scPharmaceuticals (SCPH) 10-Q 14 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 13, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	SCPH
Entity Registrant Name	SCPHARMACEUTICALS INC.
Entity Central Index Key	1,604,950
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		18,569,289

CONDENSED BALANCE SHEETS (Unaud

CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash	$ 100,768	$ 118,298
Prepaid expenses	1,608	823
VAT receivable	438	655
Other current assets	151	107
Total current assets	102,965	119,883
Restricted cash	182	182
Property and equipment, net	225	203
Right-of-use lease assets - operating (Type B), net	1,629	1,773
Deposits and other assets	8	7
Total assets	105,009	122,048
Current liabilities
Accounts payable	2,358	1,591
Accrued expenses	2,565	3,063
Term loan, short term	2,231	314
Current portion of lease obligation - operating (Type B)	309	242
Other current liabilities		1
Total current liabilities	7,463	5,211
Term loan, long term	7,331	9,105
Long term lease obligation - operating (Type B)	1,514	1,683
Other liabilities	109	52
Total liabilities	16,417	16,051
Commitments and contingencies (Note 8)
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 as of June 30, 2018; 18,534,240 and 18,569,289 shares issued and outstanding as of December 31, 2017 and June 30, 2018, respectively	2	2
Additional paid-in capital	174,189	173,011
Accumulated deficit	(85,599)	(67,016)
Total stockholders’ equity	88,592	105,997
Total liabilities and stockholders’ equity	$ 105,009	$ 122,048

CONDENSED BALANCE SHEETS (Unau3

CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
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
Common stock, shares authorized	150,000,000
Common stock, shares issued	18,569,289	18,534,240
Common stock, shares outstanding	18,569,289	18,534,240

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating expenses:
Research and development	$ 4,855	$ 4,145	$ 8,903	$ 7,030
General and administrative	5,049	2,374	9,700	4,448
Total operating expenses	9,904	6,519	18,603	11,478
Loss from operations	(9,904)	(6,519)	(18,603)	(11,478)
Other income (expense)	(11)	57	(53)	67
Interest income	424	58	775	95
Interest expense	(359)	(132)	(701)	(132)
Net loss and comprehensive loss	$ (9,850)	$ (6,536)	$ (18,582)	$ (11,448)
Net loss per share — basic and diluted	$ (0.53)	$ (6.09)	$ (1)	$ (10.68)
Weighted average common shares outstanding — basic and diluted	18,549,978	1,072,940	18,542,745	1,071,822

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss	$ (18,582,000)	$ (11,448,000)
Adjustments to reconcile net loss to cash used in operating activities
Depreciation expense	19,000	3,000
Amortization expense - right-of-use leased assets - operating (Type B)	144,000	49,000
Stock-based compensation	1,119,000	336,000
Non-cash interest expense	188,000	29,000
Changes in operating assets and liabilities
Prepaid expenses and other assets	(613,000)	(749,000)
Accounts payable, accrued expenses and other liabilities	179,000	923,000
Net cash used in operating activities	(17,546,000)	(10,857,000)
Cash flows from investing activities
Purchases of property and equipment	(41,000)	(12,000)
Net cash used in investing activities	(41,000)	(12,000)
Cash flows from financing activities
Proceeds from term loan, net of costs		9,679,000
Proceeds from the exercise of vested stock options	58,000
Purchase of restricted stock		(3,000)
Net cash provided by financing activities	57,000	9,668,000
Net decrease in cash and restricted cash	(17,530,000)	(1,201,000)
Cash and restricted cash at beginning of period	118,480,000	39,281,000
Cash and restricted cash at end of period	100,950,000	38,080,000
Supplemental cash flow information
Interest paid	513,000	89,000
Taxes paid	259,000	28,000
Initial Public Offering
Cash flows from financing activities
Costs related to issuance of stock	$ (1,000)
Series B Convertible Preferred Stock
Cash flows from financing activities
Costs related to issuance of stock		$ (8,000)

