Zosano Pharma (ZSANQ) 10-Q 14 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 08, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Registrant Name	Zosano Pharma Corp
Entity Central Index Key	0001587221
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	true
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		17,723,039

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 14,252	$ 9,140
Marketable securities at fair value	3,488	13,862
Prepaid expenses and other current assets	991	358
Total current assets	18,731	23,360
Restricted cash	455	455
Property and equipment, net	20,568	11,916
Operating lease right-of-use assets	6,016
Other long-term assets	17	49
Total assets	45,787	35,780
Current liabilities:
Accounts payable	5,985	4,450
Accrued compensation	1,459	2,092
Build-to-suit obligation, current portion	3,147	2,326
Operating lease liabilities, current portion	1,026
Other accrued liabilities	3,678	2,419
Total current liabilities	15,295	11,287
Build-to-suit obligation, long-term portion, net of debt issuance costs and discount	5,091	4,478
Operating lease liabilities, long-term portion	6,369
Other liabilities	25	18
Deferred rent	0	1,287
Total liabilities	26,780	17,070
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; none issued and outstanding as of June 30, 2019 and December 31, 2018	0	0
Common stock, $0.0001 par value; 250,000,000 shares authorized; 17,723,039 and 11,973,039 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	2	1
Additional paid-in capital	299,023	279,946
Accumulated deficit	(280,018)	(261,232)
Accumulated other comprehensive loss	0	(5)
Total stockholders’ equity	19,007	18,710
Total liabilities and stockholders’ equity	$ 45,787	$ 35,780

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	17,723,039	11,973,039
Common stock, shares outstanding (in shares)	17,723,039	11,973,039

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses
Research and development	6,640	6,533	13,256	12,339
General and administrative	2,767	2,272	5,638	4,532
Total operating expenses	9,407	8,805	18,894	16,871
Loss from operations	(9,407)	(8,805)	(18,894)	(16,871)
Other income (expense)
Interest income	82	79	162	94
Interest expense	(35)	(112)	(76)	(268)
Other income, net	0	2	22	3
Loss before provision for income taxes	(9,360)	(8,836)	(18,786)	(17,042)
Provision for income taxes	0	0	0	0
Net loss	(9,360)	(8,836)	(18,786)	(17,042)
Unrealized gain (loss) on marketable securities, net of tax	(1)	0	5	0
Comprehensive loss	$ (9,361)	$ (8,836)	$ (18,781)	$ (17,042)
Net loss per common share – basic and diluted (in USD per share)	$ (0.55)	$ (0.75)	$ (1.30)	$ (2.47)
Weighted-average shares used in computing net loss per common share – basic and diluted (in shares)	16,868,643	11,753,259	14,434,365	6,890,166

Condensed Statement of Changes

Condensed Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		1,973,039
Beginning balance at Dec. 31, 2017	$ 7,048	$ 0	$ 232,922	$ (225,874)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	139		139
Net loss	(8,206)			(8,206)
Beginning balance (in shares) at Mar. 31, 2018		1,973,039
Beginning balance at Mar. 31, 2018	(1,019)	$ 0	233,061	(234,080)	0
Beginning balance (in shares) at Dec. 31, 2017		1,973,039
Beginning balance at Dec. 31, 2017	7,048	$ 0	232,922	(225,874)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on marketable securities	0
Net loss	(17,042)
Beginning balance (in shares) at Jun. 30, 2018		11,973,039
Beginning balance at Jun. 30, 2018	36,080	$ 1	278,995	(242,916)	0
Beginning balance (in shares) at Mar. 31, 2018		1,973,039
Beginning balance at Mar. 31, 2018	(1,019)	$ 0	233,061	(234,080)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with public offering (in shares)		10,000,000
Issuance of common stock in connection with public offering	45,605	$ 1	45,604
Stock-based compensation	330		330
Unrealized loss on marketable securities	0
Net loss	(8,836)			(8,836)
Beginning balance (in shares) at Jun. 30, 2018		11,973,039
Beginning balance at Jun. 30, 2018	$ 36,080	$ 1	278,995	(242,916)	0
Beginning balance (in shares) at Dec. 31, 2018	11,973,039	11,973,039
Beginning balance at Dec. 31, 2018	$ 18,710	$ 1	279,946	(261,232)	(5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	361		361
Unrealized loss on marketable securities	6				6
Net loss	(9,426)			(9,426)
Beginning balance (in shares) at Mar. 31, 2019		11,973,039
Beginning balance at Mar. 31, 2019	$ 9,651	$ 1	280,307	(270,658)	1
Beginning balance (in shares) at Dec. 31, 2018	11,973,039	11,973,039
Beginning balance at Dec. 31, 2018	$ 18,710	$ 1	279,946	(261,232)	(5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on marketable securities	5
Net loss	$ (18,786)
Beginning balance (in shares) at Jun. 30, 2019	17,723,039	17,723,039
Beginning balance at Jun. 30, 2019	$ 19,007	$ 2	299,023	(280,018)	0
Beginning balance (in shares) at Mar. 31, 2019		11,973,039
Beginning balance at Mar. 31, 2019	9,651	$ 1	280,307	(270,658)	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with public offering (in shares)		5,750,000
Issuance of common stock in connection with public offering	18,331	$ 1	18,330
Stock-based compensation	386		386
Unrealized loss on marketable securities	(1)				(1)
Net loss	$ (9,360)			(9,360)
Beginning balance (in shares) at Jun. 30, 2019	17,723,039	17,723,039
Beginning balance at Jun. 30, 2019	$ 19,007	$ 2	$ 299,023	$ (280,018)	$ 0

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net loss	$ (18,786)	$ (17,042)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	747	469
Amortization of operating lease right-of-use assets	399
Depreciation	361	391
Deferred rent	0	515
Other	42	45
Change in operating assets and liabilities
Prepaid expenses and other assets	(657)	635
Accounts payable	635	615
Accrued compensation and other accrued liabilities	(904)	(21)
Operating lease liabilities	(451)
Net cash used in operating activities	(18,614)	(14,393)
Cash flows from investing activities
Proceeds from maturities of marketable securities	13,900	16,000
Purchases of marketable securities	(3,476)	(37,475)
Purchases of property and equipment	(6,213)	(2,106)
Net cash provided by (used in) investing activities	4,211	(23,581)
Cash flows used in financing activities
Proceeds from public offering of securities, net of underwriting commissions and offering costs	18,472	45,603
Proceeds from build-to-suit obligation, net of issuance costs	2,277	0
Principal payments on financing obligations	(1,234)	(3,083)
Net cash provided by financing activities	19,515	42,520
Net increase in cash, cash equivalents and restricted cash	5,112	4,546
Cash, cash equivalents and restricted cash at beginning of period	9,595	11,686
Cash, cash equivalents and restricted cash at end of period	14,707	16,232
Supplemental cash flow information
Cash paid for interest	365	203
Cash paid for taxes	1	0
Non-cash investing and financing activities
Total	851
Acquisition of property and equipment under accounts payable and other accrued liabilities	5,795	264
Accrued offering costs	142	98
Right-of-use assets acquired under finance lease obligations	$ 22	$ 0

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation The Company Zosano Pharma Corporation (the “Company”) is a clinical stage biopharmaceutical company focused on providing rapid systemic administration of therapeutics to patients using its proprietary Adhesive Dermally-Applied Microarray, or ADAM™, technology. Basis of Presentation The condensed financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) for interim financial information, the instructions to Form 10-Q and Regulation S-X. They do not include all the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 , or any other subsequent period. These financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2018 , included in the Company’s annual report on Form 10-K and filed with the United States Securities and Exchange Commission (“SEC”) on March 25, 2019. Use of Estimates The preparation of the accompanying condensed financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the condensed financial statements, and the reported amounts of expenses during the periods reported. Actual results could differ from those estimates. Liquidity and Substantial Doubt in Going Concern Since inception, the Company has incurred recurring operating losses and negative cash flows from operating activities, and as of June 30, 2019 , had an accumulated deficit of $280.0 million . As of June 30, 2019 , the Company had approximately $17.7 million in cash, cash equivalents and marketable securities. Presently, the Company does not have sufficient cash, cash equivalents and marketable securities to enable it to fund its anticipated level of operations and meet its obligations as they become due within twelve months following the date of issuance of this Quarterly Report on Form 10-Q. The aforementioned factors raise substantial doubt about the Company’s ability to continue as a going concern for a period of one year from the issuance of these financial statements. The financial statements do not include any adjustments that might result from the outcome of this uncertainty. On April 11, 2019, the Company closed a public offering of 5,000,000 shares of common stock at a price to the underwriter of $3.29 per share. On May 8, 2019, the underwriter purchased an additional 750,000 shares at a price to the underwriter of $3.29 per share pursuant to the exercise of the underwriter's option to purchase additional shares. The aggregate net proceeds were approximately $18.3 million , after deducting underwriting costs and estimated offering expenses. The Company plans to raise additional funding through financing, a capital offering, a license or collaboration agreement or a combination of such sources of capital. However, there are no assurances that additional funding will be achieved and that the Company will succeed in its future operations. The Company’s inability to obtain required funding in the near future or its inability to obtain funding on favorable terms will have a material adverse effect on its operations and strategic development plan for future growth. If the Company cannot successfully raise additional capital and implement its strategic development plan, its liquidity, financial condition and business prospects will be materially and adversely affected, and it may have to cease operations. The Company will continue to evaluate its timelines, strategic needs, and working capital requirements. There can be no assurance that if the Company attempts to raise additional capital, it will be successful in doing so on terms acceptable to the Company, or at all. Further, there can be no assurance that it will be able to gain access and/or be able to execute on securing new sources of funding, new development opportunities, successfully obtain regulatory approvals for and commercialize new products, achieve significant product revenues from its products (if approved), or achieve or sustain profitability in the future.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Significant Accounting Policies The Company’s significant accounting policies are included in “Part II - Item 8 - Financial Statements and Supplementary Data - Note 2 - Summary of Significant Accounting Policies” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 . As discussed in the Company's Annual Report, the Company adopted the new leases standard in the first quarter of 2019. In the second quarter of 2019, the Company made an accounting policy election to recognize the impact of stock option forfeitures on stock compensation expense in the period the award is forfeited as permitted under ASC2016-09, Compensation-Stock Compensation (Topic 718) . Previously, the Company estimated the effects of stock option forfeitures at the initial grant date and reduced stock compensation expense for the estimated effect of forfeitures over the requisite service period. There have been no other changes to the Company's significant accounting policies. Leases ASC Topic 842, Leases , requires lessees to recognize right-of-use assets and lease liabilities for most leases on the balance sheet and to provide expanded disclosures about leasing arrangements. The Company adopted Topic 842 effective January 1, 2019 using the optional transition method and did not restate comparative periods. There was no effect on accumulated deficit at adoption. The Company has elected the package of practical expedients to (i) not reassess whether expired or existing contracts are or contain leases, (ii) not reassess the lease classification for any expired or existing leases and (iii) not reassess the accounting for initial direct costs. The adoption of the new leases standard resulted in the following adjustments to the Company's balance sheet as of January 1, 2019: December 31, 2018 Adoption Impact January 1, 2019 (in thousands) (unaudited; in thousands) Operating lease right-of-use assets $ — $ 6,415 $ 6,415 Operating lease liabilities, current portion $ — $ 945 $ 945 Other accrued liabilities $ 2,414 $ (143 ) $ 2,271 Operating lease liabilities, long-term portion $ — $ 6,900 $ 6,900 Deferred rent $ 1,287 $ (1,287 ) $ — As of December 31, 2018 , the short-term portion of deferred rent was recorded in other accrued liabilities. The adoption impact was a non-cash operating activity for the six months ended June 30, 2019. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. If the interest rate implicit in the Company's lease contracts is not readily determinable, the Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments with an original maturity of 90 days or less to be cash equivalents. As of June 30, 2019 and December 31, 2018 , the Company had restricted cash of approximately $0.5 million consisting of deposits of $0.3 million to secure its building lease until the end of the lease term, a deposit of approximately $0.1 million to a utility provider and $35,000 to secure corporate purchasing cards. The following table provides a reconciliation of cash, cash equivalents and restricted cash to amounts shown in the statement of cash flows: June 30, 2019 June 30, 2018 (unaudited; in thousands) Cash and cash equivalents $ 14,252 $ 16,197 Restricted cash 455 35 Total $ 14,707 $ 16,232 Marketable Securities Marketable securities generally consist of debt securities with original maturities greater than 90 days and remaining maturities of less than one year. Marketable securities with an original maturity greater than one year, if any, would be considered long-term investments. All of the Company's investments are classified as available-for-sale and carried at fair value based upon quoted market price. The change in unrealized gains and losses related to fixed maturity debt securities is reported as a separate component of other comprehensive income (loss) on the statements of operations and comprehensive loss and as a separate component of stockholders' equity on the balance sheets. Interest income includes interest, dividends, amortization and accretion of purchase premiums and discounts and realized gains and losses on sales of securities, if any. The cost of securities sold is based on the specific-identification method. The Company monitors its investment portfolio for potential impairment on a quarterly basis. If the carrying amount of an investment in marketable securities exceeds its fair value and the decline in value is determined to be other-than-temporary, the carrying amount of the security is reduced to fair value and a loss is recognized in operating results for the amount of such decline. In order to determine whether a decline in value is other-than-temporary, the Company evaluates, among other factors, the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, and its intent and ability to hold the security to maturity or expected recovery. Fair Value Instruments The Company records its financial assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: • Level 1: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level 2: Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • 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. The carrying values of certain assets and liabilities of the Company, such as cash and cash equivalents and accounts payable approximate fair value due to their relatively short maturities. The carrying value of the Company’s short-term financial obligations approximates their fair value as the terms of the borrowing are consistent with current market rates and the duration to maturity is short. The carrying value of the Company's long-term financial obligations approximates fair value because interest rates approximate market rates that the Company could obtain for debt with similar terms and maturities. Net Loss Per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per common share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, common stock warrants and stock options are considered to be potential dilutive securities but are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented. The following outstanding common stock equivalents were excluded from the computations of diluted net loss per common share for the periods presented as the effect of including such securities would be antidilutive: June 30, 2019 June 30, 2018 (unaudited) Warrants to purchase common stock 274,524 199,524 Options to purchase common stock 1,765,742 1,186,318 Total 2,040,266 1,385,842 Recent Accounting Pronouncements In August 2018, the Financial Accounting Standards Board ("FASB") issued ASU2018-15, Intangible - Goodwill and Other - Internal-Use Software (Subtopic 350-40) , which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU2018-15 is effective for the Company in the first quarter of 2020. Early adoption is permitted. ASU2018-15 permits either a prospective or retrospective transition approach. The Company is currently evaluating ASU2018-15 to determine the impact to its financial statements and disclosures. In August 2018, the FASB issued ASU2018-13, Fair Value Measurement (Topic 820) . The new guidance modifies the disclosure requirements on fair value measurements. ASU2018-13 is effective for the Company beginning in the first quarter of 2020 and must be adopted on a modified retrospective basis, with certain exceptions. Early adoption is permitted. The Company does not expect ASU2018-13 to have a significant impact to its financial statements and disclosures. The FASB issued ASU2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments in June 2016 , ASU2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses in November 2018 , and ASU2019-05, Financial Instruments - Credit Losses, Targeted Transition Relief in May 2019. This new guidance is intended to present credit losses on available-for-sale debt securities as an allowance rather than as a write-down. Entities are required to apply the standards' provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. ASU2016-13, ASU2018-19 and ASU2019-05 are effective for the Company in the first quarter of 2020. The Company is currently evaluating these standards to determine the impact to its financial statements and disclosures.

Cash Equivalents and Investment

Cash Equivalents and Investments in Marketable Securities	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Investments in Marketable Securities	Cash Equivalents and Investments in Marketable Securities The following tables present summaries of the Company's cash equivalents and investments in marketable securities measured at fair value on a recurring basis: Fair Value Measurements Total Quoted prices Significant Significant (unaudited; in thousands) As of June 30, 2019: Money market funds $ 9,111 $ 9,111 $ — $ — Commercial paper 3,803 — 3,803 — U.S. treasuries 3,991 3,991 — — Total $ 16,905 $ 13,102 $ 3,803 $ — Classified as: Cash equivalents $ 13,417 Marketable securities at fair value 3,488 Total $ 16,905 Fair Value Measurements Total Quoted prices in active market Level 1 Significant other observable inputs Level 2 Significant unobservable inputs Level 3 (in thousands) As of December 31, 2018: Money market funds $ 4,830 $ 4,830 $ — $ — Commercial paper 1,497 — 1,497 — Corporate notes and bonds 6,989 — 6,989 — U.S. treasuries 8,375 8,375 — — Total $ 21,691 $ 13,205 $ 8,486 $ — Classified as: Cash equivalents $ 7,829 Marketable securities at fair value 13,862 Total $ 21,691 The Company did not transfer any marketable securities measured at fair value on a recurring basis to or from Level 1 and Level 2 during the six months ended June 30, 2019 . The following tables summarize the unrealized positions for available-for-sale securities disaggregated by class of instrument: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (unaudited; in thousands) As of June 30, 2019: Money market funds $ 9,111 $ — $ — $ 9,111 Commercial paper 3,804 — (1 ) 3,803 U.S. treasuries 3,990 1 — 3,991 Total $ 16,905 $ 1 $ (1 ) $ 16,905 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) As of December 31, 2018: Money market funds $ 4,830 $ — $ — $ 4,830 Commercial paper 1,497 — — 1,497 Corporate notes and bonds 6,994 — (5 ) 6,989 U.S. treasuries 8,375 — — 8,375 Total $ 21,696 $ — $ (5 ) $ 21,691

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components The following table summarizes the Company's prepaid expenses and other current assets for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Prepaid services 295 88 Prepaid insurance 231 45 Prepaid rent 190 23 Prepaid software and subscriptions 170 42 Other 105 160 Total $ 991 $ 358 The following table summarizes the Company’s property and equipment for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Leasehold improvements $ 16,951 $ 16,690 Manufacturing equipment 12,140 10,387 Laboratory and office equipment 1,817 1,434 Computer equipment and software 235 206 Construction-in-progress 16,565 9,558 47,708 38,275 Less: accumulated depreciation (27,140 ) (26,359 ) Total $ 20,568 $ 11,916 Depreciation expense was approximately $0.2 million and $0.2 million for the three months ended June 30, 2019 and 2018 , respectively. Depreciation expense was approximately $0.4 million and $0.4 million for the six months ended June 30, 2019 and 2018, respectively. The gross property and equipment and accumulated depreciation presented in the above table includes right-of-use assets acquired under finance leases and the related accumulated amortization, respectively. Right-of-use assets under finance leases were comprised of office and computer equipment of approximately $54,000 and $24,000 at June 30, 2019 and December 31, 2018 , respectively. Accumulated amortization related to right-of-use assets under finance leases was approximately $ 19,000 at June 30, 2019 . As of June 30, 2019 , construction-in-progress included $10.9 million of an asset relating to the build-to-suit arrangement for construction of the Company's commercial coating and primary packaging system, of which capitalized construction period interest was $1.0 million (See Note 6. Debt Financing ). The following table summarizes the Company’s other accrued liabilities for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Construction-in-progress obligations $ 2,055 $ 395 Pre-clinical and clinical study 891 483 Professional service fees 306 112 Contract manufacturing 158 834 Accrued taxes 20 187 Other 248 408 Total $ 3,678 $ 2,419

