Entity Central Index Key Document and entity information. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Accounts receivable prepaid expense and other current assets. Non-current accrued interest. Statement Of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Accounts receivable, prepaid expenses, and other current assets Accounts Receivable Prepaid Expense And Other Current Assets Total current assets Assets Current Property and equipment — Net Property Plant And Equipment Net Other assets Other Assets Noncurrent Total Assets LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Current portion of loan payable Loans Payable Current Accounts payable Accounts Payable Current Accrued expenses Accrued Liabilities Current Other liabilities Other Liabilities Current Total current liabilities Liabilities Current Long-term liabilities: Liabilities Noncurrent [Abstract] Loan payable — net of current portion Long Term Loans Payable Non-current accrued interest Accrued Interest Noncurrent Other Other Liabilities Noncurrent Total long-term liabilities Liabilities Noncurrent Commitments Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock, $0.01 par value; 5,000,000 shares authorized, no shares issued or outstanding Preferred Stock Value Common stock, $0.0001 par value; 120,000,000 shares authorized, 20,568,026 and 20,125,049 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders’ equity Stockholders Equity Total Liabilities And Stockholders Equity Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Income Statement [Abstract] Revenue Revenues Operating expenses: Costs And Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Other income (expense): Nonoperating Income Expense [Abstract] Interest income Investment Income Interest Interest expense Interest Expense Other expense Other Expenses Decrease in value of preferred stock warrant liability Fair Value Adjustment Of Warrants Total other (expense) income — net Nonoperating Income Expense Net loss attributable to common stockholders Net Income Loss Available To Common Stockholders Basic Net loss per share attributable to common stockholders: Earnings Per Share Basic And Diluted [Abstract] Basic and diluted Earnings Per Share Basic And Diluted Weighted-average common shares outstanding: Weighted Average Number Of Shares Outstanding [Abstract] Basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Statement Of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities [Abstract] Net loss Net Income Loss Adjustments to reconcile net loss to net cash used in operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Stock-based compensation Share Based Compensation Noncash rent expense Straight Line Rent Adjustments Change in carrying value of preferred stock warrant liability Depreciation and amortization Depreciation Depletion And Amortization Noncash interest expense Paid In Kind Interest Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Accounts receivable, prepaid expenses and other current assets Increase Decrease In Operating Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses Increase Decrease In Accrued Liabilities Net cash used in operating activities Net Cash Provided By Used In Operating Activities Continuing Operations Cash flows from investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Proceeds from sale of property and equipment Proceeds From Sale Of Property Plant And Equipment Net cash used in investing activities Net Cash Provided By Used In Investing Activities Continuing Operations Cash flows from financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from sale of common stock Proceeds From Issuance Of Common Stock Proceeds from issuance of loans payable Proceeds From Notes Payable Proceeds from issuance of convertible promissory notes Proceeds From Convertible Debt Payments on loans payable Repayments Of Notes Payable Cash paid for debt issuance costs Payments Of Debt Issuance Costs Cash paid for deferred financing costs Payments Of Financing Costs Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Net increase in cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Cash and cash equivalents — Beginning of period Cash and cash equivalents — End of period Supplemental cash flow information — Interest paid Interest Paid Net Accounting Policies [Abstract] Nature of Business and Operations Nature Of Operations Significant Accounting Policies Significant Accounting Policies [Text Block] Earnings Per Share [Abstract] Net Loss Per Share Attributable to Common Stockholders Earnings Per Share [Text Block] Payables And Accruals [Abstract] Accrued Expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Debt Disclosure [Abstract] Convertible Notes Payable to Shareholders Debt Disclosure [Text Block] Loan Agreements Long Term Debt [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock Option Plan Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Schedule of Accrued Expenses Schedule Of Accrued Liabilities Table [Text Block] Debt Instrument [Table] Debt Instrument [Table] Long-term Debt, Type Longterm Debt Type [Axis] Long-term Debt, Type Longterm Debt Type [Domain] Hercules loan agreement. Hercules Loan Agreement [Member] Hercules Loan Agreement [Member] Class of Warrant or Right Class Of Warrant Or Right [Axis] Class of Warrant or Right Class Of Warrant Or Right [Domain] Common stock warrants. Common Stock Warrants [Member] Common Stock Warrants [Member] Loan and Security Agreement with Bank [Member] Notes Payable To Banks [Member] Preferred stock warrants. Preferred Stock Warrants [Member] Preferred Stock Warrants [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Fair Value of Stock Warrants Calculated using Black-Scholes Assumptions Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques Table [Text Block] Statement [Table] Statement [Table] Award Type Award Type [Axis] Equity Award Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Non employee awards. Non Employee Awards [Member] Non Employee Awards [Member] Statement [Line Items] Statement [Line Items] Summary of Stock Option Activity for Employee, Director and Nonemployee Awards Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees, Directors and Non Employees Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Summary of Financial Assets and Liabilities Measured on Recurring Basis at Fair Value Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Organization Consolidation And Presentation Of Financial Statements [Abstract] Nature Of Business And Operations [Table] Nature Of Business And Operations [Table] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] IPO [Member] I P O [Member] Stock Conversion Description Conversion Of Stock By Unique Description [Axis] Conversion of Stock, Name Conversion Of Stock Name [Domain] Warrants To Purchase Preferred Stock Converted Into Warrants To Purchase Common Stock Member Warrants To Purchase Preferred Stock Converted Into Warrants To Purchase Common Stock [Member] Warrants To Purchase Preferred Stock Converted Into Warrants To Purchase Common Stock [Member] Nature Of Business And Operations [Line Items] Nature Of Business And Operations [Line Items] Date of Company's incorporation Entity Incorporation Date Of Incorporation Common stock issuance date Equity Issuance Dates Issuance of Common Stock from initial public offering, shares Stock Issued During Period Shares New Issues Issuance/sale of stock, price per share Shares Issued Price Per Share Proceeds from initial public offering, net Proceeds From Issuance Initial Public Offering Convertible preferred stock, shares issued upon conversion Convertible Preferred Stock Shares Issued Upon Conversion Preferred stock conversion basis Preferred Stock Conversion Basis Warrant to purchase stock, number of securities called by warrants or rights Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Options to Purchase Common Stock [Member] Stock Option [Member] Warrants [Member] Warrant [Member] Convertible Notes Payable [Member] Convertible Debt Securities [Member] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Redeemable Convertible Preferred Stock [Member] Redeemable Convertible Preferred Stock [Member] Common Stock [Member] Common Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive securities excluded from computation of diluted weighted-average shares outstanding Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Accrued clinical trial costs current. Accrued manufacturing expenses current. Debt instrument accrued interest. Accrued expenses Other Accrued Liabilities Current Accrued clinical trial costs Accrued Clinical Trial Costs Current Accrued contract manufacturing expenses Accrued Manufacturing Expenses Current Accrued compensation and benefits Employee Related Liabilities Current Accrued interest Debt Instrument Accrued Interest Total accrued expenses Debt Instruments [Abstract] Short-term Debt, Type Short Term Debt Type [Axis] Short-term Debt, Type Short Term Debt Type [Domain] Convertible Notes Payable [Member] Convertible Notes Payable [Member] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] Existing investors. Existing Investors [Member] Existing Investors [Member] New Investor. New Investor [Member] New Investor [Member] Debt instrument, Original principal amount Debt Instrument Face Amount Debt instrument stated interest rate Debt Instrument Interest Rate Stated Percentage IPO closure date Initial Offering Period Debt instrument, Conversion Ratio Debt Instrument Convertible Conversion Ratio1 Loss on extinguishment of debt Gains Losses On Extinguishment Of Debt Lender Name Line Of Credit Facility [Axis] Line of Credit Facility, Lender Line Of Credit Facility Lender [Domain] Term loan facility with Hercules Technology Growth Capital Inc. Loan and Security Agreement with Hercules Technology Growth Capital, Inc. [Member] Term Loan Facility With Hercules Technology Growth Capital Inc [Member] Range Range [Axis] Range Range [Member] Maximum [Member] Maximum [Member] Minimum [Member] Minimum [Member] Borrowings one. Borrowing One [Member] Borrowings One [Member] Borrowings two. Borrowing Two [Member] Borrowings Two [Member] Borrowings three. Borrowing Three [Member] Borrowings Three [Member] Variable Rate Variable Rate [Axis] Variable Rate Variable Rate [Domain] Prime Rate [Member] Prime Rate [Member] Scenario Statement Scenario [Axis] Scenario, Unspecified Scenario Unspecified [Domain] Payment occurs within twelve months of closing date. If Payment Occurs Within Twelve Months Of Closing Date [Member] Payment Occurs Within Twelve Months Of Closing Date [Member] Payment occurs after twelve months but on or prior to twenty four months following closing date. If Payment Occurs After Twelve Months But on or Prior to Twenty Four Months Following Closing Date [Member] Payment Occurs After Twelve Months But On Or Prior To Twenty Four Months Following Closing Date [Member]