Pulmatrix (PULM) 10-Q 14 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 12, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	PULM
Entity Registrant Name	Pulmatrix, Inc.
Entity Central Index Key	1,574,235
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		46,927,221

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 3,806	$ 3,550
Prepaid expenses and other current assets	914	696
Total current assets	4,720	4,246
Property and equipment, net	447	614
Long-term restricted cash	204	204
Goodwill	10,914	10,914
Total assets	16,285	15,978
Current liabilities:
Loan payable, net of debt discount and issuance costs		3,221
Accounts payable	1,367	457
Accrued expenses	2,284	2,162
Derivative liability		1
Total current liabilities	3,651	5,841
Commitments (Note 12)
Stockholders' equity:
Preferred stock, $0.0001 par value - 500,000 authorized and 0 issued and outstanding at September 30, 2018 and December 31, 2017
Common stock, $0.0001 par value - 200,000,000 shares authorized; 46,927,221 and 21,047,498 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	5	2
Additional paid-in capital	202,856	184,137
Accumulated deficit	(190,227)	(174,002)
Total stockholders' equity	12,634	10,137
Total liabilities and stockholders' equity	$ 16,285	$ 15,978

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	46,927,221	21,047,498
Common stock, shares outstanding	46,927,221	21,047,498

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues		$ 335	$ 153	$ 335
Operating expenses
Research and development	$ 3,056	2,618	10,290	7,654
General and administrative	1,769	2,021	5,930	5,727
Total operating expenses	4,825	4,639	16,220	13,381
Loss from operations	(4,825)	(4,304)	(16,067)	(13,046)
Interest expense		(153)	(186)	(512)
Other income, net	9	5	28	26
Net loss	$ (4,816)	$ (4,452)	$ (16,225)	$ (13,532)
Net loss per share, basic and diluted	$ (0.10)	$ (0.22)	$ (0.42)	$ (0.72)
Weighted average shares of common stock used to compute basic and diluted net loss per share	46,927,221	20,200,893	38,393,842	18,738,118

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (16,225)	$ (13,532)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	175	186
Stock-based compensation	2,358	2,077
Non-cash rent expense		16
Non-cash interest expense	55	135
Non-cash debt issuance expense	3	9
Fair value adjustment on derivative liability	(1)
Changes in operating assets and liabilities:
Accounts receivable	1	(305)
Prepaid expenses and other current assets	(219)	(308)
Accounts payable	910	259
Accrued expenses	347	198
Net cash used in operating activities	(12,596)	(11,265)
Cash flows from investing activities:
Purchases of property and equipment	(8)	(36)
Net cash used in investing activities	(8)	(36)
Cash flows from financing activities:
Proceeds from issuance of common stock and pre-funded warrants, net of issuance costs	16,364	15,170
Proceeds from the exercise of stock options		304
Term loan principal payments	(3,259)	(1,995)
End of term payments	(245)
Net cash provided by financing activities	12,860	13,479
Net increase in cash and cash equivalents	256	2,178
Cash and cash equivalents - beginning of period	3,550	4,182
Cash and cash equivalents - end of period	$ 3,806	6,360
Supplemental disclosures of noncash financing and investing activities
Fixed Asset purchases in accounts payable		$ 21

Organization

Organization	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Pulmatrix, Inc. and its subsidiaries (the “Company”) is a clinical stage biotechnology company focused on the discovery and development of a novel class of inhaled therapeutic products. The Company’s proprietary dry powder delivery platform, iSPERSE™ (inhaled Small Particles Easily Respirable and Emitted), is engineered to deliver small, dense particles with highly efficient dispersibility and delivery to the airways, which can be used with an array of dry powder inhaler technologies and can be formulated with a variety of drug substances. The Company is developing a pipeline of iSPERSE-based therapeutic candidates targeted at prevention and treatment of a range of respiratory diseases and infections with significant unmet medical needs. Liquidity At September 30, 2018, the Company had unrestricted cash and cash equivalents of $3,806, an accumulated deficit of $190,227 and working capital of $1,069. The Company will be required to raise additional capital by the end of 2018 to continue the development and commercialization of current product candidates and to continue to fund operations at the current cash expenditure levels. The Company cannot be certain that additional funding will be available on acceptable terms, or at all. To the extent that the Company raises additional funds by issuing equity securities, the Company’s stockholders may experience significant dilution. Any debt financing, if available, may involve restrictive covenants that impact the Company’s ability to conduct business. If unable to raise additional capital when required or on acceptable terms, the Company may have to (i) delay, scale back or discontinue the development and/or commercialization of one or more product candidates; (ii) seek collaborators for product candidates at an earlier stage than otherwise would be desirable and on terms that are less favorable than might otherwise be available; or (iii) relinquish or otherwise dispose of rights to technologies, product candidates or products that the Company would otherwise seek to develop or commercialize on unfavorable terms. During the nine months ended September 30, 2018, the Company issued 25,879,723 shares of common stock as the result of the sale of 24,647,061 shares of common stock pursuant to an underwritten public offering and the exercise of pre-funded At-the-Market The Company’s ability to continue as a going concern is dependent upon its ability to obtain additional equity or debt financing and, ultimately, to generate revenue. Those factors raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date of filing these condensed consolidated financial statements. The Company’s condensed consolidated financial statements as of September 30, 2018 do not include any adjustments that might become necessary should the Company be unable to continue as a going concern.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	2. 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 (“GAAP”) for interim financial reporting and as required by Regulation S-X, 10-01. 10-K

