Oncotelic Therapeutics (OTLC) 10-K 17 Apr 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Apr. 12, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	OXGN
Entity Registrant Name	MATEON THERAPEUTICS INC
Entity Central Index Key	908,259
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Accelerated Filer
Entity Common Stock, Shares Outstanding		41,169,934
Entity Public Float			$ 8,997,000

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 1,115	$ 3,535
Short-term investments		8,512
Prepaid clinical trial expenses		1,946
Other prepaid expenses and current assets	22	77
Total current assets	1,137	14,070
Property and equipment, net	2	11
Other assets	33	33
Total assets	1,172	14,114
Current liabilities:
Accounts payable	788	310
Accrued compensation and employee benefits	73	842
Accrued clinical trial expenses	509	64
Other accrued liabilities	279	398
Total current liabilities	1,649	1,614
Commitments and contingencies
Stockholders' equity/(deficit):
Preferred stock, $0.01 par value, 15,000 shares authorized; No shares issued and outstanding
Common stock, $0.01 par value, 70,000 shares authorized; 26,545 shares issued and outstanding	265	265
Additional paid-in capital	291,533	290,698
Accumulated deficit	(292,275)	(278,463)
Total stockholders' equity/(deficit)	(477)	12,500
Total liabilities and stockholders' equity/(deficit)	$ 1,172	$ 14,114

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000,000	15,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	70,000,000	70,000,000
Common stock, shares issued	26,545,000	26,545,000
Common stock, shares outstanding	26,545,000	26,545,000

Statements of Comprehensive Los

Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research and development	$ 10,471	$ 8,764
General and administrative	3,371	4,995
Total operating expenses	13,842	13,759
Loss from operations	(13,842)	(13,759)
Interest income	35	106
Other income (expense)	(5)	(1)
Net loss and comprehensive loss	$ (13,812)	$ (13,654)
Basic and diluted net loss per share attributable to common stock	$ (0.52)	$ (0.51)
Weighted-average number of common shares outstanding	26,545	26,545

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2015	$ 25,350	$ 265	$ 289,894	$ (264,809)
Beginning Balance, shares at Dec. 31, 2015		26,545
Net loss and comprehensive loss	(13,654)			(13,654)
Stock based compensation expense	804		804
Ending Balance at Dec. 31, 2016	12,500	$ 265	290,698	(278,463)
Ending Balance, shares at Dec. 31, 2016		26,545
Net loss and comprehensive loss	(13,812)			(13,812)
Stock based compensation expense	835		835
Ending Balance at Dec. 31, 2017	$ (477)	$ 265	$ 291,533	$ (292,275)
Ending Balance, shares at Dec. 31, 2017		26,545

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net loss	$ (13,812)	$ (13,654)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	9	19
Stock-based compensation	835	804
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	2,001	(1,918)
Accounts payable and accrued expenses	35	(489)
Net cash used in operating activities	(10,932)	(15,238)
Investing activities:
Purchase of short-term investments		(21,014)
Sale of short-term investments	8,512	12,502
Net cash provided by/(used in) investing activities	8,512	(8,512)
Decrease in cash and cash equivalents	(2,420)	(23,750)
Cash and cash equivalents at beginning of year	3,535	27,285
Cash and cash equivalents at end of year	$ 1,115	$ 3,535

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Description of Business	1. Description of Business Mateon Therapeutics, Inc. (“Mateon” or the “Company”) is a clinical-stage biopharmaceutical developing drugs for the treatment of orphan oncology indications, with its lead program in acute myeloid leukemia (“AML”). The Company was originally incorporated under the name OXiGENE, Inc. in 1988 in the state of New York and reincorporated in 1992 in the state of Delaware. Effective June 17, 2016, the Company changed its name to Mateon Therapeutics, Inc.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates. Cash Equivalents Highly liquid investments with original maturities of three months or less at the date of purchase are considered to be cash equivalents. Cash equivalents are stated at fair value. Short-term Investments All marketable securities have been classified as “available for sale” and are carried at fair value, based upon quoted market prices. The Company considers its available-for-sale available-for-sale Concentration of Credit Risk The Company has no significant off balance sheet concentrations of credit risk. Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash and short-term investments, which consist of U.S. government treasury bills, corporate bonds and commercial paper. The Company holds its cash and short-term investments with one financial institution. Fair Value of Financial Instruments The Company measures and reports its cash equivalents and investments at fair value. 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. Property and Equipment Property and equipment, including leasehold improvements, are recorded and stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, which range from three to five years, or the applicable lease term, whichever is less. Accrued Clinical Trial Expenses The Company utilizes contract research organizations (“CROs”), independent clinical investigators, and other third-party service providers to assist with the execution of its clinical trials. The Company records costs for clinical trial activities based upon the estimated amount of services provided but not yet invoiced for each clinical trial, and includes these costs in accrued liabilities on its Balance Sheets and within research and development expenses on its Statements of Comprehensive Loss. Contracts for clinical trials vary significantly in length and are usually composed of a fixed management fee, variable indirect reimbursable costs, monthly costs and amounts owed on a per patient basis. The Company monitors both the activity and patient enrollment levels of each clinical trial to the extent possible through communication with each service provider, detailed invoice and task completion review, analysis of actual expenses against budget, pre-approval Research and Development Expenses The Company charges all research and development costs, both internal and external, to expense when incurred. The Company’s research and development expenses consist primarily of clinical trial expenses, personnel costs, including salaries, benefits and stock-based compensation, costs associated with manufacturing the Company’s drug product for clinical use and required regulatory filings, licenses and fees, and overhead allocations consisting of various support and facility-related costs. Clinical trial expenses represent a significant component of the Company’s research and development expenses. A large portion of the costs for the Company’s clinical trials are paid to or through CROs. The Company monitors levels of services provided under each significant contract including the extent of patient enrollment and other activities through communications with its CROs and with investigator sites. Costs are accrued for clinical studies performed by CROs over the service periods specified in the contracts and estimates are adjusted, if required, based upon ongoing review of the level of effort and costs actually incurred by the CROs. The manufacturing of the Company’s drug investigational drugs is outsourced to third-party manufacturers. The drug manufacturing costs are expensed as incurred. Comprehensive Net Loss For the periods presented, there are no components of other comprehensive income or accumulated comprehensive income and the net loss is equal to the comprehensive loss. Stock-based Compensation The Company expenses the estimated fair value of all share-based payments issued to employees on a straight-line basis over the vesting period. The Company has equity incentive plans that provides for the award of stock options, restricted stock and stock appreciation rights to employees, directors and consultants to the Company. Patents and Patent Applications The Company has filed applications for patents in connection with various product candidates and technologies being developed. Costs associated with patent applications and maintaining patents are expensed as general and administrative expense as incurred. Income Taxes The Company accounts for income taxes using the liability method whereby tax rates are applied to cumulative temporary differences between carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes based on when and how they are expected to affect the tax return. Subsequent Events The Company reviews all activity subsequent to year end but prior to the issuance of the financial statements for events that could require disclosure or which could impact the carrying value of assets or liabilities as of the balance sheet date. Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-2, right-of-use In March 2016, the FASB issued ASU No. 2016-09, tax-withholding In August 2016, The FASB issued ASU No. 2016-15 Going Concern Evaluation The Company has experienced net losses every year since inception and, as of December 31, 2017, had an accumulated deficit of over $292 million. The company has no source of revenue and does not expect to receive any product revenue in the near future. The Company expects to incur significant additional operating losses over at least the next several years, principally as a result of the Company’s continuing clinical trials for its investigational drugs. The principal source of the Company’s working capital to date has been the proceeds from the sale of equity. As of December 31, 2017, the Company had approximately $1.1 million in cash and current liabilities of $1.6 million. Following the receipt of an estimated $2.4 million in net proceeds from a financing transaction in April 2018, based on the Company’s planned operations, the Company’s management expects Mateon’s existing cash to support its planned operations into the fourth quarter of 2018. Prior to this time, the Company will need to secure additional funding or could be forced to curtail or terminate operations. Because the Company does not currently have a guaranteed source of working capital that will sustain planned operations past the fourth quarter of 2018, Management has determined that there is substantial doubt about the Company’s ability to continue as a going concern. The Company will need to raise capital in order to fund its planned operations beyond this time. If the Company is unable to access additional funds when needed, it may not be able to continue the development of its investigational drugs and the Company could be required to delay, scale back or eliminate some or all of its development programs and other operations. Any additional equity financing, if available to the Company, may not be available on favorable terms, would most likely be dilutive to its current stockholders and debt financing, if available, may involve restrictive covenants. If the Company accesses funds through collaborative or licensing arrangements, it may be required to relinquish rights to some of its technologies or product candidates that it would otherwise seek to develop or commercialize on its own, on terms that are not favorable to the Company. The Company’s ability to access capital when needed is not assured and, if not achieved on a timely basis, will materially harm its business, financial condition and results of operations.

Cash, Cash Equivalents, and Sho

Cash, Cash Equivalents, and Short-Term Investments	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	3. Cash, Cash Equivalents, and Short-Term Investments Cash, cash equivalents and short-term investments consisted of the following (in thousands): December 31, 2017 Amortized Unrealized Unrealized Estimated Fair Cash $ 1,115 $ — $ — $ 1,115 $ 1,115 $ — $ — $ 1,115 December 31, 2016 Amortized Unrealized Unrealized Estimated Fair Cash $ 671 $ — $ — $ 671 Money market funds 2,864 — — 2,864 U.S. government treasury bills 3,008 — — 3,008 Corporate bonds and commercial paper 5,504 — — 5,504 $ 12,047 $ — $ — $ 12,047 Reported as: Cash and cash equivalents $ 3,535 Short-term investments 8,512 Total cash, cash equivalents and short-term investments $ 12,047 As of December 31, 2016, the Company’s cash equivalents and short-term investments had a weighted-average time to maturity of less than one year, and the Company had the ability to hold its investments through their maturity dates. There have been no significant realized gains or losses on investments for the period presented.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements Fair value is defined as the price at which an asset could be exchanged or a liability transferred in a transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or parameters are not available, valuation models are applied. Assets and liabilities recorded at fair value are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities are as follows: Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets at the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide reasonably accurate pricing information on an ongoing basis. Level 2—Inputs, other than quoted prices included in Level 1, that are either directly or indirectly observable for the asset or liability through correlation with market data at the reporting date and for the duration of the instrument’s anticipated life. The Company utilizes third party pricing services in developing fair value measurements where fair value is based on observable market inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers and other reference data. The Company uses quotes from external pricing service providers and other on-line Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities reflect management’s best estimate of what market participants would use in pricing the asset or liability at the reporting date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. Financial assets measured at fair value on a recurring basis are categorized in the tables below based upon the lowest level of significant input to the valuations (in thousands): December 31, 2016 Level 1 Level 2 Level 3 Total Money market funds $ 2,864 $ — $ — $ 2,864 U.S. government treasury bills — 3,008 — 3,008 Corporate bonds and commercial paper — 5,504 — 5,504 Total $ 2,864 $ 8,512 $ — $ 11,376

