Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Restatement Adjustment Restatement Adjustment [Member] Adjustments for Error Corrections [Axis] Adjustments for Error Corrections [Axis] Adjustments for Error Correction [Domain] Adjustments for Error Correction [Domain] Error Recognized Upon the Initial Adoption of ASC 606 Error Recognized Upon the Initial Adoption of ASC 606 [Member] Error Recognized Upon the Initial Adoption of ASC 606 [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Grant Revenue Grant [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated deficit Retained Earnings [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2014-09 Accounting Standards Update 2014-09 [Member] Project [Axis] Project [Axis] Project [Domain] Project [Domain] First Grant First Grant [Member] Represents information pertaining to first grant under NIH. Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] First Acquisition Right First Acquisition Right [Member] First Acquisition Right [Member] Skolkovo Russia Vased Development Fund Of New Technologies Development And Commercialization Center Grant Agreement [Member] Represents information pertaining to russi vased development fund of new technologies development and commercialization center grant agreement. Second Acquisition Right Second Acquisition Right [Member] Second Acquisition Right [Member] Spark License Agreement License Agreement Terms [Member] NIH National Institutes Of Health Grant Agreement [Member] Represents information pertaining to national institutes of health grant agreement. NIDA National Institute On Drug Abuse [Member] National Institute On Drug Abuse [Member] Type of Arrangement and Non-arrangement Transactions [Axis] Type of Arrangement and Non-arrangement Transactions [Axis] Arrangements and Non-arrangement Transactions [Domain] Arrangements and Non-arrangement Transactions [Domain] Spark Letter Agreement Spark Letter Agreement [Member] Spark Letter Agreement [Member] MIT Exclusive Patent License Agreement With Massachusetts Institute Of Technology [Member] Represents information pertaining to Exclusive patent license agreement with Massachusetts Institute of Technology. " Consideration for Promises Consideration For Promises [Member] Consideration For Promises [Member] Development Milestones Development Milestones [Member] Development Milestones [Member] Regulatory Milestones Regulatory Milestones [Member] Regulatory Milestones [Member] Commercial Milestones Commercial Milestones [Member] Commercial Milestones [Member] License and Supply Obligation License And Supply Obligation [Member] License And Supply Obligation [Member] Discount on Option Obligation Discount On Option Obligation [Member] Discount On Option Obligation [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Number of collaboration/grant agreements that required analysis to quantify the impact of adoption Number Of Collaboration Agreements Under Analysis To Quantify Impact Of Adoption Number Of Collaboration Agreements Under Analysis To Quantify Impact Of Adoption Upfront cash payment License And Option Agreement, Upfront Cash Payment License And Option Agreement, Upfront Cash Payment Aggregate additional payments due within twelve months License And Option Agreement, Aggregate Additional Payments Due Within Twelve Months Of Contract Date License And Option Agreement, Aggregate Additional Payments Due Within Twelve Months Of Contract Date Term loan number of payments Term Loan Number of Payments Term Loan Number of Payments Two payments due within 12 months of contract date License And Option Agreement, Two Payments Due Within Twelve Months Of Contract Date License And Option Agreement, Two Payments Due Within Twelve Months Of Contract Date Number of additional targets License And Option Agreement, Number Of Additional Targets For Which Other Party May Exercise Options For Additional Licenses License And Option Agreement, Number Of Additional Targets For Which Other Party May Exercise Options For Additional Licenses Variable fee the Company is eligible to receive for each additional target option elected License And Option Agreement, Variable Fee To Be Received For Each Additional Target Option Elected License And Option Agreement, Variable Fee To Be Received For Each Additional Target Option Elected Election period to exercise additional targets License And Option Agreement, Period For Other Party To Exercise Options For Additional Licenses License And Option Agreement, Period For Other Party To Exercise Options For Additional Licenses Additional development and regulatory milestone payments License And Option Agreement, Additional Development And Regulatory Milestone Payments That May Be Received License And Option Agreement, Additional Development And Regulatory Milestone Payments That May Be Received Commercialization milestone payments License And Option Agreement, Commercialization Milestone Payments That May Be Received License And Option Agreement, Commercialization Milestone Payments That May Be Received Sales milestone payments License And Option Agreement, Sales Milestone Payments That May Be Received License And Option Agreement, Sales Milestone Payments That May Be Received Number of obligations Revenue, Number Of Performance Obligations Revenue, Number Of Performance Obligations Period after first commercial sale when the Company is eligible to receive royalties Eligible Period To Receive Royalties Eligible Period To Receive Royalties Period for prior written notice to terminate license Period For Prior Written Notice To Terminate License Represents information pertaining to period for prior written notice to terminate license. Sale of stock, number of shares issued in transaction (in shares) Sale of Stock, Number of Shares Issued in Transaction Sale common stock Sale of Stock, Consideration Received on Transaction Share price (in dollars per share) Sale of Stock, Price Per Share Premium of average daily VWAP (as a percent) Premium Of Average Daily Volume Weighted Average Price Of Common Stock, Percent Premium Of Average Daily Volume Weighted Average