Description of Business and Bas

Description of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2018
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 transform the way therapy is delivered, advance patient care and reduce healthcare costs. The Company’s proprietary platform is designed to enable the subcutaneous administration of therapies that have previously been limited to intravenous, or IV, delivery. The Company’s headquarters and primary place of business is Burlington, Massachusetts. In June 2018, the Company received a complete response letter (“CRL”) from the U.S. Food and Drug Administration (“FDA”) regarding its New Drug Application (“NDA”). On June 15, 2018 management implemented a restructuring plan to reduce operating costs and better align its workforce with the needs of its business following receipt of the CRL. Under this restructuring plan, the Company reduced its workforce by approximately 36%, to 27 employees. The Company recorded a charge of $572,000 during the three months ended June 30, 2018 related to the restructuring plan including severance, benefits and related costs. $147,000 and $425,000 was recorded in research and development expenses and general and administrative expenses, respectively. The Company paid $115,000 of these costs during the three months ended June 30, 2018 and expects to pay $424,000 in the third quarter of 2018. The remainder of the restructuring charge consists of a non-cash charge related to the modification of stock options (Note 6). As of June 30, 2018, the Company had a balance of $424,000 in accrued expenses related to severance, benefits, and related costs. Basis of Presentation The accompanying condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information 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. Certain information and disclosures normally included in financial statements in accordance with U.S. GAAP have been condensed or omitted. Accordingly, these condensed financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 20, 2018. The Company has determined that it operates in one segment. The accompanying condensed balance sheet as of June 30, 2018, the condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2017 and 2018 and condensed statements of cash flows for the six months ended June 30, 2017 and 2018 are unaudited. The unaudited condensed financial statements have been prepared on a basis consistent with that used to prepare the Company’s audited annual financial statements and include, in the opinion of management, adjustments, consisting of normal recurring items, necessary for the fair statement of the condensed financial statements. The operating results for the three and six months ended June 30, 2018 are not necessarily indicative of the results expected for the full year ending December 31, 2018.

Significant Accounting

Significant Accounting	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Stock Split On November 6, 2017, the Company effectuated a 1-for-7.180193 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on October 27, 2017 and by the Company’s stockholders on November 6, 2017. The reverse stock split resulted in an adjustment to the preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders’ equity reflects the reverse stock split by reclassifying from common stock to additional paid-in capital an amount equal to the par value of the decreased shares resulting from the reverse stock split. 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 reported periods. Actual results could differ from those estimates. Restricted Cash As of June 30, 2018, 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 8). Fair Value of Financial Instruments Assets and liabilities that are carried at fair value are to be classified and disclosed in one of the following three categories: Level 1: Observable quoted market prices in active markets for identical assets or liabilities; Level 2: Observable inputs other than Level 1, such as quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability; and Level 3: Unobservable inputs for the asset or liability that are significant to the fair value of the assets or liabilities. The Company does not have any recurring fair value measurements as of June 30, 2018. The carrying values of the Company’s cash and restricted cash, prepaid expenses, 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. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) lease assets, current portion of lease obligations, and long term lease obligations on the Company’s balance sheets. ROU lease assets represent the Company’s right to use an underlying asset for the lease term and lease obligations represent the Company’s obligation to make lease payments arising from the lease. Operating ROU lease assets and obligations are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU lease asset also includes any lease payments made and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification (“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 June 30, 2018, the Company had no such accruals. Recently Issued Accounting Standards In May 2014, the FASB and the International Accounting Standards Board jointly issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASC 606”), which supersedes the revenue recognition requirements in ASC 605 and most industry-specific guidance. The new standard requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods and services. The update also requires additional disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASC 606 is effective for public entities for annual and interim periods within those annual periods beginning after December 15, 2017. The Company has adopted ASC 606 as of January 1, 2018. The future impact of ASC 606 will be dependent on the nature of the Company’s future revenue contracts and arrangements, if any. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 is intended to improve financial reporting of leasing transactions by requiring organizations that lease assets to recognize assets and liabilities for the rights and obligations created by leases that extend more than twelve months on the balance sheet. This accounting update also requires additional disclosures surrounding the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for financial statements issued for annual and interim periods beginning after December 15, 2018 for public business entities. Early adoption is permitted. The Company elected to early adopt ASU 2016-02 as of January 1, 2018 with retrospective application to January 1, 2016, the beginning of the earliest period to be presented in the Annual Report on Form 10-K for the year ended December 31, 2018. The Company has elected the package of practical expedients permitted in ASC Topic 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments (as of December 31, 2015) would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company does allocate the consideration between lease and non-lease components. As a result of the adoption of the new lease accounting guidance, the Company recognized on January 1, 2016 (a) a lease liability of approximately $409,000, which represents the present value of the remaining lease payments of approximately $540,000, discounted using the Company’s incremental borrowing rate of 9.63%, and (b) a right-of-use asset of approximately $396,000 which represents the lease liability of $409,000 adjusted for accrued rent of approximately $13,000. Adoption of the standard requires the Company to restate certain previously reported results, including the recognition of additional ROU assets and lease obligations for operating leases. This standard did not have a material impact on the Company’s balance sheets or cash flows from operations and had no impact on the Company’s operating results. The most significant impact was the recognition of ROU assets and lease obligations for operating leases.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Loss per Share	3. Net Loss per Share Net Loss per Share Attributable to Common Stockholders The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Net loss and comprehensive loss $ (6,536 ) $ (9,850 ) $ (11,448 ) $ (18,582 ) Weighted-average shares used in computing net loss per share 1,072,940 18,549,978 1,071,822 18,542,745 Net loss per share, basic and diluted $ (6.09 ) $ (0.53 ) $ (10.68 ) $ (1.00 ) The Company’s potentially dilutive securities, which include stock options and convertible preferred stock, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect. Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Convertible preferred stock, on an as-converted basis 10,126,771 - 10,126,771 - Stock options to purchase common stock 1,052,542 1,610,651 1,052,542 1,610,651 Unvested restricted stock 1,218 - 1,218 - Total 11,180,531 1,610,651 11,180,531 1,610,651

