F-star Therapeutics (FSTX) 10-Q 31 Jul 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 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
Trading Symbol	SBPH
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Registrant Name	Spring Bank Pharmaceuticals, Inc.
Entity Central Index Key	0001566373
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		16,459,155
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-37718
Entity Address, Address Line One	35 Parkwood Drive
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Hopkinton
Entity Address, State or Province	MA
City Area Code	508
Entity Address, Postal Zip Code	01748
Local Phone Number	473-5993
Entity Tax Identification Number	52-2386345
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 10,547	$ 14,724
Marketable securities	38,646	32,914
Prepaid expenses and other current assets	2,402	1,649
Total current assets	51,595	49,287
Marketable securities, long-term		16,804
Property and equipment, net	2,353	2,319
Operating lease right-of-use assets	2,850
Restricted cash	234	234
Other assets	35	167
Total	57,067	68,811
Current liabilities:
Accounts payable	1,725	1,880
Accrued expenses and other current liabilities	3,185	2,367
Operating lease liabilities, current	332
Total current liabilities	5,242	4,247
Warrant liabilities	805	8,511
Operating lease liabilities, noncurrent	3,052
Other long-term liabilities	27	193
Total liabilities	9,126	12,951
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.0001 par value—authorized, 10,000,000 shares at June 30, 2019 and December 31, 2018; no shares issued or outstanding at June 30, 2019 and December 31, 2018
Common stock, $0.0001 par value—authorized, 200,000,000 shares at June 30, 2019 and December 31, 2018; 16,459,155 and 16,434,614 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	2	2
Additional paid-in capital	159,975	157,931
Accumulated deficit	(111,818)	(102,068)
Accumulated other comprehensive loss	(218)	(5)
Total stockholders’ equity	47,941	55,860
Total	$ 57,067	$ 68,811

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	16,459,155	16,434,614
Common stock, shares outstanding	16,459,155	16,434,614

Consolidated Statements of Oper

Consolidated 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
Operating expenses:
Research and development	$ 7,275	$ 5,555	$ 12,842	$ 9,532
General and administrative	2,490	2,399	5,300	4,622
Total operating expenses	9,765	7,954	18,142	14,154
Loss from operations	(9,765)	(7,954)	(18,142)	(14,154)
Other income:
Interest income	325	198	686	332
Change in fair value of warrant liabilities	4,885	3,971	7,706	5,173
Net loss	(4,555)	(3,785)	(9,750)	(8,649)
Unrealized gain (loss) on marketable securities	(97)	(22)	(213)	1
Comprehensive loss	$ (4,652)	$ (3,807)	$ (9,963)	$ (8,648)
Net loss per common share - basic and diluted	$ (0.28)	$ (0.29)	$ (0.59)	$ (0.66)
Weighted-average number of shares outstanding - basic and diluted	16,443,379	13,179,072	16,440,192	13,085,820

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At-The-Market Offering [Member]	Common Stock [Member]	Common Stock [Member]At-The-Market Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]At-The-Market Offering [Member]	Accumulated Deficit [Member]	Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2017	$ 34,748		$ 1		$ 113,984		$ (79,214)	$ (23)
Balance, shares at Dec. 31, 2017			12,961,993
Stock-based compensation	1,298				1,298
Issuance of common stock for services rendered	46				46
Issuance of common stock for services rendered, shares			3,245
Issuance of common stock in connection with at-the-market offering, net of issuance costs		$ 3,213				$ 3,213
Issuance of common stock in connection with at-the-market offering, shares				217,329
Net unrealized gain (loss) on marketable securities	1							1
Net loss	(8,649)						(8,649)
Balance at Jun. 30, 2018	30,657		$ 1		118,541		(87,863)	(22)
Balance, shares at Jun. 30, 2018			13,182,567
Balance at Dec. 31, 2017	34,748		$ 1		113,984		(79,214)	(23)
Balance, shares at Dec. 31, 2017			12,961,993
Balance at Dec. 31, 2018	55,860		$ 2		157,931		(102,068)	(5)
Balance, shares at Dec. 31, 2018			16,434,614
Balance at Mar. 31, 2018	33,369		$ 1		117,469		(84,101)
Balance, shares at Mar. 31, 2018			13,153,879
Stock-based compensation	664				664
Issuance of common stock for services rendered	22				22
Issuance of common stock for services rendered, shares			1,414
Issuance of common stock in connection with at-the-market offering, net of issuance costs		386				386
Issuance of common stock in connection with at-the-market offering, shares				27,274
Net unrealized gain (loss) on marketable securities	1						23	(22)
Net unrealized gain (loss) on marketable securities	(22)
Net loss	(3,785)						(3,785)
Balance at Jun. 30, 2018	30,657		$ 1		118,541		(87,863)	(22)
Balance, shares at Jun. 30, 2018			13,182,567
Balance at Dec. 31, 2018	55,860		$ 2		157,931		(102,068)	(5)
Balance, shares at Dec. 31, 2018			16,434,614
Stock-based compensation	1,895				1,895
Issuance of common stock for services rendered	143				143
Issuance of common stock for services rendered, shares			23,941
Issuance of common stock in connection with at-the-market offering, net of issuance costs		6				6
Issuance of common stock in connection with at-the-market offering, shares				600
Net unrealized gain (loss) on marketable securities	(213)							(213)
Net loss	(9,750)						(9,750)
Balance at Jun. 30, 2019	47,941		$ 2		159,975		(111,818)	(218)
Balance, shares at Jun. 30, 2019			16,459,155
Balance at Mar. 31, 2019	51,546		$ 2		158,928		(107,263)	(121)
Balance, shares at Mar. 31, 2019			16,442,532
Stock-based compensation	982				982
Issuance of common stock for services rendered	59				59
Issuance of common stock for services rendered, shares			16,023
Issuance of common stock in connection with at-the-market offering, net of issuance costs		$ 6				$ 6
Issuance of common stock in connection with at-the-market offering, shares				600
Net unrealized gain (loss) on marketable securities	(97)							(97)
Net loss	(4,555)						(4,555)
Balance at Jun. 30, 2019	$ 47,941		$ 2		$ 159,975		$ (111,818)	$ (218)
Balance, shares at Jun. 30, 2019			16,459,155

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
At-The-Market Offering [Member]
Common stock issuance costs	$ 14	$ 139

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (9,750)	$ (8,649)
Adjustments for:
Depreciation and amortization	171	86
Loss on the disposal of property and equipment		16
Operating lease right-of-use asset amortization	130
Change in fair value of warrant liabilities	(7,706)	(5,173)
Non-cash investment income	72	110
Non-cash stock-based compensation	2,013	1,349
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(753)	(625)
Other assets	132
Accounts payable	(155)	(12)
Accrued expenses and other liabilities	1,081	(62)
Net cash used in operating activities	(14,765)	(12,960)
Cash flows from investing activities:
Proceeds from sale of marketable securities	16,787	21,951
Purchases of marketable securities	(6,000)	(22,000)
Purchases of property and equipment	(205)	(994)
Net cash provided by (used in) investing activities	10,582	(1,043)
Cash flows from financing activities:
Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs	6	3,213
Cash provided by financing activities	6	3,213
Net decrease in cash, cash equivalents and restricted cash	(4,177)	(10,790)
Cash, cash equivalents and restricted cash, beginning of period	14,958	24,133
Cash, cash equivalents and restricted cash, end of period	10,781	13,343
Supplemental disclosures of cash flow information:
Cash paid for taxes	$ 17	$ 3

