F-star Therapeutics (FSTX) 10-Q 10 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 07, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
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		17,248,545
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 Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 8,531	$ 28,709
Marketable securities	14,990	25,746
Prepaid expenses and other current assets	2,717	3,522
Total current assets	26,238	57,977
Property and equipment, net	2,043	2,234
Operating lease right-of-use assets	2,576	2,717
Restricted cash	234	234
Other assets		35
Total	31,091	63,197
Current liabilities:
Accounts payable	2,530	2,210
Accrued expenses and other current liabilities	2,239	2,438
Accrued interest payable		403
Operating lease liabilities, current	364	355
Total current liabilities	5,133	5,406
Convertible term loan, net of unamortized discount		19,070
Warrant liabilities	38	299
Operating lease liabilities, noncurrent	2,688	2,869
Other long-term liabilities		27
Total liabilities	7,859	27,671
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.0001 par value—authorized, 10,000,000 shares at June 30, 2020 and December 31, 2019; no shares issued or outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.0001 par value—authorized, 200,000,000 shares at June 30, 2020 and December 31, 2019; 17,248,545 and 16,513,763 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	2	2
Additional paid-in capital	164,118	161,924
Accumulated deficit	(140,887)	(126,165)
Accumulated other comprehensive loss	(1)	(235)
Total stockholders’ equity	23,232	35,526
Total	$ 31,091	$ 63,197

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
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	17,248,545	16,513,763
Common stock, shares outstanding	17,248,545	16,513,763

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 3,204	$ 7,275	$ 8,507	$ 12,842
General and administrative	2,164	2,490	5,043	5,300
Total operating expenses	5,368	9,765	13,550	18,142
Loss from operations	(5,368)	(9,765)	(13,550)	(18,142)
Other income (expense):
Interest income	44	325	285	686
Interest expense	(35)		(511)
Loss on extinguishment of convertible term loan	(1,207)		(1,207)
Change in fair value of warrant liabilities	22	4,885	261	7,706
Net loss	(6,544)	(4,555)	(14,722)	(9,750)
Unrealized gain/(loss) on marketable securities	157	(97)	234	(213)
Comprehensive loss	$ (6,387)	$ (4,652)	$ (14,488)	$ (9,963)
Net loss per common share - basic and diluted	$ (0.38)	$ (0.28)	$ (0.88)	$ (0.59)
Weighted-average number of shares outstanding - basic and diluted	17,052,088	16,443,379	16,787,919	16,440,192

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, 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
Balance at Dec. 31, 2019	35,526		$ 2		161,924		(126,165)	(235)
Balance, shares at Dec. 31, 2019			16,513,763
Stock-based compensation	1,241				1,241
Issuance of common stock for services rendered	50				50
Issuance of common stock for services rendered, shares			43,887
Issuance of common stock in connection with at-the-market offering, net of issuance costs		849				849
Issuance of common stock in connection with at-the-market offering, shares				690,895
Convertible term loan warrant amendment	54				54
Net unrealized gain (loss) on marketable securities	234							234
Net loss	(14,722)						(14,722)
Balance at Jun. 30, 2020	23,232		$ 2		164,118		(140,887)	(1)
Balance, shares at Jun. 30, 2020			17,248,545
Balance at Mar. 31, 2020	28,272		$ 2		162,771		(134,343)	(158)
Balance, shares at Mar. 31, 2020			16,582,444
Stock-based compensation	449				449
Issuance of common stock for services rendered	25				25
Issuance of common stock for services rendered, shares			17,006
Issuance of common stock in connection with at-the-market offering, net of issuance costs		$ 819				$ 819
Issuance of common stock in connection with at-the-market offering, shares				649,095
Convertible term loan warrant amendment	54				54
Net unrealized gain (loss) on marketable securities	157							157
Net loss	(6,544)						(6,544)
Balance at Jun. 30, 2020	$ 23,232		$ 2		$ 164,118		$ (140,887)	$ (1)
Balance, shares at Jun. 30, 2020			17,248,545

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net loss			$ (14,722)	$ (9,750)
Adjustments for:
Depreciation and amortization			191	171
Operating lease right-of-use asset amortization			141	130
Change in fair value of warrant liabilities	$ (22)	$ (4,885)	(261)	(7,706)
Loss on extinguishment of convertible term loan	1,207		1,207
Non-cash interest expense			77
Non-cash investment income (expense)			(244)	72
Non-cash stock-based compensation			1,291	2,013
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			805	(753)
Other assets			35	132
Accounts payable			320	(155)
Accrued expenses and other liabilities			(629)	1,081
Operating lease liabilities			(172)
Net cash used in operating activities			(11,961)	(14,765)
Cash flows from investing activities:
Proceeds from sale of marketable securities			32,234	16,787
Purchases of marketable securities			(21,000)	(6,000)
Purchases of property and equipment				(205)
Net cash provided by investing activities			11,234	10,582
Cash flows from financing activities:
Payment of convertible term loan and prepayment fee			(20,300)
Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs			849	6
Cash (used in) provided by financing activities			(19,451)	6
Net decrease in cash, cash equivalents and restricted cash			(20,178)	(4,177)
Cash, cash equivalents and restricted cash, beginning of period			28,943	14,958	$ 14,958
Cash, cash equivalents and restricted cash, end of period	$ 8,765	$ 10,781	8,765	10,781	$ 28,943
Supplemental disclosures of cash flow information:
Cash paid for taxes			7	$ 17
Cash paid for interest, net			$ 837