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Purchased property and equipment consist of the following (dollars in thousands): ESTIMATED USEFUL LIFE December 31, 2017 June 30, 2018 Office equipment 5 years $ 10 $ 10 Office furniture 7 years 116 116 Machinery & equipment 5 years - 41 Computer equipment 3 years 8 8 Leasehold improvements Life of lease 95 95 229 270 Less: Accumulated depreciation (26 ) (45 ) Property and equipment, net $ 203 $ 225 Depreciation expense for the three months ended June 30, 2017 and June 30, 2018 was $1,000 and $9,000, respectively. Leased property and equipment consist of the following (dollars in thousands): ESTIMATED USEFUL LIFE December 31, 2017 June 30, 2018 Right-of-use lease assets - operating (Type B) Lease term $ 2,014 $ 2,014 Less: Accumulated amortization (241 ) (385 ) Right-of-use lease assets - operating (Type B), net $ 1,773 $ 1,629 Amortization expense for the three months ended June 30, 2017 and June 30, 2018 was $25,000 and $73,000, respectively. Amortization expense for the six months ended June 30, 2017 and June 30, 2018 was $49,000 and $144,000, respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2018
Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consist of (in thousands): December 31, 2017 June 30, 2018 Contract research and development $ 1,610 $ 1,170 Consulting and professional service fees 287 275 Employee compensation and related costs 871 986 State taxes 192 82 Financing related costs 90 - Other 13 52 Total accrued expenses $ 3,063 $ 2,565

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	6. Stock-Based Compensation Stock Options The Company’s 2017 Stock Option and Incentive Plan (the “2017 Stock Plan”) became effective in November 2017, upon the closing of the Company’s initial public offering and will expire in October 2027. Under the 2017 Stock Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards and other stock-based awards. The Company’s 2014 Stock Incentive Plan (the “2014 Stock Plan”) was terminated in November 2017 effective upon the completion of the Company’s initial public offering. No further additional options will be granted under the 2014 Stock Plan. At June 30, 2018, there were 1,025,605 options outstanding under the 2014 Plan. As of June 30, 2018, there were 2,249,594 shares of the Company’s common stock authorized for issuance under the 2017 Stock Plan. At June 30, 2018, there were 1,664,548 options available for issuance and 585,046 options outstanding under the 2017 Stock Plan. Options granted under the 2017 Plan have a term of ten years. Vesting of options under the 2017 Stock Plan is determined by the board of directors, but is generally over one to four-year terms. The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions: Six Months Ended June 30, 2017 2018 Risk-free interest rate 1.89%-2.20% 2.42%-2.86% Expected dividend yield 0% 0% Expected life 5.8-6.7 years 5.5-7.0 years Expected volatility 78%-84% 77%-86% Weighted-average grant date fair value $ 2.67 $ 8.54 The following table summarizes information about stock option activity during the six months ended June 30, 2018 (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 764,950 11.83 Exercised (34,561 ) 1.69 Forfeited (315,233 ) 11.99 Outstanding, June 30, 2018 1,610,651 $ 7.23 8.85 $ 1,471 Vested and exercisable, June 30, 2018 451,663 $ 5.36 8.14 $ 587 Vested and expected to vest, June 30, 2018 1,358,562 $ 7.12 8.78 $ 1,274 Unrecognized compensation expense related to unvested awards as of June 30, 2018 was $4.7 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 3.0 years. During the three months ended June 30, 2018, as part of the restructuring plan (Note 1), the Company extended the exercise period to one year for 21,820 vested options of those affected, with a weighted average exercise price of $7.95, The Company recorded stock-based compensation expense in the following expense categories of its accompanying condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2017 and 2018 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Research and development $ 38 $ 54 $ 74 $ 240 General and administrative 190 443 262 879 Total $ 228 $ 497 $ 336 $ 1,119

