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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 07, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	SOLENO THERAPEUTICS INC
Entity Central Index Key	0001484565
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		79,593,621
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
City Area Code	213-8444
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	SLNO
Security Exchange Name	NASDAQ

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 62,499	$ 20,733
Prepaid expenses and other current assets	505	411
Total current assets	63,004	21,144
Long-term assets
Property and equipment, net	17	22
Operating lease right-of-use assets	265	398
Finance lease right-of-use assets	20	24
Intangible assets, net	15,553	16,525
Other long-term assets		59
Total assets	78,859	38,172
Current liabilities
Accounts payable	3,657	1,995
Accrued compensation	520	283
Accrued clinical trial site costs	3,444	1,999
Operating lease liabilities	298	305
Other current liabilities	444	382
Total current liabilities	8,363	4,964
Long-term liabilities
Contingent liability for Essentialis purchase price	9,364	5,938
Other long-term liabilities		147
Total liabilities	22,682	23,225
Commitments and contingencies (Note 6)
Stockholders’ equity
Common stock	80	45
Additional paid-in-capital	227,145	172,708
Accumulated deficit	(171,048)	(157,806)
Total stockholders’ equity	56,177	14,947
Total liabilities and stockholders’ equity	78,859	38,172
2017 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability	4,230	10,822
2018 PIPE Warrant Liability [Member]
Long-term liabilities
Warrant liability	$ 725	$ 1,354

Condensed Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses
Research and development	$ 6,103	$ 3,745	$ 12,798	$ 6,505
General and administrative	2,248	1,695	4,251	3,707
Change in fair value of contingent consideration	2,842	183	3,426	389
Total operating expenses	11,193	5,623	20,475	10,601
Operating loss	(11,193)	(5,623)	(20,475)	(10,601)
Other income (expense)
Change in fair value of warrants liabilities	3,808	(4,267)	7,221	(6,186)
Loss from minority interest investment		(165)		(355)
Interest income	1	47	12	104
Total other income (expense)	3,809	(4,385)	7,233	(6,437)
Net loss	$ (7,384)	$ (10,008)	$ (13,242)	$ (17,038)
Net loss per common share, basic and diluted	$ (0.16)	$ (0.31)	$ (0.29)	$ (0.54)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share	46,236,209	31,776,951	45,458,034	31,766,593

Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	IPO [Member]	Common Stock [Member]	Common Stock [Member] IPO [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] IPO [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	248				248
Issuance of common stock under equity incentive plan (shares)			21,415
Net loss	(7,030)						(7,030)
Balances at ending at Mar. 31, 2019	23,631		$ 32		157,661		(134,062)
Balances at end (shares) at Mar. 31, 2019			31,776,584
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]
Net loss	(17,038)
Balances at ending at Jun. 30, 2019	13,843		$ 32		157,881		(144,070)
Balances at end (shares) at Jun. 30, 2019			31,793,292
Balances at beginning at Mar. 31, 2019	23,631		$ 32		157,661		(134,062)
Balances at beginning (shares) at Mar. 31, 2019			31,776,584
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	220				220
Issuance of common stock under equity incentive plan (shares)			16,708
Net loss	(10,008)						(10,008)
Balances at ending at Jun. 30, 2019	13,843		$ 32		157,881		(144,070)
Balances at end (shares) at Jun. 30, 2019			31,793,292
Balances at beginning at Dec. 31, 2019	14,947		$ 45		172,708		(157,806)
Balances at beginning (shares) at Dec. 31, 2019			44,658,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	392				392
Issuance of common stock under equity incentive plan (shares)			28,757
Net loss	(5,858)						(5,858)
Balances at ending at Mar. 31, 2020	9,481		$ 45		173,100		(163,664)
Balances at end (shares) at Mar. 31, 2020			44,686,811
Balances at beginning at Dec. 31, 2019	14,947		$ 45		172,708		(157,806)
Balances at beginning (shares) at Dec. 31, 2019			44,658,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(13,242)
Balances at ending at Jun. 30, 2020	56,177		$ 80		227,145		(171,048)
Balances at end (shares) at Jun. 30, 2020			79,560,274
Balances at beginning at Mar. 31, 2020	9,481		$ 45		173,100		(163,664)
Balances at beginning (shares) at Mar. 31, 2020			44,686,811
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	341				341
Issuance of common stock under equity incentive plan	17				17
Issuance of common stock under equity incentive plan (shares)			24,979
Sale of common stock in public offering, net of costs of $3,778		$ 53,722		$ 35		$ 53,687
Sale of common stock in public offering, net of costs, (shares)				34,848,484
Net loss	(7,384)						(7,384)
Balances at ending at Jun. 30, 2020	$ 56,177		$ 80		$ 227,145		$ (171,048)
Balances at end (shares) at Jun. 30, 2020			79,560,274