Nature of Business and Summary

Nature of Business and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
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 novel therapeutics for the treatment of a range of cancers and inflammatory diseases using its proprietary small molecule nucleotide platform. The Company designs its compounds to selectively target and modulate the activity of specific proteins implicated in various disease states. internally-developed programs are primarily designed to stimulate and/or dampen immune responses. Until January 2020, the Company was also developing inarigivir, an orally-administered investigational selective immunomodulator, as a potential treatment for chronic hepatitis B virus, or HBV. Inarigivir was being evaluated in multiple clinical trials, including the Company’s Phase 2b CATALYST trials, designed to evaluate both treatment-naïve and virally-suppressed non-cirrhotic patients with HBV under multiple dosing regimens. On January 29, 2020, the Company announced that it terminated all clinical development of inarigivir for the treatment of HBV due to the occurrence of unexpected serious adverse events, including one patient death, in the Company’s Phase 2b CATALYST trial. On July 29, 2020, the Company and F-star Therapeutics Limited (“F-star”) entered into a Share Exchange Agreement (the “Exchange Agreement”) pursuant to which, subject to the satisfaction or waiver of the conditions set forth in the Exchange Agreement, the Company will acquire the entire issued share capital of F-star with F-star continuing as the combined company (the “Exchange”) (see Note 12). Since its 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 pandemic caused by an outbreak of a new strain of coronavirus, or the COVID-19 pandemic, that is affecting the U.S. and global economy and financial markets is also impacting the Company’s employees, patients, communities and business operations. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition will depend on future developments that are highly uncertain and cannot be accurately predicted, including new information that may emerge concerning COVID-19, the actions taken to contain it or treat its impact and the economic impact on local, regional, national and international markets. The Company is actively monitoring this situation and the possible effects on its financial condition, liquidity, operations, suppliers, industry, and workforce. 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, 2020 and for the three and six months ended June 30, 2020 and 2019, 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, 2020, results of operations for the three and six months ended June 30, 2020 and 2019, statement of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and its cash flows for the six months ended June 30, 2020 and 2019. 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 for the year ended December 31, 2019, as filed with the Securities and Exchange Commission (“SEC”) on February 14, 2020. The results for the three and six months ended June 30, 2020 are not necessarily indicative of the results expected for the full fiscal year or any interim period. As of June 30, 2020, the Company had an accumulated deficit of $140.9 million and $23.5 million in cash, cash equivalents and marketable securities. On April 8, 2020, the Company repaid in full its $20.0 million convertible term loan (see Note 9). There is no guarantee that the Exchange will be completed. The Company expects its $23.5 million in cash, cash equivalents and marketable securities as of June 30, 2020 will be sufficient to fund operations for at least the next twelve months. This estimate assumes no additional funding from new collaboration agreements, equity financings or further sales under the Company’s Controlled Equity Offering SM The Company does not expect to raise any additional funds prior to the completion of the Exchange. However, if the Exchange is not completed, the Company may require significant additional funds earlier than it currently expects in order to conduct clinical trials and preclinical and discovery activities. There can be no assurances, however, that additional funding will be available on favorable 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, 2020. Sperovie Biosciences, Inc. was a joint borrower with the Company under the Company’s convertible term loan (see Note 9). SBP Securities Corporation had assets primarily related to investments in marketable securities and operations consisting primarily of interest income as of June 30, 2020. SBP International Limited had operations consisting mainly of clinical trial oversight, including European data protection oversight, as of June 30, 2020. 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 warrants, 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, 2020 are money market fund investments of $7.0 million and included in cash and cash equivalents as of December 31, 2019 are money market fund investments of $21.1 million and United States treasury securities of $6.0 million, which are reported at fair value (see Note 5). Restricted Cash As of June 30, 2020 and December 31, 2019, 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, 2020, 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 accounts for freestanding warrants within stockholders equity or as liabilities based on the characteristics and provisions of each instrument. The Company evaluates outstanding warrants in accordance with ASC 480, Distinguishing Liabilities from Equity Derivatives and Hedging Stock-Based Compensation The Company’s stock-based payments include stock options, performance-based restricted stock units (“performance-based RSUs”), time-based restricted stock units (“time-based RSUs”) and grants of common stock. 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 accounts for forfeitures as they occur. The Company measures the fair value of the performance-based RSUs relating to the total share return performance using a Monte Carlo valuation model. The Company measures the fair value of the performance-based RSUs relating to the milestone performance goals 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 milestone criteria will be achieved and adjusts its estimate of the fair value, if necessary. Stock-based compensation expense is classified in the accompanying consolidated statements of operations and comprehensive loss based on the department to which the related services are provided. Financial Instruments The Company’s financial instruments consist of cash equivalents, marketable securities, accounts payable, a term loan 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 (see Note 5). The fair value of the term loan approximates its face value due to market terms. 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, 2020 and 2019, 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 as well as net operating loss and tax 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, 2020 and December 31, 2019, 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 under a non-cancelable operating lease. The Company has standard indemnification arrangements under the lease 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, 2020, 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 .

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2020
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, 2020 2019 2020 2019 Net loss $ (6,544 ) $ (4,555 ) $ (14,722 ) $ (9,750 ) Weighted-average number of shares outstanding - basic and diluted 17,052,088 16,443,379 16,787,919 16,440,192 Net loss per common share - basic and diluted $ (0.38 ) $ (0.28 ) $ (0.88 ) $ (0.59 ) 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, 2020 2019 Common stock warrants 1,927,124 1,662,124 Stock options and inducement awards 1,606,275 1,714,815 Restricted stock units 534,000 185,800

Investments

Investments	6 Months Ended
	Jun. 30, 2020
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, 2020 and December 31, 2019 (in thousands): June 30, December 31, Investments - Current: 2020 2019 Debt securities - available for sale $ 14,990 $ 25,746 Total $ 14,990 $ 25,746 A summary of the Company’s available-for-sale classified investments as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): At June 30, 2020 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: United States treasury securities $ 14,991 $ — $ (1 ) $ 14,990 Total $ 14,991 $ — $ (1 ) $ 14,990 At December 31, 2019 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 4,990 $ — $ (58 ) $ 4,932 United States treasury securities 20,979 — (165 ) 20,814 Total $ 25,969 $ — $ (223 ) (1) $ 25,746 (1) The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of June 30, 2020 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 14,991 $ 14,990 Total $ 14,991 $ 14,990

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment, Net	4. PROPERTY AND EQUIPMENT, NET Property and equipment as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): June 30, December 31, 2020 2019 Equipment $ 1,278 $ 1,278 Furniture and fixtures 423 450 Leasehold improvements 1,356 1,356 Total property and equipment 3,057 3,084 Less: accumulated depreciation and amortization (1,014 ) (850 ) Property and equipment, net $ 2,043 $ 2,234 Depreciation expense for the three and six months ended June 30, 2020 was $95,000 and $191,000, respectively. Depreciation expense for the three and six months ended June 30, 2019 was $88,000 and $171,000, respectively.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
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 United States treasury securities and fixed income 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, 2020 and December 31, 2019 is as follows (in thousands): Fair Value Measurement at June 30, 2020 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) $ 7,012 $ 7,012 $ — $ — United States treasury securities 14,990 — 14,990 — Total $ 22,002 $ 7,012 $ 14,990 $ — Liabilities: Warrant liabilities $ 38 $ — $ — $ 38 Total $ 38 $ — $ — $ 38 Fair Value Measurement at December 31, 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) $ 21,065 $ 21,065 $ — $ — United States treasury securities (1) 5,982 — 5,982 — Fixed income securities 25,746 — 25,746 — Total $ 52,793 $ 21,065 $ 31,728 $ — Liabilities: Warrant liabilities $ 299 $ — $ — $ 299 Total $ 299 $ — $ — $ 299 (1) Money market funds and United States treasury securities with maturities of less than 90 days at the date of purchase 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 three months ended June 30, 2020 (in thousands): November Private Placement Warrants Balance at December 31, 2018 $ 8,511 Change in fair value (8,212 ) Balance at December 31, 2019 299 Change in fair value (261 ) Balance at June 30, 2020 $ 38

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): June 30, December 31, 2020 2019 Preclinical and clinical studies $ 1,124 $ 1,473 Compensation and benefits 765 614 Accounting and legal 254 240 Other 96 111 Total accrued expenses and other current liabilities $ 2,239 $ 2,438

