 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. There were no unrecognized tax benefits that would impact the effective tax rate as of December 31, 2020 and December 31, 2019. As of December 31, 2020, unrecognized tax benefits of $1.3 million would be offset by a change in valuation allowance. The Company files income tax returns in the U.S. federal jurisdiction, certain state jurisdictions, United Kingdom and Ireland. 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. The Jobs Act also establishes global intangible low-taxed income (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 2020, 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 Coronavirus Aid, Relief, and Economic Security (CARES) Act, was enacted March 27, 2020. Among the business provisions, the CARES Act provided for various payroll tax incentives, changes to net operating loss carryback and carryforward rules, business interest expense limitation increases, and bonus depreciation on qualified improvement property. Additionally, the Consolidated Appropriations Act of 2021 was signed on December 27, 2020 which provided additional COVID relief provisions for businesses. The Company has evaluated the impact of both Acts and has determined that any impact is not material to its financial statements.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2020
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 or vesting of common stock awards and exercise of common stock warrants. For the years ended December 31, 2020 and 2019, 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, 2020 2019 Warrants issued to 2010/2012 convertible note holders to purchase common stock 102,070 102,070 Options to purchase common stock 2,837,739 2,123,117 Outstanding restricted stock units 581,000 — Warrants issued to underwriter to purchase common stock 16,500 16,500 Series C warrants to purchase common stock — 118,083 Series D warrants to purchase common stock — 540,540 2017 PIPE warrants — 6,024,425 2018 PIPE warrants 513,617 513,617 Total 4,050,926 9,438,352

