Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2016	Mar. 24, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	CERU
Entity Registrant Name	CERULEAN PHARMA INC.
Entity Central Index Key	0001401914
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		29,021,455
Entity Public Float			$ 47,569,338

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 34,950	$ 75,908
Accounts receivable, prepaid expenses, and other current assets	1,840	1,394
Total current assets	36,790	77,302
Property and equipment, net	668	576
Other assets	230	347
Total	37,688	78,225
Current liabilities:
Current portion of loan payable	8,382	7,652
Accounts payable	1,446	2,226
Accrued expenses	4,611	6,459
Current portion of deferred revenue	2,500
Total current liabilities	16,939	16,337
Long-term liabilities:
Loan payable, net of current portion	4,439	12,672
Deferred revenue	1,993
Other long-term liabilities	1,206	473
Total long-term liabilities	7,638	13,145
Commitments (Note 11)
Stockholders’ equity:
Preferred stock $0.01 par value; 5,000,000 shares authorized, no shares issued or outstanding
Common stock, $0.0001 par value; 120,000,000 shares authorized, 28,937,185 and 27,346,780 shares issued and outstanding at December 31, 2016 and 2015, respectively	3	3
Additional paid-in capital	213,788	210,115
Accumulated deficit	(200,680)	(161,375)
Total stockholders’ equity	13,111	48,743
Total	$ 37,688	$ 78,225

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	28,937,185	27,346,780
Common stock, shares outstanding	28,937,185	27,346,780

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 766								$ 766		$ 80
Operating expenses:
Research and development	3,184	$ 7,089	$ 7,522	$ 9,770	$ 7,157	$ 7,092	$ 6,678	$ 5,021	27,565	$ 25,948	11,772
General and administrative	2,090	2,374	2,773	3,118	2,872	2,954	2,717	2,681	10,355	11,224	8,587
Total operating expenses	5,274	9,463	10,295	12,888	10,029	10,046	9,395	7,702	37,920	37,172	20,359
Other income (expense):
Interest income	20	25	25	16	2	4	1	3	86	10	9
Interest expense	(457)	(521)	(589)	(670)	(689)	(509)	(513)	(721)	(2,237)	(2,432)	(1,083)
Loss on extinguishment of debt											(2,493)
Decrease in value of preferred stock warrant liability											504
Total other income (expense), net	(437)	(496)	(564)	(654)	(687)	(505)	(512)	(718)	(2,151)	(2,422)	(3,063)
Net loss attributable to common stockholders	$ (4,945)	$ (9,959)	$ (10,859)	$ (13,542)	$ (10,716)	$ (10,551)	$ (9,907)	$ (8,420)	$ (39,305)	$ (39,594)	$ (23,342)
Net loss per share attributable to common stockholders:
Basic and diluted	$ (0.17)	$ (0.36)	$ (0.40)	$ (0.49)	$ (0.39)	$ (0.39)	$ (0.37)	$ (0.41)	$ (1.42)	$ (1.56)	$ (1.60)
Weighted-average common shares outstanding:
Basic and diluted	28,724,083	27,383,376	27,363,965	27,362,643	27,346,780	27,307,103	26,690,673	20,350,557	27,710,403	25,431,332	14,548,516

Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Term Loan Facility [Member]	IPO [Member]	Follow-on Offering [Member]	Private Placement [Member]	Common Stock Purchase Agreement [Member]	Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] IPO [Member]	Common Stock [Member] Follow-on Offering [Member]	Common Stock [Member] Private Placement [Member]	Common Stock [Member] Common Stock Purchase Agreement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Term Loan Facility [Member]	Additional Paid-in Capital [Member] IPO [Member]	Additional Paid-in Capital [Member] Follow-on Offering [Member]	Additional Paid-in Capital [Member] Private Placement [Member]	Additional Paid-in Capital [Member] Common Stock Purchase Agreement [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2013	$ (94,299)												$ 4,140						$ (98,439)
Redeemable convertible preferred stock, Beginning balance at Dec. 31, 2013							$ 81,525
Beginning balance, shares at Dec. 31, 2013								785,531
Redeemable convertible preferred stock, Beginning balance, shares at Dec. 31, 2013							85,207,356
Exercise of stock options	140												140
Exercise of stock options, shares								41,566
Stock-based compensation	885												885
Issuance of Common Stock			$ 59,862						$ 1						$ 59,861
Issuance of Common Stock, shares									9,569,715
Conversion of convertible preferred stock into common stock	81,526						$ (81,525)	$ 1					81,525
Conversion of convertible preferred stock into common stock, shares							(85,207,356)	6,826,004
Reclassification/Issuance of warrants			$ 424												$ 424
Conversion of convertible notes	20,129												20,129
Conversion of convertible notes, shares								2,902,233
Net loss	(23,342)																		(23,342)
Ending balance at Dec. 31, 2014	45,325							$ 2					167,104						(121,781)
Ending balance, shares at Dec. 31, 2014								20,125,049
Exercise of stock options	1,628												1,628
Exercise of stock options, shares								370,230
Stock-based compensation	2,375												2,375
Issuance of Common Stock				$ 37,185	$ 1,000					$ 1						$ 37,184	$ 1,000
Issuance of Common Stock, shares								6,716,000		6,716,000	135,501
Reclassification/Issuance of warrants		$ 824												$ 824
Net loss	(39,594)																		(39,594)
Ending balance at Dec. 31, 2015	48,743							$ 3					210,115						(161,375)
Ending balance, shares at Dec. 31, 2015								27,346,780
Issuance of common stock from employee stock purchase plan	78												78
Issuance of common stock from employee stock purchase plan, shares								37,712
Issuance of common stock for services	54												54
Issuance of common stock for services, shares								52,693
Stock-based compensation	2,755												2,755
Issuance of Common Stock						$ 786												$ 786
Issuance of Common Stock, shares												1,500,000
Net loss	(39,305)																		(39,305)
Ending balance at Dec. 31, 2016	$ 13,111							$ 3					$ 213,788						$ (200,680)
Ending balance, shares at Dec. 31, 2016								28,937,185

Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Preferred stock, par value	$ 0.01	$ 0.01
Common stock, par value	$ 0.0001	$ 0.0001
Stock issuance costs			$ 187
IPO [Member]
Stock issuance costs			$ 7,126
Common Stock Purchase Agreement [Member]
Stock issuance costs	$ 214
Follow-on Offering [Member]
Stock issuance costs		$ 3,111

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (39,305)	$ (39,594)	$ (23,342)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,755	2,375	885
Noncash rent expense	153	(41)	29
Change in carrying value of preferred stock warrant liability			(504)
Depreciation and amortization	261	192	126
(Gain) loss on disposal of property and equipment	4	(6)	(28)
Loss on extinguishment of debt			2,493
Amortization of debt discount and deferred financing costs	420	739	215
Deferred revenue	5,000
Amortization of deferred revenue	(507)
Changes in operating assets and liabilities:
Accounts receivable, prepaid expenses and other current assets	(446)	342	(695)
Accounts payable	(603)	795	341
Accrued expenses	(1,268)	3,283	1,419
Net cash used in operating activities	(33,536)	(31,915)	(19,061)
Cash flows from investing activities:
Purchases of property and equipment	(535)	(277)	(225)
Proceeds from sale of property and equipment		23	40
Increase (decrease) in restricted cash	117	(230)
Net cash used in investing activities	(418)	(484)	(185)
Cash flows from financing activities:
Proceeds from sale of common stock	918	2,628	140
Proceeds from public stock offering, net		37,185	59,862
Proceeds from loan payable		21,000
Proceeds from issuance of convertible promissory notes			8,500
Payments on loan payable	(7,922)	(3,321)	(3,348)
Cash paid for debt issuance costs		(359)	(222)
Net cash (used in) provided by financing activities	(7,004)	57,133	64,932
Net increase (decrease) in cash and cash equivalents	(40,958)	24,734	45,686
Cash and cash equivalents — Beginning of year	75,908	51,174	5,488
Cash and cash equivalents — End of year	34,950	75,908	51,174
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment in accounts payable		177
Conversion of redeemable convertible preferred stock into common stock			81,526
Conversion of convertible notes and accrued interest into common stock, net			20,129
Reclassification of warrants to additional paid-in capital			424
Warrants issued with term loan facility		824
Supplemental cash flow information — Interest paid	$ 1,293	$ 1,000	$ 400

Nature of Business and Operations

12 Months Ended

Dec. 31, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Business and Operations

1.	NATURE OF BUSINESS AND OPERATIONS

Nature of Business — Cerulean Pharma Inc. (the “Company”) was incorporated on November 28, 2005, as a Delaware corporation and is located in Waltham, Massachusetts. The Company was formed to develop novel, nanotechnology-based therapeutics in the areas of oncology and other diseases. In 2013, the Company formed a wholly owned subsidiary, Cerulean Pharma Australia Pty Ltd as an Australian-based proprietary limited company to perform clinical activities in Australia.

The Company's operations have consisted primarily of raising capital, product research and development, and initial market development.

The Company has not generated any revenue related to its primary business purpose to date and is subject to a number of risks common to other development stage life science companies, including dependence on key individuals, competition from other companies, the need for development of commercially viable products, and the need to obtain adequate additional financing to fund the development of product candidates. The Company is also subject to a number of risks similar to other companies in the industry, including rapid technological change, regulatory approval of products, uncertainty of market acceptance of products, competition from substitute products and larger companies, the need to obtain additional financing, compliance with government regulations, protection of proprietary technology, dependence on third parties, product liability and dependence on key individuals.

The Company has an accumulated deficit of $200.7 million at December 31, 2016. The Company has financed its operations primarily through private placements of its preferred stock, proceeds from borrowings, an initial public offering completed in 2014 and a follow-on offering completed in 2015. In October 2016 the Company entered into a collaboration with Novartis Institutes for BioMedical Research, Inc. (“Novartis”) to develop nanoparticle-drug conjugates combining the Company’s proprietary Dynamic Tumor Targeting technology with Novartis’ proprietary compounds. Under this collaboration the Company received important funding to support its research program. The Company has not completed development of any product candidate and has devoted substantially all of its financial resources and efforts to research and development, including preclinical and clinical development. Accordingly, the Company will continue to depend on its ability to raise capital through equity and debt issuances and/or through strategic partnerships. The Company expects to continue to incur significant expenses and increasing operating losses for at least several years.

As of December 31, 2016, the Company had cash and cash equivalents of $35.0 million. The Company has no other sources of significant liquidity in place as of December 31, 2016. The Company expects that its existing cash and cash equivalents will fund its operations into the second half of 2017 based on the Company’s 2017 operating plan. The Company has undertaken a strategic review of potential financing alternatives such as the sale of the company, a merger, a business combination, a strategic investment into the company, or a sale, license or disposition of assets of the Company. If the Company is unable to obtain additional funding on a timely basis, it may be required to curtail or terminate research and development activities under its collaboration agreement with Novartis, or to scale back, suspend or terminate its business operations.

As more fully discussed in Note 17 Subsequent Events, pursuant to management’s plans, in March 2017 the Company entered into a series of transactions including the payoff of its note payable to Hercules Capital for $12.4 million. The Company sold and assigned all of its right, title and interest in and to its clinical product candidates CRLX101 and CRLX301 for proceeds of $1.5 million. The Company also agreed to sell and assign to Novartis all of its right, title and interest in and to the patent rights, know-how and third-party license agreements relating to its Dynamic Tumor Targeting Platform technology for proceeds of $6.0 million, whereby the proceeds from this asset sale are to be received upon closing of the transaction. The Company also entered into a Stock Purchase Agreement with Daré Biosciences, Inc., which if approved by the shareholders, will be consummated by an exchange of common stock shares and no cash consideration paid or received.

