Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2015	Mar. 15, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	CBYL
Entity Registrant Name	CARBYLAN THERAPEUTICS, INC.
Entity Central Index Key	0001348911
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		26,332,494
Entity Public Float			$ 88,485,047

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 53,723	$ 3,897
Prepaid expenses and other current assets	1,222	690
Total current assets	54,945	4,587
Property and equipment, net	805	180
Restricted cash	50	50
Deferred public offering costs		1,648
Other assets	991	179
Total assets	56,791	6,644
Current liabilities:
Accounts payable	1,460	1,024
Accrued expenses	1,327	1,605
Loans payable	1,455	4,435
Deferred licensing revenue	29	29
Total current liabilities	4,271	7,093
Loans payable, net of current portion	3,154
Convertible promissory notes		2,131
Derivative liability		1,495
Preferred stock warrant liability		463
Deferred licensing revenue, net of current portion	56	85
Deferred rent, net of current portion		2
Total liabilities	$ 7,481	$ 11,269
Commitments and contingencies (Note 5)
Stockholders’ equity (deficit)
Preferred stock, $0.001 par value; 5,000,000 shares authorized as of December 31, 2015 and none authorized as of December 31, 2014: no shares issued and outstanding as of December 31, 2015 and December 31, 2014
Common stock, $0.001 par value; 100,000,000 shares authorized as of December 31, 2015 and 45,000,000 shares authorized as of December 31, 2014; 26,322,494 shares issued and outstanding as of December 31, 2015 and 691,312 shares issued and outstanding as of December 31, 2014	$ 27	$ 1
Additional paid-in capital	121,904	3,593
Accumulated deficit	(72,621)	(47,775)
Total stockholders’ equity (deficit)	49,310	(44,181)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 56,791	6,644
Convertible Preferred Stock [Member]
Current liabilities:
Convertible preferred stock, $0.001 par value; no shares authorized as of December 31, 2015 and 34,371,305 shares authorized as of December 31, 2014; no shares issued and outstanding as of December 31, 2015 and 8,268,531 shares issued and outstanding as of December 31, 2014		$ 39,556

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	45,000,000
Common stock, shares issued	26,322,494	691,312
Common stock, shares outstanding	26,322,494	691,312
Convertible Preferred Stock [Member]
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	0	34,371,305
Convertible preferred stock, shares issued	0	8,268,531
Convertible preferred stock, shares outstanding	0	8,268,531

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
License Revenue	$ 29	$ 29	$ 415
Operating Expenses:
Research and development	16,199	8,294	4,229
General and administrative	4,866	3,412	1,402
Total operating expenses	21,065	11,706	5,631
Loss from Operations	(21,036)	(11,677)	(5,216)
Other Income (expense):
Interest income	5	2	2
Interest expense	(1,188)	(1,082)	(405)
Loss on extinguishment of convertible promissory notes	(3,177)
Other income (expense), net	550	(602)	(59)
Total other income (expense)	(3,810)	(1,682)	(462)
Net Loss and Comprehensive Loss	$ (24,846)	$ (13,359)	$ (5,678)
Net loss per share to common stockholders, basic and diluted	$ (1.30)	$ (21.81)	$ (13.42)
Weighted average common shares outstanding, basic and diluted	19,082,604	612,525	423,059

Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A and B Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Convertible Promissory Notes [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2012	$ (28,285)				$ 453	$ (28,738)
Balance, shares at Dec. 31, 2012			421,152
Balance at Dec. 31, 2012		$ 33,546
Balance, shares at Dec. 31, 2012		7,016,037
Exercise of stock options	17				17
Exercise of stock options, shares			21,254
Issuance of Series B Preferred Stock, net of issuance costs		$ 6,010
Issuance of Series B Preferred Stock, net of issuance costs, shares		1,252,494
Stock-based compensation expense	238				238
Net loss	(5,678)					(5,678)
Balance at Dec. 31, 2013	(33,708)				708	(34,416)
Balance, shares at Dec. 31, 2013			442,406
Balance at Dec. 31, 2013		$ 39,556
Balance, shares at Dec. 31, 2013		8,268,531
Exercise of stock options	$ 229		$ 1		228
Exercise of stock options, shares	248,909		248,906
Stock-based compensation expense	$ 381				381
Beneficial conversion feature of convertible promissory notes	2,276				2,276
Net loss	(13,359)					(13,359)
Balance at Dec. 31, 2014	(44,181)		$ 1		3,593	(47,775)
Balance, shares at Dec. 31, 2014			691,312
Balance at Dec. 31, 2014		$ 39,556
Balance, shares at Dec. 31, 2014		8,268,531
Exercise of stock options	$ 155		$ 1		154
Exercise of stock options, shares	78,983		78,986
Stock-based compensation expense	$ 785				785
Conversion of convertible promissory notes to common stock	39,556		$ 8		39,548
Conversion of convertible promissory notes to common stock, shares			8,268,531	2,287,120
Conversion of preferred stock warrants to common stock warrants	347				347
Cashless exercise of common stock warrants	0
Cashless exercise of common stock warrants, shares			56,545
Net loss	(24,846)					(24,846)
Balance at Dec. 31, 2015	49,310		$ 27		121,904	$ (72,621)
Balance, shares at Dec. 31, 2015			26,332,494
Issuance of common stock upon initial public offering, net of underwriting discounts, commissions and offering costs	66,262		$ 15		66,247
Issuance of common stock upon initial public offering, net of underwriting discounts, commissions and offering costs, shares			14,950,000
Conversion of convertible preferred stock amount Converted	(39,556)	$ (39,556)
Conversion of convertible preferred stock Shares converted		(8,268,531)
Conversion of convertible promissory notes to common stock	$ 11,232		$ 2		$ 11,230