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (13,242)	$ (17,038)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	977	978
Noncash lease expense	137	223
Stock-based compensation expense	733	468
Change in fair value of stock warrants	(7,221)	6,186
Change in fair value of contingent consideration	3,426	389
Operating loss on minority interest investment		355
Change in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	(35)	58
Due from related party		46
Accounts payable	1,619	806
Accrued compensation	237	(40)
Accrued clinical trial site costs	1,445	269
Operating lease liabilities	(7)	(239)
Other liabilities	(262)	(41)
Net cash used in operating activities	(12,193)	(7,580)
Cash flows from investing activities:
Purchases of property and equipment		(16)
Net cash used in investing activities		(16)
Cash flows from financing activities:
Proceeds from sale of common stock, net of costs	53,950
Proceeds from stock option exercises	17
Principal paid on finance lease liabilities	(8)
Net cash provided by financing activities	53,959
Net increase (decrease) in cash and cash equivalents	41,766	(7,596)
Cash and cash equivalents, beginning of period	20,733	23,099
Cash and cash equivalents, end of period	$ 62,499	$ 15,503

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 3. Summary of Significant Accounting Policies

There have been no material changes to the significant accounting policies during the six months ended June 30, 2020 as compared to the significant accounting policies described in Note 3 of the “Notes to Consolidated Financial Statements” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Below are those policies with current period updates.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements of the Company have been prepared on a going concern basis in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, the Company must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the three and six months ended June 30, 2020, are not necessarily indicative of the results that may be expected for any other interim period or for the fiscal year ending December 31, 2020. For further information, refer to the financial statements and footnotes included in the Company’s annual financial statements for the fiscal year ended December 31, 2019, which are included in the Company’s annual report on Form 10-K filed with the SEC on March 4, 2020.

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates included in the financial statements include the valuation of deferred income tax assets, the valuation of financial instruments, stock-based compensation, value and life of acquired intangibles, and the valuation of contingent liabilities. The contingent liability represents the fair value of the contingent consideration arising from the Company’s acquisition of Essentialis in 2017. As part of the purchase price, the Company is obligated to make cash earn out payments to Essentialis stockholders up to a maximum of $30 million upon the achievement of certain commercial milestones.

Recent Accounting Standards

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by the Company as of the specified effective date.

Recently Adopted Accounting Standards

In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. The ASU modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The Company has adopted this ASU at the beginning of 2020. The adoption did not have a material impact on the Company’s condensed consolidated financial statements disclosures.

Recently Issued Accounting Standards

In December 2019, the FASB issued ASU 2019-12: “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes”. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The amendments in this Update are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. The Company has not yet assessed the potential impact of adopting ASU 2019-12 on its condensed consolidated financial statements.

During the six months ended June 30, 2020, other than ASU 2019-12, there have been no new, or existing recently issued, accounting pronouncements that are of significance, or potential significance, that impact the Company’s condensed consolidated interim financial statements.

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 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 — Unadjusted quoted prices in active markets for identical assets or liabilities;

•

Level II — Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

•

Level III — Unobservable inputs that are supported by little or no market activity for the related assets or liabilities.

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 June 30, 2020
	Total		Level 1		Level 2		Level 3
Liabilities
2017 PIPE warrant liability	$	4,230	$	—	$	—	$	4,230
2018 PIPE warrant liability		725		—		—		725
Essentialis purchase price contingency liability		9,364		—		—		9,364
Total common stock warrant and contingent consideration liability	$	14,319	$	—	$	—	$	14,319

	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 2017 PIPE Warrants and the 2018 PIPE Warrants was calculated 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. Through March 31, 2020 the Company had previously 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 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.

There were no transfers between levels 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 C Warrants					2017 PIPE Warrants					2018 PIPE Warrants					Purchase Price
	Number of Warrants			Liability		Number of Warrants		Liability			Number of Warrants		Liability			Contingent Liability
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	)		—		—		—			—		—			—
Change in value of 2017 PIPE Warrants		—			—		—		(6,592	)		—		—			—
Change in value of 2018 PIPE Warrants		—			—		—		—			—		(629	)		—
Change in value of contingent liability		—			—		—		—			—		—			3,426
Balance at June 30, 2020		—		$	—		6,024,425	$	4,230			513,617	$	725		$	9,364

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Warrant Liabilities

6 Months Ended

Jun. 30, 2020

Text Block [Abstract]

Warrant Liabilities

Note 5. Warrant Liabilities

The Company has issued multiple warrant series, of which the 2017 PIPE Warrants and the 2018 PIPE Warrants (the “Warrants”) remain outstanding at June 30, 2020 and are considered liabilities pursuant to the guidance established by ASC 815 Derivatives and Hedging.

Accounting Treatment

The Company accounts for the Warrants in accordance with the guidance in ASC 815. As indicated below, the Company may be obligated to settle Warrants in cash. 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 condensed consolidated statements of operations.

Series C Warrants

As of June 30, 2020, the fair value of the Series C Warrants was zero as the warrants had expired. This balance is consistent with the balance as of December 31, 2019.