With exception of the payoff of the note payable and the sale of the clinical product candidates, these transactions are subject to certain closing conditions. There can be no assurances that these transactions will be consummated prior to the exhaustion of the Company’s cash and cash equivalent resources, if at all.

The foregoing matters give rise to substantial doubt about the Company’s ability to continue as a going concern. The accompanying financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Significant Accounting Policies

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Significant Accounting Policies

2.	SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates — The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America 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 revenues and expenses during the reporting period.

On an ongoing basis, the Company's management evaluates its estimates, including estimates related to clinical trial accruals, stock-based compensation expense, and reported amounts of revenues and expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Although the Company regularly assesses these estimates, actual results could differ from those estimates. Changes in estimates are recorded in the period in which they become known.

Principles of Consolidation — The consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated.

Segment Information — Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment; however, the Company operates in two geographic regions: United States (Waltham, MA) and Australia (Sydney, NSW). There is no revenue generated or long-lived assets located within the Australian location.

Cash and Cash Equivalents — Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase and consist primarily of money market funds.

Concentrations of Credit Risk — Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. Substantially all of the Company’s cash and cash equivalents are held at one financial institution that management believes to be of high-credit quality. Deposits with this financial institution may exceed the amount of insurance provided on such deposits; however these deposits may be redeemed upon demand and, therefore, bear minimal risk.

Restricted Cash — At December 31, 2016 and 2015, the Company had restricted cash of $230,000 and $347,000, respectively. The restricted cash balances were used to collateralize stand-by letters of credit issued by the Company as a security deposit for its current and former facility leases. The balance at December 31, 2016, was with respect to the Company’s current facility lease which is scheduled to expire in February 2021. The balance at December 31, 2015, includes the balance for the current facility lease and the Company’s former facility lease which was scheduled to expire in February 2016 but was terminated early on December 31, 2015. The restricted cash is included within other assets in the balance sheet.

Property and Equipment — Property and equipment are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Repairs and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment.

Depreciation is provided using the straight-line method over the following estimated useful lives:

Laboratory equipment		5 years
Computer equipment		3 years
Office furniture and equipment		5 years
Leasehold improvements		Lesser of useful life or remaining lease term

Impairment of Long-Lived Assets — Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If this comparison indicates that there is impairment, the amount of impairment is calculated as the difference between the carrying value and fair value. For the years ended December 31, 2016 and 2015, the Company has not recorded an impairment charge for its long-lived assets.

Revenue Recognition —

Collaborative Research and Development and Multiple-Element Arrangements

The Company has entered into a collaboration arrangement with a strategic partner for the development and commercialization of product candidates utilizing the Company’s technologies. The agreement provides for multiple deliverables by the Company (for example, license rights, research and development services and manufacturing of clinical materials) in exchange for consideration to the Company of a combination of non-refundable upfront fees, research and development funding, payments based upon achievement of clinical development or other milestones and royalties in the form of designated percentages of product net sales.

Revenue is recognized when there is persuasive evidence that an arrangement exists, delivery has occurred, the price is fixed and determinable and collection is reasonably assured. Multiple-element arrangements, such as license and development agreements, are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting. When deliverables are separable, consideration received is allocated to the separate units of accounting based on the relative selling price method and the appropriate revenue recognition principles are applied to each unit. When the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed, and revenue will be recognized over the performance period.

Deferred Revenue

Amounts received prior to satisfying the above revenue recognition criteria are recorded as deferred revenue in the accompanying consolidated balance sheets. Amounts not expected to be recognized within one year following the balance sheet date are classified as non-current deferred revenue.

Research and Development Costs — Research and development expenses consist of expenses incurred in performing research and development activities, including compensation and benefits for full-time research and development employees, an allocation of facilities expenses, overhead expenses, manufacturing process-development and scale-up activities, clinical trial and related clinical manufacturing expenses, fees paid to clinical research organizations, or CROs, and investigative sites, payments to universities under the Company’s license agreements and other outside expenses. In the early phases of development, the Company’s research and development costs are often devoted to expanding its product platform and are not necessarily allocable to a specific target. Research and development costs are expensed as incurred. Nonrefundable advanced payments, if any, for goods and services used in research and development are recognized as an expense as the related goods are delivered or services are performed.

Stock-Based Compensation — The Company accounts for stock-based awards at fair value, which is measured using the Black-Scholes option-pricing model. The fair value measurement date for employee awards is generally the date of grant. The fair value measurement date for nonemployee awards is generally the date the performance of services is completed. Stock-based compensation costs are recognized as an expense over the requisite service period, which is generally the vesting period, on a straight-line basis for all time-vested awards. The Company issued performance based grants where the vesting of the grant is tied to certain milestone performance and in these cases, the compensation is recognized as expense when the probability of the milestone is met.

Stock-based awards to nonemployees are remeasured at each reporting date and recognized as services are rendered, generally on a straight-line basis. The Company believes that the fair value of these awards is more reliably measurable than the fair value of the services rendered. Stock-based compensation is classified in the accompanying consolidated statements of operations in the department where the related services are provided.

Net Loss per Share Attributable to Common Stockholders — Basic net loss attributable to common stockholders per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period. During periods where the Company might earn net income, the Company would allocate participating securities a proportional share of net income determined by dividing total weighted average participating securities by the sum of the total weighted average common shares and participating securities (the “two-class method”). Participating securities have the effect of diluting both basic and diluted earnings per share during periods of income. During periods where the Company incurred net loss, the Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. The Company computes diluted loss per common share after giving consideration to the dilutive effect of stock options and warrants that are outstanding during the period, except where such nonparticipating securities would be antidilutive.

Income Taxes — Deferred income taxes are provided for the temporary differences arising between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and for operating loss carryforwards and credits. Deferred tax assets and liabilities are recorded using tax rates expected to be in effect in the year in which the differences are expected to reverse. A valuation allowance is provided for any net deferred tax assets for which management believes it is more likely than not that the net deferred tax assets will not be realized.

The Company provides liabilities for potential payment 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 filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At December 31, 2016 and 2015, the Company had approximately $0.7 million and $0.6 million, respectively, of total unrecognized tax benefits, which would affect income tax expense if recognized, before consideration of its valuation allowance. During fiscal year 2016, the Company did not make any payment of interest and penalties on unrecognized tax benefits. In addition, there was nothing accrued for in the consolidated balance sheets for the payment of interest and penalties at December 31, 2016.

Guarantees and Indemnification — As permitted under Delaware law, the Company indemnifies its officers and directors employees for certain events or occurrences while the officer or director is, or was serving at the Company’s request in such a capacity. The term of the indemnification is for the officer’s or director’s lifetime. During the year ended December 31, 2016, the Company did not experience any losses related to these indemnification obligations. The Company does not expect significant claims related to these indemnification obligations, and consequently, has concluded the fair value of these obligations is not material. Accordingly, as of December 31, 2016 no amounts have been accrued related to such indemnification provisions.

Recent Accounting Pronouncements — In November 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update 2016-18, “Statement of Cash Flows - Restricted Cash (Topic 230)”. This new standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for annual and interim reporting periods beginning after December 15, 2017, and required retrospective application. The Company is currently evaluating the effect this standard will have on its consolidated financial statements and related disclosures.

In August 2016, the FASB issued Accounting Standards Update 2016-15, “Statement of Cash Flows (Topic 230)” (“ASU 2016-15”). ASU 2016-15 provides guidance to clarify how cash payments for debt prepayment or debt extinguishment costs are to be classified in the statement of cash flows. The standard is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company is currently evaluating the effect this standard will have on its consolidated financial statements and related disclosures.

In March 2016, the FASB issued Accounting Standards Update 2016-09, “Compensation – Stock Compensation (Topic 718)” (“ASU 2016-09”). ASU 2016-09 is intended to simplify various aspects of how share-based payments are accounted for and presented in financial statements. The standard is effective prospectively for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016, with early adoption permitted. For amendments that are to be applied on a modified retrospective basis, a cumulative-effect adjustment will be calculated on the first day of the fiscal year of adoption, which will be recorded in retained earnings. The Company has early adopted ASU 2016-09 for its quarter ended December 31, 2016. As a result of the Company’s adoption of ASU 2016-09, it will track option deductions in its net operating loss deferred tax asset on a modified retrospective basis, and has included the option deductions in the December 31, 2016 deferred tax assets. In addition, the Company’s policy has been to estimate forfeitures as of the grant date. The Company will continue to maintain its policy to estimate forfeiture as of the grant date in the future. The gross deferred tax asset and valuation allowance as of December 31, 2016, increased $163,000 as a result of the cumulative effect of adoption of ASU 2016-09. The adoption of ASU 2016-09 did not have a material impact on the Company’s financial statements for the year ended and as of December 31, 2016.

In February 2016, the FASB issued Accounting Standards Update 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which provides new accounting guidance on leases. ASU 2016-02 requires lessees to recognize leases on their balance sheets, and leaves lessor accounting largely unchanged. The amendments in ASU 2016-02 are effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early application is permitted for all entities. ASU 2016-02 requires a modified retrospective approach for all leases existing at, or entered into after, the date of initial application, with an option to elect to use certain transition relief. The Company is currently evaluating the impact of this new standard on its consolidated financial statements and related disclosures.

In August 2014, the FASB issued Accounting Standards Update 2014-15, “Presentation of Financial Statements – Going Concern (Subtopic 205-40): Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern” (“ASU 2014-15”). ASU 2014-15 requires management to evaluate, at each annual and interim reporting period, whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern and provide related disclosures. ASU 2014-15 is effective for annual and interim reporting periods beginning January 1, 2017 and is not expected to have a material impact on the Company’s consolidated financial statements.

In May 2014, the FASB issued Accounting Standards Update 2014-09 (ASC 606), “Revenue from Contracts with Customers” (ASU 2015-09), which affects any entity that either enters into contracts with customers to transfer goods and services or enters into contracts for the transfer of nonfinancial assets. In August 2015, the FASB issued Accounting Standards Update 2015-14, “Revenue from Contracts with Customers” which defers the effective date of ASU 2014-09 for all entities by one year. ASU 2014-09, which has been codified with the Accounting Standards Codification as Topic 606, is now effective for public companies for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. ASC 606 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. In addition, ASC 606 provides guidance on accounting for certain revenue-related costs including, but not limited to, when to capitalize costs associated with obtaining and fulfilling a contract. ASC 606 provides companies with two implementation methods. Companies can choose to apply the standard retrospectively to each prior reporting period presented (full retrospective application) or retrospectively with the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings of the annual reporting period that includes the date of initial application (modified retrospective application). Since ASU 2014-09 was issued, several additional Accounting Standards Updates have been issued and incorporated within ASC 606 to clarify various elements of the guidance. The Company plans to adopt this guidance on January 1, 2018. The Company has not yet determined whether it will utilize the full retrospective or the modified retrospective adoption method and continues to evaluate the impact that adoption will have on its consolidated financial statements.

