scPharmaceuticals (SCPH) 10-K 24 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 23, 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	SCPH
Entity Registrant Name	SCPHARMACEUTICALS INC.
Entity Central Index Key	0001604950
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.0001
Security Exchange Name	NASDAQ
Entity File Number	001-38293
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5184075
Entity Address, Address Line One	2400 District Avenue
Entity Address, Address Line Two	Suite 310
Entity Address, City or Town	Burlington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01803
City Area Code	617
Local Phone Number	517-0730
Document Annual Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		20,981,880
Entity Public Float			$ 27,492,179
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE The following documents (or parts thereof) are incorporated by reference into the following parts of this Form 10-K: Certain information required in Part III of this Annual Report on Form 10-K is incorporated from the registrant’s Definitive Proxy Statement for the 2020 Annual Meeting of Shareholders.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 72,624	$ 89,478
Prepaid expenses	2,619	1,757
VAT receivable	310	479
Other current assets	94	179
Total current assets	75,647	91,893
Restricted cash	182	182
Property and equipment, net	127	164
Right-of-use lease assets - operating, net	1,179	1,506
Deposits and other assets	148	10
Total assets	77,283	93,755
Current liabilities
Accounts payable	1,142	587
Accrued expenses	3,688	2,922
Term loan, short term		2,811
Current portion of lease obligation - operating	407	353
Total current liabilities	5,237	6,673
Term loan, long term	18,915	6,826
Long term lease obligation - operating	943	1,353
Derivative liability	765
Other liabilities	58	159
Total liabilities	25,918	15,011
Commitments and contingencies (Note 11)
Stockholders’ Equity
Preferred stock, $0.0001 par value; 10,000,000 shares authorized and no shares issued and outstanding
Common stock; $0.0001 par value; 150,000,000 shares authorized at December 31, 2019; 18,569,289 and 19,418,955 shares issued and outstanding at December 31, 2018 and December 31, 2019, respectively	2	2
Additional paid-in capital	180,818	175,201
Accumulated deficit	(129,455)	(96,459)
Total stockholders’ equity	51,365	78,744
Total liabilities and stockholders’ equity	$ 77,283	$ 93,755

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	150,000,000	150,000,000
Common stock, shares issued	19,418,955	18,569,289
Common stock, shares outstanding	19,418,955	18,569,289

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	$ 24,632	$ 15,948
General and administrative	8,273	13,719
Total operating expenses	32,905	29,667
Loss from operations	(32,905)	(29,667)
Other (expense) income	16	(56)
Interest income	1,660	1,712
Interest expense	(1,767)	(1,432)
Net loss and comprehensive loss	$ (32,996)	$ (29,443)
Net loss per share, basic and diluted	$ (1.77)	$ (1.59)
Weighted—average common shares outstanding, basic and diluted	18,600,718	18,556,126

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Offering	Common Stock	Common StockAt The Market Offering	Additional Paid-in Capital	Additional Paid-in CapitalAt The Market Offering	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ 105,997		$ 2		$ 173,011		$ (67,016)
Beginning Balance, Shares at Dec. 31, 2017			18,534,240
Net loss	(29,443)						(29,443)
Offering costs	(4)				(4)
Issuance of common stock upon exercise of stock options	$ 58				58
Issuance of common stock upon exercise of stock options, Shares	34,561		34,561
Vesting of restricted stock	$ 1				1
Vesting of restricted stock, Shares			488
Stock-based compensation	2,135				2,135
Ending Balance at Dec. 31, 2018	78,744		$ 2		175,201		(96,459)
Ending Balance, Shares at Dec. 31, 2018			18,569,289
Net loss	(32,996)						(32,996)
Issuance of stock, net of underwriting discounts, commissions and offering costs		$ 4,108				$ 4,108
Issuance of stock, net of underwriting discounts, commissions and offering costs, Shares				827,525
Issuance of common stock upon exercise of stock options	$ 60				60
Issuance of common stock upon exercise of stock options, Shares	22,141		22,141
Stock-based compensation	$ 1,449				1,449
Ending Balance at Dec. 31, 2019	$ 51,365		$ 2		$ 180,818		$ (129,455)
Ending Balance, Shares at Dec. 31, 2019			19,418,955

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (32,996,000)	$ (29,443,000)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation expense	37,000	38,000
Amortization expense - right-of-use leased assets - operating	327,000	294,000
Stock-based compensation	1,449,000	2,135,000
Non-cash interest expense	385,000	374,000
Fair value adjustment to derivative liability	2,000
Changes in operating assets and liabilities
Prepaid expenses and other assets	(611,000)	(833,000)
Accounts payable, accrued expenses and other liabilities	965,000	(1,377,000)
Net cash flows used in operating activities	(30,442,000)	(28,812,000)
Cash flows from financing activities
Proceeds from common stock offering, net of underwriter discounts and offering costs		(4,000)
Proceeds from term loan, net of costs	9,555,000	(62,000)
Proceeds from at-the-market offering, net	3,973,000
Proceeds from the exercise of stock options	60,000	58,000
Net cash flows (used in) provided by financing activities	13,588,000	(8,000)
Net decrease in cash	(16,854,000)	(28,820,000)
Cash, cash equivalents and restricted cash, beginning of year	89,660,000	118,480,000
Cash, cash equivalents and restricted cash, end of year	72,806,000	89,660,000
Supplemental cash flow information
Interest paid	1,383,000	1,059,000
Taxes paid	337,000	298,000
Supplemental disclosure of non-cash activities
Issuance of derivative in connection with modification of term loan	763,000
Transfer of issuance costs from other noncurrent assets to equity	$ 54,000
Vesting of restricted stock		(1,000)
Acquisition of right-of-use leased assets - operating, net of disposal		$ 26,000

