F-star Therapeutics (FSTX) 10-K 14 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 10, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
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 Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-37718
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2386345
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
Entity Address, Postal Zip Code	01748
City Area Code	508
Local Phone Number	473-5993
Entity Public Float			$ 55.9
Entity Common Stock, Shares Outstanding		16,513,763
Documents Incorporated by Reference	Portions of the information required by Part III of Form 10-K will appear in the registrant's definitive proxy statement on Schedule 14A for the 2020 annual meeting of stockholders and are hereby incorporated by reference into this report.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 28,709	$ 14,724
Marketable securities	25,746	32,914
Prepaid expenses and other current assets	3,522	1,649
Total current assets	57,977	49,287
Marketable securities, long-term		16,804
Property and equipment, net	2,234	2,319
Operating lease right-of-use assets	2,717
Restricted cash	234	234
Other assets	35	167
Total	63,197	68,811
Current liabilities:
Accounts payable	2,210	1,880
Accrued expenses and other current liabilities	2,438	2,367
Accrued interest payable	403
Operating lease liabilities, current	355
Total current liabilities	5,406	4,247
Convertible term loan, net of unamortized discount	19,070
Warrant liabilities	299	8,511
Operating lease liabilities, noncurrent	2,869
Other long-term liabilities	27	193
Total liabilities	27,671	12,951
Commitments and contingencies (Note 12)
Stockholders’ equity:
Preferred stock, $0.0001 par value—authorized, 10,000,000 shares at December 31, 2019 and 2018; no shares issued or outstanding at December 31, 2019 and 2018
Common stock, $0.0001 par value—authorized, 200,000,000 shares at December 31, 2019 and 2018; 16,513,763 and 16,434,614 shares issued and outstanding outstanding at December 31, 2019 and 2018, respectively	2	2
Additional paid-in capital	161,924	157,931
Accumulated deficit	(126,165)	(102,068)
Accumulated other comprehensive loss	(235)	(5)
Total stockholders’ equity	35,526	55,860
Total	$ 63,197	$ 68,811

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	16,513,763	16,434,614
Common stock, shares outstanding	16,513,763	16,434,614

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 23,270	$ 19,751
General and administrative	9,751	8,719
Total operating expenses	33,021	28,470
Loss from operations	(33,021)	(28,470)
Other income (expense):
Interest income	1,254	999
Interest expense	(542)
Change in fair value of warrant liabilities	8,212	4,617
Net loss	(24,097)	(22,854)
Unrealized gain (loss) on marketable securities	(230)	18
Comprehensive loss	$ (24,327)	$ (22,836)
Net loss per common share:
Basic	$ (1.46)	$ (1.59)
Diluted	$ (1.46)	$ (1.88)
Weighted-average number of shares outstanding:
Basic	16,454,083	14,372,174
Diluted	16,454,083	14,618,976

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	At-The-Market Offering [Member]	Common Stock [Member]	Common Stock [Member]At-The-Market Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]At-The-Market Offering [Member]	Accumulated Deficit [Member]	Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2017	$ 34,748		$ 1		$ 113,984		$ (79,214)	$ (23)
Balance, shares at Dec. 31, 2017			12,961,993
Stock-based compensation	2,662				2,662
Issuance of common stock for services rendered	114				114
Issuance of common stock for services rendered, shares			9,213
Issuance of common stock in connection with offering, net of issuance costs	37,960	$ 3,212	$ 1		37,959	$ 3,212
Issuance of common stock in connection with offering, net of issuance costs, shares			3,246,079	217,329
Net unrealized gain (loss) on marketable securities	18							18
Net loss	(22,854)						(22,854)
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	3,130				3,130
Issuance of common stock for services rendered	261				261
Issuance of common stock for services rendered, shares			78,549
Issuance of common stock in connection with offering, net of issuance costs		$ 6				$ 6
Issuance of common stock in connection with offering, net of issuance costs, shares				600
Issuance of warrants in connection with term loan	552				552
Issuance of warrants to a service provider	19				19
Offering costs in connection with common stock offering	25				25
Net unrealized gain (loss) on marketable securities	(230)							(230)
Net loss	(24,097)						(24,097)
Balance at Dec. 31, 2019	$ 35,526		$ 2		$ 161,924		$ (126,165)	$ (235)
Balance, shares at Dec. 31, 2019			16,513,763

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (24,097)	$ (22,854)
Adjustments for:
Depreciation and amortization	357	288
Loss on disposal of property and equipment		52
Operating lease right-of-use asset amortization	263
Change in fair value of warrant liabilities	(8,212)	(4,617)
Non-cash interest expense	86	337
Non-cash investment income	(28)
Non-cash stock-based compensation	3,367	2,776
Non-cash issuance of warrants to a service provider	19
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,873)	(1,069)
Other assets	132	(132)
Accounts payable	330	180
Accrued expenses and other liabilities	358	(205)
Accrued interest payable	403
Operating lease liabilities	(160)
Net cash used in operating activities	(29,055)	(25,244)
Cash flows from investing activities:
Proceeds from sale of marketable securities	38,770	34,869
Purchases of marketable securities	(15,000)	(58,000)
Purchases of property and equipment	(272)	(1,972)
Net cash provided by (used in) investing activities	23,498	(25,103)
Cash flows from financing activities:
Proceeds from term loan and warrants	20,000
Issuance costs in connection with term loan and warrants	(464)
Proceeds from issuance of common stock, net of issuance costs		37,960
Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs	6	3,212
Cash provided by financing activities	19,542	41,172
Net increase (decrease) in cash, cash equivalents and restricted cash	13,985	(9,175)
Cash, cash equivalents and restricted cash, beginning of period	14,958	24,133
Cash, cash equivalents and restricted cash, end of period	28,943	14,958
Supplemental disclosures of cash flow information:
Cash paid for taxes	30	$ 3
Cash paid for interest, net	$ 53