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

3.	NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except share data and per share data):

	Years Ended December 31,
	2016			2015			2014
Net loss attributable to common stockholders — basic and diluted	$	(39,305	)	$	(39,594	)	$	(23,342	)
Weighted-average number of common shares — basic and diluted		27,710,403			25,431,332			14,548,516
Net loss per share attributable to common stockholders — basic and diluted	$	(1.42	)	$	(1.56	)	$	(1.60	)

The Company has reported a net loss for all periods presented, therefore diluted net loss per common share is the same as basic net loss per common share.

The following potentially dilutive securities outstanding have been excluded from the computation of diluted weighted-average shares outstanding, because such securities had an antidilutive impact due to the losses reported (in common stock equivalent shares):

	As of December 31,
	2016		2015		2014
Options to purchase common stock		4,020,288		3,454,926		2,126,176
Warrants to purchase common stock		365,564		300,564		128,663

Property and Equipment

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

Property and Equipment

4.	PROPERTY AND EQUIPMENT

Property and equipment consist of the following (in thousands):

	As of December 31,
	2016			2015
Laboratory equipment	$	1,548		$	1,314
Computer equipment		371			350
Office furniture and equipment		66			25
Leasehold improvements		75			33
		2,060			1,722
Less accumulated depreciation and amortization		(1,392	)		(1,146	)
Property and equipment, net	$	668		$	576

Depreciation and amortization expense for the years ended December 31, 2016, 2015, and 2014, was $261,000, $192,000, and $126,000, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2016

Payables And Accruals [Abstract]

Accrued Expenses

5.	ACCRUED EXPENSES

Accrued expenses consist of the following (in thousands):

	As of December 31,
	2016		2015
Accrued clinical trial costs	$	2,648	$	2,631
Accrued contract manufacturing expenses		226		945
Accrued compensation and benefits		1,080		1,864
Accrued interest		82		136
Other accrued expenses		575		883
Total accrued expenses	$	4,611	$	6,459

Loan Agreements

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Loan Agreements

6.	LOAN AGREEMENTS

On January 8, 2015 (the “Closing Date”), the Company entered into a term loan facility of up to $26.0 million (the “Term Loan”) with Hercules Technology Growth Capital, Inc. (“Hercules”). The proceeds were used to repay the Company’s existing term loan facility with Lighthouse Capital Partners VI, L.P. (“Lighthouse Capital”) and for general corporate and working capital purposes. At December 31, 2016, the Company had $13.1 million in principal outstanding under the Term Loan.

The Term Loan is governed by a loan and security agreement, dated January 8, 2015, between the Company and Hercules (the “Hercules Loan Agreement”). The Hercules Loan Agreement provided for up to three separate borrowings, the first of which was funded in the amount of $15.0 million on the Closing Date. On November 24, 2015, the Company drew a second tranche in the amount of $6.0 million. The Company elected not to commence a randomized Phase 2 clinical study of CRLX101 in combination with chemoradiotherapy on or prior to December 15, 2015, which was a condition of obtaining an additional tranche in an amount of up to $5.0 million. As a result, the Company is no longer eligible to borrow this amount under the Term Loan.

The Term Loan will mature on July 1, 2018. Each advance under the Term Loan accrues interest at a floating per annum rate equal to the greater of (i) 7.30% or (ii) the sum of 7.30% plus the prime rate minus 5.75%. The Term Loan provided for interest-only payments on a monthly basis until December 31, 2015. Thereafter, payments are payable monthly in equal installments of principal and interest to fully amortize the outstanding principal over the remaining term of the loan, subject to recalculation upon a change in the prime rate. The Company may prepay the Term Loan in whole or in part upon seven business days’ prior written notice to Hercules. Any such prepayment of the Term Loan is subject to a prepayment charge of 1.0%. Amounts outstanding during an event of default are payable upon Hercules’ demand and shall accrue interest at an additional rate of 5.0% per annum of the past due amount outstanding. The minimum future principal payments are as follows (in thousands):

Year Ending December 31,
2017	$	8,533
2018		4,544
Unamortized discount relating to warrants and deferred financing costs		(256	)
Total		12,821
Less current portion		(8,382	)
Long-term portion	$	4,439

At the end of the loan term (whether at maturity, by prepayment in full or otherwise), the Company shall pay a final end of term charge to Hercules in the amount of 6.7% of the aggregate original principal amount advanced by Hercules. The amount of the end of term charge is being accrued over the loan term as interest expense. As of December 31, 2016, the Company has accrued $1.1 million related to the end of term charge, which has been classified as other long-term liabilities.

In connection with the Hercules Loan Agreement, the Company issued to Hercules a warrant to purchase shares of the common stock of the Company at an exercise price of $6.05 per share. The warrant is exercisable for 171,901 shares of common stock. The warrant is exercisable until January 8, 2020. The Company estimated the fair value of the warrant for shares exercisable on the issue date in January 2015 to be $824,000. The value of the warrant was recorded as a discount to the loan. The fair value of the warrant was estimated on the date of issue for the exercisable shares at that date using the Black-Scholes option-pricing model. The following table shows the Black-Scholes assumptions used to value the warrant:

	January 8, 2015
Contractual life	5 years
Volatility rate		61	%
Risk-free interest rate		1.5	%
Expected dividends		—

At December 31, 2016, the Company’s balance of unamortized deferred financing costs and unamortized debt discount were $0.1 million and $0.2 million, respectively. These costs are being amortized to interest expense using the effective interest method over the term of the loan.

In connection with the Hercules Loan Agreement, the Company entered into a stock purchase agreement with Hercules, whereby Hercules purchased 135,501 shares of common stock from the Company at a price per share of $7.38, which was equal to the closing price of the common stock on the NASDAQ Global Market on January 7, 2015, for an aggregate purchase price of approximately $1.0 million.

In December 2011, the Company entered into a loan and security agreement with Lighthouse Capital to borrow up to $10.0 million in one or more advances by December 31, 2012. In both March 2012 and August 2012, the Company borrowed $5.0 million under the loan and security agreement, for a total of $10.0 million. This amount was being repaid over 36 months beginning on December 1, 2012, at an interest rate of 8.25%. In addition, the Company was required to make an additional payment in the amount of $600,000 at the end of the loan term. The amount was accrued over the loan term as interest expense. The amount accrued as of December 31, 2014 was $574,000, and it was included in accrued expense in the Company’s consolidated balance sheet. In January 2015, the Company repaid in full the amount outstanding under the Lighthouse Capital agreement, or $3.6 million, with the proceeds from the Hercules Loan Agreement.

In connection with the loan and security agreement with Lighthouse Capital, the Company issued Lighthouse Capital a warrant to purchase a maximum of 66,436 shares of the Company’s Series D Preferred Stock, at an exercise price of $12.04 per share and with an expiration date 10 years from the date of issue (December 2021). The Company determined the fair value of the warrant at the end of each reporting period using the Black-Scholes option pricing model until the warrant converted to a warrant to purchase 66,436 shares of common stock upon the completion of the IPO. The value of the warrant was recorded as a discount to the loan and was being amortized as interest expense using the effective interest method over the 36-month repayment term. The unamortized discount relating to the warrants, or $0.2 million, was expensed as interest expense upon repayment of the loan in January 2015.

Stockholder's Equity

12 Months Ended

Dec. 31, 2016

Stockholders Equity Note [Abstract]

Stockholder's Equity (Deficit)

7.	STOCKHOLDERS’ EQUITY

Common Stock — In 2015, the Company issued 6,716,000 shares of common stock in connection with an underwritten public offering and during 2014 the Company issued 19,297,952 shares of common stock in connection with its IPO, the conversion of preferred stock and convertible notes into common stock, and the partial exercise of the underwriters’ overallotment option in the IPO.

Common Stock Purchase Agreement – On October 14, 2016, the Company entered into a common stock purchase agreement (the “Purchase Agreement”) with Aspire Capital Fund, LLC (“Aspire Capital”), which provides that, upon the terms and subject to the conditions and limitations set forth therein, Aspire Capital is committed to purchase up to an aggregate of $20.0 million of shares of the Company’s common stock over a term of 24 months from the execution of the Purchase Agreement. Immediately following the execution of the Purchase Agreement, the Company made an initial sale to Aspire Capital under the Purchase Agreement of 800,000 shares of common stock at a price of $1.25 per share, for gross proceeds of $1.0 million, and concurrently entered into a registration rights agreement with Aspire Capital registering the shares of the Company’s common stock that have been and may be issued to Aspire Capital under the Purchase Agreement. In consideration for entering into the Purchase Agreement, the Company issued to Aspire Capital 700,000 shares of the Company’s common stock as a commitment fee. The net proceeds of the Aspire Capital transaction, after offering expenses, to the Company were approximately $786,000. At December 31, 2016, up to $19.0 million of the Company’s common stock that may be sold at the prevailing share price at the time of sale subject to conditions specified in the Purchase Agreement remains available.

Reserved Shares of Common Stock — The Company has reserved the following number of shares of common stock at December 31, 2016 and 2015:

	As of December 31,
	2016		2015
Warrants to purchase common stock		365,564		300,564
Common stock options		4,020,288		3,995,876
Total		4,385,852		4,296,440

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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+ Details

Stock Option Plans

12 Months Ended

Dec. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Plans

8.	STOCK OPTION PLANS

2007 Stock Incentive Plan – The Company’s 2007 Incentive Stock Plan, or the 2007 Plan, provides for the grant of qualified incentive stock options and nonqualified stock options or other awards to the Company’s employees, officers, directors, advisors, and outside consultants to purchase up to an aggregate of 1,275,211 shares of the Company’s common stock, as amended in January 2014. The stock options generally vest over a four-year period and expire 10 years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the 2007 Plan. Effective with the IPO, no additional grants will be issued from the 2007 Plan and all shares available for grant under the 2007 Plan were transferred to the 2014 Plan. Accordingly, at December 31, 2016 and 2015, there were no shares available for future grant under the 2007 Plan.

Prior to the IPO, in determining the exercise prices for options granted, the Company’s board of directors considered the fair value of the common stock as of the measurement date. The fair value of the common stock was determined by the board of directors at each award grant date based upon a variety of factors, including the results obtained from a common stock valuation, the Company’s financial position and historical financial performance, the status of technological developments within the Company’s products, the composition and ability of the current research and management team, an evaluation or benchmark of the Company’s competition, the current business climate in the marketplace, the illiquid nature of the common stock, arm’s-length sales of the Company’s capital stock (including redeemable convertible preferred stock), the effect of the rights and preferences of the preferred shareholders, and the prospects of a liquidity event, among others.

2014 Stock Incentive Plan – In March 2014, the Company’s board of directors adopted and its stockholders approved the 2014 Stock Incentive Plan, or the 2014 Plan, which became effective upon the closing of the IPO. The 2014 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. The 2014 Plan provides an annual increase in the number of shares available for grant on the first day of each calendar year beginning with the fiscal year ended December 31, 2015 and continuing for each fiscal year until, and including, the fiscal year ending December 31, 2024, equal to the lesser of (i) 1,000,000 shares of common stock, (ii) 4% of the number of outstanding shares of common stock on such date and (iii) an amount determined by the Company’s board of directors. As of December 31, 2016, there were 924,400 shares available for future grant under the 2014 Plan.