Property and equipment

Property and equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and equipment	5. Property and equipment Property and equipment consists of the following (in thousands): December 31, 2017 2016 Equipment $ 226 $ 226 Furniture and fixtures 36 36 Leasehold improvements 6 6 Total assets 268 268 Less accumulated depreciation (266 ) (257 ) Total property and equipment, net $ 2 $ 11

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	6. Stockholders’ Equity Warrants The following is a summary of the Company’s outstanding common stock warrants: Exercise December 31, 2017 2016 Expiration Date (in thousands) 06/14/17 $ 3.70 — 216 04/16/18 $ 3.40 1,460 1,460 09/23/18 $ 2.80 147 147 02/11/19 $ 2.56 293 293 02/18/19 $ 2.75 1,872 1,872 08/28/19 $ 2.90 2,700 2,700 03/20/20 $ 2.13 234 234 03/25/20 $ 1.71 2,920 2,920 Total Warrants Outstanding 9,626 9,842 No warrants were exercised during the years ended December 31, 2017 and 2016. All warrants outstanding at December 31, 2017 and 2016 were recorded by the Company as equity at the time of issuance. Options and restricted stock As of December 31, 2017, options to purchase common stock were outstanding under three stock option plans—the 2017 Equity Incentive Plan (the “2017 Plan”), the 2015 Equity Incentive Plan (the “2015 Plan”) and the 2005 Stock Plan (the “2005 Plan”). Options to purchase common stock may no longer be made under the 2005 Plan, although options previously granted remain outstanding in accordance with their terms. Under the 2017 Plan, up to 2,000,000 shares of the Company’s common stock may be issued pursuant to awards granted in the form of nonqualified stock options, restricted and unrestricted stock awards, and other stock-based awards to employees, consultants, and directors. Under the 2015 Plan, up to 4,000,000 shares of the Company’s common stock may be issued pursuant to awards granted in the form of incentive stock options, nonqualified stock options, restricted and unrestricted stock awards, and other stock-based awards to employees, consultants, and directors. The 2015 Plan also allows additional shares of the Company’s common stock to be issued if awards previously authorized or outstanding under the Company’s 2005 Stock Plan are cancelled, forfeited, surrendered, or terminated. Under the 2005 Plan, up to 726,000 shares of the Company’s common may be issued or transferred to the 2015 Plan. The following is a summary of the Company’s stock option activity under its 2017, 2015 and 2005 Plans: Options Options Weighted Weighted Aggregate (in thousands) (years) (in thousands) Balance at December 31, 2015 2,695 2,031 $ 2.01 8.44 Options granted (2,569 ) 2,569 $ 0.70 Options forfeited 423 (423 ) $ 1.74 Balance at December 31, 2016 549 4,177 $ 1.47 8.14 Options granted (2,484 ) 2,484 $ 0.42 Options forfeited 1,781 (1,781 ) $ 1.16 Options authorized 2,000 — Balance at December 31, 2017 1,846 4,880 $ 1.05 7.63 $ — Vested and exercisable at December 31, 2017 2,052 $ 1.13 7.35 $ — Vested and expected to vest at December 31, 2017 4,084 $ 0.88 7.53 $ — Unvested at December 31, 2017 2,828 $ 1.00 As of December 31, 2017, there was approximately $0.9 million of unrecognized compensation cost related to stock option awards that is expected to be recognized as expense over a weighted average period of approximately 2 years. The weighted average fair value of stock options issued in 2017 and 2016 was $0.34 and $0.51, respectively. The fair values for the stock options granted were estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Year ended 2017 2016 Risk-free interest rate 2.0 % 1.5 % Expected life (years) 6.0 6.0 Expected volatility 88 % 88 % Dividend yield 0 % 0 % In calculating the estimated fair value of its stock options, the Company used the Black-Scholes option pricing model which requires the consideration of the following variables for purposes of estimating fair value: • the stock option exercise price, • the grant date price of the Company’s common stock, • the expected term of the option, • the expected volatility of the Company’s common stock, • the expected dividends on the Company’s common stock, and • the risk-free interest rate for the expected option term. Stock Option Exercise Price and Grant Date Price of the Company’s common stock — The closing market price of the Company’s common stock on the date of grant. Expected Term—The expected term of options represents the period of time for which the options are expected to be outstanding, and is calculated based on the average of the vesting period and the option term. Expected Volatility—The expected volatility is a measure of the amount by which the Company’s stock price is expected to fluctuate during the term of the option granted. The Company determines the expected volatility based on the historical volatility of its common stock over a period commensurate with the option’s expected term. Expected Dividends—Because the Company has never declared or paid any cash dividends on any of its common stock and does not expect to do so in the foreseeable future, the Company uses an expected dividend yield of zero to calculate the grant date fair value of a stock option. Risk-Free Interest Rate—The risk-free interest rate is the implied yield available on U.S. Treasury issues with a remaining life consistent with the option’s expected term on the date of grant. The Company estimates the level of award forfeitures expected to occur and records compensation expense only for those awards that are ultimately expected to vest.