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases, Finance	Leases Operating Leases The Company has a non-cancelable operating lease for office, research and development, and manufacturing facilities in Fremont, California through August 31, 2024, with an option to further extend the lease for an additional 60 months subject to certain terms and conditions. The operating lease right-of-use asset and associated lease liability do not consider the option to extend the term after August 31, 2024, as the Company is not reasonably certain of exercising the extension option. The lease agreement calls for monthly base rent of approximately $136,000 for the period commencing September 1, 2017, with annual increases on September 1 of each subsequent year until the lease year beginning September 1, 2023. The agreement also provided for rent abatements, subject to certain conditions, totaling $0.3 million and certain tenant improvements to be completed at the landlord’s expense of approximately $1.0 million . The Company entered into a three year, non-cancelable lease for telephone equipment in January 2018. Per the terms of the agreements, the Company does not have any residual value guarantees, restrictions or covenants. In calculating the present value of the lease payments, the Company utilized its incremental borrowing rate, as the rates implicit in the leases were not readily determinable. The Company accounts for lease and non-lease components separately. The building lease includes non-lease components (i.e. common area maintenance) which are charged and paid separately from rent based on actual costs incurred and therefore are not included in the right-of-use asset and lease liability but reflected in operating expense in the period incurred. Finance Leases The Company leases certain equipment under non-cancelable agreements which expire between 2021 and 2022 that were accounted for as capital leases under ASC840. The leases were not reassessed at adoption of ASC842 as the Company elected the practical expedient to not reassess existing leases. The finance lease obligations were as follows: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Finance lease obligations, current portion $ 15 $ 5 Finance lease obligations, long-term portion $ 25 $ 18 The components of lease cost were as follows: Description of lease costs Three months ended Six months ended (unaudited; in thousands) Finance Lease Cost Amortization of finance lease right-of-use assets $ 4 $ 19 Interest on finance lease obligations 3 12 Operating lease costs 410 820 Total $ 417 $ 851 Cash payments for leases were as follows: Description of cash payment Six months ended June 30, 2019 (unaudited; in thousands) Operating cash flows from operating leases $ 872 Operating cash flows from finance leases $ 6 Financing cash flows from finance leases $ 6 Lease term and discount rate were as follows: June 30, 2019 Description of other lease information Operating leases Finance leases (unaudited) Weighted-average remaining lease term (in years) 5.25 2.28 Weighted average discount rate 11 % 27 % As of June 30, 2019 , annual scheduled lease payments were as follows: Year Operating leases Finance leases (unaudited; in thousands) Remainder of 2019 $ 889 $ 12 2020 1,815 24 2021 1,863 14 2022 1,914 3 2023 1,970 — 2024 1,340 — Total undiscounted cash flows 9,791 53 Less: amount representing interest (2,396 ) (13 ) Present value of lease liabilities $ 7,395 $ 40
Leases, Operating	Leases Operating Leases The Company has a non-cancelable operating lease for office, research and development, and manufacturing facilities in Fremont, California through August 31, 2024, with an option to further extend the lease for an additional 60 months subject to certain terms and conditions. The operating lease right-of-use asset and associated lease liability do not consider the option to extend the term after August 31, 2024, as the Company is not reasonably certain of exercising the extension option. The lease agreement calls for monthly base rent of approximately $136,000 for the period commencing September 1, 2017, with annual increases on September 1 of each subsequent year until the lease year beginning September 1, 2023. The agreement also provided for rent abatements, subject to certain conditions, totaling $0.3 million and certain tenant improvements to be completed at the landlord’s expense of approximately $1.0 million . The Company entered into a three year, non-cancelable lease for telephone equipment in January 2018. Per the terms of the agreements, the Company does not have any residual value guarantees, restrictions or covenants. In calculating the present value of the lease payments, the Company utilized its incremental borrowing rate, as the rates implicit in the leases were not readily determinable. The Company accounts for lease and non-lease components separately. The building lease includes non-lease components (i.e. common area maintenance) which are charged and paid separately from rent based on actual costs incurred and therefore are not included in the right-of-use asset and lease liability but reflected in operating expense in the period incurred. Finance Leases The Company leases certain equipment under non-cancelable agreements which expire between 2021 and 2022 that were accounted for as capital leases under ASC840. The leases were not reassessed at adoption of ASC842 as the Company elected the practical expedient to not reassess existing leases. The finance lease obligations were as follows: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Finance lease obligations, current portion $ 15 $ 5 Finance lease obligations, long-term portion $ 25 $ 18 The components of lease cost were as follows: Description of lease costs Three months ended Six months ended (unaudited; in thousands) Finance Lease Cost Amortization of finance lease right-of-use assets $ 4 $ 19 Interest on finance lease obligations 3 12 Operating lease costs 410 820 Total $ 417 $ 851 Cash payments for leases were as follows: Description of cash payment Six months ended June 30, 2019 (unaudited; in thousands) Operating cash flows from operating leases $ 872 Operating cash flows from finance leases $ 6 Financing cash flows from finance leases $ 6 Lease term and discount rate were as follows: June 30, 2019 Description of other lease information Operating leases Finance leases (unaudited) Weighted-average remaining lease term (in years) 5.25 2.28 Weighted average discount rate 11 % 27 % As of June 30, 2019 , annual scheduled lease payments were as follows: Year Operating leases Finance leases (unaudited; in thousands) Remainder of 2019 $ 889 $ 12 2020 1,815 24 2021 1,863 14 2022 1,914 3 2023 1,970 — 2024 1,340 — Total undiscounted cash flows 9,791 53 Less: amount representing interest (2,396 ) (13 ) Present value of lease liabilities $ 7,395 $ 40

Debt Financing (Notes)

Debt Financing (Notes)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Debt Financing	Debt Financing Build-to-Suit Obligation with Trinity In September 2018, the Company entered into a build-to-suit arrangement with Trinity Capital Fund III, L.P. ("Trinity") in order to obtain financing for the third party construction of the Company's commercial coating and primary packaging system (the "Equipment"), expected to be completed in the second quarter of 2020. Under the agreement, Trinity will make available to the Company $14.0 million for equipment costs and associated soft costs ("Total Cost"), with an initial drawdown of $5.0 million and additional drawdowns in increments of not less than $0.5 million , until March 30, 2020. At March 30, 2020, any unused portion of the $14.0 million will be subject to a non-utilization fee equal to 3% of the unused amount. In consideration of the financing arrangement, as collateral, the Company granted Trinity a first-priority lien and security interest in substantially all of the Company's assets. The Company determined that it controls the Equipment during the construction period due to its involvement in and its obligations related to the construction of the Equipment. Accordingly, construction costs incurred were recorded as construction-in-progress, a component of property and equipment on the balance sheet, and the Trinity financing obligation was recorded as a build-to-suit obligation on the balance sheet. Under the financing arrangement, each individual drawdown represents a separate financing arrangement with its own 36 -month-term and stated interest rate. Each drawdown is non-cancelable, with no prepayment options. Each drawdown has embedded optional purchase options to (i) extend the term for an additional three months , with the option to purchase the equipment at 4% of the Total Cost, which is equal to the drawdown amount, following the end of such extended term, or (ii) purchase the equipment at 12% of the Total Cost, which is equal to the drawdown amount, at the end of the 36-month-term. The Company intends to exercise the optional purchase option of 12% at the end of each 36 -month-term ("Purchase Option Fee"). The transfer of title from Trinity to the Company will occur at the end of the final 36 -month-term, provided that the purchase option was executed, and the Purchase Option Fee was paid in full at the end of each 36 - month-term . Failure to pay any of the Purchase Option Fees will result in Trinity retaining title to the Equipment and the Company paying a 6% restocking fee. As of June 30, 2019 , the Company had drawn down a total of $10.1 million and had a remaining available balance under the line of credit of $3.9 million , which it will use to fund the construction of the Equipment. As of June 30, 2019 , the Company had an aggregate commercial coating and primary packaging system construction-in-progress ("CIP") balance of $10.9 million that included $1.0 million of interest related to its build-to-suit obligation, and a net build-to-suit obligation of $8.2 million . In connection with the build-to-suit arrangement, the Company issued common stock warrants (“Trinity Warrants”) for a total of 75,000 shares of common stock at an exercise price of $3.59 per share. The Trinity Warrants will expire on September 25, 2025 . Proceeds allocated to the Trinity Warrants based on their relative fair value approximated $243,000 and were recorded as a discount to the initial $5.0 million drawdown under the Trinity financing arrangement and are being amortized as interest over the term of the September 2018 drawdown. The Trinity build-to-suit arrangement requires compliance with various affirmative and restrictive covenants in regard to making certain investments and other restricted payments, engaging in mergers or consolidations, and the sale or transfer of certain assets. Failure to comply with any of these covenants, or pay principal, interest or other amounts when due, would constitute an event of default under the applicable agreement. The Company was in compliance with its covenants with respect to the Trinity build-to-suit arrangement as of June 30, 2019 . The following table summarizes the debt obligations as of June 30, 2019 : Drawdown Date Drawdown Amount Principal Balance as of 6/30/19 Purchase Option Fee Discount on Purchase Option Fee Unamortized Discounts and Issuance Costs Monthly Payment Stated Interest Rate Effective Interest Rate Maturity Date (unaudited; in thousands) 09/25/2018 $ 5,000 $ 3,720 $ 600 $ (85 ) $ (520 ) $ 160 9.43 % 26.28 % 10/01/2021 12/11/2018 2,800 2,299 336 (60 ) (201 ) 90 9.68 % 19.58 % 01/01/2022 06/06/2019 2,300 2,171 276 (71 ) (227 ) 74 9.93 % 19.77 % 07/01/2022 Total $ 10,100 $ 8,190 $ 1,212 $ (216 ) $ (948 ) $ 324 The following table is a summary of the Company's build-to-suit obligation as of June 30, 2019 (unaudited; in thousands) : Build-to-suit obligation principal amount $ 8,190 Build-to-suit obligation Purchase Option Fees at present value 996 Less: unamortized Purchase Option Fees (647 ) unamortized fair value of free-standing warrants (141 ) unamortized debt discount (145 ) unamortized debt issuance costs (15 ) Build-to-suit obligation, net of debt issuance costs and discount $ 8,238 Build-to-suit obligation, current portion $ 3,147 Build-to-suit obligation, long-term portion, net of debt issuance costs and discount 5,091 Build-to-suit obligation, net of debt issuance costs and discount $ 8,238 Future minimum payments on the Company’s build-to-suit obligation, including payment of principal and interest and Purchase Option Fees for each year ending December 31 were as follows: Year Principal Interest Purchase Option Fees (unaudited; in thousands) Remainder of 2019 $ 1,508 $ 363 $ — 2020 3,359 530 — 2021 2,964 194 600 2022 359 12 612 Total $ 8,190 $ 1,099 $ 1,212 Senior Secured Term Loan with Hercules In June 2014 and June 2015, the Company entered into a loan and security agreement and the first amendment to the loan and security agreement, respectively, with Hercules Capital Inc. (“Hercules”). Hercules provided the Company a $15.0 million loan (“Hercules Term Loan”) of which equal installment payments of principal and interest were due monthly, with a scheduled maturity date of December 1, 2018 . The Hercules Term Loan bore interest at a variable rate equal to the greater of (i) 7.95% , or (ii) 7.95% plus the prime rate as quoted in the Wall Street Journal minus 5.25% . On September 25, 2018, the Company paid all its outstanding obligations under the Hercules Term Loan, including an end of term charge of $0.4 million . For the three and six months ended June 30, 2018 , the Company recorded total interest expense of $0.1 million and $0.3 million , respectively, related to the Hercules Term Loan.