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities
Net loss	$ (24,846)	$ (13,359)	$ (5,678)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	133	54	27
Stock based compensation	785	381	238
Change in fair value of preferred stock warrant liability and derivative liability	(520)	605	63
Non-cash interest expense	229	64	32
Amortization of loan and convertible promissory notes discount	780	384
Loss on extinguishment of convertible promissory notes	3,177
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(532)	(561)	(46)
Other assets	(97)	(109)
Accounts payable	355	487	315
Accrued expenses	(298)	830	185
Deferred licensing revenue	(29)	(29)	6
Net cash used in operating activities	(20,863)	(11,253)	(4,858)
Cash Flows from Investing Activities
Purchase of property and equipment	(659)	(159)	(18)
Deposit for leasehold improvements	(715)
Net cash used in investing activities	(1,374)	(159)	(18)
Cash Flows from Financing Activities
Proceeds from issuance of common stock upon exercise of options, net	155	229	17
Proceeds from issuance of common stock, net	67,908	(1,201)
Proceeds from issuance of convertible preferred stock, net			6,010
Proceeds from loans payable		2,208	546
Repayment of loans payable		(708)	(158)
Proceeds from convertible promissory notes	4,000	5,000
Net cash provided by financing activities	72,063	5,528	6,415
Net increase/(decrease) in cash and cash equivalents	49,826	(5,884)	1,539
Cash and cash equivalents at beginning of year	3,897	9,781	8,242
Cash and cash equivalents at end of year	53,723	3,897	9,781
Supplemental Cash Flow Information
Cash paid for interest	180	626	367
Supplemental Disclosures of Non-cash Financing Activities
Issuance of preferred stock warrants		103	$ 42
Conversion of preferred stock warrants to common stock warrants	347
Conversion of preferred stock to common stock	39,556
Increase of accrual for deferred public offering costs		447
Increase of derivative related to convertible promissory notes	1,196	1,067
Increase of beneficial conversion feature for convertible promissory notes	519	$ 2,275
Property and equipment additions in accounts payable and accrued expenses	$ 99

Formation and Business of the Company	12 Months Ended
Formation and Business of the Company	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Formation and Business of the Company	Note 1. Formation and Business of the Company Carbylan Therapeutics, Inc. (the “Company”) is a clinical-stage specialty pharmaceutical company focused on the development and commercialization of novel and proprietary combination therapies that address significant unmet medical needs. The Company’s initial focus is on the development of Hydros-TA, its proprietary, potentially best-in-class intra-articular injectable product candidate to treat pain associated with osteoarthritis of the knee. The Company was incorporated in the state of Delaware on March 26, 2004 as Sentrx Surgical, Inc. The name of the Company was changed to Carbylan Biosurgery, Inc. on December 14, 2005. The name of the Company was changed to Carbylan Therapeutics, Inc. on March 7, 2014. Since commencing operations in 2004, the Company has devoted substantially all of its efforts to identifying and developing product candidates for therapeutic markets, recruiting personnel and raising capital. The Company has devoted predominantly all of its resources to the preclinical and clinical development of, and manufacturing capabilities for, Hydros-TA. The Company has never been profitable and has not yet commenced commercial operations. At December 31, 2015, the Company had an accumulated deficit of approximately $72.6 million. The Company expects to incur increased research and development expenses during the current Phase 3 trial of Hydros-TA. Management’s plans with respect to these matters include utilizing a substantial portion of the Company’s capital resources and efforts in completing the development and obtaining regulatory approval for Hydros-TA and expanding the Company’s organization. In March 2015, the Company’s board of directors and stockholders approved a 4-for-1 reverse stock split of the Company’s common and preferred stock. The Company filed an amendment to its certificate of incorporation effecting the reverse stock split on March 13, 2015. All share and per share amounts contained in these financial statements and notes thereto, have been adjusted retroactively to reflect the reverse stock split. On April 8, 2015, the Company’s registration statement on Form S-1 (File No. 333-201278) relating to the IPO of its common stock was declared effective by the SEC. The IPO closed on April 14, 2015 at which time the Company sold 14,950,000 shares of common stock, which included 1,950,000 shares of common stock purchased by the underwriters upon the full exercise of their option to purchase additional shares of common stock. The Company received cash proceeds of approximately $66.3 million from the IPO, net of underwriting discounts and commissions and offering costs paid by the Company. Prior to the closing of the IPO, all outstanding shares of convertible preferred stock converted into 8,268,531 shares of common stock with the related carrying value of $39.6 million reclassified to common stock and additional paid-in capital. In addition, all convertible preferred stock warrants were converted into warrants exercisable for common stock and the convertible promissory notes were converted in to 2,287,120 shares of common stock. On April 14, 2015, the Company filed its Amended and Restated Certificate of Incorporation, authorizing 105,000,000 shares of capital stock, including 100,000,000 shares of authorized common stock and 5,000,000 shares of authorized undesignated preferred stock. Both the common stock and preferred stock have a par value of $0.001 per share. There are no shares of preferred stock outstanding at December 31, 2015.

Summary of Significant Accounting Policies and Basis of Presentation

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Summary of Significant Accounting Policies and Basis of Presentation

Note 2. Summary of Significant Accounting Policies and Basis of Presentation

Basis of Presentation

The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Use of Estimates

The preparation of the Company’s financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, 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 periods. On an ongoing basis, the Company evaluates its estimates, including those related to common stock, stock-based compensation expense, warrant liabilities, accruals, derivative liability, deferred tax valuation allowance and revenue recognition. Management bases its estimates on historical experience or on various other assumptions, including information received from its service providers, which it believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Risks and Uncertainties

The product candidates developed by the Company require approvals from the U.S. Food and Drug Administration (“FDA”) or foreign regulatory agencies prior to commercial sales. There can be no assurance that the Company’s current and future product candidates will receive the necessary approvals. If the Company is denied approval or approval is delayed, it may have a material adverse impact on the Company’s business and its financial statements.

The Company is subject to risks common to companies in the pharmaceutical industry with no commercial operating history, including, but not limited to, dependency on the clinical and commercial success of its product candidates, ability to obtain regulatory approval of its product candidates, the need for substantial additional financing to achieve its goals, uncertainty of broad adoption of its approved products, if any, by physicians and consumers, significant competition and untested manufacturing capabilities.

The Company expects to incur substantial operating losses for the next several years and will need to obtain additional financing in order to launch and commercialize any products or product candidates for which it receives regulatory approval. There can be no assurance that such financing will be available or will be at terms acceptable by the Company.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents. The Company invests its excess cash in money market accounts. The Company’s cash and cash equivalents are held by a single financial institution and all cash is held in the United States. Such deposits may, at times, exceed federally insured limits. The Company has not recognized any losses during the periods presented and management does not believe that the Company is exposed to significant credit risk from its cash and cash equivalents.

Segment Reporting

The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company is a specialty pharmaceutical company focused on the development and commercialization of novel and proprietary combination therapies that address significant unmet medical needs. No product revenue has been generated since inception, and all assets are held in North America.

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with an original maturity date of 90 days or less on the date of purchase to be cash equivalents. The Company invests its cash in bank deposits and money market funds.