Nature of Business and Summary

Nature of Business and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Nature of Business and Summary of Significant Accounting Policies	1. NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Business Spring Bank Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company engaged in the discovery and development of a novel class of therapeutics using a proprietary small molecule nucleotide platform. The Company is developing its most advanced product candidate, inarigivir soproxil (“inarigivir”), for the treatment of chronic hepatitis B virus. Since inception in 2002 and prior to its initial public offering (“IPO”) in May 2016, the Company built its technology platform and product candidate pipeline, supported by grants and through private financings. The Company has three wholly owned subsidiaries: Sperovie Biosciences, Inc. formed in September 2015, SBP Securities Corporation formed in December 2016 and SBP International Limited formed in May 2019. The Company’s success is dependent upon its ability to successfully complete clinical development and obtain regulatory approval of its product candidates, successfully commercialize approved products, generate revenue, and, ultimately, attain profitable operations. The Company’s operations to date have been primarily limited to the development of inarigivir, SB 11285, SB 9225 and the Company’s other product candidates. Basis of Presentation and Liquidity The accompanying consolidated financial statements have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). The accompanying interim financial statements as of June 30, 2019 and for the three and six months ended June 30, 2019 and 2018, and related interim information contained within the notes to the financial statements, are unaudited. In management’s opinion, the unaudited interim consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include all adjustments (including normal recurring adjustments) necessary for the fair presentation of the Company’s financial position as of June 30, 2019, results of operations for the three and six months ended June 30, 2019 and 2018, statement of stockholders’ equity for the three and six months ended June 30, 2019 and 2018 and its cash flows for the six months ended June 30, 2019 and 2018. These interim financial statements should be read in conjunction with the Company’s audited financial statements and accompanying notes contained in the Company’s Annual Report on Form 10-K As of June 30, 2019, the Company had an accumulated deficit of $111.8 million and $49.2 million in cash, cash equivalents and marketable securities. The Company expects to continue to incur significant and increasing losses for the foreseeable future. The Company anticipates that its expenses will increase significantly as it continues to develop inarigivir, SB 11285, SB 9225 and its other product candidates. The Company does not have any committed external source of funds. As a result, the Company will need additional financing to support its continuing operations. Adequate additional funds may not be available to the Company on acceptable terms, or at all. To the extent that the Company raises additional capital through the sale of equity or convertible debt securities, stockholders’ ownership interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect common stockholder rights. If the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, the Company may have to relinquish valuable rights to its technologies, future revenue streams, research programs, or product candidates or grant licenses on terms that may not be favorable to the Company. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sperovie Biosciences, Inc., SBP Securities Corporation and SBP International Limited. Sperovie Biosciences, Inc. had operations consisting mainly of legal fees associated with intellectual property activities as of June 30, 2019. SBP Securities Corporation had assets primarily related to investments in marketable securities and operations consisting primarily of interest income as of June 30, 2019. SBP International Limited had operations consisting mainly of clinical trial oversight, including European data protection oversight, as of June 30, 2019. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates relied upon in preparing the accompanying financial statements related to the fair value of common stock and warrant liabilities, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, and accounting for certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates. Cash and Cash Equivalents Cash equivalents are stated at fair value and include short-term, highly liquid investments with remaining maturities of 90 days or less at the date of purchase. Included in cash and cash equivalents as of June 30, 2019 and December 31, 2018 are money market fund investments of $9.0 million and $13.3 million, respectively, which are reported at fair value (Note 5). Restricted Cash As of June 30, 2019 and December 31, 2018, restricted cash consists of approximately $234,000, which is held as a security deposit required in conjunction with a lease agreement for the Company’s principal office and laboratory space entered into in October 2017. Concentration of Credit Risk Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash and marketable securities. Substantially all of the Company’s cash is held at financial institutions that management believes to be of high credit quality. Deposits with these financial institutions may exceed the amount of insurance provided on such deposits; however, these deposits may be redeemed upon demand and, therefore, bear minimal risk. Investments in Marketable Securities The Company invests excess cash balances in short-term and long-term marketable securities. The Company classifies investments in marketable securities as either held-to-maturity or available-for-sale based on facts and circumstances present at the time of purchase. At each balance sheet date presented, all investments in securities are classified as available-for-sale. The Company reports available-for-sale investments at fair value at each balance sheet date and includes any unrealized holding gains and losses (the adjustment to fair value) in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses are determined using the specific identification method and are included in other income (expense). If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the intention to sell and, if so, marks the investment to market through a charge to the Company’s consolidated statements of operations and comprehensive loss. Property and Equipment, Net Property and equipment are recorded at cost. Costs associated with maintenance and repairs are expensed as incurred. Depreciation is provided using the straight-line method over the estimated useful lives: Asset Category Useful Life Equipment 5-7 years Furniture and fixtures 5 years Leasehold improvements Lesser of 10 years or the remaining term of the respective lease Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease right-of-use (“ROU”) assets, other current liabilities and operating lease liabilities in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company’s leases do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. This is the rate the Company would have to pay if borrowing on a collateralized basis over a similar term to each lease. The operating lease ROU asset also includes any lease payments made and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Impairment of Long-Lived Assets Long-lived assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If the undiscounted cash flows are insufficient to recover the carrying value, an impairment loss is recorded for the difference between the carrying value and fair value of the asset. As of June 30, 2019, no such impairment has occurred. Research and Development Costs Research and development expenses consist primarily of costs incurred for the Company’s research activities, including discovery efforts, and the development of product candidates, which include: • expenses incurred under agreements with third parties, including contract research organizations, or CROs, that conduct research, preclinical activities and clinical trials on the Company’s behalf as well as contract manufacturing organizations, or CMOs, that manufacture drug products for use in the Company’s preclinical and clinical trials; • salaries, benefits and other related costs, including stock-based compensation expense, for personnel in the Company’s research and development functions; • costs of outside consultants, including their fees, stock-based compensation and related travel expenses; • the cost of laboratory supplies and acquiring, developing and manufacturing preclinical study and clinical trial materials; • costs related to compliance with regulatory requirements; and • facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs. The Company expenses research and development costs as incurred. The Company recognizes external development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors and its clinical investigative sites. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected in the Company’s consolidated financial statements as prepaid or accrued research and development expenses. Warrants The Company reviews the terms of all warrants issued and classifies the warrants as a component of permanent equity if they are freestanding financial instruments that are legally detachable and separately exercisable, contingently exercisable, do not embody an obligation for the Company to repurchase its own shares, and permit the holders to receive a fixed number of shares of common stock upon exercise. In addition, the warrants must require physical settlement and may not provide any guarantee of value or return. Warrants that meet these criteria are initially recorded at their grant date fair value and are not subsequently remeasured. Warrants that do not meet these criteria are classified as liabilities and remeasured to their fair value at each reporting period. Stock-Based Compensation The Company’s stock-based payments include stock options, performance-based restricted stock units and grants of common stock, including common stock subject to vesting. The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is generally the vesting period, on a straight-line basis. The Company measures the fair value of the performance-based restricted stock units relating to the total share return performance using a Monte Carlo valuation model. The Company adopted ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting Financial Instruments The Company’s financial instruments consist of cash equivalents, marketable securities, accounts payable and liability classified warrants. The carrying amounts of cash and cash equivalents and accounts payable approximate their fair value due to the short-term nature of those financial instruments. The fair value of the marketable securities and liability classified warrants are remeasured to fair value each reporting period as described in Note 5. Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company’s assets and liabilities measured at fair value on a recurring basis include cash equivalents, marketable securities and warrant liabilities. Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period, determined using the treasury-stock method and the as if-converted method, for convertible securities, if inclusion of these instruments is dilutive. For the three and six months ended June 30, 2019 and 2018, both methods are equivalent. Basic and diluted net loss per share is described further in Note 2. Income Taxes Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities and for loss and credit carryforwards using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The Company assesses its income tax positions and records tax benefits based upon management’s evaluation of the facts, circumstances and information available at the reporting date. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority having full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the consolidated financial statements. The Company classifies interest and penalties associated with such uncertain tax positions as a component of interest expense. As of June 30, 2019 and December 31, 2018, the Company has not identified any material uncertain tax positions. Guarantees and Indemnifications As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The Company leases its principal office and laboratory space in Hopkinton, Massachusetts and previously leased research and development space in Milford, Massachusetts under non-cancelable operating leases. The Company has standard indemnification arrangements under these leases that require it to indemnify the landlords against liability for injury, loss, accident, or damage from any claims, actions, proceedings, or costs resulting from certain acts, breaches, violations, or nonperformance under the Company’s lease. Through June 30, 2019, the Company had not experienced any losses related to these indemnification obligations and no material claims were outstanding. The Company does not expect significant claims related to these indemnification obligations, and consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established. Segment Information Operating segments are identified as components of an enterprise about which separate and discrete financial information is available for evaluation by the chief operating decision maker, the Company’s chief executive officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and does not track expenses on a program-by-program basis. Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework – Changes to the Disclosure Requirement for Fair Value Measurement . In February 2016, the FASB issued ASU No. 2016-02, Leases “Codification Improvements to Topic 842, Leases” The Company adopted the standard on the effective date of January 1, 2019 by applying the new lease requirements at the effective date. Prior periods continue to be presented based on the accounting standards originally in effect for such periods. The Company also elected the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carry forward the historical lease classification. The Company will also apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The standard had an impact of approximately $3.0 million on the Company’s assets and $3.4 million on its liabilities, as of January 1, 2019, for the recognition of right-of-use assets and lease liabilities, which are primarily related to the lease of its corporate headquarters in Hopkinton, Massachusetts. The standard did not have a material impact on the Company’s results of operations or liquidity (see Note 8) In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception .

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	2. NET LOSS PER SHARE The following table summarizes the computation of basic and diluted net loss per share of the Company for such periods (in thousands, except share and per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Net loss $ (4,555 ) $ (3,785 ) $ (9,750 ) $ (8,649 ) Weighted-average number of shares outstanding - basic and diluted 16,443,379 13,179,072 16,440,192 13,085,820 Net loss per common share - basic and diluted $ (0.28 ) $ (0.29 ) $ (0.59 ) $ (0.66 ) Diluted net loss per common share is the same as basic net loss per common share for all periods presented. The following potentially dilutive securities outstanding, prior to the use of the treasury stock method or if-converted method, have been excluded from the computation of diluted weighted-average shares outstanding, because such securities had an antidilutive impact due to the losses reported: For the Three and Six Months Ended June 30, 2019 2018 Common stock warrants 1,662,124 1,787,124 Stock options, RSUs and Inducement awards 1,900,615 1,338,565

Investments

Investments	6 Months Ended
	Jun. 30, 2019
Investments Debt And Equity Securities [Abstract]
Investments	3. INVESTMENTS Cash in excess of the Company’s immediate requirements is invested in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. The following table summarizes the Company’s investments, by category, as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, Investments - Current: 2019 2018 Debt securities - available for sale $ 38,646 $ 32,914 Total $ 38,646 $ 32,914 Investments - Noncurrent: Debt securities - available for sale $ — $ 16,804 Total $ — $ 16,804 A summary of the Company’s available-for-sale classified investments as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): At June 30, 2019 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 10,975 $ — $ (51 ) $ 10,924 United States treasury securities 27,889 — (167 ) 27,722 Total $ 38,864 $ — $ (218 ) $ 38,646 At December 31, 2018 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 16,028 $ — $ (19 ) $ 16,009 United States treasury securities 16,913 — (8 ) 16,905 Total $ 32,941 $ — $ (27 ) $ 32,914 Investments - Noncurrent: Corporate bonds $ 4,930 $ 2 $ — $ 4,932 United States treasury securities 11,852 20 — 11,872 Total $ 16,782 $ 22 $ — $ 16,804 The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of June 30, 2019 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 38,864 $ 38,646 Due after one year through two years — — Total $ 38,864 $ 38,646

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	4. PROPERTY AND EQUIPMENT, NET Property and equipment as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): June 30, December 31, 2019 2018 Equipment $ 1,278 $ 1,064 Furniture and fixtures 382 400 Leasehold improvements 1,356 1,347 Total property and equipment 3,016 2,811 Less: accumulated depreciation and amortization (663 ) (492 ) Property and equipment, net $ 2,353 $ 2,319 Depreciation expense for the three and six months ended June 30, 2019 was $88,000 and $171,000, respectively. Depreciation expense for the three and six months ended June 30, 2018 was $41,000 and $86,000, respectively.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. FAIR VALUE MEASUREMENTS Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The Company classified its money market funds within Level 1 because their fair values are based on their quoted market prices. The Company classified its commercial paper, corporate bonds and United States treasury securities within Level 2 because their fair values are determined using alternative pricing sources or models that utilized market observable inputs. A summary of the assets and liabilities that are measured at fair value as of June 30, 2019 and December 31, 2018 is as follows (in thousands): Fair Value Measurement at June 30, 2019 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 9,011 $ 9,011 $ — $ — Fixed income securities 38,646 — 38,646 — Total $ 47,657 $ 9,011 $ 38,646 $ — Liabilities: Warrant liabilities $ 805 $ — $ — $ 805 Total $ 805 $ — $ — $ 805 Fair Value Measurement at December 31, 2018 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 13,264 $ 13,264 $ — $ — Fixed income securities 49,718 — 49,718 — Total $ 62,982 $ 13,264 $ 49,718 $ — Liabilities: Warrant liabilities $ 8,511 $ — $ — $ 8,511 Total $ 8,511 $ — $ — $ 8,511 (1) Money market funds are included within cash and cash equivalents in the accompanying consolidated balance sheets and are recognized at fair value. The following table reflects the change in the Company’s Level 3 liabilities, which consists of the warrants issued in a private placement in November 2016 (see Note 7), for the period ended June 30, 2019 (in thousands): November Private Placement Warrants Balance at December 31, 2017 $ 13,128 Change in fair value (4,617 ) Balance at December 31, 2018 8,511 Change in fair value (7,706 ) Balance at June 30, 2019 $ 805

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): June 30, December 31, 2019 2018 Clinical $ 2,393 $ 941 Compensation and benefits 504 830 Accounting and legal 218 227 Other 70 369 Total accrued expenses and other current liabilities $ 3,185 $ 2,367