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	Note 13. 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. During the year ended December 31, 2019 the Company made matching contributions of approximately $37,000 to the 401(k) Plan, and no matching contributions during the year ended December 31, 2020.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Note 14. Subsequent Events The Company has evaluated its subsequent events from December 31, 2020 through the date these consolidated financial statements were issued and has determined that there are no subsequent events requiring disclosure in these consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
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 (GAAP), and the applicable rules and regulations of the Securities and Exchange Commission (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.
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, accrued costs for services rendered in connection with third-party contactor clinical trial activities, 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. Cash and cash equivalents deposited with this commercial bank exceeded the Federal Deposit Insurance Corporation insurable limit at December 31, 2020 and 2019. 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 U.S.
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., the U.K. and Ireland and include deposits in a money market fund which was unrestricted as to withdrawal or use.
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of payments primarily related to clinical trials, insurance and short-term deposits. Prepaid expenses are initially recorded upon payment and are expensed as goods or services are received.
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.
Leases	Leases The Company determines whether an arrangement is a lease at inception. Specifically, it considers whether it controls the underlying asset and has the right to obtain substantially all the economic benefits or outputs from the asset. If the contractual arrangement contains a lease, the Company then determines whether it is an operating or finance lease. Right-of-Use (ROU) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. The Company does not separate lease components from non-lease components, such as common area maintenance charges, and instead accounts for the lease and non-lease components as a single component. The Company does not recognize lease assets and lease liabilities for leases with an original lease term of less than one year.
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 measures equity method investments 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. was sold in September 2019. (See Note 9.)
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.
Intangible Assets	Intangible Assets In March 2017, the Company completed the acquisition of Essentialis in accordance with the merger agreement by and between the Company Soleno Therapeutics and Essentialis dated December 22, 2016 (the “Merger Agreement”). The merger transaction was accounted for as an asset acquisition under the acquisition method of accounting and accordingly, the value of $22.0 million was assigned to the identifiable intangible asset relating to the patent for DCCR, which patent expires in June 2028. Intangible assets with finite lives are amortized on a straight-line basis over their estimated useful lives, which for the patent is 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.
Research and Development	Research and Development Research and development costs are charged to operations as incurred. Research and development costs consist primarily of salaries, benefits, bonus, share-based compensation, consultant fees, certain facility costs and other costs associated with clinical trials. Clinical trial costs are a significant component of research and development expenses and include costs associated with third-party contractors and other vendors. Invoicing from third-party contractors for services performed can often occur several months later. We accrue the costs of service rendered in connection with third-party contractor activities based on our estimate of fees and costs associate with the contract that were rendered during the period and they are expensed as incurred. 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.
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.
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 and restricted stock units granted to employees, nonemployees and directors are measured at the date of grant based on the estimated fair value of the award. For restricted stock units this fair value is based on the Company’s common stock price on the grant date. The Company estimates the grant date fair value of stock options, 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 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 the Company had made different assumptions, its 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 the volatility of its common stock together with 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 August 2018, the Financial Accounting Standards Board (FASB) Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. In October 2020, the FASB issued ASU 2020-10, “ Codification Improvements”. Recently Issued Accounting Standards During the year ended December 31, 2020, there have been no new, or existing recently issued, accounting pronouncements that are of significance, or potential significance, that impact the Company’s consolidated financial statements.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 Total Level 1 Level 2 Level 3 Liabilities 2018 PIPE warrant liability $ 539 $ — $ — $ 539 Essentialis purchase price contingency liability 10,278 — — 10,278 Total common stock warrant and contingent consideration liability $ 10,817 $ — $ — $ 10,817 Fair Value Measurements at December 31, 2019 Total Level 1 Level 2 Level 3 Liabilities 2017 PIPE warrant liability $ 10,822 $ — $ — $ 10,822 2018 PIPE warrant liability 1,354 — — 1,354 Essentialis purchase price contingency liability 5,938 — — 5,938 Total common stock warrant and contingent consideration liability $ 18,114 $ — $ — $ 18,114
Summary of Changes in Fair Value of Level 3 Financial Instruments	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 liabilities (dollars in thousands). Series A Warrants Series C Warrants 2017 PIPE Warrants 2018 PIPE Warrants Purchase Price Number of Number of Number of Number of Contingent Warrants Liability Warrants Liability Warrants Liability Warrants Liability Liability Balance at January 1, 2019 485,121 $ 49 118,083 $ — 6,024,425 $ 4,563 513,617 $ 600 $ 5,649 Expiration of Series A Warrants (485,121 ) (49 ) — — — — — — — Change in value of 2017 PIPE Warrants — — — — — 6,259 — — — Change in value of 2018 PIPE Warrants — — — — — — — 754 — Change in value of contingent liability — — — — — — — — 289 Balance at December 31, 2019 — — 118,083 — 6,024,425 10,822 513,617 1,354 5,938 Expiration of Series C Warrants — — (118,083 ) — — — — — — Expiration of 2017 PIPE Warrants — — — — (6,024,425 ) (10,822 ) — — — Change in value of 2018 PIPE Warrants — — — — — — — (815 ) — Change in value of contingent liability — — — — — — — — 4,340 Balance at December 31, 2020 — $ — — $ — — $ — 513,617 $ 539 $ 10,278

Other Financial Statement Det_2

Other Financial Statement Details (Tables)	12 Months Ended
	Dec. 31, 2020
Other Financial Statement Details Disclosure [Abstract]
Schedule of Property and Equipment	Property and equipment are summarized in the following table (in thousands). December 31, 2020 December 31, 2019 Computer hardware $ 53 $ 52 Computer software — — Furniture and fixtures 1 1 Leasehold improvements — — 54 53 Less accumulated depreciation and amortization (35 ) (31 ) Total $ 19 $ 22
Schedule of Intangible Assets	Intangible assets consist of the following (in thousands). December 31, 2020 December 31, 2019 Amount Accumulated Amortization Net Amount Amount Accumulated Amortization Net Amount Patents and merger costs $ 22,003 $ (7,422 ) $ 14,581 $ 22,003 $ (5,478 ) $ 16,525 Total $ 22,003 $ (7,422 ) $ 14,581 $ 22,003 $ (5,478 ) $ 16,525
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 2021 $ 1,944 2022 1,944 2023 1,944 2024 1,944 2025 1,944 2026 and thereafter 4,861 Total $ 14,581