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss Per Share	7. Net Loss Per Share Basic and diluted net loss per share was calculated by dividing the net loss per share attributed to the Company’s common shares by the weighted-average number of common shares outstanding. Diluted net loss per share includes the effect of all dilutive, potentially issuable common equivalent shares as defined using the treasury stock method. All of the Company’s common stock equivalents are anti-dilutive due to the Company’s net loss position for all periods presented. Accordingly, common stock equivalents of approximately 4,880,000 stock options and 9,626,000 warrants at December 31, 2017 and 4,177,000 stock options and 9,842,000 warrants at December 31, 2016, were excluded from the calculation of weighted average shares for diluted net loss per share.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The components of the Company’s deferred tax assets are as follows (in thousands): December 31, 2017 2016 Net operating loss carryforwards $ 55,265 $ 85,148 Stock based compensation 297 435 Research and development credits 3,229 2,925 Fixed assets 3,477 2,617 Accruals 35 391 Total Deferred tax assets 62,303 91,516 Valuation allowance (62,303 ) (91,516 ) Net deferred tax asset $ — $ — After consideration of the available evidence, both positive and negative, the Company has determined that a full valuation allowance at December 31, 2017 and 2016 is necessary to reduce the deferred tax assets to the amount that will more likely than not be realized. The valuation allowance decreased by approximately $29,213,000 for the year ended December 31, 2017 and increased by $4,757,000 for the year ended December 31, 2016. As all of the Company’s deferred tax assets have been reserved for in a valuation allowance, no provision for (benefit from) income taxes has been recorded in the accompanying financial statements. At December 31, 2017, the Company had net operating loss carry-forwards of approximately $246,998,000 for Federal income tax purposes which will begin to expire in 2020, and net operating loss carry-forwards for California state income tax purposes of $52,948,000 which will begin to expire in 2028. The Company had federal research and development tax credits of $3,301,000 which will begin to expire in 2021. The Company also had state research and development tax credits in California of $1,276,000 which have no expiration. The utilization of the Company’s net operating losses and credits may be subject to a substantial annual limitation due to the “change in ownership” provisions of the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization. A reconciliation of the federal statutory rate to the Company’s effective tax rate is as follows: Years ended 2017 2016 Federal Statutory Rate 34.0 % 34.0 % State Tax 0.2 0.4 Change in Valuation Allowance 216.8 (34.8 ) Stock-Based Compensation (0.5 ) (0.4 ) Research Credits 0.3 1.7 Other (0.1 ) (1.0 ) Tax Reform—Tax Rate Change (250.7 ) — Provision for income taxes (0.0 )% (0.0 )% At December 31, 2017, the Company had $1,147,000 of unrecognized tax benefits related to research and development credits. The change in unrecognized tax benefits is as follows (in thousands): Unrecognized tax benefits as of December 31, 2015 $ 1,410 Decrease in prior year unrecognized tax benefits (447 ) Increase in current year unrecognized tax benefits 109 Unrecognized tax benefits as of December 31, 2016 1,072 Increase in current year unrecognized tax benefits 75 Unrecognized tax benefits as of December 31, 2017 $ 1,147 The Company does not expect its unrecognized tax benefits to change significantly over the next twelve months. As of December 31, 2017, due to a valuation allowance against the Company’s deferred tax assets, none of the unrecognized tax benefits, if recognized, would affect the Company’s effective tax rate. There are currently no federal or state audits in progress. Tax years still subject to examination for Federal and the State authorities include all prior years due to the existence of net operating loss carry-forwards. It is the Company’s practice to recognize interest and penalties related to income tax matters in income tax expense. As of December 31, 2017, the Company has no accrued interest and penalties related to uncertain tax positions.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies The Company has a lease for its corporate headquarters which expires on June 30, 2019. The lease is for a total of 5,275 square feet of office space located in South San Francisco, California. Rental expense for both years ended December 31, 2017 and 2016 was $208,000 each year. The future minimum lease payments required under the lease are as follows: Amount 2018 $ 221 2019 112 Total lease obligations $ 333

Retirement Savings Plan

Retirement Savings Plan	12 Months Ended
	Dec. 31, 2017
Postemployment Benefits [Abstract]
Retirement Savings Plan	10. Retirement Savings Plan The Company sponsors a savings plan available to all employees, which qualifies under Section 401(k) of the Internal Revenue Code. Employees may contribute from 1% to 99% of their pre-tax

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	11. Related Party Transactions A portion of the compensation paid to the Company’s Chief Scientific Officer, David J. Chaplin, Ph.D., was paid to Aston Biopharma Ltd. (“Aston”) for services that Dr. Chaplin performed for the Company while he was in the United Kingdom. The amounts paid to Aston aggregated $16,000 and $137,000 in 2017 and 2016, respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events On April 12, 2018, the Company entered into a private placement transaction with accredited investors, raising gross proceeds of approximately $2.9 million, with estimated net proceeds of approximately $2.4 million. In the private placement transaction, the Company sold 14,625,000 shares of its common stock and warrants to purchase 14,625,000 shares of common stock. The purchase price of the common stock was $0.20 per share and warrants are exercisable at $0.40 per share.