The Company calculated the fair value of the Series C Warrants as of December 31, 2019 using a Black-Scholes pricing model. The Black-Scholes pricing model requires the input of highly subjective assumptions including the expected stock price volatility. The Company used the following inputs.

	December 31, 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 entitle the holder of each of the 8,141,116 units to purchase 0.74 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 2017 PIPE Warrants and terminating on December 15, 2020.

The exercise price and number of shares of common stock issuable upon exercise of the 2017 PIPE Warrants may be adjusted in certain circumstances, including the event of a stock split, stock dividend, extraordinary dividend, or recapitalization, reorganization, merger or consolidation. However, the exercise price of the 2017 PIPE Warrants will not be reduced below $1.72.

In the event of a change of control of the Company, the holders of unexercised warrants may present their unexercised warrants to the Company, or its successor, to be purchased by the Company, or its successor, in an amount equal to the per share value determined by the Black Scholes methodology.

As of June 30, 2020, the fair value of the 2017 PIPE Warrants was estimated at $4.2 million. The decrease in the fair value of the liability for the 2017 PIPE Warrants of $3.4 million during the three months ended June 30, 2020 and the decrease in the fair value of $6.6 million during the six months ended June 30, 2020 were recorded as other income (expense) in the condensed consolidated statements of operations.

The Company has calculated the fair value of the 2017 PIPE Warrants as of June 30, 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. Both models requires the input of highly subjective assumptions including the expected stock price volatility. The following summarizes certain key assumptions used in estimating the fair values.

	June 30, 2020			December 31, 2019
Volatility		115	%		99	%
Contractual term (years)		0.5			1.0
Expected dividend yield		—	%		—	%
Risk-free rate		0.20	%		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 of each of the 10,272,375 units to purchase 0.05 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2018 PIPE Warrants and terminating on December 21, 2023.

The exercise price and number of shares of common stock issuable upon exercise of the 2018 PIPE Warrants may be adjusted in certain circumstances, including 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.

As of June 30, 2020, the fair value of the 2018 PIPE Warrants was estimated at $0.7 million. The $0.4 million decrease in the fair value of the liability for the 2018 PIPE Warrants during the three months ended June 30, 2020 and the decrease in the fair value of $0.6 million during the six months ended June 30, 2020 were recorded as other income (expense) in the condensed consolidated statements of operations.

The Company has calculated the fair value of the 2018 PIPE Warrants as of June 30, 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. Both models require the input of highly subjective assumptions including the expected stock price volatility. The following summarizes certain key assumptions used in estimating the fair values.

	June 30, 2020			December 31, 2019
Volatility		94	%		99	%
Contractual term (years)		3.5			4.0
Expected dividend yield		—	%		—	%
Risk-free rate		0.20	%		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.

•

Contractual term: The expected life of the warrants, which is based on the contractual term of the warrants.

•

Expected dividend yield: The Company has never declared or paid any cash dividends and does not currently plan to pay cash dividends in the foreseeable future. Consequently, the Company used an expected dividend yield of zero.

•

Risk-free rate: The risk-free interest rate is based on the U.S. Treasury rate for similar periods as those of expected volatility.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 6. Commitments and Contingencies

Facility 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. Sublease income received from Capnia during the three and six months ended June 30, 2019 was approximately $25,000 and $49,000, respectively.

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 new lease as an operating lease for the office space and a finance lease for the office furniture, based on their relative standalone prices.

The components of lease expense during the three and six months ended June 30, 2020 and 2019 were as follows (in thousands):

	Three Months Ended June 30,					Six Months Ended June 30,
	2020		2019			2020		2019
Operating lease cost:
Operating lease cost	$	77	$	113		$	153	$	232
Sublease income		—		(65	)		—		(130	)
Total operating lease cost	$	77	$	48		$	153	$	102

Finance lease cost:
Amortization of right-of-use assets	$	3	$	—		$	5	$	—
Interest on lease liabilities		—		—			1		—
Total finance lease cost	$	3	$	—		$	6	$	—

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.

Stockholders' Equity

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Stockholders' Equity

Note 8. Stockholders’ Equity

Equity Incentive Plans

The Company has adopted the 2014 Equity Incentive Plan, or the Plan. Under the 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 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 June 30, 2020, a total of 1,818,603 shares are available for future grant under the Plan.

The Company recognizes stock-based compensation expense related to options and restricted stock units granted to employees, directors and consultants. The compensation expense is allocated on a departmental basis, based on the classification of the award holder. No income tax benefits have been recognized in the statements of operations for stock-based compensation arrangements during any of the periods presented.

Stock-based compensation expense was recognized in the condensed consolidated statements of operations as follows (in thousands).

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	62	$	49	$	161	$	90
General and administrative		279		171		572		378
Total	$	341	$	220	$	733	$	468

Stock Options

The Company granted options to purchase 452,650 and 114,142 of the Company’s common stock during the three months ended June 30, 2020 and 2019, respectively, and granted options to purchase 452,650 and 578,142 of the Company’s common stock during the six months ended June 30, 2020 and 2019, respectively. The fair value of each award was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions.