Nature of Business, Basis of Pr

Nature of Business, Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Nature of Business, Basis of presentation and Summary of Significant Accounting Policies	1. NATURE OF BUSINESS, BASIS OF PRESENTATION 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 recently, the Company was focused 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. 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”). As of December 31, 2019, the Company had an accumulated deficit of $126.2 million and $54.5 million in cash, cash equivalents and marketable securities. The Company expects to continue to incur significant and increasing losses for the foreseeable future. The Company anticipates that its expenses will increase significantly as it continues to develop SB 11285 and its other product candidates. The Company does not have any committed external source of funds. As a result, the Company will need additional financing to support its continuing operations. Adequate additional funds may not be available to the Company on acceptable terms, or at all. To the extent that the Company raises additional capital through the sale of equity or convertible debt securities, stockholders’ ownership interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect common stockholder rights. If the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, the Company may have to relinquish valuable rights to its technologies, future revenue streams, research programs, or product candidates or grant licenses on terms that may not be favorable to the Company. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sperovie Biosciences, Inc., SBP Securities Corporation and SBP International Limited. Sperovie Biosciences, Inc. had operations consisting mainly of legal fees associated with intellectual property activities as of December 31, 2019. Sperovie Biosciences, Inc. is a joint borrower with the Company under the Company’s term loan (see Note 9). 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 warrant liabilities, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, and accounting for certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates. Cash and Cash Equivalents Cash equivalents are stated at fair value and include short-term, highly liquid investments with remaining maturities of 90 days or less at the date of purchase. Included in cash and cash equivalents as of 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. As of December 31, 2018, included in cash and cash equivalents are money market fund investments of $13.3 million, which are reported at fair value (Note 5). Restricted Cash As of December 31, 2019 and 2018, restricted cash consisted of approximately $234,000, which is held as a security deposit required in conjunction with the 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 and amortization are 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 the commencement date of a lease 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 the 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 incentive amounts. 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. Through December 31, 2019, no such impairment has occurred. Research and Development Costs Research and development expenses consist primarily of costs incurred for the Company’s research activities, including discovery efforts, and the development of product candidates, which include: • expenses incurred under agreements with third parties, including contract research organizations, or CROs, that conduct research, preclinical activities and clinical trials on the Company’s behalf as well as contract manufacturing organizations, or CMOs, that manufacture drug products for use in the Company’s preclinical and clinical trials; • salaries, benefits and other related costs, including stock-based compensation expense, for personnel in the Company’s research and development functions; • costs of outside consultants, including their fees, stock-based compensation and related travel expenses; • the cost of laboratory supplies and acquiring, developing and manufacturing preclinical study and clinical trial materials; • costs related to compliance with regulatory requirements; and • facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs. The Company expenses research and development costs as incurred. The Company recognizes external development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors and its clinical investigative sites. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected in the Company’s consolidated financial statements as prepaid or accrued research and development expenses. Warrants The Company 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 (“RSUs”) and grants of common stock, including common stock subject to vesting. The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employee’s 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 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 year ended December 31, 2019, both methods are equivalent. For the year ended December 31, 2018, diluted net loss per share amounts were calculated based on the dilutive effect of the total number of shares of common stock related to the November 2016 Private Placement warrants and the change in the fair value of the warrant liability. Basic and diluted net loss per share are 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 tax expense. As of December 31, 2019 and 2018, the Company has not identified any material uncertain tax positions. Guarantees and Indemnifications As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The Company leases office and laboratory space in Hopkinton, Massachusetts and previously leased research and development space in Milford, Massachusetts under non-cancelable operating leases. The Company has standard indemnification arrangements under these leases that require it to indemnify the landlords against liability for injury, loss, accident, or damage from any claims, actions, proceedings, or costs resulting from certain acts, breaches, violations, or nonperformance under the Company’s lease. Through December 31, 2019, the Company had not experienced any losses related to these indemnification obligations and no material claims were outstanding. The Company does not expect significant claims related to these indemnification obligations, and consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established. Segment Information Operating segments are identified as components of an enterprise about which separate and discrete financial information is available for evaluation by the chief operating decision maker, the Company’s Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and does not track expenses on a program-by-program basis. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases “Codification Improvements to Topic 842, Leases” The Company adopted the standard on the effective date of January 1, 2019 by applying the new lease requirements at the effective date. Prior periods continue to be presented based on the accounting standards originally in effect for such periods. The Company also elected the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carry forward the historical lease classification. The Company will also apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The standard had an impact of approximately $3.0 million on the Company’s assets and $3.4 million on its liabilities, as of January 1, 2019, for the recognition of right-of-use assets and lease liabilities, which are primarily related to the lease of its corporate headquarters in Hopkinton, Massachusetts. The standard did not have a material impact on the Company’s results of operations or liquidity (see Note 10) In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception . 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	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	2. NET LOSS PER SHARE The following table summarizes the computation of basic and diluted net loss per share of the Company for the years ended December 31, 2019 and 2018 (in thousands, except share and per share data): Year Ended December 31, 2019 Net loss $ (24,097 ) Weighted-average number of shares outstanding - basic and diluted 16,454,083 Net loss per common share - basic and diluted $ (1.46 ) For the year ended December 31, 2019, the diluted net loss per common share is the same as basic net loss per common share. Year Ended December 31, 2018 Net loss $ (22,854 ) Less: decrease in change in fair value of warrant liabilities (4,617 ) Net loss available to common shareholders $ (27,471 ) Weighted-average number of shares outstanding: Basic 14,372,174 Effect of dilutive securities: Common stock warrants 246,802 Dilutive potential common shares 14,618,976 Net loss per common share: Basic $ (1.59 ) Diluted $ (1.88 ) For the year ended December 31, 2018, the diluted net loss per common share amounts under the treasury stock method was calculated based on the dilutive effect of the total number of shares of common stock related to the November 2016 Private Placement Warrants of 1,633,777 shares with an exercise price of $10.79. For the period ended December 31, 2018, the average stock price was $12.71, providing 246,802 dilutive shares for the November 2016 Private Placement Warrants. The change in the fair value of the warrant liability of $4.6 million is included in the net loss available to common shareholders for the diluted net loss per common share amount. 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: Year 2019 2018 Convertible debt 2,329,143 — Common stock warrants 1,927,124 28,347 Stock options 1,901,665 1,349,565

Investments

Investments	12 Months Ended
	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Investments	3 . INVESTMENTS Cash in excess of the Company’s immediate requirements is invested in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. The following table summarizes the Company’s investments, by category, as of December 31, 2019 and 2018 (in thousands): December 31, December 31, Investments - Current: 2019 2018 Debt securities - available for sale $ 25,746 $ 32,914 Total $ 25,746 $ 32,914 Investments - Noncurrent: Debt securities - available for sale $ — $ 16,804 Total $ — $ 16,804 A summary of the Company’s available-for-sale classified investments as of December 31, 2019 and 2018 consisted of the following (in thousands): At December 31, 2019 Cost Basis Unrealized Gains 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) unrealized losses at December 31, 2019. At December 31, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 16,028 $ — $ (19 ) $ 16,009 United States treasury securities 16,913 — (8 ) 16,905 Total $ 32,941 $ — $ (27 ) $ 32,914 Investments - Noncurrent: Corporate bonds $ 4,930 $ 2 $ — $ 4,932 United States treasury securities 11,852 20 — 11,872 Total $ 16,782 $ 22 $ — $ 16,804 The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of December 31, 2019 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 25,969 $ 25,746 Due after one year through two years — — Total $ 25,969 $ 25,746

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	4. PROPERTY AND EQUIPMENT, NET Property and equipment as of December 31, 2019 and 2018 consisted of the following (in thousands): December 31, December 31, 2019 2018 Equipment $ 1,278 $ 1,064 Furniture and fixtures 450 400 Leasehold improvements 1,356 1,347 Total property and equipment 3,084 2,811 Less: accumulated depreciation (850 ) (492 ) Property and equipment, net $ 2,234 $ 2,319 Depreciation expense for the years ended December 31, 2019 and 2018 was $357,000 and $288,000, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	5 . FAIR VALUE MEASUREMENTS Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The Company classified its money market funds within Level 1 because their fair values are based on their quoted market prices. The Company classified its 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 December 31, 2019 and 2018 is as follows (in thousands): 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 Fair Value Measurement at December 31, 2018 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 13,264 $ 13,264 $ — $ — Fixed income securities 49,718 — 49,718 — Total $ 62,982 $ 13,264 $ 49,718 $ — Liabilities: Warrant liabilities $ 8,511 $ — $ — $ 8,511 Total $ 8,511 $ — $ — $ 8,511 (1) Money market funds and United States treasury securities with maturities of 90 days or less 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 consist of the warrants issued in a private placement in November 2016 (see Note 7), for the years ended December 31, 2019 and 2018 (in thousands): November Private Placement Warrants Balance at December 31, 2017 $ 13,128 Change in fair value (4,617 ) Balance at December 31, 2018 $ 8,511 Change in fair value (8,212 ) Balance at December 31, 2019 $ 299

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6 . ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses as of December 31, 2019 and 2018 consisted of the following (in thousands): December 31, December 31, 2019 2018 Preclinical and clinical studies $ 1,473 $ 941 Compensation and benefits 614 830 Accounting and legal 240 227 Other 111 369 Total accrued expenses and other current liabilities $ 2,438 $ 2,367

Warrants

Warrants	12 Months Ended
	Dec. 31, 2019
Warrants And Rights Note Disclosure [Abstract]
Warrants	7 . WARRANTS In connection with the amendment and restatement of a license agreement with BioHEP Technologies Ltd. (“BioHEP”) in February 2016, the Company issued a warrant to purchase 125,000 shares of the Company’s common stock to BioHEP (the “BioHEP Warrant”). The BioHEP Warrant had an exercise price of $16.00 per share. The Company evaluated the terms of the warrant and concluded that it should be equity-classified. The fair value of the warrant, $0.8 million, was estimated on the issuance date using a Black-Scholes pricing model based on the following assumptions: an expected term of two and a half years, expected stock price volatility of 71%, a risk-free rate of 1.01%, and a dividend yield of 0%. The fair value was expensed as research and development costs. The warrant expired unexercised on August 1, 2018. In connection with the Company’s IPO, the Company issued to the sole book-running manager for the IPO a warrant to purchase 27,600 shares of common stock in May 2016 and a warrant to purchase 747 shares of common stock in June 2016 (together, the “IPO Warrants”). The IPO Warrants are exercisable at an exercise price of $15.00 per share and expire on May 5, 2021. The Company evaluated the terms of the IPO Warrants and concluded that they should be equity-classified. The fair value of the May 2016 IPO Warrants was estimated on the applicable issuance dates using a Black Scholes pricing model based on the following assumptions: an expected term of 4.99 years; expected stock price volatility of 87%; a risk-free rate of 1.20%; and a dividend yield of 0%. The fair value of the June 2016 IPO Warrants was estimated on the applicable issuance dates using a Black Scholes pricing model based on the following assumptions: an expected term of 4.92 years; expected stock price volatility of 87%; a risk-free rate of 1.23%; and a dividend yield of 0%. The aggregate fair value of the IPO Warrants was $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 December 31, 2019 and 2018, the fair value of the November 2016 Private Placement Warrants was approximately $0.3 million and $8.5 million, respectively and 10,960 shares have been exercised (see Note 5). A summary of the Black Scholes pricing model assumptions used to record the fair value of the warrants is as follows: For the Year Ended December 31, 2019 2018 Risk-free interest rate 1.6 % 2.5 % Expected term (in years) 1.9 2.9 Expected volatility 100.0 % 78.1 % 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”). The Pontifax Warrants are exercisable at an exercise price of $6.57 per share and 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 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. 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 was approximately $19,000 and will be expensed over the life of the service contract. As of December 31, 2019, approximately $6,000 has been expensed. A summary of the warrant activity for the years ended December 31, 2019 and 2018 is as follows: Warrants Outstanding at December 31, 2017 1,787,124 Grants — Exercises — Expirations/cancellations (125,000 ) Outstanding at December 31, 2018 1,662,124 Grants 265,000 Exercises — Expirations/cancellations — Outstanding at December 31, 2019 1,927,124

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	8 . STOCKHOLDERS’ EQUITY Common Stock In August 2017, the Company entered into a Controlled Equity Offering SM In August 2018, the Company issued and sold in an underwritten public offering an aggregate of 3,246,079 shares of its common stock at $12.50 per share, which included 246,079 shares pursuant to the exercise of an option to purchase additional shares granted to the underwriters in connection with the offering. The offering resulted in $38.0 million of net proceeds, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. 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 (together with the 2014 Plan, the 2015 Plan, the “Stock Incentive Plans”). Pursuant to the Amended and Restated 2015 Plan, there are 1,666,863 shares authorized for issuance. In addition, to the extent any outstanding awards under the 2014 Plan expire, terminate or are otherwise surrendered, cancelled or forfeited after the closing of the Company’s IPO, those shares are added to the authorized shares under the Amended and Restated 2015 Plan. The total amount of shares authorized for issuance under both the 2014 Plan and the Amended and Restated 2015 Plan is 2,300,000. As of December 31, 2019, the Company had 348,673 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 years ended December 31, 2019 and 2018: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2017 988,565 $ 10.83 $ 2,617,859 Granted 311,000 12.28 — Exercised — — — Cancelled — — — Options outstanding at December 31, 2018 1,299,565 $ 11.18 $ 2,617,859 Granted 395,500 9.61 — Exercised — — — Cancelled (22,750 ) 13.36 — Options outstanding at December 31, 2019 1,672,315 $ 10.78 $ — Options exercisable at December 31, 2019 1,072,811 $ 11.13 $ — As of December 31, 2019, options outstanding have a weighted-average remaining contractual life of 7.2 years. The weighted-average fair value of all stock options granted for the year ended December 31, 2019 was $6.74. The intrinsic value at December 31, 2019 and 2018 is based on the closing price of the Company’s common stock on that date of $1.58 per share and $10.39 per share, respectively. In January 2018, the Company issued a stock option award as an inducement grant for the purchase of an aggregate of 50,000 shares of the Company’s common stock, outside of the Stock Incentive Plans, at an exercise price of $12.02 per share. In February 2019, the Company issued a stock option award as an inducement grant for the purchase of an aggregate of 40,000 shares of the Company’s common stock, outside of the Stock Incentive Plans, at an exercise price of $10.39 per share. These inducement grants are excluded from the option activity table above. The assumptions the Company used to determine the fair value of stock options granted in 2019 and 2018 are as follows, presented on a weighted-average basis: For the Year Ended December 31, 2019 2018 Risk-free interest rate 2.5 % 2.5 % Expected term (in years) 5.9 5.9 Expected volatility 81.1 % 82.5 % Expected dividend yield 0 % 0 % Performance-Based Restricted Stock Units In January 2019, the Company issued RSUs to senior management under the 2015 Plan that represent shares potentially issuable in the future subject to the satisfaction of certain performance milestones as well as a service condition. The vesting of 50% of the RSUs is based upon the Company’s performance relative to a peer group over a two-year performance period, from January 1, 2019 through December 31, 2020, measured by the Company’s relative total shareholder return. The vesting of 25% of the RSUs is based on the achievement of a performance goal milestone as of December 31, 2019 and the vesting of the remaining 25% of the RSUs is based upon the achievement of a performance goal milestone as of December 31, 2020. The Company estimates the fair value of total shareholder return 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 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 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 fair value of the performance-based RSUs granted to management in 2019 for the Company’s relative total share return units is based on the Monte Carlo Simulation method on the grant date, which the weighted average fair value as of the year ended December 31, 2019 was $6.62 per share. The Company estimates the fair value of performance milestone-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 RSUs granted to management during the year ended December 31, 2019 for the performance goal milestone units is based on the market price of the award on the grant date, which was a weighted average fair value for the year ended December 31, 2019 of $10.35 per share. 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. As of December 31, 2019, the Company has determined that it has not met the December 31, 2019 clinical milestones and reversed $0.1 million for previously recognized stock-based compensation expense and returned 46,450 shares to the plan. As of December 31, 2019, the Company estimates that it is currently not probable that it will achieve the December 31, 2020 clinical milestones applicable to the milestone-based RSUs and has not recognized stock-based compensation expense for these RSUs as it relates to the December 31, 2020 milestone base goals. As of December 31, 2019, the Company reduced stock-based compensation by approximately $0.2 million for previously recognized stock-based compensation for the December 31, 2020 clinical milestones currently estimated to be not probable. The total stock-based compensation recognized for the year ended December 31, 2019 for the RSUs related to the total shareholder return PSUs was approximately $0.3 million. The following table is a rollforward of RSU activity under the Stock Incentive Plans for the year ended December 31, 2019: Restricted Stock Units Weighted-Average Grant Date Fair Value Total nonvested units at December 31, 2018 — $ — Granted 203,700 8.49 Vested — — Cancelled (64,350 ) 9.83 Total nonvested units at December 31, 2019 139,350 $ 7.86 Stock-Based Compensation The following table summarizes the stock-based compensation expense for the years ended December 31, 2019 and 2018 (in thousands): For the Year Ended December 31, Stock-based compensation: 2019 2018 Research and development $ 1,223 $ 843 General and administrative 2,144 1,933 Total Stock-based compensation $ 3,367 $ 2,776 The fair value of stock options vested during the year ended December 31, 2019 was $2.7 million. At December 31, 2019, there was $4.1 million of unrecognized stock-based compensation expense relating to stock options granted pursuant to the Plans, which will be recognized over the weighted-average remaining vesting period of 2.47 years. At December 31, 2019, there was $0.3 million of unrecognized stock-based compensation expense relating to performance-based RSUs granted pursuant to the Stock Incentive Plans, which will be recognized over the weighted-average remaining vesting period of 1.0 years. Reserved Shares As of December 31, 2019 and 2018, the Company reserved the following shares of common stock for issuance of shares resulting from the exercise of outstanding warrants and options, as well as the future issuance of shares available for grant under the Stock Incentive Plans: December 31, 2019 2018 IPO Warrants 28,347 28,347 November Private Placement Warrants 1,633,777 1,633,777 Convertible Term Loan and Accrued Interest Payable 2,329,143 — Pontifax Warrants 250,000 — September 2019 Warrants 15,000 — 2015 Amended and Restated Stock Incentive Plan 2,160,338 2,238,887 Inducement Awards 90,000 50,000 Total 6,506,605 3,951,011

Convertible Term Loan

Convertible Term Loan	12 Months Ended
	Dec. 31, 2019
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 Convertible Term Loan bears interest at an annual rate of 8.0%. The Convertible Term Loan provides for interest-only payments for twenty-four months and repayment of the aggregate outstanding principal balance of the Convertible Term Loan in quarterly installments starting upon expiration of the interest only period and continuing through September 19, 2023 (the “Maturity Date”). The Company incurred issuance costs of $0.4 million. The Convertible Term Loan issuance 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 the Maturity Date. The Company may, at its option, 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 Company’s obligations are 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 contains customary events of default, representations, warranties and covenants, including a material adverse effect clause. The Company must maintain a minimum cash balance of $7.0 million in Spring Bank Pharmaceuticals, Inc. accounts, or it is in breach of the Convertible Term Loan, which the Company is in compliance with as of December 31, 2019. Upon the occurrence of an event of default, a default interest rate of an additional 4% per annum may be applied to the outstanding loan balances, and the Lenders may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Convertible Term Loan and under applicable law. The Company evaluated the accounting for the Convertible Term Loan and identified an embedded derivative related to the contingent interest feature. At issuance and as of December 31, 2019, the Company determined the fair value of the contingent interest feature to be di minimis and will re-value the derivative at the end of each reporting period. 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 are exercisable for a period of six years from the Closing Date at an exercise price of $6.57 per share, which is equal to 1.5 times 30-day VWAP. The aggregate fair value of the Pontifax Warrants 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 During the year ended December 31, 2019, the Company recorded interest expense of approximately $0.5 million in connection with the Convertible Term Loan. The fair value of the term loan as of December 31, 2019 approximates its face value due to market terms. The following table summarizes the Company’s future principal debt payments on the Convertible Term Loan as of December 31, 2019 (in thousands): December 31, 2019 2020 $ — 2021 2,500 2022 10,000 2023 7,500 Total principal payments $ 20,000 Less: unamortized debt discount (930 ) Term loan, long-term $ 19,070

Leases

Leases	12 Months Ended
	Dec. 31, 2019
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 2 years for its former headquarters. The Company’s former headquarters location is subleased through the remainder of the lease term. Other information related to leases as of December 31, 2019 was as follows: For the Year Ended December 31, Cash paid for amounts included in the measurement of lease liabilities: 2019 Operating cash flow from operating leases (in thousands) $ 417 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ 2,980 Weighted Average Remaining Lease Term Operating leases 8.3 years Weighted Average Discount Rate Operating leases 8.0 % Operating lease costs under the leases for the year ended December 31, 2019 were approximately $646,000, offset by $81,000, for sublease income and variable lease cost payments. Total rent expense for the year ended December 31, 2018 was $429,000, which included payments for a lease of the Company’s research and development facility. The lease term of the research and development facility ended as of June 30, 2018. The following table summarizes the Company’s maturities of operating lease liabilities as of December 31, 2019 (in thousands): Year 2020 $ 588 2021 508 2022 450 2023 462 2024 474 Thereafter 1,931 Total lease payments $ 4,413 Less: present value discount (1,189 ) Total $ 3,224 For comparative purposes, the Company’s aggregate future minimum non-cancellable commitments under operating leases as of December 31, 2018 were as follows (in thousands): Year 2019 $ 417 2020 588 2021 508 2022 450 2023 462 Thereafter 2,405 Total minimum lease payments $ 4,830

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	11 . INCOME TAXES In general, the Company has not recorded a provision for federal or state income taxes as it has had cumulative net operating losses since inception. A reconciliation of the statutory U.S. Federal Tax Rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2019 2018 U.S. statutory federal income tax rate (21.0 )% (21.0 )% State income taxes, net of federal income tax benefit (8.4 )% (7.6 )% Warrant adjustment (7.2 )% (4.2 )% Permanent items 0.7 % 0.6 % R&D credit (0.6 )% (0.6 )% Change in valuation allowance 36.5 % 32.7 % Change in federal rate impact — — Other — 0.1 % Effective income tax rate 0.0 % 0.0 % The significant components of the Company’s deferred tax assets as of December 31, 2019 and 2018 are as follows (in thousands): December 31, 2019 2018 Net operating loss carryforwards $ 31,637 $ 23,582 Research and development credits 798 649 Lease liability 881 — Accrued expenses 173 209 License payments 561 612 Stock based compensation 2,004 1,383 Other – net 101 138 Deferred tax asset 36,155 26,573 Valuation allowance (35,389 ) (26,536 ) Net deferred tax asset $ 766 $ 37 Right of use assets $ (742 ) $ — Property and equipment (24 ) (37 ) Net deferred tax liability $ (766 ) $ — Net deferred tax asset and liability $ — $ — Because of the Company’s recurring losses since inception, management has concluded that it is more likely than not that its net deferred tax assets will not be realized and, accordingly, the Company provided a full valuation allowance against the net deferred tax assets. The valuation allowance increased by approximately $8.9 million in 2019 due to the increase in the deferred tax assets (primarily due to the net operating loss carryforwards). In comparison, the valuation allowance increased by approximately $7.5 million in 2018 due to the increase in the deferred tax assets (primarily due to the net operating loss carryforwards). At December 31, 2019, the Company had federal and state net operating loss carryforwards of approximately $115.6 million and $116.5 million, respectively, available to reduce future taxable income, if any. The federal net operating loss carryforwards expire beginning in 2029 and ending in 2037, with the exception of federal net operating losses created after tax years ending December 31, 2017. These net operating loss carryforwards of approximately $54.1 million have an indefinite life and do not expire. The state net operating loss carryforwards expire beginning in 2030 and ending in 2039. At December 31, 2019, the Company had available federal and state income tax credits of approximately $0.3 million and $0.6 million, respectively, which are available to reduce future income taxes, if any, through 2039. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. Under the provisions of the Internal Revenue Code, the net operating loss and tax credit carry-forwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carry-forwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitations is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception, which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future. The Company has performed a Section 382 study from its inception through December 31, 2017. The Company determined it experienced two ownership changes, but it expects to be able to utilize all its tax attributes despite the limitations calculated from the ownership changes. If ownership changes occur in the future, they could limit the amount of tax attributes available to offset tax due and increase the Company’s tax expense adversely. The Company will continue to monitor changes in its ownership and update its Section 382 study in the future for those changes before its tax attributes are utilized. The Company has generated research and development tax credits but has not conducted a study to document its activities that qualify for research and development tax credits. This study may result in an adjustment to the Company’s research and development credit carryforwards; however, since the Company has not conducted a study any adjustment is unknown, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development tax credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development tax credit carry-forwards and the valuation allowance. The Company files income tax returns in the U.S. federal and Massachusetts jurisdictions. The statute of limitations for assessment by the Internal Revenue Service, or IRS, and state tax authorities is closed for tax years prior to 2015, although carryforward attributes that were generated prior to tax year 2015 may still be adjusted upon examination by the IRS or state tax authorities if they either have been or will be used in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years. The Company’s policy is to record interest and penalties on any unrecognized tax benefits as part of tax expense. The Company has not recorded any interest or penalties on any unrecognized tax benefits since its inception. The Company does not believe material uncertain tax positions have arisen to date.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	12 . 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.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
401(k) Plan	1 3 . 401(k) PLAN The Company has a 401(k)-defined contribution plan (the “401(k) Plan”) for substantially all of its employees. Eligible employees may make pretax contributions to the 401(k) Plan up to statutory limits. At the election of its Board, the Company may elect to match employee contributions. For the years ended December 31, 2019 and 2018, the Company paid a match of up to 4%, up to the maximum permitted by the Internal Revenue Code, which amounted to $0.2 million and $0.1 million, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	1 4 . RELATED PARTY TRANSACTIONS During the years ended December 31, 2019 and 2018, the Company had no material related party transactions.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	1 5 . SUBSEQUENT EVENTS The Company has evaluated subsequent events through the date on which the consolidated financial statements were issued, to ensure that this submission includes appropriate disclosure of events both recognized in the consolidated financial statements and events which occurred subsequently but were not recognized in the consolidated financial statements.