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Description of Business scPharmaceuticals LLC was formed as a Limited Liability Company under the laws of the State of Delaware on February 19, 2013. On March 24, 2014, scPharmaceuticals LLC was converted to a Delaware Corporation and changed its name to scPharmaceuticals Inc. (“the Company”). The Company is a pharmaceutical company focused on developing and commercializing products that have the potential to optimize the delivery of infused therapies, advance patient care and reduce healthcare costs. The Company’s strategy is designed to enable the subcutaneous administration of therapies that have previously been limited to intravenous (“IV”) delivery. The Company’s headquarters and primary place of business is Burlington, Massachusetts. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) and have been prepared on a basis which assumes that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary, scPharmaceuticals Securities Corporation. All significant intercompany balances and transactions have been eliminated in consolidation. At December 31, 2019, the Company had cash, cash equivalents and restricted cash of $72.8 million and working capital of $70.4 million. During the year ended December 31, 2019, the Company incurred a net loss totaling $33.0 million and used cash in operating activities totaling $30.4 million. The Company expects to continue to incur losses and use cash in operating activities in 2020. In November 2017, the Company completed an initial public offering ("IPO"), in which the Company issued and sold 7,294,968 shares of common stock at a public offering price of $14.00 per share, resulting in net proceeds of $92.7 million after deducting underwriting discounts and commissions and offering costs. Prior to the IPO, the Company funded its operations primarily through convertible notes and the sale of equity in private placements. The Company believes that, based on its current development plans and activities, its cash balance of $72.6 million as of December 31, 2019 will be sufficient to satisfy its liquidity requirements for more than one year from the issuance date of these consolidated financial statements.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include accruals related to development costs and clinical activities, and the establishment of the tax valuation allowance. Actual results could differ from those estimates. Foreign Currency Transactions The functional currency of the Company is the U.S. dollar. Accordingly, gains and losses resulting from translating transactions denominated in currencies and balances of assets and liabilities outstanding at the balance sheet date, other than U.S. dollars, are included in net loss in the Statements of Operations and Comprehensive Loss. Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company places its cash and cash equivalents with institutions with high credit quality. However, at certain times such cash and cash equivalents may be in excess of Federal Deposit Insurance Corporation and Securities Investor Protection Corporation insurance limits. The Company has not experienced any losses with respect to these accounts. As of December 31, 2019, the Company classified $182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 11). Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, 2018 December 31, 2019 Cash and cash equivalents $ 89,478 $ 72,624 Restricted cash 182 182 Cash, cash equivalents and restricted cash $ 89,660 $ 72,806 Research and Development Costs Research and development costs are expensed as incurred. Nonrefundable advance payments, if any, for goods or services used in research and development are initially recorded as an asset and then recognized as an expense as the related goods are delivered or services are performed. Research and development expenses include contract services, consulting, salaries, materials and supplies and overhead. Income Taxes The Company accounts for income taxes in accordance with the ASC 740, Income Taxes. The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. The tax benefits recorded are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming that the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At December 31, 2018 and 2019, the Company had no such accruals. Stock-Based Compensation Stock-based compensation expense for stock options is recognized based on the grant-date fair value using the Black-Scholes valuation model. Restricted stock units are valued at the fair market value per share of the Company’s common stock on the date of grant. The Company recognizes compensation expense only for those stock-based awards expected to vest after considering expected forfeitures. Cumulative compensation expense is at least equal to the compensation expense for vested awards. Stock-based compensation is recognized on a straight-line basis over the service period of each award. Stock compensation costs have not been capitalized by the Company. Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s chief executive officer is the CODM, and he uses consolidated financial information in determining how to allocate resources and assess performance. The Company has determined that it operates in one segment. All of the Company’s assets are located in the United States. Recently Issued Accounting Standards In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820)

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss per Share	3. Net Loss per Share Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period without consideration of dilutive common stock equivalents. Diluted net loss per share is the same as basic net loss per common share, since the effects of potentially dilutive securities are anti-dilutive. Dilutive common stock equivalents are comprised of unexercised stock options outstanding under the Company’s equity plan and unvested restricted stock. The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except shares and per share data): FOR THE YEAR ENDED DECEMBER 31, 2018 DECEMBER 31, 2019 Net loss and comprehensive loss $ (29,443 ) $ (32,996 ) Weighted—average common shares outstanding, basic and diluted 18,556,126 18,600,718 Net loss per share, basic and diluted $ (1.59 ) $ (1.77 ) The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive (in common stock equivalent shares): FOR THE YEAR ENDED DECEMBER 31, 2018 DECEMBER 31, 2019 Stock options to purchase common stock 1,588,306 1,439,518 Unvested restricted stock — 160,900 1,588,306 1,600,418

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Purchased property and equipment consist of the following as of December 31, 2018 and 2019 (in thousands): ESTIMATED USEFUL LIFE 2018 2019 Office equipment 5 years $ 10 $ 10 Office furniture 7 years 116 116 Computer equipment 3 years 8 8 Leasehold improvements Life of lease 95 95 229 229 Less: Accumulated depreciation (65 ) (102 ) Property and equipment, net $ 164 $ 127 Depreciation expense for the years ended December 31, 2018 and 2019 was $38,000 and $37,000, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses at December 31, 2018 and 2019 consist of (in thousands): 2018 2019 Contract research and development $ 1,492 $ 2,001 Employee compensation and related costs 860 1,250 Consulting and professional service fees 356 296 Interest 47 91 State taxes 165 49 Other 2 1 Total accrued expenses $ 2,922 $ 3,688

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes The Company accounts for income taxes in accordance with ASC 740, Income Taxes Accordingly, the Company had no net income tax provision or benefit during the years ended December 31, 2018 and 2019. Components of the net deferred tax assets at December 31, 2018 and 2019 are as follows (in thousands): 2018 2019 Deferred tax assets: Federal net operating loss carryforwards $ 6,189 $ 7,638 State net operating loss carryforwards 1,670 2,117 Research and development tax credits 1,824 2,410 Accrued liabilities 257 407 Stock-based compensation 510 778 Depreciation and amortization 10 1,330 Capitalized research and development costs 14,227 19,294 Lease liabilities — 359 Other 20 — Total deferred tax assets $ 24,707 $ 34,333 Deferred tax liabiities: Right-of-use lease assets — (314 ) Other — (21 ) Total deferred tax liabilities $ — $ (335 ) Valuation allowance $ (24,707 ) $ (33,998 ) Net deferred tax assets $ — $ — At December 31, 2019, the Company had available federal net operating loss carryforwards of $17.5 million, which expire at various dates through 2038, and $18.9 million, which may be carried forward indefinitely. At December 31, 2019, the Company had available state net operating loss carryforwards of $33.5 million, which expire at various dates through 2039, and $0.1 million, which may be carried forward indefinitely. In assessing the realizability of net deferred tax assets, management considers whether it is more likely than not that the net deferred tax assets will be realized. The ultimate realization of net deferred tax assets is dependent upon the generation of future taxable income during the periods in which temporary differences representing future deductible amounts become deductible. Management has established a full valuation allowance against the net deferred tax assets at December 31, 2018 and 2019 since it is more likely than not that these future tax benefits will not be realized. During 2019, the valuation allowance increased by $9.3 million. At December 31, 2019, the Company had federal and state research and development credit carryforwards of $2.0 million and $0.5 million, respectively. The net credit carryforwards may be used to offset future income taxes and expire at various dates through 2039. Changes in the Company’s ownership, as defined in the U.S. Internal Revenue Code, may limit the Company’s ability to utilize the tax credit and net operating loss carryforwards. On December 22, 2017, the United States enacted new tax reform (“Tax Cuts and Jobs Act”). The Tax Cuts and Jobs Act contains provisions with separate effective dates but is generally effective for taxable years beginning after December 31, 2017. Beginning with the year ending December 31, 2018, the corporate statutory rates on U.S. earnings was reduced from 34% to 21% . A reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the consolidated financial statements at December 31, 2018 and 2019 are as follows: 2018 2019 Federal income tax at statutory rate 21.00 % 21.00 % State income tax, net of federal benefit 5.45 % 5.68 % Research and development credits 2.35 % 2.16 % Book compensation related to stock options (0.61 )% (0.27 )% Change in income tax rate (0.38 )% (0.05 )% Other (0.45 )% (0.34 )% Increase in valuation allowance (27.36 )% (28.18 )% Effective tax rate — % — % The Company files tax returns in the United States, Massachusetts and other states. The tax years 2015 through 2019 remain open to examination by major taxing jurisdictions to which the Company is subject, which are primarily the United States federal and Massachusetts, as carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service or state tax authorities if they have 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 recognizes both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company has not recorded any interest or penalties on any unrecognized tax benefits since its inception. A reconciliation of the beginning and ending amount of uncertain tax benefits is as follows (in thousands): 2018 2019 Beginning uncertain tax benefits $ 284 $ 476 Prior year - increases 46 — Current year - decreases — — Current year - increases 146 152 Ending uncertain tax benefits $ 476 $ 628

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	7. Stock-Based Compensation Stock Options In October 2017, the board of directors approved the 2017 Stock Option and Incentive Plan (the “2017 Stock Plan”) which became effective in November 2017, upon the closing of the Company’s IPO. The 2017 Stock Plan will expire in October 2027. Under the 2017 Stock Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units (“RSUs”) and other stock-based awards. The Company’s 2014 Stock Incentive Plan (the “2014 Stock Plan”) terminated in November 2017 effective upon the completion of the Company’s IPO. No additional options will be granted under the 2014 Stock Plan. At December 31, 2019, there were 828,962 options outstanding under the 2014 Stock Plan. There were 1,430,000 shares of the Company’s common stock initially reserved for issuance under the 2017 Stock Plan. In addition, the number of shares of common stock that may be issued under the 2017 Stock Plan automatically increases on each January 1, beginning on January 1, 2018 and ending on January 1, 2027, by a number of shares equal to 4% of the Company’s shares of common stock outstanding on the immediately preceding December 31, subject to limitation. On January 1, 2018, 2019 and 2020, the number of shares issuable under the 2017 Stock Plan increased by 741,389, 742,772 and 776,758 shares, respectively. At December 31, 2019, there were 3,166,868 shares of the Company’s common stock authorized for issuance under the 2017 Stock Plan, including 252,707 options that have been forfeited from the 2014 Stock Plan. At December 31, 2019, there were 2,395,412 options available for issuance, 610,556 options outstanding and 160,900 restricted stock units outstanding under the 2017 Stock Plan. Options granted under the 2017 Stock Plan have a term of ten years. Vesting of options under the 2017 Stock Plan is determined by the compensation committee of the board of directors but is generally a four-year term. The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2019 Risk-free interest rate 2.42%—2.86% 1.59%—2.51% Expected dividend yield 0% 0% Expected life 5.5—7.0 years 5.5—6.1 years Expected volatility 76%—86% 72%—74% Weighted-average grant date fair value $ 7.57 $ 2.31 Due to the lack of a public market for the trading of the Company’s common stock prior to its initial public offering and the lack of company-specific historical volatility, volatility was estimated using historical volatilities of similar companies. The expected life of the awards is estimated based on the simplified method, which calculates the expected life based upon the midpoint of the term of the award and the vesting period. The Company uses the simplified method because it does not have sufficient option exercise data to provide a reasonable basis upon which to estimate the expected term. The Company has no history of paying dividends nor does management expect to pay dividends over the contractual terms of these options. The risk-free interest rates are based on the United States Treasury yield curve in effect at the time of grant, with maturities approximating the expected life of the stock options. The following table summarizes information about stock option activity during 2018 and 2019 (in thousands, except share and per share data): NUMBER OF SHARES WEIGHTED- AVERAGE EXERCISE PRICE WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM AGGREGATE INTRINSIC VALUE Outstanding, December 31, 2017 1,195,495 $ 5.38 Granted 939,296 10.54 Exercised (34,561 ) 1.69 Forfeited (511,924 ) 10.85 Outstanding, December 31, 2018 1,588,306 $ 6.75 Granted 162,522 3.56 Exercised (22,141 ) 2.73 Forfeited (289,169 ) 8.54 Outstanding, December 31, 2019 1,439,518 $ 6.09 7.62 $ 1,642 Vested and exercisable, December 31, 2019 911,924 $ 6.20 7.22 $ 977 Vested and expected to vest, December 31, 2019 1,341,385 $ 6.13 7.54 $ 1,520 The following table summarizes information about RSU activity during the year ended December 31, 2019: RSUs AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE) RSUs outstanding, December 31, 2018 — $ — Granted 160,900 3.25 Exercised — — Forfeited — — RSUs outstanding, December 31, 2019 160,900 $ 3.25 During 2018 and 2019, the Company received $58,000 and $60,000, respectively, upon exercise of stock options. The intrinsic value of the options exercised in 2018 and 2019 was $270,000 and $47,000, respectively. Unrecognized compensation expense related to unvested options as of December 31, 2019 was $1.6 million and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 1.8 years. Unrecognized compensation expense related to unvested RSUs as of December 31, 2019 was $237,000 and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 1.1 years. During the year ended December 31, 2018, the Company extended the exercise period for 102,661 vested options with a weighted average exercise price of $7.33 pursuant to separation agreements. The Company recorded incremental stock-based compensation expense of $117,000. During The Company recorded stock-based compensation expense in the following expense categories of its accompanying condensed consolidated statements of operations and comprehensive loss for employees, directors and non-employees during the years ended December 31, 2018 and 2019 as follows (in thousands): 2018 2019 Research and development $ 567 $ 327 General and administrative 1,568 1,122 Total $ 2,135 $ 1,449

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	8. Fair Value of Financial Instruments The Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) Topic, Fair Value Measurements and Disclosures (“ASC 820”), 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 observable. 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 carrying values of the Company’s cash and restricted cash, prepaid expenses, value added tax, or VAT, receivable and deposits approximate their fair values due to their short-term nature. The carrying value of the Company’s loan payable was considered a reasonable estimate of fair value because the Company’s interest rate is near current market rates for instruments with similar characteristics. The following table summarizes the Company’s assets and liabilities as of December 31, 2019 that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): TOTAL Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Cash equivalents $ 67,824 $ 67,824 $ — $ — Total $ 67,824 $ 67,824 $ — $ — Liabilities: Derivative liability $ 765 $ — $ — $ 765 Total $ 765 $ — $ — $ 765 The fair value of the derivative liability recognized in connection with the Company’s 2019 Loan Agreement (Note 9) was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the derivative liability was determined using the probability-weighted expected return method, which considered as inputs the timing and probability of occurrence of an exit event, the amount of the payment, and the risk-free discount rate reflecting the expected risk profile for each of the potential settlement scenarios.

Term Loan

Term Loan	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Term Loan	9. Term Loan In May 2017, the Company entered into a loan and security agreement (the “2017 Loan Agreement”), with Solar Capital Ltd. and Silicon Valley Bank, (together, the “Lenders”) for $10.0 million. The 2017 Loan Agreement had a maturity date of May 1, 2021. Debt issuance costs for the 2017 Loan Agreement were to be amortized to interest expense over the remaining term of the 2017 Loan Agreement using the effective-interest method. The interest rate under the 2017 Loan Agreement was LIBOR plus 8.45%. The initial interest-only period was until November 30, 2018, followed by a 30-month principal and interest period. The First Amendment to the Loan and Security Agreement, entered into in November 2018, extended the interest-only period through May 2019. The Third Amendment to the Loan and Security Agreement, entered into in May 2019, extended the interest-only period through August 2019, with the ability to further extend the interest only period to November 2019. Pursuant to the 2017 Loan Agreement, the Company provided a first priority security interest in all existing and after-acquired assets, excluding intellectual property, owned by the Company. For the year ended December 31, 2019, the Company recorded $169,000 related to the amortization of debt discount associated with the 2017 Loan Agreement. For the year ended December 31, 2018, the Company recorded $280,000 related to the amortization of debt discount associated with the 2017 Loan Agreement. The 2017 Loan Agreement allowed the Company to voluntarily prepay all (but not less than all) of the outstanding principal at any time. A prepayment premium of 1% would be assessed on the outstanding principal. A final payment fee of $250,000 was due upon the earlier to occur of the maturity date or prepayment of such borrowings. The final payment fee was increased to $325,000 in the First Amendment to the 2017 Loan Agreement. For the year ended December 31, 2019, the Company recorded $80,000, related to the amortization of the final payment fee associated with the 2017 Loan Agreement. For the year ended December 31, 2018, the Company recorded $94,000, related to the amortization of the final payment fee associated with the 2017 Loan Agreement. In September 2019, the Company replaced the 2017 Loan Agreement with a new $20.0 million term loan with the Lenders, the 2019 Loan Agreement. The restructured four-year term loan facility allows for an expansion of the 2017 Loan Agreement. Some of the proceeds from the 2019 Loan Agreement were used to pay off the 2017 Loan Agreement including the final fee of $325,000. The 2019 Loan Agreement extends the term of the credit facility until The interest rate under the 2019 Loan Agreement is the higher of (i) LIBOR plus 7.95% or (ii) 10.18% and there is an interest-only period until September 30, 2021. The rate at December 31, 2019 was 10.18%. Pursuant to the 2019 Loan Agreement, the Company provided a first priority security interest in substantially all of the Company’s assets, including intellectual property, subject to certain exceptions. The Company entered into the Exit Agreement in connection with the 2019 Loan Agreement which provides for an aggregate payment of 4% of the loan commitment, or $800,000, to the Lenders upon the occurrence of an exit event. The Company concluded that the exit payment obligation met the definition of a derivative that was required to be accounted for as a separate unit of accounting. The Company recorded the issuance-date fair value of the derivative liability of $763,000 as a debt discount and as a derivative liability in the Company’s balance sheet. As of December 31, 2019, unpaid borrowings under the 2019 Loan Agreement totaled $20.0 million. For the year ended December 31, 2019, the Company recorded $90,000 related to the amortization of debt discount associated with the 2019 Loan Agreement. The 2019 Loan Agreement allows the Company to voluntarily prepay all (but not less than all) of the outstanding principal at any time. A prepayment premium of 3% or 1% through the one-year anniversary and the two-year anniversary, respectively, would be assessed on the outstanding principal. After the two-year anniversary, a 0.5% prepayment premium would be assessed on the outstanding principal. A final payment fee of $500,000 is due upon the earlier to occur of the maturity date or prepayment of such borrowings. For the year ended December 31, 2019, the Company recorded $46,000 related to the amortization of the final payment fee associated with the 2019 Loan Agreement. In an event of default under the 2019 Loan Agreement, the interest rate will be increased by 5% and the balance under the loan may become immediately due and payable at the option of the lenders. The 2019 Loan Agreement includes restrictions on, among other things, the Company’s ability to incur additional indebtedness, change the name or location of the Company’s business, merge with or acquire other entities, pay dividends or make other distributions to holders of its capital stock, make certain investments, engage in transactions with affiliates, create liens, sell assets or pay subordinated debt. Total term loan and unamortized debt discount balances are as follows (in thousands): DECEMBER 31, 2018 DECEMBER 31, 2019 Face value $ 10,000 $ 20,000 Less: discount (363 ) (1,085 ) Total $ 9,637 $ 18,915 Less: current portion (2,811 ) — Long-term portion $ 6,826 $ 18,915 As of December 31, 2019, future principal payments due under the 2019 Loan Agreement are as follows (in thousands): Year ended: December 31, 2021 $ 2,500 December 31, 2022 10,000 December 31, 2023 7,500 Total minimum principal payments $ 20,000

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Common Stock At December 31, 2018 and 2019, the Company had 150,000,000 shares of common stock authorized with a par value of $0.0001. There were 18,569,289 and 19,418,955 shares issued and outstanding at December 31, 2018 and 2019, respectively. Voting, dividend and liquidation rights of the holders of the common stock are subject to the Company’s articles of incorporation, corporate bylaws and underlying shareholder agreements. Reserved Shares The Company has reserved 1,439,518 and 160,900 shares of common stock for the exercise of outstanding options to purchase common stock and for the vesting of RSUs, respectively. At-the-Market Issuance Sales Agreement On August 23, 2019, the Company entered into an Open Market Sale Agreement SM Subject to the terms and conditions of the ATM Agreement, Jefferies will use its commercially reasonable efforts to sell the ATM Shares, based upon instructions from the Company, consistent with its normal trading and sales practices. The Company will pay Jefferies a commission equal to 3.0% of the gross sales proceeds of such ATM Shares. During the year ended December 31, 2019, the Company sold a total of 827,525 ATM Shares under the ATM Agreement, in the open market, at an average gross selling price of $5.18 per share for proceeds of $4.2 million, net of commissions. The Company incurred $189,000 of legal, accounting and other costs to establish and activate the ATM program. The Company charged $54,000 of these costs against additional paid in capital upon issuance of shares during the year ended December 31, 2019. Preferred Stock At December 31, 2018 and 2019, the Company had 10,000,000 shares of preferred stock authorized with a par value of $0.0001 and no shares of preferred stock were issued or outstanding.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Operating Leases The Company entered into noncancelable operating leases for office facilities located in Lexington, Massachusetts and Burlington, Massachusetts through December 31, 2022 and November 30, 2022, respectively. Rent expense under the operating leases totaled $0.5 million and $0.5 million for the years ended December 31, 2018 and 2019, respectively. Certain leases provide for increases in future minimum annual rental payments as defined in the lease agreements. The leases generally also include real estate taxes and common area maintenance (“CAM”) charges in the annual rental payments. Pursuant to the terms of its lease agreement for the Company’s headquarters in Burlington, Massachusetts, the Company obtained a letter of credit in the amount of approximately $182,000 as security on the lease obligation. The letter of credit is listed as restricted cash on the Company’s consolidated balance sheets. Short-term leases are leases having a term of twelve months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases. The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of December 31, 2019 (in thousands): Year ended: December 31, 2020 $ 528 December 31, 2021 537 December 31, 2022 496 Total minimum lease payments 1,561 Less imputed interest (211 ) Total $ 1,350 2018 2019 Lease cost: Operating lease cost $ 483 $ 490 Short-term lease cost 8 8 Sublease income (39 ) (56 ) Total lease cost $ 452 $ 442 Other information Cash paid for amounts included in the measurement of liabilities $ 429 $ 514 Operating cash flows from operating leases $ 49 $ (30 ) Weighted-average remaining lease term - operating leases 3.9 years 2.9 years Weighted-average discount rate - operating leases 10.1 % 10.1 % In February 2018, the Company signed a sublease agreement for its facility located in Lexington, Massachusetts. The sublease commenced on April 1, 2018 and has an initial term of three years with an extension term through December 2022. In February 2020, the sublease was extended until December 31, 2022. Research and Development Agreements As part of the Company’s research and development efforts, the Company enters into research and development agreements with unrelated companies. These agreements contain varying terms and provisions which include fees and milestones to be paid by the Company. Some of these agreements also contain provisions which require the Company to make payments for exclusivity in the development of products in the area of loop diuretics. Contingencies The Company follows subtopic 450-20 of the FASB Accounting Standards Codification to report accounting for contingencies. Certain conditions may exist as of the date the financial statements are issued, which may result in a loss to the Company but which will only be resolved when one or more future events occur or fail to occur. The Company assesses such contingent liabilities, and such assessment inherently involves an exercise of judgment. If the assessment of a contingency indicates that it is probable that a material loss has been incurred and the amount of the liability can be estimated, then the estimated liability would be accrued in the Company’s financial statements. If the assessment indicates that a potential material loss contingency is not probable but is reasonably possible, or is probable but cannot be estimated, then the nature of the contingent liability, and an estimate of the range of possible losses, if determinable and material, would be disclosed. Loss contingencies considered remote are generally not disclosed unless they involve guarantees, in which case the guarantees would be disclosed. Due to the discontinuation of use of the Company’s first generation product candidate, sc2Wear Infusor, the Company has received notice of termination costs from vendors related to the program. The Company has accrued all costs for which it either believes it is contractually liable or for which the Company has negotiated settlement agreements in good faith. However, certain of the Company’s vendors have claimed or billed for additional costs for which the Company believes it is not obligated. At this time, the Company estimates that additional termination costs, if any, will be immaterial to the Company’s financial statements.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
401(k) Savings Plan	12. 401(k) Savings Plan In July 2014, the Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code covering all of its employees. Employees may make contributions by withholding a percentage of their salary. The plan includes an employer match equal to 100% on the first 3% of deferred compensation and an additional 50% on the next 2% of deferred compensation. During the years ended December 31, 2018 and 2019, the Company has recognized compensation expense of $225,000 and $104,000, respectively, for the employer match contribution.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. In the period beginning January 1, 2020 through the date of this Annual Report on Form 10-K, the Company issued and sold an additional 1,502,892 shares of its common stock under the ATM program, resulting in the receipt of $10.4 million in net proceeds. With the shares sold in 2020, the ATM program is complete.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include accruals related to development costs and clinical activities, and the establishment of the tax valuation allowance. Actual results could differ from those estimates.
Foreign Currency Transactions	Foreign Currency Transactions The functional currency of the Company is the U.S. dollar. Accordingly, gains and losses resulting from translating transactions denominated in currencies and balances of assets and liabilities outstanding at the balance sheet date, other than U.S. dollars, are included in net loss in the Statements of Operations and Comprehensive Loss.
Cash Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash, cash equivalents and restricted cash consists of bank deposits, certificates of deposit and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company places its cash and cash equivalents with institutions with high credit quality. However, at certain times such cash and cash equivalents may be in excess of Federal Deposit Insurance Corporation and Securities Investor Protection Corporation insurance limits. The Company has not experienced any losses with respect to these accounts. As of December 31, 2019, the Company classified $182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 11). Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, 2018 December 31, 2019 Cash and cash equivalents $ 89,478 $ 72,624 Restricted cash 182 182 Cash, cash equivalents and restricted cash $ 89,660 $ 72,806
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Nonrefundable advance payments, if any, for goods or services used in research and development are initially recorded as an asset and then recognized as an expense as the related goods are delivered or services are performed. Research and development expenses include contract services, consulting, salaries, materials and supplies and overhead.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the ASC 740, Income Taxes. The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. The tax benefits recorded are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming that the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At December 31, 2018 and 2019, the Company had no such accruals.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense for stock options is recognized based on the grant-date fair value using the Black-Scholes valuation model. Restricted stock units are valued at the fair market value per share of the Company’s common stock on the date of grant. The Company recognizes compensation expense only for those stock-based awards expected to vest after considering expected forfeitures. Cumulative compensation expense is at least equal to the compensation expense for vested awards. Stock-based compensation is recognized on a straight-line basis over the service period of each award. Stock compensation costs have not been capitalized by the Company.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s chief executive officer is the CODM, and he uses consolidated financial information in determining how to allocate resources and assess performance. The Company has determined that it operates in one segment. All of the Company’s assets are located in the United States.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820)

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of Cash, Cash Equivalents and Restricted Cash	As of December 31, 2019, the Company classified $182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 11). Cash, cash equivalents and restricted cash consists of the following (in thousands): December 31, 2018 December 31, 2019 Cash and cash equivalents $ 89,478 $ 72,624 Restricted cash 182 182 Cash, cash equivalents and restricted cash $ 89,660 $ 72,806

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share of Common Stock	The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except shares and per share data): FOR THE YEAR ENDED DECEMBER 31, 2018 DECEMBER 31, 2019 Net loss and comprehensive loss $ (29,443 ) $ (32,996 ) Weighted—average common shares outstanding, basic and diluted 18,556,126 18,600,718 Net loss per share, basic and diluted $ (1.59 ) $ (1.77 )
Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive (in common stock equivalent shares): FOR THE YEAR ENDED DECEMBER 31, 2018 DECEMBER 31, 2019 Stock options to purchase common stock 1,588,306 1,439,518 Unvested restricted stock — 160,900 1,588,306 1,600,418

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Schedule of Purchased Property and Equipment	Purchased property and equipment consist of the following as of December 31, 2018 and 2019 (in thousands): ESTIMATED USEFUL LIFE 2018 2019 Office equipment 5 years $ 10 $ 10 Office furniture 7 years 116 116 Computer equipment 3 years 8 8 Leasehold improvements Life of lease 95 95 229 229 Less: Accumulated depreciation (65 ) (102 ) Property and equipment, net $ 164 $ 127

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses at December 31, 2018 and 2019 consist of (in thousands): 2018 2019 Contract research and development $ 1,492 $ 2,001 Employee compensation and related costs 860 1,250 Consulting and professional service fees 356 296 Interest 47 91 State taxes 165 49 Other 2 1 Total accrued expenses $ 2,922 $ 3,688

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Net Deferred Tax Assets	. Components of the net deferred tax assets at December 31, 2018 and 2019 are as follows (in thousands): 2018 2019 Deferred tax assets: Federal net operating loss carryforwards $ 6,189 $ 7,638 State net operating loss carryforwards 1,670 2,117 Research and development tax credits 1,824 2,410 Accrued liabilities 257 407 Stock-based compensation 510 778 Depreciation and amortization 10 1,330 Capitalized research and development costs 14,227 19,294 Lease liabilities — 359 Other 20 — Total deferred tax assets $ 24,707 $ 34,333 Deferred tax liabiities: Right-of-use lease assets — (314 ) Other — (21 ) Total deferred tax liabilities $ — $ (335 ) Valuation allowance $ (24,707 ) $ (33,998 ) Net deferred tax assets $ — $ —
Schedule of Reconciliation of Income Tax (Expense) Benefit	A reconciliation of income tax (expense) benefit at the statutory federal income tax rate and income taxes as reflected in the consolidated financial statements at December 31, 2018 and 2019 are as follows: 2018 2019 Federal income tax at statutory rate 21.00 % 21.00 % State income tax, net of federal benefit 5.45 % 5.68 % Research and development credits 2.35 % 2.16 % Book compensation related to stock options (0.61 )% (0.27 )% Change in income tax rate (0.38 )% (0.05 )% Other (0.45 )% (0.34 )% Increase in valuation allowance (27.36 )% (28.18 )% Effective tax rate — % — %
Schedule of Reconciliation of Uncertain Tax Benefits	A reconciliation of the beginning and ending amount of uncertain tax benefits is as follows (in thousands): 2018 2019 Beginning uncertain tax benefits $ 284 $ 476 Prior year - increases 46 — Current year - decreases — — Current year - increases 146 152 Ending uncertain tax benefits $ 476 $ 628

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Estimated Fair Value of Options Valuation Assumptions	The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions: 2018 2019 Risk-free interest rate 2.42%—2.86% 1.59%—2.51% Expected dividend yield 0% 0% Expected life 5.5—7.0 years 5.5—6.1 years Expected volatility 76%—86% 72%—74% Weighted-average grant date fair value $ 7.57 $ 2.31
Summary of Information about Stock Option Activity	The following table summarizes information about stock option activity during 2018 and 2019 (in thousands, except share and per share data): NUMBER OF SHARES WEIGHTED- AVERAGE EXERCISE PRICE WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM AGGREGATE INTRINSIC VALUE Outstanding, December 31, 2017 1,195,495 $ 5.38 Granted 939,296 10.54 Exercised (34,561 ) 1.69 Forfeited (511,924 ) 10.85 Outstanding, December 31, 2018 1,588,306 $ 6.75 Granted 162,522 3.56 Exercised (22,141 ) 2.73 Forfeited (289,169 ) 8.54 Outstanding, December 31, 2019 1,439,518 $ 6.09 7.62 $ 1,642 Vested and exercisable, December 31, 2019 911,924 $ 6.20 7.22 $ 977 Vested and expected to vest, December 31, 2019 1,341,385 $ 6.13 7.54 $ 1,520
Schedule of RSU Activity	The following table summarizes information about RSU activity during the year ended December 31, 2019: RSUs AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE) RSUs outstanding, December 31, 2018 — $ — Granted 160,900 3.25 Exercised — — Forfeited — — RSUs outstanding, December 31, 2019 160,900 $ 3.25
Summary of Stock-Based Compensation Expense	The Company recorded stock-based compensation expense in the following expense categories of its accompanying condensed consolidated statements of operations and comprehensive loss for employees, directors and non-employees during the years ended December 31, 2018 and 2019 as follows (in thousands): 2018 2019 Research and development $ 567 $ 327 General and administrative 1,568 1,122 Total $ 2,135 $ 1,449

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes the Company’s assets and liabilities as of December 31, 2019 that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): TOTAL Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Cash equivalents $ 67,824 $ 67,824 $ — $ — Total $ 67,824 $ 67,824 $ — $ — Liabilities: Derivative liability $ 765 $ — $ — $ 765 Total $ 765 $ — $ — $ 765

Term Loan (Tables)

Term Loan (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Total Term Loan and Unamortized Debt Discount	Total term loan and unamortized debt discount balances are as follows (in thousands): DECEMBER 31, 2018 DECEMBER 31, 2019 Face value $ 10,000 $ 20,000 Less: discount (363 ) (1,085 ) Total $ 9,637 $ 18,915 Less: current portion (2,811 ) — Long-term portion $ 6,826 $ 18,915
Schedule of Future Principal Payments Due	As of December 31, 2019, future principal payments due under the 2019 Loan Agreement are as follows (in thousands): Year ended: December 31, 2021 $ 2,500 December 31, 2022 10,000 December 31, 2023 7,500 Total minimum principal payments $ 20,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities	The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of December 31, 2019 (in thousands): Year ended: December 31, 2020 $ 528 December 31, 2021 537 December 31, 2022 496 Total minimum lease payments 1,561 Less imputed interest (211 ) Total $ 1,350
Schedule of Lease Cost and Other Information of Operating Lease Liabilities	2018 2019 Lease cost: Operating lease cost $ 483 $ 490 Short-term lease cost 8 8 Sublease income (39 ) (56 ) Total lease cost $ 452 $ 442 Other information Cash paid for amounts included in the measurement of liabilities $ 429 $ 514 Operating cash flows from operating leases $ 49 $ (30 ) Weighted-average remaining lease term - operating leases 3.9 years 2.9 years Weighted-average discount rate - operating leases 10.1 % 10.1 %

Description of Business and B_2

Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Description Of Business And Basis Of Presentation [Line Items]
Cash, cash equivalents and restricted cash		$ 72,806	$ 89,660	$ 118,480
Working capital		70,400
Net loss		32,996	29,443
Net cash flows used in operating activities		30,442	28,812
Proceeds from initial offering after deducting underwriting discounts and commissions			$ (4)
Cash balance		$ 72,600
IPO
Description Of Business And Basis Of Presentation [Line Items]
Common stock issued and sold	7,294,968
Public offering price of common stock	$ 14
Proceeds from initial offering after deducting underwriting discounts and commissions	$ 92,700

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)
Schedule Of Accounting Policies [Line Items]
Restricted cash	$ 182,000	$ 182,000
Potential interest and penalties associated with uncertain tax positions, accruals	$ 0	$ 0
Number of operating segments | Segment	1
Letter of Credit
Schedule Of Accounting Policies [Line Items]
Restricted cash	$ 182,000

Significant Accounting Polici_5

Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 72,624	$ 89,478
Restricted cash	182	182
Cash, cash equivalents and restricted cash	$ 72,806	$ 89,660	$ 118,480

Net Loss per Share - Computatio

Net Loss per Share - Computation of Basic and Diluted Net Loss Per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss and comprehensive loss	$ (32,996)	$ (29,443)
Weighted—average common shares outstanding, basic and diluted	18,600,718	18,556,126
Net loss per share, basic and diluted	$ (1.77)	$ (1.59)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	1,600,418	1,588,306
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	1,439,518	1,588,306
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	160,900

Property and Equipment - Schedu

Property and Equipment - Schedule of Purchased Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 229	$ 229
Less: Accumulated depreciation	(102)	(65)
Property and equipment, net	$ 127	164
Office Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years
Property and equipment, gross	$ 10	10
Office Furniture
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	7 years
Property and equipment, gross	$ 116	116
Computer Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	3 years
Property and equipment, gross	$ 8	8
Leasehold Improvements
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	Life of lease
Property and equipment, gross	$ 95	$ 95

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 37,000	$ 38,000

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accruals [Abstract]
Contract research and development	$ 2,001	$ 1,492
Employee compensation and related costs	1,250	860
Consulting and professional service fees	296	356
Interest	91	47
State taxes	49	165
Other	1	2
Total accrued expenses	$ 3,688	$ 2,922

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Net income tax provision or benefit	$ 0	$ 0
Federal net operating loss carryforwards expiration year	2038
State net operating loss carryforwards expiration year	2039
Increase in valuation allowance	$ 9,300,000
Research and development credit carryforwards	$ 2,410,000	$ 1,824,000
Federal and state research and development credit carryforwards expiration year	2039
Federal income tax at statutory rate	21.00%	21.00%	34.00%
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 18,900,000
Research and development credit carryforwards	2,000,000
Federal | 2037
Income Taxes [Line Items]
Net operating loss carryforwards	17,500,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	100,000
Research and development credit carryforwards	500,000
State | 2038
Income Taxes [Line Items]
Net operating loss carryforwards	$ 33,500,000

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Federal net operating loss carryforwards	$ 7,638	$ 6,189
State net operating loss carryforwards	2,117	1,670
Research and development tax credits	2,410	1,824
Accrued liabilities	407	257
Stock-based compensation	778	510
Depreciation and amortization	1,330	10
Capitalized research and development costs	19,294	14,227
Lease liabilities	359
Other		20
Total deferred tax assets	34,333	24,707
Deferred tax liabiities:
Right-of-use lease assets	(314)
Other	(21)
Total deferred tax liabilities	(335)
Valuation allowance	$ (33,998)	$ (24,707)

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Tax (Expense) Benefit (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	21.00%	21.00%	34.00%
State income tax, net of federal benefit	5.68%	5.45%
Research and development credits	2.16%	2.35%
Book compensation related to stock options	(0.27%)	(0.61%)
Change in income tax rate	(0.05%)	(0.38%)
Other	(0.34%)	(0.45%)
Increase in valuation allowance	(28.18%)	(27.36%)

Income Taxes - Schedule of Re_2

Income Taxes - Schedule of Reconciliation of Uncertain Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Beginning uncertain tax benefits	$ 476	$ 284
Prior year - increases		46
Current year - increases	152	146
Ending uncertain tax benefits	$ 628	$ 476

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	Jan. 01, 2020	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional options granted				162,522	939,296
Stock option, number of shares outstanding				1,439,518	1,588,306	1,195,495
Cash received upon exercise of stock options				$ 60,000	$ 58,000
Intrinsic value of options exercised				47,000	$ 270,000
Unrecognized compensation expense				$ 1,600,000
Recognition period (in years)				1 year 9 months 18 days
Number of options vested					102,661
Weighted average exercise price for vested options				$ 8.41	$ 7.33
Incremental stock-based compensation expense				$ 70,000	$ 117,000
Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term				1 year
Number of options vested				55,677
Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term				2 years
Number of options vested				85,432
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option, number of shares outstanding				160,900
Number of restricted stock units outstanding				160,900
Unrecognized compensation expense				$ 237,000
Recognition period (in years)				1 year 1 month 6 days
2017 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option and incentive plan effective date				Nov. 30, 2017
Stock option and incentive plan expiration date				Oct. 31, 2027
Stock option, number of shares outstanding				610,556
Number of common stock initially reserved for issuance				3,166,868			1,430,000
Percentage of shares issued on common stock outstanding				4.00%
Shares issuable increased during the period		742,772	741,389
Stock options, available for issuance				2,395,412
Term of option granted				10 years
Stock option vesting term				4 years
2017 Stock Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding				160,900
2017 Stock Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issuable increased during the period	776,758
2014 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option and incentive plan expiration date				Nov. 30, 2017
Additional options granted				0
Stock option, number of shares outstanding				828,962
Number of options forfeited				252,707

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Estimated Fair Value of Options Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	1.59%	2.42%
Risk-free interest rate, maximum	2.51%	2.86%
Expected dividend yield	0.00%	0.00%
Expected volatility, minimum	72.00%	76.00%
Expected volatility, maximum	74.00%	86.00%
Weighted-average grant date fair value	$ 2.31	$ 7.57
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	6 years 1 month 6 days	7 years

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Information about Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
NUMBER OF SHARES
Number of shares outstanding, beginning balance	1,588,306	1,195,495
Additional options granted	162,522	939,296
Number of shares exercised	(22,141)	(34,561)
Number of shares forfeited	(289,169)	(511,924)
Number of shares outstanding, ending balance	1,439,518	1,588,306
Vested and exercisable, ending balance	911,924
Vested and expected to vest, ending balance	1,341,385
WEIGHTED-AVERAGE EXERCISE PRICE
Weighted average exercise prices, outstanding beginning balance	$ 6.75	$ 5.38
Weighted average exercise prices, granted	3.56	10.54
Weighted average exercise prices, exercised	2.73	1.69
Weighted average exercise prices, forfeited	8.54	10.85
Weighted average exercise prices, outstanding ending balance	6.09	$ 6.75
Weighted average exercise prices, vested and exercisable ending balance	6.20
Weighted average exercise prices, vested and expected to vest ending balance	$ 6.13
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM
Weighted average remaining contractual term, outstanding	7 years 7 months 13 days
Weighted average remaining contractual term, vested and exercisable	7 years 2 months 19 days
Weighted average remaining contractual term, vested and expected to vest	7 years 6 months 14 days
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, outstanding ending balance	$ 1,642
Aggregate intrinsic value, vested and exercisable ending balance	977
Aggregate intrinsic value, vested and expected to vest ending balance	$ 1,520

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of RSU Activity (Details) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Granted | shares	160,900
RSUs outstanding, December 31, 2019 | shares	160,900
AVERAGE GRANT DATE FAIR VALUE, Granted | $ / shares	$ 3.25
AVERAGE GRANT DATE FAIR VALUE, RSUs outstanding at September 30, 2019 | $ / shares	$ 3.25

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,449	$ 2,135
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	327	567
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,122	$ 1,568

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring $ in Thousands	Dec. 31, 2019USD ($)
Assets:
Cash equivalents	$ 67,824
Total	67,824
Liabilities:
Derivative liability	765
Total	765
Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Cash equivalents	67,824
Total	67,824
Significant Unobservable Inputs (Level 3) [Member]
Liabilities:
Derivative liability	765
Total	$ 765

Term Loan - Additional Informat

Term Loan - Additional Information (Details) - Solar Capital Ltd. and Silicon Valley Bank - USD ($)	1 Months Ended			12 Months Ended
	Sep. 30, 2019	Nov. 30, 2018	May 31, 2017	Dec. 31, 2019	Dec. 31, 2018
2017 Loan Agreement
Debt Instrument [Line Items]
Loan and security agreement, amount			$ 10,000,000
Loan agreement, maturity date			May 1, 2021
Amortization of debt discount				$ 169,000	$ 280,000
Prepayment premium thereafter				1.00%
Final payment fee				$ 250,000
Amortization of final payment fee				80,000	94,000
Payment of final fee	$ 325,000
2017 Loan Agreement | Libor
Debt Instrument [Line Items]
Basis spread on variable base rate			8.45%
First Amendment to Loan and Security Agreement
Debt Instrument [Line Items]
Final payment fee		$ 325,000
2019 Loan Agreement
Debt Instrument [Line Items]
Loan and security agreement, amount	$ 20,000,000
Loan agreement, maturity date	Sep. 17, 2023
Amortization of debt discount				90,000
Final payment fee				500,000
Amortization of final payment fee				$ 46,000
Loan agreement, term	4 years
Debt instrument, interest rate terms				The interest rate under the 2019 Loan Agreement is the higher of (i) LIBOR plus 7.95% or (ii) 10.18%
Debt instrument, effective interest rate				10.18%
Exit fee, percentage				4.00%
Exit fee				$ 800,000
Derivative liability recorded against exit fee obligation				763,000
Unpaid borrowings				$ 20,000,000	$ 10,000,000
Prepayment premium percentage after year two				0.50%
Increase in interest rate on default				5.00%
2019 Loan Agreement | Minimum
Debt Instrument [Line Items]
Interest rate, minimum				10.18%
Prepayment premium percentage				1.00%
2019 Loan Agreement | Maximum
Debt Instrument [Line Items]
Prepayment premium percentage				3.00%
2019 Loan Agreement | Libor
Debt Instrument [Line Items]
Basis spread on variable base rate				7.95%

Term Loan - Schedule of Total T

Term Loan - Schedule of Total Term Loan and Unamortized Debt Discount (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Less: current portion		$ (2,811)
Long-term portion	$ 18,915	6,826
2019 Loan Agreement | Solar Capital Ltd. and Silicon Valley Bank
Debt Instrument [Line Items]
Face value	20,000	10,000
Less: discount	(1,085)	(363)
Total	18,915	9,637
Less: current portion		(2,811)
Long-term portion	$ 18,915	$ 6,826

Term Loan - Schedule of Future

Term Loan - Schedule of Future Principal Payments Due (Details) - 2019 Loan Agreement - Solar Capital Ltd. and Silicon Valley Bank - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
December 31, 2021	$ 2,500
December 31, 2022	10,000
December 31, 2023	7,500
Total minimum principal payments	$ 20,000	$ 10,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	Aug. 23, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders Equity Note [Line Items]
Common stock, shares authorized		150,000,000	150,000,000
Common stock, par value		$ 0.0001	$ 0.0001
Common stock, shares issued		19,418,955	18,569,289
Common stock, shares outstanding		19,418,955	18,569,289
Reserved shares of common stock for exercise of outstanding options to purchase common stock		1,439,518	1,588,306	1,195,495
Preferred stock, shares authorized		10,000,000	10,000,000
Preferred stock, par value		$ 0.0001	$ 0.0001
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
ATM Agreement | Legal Accounting and Other Costs
Stockholders Equity Note [Line Items]
Stock issuance cost		$ 189,000
ATM Agreement | Additional Paid-in Capital | Legal Accounting and Other Costs
Stockholders Equity Note [Line Items]
Stock issuance cost		$ 54,000
ATM Agreement | Jefferies | Common Stock
Stockholders Equity Note [Line Items]
Common stock, par value	$ 0.0001
Percentage of commission on gross sales proceeds	3.00%
Number of shares sold		827,525
Selling price per share		$ 5.18
Proceeds from sale of shares, net of commissions		$ 4,200,000
ATM Agreement | Jefferies | Common Stock | Maximum
Stockholders Equity Note [Line Items]
Aggregate offering price	$ 15,000,000
Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
Reserved shares of common stock for exercise of outstanding options to purchase common stock		160,900

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies [Line Items]
Operating leases rent expense		$ 500,000	$ 500,000
Restricted cash		182,000	182,000
Short-term lease asset		1,179,000	1,506,000
Short-term lease liability		407,000	$ 353,000
Operating sublease term	3 years
Short-term Leases Recognized on Straight-line Basis
Commitments And Contingencies [Line Items]
Short-term lease asset		0
Short-term lease liability		0
Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash		$ 182,000
Lexington, Massachusetts
Commitments And Contingencies [Line Items]
Operating leases expiration date		Dec. 31, 2022
Burlington, Massachusetts
Commitments And Contingencies [Line Items]
Operating leases expiration date		Nov. 30, 2022
Burlington, Massachusetts | Letter of Credit | Lease Agreement Require Standby Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash		$ 182,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2019USD ($)
Year ended:
December 31, 2020	$ 528
December 31, 2021	537
December 31, 2022	496
Total minimum lease payments	1,561
Less imputed interest	(211)
Total	$ 1,350

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Lease Cost and Other Information of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Lease cost:
Operating lease cost	$ 490	$ 483
Short-term lease cost	8	8
Sublease income	(56)	(39)
Total lease cost	442	452
Other information
Cash paid for amounts included in the measurement of liabilities	514	429
Operating cash flows from operating leases	$ (30)	$ 49
Weighted-average remaining lease term - operating leases	2 years 10 months 24 days	3 years 10 months 24 days
Weighted-average discount rate - operating leases	10.10%	10.10%

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Details) - USD ($)	Jul. 31, 2014	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Defined Benefit Plan, Tax Status [Extensible List]		us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember
Compensation expense for employer match contribution		$ 104,000	$ 225,000
First 3% of Deferred Compensation
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	100.00%
Employer matching contribution percentage of employees contributions of deferred compensation	3.00%
Defined Benefit Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember
Next 2% of Deferred Compensation
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	50.00%
Employer matching contribution percentage of employees contributions of deferred compensation	2.00%
Defined Benefit Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Common stock, shares issued		19,418,955	18,569,289
ATM Agreement | Scenario Forecast
Subsequent Event [Line Items]
Common stock, shares issued	1,502,892
Proceeds from sale of shares, net of commissions	$ 10.4