Warrant Liabilities (Tables)

Warrant Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Series C Warrant [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	The Company used the following inputs at December 31, 2019. Volatility 90 % Contractual term (years) 0.17 Expected dividend yield — % Risk-free rate 1.52 %
2017 PIPE Warrant Liability [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	The following summarizes certain key assumptions used in estimating the fair value as of December 31, 2019. Volatility 99 % Contractual term (years) 1.0 Expected dividend yield — % Risk-free rate 1.60 %
2018 PIPE Warrant Liability [Member]
Fair Value of Convertible Preferred Stock Warrant Liability	December 31, 2020 December 31, 2019 Volatility 88 % 99 % Contractual term (years) 3.0 4.0 Expected dividend yield — % — % Risk-free rate 0.17 % 1.56 %

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Components of Lease Expense	The components of lease expense were as follows (in thousands): Year Ended December 31, 2020 December 31, 2019 Operating lease cost: Operating lease cost $ 305 $ 418 Sublease income — (173 ) Total operating lease cost $ 305 $ 245 Finance lease cost: Amortization of right-of-use assets $ 9 $ 3 Interest on lease liabilities 2 1 Total finance lease cost $ 11 $ 4
Schedule Of Supplemental Cash Flow Information Related To Leases	Supplemental cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2020 December 31, 2019 Right-of use assets obtained in exchange for lease obligations (noncash): Operating leases $ — $ 484 Finance leases $ — $ 27
Operating Lease and Finance Lease Liability Maturity	The following is a schedule by year of future maturities of the Company’s lease liabilities as of December 31, 2020 (in thousands): Operating Lease Finance Lease 2021 $ 143 $ 8 Total lease payments 143 8 Less interest (4 ) — Total $ 139 $ 8

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Summary of Stock Based Compensation Expense	Stock compensation expense was allocated between departments as follows (in thousands). Year ended December 31, 2020 December 31, 2019 Research and development $ 348 $ 158 General and administrative 1,152 667 Total $ 1,500 $ 825
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, 2020 December 31, 2019 Expected life (years) 5.5-6.1 5.5-6.1 Risk-free interest rate 0.4%-0.5% 1.6%-2.6% Volatility 64%-96% 70%-75% Dividend rate — % — %
Summary of Stock Option and Restricted Stock Unit Transactions	The following table summarizes stock option and restricted stock unit transactions for the years ended December 31, 2020 and 2019 as issued under the 2014 Plan. Number of Options Weighted- Average Exercise Price per Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding Share (in years) (in thousands) Balance at January 1, 2019 1,667,153 $ 6.03 8.27 Options granted 658,285 $ 1.77 Options canceled/forfeited (202,321 ) $ 6.99 — Balance at December 31, 2019 2,123,117 $ 4.62 7.87 Options granted 824,150 $ 2.79 Options exercised (8,518 ) $ 1.96 Options canceled/forfeited (101,010 ) $ 2.34 Balance at December 31, 2020 2,837,739 $ 4.18 7.62 $ 347 Options vested at December 31, 2020 1,577,255 $ 5.64 6.62 $ 205 Options vested and expected to vest at December 31, 2020 2,837,739 $ 4.18 7.62 $ 347
Summary of Restricted Stock Unit Transactions	The following table summarizes restricted stock unit transactions for the years ended December 31, 2020 and 2019 as issued under the 2014 Plan: Number of Restricted Stock Units Weighted- Average Grant-Date Fair Value per Share Outstanding at January 1, 2019 — Restricted stock units granted 61,218 $ 2.17 Restricted stock units vested (61,218 ) $ 2.17 Outstanding at December 31, 2019 — Restricted stock units granted 751,633 $ 3.68 Restricted stock units vested (103,133 ) $ 2.60 Restricted stock units cancelled (67,500 ) $ 3.85 Outstanding at December 31, 2020 581,000 $ 3.85