Nature of Business, Basis of _2

Nature of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation and Liquidity	Basis of Presentation and Liquidity The accompanying consolidated financial statements have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). As of December 31, 2019, the Company had an accumulated deficit of $126.2 million and $54.5 million in cash, cash equivalents and marketable securities. The Company expects to continue to incur significant and increasing losses for the foreseeable future. The Company anticipates that its expenses will increase significantly as it continues to develop SB 11285 and its other product candidates. The Company does not have any committed external source of funds. As a result, the Company will need additional financing to support its continuing operations. Adequate additional funds may not be available to the Company on acceptable terms, or at all. To the extent that the Company raises additional capital through the sale of equity or convertible debt securities, stockholders’ ownership interests will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect common stockholder rights. If the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, the Company may have to relinquish valuable rights to its technologies, future revenue streams, research programs, or product candidates or grant licenses on terms that may not be favorable to the Company.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sperovie Biosciences, Inc., SBP Securities Corporation and SBP International Limited. Sperovie Biosciences, Inc. had operations consisting mainly of legal fees associated with intellectual property activities as of December 31, 2019. Sperovie Biosciences, Inc. is a joint borrower with the Company under the Company’s term loan (see Note 9).
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 warrant liabilities, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, and accounting for certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis. The Company’s actual results may differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents are stated at fair value and include short-term, highly liquid investments with remaining maturities of 90 days or less at the date of purchase. Included in cash and cash equivalents as of 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. As of December 31, 2018, included in cash and cash equivalents are money market fund investments of $13.3 million, which are reported at fair value (Note 5).
Restricted Cash	Restricted Cash As of December 31, 2019 and 2018, restricted cash consisted of approximately $234,000, which is held as a security deposit required in conjunction with the 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 and amortization are 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 the commencement date of a lease 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 the 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 incentive amounts. 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. Through December 31, 2019, no such impairment has occurred.
Research and Development Costs	Research and Development Costs Research and development expenses consist primarily of costs incurred for the Company’s research activities, including discovery efforts, and the development of product candidates, which include: • expenses incurred under agreements with third parties, including contract research organizations, or CROs, that conduct research, preclinical activities and clinical trials on the Company’s behalf as well as contract manufacturing organizations, or CMOs, that manufacture drug products for use in the Company’s preclinical and clinical trials; • salaries, benefits and other related costs, including stock-based compensation expense, for personnel in the Company’s research and development functions; • costs of outside consultants, including their fees, stock-based compensation and related travel expenses; • the cost of laboratory supplies and acquiring, developing and manufacturing preclinical study and clinical trial materials; • costs related to compliance with regulatory requirements; and • facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs. The Company expenses research and development costs as incurred. The Company recognizes external development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors and its clinical investigative sites. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected in the Company’s consolidated financial statements as prepaid or accrued research and development expenses.
Warrants	Warrants The Company 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 (“RSUs”) and grants of common stock, including common stock subject to vesting. The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employee’s 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 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 year ended December 31, 2019, both methods are equivalent. For the year ended December 31, 2018, diluted net loss per share amounts were calculated based on the dilutive effect of the total number of shares of common stock related to the November 2016 Private Placement warrants and the change in the fair value of the warrant liability. Basic and diluted net loss per share are 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 tax expense. As of December 31, 2019 and 2018, the Company has not identified any material uncertain tax positions.
Guarantees and Indemnifications	Guarantees and Indemnifications As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The Company leases office and laboratory space in Hopkinton, Massachusetts and previously leased research and development space in Milford, Massachusetts under non-cancelable operating leases. The Company has standard indemnification arrangements under these leases that require it to indemnify the landlords against liability for injury, loss, accident, or damage from any claims, actions, proceedings, or costs resulting from certain acts, breaches, violations, or nonperformance under the Company’s lease. Through December 31, 2019, the Company had not experienced any losses related to these indemnification obligations and no material claims were outstanding. The Company does not expect significant claims related to these indemnification obligations, and consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate and discrete financial information is available for evaluation by the chief operating decision maker, the Company’s Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and does not track expenses on a program-by-program basis.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases “Codification Improvements to Topic 842, Leases” The Company adopted the standard on the effective date of January 1, 2019 by applying the new lease requirements at the effective date. Prior periods continue to be presented based on the accounting standards originally in effect for such periods. The Company also elected the package of practical expedients permitted under the transition guidance within the new standard, which, among other things, allows the Company to carry forward the historical lease classification. The Company will also apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The standard had an impact of approximately $3.0 million on the Company’s assets and $3.4 million on its liabilities, as of January 1, 2019, for the recognition of right-of-use assets and lease liabilities, which are primarily related to the lease of its corporate headquarters in Hopkinton, Massachusetts. The standard did not have a material impact on the Company’s results of operations or liquidity (see Note 10) In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception . 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, Basis of _3

Nature of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Estimated Useful Lives of Property and Equipment	Depreciation and amortization are 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)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the computation of basic and diluted net loss per share of the Company for the years ended December 31, 2019 and 2018 (in thousands, except share and per share data): Year Ended December 31, 2019 Net loss $ (24,097 ) Weighted-average number of shares outstanding - basic and diluted 16,454,083 Net loss per common share - basic and diluted $ (1.46 ) For the year ended December 31, 2019, the diluted net loss per common share is the same as basic net loss per common share. Year Ended December 31, 2018 Net loss $ (22,854 ) Less: decrease in change in fair value of warrant liabilities (4,617 ) Net loss available to common shareholders $ (27,471 ) Weighted-average number of shares outstanding: Basic 14,372,174 Effect of dilutive securities: Common stock warrants 246,802 Dilutive potential common shares 14,618,976 Net loss per common share: Basic $ (1.59 ) Diluted $ (1.88 )
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: Year 2019 2018 Convertible debt 2,329,143 — Common stock warrants 1,927,124 28,347 Stock options 1,901,665 1,349,565

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Summary of Investments by Category	The following table summarizes the Company’s investments, by category, as of December 31, 2019 and 2018 (in thousands): December 31, December 31, Investments - Current: 2019 2018 Debt securities - available for sale $ 25,746 $ 32,914 Total $ 25,746 $ 32,914 Investments - Noncurrent: Debt securities - available for sale $ — $ 16,804 Total $ — $ 16,804
Summary of Available-for-Sale Classified Investments	A summary of the Company’s available-for-sale classified investments as of December 31, 2019 and 2018 consisted of the following (in thousands): At December 31, 2019 Cost Basis Unrealized Gains 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) unrealized losses at December 31, 2019. At December 31, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Investments - Current: Corporate bonds $ 16,028 $ — $ (19 ) $ 16,009 United States treasury securities 16,913 — (8 ) 16,905 Total $ 32,941 $ — $ (27 ) $ 32,914 Investments - Noncurrent: Corporate bonds $ 4,930 $ 2 $ — $ 4,932 United States treasury securities 11,852 20 — 11,872 Total $ 16,782 $ 22 $ — $ 16,804
Schedule of Amortized Cost and Fair Value of Available-for-Sale Investments, by Contract Maturity	The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of December 31, 2019 consisted of the following (in thousands): Amortized Cost Fair Value Due in one year or less $ 25,969 $ 25,746 Due after one year through two years — — Total $ 25,969 $ 25,746

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment as of December 31, 2019 and 2018 consisted of the following (in thousands): December 31, December 31, 2019 2018 Equipment $ 1,278 $ 1,064 Furniture and fixtures 450 400 Leasehold improvements 1,356 1,347 Total property and equipment 3,084 2,811 Less: accumulated depreciation (850 ) (492 ) Property and equipment, net $ 2,234 $ 2,319

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Measured at Fair Value	A summary of the assets and liabilities that are measured at fair value as of December 31, 2019 and 2018 is as follows (in thousands): 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 Fair Value Measurement at December 31, 2018 Assets: Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds (1) $ 13,264 $ 13,264 $ — $ — Fixed income securities 49,718 — 49,718 — Total $ 62,982 $ 13,264 $ 49,718 $ — Liabilities: Warrant liabilities $ 8,511 $ — $ — $ 8,511 Total $ 8,511 $ — $ — $ 8,511 (1) Money market funds and United States treasury securities with maturities of 90 days or less 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 consist of the warrants issued in a private placement in November 2016 (see Note 7), for the years ended December 31, 2019 and 2018 (in thousands): November Private Placement Warrants Balance at December 31, 2017 $ 13,128 Change in fair value (4,617 ) Balance at December 31, 2018 $ 8,511 Change in fair value (8,212 ) Balance at December 31, 2019 $ 299

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of December 31, 2019 and 2018 consisted of the following (in thousands): December 31, December 31, 2019 2018 Preclinical and clinical studies $ 1,473 $ 941 Compensation and benefits 614 830 Accounting and legal 240 227 Other 111 369 Total accrued expenses and other current liabilities $ 2,438 $ 2,367

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2019
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: For the Year Ended December 31, 2019 2018 Risk-free interest rate 1.6 % 2.5 % Expected term (in years) 1.9 2.9 Expected volatility 100.0 % 78.1 % Expected dividend yield 0 % 0 %
Summary of Warrant Activity	A summary of the warrant activity for the years ended December 31, 2019 and 2018 is as follows: Warrants Outstanding at December 31, 2017 1,787,124 Grants — Exercises — Expirations/cancellations (125,000 ) Outstanding at December 31, 2018 1,662,124 Grants 265,000 Exercises — Expirations/cancellations — Outstanding at December 31, 2019 1,927,124

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Option Activity	The following table summarizes the option activity under the Stock Incentive Plans for the years ended December 31, 2019 and 2018: Options Weighted-Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2017 988,565 $ 10.83 $ 2,617,859 Granted 311,000 12.28 — Exercised — — — Cancelled — — — Options outstanding at December 31, 2018 1,299,565 $ 11.18 $ 2,617,859 Granted 395,500 9.61 — Exercised — — — Cancelled (22,750 ) 13.36 — Options outstanding at December 31, 2019 1,672,315 $ 10.78 $ — Options exercisable at December 31, 2019 1,072,811 $ 11.13 $ —
Summary of Assumptions to Determine Fair Value of Stock Options Granted	The assumptions the Company used to determine the fair value of stock options granted in 2019 and 2018 are as follows, presented on a weighted-average basis For the Year Ended December 31, 2019 2018 Risk-free interest rate 2.5 % 2.5 % Expected term (in years) 5.9 5.9 Expected volatility 81.1 % 82.5 % Expected dividend yield 0 % 0 %
Summary of RSU Activity	The following table is a rollforward of RSU activity under the Stock Incentive Plans for the year ended December 31, 2019: Restricted Stock Units Weighted-Average Grant Date Fair Value Total nonvested units at December 31, 2018 — $ — Granted 203,700 8.49 Vested — — Cancelled (64,350 ) 9.83 Total nonvested units at December 31, 2019 139,350 $ 7.86
Summary of Stock-Based Compensation Expense	The following table summarizes the stock-based compensation expense for the years ended December 31, 2019 and 2018 (in thousands): For the Year Ended December 31, Stock-based compensation: 2019 2018 Research and development $ 1,223 $ 843 General and administrative 2,144 1,933 Total Stock-based compensation $ 3,367 $ 2,776
Summary of Shares of Common Stock Reserved	As of December 31, 2019 and 2018, the Company reserved the following shares of common stock for issuance of shares resulting from the exercise of outstanding warrants and options, as well as the future issuance of shares available for grant under the Stock Incentive Plans: December 31, 2019 2018 IPO Warrants 28,347 28,347 November Private Placement Warrants 1,633,777 1,633,777 Convertible Term Loan and Accrued Interest Payable 2,329,143 — Pontifax Warrants 250,000 — September 2019 Warrants 15,000 — 2015 Amended and Restated Stock Incentive Plan 2,160,338 2,238,887 Inducement Awards 90,000 50,000 Total 6,506,605 3,951,011

Convertible Term Loan (Tables)

Convertible Term Loan (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Future Principal Payments on Convertible Term Loan	The following table summarizes the Company’s future principal debt payments on the Convertible Term Loan as of December 31, 2019 (in thousands): December 31, 2019 2020 $ — 2021 2,500 2022 10,000 2023 7,500 Total principal payments $ 20,000 Less: unamortized debt discount (930 ) Term loan, long-term $ 19,070

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Summary of Other Information Related to Leases	Other information related to leases as of December 31, 2019 was as follows: For the Year Ended December 31, Cash paid for amounts included in the measurement of lease liabilities: 2019 Operating cash flow from operating leases (in thousands) $ 417 Right-of-use assets obtained in exchange for lease obligations: Operating leases (in thousands) $ 2,980 Weighted Average Remaining Lease Term Operating leases 8.3 years Weighted Average Discount Rate Operating leases 8.0 %
Summary of Maturities of Operating Lease Liabilities	The following table summarizes the Company’s maturities of operating lease liabilities as of December 31, 2019 (in thousands): Year 2020 $ 588 2021 508 2022 450 2023 462 2024 474 Thereafter 1,931 Total lease payments $ 4,413 Less: present value discount (1,189 ) Total $ 3,224
Summary of Aggregate Future Minimum Non-Cancellable Commitments Under Operating Leases	For comparative purposes, the Company’s aggregate future minimum non-cancellable commitments under operating leases as of December 31, 2018 were as follows (in thousands): Year 2019 $ 417 2020 588 2021 508 2022 450 2023 462 Thereafter 2,405 Total minimum lease payments $ 4,830

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Reconciliation of Statutory U.S. Federal Tax Rate with Effective Tax Rate	A reconciliation of the statutory U.S. Federal Tax Rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2019 2018 U.S. statutory federal income tax rate (21.0 )% (21.0 )% State income taxes, net of federal income tax benefit (8.4 )% (7.6 )% Warrant adjustment (7.2 )% (4.2 )% Permanent items 0.7 % 0.6 % R&D credit (0.6 )% (0.6 )% Change in valuation allowance 36.5 % 32.7 % Change in federal rate impact — — Other — 0.1 % Effective income tax rate 0.0 % 0.0 %
Components of Deferred Tax Assets	The significant components of the Company’s deferred tax assets as of December 31, 2019 and 2018 are as follows (in thousands): December 31, 2019 2018 Net operating loss carryforwards $ 31,637 $ 23,582 Research and development credits 798 649 Lease liability 881 — Accrued expenses 173 209 License payments 561 612 Stock based compensation 2,004 1,383 Other – net 101 138 Deferred tax asset 36,155 26,573 Valuation allowance (35,389 ) (26,536 ) Net deferred tax asset $ 766 $ 37 Right of use assets $ (742 ) $ — Property and equipment (24 ) (37 ) Net deferred tax liability $ (766 ) $ — Net deferred tax asset and liability $ — $ —

Nature of Business, Basis of _4

Nature of Business, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019USD ($)SubsidiarySegment	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Nature Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of wholly owned subsidiaries | Subsidiary	3
Accumulated deficit	$ (126,165,000)		$ (102,068,000)
Cash, cash equivalents and marketable securities	54,500,000
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
Right-of-use-assets	$ 2,717,000
Lease liabilities	3,224,000
ASU 2016-02 [Member]
Nature Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Right-of-use-assets		$ 3,000,000
Lease liabilities		$ 3,400,000
Money Market Funds [Member]
Nature Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents fair value	21,100,000		$ 13,300,000
United States Treasury Securities [Member]
Nature Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents fair value	$ 6,000,000

Nature of Business, Basis of _5

Nature of Business, Basis of Presentation and Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2019
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	Lesser of 10 years or the remaining term of the respective lease

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share Basic And Diluted [Abstract]
Net loss	$ (24,097)	$ (22,854)
Weighted-average number of shares outstanding - basic and diluted	16,454,083
Net loss per common share - basic and diluted	$ (1.46)
Less: decrease in change in fair value of warrant liabilities	$ (8,212)	(4,617)
Net loss available to common shareholders		$ (27,471)
Weighted-average number of shares outstanding:
Basic	16,454,083	14,372,174
Effect of dilutive securities:
Common stock warrants		246,802
Dilutive potential common shares		14,618,976
Net loss per common share:
Basic	$ (1.46)	$ (1.59)
Diluted	$ (1.46)	$ (1.88)

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrant	6,506,605	3,951,011
Dilutive shares of common stock warrants		246,802
Average stock price per share		$ 12.71
Change in fair value of warrant liabilities	$ 8,212	$ 4,617
Private Placement [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock warrant		1,633,777
Exercise price		$ 10.79	$ 10.79

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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Convertible Debt [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	2,329,143
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	28,347
Stock Options [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	1,901,665	1,349,565

Investments - Summary of Invest

Investments - Summary of Investments by Category (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments - Current:
Debt securities - available for sale	$ 25,746	$ 32,914
Total	$ 25,746	32,914
Investments - Noncurrent:
Debt securities - available for sale		16,804
Total		$ 16,804

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Classified Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	$ 25,969
Fair Value	25,746
Investments - Current [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	25,969	$ 32,941
Unrealized Losses	(223)	(27)
Fair Value	25,746	32,914
Investments - Current [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	4,990	16,028
Unrealized Losses	(58)	(19)
Fair Value	4,932	16,009
Investments - Current [Member] | United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis	20,979	16,913
Unrealized Losses	(165)	(8)
Fair Value	$ 20,814	16,905
Investments - Noncurrent [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		16,782
Unrealized Gains		22
Fair Value		16,804
Investments - Noncurrent [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		4,930
Unrealized Gains		2
Fair Value		4,932
Investments - Noncurrent [Member] | United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost Basis		11,852
Unrealized Gains		20
Fair Value		$ 11,872

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	Dec. 31, 2019USD ($)
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 25,969
Cost Basis	25,969
Due in one year or less, Fair Value	25,746
Total, Fair Value	$ 25,746

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,084	$ 2,811
Less: accumulated depreciation	(850)	(492)
Property and equipment, net	2,234	2,319
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,278	1,064
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	450	400
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,356	$ 1,347

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 357	$ 288

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 21,100	$ 13,300
United States Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	6,000
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	52,793	62,982
Liabilities, Total	299	8,511
Carrying Value [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	21,065	13,264
Carrying Value [Member] | United States Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed income securities	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	49,718
Carrying Value [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	299	8,511
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	21,065	13,264
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	21,065	13,264
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Total	31,728	49,718
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	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	49,718
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Total	299	8,511
Significant Unobservable Inputs (Level 3) [Member] | Warrant Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	$ 299	$ 8,511

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Change in Company's Level 3 Liabilities, Warrants Issued in a Private Placement (Detail) - Private Placement [Member] - Warrants [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	$ 8,511	$ 13,128
Change in fair value	(8,212)	(4,617)
Ending balance	$ 299	$ 8,511

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities And Other Liabilities [Abstract]
Preclinical and clinical studies	$ 1,473	$ 941
Compensation and benefits	614	830
Accounting and legal	240	227
Other	111	369
Total accrued expenses and other current liabilities	$ 2,438	$ 2,367

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Sep. 30, 2019	Nov. 30, 2016	Jun. 30, 2016	May 31, 2016	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Dividend yield					0.00%	0.00%
Expected life (in years)					5 years 10 months 24 days	2 years 10 months 24 days
Long-term debt					$ 20,000
Change in fair value of warrant liabilities					(8,212)	$ (4,617)
Convertible Term Loan [Member]
Class of Warrant or Right [Line Items]
Long-term debt	$ 20,000
May 2016 IPO warrants [Member]
Class of Warrant or Right [Line Items]
Expected volatility of common stock Minimum				87.00%
Risk free rate				1.20%
Dividend yield				0.00%
Expected life (in years)				4 years 11 months 26 days
June 2016 IPO warrants [Member]
Class of Warrant or Right [Line Items]
Expected volatility of common stock Minimum			87.00%
Risk free rate			1.23%
Dividend yield			0.00%
Expected life (in years)			4 years 11 months 1 day
September 2019 Warrants [Member]
Class of Warrant or Right [Line Items]
Fair value of equity	$ 19,000
Expected volatility of common stock Minimum	69.40%
Risk free rate	1.70%
Dividend yield	0.00%
Expected life (in years)	2 years
Exercise price	$ 4.21
Warrants expiration date	Sep. 19, 2021
Warrants issued to purchase shares of common stock	15,000
Change in fair value of warrant liabilities					6,000
IPO [Member]
Class of Warrant or Right [Line Items]
Fair value of equity					$ 200
Exercise price				$ 15
Warrants expiration date					May 5, 2021
Warrants issued to purchase shares of common stock			747	27,600
Private Placement [Member]
Class of Warrant or Right [Line Items]
Issuance of common stock		1,644,737
Exercise price		$ 10.79				$ 10.79
Warrants expiration date		Nov. 23, 2021
Warrants issued to purchase shares of common stock		1,644,737
Shares issued price per share		$ 9.12
Common Stock Warrants [Member] | Pontifax [Member]
Class of Warrant or Right [Line Items]
Fair value of equity	$ 600				$ 600
Expected volatility of common stock Minimum	83.20%
Risk free rate	1.70%
Dividend yield	0.00%
Expected life (in years)	6 years				6 years
Exercise price	$ 6.57				$ 6.57
Warrants expiration date	Sep. 19, 2025
Warrants issued to purchase shares of common stock	250,000				250,000
Common Stock Warrants [Member] | Private Placement [Member]
Class of Warrant or Right [Line Items]
Fair value of equity		$ 8,300			$ 300	$ 8,500
Shares Exercised During the period					10,960
Common Stock Warrants [Member] | BioHEP Technologies Ltd. [Member]
Class of Warrant or Right [Line Items]
Issuance of common stock					125,000
Fair value of equity					$ 800
Expected volatility of common stock Minimum					71.00%
Risk free rate					1.01%
Dividend yield					0.00%
Expected life (in years)					2 years 6 months
Exercise price					$ 16
Warrants expiration date					Aug. 1, 2018

Warrants - Summary of Assumptio

Warrants - Summary of Assumptions Used to Record Fair Value of Warrants (Detail) - Warrants [Member]	Dec. 31, 2019	Dec. 31, 2018
Risk-Free Interest Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	1.60%	2.50%
Expected Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input (in years)	1 year 10 months 24 days	2 years 10 months 24 days
Expected Volatility [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value input	100.00%	78.10%
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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Outstanding, Beginning Balance	1,662,124	1,787,124
Grants	265,000	0
Exercises	0	0
Expirations/cancellations	0	(125,000)
Outstanding, Ending balance	1,927,124	1,662,124

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	May 11, 2016	Feb. 28, 2019	Jan. 31, 2019	Aug. 31, 2018	Mar. 31, 2018	Jan. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015	Aug. 31, 2017	Apr. 30, 2014
Class of Stock [Line Items]
Net proceeds from initial public offering of common stock								$ 37,960,000
Stock options granted									0
Stock-based compensation expense							$ 3,367,000	$ 2,776,000
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 RSUs to senior management under the 2015 Plan that represent shares potentially issuable in the future subject to the satisfaction of certain performance milestones as well as a service condition.
Share-based Compensation Arrangement by Share-based Payment Award, Award, Vesting Description							The vesting of 50% of the RSUs is based upon the Company’s performance relative to a peer group over a two-year performance period, from January 1, 2019 through December 31, 2020, measured by the Company’s relative total shareholder return. The vesting of 25% of the RSUs is based on the achievement of a performance goal milestone as of December 31, 2019 and the vesting of the remaining 25% of the RSUs is based upon the achievement of a performance goal milestone as of December 31, 2020.
Weighted-average fair value of restricted stock units granted							$ 8.49
Reversal of stock-based compensation expense upon non-achievement of clinical milestone							$ 100,000
Share Based Compensation, milestone base goals and shares returned							46,450
Stock-based compensation expense							$ 300,000
Reduction in stock-based compensation							$ 200,000
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%
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%
Relative Total Share Return Units [Member]
Class of Stock [Line Items]
Weighted-average fair value of restricted stock units granted							$ 6.62
Performance Goal Milestone Units [Member]
Class of Stock [Line Items]
Weighted-average fair value of restricted stock units granted							$ 10.35
2014 Stock Incentive Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock to be issued											750,000
Number of shares remain available for grant	0
Weighted-average remaining contractual life							7 years 2 months 12 days
Weighted-average fair value of all stock options granted							$ 6.74
2015 Stock Incentive Plan [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock to be issued					1,666,863
Number of shares remain available for grant							348,673
Number of shares common stock reserved for issuance, increase					800,000
Expiry date of stock options awarded	10 years
2014 and 2015 Stock Incentive Plans [Member]
Class of Stock [Line Items]
Number of authorized shares of common stock to be issued					2,300,000
Stock options granted							395,500	311,000
Fair value of stock options vested							$ 2,700,000
Unrecognized stock-based compensation expense							$ 4,100,000
Weighted-average remaining vesting period							2 years 5 months 19 days
2014 and 2015 Stock Incentive Plans [Member] | Performance-Based Restricted Stock Units [Member]
Class of Stock [Line Items]
Unrecognized stock-based compensation expense							$ 300,000
Weighted-average remaining vesting period							1 year
Common Stock [Member]
Class of Stock [Line Items]
Issuance of common stock								3,246,079
Common Stock [Member] | 2014 Stock Incentive Plan [Member]
Class of Stock [Line Items]
Shares issued price per share							$ 1.58	$ 10.39
Common Stock [Member] | Public Offering [Member]
Class of Stock [Line Items]
Issuance of common stock				3,246,079
Net proceeds from initial public offering of common stock				$ 38,000,000
Shares issued price per share				$ 12.50
Exercise of an option to purchase additional shares granted to underwriters in connection with offering				246,079
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							600	217,329
Weighted average selling price per share							$ 10.03	$ 15.42
Net proceeds from initial public offering of common stock								$ 3,200,000
Sales Agreement [Member] | Cantor Fitzgerald & Co. [Member] | Maximum [Member]
Class of Stock [Line Items]
Aggregate offering price										$ 50,000,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted			0
2014 and 2015 Stock Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Beginning Balance	1,299,565	988,565
Options Granted	395,500	311,000
Options Cancelled	(22,750)
Options outstanding, Ending balance	1,672,315	1,299,565
Options exercisable	1,072,811
Weighted-Average Exercise Price Per Share, Options outstanding, Beginning Balance	$ 11.18	$ 10.83
Weighted-Average Exercise Price Per Share, Granted	9.61	12.28
Weighted-Average Exercise Price Per Share, Cancelled	13.36
Weighted-Average Exercise Price Per Share, Options outstanding, Ending Balance	10.78	$ 11.18
Weighted-Average Exercise Price Per Share, Options exercisable	$ 11.13
Aggregate Intrinsic Value, Options outstanding, Beginning Balance	$ 2,617,859	$ 2,617,859
Aggregate Intrinsic Value, Options outstanding, Ending Balance		$ 2,617,859

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Assumptions to Determine Fair Value of Stock Options Granted (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	2.50%	2.50%
Expected term (in years)	5 years 10 months 24 days	2 years 10 months 24 days
Expected volatility	81.10%	82.50%
Expected dividend yield	0.00%	0.00%

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of RSU Activity (Detail) - Performance-Based Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested units, Granted | shares	203,700
Nonvested units, Cancelled | shares	(64,350)
Nonvested units, Ending Balance | shares	139,350
Weighted-Average Grant Date Fair Value Granted | $ / shares	$ 8.49
Weighted-Average Grant Date Fair Value Cancelled | $ / shares	9.83
Weighted-Average Grant Date Fair Value Nonvested units, Ending Balance | $ / shares	$ 7.86

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,367	$ 2,776
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	3,367	2,776
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	1,223	843
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	$ 2,144	$ 1,933

Stockholders' Equity - Summar_5

Stockholders' Equity - Summary of Shares of Common Stock Reserved (Detail) - shares	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	6,506,605	3,951,011
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 and Accrued Interest Payable [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
September 2019 Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	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	2,160,338	2,238,887
Inducement Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved	90,000	50,000

Convertible Term Loan - Additio

Convertible Term Loan - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2019USD ($)Day$ / sharesshares	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term debt		$ 20,000
Expected life (in years)		5 years 10 months 24 days	2 years 10 months 24 days
Pontifax [Member] | Common Stock Warrants [Member]
Debt Instrument [Line Items]
Warrants issued to purchase shares of common stock | shares	250,000	250,000
Exercise price | $ / shares	$ 6.57	$ 6.57
Expected life (in years)	6 years	6 years
Fair value of equity	$ 600	$ 600
Convertible Term Loan [Member]
Debt Instrument [Line Items]
Long-term debt	$ 20,000
Debt instrument, interest rate, stated percentage	8.00%
Debt instrument, payment terms		The Convertible Term Loan provides for interest-only payments for twenty-four months and repayment of the aggregate outstanding principal balance of the Convertible Term Loan in quarterly installments starting upon expiration of the interest only period and continuing through September 19, 2023 (the “Maturity Date”).
Debt instrument, maturity date		Sep. 19, 2023
Debt issuance cost		$ 400
Debt instrument, convertible, conversion price | $ / shares		$ 8.76
Prepayment charge percentage		3.00%
Debt instrument, convertible, threshold trading days | Day		30
Minimum cash balance maintained in accounts		$ 7,000
Additional interest rate upon occurrence of an event of default		4.00%
Interest expense, debt		$ 500

Convertible Term Loan - Future

Convertible Term Loan - Future Principal Debt Payments on Convertible Term Loan (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
2021	$ 2,500
2022	10,000
2023	7,500
Total principal payments	20,000
Less: unamortized debt discount	(930)
Term loan, long-term	$ 19,070

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	8 years 3 months 18 days
Operating lease costs	$ 646,000
Sublease income and variable lease cost payments	$ 81,000
Operating leases, total rent expense		$ 429,000
Principal Office and Laboratory Space [Member]
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	8 years 3 months 18 days
Operating leases, extendable lease term	5 years
Operating leases, option to extend lease	an option to extend the lease for up to 5 years
Operating Lease, existence of option to extend	true
Former Headquarters [Member]
Lessee Lease Description [Line Items]
Operating leases, remaining lease term	2 years
Research and Development Facility [Member]
Lessee Lease Description [Line Items]
Lease term expiration date	Jun. 30, 2018

Leases - Summary of Other Infor

Leases - Summary of Other Information Related to Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow from operating leases (in thousands)	$ 417
Right-of-use assets obtained in exchange for lease obligations:
Operating leases (in thousands)	$ 2,980
Weighted Average Remaining Lease Term
Operating leases	8 years 3 months 18 days
Weighted Average Discount Rate
Operating leases	8.00%

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 588
2021	508
2022	450
2023	462
2024	474
Thereafter	1,931
Total lease payments	4,413
Less: present value discount	(1,189)
Total	$ 3,224

Leases - Summary of Aggregate F

Leases - Summary of Aggregate Future Minimum Non-Cancellable Commitments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 417
2020	588
2021	508
2022	450
2023	462
Thereafter	2,405
Total minimum lease payments	$ 4,830

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of The Statutory Federal Tax Rate to The Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
U.S. statutory federal income tax rate	(21.00%)	(21.00%)
State income taxes, net of federal income tax benefit	(8.40%)	(7.60%)
Warrant adjustment	(7.20%)	(4.20%)
Permanent items	0.70%	0.60%
R&D credit	(0.60%)	(0.60%)
Change in valuation allowance	36.50%	32.70%
Other		0.10%
Effective income tax rate	(0.00%)	(0.00%)

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of the Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Components Of Deferred Tax Assets And Liabilities [Abstract]
Net operating loss carryforwards	$ 31,637	$ 23,582
Research and development credits	798	649
Lease liability	881
Accrued expenses	173	209
License payments	561	612
Stock based compensation	2,004	1,383
Other – net	101	138
Deferred tax asset	36,155	26,573
Valuation allowance	(35,389)	(26,536)
Net deferred tax asset	766	37
Right of use assets	(742)
Property and equipment	(24)	$ (37)
Net deferred tax liability	$ (766)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Increase in valuation allowance due to increase in deferred tax assets	$ 8,900,000	$ 7,500,000
Period for cumulative change in ownership	3 years
Cumulative change in ownership interest percentage	50.00%
Uncertain tax positions	$ 0	$ 0
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 115,600,000
Operating loss carryforwards expiration beginning year	2029
Operating loss carryforwards expiration ending year	2037
Net operating loss carryforwards with indefinite life	$ 54,100,000
Income tax credits	$ 300,000
Income tax credit carryforward expiration year	Dec. 31, 2039
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 116,500,000
Operating loss carryforwards expiration beginning year	2030
Operating loss carryforwards expiration ending year	2039
Income tax credits	$ 600,000
Income tax credit carryforward expiration year	Dec. 31, 2039

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Accruals for contingent liabilities	$ 0

401(k) Plan - Additional Inform

401(k) Plan - Additional Information (Detail) - Internal Revenue Code [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Sponsor Location [Extensible List]	us-gaap:DomesticPlanMember	us-gaap:DomesticPlanMember
Defined Contribution Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember
Contribution by company	$ 0.2	$ 0.1
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match	4.00%	4.00%