Accounting Policies [Abstract] Accounting Policies [Abstract] Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Accrued Expenses and Other Current Liabilities Accounts Payable, Current Accounts payable Accrued clinical costs current. Accrued Clinical Costs Current Accrued clinical costs Accrued Liabilities and Other Liabilities Accrued expenses and other current liabilities Total accrued expenses Accrued Professional Fees, Current Accrued professional fees Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Accumulated other comprehensive income AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income [Member] Additional Paid in Capital, Common Stock Additional paid-in capital Additional Paid-in Capital [Member] Additional Paid-In Capital [Member] Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation expense Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Offering costs Adjustments to Additional Paid in Capital, Stock Split Repurchase of fractional shares resulting from reverse stock splits Adjustments to Additional Paid in Capital, Warrant Issued Reclassification of common stock warrant liability Reclassification of common stock warrant liability to additional paid-in capital Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash from operating activities: Aggregate potential milestone payable. Aggregate Potential Milestone Payable Aggregate potential milestone payable Allocated Share-based Compensation Expense Share based compensation expense, total Amendment Flag Amendment Flag Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Anti-dilutive securities excluded from computation of diluted net loss per common share Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Arrangements and Non-arrangement Transactions [Domain] Arrangements and Non-arrangement Transactions [Domain] Assets Total assets Assets [Abstract] ASSETS Assets, Current Total current assets Assets, Current [Abstract] Current assets: Assets, Fair Value Disclosure Total assets Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Unrealized Losses Available-for-sale Debt Securities, Amortized Cost Basis Amortized Cost Available-for-sale Securities, Debt Securities Available for sale debt securities fair value Fair Value Available For Sale Securities Fair Value Disclosure [Abstract] Available For Sale Securities Fair Value Disclosure [Abstract] Available For Sale Securities Fair Value Disclosure [Abstract] Available-for-sale Securities, Gross Realized Gain (Loss) Realized gains or losses recognized on the sale or maturity of available-for-sale securities Available-for-sale Securities [Table Text Block] Summary of Available-for-Sale Securities Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Bayer Pharma AG . Bayer Pharma AG [Member] Bayer Pharma AG [Member] Business Description and Basis of Presentation [Text Block] Basis of Presentation Reported Value Measurement [Member] Carrying Value [Member] Cash and Cash Equivalents, at Carrying Value CASH AND CASH EQUIVALENTS-end of period CASH AND CASH EQUIVALENTS-beginning of period Cash and cash equivalents Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents, Fair Value Disclosure Cash equivalents Cash equivalents fair value Cash and Cash Equivalents, Period Increase (Decrease) NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS Cash Flow, Supplemental Disclosures [Text Block] Supplemental Cash Flow Information Class of Stock [Domain] Class of Stock [Domain] Class of Stock [Line Items] Class of Stock [Line Items] Class of Warrant or Right, Exercise Price of Warrants or Rights Average Exercise Price Warrant exercisable Class of Warrant or Right [Line Items] Class of Warrant or Right [Line Items] Class of Warrant or Right, Number of Securities Called by Warrants or Rights Shares of Common Stock Issuable Under the Warrant Total Shares of Common Stock Issuable Under the Warrant Class of Warrant or Right [Table] Class of Warrant or Right [Table] Clinical Trial [Member] Clinical Trial [Member] Clinical Trial [Member] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Commercial Paper, Not Included with Cash and Cash Equivalents [Member] Commercial Paper [Member] Commitments and Contingencies Commitments Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Common Stock, Capital Shares Reserved for Future Issuance Shares available for issuance Common stock issuable upon exercise of warrant. Common Stock Issuable Upon Exercise of Warrant Number of shares of common stock issuable upon exercise of the warrant Common Stock [Member] Common Stock [Member] Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Common Stock, Value, Issued Common stock, $0.0001 par value, 100,000,000 and 20,800,000 shares authorized; 18,179,803 and 85,440 shares outstanding at September 30, 2016 and December 31, 2015, respectively Common Stock Warrant Liability Common Stock Warrant Liability [Member] Common Stock Warrant Liability [Member] Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Consolidation, Policy [Policy Text Block] Principles of Consolidation Contractual Obligation Aggregate payment obligation Contractual obligations term. Contractual