Restricted Cash

The Company is required to guarantee the credit limit on its corporate credit card with a certificate of deposit of $50,000. The balance is included as restricted cash on the accompanying financial statements.

Beneficial Conversion Feature

From time to time, the Company may issue convertible promissory notes that have conversion prices that create an embedded beneficial conversion feature on the issuance date. A beneficial conversion feature exists on the date a convertible promissory note is issued when the fair value of the underlying common stock to which the note is convertible into is in excess of the remaining unallocated proceeds of the note after first considering the allocation of a portion of the note proceeds to the fair value of any attached equity instruments, if any related equity instruments were granted with the debt. The intrinsic value of the beneficial conversion feature is recorded as a debt discount with a corresponding amount to additional paid-in capital. The debt discount is amortized to interest expense over the term of the note using the effective interest method.

Embedded Derivatives Related to Convertible Promissory Notes

Embedded derivatives that are required to be bifurcated from the underlying debt instrument (i.e. host) are accounted for and valued as a separate financial instrument. The Company evaluated the terms and features of the convertible promissory notes issued in September 2014 and February 2015 and identified embedded derivatives requiring bifurcation and accounting at fair value because the economic and contractual characteristics of the embedded derivatives met the criteria for bifurcation and separate accounting due to the conversion features (see Note 8 for a description of the conversion features).

Fair Value of Financial Instruments

Fair value accounting is applied for all financial assets and liabilities, and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually).

Property and Equipment, Net

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, which are as follows:

Computer equipment		3 years
Lab equipment		3 years
Furniture and fixtures		5 years
Machinery and equipment		3 years
Manufacturing equipment		7 years

Leasehold improvements are amortized over the lesser of their useful lives or the term of the lease. Upon sale or retirement of the assets, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is recognized in the accompanying statement of operations and comprehensive loss in other income (expense), net. Maintenance and repairs are charged to operations as incurred.

Pre-clinical and Clinical Trial Accruals

The Company’s clinical trial accruals are based on estimates of patient enrollment and related costs at clinical investigator sites as well as estimates for the services received and efforts expended pursuant to contracts with clinical research organizations that conduct and manage preclinical and clinical trials on the Company’s behalf. If timelines or contracts are modified based upon changes in the clinical trial protocol or scope of work to be performed, the Company modifies the estimates of accrued expenses accordingly. To date, there have been no material differences from its estimates to the amount actually incurred.

Preferred Stock Warrant Liability

The Company accounts for its warrants as either equity or liabilities based upon the characteristics and provisions of each instrument. Warrants classified as derivative liabilities are recorded on the Company’s accompanying balance sheets at their fair value on the date of issuance and are revalued at each subsequent balance sheet date, with fair value changes recognized as increases or reductions to other income (expense), net in the statements of operations and comprehensive loss.

License Revenue

Revenue under the Company’s license arrangement is recognized based on the performance requirements of the contract. Determinations of whether persuasive evidence of an arrangement exists and whether delivery has occurred or services have been rendered are based on management’s judgments regarding the fixed nature of the fees charged for deliverables and the collectability of those fees. Should changes in conditions cause management to determine that these criteria are not met for any new or modified transactions, revenue recognized could be adversely affected.

The Company recognizes revenue related to its license arrangement in accordance with the provisions of Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 605-25, Revenue Recognition — Multiple-Element Arrangements (“ASC Topic 605-25,”) which provides guidance on how deliverables in an arrangement should be separated and how the arrangement consideration should be allocated to the separate units of accounting:

requiring an entity to determine the selling price of a separate deliverable using a hierarchy of (i) vendor-specific objective evidence (“VSOE,”), (ii) third-party evidence (“TPE,”) or (iii) best estimate of selling price (“BESP”); and

requiring the allocation of the arrangement consideration, at the inception of the arrangement, to the separate units of accounting based on relative fair value.

The Company evaluates all deliverables within an arrangement to determine whether or not they provide value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. The Company may exercise significant judgment in determining whether a deliverable is a separate unit of accounting, as well as in estimating the selling prices of such unit of accounting.

To determine the selling price of a separate deliverable, the Company uses the hierarchy as prescribed in ASC Topic 605-25 based on VSOE, TPE or BESP. VSOE is based on the price charged when the element is sold separately and is the price actually charged for that deliverable. TPE is determined based on third-party evidence for a similar deliverable when sold separately and BESP is the price at which the Company would transact a sale if the elements of collaboration and license arrangements were sold on a stand-alone basis. The Company may not be able to establish VSOE or TPE for the deliverables within collaboration and license arrangements, as the Company does not have a history of entering into such arrangements or selling the individual deliverables within such arrangements separately. In addition, there may be significant differentiation in these arrangements, which indicates that comparable third-party pricing may not be available. The Company may determine that the selling price for the deliverables within collaboration and license arrangements should be determined using BESP. The process for determining BESP involves significant judgment on the Company’s part and includes consideration of multiple factors such as estimated direct expenses and other costs, and available data.

For each unit of accounting identified within an arrangement, the Company determines the period over which the performance obligation occurs. The Company allocates the arrangement consideration to the separate units of accounting based on the relative selling prices. Revenue is recognized immediately if the performance obligation has been met. The Company recognizes the revenue that is deferred using the straight-line method over the expected delivery period of the unit of accounting. Non-substantive regulatory milestone and commercialization royalty payments are recognized in proportion to the two units of accounting identified at the inception of the agreement. Each portion will be recognized in accordance with the underlying unit of accounting. The Company accounts for revenue net of applicable foreign taxes.

Research and Development Expenditures

Costs incurred to further the Company’s research and development include salaries and related employee benefits, stock-based compensation expense, costs associated with clinical studies, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on behalf of the Company.

Stock-Based Compensation

The Company maintains performance incentive plans under which incentive stock options and non-qualified stock options may be granted to employees and non-employees. The Company accounts for stock-based compensation arrangements with employees in accordance with ASC 718, Compensation — Stock Compensation. ASC 718 requires the recognition of compensation expense, using a fair value-based method, for costs related to all share-based payments including stock options.

The Company’s determination of the fair value of stock options on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by its common stock price as well as changes in assumptions regarding a number of subjective variables. These variables include, but are not limited to, expected term that options will remain outstanding, expected common stock price volatility over the term of the option awards, risk-free interest rates and expected dividends.

The fair value is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period), on a straight-line basis. Stock-based compensation expense recognized at fair value includes the impact of estimated forfeitures. The Company estimates future forfeitures at the date of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

Income Taxes

The Company accounts for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

The Company accounts for uncertain tax positions in accordance with ASC 740-10, Accounting for Uncertainty in Income Taxes. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

It is the Company’s policy to include penalties and interest expense related to income taxes as a component of other expense and interest expense as necessary. There was no interest or penalties accrued at December 31, 2015, 2014 and 2013.

Net Loss per Share Attributable to Common Stockholders

The Company calculates its basic and diluted net income (loss) per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities, which are securities other than common stock that are entitled to receive dividends. The Company’s convertible preferred stockholders are entitled to participate in dividends and earnings of the Company when dividends are paid on common stock. Under the two-class method, the Company determines whether it has net income attributable to common stockholders, which includes the results of operations, capital contributions and deemed dividends less current period convertible preferred stock non-cumulative dividends. If it is determined that the Company does have net income attributable to common stockholders during a period, the related undistributed earnings are then allocated between common stock and the convertible preferred stock based on the weighted average number of shares outstanding during the period to determine the numerator for the basic net income per share attributable to common stockholders. In computing diluted net income attributable to common stockholders, undistributed earnings are re- allocated to reflect the potential impact of dilutive securities to determine the numerator for the diluted net income per share attributable to common stockholders.

The Company’s basic net income (loss) per share attributable to common stockholders is calculated by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. The diluted net income (loss) per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. For purposes of this calculation, options to purchase common stock and common stock warrants are considered common stock equivalents. For periods in which the Company has reported net losses, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders for the years ended December 31, 2015, 2014 and 2013.

Reverse Stock Split

In March 2015, the Company’s board of directors and stockholders approved a 4-for-1 reverse stock split of the Company’s common and preferred stock. The Company filed an amendment to its certificate of incorporation effecting the reverse stock split on March 13, 2015. All share and per share amounts for all periods presented in these financial statements and notes thereto, have been adjusted retroactively to reflect the reverse stock split.

Recent Accounting Pronouncement

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards update (“ASU”) 2014-09, “Revenue from Contracts with Customers,” requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. In July 2015, the FASB voted to defer the effective date for annual reporting periods beginning after December 15, 2017 (including interim reporting periods within those periods) and permitted early adoption of the standard, but not before the original effective date of December 15, 2016. The Company expects to adopt the updated standard in the first quarter of fiscal 2018. The Company has not yet selected a transition method and is currently evaluating the effect that the updated standard will have on the financial statements and related disclosures.

In August 2014, the FASB issued ASU NO. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, or ASU 2014-15. ASU 2014-15 requires management to perform interim and annual assessments of an entity’s ability to continue as a going concern within one year of the date the financial statements are issued and provides guidance on determining when and how to disclose going concern uncertainties in the financial statements. Certain disclosures will be required if conditions give rise to substantial doubt about an entity’s ability to continue as a going concern. ASU 2014-15 applies to all entities and is effective for annual and interim reporting periods ending after December 15, 2016, with early adoption permitted. The Company does not expect that the adoption of this guidance will have a material effect on its financial statements.

In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. ASU 2015-03 requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the related debt liability, similar to debt discounts. The standard will be effective for financial statements issued for annual periods beginning after December 15, 2015, and interim periods within those annual periods. Early adoption is permitted for financial statements that have not been previously issued. The Company is evaluating the effect that the standard will have on our financial statements.

In November 2015, the FASB issued ASU No. 2015-17 (Topic 740), Balance Sheet Classification of Deferred Taxes. ASU 2015-17 requires deferred tax liabilities and assets to be classified as noncurrent in the balance sheet. The standard will be effective for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted for financial statements that have not been previously issued. The ASU may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The Company adopted this ASU on a prospective basis in the fourth quarter of fiscal 2015. The adoption did not have a material effect on the Company’s financial statements.

In February 2016, the FASB issued new lease accounting guidance in Accounting Standards Update No. 2016-02, Leases (Topic 842). Under the new guidance, lessees will be required to recognize for all leases (with the exception of short-term leases) at the commencement date: (1) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Lessor accounting, however, remains largely unchanged. In addition, the new lease guidance simplified the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees will no longer be provided with a source of off-balance sheet financing. The new lease guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted, however, the Company does not intend to early adopt. The Company also believes that adoption of this new guidance will not have a material impact on the Company’s financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 3. Fair Value Measurements

The Company follows ASC 820-10, Fair Value Measurements and Disclosures, which among other things, defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows:

Level 1

Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2

Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life.

Level 3

Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

The Company’s investments in money market funds are measured at fair value on a recurring basis. The fair value of the money market fund investments is classified as Level 1.

The fair value of the certificates of deposit is classified as Level 2 due to the nature of a contractual restriction with a financial institution that requires the certificate of deposit to remain in place as collateral, and therefore the ability to liquidate the investment is limited.

As of December 31, 2015, based on borrowing rates that are available to the Company for loans of similar terms and consideration of the Company’s credit risk, the carrying value of the loan payable approximates the fair value using Level 2 inputs.

There were no transfers between Level 1 and Level 2 during the periods presented.

In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3. On a recurring basis, the Company estimates the fair value of the warrant liability. The Company used the Black-Scholes option-pricing method to calculate the fair value of the warrant liability. Generally, increases or decreases in the fair value of the underlying convertible preferred stock would result in a similar impact in the fair value measurement of the warrant liability.

The fair value of the derivative of the September 2014 and February 2015 convertible promissory notes (see Note 8) was recorded as a derivative liability instrument that is measured at fair value at each reporting period. In connection with the IPO, the convertible promissory notes were converted in to shares of common stock, and therefore there is no derivative liability at December 31, 2015. At December 31, 2014, the Company remeasured the fair value of the derivative for the September 2014 convertible promissory notes by estimating the fair value of the convertible promissory notes with and without the conversion derivative. To calculate the fair value of the convertible promissory notes without the conversion derivative, the Company estimated the present value of the expected cash payments at an assumed discount rate. To calculate the fair value of the convertible promissory notes with the conversion feature, the Company calculated the present value of the convertible promissory notes upon conversion at an initial public offering, and the present value of the convertible promissory notes at an equity financing. The Company applied a probability of occurrence to all of the conversion scenarios and estimated a weighted value of the notes with the conversion feature. The difference between the fair value of the convertible promissory notes with and without the conversion features is the fair value of the derivative.

The following table presents the Company’s fair value hierarchy for assets and liabilities measured at fair value on a recurring basis:

	Fair Value Measurements as of December 31, 2015 (in thousands)
	Quoted Price in Active Markets for Identical Assets		Significant other Observable Inputs		Significant Unobservable Inputs
	Level 1		Level 2		Level 3		Total
Assets
Money market funds⁽¹⁾	$	53,625	$	—	$	—	$	53,625
Certificate of deposit		—		50		—		50
	$	53,625	$	50	$	—	$	53,675

	Fair Value Measurements as of December 31, 2014 (in thousands)
	Quoted Price in Active Markets for Identical Assets		Significant other Observable Inputs		Significant Unobservable Inputs
	Level 1		Level 2		Level 3		Total
Assets
Money market funds⁽¹⁾	$	3,825	$	—	$	—	$	3,825
Certificate of deposit		—		50		—		50
	$	3,825	$	50	$	—	$	3,875
Liabilities
Derivative liability	$	—	$	—	$	1,495	$	1,495
Preferred stock warrant liability		—		—		463		463
	$	—	$	—	$	1,958	$	1,958

(1)	Included in cash and cash equivalents in the Company’s balance sheet.

The change in the fair value of the preferred stock warrant liability is summarized below:

Fair value as of December 31, 2013	$	184
Fair value of new warrant issued		103
Change in fair value recorded in other income (expense), net		176
Fair value as of December 31, 2014	$	463
Change in fair value recorded in other income (expense), net		(116	)
Conversion to common stock warrants at IPO date		(347	)
Fair value as of December 31, 2015	$	—

The following is a summary of the activity of the derivative liability:

Fair value as of December 31, 2013	$	—
Embedded derivative liability upon issuance of convertible promissory notes		1,067
Change in fair value recorded in other income (expense), net		428
Fair value as of December 31, 2014	$	1,495
Embedded derivative liability upon issuance of convertible promissory notes		1,196
Change in fair value recorded in other income (expense), net		(404	)
Conversion of convertible promissory notes		(2,287	)
Fair value as of December 31, 2015	$	—

The fair value of the derivative liability was determined using the following assumptions (see Note 8):

	At Issuance			At December 31, 2014			At December 31, 2015
Discount Rate		8.25	%		8.25	%		—
Embedded derivative liability upon issuance of convertible promissory notes		0.05	%		0.05	%		—
Change in fair value recorded in other income (expense), net		0.15	%		0.12	%		—

- 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

Balance Sheet Components

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

Note 4. Balance Sheet Components

Property and Equipment, Net

The following table represents the components of property and equipment (in thousands):

	December 31,			December 31,
	2015			2014
Computer equipment	$	30		$	30
Lab equipment		697			543
Furniture and fixtures		21			21
Machinery and equipment		262			26
Leasehold improvements		55			55
Construction in progress		368			—
		1,433			675
Less: Accumulated depreciation and amortization		(628	)		(495	)
Total property and equipment, net	$	805		$	180

Depreciation expense for the years ended December 31, 2015, 2014 and 2013, was $133,000, $54,000 and $27,000, respectively.

Accrued Liabilities

(in thousands)

	December 31,		December 31,
	2015		2014
Accrued payroll and related expenses	$	727	$	723
Accrued legal expenses		77		159
Accrued research and clinical trial expenses		338		380
Accrued professional services		185		343
	$	1,327	$	1,605

Commitments and Contingencies

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 5. Commitments and Contingencies

Operating Lease

The Company leases facilities in Palo Alto, California under a noncancelable operating lease which expires May 2016. The terms of the lease agreement required the Company to provide a security deposit of $69,000. The security deposit is included in other assets on the accompanying balance sheets. The Company had a sub-lease agreement with a tenant for approximately thirty-seven percent of the square footage of the corporate headquarters. Under this agreement, the Company received $16,000 per month as rental income which is accounted for as a reduction of rent expense. The sub-lease agreement expired February 29, 2016.

Gross rent expense for the years ended December 31, 2015, 2014 and 2013 was $431,000, $429,000 and $413,000 , respectively. The rental expense is reduced by the sublease rental income amounts of $195,000, $190,000 and $186,000, respectively, for the same periods.

On July 13, 2015, the Company entered into a lease for an approximately 18,700 square foot facility located in Newark, California (the “Newark Lease”), with office, R&D and laboratory space. Under the Newark Lease, the landlord provided an allowance of $599,000 to fund certain improvements to the facility. In March 2016, the Company determined not occupy to the Newark facility and is attempting to sublease the facility. (See Note 18.)

The Newark Lease has an initial term of approximately six and a half years, with a monthly rental rate starting at $2.65 per square foot in the first year of the lease, escalating each year by 3.0%. The annual rent obligation is expected to be approximately $599,000 for the first year of the lease. The Company is also responsible for certain other costs, including insurance, taxes, utilities, maintenance and repairs, a property management fee, and reimbursement of certain expenses related to maintenance of common areas. The Company delivered a security deposit of approximately $149,000 in connection with the execution of the Newark lease, which is recorded in other assets on the balance sheets.

The aggregate future minimum lease payments under the current and future operating lease are as follows:

Years ending December 31,	(in thousands)
2016	$	618
2017		611
2018		629
2019		648
2020		668
Remaining years		1,100
Total minimum lease payments	$	4,274

Indemnification

In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves future claims that may be made against the Company but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations No amounts associated with such indemnifications have been recorded to date.

Contingencies

From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. There have been no contingent liabilities requiring accrual or disclosure at December 31, 2015.

License Agreement with Shanghai Jingfeng Pharmaceutical Co. Ltd.

12 Months Ended

Dec. 31, 2015

License Agreement [Abstract]

License Agreement with Shanghai Jingfeng Pharmaceutical Co. Ltd.

Note 6. License Agreement with Shanghai Jingfeng Pharmaceutical Co. Ltd.

In November 2012, the Company entered into a technology license agreement (the “Agreement”) with Shanghai Jingfeng Pharmaceutical Co. Ltd. (“Jingfeng”), pursuant to which the Company granted to Jingfeng the exclusive right and license under certain patents to develop, manufacture and commercialize Hydros-TA for human and veterinary uses in China, Taiwan, Hong Kong and Macau. In these countries, Jingfeng is responsible for the manufacture and supply of Hydros-TA, the management and funding of all development activities, regulatory submissions and regulatory approvals for Hydros-TA and the commercialization of Hydros-TA. The Company has also agreed to provide know-how and reasonable professional and technical support services to Jingfeng until Jingfeng performs all efforts necessary to bring the product to commercialization and begins selling the product upon regulatory approval in the aforementioned territory. The Agreement provides for an up-front license payment of $2,000,000 ($1,674,000 net of Chinese withholding taxes), regulatory milestone payments of up to $2,000,000 (excluding Chinese withholding taxes) and future commercial milestone payments of up to approximately $5,000,000 (excluding Chinese withholding taxes) at current exchange rates based on Jingfeng achieving certain gross sales thresholds.

The Company has identified the following non-contingent performance deliverables at the inception of the Agreement: (i) an exclusive royalty bearing license to certain of the Company’s patents relating to Hydros-TA (the “License”), which was transferred immediately upon signing of the Agreement, and (ii) know-how, reasonable professional and technical support services to be provided by the Company to assist Jingfeng in manufacturing, developing and/or commercializing the licensed product (the “Services”) throughout the period of the Agreement. The Company has determined that the License represents a separate unit of accounting as the License has standalone value apart from the Services because the development, manufacturing and commercialization rights conveyed would allow Jingfeng to perform all efforts necessary to use the Company’s technologies to bring the product to commercialization and begin selling the product upon regulatory approval. Jingfeng can sublicense its rights to the License; and the Services provided by the Company could be performed by a third-party. Therefore, the License and Services represent separate units of accounting.

The Company has determined the BESP for the License unit of accounting using a discounted cash flow analysis. This measurement is based on the value indicated by current estimates of future payments to be received under the agreement and reflects management determined estimates and assumptions. These estimates and assumptions include but are not limited to estimated sales prices, estimated market opportunity, expected market share, the likelihood that clinical trials will be successful, the likelihood that regulatory approval will be received, the likelihood that the products will become commercialized, the determination of the markets served and the discount rate. The Company reduced the future payment to be received by the estimated amount of the professional service costs plus an estimated margin, which was based on industry benchmarking of similar companies. These estimates and assumptions formed the basis of an expected net future cash flow that was discounted based on an estimated weighted average cost of capital. The Company has also determined the BESP for the Services unit of accounting based on the estimated cost of the professional services plus an estimated margin which was based on industry benchmarking of similar companies. These estimates and assumptions formed the basis of an expected net future cash flow that was discounted based on an estimated weighted average cost of capital.

The considerations of the Agreement have been allocated to the units of accounting based on the relative selling price method. Of the $1,674,000 upfront payment received, $1,534,000 was allocated to the License and $140,000 to the Services. The Company has recognized license revenue upon execution of the Agreement as the license has been delivered pursuant to the terms of the Agreement. The $140,000 allocated to Services will be recognized as revenue on a straight-line over the estimated performance period through January 2019. The way in which the Company will provide professional services does not give rise to a more precise pattern of recognition and the Company therefore will recognize revenue on a straight-line basis over the performance period.

Of the $421,000 regulatory milestone payment received in November 2013 upon the successful production by Jingfeng of the first batch of Hydros-TA, $385,000 was allocated to the License and $35,000 was allocated to the Services. The Company has recognized license revenue upon execution of the Agreement as the associated unit of accounting had been delivered pursuant to the terms of the Agreement. The $35,000 allocated to Services will be recognized as revenue on a straight-line basis over the performance period which is currently estimated to be January 2019.

Total revenue recognized with respect to the Agreement consisted of the following (in thousands):

	Year Ended December 31,
	2015		2014		2013

License and Services revenue	$	29	$	29	$	415

The Company has determined that the regulatory milestones and commercialization royalty are contingent revenue that will be allocated to the two units of accounting (License and Services) described above, rather than recognized immediately upon satisfaction of the milestone, as they do not meet the definition of a milestone as described in the applicable accounting literature. Certain regulatory milestones do not require performance by the Company to be achieved. The payments the Company would receive for the remaining regulatory milestones are not commensurate with the performance by the Company to achieve such milestones.

Loan and Security Agreement

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Loan and Security Agreement

Note 7. Loan and Security Agreement

In October 2011, the Company entered into a loan and security agreement (the “Loan and Security Agreement”) with a financial institution. In September 2014, the Loan and Security Agreement was amended to provide for a new loan of $4,500,000 and repayment of the outstanding principal of the loan amounts previously disbursed in February 2013 and January 2014, with the remaining proceeds of approximately $0.5 million provided to the Company. The interest rate is 3.95% per annum and the loan is repayable in thirty-six equal monthly installments, following an eighteen-month interest only period. The final balloon interest payment is approximately $0.5 million and is accreted over the life of the loan. As a result of the Company’s IPO, the interest only period has been extended to April 1, 2016. The amendment was accounted for as a modification of loans payable, and the unamortized debt discount as of the date of the modification will be amortized over the new loan period, using the effective interest rate method.

The Loan and Security Agreement contains customary representations and warranties, covenants, closing and advancing conditions, events of defaults and termination provisions. The Loan and Security Agreement provides that an event of default will occur if (1) the financial institution determines that it is the clear intention of the Company’s investors to not continue to fund the Company in the amounts and timeframe necessary to enable the Company to satisfy the Company’s financial obligations, (2) there is a material impairment in the financial institution’s security interest in the personal property that is the collateral, (3) the Company defaults in the payment of any amount payable under the agreement when due or (4) the Company breaches any negative covenant or certain affirmative covenants in the agreement (subject to a grace period in certain cases). The repayment of the loan is accelerated following the occurrence of an event of default or otherwise, which would require the Company to immediately pay an amount equal to: (i) all outstanding principal plus accrued but unpaid interest, (ii) the final payment, plus (iii) all other sums, that shall have become due and payable but have not been paid, including interest at the default rate with respect to any past due amounts. As of December 31, 2015, the Company was in compliance with all the covenants in the Loan and Security Agreement.

Aggregated annual payments due under the Loan and Security Agreement are as follows:

As of December 31, 2015 (in thousands)
2016	$	1,775
2017		2,095
2018		1,391
Total payments		5,261
Less: Interest		(761	)
Present value of loans payable		4,500
Less: Debt discount		(83	)
Add: Final balloon payment		517
Less: Unamortized portion of final balloon payment		(325	)
Loans payable		4,609
Less: Current portion		(1,455	)
Loans payable, net of current portion	$	3,154

Convertible Promissory Notes

12 Months Ended

Dec. 31, 2015

Long Term Debt [Abstract]

Convertible Promissory Notes

Note 8. Convertible Promissory Notes

On September 29, 2014 and February 19, 2015, the Company entered into convertible note purchase agreements and issued convertible promissory notes (the “Notes”) in an aggregate principal amount of $5.0 million and $4.0 million, respectively, to several related parties that own more than 10% of the Company’s capital stock. All principal and accrued interest on the Notes was converted to the Company’s common stock upon the completion of the Company’s initial public offering in April 2015. Upon conversion, 2,287,120 shares of common stock were issued.

The Notes provided that upon completion of an initial public offering, the Notes would automatically convert into a number of shares of the Company’s common stock equal to the quotient obtained by dividing the entire principal amount and accrued interest on the Notes by 80% of the initial public offering price per share of the Company’s common stock. The Notes bore interest at a rate of 5% per annum, compounded annually.

Due to the automatic conversion features contained in the Notes, the actual number of shares of common stock or preferred stock that would be required if a conversion of the Notes was made through the issuance of the Company’s common or preferred stock could not be predicted prior to the conversion taking place. In addition, the conversion that would occur upon a change in control of the Company met the definition of a put option and was not closely related to the debt. As a result, the automatic conversion features and put option, exclusive of the Series B conversion feature, required derivative accounting treatment and were bifurcated from the Notes and marked to market each reporting period through the statement of operations and comprehensive loss. The fair value of the automatic conversion features and put option of the Notes, exclusive of the Series B conversion feature, were recorded as a derivative liability instrument and measured at fair value at each reporting period.

As of December 31, 2014, the Company estimated the fair value of the derivative by estimating the fair value of the Notes with and without the conversion derivative. To calculate the fair value of the Notes without the conversion derivative, the Company estimated the present value of the expected cash payments at an assumed discount rate of 8.25%. To calculate the fair value of the Notes with the conversion feature, the Company calculated the present value of the Notes upon conversion at an initial public offering, and the present value of the Notes at an equity financing. The risk-free rate for the assumed discount period is estimated at 0.05% and 0.15% in the respective conversion scenarios. The risk-free rate for the assumed discount period is estimated at 0.05% and 0.12% in the respective conversion scenarios at the valuation date of December 31, 2014. The Company applied a probability of occurrence to all of the conversion scenarios associated with the derivative and estimated a weighted value of the Notes with the conversion feature. The difference between the fair value of the Notes with and without the conversion features is the derivative. The fair value of the derivative was $1,495,000 as of December 31, 2014.

Upon issuance of the February 2015 Notes, the Company calculated the derivative liability using the same methodology and assumptions as those used as of December 31, 2014 because there were not significant changes in the Company or in the operations of the Company that had occurred in that intervening time period. The additional derivative liability recorded upon issuance of the February 2015 Notes was $1,196,000.

At April 8, 2015, the Company remeasured the fair value of the derivative liability for the Notes using a methodology similar to the methodology used at December 31, 2014, with a minimal discount period. The fair value of the derivative was $2,287,000.

The Company determined that the Notes contain a beneficial conversion feature related to the conversion feature of the Notes into Series B convertible preferred stock. The beneficial conversion feature results from the difference between the fair value of the Company’s common stock at the date of issuance and the Series B Preferred Stock Conversion price of $4.8104 at the date of issuance. The beneficial conversion feature amounted to $2,275,000 for the September 2014 Notes and $158,000 for the February 2015 Notes as of the date of issuance of the respective Notes, and was recorded as a debt discount that would be amortized through the maturity date of the Notes.

At April 8, 2015, the beneficial conversion feature amounted to $202,000 for the September 2014 Notes and $158,000 for the February 2015 Notes. The fair value of the shares issued upon conversion of the convertible promissory notes was first allocated to the beneficial conversion feature of $360,000.

At April 8, 2015, the loss on extinguishment of the convertible promissory notes was calculated as follows:

Fair value of common stock issued upon conversion of convertible promissory notes and accrued interest	$	11,435
Less:
Fair value of beneficial conversion feature on conversion date		(360	)
Net book value of convertible promissory notes		(5,611	)
Fair Value of derivative liability at conversion date		(2,287	)
Loss on extinguishment of convertible promissory notes	$	3,177

Convertible Preferred Stock

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Convertible Preferred Stock

Note 9. Convertible Preferred Stock

The Company has no outstanding convertible preferred stock as of December 31, 2015.

Convertible preferred stock as of December 31, 2014 consisted of the following (in thousands, except share data):

	Shares				Liquidation		Proceeds Net of Issuance
Series	Authorized		Outstanding		Amount		Costs
A		6,574,364		1,611,089	$	7,750	$	7,595
B		27,796,941		6,657,442		32,025		31,961
		34,371,305		8,268,531	$	39,775	$	39,556

The rights, privileges and preferences of convertible preferred stock are as follows:

Dividends

The holders of the Series A and Series B convertible preferred stock were entitled to receive noncumulative annual dividends at the rate of 8% of the original issuance price, or approximately $0.38 per share, respectively, when, as and if declared by the Board of Directors. Dividends on preferred stock shall be payable in preference to and prior to payment of dividends on common stock. In the event that dividends are paid on common stock, an additional dividend shall be paid on preferred stock in an amount equal per share (on an as-if-converted basis) to the amount paid for each share of common stock. No dividends were declared from inception to December 31, 2014.

Liquidation Rights

In the event of any liquidation, dissolution or winding up of the Company, the holders of the Company’s convertible preferred stock shall be entitled to receive, prior to any distribution of the Company’s assets to the holders of common stock, an amount equal to $4.8104 per share for each outstanding share of Series A and Series B convertible preferred stock, plus any declared but unpaid dividends. If the Company’s assets shall be insufficient to provide for such preferential distributions, the preferred stockholders shall be entitled to pro rata distributions. The remaining assets of the Company shall be distributed among the preferred stockholders and the common stockholders pro rata on an as-if-converted basis until the holders of Series A and Series B preferred stock have received an aggregate of $14.43 per share, respectively. Thereafter, if assets remain in the Company, the common stockholders shall receive all of the Company’s remaining assets on a pro rata basis. A sale of all or substantially all of the assets of the Company, merger or consolidation, which result in the Company’s stockholders immediately prior to such transaction not holding at least 50% of the voting power of the surviving, continuing or purchasing entity shall be deemed a liquidation of the Company.

Due to the liquidation rights in a deemed liquidation, the Company’s convertible preferred stock was classified outside of permanent equity (deficit) as mezzanine.