Price Of Common Stock, Percent Deferred revenue related to agreement Contract with Customer, Liability Deferred revenue, current portion Contract with Customer, Liability, Current Deferred revenue, net of current portion Contract with Customer, Liability, Noncurrent Consecutive calendar days leading up to and ending on the day prior to the Contract Date Consecutive Calendar Days Leading Up To Contract Date Consecutive Calendar Days Leading Up To Contract Date Aggregate purchase price Aggregate Purchase Price Aggregate Purchase Price Aggregate price of shares Spark will have the right to purchase Stock Purchase Agreement, Authorized Amount Of Stock To Sell Stock Purchase Agreement, Authorized Amount Of Stock To Sell Number of shares authorized to be issued pursuant to the Stock Purchase Agreement (in shares) Stock Purchase Program, Number Of Shares Authorized To Be Sold Stock Purchase Program, Number Of Shares Authorized To Be Sold License and option agreement, additional sub-license payment received liability License And Option Agreement, Additional Sub-License Payment Received Liability License And Option Agreement, Additional Sub-License Payment Received Liability License and option agreement, payments made relative to calculated premium paid for initial equity investment made under the purchase agreement License And Option Agreement, Calculated Premium Paid For Equity Investment Under Purchase Agreement License And Option Agreement, Calculated Premium Paid For Equity Investment Under Purchase Agreement Number of agreements combined and evaluated into a single agreement Number Of Agreements Combined Into Single Agreement For Evaluation Number Of Agreements Combined Into Single Agreement For Evaluation Fair value of initial purchase of common stock combined with the embedded future stock Acquisition Rights Stock Issued During Period, Value, Purchase of Assets Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Performance obligation per each option Revenue, Remaining Performance Obligation, Each Option Revenue, Remaining Performance Obligation, Each Option Incremental costs of obtaining a contract Capitalized Contract Cost, Net Percentage of sublicense income Percentage Of Sublicense Income Represents information pertaining to percentage of sublicense income. Current assets Assets, Current Long-term assets Assets, Noncurrent Accumulated deficit Retained Earnings (Accumulated Deficit) Revenue recognized Contract with Customer, Liability, Deferred Revenue, Revenue Recognized Contract with Customer, Liability, Deferred Revenue, Revenue Recognized Aggregate purchase price per share (in dollar per share) Stock Purchase Program, Aggregate Purchase Price Per Share Stock Purchase Program, Aggregate Purchase Price Per Share Aggregate amount of grant Grants From Entities Amount Of Grant Award Represents information pertaining to aggregate amount of grant. Percentage of estimated total cost of research plan Percentage Of Estimated Cost Of Research Plan Represents information pertaining to percentage of estimated cost of research plan. Remaining percentage of estimated costs to be contributed by the Company Remaining Percentage Contributed By The Entity Represents information pertaining to remaining percentage contributed by the entity. Payments received Increase Decrease In Contingently Repayable Grant Funding The increase (decrease) during the reporting period in contingently repayable grant funding that are used in an entity's business. Adoption of new accounting principle Cumulative Effect of New Accounting Principle in Period of Adoption Grants from entities, unused grant funds Grants From Entities Unused Grant Funds Grants From Entities Unused Grant Funds Overspent costs Overspent Costs Overspent Costs Period after completion of project when Company may be required to reimburse the funds received Period To Audit Expenditure Incurred Represents information pertaining to period to audit expenditure incurred. Grant and collaboration revenue Revenue from Contract with Customer, Excluding Assessed Tax Remaining amount not recognized Grant Revenue, Available Under Grant Not Recognized Grant Revenue, Available Under Grant Not Recognized Reimbursement invoices Reimbursement Invoice Reimbursement Invoice Other liabilities Other Liabilities Property, Plant and Equipment [Abstract] Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] President President [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Employment Inducement Incentive Award Plan Employment Inducement Incentive Award Plan [Member] Employment Inducement Incentive Award Plan [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Unvested restricted stock units Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Common stock authorized and reserved for future issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Number of shares authorized for grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Schedule of Weighted Average Assumptions Used Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Summary of Activity Under the 2008 Plan and the 2016 Plan Share-based Compensation, Stock Options, Activity [Table Text Block] Disclosure of Share-based Compensation Arrangements by Share-based Payment Award Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] One-time Termination Benefits One-time Termination Benefits [Member] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Public Stock Offering Public Stock Offering [Member] Public Stock Offering [Member] Over-Allotment Option Over-Allotment Option [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Workforce reduction, percentage Workforce Reduction, Percentage Workforce Reduction, Percentage Number of employment positions terminated Number Of Employment Positions Terminated Number Of Employment Positions, Terminated Payments for restructuring Payments for Restructuring Number of employment positions Number Of Employment Positions Number Of Employment Positions Common stock, shares issued Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Sale Of Stock, Granted Exercisable Share Option, Time Period To Purchase Sale Of Stock, Granted Exercisable Share Option, Time Period To Purchase Sale Of Stock, Granted Exercisable Share Option, Time Period To Purchase Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Equity [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Exercise of common warrants Warrant [Member] Shares available for future stock incentive awards Stock Compensation Plan [Member] Outstanding common stock options Employee Stock Option [Member] Class of Stock [Line Items] Class of Stock [Line Items] Total (in shares) Accounting Policies [Abstract] Impairment of intangible assets, finite-lived Impairment of Intangible Assets, Finite-lived Earnings Per Share [Abstract] Net Loss Per Share Earnings Per Share [Text Block] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash and Cash Equivalents, Current Restricted cash included in other assets Restricted Cash and Cash Equivalents, Noncurrent Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents ESPP Employee Stock Purchase Plan2016 [Member] Represent information pertaining to the 2016 Employee Stock Purchase Plan. Number of offering periods under the ESPP Number Of Offering Periods Number Of Offering Periods Term of each offering period Offering Period Offering Period Eligible compensation withheld for use (up to) (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Purchase price of shares (not less than) (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Number of shares of common stock outstanding (as a percent) Employee Stock Purchase Plan Maximum Percentage Of Shares Reserved Based On Shares Outstanding The maximum percentage increase in the shares reserved for future issuance each year based on the number of common stock outstanding at the last day of the year. Number of shares authorized, increase (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Shares Available For Grant, Increase (Decrease) Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Shares Available For Grant, Increase (Decrease) Shares of common stock issued to employees under the ESPP (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Stock-based compensation expense Allocated Share-based Compensation Expense Schedule of Future Minimum Lease Payments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Document and Entity Information 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 Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Entity Voluntary Filers Entity Voluntary Filers Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Emerging Growth Company Entity Emerging Growth Company Entity Smaller Reporting Company Entity Small Business Entity Extended Transition Period Entity Ex Transition Period Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Public Float Entity Public Float Entity Current Reporting Status Entity Current Reporting Status Income Tax Disclosure [Abstract] Statutory U.S. federal rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent State income taxes - net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Permanent items Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent Research tax credits/other Effective Income Tax Rate Reconciliation, Tax Credit, Percent Change in enacted rates Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Valuation allowance, net Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Payables and Accruals [Abstract] Schedule of Accrued Expenses Schedule of Accrued Liabilities [Table Text Block] Computation of Basic and Diluted Net Loss Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Potential Common Shares Issuable Upon Conversion of Warrants Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series A Redeemable Convertible Preferred Stock Series A Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series A redeemable convertible preferred stock. Series B Redeemable Convertible Preferred Stock Series B Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series B redeemable convertible preferred stock. Series C Redeemable Convertible Preferred Stock Series C Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series C redeemable convertible preferred stock. Series D Redeemable Convertible Preferred Stock Series D Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series D redeemable convertible preferred stock. Series SRN Redeemable Convertible Preferred Stock Series SRN Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series SRN redeemable convertible preferred stock. Series E Redeemable Convertible Preferred Stock Series E Redeemable Convertible Preferred Stock [Member] Represents information pertaining to series E redeemable convertible preferred stock. Preferred Stock Preferred Stock [Member] Common stock Common Stock [Member] Additional paid-In Capital Additional Paid-in Capital [Member] Stock option receivable Receivables from Stockholder [Member] Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Temporary equity, shares outstanding at the beginning of the period (in shares) Temporary Equity, Shares Outstanding Temporary equity, outstanding at the beginning of the period Temporary Equity, Carrying Amount, Attributable to Parent Beginning balance (in shares) Common Stock, Shares, Outstanding Beginning balance Stockholders' Equity Attributable to Parent Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Vesting of restricted common stock (in shares) Stock Vested During Period Share Restricted Common Stock Represents the total number of shares vested during the period as a result of Restricted Common Stock. Vesting of restricted common stock Stock Vested During Period Value Restricted Common Stock Represents the aggregate value of stock related to Restricted Common Stock vested during the period. Issuance of common stock upon exercise of options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of common stock upon exercise of options Stock Issued During Period, Value, Stock Options Exercised Stock‑based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Accretion of preferred stock to redemption value Temporary Equity, Accretion to Redemption Value Accretion of preferred stock to redemption value Stockholders Equity Accretion to Redemption Value Represents the value of accretion of temporary equity to redemption value during the period. Currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Net loss Net Income (Loss) Attributable to Parent Exercise of common warrants (in shares) Stock Issued During Period Shares Warrants Exercised Number of warrants exercised during the current period. Temporary equity, conversion of convertible stock upon listing (in shares) Temporary Equity, Stock Issued During Period, Shares, Conversion Of Convertible Securities Temporary Equity, Stock Issued During Period, Shares, Conversion of Convertible Securities Common stock, conversion of convertible stock upon listing (in shares) Stock Issued During Period, Shares, Conversion of Convertible Securities Conversion of convertible stock upon listing Stock Issued During Period, Value, Conversion of Convertible Securities Issuance of common stock, initial public offering net of issuance costs (in shares) Stock Issued During Period, Shares, New Issues Issuance of common stock, Initial public offering net of issuance costs Stock Issued During Period, Value, New Issues Issuance of common stock, license agreement (in shares) Stock Issued During Period, Shares, Purchase of Assets Issuance of common stock, license agreement Issuance of common stock, Private placement net of issuance costs (in shares) Stock Issued During Period Value Conversion Preferred Stock Warrants, Shares Stock Issued During Period Value Conversion Preferred Stock Warrants, Shares Issuance of common stock, Private placement net of issuance costs Stock Issued During Period Value Conversion Preferred Stock Warrants The gross value of stock issued during the period upon the conversion of preferred stock warrants. Issuance of common stock under Employee Stock Purchase Plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Issuance of common stock under Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Unrealized gains (losses) on securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Temporary equity, shares outstanding at the end of the period (in shares) Temporary equity, outstanding at the end of the period Ending balance (in shares) Ending balance Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Foreign currency translation adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Unrealized gains (losses) on available-for-sale securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI Attributable to Parent, Net of Tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Other comprehensive loss during the year Other Comprehensive Income (Loss), Net of Tax Retirement Benefits [Abstract] Vesting period Defined Contribution Plan Employers Matching Contribution Vesting Period Period which an employee's right to exercise a plan is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Employer contribution made Defined Contribution Plan, Cost Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Furniture and fixtures Furniture and Fixtures [Member] Laboratory and office equipment Equipment [Member] Computer equipment Computer Equipment [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Estimated useful life Property, Plant and Equipment, Useful Life Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] 3SBio License License Agreement With Shenyang Sunshine Pharmaceutical Company Limited [Member] Represents information pertaining to License agreement with Shenyang Sunshine Pharmaceutical co., ltd. Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Period after approval to commercialize product Period For Commercialization Of Product Represents information pertaining to period for commercialization of product. Aggregate amount of upfront and milestone-based payments Aggregate Amount Of Upfront And Milestone Based Payments Paid Aggregate Amount Of Upfront And Milestone Based Payments Paid Additional liability for milestone payments expensed in 2016 Upfront And Milestone Based Payments, Additional Liability Upfront And Milestone Based Payments, Additional Liability Aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for products containing SVP technology Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Containing Svp Technology Represents information pertaining to aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for product containing SVP technology. Aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for products without SVP technology Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Without Svp Technology Represents information pertaining to aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for product without SVP technology. Maximum paid on tiered royalties (percent) Maximum Percentage Paid On Tiered Royalties Maximum Percentage Paid On Tiered Royalties Period for prior written notice to terminate license Investments, Debt and Equity Securities [Abstract] Fair Value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Less than one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Less than one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Stock Options And Restricted Common Stock [Member] Stock Options And Restricted Common Stock [Member] Stock Options And Restricted Common Stock [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research and development Research And Development [Member] Represents the information pertaining to research and development expenses included in the income statement. General and administrative General and Administrative Expense [Member] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Total stock-based compensation expense Realized gains or losses on sale of investments Realized Investment Gains (Losses) Debt Disclosure [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] 2017 Term Loans 2017 Term Loans [Member] 2017 Term Loans [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Year ended December 31, Long-term Debt, Fiscal Year Maturity [Abstract] 2019 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2020 Long-term Debt, Maturities, Repayments of Principal in Year Two 2021 Long-term