Obligations Term Period of contractual obligation Conversion of Stock, Amount Converted Conversion of preferred stock to common stock upon closing of initial public offering Convertible Preferred Stock [Member] Convertible Preferred Stock [Member] Convertible Preferred Stock, Shares Issued upon Conversion Conversion of convertible preferred stock to shares of common stock Convertible preferred stock converted in to common stock Corporate Bonds And Commercial Paper [Member] Corporate Bonds And Commercial Paper [Member] Corporate Bonds And Commercial Paper [Member] Corporate Debt Securities [Member] Corporate Bonds [Member] Counterparty Name [Axis] Counterparty Name [Axis] Current Fiscal Year End Date Current Fiscal Year End Date Debt Conversion, Converted Instrument, Amount Conversion of convertible notes and accrued interest into Series C-1 convertible preferred stock Debt Instrument, Unamortized Discount Initial fair value of derivative recorded as debt discount Debt Issuance Costs Incurred During Noncash or Partial Noncash Transaction Issuance costs included in accounts payable and accrued expenses Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Schedule of Prepaid Expenses and Other Current Assets Deferred Offering Costs Capitalized deferred issuance costs Deferred Revenue Deferred revenue from license agreement Deferred Revenue, Current Current portion of deferred revenue Deferred Revenue, Noncurrent Deferred revenue, less current portion Deposits Assets, Current Short-term deposits Depreciation, Amortization and Accretion, Net Depreciation, amortization and accretion Derivative Liability, Fair Value, Gross Liability Derivative liability Fair Value of Warrant Liability Derivative Financial Instruments, Liabilities [Member] Derivative Liability [Member] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Document Period End Date Document Period End Date Document Type Document Type Earnings Per Share [Abstract] Earnings Per Share [Abstract] Earnings Per Share, Basic and Diluted Net loss per share attributable to common stockholders-basic and diluted Earnings Per Share [Text Block] Net Loss per Share Attributable to Common Stockholders Eastern Cooperative Oncology Group. Eastern Cooperative Oncology Group [Member] Eastern Cooperative Oncology Group [Member] Employee-related Liabilities, Current Accrued compensation and related costs Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Weighted average period to recognize compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Unrecognized compensation expense related to stock option Employee Stock Option [Member] Options to Purchase Common Stock [Member] Entity Central Index Key Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Filer Category Entity Filer Category Entity Incorporation, Date of Incorporation Entity incorporation date Entity Registrant Name Entity Registrant Name Equity [Abstract] Equity [Abstract] Equity Component [Domain] Equity Component [Domain] Fair Value Adjustment of Warrants Change in fair value of common stock warrant liability Fair value adjustment of warrants and derivative liabilities. Fair Value Adjustment Of Warrants And Derivative Liabilities Change in fair value of warrants and derivative Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Assumptions, Expected Dividend Rate Estimated Dividend Yield Fair Value Assumptions, Expected Term Estimated Remaining Contractual Life (in years) Fair Value Assumptions, Expected Volatility Rate Estimated Volatility Fair Value Assumptions, Risk Free Interest Rate Risk-Free Interest Rate Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Liability Class [Axis] Liability Class [Axis] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Fair Value, Inputs, Level 1 [Member] Quoted Prices in Active Markets Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Significant Other Observable Inputs Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Significant Unobservable Inputs Level 3 [Member] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Summary of Changes in Fair Value of Common Stock Warrant Liability and Derivative Liability Inputs Fair Value, Measurement Inputs, Disclosure [Text Block] Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value Measurements [Line Items] Fair Value Measurements [Line Items] Fair Value Measurements [Line Items] Fair Value Measurements [Table] Fair Value Measurements [Table] Fair Value Measurements [Table] Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Change In Fair Value Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Change In Fair Value Change in fair value Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Reclassification To Equity Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Reclassification To Equity Reclassification Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Ending Balance Beginning Balance Financial Instrument [Axis] Financial Instrument [Axis] General and Administrative Expense General and administrative General and Administrative Expense [Member] General and Administrative Expense [Member] Income Statement [Abstract] Income Statement [Abstract] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Taxes Income Tax Expense (Benefit) Net tax provision Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Accrued expenses and other liabilities Increase decrease in contractual obligation. Increase Decrease In Contractual Obligation Increase in contractual obligation Increase (Decrease) in Deferred Revenue Deferred revenue Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other assets Increase (Decrease) in Restricted Cash Increase in restricted cash Interest Income (Expense), Nonoperating, Net Interest income (expense), net Interest Paid Interest paid Interest Receivable, Current Interest receivable on short-term investments IPO [Member] Initial Public Offering [Member] Kyowa Hakko Kirin Co Ltd Kyowa Hakko Kirin Co Ltd [Member] Kyowa Hakko Kirin Co., Ltd. [Member] Liabilities Total liabilities Liabilities and Equity Total liabilities, convertible preferred stock and stockholders' equity (deficit) Liabilities and Equity [Abstract] LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) Liabilities, Current Total current liabilities Liabilities, Current [Abstract] Current liabilities: Financial and Nonfinancial Liabilities, Fair Value Disclosure Total liabilities Liabilities, Noncurrent Total long-term liabilities Liabilities, Noncurrent [Abstract] Long-term liabilities: License Agreement [Member] License Agreement [Member] License Agreement [Member] License agreements expiration period. License Agreements Expiration Period License expiration year Licenses Revenue License fees Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Marketable Securities, Unrealized Gain (Loss) Unrealized gain on short-term investments Maximum [Member] Maximum [Member] Milestone payment due. Milestone Payment Due Milestone payment payable Minimum [Member] Minimum [Member] Money Market Funds [Member] Money Market Funds [Member] Nature of Business [Line Items] Nature Of Business [Line Items] Nature of Business [Line Items] Nature Of Business [Table] Nature Of Business [Table] Nature Of Business [Table] Nature of Operations [Text Block] Nature of Business Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Income (Loss) Attributable to Parent Net loss Net loss Net Income (Loss) Attributable to Parent [Abstract] Numerator-basic and diluted: Net Income (Loss) Available to Common Stockholders, Basic Net loss attributable to common stockholders Net loss attributable to common stockholders-basic and diluted New Accounting Pronouncements, Policy [Policy Text Block] Recently Issued Accounting Pronouncements Noncash Investing and Financing Items [Abstract] SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES: Nonoperating Income (Expense) Total other income (expense) Nonoperating Income (Expense) [Abstract] Other income (expense): Non Refundable Up Front Payment Received Non Refundable Up Front Payment Received Upfront license fee received Number of executives options vested. Number Of Executives Options Vested Number of company executives Operating Expenses Total operating expenses Operating Expenses [Abstract] Operating expenses: Operating Income (Loss) Loss from operations Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Other Accrued Liabilities, Current Other Other Assets, Noncurrent Other assets Disclosure of accounting policy for other noncurrent assets. Other Assets [Policy Text Block] Other Assets Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive loss: Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Unrealized (losses) gains on marketable securities Other Current Assets [Text Block] Prepaid Expenses and Other Current Assets Other Liabilities, Noncurrent Other long-term liabilities Other Long-term Debt, Noncurrent Success fee payable included in other long-term liabilities Other Nonoperating Income (Expense) Other income (expense) Other Prepaid Expense, Current Other Over-Allotment Option [Member] Over-Allotment Option [Member] Payables and Accruals [Abstract] Payables and Accruals [Abstract] Payment of Financing and Stock Issuance Costs Deferred debt issuance and financing costs Payments of Stock Issuance Costs Offering expenses Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Payments to Acquire Short-term Investments Purchases of short-term investments Percentage of shares issuable on conversion of warrant. Percentage Of Shares Issuable On Conversion Of Warrant Percentage of shares issuable upon conversion of warrant Period of termination after first commercial sale of first licensed product. Period of Termination After First Commercial Sale of First Licensed Product Period of termination after first commercial sale of first licensed product Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Potential Milestone Payments Receivable Potential Milestone Payments Receivable Milestone payment receivable upon achievement of development and commercial milestone Potential Milestone Payments Upon Achievement Of Milestone Potential Milestone Payments Upon Achievement Of Milestone Potential milestone payments to be made Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred Stock, Redemption Amount Accretion to redemption value Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock issued, shares Preferred stock, shares issued Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Preferred Stock [Text Block] Convertible Preferred Stock Preferred Stock, Value, Issued Preferred stock, value Upfront payment allocated to preferred stock value Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Total prepaid expenses and other current assets Prepaid Insurance Prepaid insurance Proceeds from Issuance Initial Public Offering Proceeds from issuance of common stock in initial public stock offering, net Proceeds from public stock offering, net of issuance costs Proceeds from Issuance of Convertible Preferred Stock Proceeds from issuance of convertible preferred stock Proceeds received from preferred stock issuance Proceeds from (Payments for) Other Financing Activities Other Proceeds from (Repayments of) Debt Payments on debt Proceeds from Sale and Maturity of Available-for-sale Securities Proceeds from sales and maturities of short-term investments Proceeds from Stock Options Exercised Proceeds from stock option exercises Stock options exercised Property, Plant and Equipment, Net Property and equipment, net Range [Axis] Range [Axis] Range [Domain] Range [Domain] Reclassification of common stock warrant liability to additional paid in capital. Reclassification Of Common Stock Warrant Liability To Additional Paid In Capital Reclassification of common stock warrant liability to additional paid-in capital Recognition of Deferred Revenue Revenue recognized during period Remaining contractual obligation. Remaining Contractual Obligation Remaining contractual obligation Counterparty Name [Domain] Counterparty Name [Domain] Research and Development Expense Research and development Research and development expense Research and Development Expense [Member] Research and Development Expense [Member] Restricted Cash and Cash Equivalents, Current Restricted cash Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Restricted Stock [Member] Restricted Stock Subject to Future Vesting [Member] Retained Earnings (Accumulated Deficit) Accumulated deficit Retained Earnings [Member] Accumulated Deficit [Member] Revaluation date of warrant. Revaluation Date Of Warrant Revaluation Date of Warrant Reverse stock split. Reverse Stock Split [Policy Text Block] Reverse Stock Split Sale of Stock [Domain] Sale of Stock [Domain] Revenue, Net Total revenues Revenue, Net [Abstract] Revenue: Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Schedule of Accrued Expenses and Other Current Liabilities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Potential Dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Supplemental Disclosures of Cash Flow Information Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Share Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non Employees Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block] Schedule of Assumptions Used to Value Shares of Common Stock Issuable Pursuant to Warrant Schedule of Stockholders Equity [Table Text Block] Summary of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) Series A Convertible Preferred Stock [Member] Series A- Convertible Preferred Stock [Member] Series A Convertible Preferred Stock [Member] Series A-1. Series A- One Preferred Stock [Member] Series A- 1 [Member] Series A Preferred Stock [Member] Series A [Member] Series B-1. Series B One Preferred Stock [Member] Series B-1 [Member] Series B Preferred Stock [Member] Series B [Member] Series C-1. Series C One Preferred Stock [Member] Series C-1 [Member] Share-based Compensation Stock-based compensation Share based compensation arrangement by share based payment award annual increase percentage in number of shares available for grant. Share Based Compensation Arrangement By Share Based Payment Award Annual Increase Percentage In Number Of Shares Available For Grant Common stock outstanding Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Common stock reserved for issuance Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Stock option granted to certain executives and employees Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted average grant date fair value of options Share based compensation arrangement by share based payment award stock option grant date fair value. Share Based Compensation Arrangement By Share Based Payment Award Stock Option Grant Date Fair Value Options grant date fair value amount Share Price Fair Value of Common Stock Preferred share price per share Shares Issued, Price Per Share Sale of stock, price per share Shares, Outstanding Ending balance, Shares Beginning balance, Shares Short-term Investments Short-term investments Significant Accounting Policies Policy. Significant Accounting Policies [Policy Text Block] Significant Accounting Policies Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Significant agreements disclosure. Significant Agreements Disclosure [Text Block] Significant Agreements Class of Stock [Axis] Class of Stock [Axis] Equity Components [Axis] Equity Components [Axis] Statement [Line Items] Statement [Line