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Geographical Distribution of Loss before Income Taxes	The geographical distribution of loss before income taxes are summarized below (in thousands). December 31, 2020 2019 United States $ (22,197 ) $ (30,729 ) Foreign (2,442 ) (45 ) Loss before income taxes $ (24,639 ) $ (30,774 )
Provision for Income Tax Benefit by Applying Statutory Federal Income Tax Rate to Operating Loss	The provision for income tax benefit differs from the amount estimated by applying the statutory federal income tax rate to the operating loss due to the following (in thousands). December 31, 2020 2019 Tax on the loss before income tax expense computed at the federal statutory rate $ (5,174 ) $ (6,463 ) State tax (benefit) at statutory rate, net of federal benefit (2,293 ) (1,691 ) Foreign rate differential 51 10 Change in valuation allowance 8,231 6,696 Change in research and development credits (303 ) (200 ) Stock based compensation—ISOs 71 149 Change in fair value of warrants (2,444 ) 1,461 Change in fair value of contingent consideration 911 61 Change in net operating loss true up 846 (725 ) Change in state rate true up — 701 Change in temporary difference true up — — Other 104 1 Provision for income tax benefit $ — $ —
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, 2020 and 2019 (in thousands). December 31, 2020 2019 Non-current deferred tax assets: Federal and state net operating loss carryforwards $ 41,999 $ 35,091 Research and other credits 2,803 2,349 Reserves and accruals 236 77 Fixed assets 63 71 Capital loss carryover 1,115 1,115 Stock based compensation 337 85 Lease liability 41 131 Other deferred tax assets 129 196 Gross non-current deferred tax assets 46,723 39,115 Intangible assets (4,080 ) (4,623 ) Right-of-use assets (39 ) (118 ) Total non-current deferred tax liabilities (4,119 ) (4,741 ) Total deferred tax assets 42,604 34,374 Valuation allowance (42,604 ) (34,374 ) 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, 2020 2019 Beginning balance $ 1,111 $ 964 Increase related to prior year tax positions — 7 Decrease related to prior year tax positions (4 ) (4 ) Increase related to current year tax positions 216 144 Ending balance $ 1,323 $ 1,111

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 Warrants issued to 2010/2012 convertible note holders to purchase common stock 102,070 102,070 Options to purchase common stock 2,837,739 2,123,117 Outstanding restricted stock units 581,000 — Warrants issued to underwriter to purchase common stock 16,500 16,500 Series C warrants to purchase common stock — 118,083 Series D warrants to purchase common stock — 540,540 2017 PIPE warrants — 6,024,425 2018 PIPE warrants 513,617 513,617 Total 4,050,926 9,438,352

Liquidity - Additional Informat

Liquidity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jun. 26, 2020	Oct. 25, 2019	Dec. 31, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Net loss			$ (24,639)	$ (30,774)
Accumulated deficit			(182,445)	(157,806)
Cash and cash equivalents			49,224	20,733
Net cash used in operating activities			$ (25,224)	$ (17,375)
Underwritten Public Offering [Member]
Cash And Cash Equivalents [Line Items]
Sale of common stock in public offering, net of costs, (shares)	34,848,484	12,841,667
Price per unit	$ 1.65	$ 1.20
Proceeds from sale of common stock, net of costs	$ 53,700

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)BankSegment	Dec. 31, 2019
Schedule Of Significant Accounting Policies [Line Items]
Number of commercial banks | Bank	1
Number of operating segments | Segment	1
Estimated useful life	11 years
Expected dividend yield	0.00%	0.00%
ASU 2018-13 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020
Change in accounting principle, accounting standards update, early adoption	false
Change in accounting principle, accounting standards update, immaterial effect	true
ASU 2020-10 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020
Change in accounting principle, accounting standards update, early adoption	true
Change in accounting principle, accounting standards update, immaterial effect	true
Stock Options and Restricted Stock Units [Member]
Schedule Of Significant Accounting Policies [Line Items]
Vesting period	4 years
Stock Options [Member]
Schedule Of Significant Accounting Policies [Line Items]
Expected dividend yield	0.00%
Essentialis, Inc. [Member]
Schedule Of Significant Accounting Policies [Line Items]
Net intangible assets acquired | $	$ 22
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