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies In the three and nine months ended September 30, 2018, there were no changes to the Company’s significant accounting policies identified in the Company’s most recent annual financial statements for the fiscal year ended December 31, 2017, which are included in the Company’s annual report on Form 10-K Recently Issued Accounting Standards In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-13, 2018-13 ASU 2018-13 No. 2018-13 In June 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-07, Compensation — Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting 505-50, Non-Employees, In March 2018, the FASB issued ASU No. 2018-05, “Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118” 2018-05”) Tax Cuts and Jobs Act 2018-05 In February 2018, the FASB issued ASU No. 2018-02, “Income Statement — Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” 2018-02”), 2018-02 In February 2016, the FASB issued authoritative guidance under ASU 2016-02, 2016-02 2016-02, 2016-02 right-of-use 2018-01, 2018-10, 2018-11, In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09”). 2014-09 605-35, Revenue Recognition — Construction-Type and Production-Type Contracts 2014-09 2014-09 2014-09 2014-09 2014-09 2014-09 2014-09 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date 2014-09 2015-14 Use of Estimates In preparing consolidated financial statements in conformity with U.S. GAAP, management is required 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, as well as the reported amounts of expenses during the reporting period. Due to inherent uncertainty involved in making estimates, actual results may differ from these estimates. On an ongoing basis, the Company evaluates its estimates and assumptions. These estimates and assumptions include valuing equity securities in share-based payments, estimating fair value of equity instruments recorded as derivative liabilities, estimating the useful lives of depreciable and amortizable assets, valuation allowance against deferred tax assets, goodwill impairment, and estimating the fair value of long-lived assets to assess whether impairment charges may apply. Revenue Recognition The Company’s principal sources of revenue during the reporting period were reimbursement of clinical study costs. In all instances, revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, and collectability of the resulting receivable is reasonably assured. Goodwill Goodwill represents the difference between the consideration transferred and the fair value of the net assets acquired, and liabilities assumed under the acquisition method of accounting for push-down accounting. Goodwill is not amortized but is evaluated for impairment within the Company’s single reporting unit on an annual basis, during the fourth quarter, or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of the Company’s reporting unit below its carrying amount. When performing the impairment assessment, the accounting standard for testing goodwill for impairment permits a company to first assess the qualitative factors to determine whether the existence of events and circumstances indicates that it is more likely than not that the goodwill is impaired. If the Company believes, as a result of the qualitative assessment, that it is more likely than not that the fair value of goodwill is impaired, the Company must perform a quantitative impairment test. The Company completed a qualitative assessment and determined that there was no impairment of goodwill as of September 30, 2018.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Prepaid Expenses and Other Current Assets	4. Prepaid Expenses and Other Current Assets Prepaid expenses consisted of the following: At September 30, 2018 At December 31, 2017 Prepaid Insurance $ 291 $ 204 Prepaid Clinical Trials 43 421 Prepaid Other 131 44 Deferred Clinical and Operating Costs 449 27 Total prepaid expenses and other current assets $ 914 $ 696

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	5. Debt Loan and Security Agreement and Warrant Agreement On June 11, 2015, Pulmatrix Operating entered into a Loan and Security Agreement (“LSA”) with Hercules Technology Growth Capital, Inc. (“Hercules”), for a term loan in a principal amount of $7,000 (“Term Loan”). The term loan was secured by substantially all of the Company’s assets, excluding intellectual property. Final payments were made in June 2018 and, as of June 30, 2018, the term loan was paid in full. The term loan bore interest at a floating annual rate equal to the greater of (i) 9.50% and (ii) the sum of (a) the prime rate as reported by The Wall Street Journal minus 3.25% plus (b) 8.50%. The Company was required to make interest payments in cash on the first business day of each month, beginning on July 1, 2015. Since August 1, 2016, the Company has been required to make monthly payments on the first business day of each month consisting of principal and interest based upon a 30-month During the term of the loan, the Company could have elected to prepay all, but not less than all, of the outstanding principal balance of the term loan, subject to a prepayment fee of 1% – 3%, depending on the date of repayment. Contingent on the occurrence of several events, including that the Company’s closing stock price exceed $11.73 per share for the seven days preceding a payment date, the Company could have elected to pay, in whole or in part, any regularly scheduled installment of principal up to an aggregate maximum amount of $1,000 by converting a portion of the principal into shares of the Company’s common stock at a price of $11.73 per share. Hercules may have elected to receive payments in the Company common stock by requiring the Company to affect a conversion option whereby Hercules could have elected to receive a principal installment payment in shares of the Company common stock based on a price of $11.73 per share, subject to an aggregate maximum principal amount of $1,000. The Company determined that the Company’s provisions allowing conversion of all or a portion of the LSA contained a beneficial conversion feature (“BCF”). The BCF is contingent upon the occurrence of certain events and as such, the Company will not record the BCF until the contingency is resolved. As the conversion feature was not executed during the life of the LSA, the BCF was not recorded. The credit facility included affirmative and negative covenants. The affirmative covenants include, among others, covenants requiring the Company to maintain its legal existence and governmental approvals deliver certain financial reports and maintain insurance coverage. The negative covenants included, among others, restrictions on transferring collateral, incurring additional indebtedness, engaging in mergers or acquisitions, paying dividends or making other distributions, making investments, creating liens, selling assets, and undergoing a change in control, in each case subject to certain exceptions. In general, the Term Loan prohibited the Company from (i) repurchasing or redeeming any class of capital stock, including common stock or (ii) declaring or paying any cash dividend or making cash distribution on any class of capital stock, including common stock. The LSA included provisions requiring the embedded interest rate reset upon an event of default and the put option upon an event of default or qualified change of control each represent an embedded derivative instrument requiring bifurcation from the loan. The embedded derivatives were bundled and valued as one compound derivative in accordance with the applicable accounting guidance for derivatives and hedging. The fair value of the compound derivative at issuance of $11 was recorded as a derivative liability and as a discount to the debt. The derivative liability is remeasured at fair value at each reporting date, with changes in fair value being recorded as other income (expense) in the statements of operations (Note 10). At September 30, 2018 and December 31, 2017, the fair value of the derivative liability was valued at $0 and $1, respectively. The net debt discounts resulting from the embedded compound derivative and lender fees have been amortized as interest expense from the date of issuance through the maturity date using the effective interest method. The Company incurred interest expense of $0 and $186 during the three and nine months ended September 30, 2018 and $153 and $512 during the three and nine months ended September 30, 2017, respectively. Of the total interest expense, $0 and $131 was payable in cash during the three and nine months ended September 30, 2018 and $112 and $377 was payable in cash during the three and nine months ended September 30, 2017, respectively. The carrying amounts of the Company’s Term Loan as of September 30, 2018 and December 31, 2017 were as follows: Hercules Debt Issuance Total Balance — January 1, 2018 $ 3,259 $ (35 ) $ (3 ) $ 3,221 Accretion of debt discount 35 35 Accretion of issuance costs 3 3 Principal payments (3,259 ) (3,259 ) Balance — September 30, 2018 $ 0 $ 0 $ 0 $ 0