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity	7. STOCKHOLDERS’ EQUITY Common and Preferred Stock In August 2017, the Company entered into a Controlled Equity Offering SM In August 2018, the Company issued and sold in an underwritten public offering an aggregate of 3,246,079 shares of its common stock at $12.50 per share, which included 246,079 shares pursuant to the exercise of an option to purchase additional shares granted to the underwriters in connection with the offering. The offering resulted in $38.0 million of net proceeds, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Warrants In connection with the amendment and restatement of a license agreement with BioHEP Technologies Ltd. (“BioHEP”) in February 2016, the Company issued a warrant to purchase 125,000 shares of the Company’s common stock to BioHEP (the “BioHEP Warrant”). The BioHEP Warrant had an exercise price of $16.00 per share and expired unexercised on August 1, 2018. The Company evaluated the terms of the warrant and concluded that it should be equity-classified. The fair value of the warrant, $0.8 million, was estimated on the issuance date using a Black-Scholes pricing model based on the following assumptions: an expected term of two and a half years, expected stock price volatility of 71%, a risk-free rate of 1.01%, and a dividend yield of 0%. The fair value was expensed as research and development costs. In connection with the Company’s IPO, the Company issued to the sole book-running manager for the IPO a warrant to purchase 27,600 shares of common stock in May 2016 and a warrant to purchase 747 shares of common stock in June 2016 (together, the “IPO Warrants”). The IPO Warrants are exercisable at an exercise price of $15.00 per share and expire on May 5, 2021. The Company evaluated the terms of the IPO Warrants and concluded that they should be equity-classified. The fair value of the May 2016 IPO Warrants was estimated on the applicable issuance dates using a Black-Scholes pricing model based on the following assumptions: an expected term of 4.99 years; expected stock price volatility of 87%; a risk-free rate of 1.20%; and a dividend yield of 0%. The fair value of the June 2016 IPO Warrants was estimated on the applicable issuance dates using a Black-Scholes pricing model based on the following assumptions: an expected term of 4.92 years; expected stock price volatility of 87%; a risk-free rate of 1.23%; and a dividend yield of 0%. The aggregate fair value of the IPO Warrants was approximately $0.2 million. In November 2016, the Company entered into a definitive agreement with respect to the private placement of 1,644,737 shares of common stock and warrants to purchase 1,644,737 shares of common stock (the “November 2016 Private Placement Warrants”) to a group of accredited investors. These investors paid $9.12 for each share of common stock and warrant to purchase one share of common stock. The November 2016 Private Placement Warrants are exercisable at an exercise price of $10.79 per share and expire on November 23, 2021. The Company evaluated the terms of these warrants and concluded that they are liability-classified. In November 2016, the Company recorded the fair value of these warrants of approximately $8.3 million using a Black-Scholes pricing model. The Company must recognize any change in the value of the warrant liability each reporting period in the statement of operations. As of June 30, 2019 and December 31, 2018, the fair value of the November 2016 Private Placement Warrants was approximately $0.8 million and $8.5 million, respectively (see Note 5). A summary of the Black-Scholes pricing model assumptions used to record the fair value of the warrants is as follows: June 30, 2019 December 31, 2018 Risk-free interest rate 1.7 % 2.5 % Expected term (in years) 2.4 2.9 Expected volatility 66.9 % 78.1 % Expected dividend yield 0 % 0 % A summary of the warrant activity for the six months ended June 30, 2019 and for the year ended December 31, 2018 is as follows: Warrants Outstanding at December 31, 2017 1,787,124 Grants — Exercises — Expirations/cancellations (125,000 ) Outstanding at December 31, 2018 1,662,124 Grants — Exercises — Expirations/cancellations — Outstanding at June 30, 2019 1,662,124 2014 Stock Incentive Plan In April 2014, the Company’s Board of Directors approved the 2014 Stock Incentive Plan (the “2014 Plan”) and authorized 750,000 shares of common stock to be issued under the 2014 Plan. The Company’s 2014 Plan provides for the issuance of common stock, stock options and other stock-based awards to employees, officers, directors, consultants, and advisors. The Company’s 2015 Stock Incentive Plan (the “2015 Plan”) became effective immediately prior to the closing of the Company’s IPO on May 11, 2016. Upon the effectiveness of the 2015 Plan, 116,863 shares of common stock that remained available for grant under the 2014 Plan became available for grant under the 2015 Plan, and no further awards were available to be issued under the 2014 Plan. 2015 Stock Incentive Plan and Amended and Restated 2015 Stock Incentive Plan The Company’s Board of Directors initially adopted the 2015 Plan in December 2015, subject to stockholder approval, and authorized 750,000 shares of Common Stock to be issued under the 2015 Plan. The 2015 Plan became effective upon the closing of the Company’s IPO on May 11, 2016 after approval by the Company’s stockholders. The 2015 Plan provides for the issuance of common stock, stock options and other stock-based awards to employees, officers, directors, consultants and advisors of the Company. In June 2018, upon receipt of stockholder approval at the Company’s 2018 annual meeting, the 2015 Plan was amended and restated in its entirety increasing the authorized number of shares of common stock reserved for issuance by 800,000 shares (together with the 2014 Plan, the 2015 Plan, the “Stock Incentive Plans”). The Board approved the Amended and Restated 2015 Plan on March 9, 2018. Pursuant to the Amended and Restated 2015 Plan, there are 1,666,863 shares authorized for issuance. In addition, to the extent any outstanding awards under the 2014 Plan expire, terminate or are otherwise surrendered, cancelled or forfeited after the closing of the Company’s IPO, those shares are added to the authorized shares under the Amended and Restated 2015 Plan. The total amount of shares authorized for issuance under both the 2014 Plan and the Amended and Restated 2015 Plan is 2,300,000. As of June 30, 2019, the Company had 404,331 shares available for issuance under the Amended and Restated 2015 Plan. The exercise price of stock options cannot be less than the fair value of the common stock on the date of grant. Stock options awarded under the Stock Incentive Plans expire 10 years after the grant date, unless the Board sets a shorter term. There were no stock options granted prior to 2015. The following table summarizes the option activity under the Stock Incentive Plans for the six months ended June 30, 2019 and the year ended December 31, 2018: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2017 988,565 $ 10.83 $ 2,617,859 Granted 311,000 12.28 — Exercised — — — Cancelled — — — Outstanding at December 31, 2018 1,299,565 11.18 881,385 Granted 343,000 10.37 — Exercised — — — Cancelled (17,750 ) 14.28 — Options outstanding at June 30, 2019 1,624,815 $ 10.97 $ — Options exercisable at June 30, 2019 952,547 $ 11.28 $ — As of June 30, 2019, all options outstanding have a weighted-average remaining contractual life of 7.6 years. The weighted-average fair value of all stock options granted for the six months ended June 30, 2019 was $7.30. Intrinsic value at June 30, 2019 and December 31, 2018 is based on the closing price of the Company’s common stock on that date of $3.69 per share and $10.39 per share, respectively. In January 2018, the Company issued a stock option award as an inducement grant for the purchase of an aggregate of 50,000 shares of the Company’s common stock, outside of the Stock Incentive Plans, at an exercise price of $12.02 per share. In February 2019, the Company issued a stock option award as an inducement grant for the purchase of an aggregate of 40,000 shares of the Company’s common stock, outside of the Stock Incentive Plans, at an exercise price of $10.39 per share. These inducement grants are excluded from the option activity table above. The assumptions the Company used to determine the fair value of stock options granted to employees and directors during the six months ended June 30, 2019 and 2018 are as follows, presented on a weighted-average basis: Six Months Ended June 30, 2019 2018 Risk-free interest rate 2.6 % 2.5 % Expected term (in years) 6.0 5.9 Expected volatility 81.1 % 82.6 % Expected dividend yield 0 % 0 % Performance-Based Restricted Stock Units In January 2019, the Company issued performance-based restricted stock units (“RSUs”) to senior management under the 2015 Plan that represent shares potentially issuable in the future subject to the satisfaction of certain performance milestones as well as a service condition The Company estimates the fair value of market-based RSUs at the date of grant using a Monte Carlo valuation methodology and amortizes those fair values over the requisite service period for each separately vesting tranche of the award. The Monte Carlo methodology that the Company uses to estimate the fair value of market-based RSUs at the date of grant incorporates into the valuation the possibility that the market condition may not be satisfied. Provided that the requisite service is rendered, the total fair value of the market-based RSUs at the date of grant must be recognized as compensation expense even if the market condition is not achieved. However, the number of shares that ultimately vest can vary significantly with the performance of the specified market criteria. The Company estimates the fair value of performance-based RSUs at the date of grant using the fair value method and the probability that the specified performance criteria will be met. Each quarter the Company updates its assessment of the probability that the specified performance criteria will be achieved and adjusts its estimate of the fair value of the performance-based RSUs, if necessary. The Company amortizes the fair values of performance-based RSUs over the requisite service period for each separately vesting tranche of the award. As of June 30, 2019, the Company estimates that it is currently probable that it will achieve the clinical milestones included in the PSU performance goals and has recognized the stock-based compensation expense for the RSUs issued as it relates to the milestone base performance goals. The total stock-based compensation recognized for the three and six months ended June 30, 2019 for the RSUs was approximately $189,000 and $347,000, respectively. The following table is a rollforward of performance-based restricted stock unit activity under the Stock Incentive Plans for the six months ended June 30, 2019: Restricted Stock Units Weighted-Average Grant Date Fair Value Total Nonvested Units at December 31, 2018 — $ — Granted 203,700 8.49 Exercised — — Vested — — Cancelled (17,900 ) 8.49 Total Nonvested Units at June 30, 2019 185,800 $ 8.49 There were no performance-based restricted stock units exercisable as of June 30, 2019. The assumptions used to determine the fair value of the performance-based restricted stock units granted to management during the six months ended June 30, 2019 for the performance goal milestone units is based on the market price of the award on the grant date, which was a weighted average fair value for the six months ended June 30, 2019 of $10.35 per share. The fair value of the performance-based restricted stock units granted to management in 2019 for the Company’s relative total share return units is based on the Monte Carlo Simulation method on the grant date, which the weighted average fair value as of the six months ended June 30, 2019 was $6.62 per share. Stock-Based Compensation The following table summarizes the Company’s stock-based compensation expense for the three and six months ended June 30, 2019 and 2018 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, Stock-based compensation: 2019 2018 2019 2018 Research and development $ 339 $ 213 $ 656 $ 414 General and administrative 702 480 1,357 935 Total Stock-based compensation $ 1,041 $ 693 $ 2,013 $ 1,349 The fair value of stock options vested during the six months ended June 30, 2019 was $1.9 million. At June 30, 2019, there was $5.2 million of unrecognized stock-based compensation expense relating to stock options granted pursuant to the Stock Incentive Plans, which will be recognized over the weighted-average remaining vesting period of 2.8 years. The expense recognized is partially dependent upon the Company’s estimate of the number of shares that will ultimately be issued. At June 30, 2019, there was $1.2 million of unrecognized stock-based compensation expense relating to performance-based restricted stock units granted pursuant to the Stock Incentive Plans, which will be recognized over the weighted-average remaining vesting period of 1.5 years. Reserved Shares As of June 30, 2019 and December 31, 2018, the Company reserved the following shares of common stock for issuance of shares resulting from exercise of outstanding warrants, options and performance-based restricted stock units, as well as issuance of shares available for grant under the Stock Incentive Plans: June 30, December 31, 2019 2018 2016 IPO warrants 28,347 28,347 November Private Placement Warrants 1,633,777 1,633,777 2015 Amended and Restated Stock Incentive Plan 2,214,946 2,238,887 Inducement Awards 90,000 50,000 Total 3,967,070 3,951,011

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	8. LEASES The Company has operating leases for its principal office and laboratory space and the Company’s former headquarters. The Company’s leases have remaining lease terms of approximately 10 years for its principal office and laboratory space, which includes an option to extend the lease for up to 5 years, and approximately 2 years for its former headquarters. The Company’s former headquarters location is subleased through the remainder of the lease term. Other information related to leases was as follows: Six Months Ended June 30, Cash paid for amounts included in the measurement of lease liabilities: 2019 Operating cash flow from operating leases (in thousands) $ 130 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ 2,980 Weighted Average Remaining Lease Term Operating leases 8.7 years Weighted Average Discount Rate Operating leases 8.0 % Operating lease costs under the leases for the three and six months ended June 30, 2019 were approximately $130,000 and $260,000, respectively. Total operating lease costs for the three and six months ended June 30, 2019 were offset by $18,000 and $37,000, respectively, for sublease income and variable lease cost payments. Total rent expense for the three and six months ended June 30, 2018 was $69,000 and $142,000 respectively, which included payments for a lease of the Company’s research and development facility. The lease term of the research and development facility ended as of June 30, 2018. The following table summarizes the Company’s maturities of operating lease liabilities as of June 30, 2019 (in thousands): Year 2019 (excluding the six months ended June 30, 2019) $ 288 2020 588 2021 508 2022 450 2023 462 Thereafter 2,405 Total lease payments $ 4,701 Less: present value discount (1,317 ) Total $ 3,384 For comparative purposes, the Company’s aggregate future minimum non-cancellable commitments under operating leases as of December 31, 2018 were as follows (in thousands): Year 2019 $ 417 2020 588 2021 508 2022 450 Thereafter 2,867 Total minimum lease payments $ 4,830