Warrants

Warrants	6 Months Ended
	Jun. 30, 2020
Warrants And Rights Note Disclosure [Abstract]
Warrants	7. WARRANTS 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 interest rate of 1.23%; and a dividend yield of 0%. The aggregate fair value of the IPO Warrants on the date of issuance 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, 2020 and December 31, 2019, the fair value of the November 2016 Private Placement Warrants was approximately $38,000 and $0.3 million, respectively, and 10,960 shares have been exercised to date (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, 2020 December 31, 2019 Risk-free interest rate 0.2 % 1.6 % Expected term (in years) 1.4 1.9 Expected volatility 80.9 % 100.0 % Expected dividend yield 0 % 0 % In September 2019, the Company entered into a term loan (the “Convertible Term Loan”) with Pontifax Medison Finance (Israel) L.P. and Pontifax Medison Finance (Cayman) L.P., as lenders, and Pontifax Medison Finance GP, L.P., in its capacity as administrative agent and collateral agent for itself and the lenders, providing for a $20.0 million term loan (see Note 9) In connection with the Company’s , the Company issued to certain lenders warrants to purchase 250,000 shares of common stock (the “Pontifax Warrants”). Prior to their amendment in April 2020 (see Note 9), the Pontifax Warrants were exercisable at an exercise price of $6.57 per share. The Pontifax Warrants expire on September 19, 2025. The Company evaluated the terms of the Pontifax Warrants and concluded that they are equity-classified. The fair value of the Pontifax Warrants was estimated on the issuance date using a Black-Scholes pricing model based on the following assumptions: an expected term of 6.0 years; expected stock price volatility of 83.2%; a risk-free interest rate of 1.7%; and a dividend yield of 0%. The aggregate fair value of the Pontifax Warrants on the date of issuance was approximately $0.6 million and was recorded as a discount to the term loan and will be amortized over the life of the term loan using the effective interest rate method. The aggregate fair value remaining on the payoff date was $0.5 million and was included in the loss on extinguishment of the Convertible Term Loan upon repayment (see Note 9). In connection with the repayment of the Convertible Term Loan, the Pontifax Warrants were amended and restated to amend the exercise price to $2.08 per share, which was equal to 1.5 times the weighted-average closing price of the Company’s Common Stock during the 90 days prior to the repayment date. All other terms of the Pontifax Warrants remained the same. During the three months ended June 30, 2020, there was an incremental expense of approximately $54,000 for the amendment of the Pontifax Warrant exercise price. In September 2019, the Company issued warrants to a service provider to purchase 15,000 shares of common stock (the “September 2019 Warrants”). The September 2019 Warrants are exercisable at an exercise price of $4.21 per share and expire on September 19, 2021. The Company evaluated the terms of the September 2019 Warrants and concluded that they are equity-classified. The fair value of the September 2019 Warrants was estimated on the applicable issuance date using a Black-Scholes pricing model based on the following assumptions: an expected term of 2.0 years; expected stock price volatility of 69.4%; a risk-free interest rate of 1.7%; and a dividend yield of 0%. The aggregate fair value of the September 2019 Warrants on the date of issuance was approximately $19,000. Approximately $13,000 and $6,000 has been expensed during the periods ended June 30, 2020 and December 31, 2019, respectively. A summary of the warrant activity for the six months ended June 30, 2020 and for the year ended December 31, 2019 is as follows: Warrants Outstanding at December 31, 2018 1,662,124 Grants 265,000 Exercises — Expirations/cancellations — Outstanding at December 31, 2019 1,927,124 Grants — Exercises — Expirations/cancellations — Outstanding at June 30, 2020 1,927,124

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Equity	8. STOCKHOLDERS’ EQUITY Common and Preferred Stock In August 2017, the Company entered into a Controlled Equity Offering SM 2014 Stock Incentive Plan and 2015 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 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. 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 2014 Plan and 2015 Plan provide for the issuance of common stock, stock options and other stock-based awards to employees, officers, directors, consultants and advisors of the Company. Amended and Restated 2015 Stock Incentive Plan In March 2018, the Board approved the Amended and Restated 2015 Plan. Upon receipt of stockholder approval at the Company’s 2018 annual meeting in June 2018, 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 (the Amended and Restated 2015 Plan, and together with the 2014 Plan, the “Stock Incentive Plans”). Upon receipt of stockholder approval at the Company’s 2020 annual meeting in June 2020, the Amended and Restated 2015 Plan was further amended to increase the authorized number of shares of common stock reserved for issuance by 1,150,000 shares. Following this approval, there are 2,816,863 shares authorized for issuance pursuant to the Amended and Restated 2015 Plan. 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 all Stock Incentive Plans is 3,450,000. As of June 30, 2020, the Company had 1,216,176 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, 2020 and the year ended December 31, 2019: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Outstanding at December 31, 2018 1,299,565 $ 11.18 $ 881,385 Granted 395,500 9.61 — Exercised — — — Cancelled (22,750 ) 13.36 — Outstanding at December 31, 2019 1,672,315 10.78 — Granted 270,000 1.44 — Exercised — — — Cancelled (426,040 ) 10.45 — Options outstanding at June 30, 2020 1,516,275 $ 9.21 $ — Options exercisable at June 30, 2020 1,017,853 $ 10.79 $ — As of June 30, 2020, all options outstanding have a weighted-average remaining contractual life of 6.6 years. The weighted-average fair value of all stock options granted for the six months ended June 30, 2020 was $0.99. Intrinsic value at June 30, 2020 and December 31, 2019 is based on the closing price of the Company’s common stock on that date of $1.47 per share and $1.58 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, 2020 and 2019 are as follows, presented on a weighted-average basis: For the Six Months Ended June 30, 2020 2019 Risk-free interest rate 0.7 % 2.6 % Expected term (in years) 5.9 6.0 Expected volatility 82.8 % 81.1 % Expected dividend yield 0 % 0 % Restricted Stock Units Performance-Based Restricted Stock Units In January 2019, the Company issued performance-based RSUs to senior management under the Amended and Restated 2015 Plan that represented shares potentially issuable in the future subject to the satisfaction of certain performance milestones as well as a service condition. The vesting of 50% of the performance-based RSUs was 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. The vesting of 25% of the performance-based RSUs was based on the achievement of a performance goal milestone as of December 31, 2019 and the vesting of the remaining 25% of the performance-based RSUs was based upon the achievement of a performance goal milestone as of December 31, 2020. The Company estimated the fair value of total shareholder return performance-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 total shareholder return performance-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 total shareholder return performance-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 milestone performance-based RSUs at the date of grant using the fair value method and the probability that the specified performance criteria will be met and amortizes the fair value over the requisite service period for each separately vesting tranche of the award when attainment of the milestone is deemed probable. The assumption used to determine the fair value of the performance-based RSUs granted to management in 2019 for the performance goal milestone units is based on the market price of the award on the grant date . Each quarter the Company updates its assessment of the probability that the specified criteria will be achieved and adjusts its estimate of the fair value, if necessary. As of December 31, 2019, the Company did not meet the 2019 milestone under the performance-based RSUs, and accordingly 46,450 shares were returned to the Amended and Restated 2015 Plan. The previously recognized expense of $0.3 million related to the 2019 milestone was reversed during the year ended December 31, 2019. The 2020 milestone was not deemed probable, and the previously recognized expense of $0.1 million was reversed during the year ended December 31, 2019. The Company recognized $0.3 million expense related to the total shareholder return component of the performance-based RSUs during the year ended December 31, 2019 . In March 2020, the Company and the recipients of these performance-based RSUs agreed to cancel the agreements and as a result, 139,350 shares were returned to the Amended and Restated 2015 Plan. The Company recognized the remaining expense for the total shareholder return performance-based RSUs in the amount of $0.3 million during the six months ended June 30, 2020. The Company did not recognize any expense related to the milestone performance-based RSUs. In April 2020, the Company issued 360,000 performance-based RSUs to senior management under the Amended and Restated 2015 Plan that represented shares potentially issuable in the future subject to the satisfaction of certain performance milestones. The vesting of 50% of the performance-based RSUs is based on the achievement of a performance goal milestone as of December 31, 2020 and the vesting of the remaining 50% of the performance-based RSUs is based upon the achievement of a performance goal milestone as of December 31, 2021. For the three and six months ended June 30, 2020, the Company recognized approximately $44,000 expense related to the performance-based RSUs. Time-Based Restricted Stock Units In March 2020, the Company issued 199,000 time-based RSUs to employees under the Amended and Restated 2015 Plan. The weighted average grant date fair value of the time-based RSUs was $1.41 for the three and six months ended June 30, 2020. The vesting for the time-based RSUs is 50% after one-year from the grant date and the remaining 50% as of December 31, 2021. For the three and six months ended June 30, 2020, the Company recognized approximately $32,000 and $43,000 expense related to the time-based RSUs, respectively. The following table is a rollforward of all RSU activity under the Stock Incentive Plans for the six months ended June 30, 2020: Restricted Stock Units Weighted-Average Grant Date Fair Value Total nonvested units at December 31, 2019 139,350 $ 7.86 Granted 559,000 1.41 Vested — — Cancelled (164,350 ) 6.88 Total nonvested units at June 30, 2020 534,000 $ 1.07 Stock-Based Compensation The following table summarizes the Company’s stock-based compensation expense for the three and six months ended June 30, 2020 and 2019 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, Stock-based compensation: 2020 2019 2020 2019 Research and development $ 171 $ 339 $ 446 $ 656 General and administrative 303 702 845 1,357 Total Stock-based compensation $ 474 $ 1,041 $ 1,291 $ 2,013 The fair value of stock options vested during the six months ended June 30, 2020 was $1.5 million. At June 30, 2020, there was $2.4 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 2.2 years. At June 30, 2020, there was $0.5 million of unrecognized stock-based compensation expense relating to the time-based RSUs 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, 2020 and December 31, 2019, the Company reserved the following shares of common stock for issuance of shares resulting from exercise of outstanding warrants and options, convertible shares from the Convertible Term Loan, as well as issuance of shares available for grant under the Stock Incentive Plans: June 30, December 31, 2020 2019 IPO warrants 28,347 28,347 November private placement warrants 1,633,777 1,633,777 Convertible term loan — 2,329,143 Pontifax warrants 250,000 250,000 September 2019 warrants 15,000 15,000 Amended and restated 2015 stock incentive plan 3,266,451 2,160,338 Inducement awards 90,000 90,000 Total 5,283,575 6,506,605