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, 2020	Dec. 31, 2019
Liabilities
Contingent liability for Essentialis purchase price	$ 10,278	$ 5,938
2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability		10,822
2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	539	1,354
Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	10,817	18,114
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability		10,822
Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	539	1,354
Essentialis, Inc. [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	10,278	5,938
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	10,817	18,114
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability		10,822
Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Liabilities | 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	539	1,354
Level 3 [Member] | Essentialis, Inc. [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	$ 10,278	$ 5,938

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 3 Financial Instruments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Purchase price contingent liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 5,938	$ 5,649
Change in value of liabilities	4,340	289
Balance at end of period	$ 10,278	5,938
Series A 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		$ 49
Balance at the beginning of period, in shares		485,121
Expiration of warrants, in shares		(485,121)
Expiration of warrants		$ (49)
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, in shares	118,083	118,083
Expiration of warrants, in shares	(118,083)
Balance at the end of period, in 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	$ 10,822	$ 4,563
Balance at the beginning of period, in shares	6,024,425	6,024,425
Change in value of liabilities		$ 6,259
Expiration of warrants, in shares	(6,024,425)
Expiration of warrants	$ (10,822)
Balance at end of period		$ 10,822
Balance at the end of period, in 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]
Balance at the beginning of period	$ 1,354	$ 600
Balance at the beginning of period, in shares	513,617	513,617
Change in value of liabilities	$ (815)	$ 754
Balance at end of period	$ 539	$ 1,354
Balance at the end of period, in shares	513,617	513,617

Other Financial Statement Det_3

Other Financial Statement Details - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 54	$ 53
Less accumulated depreciation and amortization	(35)	(31)
Total	19	22
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	53	52
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1	$ 1

Other Financial Statement Det_4

Other Financial Statement Details - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Other Financial Statement Details Disclosure [Abstract]
Depreciation expense	$ 11,000	$ 11,000
Amortization	$ 1,900,000	$ 1,900,000

Other Financial Statements Deta

Other Financial Statements Details - Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Amount	$ 22,003	$ 22,003
Accumulated Amortization	(7,422)	(5,478)
Net Amount	14,581	16,525
Patents and Merger Costs [Member]
Finite Lived Intangible Assets [Line Items]
Amount	22,003	22,003
Accumulated Amortization	(7,422)	(5,478)
Net Amount	$ 14,581	$ 16,525

Other Financial Statement Det_5

Other Financial Statement Details - Future Amortization Expense (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Net Amount	$ 14,581	$ 16,525
Patents And Trademark [Member]
Finite Lived Intangible Assets [Line Items]
2021	1,944
2022	1,944
2023	1,944
2024	1,944
2025	1,944
2026 and thereafter	4,861
Net Amount	$ 14,581