Debt, Maturities, Repayments of Principal in Year Three 2022 Long-term Debt, Maturities, Repayments of Principal in Year Four Total minimum debt payments Long-term Debt Less: Amount representing interest Debt Instrument Interest Portion The interest portion of gross outstanding debt. Less: Debt discount and deferred charges Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Less: Current portion of loan payable Long-term Debt, Current Maturities Loan payable, net of current portion Long-term Debt, Excluding Current Maturities The 2008 Plan and the 2016 Plan The 2008 Plan And The 2016 Plan [Member] The 2008 Plan And The 2016 Plan [Member] Employee Awards Non‑Employee Awards Non Employee Stock Option [Member] An arrangement whereby a non-employee is entitled to receive in the future, subject to vesting and other restrictions, a number of shares in the entity at a specified price, as defined in the agreement. Number of Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Ending balance (in shares) Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Vested and expected to vest (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Weighted-average exercise price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Ending balance (in dollars per share) Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Exercise Price Vested and expected to vest (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Weighted-average remaining contractual term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term [Abstract] n/a Outstanding, term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Vested, term Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Weighted Average Remaining Contractual Term Vested and expected to vest, term Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value [Abstract] n/a Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Vested Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Intrinsic Value Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Intrinsic Value Vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Less: accretion on preferred stock Temporary Equity, Accretion to Redemption Value, Adjustment Net (loss) income attributable to common stockholders - basic & diluted Net Income (Loss) Available to Common Stockholders, Basic Denominator: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted‑average common shares outstanding—basic and diluted (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Net loss per share attributable to common stockholders—basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted Contract liabilities: Change In Contract With Customer, Liability [Roll Forward] Change In Contract With Customer, Liability [Roll Forward] Deferred revenue, beginning of period Contract with Customer, Liability, Deferred Revenue Contract with Customer, Liability, Deferred Revenue Other liabilities, beginning of period Contract with Customer, Liability, Other Contract with Customer, Liability, Other Contract liabilities, beginning of period Deferred revenue, additions Contract with Customer, Liability, Deferred Revenue, Increase From Cash Receipts Contract with Customer, Liability, Deferred Revenue, Increase From Cash Receipts Other liabilities, additions Contract with Customer, Liability, Other, Increase From Cash Receipts Contract with Customer, Liability, Other, Increase From Cash Receipts Contract liabilities, additions Contract with Customer, Liability, Increase From Cash Receipts Contract with Customer, Liability, Increase From Cash Receipts Deferred revenue, deductions Other liabilities, deductions Contract with Customer, Liability, Other, Revenue Recognized Contract with Customer, Liability, Other, Revenue Recognized Contract liabilities, deductions Contract with Customer, Liability, Revenue Recognized Deferred revenue, end of period Other liabilities, end of period Contract liabilities, end of period Other liabilities, current portion Contract with Customer, Liability, Other, Current Contract with Customer, Liability, Other, Current Other liabilities, noncurrent portion Contract with Customer, Liability, Other, Noncurrent Contract with Customer, Liability, Other, Noncurrent Statement of Financial Position [Abstract] Preferred stock, par value (in dollars per share) 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, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Subsequent Events Subsequent Events [Text Block] Available-for-Sale Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Income Tax Holiday [Table] Income Tax Holiday [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Domestic Tax Authority Domestic Tax Authority [Member] State and Local Jurisdiction State and Local Jurisdiction [Member] Domestic And State Tax Authority Domestic And State Tax Authority [Member] Domestic And State Tax Authority [Member] Income Tax Holiday [Line Items] Income Tax Holiday [Line Items] Valuation allowance, deferred tax asset, increase (decrease), amount Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Current income tax expense or benefit Current Income Tax Expense (Benefit) Deferred income tax expense or benefit Deferred Income Tax Expense (Benefit) Term of tax holiday granted to Russian subsidiary Income Tax Holiday, Term Income Tax Holiday, Term Operating loss carryforwards Operating Loss Carryforwards Operating loss carryforwards, carried forward indefinitely Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration Increase in net operating losses, deferred tax assets Deferred Tax Assets, Operating Loss Carryforwards Research and development credits Deferred Tax Assets, Tax Credit Carryforwards, Research Tax Cuts and Jobs Act, reduction of deferred tax assets Tax Cuts and Jobs Act, Change in Tax Rate, Increase (Decrease) In Deferred Tax Asset Tax Cuts and Jobs Act, Change in Tax Rate, Increase (Decrease) In Deferred Tax Asset Operating loss carryforwards, subject to expiration Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration Full valuation allowance Tax Cuts and Jobs Act, Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Tax Cuts and Jobs