Warrants

Warrants	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Warrants	Warrants The following table summarizes the warrants issued and outstanding as of June 30, 2019 : Warrants Warrants Issued Warrants Exercised Warrants Expired Warrants Exercise Price Expiration Date (unaudited) PIPE Financing - Series B 195,906 — — — 195,906 $ 31.00 8/19/2021 Hercules - June 2014 1,583 — — — 1,583 $ 176.80 1/27/2020 Hercules - June 2015 2,035 — — — 2,035 $ 147.40 6/23/2020 Trinity - September 2018 75,000 — — — 75,000 $ 3.59 9/25/2025 Total 274,524 — — — 274,524

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Employment Arrangements The Company has entered into employment agreements with its executive officers. Generally, the terms of these agreements provide for base salary, health care coverage, annual bonus and stock options. In addition, if the Company terminates the officer other than for cause, death, or disability, or if the officer terminates his or her employment with the Company for good cause, the officer shall be entitled to receive certain severance compensation and benefits as described in each such agreement as well as automatic acceleration of vesting, at a certain percentage ( 25% or 100% ), of their unvested stock options and other equity awards on the date of such termination. Equipment Purchase Commitments The Company has a remaining commitment of $6.3 million with an equipment manufacturer for the construction and purchase of a commercial coating and primary packaging system for the production of its product candidate, Qtrypta™ (M207). The terms of the purchase commitment are contingent upon performance of certain milestones. The Company anticipates that the obligation will be paid within the next 12 months. The Company also has commitments with equipment manufacturers to produce its patch assembly machine and its applicator and retainer machinery. The aggregate purchase price of this equipment is $3.9 million of which $2.0 million was paid as of June 30, 2019 . Contract Manufacturing Organizations In September 2018, the Company entered into a technology transfer agreement and a manufacturing and supply agreement with a contract manufacturing organization ("CMO") to provide services related to the manufacture and commercialization of Qtrypta™ (M207). During the term of the agreement, the CMO will provide services related to processing, packaging, labeling and storing Qtrypta™ (M207), in addition to other services such as stability testing, quality control and assurance, and waste disposal. The agreements call for annual fees of $1.0 million in 2019 escalating to $14.0 million in 2024 , to be paid in equal monthly installments. Beginning in 2020, the annual fee includes the production of a defined number of units with an option to purchase additional units at a defined price. The agreement contains negotiated representations and warranties, indemnification, limitations of liability, and other provisions. The initial term of the agreement continues until the seventh anniversary of the date on which the Company receives New Drug Application approval of Qtrypta™ (M207) in the United States. The Company may terminate the agreements upon denial of regulatory approvals or if regulatory approvals are withdrawn under certain circumstances. If the Company elects to terminate the contracts for convenience, the Company would incur cancellation fees in the amount of 50% of the annual fee due in the year that the contract is terminated, and costs to remove the Company's equipment and restore the CMO's facility to its original condition. The Company or the CMO may terminate the agreement for the other’s uncured material breach, uncured force majeure or bankruptcy or insolvency-related events. As of June 30, 2019 , the Company had entered into agreements with two CMOs for the construction of manufacturing space and technology transfer fees for $11.7 million of which $2.8 million had been paid. Indemnification and Guarantees In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. The Company also has indemnification obligations to its officers and directors for specified events or occurrences, subject to some limits, while they are serving at the Company’s request in such capacities. There have been no claims to date and the Company has director and officer insurance that may enable the Company to recover a portion of any amounts paid for future potential claims. The Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company has not recorded any liabilities for these agreements as of June 30, 2019 . Legal Proceedings The Company is not party to any material pending legal proceedings. However, it may from time to time become involved in litigation relating to claims arising in the ordinary course of business. Such matters are subject to many uncertainties and outcomes and are not predictable with assurance. The Company accrues for contingencies when it believes that a loss is probable and that it can reasonably estimate the amount of any such loss. To the extent that there is a reasonable possibility that a loss exceeding amounts already recognized may be incurred and the amount of such additional loss would be material, the Company will either disclose the estimated additional loss or state that such an estimate cannot be made.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Amended and Restated 2014 Equity and Incentive Plan The Amended and Restated 2014 Equity and Incentive Plan (“2014 Plan”) provides for the issuance of (i) cash awards and (ii) equity-based awards, denominated in shares of the Company’s common stock, including incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, performance share awards and dividend equivalent rights. Incentive stock options may be granted only to Company employees. Nonqualified stock options may be granted to Company employees, outside directors and consultants. As of June 30, 2019 , the Company had reserved 1,771,012 shares of its common stock for issuance under the 2014 Plan and a previously terminated plan, subject to automatic annual increases as set forth in the 2014 Plan. Options and awards under the 2014 Plan may be granted for periods of up to ten years . Employee options granted by the Company generally vest over four years . Restricted stock awards granted to employees, directors and consultants can be subject to the same vesting conditions and the right of repurchase by the Company of unvested shares as determined by its board of directors. As of June 30, 2019 , the Company had 17,357 shares available for grant under the 2014 Plan. During the six months ended June 30, 2019 , the Company granted stock options to purchase 32,500 shares of common stock to non-employee directors. The following table summarizes option and award activity, excluding inducement grants, for the six months ended June 30, 2019 (unaudited) : Shares Available for Grant Number of Shares Subject to Outstanding Options Weighted- Average Exercise Price per Share Weighted- Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at January 1, 2019 55,799 1,296,157 $ 5.75 9.23 $ — Additional shares reserved 419,056 — $ — Options granted (496,950 ) 496,950 $ 3.27 Options canceled/forfeited/expired 39,452 (39,452 ) $ 5.23 Balance at June 30, 2019 17,357 1,753,655 $ 5.06 9.05 $ 197 Exercisable at June 30, 2019 366,022 $ 8.55 8.49 $ 1 Vested or expected to vest at June 30, 2019 1,627,577 $ 5.15 9.03 $ 176 The aggregate intrinsic value is calculated as the difference between the exercise price of the option and the estimated fair value of the Company’s common stock for in-the-money options at June 30, 2019 . Inducement Grants The Company has also awarded inducement grants to purchase common stock to new employees outside the existing equity compensation plans in accordance with Nasdaq listing rule 5635(c)(4). Such options vest at a rate of 25% of the shares on the first anniversary of the commencement of such employee’s employment with the Company, and then one forty-eighth (1/48) of the shares monthly thereafter subject to such employee’s continued service. The following table summarizes the Company’s inducement grant stock option activity (unaudited) : Number of Shares Subject to Outstanding Options Weighted- Average Exercise Price per Share Weighted-Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at January 1, 2019 13,837 $ 20.60 4.52 $ — Options granted — $ — Options canceled/forfeited/expired (1,750 ) $ 22.80 Balance at June 30, 2019 12,087 $ 20.28 3.51 $ — Exercisable at June 30, 2019 9,795 $ 18.66 2.47 $ — Vested or expected to vest at June 30, 2019 11,952 $ 20.20 3.46 $ — Stock-Based Compensation Expense Total stock-based compensation expense recognized was as follows: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (unaudited; in thousands) (unaudited; in thousands) Research and development $ 178 $ 142 $ 343 $ 209 General and administrative 208 188 404 260 Total $ 386 $ 330 $ 747 $ 469 As of June 30, 2019 , the Company had $4.4 million of total unrecognized stock-based compensation related to outstanding stock options that will be recognized over a weighted-average period of 3.06 years. The Company’s stock-based compensation expense for stock options is estimated at the grant date based on the award’s fair value as calculated by the Black-Scholes option pricing model and is recognized as expense over the requisite service period. The Black-Scholes option pricing model requires various highly judgmental assumptions including expected volatility and expected term. As the Company does not have sufficient historical stock price information to meet the expected life of the stock-based awards, the Company uses a blended volatility that includes the Company's common stock trading history and supplements the remaining historical information with the trading history from the common stock of a set of comparable publicly traded biopharmaceutical companies. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of the Company's stock price becomes available. To estimate the expected term, the Company has opted to use the simplified method which is the use of the midpoint of the vesting term and the contractual term. If any of the assumptions used in the Black-Scholes option pricing model changes significantly, stock-based compensation expense may differ materially in the future from that recorded. Through March 31, 2019, the Company estimated the forfeiture rate based on historical experience and its expectations regarding future pre-vesting termination behavior of employees. In the second quarter of 2019, the Company made an accounting policy election to recognize the impact of forfeitures on compensation cost in the period the award is forfeited. The following table presents the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted (unaudited) : Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Dividend yield —% —% —% —% Risk-free interest rate 1.97% - 2.45% 2.74% - 3.11% 1.97% - 2.66% 2.74% - 3.11% Expected volatility 108% 89% 106% - 108% 89% Expected term (years) 5.96 - 6.08 6.08 5.96 - 6.08 6.08