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses consisted of the following: At September 30, 2018 At December 31, 2017 Accrued vacation $ 71 $ 57 Accrued wages and incentive 1,229 1,113 Accrued clinical & consulting 812 568 Accrued legal & patent 93 61 Accrued end of term fee — 225 Deferred Rent 67 68 Accrued other expenses 12 70 Total accrued expenses $ 2,284 $ 2,162

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Common Stock	7. Common Stock Public Offering On April 3, 2018, the Company closed its firm commitment underwritten public offering in which, pursuant to the underwriting agreement (the “Underwriting Agreement”) entered into between the Company and Oppenheimer & Co. Inc., as representative of the underwriters (the “Underwriters”), dated March 28, 2018, the Company issued and sold (i) 15,660,000 common units (“Common Units”), with each Common Unit being comprised of one share of the Company’s common stock, par value $0.0001 per share, one Series A warrant (collectively, the “Series A Warrants”) to purchase one share of common stock and one Series B warrant (collectively, the “Series B Warrants”) to purchase one share of common stock, and (ii) 7,840,000 pre-funded units (the “Pre-Funded Units” each Pre-Funded Unit one pre-funded warrant per Pre-Funded Unit, In addition, on April 4, 2018, the Company closed on the sale of 1,150,000 additional Common Units pursuant to the Underwriters’ option to purchase up to an additional 1,150,000 Units, which were exercised in full. After giving effect to the exercise of the Underwriters’ overallotment option, the gross aggregate proceeds from the offering on April 3 and 4 were $15,944, prior to deducting underwriting discounts and commissions and other estimated offering expenses. All of the pre-funded The Series A Warrants included in the Common Units and the Pre-Funded Units the Pre-Funded Units or Pre-Funded Warrants the Pre-Funded Units, the Pre-Funded Units The Company agreed to pay Oppenheimer a commission of (a) 7% of the gross proceeds raised up to $5,000 and (b) 6.5% of the gross proceeds raised in excess of $5,000. The Company also agreed to pay or reimburse certain expenses on behalf of Oppenheimer. A total of $1,505 of commissions and other issuance costs were associated with the public offering. The net proceeds to the Company from the Offering were approximately $14,517, after deducting the underwriting discounts and commissions and estimated offering expenses payable by the Company. The Company intends to use the net proceeds from the Offering for research and development of its therapeutic candidates, particularly the development of Pulmazole, as well as for working capital and general corporate purposes. At-the-Market On March 17, 2017, the Company entered into an At-The-Market at-the-market S-3, No. 333-212546), BTIG is entitled to compensation at a fixed commission rate of 3.0% of the gross proceeds from the sale of the Company’s common stock pursuant to the Sales Agreement. During the nine month period ended September 30, 2018, the Company sold 1,232,662 shares of its common stock under the Sales Agreement at an average selling price of approximately $1.54 per share which resulted in gross proceeds of approximately $1,904 and net proceeds of approximately $1,847 after payment of 3% commission to BTIG and other issuance costs.

Warrants

Warrants	9 Months Ended
	Sep. 30, 2018
Federal Home Loan Banks [Abstract]
Warrants	8. Warrants A rollforward of the common stock warrants outstanding at September 30, 2018 is as follows. Number of Weighted Weighted Aggregate Outstanding January 1, 2018 3,284,440 $ 7.79 $ — Series A warrants issued 24,650,000 $ 0.65 Series B warrants issued 24,650,000 $ 0.75 Pre-funded 7,840,000 $ 0.65 Pre-funded (7,840,000 ) $ (0.65 ) Outstanding September 30, 2018 52,584,440 $ 1.14 2.22 $ —