Term Loan

Term Loan	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Term Loan	7. 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 for $10.0 million. The 2017 Loan Agreement has a maturity date of May 1, 2021. Debt issuance costs for the 2017 Loan Agreement will 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 is LIBOR plus 8.45%, and there is an interest-only period until November 30, 2018, followed by a 30-month principal and interest period. 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. The Company entered into an exit fee agreement in connection with the 2017 Loan Agreement for an aggregate payment of 4% of the loan commitment, or $400,000, to the lenders upon the occurrence of an exit event, including an initial public offering. 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 $392,000 as a debt discount and as a derivative liability in the Company’s balance sheet. The Company paid the fee in November 2017 in conjunction with the Company’s IPO. As of June 30, 2018, unpaid borrowings under the 2017 Loan Agreement totaled $10.0 million. For the three and six months ended June 30, 2018 the Company recorded $75,000 and $144,000, respectively, related to the amortization of debt discount associated with the 2017 Loan Agreement. For the three and six months ended June 30, 2017 the Company recorded $20,000 related to the amortization of debt discount associated with the 2017 Loan Agreement. The 2017 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 initially 3% reducing to 1% following the one year anniversary would be assessed on the outstanding principal. A final payment fee of $250,000 is due upon the earlier to occur of the maturity date or prepayment of such borrowings. For the three and six months ended June 30, 2018, the Company recorded $23,000 and $44,000, respectively, related to the amortization of the final payment fee associated with the 2017 Loan Agreement. For the three and six months ended June 30, 2017, the Company recorded $9,000 related to the amortization of the final payment fee associated with the 2017 Loan Agreement. In an event of default under the 2017 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 2017 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): June 30, 2018 Face value $ 10,000 Less: discount (438 ) Total $ 9,562 Less: current portion (2,231 ) Total $ 7,331 As of June 30, 2018, future principal payments due under the 2017 Loan Agreement are as follows (in thousands): Year ended: December 31, 2018 $ 333 December 31, 2019 4,000 December 31, 2020 4,000 December 31, 2021 1,667 Total $ 10,000

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases The Company leases office facilities and equipment under long-term, non-cancelable operating lease agreements. The leases expire at various dates through 2022 and do not include renewal options. 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, 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 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 of the operating lease liabilities as of June 30, 2018 (in thousands): Year ended: December 31, 2018 $ 234 December 31, 2019 499 December 31, 2020 512 December 31, 2021 524 December 31, 2022 496 Total minimum lease payments $ 2,265 Six Months Ended June 30, 2017 2018 Lease cost: Operating lease cost $ 96 $ 237 Short-term lease cost 2 4 Sublease income - (13 ) Total lease cost $ 98 $ 228 Other information Cash paid for amounts included in the measurement of lease liabilities $ 51 $ 194 Operating cash flows from operating leases $ 13 $ 43 Weighted-average remaining lease term - operating leases 5.4 years 4.5 years Weighted-average discount rate - operating leases 9.6 % 10.1 % In February 2018, the Company signed a sublease agreement for its facility located in Lexington, Massachusetts. The lease commenced on April 1, 2018 and has an initial term of three years with an extension term through December 2022.