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. COMMITMENTS AND CONTINGENCIES BioHEP Technologies Ltd. License Agreement In January 2016, the Company entered into an amended and restated license agreement with BioHEP, which became effective on February 1, 2016. Under the amended and restated license agreement, the Company agreed to pay BioHEP up to $3.5 million in development and regulatory milestone payments for disease(s) caused by each distinct virus for which the Company develops licensed product(s). BioHEP is also eligible to receive tiered royalties in the low-to-mid single-digits on net product sales of licensed products by the Company and its affiliates and sub licensees, and a specified share of non-royalty sublicensing revenues the Company and its affiliates receive from sub licensees, which share of sublicensing revenues is capped at a maximum aggregate of $2.0 million under all such sublicenses. Milestone and royalty payments associated with the Company’s amended and restated license agreement with BioHEP cannot be reasonably estimated as to whether or when they will occur. As of June 30, 2019, there have been no milestone or royalty payments made to BioHEP. Contingencies The Company accrues for contingent liabilities to the extent that the liability is probable and estimable. There are no accruals for contingent liabilities in these consolidated financial statements.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	10. SUBSEQUENT EVENTS The Company has evaluated subsequent events through the date on which the consolidated financial statements were issued, to ensure that this submission includes appropriate disclosure of events both recognized in the consolidated financial statements and events which occurred subsequently but were not recognized in the consolidated financial statements.

Nature of Business and Summar_2

Nature of Business and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation and Liquidity	Basis of Presentation and Liquidity The accompanying consolidated financial statements have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). The accompanying interim financial statements as of June 30, 2019 and for the three and six months ended June 30, 2019 and 2018, and related interim information contained within the notes to the financial statements, are unaudited. In management’s opinion, the unaudited interim consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include all adjustments (including normal recurring adjustments) necessary for the fair presentation of the Company’s financial position as of June 30, 2019, results of operations for the three and six months ended June 30, 2019 and 2018, statement of stockholders’ equity for the three and six months ended June 30, 2019 and 2018 and its cash flows for the six months ended June 30, 2019 and 2018. These interim financial statements should be read in conjunction with the Company’s audited financial statements and accompanying notes contained in the Company’s Annual Report on Form 10-K As of June 30, 2019, the Company had an accumulated deficit of $111.8 million and $49.2 million in cash, cash equivalents and marketable securities. The Company expects to continue to incur significant and increasing losses for the foreseeable future. The Company anticipates that its expenses will increase significantly as it continues to develop inarigivir, SB 11285, SB 9225 and its other product candidates. The Company does not have any committed external source of funds. As a result, the Company will need additional financing to support its continuing operations. Adequate additional funds may not be available to the Company on acceptable terms, or at all. To the extent that the Company raises additional capital through the sale of equity or convertible debt securities, stockholders’ ownership interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect common stockholder rights. If the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, the Company may have to relinquish valuable rights to its technologies, future revenue streams, research programs, or product candidates or grant licenses on terms that may not be favorable to the Company.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sperovie Biosciences, Inc., SBP Securities Corporation and SBP International Limited. Sperovie Biosciences, Inc. had operations consisting mainly of legal fees associated with intellectual property activities as of June 30, 2019. SBP Securities Corporation had assets primarily related to investments in marketable securities and operations consisting primarily of interest income as of June 30, 2019. SBP International Limited had operations consisting mainly of clinical trial oversight, including European data protection oversight, as of June 30, 2019. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates relied upon in preparing the accompanying financial statements related to the fair value of common stock and warrant liabilities, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, and accounting for certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents are stated at fair value and include short-term, highly liquid investments with remaining maturities of 90 days or less at the date of purchase. Included in cash and cash equivalents as of June 30, 2019 and December 31, 2018 are money market fund investments of $9.0 million and $13.3 million, respectively, which are reported at fair value (Note 5).
Restricted Cash	Restricted Cash As of June 30, 2019 and December 31, 2018, restricted cash consists of approximately $234,000, which is held as a security deposit required in conjunction with a lease agreement for the Company’s principal office and laboratory space entered into in October 2017.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash and marketable securities. Substantially all of the Company’s cash is held at financial institutions that management believes to be of high credit quality. Deposits with these financial institutions may exceed the amount of insurance provided on such deposits; however, these deposits may be redeemed upon demand and, therefore, bear minimal risk.
Investments in Marketable Securities	Investments in Marketable Securities The Company invests excess cash balances in short-term and long-term marketable securities. The Company classifies investments in marketable securities as either held-to-maturity or available-for-sale based on facts and circumstances present at the time of purchase. At each balance sheet date presented, all investments in securities are classified as available-for-sale. The Company reports available-for-sale investments at fair value at each balance sheet date and includes any unrealized holding gains and losses (the adjustment to fair value) in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses are determined using the specific identification method and are included in other income (expense). If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the intention to sell and, if so, marks the investment to market through a charge to the Company’s consolidated statements of operations and comprehensive loss.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are recorded at cost. Costs associated with maintenance and repairs are expensed as incurred. Depreciation is provided using the straight-line method over the estimated useful lives: Asset Category Useful Life Equipment 5-7 years Furniture and fixtures 5 years Leasehold improvements Lesser of 10 years or the remaining term of the respective lease
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in operating lease right-of-use (“ROU”) assets, other current liabilities and operating lease liabilities in the Company’s consolidated balance sheets. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company’s leases do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. This is the rate the Company would have to pay if borrowing on a collateralized basis over a similar term to each lease. The operating lease ROU asset also includes any lease payments made and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If the undiscounted cash flows are insufficient to recover the carrying value, an impairment loss is recorded for the difference between the carrying value and fair value of the asset. As of June 30, 2019, no such impairment has occurred.
Research and Development Costs	Research and Development Costs Research and development expenses consist primarily of costs incurred for the Company’s research activities, including discovery efforts, and the development of product candidates, which include: • expenses incurred under agreements with third parties, including contract research organizations, or CROs, that conduct research, preclinical activities and clinical trials on the Company’s behalf as well as contract manufacturing organizations, or CMOs, that manufacture drug products for use in the Company’s preclinical and clinical trials; • salaries, benefits and other related costs, including stock-based compensation expense, for personnel in the Company’s research and development functions; • costs of outside consultants, including their fees, stock-based compensation and related travel expenses; • the cost of laboratory supplies and acquiring, developing and manufacturing preclinical study and clinical trial materials; • costs related to compliance with regulatory requirements; and • facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs. The Company expenses research and development costs as incurred. The Company recognizes external development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors and its clinical investigative sites. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected in the Company’s consolidated financial statements as prepaid or accrued research and development expenses.
Warrants	Warrants The Company reviews the terms of all warrants issued and classifies the warrants as a component of permanent equity if they are freestanding financial instruments that are legally detachable and separately exercisable, contingently exercisable, do not embody an obligation for the Company to repurchase its own shares, and permit the holders to receive a fixed number of shares of common stock upon exercise. In addition, the warrants must require physical settlement and may not provide any guarantee of value or return. Warrants that meet these criteria are initially recorded at their grant date fair value and are not subsequently remeasured. Warrants that do not meet these criteria are classified as liabilities and remeasured to their fair value at each reporting period.
Stock-Based Compensation	Stock-Based Compensation The Company’s stock-based payments include stock options, performance-based restricted stock units and grants of common stock, including common stock subject to vesting. The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is generally the vesting period, on a straight-line basis. The Company measures the fair value of the performance-based restricted stock units relating to the total share return performance using a Monte Carlo valuation model. The Company adopted ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting
Financial Instruments	Financial Instruments The Company’s financial instruments consist of cash equivalents, marketable securities, accounts payable and liability classified warrants. The carrying amounts of cash and cash equivalents and accounts payable approximate their fair value due to the short-term nature of those financial instruments. The fair value of the marketable securities and liability classified warrants are remeasured to fair value each reporting period as described in Note 5.
Fair Value Measurements	Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company’s assets and liabilities measured at fair value on a recurring basis include cash equivalents, marketable securities and warrant liabilities.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period, determined using the treasury-stock method and the as if-converted method, for convertible securities, if inclusion of these instruments is dilutive. For the three and six months ended June 30, 2019 and 2018, both methods are equivalent. Basic and diluted net loss per share is described further in Note 2.
Income Taxes	Income Taxes Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities and for loss and credit carryforwards using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The Company assesses its income tax positions and records tax benefits based upon management’s evaluation of the facts, circumstances and information available at the reporting date. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority having full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the consolidated financial statements. The Company classifies interest and penalties associated with such uncertain tax positions as a component of interest expense. As of June 30, 2019 and December 31, 2018, the Company has not identified any material uncertain tax positions.
Guarantees and Indemnifications	Guarantees and Indemnifications As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The Company leases its principal office and laboratory space in Hopkinton, Massachusetts and previously leased research and development space in Milford, Massachusetts under non-cancelable operating leases. The Company has standard indemnification arrangements under these leases that require it to indemnify the landlords against liability for injury, loss, accident, or damage from any claims, actions, proceedings, or costs resulting from certain acts, breaches, violations, or nonperformance under the Company’s lease. Through June 30, 2019, the Company had not experienced any losses related to these indemnification obligations and no material claims were outstanding. The Company does not expect significant claims related to these indemnification obligations, and consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate and discrete financial information is available for evaluation by the chief operating decision maker, the Company’s chief executive officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and does not track expenses on a program-by-program basis.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework – Changes to the Disclosure Requirement for Fair Value Measurement . In February 2016, the FASB issued ASU No. 2016-02, Leases “Codification Improvements to Topic 842, Leases” The Company adopted the standard on the effective date of January 1, 2019 by applying the new lease requirements at the effective date. Prior periods continue to be presented based on the accounting standards originally in effect for such periods. The Company also elected the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carry forward the historical lease classification. The Company will also apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The standard had an impact of approximately $3.0 million on the Company’s assets and $3.4 million on its liabilities, as of January 1, 2019, for the recognition of right-of-use assets and lease liabilities, which are primarily related to the lease of its corporate headquarters in Hopkinton, Massachusetts. The standard did not have a material impact on the Company’s results of operations or liquidity (see Note 8) In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception .

Nature of Business and Summar_3

Nature of Business and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Estimated Useful Lives of Property and Equipment	Depreciation is provided using the straight-line method over the estimated useful lives: Asset Category Useful Life Equipment 5-7 years Furniture and fixtures 5 years Leasehold improvements Lesser of 10 years or the remaining term of the respective lease

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the computation of basic and diluted net loss per share of the Company for such periods (in thousands, except share and per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Net loss $ (4,555 ) $ (3,785 ) $ (9,750 ) $ (8,649 ) Weighted-average number of shares outstanding - basic and diluted 16,443,379 13,179,072 16,440,192 13,085,820 Net loss per common share - basic and diluted $ (0.28 ) $ (0.29 ) $ (0.59 ) $ (0.66 )
Summary of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted-Average Shares Outstanding	The following potentially dilutive securities outstanding, prior to the use of the treasury stock method or if-converted method, have been excluded from the computation of diluted weighted-average shares outstanding, because such securities had an antidilutive impact due to the losses reported: For the Three and Six Months Ended June 30, 2019 2018 Common stock warrants 1,662,124 1,787,124 Stock options, RSUs and Inducement awards 1,900,615 1,338,565

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2019
Investments Debt And Equity Securities [Abstract]
Summary of Investments by Category	The following table summarizes the Company’s investments, by category, as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, Investments - Current: 2019 2018 Debt securities - available for sale $ 38,646 $ 32,914 Total $ 38,646 $ 32,914 Investments - Noncurrent: Debt securities - available for sale $ — $ 16,804 Total $ — $ 16,804
Summary of Available-for-Sale Classified Investments	A summary of the Company’s available-for-sale classified investments as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): At June 30, 2019 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 10,975 $ — $ (51 ) $ 10,924 United States treasury securities 27,889 — (167 ) 27,722 Total $ 38,864 $ — $ (218 ) $ 38,646 At December 31, 2018 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 16,028 $ — $ (19 ) $ 16,009 United States treasury securities 16,913 — (8 ) 16,905 Total $ 32,941 $ — $ (27 ) $ 32,914 Investments - Noncurrent: Corporate bonds $ 4,930 $ 2 $ — $ 4,932 United States treasury securities 11,852 20 — 11,872 Total $ 16,782 $ 22 $ — $ 16,804
Schedule of Amortized Cost and Fair Value of Available-for-Sale Investments, by Contract Maturity	The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of June 30, 2019 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 38,864 $ 38,646 Due after one year through two years — — Total $ 38,864 $ 38,646

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): June 30, December 31, 2019 2018 Equipment $ 1,278 $ 1,064 Furniture and fixtures 382 400 Leasehold improvements 1,356 1,347 Total property and equipment 3,016 2,811 Less: accumulated depreciation and amortization (663 ) (492 ) Property and equipment, net $ 2,353 $ 2,319

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Measured at Fair Value	A summary of the assets and liabilities that are measured at fair value as of June 30, 2019 and December 31, 2018 is as follows (in thousands): Fair Value Measurement at June 30, 2019 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 9,011 $ 9,011 $ — $ — Fixed income securities 38,646 — 38,646 — Total $ 47,657 $ 9,011 $ 38,646 $ — Liabilities: Warrant liabilities $ 805 $ — $ — $ 805 Total $ 805 $ — $ — $ 805 Fair Value Measurement at December 31, 2018 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 13,264 $ 13,264 $ — $ — Fixed income securities 49,718 — 49,718 — Total $ 62,982 $ 13,264 $ 49,718 $ — Liabilities: Warrant liabilities $ 8,511 $ — $ — $ 8,511 Total $ 8,511 $ — $ — $ 8,511 (1) Money market funds are included within cash and cash equivalents in the accompanying consolidated balance sheets and are recognized at fair value.
Summary of Change in Company's Level 3 Liabilities, Warrants Issued in Private Placement	The following table reflects the change in the Company’s Level 3 liabilities, which consists of the warrants issued in a private placement in November 2016 (see Note 7), for the period ended June 30, 2019 (in thousands): November Private Placement Warrants Balance at December 31, 2017 $ 13,128 Change in fair value (4,617 ) Balance at December 31, 2018 8,511 Change in fair value (7,706 ) Balance at June 30, 2019 $ 805

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of June 30, 2019 and December 31, 2018 consisted of the following (in thousands): June 30, December 31, 2019 2018 Clinical $ 2,393 $ 941 Compensation and benefits 504 830 Accounting and legal 218 227 Other 70 369 Total accrued expenses and other current liabilities $ 3,185 $ 2,367

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Summary of Assumptions Used to Record Fair Value of Warrants	A summary of the Black-Scholes pricing model assumptions used to record the fair value of the warrants is as follows: June 30, 2019 December 31, 2018 Risk-free interest rate 1.7 % 2.5 % Expected term (in years) 2.4 2.9 Expected volatility 66.9 % 78.1 % Expected dividend yield 0 % 0 %
Summary of Warrant Activity	A summary of the warrant activity for the six months ended June 30, 2019 and for the year ended December 31, 2018 is as follows: Warrants Outstanding at December 31, 2017 1,787,124 Grants — Exercises — Expirations/cancellations (125,000 ) Outstanding at December 31, 2018 1,662,124 Grants — Exercises — Expirations/cancellations — Outstanding at June 30, 2019 1,662,124
Summary of Option Activity	The following table summarizes the option activity under the Stock Incentive Plans for the six months ended June 30, 2019 and the year ended December 31, 2018: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2017 988,565 $ 10.83 $ 2,617,859 Granted 311,000 12.28 — Exercised — — — Cancelled — — — Outstanding at December 31, 2018 1,299,565 11.18 881,385 Granted 343,000 10.37 — Exercised — — — Cancelled (17,750 ) 14.28 — Options outstanding at June 30, 2019 1,624,815 $ 10.97 $ — Options exercisable at June 30, 2019 952,547 $ 11.28 $ —
Summary of Assumptions to Determine Fair Value of Stock Options Granted to Employees and Directors	The assumptions the Company used to determine the fair value of stock options granted to employees and directors during the six months ended June 30, 2019 and 2018 are as follows, presented on a weighted-average basis: Six Months Ended June 30, 2019 2018 Risk-free interest rate 2.6 % 2.5 % Expected term (in years) 6.0 5.9 Expected volatility 81.1 % 82.6 % Expected dividend yield 0 % 0 %
Summary of Performance Based Restricted Stock Units Activity	The following table is a rollforward of performance-based restricted stock unit activity under the Stock Incentive Plans for the six months ended June 30, 2019: Restricted Stock Units Weighted-Average Grant Date Fair Value Total Nonvested Units at December 31, 2018 — $ — Granted 203,700 8.49 Exercised — — Vested — — Cancelled (17,900 ) 8.49 Total Nonvested Units at June 30, 2019 185,800 $ 8.49
Summary of Stock-Based Compensation Expense	The following table summarizes the Company’s stock-based compensation expense for the three and six months ended June 30, 2019 and 2018 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, Stock-based compensation: 2019 2018 2019 2018 Research and development $ 339 $ 213 $ 656 $ 414 General and administrative 702 480 1,357 935 Total Stock-based compensation $ 1,041 $ 693 $ 2,013 $ 1,349
Summary of Shares of Common Stock Reserved	As of June 30, 2019 and December 31, 2018, the Company reserved the following shares of common stock for issuance of shares resulting from exercise of outstanding warrants, options and performance-based restricted stock units, as well as issuance of shares available for grant under the Stock Incentive Plans: June 30, December 31, 2019 2018 2016 IPO warrants 28,347 28,347 November Private Placement Warrants 1,633,777 1,633,777 2015 Amended and Restated Stock Incentive Plan 2,214,946 2,238,887 Inducement Awards 90,000 50,000 Total 3,967,070 3,951,011