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation The Company sponsors the Pulmatrix, Inc. 2013 Employee, Director and Consultant Equity Incentive Plan (the “2013 Plan). As of September 30, 2018, the 2013 Plan provides for the grant of up to 12,500,000 shares of common stock, of which 2,034,088 shares remained available for future grant. In addition, the Company has two legacy plans: The Pulmatrix Operating’s 2013 Employee, Director and Consultant Equity Incentive Plan (the “Original 2013 Plan”) and Pulmatrix Operating’s 2003 Employee, Director, and Consultant Stock Plan (the “2003 Plan”). As of September 30, 2018, a total of 490,790 shares of common stock may be delivered under options outstanding under the Original 2013 Plan and the 2003 Plan, however no additional awards may be granted under the Original 2013 Plan or the 2003 Plan. Options During the three months ended September 30, 2018, the Company granted 34,000 options to employees and no options to directors or consultants. At the date of grant, the fair value of the options awarded to employees was $11. During the nine months ended September 30, 2018 the Company granted 5,966,000 to employees and 775,000 to directors. At the date of the grant, the fair value of the options awarded to employees and directors was $1,895 and $248, respectively. The stock options granted vest over either 36 or 48 months (the “Time Based Options”). Subject to the grantees’ continuous service with the Company and as defined in the grant agreement, Time Based Options vest in one of the following ways: (i) 25% on the first anniversary of the option grant date and the remainder in 36 equal monthly installments beginning in the month after the vesting start date, (ii) 25% on the option grant date and the remainder in 36 equal monthly installments beginning in the month after the vesting start date or (iii) in 48 equal monthly installments beginning on the monthly anniversary of the vesting start date. Stock options generally expire ten years after the date of grant. The following table summarizes stock option activity for the nine months ended September 30, 2018: Number of Weighted- Weighted- Aggregate Outstanding — January 1, 2018 3,695,634 $ 5.69 $ — Granted 6,741,000 $ 0.47 Exercised — $ — Forfeited or expired (23,090 ) $ (2.28 ) Outstanding — September 30, 2018 10,413,544 $ 2.32 8.75 $ — Exercisable — September 30, 2018 4,502,002 $ 3.89 7.94 $ — Vested and expected to vest — September 30, 2018 10,247,905 $ 2.34 8.74 $ — The estimated fair values of employee stock options granted during the three and nine months ended September 30, 2018 and 2017, were determined on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Expected option life (years) 6.05 6.08 5.58 6.13 Risk-free interest rate 2.79 % 2.04 % 2.77 % 2.07 % Expected volatility 78.91 % 75.00 % 79.67 % 77.23 % Expected dividend yield 0 % 0 % 0 % 0 % The risk-free interest rate was obtained from U.S. Treasury rates for the applicable periods. The Company’s expected volatility was based upon the historical volatility for industry peers and used an average of those volatilities. The expected life of the Company’s options was determined using the simplified method as a result of limited historical data regarding the Company’s activity. The dividend yield considers that the Company has not historically paid dividends and does not expect to pay dividends in the foreseeable future. As of September 30, 2018, there was $4,218 of unrecognized stock-based compensation expense related to unvested stock options granted under the Company’s stock award plans. This expense is expected to be recognized over a weighted-average period of approximately 2.0 years. The following table presents total stock-based compensation expense for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Research and development $ 244 $ 184 $ 760 $ 514 General and administrative 416 556 $ 1,598 $ 1,563 Total stock based compensation expense $ 660 $ 740 $ 2,358 $ 2,077 Restricted Stock Units (RSU) In August 2015, the Company granted 10,374 RSUs to other employees that vested over a two year period. The Company recorded no stock-based compensation expense for the RSUs during the three and nine months ended September 30, 2018 and $0 and $13 for the RSUs during the three and nine months ended September 30, 2017, respectively. At September 30, 2018, no RSUs were outstanding.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	10. Fair Value Measurements Information about the liabilities measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017, and the input categories associated with those liabilities, is as follows: September 30, 2018 Fair Value Measurements Using Level 1 Level 2 Level 3 Total Liabilities: Embedded compound derivative $ — $ — $ — $ — December 31, 2017 Fair Value Measurements Using Level 1 Level 2 Level 3 Total Liabilities: Embedded compound derivative $ — $ — $ 1 $ 1 Embedded Compound Derivatives — LSA with Hercules As described in Note 5, the LSA contained an interest rate reset upon an event of default and a put option upon an event of default or qualified change of control. Each of these features represents an embedded derivative instrument requiring bifurcation from the Term Loan. The embedded derivatives were bundled and valued as one compound derivative in accordance with the applicable accounting guidance for derivatives and hedging. The proceeds from the issuance of the Term Loan were allocated first to the warrant and compound derivative at their respective fair values, with the residual going to the carrying amount of the loan resulting in a discount to the face value of the debt. The fair value of the compound derivative upon issuance of $11 was recognized as a derivative liability and was adjusted to fair value at each reporting date. The loan was repaid in its entirety according to its terms and as of September 30, 2018, the derivative liability had a fair value of zero. A roll-forward of the preferred stock warrant liability and derivative liability categorized with Level 3 inputs is as follows: Derivative Instruments Balance — January 1, 2018 $ 1 Change in fair value (1 ) Balance — September 30, 2018 $ — Gains and/or losses arising from changes in the estimated fair value of the warrants and embedded compound derivatives were recorded within other income, net, on the condensed consolidated statement of operations.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net Loss Per Share The Company computes basic and diluted net loss per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class two-class The following potentially dilutive securities outstanding prior to the use of the treasury stock method have been excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive. As of September 30, 2018 2017 Options to purchase common stock 10,413,544 3,336,368 Warrants to purchase common stock 52,584,440 3,284,440 Settlement of term loan — 85,251