	Three Months Ended June 30,		Six Months Ended June 30,
	2020	2019	2020	2019
Expected life (years)	5.5-6.0	5.5-6.0	5.5-6.0	5.5-6.1
Risk-free interest rate	0.4%-0.5%	1.9%-2.3%	0.4%-0.5%	1.9%-2.6%
Volatility	64%	70%-71%	64%	70%-71%
Dividend rate	— %	— %	— %	— %

The Black-Scholes option-pricing model requires the use of highly subjective assumptions to estimate the fair value of stock-based awards. These assumptions include the following estimates:

•

Expected life: The expected life of stock options represents the average of the contractual term of the options and the weighted-average vesting period, as permitted under the simplified method. The Company does not believe it is able to rely on historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term for use in estimating the fair value-based measurement of stock options. Therefore, it has opted to use the “simplified method” for estimating the expected term of options.

•

Risk-free interest rate: The risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected time to liquidity.

•

Volatility: The estimated volatility rate based on the volatilities of common stock of comparable companies in the Company’s industry.

•

Dividend rate: The Company has never declared or paid any cash dividends and does not presently plan to pay cash dividends in the foreseeable future. Consequently, the Company used an expected dividend yield of zero.

The following table summarizes stock option transactions for the six months ended June 30, 2020 as issued under the 2014 Plan:

	Number of Options			Weighted- Average Exercise Price per		Weighted Average Remaining Contractual Term
	Outstanding			Share		(in years)
Balance at December 31, 2019		2,123,117		$	4.62		7.87
Options granted		452,650		$	3.41
Options exercised		(8,518	)	$	1.96
Options canceled/forfeited		(67,969	)	$	2.26
Balance at June 30, 2020		2,499,280		$	4.47		7.79
Options vested at June 30, 2020		1,362,956		$	6.18		6.93
Options vested and expected to vest at June 30, 2020		2,499,280		$	4.47		7.79

The weighted-average grant date fair value of options granted was $1.95 and $1.18 per share for the six months ended June 30, 2020 and 2019, respectively. At June 30, 2020 total unrecognized employee stock-based compensation related to stock options was $1.6 million, which is expected to be recognized over the weighted-average remaining vesting period of 2.7 years. As of June 30, 2020, the outstanding stock options had an intrinsic value of $0.7 million.

Restricted Stock Units

There were 16,461 and 16,708 restricted stock units granted by the Company during the three months ended June 30, 2020 and 2019, respectively, and 703,718 and 38,123 restricted stock units granted during the six months ended June 30, 2020 and 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 six months ended June 30, 2020 as issued under the Plan:

	Number of Restricted Stock Units			Weighted- Average Grant-Date Fair Value per Share
Outstanding at December 31, 2019		-
Restricted stock units granted		703,718		$	3.81
Restricted stock units vested		(45,218	)	$	3.25
Restricted stock units cancelled		(67,500	)	$	3.85
Outstanding at June 30, 2020		591,000		$	3.85

The weighted-average grant-date fair value of all restricted stock units granted during the six months ended June 30, 2020 and June 30, 2019 was $3.81 and $2.42, respectively. The fair value of all restricted stock units vested during the six months ended June 30, 2020 and June 30, 2019 was $0.1 million and approximately $92,000, respectively. At June 30, 2020 total unrecognized employee stock-based compensation related to restricted stock units was $2.0 million, which is expected to be recognized over the weighted-average remaining vesting period of 3.5 years.

2014 Employee Stock Purchase Plan

The Company’s board of directors and stockholders have adopted the 2014 Employee Stock Purchase Plan, or the ESPP. The ESPP has become effective, and the board of directors will implement commencement of offers thereunder in its discretion. A total of 27,967 shares of the Company’s common stock has been made available for sale under the ESPP. In addition, the ESPP provides for annual increases in the number of shares available for issuance under the plan on the first day of each year beginning in the year following the initial date that the board of directors authorizes commencement, equal to the least of:

•

1.0% of the outstanding shares of the Company’s common stock on the first day of such year;

•

55,936 shares; or

•

such amount as determined by the board of directors.

As of June 30, 2020, there were no purchases by employees under this plan.

Series D Warrants

The Company issued 270,270 Series D Warrants in October 2015, which are exercisable into 540,540 shares of the Company’s common stock, with an exercise price of $8.75 and a term of five years expiring on October 15, 2020. The Company’s Series D Warrants contain standard anti-dilution provisions for stock dividends, stock splits, subdivisions, combinations and similar types of recapitalization events. They also contain a cashless exercise feature that provides for their net share settlement at the option of the holder in the event that there is no effective registration statement covering the continuous offer and sale of the warrants and underlying shares. The Company is required to comply with certain requirements to cause or maintain the effectiveness of a registration statement for the offer and sale of these securities. The Series D Warrant agreement further provides for the payment of liquidated damages at an amount per month equal to 1% of the aggregate VWAP of the shares into which each Series D Warrant is convertible in the event that the Company is unable to maintain the effectiveness of a registration statement as described herein. The Company evaluated the registration payment arrangement stipulated in the terms of this securities agreement and determined that it is probable that the Company will maintain an effective registration statement and has therefore not allocated any portion of the proceeds to the registration payment arrangement. The Series D Warrant agreement specifically provides that under no circumstances will the Company be required to settle any Series D Warrant exercise for cash, whether by net settlement or otherwise.