A summary of stock option activity for employee and nonemployee awards under the 2007 Plan and the 2014 Plan during the year ended December 31, 2016 is presented below (Aggregate Intrinsic Value in thousands):

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2016		3,454,926		$	5.39		8.9	$	—
Granted		1,597,570			1.86
Exercised		—
Forfeited		(1,032,208	)		4.12
Outstanding at December 31, 2016		4,020,288		$	4.31		8.4	$	—
Options exercisable at December 31, 2016		1,634,944		$	5.41		7.7	$	—
Options vested and expected to vest at December 31, 2016		3,900,976		$	4.33		8.4	$	—

The total intrinsic value of stock options exercised in the years ended December 31, 2016, 2015, and 2014 was $0, $0, and $161,000, respectively.

The weighted-average per share grant date fair value of options granted during 2016, 2015, and 2014 was $1.07, $3.22, and $3.33, respectively.

The Company has recorded stock-based compensation expense of $2.7 million, $2.4 million, and $885,000 during the years ended December 31, 2016, 2015, and 2014, respectively, which is based on the number of awards ultimately expected to vest. As of December 31, 2016, there was $4.1 million of unrecognized compensation cost related to unvested stock-based compensation arrangements granted under the 2007 Plan and the 2014 Plan. The compensation is expected to be recognized over a weighted-average period of 2.02 years at December 31, 2016.

Stock-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):

	As of December 31,
	2016		2015		2014
Research and development	$	1,098	$	795	$	317
General and administrative		1,657		1,580		568
Total	$	2,755	$	2,375	$	885

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model based on the assumptions noted in the table below. Expected volatility for the Company’s common stock was determined based on an average of the historical volatility of a peer-group of similar public companies. The Company has limited option exercise information, as such, the expected term of the options granted was calculated using the simplified method that represents the average of the contractual term of the option and the weighted-average vesting period of the option. The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future. The risk-free rate for periods within the contractual life of the option is based upon the U.S. Treasury yield curve in effect at the time of grant.

The assumptions used in the Black-Scholes option-pricing model for stock options granted to employees during the years ended December 31, 2016, 2015, and 2014 are as follows:

	December 31,
	2016	2015	2014
Expected life	6 years	6 years	6 years
Risk-free interest rate	1.20%-2.32%	1.45%-2.02%	1.71%-2.00%
Expected volatility	61%-68%	51%-63%	54%-60%
Expected dividend rate	—%	—%	—%

The Company recorded stock-based compensation expense related to nonemployee awards of $77,000, $173,000, and $56,000 for the years ended December 31, 2016, 2015, and 2014, respectively. The compensation expense related to the nonemployee awards is included in the total stock-based compensation each year and is subject to re-measurement until the options vest. The Black-Scholes assumptions used to estimate the fair value of these awards for the years ended December 31, 2016, 2015, and 2014 were as follows:

	December 31,
	2016	2015	2014
Expected life	10 years	10 years	8 years
Risk-free interest rate	1.56%-2.43%	2.10%-2.25%	1.86%-2.53%
Expected volatility	60%-61%	60%-61%	56%-62%
Expected dividend rate	—%	—%	—%

During the year ended December 31, 2016, the Company granted nonemployee stock options to consultants for the purchase of 140,000 shares of the Company’s common stock. The weighted-average exercise price and the weighted-average fair value of nonemployee stock options granted for the year ended December 31, 2016, was $1.08 per share and $0.46 per share, respectively. The fair value of the grants is being expensed over the vesting period of the options on a straight-line basis as the services are being provided. On September 4, 2015, nonemployee stock options to purchase 90,000 shares of the Company’s common stock were converted to employee stock options upon the appointment of the Company’s Chief Medical Officer who had been serving as a consultant to the Company until his appointment. The exercise price and the fair value of these stock options is $4.71 per share and $2.71 per share, respectively. The Company did not grant any nonemployee stock option grants in 2014.

In 2012, the Company granted options to purchase 60,934 common shares to an officer of the Company, now the Company’s Chief Executive Officer, that will vest upon the achievement of business milestones as defined within the stock option agreement. These awards have not vested as of December 31, 2016. Compensation expense for the awards will be recorded if and when the awards are determined to be probable.

2014 Employee Stock Purchase Plan – In March 2014, the Company’s board of directors adopted and its stockholders approved the 2014 Employee Stock Purchase Plan (the “2014 ESPP”), which became effective upon the closing of the IPO. The 2014 ESPP will be administered by the Company’s board of directors or by a committee appointed by the Company’s board of directors. The 2014 ESPP initially provides participating employees with the opportunity to purchase up to an aggregate 500,000 of shares of the Company’s common stock. The number of shares of the Company’s common stock reserved for issuance under the 2014 ESPP will automatically increase on the first day of each fiscal year, commencing on January 1, 2015 and ending January 1, 2024, in an amount equal to the least of (i) 600,000 shares of the Company’s common stock, (ii) 1% of the total number of shares of the Company’s common stock outstanding on the first day of the applicable year, or (iii) an amount determined by the Company’s board of directors. There are two six-month offerings per year. The first offering period under the 2014 ESPP began on July 1, 2015. The compensation expense related to the 2014 ESPP is included in the total stock-based compensation. The stock-based compensation expense related to the ESPP for the year ended December 31, 2016 and 2015, was $24,000 and $27,000, respectively. There was no stock-based compensation related to the 2014 ESPP recorded for the year ended December 31, 2014.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Fair Value Measurements

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

9.	FAIR VALUE MEASUREMENTS

The Company’s financial instruments consist of cash equivalents, accounts payable, accrued expenses, debt obligations, and preferred stock warrants. The carrying amount of accounts payable and accrued expenses are considered a reasonable estimate of their fair value, due to the short-term maturity of these instruments. The carrying amount of debt is also considered to be a reasonable estimate of the fair value based on the short-term nature of the debt and that the debt bears interest at the prevailing market rate for instruments with similar characteristics. If recorded at fair value, Level 2 measurements, as defined below, would have been used to estimate the fair value. Included in cash and cash equivalents as of December 31, 2016 and 2015, are money market fund investments of $35.0 million and $75.3 million, respectively, which are reported at fair value.

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs.

The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following:

Level 1 — Quoted prices (unadjusted) in active markets that are accessible at the market date for identical unrestricted assets or liabilities.

Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

A summary of the financial assets and liabilities that are measured on a recurring basis at fair value as of December 31, 2016 and 2015, is as follows (in thousands):

			Fair Value Measurements Using
	Carrying		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
December 31, 2016
Money market funds	$	34,950	$	—	$	34,950	$	—
December 31, 2015
Money market funds	$	75,325	$	—	$	75,325	$	—

The Company’s money market funds have been valued on the basis of valuations provided by third-party pricing services, as derived from such services’ pricing models. Inputs to the models may include, but are not limited to, reported trades, executable bid and asked prices, broker/dealer quotations, prices or yields of securities with similar characteristics, benchmark curves or information pertaining to the issuer, as well as industry and economic events. The pricing services may use a matrix approach, which considers information regarding securities with similar characteristics to determine the valuation for a security. The Company is ultimately responsible for the consolidated financial statements and underlying estimates. Accordingly, the Company assesses the reasonableness of the valuations provided by the third-party pricing services by reviewing actual trade data, broker/dealer quotes and other similar data, which are obtained from quoted market prices or other sources.

For the years ended December 31, 2016 and 2015, there have been no transfers between levels.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

10.	INCOME TAXES

Significant components of the Company’s deferred taxes at December 31, 2016, and 2015 are as follows:

	2016			2015
Net operating loss carryforwards	$	42,211		$	35,797
Research and development credit carryforwards		2,486			2,066
Capitalized costs		4,453			3,977
Capitalized research and development costs		24,923			17,715
Other		1,878			903
Total deferred tax assets		75,951			60,458
Valuation allowance		(75,951	)		(60,458	)
Net deferred tax assets	$	—		$	—

The Company has provided a valuation allowance for the full amount of deferred tax assets as the realization of the deferred tax assets is not determined to be more-likely-than-not. The valuation allowance increased in 2016 and 2015 by approximately $15.5 million and $15.6 million, respectively, due to the increases in the deferred tax assets by the same amounts. The increases are mainly attributable to operating losses generated in the period.

A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows:

	Years Ended December 31,
	2016			2015
Federal income tax expense at statutory rate		34.0	%		34.0	%
State income tax, net of federal benefit		5.0	%		5.0	%
Permanent differences		(0.6	%)		(0.5	%)
Research and development credit		1.1	%		0.9	%
Stock compensation		(0.5	%)		(0.7	%)
Other		0.2	%		0.4	%
Change in valuation allowance		(39.2	%)		(39.1	%)
Effective income tax rate		0.0	%		0.0	%

At December 31, 2016, the Company has approximately $109.7 million of federal and $90.2 million of state net operating loss carryforwards that expire at various dates through 2036. At December 31, 2016, the Company has approximately $1.7 million of federal and $1.1 million of state research and development credit carryforwards that expire at various dates through 2036 for federal credits and 2031 for state credits.

At December 31, 2015, the Company has approximately $93.7 million of federal and $74.1 million of state net operating loss carryforwards that expire at various dates through 2035. At December 31, 2015, the Company has approximately $1.4 million of federal and $0.9 million of state research and development credit carryforwards that expire at various dates through 2035 for federal credits and 2030 for state credits.

The Company has early adopted the provisions of ASU 2016-09, Compensation – Stock Compensation (Topic 718 Improvements to Employee Share-Based Payment Accounting), for its quarter ended December 31, 2016. ASU 2016-09 requires companies to include the benefit of an option deduction in its net operating loss carryforward deferred tax asset. Prior to its adoption of ASU 2016-09, the Company’s excess tax benefits associated with option deductions were maintained in the Company’s APIC pool of windfall tax benefits, which was tracked off balance sheet and not included in its deferred tax assets. As a result of the Company’s adoption of ASU 2016-09, it will track option deductions in its net operating loss deferred tax asset on a modified retrospective basis, and has included the option deductions in the December 31, 2016 deferred tax assets. The gross deferred tax asset and valuation allowance as of December 31, 2016 increased $163,000 as a result of the cumulative effect of adoption of ASU 2016-09. The Company has not recast its December 31, 2015 and December 31, 2014 deferred tax assets or its rate reconciliation, and therefore the option deductions in 2015 and 2014 are not included in the net operating loss deferred tax asset as originally reported. Since the Company has historically maintained a full valuation allowance on its net worldwide deferred tax asset, there is no net impact to retained earnings from the adoption of ASU 2016-09.

Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. The future realization of the net operating loss carryforwards may also be limited by the change of ownership rules of the Internal Revenue Service under Section 382 and 383 of the Internal Revenue Code. If substantial changes in ownership should occur, there could be annual limitations on the amount of carryforwards that can be realized in future periods. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed numerous financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future.

The Company files income tax returns in the United States, the Commonwealth of Massachusetts, and Australia. The tax years 2008 through 2016 remain open to examination by these taxing jurisdictions, as carryforwards attributes generated in past years may be adjusted in a future period. The Company is currently not under examination by the Internal Revenue Service or any other jurisdictions for any tax years. At December 31, 2016 and 2015, the Company had approximately $0.7 million and $0.6 million, respectively, of total unrecognized tax benefits, which would affect income tax expense if recognized, before consideration of the Company’s valuation allowance. During fiscal year 2016, the Company did not make any payment of interest and penalties on unrecognized tax benefits. In addition, there was nothing accrued for in the consolidated balance sheets for the payment of interest and penalties at December 31, 2016.