Convertible Term Loan

Convertible Term Loan	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Convertible Term Loan	9. CONVERTIBLE TERM LOAN In September 2019, the Company entered into a Convertible Term Loan with Pontifax Medison Finance (Israel) L.P. and Pontifax Medison Finance (Cayman) L.P., as lenders, and Pontifax Medison Finance GP, L.P., in its capacity as administrative agent and collateral agent for itself and the lenders (collectively, the “Lenders”), providing for a $20.0 million term loan (the “Convertible Term Loan”), which the Company received on September 19, 2019 (the “Closing Date”). The Company incurred issuance costs of $0.4 million and Pontifax Warrants costs of $0.6 million. The Convertible Term Loan issuance costs and Pontifax Warrant costs are shown as an offset to the Convertible Term Loan on the balance sheet and are amortized using the effective interest method to interest expense through September 23, 2023 (the “Maturity Date”). In April 2020, the Company entered into a prepayment notice and pay-off letter with the Lenders, which provided for the full repayment in cash of the $20.0 million Convertible Term Loan and amended the exercise price with respect to the Pontifax Warrants. Upon repayment of the Convertible Term Loan, the Company incurred a loss on extinguishment of debt, which included $0.3 million for a prepayment fee, $0.4 million of unamortized issuance costs, $0.5 million in unamortized Pontifax Warrant costs and approximately $54,000 for the Pontifax Warrant amendment (see Note 7). Pursuant to the Convertible Term Loan, t he Company was entitled, at its option, to prepay some or all of the then outstanding principal balance and all accrued and unpaid interest on the Convertible Term Loan, together with a prepayment charge equal to 3% of the principal amount being prepaid. The Lenders were entitled, at their option, to elect to convert the then outstanding Convertible Term Loan amount and all accrued and unpaid interest thereon into shares of the Company’s common stock at a conversion price of $8.76 per share. The Company’s obligations were secured by a security interest, senior to any current and future debts and to any security interest, in all of the Company’s right, title, and interest in, to and under all of its property and other assets, subject to limited exceptions including the Company’s intellectual property. The Convertible Term Loan contained customary events of default, representations, warranties and covenants, including a material adverse effect clause. The Company was required to maintain a minimum cash balance of $7.0 million in its accounts. Upon the occurrence of an event of default, a default interest rate of an additional 4% per annum would have been applied to the outstanding loan balances, and the Lenders would have been able to declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Convertible Term Loan Convertible Term Loan In addition, the Company issued the Lenders warrants to purchase an aggregate of 250,000 shares of the Company’s common stock (the “Pontifax Warrants”). The Pontifax Warrants are exercisable for a period of six years from the Closing Date and were exercisable at an exercise price of $6.57 per share prior to their amendment in April 2020. The aggregate fair value of the Pontifax Warrants on the date of issuance was approximately $0.6 million and was recorded as a discount to the term loan and will be amortized over the life of the term loan using the effective interest rate method The aggregate fair value remaining on the payoff date was $0.5 million and was included in the loss on extinguishment of the Convertible Term Loan upon repayment. In connection with the repayment of the Convertible Term Loan, the Pontifax Warrants were amended and restated to amend the exercise price to $2.08 per share, which was equal to 1.5 times the weighted-average closing price of the Company’s Common Stock during the 90 days prior to the repayment date. All other terms of the Pontifax Warrants remained the same. During the three months ended June 30, 2020, there was an incremental expense of approximately $ 54,000 for the amendment of the Pontifax Warrant exercise price , which is included in the loss on extinguishment of debt (s ee Note 7 ) . During the three and six months ended June 30, 2020, the Company recorded interest expense of approximately $35,000 and $511,000, respectively, in connection with the Convertible Term Loan. There was no interest expense recorded during the three and six months ended June 30, 2019.

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases	10. 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 8.3 years for its principal office and laboratory space, which includes an option to extend the lease for up to 5 years, and approximately 0.9 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 as of June 30, 2020 and 2019 was as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, Cash paid for amounts included in the measurement of lease liabilities: 2020 2019 2020 2019 Operating cash flow from operating leases (in thousands) $ 147 $ 91 $ 291 $ 130 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ — $ 2,980 $ — $ 2,980 As of June 30, 2020 and December 31, 2019, the weighted average remaining lease term for operating leases was 8.0 years and 8.3 years, respectively. As of June 30, 2020 and December 31, 2019, the weighted average discount rate for operating leases was 8% for both periods. Operating lease costs under the leases for the three and six months ended June 30, 2020 were approximately $165,000 and $330,000, respectively. Total operating lease costs for the three and six months ended June 30, 2020 were offset by $21,000 and $50,000, respectively, for sublease income and variable lease cost payments. 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. The following table summarizes the Company’s maturities of operating lease liabilities as of June 30, 2020 (in thousands): Year 2020 (excluding the six months ended June 30, 2020) $ 297 2021 508 2022 450 2023 462 2024 474 Thereafter 1,931 Total lease payments $ 4,122 Less: present value discount (1,070 ) Total $ 3,052