Accounting Treatment

The Company accounts for the Series D Warrants in accordance with the guidance in ASC 815 Derivatives and Hedging. As indicated above, the Company is not required under any circumstance to settle any Series D Warrant exercise for cash. The Company has therefore classified the value of the Series D Warrants as permanent equity.

Other Common Stock Warrants

As of June 30, 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 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.

Net loss per share

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Net loss per share

Note 9. Net loss per share

Basic net loss per share is computed by dividing net loss by the weighted-average number of common stock actually outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock outstanding and dilutive potential common stock that would be issued upon the exercise of common stock warrants and options. For the three and six months ended June 30, 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 June 30,
	2020		2019
Warrants issued to 2010/2012 convertible note holders to purchase common stock		102,070		102,070
Options to purchase common stock		2,500,113		2,196,278
Outstanding restricted stock units		591,000		—
Warrants issued to underwriter to purchase common stock		16,500		16,500
Series A warrants to purchase common stock		—		485,121
Series C warrants to purchase common stock		—		118,083
Series D warrants to purchase common stock		540,540		540,540
2017 PIPE warrants		6,024,425		6,024,425
2018 PIPE warrants		513,617		513,617
Total		10,288,265		9,996,634

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared on a going concern basis in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, the Company must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the three and six months ended June 30, 2020, are not necessarily indicative of the results that may be expected for any other interim period or for the fiscal year ending December 31, 2020. For further information, refer to the financial statements and footnotes included in the Company’s annual financial statements for the fiscal year ended December 31, 2019, which are included in the Company’s annual report on Form 10-K filed with the SEC on March 4, 2020.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of expenses in the financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates included in the financial statements include the valuation of deferred income tax assets, the valuation of financial instruments, stock-based compensation, value and life of acquired intangibles, and the valuation of contingent liabilities. The contingent liability represents the fair value of the contingent consideration arising from the Company’s acquisition of Essentialis in 2017. As part of the purchase price, the Company is obligated to make cash earn out payments to Essentialis stockholders up to a maximum of $30 million upon the achievement of certain commercial milestones.
Recent Accounting Standards	Recent Accounting Standards From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by the Company as of the specified effective date. Recently Adopted Accounting Standards In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”. The ASU modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The Company has adopted this ASU at the beginning of 2020. The adoption did not have a material impact on the Company’s condensed consolidated financial statements disclosures. Recently Issued Accounting Standards In December 2019, the FASB issued ASU 2019-12: “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes”. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The amendments in this Update are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. The Company has not yet assessed the potential impact of adopting ASU 2019-12 on its condensed consolidated financial statements. During the six months ended June 30, 2020, other than ASU 2019-12, there have been no new, or existing recently issued, accounting pronouncements that are of significance, or potential significance, that impact the Company’s condensed consolidated interim financial statements.

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2020
	Total		Level 1		Level 2		Level 3
Liabilities
2017 PIPE warrant liability	$	4,230	$	—	$	—	$	4,230
2018 PIPE warrant liability		725		—		—		725
Essentialis purchase price contingency liability		9,364		—		—		9,364
Total common stock warrant and contingent consideration liability	$	14,319	$	—	$	—	$	14,319

	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 C Warrants					2017 PIPE Warrants					2018 PIPE Warrants					Purchase Price
	Number of Warrants			Liability		Number of Warrants		Liability			Number of Warrants		Liability			Contingent Liability
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	)		—		—		—			—		—			—
Change in value of 2017 PIPE Warrants		—			—		—		(6,592	)		—		—			—
Change in value of 2018 PIPE Warrants		—			—		—		—			—		(629	)		—
Change in value of contingent liability		—			—		—		—			—		—			3,426
Balance at June 30, 2020		—		$	—		6,024,425	$	4,230			513,617	$	725		$	9,364

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Warrant Liabilities (Tables)

6 Months Ended

Jun. 30, 2020

Series C Warrant [Member]

Fair Value of Convertible Preferred Stock Warrant Liability

The Company used the following inputs.

	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 values.

	June 30, 2020			December 31, 2019
Volatility		115	%		99	%
Contractual term (years)		0.5			1.0
Expected dividend yield		—	%		—	%
Risk-free rate		0.20	%		1.60	%

2018 PIPE Warrant Liability [Member]

Fair Value of Convertible Preferred Stock Warrant Liability

The following summarizes certain key assumptions used in estimating the fair values.