Significant Accounting (Policie

Significant Accounting (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Stock Split	Stock Split On November 6, 2017, the Company effectuated a 1-for-7.180193 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on October 27, 2017 and by the Company’s stockholders on November 6, 2017. The reverse stock split resulted in an adjustment to the preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders’ equity reflects the reverse stock split by reclassifying from common stock to additional paid-in capital an amount equal to the par value of the decreased shares resulting from the reverse stock split.
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 reported periods. Actual results could differ from those estimates.
Restricted Cash	Restricted Cash As of June 30, 2018, 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 8).
Fair Value of Financial Instruments	Fair Value of Financial Instruments Assets and liabilities that are carried at fair value are to be classified and disclosed in one of the following three categories: Level 1: Observable quoted market prices in active markets for identical assets or liabilities; Level 2: Observable inputs other than Level 1, such as quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability; and Level 3: Unobservable inputs for the asset or liability that are significant to the fair value of the assets or liabilities. The Company does not have any recurring fair value measurements as of June 30, 2018. The carrying values of the Company’s cash and restricted cash, prepaid expenses, 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.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) lease assets, current portion of lease obligations, and long term lease obligations on the Company’s balance sheets. ROU lease assets represent the Company’s right to use an underlying asset for the lease term and lease obligations represent the Company’s obligation to make lease payments arising from the lease. Operating ROU lease assets and obligations are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU lease asset also includes any lease payments made and excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification (“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 June 30, 2018, the Company had no such accruals.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the FASB and the International Accounting Standards Board jointly issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASC 606”), which supersedes the revenue recognition requirements in ASC 605 and most industry-specific guidance. The new standard requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods and services. The update also requires additional disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASC 606 is effective for public entities for annual and interim periods within those annual periods beginning after December 15, 2017. The Company has adopted ASC 606 as of January 1, 2018. The future impact of ASC 606 will be dependent on the nature of the Company’s future revenue contracts and arrangements, if any. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 is intended to improve financial reporting of leasing transactions by requiring organizations that lease assets to recognize assets and liabilities for the rights and obligations created by leases that extend more than twelve months on the balance sheet. This accounting update also requires additional disclosures surrounding the amount, timing, and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for financial statements issued for annual and interim periods beginning after December 15, 2018 for public business entities. Early adoption is permitted. The Company elected to early adopt ASU 2016-02 as of January 1, 2018 with retrospective application to January 1, 2016, the beginning of the earliest period to be presented in the Annual Report on Form 10-K for the year ended December 31, 2018. The Company has elected the package of practical expedients permitted in ASC Topic 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments (as of December 31, 2015) would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company does allocate the consideration between lease and non-lease components. As a result of the adoption of the new lease accounting guidance, the Company recognized on January 1, 2016 (a) a lease liability of approximately $409,000, which represents the present value of the remaining lease payments of approximately $540,000, discounted using the Company’s incremental borrowing rate of 9.63%, and (b) a right-of-use asset of approximately $396,000 which represents the lease liability of $409,000 adjusted for accrued rent of approximately $13,000. Adoption of the standard requires the Company to restate certain previously reported results, including the recognition of additional ROU assets and lease obligations for operating leases. This standard did not have a material impact on the Company’s balance sheets or cash flows from operations and had no impact on the Company’s operating results. The most significant impact was the recognition of ROU assets and lease obligations for operating leases.

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2018
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 share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Net loss and comprehensive loss $ (6,536 ) $ (9,850 ) $ (11,448 ) $ (18,582 ) Weighted-average shares used in computing net loss per share 1,072,940 18,549,978 1,071,822 18,542,745 Net loss per share, basic and diluted $ (6.09 ) $ (0.53 ) $ (10.68 ) $ (1.00 )
Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share	The Company’s potentially dilutive securities, which include stock options and convertible preferred stock, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect. Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Convertible preferred stock, on an as-converted basis 10,126,771 - 10,126,771 - Stock options to purchase common stock 1,052,542 1,610,651 1,052,542 1,610,651 Unvested restricted stock 1,218 - 1,218 - Total 11,180,531 1,610,651 11,180,531 1,610,651