Significant Accounting Polici19

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates.
Cash Equivalents	Cash Equivalents Highly liquid investments with original maturities of three months or less at the date of purchase are considered to be cash equivalents. Cash equivalents are stated at fair value.
Short-term Investments	Short-term Investments All marketable securities have been classified as “available for sale” and are carried at fair value, based upon quoted market prices. The Company considers its available-for-sale available-for-sale
Concentration of Credit Risk	Concentration of Credit Risk The Company has no significant off balance sheet concentrations of credit risk. Financial instruments that potentially subject the Company to concentrations of credit risk primarily consist of cash and short-term investments, which consist of U.S. government treasury bills, corporate bonds and commercial paper. The Company holds its cash and short-term investments with one financial institution.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company measures and reports its cash equivalents and investments at fair value. 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.
Property and Equipment	Property and Equipment Property and equipment, including leasehold improvements, are recorded and stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, which range from three to five years, or the applicable lease term, whichever is less.
Accrued Clinical Trial Expenses	Accrued Clinical Trial Expenses The Company utilizes contract research organizations (“CROs”), independent clinical investigators, and other third-party service providers to assist with the execution of its clinical trials. The Company records costs for clinical trial activities based upon the estimated amount of services provided but not yet invoiced for each clinical trial, and includes these costs in accrued liabilities on its Balance Sheets and within research and development expenses on its Statements of Comprehensive Loss. Contracts for clinical trials vary significantly in length and are usually composed of a fixed management fee, variable indirect reimbursable costs, monthly costs and amounts owed on a per patient basis. The Company monitors both the activity and patient enrollment levels of each clinical trial to the extent possible through communication with each service provider, detailed invoice and task completion review, analysis of actual expenses against budget, pre-approval
Research and Development Expenses	Research and Development Expenses The Company charges all research and development costs, both internal and external, to expense when incurred. The Company’s research and development expenses consist primarily of clinical trial expenses, personnel costs, including salaries, benefits and stock-based compensation, costs associated with manufacturing the Company’s drug product for clinical use and required regulatory filings, licenses and fees, and overhead allocations consisting of various support and facility-related costs. Clinical trial expenses represent a significant component of the Company’s research and development expenses. A large portion of the costs for the Company’s clinical trials are paid to or through CROs. The Company monitors levels of services provided under each significant contract including the extent of patient enrollment and other activities through communications with its CROs and with investigator sites. Costs are accrued for clinical studies performed by CROs over the service periods specified in the contracts and estimates are adjusted, if required, based upon ongoing review of the level of effort and costs actually incurred by the CROs. The manufacturing of the Company’s drug investigational drugs is outsourced to third-party manufacturers. The drug manufacturing costs are expensed as incurred.
Comprehensive Net Loss	Comprehensive Net Loss For the periods presented, there are no components of other comprehensive income or accumulated comprehensive income and the net loss is equal to the comprehensive loss.
Stock-based Compensation	Stock-based Compensation The Company expenses the estimated fair value of all share-based payments issued to employees on a straight-line basis over the vesting period. The Company has equity incentive plans that provides for the award of stock options, restricted stock and stock appreciation rights to employees, directors and consultants to the Company.
Patents and Patent Applications	Patents and Patent Applications The Company has filed applications for patents in connection with various product candidates and technologies being developed. Costs associated with patent applications and maintaining patents are expensed as general and administrative expense as incurred.
Income Taxes	Income Taxes The Company accounts for income taxes using the liability method whereby tax rates are applied to cumulative temporary differences between carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes based on when and how they are expected to affect the tax return.
Subsequent Events	Subsequent Events The Company reviews all activity subsequent to year end but prior to the issuance of the financial statements for events that could require disclosure or which could impact the carrying value of assets or liabilities as of the balance sheet date.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-2, right-of-use In March 2016, the FASB issued ASU No. 2016-09, tax-withholding In August 2016, The FASB issued ASU No. 2016-15
Going Concern Evaluation	Going Concern Evaluation The Company has experienced net losses every year since inception and, as of December 31, 2017, had an accumulated deficit of over $292 million. The company has no source of revenue and does not expect to receive any product revenue in the near future. The Company expects to incur significant additional operating losses over at least the next several years, principally as a result of the Company’s continuing clinical trials for its investigational drugs. The principal source of the Company’s working capital to date has been the proceeds from the sale of equity. As of December 31, 2017, the Company had approximately $1.1 million in cash and current liabilities of $1.6 million. Following the receipt of an estimated $2.4 million in net proceeds from a financing transaction in April 2018, based on the Company’s planned operations, the Company’s management expects Mateon’s existing cash to support its planned operations into the fourth quarter of 2018. Prior to this time, the Company will need to secure additional funding or could be forced to curtail or terminate operations. Because the Company does not currently have a guaranteed source of working capital that will sustain planned operations past the fourth quarter of 2018, Management has determined that there is substantial doubt about the Company’s ability to continue as a going concern. The Company will need to raise capital in order to fund its planned operations beyond this time. If the Company is unable to access additional funds when needed, it may not be able to continue the development of its investigational drugs and the Company could be required to delay, scale back or eliminate some or all of its development programs and other operations. Any additional equity financing, if available to the Company, may not be available on favorable terms, would most likely be dilutive to its current stockholders and debt financing, if available, may involve restrictive covenants. If the Company accesses funds through collaborative or licensing arrangements, it may be required to relinquish rights to some of its technologies or product candidates that it would otherwise seek to develop or commercialize on its own, on terms that are not favorable to the Company. The Company’s ability to access capital when needed is not assured and, if not achieved on a timely basis, will materially harm its business, financial condition and results of operations.