	June 30, 2020			December 31, 2019
Volatility		94	%		99	%
Contractual term (years)		3.5			4.0
Expected dividend yield		—	%		—	%
Risk-free rate		0.20	%		1.56	%

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Components of Lease Expense

The components of lease expense during the three and six months ended June 30, 2020 and 2019 were as follows (in thousands):

	Three Months Ended June 30,					Six Months Ended June 30,
	2020		2019			2020		2019
Operating lease cost:
Operating lease cost	$	77	$	113		$	153	$	232
Sublease income		—		(65	)		—		(130	)
Total operating lease cost	$	77	$	48		$	153	$	102

Finance lease cost:
Amortization of right-of-use assets	$	3	$	—		$	5	$	—
Interest on lease liabilities		—		—			1		—
Total finance lease cost	$	3	$	—		$	6	$	—

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Summary of Stock Based Compensation Expense

Stock-based compensation expense was recognized in the condensed consolidated statements of operations as follows (in thousands).

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	62	$	49	$	161	$	90
General and administrative		279		171		572		378
Total	$	341	$	220	$	733	$	468

Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model

The fair value of each award was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions

	Three Months Ended June 30,		Six Months Ended June 30,
	2020	2019	2020	2019
Expected life (years)	5.5-6.0	5.5-6.0	5.5-6.0	5.5-6.1
Risk-free interest rate	0.4%-0.5%	1.9%-2.3%	0.4%-0.5%	1.9%-2.6%
Volatility	64%	70%-71%	64%	70%-71%
Dividend rate	— %	— %	— %	— %

Summary of Stock Option Transactions

The following table summarizes stock option transactions for the six months ended June 30, 2020 as issued under the 2014 Plan:

	Number of Options			Weighted- Average Exercise Price per		Weighted Average Remaining Contractual Term
	Outstanding			Share		(in years)
Balance at December 31, 2019		2,123,117		$	4.62		7.87
Options granted		452,650		$	3.41
Options exercised		(8,518	)	$	1.96
Options canceled/forfeited		(67,969	)	$	2.26
Balance at June 30, 2020		2,499,280		$	4.47		7.79
Options vested at June 30, 2020		1,362,956		$	6.18		6.93
Options vested and expected to vest at June 30, 2020		2,499,280		$	4.47		7.79

Summary of Restricted Stock Unit Transactions

The following table summarizes restricted stock unit transactions for the six months ended June 30, 2020 as issued under the Plan:

	Number of Restricted Stock Units			Weighted- Average Grant-Date Fair Value per Share
Outstanding at December 31, 2019		-
Restricted stock units granted		703,718		$	3.81
Restricted stock units vested		(45,218	)	$	3.25
Restricted stock units cancelled		(67,500	)	$	3.85
Outstanding at June 30, 2020		591,000		$	3.85

Net loss per share (Tables)

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Schedule of Potentially Dilutive Securities Outstanding Excluded from Computations of Diluted Weighted-Average Shares Outstanding

	As of June 30,
	2020		2019
Warrants issued to 2010/2012 convertible note holders to purchase common stock		102,070		102,070
Options to purchase common stock		2,500,113		2,196,278
Outstanding restricted stock units		591,000		—
Warrants issued to underwriter to purchase common stock		16,500		16,500
Series A warrants to purchase common stock		—		485,121
Series C warrants to purchase common stock		—		118,083
Series D warrants to purchase common stock		540,540		540,540
2017 PIPE warrants		6,024,425		6,024,425
2018 PIPE warrants		513,617		513,617
Total		10,288,265		9,996,634

Liquidity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended				6 Months Ended
	Jun. 26, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Net loss		$ (7,384)	$ (5,858)	$ (10,008)	$ (7,030)	$ (13,242)	$ (17,038)
Accumulated deficit		(171,048)				(171,048)		$ (157,806)
Cash on hand		$ 62,500				62,500
Net cash used in operating activities						(12,193)	$ (7,580)
Proceeds from sale of common stock, net of costs						$ 53,950
Underwritten Public Offering [Member]
Cash And Cash Equivalents [Line Items]
Sale of common stock in public offering, net of costs, (shares)	34,848,484
Price per unit	$ 1.65
Proceeds from sale of common stock, net of costs	$ 53,700

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Warrant Liabilities - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 19, 2018 $ / shares shares	Dec. 15, 2017 $ / shares shares
Class Of Warrant Or Right [Line Items]
Change in fair value of stock warrants	$ (3,808)	$ 4,267	$ (7,221)	$ 6,186
Expected Dividend Yield [Member]
Class Of Warrant Or Right [Line Items]
Measurement input	0.00		0.00
Series C Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	$ 0		$ 0
2017 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	4,230		$ 4,230		$ 10,822
Number of warrants issued to purchase common stock \| shares							8,141,116
Warrant to call common stock \| shares							0.74
Exercise price of warrants exercised \| $ / shares							$ 2.00
Warrant issuance description			The 2017 PIPE Warrants were issued on December 15, 2017 in the 2017 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2017 PIPE Offering, and entitle the holder of each of the 8,141,116 units to purchase 0.74 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 2017 PIPE Warrants and terminating on December 15, 2020.
Change in fair value of stock warrants	(3,400)		$ (6,600)
Fair value of estimated warrants	$ 4,200		$ 4,200
2017 PIPE Warrant Liability [Member] \| Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised \| $ / shares	$ 1.72		$ 1.72
2018 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	$ 725		$ 725		$ 1,354
Number of warrants issued to purchase common stock \| shares						10,272,375
Warrant to call common stock \| shares						0.05
Exercise price of warrants exercised \| $ / shares						$ 2.00
Warrant issuance description			The 2018 PIPE Warrants were issued on December 19, 2018 in the 2018 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2018 PIPE Offering, and entitle the holders of each of the 10,272,375 units to purchase 0.05 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2018 PIPE Warrants and terminating on December 21, 2023.
Change in fair value of stock warrants	(400)		$ (600)
Fair value of estimated warrants	$ 700		$ 700
2018 PIPE Warrant Liability [Member] \| Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised \| $ / shares	$ 2.00		$ 2.00

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended			3 Months Ended	6 Months Ended
	Sep. 30, 2020 USD ($)	Nov. 30, 2019 USD ($)	Jul. 31, 2019 USD ($) ft²	Jun. 30, 2019 USD ($)	Jun. 30, 2020	Jun. 30, 2019 USD ($)
Commitments and Contingencies [Line Items]
Sublease income				$ 65,000		$ 130,000
Redwood City, California [Member]
Commitments and Contingencies [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		$ 29,000
Redwood City, California [Member] \| Forecast [Member]
Commitments and Contingencies [Line Items]
Future minimum commitment under non-cancelable operating lease	$ 30,000
Capnia Inc Joint Venture [Member] \| Redwood City, California [Member]
Commitments and Contingencies [Line Items]
Sublease income				$ 25,000		$ 49,000

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Oct. 31, 2015	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield		0.00%	0.00%	0.00%	0.00%
Weighted average grant date fair value per option granted (in dollars per share)				$ 1.95	$ 1.18
Stock options outstanding, intrinsic value		$ 700,000		$ 700,000
Number of shares available for issuance under the plan on the first day of each year		79,560,274		79,560,274		44,658,054
Series D Warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants outstanding (in shares)	270,270
Number of common stock purchased upon issuance of warrants	540,540
Exercise price of warrants (in dollars per share)	$ 8.75
Warrants term	5 years
Warrants expiration date	Oct. 15, 2020
Liquidated damages amount percent of VWAP (percent)	1.00%
Warrants to Purchase Stock [Member] \| 2010 and 2012 Convertible Promissory Notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants outstanding (in shares)		102,070		102,070
Exercise price of warrants (in dollars per share)		$ 24.35		$ 24.35
Warrants term				10 years
Warrants expiration period				2024-11
Underwriter [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants outstanding (in shares)		16,500		16,500
Exercise price of warrants (in dollars per share)		$ 35.70		$ 35.70
Warrants term				10 years
Warrants expiration period				2024-11
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant		27,967		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		55,936
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%		10.00%
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period				4 years
Number of shares available for grant		1,818,603		1,818,603
Income tax benefits recognized from stock-based compensation		$ 0	$ 0	$ 0	$ 0
Number of options granted		452,650	114,142	452,650	578,142
Future stock-based compensation for unvested employee options granted and outstanding		$ 1,600,000		$ 1,600,000
Future stock-based compensation, requisite service period				2 years 8 months 12 days
Stock Options [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value				110.00%
Stock Options [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term of option				10 years
ISOs [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term of option				5 years
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period				4 years
Future stock-based compensation for unvested employee options granted and outstanding		$ 2,000,000		$ 2,000,000
Stock units granted		16,461	16,708	703,718	38,123
Vesting percentage				100.00%
Weighted average grant-date fair value of all restricted stock units granted				$ 3.81	$ 2.42
Fair value of restricted stock units vested				$ 100,000	$ 92,000
Weighted average remaining vesting period				3 years 6 months

Stockholders' Equity - Summary of Stock Option Transactions (Detail) - Stock Options [Member] - $ / shares	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance			2,123,117
Options granted	452,650	114,142	452,650	578,142
Options exercised			(8,518)
Options canceled/forfeited			(67,969)
Ending balance	2,499,280		2,499,280		2,123,117
Options vested at end of period (shares)			1,362,956
Options vested and expected to vest at end of period (shares)	2,499,280		2,499,280
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)			$ 4.62
Options granted (in dollars per share)			3.41
Options exercised (in dollars per share)			1.96
Options canceled/forfeited (in dollars per share)			2.26
Ending balance (in dollars per share)	$ 4.47		4.47		$ 4.62
Options vested at end of period (in dollars per share)			6.18
Options vested and expected to vest at end of period (in dollars per share)	$ 4.47		$ 4.47
Weighted Average Remaining Contractual Term
Options outstanding at end of period			7 years 9 months 14 days		7 years 10 months 13 days
Options vested at end of period			6 years 11 months 4 days
Options vested and expected to vest at end of period			7 years 9 months 14 days