Commitments

12 Months Ended

Dec. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments

11.	COMMITMENTS

Facility Lease — On July 9, 2015, the Company entered into a noncancelable operating lease with a third party for office, laboratory and vivarium space that is scheduled to expire in February 2021, subject to a three-year renewal option. The lease agreement includes base rent escalation over the lease term which will be amortized on a straight-line basis over the lease term with the resulting deferred liability recorded in other current and long-term liabilities. The resulting deferred liability recorded in other current and long-term liabilities as of December 31, 2016 was $153,000. The lease requires the Company to share in prorated expenses and property taxes based upon actual amounts incurred; those amounts are not fixed for future periods and, therefore, not included in the future minimum obligations listed below. Rent expense under this lease was $728,000 for the year ended December 31, 2016.

The Company amended the lease, effective March 29, 2017, to remove 1,753 square feet from the lease, which space was previously used for vivarium and vivarium support purposes. The Company’s base rent and share in expenses and property taxes have been reduced based on the revised pro-rata allocation of the premises.

Future minimum lease payments under the non-cancelable operating lease are as follows (in thousands):

	Operating
Years Ending December 31,	Leases
2017	$	690
2018		738
2019		786
2020		830
2021		140
Total	$	3,184

Potential Payments upon Termination or Change in Control — On March 19, 2017, the Company entered into retention agreements with certain executive officers. These retention agreements supersede the provisions of such executive officers’ employment agreements and retention letters with the Company providing for post-separation benefits, and provide for certain lump sum payments ranging from 6 to 18 months of salary, plus health and dental insurance coverage, while also providing the covered executives with a cash bonus upon completion of a change in control. Under the terms of the retention agreements, the Company may be required to pay up to approximately $1.8 million.

Licensing Agreements

12 Months Ended

Dec. 31, 2016

Research And Development Expense [Abstract]

Licensing Agreements

12.	LICENSING AGREEMENTS

Calando License — The Company has a product license agreement and a platform license agreement with Calando Pharmaceuticals, Inc. (“Calando”). Under the product license agreement, the Company may be required to pay Calando up to $32.8 million upon the achievement of specified regulatory and commercial milestones and pay tiered royalty payment ranging from low-to mid-single digits on commercial sales.

Under the platform license agreement, the Company paid Calando a $250,000 clinical development milestone which was recorded in December 2014 upon initiation of the Phase 1/2a clinical trial for CRLX301. The Company may be required to make additional milestone payments to Calando of up to $17.8 million, in the aggregate, upon the achievement of specified regulatory and commercial milestones and pay royalty payments ranging from low-to mid-single digits on commercial sales.

In March 2014, Calando entered Chapter 7 bankruptcy in the District of Delaware and, as a result, the intellectual property rights the Company has obtained from Calando are subject to potential risks that may arise in connection with bankruptcy. For instance, while the Company’s ability to develop and/or commercialize its current product candidates and its ability to utilize its platform are not dependent on the rights that it licenses from Calando, its license agreements with Calando could be rejected in connection with Calando’s bankruptcy, in which case, the Company could, subject to elections and other rights and defenses that may be available to it, lose certain rights granted to it under such licenses. On March 3, 2015, Calando’s bankruptcy trustee submitted an application with the bankruptcy court seeking authority to retain a broker to sell Calando’s rights in certain assets including its rights in the license agreements with the Company, the Company has reserved its rights with respect to any such sale. The trustee’s last deadline was February 7, 2017. To our knowledge, no sale of such rights was ever consummated.

SUNY License — The Company is party to a license agreement with The Research Foundation of State University of New York (“SUNY”) for certain intellectual property. The agreement as amended requires the Company to pay nonrefundable annual license maintenance fees each year until the date of first commercial sale of a licensed product pursuant to the license agreement, as amended. The annual license fee is not material in any individual year. In the event of future partner collaborations or product sales incorporating technology covered by this license agreement, the Company may be required to pay milestone payments and/or product royalties. In connection with this agreement, the Company recorded research and development expense of $30,000, $30,000, and $25,000 for the years ended December 31, 2016, 2015, and 2014, respectively.

Massachusetts Institute of Technology License — The Company delivered a notice of termination which became effective on November 1, 2015, with respect to the Company’s license agreement with the Massachusetts Institute of Technology (“MIT”). The agreement as amended required the Company to pay MIT nonrefundable annual license maintenance fees that increased each year beginning in 2015. In connection with this agreement, the Company recorded research and development expense for annual maintenance fees of $50,000 for the year ended December 31, 2015, and $10,000 in the year ended December 31, 2014.

Retirement Plans

12 Months Ended

Dec. 31, 2016

Compensation And Retirement Disclosure [Abstract]

Retirement Plans

13.	RETIREMENT PLANS

The Company has a 401(k) retirement and profit-sharing plan (the “401(k) Plan”) covering all qualified employees. The 401(k) Plan allows each participant to contribute a portion of their base wages up to an amount not to exceed an annual statutory maximum. Effective January 1, 2010, the Company adopted a Safe Harbor Plan that provides a Company match up to 4% of salary. The Company contributed a match of $292,000, $264,000, and $163,000 to the 401(k) Plan for the years ended December 31, 2016, 2015, and 2014, respectively.

Related Party Transactions

12 Months Ended

Dec. 31, 2016

Related Party Transactions

14.	RELATED PARTY TRANSACTIONS

In April 2013, the Company entered into a laboratory, equipment sharing, services and license agreement with an entity affiliated with one of the Company’s directors. Fees recorded offsetting research and development expenses under this agreement and paid in the year ended December 31, 2014, were $39,000. On April 1, 2014, the Company sold used equipment to this entity and recorded proceeds from the sale of $30,000. The agreement was terminated on April 1, 2014.

Revenue

12 Months Ended

Dec. 31, 2016

Revenues [Abstract]

Revenue

15.

REVENUE

In October 2016, the Company entered into a research collaboration agreement with Novartis pursuant to which the Company granted to Novartis certain exclusive, world-wide licenses to the Company’s intellectual property relating to its platform technology and know-how. Under the collaboration, the Company and Novartis agreed to collaborate, over an initial research term of two years, with respect to the pre-clinical development of nanoparticle drug conjugates comprised of the Company’s proprietary polymer covalently linked to Novartis-selected active pharmaceutical ingredients for up to five targets to be agreed upon by the Company and Novartis. Novartis may extend the initial research term by up to two additional one-year periods. In October 2016, the Company received a $5.0 million upfront payment under the collaboration which it will recognize on a straight-line basis over the initial term of the collaboration. The Company will also receive funding from Novartis for up to five full-time employees of the Company to be engaged in activities under the collaboration during the research term. For the year ended December 31, 2016, the Company recognized revenue of $507,000 in connection with the upfront fee and $259,000 in connection with the funding for activities performed under the collaboration during the research term.

In 2013, the Company entered into material transfer agreements with two separate biopharmaceutical companies to conduct feasibility studies using the Company’s proprietary technology. The Company recognized revenue of $80,000 for the year ended December 31, 2014, in connection with these material transfer agreements. The Company had no revenue for the years ended December 31, 2016 and 2015 related to these agreements.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

16.	QUARTERLY FINANCIAL DATA (unaudited)

The following table summarizes the unaudited quarterly financial data for the last two fiscal years:

CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except share data and per share data)

	Year Ended December 31, 2016
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Revenue	$	—		$	—		$	—		$	766
Operating expenses:
Research and development		9,770			7,522			7,089			3,184
General and administrative		3,118			2,773			2,374			2,090
Total operating expenses		12,888			10,295			9,463			5,274
Other income (expense):
Interest income		16			25			25			20
Interest expense		(670	)		(589	)		(521	)		(457	)
Total other income (expense) — net		(654	)		(564	)		(496	)		(437	)
Net loss attributable to common stockholders	$	(13,542	)	$	(10,859	)	$	(9,959	)	$	(4,945	)
Net loss per share attributable to common stockholders:
Basic and diluted	$	(0.49	)	$	(0.40	)	$	(0.36	)	$	(0.17	)
Weighted-average common shares outstanding:
Basic and diluted		27,362,643			27,363,965			27,383,376			28,724,083

	Year Ended December 31, 2015
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Revenue	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		5,021			6,678			7,092			7,157
General and administrative		2,681			2,717			2,954			2,872
Total operating expenses		7,702			9,395			10,046			10,029
Other income (expense):
Interest income		3			1			4			2
Interest expense		(721	)		(513	)		(509	)		(689	)
Total other income (expense) — net		(718	)		(512	)		(505	)		(687	)
Net loss attributable to common stockholders	$	(8,420	)	$	(9,907	)	$	(10,551	)	$	(10,716	)
Net loss per share attributable to common stockholders:
Basic and diluted	$	(0.41	)	$	(0.37	)	$	(0.39	)	$	(0.39	)
Weighted-average common shares outstanding:
Basic and diluted		20,350,557			26,690,673			27,307,103			27,346,780

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	17. SUBSEQUENT EVENTS In February 2017, the Company announced that its board of directors initiated a review of strategic alternatives that could result in changes to the Company’s business strategy and future operations. As part of this process, the board determined to review alternatives with the goal of maximizing stockholder value, including a potential sale of the Company, a reverse merger, a business combination or a sale, license or other disposition of company assets. The Company entered into a payoff letter dated as of March 17, 2017 with Hercules pursuant to which the Company agreed to pay off and thereby terminate the Hercules Loan Agreement. Pursuant to the payoff letter, the Company paid, on March 20, 2017, a total of $12.4 million to Hercules, representing the principal, accrued and unpaid interest, fees, costs and expenses outstanding under the Hercules Loan Agreement in repayment of its outstanding obligations under the Hercules Loan Agreement. This payoff amount included a final end of term charge to Hercules in the amount of $1.4 million, representing 6.7% of the aggregate original principal amount advanced by Hercules. As of December 31, 2016, the Company has accrued $1.1 million of the end of term charge. Upon the payment of the $12.4 million pursuant to the payoff letter, all outstanding indebtedness and obligations owed to Hercules under the Loan Agreement were deemed paid in full, and the Loan Agreement was terminated. On March 19, 2017, the Company entered into an asset purchase agreement (the “Novartis Asset Purchase Agreement”) with Novartis. Under the Novartis Asset Purchase Agreement the Company agreed to sell and assign to Novartis all of the Company’s right, title and interest in and to the patent rights, know-how and third-party license agreements relating to the Company’s proprietary Dynamic Tumor Targeting Platform (the “Platform”). At the closing of the Novartis transaction, Novartis will be obligated to pay a purchase price of $6.0 million. Consummation of the Novartis transaction is subject to certain closing conditions, including, among other things, approval by the Company’s stockholders. On March 19, 2017, the Company also entered into an asset purchase agreement (the “BlueLink Asset Purchase Agreement) with BlueLink Pharmaceuticals, Inc. (“BlueLink”). Under the BlueLink Asset Purchase Agreement the Company sold and assigned to BlueLink all of the Company’s right, title and interest in and to its clinical product candidates CRLX101 and CRLX301 (the “Products”). The Company also transferred and assigned to BlueLink the accompanying intellectual property rights and know-how to the Products. On March 21, 2017, BlueLink paid the purchase price of $1.5 million. Also in connection with the BlueLink Asset Purchase Agreement, the Company and BlueLink entered into a license agreement in favor of BlueLink, pursuant to which the Company agreed to grant to BlueLink an exclusive, worldwide, perpetual, sublicensable right and license, under the Platform, to research, develop and commercialize the Products. Pursuant to the Novartis Asset Purchase Agreement between the Company and Novartis, Novartis will assume the BlueLink License upon the closing of the Novartis transaction. On March 19, 2017, the Company also entered into a stock purchase agreement (the “Stock Purchase Agreement”)with Daré Bioscience, Inc. (“Daré”), and the holders of capital stock and securities convertible into capital stock of Daré named therein (“Selling Stockholders”), pursuant to which, among other things, the Selling Stockholders agreed to sell to the Company, and the Company agreed to purchase from the Selling Stockholders, all of the outstanding shares of capital stock, including those issuable upon conversion of convertible securities, of Daré (the “Daré Transaction”). Immediately following the closing of the Daré Transaction, the Selling Stockholders are expected to own between approximately 51% and 70% (depending on the net cash positions of the Company and Daré at closing) of the outstanding equity securities of Cerulean Pharma Inc. Consummation of the Daré Transaction is subject to certain closing conditions, including, among other things, approval by the Company’s stockholders. The exchange ratio, and therefore fair value of exchange consideration, are indeterminable at this time, and as such the full disclosures required under Accounting Standards Codification 805, Business Combinations, are impracticable. The Stock Purchase Agreement contains certain termination rights for both the Company and Daré, and further provides that, upon termination of the Stock Purchase Agreement under specified circumstances, the Company may be required to pay Daré a termination fee of $0.3 million, or Daré may be required to pay the Company a termination fee of $0.45 million. There can be no assurances that the Daré Transaction will be consummated. On March 20, 2017, the Company announced a restructuring including the elimination of approximately 58% of its workforce, to a total of eight full-time equivalent employees, under a plan expected to be completed during the second quarter of 2017.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Use of Estimates