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) for interim financial information, the instructions to Form 10-Q and Regulation S-X. They do not include all the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 , or any other subsequent period. These financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2018 , included in the Company’s annual report on Form 10-K and filed with the United States Securities and Exchange Commission (“SEC”) on March 25, 2019.
Use of Estimates	Use of Estimates The preparation of the accompanying condensed financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the condensed financial statements, and the reported amounts of expenses during the periods reported. Actual results could differ from those estimates.
Liquidity and Substantial Doubt in Going Concern	Liquidity and Substantial Doubt in Going Concern Since inception, the Company has incurred recurring operating losses and negative cash flows from operating activities, and as of June 30, 2019 , had an accumulated deficit of $280.0 million . As of June 30, 2019 , the Company had approximately $17.7 million in cash, cash equivalents and marketable securities. Presently, the Company does not have sufficient cash, cash equivalents and marketable securities to enable it to fund its anticipated level of operations and meet its obligations as they become due within twelve months following the date of issuance of this Quarterly Report on Form 10-Q. The aforementioned factors raise substantial doubt about the Company’s ability to continue as a going concern for a period of one year from the issuance of these financial statements. The financial statements do not include any adjustments that might result from the outcome of this uncertainty. On April 11, 2019, the Company closed a public offering of 5,000,000 shares of common stock at a price to the underwriter of $3.29 per share. On May 8, 2019, the underwriter purchased an additional 750,000 shares at a price to the underwriter of $3.29 per share pursuant to the exercise of the underwriter's option to purchase additional shares. The aggregate net proceeds were approximately $18.3 million , after deducting underwriting costs and estimated offering expenses. The Company plans to raise additional funding through financing, a capital offering, a license or collaboration agreement or a combination of such sources of capital. However, there are no assurances that additional funding will be achieved and that the Company will succeed in its future operations. The Company’s inability to obtain required funding in the near future or its inability to obtain funding on favorable terms will have a material adverse effect on its operations and strategic development plan for future growth. If the Company cannot successfully raise additional capital and implement its strategic development plan, its liquidity, financial condition and business prospects will be materially and adversely affected, and it may have to cease operations. The Company will continue to evaluate its timelines, strategic needs, and working capital requirements. There can be no assurance that if the Company attempts to raise additional capital, it will be successful in doing so on terms acceptable to the Company, or at all. Further, there can be no assurance that it will be able to gain access and/or be able to execute on securing new sources of funding, new development opportunities, successfully obtain regulatory approvals for and commercialize new products, achieve significant product revenues from its products (if approved), or achieve or sustain profitability in the future.
Leases	Leases ASC Topic 842, Leases , requires lessees to recognize right-of-use assets and lease liabilities for most leases on the balance sheet and to provide expanded disclosures about leasing arrangements. The Company adopted Topic 842 effective January 1, 2019 using the optional transition method and did not restate comparative periods. There was no effect on accumulated deficit at adoption. The Company has elected the package of practical expedients to (i) not reassess whether expired or existing contracts are or contain leases, (ii) not reassess the lease classification for any expired or existing leases and (iii) not reassess the accounting for initial direct costs. The adoption of the new leases standard resulted in the following adjustments to the Company's balance sheet as of January 1, 2019: December 31, 2018 Adoption Impact January 1, 2019 (in thousands) (unaudited; in thousands) Operating lease right-of-use assets $ — $ 6,415 $ 6,415 Operating lease liabilities, current portion $ — $ 945 $ 945 Other accrued liabilities $ 2,414 $ (143 ) $ 2,271 Operating lease liabilities, long-term portion $ — $ 6,900 $ 6,900 Deferred rent $ 1,287 $ (1,287 ) $ — As of December 31, 2018 , the short-term portion of deferred rent was recorded in other accrued liabilities. The adoption impact was a non-cash operating activity for the six months ended June 30, 2019. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. If the interest rate implicit in the Company's lease contracts is not readily determinable, the Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments with an original maturity of 90 days or less to be cash equivalents.
Marketable Securities	Marketable Securities Marketable securities generally consist of debt securities with original maturities greater than 90 days and remaining maturities of less than one year. Marketable securities with an original maturity greater than one year, if any, would be considered long-term investments. All of the Company's investments are classified as available-for-sale and carried at fair value based upon quoted market price. The change in unrealized gains and losses related to fixed maturity debt securities is reported as a separate component of other comprehensive income (loss) on the statements of operations and comprehensive loss and as a separate component of stockholders' equity on the balance sheets. Interest income includes interest, dividends, amortization and accretion of purchase premiums and discounts and realized gains and losses on sales of securities, if any. The cost of securities sold is based on the specific-identification method. The Company monitors its investment portfolio for potential impairment on a quarterly basis. If the carrying amount of an investment in marketable securities exceeds its fair value and the decline in value is determined to be other-than-temporary, the carrying amount of the security is reduced to fair value and a loss is recognized in operating results for the amount of such decline. In order to determine whether a decline in value is other-than-temporary, the Company evaluates, among other factors, the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, and its intent and ability to hold the security to maturity or expected recovery.
Fair Value Instruments	Fair Value Instruments The Company records its financial assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: • Level 1: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level 2: Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • 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. The carrying values of certain assets and liabilities of the Company, such as cash and cash equivalents and accounts payable approximate fair value due to their relatively short maturities. The carrying value of the Company’s short-term financial obligations approximates their fair value as the terms of the borrowing are consistent with current market rates and the duration to maturity is short. The carrying value of the Company's long-term financial obligations approximates fair value because interest rates approximate market rates that the Company could obtain for debt with similar terms and maturities.
Net Loss Per Common Share	Net Loss Per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per common share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, common stock warrants and stock options are considered to be potential dilutive securities but are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2018, the Financial Accounting Standards Board ("FASB") issued ASU2018-15, Intangible - Goodwill and Other - Internal-Use Software (Subtopic 350-40) , which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU2018-15 is effective for the Company in the first quarter of 2020. Early adoption is permitted. ASU2018-15 permits either a prospective or retrospective transition approach. The Company is currently evaluating ASU2018-15 to determine the impact to its financial statements and disclosures. In August 2018, the FASB issued ASU2018-13, Fair Value Measurement (Topic 820) . The new guidance modifies the disclosure requirements on fair value measurements. ASU2018-13 is effective for the Company beginning in the first quarter of 2020 and must be adopted on a modified retrospective basis, with certain exceptions. Early adoption is permitted. The Company does not expect ASU2018-13 to have a significant impact to its financial statements and disclosures. The FASB issued ASU2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments in June 2016 , ASU2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses in November 2018 , and ASU2019-05, Financial Instruments - Credit Losses, Targeted Transition Relief in May 2019. This new guidance is intended to present credit losses on available-for-sale debt securities as an allowance rather than as a write-down. Entities are required to apply the standards' provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. ASU2016-13, ASU2018-19 and ASU2019-05 are effective for the Company in the first quarter of 2020. The Company is currently evaluating these standards to determine the impact to its financial statements and disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Schedule of Adoption of New Lease Standard	The adoption of the new leases standard resulted in the following adjustments to the Company's balance sheet as of January 1, 2019: December 31, 2018 Adoption Impact January 1, 2019 (in thousands) (unaudited; in thousands) Operating lease right-of-use assets $ — $ 6,415 $ 6,415 Operating lease liabilities, current portion $ — $ 945 $ 945 Other accrued liabilities $ 2,414 $ (143 ) $ 2,271 Operating lease liabilities, long-term portion $ — $ 6,900 $ 6,900 Deferred rent $ 1,287 $ (1,287 ) $ —
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash to amounts shown in the statement of cash flows: June 30, 2019 June 30, 2018 (unaudited; in thousands) Cash and cash equivalents $ 14,252 $ 16,197 Restricted cash 455 35 Total $ 14,707 $ 16,232
Schedule of Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash to amounts shown in the statement of cash flows: June 30, 2019 June 30, 2018 (unaudited; in thousands) Cash and cash equivalents $ 14,252 $ 16,197 Restricted cash 455 35 Total $ 14,707 $ 16,232
Schedule of Outstanding Common Stock Equivalents Excluded From Computations of Diluted Net Loss per Common Share	The following outstanding common stock equivalents were excluded from the computations of diluted net loss per common share for the periods presented as the effect of including such securities would be antidilutive: June 30, 2019 June 30, 2018 (unaudited) Warrants to purchase common stock 274,524 199,524 Options to purchase common stock 1,765,742 1,186,318 Total 2,040,266 1,385,842