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. COMMITMENTS AND CONTINGENCIES 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, 2020
Subsequent Events [Abstract]
Subsequent Events	1 2 . SUBSEQUENT EVENTS On July 29, 2020, the Company entered into the Exchange Agreement with F-star and the holders of outstanding shares and convertible notes of F-star. Under the terms of the Exchange, subject to the satisfaction or waiver of the conditions set forth in the Exchange Agreement, the Company will acquire the entire issued share capital of F-star, with F-star to continue as the combined company. The Exchange has been approved by the boards of directors of both companies and the equity holders of F-star and is expected to close in late 2020, subject to customary closing conditions, including the approval of the Company’s stockholders. Upon completion of the Exchange, Spring Bank Pharmaceuticals, Inc. will be renamed F-star Therapeutics, Inc., and is expected to trade on the Nasdaq Capital Market under the ticker symbol “FSTX”. The Exchange is intended to create a company focused on transforming the lives of patients with cancer through the development of innovative tetravalent bispecific (mAb2™) antibodies. The combined company will advance its immuno-oncology pipeline of multiple tetravalent bispecific antibody programs, including the Company’s STING (STimulator of INterferon Gene) agonist, SB 11285, currently in a Phase 1/2 clinical trial. The combined company will be led by Eliot Forster, Ph.D., MBA, F-star President and Chief Executive Officer, and will be headquartered in United Kingdom. The initial size of the Board of Directors of the Company will be eight and the initial directors are expected to be Nessan Bermingham, Ph.D., who shall be Chairman; David Arkowitz, MBA (continuing Company director); Edward Benz, MD; Todd Brady, MD, Ph.D. (continuing Company director); Eliot Forster, Ph.D., MBA; Pamela Klein, MD (continuing Company director); Patrick Krol, MBA; and Geoffrey Race, FCMA MBA. The resignations from the Company’s board of directors of each of Timothy Clackson, Ph.D., Martin Driscoll, Kurt Eichler and Scott Smith will be effective as of the closing of the proposed Exchange. The Company continues to conduct activities with respect to SB 11285, its intravenously-administered STING agonist product candidate, as well as other preclinical activities as described further in this Quarterly Report on Form 10-Q. The Company has evaluated subsequent events through the date on which the consolidated financial statements were issued to ensure that this Quarterly Report on Form 10-Q 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, 2020
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, 2020 and for the three and six months ended June 30, 2020 and 2019, 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, 2020, results of operations for the three and six months ended June 30, 2020 and 2019, statement of stockholders’ equity for the three and six months ended June 30, 2020 and 2019 and its cash flows for the six months ended June 30, 2020 and 2019. 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 for the year ended December 31, 2019, as filed with the Securities and Exchange Commission (“SEC”) on February 14, 2020. The results for the three and six months ended June 30, 2020 are not necessarily indicative of the results expected for the full fiscal year or any interim period. As of June 30, 2020, the Company had an accumulated deficit of $140.9 million and $23.5 million in cash, cash equivalents and marketable securities. On April 8, 2020, the Company repaid in full its $20.0 million convertible term loan (see Note 9). There is no guarantee that the Exchange will be completed. The Company expects its $23.5 million in cash, cash equivalents and marketable securities as of June 30, 2020 will be sufficient to fund operations for at least the next twelve months. This estimate assumes no additional funding from new collaboration agreements, equity financings or further sales under the Company’s Controlled Equity Offering SM The Company does not expect to raise any additional funds prior to the completion of the Exchange. However, if the Exchange is not completed, the Company may require significant additional funds earlier than it currently expects in order to conduct clinical trials and preclinical and discovery activities. There can be no assurances, however, that additional funding will be available on favorable 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, 2020. Sperovie Biosciences, Inc. was a joint borrower with the Company under the Company’s convertible term loan (see Note 9). SBP Securities Corporation had assets primarily related to investments in marketable securities and operations consisting primarily of interest income as of June 30, 2020. SBP International Limited had operations consisting mainly of clinical trial oversight, including European data protection oversight, as of June 30, 2020. 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 warrants, 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, 2020 are money market fund investments of $7.0 million and included in cash and cash equivalents as of December 31, 2019 are money market fund investments of $21.1 million and United States treasury securities of $6.0 million, which are reported at fair value (see Note 5).
Restricted Cash	Restricted Cash As of June 30, 2020 and December 31, 2019, 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, 2020, 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 accounts for freestanding warrants within stockholders equity or as liabilities based on the characteristics and provisions of each instrument. The Company evaluates outstanding warrants in accordance with ASC 480, Distinguishing Liabilities from Equity Derivatives and Hedging
Stock-Based Compensation	Stock-Based Compensation The Company’s stock-based payments include stock options, performance-based restricted stock units (“performance-based RSUs”), time-based restricted stock units (“time-based RSUs”) and grants of common stock. 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 accounts for forfeitures as they occur. The Company measures the fair value of the performance-based RSUs relating to the total share return performance using a Monte Carlo valuation model. The Company measures the fair value of the performance-based RSUs relating to the milestone performance goals 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 milestone criteria will be achieved and adjusts its estimate of the fair value, if necessary. Stock-based compensation expense is classified in the accompanying consolidated statements of operations and comprehensive loss based on the department to which the related services are provided.
Financial Instruments	Financial Instruments The Company’s financial instruments consist of cash equivalents, marketable securities, accounts payable, a term loan 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 (see Note 5). The fair value of the term loan approximates its face value due to market terms.
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, 2020 and 2019, 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 as well as net operating loss and tax 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, 2020 and December 31, 2019, 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 under a non-cancelable operating lease. The Company has standard indemnification arrangements under the lease 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, 2020, 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 .

Nature of Business and Summar_3

Nature of Business and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020
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, 2020 2019 2020 2019 Net loss $ (6,544 ) $ (4,555 ) $ (14,722 ) $ (9,750 ) Weighted-average number of shares outstanding - basic and diluted 17,052,088 16,443,379 16,787,919 16,440,192 Net loss per common share - basic and diluted $ (0.38 ) $ (0.28 ) $ (0.88 ) $ (0.59 )
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, 2020 2019 Common stock warrants 1,927,124 1,662,124 Stock options and inducement awards 1,606,275 1,714,815 Restricted stock units 534,000 185,800

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 and December 31, 2019 (in thousands): June 30, December 31, Investments - Current: 2020 2019 Debt securities - available for sale $ 14,990 $ 25,746 Total $ 14,990 $ 25,746
Summary of Available-for-Sale Classified Investments	A summary of the Company’s available-for-sale classified investments as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): At June 30, 2020 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: United States treasury securities $ 14,991 $ — $ (1 ) $ 14,990 Total $ 14,991 $ — $ (1 ) $ 14,990 At December 31, 2019 Cost Basis Accumulated Unrealized Gains Accumulated Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 4,990 $ — $ (58 ) $ 4,932 United States treasury securities 20,979 — (165 ) 20,814 Total $ 25,969 $ — $ (223 ) (1) $ 25,746 (1)
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, 2020 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 14,991 $ 14,990 Total $ 14,991 $ 14,990

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): June 30, December 31, 2020 2019 Equipment $ 1,278 $ 1,278 Furniture and fixtures 423 450 Leasehold improvements 1,356 1,356 Total property and equipment 3,057 3,084 Less: accumulated depreciation and amortization (1,014 ) (850 ) Property and equipment, net $ 2,043 $ 2,234