Principles of Consolidation

Segment Information

Cash and Cash Equivalents

Cash and Cash Equivalents — Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase and consist primarily of money market funds.

Concentrations of Credit Risk

Restricted Cash

Property and Equipment

Depreciation is provided using the straight-line method over the following estimated useful lives:

Laboratory equipment		5 years
Computer equipment		3 years
Office furniture and equipment		5 years
Leasehold improvements		Lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

Revenue Recognition

Revenue Recognition —

Collaborative Research and Development and Multiple-Element Arrangements

Deferred Revenue

Research and Development Costs

Stock-Based Compensation

Net Loss per Share Attributable to Common Stockholders

Income Taxes

Guarantees and Indemnification

Recent Accounting Pronouncements

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Common Share

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands, except share data and per share data):

	Years Ended December 31,
	2016			2015			2014
Net loss attributable to common stockholders — basic and diluted	$	(39,305	)	$	(39,594	)	$	(23,342	)
Weighted-average number of common shares — basic and diluted		27,710,403			25,431,332			14,548,516
Net loss per share attributable to common stockholders — basic and diluted	$	(1.42	)	$	(1.56	)	$	(1.60	)

Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding

	As of December 31,
	2016		2015		2014
Options to purchase common stock		4,020,288		3,454,926		2,126,176
Warrants to purchase common stock		365,564		300,564		128,663

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

Summary of Property and Equipment

Property and equipment consist of the following (in thousands):

	As of December 31,
	2016			2015
Laboratory equipment	$	1,548		$	1,314
Computer equipment		371			350
Office furniture and equipment		66			25
Leasehold improvements		75			33
		2,060			1,722
Less accumulated depreciation and amortization		(1,392	)		(1,146	)
Property and equipment, net	$	668		$	576

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2016

Payables And Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consist of the following (in thousands):

	As of December 31,
	2016		2015
Accrued clinical trial costs	$	2,648	$	2,631
Accrued contract manufacturing expenses		226		945
Accrued compensation and benefits		1,080		1,864
Accrued interest		82		136
Other accrued expenses		575		883
Total accrued expenses	$	4,611	$	6,459

Loan Agreements (Tables)

12 Months Ended

Dec. 31, 2016

Debt Instrument [Line Items]

Summary of Minimum Future Principal Payments

The minimum future principal payments are as follows (in thousands):

Year Ending December 31,
2017	$	8,533
2018		4,544
Unamortized discount relating to warrants and deferred financing costs		(256	)
Total		12,821
Less current portion		(8,382	)
Long-term portion	$	4,439

Hercules Loan Agreement [Member] | Common Stock Warrants [Member]

Debt Instrument [Line Items]

Fair Value of Stock Warrants Calculated using Black-Scholes Assumptions

The following table shows the Black-Scholes assumptions used to value the warrant:

	January 8, 2015
Contractual life	5 years
Volatility rate		61	%
Risk-free interest rate		1.5	%
Expected dividends		—

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Stockholders Equity Note [Abstract]

Summary of Number of Shares of Common Stock Reserved

The Company has reserved the following number of shares of common stock at December 31, 2016 and 2015:

	As of December 31,
	2016		2015
Warrants to purchase common stock		365,564		300,564
Common stock options		4,020,288		3,995,876
Total		4,385,852		4,296,440

Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Stock Option Activity for Employee and Nonemployee Awards under Plan

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2016		3,454,926		$	5.39		8.9	$	—
Granted		1,597,570			1.86
Exercised		—
Forfeited		(1,032,208	)		4.12
Outstanding at December 31, 2016		4,020,288		$	4.31		8.4	$	—
Options exercisable at December 31, 2016		1,634,944		$	5.41		7.7	$	—
Options vested and expected to vest at December 31, 2016		3,900,976		$	4.33		8.4	$	—

Schedule of Stock-based Compensation Expense

Stock-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):

	As of December 31,
	2016		2015		2014
Research and development	$	1,098	$	795	$	317
General and administrative		1,657		1,580		568
Total	$	2,755	$	2,375	$	885

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees and Non Employees

The assumptions used in the Black-Scholes option-pricing model for stock options granted to employees during the years ended December 31, 2016, 2015, and 2014 are as follows:

	December 31,
	2016	2015	2014
Expected life	6 years	6 years	6 years
Risk-free interest rate	1.20%-2.32%	1.45%-2.02%	1.71%-2.00%
Expected volatility	61%-68%	51%-63%	54%-60%
Expected dividend rate	—%	—%	—%

Non Employee Awards [Member]

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees and Non Employees

The Black-Scholes assumptions used to estimate the fair value of these awards for the years ended December 31, 2016, 2015, and 2014 were as follows:

	December 31,
	2016	2015	2014
Expected life	10 years	10 years	8 years
Risk-free interest rate	1.56%-2.43%	2.10%-2.25%	1.86%-2.53%
Expected volatility	60%-61%	60%-61%	56%-62%
Expected dividend rate	—%	—%	—%

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Measured on Recurring Basis at Fair Value

A summary of the financial assets and liabilities that are measured on a recurring basis at fair value as of December 31, 2016 and 2015, is as follows (in thousands):

			Fair Value Measurements Using
	Carrying		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
December 31, 2016
Money market funds	$	34,950	$	—	$	34,950	$	—
December 31, 2015
Money market funds	$	75,325	$	—	$	75,325	$	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Significant Components of Company's Deferred Taxes

Significant components of the Company’s deferred taxes at December 31, 2016, and 2015 are as follows:

	2016			2015
Net operating loss carryforwards	$	42,211		$	35,797
Research and development credit carryforwards		2,486			2,066
Capitalized costs		4,453			3,977
Capitalized research and development costs		24,923			17,715
Other		1,878			903
Total deferred tax assets		75,951			60,458
Valuation allowance		(75,951	)		(60,458	)
Net deferred tax assets	$	—		$	—

Reconciliation of Income Tax Expense Computed at Statutory Federal Income Tax Rate to Income Taxes

A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows:

	Years Ended December 31,
	2016			2015
Federal income tax expense at statutory rate		34.0	%		34.0	%
State income tax, net of federal benefit		5.0	%		5.0	%
Permanent differences		(0.6	%)		(0.5	%)
Research and development credit		1.1	%		0.9	%
Stock compensation		(0.5	%)		(0.7	%)
Other		0.2	%		0.4	%
Change in valuation allowance		(39.2	%)		(39.1	%)
Effective income tax rate		0.0	%		0.0	%

Commitments (Tables)

12 Months Ended

Dec. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Summary of Future Minimum Lease Payments under Non-cancelable Operating Leases

Future minimum lease payments under the non-cancelable operating lease are as follows (in thousands):

	Operating
Years Ending December 31,	Leases
2017	$	690
2018		738
2019		786
2020		830
2021		140
Total	$	3,184

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Data

The following table summarizes the unaudited quarterly financial data for the last two fiscal years:

CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except share data and per share data)

	Year Ended December 31, 2016
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Revenue	$	—		$	—		$	—		$	766
Operating expenses:
Research and development		9,770			7,522			7,089			3,184
General and administrative		3,118			2,773			2,374			2,090
Total operating expenses		12,888			10,295			9,463			5,274
Other income (expense):
Interest income		16			25			25			20
Interest expense		(670	)		(589	)		(521	)		(457	)
Total other income (expense) — net		(654	)		(564	)		(496	)		(437	)
Net loss attributable to common stockholders	$	(13,542	)	$	(10,859	)	$	(9,959	)	$	(4,945	)
Net loss per share attributable to common stockholders:
Basic and diluted	$	(0.49	)	$	(0.40	)	$	(0.36	)	$	(0.17	)
Weighted-average common shares outstanding:
Basic and diluted		27,362,643			27,363,965			27,383,376			28,724,083

	Year Ended December 31, 2015
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Revenue	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		5,021			6,678			7,092			7,157
General and administrative		2,681			2,717			2,954			2,872
Total operating expenses		7,702			9,395			10,046			10,029
Other income (expense):
Interest income		3			1			4			2
Interest expense		(721	)		(513	)		(509	)		(689	)
Total other income (expense) — net		(718	)		(512	)		(505	)		(687	)
Net loss attributable to common stockholders	$	(8,420	)	$	(9,907	)	$	(10,551	)	$	(10,716	)
Net loss per share attributable to common stockholders:
Basic and diluted	$	(0.41	)	$	(0.37	)	$	(0.39	)	$	(0.39	)
Weighted-average common shares outstanding:
Basic and diluted		20,350,557			26,690,673			27,307,103			27,346,780

Nature of Business and Operations - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Mar. 21, 2017	Mar. 20, 2017	Dec. 31, 2016	Mar. 19, 2017	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nature Of Business And Operations [Line Items]
Date of Company's incorporation			Nov. 28, 2005
Accumulated deficit			$ 200,680		$ 161,375
Cash and cash equivalents			$ 34,950		$ 75,908	$ 51,174	$ 5,488
Subsequent Events [Member] \| BlueLink Pharmaceuticals, Inc. [Member] \| Asset Purchase Agreement [Member]
Nature Of Business And Operations [Line Items]
Proceeds from sale of assets	$ 1,500
Subsequent Events [Member] \| Novartis Institutes for BioMedical Research, Inc [Member] \| Asset Purchase Agreement [Member]
Nature Of Business And Operations [Line Items]
Purchase price receivable from sale of assets				$ 6,000
Subsequent Events [Member] \| Hercules Loan Agreement [Member]
Nature Of Business And Operations [Line Items]
Pay off loan agreement, amount paid		$ 12,400