Cash, Cash Equivalents, and S20

Cash, Cash Equivalents, and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Short-Term Investments	Cash, cash equivalents and short-term investments consisted of the following (in thousands): December 31, 2017 Amortized Unrealized Unrealized Estimated Fair Cash $ 1,115 $ — $ — $ 1,115 $ 1,115 $ — $ — $ 1,115 December 31, 2016 Amortized Unrealized Unrealized Estimated Fair Cash $ 671 $ — $ — $ 671 Money market funds 2,864 — — 2,864 U.S. government treasury bills 3,008 — — 3,008 Corporate bonds and commercial paper 5,504 — — 5,504 $ 12,047 $ — $ — $ 12,047 Reported as: Cash and cash equivalents $ 3,535 Short-term investments 8,512 Total cash, cash equivalents and short-term investments $ 12,047

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on a Recurring Basis	Financial assets measured at fair value on a recurring basis are categorized in the tables below based upon the lowest level of significant input to the valuations (in thousands): December 31, 2016 Level 1 Level 2 Level 3 Total Money market funds $ 2,864 $ — $ — $ 2,864 U.S. government treasury bills — 3,008 — 3,008 Corporate bonds and commercial paper — 5,504 — 5,504 Total $ 2,864 $ 8,512 $ — $ 11,376

Property and equipment (Tables)

Property and equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consists of the following (in thousands): December 31, 2017 2016 Equipment $ 226 $ 226 Furniture and fixtures 36 36 Leasehold improvements 6 6 Total assets 268 268 Less accumulated depreciation (266 ) (257 ) Total property and equipment, net $ 2 $ 11

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of the Company's Outstanding Common Stock Warrants	The following is a summary of the Company’s outstanding common stock warrants: Exercise December 31, 2017 2016 Expiration Date (in thousands) 06/14/17 $ 3.70 — 216 04/16/18 $ 3.40 1,460 1,460 09/23/18 $ 2.80 147 147 02/11/19 $ 2.56 293 293 02/18/19 $ 2.75 1,872 1,872 08/28/19 $ 2.90 2,700 2,700 03/20/20 $ 2.13 234 234 03/25/20 $ 1.71 2,920 2,920 Total Warrants Outstanding 9,626 9,842
Summary of the Company's Stock Option Activity under 2017,2015 and 2005 Plans	The following is a summary of the Company’s stock option activity under its 2017, 2015 and 2005 Plans: Options Options Weighted Weighted Aggregate (in thousands) (years) (in thousands) Balance at December 31, 2015 2,695 2,031 $ 2.01 8.44 Options granted (2,569 ) 2,569 $ 0.70 Options forfeited 423 (423 ) $ 1.74 Balance at December 31, 2016 549 4,177 $ 1.47 8.14 Options granted (2,484 ) 2,484 $ 0.42 Options forfeited 1,781 (1,781 ) $ 1.16 Options authorized 2,000 — Balance at December 31, 2017 1,846 4,880 $ 1.05 7.63 $ — Vested and exercisable at December 31, 2017 2,052 $ 1.13 7.35 $ — Vested and expected to vest at December 31, 2017 4,084 $ 0.88 7.53 $ — Unvested at December 31, 2017 2,828 $ 1.00
Weighted-Average Assumptions	The fair values for the stock options granted were estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions: Year ended 2017 2016 Risk-free interest rate 2.0 % 1.5 % Expected life (years) 6.0 6.0 Expected volatility 88 % 88 % Dividend yield 0 % 0 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Deferred Tax Assets	The components of the Company’s deferred tax assets are as follows (in thousands): December 31, 2017 2016 Net operating loss carryforwards $ 55,265 $ 85,148 Stock based compensation 297 435 Research and development credits 3,229 2,925 Fixed assets 3,477 2,617 Accruals 35 391 Total Deferred tax assets 62,303 91,516 Valuation allowance (62,303 ) (91,516 ) Net deferred tax asset $ — $ —
Reconciliation of the Federal Statutory Rate to the Company's Effective Tax Rate	A reconciliation of the federal statutory rate to the Company’s effective tax rate is as follows: Years ended 2017 2016 Federal Statutory Rate 34.0 % 34.0 % State Tax 0.2 0.4 Change in Valuation Allowance 216.8 (34.8 ) Stock-Based Compensation (0.5 ) (0.4 ) Research Credits 0.3 1.7 Other (0.1 ) (1.0 ) Tax Reform—Tax Rate Change (250.7 ) — Provision for income taxes (0.0 )% (0.0 )%
Changes in Unrecognized Tax Benefits	The change in unrecognized tax benefits is as follows (in thousands): Unrecognized tax benefits as of December 31, 2015 $ 1,410 Decrease in prior year unrecognized tax benefits (447 ) Increase in current year unrecognized tax benefits 109 Unrecognized tax benefits as of December 31, 2016 1,072 Increase in current year unrecognized tax benefits 75 Unrecognized tax benefits as of December 31, 2017 $ 1,147

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Under Lease	The future minimum lease payments required under the lease are as follows: Amount 2018 $ 221 2019 112 Total lease obligations $ 333

Significant Accounting Polici26

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 12, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Cash equivalents maturities, term		three months or less
Accumulated deficit		$ (292,275)	$ (278,463)
Cash		1,115	3,535	$ 27,285
Current liabilities		$ 1,649	$ 1,614
Substantial doubt about going concern, management's evaluation		Mateon’s existing cash to support its planned operations into the fourth quarter of 2018. Prior to this time, the Company will need to secure additional funding or could be forced to curtail or terminate operations. Because the Company does not currently have a guaranteed source of working capital that will sustain planned operations past the fourth quarter of 2018, Management has determined that there is substantial doubt about the Company’s ability to continue as a going concern.
Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Estimated net proceeds from private placement transaction	$ 2,400
Minimum [Member]
Subsidiary, Sale of Stock [Line Items]
Estimated useful lives of the assets		3 years
Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Estimated useful lives of the assets		5 years

Cash, Cash Equivalents, and S27

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents, and Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,115	$ 12,047
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Estimated Fair Value	1,115	12,047
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,115	671
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Estimated Fair Value	$ 1,115	671
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,864
Unrealized Gain		0
Unrealized (Loss)		0
Estimated Fair Value		2,864
U.S. Government Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		3,008
Unrealized Gain		0
Unrealized (Loss)		0
Estimated Fair Value		3,008
Corporate Bonds and Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		5,504
Unrealized Gain		0
Unrealized (Loss)		0
Estimated Fair Value		5,504
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Gain		0
Unrealized (Loss)		0
Estimated Fair Value		3,535
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Gain		0
Unrealized (Loss)		0
Estimated Fair Value		$ 8,512

Cash, Cash Equivalents, and S28

Cash, Cash Equivalents, and Short-Term Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Realized gains or losses on investments	$ 0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents and short-term investments weighted-average time to maturity	1 year

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - Fair Value Measurements Recurring [Member] $ in Thousands	Dec. 31, 2016USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 11,376
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	2,864
U.S. Government Treasury Bills [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	3,008
Corporate Bonds and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	5,504
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	2,864
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	2,864
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	8,512
Level 2 [Member] | U.S. Government Treasury Bills [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	3,008
Level 2 [Member] | Corporate Bonds and Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	$ 5,504

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total gross assets	$ 268	$ 268
Less accumulated depreciation	(266)	(257)
Total furniture and fixtures, equipment and leasehold improvements	2	11
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total gross assets	226	226
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total gross assets	36	36
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total gross assets	$ 6	$ 6

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Company's Outstanding Common Stock Warrants (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Number of warrants outstanding	9,626	9,842
Private Placement Series A [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Apr. 16, 2018
Exercise Price		$ 3.40
Number of warrants outstanding	1,460	1,460
2013 Private Placement [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Sep. 23, 2018
Exercise Price		$ 2.80
Number of warrants outstanding	147	147
2014 Public Offering [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Feb. 18, 2019
Exercise Price		$ 2.75
Number of warrants outstanding	1,872	1,872
2014 Public Offering [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Feb. 11, 2019
Exercise Price		$ 2.56
Number of warrants outstanding	293	293
2014 Private Placement [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Aug. 28, 2019
Exercise Price		$ 2.90
Number of warrants outstanding	2,700	2,700
2014 Private Placement [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Jun. 14, 2017
Exercise Price		$ 3.70
Number of warrants outstanding		216
2015 Private Placement [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Mar. 25, 2020
Exercise Price		$ 1.71
Number of warrants outstanding	2,920	2,920
2015 Private Placement [Member]
Class of Warrant or Right [Line Items]
Expiration Date	Mar. 20, 2020
Exercise Price		$ 2.13
Number of warrants outstanding	234	234

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Stock_Plan$ / sharesshares	Dec. 31, 2016$ / sharesshares
Stockholders Equity [Line Items]
Number of shares authorized for grant	2,000,000
Options to purchase common stock outstanding, number of stockholder-approved plans | Stock_Plan	3
Weighted average period for recognizing unrecognized compensation cost as expense	2 years
Unrecognized compensation cost related to stock option awards | $	$ 0.9
Weighted average fair value | $ / shares	$ 0.34	$ 0.51
Dividend yield	0.00%	0.00%
Common Stock [Member]
Stockholders Equity [Line Items]
Warrants exercised	0	0
2015 Equity Incentive Plan [Member]
Stockholders Equity [Line Items]
Number of shares authorized for grant	4,000,000
Number of additional shares authorized for grant	726,000
2017 Equity Incentive Plan [Member]
Stockholders Equity [Line Items]
Number of shares authorized for grant	2,000,000