Cash Equivalents and Investme_2

Cash Equivalents and Investments in Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following tables present summaries of the Company's cash equivalents and investments in marketable securities measured at fair value on a recurring basis: Fair Value Measurements Total Quoted prices Significant Significant (unaudited; in thousands) As of June 30, 2019: Money market funds $ 9,111 $ 9,111 $ — $ — Commercial paper 3,803 — 3,803 — U.S. treasuries 3,991 3,991 — — Total $ 16,905 $ 13,102 $ 3,803 $ — Classified as: Cash equivalents $ 13,417 Marketable securities at fair value 3,488 Total $ 16,905 Fair Value Measurements Total Quoted prices in active market Level 1 Significant other observable inputs Level 2 Significant unobservable inputs Level 3 (in thousands) As of December 31, 2018: Money market funds $ 4,830 $ 4,830 $ — $ — Commercial paper 1,497 — 1,497 — Corporate notes and bonds 6,989 — 6,989 — U.S. treasuries 8,375 8,375 — — Total $ 21,691 $ 13,205 $ 8,486 $ — Classified as: Cash equivalents $ 7,829 Marketable securities at fair value 13,862 Total $ 21,691
Summary of Available-for-sale Fixed Maturity Debt Securities	The following tables summarize the unrealized positions for available-for-sale securities disaggregated by class of instrument: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (unaudited; in thousands) As of June 30, 2019: Money market funds $ 9,111 $ — $ — $ 9,111 Commercial paper 3,804 — (1 ) 3,803 U.S. treasuries 3,990 1 — 3,991 Total $ 16,905 $ 1 $ (1 ) $ 16,905 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) As of December 31, 2018: Money market funds $ 4,830 $ — $ — $ 4,830 Commercial paper 1,497 — — 1,497 Corporate notes and bonds 6,994 — (5 ) 6,989 U.S. treasuries 8,375 — — 8,375 Total $ 21,696 $ — $ (5 ) $ 21,691

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Other Accrued Liabilities	The following table summarizes the Company’s other accrued liabilities for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Construction-in-progress obligations $ 2,055 $ 395 Pre-clinical and clinical study 891 483 Professional service fees 306 112 Contract manufacturing 158 834 Accrued taxes 20 187 Other 248 408 Total $ 3,678 $ 2,419
Schedule of Property and Equipment	The following table summarizes the Company’s property and equipment for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Leasehold improvements $ 16,951 $ 16,690 Manufacturing equipment 12,140 10,387 Laboratory and office equipment 1,817 1,434 Computer equipment and software 235 206 Construction-in-progress 16,565 9,558 47,708 38,275 Less: accumulated depreciation (27,140 ) (26,359 ) Total $ 20,568 $ 11,916
Schedule of Prepaid Expenses and Other Current Assets	The following table summarizes the Company's prepaid expenses and other current assets for each of the periods presented: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Prepaid services 295 88 Prepaid insurance 231 45 Prepaid rent 190 23 Prepaid software and subscriptions 170 42 Other 105 160 Total $ 991 $ 358

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Supplemental Balance Sheet Information	The finance lease obligations were as follows: June 30, 2019 December 31, 2018 (unaudited; in thousands) (in thousands) Finance lease obligations, current portion $ 15 $ 5 Finance lease obligations, long-term portion $ 25 $ 18
Lease, Cost	Cash payments for leases were as follows: Description of cash payment Six months ended June 30, 2019 (unaudited; in thousands) Operating cash flows from operating leases $ 872 Operating cash flows from finance leases $ 6 Financing cash flows from finance leases $ 6 Lease term and discount rate were as follows: June 30, 2019 Description of other lease information Operating leases Finance leases (unaudited) Weighted-average remaining lease term (in years) 5.25 2.28 Weighted average discount rate 11 % 27 % The components of lease cost were as follows: Description of lease costs Three months ended Six months ended (unaudited; in thousands) Finance Lease Cost Amortization of finance lease right-of-use assets $ 4 $ 19 Interest on finance lease obligations 3 12 Operating lease costs 410 820 Total $ 417 $ 851
Lessee, Operating Lease, Liability, Maturity	As of June 30, 2019 , annual scheduled lease payments were as follows: Year Operating leases Finance leases (unaudited; in thousands) Remainder of 2019 $ 889 $ 12 2020 1,815 24 2021 1,863 14 2022 1,914 3 2023 1,970 — 2024 1,340 — Total undiscounted cash flows 9,791 53 Less: amount representing interest (2,396 ) (13 ) Present value of lease liabilities $ 7,395 $ 40
Finance Lease, Liability, Maturity	As of June 30, 2019 , annual scheduled lease payments were as follows: Year Operating leases Finance leases (unaudited; in thousands) Remainder of 2019 $ 889 $ 12 2020 1,815 24 2021 1,863 14 2022 1,914 3 2023 1,970 — 2024 1,340 — Total undiscounted cash flows 9,791 53 Less: amount representing interest (2,396 ) (13 ) Present value of lease liabilities $ 7,395 $ 40

Debt Financing (Tables)

Debt Financing (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table summarizes the debt obligations as of June 30, 2019 : Drawdown Date Drawdown Amount Principal Balance as of 6/30/19 Purchase Option Fee Discount on Purchase Option Fee Unamortized Discounts and Issuance Costs Monthly Payment Stated Interest Rate Effective Interest Rate Maturity Date (unaudited; in thousands) 09/25/2018 $ 5,000 $ 3,720 $ 600 $ (85 ) $ (520 ) $ 160 9.43 % 26.28 % 10/01/2021 12/11/2018 2,800 2,299 336 (60 ) (201 ) 90 9.68 % 19.58 % 01/01/2022 06/06/2019 2,300 2,171 276 (71 ) (227 ) 74 9.93 % 19.77 % 07/01/2022 Total $ 10,100 $ 8,190 $ 1,212 $ (216 ) $ (948 ) $ 324 The following table is a summary of the Company's build-to-suit obligation as of June 30, 2019 (unaudited; in thousands) : Build-to-suit obligation principal amount $ 8,190 Build-to-suit obligation Purchase Option Fees at present value 996 Less: unamortized Purchase Option Fees (647 ) unamortized fair value of free-standing warrants (141 ) unamortized debt discount (145 ) unamortized debt issuance costs (15 ) Build-to-suit obligation, net of debt issuance costs and discount $ 8,238 Build-to-suit obligation, current portion $ 3,147 Build-to-suit obligation, long-term portion, net of debt issuance costs and discount 5,091 Build-to-suit obligation, net of debt issuance costs and discount $ 8,238
Schedule of Maturities of Long-term Debt	Future minimum payments on the Company’s build-to-suit obligation, including payment of principal and interest and Purchase Option Fees for each year ending December 31 were as follows: Year Principal Interest Purchase Option Fees (unaudited; in thousands) Remainder of 2019 $ 1,508 $ 363 $ — 2020 3,359 530 — 2021 2,964 194 600 2022 359 12 612 Total $ 8,190 $ 1,099 $ 1,212

Warrants (Tables)

Warrants (Tables)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Summary of Warrants Issued and Outstanding	The following table summarizes the warrants issued and outstanding as of June 30, 2019 : Warrants Warrants Issued Warrants Exercised Warrants Expired Warrants Exercise Price Expiration Date (unaudited) PIPE Financing - Series B 195,906 — — — 195,906 $ 31.00 8/19/2021 Hercules - June 2014 1,583 — — — 1,583 $ 176.80 1/27/2020 Hercules - June 2015 2,035 — — — 2,035 $ 147.40 6/23/2020 Trinity - September 2018 75,000 — — — 75,000 $ 3.59 9/25/2025 Total 274,524 — — — 274,524