Act, Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Unrecognized tax benefits Unrecognized Tax Benefits Related interest and penalties accrued Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Accrued interest related to uncertain tax positions Unrecognized Tax Benefits, Interest on Income Taxes Accrued Number of operating segments Number of Operating Segments Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Springer Purchase Agreement Springer Purchase Agreement [Member] Springer Purchase Agreement [Member] Stock warrants to purchase common stock Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Founders Founder [Member] Represents information pertaining to founder member. Related Party Transaction [Line Items] Related Party Transaction [Line Items] Stock issued (in shares) Exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Expiration period of warrants Class Of Warrants Or Rights, Term Period of time between issuance and maturity of warrant, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Share price (in dollars per share) Class of Warrant or Right, Issued to Purchase Common Stock Class of Warrant or Right, Issued to Purchase Common Stock Consulting services expenses Related Party Transaction, Expenses from Transactions with Related Party Temporary Equity Disclosure [Abstract] Preferred Stock Temporary Equity Disclosure [Text Block] The entire disclosure for temporary equity. Principles of Consolidation Consolidation, Policy [Policy Text Block] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Segment Information Segment Reporting, Policy [Policy Text Block] Cash Equivalents and Short Term Investments Cash Equivalents And Short Term Investments [Policy Text Block] Disclosure of accounting policy for cash equivalents and short term investments. Concentrations of Credit Risk and Off-Balance Sheet Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Debt Issuance Costs Debt, Policy [Policy Text Block] Accumulated Other Comprehensive Income (Loss) Comprehensive Income, Policy [Policy Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Research and Development Costs Research and Development Expense, Policy [Policy Text Block] Clinical Trial Costs Clinical Trial Costs [Policy Text Block] Disclosure of accounting policy for clinical trial costs. Income Taxes Income Tax, Policy [Policy Text Block] Warrants Warrants [Policy Text Block] Disclosure of accounting policy for warrants. Stock-Based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Net Loss Per Share Earnings Per Share, Policy [Policy Text Block] Deferred Rent Deferred Rent [Policy Text Block] Disclosure of accounting policy for deferred rent. Contingent Liabilities Contingent Liability Reserve Estimate, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Fair Value Disclosures [Abstract] Summary of Assets Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] 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] Depreciation Depreciation Amortization of premiums (accretion of discounts) on investments Accretion (Amortization) of Discounts and Premiums, Investments (Gain) loss on disposal of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Stock‑based compensation expense Non‑cash interest expense Paid-in-Kind Interest Loss on extinguishment of debt Gain (Loss) on Extinguishment of Debt Net unrealized losses on investments Fair Value Adjustment of Warrants Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses, deposits and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable Increase (Decrease) in Accounts Payable Deferred revenue Increase (Decrease) in Contract with Customer, Liability Contingently repayable grant funding Accrued expenses and other liabilities Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Receipts from the maturity of short-term investments Proceeds from Maturities, Prepayments and Calls of Short-term Investments Purchases of short-term investments Payments to Acquire Short-term Investments Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from the sale of property and equipment Proceeds from Sale of Property, Plant, and Equipment Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Proceeds from issuance of long-term debt, net of expenses Proceeds from Lines of Credit Repayments of long-term debt Repayments of Long-term Debt Proceeds from Initial Public Offering, net of underwriters' discounts and commissions Proceeds from Issuance Initial Public Offering Deferred IPO costs paid Payments of Stock Issuance Costs Proceeds from Private Placement, net of issuance costs ($2.9 million) Proceeds from Issuance of Private Placement Proceeds from issuance of common stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Proceeds from issuance of common stock under Employee Stock Purchase Plan Proceeds from Stock Plans Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash Effect of Exchange Rate on Cash and Cash Equivalents Net change in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents, and restricted cash at beginning of period Cash, cash equivalents, and restricted cash at end of period Supplement cash flow information Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activities Noncash investing activities Noncash Investing and Financing Items [Abstract] Purchase of property and equipment not yet paid Capital Expenditures Incurred but Not yet Paid Unrealized gain (loss) on marketable securities Marketable Securities, Unrealized Gain (Loss) Reclassification of deferred IPO costs from non-current assets to additional paid-in capital Noncash or Partial Noncash Reclassification Of Deferred IPO Costs From Non Current Assets To Additional Paid In Capital Reclassification of deferred IPO costs from non-current assets to additional paid-in capital. Debt issuance costs included in accounts payable Initial Public Offering Costs Incurred But Not Yet Paid Initial Public Offering Costs Incurred But Not Yet Paid Accrued dividends and accretion of preferred stock to redemption value Year ending December 31, Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years Total minimum lease payments Operating Leases, Future Minimum Payments