Modification of Series B Convertible Preferred Stock

In December 2012, the Company approved the adjustment of the Series B convertible preferred stock liquidation preference from $5.52 per share to $4.8104 per share. In order to preserve the aggregate liquidation preference of the Series B convertible preferred stockholders at that time, the Company issued 534,467 shares of Series B convertible preferred stock to such holders. As part of this analysis, the Company assessed the economic characteristics and risks of its convertible preferred stock, including conversion, liquidation and redemption features, as well as dividend and voting rights. Based on the Company’s determination that each series of its convertible preferred stock is an “equity host,” the Company determined that the features of the convertible preferred stock are most closely associated with an equity host and, although the convertible preferred stock includes conversion features, such conversion features do not require bifurcation as a derivative liability. The Company also determined that the conversion option with a contingent reduction in the conversion price, upon occurrence of certain dilutive events, is a potential contingent beneficial conversion feature. In accordance with certain antidilution provisions contained in the Series B convertible preferred stock agreements, issuances of Series B convertible preferred stock in 2012 resulted in an antidilution adjustment of the conversion prices for the Series B convertible preferred stock during the year ended December 31, 2012. As a result, the Company performed a calculation to determine if a beneficial conversion feature was triggered for the Series B convertible preferred stock at each issuance of Series B in 2012. The fair value of common stock, as determined by management and the Board of Directors, on the corresponding issuance dates of Series B convertible preferred stock in each instance was below the adjusted accounting conversion prices. Therefore, no beneficial conversion feature was identified. The Company will continue to evaluate if a beneficial conversion feature needs to be recorded upon each subsequent adjustment of the conversion price based upon the difference between the adjusted conversion price and the fair market value of common stock at the original issuance date. This change is treated as a modification of the Series B preferences and results in a deemed dividend of Series B convertible preferred stock of $111,000. This amount is recorded as a reduction of additional paid-in-capital and an increase in the Series B convertible preferred stock in the accompanying financial statements.

Conversion Rights

The Company’s preferred stock was convertible, at the option of the holder, into common stock on a one-for-one basis with the conversion ratio subject to adjustment in the event of certain dilutive stock issuances or other future events. Conversion was automatic upon the closing of a firm commitment underwritten public offering in which the aggregate gross proceeds equals or exceeds $30,000,000, or the date specified by written agreement of the holders of at least two-thirds of the preferred stock then issued and outstanding on an as-if-converted basis.

Voting Rights

The holder of each share of the Company’s convertible preferred stock had the right to one vote for each share of common stock into which such convertible preferred stock could be converted. The holders of Series A convertible preferred stock and series B convertible preferred stock, voting as separate classes, were entitled to elect two members each of the Board of Directors, and the holders of common stock, voting as a separate class, were entitled to elect one member of the Board of Directors. The holders of common stock and preferred stock, voting together as a single class on an as-if-converted basis, were entitled to elect all remaining members of the Board of Directors.

Prior to the closing of the IPO, all outstanding shares of convertible preferred stock converted into 8,268,531 shares of common stock with the related carrying value of $39.6 million reclassified to common stock and additional paid-in capital. In addition, all convertible preferred stock warrants were converted into warrants exercisable for common stock and the convertible promissory notes were converted in to 2,287,120 shares of common stock.

Convertible Preferred Stock Warrants

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Convertible Preferred Stock Warrants

Note 10. Convertible Preferred Stock Warrants

The Company issued warrants to purchase shares of the Company’s convertible preferred stock at various times in connection with loans payable. Immediately prior to the closing of the IPO, all convertible preferred stock warrants were converted in to warrants exercisable for common stock. The convertible preferred stock warrants outstanding as of December 31, 2014 were as follows (in thousands, except share and per share amounts):

	Number of Shares Underlying Warrants		Exercise Price per Share		Fair Value, as of December 31, 2014
Series A preferred stock		20,788	$	4.8104	$	46
Series B preferred stock		103,941	$	4.8104	$	417
		124,729			$	463

The fair value of the convertible preferred stock warrant liability was remeasured as of each period end. As of December 31, 2014, the Company remeasured the fair value using a Black-Scholes option-pricing method with the following assumptions: a weighted average remaining life of 6.7 years, an expected volatility of 58.9%, a weighted average risk-free interest rate of 1.80% and no expected dividend. As of April 14, 2015, the Company remeasured the fair of the convertible preferred stock warrant liability using a Black-Scholes option-pricing method with the following assumptions: the Company’s IPO price of $5.00 per share, a weighted average remaining life of 6.4 years, an expected volatility of 58.3%, a weighted average risk-free interest rate of 1.51% and no expected dividend. The Company evaluated the down-round protection provisions of the warrant agreements by using a Monte Carlo simulation model and determined that the impact of such provisions was immaterial to the fair value of the warrants at the reporting dates. The assumptions are further described as follows:

Expected Time to liquidity event — The Company estimated the time to liquidity event based on management’s analysis of the business, market conditions and clinical development.

Expected Volatility — The Company estimates the expected volatility based on the average volatility for comparable publicly traded biopharmaceutical companies over a period equal to the expected time to liquidity event. When selecting the publicly traded biopharmaceutical companies, the Company selected companies with comparable characteristics to it, including enterprise value and risk profiles, and with historical share price information sufficient to meet the time to liquidity event. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Risk-Free Interest Rate — The risk-free interest rate is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected time to the liquidity event.

Expected Dividend Rate — The Company has never paid any dividends and does not plan to pay dividends in the foreseeable future, and, therefore, used an expected dividend rate of zero in the valuation model.

On April 8, 2015, the convertible preferred stock warrants automatically converted to common stock warrants. The convertible preferred stock warrant liability was reclassified to additional paid-in capital. During June 2015, the holder of the common stock warrants exercised those warrants for 56,545 shares of common stock in a cashless exercise.

Common Stock	12 Months Ended
Common Stock	Dec. 31, 2015
Federal Home Loan Banks [Abstract]
Common Stock	Note 11. Common Stock As of December 31, 2015 the Company’s Amended and Restated Certificate of Incorporation, as amended, has authorized 100,000,000 shares of common stock at $0.001 par value. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to the preferential dividend rights of the holders of the Series A and B convertible preferred stock. As of December 31, 2015, no dividends have been declared.

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
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-Subparagraph (SAB TOPIC 4.E)
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
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-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 505
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - Series B Preferred Stock [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2013 USD ($) $ / shares
Stock issued, price per share \| $ / shares	$ 4.8104
Stock issuance costs \| $	$ 14

401(k) Plan	12 Months Ended
401(k) Plan	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
401(k) Plan	Note 12. 401(k) Plan The Company sponsors a 401(k) Plan that stipulates that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. Pursuant to the 401(k) Plan, the Company does not match any employee contributions.