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option and Award Activity Excluding Inducement Grants	The following table summarizes option and award activity, excluding inducement grants, for the six months ended June 30, 2019 (unaudited) : Shares Available for Grant Number of Shares Subject to Outstanding Options Weighted- Average Exercise Price per Share Weighted- Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at January 1, 2019 55,799 1,296,157 $ 5.75 9.23 $ — Additional shares reserved 419,056 — $ — Options granted (496,950 ) 496,950 $ 3.27 Options canceled/forfeited/expired 39,452 (39,452 ) $ 5.23 Balance at June 30, 2019 17,357 1,753,655 $ 5.06 9.05 $ 197 Exercisable at June 30, 2019 366,022 $ 8.55 8.49 $ 1 Vested or expected to vest at June 30, 2019 1,627,577 $ 5.15 9.03 $ 176
Summary of Company's Inducement Grant Stock Option Activities	The following table summarizes the Company’s inducement grant stock option activity (unaudited) : Number of Shares Subject to Outstanding Options Weighted- Average Exercise Price per Share Weighted-Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at January 1, 2019 13,837 $ 20.60 4.52 $ — Options granted — $ — Options canceled/forfeited/expired (1,750 ) $ 22.80 Balance at June 30, 2019 12,087 $ 20.28 3.51 $ — Exercisable at June 30, 2019 9,795 $ 18.66 2.47 $ — Vested or expected to vest at June 30, 2019 11,952 $ 20.20 3.46 $ —
Summary of Stock-Based Compensation Expense	Total stock-based compensation expense recognized was as follows: Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 (unaudited; in thousands) (unaudited; in thousands) Research and development $ 178 $ 142 $ 343 $ 209 General and administrative 208 188 404 260 Total $ 386 $ 330 $ 747 $ 469
Schedule of Weighted-Average Assumptions for the Black-Scholes Option-Pricing Model Used in Determining the Fair Value of Options Granted	The following table presents the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted (unaudited) : Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Dividend yield —% —% —% —% Risk-free interest rate 1.97% - 2.45% 2.74% - 3.11% 1.97% - 2.66% 2.74% - 3.11% Expected volatility 108% 89% 106% - 108% 89% Expected term (years) 5.96 - 6.08 6.08 5.96 - 6.08 6.08

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	May 08, 2019	Apr. 11, 2019	May 08, 2019	Jun. 30, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Accumulated deficit				$ 280,018	$ 261,232
Cash, cash equivalents and investments				$ 17,700
Consideration from sale of stock			$ 18,300
Public Stock Offering
Subsequent Event [Line Items]
Shares issued in transaction (in shares)		5,000,000
Over-Allotment Option
Subsequent Event [Line Items]
Shares issued in transaction (in shares)	750,000
Price of stock sold (in USD per share)	$ 3.29		$ 3.29

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Lease Standards (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 6,016	$ 6,415
Operating leases liabilities, current portion	1,026	945
Other accrued liabilities		2,271	$ 2,414
Operating lease liabilities, long-term portion	6,369	6,900
Deferred rent	$ 0	0	$ 1,287
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		6,415
Operating leases liabilities, current portion		945
Other accrued liabilities		(143)
Operating lease liabilities, long-term portion		6,900
Deferred rent		$ (1,287)

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 455	$ 455	$ 35
Deposit, Building Lease
Cash and Cash Equivalents [Line Items]
Restricted cash	300	300
Deposit, Utility Provider
Cash and Cash Equivalents [Line Items]
Restricted cash	100	100
Corporate Purchasing Cards
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 35	$ 35

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash and Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 14,252	$ 9,140	$ 16,197
Restricted cash	455	455	35
Total	$ 14,707	$ 9,595	$ 16,232	$ 11,686

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Outstanding Common Stock Equivalents Excluded From Computations of Diluted Net Loss per Common Share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock excluded from computation of diluted net loss per share (in shares)	2,040,266	1,385,842
Warrants to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock excluded from computation of diluted net loss per share (in shares)	274,524	199,524
Options to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock excluded from computation of diluted net loss per share (in shares)	1,765,742	1,186,318

Cash Equivalents and Investme_3

Cash Equivalents and Investments in Marketable Securities - Summary of Cash Equivalents and Investments Carried at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	$ 16,905	$ 21,691
Total	17,700
Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	16,905	21,691
Cash equivalents	13,417	7,829
Marketable securities at fair value	3,488	13,862
Total	16,905	21,691
Recurring | Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	13,102	13,205
Recurring | Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	8,486
Recurring | Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Money market funds
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds | Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds | Recurring | Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds | Recurring | Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Money market funds | Recurring | Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Commercial paper
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper | Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper | Recurring | Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Commercial paper | Recurring | Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper | Recurring | Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Corporate notes and bonds
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds | Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds | Recurring | Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		0
Corporate notes and bonds | Recurring | Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds | Recurring | Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		0
U.S. treasuries
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries | Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries | Recurring | Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries | Recurring | Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
U.S. treasuries | Recurring | Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	$ 0	$ 0

Cash Equivalents and Investme_4

Cash Equivalents and Investments in Marketable Securities - Summary of Investment Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 16,905	$ 21,696
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(1)	(5)
Fair Value	16,905	21,691
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,111	4,830
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	9,111	4,830
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,804	1,497
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	3,803	1,497
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		6,994
Gross Unrealized Gains		0
Gross Unrealized Losses		(5)
Fair Value		6,989
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,990	8,375
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Fair Value	$ 3,991	$ 8,375

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Prepaid services	$ 295	$ 88
Prepaid insurance	231	45
Prepaid rent	190	23
Prepaid software and subscriptions	170	42
Other	105	160
Prepaid expenses and other current assets	$ 991	$ 358

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 47,708	$ 38,275
Less: accumulated depreciation	(27,140)	(26,359)
Property and equipment, net	20,568	11,916
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16,951	16,690
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,140	10,387
Laboratory and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,817	1,434
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	235	206
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 16,565	$ 9,558

Balance Sheet Components - Nara

Balance Sheet Components - Narative (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 200	$ 200	$ 400	$ 400
Property and equipment	20,568		20,568		$ 11,916
Finance lease, accumulated amortization	19		19
Property and equipment, gross	47,708		47,708		38,275
Accumulated capitalized interest costs	1,000		1,000
Assets Held Under Finance Leases
Property, Plant and Equipment [Line Items]
Property and equipment	54		54
Assets Held Under Finance Leases
Property, Plant and Equipment [Line Items]
Property and equipment					$ 24
Construction in Progress, Build-to-suit
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,900		$ 10,900

Balance Sheet Components - Othe

Balance Sheet Components - Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Construction-in-progress obligations	$ 2,055	$ 395
Pre-clinical and clinical study	891	483
Professional service fees	306	112
Contract manufacturing	158	834
Accrued taxes	20	187
Other	248	408
Total	$ 3,678	$ 2,419

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	Sep. 01, 2017	Jun. 30, 2019	Jan. 31, 2018
Lessee, Lease, Description [Line Items]
Renewal term		60 months
Monthly base rent	$ 136
Incentive rent abatements		$ 300
Landlord's tenant improvements		$ 1,000
Telephone Equipment
Lessee, Lease, Description [Line Items]
Term of lease			3 years

Leases - Finance Lease Obligati

Leases - Finance Lease Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Finance lease obligations, current portion	$ 15
Finance lease obligations, current portion		$ 5
Finance lease obligations, long-term portion	$ 25
Finance lease obligations, long-term portion		$ 18

Leases - Description of Lease C

Leases - Description of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Finance Lease Cost
Amortization of finance lease right-of-use assets	$ 4	$ 19
Interest on finance lease obligations	3	12
Operating lease costs	410	820
Total	$ 417	$ 851

Leases - Description of Cash Pa

Leases - Description of Cash Payment (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 872
Operating cash flows from finance leases	6
Financing cash flows from finance leases	$ 6

Leases - Description of Other L

Leases - Description of Other Lease Information (Details)	Jun. 30, 2019
Leases [Abstract]
Weighted average remaining lease term, operating lease	5 years 2 months 30 days
Weighted average remaining lease term, financing lease	2 years 3 months 11 days
Weighted average discount rate, operating lease	11.00%
Weighted average discount rate, finance lease	27.00%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) $ in Thousands	Jun. 30, 2019USD ($)
Operating leases
Remainder of 2019	$ 889
2020	1,815
2021	1,863
2022	1,914
2023	1,970
2024	1,340
Total undiscounted cash flows	9,791
Less: amount representing interest	(2,396)
Present value of lease liabilities	7,395
Finance leases
Remainder of 2019	12
2020	24
2021	14
2022	3
2023	0
2024	0
Total undiscounted cash flows	53
Less: amount representing interest	(13)
Present value of lease liabilities	$ 40

Debt Financing - Additional Inf

Debt Financing - Additional Information (Detail) - USD ($)	Mar. 20, 2020	Sep. 25, 2018	Sep. 30, 2018	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Restocking fee							6.00%
Property and equipment, gross							$ 47,708,000		$ 38,275,000
Accumulated capitalized interest costs							$ 1,000,000
Common stock issued (in shares)							17,723,039		11,973,039
Interest expense						$ 100,000		$ 300,000
Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Build-to-suit obligation							$ 10,100,000
Proceeds from issuance of warrants			$ 243,000
Trinity Capital Fund III, L.P. | Warrants to Purchase Common Stock
Debt Instrument [Line Items]
Common stock issued (in shares)			75,000
Build to Suit Obligation | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Build-to-suit obligation, aggregate principal amount			$ 14,000,000
Drawdown amount		$ 5,000,000
Build-to-suit obligation			5,000,000				$ 8,200,000
Incremental drawdowns, minimum			$ 500,000
Debt instrument term							36 months
Remaining available balance							$ 3,900,000
Debt discount and issuance costs							948,000
Common stock warrant exercise price (in USD per share)			$ 3.59
Drawdown Amount							$ 10,100,000
Build-to-Suit Obligation, Condition Two | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Purchase percentage of equipment cost							4.00%
Build-to-Suit Obligation, Condition One | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Purchase percentage of equipment cost							12.00%
Senior Subordinated Notes | Amended Hercules Secured Term Loan
Debt Instrument [Line Items]
Drawdown Amount				$ 15,000,000	$ 15,000,000
Effective Interest Rate				7.95%	7.95%
Debt variable interest rate					7.95%
Debt additional variable interest rate decrease				5.25%
Additional debt end of term charge		$ 400,000
Construction In Progress, Build-to-suit
Debt Instrument [Line Items]
Property and equipment, gross							$ 10,900,000
Forecast | Build to Suit Obligation | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Non-utilization fee percentage	3.00%