Warrant Liabilities - Additiona

Warrant Liabilities - Additional Information (Detail)	Dec. 15, 2017$ / sharesshares	Apr. 30, 2015$ / shares	Mar. 05, 2015USD ($)$ / sharesshares	Jul. 31, 2015USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 19, 2018$ / sharesshares
Class Of Warrant Or Right [Line Items]
Change in fair value of stock warrants					$ (11,637,000)	$ 6,964,000
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]
Warrants exercised (in shares) | shares					4,800
Change in fair value of stock warrants							$ (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
Tender offer expiration date		Mar. 5, 2020	Mar. 5, 2020		Mar. 5, 2020
Proceeds from issuance of common stock under tender offer				$ 6,000
Warrants cashless exercised (in shares) | shares				181
Aggregate VWAP (percent)					1.00%
Warrant liability						0
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]
Number of common stock purchased upon issuance of warrants | shares	6,024,425
Exercise price of warrants exercised | $ / shares	$ 2
Change in fair value of stock warrants					$ (10,800,000)	6,300,000
Tender offer expiration date	Dec. 15, 2020
Warrant liability						10,822,000
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 prior to their expiration on December 15, 2020, entitled the holders to purchase 6,024,425 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to certain adjustments.
Fair value of estimated warrants					$ 0	10,800,000
Warrants exercised prior to expiration | shares					0
2018 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon issuance of warrants | shares								513,617
Exercise price of warrants exercised | $ / shares								$ 2
Change in fair value of stock warrants					$ (800,000)	800,000
Warrant liability					$ 539,000	$ 1,354,000
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 to purchase 513,617 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					$ 500,000
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, 2020	Dec. 31, 2019
Expected Dividend Yield [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0
Series C Warrant [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.90
Series C Warrant [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term		2 months 1 day
Series C Warrant [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.0152
2017 PIPE Warrant Liability [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.99
2017 PIPE Warrant Liability [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term		1 year
2017 PIPE Warrant Liability [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.0160
2018 PIPE Warrant Liability [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.88	0.99
2018 PIPE Warrant Liability [Member] | Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	3 years	4 years
2018 PIPE Warrant Liability [Member] | Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0017	0.0156

Leases - Additional Information

Leases - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Sep. 30, 2020USD ($)	Nov. 30, 2019USD ($)	Jul. 31, 2019USD ($)ft²	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Lessee Lease Description [Line Items]
Sublease income					$ 173,000
Current finance lease liabilities				$ 8,000	$ 17,000
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Long-term operating lease liabilities				$ 0	$ 100,000
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Long-term finance lease liabilities				$ 0	$ 8,000
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Finance lease, weighted-average remaining lease term				4 months 24 days	1 year 4 months 24 days
Finance lease, discount rate				10.00%	10.00%
Operating lease, weighted-average remaining lease term				4 months 24 days	1 year 4 months 24 days
Operating lease, discount rate				10.00%	10.00%
Redwood City, California [Member]
Lessee Lease Description [Line Items]
Area of operating lease | ft²			6,368
Operating lease, description				the Company executed a non-cancellable lease agreement for 6,368 square feet of new space in Redwood City, California, which began in September 2019 and expires in May 2021.
Operating lease beginning date			2019-09
Operating lease, expiration			2021-05
Payment to acquire office furniture under operating lease			$ 1
Future minimum commitment under non-cancelable operating lease	$ 30,000	$ 29,000
Capnia Inc Joint Venture [Member] | Redwood City, California [Member]
Lessee Lease Description [Line Items]
Sublease income					$ 65,000

Leases - Schedule of Components

Leases - Schedule of Components of Lease Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 305	$ 418
Sublease income		(173)
Total operating lease cost	305	245
Amortization of right-of-use assets	9	3
Interest on lease liabilities	2	1
Total finance lease cost	$ 11	$ 4

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Right-of use assets obtained in exchange for lease obligations (noncash):
Operating leases	$ 484
Finance leases	$ 27

Leases - Schedule Of Future Mat

Leases - Schedule Of Future Maturities (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Operating Leases
2021	$ 143
Total lease payments	143
Less interest	(4)
Total	139
Finances Lease
2021	8
Total lease payments	8
Total	$ 8