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2018
Property Plant And Equipment [Abstract]
Schedule of Purchased Property and Equipment	Purchased property and equipment consist of the following (dollars in thousands): ESTIMATED USEFUL LIFE December 31, 2017 June 30, 2018 Office equipment 5 years $ 10 $ 10 Office furniture 7 years 116 116 Machinery & equipment 5 years - 41 Computer equipment 3 years 8 8 Leasehold improvements Life of lease 95 95 229 270 Less: Accumulated depreciation (26 ) (45 ) Property and equipment, net $ 203 $ 225
Schedule of Leased Property and Equipment	Leased property and equipment consist of the following (dollars in thousands): ESTIMATED USEFUL LIFE December 31, 2017 June 30, 2018 Right-of-use lease assets - operating (Type B) Lease term $ 2,014 $ 2,014 Less: Accumulated amortization (241 ) (385 ) Right-of-use lease assets - operating (Type B), net $ 1,773 $ 1,629

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2018
Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of (in thousands): December 31, 2017 June 30, 2018 Contract research and development $ 1,610 $ 1,170 Consulting and professional service fees 287 275 Employee compensation and related costs 871 986 State taxes 192 82 Financing related costs 90 - Other 13 52 Total accrued expenses $ 3,063 $ 2,565

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
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: Six Months Ended June 30, 2017 2018 Risk-free interest rate 1.89%-2.20% 2.42%-2.86% Expected dividend yield 0% 0% Expected life 5.8-6.7 years 5.5-7.0 years Expected volatility 78%-84% 77%-86% Weighted-average grant date fair value $ 2.67 $ 8.54
Summary of Information about Stock Option Activity	The following table summarizes information about stock option activity during the six months ended June 30, 2018 (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 764,950 11.83 Exercised (34,561 ) 1.69 Forfeited (315,233 ) 11.99 Outstanding, June 30, 2018 1,610,651 $ 7.23 8.85 $ 1,471 Vested and exercisable, June 30, 2018 451,663 $ 5.36 8.14 $ 587 Vested and expected to vest, June 30, 2018 1,358,562 $ 7.12 8.78 $ 1,274
Summary of Stock-Based Compensation Expense	The Company recorded stock-based compensation expense in the following expense categories of its accompanying condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2017 and 2018 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2018 2017 2018 Research and development $ 38 $ 54 $ 74 $ 240 General and administrative 190 443 262 879 Total $ 228 $ 497 $ 336 $ 1,119

Term Loan (Tables)

Term Loan (Tables)	6 Months Ended
	Jun. 30, 2018
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): June 30, 2018 Face value $ 10,000 Less: discount (438 ) Total $ 9,562 Less: current portion (2,231 ) Total $ 7,331
Schedule of Future Principal Payments Due	As of June 30, 2018, future principal payments due under the 2017 Loan Agreement are as follows (in thousands): Year ended: December 31, 2018 $ 333 December 31, 2019 4,000 December 31, 2020 4,000 December 31, 2021 1,667 Total $ 10,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2018
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 of the operating lease liabilities as of June 30, 2018 (in thousands): Year ended: December 31, 2018 $ 234 December 31, 2019 499 December 31, 2020 512 December 31, 2021 524 December 31, 2022 496 Total minimum lease payments $ 2,265
Schedule of Lease Cost and Other Information of Operating Lease Liabilities	Six Months Ended June 30, 2017 2018 Lease cost: Operating lease cost $ 96 $ 237 Short-term lease cost 2 4 Sublease income - (13 ) Total lease cost $ 98 $ 228 Other information Cash paid for amounts included in the measurement of lease liabilities $ 51 $ 194 Operating cash flows from operating leases $ 13 $ 43 Weighted-average remaining lease term - operating leases 5.4 years 4.5 years Weighted-average discount rate - operating leases 9.6 % 10.1 %

Description of Business and B21

Description of Business and Basis of Presentation - Additional Information (Details)	1 Months Ended	3 Months Ended
	Jun. 15, 2018Employee	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of number of employees reduced	36.00%
Number of positions remaining | Employee	27
Restructuring charges			$ 572,000
Restructuring cost paid			115,000
Severance, benefits, and related costs			424,000
Scenario, Forecast
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Restructuring cost paid		$ 424,000
Research and Development
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Restructuring charges			147,000
General and Administrative
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Restructuring charges			$ 425,000

Significant Accounting Policies

Significant Accounting Policies - Additional Information (Details) - USD ($)	Jan. 01, 2016	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Schedule of Accounting Policies [Line Items]
Reverse stock split		1-for-7.180193
Common stock, par value		$ 0.0001
Restricted cash		$ 182,000		$ 182,000
Potential interest and penalties associated with uncertain tax positions, accruals		0
Remaining lease payments		43,000	$ 13,000
Right-of-use asset		1,629,000		$ 1,773,000
Accounting Standards Update 2016-02
Schedule of Accounting Policies [Line Items]
Lease liability	$ 409,000
Remaining lease payments	$ 540,000
Incremental borrowing rate	9.63%
Right-of-use asset	$ 396,000
Accrued rent	$ 13,000
Letter of Credit
Schedule of Accounting Policies [Line Items]
Restricted cash		$ 182,000

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	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net loss and comprehensive loss	$ (9,850)	$ (6,536)	$ (18,582)	$ (11,448)
Weighted-average shares used in computing net loss per share	18,549,978	1,072,940	18,542,745	1,071,822
Net loss per share — basic and diluted	$ (0.53)	$ (6.09)	$ (1)	$ (10.68)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	1,610,651	11,180,531	1,610,651	11,180,531
Convertible Preferred Stock, on an if-converted Basis
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		10,126,771		10,126,771
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	1,610,651	1,052,542	1,610,651	1,052,542
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		1,218		1,218

Property and Equipment - Schedu

Property and Equipment - Schedule of Purchased Property and Equipment (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	Lease term
Property and equipment, gross	$ 270	$ 229
Less: Accumulated depreciation	(45)	(26)
Property and equipment, net	$ 225	203
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
Machinery and Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years
Property and equipment, gross	$ 41
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 ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 9,000	$ 1,000	$ 19,000	$ 3,000
Amortization expense	$ 73,000	$ 25,000	$ 144,000	$ 49,000

Property and Equipment - Sche27

Property and Equipment - Schedule of Leased Property and Equipment (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Right-of-use lease assets - operating (Type B)	$ 2,014	$ 2,014
Less: Accumulated amortization	(385)	(241)
Right-of-use lease assets - operating (Type B), net	$ 1,629	$ 1,773
ESTIMATED USEFUL LIFE	Lease term

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accruals [Abstract]
Contract research and development	$ 1,170	$ 1,610
Consulting and professional service fees	275	287
Employee compensation and related costs	986	871
State taxes	82	192
Financing related costs		90
Other	52	13
Total accrued expenses	$ 2,565	$ 3,063

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional options granted		764,950
Stock option, number of shares outstanding	1,610,651	1,610,651	1,195,495
Stock option vesting term	1 year
Unrecognized compensation expense	$ 4,700	$ 4,700
Recognition period (in years)		3 years
Number of options vested	21,820
Weighted average exercise price for vested options	$ 7.95
Incremental stock-based compensation expense	$ 33,000
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	585,046	585,046
Number of common shares authorized for issuance	2,249,594	2,249,594
Stock options, available for issuance	1,664,548	1,664,548
Term of option granted		10 years
Stock option vesting term		4 years
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	1,025,605	1,025,605

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Estimated Fair Value of Options Valuation Assumptions (Details) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	2.42%	1.89%
Risk-free interest rate, maximum	2.86%	2.20%
Expected dividend yield	0.00%	0.00%
Expected volatility, minimum	77.00%	78.00%
Expected volatility, maximum	86.00%	84.00%
Weighted-average grant date fair value	$ 8.54	$ 2.67
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	5 years 6 months	5 years 9 months 18 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	7 years	6 years 8 months 12 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Information about Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)$ / sharesshares
NUMBER OF SHARES
Number of shares outstanding, beginning balance | shares	1,195,495
Additional options granted | shares	764,950
Number of shares exercised | shares	(34,561)
Number of shares forfeited | shares	(315,233)
Number of shares outstanding, ending balance | shares	1,610,651
Vested and exercisable, ending balance | shares	451,663
Vested and expected to vest, ending balance | shares	1,358,562
WEIGHTED-AVERAGE EXERCISE PRICE
Weighted average exercise prices, outstanding beginning balance | $ / shares	$ 5.38
Weighted average exercise prices, granted | $ / shares	11.83
Weighted average exercise prices, exercised | $ / shares	1.69
Weighted average exercise prices, forfeited | $ / shares	11.99
Weighted average exercise prices, outstanding ending balance | $ / shares	7.23
Weighted average exercise prices, vested and exercisable ending balance | $ / shares	5.36
Weighted average exercise prices, vested and expected to vest ending balance | $ / shares	$ 7.12
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM
Weighted average remaining contractual term, outstanding	8 years 10 months 6 days
Weighted average remaining contractual term, vested and exercisable	8 years 1 month 20 days
Weighted average remaining contractual term, vested and expected to vest	8 years 9 months 10 days
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, outstanding ending balance | $	$ 1,471
Aggregate intrinsic value, vested and exercisable ending balance | $	587
Aggregate intrinsic value, vested and expected to vest ending balance | $	$ 1,274