Commitments

Commitments	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments	12. Commitments Future minimum lease payments under the non-cancelable Amount 2018 $ 164 2019 676 2020 698 Total $ 1,538

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events The Series A warrants, issued on April 3 and 4, 2018 expired according to their terms, on October 3 and 4, 2018, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Recently Issued Accounting Standards	Recently Issued Accounting Standards In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-13, 2018-13 ASU 2018-13 No. 2018-13 In June 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-07, Compensation — Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting 505-50, Non-Employees, In March 2018, the FASB issued ASU No. 2018-05, “Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118” 2018-05”) Tax Cuts and Jobs Act 2018-05 In February 2018, the FASB issued ASU No. 2018-02, “Income Statement — Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” 2018-02”), 2018-02 In February 2016, the FASB issued authoritative guidance under ASU 2016-02, 2016-02 2016-02, 2016-02 right-of-use 2018-01, 2018-10, 2018-11, In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09”). 2014-09 605-35, Revenue Recognition — Construction-Type and Production-Type Contracts 2014-09 2014-09 2014-09 2014-09 2014-09 2014-09 2014-09 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date 2014-09 2015-14
Use of Estimates	Use of Estimates In preparing consolidated financial statements in conformity with U.S. GAAP, management is required 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, as well as the reported amounts of expenses during the reporting period. Due to inherent uncertainty involved in making estimates, actual results may differ from these estimates. On an ongoing basis, the Company evaluates its estimates and assumptions. These estimates and assumptions include valuing equity securities in share-based payments, estimating fair value of equity instruments recorded as derivative liabilities, estimating the useful lives of depreciable and amortizable assets, valuation allowance against deferred tax assets, goodwill impairment, and estimating the fair value of long-lived assets to assess whether impairment charges may apply.
Revenue Recognition	Revenue Recognition The Company’s principal sources of revenue during the reporting period were reimbursement of clinical study costs. In all instances, revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, and collectability of the resulting receivable is reasonably assured.
Goodwill	Goodwill Goodwill represents the difference between the consideration transferred and the fair value of the net assets acquired, and liabilities assumed under the acquisition method of accounting for push-down accounting. Goodwill is not amortized but is evaluated for impairment within the Company’s single reporting unit on an annual basis, during the fourth quarter, or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of the Company’s reporting unit below its carrying amount. When performing the impairment assessment, the accounting standard for testing goodwill for impairment permits a company to first assess the qualitative factors to determine whether the existence of events and circumstances indicates that it is more likely than not that the goodwill is impaired. If the Company believes, as a result of the qualitative assessment, that it is more likely than not that the fair value of goodwill is impaired, the Company must perform a quantitative impairment test. The Company completed a qualitative assessment and determined that there was no impairment of goodwill as of September 30, 2018.

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Text Block [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses consisted of the following: At September 30, 2018 At December 31, 2017 Prepaid Insurance $ 291 $ 204 Prepaid Clinical Trials 43 421 Prepaid Other 131 44 Deferred Clinical and Operating Costs 449 27 Total prepaid expenses and other current assets $ 914 $ 696

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Summary of Carrying Amount of Company's Notes	The carrying amounts of the Company’s Term Loan as of September 30, 2018 and December 31, 2017 were as follows: Hercules Debt Issuance Total Balance — January 1, 2018 $ 3,259 $ (35 ) $ (3 ) $ 3,221 Accretion of debt discount 35 35 Accretion of issuance costs 3 3 Principal payments (3,259 ) (3,259 ) Balance — September 30, 2018 $ 0 $ 0 $ 0 $ 0

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following: At September 30, 2018 At December 31, 2017 Accrued vacation $ 71 $ 57 Accrued wages and incentive 1,229 1,113 Accrued clinical & consulting 812 568 Accrued legal & patent 93 61 Accrued end of term fee — 225 Deferred Rent 67 68 Accrued other expenses 12 70 Total accrued expenses $ 2,284 $ 2,162

Warrants (Tables)

Warrants (Tables)	9 Months Ended
	Sep. 30, 2018
Federal Home Loan Banks [Abstract]
Summary of Common Stock Warrants Outstanding	A rollforward of the common stock warrants outstanding at September 30, 2018 is as follows. Number of Weighted Weighted Aggregate Outstanding January 1, 2018 3,284,440 $ 7.79 $ — Series A warrants issued 24,650,000 $ 0.65 Series B warrants issued 24,650,000 $ 0.75 Pre-funded 7,840,000 $ 0.65 Pre-funded (7,840,000 ) $ (0.65 ) Outstanding September 30, 2018 52,584,440 $ 1.14 2.22 $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2018: Number of Weighted- Weighted- Aggregate Outstanding — January 1, 2018 3,695,634 $ 5.69 $ — Granted 6,741,000 $ 0.47 Exercised — $ — Forfeited or expired (23,090 ) $ (2.28 ) Outstanding — September 30, 2018 10,413,544 $ 2.32 8.75 $ — Exercisable — September 30, 2018 4,502,002 $ 3.89 7.94 $ — Vested and expected to vest — September 30, 2018 10,247,905 $ 2.34 8.74 $ —
Calculation of Fair Value Assumptions Using Black Scholes Option Model	The estimated fair values of employee stock options granted during the three and nine months ended September 30, 2018 and 2017, were determined on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Expected option life (years) 6.05 6.08 5.58 6.13 Risk-free interest rate 2.79 % 2.04 % 2.77 % 2.07 % Expected volatility 78.91 % 75.00 % 79.67 % 77.23 % Expected dividend yield 0 % 0 % 0 % 0 %
Stock-Based Compensation Expense	The following table presents total stock-based compensation expense for the three and nine months ended September 30, 2018 and 2017: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Research and development $ 244 $ 184 $ 760 $ 514 General and administrative 416 556 $ 1,598 $ 1,563 Total stock based compensation expense $ 660 $ 740 $ 2,358 $ 2,077