CoSense Joint Venture Agreeme_2

CoSense Joint Venture Agreement - Additional Information (Detail) $ / shares in Units, $ in Thousands	Oct. 16, 2018shares	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2017USD ($)$ / shares
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Current period gain recognized			$ 2,000
Loss from minority interest investment							$ (478)
Gain in minority interest investment						$ 33,000
Sinon Investments LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total purchase price		$ 500
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
Percentage of ownership interest		47.00%		47.00%
Number of shares owned | shares				1,480,000
Percentage of discount for lack of control				0.23
Loss from minority interest investment					$ 500
Capnia Inc Joint Venture [Member] | Sinon Investments LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Minority interest investment in former subsidiary		$ 500			$ 500
OAHL [Member] | Capnia Inc Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Minority interest investment in former subsidiary						$ 0
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								$ 2,200
Negotiated price per share | $ / shares								$ 1
Investment threshold requirement stock issuance				$ 1,200				$ 1,200
Issuance of common stock (shares) | shares	1,690,322
Percentage of ownership interest	53.00%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Jun. 26, 2020	Oct. 25, 2019	Dec. 19, 2018	Mar. 07, 2017	Dec. 31, 2020	Dec. 31, 2019	Sep. 28, 2020	Dec. 11, 2017	Oct. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Convertible preferred stock, shares authorized					10,000,000
Stock-based compensation expense					$ 1,500,000	$ 825,000
Expected dividend yield					0.00%	0.00%
Weighted average grant date fair value per option granted (in dollars per share)					$ 1.76	$ 1.14
Future stock-based compensation for unvested employee options granted and outstanding					$ 1,800,000
Stock options exercised, intrinsic value					$ 10,000
Number of shares available for issuance under the plan on the first day of each year					79,615,692	44,658,054
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 exercised									0
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
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%
2020 Inducement Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant					1,500,000
Number of shares reserved for issuance							1,500,000
Stock units granted					0
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Income tax benefits recognized from stock-based compensation					$ 0	$ 0
Number of options granted					824,150	658,285
Expected dividend yield					0.00%
Future stock-based compensation, requisite service period					2 years 8 months 12 days
Stock Options [Member] | 2014 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					4 years
Number of shares available for grant					1,432,229
Number of options granted					824,150	658,285
Stock Options [Member] | 2014 Equity Incentive Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value					110.00%
Stock Options [Member] | 2014 Equity Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term of option					10 years
ISOs [Member] | 2014 Equity Incentive Plan [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]
Vesting period					4 years
Stock units granted					751,633	61,218
Future stock-based compensation for unvested employee options granted and outstanding					$ 1,700,000
Vesting percentage					100.00%
Restricted stock units granted (in dollars per share)					$ 300,000	$ 100,000
Weighted average remaining vesting period					3 years 1 month 6 days
Restricted Stock Units [Member] | 2014 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units granted					751,633	61,218
Restricted stock units granted (in dollars per share)					$ 3.68	$ 2.17
Warrants expiration date					$ 3.85
Underwritten Public Offering [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of newly issued	34,848,484	12,841,667
Price per unit	$ 1.65	$ 1.20
Shares issued upon exercise of underwriters options	4,545,454	1,675,000
Net proceeds from issuance of public offering	$ 53,700,000	$ 14,500,000
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
Equity Unit Purchase Agreements [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of newly issued			10,272,375
Price per unit			$ 1.61
Gross Proceeds from issuance of units			$ 16,500,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of newly issued					34,848,484	12,841,667
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
Exercise price of warrants (in dollars per share)			$ 2					$ 2
Number of common stock purchased upon issuance of warrants			513,617					6,024,425
Essentialis, Inc. [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares issued in acquisition (shares)				4,867,422
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

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,500	$ 825
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	348	158
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,152	$ 667

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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
Risk-free interest rate	0.40%	1.60%
Volatility	64.00%	70.00%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life (years)	6 years 1 month 6 days	6 years 1 month 6 days
Risk-free interest rate	0.50%	2.60%
Volatility	96.00%	75.00%

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Stock Option and Restricted Stock Unit Transactions (Detail) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted	824,150	658,285
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance	2,123,117	1,667,153
Options granted	824,150	658,285
Options exercised	(8,518)
Options canceled/forfeited	(101,010)	(202,321)
Ending balance	2,837,739	2,123,117	1,667,153
Options vested at end of period (shares)	1,577,255
Options vested and expected to vest at end of period (shares)	2,837,739
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 4.62	$ 6.03
Options granted (in dollars per share)	2.79	1.77
Options exercised (in dollars per share)	1.96
Options canceled/forfeited (in dollars per share)	2.34	6.99
Ending balance (in dollars per share)	4.18	$ 4.62	$ 6.03
Options vested at end of period (in dollars per share)	5.64
Options vested and expected to vest at end of period (in dollars per share)	$ 4.18
Weighted Average Remaining Contractual Term
Options outstanding at end of period	7 years 7 months 13 days	7 years 10 months 13 days	8 years 3 months 7 days
Options vested at end of period	6 years 7 months 13 days
Options vested and expected to vest at end of period	7 years 7 months 13 days
Aggregate Intrinsic Value
Options outstanding at end of period	$ 347
Options vested at end of period	205
Options vested and expected to vest at end of period	$ 347