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Summary of Other Information Related to Leases	Other information related to leases was as follows: Six Months Ended June 30, Cash paid for amounts included in the measurement of lease liabilities: 2019 Operating cash flow from operating leases (in thousands) $ 130 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ 2,980 Weighted Average Remaining Lease Term Operating leases 8.7 years Weighted Average Discount Rate Operating leases 8.0 %
Summary of Maturities of Operating Lease Liabilities	The following table summarizes the Company’s maturities of operating lease liabilities as of June 30, 2019 (in thousands): Year 2019 (excluding the six months ended June 30, 2019) $ 288 2020 588 2021 508 2022 450 2023 462 Thereafter 2,405 Total lease payments $ 4,701 Less: present value discount (1,317 ) Total $ 3,384
Summary of Aggregate Future Minimum Non-Cancellable Commitments Under Operating Leases	The following table summarizes the Company’s maturities of operating lease liabilities as of June 30, 2019 (in thousands): Year 2019 (excluding the six months ended June 30, 2019) $ 288 2020 588 2021 508 2022 450 2023 462 Thereafter 2,405 Total lease payments $ 4,701 Less: present value discount (1,317 ) Total $ 3,384

Nature of Business and Summar_4

Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2019USD ($)SubsidiarySegment	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Jun. 30, 2018USD ($)
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of wholly owned subsidiaries | Subsidiary	3
Accumulated deficit	$ (111,818,000)		$ (102,068,000)
Cash, cash equivalents and marketable securities	49,200,000
Restricted cash	234,000		234,000
Impairment of long-lived assets	0
Income tax benefit	0
Uncertain tax positions	0		0
Indemnification obligations loss	0
Outstanding material claims	0
Indemnification obligation reserve	$ 0
Number of operating segment | Segment	1
Right-of-use-assets	$ 2,850,000
Lease liabilities				$ 3,384,000
ASU 2016-02 [Member]
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Right-of-use-assets		$ 3,000,000
Lease liabilities		$ 3,400,000
Money Market Funds [Member]
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents fair value	$ 9,000,000		$ 13,300,000

Nature of Business and Summar_5

Nature of Business and Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Property and Equipment (Detail)	6 Months Ended
	Jun. 30, 2019
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	Lesser of 10 years or the remaining term of the respective lease

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share Basic And Diluted [Abstract]
Net loss	$ (4,555)	$ (3,785)	$ (9,750)	$ (8,649)
Weighted-average number of shares outstanding - basic and diluted	16,443,379	13,179,072	16,440,192	13,085,820
Net loss per common share - basic and diluted	$ (0.28)	$ (0.29)	$ (0.59)	$ (0.66)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Common Stock Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from the computation of diluted weighted-average shares outstanding	1,662,124	1,787,124	1,662,124	1,787,124
Stock Options, Restricted Stock Units and Inducement Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding excluded from the computation of diluted weighted-average shares outstanding	1,900,615	1,338,565	1,900,615	1,338,565

Investments - Summary of Invest

Investments - Summary of Investments by Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments - Current:
Debt securities - available for sale	$ 38,646	$ 32,914
Total	$ 38,646	32,914
Investments - Noncurrent:
Debt securities - available for sale		16,804
Total		$ 16,804

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Classified Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$ 38,864
Fair Value	38,646
Investments - Current [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	38,864	$ 32,941
Accumulated Unrealized Losses	(218)	(27)
Fair Value	38,646	32,914
Investments - Current [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	10,975	16,028
Accumulated Unrealized Losses	(51)	(19)
Fair Value	10,924	16,009
Investments - Current [Member] | United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	27,889	16,913
Accumulated Unrealized Losses	(167)	(8)
Fair Value	$ 27,722	16,905
Investments - Noncurrent [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		16,782
Accumulated Unrealized Gains		22
Fair Value		16,804
Investments - Noncurrent [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		4,930
Accumulated Unrealized Gains		2
Fair Value		4,932
Investments - Noncurrent [Member] | United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		11,852
Accumulated Unrealized Gains		20
Fair Value		$ 11,872

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost and Fair Value of Available-for-Sale Investments, by Contract Maturity (Detail) $ in Thousands	Jun. 30, 2019USD ($)
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 38,864
Cost Basis	38,864
Due in one year or less, Fair Value	38,646
Total, Fair Value	$ 38,646

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,016	$ 2,811
Less: accumulated depreciation and amortization	(663)	(492)
Property and equipment, net	2,353	2,319
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,278	1,064
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	382	400
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,356	$ 1,347

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 88	$ 41	$ 171	$ 86

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 9,000	$ 13,300
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	47,657	62,982
Liabilities, Total	805	8,511
Carrying Value [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	9,011	13,264
Carrying Value [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities	38,646	49,718
Carrying Value [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	805	8,511
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	9,011	13,264
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	9,011	13,264
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	38,646	49,718
Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities	38,646	49,718
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Total	805	8,511
Significant Unobservable Inputs (Level 3) [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	$ 805	$ 8,511

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Change in Company's Level 3 Liabilities, Warrants Issued in Private Placement (Detail) - Private Placement [Member] - Warrants [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	$ 8,511	$ 13,128
Change in fair value	(7,706)	(4,617)
Ending balance	$ 805	$ 8,511

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities And Other Liabilities [Abstract]
Clinical	$ 2,393	$ 941
Compensation and benefits	504	830
Accounting and legal	218	227
Other	70	369
Total accrued expenses and other current liabilities	$ 3,185	$ 2,367

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)

May 11, 2016

Feb. 28, 2019

Jan. 31, 2019

Aug. 31, 2018

Jun. 18, 2018

Jan. 31, 2018

Nov. 30, 2016

Jun. 30, 2016

May 31, 2016

Jun. 30, 2019

Jun. 30, 2019

Jun. 30, 2018

Dec. 31, 2018

Dec. 31, 2015

Mar. 09, 2018

Aug. 31, 2017

Apr. 30, 2014

Class of Stock [Line Items]

Dividend yield

0.00%

0.00%

Expected life (in years)

6 years

5 years 10 months 24 days

Stock options granted

0

Stock-based compensation expense

$ 2,013,000

$ 1,349,000

Performance-based restricted stock units exercisable

0

2018 New Hire Inducement Stock Option Award [Member]

Class of Stock [Line Items]

Issuance of common stock

50,000

Shares issued price per share

$ 12.02

2019 New Hire Inducement Stock Option Award [Member]

Class of Stock [Line Items]

Issuance of common stock

40,000

Shares issued price per share

$ 10.39

Performance-Based Restricted Stock Unit [Member]

Class of Stock [Line Items]

Share-based Compensation Arrangement by Share-based Payment Award, Description

In January 2019, the Company issued performance-based restricted stock units (“RSUs”) to senior management under the 2015 Plan that represent shares potentially issuable in the future subject to the satisfaction of certain performance milestones as well as a service condition

Share-based Compensation Arrangement by Share-based Payment Award, Award, Vesting Description

The vesting of 50% of the RSUs is based upon the Company’s performance relative to a peer group over a two-year performance period, from January 1, 2019 through December 31, 2020, measured by the Company’s relative total shareholder return for the market-based RSUs. The vesting of 25% of the RSUs is based on the achievement of a performance goal milestone as of December 31, 2019 and vesting of the remaining 25% of the RSUs is based upon the achievement of a performance goal milestone as of December 31, 2020.