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Number of operating segments \| Segment		1
Revenue	$ 766,000	$ 766,000		$ 80,000
Restricted cash	230,000	$ 230,000	$ 347,000
Facility lease scheduled expiration period		2021-02	2016-02
Total unrecognized tax benefits, which would affect income tax expense if recognized	700,000	$ 700,000	$ 600,000
Payment of interest and penalties on unrecognized tax benefits		0
Accrued indemnification provisions	0	0
Losses related to indemnification obligations		0
Claims related to indemnification obligations	0	0
Increase in gross deferred tax asset and valuation allowance		15,500,000	$ 15,600,000
ASU 2016-09 [Member]
Significant Accounting Policies [Line Items]
Increase in gross deferred tax asset and valuation allowance		163,000
Sydney, NSW [Member]
Significant Accounting Policies [Line Items]
Revenue		0
Long-lived assets	$ 0	$ 0

Significant Accounting Policies - Schedule of Property and Equipment Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2016
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	5 years
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	3 years
Office Furniture and Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	5 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	Lesser of useful life or remaining lease term

Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss attributable to common stockholders — basic and diluted									$ (39,305)	$ (39,594)	$ (23,342)
Weighted-average number of common shares — basic and diluted	28,724,083	27,383,376	27,363,965	27,362,643	27,346,780	27,307,103	26,690,673	20,350,557	27,710,403	25,431,332	14,548,516
Net loss per share attributable to common stockholders — basic and diluted	$ (0.17)	$ (0.36)	$ (0.40)	$ (0.49)	$ (0.39)	$ (0.39)	$ (0.37)	$ (0.41)	$ (1.42)	$ (1.56)	$ (1.60)

Net Loss Per Share Attributable to Common Stockholders - Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted weighted-average shares outstanding	4,020,288	3,454,926	2,126,176
Warrants [Member] \| Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted weighted-average shares outstanding	365,564	300,564	128,663

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,060	$ 1,722
Less accumulated depreciation and amortization	(1,392)	(1,146)
Property and equipment, net	668	576
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,548	1,314
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	371	350
Office Furniture and Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	66	25
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 75	$ 33

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued clinical trial costs	$ 2,648	$ 2,631
Accrued contract manufacturing expenses	226	945
Accrued compensation and benefits	1,080	1,864
Accrued interest	82	136
Other accrued expenses	575	883
Total accrued expenses	$ 4,611	$ 6,459

Loan Agreements - Additional Information (Detail)		1 Months Ended				6 Months Ended	12 Months Ended
Loan Agreements - Additional Information (Detail)	Jan. 08, 2015 USD ($) Tranches $ / shares shares	Jan. 31, 2015 USD ($)	Aug. 31, 2012 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2011 USD ($) $ / shares shares	Aug. 31, 2012 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Dec. 15, 2015 USD ($)	Nov. 24, 2015 USD ($)	Apr. 30, 2014 shares
Debt Instrument [Line Items]
Principal outstanding under the Term Loan							$ 12,821,000
Proceeds from issuance of common stock							918,000	$ 2,628,000	$ 140,000
Unamortized deferred financing costs							100,000
Unamortized discount on debt, relating to warrants							200,000
Proceeds from loan payable								21,000,000
Accrued interest							$ 82,000	$ 136,000
Common Stock [Member]
Debt Instrument [Line Items]
Issuance of Common Stock, shares \| shares								6,716,000
Hercules Loan Agreement [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Prior written notice period to prepay term loan							7 days
Loan and Security Agreement with Lighthouse Capital [Member]
Debt Instrument [Line Items]
Accrued interest									$ 574,000
Loan and Security Agreement with Lighthouse Capital [Member] \| Loans payable [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum borrowing capacity					$ 10,000,000
Unamortized discount on debt, relating to warrants		$ 200,000
Proceeds from loan payable			$ 5,000,000	$ 5,000,000		$ 10,000,000
Loan and security agreement, borrowings repayment period					36 months
Debt instrument stated interest rate					8.25%
Loan and security agreement, borrowings repayment start date							Dec. 01, 2012
Line of credit facility, additional interest payment							$ 600,000
Repayments of notes payable		3,600,000
Loan and Security Agreement with Lighthouse Capital [Member] \| Loans payable [Member] \| Series D Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Exercise price of warrant \| $ / shares					$ 12.04
Warrant expiration date							2021-12
Warrant expiration period					10 years
Loan and Security Agreement with Lighthouse Capital [Member] \| Loans payable [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Warrant to purchase stock, number of securities called by warrants or rights \| shares												66,436
Loan and Security Agreement with Lighthouse Capital [Member] \| Maximum [Member] \| Loans payable [Member] \| Series D Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Warrant to purchase stock, number of securities called by warrants or rights \| shares					66,436
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Stock Purchase Agreement [Member]
Debt Instrument [Line Items]
Issuance of Common Stock, shares \| shares	135,501
Issuance/sale of stock, price per share \| $ / shares	$ 7.38
Proceeds from issuance of common stock	$ 1,000,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum borrowing capacity	$ 26,000,000
Principal outstanding under the Term Loan							$ 13,100,000
Term loan facility, maturity date							Jul. 01, 2018
Term loan facility, interest rate terms							The Term Loan will mature on July 1, 2018. Each advance under the Term Loan accrues interest at a floating per annum rate equal to the greater of (i) 7.30% or (ii) the sum of 7.30% plus the prime rate minus 5.75%. The Term Loan provided for interest-only payments on a monthly basis until December 31, 2015.
Additional interest rate during an event of default	5.00%
Term loan facility, interest rate	7.30%
Debt prepayment charge	1.00%
Final payment as percentage of aggregate original principal amount	6.70%
Class of warrant or right, date until which warrants exercisable							Jan. 08, 2020
Estimated fair value of warrant		$ 824,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Exercise price of warrant \| $ / shares	$ 6.05
Warrant to purchase stock, number of securities called by warrants or rights \| shares	171,901
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Other Long-term Liabilities [Member]
Debt Instrument [Line Items]
Accrued end of term charge							$ 1,100,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Prime Rate [Member]
Debt Instrument [Line Items]
Term loan facility, interest rate spread	5.75%
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Borrowing One [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum borrowing capacity	$ 15,000,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Second Tranche [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum borrowing capacity											$ 6,000,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Up on Meeting Certain Clinical Milestone on or Prior to Dec. 15, 2015 [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum borrowing capacity										$ 5,000,000
Hercules Technology Growth Capital, Inc. [Member] \| Hercules Loan Agreement [Member] \| Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Number of tranches \| Tranches	3

Loan Agreements - Summary of Minimum Future Principal Payments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
2017	$ 8,533
2018	4,544
Unamortized discount relating to warrants and deferred financing costs	(256)
Total	12,821
Less current portion	(8,382)	$ (7,652)
Long-term portion	$ 4,439	$ 12,672

Loan Agreements - Fair Value of Preferred Stock Warrants Calculated using Black-Scholes Assumptions (Detail) - Hercules Technology Growth Capital, Inc. [Member] - Hercules Loan Agreement [Member]	Jan. 08, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Contractual life	5 years
Volatility rate	61.00%
Risk-free interest rate	1.50%

Stockholders' Equity - Additional Information (Detail) - USD ($)		12 Months Ended
	Oct. 14, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class Of Stock [Line Items]
Proceeds from issuance of common stock		$ 918,000	$ 2,628,000	$ 140,000
Aspire Capital Fund, LLC [Member] \| Stock Purchase Agreement [Member]
Class Of Stock [Line Items]
Number of shares issued	700,000
Stock purchase term	24 months
Proceeds from issuance of common stock	$ 786,000
Aspire Capital Fund, LLC [Member] \| Stock Purchase Agreement [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Purchase of common stock aggregate commitment amount	$ 20,000,000
Remaining available value under common stock purchase agreement		$ 19,000,000
Aspire Capital Fund, LLC [Member] \| Initial Sale Under Stock Purchase Agreement [Member]
Class Of Stock [Line Items]
Number of shares issued	800,000
Common stock price per share	$ 1.25
Proceeds from issuance of common stock	$ 1,000,000
Common Stock [Member]
Class Of Stock [Line Items]
Number of shares issued			6,716,000
Issuance of common stock, shares				19,297,952

Stockholders' Equity - Summary of Number of Shares of Common Stock Reserved (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015
Class Of Stock [Line Items]
Reserved shares of common stock	4,385,852	4,296,440
Common stock options [Member]
Class Of Stock [Line Items]
Reserved shares of common stock	4,020,288	3,995,876
Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Reserved shares of common stock	365,564	300,564

Stock Option Plans - Additional Information (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 04, 2015 $ / shares shares	Dec. 31, 2016 USD ($) Offering Period $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2012 shares	Jan. 01, 2016 shares	Jan. 31, 2014 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense \| $		$ 2,755	$ 2,375	$ 885
Number of Shares, Granted		1,597,570
Weighted-Average Exercise Price, Options exercisable \| $ / shares		$ 5.41
2007 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum shares of common stock provided under stock incentive plan							1,275,211
Stock options vesting period		4 years
Stock options expiration period		10 years
Shares available for future grant		0	0
2014 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum shares of common stock provided under stock incentive plan						1,000,000
Shares available for future grant		924,400
Percentage of common stock outstanding stock on first day of the year						4.00%
Total intrinsic value of stock options exercised \| $		$ 0	$ 0	$ 161
Weighted-average per share grant date fair value of options granted \| $ / shares		$ 1.07	$ 3.22	$ 3.33
2014 Stock Incentive Plan [Member] \| CEO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted					60,934
2014 Stock Incentive Plan [Member] \| Non Employee Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average per share grant date fair value of options granted \| $ / shares	$ 2.71	$ 0.46
Stock-based compensation expense \| $		$ 77	$ 173	$ 56
Number of Shares, Granted	90,000	140,000		0
Weighted-Average Exercise Price, Options exercisable \| $ / shares	$ 4.71	$ 1.08
2007 and 2014 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to unvested stock-based compensation arrangements \| $		$ 4,100
Weighted-average period of recognition of unrecognized compensation cost related to unvested stock-based compensation arrangements		2 years 7 days
2014 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum shares of common stock provided under stock incentive plan		500,000				600,000
Percentage of common stock outstanding stock on first day of the year						1.00%
Stock-based compensation expense \| $		$ 24	$ 27	$ 0
Offering period		6 months
Number of offerings per year \| Offering Period		2

Stock Option Plans -Summary of Stock Option Activity for Employee and Nonemployee Awards under Plan (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Number of shares
Number of Shares, Outstanding	3,454,926
Number of Shares, Granted	1,597,570
Number of Shares, Forfeited	(1,032,208)
Number of Shares, Outstanding	4,020,288	3,454,926
Number of Shares, Options exercisable	1,634,944
Number of Shares, Options vested and expected to vest	3,900,976
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Outstanding	$ 5.39
Weighted-Average Exercise Price, Granted	1.86
Weighted-Average Exercise Price, Forfeited	4.12
Weighted-Average Exercise Price, Outstanding	4.31	$ 5.39
Weighted-Average Exercise Price, Options exercisable	5.41
Weighted-Average Exercise Price, Options vested and expected to vest	$ 4.33
Weighted-Average Remaining Contractual Life (Years)
Weighted-Average Remaining Contractual Life (Years)	8 years 4 months 24 days	8 years 10 months 24 days
Weighted-Average Remaining Contractual Life (Years), Options exercisable at December 31, 2016	7 years 8 months 12 days
Weighted-Average Remaining Contractual Life (Years), Options vested and expected to vest at December 31, 2016	8 years 4 months 24 days