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Restricted Stock Unit Transactions (Detail) - Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock units granted	751,633	61,218
Weighted-average grant date fair value
Restricted stock units granted (in dollars per share)	$ 300,000	$ 100,000
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock units granted	751,633	61,218
Restricted stock units vested	(103,133)	(61,218)
Restricted stock units cancelled	(67,500)
Ending balance	581,000
Weighted-average grant date fair value
Restricted stock units granted (in dollars per share)	$ 3.68	$ 2.17
Restricted stock units vested (in dollars per share)	2.60	$ 2.17
Restricted stock units cancelled (in dollars per share)	3.85
Ending balance (in dollars per share)	$ 3.85

Income Taxes - Schedule of Geog

Income Taxes - Schedule of Geographical Distribution of Loss before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
United States	$ (22,197)	$ (30,729)
Foreign	(2,442)	(45)
Loss before income taxes	$ (24,639)	$ (30,774)

Income Taxes - Provision for In

Income Taxes - Provision for Income Tax Benefit by Applying Statutory Federal Income Tax Rate to Operating Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Tax on the loss before income tax expense computed at the federal statutory rate	$ (5,174)	$ (6,463)
State tax (benefit) at statutory rate, net of federal benefit	(2,293)	(1,691)
Foreign rate differential	51	10
Change in valuation allowance	8,231	6,696
Change in research and development credits	(303)	(200)
Stock based compensation—ISOs	71	149
Change in fair value of warrants	(2,444)	1,461
Change in fair value of contingent consideration	911	61
Change in net operating loss true up	846	(725)
Change in state rate true up		701
Other	$ 104	$ 1

Income Taxes - Significant Comp

Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Non-current deferred tax assets:
Federal and state net operating loss carryforwards	$ 41,999	$ 35,091
Research and other credits	2,803	2,349
Reserves and accruals	236	77
Fixed assets	63	71
Capital loss carryover	1,115	1,115
Stock based compensation	337	85
Lease liability	41	131
Other deferred tax assets	129	196
Gross non-current deferred tax assets	46,723	39,115
Intangible assets	(4,080)	(4,623)
Right-of-use assets	(39)	(118)
Total non-current deferred tax liabilities	(4,119)	(4,741)
Total deferred tax assets	42,604	34,374
Valuation allowance	$ (42,604)	$ (34,374)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance	$ 8,200,000
Unrecognized assets and liabilities related to uncertain tax positions	1,300,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0	$ 0
Unrecognized tax benefit offset by change in valuation allowance	1,300,000
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	164,700,000
Operating loss carryforwards, carried forward indefinitely	57,400,000
U.S. Federal Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	1,700,000
State Tax Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	98,600,000
State Tax Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	1,100,000
Foreign Tax Authority [Member] | Her Majesty's Revenue and Customs (HMRC) [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 2,200,000

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Beginning balance	$ 1,111	$ 964
Increase related to prior year tax positions		7
Decrease related to prior year tax positions	(4)	(4)
Increase related to current year tax positions	216	144
Ending balance	$ 1,323	$ 1,111

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, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	4,050,926	9,438,352
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	2,837,739	2,123,117
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	581,000
Warrants Issued to Underwriter to Purchase Common [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 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
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		540,540
2017 PIPE Warrant [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
2018 PIPE Warrant [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	513,617

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Matching contribution by Company	$ 0	$ 37,000