Stock-based compensation expense

$ 189,000,000

$ 347,000,000

Weighted-average fair value of restricted stock units granted

$ 8.49

Performance-Based Restricted Stock Unit [Member] | Performance Relative to a Peer Group over a Two-year Performance Period, from January 1, 2019 through December 31, 2020 [Member]

Class of Stock [Line Items]

Share-based Compensation Arrangement by Share-based Payment Award, Vesting percentage

50.00%

Performance-Based Restricted Stock Unit [Member] | Achievement of a Performance Goal Milestone as of December 31, 2019 [Member]

Class of Stock [Line Items]

Share-based Compensation Arrangement by Share-based Payment Award, Vesting percentage

25.00%

Performance-Based Restricted Stock Unit [Member] | Achievement of a Performance Goal Milestone as of December 31, 2020 [Member]

Class of Stock [Line Items]

Share-based Compensation Arrangement by Share-based Payment Award, Vesting percentage

25.00%

Performance Goal Milestone Units [Member]

Class of Stock [Line Items]

Weighted-average fair value of restricted stock units granted

10.35

Relative Total Share Return Units [Member]

Class of Stock [Line Items]

Weighted-average fair value of restricted stock units granted

$ 6.62

2014 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Number of authorized shares of common stock to be issued

750,000

Number of shares remain available for grant

0

Weighted-average remaining contractual life

7 years 7 months 6 days

Weighted-average fair value of all stock options granted

$ 7.30

2015 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Number of authorized shares of common stock to be issued

750,000

1,666,863

Number of shares remain available for grant

404,331

404,331

Number of shares common stock reserved for issuance, increase

800,000

Expiry date of stock options awarded

10 years

2014 and 2015 Stock Incentive Plans [Member]

Class of Stock [Line Items]

Number of authorized shares of common stock to be issued

2,300,000

Stock options granted

343,000

311,000

Fair value of stock options vested

$ 1,900,000

Unrecognized stock-based compensation expense

$ 5,200,000

$ 5,200,000

Weighted-average remaining vesting period

2 years 9 months 18 days

2014 and 2015 Stock Incentive Plans [Member] | Performance-Based Restricted Stock Unit [Member]

Class of Stock [Line Items]

Unrecognized stock-based compensation expense

1,200,000

$ 1,200,000

Weighted-average remaining vesting period

1 year 6 months

May 2016 IPO warrants [Member]

Class of Stock [Line Items]

Expected volatility of common stock Minimum

87.00%

Risk free rate

1.20%

Dividend yield

0.00%

Expected life (in years)

4 years 11 months 26 days

June 2016 IPO warrants [Member]

Class of Stock [Line Items]

Expected volatility of common stock Minimum

87.00%

Risk free rate

1.23%

Dividend yield

0.00%

Expected life (in years)

4 years 11 months 1 day

IPO [Member]

Class of Stock [Line Items]

Fair value of equity

$ 200,000

$ 200,000

Exercise price

$ 15

Warrants expiration date

May 5, 2021

Warrants issued to purchase shares of common stock

747

27,600

Private Placement [Member]

Class of Stock [Line Items]

Issuance of common stock

1,644,737

Shares issued price per share

$ 9.12

Exercise price

$ 10.79

Warrants expiration date

Nov. 23, 2021

Warrants issued to purchase shares of common stock

1,644,737

Common Stock [Member] | 2014 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Shares issued price per share

$ 3.69

$ 3.69

$ 10.39

Common Stock [Member] | 2014 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Issuance of common stock

3,246,079

Net proceeds from initial public offering of common stock

$ 38,000,000

Shares issued price per share

$ 12.50

Exercise of an option to purchase additional shares granted to underwriters in connection with offering

246,079

Common Stock Warrants [Member]

Class of Stock [Line Items]

Issuance of common stock

125,000

Fair value of equity

$ 8,300,000

$ 800,000

$ 800,000

Expected volatility of common stock Minimum

71.00%

Risk free rate

1.01%

Dividend yield

0.00%

Expected life (in years)

2 years 6 months

Exercise price

$ 16

$ 16

Warrants expiration date

Aug. 1, 2018

Common Stock Warrants [Member] | Private Placement [Member]

Class of Stock [Line Items]

Fair value of equity

$ 800,000

$ 800,000

$ 8,500,000

Maximum [Member] | 2015 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Number of shares remain available for grant

116,863

Sales Agreement [Member] | Cantor Fitzgerald & Co. [Member]

Class of Stock [Line Items]

Sales commission percentage on common stock

3.00%

Issuance of common stock

217,329

Weighted average selling price per share

$ 15.42

Net proceeds from initial public offering of common stock

$ 3,200,000

Sales Agreement [Member] | Cantor Fitzgerald & Co. [Member] | Maximum [Member]

Class of Stock [Line Items]

Aggregate offering price

$ 50,000,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Assumptions Used to Record Fair Value of Warrants (Detail) - Warrants [Member]	Jun. 30, 2019	Dec. 31, 2018
Risk-Free Interest Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	1.70%	2.50%
Expected Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input (in years)	2 years 4 months 24 days	2 years 10 months 24 days
Expected Volatility [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	66.90%	78.10%
Expected Dividend Yield [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	0.00%	0.00%

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Warrant Activity (Detail) - Common Stock Warrants [Member] - shares	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Outstanding, Beginning Balance	1,662,124	1,787,124
Grants	0	0
Exercises	0	0
Expirations/cancellations	0	(125,000)
Outstanding, Ending balance	1,662,124	1,662,124

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Option Activity (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted			0
2014 and 2015 Stock Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Beginning Balance	1,299,565	988,565
Options Granted	343,000	311,000
Options Cancelled	(17,750)
Options outstanding, Ending balance	1,624,815	1,299,565
Options exercisable	952,547
Weighted-Average Exercise Price Per Share, Options outstanding, Beginning Balance	$ 11.18	$ 10.83
Weighted-Average Exercise Price Per Share, Granted	10.37	12.28
Weighted-Average Exercise Price Per Share, Cancelled	14.28
Weighted-Average Exercise Price Per Share, Options outstanding, Ending Balance	10.97	$ 11.18
Weighted-Average Exercise Price Per Share, Options exercisable	$ 11.28
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$ 881,385	$ 2,617,859
Aggregate Intrinsic Value, Options outstanding, Ending Balance		$ 881,385

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Assumptions to Determine Fair Value of Stock Options Granted to Employees and Directors (Detail)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	2.60%	2.50%
Expected term (in years)	6 years	5 years 10 months 24 days
Expected volatility	81.10%	82.60%
Expected dividend yield	0.00%	0.00%

Stockholders' Equity - Summar_5

Stockholders' Equity - Summary of Performance-based Restricted Stock Unit Activity (Detail)	6 Months Ended
	Jun. 30, 2019$ / sharesshares
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested Units, Granted | shares	203,700
Nonvested Units, Cancelled | shares	(17,900)
Nonvested Units, Ending Balance | shares	185,800
Performance-Based Restricted Stock Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Grant Date Fair Value Granted | $ / shares	$ 8.49
Weighted-Average Grant Date Fair Value Cancelled | $ / shares	8.49
Weighted-Average Grant Date Fair Value Nonvested Units, Ending Balance | $ / shares	$ 8.49

Stockholders' Equity - Summar_6

Stockholders' Equity - 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 [Line Items]
Stock-based compensation expense			$ 2,013	$ 1,349
2014 and 2015 Stock Incentive Plans [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,041	$ 693	2,013	1,349
2014 and 2015 Stock Incentive Plans [Member] | Stock Options [Member] | Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	339	213	656	414
2014 and 2015 Stock Incentive Plans [Member] | Stock Options [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 702	$ 480	$ 1,357	$ 935

Stockholders' Equity - Summar_7

Stockholders' Equity - Summary of Shares of Common Stock Reserved (Detail) - shares	Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	3,967,070	3,951,011
Inducement Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	90,000	50,000
2015 Amended and Restated Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	2,214,946	2,238,887
Private Placement Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	1,633,777	1,633,777
2016 IPO warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	28,347	28,347

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	8 years 8 months 12 days		8 years 8 months 12 days
Operating lease costs	$ 130,000		$ 260,000
Sublease income and variable lease cost payments	$ 18,000		$ 37,000
Operating leases, total rent expense		$ 69,000		$ 142,000
Principal Office and Laboratory Space [Member]
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	10 years		10 years
Operating leases, extendable lease term	5 years		5 years
Operating leases, option to extend lease			an option to extend the lease for up to 5 years
Operating Lease, existence of option to extend			true
Former Headquarters [Member]
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	2 years		2 years
Research and Development Facility [Member]
Lessee Lease Description [Line Items]
Lease term expiration date			Jun. 30, 2018

Leases - Summary of Other Infor

Leases - Summary of Other Information Related to Leases (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow from operating leases (in thousands)	$ 130
Right-of-use assets obtained in exchange for lease obligations:
Operating leases (in thousands)	$ 2,980
Weighted Average Remaining Lease Term
Operating leases	8 years 8 months 12 days
Weighted Average Discount Rate
Operating leases	8.00%

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Detail) $ in Thousands	Jun. 30, 2018USD ($)
Leases [Abstract]
2019 (excluding the six months ended June 30, 2019)	$ 288
2020	588
2021	508
2022	450
2023	462
Thereafter	2,405
Total lease payments	4,701
Less: present value discount	(1,317)
Total	$ 3,384

Leases - Summary of Aggregate F

Leases - Summary of Aggregate Future Minimum Non-Cancellable Commitments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 417
2020	588
2021	508
2022	450
Thereafter	2,867
Total minimum lease payments	$ 4,830

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2019USD ($)
Commitments And Contingencies [Line Items]
Accruals for contingent liabilities	$ 0
License Agreement [Member] | BioHEP Technologies Ltd. [Member]
Commitments And Contingencies [Line Items]
Maximum estimated development and regulatory milestone payments	3,500,000
Maximum aggregate sublicensing revenues	2,000,000
Milestone and royalty payments	$ 0