Stock Option Plans - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,755	$ 2,375	$ 885
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,098	795	317
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,657	$ 1,580	$ 568

Stock Option Plans - Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees and Non Employees (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	6 years	6 years	6 years
Risk-free interest rate, minimum	1.20%	1.45%	1.71%
Risk-free interest rate, maximum	2.32%	2.02%	2.00%
Expected volatility, minimum	61.00%	51.00%	54.00%
Expected volatility, maximum	68.00%	63.00%	60.00%
Non Employee Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	10 years	10 years	8 years
Risk-free interest rate, minimum	1.56%	2.10%	1.86%
Risk-free interest rate, maximum	2.43%	2.25%	2.53%
Expected volatility, minimum	60.00%	60.00%	56.00%
Expected volatility, maximum	61.00%	61.00%	62.00%

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured on Recurring Basis at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 35,000	$ 75,300
Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member] \| Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	34,950	75,325
Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member] \| Fair Value Measurements [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 34,950	$ 75,325

Income Taxes - Significant Components of Company's Deferred Taxes (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 42,211	$ 35,797
Research and development credit carryforwards	2,486	2,066
Capitalized costs	4,453	3,977
Capitalized research and development costs	24,923	17,715
Other	1,878	903
Total deferred tax assets	75,951	60,458
Valuation allowance	(75,951)	(60,458)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 15,500,000	$ 15,600,000
Net operating loss carryforwards expiration year	2036	2035
Total unrecognized tax benefits, which would affect income tax expense if recognized	$ 700,000	$ 600,000
Payment of interest and penalties on unrecognized tax benefits	$ 0
Internal Revenue Service (IRS) [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax year open to examination	2008
Internal Revenue Service (IRS) [Member] \| Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax year open to examination	2016
ASU 2016-09 [Member]
Operating Loss Carryforwards [Line Items]
Increase (decrease) in valuation allowance	$ 163,000
Net impact to retained earnings	0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	109,700,000	93,700,000
Federal [Member] \| Research [Member]
Operating Loss Carryforwards [Line Items]
Research and development credit carryforwards	$ 1,700,000	$ 1,400,000
Research and development tax credit carryforwards expiration year	2036	2035
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 90,200,000	$ 74,100,000
State [Member] \| Research [Member]
Operating Loss Carryforwards [Line Items]
Research and development credit carryforwards	$ 1,100,000	$ 900,000
Research and development tax credit carryforwards expiration year	2031	2030

Income Taxes - Reconciliation of Income Tax Expense Computed at Statutory Federal Income Tax Rate to Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	34.00%	34.00%
State income tax, net of federal benefit	5.00%	5.00%
Permanent differences	(0.60%)	(0.50%)
Research and development credit	1.10%	0.90%
Stock compensation	(0.50%)	(0.70%)
Other	0.20%	0.40%
Change in valuation allowance	(39.20%)	(39.10%)
Effective income tax rate	0.00%	0.00%

Commitments - Additional Information (Detail) $ in Thousands			12 Months Ended
	Mar. 19, 2017 USD ($)	Jul. 09, 2015	Dec. 31, 2016 USD ($)	Mar. 29, 2017 ft²
Operating Leased Assets [Line Items]
Deferred liability related to facility lease			$ 153
Noncancelable operating lease rent expenses			$ 728
Subsequent Events [Member] \| Certain Executive Officers [Member] \| Minimum [Member]
Operating Leased Assets [Line Items]
Retention agreements period of salary compensation as lump sum payments (in months)	6 months
Subsequent Events [Member] \| Certain Executive Officers [Member] \| Maximum [Member]
Operating Leased Assets [Line Items]
Retention agreements period of salary compensation as lump sum payments (in months)	18 months
Amount required to pay under retention agreements	$ 1,800
Office Laboratory and Vivarium Space Facility Lease [Member]
Operating Leased Assets [Line Items]
Noncancelable operating lease expire date			Feb. 28, 2021
Noncancelable operating leases renewal option period		3 years
Effective date of lease amendment			Mar. 29, 2017
Office Laboratory and Vivarium Space Facility Lease [Member] \| Subsequent Events [Member]
Operating Leased Assets [Line Items]
Area removed from lease agreement \| ft²				1,753

Commitments - Summary of Future Minimum Lease Payments under Non-cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2017	$ 690
2018	738
2019	786
2020	830
2021	140
Total	$ 3,184

Licensing Agreements - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development	$ 3,184,000	$ 7,089,000	$ 7,522,000	$ 9,770,000	$ 7,157,000	$ 7,092,000	$ 6,678,000	$ 5,021,000	$ 27,565,000	$ 25,948,000	$ 11,772,000
Calando Pharmaceuticals, Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Bankruptcy proceedings, court where petition was filed									District of Delaware
Bankruptcy petition date filed									Mar. 03, 2015
Bankruptcy description									In March 2014, Calando entered Chapter 7 bankruptcy in the District of Delaware and, as a result, the intellectual property rights the Company has obtained from Calando are subject to potential risks that may arise in connection with bankruptcy.
Trustee's last deadline to company knowledge on sale of rights ever consummated									Feb. 07, 2017
Calando Product License Agreement [Member] \| Upon achievement of specified regulatory and commercial milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment									$ 32,800,000
Calando Platform License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment									17,800,000
Calando Platform License Agreement [Member] \| CRLX301 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment									250,000
SUNY License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development									$ 30,000	30,000	25,000
MIT License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development										$ 50,000	$ 10,000

Retirement Plans - Additional Information (Detail) - Safe Harbor Plan [Member] - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2010	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match	4.00%
Defined contribution plan, employer matching contribution		$ 292	$ 264	$ 163

Related Party Transactions - Additional Information (Detail) - USD ($)		12 Months Ended
	Apr. 01, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Proceeds from sale of equipment	$ 30,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Fees recorded offsetting research and development expenses		$ 39,000

Revenue - Additional Information (Detail)	1 Months Ended	3 Months Ended	12 Months Ended
Revenue - Additional Information (Detail)	Oct. 31, 2016 USD ($) Employee	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 Entity
Revenue Recognition Milestone Method [Line Items]
Revenue		$ 766,000	$ 766,000		$ 80,000
Material Transfer Agreement [Member]
Revenue Recognition Milestone Method [Line Items]
Revenue			$ 0	$ 0	$ 80,000
Agreements with number of biopharmaceutical companies \| Entity						2
Novartis Institutes for BioMedical Research, Inc [Member] \| Collaboration Agreement [Member]
Revenue Recognition Milestone Method [Line Items]
Upfront payment received	$ 5,000,000
Initial research term of agreement	2 years
Number of full-time employees engaged in research activities under the collaboration \| Employee	5
Research term of the agreement, description			the initial research term by up to two additional one-year periods
Novartis Institutes for BioMedical Research, Inc [Member] \| Collaboration Agreement [Member] \| Upfront Fee [Member]
Revenue Recognition Milestone Method [Line Items]
Revenue			$ 507,000
Novartis Institutes for BioMedical Research, Inc [Member] \| Collaboration Agreement [Member] \| Funding for Activities Performed [Member]
Revenue Recognition Milestone Method [Line Items]
Revenue			$ 259,000

Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 766								$ 766		$ 80
Operating expenses:
Research and development	3,184	$ 7,089	$ 7,522	$ 9,770	$ 7,157	$ 7,092	$ 6,678	$ 5,021	27,565	$ 25,948	11,772
General and administrative	2,090	2,374	2,773	3,118	2,872	2,954	2,717	2,681	10,355	11,224	8,587
Total operating expenses	5,274	9,463	10,295	12,888	10,029	10,046	9,395	7,702	37,920	37,172	20,359
Other income (expense):
Interest income	20	25	25	16	2	4	1	3	86	10	9
Interest expense	(457)	(521)	(589)	(670)	(689)	(509)	(513)	(721)	(2,237)	(2,432)	(1,083)
Total other income (expense), net	(437)	(496)	(564)	(654)	(687)	(505)	(512)	(718)	(2,151)	(2,422)	(3,063)
Net loss attributable to common stockholders	$ (4,945)	$ (9,959)	$ (10,859)	$ (13,542)	$ (10,716)	$ (10,551)	$ (9,907)	$ (8,420)	$ (39,305)	$ (39,594)	$ (23,342)
Net loss per share attributable to common stockholders:
Basic and diluted	$ (0.17)	$ (0.36)	$ (0.40)	$ (0.49)	$ (0.39)	$ (0.39)	$ (0.37)	$ (0.41)	$ (1.42)	$ (1.56)	$ (1.60)
Weighted-average common shares outstanding:
Basic and diluted	28,724,083	27,383,376	27,363,965	27,362,643	27,346,780	27,307,103	26,690,673	20,350,557	27,710,403	25,431,332	14,548,516

Subsequent Events - Additional Information (Detail) $ in Thousands				12 Months Ended
	Mar. 21, 2017 USD ($)	Mar. 20, 2017 USD ($) Employee	Mar. 19, 2017 USD ($)	Dec. 31, 2016 USD ($)
Daré Bioscience, Inc. [Member] \| Stock Purchase Agreement [Member]
Subsequent Event [Line Items]
Termination rights, description				The Stock Purchase Agreement contains certain termination rights for both the Company and Daré, and further provides that, upon termination of the Stock Purchase Agreement under specified circumstances, the Company may be required to pay Daré a termination fee of $0.3 million, or Daré may be required to pay the Company a termination fee of $0.45 million.
Subsequent Events [Member]
Subsequent Event [Line Items]
Percentage of workforce elimination		58.00%
Total number of full-time equivalent remaining employees \| Employee		8
Subsequent Events [Member] \| Novartis Institutes for BioMedical Research, Inc [Member] \| Asset Purchase Agreement [Member]
Subsequent Event [Line Items]
Purchase price receivable from sale of assets			$ 6,000
Subsequent Events [Member] \| BlueLink Pharmaceuticals, Inc. [Member] \| Asset Purchase Agreement [Member]
Subsequent Event [Line Items]
Proceeds from sale of assets	$ 1,500
Subsequent Events [Member] \| Daré Bioscience, Inc. [Member] \| Stock Purchase Agreement [Member]
Subsequent Event [Line Items]
Termination fee payable upon termination of agreement			300
Termination fee receivable upon termination of agreement			$ 450
Subsequent Events [Member] \| Daré Bioscience, Inc. [Member] \| Minimum [Member] \| Stock Purchase Agreement [Member]
Subsequent Event [Line Items]
Selling stockholders expected ownership percentage			51.00%
Subsequent Events [Member] \| Daré Bioscience, Inc. [Member] \| Maximum [Member] \| Stock Purchase Agreement [Member]
Subsequent Event [Line Items]
Selling stockholders expected ownership percentage			70.00%
Hercules Loan Agreement [Member]
Subsequent Event [Line Items]
Accrued end of term charge				$ 1,100
Hercules Loan Agreement [Member] \| Subsequent Events [Member]
Subsequent Event [Line Items]
Pay off loan agreement, amount paid		$ 12,400
Pay off loan agreement, final end of term charge amount		$ 1,400
Final payment as percentage of aggregate original principal amount		6.70%

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Money market fund investments	$ 35.0	$ 75.3