Debt Financing - Summary of Deb

Debt Financing - Summary of Debt Obligations (Details) - Build to Suit Obligation $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Debt Instrument [Line Items]
Principal Balance	$ 8,190
Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Drawdown Amount	10,100
Principal Balance	8,190
Purchase Option Fee	1,212
Discount on Purchase Option Fee	(216)
Unamortized Discounts and Issuance Costs	(948)
Monthly Payment	324
Drawdown Maturity Date Of October 1, 2021 | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Drawdown Amount	5,000
Principal Balance	3,720
Purchase Option Fee	600
Discount on Purchase Option Fee	(85)
Unamortized Discounts and Issuance Costs	(520)
Monthly Payment	$ 160
Stated Interest Rate	9.43%
Effective Interest Rate	26.28%
Drawdown Maturity Date Of January 1, 2022 | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Drawdown Amount	$ 2,800
Principal Balance	2,299
Purchase Option Fee	336
Discount on Purchase Option Fee	(60)
Unamortized Discounts and Issuance Costs	(201)
Monthly Payment	$ 90
Stated Interest Rate	9.68%
Effective Interest Rate	19.58%
Drawdown Maturity Date Of July 1, 2022 | Trinity Capital Fund III, L.P.
Debt Instrument [Line Items]
Drawdown Amount	$ 2,300
Principal Balance	2,171
Purchase Option Fee	276
Discount on Purchase Option Fee	(71)
Unamortized Discounts and Issuance Costs	(227)
Monthly Payment	$ 74
Stated Interest Rate	9.93%
Effective Interest Rate	19.77%

Debt Financing - Schedule of L

Debt Financing - Schedule of Long-term Debt Instruments (Details) - Build to Suit Obligation $ in Thousands	Jun. 30, 2019USD ($)
Debt Instrument [Line Items]
Build-to-suit obligation principal amount	$ 8,190
Build-to-suit obligation Purchase Option Fees at present value	996
Less: unamortized Purchase Option Fees	(647)
unamortized fair value of free-standing warrants	(141)
unamortized debt discount	(145)
unamortized debt issuance costs	(15)
Build-to-suit obligation, net of debt issuance costs and discount	8,238
Build-to-suit obligation, current portion	3,147
Build-to-suit obligation, long-term portion, net of debt issuance costs and discount	$ 5,091

Debt Financing - Future Minimu

Debt Financing - Future Minimum Payments (Details) $ in Thousands	Jun. 30, 2019USD ($)
Debt Principal [Abstract]
Remainder of 2019	$ 1,508
2020	3,359
2021	2,964
2022	359
Total	8,190
Debt Interest Payment [Abstract]
Remainder of 2019	363
2020	530
2021	194
2022	12
Total	1,099
Debt Purchase Option Fee [Abstract]
Remainder of 2019	0
2020	0
2021	600
2022	612
Total	$ 1,212

Warrants (Detail)

Warrants (Detail)	6 Months Ended
	Jun. 30, 2019$ / sharesshares
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	274,524
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	274,524
Hercules - June 2014
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	1,583
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	1,583
Exercise Price (in USD per share) | $ / shares	$ 176.80
Expiration Date	Jan. 27, 2020
Hercules - June 2015
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	2,035
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	2,035
Exercise Price (in USD per share) | $ / shares	$ 147.40
Expiration Date	Jun. 23, 2020
Trinity - September 2018
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	75,000
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	75,000
Exercise Price (in USD per share) | $ / shares	$ 3.59
Expiration Date	Sep. 25, 2025
Private Investment in Public Equity (PIPE) | Series B
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	195,906
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	195,906
Exercise Price (in USD per share) | $ / shares	$ 31
Expiration Date	Aug. 19, 2021

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Cancellation fees	50.00%
Construction agreement and transfer fees		$ 11.7
Payment		2.8
Commercial Coating and Primary Packaging System
Other Commitments [Line Items]
Purchase commitments related to fixed assets		6.3
Equipment, Patch Assembly and Applicator, Retainer Machinery
Other Commitments [Line Items]
Purchase commitments related to fixed assets		$ 3.9
Aggregate purchase price paid			$ 2
Minimum
Other Commitments [Line Items]
Annual fees	$ 1
Maximum
Other Commitments [Line Items]
Annual fees	$ 14
Employee Stock Option | Minimum
Other Commitments [Line Items]
Vesting rights upon termination		25.00%
Employee Stock Option | Maximum
Other Commitments [Line Items]
Vesting rights upon termination		100.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	17,357	55,799
Stock option awards granted (in shares)	496,950
Unrecognized stock-based compensation expense	$ 4.4
Weighted-average period of unrecognized stock-based compensation expense	3 years 21 days
New Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards granted (in shares)	32,500
Vesting percentage	25.00%
Vesting rights	Options vest at a rate of 25% of the shares on the first anniversary of the commencement of such employee’s employment with the Company, and then one forty-eighth (1/48) of the shares monthly thereafter subject to such employee’s continued service.
Amended and Restated 2014 Equity and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)	1,771,012
Options vested period	4 years
Shares available for grant (in shares)	17,357
Amended and Restated 2014 Equity and Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options grant period	10 years

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option and Award Activity Excluding Inducement Grants (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Shares Available for Grant
Beginning balance (in shares)	55,799
Additional shares reserved (in shares)	419,056
Options granted (in shares)	(496,950)
Options canceled/forfeited/expired (in shares)	39,452
Ending balance (in shares)	17,357	55,799
Number of Shares Subject to Outstanding Options
Beginning balance (in shares)	1,296,157
Options granted (in shares)	496,950
Options canceled/forfeited/expired (in shares)	(39,452)
Ending balance (in shares)	1,753,655	1,296,157
Exercisable (in shares)	366,022
Vested or expected to vest (in shares)	1,627,577
Weighted-Average Exercise Price per Share
Beginning balance (in USD per share)	$ 5.75
Options granted (in USD per share)	3.27
Option canceled/forfeited/expired (in USD per share)	5.23
Ending balance (in USD per share)	5.06	$ 5.75
Exercisable (in USD per share)	8.55
Vested or expected to vest (in USD per share)	$ 5.15
Weighted-Average Remaining Contractual Term (In Years)
Weighted-average remaining contractual term	9 years 18 days	9 years 2 months 23 days
Exercisable	8 years 5 months 26 days
Vested or expected to vest	9 years 10 days
Aggregate Intrinsic Value
Balance	$ 197
Exercisable	1
Vested or expected to vest	$ 176

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Company's Inducement Grant Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Number of Shares Subject to Outstanding Options
Beginning balance (in shares)	1,296,157
Options granted (in shares)	496,950
Options canceled/forfeited/expired (in shares)	(39,452)
Ending balance (in shares)	1,753,655	1,296,157
Exercisable (in shares)	366,022
Vested or expected to vest (in shares)	1,627,577
Weighted-Average Exercise Price per Share
Beginning balance (in USD per share)	$ 5.75
Options granted (in USD per share)	3.27
Option canceled/forfeited/expired (in USD per share)	5.23
Ending balance (in USD per share)	5.06	$ 5.75
Exercisable (in USD per share)	8.55
Vested or expected to vest (in USD per share)	$ 5.15
Weighted-Average Remaining Contractual Term (In Years)
Weighted-average remaining contractual term	9 years 18 days	9 years 2 months 23 days
Exercisable	8 years 5 months 26 days
Vested or expected to vest	9 years 10 days
Aggregate Intrinsic Value
Balance	$ 197
Exercisable	1
Vested or expected to vest	$ 176
Inducement Grant
Number of Shares Subject to Outstanding Options
Beginning balance (in shares)	13,837
Options granted (in shares)	0
Options canceled/forfeited/expired (in shares)	(1,750)
Ending balance (in shares)	12,087	13,837
Exercisable (in shares)	9,795
Vested or expected to vest (in shares)	11,952
Weighted-Average Exercise Price per Share
Beginning balance (in USD per share)	$ 20.60
Options granted (in USD per share)	0
Option canceled/forfeited/expired (in USD per share)	22.80
Ending balance (in USD per share)	20.28	$ 20.60
Exercisable (in USD per share)	18.66
Vested or expected to vest (in USD per share)	$ 20.20
Weighted-Average Remaining Contractual Term (In Years)
Weighted-average remaining contractual term	3 years 6 months 3 days	4 years 6 months 7 days
Exercisable	2 years 5 months 18 days
Vested or expected to vest	3 years 5 months 16 days
Aggregate Intrinsic Value
Balance	$ 0
Exercisable	0
Vested or expected to vest	$ 0

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 386	$ 330	$ 747	$ 469
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	178	142	343	209
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 208	$ 188	$ 404	$ 260

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Weighted-Average Assumptions for the Black-Scholes Option-Pricing Model Used in Determining the Fair Value of Options Granted (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%	0.00%
Risk free interest rate, minimum	1.97%	2.74%	1.97%	2.74%
Risk free interest rate, maximum	2.45%	3.11%	2.66%	3.11%
Expected volatility	108.00%	89.00%		89.00%
Expected term		6 years 30 days		6 years 30 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility			108.00%
Expected term	6 years 29 days		6 years 29 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility			106.00%
Expected term	5 years 11 months 15 days		5 years 11 months 15 days