Stockholders' Equity - Summary of Restricted Stock Unit Transactions (Detail) - Restricted Stock Units [Member] - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 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	16,461	16,708	703,718	38,123
Restricted stock units vested			(45,218)
Restricted stock units cancelled			(67,500)
Ending balance	591,000		591,000
Weighted-average grant date fair value
Restricted stock units granted (in dollars per share)			$ 3.81	$ 2.42
Restricted stock units vested (in dollars per share)			3.25
Restricted stock units vested (in dollars per share)			3.85
Ending balance (in dollars per share)	$ 3.85		$ 3.85

Net loss per share - Schedule of Potentially Dilutive Securities Outstanding Excluded from Computations of Diluted Weighted-Average Shares Outstanding (Detail) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	10,288,265	9,996,634
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	2,500,113	2,196,278
Outstanding 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	591,000
Warrants Issued to Underwriter 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	16,500	16,500
Series A Warrants 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		485,121
Series C Warrants 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 Warrants 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	540,540
2017 PIPE Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computations of diluted weighted-average shares outstanding	6,024,425	6,024,425
2018 PIPE Warrants [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

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 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	100,000,000	100,000,000
Common stock, shares issued	79,560,274	44,658,054
Common stock, shares outstanding	79,560,274	44,658,054

Condensed Consolidated Statements of Stockholders' Equity (unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2020 USD ($)
Statement Of Stockholders Equity [Abstract]
Payments of stock issuance costs	$ 3,778

Summary of Significant Accounting Policies - Additional Information (Detail)	Jun. 30, 2020 USD ($)
Essentialis, Inc. [Member] \| Earnout Payments [Member]
Schedule Of Significant Accounting Policies [Line Items]
Maximum potential cash earnout payments	$ 30,000,000

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 3 Financial Instruments (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) shares
Purchase price contingent liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 5,938
Change in value of liabilities	3,426
Balance at end of period	$ 9,364
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 \| shares	118,083
Expiration of warrants, in shares \| shares	(118,083)
2017 PIPE Warrant Liability [Member] \| Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 10,822
Balance at the beginning of period, in shares \| shares	6,024,425
Change in value of liabilities	$ (6,592)
Balance at end of period	$ 4,230
Balance at the end of period, in shares \| shares	6,024,425
2018 PIPE Warrant Liability [Member] \| Common stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of period	$ 1,354
Balance at the beginning of period, in shares \| shares	513,617
Change in value of liabilities	$ (629)
Balance at end of period	$ 725
Balance at the end of period, in shares \| shares	513,617

Warrant Liabilities - Fair Value of Convertible Preferred Stock Warrant Liability (Detail)	Jun. 30, 2020	Dec. 31, 2019
Expected Dividend Yield [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.00
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	1.15	0.99
2017 PIPE Warrant Liability [Member] \| Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	6 months	1 year
2017 PIPE Warrant Liability [Member] \| Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0020	0.0160
2018 PIPE Warrant Liability [Member] \| Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.94	0.99
2018 PIPE Warrant Liability [Member] \| Contractual Term [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement term	3 years 6 months	4 years
2018 PIPE Warrant Liability [Member] \| Risk-free Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0020	0.0156

Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Liabilities
Contingent liability for Essentialis purchase price	$ 9,364	$ 5,938
2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,230	10,822
2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	725	1,354
Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	14,319	18,114
Fair Value, Measurements, Recurring [Member] \| Derivative Financial Instruments, Liabilities \| 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,230	10,822
Fair Value, Measurements, Recurring [Member] \| Derivative Financial Instruments, Liabilities \| 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	725	1,354
Essentialis, Inc. [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	9,364	5,938
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities
Total common stock warrant and contingent consideration liability	14,319	18,114
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Derivative Financial Instruments, Liabilities \| 2017 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	4,230	10,822
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Derivative Financial Instruments, Liabilities \| 2018 PIPE Warrant Liability [Member]
Liabilities
Warrant liability	725	1,354
Level 3 [Member] \| Essentialis, Inc. [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities
Contingent liability for Essentialis purchase price	$ 9,364	$ 5,938

CoSense Joint Venture Agreement and Discontinued Operations - Additional Information (Detail) - Capnia Inc Joint Venture [Member] - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Oct. 16, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership interest		47.00%	47.00%
OAHL [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining interest		$ 0
OAHL [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				$ 1.00
Investment threshold requirement stock issuance			$ 1,200	$ 1,200
Sale of common stock in public offering, net of costs, (shares)	1,690,322
Percentage of ownership interest	53.00%