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 and December 31, 2019 is as follows (in thousands): Fair Value Measurement at June 30, 2020 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) $ 7,012 $ 7,012 $ — $ — United States treasury securities 14,990 — 14,990 — Total $ 22,002 $ 7,012 $ 14,990 $ — Liabilities: Warrant liabilities $ 38 $ — $ — $ 38 Total $ 38 $ — $ — $ 38 Fair Value Measurement at December 31, 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) $ 21,065 $ 21,065 $ — $ — United States treasury securities (1) 5,982 — 5,982 — Fixed income securities 25,746 — 25,746 — Total $ 52,793 $ 21,065 $ 31,728 $ — Liabilities: Warrant liabilities $ 299 $ — $ — $ 299 Total $ 299 $ — $ — $ 299 (1) Money market funds and United States treasury securities with maturities of less than 90 days at the date of purchase 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 a 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 three months ended June 30, 2020 (in thousands): November Private Placement Warrants Balance at December 31, 2018 $ 8,511 Change in fair value (8,212 ) Balance at December 31, 2019 299 Change in fair value (261 ) Balance at June 30, 2020 $ 38

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of June 30, 2020 and December 31, 2019 consisted of the following (in thousands): June 30, December 31, 2020 2019 Preclinical and clinical studies $ 1,124 $ 1,473 Compensation and benefits 765 614 Accounting and legal 254 240 Other 96 111 Total accrued expenses and other current liabilities $ 2,239 $ 2,438

Warrants (Tables)

Warrants (Tables)	6 Months Ended
	Jun. 30, 2020
Warrants And Rights Note Disclosure [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, 2020 December 31, 2019 Risk-free interest rate 0.2 % 1.6 % Expected term (in years) 1.4 1.9 Expected volatility 80.9 % 100.0 % Expected dividend yield 0 % 0 %
Summary of Warrant Activity	A summary of the warrant activity for the six months ended June 30, 2020 and for the year ended December 31, 2019 is as follows: Warrants Outstanding at December 31, 2018 1,662,124 Grants 265,000 Exercises — Expirations/cancellations — Outstanding at December 31, 2019 1,927,124 Grants — Exercises — Expirations/cancellations — Outstanding at June 30, 2020 1,927,124

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Summary of Option Activity	The following table summarizes the option activity under the Stock Incentive Plans for the six months ended June 30, 2020 and the year ended December 31, 2019: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Outstanding at December 31, 2018 1,299,565 $ 11.18 $ 881,385 Granted 395,500 9.61 — Exercised — — — Cancelled (22,750 ) 13.36 — Outstanding at December 31, 2019 1,672,315 10.78 — Granted 270,000 1.44 — Exercised — — — Cancelled (426,040 ) 10.45 — Options outstanding at June 30, 2020 1,516,275 $ 9.21 $ — Options exercisable at June 30, 2020 1,017,853 $ 10.79 $ —
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, 2020 and 2019 are as follows, presented on a weighted-average basis: For the Six Months Ended June 30, 2020 2019 Risk-free interest rate 0.7 % 2.6 % Expected term (in years) 5.9 6.0 Expected volatility 82.8 % 81.1 % Expected dividend yield 0 % 0 %
Summary of RSU Activity	The following table is a rollforward of all RSU activity under the Stock Incentive Plans for the six months ended June 30, 2020: Restricted Stock Units Weighted-Average Grant Date Fair Value Total nonvested units at December 31, 2019 139,350 $ 7.86 Granted 559,000 1.41 Vested — — Cancelled (164,350 ) 6.88 Total nonvested units at June 30, 2020 534,000 $ 1.07
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, 2020 and 2019 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, Stock-based compensation: 2020 2019 2020 2019 Research and development $ 171 $ 339 $ 446 $ 656 General and administrative 303 702 845 1,357 Total Stock-based compensation $ 474 $ 1,041 $ 1,291 $ 2,013
Summary of Shares of Common Stock Reserved	As of June 30, 2020 and December 31, 2019, the Company reserved the following shares of common stock for issuance of shares resulting from exercise of outstanding warrants and options, convertible shares from the Convertible Term Loan, as well as issuance of shares available for grant under the Stock Incentive Plans: June 30, December 31, 2020 2019 IPO warrants 28,347 28,347 November private placement warrants 1,633,777 1,633,777 Convertible term loan — 2,329,143 Pontifax warrants 250,000 250,000 September 2019 warrants 15,000 15,000 Amended and restated 2015 stock incentive plan 3,266,451 2,160,338 Inducement awards 90,000 90,000 Total 5,283,575 6,506,605

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Summary of Other Information Related to Leases	Other information related to leases as of June 30, 2020 and 2019 was as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, Cash paid for amounts included in the measurement of lease liabilities: 2020 2019 2020 2019 Operating cash flow from operating leases (in thousands) $ 147 $ 91 $ 291 $ 130 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ — $ 2,980 $ — $ 2,980
Summary of Maturities of Operating Lease Liabilities	The following table summarizes the Company’s maturities of operating lease liabilities as of June 30, 2020 (in thousands): Year 2020 (excluding the six months ended June 30, 2020) $ 297 2021 508 2022 450 2023 462 2024 474 Thereafter 1,931 Total lease payments $ 4,122 Less: present value discount (1,070 ) Total $ 3,052

Nature of Business and Summar_4

Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail)	Apr. 08, 2020USD ($)	Jun. 30, 2020USD ($)SubsidiarySegment	Dec. 31, 2019USD ($)
Nature of Business and Summary of Significant Accounting Policies [Line Items]
Number of wholly owned subsidiaries | Subsidiary		3
Accumulated deficit		$ (140,887,000)	$ (126,165,000)
Cash, cash equivalents and marketable securities		23,500,000
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
United States Treasury Securities [Member]
Nature of Business and Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents fair value			6,000,000
Money Market Funds [Member]
Nature of Business and Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents fair value		$ 7,000,000	$ 21,100,000
Convertible Term Loan [Member] | Prepayment Notice and Pay-Off Letter [Member]
Nature of Business and Summary of Significant Accounting Policies [Line Items]
Repayment of long-term debt	$ 20,000,000

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, 2020
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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share Basic And Diluted [Abstract]
Net loss	$ (6,544)	$ (4,555)	$ (14,722)	$ (9,750)
Weighted-average number of shares outstanding - basic and diluted	17,052,088	16,443,379	16,787,919	16,440,192
Net loss per common share - basic and diluted	$ (0.38)	$ (0.28)	$ (0.88)	$ (0.59)

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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
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	1,927,124	1,662,124	1,927,124	1,662,124
Stock Options 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	1,606,275	1,714,815	1,606,275	1,714,815
Restricted Stock Units [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	534,000	185,800	534,000	185,800

Investments - Summary of Invest

Investments - Summary of Investments by Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Investments - Current:
Debt securities - available for sale	$ 14,990	$ 25,746
Total	$ 14,990	$ 25,746

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Classified Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$ 14,991
Fair Value	14,990
Investments - Current [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	14,991	$ 25,969
Accumulated Unrealized Losses	(1)	(223)
Fair Value	14,990	25,746
Investments - Current [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		4,990
Accumulated Unrealized Losses		(58)
Fair Value		4,932
Investments - Current [Member] | United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	14,991	20,979
Accumulated Unrealized Losses	(1)	(165)
Fair Value	$ 14,990	$ 20,814

Investments - Summary of Avai_2

Investments - Summary of Available-for-Sale Classified Investments (Parenthetical) (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Investments Debt And Equity Securities [Abstract]
Unrealized losses included in cash and cash equivalents	$ (12)
Total net unrealized losses	$ (235)

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, 2020USD ($)
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 14,991
Cost Basis	14,991
Due in one year or less, Fair Value	14,990
Total, Fair Value	$ 14,990