Items] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Statement [Table] Statement [Table] Stock Based Compensation Due To Accelerated Vesting Of Stock Options Stock Based Compensation Due To Accelerated Vesting Of Stock Options Additional stock compensation expense Stockholders' Equity Attributable to Parent Ending balance Beginning balance Total stockholders' equity (deficit) Stockholders' Equity Attributable to Parent [Abstract] Stockholders' equity (deficit): Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity (Deficit) Stockholders' Equity Note, Stock Split, Conversion Ratio Stock split, conversion ratio Stock Issued During Period, Shares, Conversion of Convertible Securities Conversion of preferred stock into common stock, Shares Stock Issued During Period, Shares, New Issues Common stock, new shares issued Proceeds from IPO, net of offering costs of $7,186, Shares Stock Issued During Period, Shares, Restricted Stock Award, Gross Vesting of restricted stock, Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options, Shares Stock options exercised, shares Stock Issued During Period, Value, Conversion of Convertible Securities Conversion of preferred stock into common stock, Value Stock Issued During Period, Value, New Issues Proceeds from IPO, net of offering costs of $7,186, Value Stock Issued During Period, Value, Restricted Stock Award, Gross Vesting of restricted stock, Value Stock Issued During Period, Value, Stock Options Exercised Exercise of stock options, Value Sale of Stock [Axis] Sale of Stock [Axis] Success fee payable. Success Fee Payable [Member] Success Fee Payable [Member] Summary of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Information [Abstract] SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION: Prepaid Supplies Prepaid clinical supplies Temporary Equity, Accretion of Dividends Accretion for convertible preferred stock dividends Temporary Equity, Accretion to Redemption Value, Adjustment Accretion of convertible preferred stock to redemption value Accretion of convertible preferred stock to redemption value Temporary Equity, by Class of Stock [Table] Temporary Equity, by Class of Stock [Table] Temporary Equity, Carrying Amount, Attributable to Parent Beginning balance Carrying Value Convertible preferred stock Temporary Equity Disclosure [Abstract] Temporary Equity Disclosure [Abstract] Temporary Equity, Dividends, Adjustment Accretion of dividends on convertible preferred stock Accretion for convertible preferred stock dividends Accretion of convertible preferred stock dividends Temporary equity issuance date. Temporary Equity Issuance Date1 Issuance Date Temporary Equity Issuance Dates Temporary Equity Issuance Dates Issuance Date Temporary Equity [Line Items] Temporary Equity [Line Items] Temporary Equity, Liquidation Preference Liquidation preference Temporary Equity, Shares Authorized Preferred Shares Designated Temporary Equity, Shares Issued Convertible preferred stock issued Preferred Shares Issued Temporary Equity, Shares Outstanding Beginning balance, Shares Convertible preferred stock outstanding Preferred Shares Outstanding Temporary Equity [Table Text Block] Schedule of Convertible Preferred Stock Term Loan [Member] Term Loan [Member] Term Loan [Member] Trading Symbol Trading Symbol Financial Instruments [Domain] Financial Instruments [Domain] Two Thousand And Seven Stock Incentive Plan [Member] Two Thousand And Seven Stock Incentive Plan [Member] 2007 Plan [Member] Two Thousand Fifteen Omnibus Incentive Plan [Member] Two Thousand Fifteen Omnibus Incentive Plan [Member] 2015 Plan [Member] Type of Arrangement and Non-arrangement Transactions [Axis] Type of Arrangement and Non-arrangement Transactions [Axis] UCB Biopharma. UCB Biopharma [Member] UCB Biopharma [Member] UCB license agreement. UCB License Agreement [Member] UCB License Agreement [Member] Underwriting discounts and commissions. Underwriting Discounts And Commissions Underwriting discounts and commissions Upfront license fees paid. Upfront License Fees Paid Upfront license fee paid Upfront payment allocated to license fee. Upfront Payment Allocated to License Fee Upfront payment allocated to license fee Upfront payments Upfront Payments Upfront milestone payable Upfront payments received Upfront payments received License agreement upfront payment received Use of Estimates, Policy [Policy Text Block] Use of Estimates Vesting of restricted stock value. Vesting Of Restricted Stock Value Vesting of restricted stock Warrant expiration term. Warrant Expiration Term Warrant expiration period Warrant [Member] Common Stock Warrants [Member] Warrants and Rights Note Disclosure [Abstract] Warrants and Rights Note Disclosure [Abstract] Warrants and Rights Outstanding Common stock warrant liability Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted-average common shares used to compute net loss per share-basic and diluted Weighted-average number of common shares used to compute net loss per share attributable to common stockholders-basic and diluted Weighted Average Number of Shares Outstanding, Diluted [Abstract] Denominator-basic and diluted: