Clearside Biomedical (CLSD) 10-Q 8 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 06, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	Clearside Biomedical, Inc.
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	CLSD
Document Type	10-Q
Entity Central Index Key	1,539,029
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		32,024,223

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 35,185	$ 9,224
Short-term investments	49,245	28,416
Prepaid expenses	2,391	1,445
Other current assets		116
Total current assets	86,821	39,201
Property and equipment, net	791	885
Restricted cash	360	360
Other assets	44	47
Total assets	88,016	40,493
Current liabilities:
Accounts payable	8,372	5,384
Accrued liabilities	2,368	4,716
Current portion of long-term debt		3,200
Current portion of deferred rent	206	199
Other current liabilities		20
Total current liabilities	10,946	13,519
Long-term debt	9,848	4,809
Deferred rent	550	610
Deferred revenue		140
Total liabilities	21,344	19,078
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized and no shares issued at June 30, 2018 and December 31, 2017
Common stock, $0.001 par value; 100,000,000 shares authorized at June 30, 2018 and December 31, 2017; 32,024,223 and 25,354,651 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	32	25
Additional paid-in capital	228,007	145,618
Accumulated deficit	(161,368)	(124,220)
Accumulated other comprehensive gain (loss)	1	(8)
Total stockholders’ equity	66,672	21,415
Total liabilities and stockholders’ equity	$ 88,016	$ 40,493

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares, issued	32,024,223	25,354,651
Common stock, shares outstanding	32,024,223	25,354,651

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
License and collaboration revenue		$ 130		$ 135
Type of Revenue [Extensible List]	clsd:LicenseAndCollaborationMember	clsd:LicenseAndCollaborationMember	clsd:LicenseAndCollaborationMember	clsd:LicenseAndCollaborationMember
Operating expenses:
Research and development	$ 17,343	$ 11,478	$ 30,722	$ 19,068
General and administrative	3,561	2,290	6,635	4,961
Total operating expenses	20,904	13,768	37,357	24,029
Loss from operations	(20,904)	(13,638)	(37,357)	(23,894)
Other income (expense), net	203	(135)	49	(252)
Net loss	$ (20,701)	$ (13,773)	$ (37,308)	$ (24,146)
Net loss per share of common stock — basic and diluted	$ (0.65)	$ (0.54)	$ (1.27)	$ (0.96)
Weighted average shares outstanding — basic and diluted	31,979,158	25,309,966	29,412,904	25,280,314
Net loss	$ (20,701)	$ (13,773)	$ (37,308)	$ (24,146)
Unrealized gain (loss) on available-for-sale investments	2	(2)	9	(10)
Comprehensive loss	$ (20,699)	$ (13,775)	$ (37,299)	$ (24,156)

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net loss	$ (37,308)	$ (24,146)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	94	87
Share-based compensation expense	2,337	1,531
Non-cash interest expense	60	105
Accretion of debt discount	79	105
Amortization and accretion on available-for-sale investments, net	(244)	30
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(830)	(239)
Other assets	3	(48)
Accounts payable and accrued liabilities	640	(14)
Deferred revenue		(10)
Deferred rent	(53)	70
Net cash used in operating activities	(35,222)	(22,529)
Investing activities
Purchase of available-for-sale investments	(52,446)	(25,603)
Maturities of available-for-sale investments	31,870	25,010
Acquisition of property and equipment		(319)
Net cash used in investing activities	(20,576)	(912)
Financing activities
Proceeds from follow-on public offering, net of issuance costs	79,581	5,057
Proceeds from exercise of stock options	433	195
Proceeds from shares issued under employee stock purchase plan	45	40
Proceeds from long-term debt	10,000
Payments made on long-term debt	(8,300)
Net cash provided by financing activities	81,759	5,292
Net increase (decrease) in cash, cash equivalents and restricted cash	25,961	(18,149)
Cash, cash equivalents and restricted cash, beginning of period	9,584	35,184
Cash, cash equivalents and restricted cash, end of period	$ 35,545	17,035
Supplemental schedule of noncash investing and financing activities
Tenant improvements paid by landlord		$ 637

The Company

The Company	6 Months Ended
	Jun. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
The Company	1. The Company Clearside Biomedical, Inc. (the “Company”) is a late-stage clinical biopharmaceutical company developing first-in-class drug therapies to treat blinding diseases of the eye. The Company’s current product candidates are injected into the suprachoroidal space (“SCS”) using its proprietary SCS Microinjector, and focus on the treatment of diseases affecting the retina and choroid, especially diseases associated with macular edema. Incorporated in the State of Delaware on May 26, 2011, the Company has its corporate headquarters in Alpharetta, Georgia. The Company’s activities since inception have primarily consisted of developing product and technology rights, raising capital and performing research and development activities. The Company has no current source of revenue to sustain present activities, and does not expect to generate meaningful revenue until and unless the Company receives regulatory approval of, and successfully commercializes, its product candidates. The Company is subject to a number of risks and uncertainties similar to those of other life science companies at a similar stage of development, including, among others, the need to obtain adequate additional financing, successful development efforts, regulatory approval of products, compliance with government regulations, successful commercialization of potential products, protection of proprietary technology and dependence on key individuals. Liquidity The Company has funded its operations primarily through the proceeds of its public offerings of common stock, sale of convertible preferred stock and the issuance of long-term debt. On March 12, 2018, the Company closed a follow-on public offering in which it sold 6,538,462 shares of common stock at a public offering price of $13.00 per share, resulting in net proceeds of $79.6 million after deducting underwriting discounts and commissions and estimated offering expenses. On May 14, 2018, the Company entered into a second amended and restated loan agreement, which provides for up to $20.0 million in term loans, of which the Company borrowed $10.0 million on May 14, 2018 (see Note 5). The Company will continue to need to obtain additional financing to fund future operations, including completing the development and commercialization of its primary product candidates. The Company will need to expend substantial resources for research and development, including costs associated with the clinical testing of its product candidates. The Company will also need to obtain additional financing to conduct additional trials for the regulatory approval of its product candidates if requested by regulatory bodies, and to complete the development of any additional product candidates that might be acquired. If such products were to receive regulatory approval, the Company would need to prepare for the potential commercialization of its product candidates and fund the commercial launch of the products, if the Company decides to commercialize the products on its own. Moreover, the Company’s fixed expenses such as rent and other contractual commitments are substantial and are expected to increase in the future. The Company had cash, cash equivalents and short-term investments of $84.4 million as of June 30, 2018. In the absence of product or other revenues, the amount, timing, nature or source of which cannot be predicted, the Company’s losses will continue as it conducts its research and development activities. Until the Company can generate a sufficient amount of revenue, the Company may finance future cash needs through public or private equity offerings, license agreements, debt financings, collaborations, strategic alliances and marketing or distribution arrangements. The Company has incurred losses and negative cash flows since inception and expects operating losses and negative cash flows to continue into the foreseeable future. Absent raising additional funds, the Company expects that it will be able to delay, reduce or eliminate certain research and development programs or reduce administrative expense while still advancing clinical trials for key product candidates in order that the cash on hand as of the filing date, August 8, 2018, will be sufficient to fund its operations into the fourth quarter of 2019.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Unaudited Interim Financial Information The accompanying balance sheet as of June 30, 2018, statements of operations and comprehensive loss for the three and six months ended June 30, 2018 and 2017 and statements of cash flows for the six months ended June 30, 2018 and 2017 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of June 30, 2018 and its results of its operations for the three and six months ended June 30, 2018 and 2017 and its cash flows for the six months ended June 30, 2018 and 2017. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2018 and 2017 are unaudited. The results for the three and six months ended June 30, 2018 are not indicative of results to be expected for the year ending December 31, 2018, any other interim periods or any future year or period. These unaudited financial statements should be read in conjunction with the audited financial statements and related footnotes, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. 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 disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of income and expenses during the reporting periods. Significant items subject to such estimates and assumptions include the accounting for useful lives to calculate depreciation and amortization, clinical trial estimates and related accrued liabilities, share-based compensation expense and income tax valuation allowance. Actual results could differ from these estimates. Research and Development Costs Research and development costs are charged to expense as incurred and include, but are not limited to: • employee-related expenses, including salaries, benefits, travel and share-based compensation expense for research and development personnel; • expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies; • costs associated with nonclinical and clinical development activities; • costs associated with technology and intellectual property licenses; • costs for the Company’s research and development facility; and • depreciation expense for assets used in research and development activities. Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as prepaid or accrued expense. No material adjustments to these estimates have been recorded in these financial statements. Share-Based Compensation Compensation cost related to share-based awards granted to employees is measured based on the estimated fair value of the award at the grant date. The Company estimates the fair value of stock options using a Black-Scholes option pricing model. Compensation expense for options granted to non-employees is determined as the fair value of consideration received or the fair value of the equity instruments issued, whichever is more reliably measured. The fair value of awards granted to non-employees is re-measured each period until the related service is complete. Share-based compensation costs are expensed on a straight-line basis over the relevant vesting period. Compensation cost related to shares purchased through the Company’s employee stock purchase plan, which is considered compensatory, is based on the estimated fair value of the shares on the offering date, including consideration of the discount and the look back period. The Company estimates the fair value of the shares using a Black-Scholes option pricing model. Compensation expense is recognized over the six-month withholding period prior to the purchase date. All share-based compensation costs are recorded in general and administrative or research and development costs in the statements of operations and comprehensive loss based upon the underlying employees’ roles within the Company. Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with an original term of three months or less at the date of purchase. Short-Term Investments Short-term investments are investments with original maturities of between 90 and 365 days when purchased and are comprised of commercial paper and treasury bills. The Company classifies its short-term investments as available-for-sale securities. Short-term investments are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive income (loss) until realized. In addition, the Company evaluates the short-investments with unrealized losses to determine whether such losses are other-than-temporary. Concentration of Credit Risk Arising From Cash Deposits in Excess of Insured Limits The Company maintains its cash in bank deposits that at times may exceed federally insured limits. The Company has not experienced any loss in such accounts. The Company believes it is not exposed to any significant risks with respect to its cash balances. Recent Accounting Pronouncements Accounting Pronouncements Recently Adopted In May 2014, the Financial Accounting Standards Board (“FASB”) Revenue from Contracts with Customers The Company adopted the standard effective January 1, 2018 using the modified retrospective transition method. After evaluating its current and prior license agreements, as well as its other collaboration agreements, the Company recorded the remaining $160,000 of deferred revenue as a cumulative adjustment to accumulated deficit. The adoption of the new standard did not have a material impact on the Company’s financial statements and related disclosures. In August 2016, the FASB Statement of Cash Flows Classification of Certain Cash Receipts and Cash Payments In November 2016, the FASB issued ASU 2016-18, Restricted Cash, The following table is a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total amounts in the statements of cash flows (in thousands). June 30, 2018 2017 Cash and cash equivalents $ 35,185 $ 16,675 Restricted cash 360 360 Cash, cash equivalents and restricted cash shown on the statements of cash flows $ 35,545 $ 17,035 Restricted cash consists of amounts held by a financial institution under a contractual agreement. In May 2017, the FASB issued ASU 2017-9 , Compensation-Stock Compensation: Scope of Stock Compensation Modification Accounting financial statements and related disclosure would depend on any future modifications to its share-based awards. Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (ASC 842), In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation: Improvements to Nonemployee Shared-Based Payment Accounting Revenue from Contracts with Customers The Company is currently assessing the impact that adopting this new accounting standard will have on its financial statements and related disclosures.

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2018
Property Plant And Equipment [Abstract]
Property and Equipment, Net	3. Property and Equipment, Net Property and equipment, net consisted of the following (dollar amounts in thousands): Estimated Useful Lives (Years) June 30, 2018 December 2017 Furniture and fixtures 5 $ 303 $ 303 Machinery and equipment 5 121 121 Computer equipment 3 32 41 Leasehold improvements Lesser of useful life remaining lease term 667 667 1,123 1,132 Less: Accumulated depreciation (332 ) (247 ) $ 791 $ 885

Accrued Liabilities

Accrued Liabilities	6 Months Ended
	Jun. 30, 2018
Payables And Accruals [Abstract]
Accrued Liabilities	4. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): June 30, December 2018 2017 Accrued research and development $ 1,208 $ 3,360 Accrued bonuses 554 920 Accrued professional fees 68 62 Accrued vacation 88 113 Accrued interest payable 71 58 Accrued expense 379 203 $ 2,368 $ 4,716

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	5. Long-Term Debt Loan and Security Agreements In September 2016, the Company entered into an amended and restated loan and security agreement, which was subsequently amended on October 31, 2017 (as amended, the “1 st st Under the terms of the 1 st st st On May 14, 2018, the Company entered into a second amended and restated loan and security agreement (the “2 nd st nd The Company borrowed an initial tranche of $10.0 million on May 14, 2018, of which $7.0 million was used to repay all amounts outstanding under the 1 st Of the remaining $10.0 million available under the 2 nd . Once the draw period for the Term B Loan or the Term C Loan, as applicable, has commenced, the Company may draw funds under the applicable loan at its discretion until the earlier of (i) March 31, 2019 and (ii) the occurrence of an event of default. nd followed by consecutive equal monthly payments of principal and interest in arrears continuing through the maturity date of October 1, 2022 3% of the original principal amount of each term loan for any prepayment prior the first anniversary of the date such term loan is funded or 2% of the original principal amount of each term loan for any prepayment on or after the first anniversary of the date such term loan is funded but prior to October 1, 2022 The Company accounted for the 2 nd Debt st st nd The term loans under the 2 nd Interest expense on the borrowings under the loan agreements was $186,000 and $162,000 for the three months ended June 30, 2018 and 2017, respectively, and $346,000 and $317,000 for the six months ended June 30, 2018 and 2017, respectively. Accretion of the scheduled final payment was $11,000 and $53,000 for the three months ended June 30, 2018 and 2017, respectively, and $60,000 and $105,000 for the six months ended June 30, 2018 and 2017, respectively. Accretion of the deferred debt issuance costs was $9,000 and $53,000 for the three months ended June 30, 2018 and 2017, respectively, and $23,000 and $105,000 for the six months ended June 30, 2018 and 2017, respectively. As of June 30, 2018, the scheduled payments for the 2 nd Year Ending December 31, Principal Interest and Final Total 2018 $ — $ 429 $ 429 2019 556 845 1,401 2020 3,333 651 3,984 2021 3,333 365 3,698 2022 2,778 638 3,416 $ 10,000 $ 2,928 $ 12,928

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Common Stock	6. Common Stock The Company’s amended and restated certificate of incorporation authorizes the Company to issue 100,000,000 shares of $0.001 par value common stock. As of June 30, 2018 and December 31, 2017, there were 32,024,223 and 25,354,651 shares of common stock outstanding, respectively.

Stock Purchase Warrants

Stock Purchase Warrants	6 Months Ended
	Jun. 30, 2018
Stock Purchase Warrants [Abstract]
Stock Purchase Warrants	7. Stock Purchase Warrants In September 2016, in connection with the 1 st .

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	8. Share-Based Compensation Share-based compensation is accounted for in accordance with the provisions of ASC 718, Compensation-Stock Compensation Stock Options The Company has granted stock option awards to employees, directors and consultants from its 2011 Stock Incentive Plan (the “2011 Plan”) and its 2016 Equity Incentive Plan (the “2016 Plan”). The estimated fair value of options granted is determined as of the date of grant using the Black-Scholes option pricing model. The resulting fair value is recognized ratably over the requisite service period, which is generally the vesting period of the awards. Options granted to non-employees are re-measured at each financial reporting period until required services are performed. Share-based compensation expense for options granted under the 2011 Plan and the 2016 Plan is reflected in the statements of operations and comprehensive loss as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Research and development $ 443 $ 332 $ 873 $ 657 General and administrative 753 438 1,456 856 Total $ 1,196 $ 770 $ 2,329 $ 1,513 The following table summarizes the activity related to stock options during the six months ended June 30, 2018: Weighted Number of Average Shares Exercise Price Options outstanding at January 1, 2018 3,075,349 $ 6.17 Granted 318,750 8.93 Exercised (123,724 ) 3.51 Forfeited (49,875 ) 8.12 Options outstanding at June 30, 2018 3,220,500 6.51 Options exercisable at December 31, 2017 1,114,286 3.94 Options exercisable at June 30, 2018 1,278,725 4.90 As of June 30, 2018, the Company had $11.3 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted average period of 2.7 years. Employee Stock Purchase Plan In January 2016, the Company’s board of directors adopted and approved, and in January 2016 the Company’s stockholders approved, the Clearside Biomedical, Inc. 2016 Employee Stock Purchase Plan (the “2016 ESPP”) which became effective on June 1, 2016. The first offering period for the 2016 ESPP commenced January 1, 2017. The 2016 ESPP is considered a compensatory plan and the fair value of the discount and the look-back period are estimated using the Black-Scholes option pricing model and expense is recognized over the six month withholding period prior to the purchase date. The Company has issued a total of 17,078 shares of common stock purchased under the 2016 ESPP. The Company has recorded $3,000 and $9,000 of share-based compensation expense for the three months ended June 30, 2018 and 2017, respectively, and $9,000 and $18,000 for the six months ended June 30, 2018 and 2017, respectively, in the statements of operations and comprehensive loss for the estimated number of shares to be purchased on the next purchase date following the conclusion of the applicable reporting period.

Commitment and Contingencies

Commitment and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Lease Commitment Summary In November 2016, the Company signed an office lease agreement to lease approximately 20,000 square feet of office space in Alpharetta, Georgia for its corporate headquarters. The lease agreement is for a 6.5 year term with a renewal option for one additional five-year term. Rental payments are $35,145 per month subject to an increase of 3% per year. Rent expense under this lease is recognized on a straight-line basis over the term of the lease. In addition, the lease agreement requires payment of the pro-rata share of the annual operating expenses associated with the premises. The Company relocated to this new space in March 2017. Total future minimum lease payments were as follows at June 30, 2018 (in thousands): Year Ending December 31, 2018 $ 217 2019 444 2020 458 2021 472 Thereafter 860 Total minimum lease payments $ 2,451 Rent expense was $58,000 for each of the three months ended June 30, 2018 and 2017 and $116,000 and $98,000 for the six months ended June 30, 2018 and 2017, respectively. Contract Service Providers In the course of the Company’s normal business operations, it has agreements with contract service providers to assist in the performance of its research and development, clinical research and manufacturing. Substantially all of these contracts are on an as needed basis.

License and Collaboration Agree

License and Collaboration Agreements	6 Months Ended
	Jun. 30, 2018
License And Collaboration Agreements [Abstract]
License and Collaboration Agreements	10. License and Collaboration Agreements In August 2014, the Company entered into a royalty-bearing license agreement with NovaMedica LLC (“NovaMedica”). Under this agreement, the Company granted to NovaMedica the right to use the Company’s intellectual property to develop and commercialize the intended products (the “Covered Products”) and to have the exclusive right to sell those products in Russia and specified adjacent territories involving the use of the corticosteroid triamcinolone acetonide as the sole active pharmaceutical ingredient for administration in the SCS. In connection with this royalty-bearing license, NovaMedica made an upfront payment to the Company of $200,000. The Company is currently developing product candidates that, when completed, would be subject to this license giving NovaMedica the exclusive right to then sell the products in the specified geographic territories. In mid-December 2015, the Company received positive results from the Phase 2 clinical trial relating to the product candidate and determined, based on these results, that the intellectual property could become commercially feasible. Beginning in the first quarter of 2016, the Company began recognizing the $200,000 to revenue over the period of time estimated to complete clinical development and commercialization of the Covered Products and the beginning of the first set of patent expirations in 2027. On January 1, 2018, upon the adoption of ASU 2014-09, the Company accelerated the recognition of the deferred revenue and recorded the remaining balance of $160,000 as a cumulative adjustment to accumulated deficit. The Company recorded $5,000 and $10,000 of license revenue during the three and six months ended June 30, 2017, respectively, from this license agreement. NovaMedica is jointly owned by Rusnano MedInvest LLC and Domain Russia Investments Limited. The Company has periodically entered into other short-term collaboration agreements, generally with performance obligations of one to two months, to evaluate the potential use of its proprietary SCS Microinjector with third-party product candidates for the treatment of various diseases. Funds received from these collaboration agreements are recognized as revenue over the term of the agreement. The Company recorded $125,000 of revenue from these collaboration agreements during the three and six months ended June 30, 2017.

Available-for-Sale Investments

Available-for-Sale Investments	6 Months Ended
	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Available-for-Sale Investments	11. Available-for-Sale Investments The following table summarizes the Company’s available-for-sale investments (in thousands): June 30, 2018 Amortized Unrealized Fair Cost Losses Value Commercial paper $ 40,784 $ — $ 40,784 Treasury bills 8,461 — 8,461 Total available-for-sale investments $ 49,245 $ — $ 49,245

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	12. Fair Value Measurements The Company records certain financial assets and liabilities at fair value in accordance with the provisions of ASC Topic 820, Fair Value Measurements and Disclosures • Level 1—Unadjusted quoted prices in active, accessible markets for identical assets or liabilities. • Level 2—Other inputs that are directly or indirectly observable in the marketplace. • Level 3—Unobservable inputs that are supported by little or no market activity. The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The Company’s material financial instruments at June 30, 2018 and December 31, 2017 consisted primarily of cash and cash equivalents, short-term investments and long-term debt. The fair value of cash and cash equivalents, government bonds, other current assets and accounts payable approximate their respective carrying values due to the short term nature of these instruments and are classified as Level 1 in the fair hierarchy. The fair value of long-term debt approximates the carrying value due to variable interest rates that correspond to market rates. The Company has determined its short-term investments, comprised of commercial paper, certificates of deposit, and corporate bonds, to be Level 2 in the fair value hierarchy. The fair value was determined using a market approach, based on prices and other relevant information generated by market transactions involving similar assets. The short-term investments consist of investments with original maturity dates from date of acquisition of 90 to 365 days and are classified as available-for-sale. There were no significant transfers between Levels 1, 2 and 3 during the six months ended June 30, 2018 and the year ended December 31, 2017. The following tables summarize the fair value of financial assets that are measured at fair value and the classification by level of input within the fair value hierarchy (in thousands): June 30, 2018 Level 1 Level 2 Level 3 Recorded Value Financial Assets: Cash and money markets $ 20,913 $ — $ — $ 20,913 Restricted cash money market 360 — — 360 Treasury bills 8,462 — — 8,462 Commercial paper — 55,055 — 55,055 Total financial assets $ 29,735 $ 55,055 $ — $ 84,790 December 31, 2017 Level 1 Level 2 Level 3 Recorded Value Financial Assets: Cash and money markets $ 9,224 $ — $ — $ 9,224 Restricted cash money market 360 — — 360 Government bonds 11,238 — — 11,238 Certificates of deposit — 1,960 — 1,960 Corporate bonds — 5,064 — 5,064 Commercial paper — 10,154 — 10,154 Total financial assets $ 20,822 $ 17,178 $ — $ 38,000

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	13. 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 for the period, without consideration of the dilutive effect of potential common stock equivalents. Diluted net loss per share gives effect to all dilutive potential shares of common stock outstanding during this period. For all periods presented, the Company’s potential common stock equivalents, which included stock options and stock purchase warrants, have been excluded from the computation of diluted net loss per share as their inclusion would have the effect of reducing the net loss per share. Therefore, the denominator used to calculate both basic and diluted net loss per share is the same in all periods presented. The Company’s potential common stock equivalents that have been excluded from the computation of diluted net loss per share for all periods presented because of their antidilutive effect consisted of the following: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Outstanding stock options 3,220,500 2,235,378 3,220,500 2,235,378 Stock purchase warrants 29,796 29,796 29,796 29,796 3,250,296 2,265,174 3,250,296 2,265,174

Significant Accounting Polici19

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying balance sheet as of June 30, 2018, statements of operations and comprehensive loss for the three and six months ended June 30, 2018 and 2017 and statements of cash flows for the six months ended June 30, 2018 and 2017 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of June 30, 2018 and its results of its operations for the three and six months ended June 30, 2018 and 2017 and its cash flows for the six months ended June 30, 2018 and 2017. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2018 and 2017 are unaudited. The results for the three and six months ended June 30, 2018 are not indicative of results to be expected for the year ending December 31, 2018, any other interim periods or any future year or period. These unaudited financial statements should be read in conjunction with the audited financial statements and related footnotes, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.
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 disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of income and expenses during the reporting periods. Significant items subject to such estimates and assumptions include the accounting for useful lives to calculate depreciation and amortization, clinical trial estimates and related accrued liabilities, share-based compensation expense and income tax valuation allowance. Actual results could differ from these estimates.
Research and Development Costs	Research and Development Costs Research and development costs are charged to expense as incurred and include, but are not limited to: • employee-related expenses, including salaries, benefits, travel and share-based compensation expense for research and development personnel; • expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies; • costs associated with nonclinical and clinical development activities; • costs associated with technology and intellectual property licenses; • costs for the Company’s research and development facility; and • depreciation expense for assets used in research and development activities. Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as prepaid or accrued expense. No material adjustments to these estimates have been recorded in these financial statements.
Share-Based Compensation	Share-Based Compensation Compensation cost related to share-based awards granted to employees is measured based on the estimated fair value of the award at the grant date. The Company estimates the fair value of stock options using a Black-Scholes option pricing model. Compensation expense for options granted to non-employees is determined as the fair value of consideration received or the fair value of the equity instruments issued, whichever is more reliably measured. The fair value of awards granted to non-employees is re-measured each period until the related service is complete. Share-based compensation costs are expensed on a straight-line basis over the relevant vesting period. Compensation cost related to shares purchased through the Company’s employee stock purchase plan, which is considered compensatory, is based on the estimated fair value of the shares on the offering date, including consideration of the discount and the look back period. The Company estimates the fair value of the shares using a Black-Scholes option pricing model. Compensation expense is recognized over the six-month withholding period prior to the purchase date. All share-based compensation costs are recorded in general and administrative or research and development costs in the statements of operations and comprehensive loss based upon the underlying employees’ roles within the Company.
Cash Equivalents	Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with an original term of three months or less at the date of purchase.
Short-Term Investments	Short-Term Investments Short-term investments are investments with original maturities of between 90 and 365 days when purchased and are comprised of commercial paper and treasury bills. The Company classifies its short-term investments as available-for-sale securities. Short-term investments are recorded at fair value and unrealized gains and losses are recorded within accumulated other comprehensive income (loss) until realized. In addition, the Company evaluates the short-investments with unrealized losses to determine whether such losses are other-than-temporary.
Concentration of Credit Risk Arising From Cash Deposits in Excess of Insured Limits	Concentration of Credit Risk Arising From Cash Deposits in Excess of Insured Limits The Company maintains its cash in bank deposits that at times may exceed federally insured limits. The Company has not experienced any loss in such accounts. The Company believes it is not exposed to any significant risks with respect to its cash balances.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Pronouncements Recently Adopted In May 2014, the Financial Accounting Standards Board (“FASB”) Revenue from Contracts with Customers The Company adopted the standard effective January 1, 2018 using the modified retrospective transition method. After evaluating its current and prior license agreements, as well as its other collaboration agreements, the Company recorded the remaining $160,000 of deferred revenue as a cumulative adjustment to accumulated deficit. The adoption of the new standard did not have a material impact on the Company’s financial statements and related disclosures. In August 2016, the FASB Statement of Cash Flows Classification of Certain Cash Receipts and Cash Payments In November 2016, the FASB issued ASU 2016-18, Restricted Cash, The following table is a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total amounts in the statements of cash flows (in thousands). June 30, 2018 2017 Cash and cash equivalents $ 35,185 $ 16,675 Restricted cash 360 360 Cash, cash equivalents and restricted cash shown on the statements of cash flows $ 35,545 $ 17,035 Restricted cash consists of amounts held by a financial institution under a contractual agreement. In May 2017, the FASB issued ASU 2017-9 , Compensation-Stock Compensation: Scope of Stock Compensation Modification Accounting financial statements and related disclosure would depend on any future modifications to its share-based awards. Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (ASC 842), In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation: Improvements to Nonemployee Shared-Based Payment Accounting Revenue from Contracts with Customers The Company is currently assessing the impact that adopting this new accounting standard will have on its financial statements and related disclosures.

Significant Accounting Polici20

Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash and Cash Equivalents and Restricted Cash	The following table is a reconciliation of cash and cash equivalents and restricted cash reported within the balance sheets that sum to the total amounts in the statements of cash flows (in thousands). June 30, 2018 2017 Cash and cash equivalents $ 35,185 $ 16,675 Restricted cash 360 360 Cash, cash equivalents and restricted cash shown on the statements of cash flows $ 35,545 $ 17,035

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2018
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (dollar amounts in thousands): Estimated Useful Lives (Years) June 30, 2018 December 2017 Furniture and fixtures 5 $ 303 $ 303 Machinery and equipment 5 121 121 Computer equipment 3 32 41 Leasehold improvements Lesser of useful life remaining lease term 667 667 1,123 1,132 Less: Accumulated depreciation (332 ) (247 ) $ 791 $ 885

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): June 30, December 2018 2017 Accrued research and development $ 1,208 $ 3,360 Accrued bonuses 554 920 Accrued professional fees 68 62 Accrued vacation 88 113 Accrued interest payable 71 58 Accrued expense 379 203 $ 2,368 $ 4,716

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Second Amended and Restated Loan and Security Agreement
Scheduled Payments for the Second Amended and Restated Loan and Security Agreement	As of June 30, 2018, the scheduled payments for the 2 nd Year Ending December 31, Principal Interest and Final Total 2018 $ — $ 429 $ 429 2019 556 845 1,401 2020 3,333 651 3,984 2021 3,333 365 3,698 2022 2,778 638 3,416 $ 10,000 $ 2,928 $ 12,928

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Share-based Compensation Expense	Share-based compensation expense for options granted under the 2011 Plan and the 2016 Plan is reflected in the statements of operations and comprehensive loss as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Research and development $ 443 $ 332 $ 873 $ 657 General and administrative 753 438 1,456 856 Total $ 1,196 $ 770 $ 2,329 $ 1,513
Summary of Activity Related to Stock Options	The following table summarizes the activity related to stock options during the six months ended June 30, 2018: Weighted Number of Average Shares Exercise Price Options outstanding at January 1, 2018 3,075,349 $ 6.17 Granted 318,750 8.93 Exercised (123,724 ) 3.51 Forfeited (49,875 ) 8.12 Options outstanding at June 30, 2018 3,220,500 6.51 Options exercisable at December 31, 2017 1,114,286 3.94 Options exercisable at June 30, 2018 1,278,725 4.90

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Total Future Minimum Commitments Due Under Non-Cancelable Operating Leases	Total future minimum lease payments were as follows at June 30, 2018 (in thousands): Year Ending December 31, 2018 $ 217 2019 444 2020 458 2021 472 Thereafter 860 Total minimum lease payments $ 2,451

Available-for-Sale Investments

Available-for-Sale Investments (Tables)	6 Months Ended
	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Summary of Company's Available-For-Sale Investments	The following table summarizes the Company’s available-for-sale investments (in thousands): June 30, 2018 Amortized Unrealized Fair Cost Losses Value Commercial paper $ 40,784 $ — $ 40,784 Treasury bills 8,461 — 8,461 Total available-for-sale investments $ 49,245 $ — $ 49,245

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Summary of Assets Measured at Fair Value	The following tables summarize the fair value of financial assets that are measured at fair value and the classification by level of input within the fair value hierarchy (in thousands): June 30, 2018 Level 1 Level 2 Level 3 Recorded Value Financial Assets: Cash and money markets $ 20,913 $ — $ — $ 20,913 Restricted cash money market 360 — — 360 Treasury bills 8,462 — — 8,462 Commercial paper — 55,055 — 55,055 Total financial assets $ 29,735 $ 55,055 $ — $ 84,790 December 31, 2017 Level 1 Level 2 Level 3 Recorded Value Financial Assets: Cash and money markets $ 9,224 $ — $ — $ 9,224 Restricted cash money market 360 — — 360 Government bonds 11,238 — — 11,238 Certificates of deposit — 1,960 — 1,960 Corporate bonds — 5,064 — 5,064 Commercial paper — 10,154 — 10,154 Total financial assets $ 20,822 $ 17,178 $ — $ 38,000

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Potential Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	The Company’s potential common stock equivalents that have been excluded from the computation of diluted net loss per share for all periods presented because of their antidilutive effect consisted of the following: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Outstanding stock options 3,220,500 2,235,378 3,220,500 2,235,378 Stock purchase warrants 29,796 29,796 29,796 29,796 3,250,296 2,265,174 3,250,296 2,265,174

The Company - Additional Inform

The Company - Additional Information (Details) - USD ($)	Mar. 12, 2018	Jun. 30, 2018	Jun. 30, 2017	May 14, 2018
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Entity incorporation date		May 26, 2011
Issuance of common stock for follow-on public offering, shares	6,538,462
Common stock, Share offering price	$ 13
Net offering proceeds after deducting underwriting discount and commissions and estimated offering expenses	$ 79,600,000	$ 79,581,000	$ 5,057,000
Cash, cash equivalents and short-term investments		84,400,000
Second Amended and Restated Loan and Security Agreement
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Long term debt		$ 10,000,000
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Line of credit facility, maximum borrowing capacity				$ 20,000,000
Long term debt				$ 10,000,000

Significant Accounting Polici30

Significant Accounting Policies - Additional Information (Details) - USD ($)	Jan. 01, 2018	Jun. 30, 2018
Significant Accounting Policies [Line Items]
Short-term investments maturity start period		90 days
Short-term investments maturity end period		365 days
ASU 2014-09
Significant Accounting Policies [Line Items]
Cumulative adjustment to accumulated deficit	$ 160,000

Significant Accounting Polici31

Significant Accounting Policies - Schedule on Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 35,185	$ 9,224	$ 16,675
Restricted cash	360	360	360
Cash, cash equivalents and restricted cash shown on the statements of cash flows	$ 35,545	$ 9,584	$ 17,035	$ 35,184

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 1,123	$ 1,132
Less: Accumulated depreciation	(332)	(247)
Property and equipment, net	791	885
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 303	303
Estimated Useful Lives (Years)	5 years
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 121	121
Estimated Useful Lives (Years)	5 years
Computer Equipment
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 32	41
Estimated Useful Lives (Years)	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 667	$ 667
Estimated Useful Lives (Years)	Lesser of useful life or remaining lease term

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued research and development	$ 1,208	$ 3,360
Accrued bonuses	554	920
Accrued professional fees	68	62
Accrued vacation	88	113
Accrued interest payable	71	58
Accrued expense	379	203
Accrued liabilities, current	$ 2,368	$ 4,716

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) - USD ($)	May 14, 2018	Sep. 28, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Oct. 31, 2018
Debt Instrument [Line Items]
Interest expense on borrowings				$ 186,000	$ 162,000	$ 346,000	$ 317,000
Accretion of scheduled final payment				11,000	53,000	60,000	105,000
Accretion of deferred debt issuance costs				9,000	$ 53,000	23,000	$ 105,000
Second Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Long term debt				10,000,000		$ 10,000,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust | First Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Interest rate			0.50%
Debt instrument, description of variable rate basis						30-day U.S. LIBOR
Line of credit facility, maximum borrowing capacity			$ 15,000,000
Long term debt		$ 8,000,000
Line of credit facility, remaining borrowing capacity				7,000,000		$ 7,000,000
Debt Instrument, Payment Terms						The Company was required to pay accrued interest only on the outstanding $8.0 million balance through December 31, 2017, followed by 30 equal payments of principal and accrued interest.
Final payment during maturity				$ 500,000		$ 500,000
Debt instrument, maturity date						Jun. 1, 2020
Repay all the amount outstanding under the loan agreement including fees		$ 5,300,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust | First Amended and Restated Loan and Security Agreement | Final Payment
Debt Instrument [Line Items]
Repay all the amount outstanding under the loan agreement including fees	$ 7,000,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust | First Amended and Restated Loan and Security Agreement | Prepayments Through May 31, 2020
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount of the aggregate term loans			2.00%
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust | Floating Interest Rate | First Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Interest rate			7.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Interest rate	1.89%
Debt instrument, description of variable rate basis						30-day U.S. LIBOR
Line of credit facility, maximum borrowing capacity	$ 20,000,000
Long term debt	10,000,000
Debt instrument, maturity date						Oct. 1, 2022
Final payment during maturity, percentage						5.50%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement | Term B Loan
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity								$ 5,000,000
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement | Term C Loan
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity								$ 5,000,000
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement | Prepayment Prior the First Anniversary
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount of the each term loan				3.00%		3.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Second Amended and Restated Loan and Security Agreement | Prepayment on or After First Anniversary but Prior to October 1, 2022
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount of the each term loan				2.00%		2.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | First Amended and Restated Loan and Security Agreement, Initial Tranche
Debt Instrument [Line Items]
Long term debt	$ 10,000,000
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust | Floating Interest Rate | Second Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Interest rate	6.50%

Long-Term Debt - Scheduled Paym

Long-Term Debt - Scheduled Payments for the Second Amended and Restated Loan and Security Agreement (Details) - Second Amended and Restated Loan and Security Agreement $ in Thousands	Jun. 30, 2018USD ($)
Debt Instrument [Line Items]
Principal, 2019	$ 556
Principal, 2020	3,333
Principal, 2021	3,333
Principal, 2022	2,778
Principal	10,000
Interest and Final Payment, 2018	429
Interest and Final Payment, 2019	845
Interest and Final Payment, 2020	651
Interest and Final Payment, 2021	365
Interest and Final Payment, 2022	638
Interest and Final Payment	2,928
Total, 2018	429
Total, 2019	1,401
Total, 2020	3,984
Total, 2021	3,698
Total, 2022	3,416
Total	$ 12,928

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Equity [Abstract]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares outstanding	32,024,223	25,354,651

Stock Purchase Warrants - Addit

Stock Purchase Warrants - Additional Information (Details) - Convertible Stock Warrant - First Amended and Restated Loan and Security Agreement - $ / shares	1 Months Ended	6 Months Ended
	Sep. 30, 2016	Jun. 30, 2018
Class Of Warrant Or Right [Line Items]
Class of warrant Exercise	$ 10.74
Warrants expiration term	2026-09
Weighted average remaining life of warrants		8 years 3 months
Maximum
Class Of Warrant Or Right [Line Items]
Number of stock that can be purchased by each warrant	29,796

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-based Compensation Expense (Details) - Stock Options - 2011 Stock Incentive Plan, 2016 Equity Incentive Plan - 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]
Share-based compensation expense	$ 1,196	$ 770	$ 2,329	$ 1,513
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	443	332	873	657
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 753	$ 438	$ 1,456	$ 856

Share-Based Compensation - Su39

Share-Based Compensation - Summary of Activity Related to Stock Options (Details) - Stock Options - $ / shares	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Options outstanding, Beginning balance	3,075,349
Number of Shares, Granted	318,750
Number of Shares, Exercised	(123,724)
Number of Shares, Forfeited	(49,875)
Number of Shares, Options outstanding, Ending balance	3,220,500
Number of Shares, Options exercisable	1,278,725	1,114,286
Weighted Average Exercise Price, Options outstanding, Beginning balance	$ 6.17
Weighted Average Exercise Price, Granted	8.93
Weighted Average Exercise Price, Exercised	3.51
Weighted Average Exercise Price, Forfeited	8.12
Weighted Average Exercise Price, Options outstanding, Ending balance	6.51
Weighted Average Exercise Price, Options exercisable	$ 4.90	$ 3.94

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
2016 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock purchased			17,078
Share-based compensation expense	$ 3,000	$ 9,000	$ 9,000	$ 18,000
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to unvested stock options	$ 11,300,000		$ 11,300,000
Expected to be recognized over a weighted average period			2 years 8 months 12 days

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2016USD ($)ft²	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)
Commitment And Contingencies [Line Items]
Rent expense		$ 58,000	$ 58,000	$ 116,000	$ 98,000
GEORGIA
Commitment And Contingencies [Line Items]
Area of office leased | ft²	20,000
Operating lease agreement term	6 years 6 months
Operating lease agreement renewal option term	5 years
Minimum monthly lease payments	$ 35,145
Percentage of increase per year	3.00%

Commitment and Contingencies 42

Commitment and Contingencies - Total Future Minimum Commitments Due Under Non-Cancelable Operating Leases (Details) $ in Thousands	Jun. 30, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,018	$ 217
2,019	444
2,020	458
2,021	472
Thereafter	860
Total minimum lease payments	$ 2,451

License and Collaboration Agr43

License and Collaboration Agreements - Additional Information (Detail) - USD ($)	Jan. 01, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2016	Aug. 31, 2014
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue		$ 130,000		$ 135,000
Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Other short-term collaboration agreements performance obligations period			1 month
Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Other short-term collaboration agreements performance obligations period			2 months
Collaboration Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue		125,000		125,000
ASU 2014-09
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cumulative adjustment to accumulated deficit	$ 160,000
NovaMedica
Research And Development Arrangement Contract To Perform For Others [Line Items]
Patent expirations period			2,027
NovaMedica | License
Research And Development Arrangement Contract To Perform For Others [Line Items]
Revenue		$ 5,000		$ 10,000
NovaMedica | ASU 2014-09
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cumulative adjustment to accumulated deficit	$ 160,000
NovaMedica | Upfront payment
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue					$ 200,000	$ 200,000

Available-for-Sale Investment44

Available-for-Sale Investments - Summary of Company's Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 49,245
Fair Value	49,245	$ 28,416
Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	40,784
Fair Value	40,784
Treasury Bills
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,461
Fair Value	$ 8,461

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Short-term investments maturity start period	90 days
Short-term investments maturity end period	365 days
Significant transfers between Levels 1, 2 and 3	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial Assets:
Total financial assets	$ 84,790	$ 38,000
Treasury Bills
Financial Assets:
Total financial assets	8,462
Corporate Bonds
Financial Assets:
Total financial assets		5,064
Commercial Paper
Financial Assets:
Total financial assets	55,055	10,154
Cash and Money Markets
Financial Assets:
Total financial assets	20,913	9,224
Restricted Cash Money Market
Financial Assets:
Total financial assets	360	360
Government Bonds
Financial Assets:
Total financial assets		11,238
Certificates of Deposit
Financial Assets:
Total financial assets		1,960
Level 1
Financial Assets:
Total financial assets	29,735	20,822
Level 1 | Treasury Bills
Financial Assets:
Total financial assets	8,462
Level 1 | Cash and Money Markets
Financial Assets:
Total financial assets	20,913	9,224
Level 1 | Restricted Cash Money Market
Financial Assets:
Total financial assets	360	360
Level 1 | Government Bonds
Financial Assets:
Total financial assets		11,238
Level 2
Financial Assets:
Total financial assets	55,055	17,178
Level 2 | Corporate Bonds
Financial Assets:
Total financial assets		5,064
Level 2 | Commercial Paper
Financial Assets:
Total financial assets	$ 55,055	10,154
Level 2 | Certificates of Deposit
Financial Assets:
Total financial assets		$ 1,960

Net Loss Per Share - Potential

Net Loss Per Share - Potential Common Stock Equivalents Excluded from Computation of Diluted 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]
Antidilutive securities excluded from computation of earnings per share	3,250,296	2,265,174	3,250,296	2,265,174
Outstanding Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	3,220,500	2,235,378	3,220,500	2,235,378
Stock Purchase Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	29,796	29,796	29,796	29,796