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Liabilities Measured at Fair Value on a Recurring Basis	Information about the liabilities measured at fair value on a recurring basis as of September 30, 2018 and December 31, 2017, and the input categories associated with those liabilities, is as follows: September 30, 2018 Fair Value Measurements Using Level 1 Level 2 Level 3 Total Liabilities: Embedded compound derivative $ — $ — $ — $ — December 31, 2017 Fair Value Measurements Using Level 1 Level 2 Level 3 Total Liabilities: Embedded compound derivative $ — $ — $ 1 $ 1
Schedule of Preferred Stock Warrant Liability and Derivative Liability Categorized with Level 3	A roll-forward of the preferred stock warrant liability and derivative liability categorized with Level 3 inputs is as follows: Derivative Instruments Balance — January 1, 2018 $ 1 Change in fair value (1 ) Balance — September 30, 2018 $ —

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Computation of Diluted Weighted-Average Shares Outstanding Anti-Dilutive	The following potentially dilutive securities outstanding prior to the use of the treasury stock method have been excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive. As of September 30, 2018 2017 Options to purchase common stock 10,413,544 3,336,368 Warrants to purchase common stock 52,584,440 3,284,440 Settlement of term loan — 85,251

Commitments (Tables)

Commitments (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments under the Non-Cancelable Operating Lease for Office and Lab Space	Future minimum lease payments under the non-cancelable Amount 2018 $ 164 2019 676 2020 698 Total $ 1,538

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Organization And Basis Of Presentation [Line Items]
Accumulated deficit	$ (190,227)	$ (174,002)
Unrestricted cash and cash equivalents	3,806	$ 3,550
Working capital deficit	1,069
BTIG LLC [Member]
Organization And Basis Of Presentation [Line Items]
Proceeds from sale of common stock	$ 16,364
BTIG LLC [Member] | Underwritten Public Offering [Member] | Prefunded Warrants [Member]
Organization And Basis Of Presentation [Line Items]
Sale of stock, number of shares sold in transaction	24,647,061
Common stock shares issued	25,879,723
BTIG LLC [Member] | At the Market Offering [Member]
Organization And Basis Of Presentation [Line Items]
Sale of stock, number of shares sold in transaction	1,232,662
Proceeds from sale of common stock	$ 1,847

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Impairment of goodwill	$ 0

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Insurance	$ 291	$ 204
Prepaid Clinical Trials	43	421
Prepaid Other	131	44
Deferred Clinical and Operating Costs	449	27
Total prepaid expenses and other current assets	$ 914	$ 696

Debt - Loan and Security Agreem

Debt - Loan and Security Agreement and Warrant Agreement - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)d$ / shares	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2015USD ($)	Jun. 11, 2015USD ($)
Debt Instrument [Line Items]
Fair value of warrant derivative liabilities at issuance, recorded as debt discount			$ 0		$ 1,000	$ 11,000
Hercules Loan and Security Agreement [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Term loan principal amount							$ 7,000,000
Debt instrument basis spread			8.50%
Basis of debt instrument interest rate			The prime rate as reported by The Wall Street Journal minus 3.25% plus (b) 8.50%.
Debt instrument payment terms			The Company has been required to make monthly payments on the first business day of each month consisting of principal and interest based upon a 30-month amortization schedule
Debt instrument periodic payment frequency			30-month amortization schedule
Repayment charges			$ 245,000
Debt prepayment penalty			0
Liabilites to Hercules	$ 0		$ 0
Percentage of prepayment fee	1.00%		1.00%
Percentage of prepayment fee	3.00%		3.00%
Maximum principal amount available for conversion into common shares	$ 1,000,000		$ 1,000,000
Debt instrument, convertible, stock price trigger | $ / shares			$ 11.73
Debt instrument, convertible, threshold trading days | d			7
Interest expense	0	$ 153,000	$ 186,000	$ 512,000
Interest expense payable in cash	$ 0	$ 112,000	$ 131,000	$ 377,000
Hercules Loan and Security Agreement [Member] | Term Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Floating annual rate	9.50%		9.50%
Hercules Loan and Security Agreement [Member] | Term Loan [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Debt instrument basis spread			3.25%

Debt - Summary of Carrying Amou

Debt - Summary of Carrying Amount of Company's Notes (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Short And Long Term Debt [Line Items]
Beginning balance	$ (35)
Accretion of debt discount	35
Accretion of issuance costs, debt discount	0
Ending balance	0
Beginning balance	(3)
Accretion of issuance costs, issuance costs	3
Ending balance	0
Beginning balance	3,221
Accretion of debt discount	35
Accretion of issuance costs	3
Principal payments	(3,259)
Ending balance	0
Hercules Term Loan [Member]
Short And Long Term Debt [Line Items]
Beginning balance	3,259
Accretion of issuance costs	0
Principal payments	(3,259)
Ending balance	$ 0

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued vacation	$ 71	$ 57
Accrued wages and incentive	1,229	1,113
Accrued clinical & consulting	812	568
Accrued legal & patent	93	61
Accrued end of term fee		225
Deferred Rent	67	68
Accrued other expenses	12	70
Total accrued expenses	$ 2,284	$ 2,162

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - USD ($)	Apr. 04, 2018	Apr. 03, 2018	Apr. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Mar. 17, 2017
Temporary Equity [Line Items]
Common stock, par value				$ 0.0001	$ 0.0001
Common Units [Member]
Temporary Equity [Line Items]
Proceeds from sale of common stock	$ 15,944,000
Underwriting Agreement [Member]
Temporary Equity [Line Items]
Payment of commissions and other issuance costs				$ 1,505,000
Proceeds from sale of common stock				$ 14,517,000
Underwriting Agreement [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Warrants exercisable price				$ 0.65
Underwriting Agreement [Member] | Series B Warrants [Member]
Temporary Equity [Line Items]
Warrants exercisable price				$ 0.75
Warrants expiration period				5 years
Underwriting Agreement [Member] | Common Units [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Warrants expired date				Oct. 3, 2018
Underwriting Agreement [Member] | Pre-funded Units [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Warrants expired date				Oct. 4, 2018
Underwriting Agreement [Member] | Common Units [Member]
Temporary Equity [Line Items]
Number of shares issued and sold		15,660,000
Average selling price of common stock		$ 0.65
Proceeds from sale of common stock		$ 15,197,000
Underwriting Agreement [Member] | Common Units [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Number of shares		1
Underwriting Agreement [Member] | Common Units [Member] | Series B Warrants [Member]
Temporary Equity [Line Items]
Number of shares		1
Underwriting Agreement [Member] | Common Units [Member] | Common Stock [Member]
Temporary Equity [Line Items]
Number of shares		1
Common stock, par value		$ 0.0001
Underwriting Agreement [Member] | Common Units [Member] | Common Stock [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Number of shares called by each warrant		1
Underwriting Agreement [Member] | Common Units [Member] | Common Stock [Member] | Series B Warrants [Member]
Temporary Equity [Line Items]
Number of shares called by each warrant		1
Underwriting Agreement [Member] | Pre-funded Units [Member]
Temporary Equity [Line Items]
Number of shares issued and sold		7,840,000
Average selling price of common stock		$ 0.64
Underwriting Agreement [Member] | Pre-funded Units [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Number of shares		1
Underwriting Agreement [Member] | Pre-funded Units [Member] | Series B Warrants [Member]
Temporary Equity [Line Items]
Number of shares		1
Underwriting Agreement [Member] | Pre-funded Units [Member] | Common Stock [Member] | Series A Warrants [Member]
Temporary Equity [Line Items]
Number of shares called by each warrant		1
Underwriting Agreement [Member] | Pre-funded Units [Member] | Common Stock [Member] | Series B Warrants [Member]
Temporary Equity [Line Items]
Number of shares called by each warrant		1
Underwriting Agreement [Member] | Prefunded Warrants [Member]
Temporary Equity [Line Items]
Number of warrants exercised			150,000
Issuance of common stock shares			7,837,061
Gross proceeds from sale of shares			$ 78,000
Gross Proceeds up to Five Thousand [Member] | Underwriting Agreement [Member]
Temporary Equity [Line Items]
Commission rate on sale of stock				7.00%
Gross Proceeds in excess of Five Thousand [Member] | Underwriting Agreement [Member]
Temporary Equity [Line Items]
Commission rate on sale of stock				6.50%
Maximum [Member] | Underwriting Agreement [Member]
Temporary Equity [Line Items]
Gross proceeds from sale of shares				$ 5,000,000
Minimum [Member] | Underwriting Agreement [Member]
Temporary Equity [Line Items]
Gross proceeds from sale of shares				5,000,000
BTIG LLC [Member]
Temporary Equity [Line Items]
Proceeds from sale of common stock				$ 16,364,000
At the Market Offering [Member] | BTIG LLC [Member]
Temporary Equity [Line Items]
Average selling price of common stock				$ 1.54
Gross proceeds from sale of shares				$ 1,904,000
Proceeds from sale of common stock				$ 1,847,000
Fixed commission rate entitled to placement agent				3.00%
Sale of stock, number of shares sold in transaction				1,232,662
At the Market Offering [Member] | BTIG LLC [Member] | Maximum [Member]
Temporary Equity [Line Items]
Aggregate offering on sale of common stock						$ 11,000,000
Over-Allotment Option [Member] | Common Units [Member]
Temporary Equity [Line Items]
Number of shares issued and sold	1,150,000

Warrants - Summary of Common St

Warrants - Summary of Common Stock Warrants Outstanding (Detail) - Warrant [Member]	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Class of Warrant or Right [Line Items]
Number of warrants, Outstanding, Beginning balance | shares	3,284,440
Number of warrants, Outstanding, Ending balance | shares	52,584,440
Weighted average exercise price, Beginning balance | $ / shares	$ 7.79
Weighted average exercise price, Ending balance | $ / shares	$ 1.14
Weighted average remaining contractual term, Ending balance	2 years 2 months 19 days
Aggregate intrinsic value, Beginning balance | $	$ 0
Aggregate intrinsic value, Ending balance | $	$ 0
Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Number of warrants, issued | shares	24,650,000
Weighted average exercise price, Warrants issued | $ / shares	$ 0.65
Aggregate intrinsic value, Warrants issued | $	$ 0
Series B Warrants [Member]
Class of Warrant or Right [Line Items]
Number of warrants, issued | shares	24,650,000
Weighted average exercise price, Warrants issued | $ / shares	$ 0.75
Aggregate intrinsic value, Warrants issued | $	$ 0
Pre Funded Warrants1 [Member]
Class of Warrant or Right [Line Items]
Number of warrants, issued | shares	7,840,000
Weighted average exercise price, Warrants issued | $ / shares	$ 0.65
Aggregate intrinsic value, Warrants issued | $	$ 0
Pre Funded Warrants2 [Member]
Class of Warrant or Right [Line Items]
Number of warrants, exercised | shares	(7,840,000)
Weighted average exercise price, Warrants exercised | $ / shares	$ (0.65)
Aggregate intrinsic value, Warrants exercised | $	$ 0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2015shares	Sep. 30, 2018USD ($)shares	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)Installmentshares	Sep. 30, 2017USD ($)	Dec. 31, 2017shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding		10,413,544		10,413,544		3,695,634
Number of options to purchase common stock, Granted				6,741,000
Unrecognized stock-based compensation expenses | $		$ 4,218,000		$ 4,218,000
Unrecognized stock-based compensation expense, period for recognition				2 years
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period				10 years
Employee Stock Option [Member] | Time Based Options Vesting 48 Month [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				48 months
Award vesting percentage				25.00%
Number of equal vesting installments | Installment				36
Award vesting term				25% on the option grant date and the remainder in 36 equal monthly installments beginning in the month after the vesting start date
Employee Stock Option [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options to purchase common stock, Granted		34,000		5,966,000
Aggregate weighted average amount of fair value of options | $		$ 11,000		$ 1,895,000
Employee Stock Option [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options to purchase common stock, Granted		0		775,000
Aggregate weighted average amount of fair value of options | $				$ 248,000
Award expiration period				10 years
Employee Stock Option [Member] | Director [Member] | Time Based Options Vesting 24 Month [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				36 months
Employee Stock Option [Member] | Director [Member] | Time Based Options vesting Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				48 months
Employee Stock Option [Member] | Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options to purchase common stock, Granted		0
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, outstanding		0		0
Restricted Stock Units [Member] | Other Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	2 years
Restricted stock units, granted	10,374
Stock-based compensation | $		$ 0	$ 0	$ 0	$ 13,000
2013 Employee, Director and Consultant Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate shares of Common Stock that may be delivered under options outstanding		12,500,000		12,500,000
Shares available for future grant		2,034,088		2,034,088
Legacy Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate shares of Common Stock that may be delivered under options outstanding		0		0
Shares outstanding		490,790		490,790
Number of legacy stock-based compensation plans				2

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Outstanding beginning balance	3,695,634
Number of options, Granted	6,741,000
Number of options, Exercised	0
Number of options, Forfeited or expired	(23,090)
Number of options, Outstanding ending balance	10,413,544
Number of options, Exercisable	4,502,002
Number of options, Vested and expected to vest	10,247,905
Weighted average exercise price, Outstanding beginning balance	$ 5.69
Weighted average exercise price, Granted	0.47
Weighted average exercise price, Exercised	0
Weighted average exercise price, Forfeited or expired	(2.28)
Weighted average exercise price, Outstanding ending balance	2.32
Weighted average exercise price, Exercisable	3.89
Weighted average exercise price, Vested and expected to vest	$ 2.34
Weighted average remaining contractual term, Outstanding ending balance	8 years 9 months
Weighted average remaining contractual term, Exercisable	7 years 11 months 8 days
Weighted average remaining contractual term, Vested and expected to vest	8 years 8 months 26 days
Aggregate intrinsic value, Outstanding	$ 0
Aggregate intrinsic value, Exercised	$ 0
Aggregate intrinsic value, Forfeited or expired	$ 0
Aggregate intrinsic value, Outstanding	$ 0
Aggregate intrinsic value, Exercisable	0
Aggregate intrinsic value, Vested and expected to vest	$ 0

Stock-Based Compensation - Esti

Stock-Based Compensation - Estimated Fair Values of Employee Stock Options Granted (Detail) - Employee Stock Option [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life (years)	6 years 18 days	6 years 29 days	5 years 6 months 29 days	6 years 1 month 17 days
Risk-free interest rate	2.79%	2.04%	2.77%	2.07%
Expected volatility	78.91%	75.00%	79.67%	77.23%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$ 660	$ 740	$ 2,358	$ 2,077
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	244	184	760	514
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$ 416	$ 556	$ 1,598	$ 1,563

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - Preferred Stock Warrants [Member] $ in Thousands	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Derivative liability	$ 1
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Derivative liability	$ 1

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - Fair Value, Measurements, Recurring [Member] - Level 3 [Member] - Embedded Compound Derivative [Member] $ in Thousands	Sep. 30, 2018USD ($)
Fair Value Assets Liabilities Quantitative Information [Line Items]
Derivative liability	$ 11
Fair value of derivative liability	$ 0

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Preferred Stock Warrant Liability and Derivative Liability Categorized with Level 3 (Detail) - Derivative Instruments [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1
Change in fair value	$ (1)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Computation of Diluted Weighted-Average Shares Outstanding Anti-Dilutive (Detail) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Term Loan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share		85,251
Warrants To Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	52,584,440	3,284,440
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	10,413,544	3,336,368

Commitments - Schedule of Futur

Commitments - Schedule of Future Minimum Lease Payments under the Non-Cancelable Operating Lease for Office and Lab Space (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 164
2,019	676
2,020	698
Total	$ 1,538