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,057	$ 3,084
Less: accumulated depreciation and amortization	(1,014)	(850)
Property and equipment, net	2,043	2,234
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,278	1,278
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	423	450
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,356	$ 1,356

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 95	$ 88	$ 191	$ 171

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 7,000	$ 21,100
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	22,002	52,793
Liabilities, Total	38	299
Carrying Value [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	7,012	21,065
Carrying Value [Member] | United States Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities	14,990	5,982
Carrying Value [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities		25,746
Carrying Value [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	38	299
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	7,012	21,065
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	7,012	21,065
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	14,990	31,728
Significant Other Observable Inputs (Level 2) [Member] | United States Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities	14,990	5,982
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		25,746
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Total	38	299
Significant Unobservable Inputs (Level 3) [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	$ 38	$ 299

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, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	$ 299	$ 8,511
Change in fair value	(261)	(8,212)
Ending balance	$ 38	$ 299

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities And Other Liabilities [Abstract]
Preclinical and clinical studies	$ 1,124	$ 1,473
Compensation and benefits	765	614
Accounting and legal	254	240
Other	96	111
Total accrued expenses and other current liabilities	$ 2,239	$ 2,438

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($)	1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2019	Nov. 30, 2016	Jun. 30, 2016	May 31, 2016	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Apr. 08, 2020	Sep. 19, 2019
Class of Warrant or Right [Line Items]
Expected life (in years)							5 years 10 months 24 days	6 years
Dividend yield							0.00%	0.00%
Amount included in loss on extinguishment of convertible term loan					$ (1,207,000)		$ (1,207,000)
Change in fair value of warrant liabilities					$ (22,000)	$ (4,885,000)	$ (261,000)	$ (7,706,000)
Convertible Term Loan [Member]
Class of Warrant or Right [Line Items]
Long-term debt	$ 20,000,000										$ 20,000,000
Common Stock Warrants [Member] | Pontifax [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase shares of common stock	250,000				250,000		250,000
Exercise price	$ 6.57				$ 6.57		$ 6.57			$ 2.08
Warrant expiration date	Sep. 19, 2025
Expected life (in years)	6 years						6 years
Expected volatility of common stock Minimum	83.20%
Risk free interest rate	1.70%
Dividend yield	0.00%
Fair value of equity	$ 600,000				$ 600,000		$ 600,000
Amount included in loss on extinguishment of convertible term loan	$ 500,000
Incremental expense of warrant liabilities					$ 54,000
May 2016 IPO warrants [Member]
Class of Warrant or Right [Line Items]
Expected life (in years)				4 years 11 months 26 days
Expected volatility of common stock Minimum				87.00%
Risk free interest rate				1.20%
Dividend yield				0.00%
June 2016 IPO warrants [Member]
Class of Warrant or Right [Line Items]
Expected life (in years)			4 years 11 months 1 day
Expected volatility of common stock Minimum			87.00%
Risk free interest rate			1.23%
Dividend yield			0.00%
September 2019 Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase shares of common stock	15,000
Exercise price	$ 4.21
Warrant expiration date	Sep. 19, 2021
Expected life (in years)	2 years
Expected volatility of common stock Minimum	69.40%
Risk free interest rate	1.70%
Dividend yield	0.00%
Fair value of equity	$ 19,000
Change in fair value of warrant liabilities							$ 13,000		$ 6,000
IPO [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase shares of common stock			747	27,600
Exercise price					$ 15		$ 15
Warrant expiration date							May 5, 2021
Fair value of equity			$ 200,000
Private Placement [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase shares of common stock		1,644,737
Exercise price		$ 10.79
Warrant expiration date		Nov. 23, 2021
Issuance of common stock		1,644,737
Shares issued price per share		$ 9.12
Private Placement [Member] | Common Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Fair value of equity		$ 8,300,000			$ 38,000		$ 38,000		$ 300,000
Shares Exercised During the period							10,960

Warrants - Summary of Assumptio

Warrants - Summary of Assumptions Used to Record Fair Value of Warrants (Detail) - Warrants [Member]	Jun. 30, 2020	Dec. 31, 2019
Risk-Free Interest Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	0.20%	1.60%
Expected Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input (in years)	1 year 4 months 24 days	1 year 10 months 24 days
Expected Volatility [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	80.90%	100.00%
Expected Dividend Yield [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	0.00%	0.00%

Warrants - Summary of Warrant A

Warrants - Summary of Warrant Activity (Detail) - Common Stock Warrants [Member] - shares	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Class of Warrant or Right [Line Items]
Outstanding, Beginning Balance	1,927,124	1,662,124
Grants	0	265,000
Exercises	0	0
Expirations/cancellations	0	0
Outstanding, Ending balance	1,927,124	1,927,124

Stockholders' Equity - Addition

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

May 11, 2016

Apr. 30, 2020

Mar. 31, 2020

Feb. 28, 2019

Jan. 31, 2019

Mar. 31, 2018

Jan. 31, 2018

Jun. 30, 2020

Jun. 30, 2019

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2019

Dec. 31, 2015

Aug. 31, 2017

Apr. 30, 2014

Class of Stock [Line Items]

Stock options granted

0

Stock-based compensation expense

$ 1,291,000

$ 2,013,000

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 Units [Member]

Class of Stock [Line Items]

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

In January 2019, the Company issued performance-based RSUs to senior management under the Amended and Restated 2015 Plan that represented 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 performance-based RSUs was 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. The vesting of 25% of the performance-based RSUs was based on the achievement of a performance goal milestone as of December 31, 2019 and the vesting of the remaining 25% of the performance-based RSUs was based upon the achievement of a performance goal milestone as of December 31, 2020.

Share based compensation, milestone base goals and shares returned

46,450

Stock-based compensation expense

$ 300,000

$ 300,000

Cancellation of shares

139,350

164,350

RSUs issued

559,000

Weighted-average fair value of restricted stock units granted

$ 1.41

Performance-Based Restricted Stock Units [Member] | Senior Management [Member]

Class of Stock [Line Items]

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

In April 2020, the Company issued 360,000 performance-based RSUs to senior management under the Amended and Restated 2015 Plan that represented shares potentially issuable in the future subject to the satisfaction of certain performance milestones.

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

The vesting of 50% of the performance-based RSUs is based on the achievement of a performance goal milestone as of December 31, 2020 and the vesting of the remaining 50% of the performance-based RSUs is based upon the achievement of a performance goal milestone as of December 31, 2021. For the three and six months ended June 30, 2020, the Company recognized approximately $44,000 expense related to the performance-based RSUs.

Performance-Based Restricted Stock Units [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 Units [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%

Reversal of stock-based compensation expense upon non-achievement of clinical milestone

300,000

Performance-Based Restricted Stock Units [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%

Reversal of stock-based compensation expense upon non-achievement of clinical milestone

$ 100,000

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

Class of Stock [Line Items]

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

50.00%

Performance-Based Restricted Stock Units [Member] | Achievement of a Performance Goal Milestone as of December 31, 2021 [Member] | Senior Management [Member]

Class of Stock [Line Items]

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

50.00%

Stock-based compensation expense

$ 44,000

$ 44,000

RSUs issued

360,000

Time-Based Restricted Stock Units [Member]

Class of Stock [Line Items]

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

The vesting for the time-based RSUs is 50% after one-year from the grant date and the remaining 50% as of December 31, 2021.