Stock-Based Compensation - Su32

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 497	$ 228	$ 1,119	$ 336
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	54	38	240	74
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 443	$ 190	$ 879	$ 262

Term Loan - Additional Informat

Term Loan - Additional Information (Details) - 2017 Loan Agreement - Solar Capital Ltd. and Silicon Valley Bank - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
Loan and security agreement, amount	$ 10,000,000
Loan agreement, maturity date	May 1, 2021
Exit fee, percentage	4.00%
Exit fee	$ 400,000
Derivative liability recorded against exit fee obligation	$ 392,000
Unpaid borrowings		$ 10,000,000		$ 10,000,000
Amortization of debt discount		75,000	$ 20,000	$ 144,000	$ 20,000
Initial prepayment premium				3.00%
Reduced prepayment premium				1.00%
Final payment fee				$ 250,000
Amortization of final payment fee		$ 23,000	$ 9,000	$ 44,000	$ 9,000
Increase in interest rate on default				5.00%
Libor
Debt Instrument [Line Items]
Basis spread on variable base rate	8.45%

Term Loan - Schedule of Total T

Term Loan - Schedule of Total Term Loan and Unamortized Debt Discount (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Less: current portion	$ (2,231)	$ (314)
Term loan, long term	7,331	$ 9,105
2017 Loan Agreement | Solar Capital Ltd. and Silicon Valley Bank
Debt Instrument [Line Items]
Face value	10,000
Less: discount	(438)
Total	9,562
Less: current portion	(2,231)
Term loan, long term	$ 7,331

Term Loan - Schedule of Future

Term Loan - Schedule of Future Principal Payments Due (Details) - 2017 Loan Agreement - Solar Capital Ltd. and Silicon Valley Bank $ in Thousands	Jun. 30, 2018USD ($)
Debt Instrument [Line Items]
December 31, 2018	$ 333
December 31, 2019	4,000
December 31, 2020	4,000
December 31, 2021	1,667
Total	$ 10,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	6 Months Ended
	Feb. 28, 2018	Jun. 30, 2018	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Operating leases expire		2,022
Restricted cash		$ 182,000	$ 182,000
Right-of-use lease assets - operating (Type B), net		1,629,000	1,773,000
Current portion of lease obligation - operating (Type B)		309,000	$ 242,000
Operating sublease term	3 years
Short-term Leases Recognized on Straight-line Basis
Commitments And Contingencies [Line Items]
Right-of-use lease assets - operating (Type B), net		0
Current portion of lease obligation - operating (Type B)		0
Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash		182,000
Letter of Credit | Lease Agreement Require Standby Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash		$ 182,000

Commitments and Contingencies37

Commitments and Contingencies - Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities (Details) $ in Thousands	Jun. 30, 2018USD ($)
Year ended:
December 31, 2018	$ 234
December 31, 2019	499
December 31, 2020	512
December 31, 2021	524
December 31, 2022	496
Total minimum lease payments	$ 2,265

Commitments and Contingencies38

Commitments and Contingencies - Schedule of Lease Cost and Other Information of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Lease cost:
Operating lease cost	$ 237	$ 96
Short-term lease cost	4	2
Sublease income	(13)
Total lease cost	228	98
Other information
Cash paid for amounts included in the measurement of lease liabilities	194	51
Operating cash flows from operating leases	$ 43	$ 13
Weighted-average remaining lease term - operating leases	4 years 6 months	5 years 4 months 24 days
Weighted-average discount rate - operating leases	10.10%	9.60%