Stockholders' Equity - Summar33

Stockholders' Equity - Summary of the Company's Stock Option Activity under 2017, 2015 and 2005 Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options Available for Grant, Beginning Balance	549,000	2,695,000
Options Available for Grant, Options granted	(2,484,000)	(2,569,000)
Options Available for Grant, Options forfeited	1,781,000	423,000
Options Available for Grant, Options authorized	2,000,000
Options Available for Grant, Ending Balance	1,846,000	549,000
Options Outstanding, Beginning Balance	4,177,000	2,031,000
Options Outstanding, Options granted	2,484,000	2,569,000
Options Outstanding, Options forfeited	(1,781,000)	(423,000)
Options Outstanding, Ending Balance	4,880,000	4,177,000
Weighted Average Exercise Price, Beginning Balance	$ 1.47	$ 2.01
Options Outstanding, Vested and exercisable	2,052,000
Weighted Average Exercise Price, Options granted	$ 0.42	0.70
Options Outstanding, Vested and expected to vest, Ending Balance	4,084,000
Weighted Average Exercise Price, Options forfeited	$ 1.16	1.74
Options Outstanding, Unvested	2,828,000
Weighted Average Exercise Price, Ending Balance	$ 1.05	$ 1.47
Weighted Average Exercise Price, Vested and exercisable	1,130
Weighted Average Exercise Price, Vested and expected to vest, Ending Balance	0.88
Weighted Average Exercise Price, Unvested	$ 1,000
Weighted Average Remaining Contractual Life, Beginning Balance	8 years 5 months 9 days
Weighted Average Remaining Contractual Life, Ending Balance	8 years 1 month 20 days
Weighted Average Remaining Contractual Life, Ending Balance	7 years 7 months 17 days
Weighted Average Remaining Contractual Life, Vested and exercisable	7 years 4 months 6 days
Weighted Average Remaining Contractual Life, Vested and expected to vest, Ending Balance	7 years 6 months 10 days
Aggregate Intrinsic Value	$ 0
Aggregate Intrinsic Value, Vested and exercisable	0
Aggregate Intrinsic Value, Vested and expected to vest, Ending Balance	$ 0

Stockholders' Equity - Weighted

Stockholders' Equity - Weighted-Average Assumptions (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	2.00%	1.50%
Expected life (years)	6 years	6 years
Expected volatility	88.00%	88.00%
Dividend yield	0.00%	0.00%

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock excluded from the calculation of weighted average shares for diluted net loss per share	4,880,000	4,177,000
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock excluded from the calculation of weighted average shares for diluted net loss per share	9,626,000	9,842,000

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 55,265	$ 85,148
Stock based compensation	297	435
Research and development credits	3,229	2,925
Fixed assets	3,477	2,617
Accruals	35	391
Total Deferred tax assets	62,303	91,516
Valuation allowance	(62,303)	(91,516)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Change in valuation allowance	$ (29,213,000)	$ 4,757,000
Unrecognized tax benefits	1,147,000	$ 1,072,000	$ 1,410,000
Accrued interest expense and penalties related to uncertain tax positions	0
Research and Development Credit [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	1,147,000
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Operating loss carry-forwards	$ 246,998,000
Expiry year of operating loss carry-forwards	2,020
Tax credits related to federal and state research and development	$ 3,301,000
Expiry year of operating loss carry-forwards related to federal and state research and development activities	2,021
California [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carry-forwards	$ 52,948,000
Expiry year of operating loss carry-forwards	2,028
Tax credits related to federal and state research and development	$ 1,276,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Federal Statutory Rate to the Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal Statutory Rate	34.00%	34.00%
State Tax	0.20%	0.40%
Change in Valuation Allowance	216.80%	(34.80%)
Stock-Based Compensation	(0.50%)	(0.40%)
Research Credits	0.30%	1.70%
Other	(0.10%)	(1.00%)
Tax Reform-Tax Rate Change	(250.70%)
Provision for income taxes	0.00%	0.00%

Income Taxes - Changes in Unrec

Income Taxes - Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, Beginning Balance	$ 1,072	$ 1,410
Decrease in prior year unrecognized tax benefits		(447)
Increase in current year unrecognized tax benefits	75	109
Unrecognized tax benefits, Ending Balance	$ 1,147	$ 1,072

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)ft²	Dec. 31, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
Lease expiration date	Jun. 30, 2019
Area of facility lease | ft²	5,275
Rent expense | $	$ 208,000	$ 208,000

Commitments and Contingencies41

Commitments and Contingencies - Future Minimum Lease Payments Under Lease (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 221
2,019	112
Total lease obligations	$ 333

Retirement Savings Plan - Addit

Retirement Savings Plan - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee's contribute maximum	99.00%
Employee's contribute minimum	1.00%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Aston Biopharma Ltd [Member]
Related Party Transaction [Line Items]
Compensation paid	$ 16,000	$ 137,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ / shares in Units, $ in Millions	Apr. 12, 2018USD ($)$ / sharesshares
Subsequent Event [Line Items]
Gross proceeds from private placement transaction | $	$ 2.9
Estimated net proceeds from private placement transaction | $	$ 2.4
Sale of common stock shares | shares	14,625,000
Warrants to purchase shares of common stock | shares	14,625,000
Purchase price of common stock per share | $ / shares	$ 0.20
Warrants exercise price per share | $ / shares	$ 0.40