Stock-based compensation expense

$ 32,000

$ 43,000

RSUs issued

199,000

Weighted-average fair value of restricted stock units granted

$ 1.41

$ 1.41

Time-Based Restricted Stock Units [Member] | Achievement of a Performance Goal Milestone as of December 31, 2021 [Member]

Class of Stock [Line Items]

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

50.00%

Time-Based Restricted Stock Units [Member] | Vesting After One-Year from Grant Date

Class of Stock [Line Items]

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

50.00%

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

6 years 7 months 6 days

Weighted-average fair value of all stock options granted

$ 0.99

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

Class of Stock [Line Items]

Shares issued price per share

$ 1.47

$ 1.47

$ 1.58

2015 Stock Incentive Plan [Member]

Class of Stock [Line Items]

Number of authorized shares of common stock to be issued

2,816,863

Number of shares remain available for grant

1,216,176

1,216,176

Number of shares common stock reserved for issuance, increase

800,000

1,150,000

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

3,450,000

3,450,000

Stock options granted

270,000

395,500

Fair value of stock options vested

$ 1,500,000

Unrecognized stock-based compensation expense

$ 2,400,000

$ 2,400,000

Weighted-average remaining vesting period

2 years 2 months 12 days

2014 and 2015 Stock Incentive Plans [Member] | Time-Based Restricted Stock Units [Member]

Class of Stock [Line Items]

Unrecognized stock-based compensation expense

$ 500,000

$ 500,000

Weighted-average remaining vesting period

1 year 6 months

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

649,095

600

690,895

600

Weighted average selling price per share

$ 1.32

$ 10.03

$ 1.32

$ 10.03

Net proceeds from initial public offering of common stock

$ 800,000

$ 800,000

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 Option Activity (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	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	1,672,315	1,299,565
Options Granted	270,000	395,500
Options Cancelled	(426,040)	(22,750)
Options outstanding, Ending balance	1,516,275	1,672,315
Options exercisable	1,017,853
Weighted-Average Exercise Price Per Share, Options outstanding, Beginning Balance	$ 10.78	$ 11.18
Weighted-Average Exercise Price Per Share, Granted	1.44	9.61
Weighted-Average Exercise Price Per Share, Cancelled	10.45	13.36
Weighted-Average Exercise Price Per Share, Options outstanding, Ending Balance	9.21	$ 10.78
Weighted-Average Exercise Price Per Share, Options exercisable	$ 10.79
Aggregate Intrinsic Value, Options outstanding, Beginning Balance		$ 881,385

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Assumptions to Determine Fair Value of Stock Options Granted to Employees and Directors (Detail)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	0.70%	2.60%
Expected term (in years)	5 years 10 months 24 days	6 years
Expected volatility	82.80%	81.10%
Expected dividend yield	0.00%	0.00%

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of RSU Activity (Detail) - Performance-Based Restricted Stock Units [Member] - $ / shares	1 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested units, Beginning Balance		139,350
Nonvested units, Granted		559,000
Nonvested units, Cancelled	(139,350)	(164,350)
Nonvested units, Ending Balance		534,000
Weighted-Average Grant Date Fair Value Nonvested units, Beginning Balance		$ 7.86
Weighted-Average Grant Date Fair Value Granted		1.41
Weighted-Average Grant Date Fair Value Cancelled		6.88
Weighted-Average Grant Date Fair Value Nonvested units, Ending Balance		$ 1.07

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 1,291	$ 2,013
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	$ 474	$ 1,041	1,291	2,013
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	171	339	446	656
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	$ 303	$ 702	$ 845	$ 1,357

Stockholders' Equity - Summar_5

Stockholders' Equity - Summary of Shares of Common Stock Reserved (Detail) - shares	Jun. 30, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	5,283,575	6,506,605
IPO Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	28,347	28,347
November 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
Convertible Term Loan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved		2,329,143
Pontifax Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	250,000	250,000
September 2019 Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	15,000	15,000
2015 Amended and Restated Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	3,266,451	2,160,338
Inducement Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	90,000	90,000

Convertible Term Loan - Additio

Convertible Term Loan - Additional Information (Detail) - USD ($)	Apr. 08, 2020	Sep. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 19, 2019
Debt Instrument [Line Items]
Expected life (in years)					5 years 10 months 24 days	6 years
Amount included in loss on extinguishment of convertible term loan			$ (1,207,000)		$ (1,207,000)
Pontifax [Member] | Common Stock Warrants [Member]
Debt Instrument [Line Items]
Incremental expense of warrant liabilities			$ 54,000
Warrants issued to purchase shares of common stock		250,000	250,000		250,000
Exercise price	$ 2.08	$ 6.57	$ 6.57		$ 6.57
Expected life (in years)		6 years			6 years
Fair value of equity		$ 600,000	$ 600,000		$ 600,000
Amount included in loss on extinguishment of convertible term loan		500,000
Convertible Term Loan [Member]
Debt Instrument [Line Items]
Long-term debt		$ 20,000,000					$ 20,000,000
Debt instrument, maturity date					Sep. 23, 2023
Debt issuance cost			$ 400,000		$ 400,000
Debt instrument, convertible, conversion price			$ 8.76		$ 8.76
Prepayment charge percentage			3.00%		3.00%
Minimum cash balance maintained in accounts			$ 7,000,000		$ 7,000,000
Additional interest rate upon occurrence of an event of default					4.00%
Interest expense, debt			35,000	$ 0	$ 511,000	$ 0
Convertible Term Loan [Member] | Prepayment Notice and Pay-Off Letter [Member]
Debt Instrument [Line Items]
Repayment of long-term debt	$ 20,000,000
Debt instrument prepayment fee			300,000		300,000
Unamortized debt issuance cost			400,000		400,000
Convertible Term Loan [Member] | Pontifax [Member]
Debt Instrument [Line Items]
Warrant costs			600,000		600,000
Convertible Term Loan [Member] | Pontifax [Member] | Prepayment Notice and Pay-Off Letter [Member]
Debt Instrument [Line Items]
Unamortized warrant costs			500,000		$ 500,000
Incremental expense of warrant liabilities			$ 54,000

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Lessee Lease Description [Line Items]
Operating leases, weighted average remaining lease term	8 years		8 years		8 years 3 months 18 days
Operating leases, weighted average discount rate	8.00%		8.00%		8.00%
Operating lease costs	$ 165,000	$ 130,000	$ 330,000	$ 260,000
Sublease income and variable lease cost payments	$ 21,000	$ 18,000	$ 50,000	$ 37,000
Principal Office and Laboratory Space [Member]
Lessee Lease Description [Line Items]
Operating leases, weighted average remaining lease term	8 years 3 months 18 days		8 years 3 months 18 days
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, weighted average remaining lease term	10 months 24 days		10 months 24 days

Leases - Summary of Other Infor

Leases - Summary of Other Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow from operating leases (in thousands)	$ 147	$ 91	$ 291	$ 130
Right-of-use assets obtained in exchange for lease obligations:
Operating leases (in thousands)		$ 2,980		$ 2,980

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Detail) $ in Thousands	Jun. 30, 2020USD ($)
Leases [Abstract]
2020 (excluding the six months ended June 30, 2020)	$ 297
2021	508
2022	450
2023	462
2024	474
Thereafter	1,931
Total lease payments	4,122
Less: present value discount	(1,070)
Total	$ 3,052

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Jun. 30, 2020USD ($)
Commitments And Contingencies Disclosure [Abstract]
Accruals for contingent liabilities	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	Jul. 29, 2020Director
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of board of directors	8