Due Term Loans Term Loan [Member] Represents information pertaining to term loan member. Debt Covenant Period [Axis] Debt Covenant Period [Axis] Debt Covenant Period [Axis] Debt Covenant Period [Domain] Debt Covenant Period [Domain] [Domain] for Debt Covenant Period [Axis] Prepaid before the first anniversary Term Loan Prepaid Before the First Anniversary [Member] Term Loan Prepaid Before the First Anniversary [Member] Prepaid after to first anniversary but before second Term Loan Prepaid After First Anniversary But Before Second Anniversary [Member] Represents information pertaining to prepayment of term loan after first anniversary but prior to second anniversary. Prepaid after second anniversary Term Loan Prepaid After Second Anniversary [Member] Represents information pertaining to prepayment of term loan after second anniversary. Conversion of Series D Preferred Conversion of Series E Preferred Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Convertible Debt Convertible Debt [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Base Rate Base Rate [Member] Borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Borrowings on loan and security agreement Interest rate per annum Line of Credit Facility, Interest Rate During Period Number of monthly installments Debt Instrument, Term Prepayment fee (as a percent) Early Extinguishment Of Debt, Prepayment Fee Percentage Percentage of fee payable on early extinguishment of debt. Final payment fee (as a percent) Final Payment Fee Percentage Percentage of final fee payment payable on aggregate principal amounts borrowed. Final payment fee Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid Warrants issued for purchase of stock (in shares) Class of Warrant or Right, Number of Securities Called by Warrants or Rights Initial grant date fair value of warrants Warrants, Grant Date Fair Value Represents the initial grant date fair value of the warrants. Number of warrants exercised to purchase common stock (in shares) Number Of Warrants Exercised To Purchase Common Stock Number Of Warrants Exercised To Purchase Common Stock Net shares of common stock issued (in shares) Stock Issued During Period, Shares, Common Stock Issued Upon Exercise Of Warrants Stock Issued During Period, Shares, Common Stock Issued Upon Exercise Of Warrants Term loan facility Long-term Line of Credit Repayments of debt Repayments of Lines of Credit Loss on extinguishment of debt Debt issuance costs, line of credit arrangements (less than) Debt Issuance Costs, Line of Credit Arrangements, Net Minimum assets trigger Debt Instrument, Event Of Default, Minimum Assets Trigger Debt Instrument, Event Of Default, Minimum Assets Trigger Minimum amount in excess of indebtedness trigger Debt Instrument, Event Of Default, Minimum Amount In Excess Of Indebtedness Trigger Debt Instrument, Event Of Default, Minimum Amount In Excess Of Indebtedness Trigger Interest expense related to the Term Loan Interest Expense Debt instrument, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Accrued Expenses Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Debt Debt Disclosure [Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Technology License Agreements Technology License Agreements [Text Block] The entire disclosure for technology license agreements. MEE License Agreement With Massachusetts Eye And Ear Infirmary And Schepens Eye Research Institute Inc. [Member] Represents information pertaining to License agreement with Massachusetts Eye and Ear Infirmary and The Schepens Eye Research Institute, Inc. Minimum number of products for each target sequence Number Of Products Marketed And Sold Represents the number of products the Company has agreed to market and sell for each target sequence for which the Company exercised its option as soon as reasonably practicable. Payment under development milestone method Development Milestone Method, Amount Paid The amount of consideration paid during the period for the development milestone or milestones. Payment under sales milestone method Sales Milestone Method, Amount Paid The amount of consideration paid during the period for the sales milestone or milestones. License fees due under agreement Initial License Fee Paid Initial License Fee Paid Accrued license fees Accrued License Fees Accrued License Fees Organization, Consolidation and Presentation of Financial Statements [Abstract] Accumulated deficit Schedule of Cash and Cash Equivalents [Table] Schedule of Cash and Cash Equivalents [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Russian subsidiary RUSSIAN FEDERATION Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Unrestricted cash Unrestricted Cash [Member] Unrestricted Cash [Member] Cash and Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Laboratory equipment Laboratory Equipment [Member] Represents information pertaining to laboratory equipment. Computer equipment and software Leasehold improvements Leasehold Improvements [Member] Office equipment Office Equipment [Member] Construction in process Construction in Progress [Member] Total property and equipment Property, Plant and Equipment, Gross Less accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property and equipment, net Property, Plant and Equipment, Net Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] U.S. government and agency securities US Treasury and Government [Member] Corporate bonds Corporate Bond Securities [Member] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Fair Value Debt Securities, Available-for-sale Common Stock Stockholders' Equity Note Disclosure [Text Block] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] ASU 2016-02 Accounting Standards Update 2016-02 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Lease liabilities Operating Lease, Liability Lease, right-of-use asset Operating Lease, Right-of-Use Asset Schedule of Future Minimum Payments on the Term Loans Schedule of Maturities of Long-term Debt [Table Text Block] Defined Contribution Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] At-The-Market Offering At-The-Market Offering [Member] At-The-Market Offering [Member] 2017 PIPE 2017 PIPE [Member] 2017 PIPE [Member] IPO IPO [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Public securities offering, amount authorized Public Securities Offering, Amount Authorized Public Securities Offering, Amount Authorized Public stock offering, amount authorized Public Stock Offering, Amount Authorized Public Stock Offering, Amount Authorized Convertible preferred stock, shares issued upon conversion (in shares) Convertible Preferred Stock, Shares Issued upon Conversion Common stock, shares authorized (in shares) Number of votes per share that common stockholders are entitled to Votes Per Share of Common Stock Votes Per Share of Common Stock Dividends declared or paid on common stock Dividends, Common Stock Payroll and employee related expenses Employee-related Liabilities, Current Current portion of deferred rent and lease incentive Accrued Rent And Lease Incentive Payable Current " Carrying value as of the balance sheet date of obligations incurred through that date and payable for contractual rent under lease arrangements and an incentive or inducement contractually stipulated between parties to a lease whereby the lessor has committed to provide the entity (lessee) with a cash payment as inducement to enter the lease. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer)." Collaboration and licensing Accrued Collaboration and Licensing Accrued Collaboration and Licensing Accrued patent fees Accrued Patent Fees Current Carrying value as of the balance sheet date of patent fees. Accrued external research and development costs Accrued Research And Development Costs Current Carrying value as of the balance sheet date of research and development costs. Accrued professional and consulting services Accrued Audit Fees, Current Accrued Audit Fees, Current Accrued grant refund Accrued Grant Refund, Current Accrued Grant Refund, Current Accrued interest Interest Payable, Current Other Other Accrued Liabilities, Current Accrued expenses Accrued Liabilities, Current Non-employee stock options Employee stock option grants Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected term Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Weighted-average fair value of common stock (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Fair Value Weighed-average fair value relating to the share-based payment award. Share-based Goods and Nonemployee Services Transaction [Abstract] Share-based Goods and Nonemployee Services Transaction [Abstract] Risk-free interest rate Share-based Goods and Nonemployee Services Transaction, Valuation Method, Risk Free Interest Rate Dividend yield Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Dividend Rate Expected term Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Term Expected volatility Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Volatility Rate Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] 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] Average maturity, term Investments Maturity Period Represents information pertaining to US treasury obligations in investments maturity period. Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block] 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 [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options to purchase common stock Unvested restricted stock units Restricted Stock [Member] Potential common shares Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of Changes in Contract Liabilities Contract with Customer, Asset and Liability [Table Text Block] Chief Executive Officer Chief Executive Officer [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Tranche One Share-based Compensation Award, Tranche One [Member] Tranche Two Share-based Compensation Award, Tranche Two [Member] 2008 Plan Stock Incentive Plan2008 [Member] Represents the information pertaining to the 2008 stock incentive plan, which provides for the granting of stock based awards to employees, directors, and consultants under terms and provisions established by the board of directors. 2016 Plan Stock Incentive Plan2016 [Member] Represents the information pertaining to the 2016 stock incentive plan, which provides for the granting of stock based awards to employees, directors, and consultants under terms and provisions established by the board of directors. Exercise price of incentive stock options (not less than) Combined voting power of participants (as a percent) Share-based Compensation Arrangement By Share-based Payment Award, Voting Rights of Common Stock, Holding Percentage Represents the percentage of voting rights of all classes of stock held by the employees. Award vesting term Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Award expiration term Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Automatic increase in the number of shares that may be issued (as a percent) Estimated forfeitures rate Share-based Compensation Arrangement By Share-based Payment Award Forfeitures Rate Represents the percentage of forfeitures rate of the stock options based on the historical trends. Weighted average grant date fair value of stock options (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Shares exercises in period by employees (in shares) Aggregate intrinsic value of stock options exercised Unrecognized compensation expense related to unvested employee stock options Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Weighted average period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Unvested stock option awards (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares Forfeited (in shares) Vested and expected to vest, exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number Unrecognized compensation expense related to unvested non-employee stock options Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options Unrecognized compensation expense related to unvested non-employee stock options, period Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options, Period Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options, Period Shares issued (in shares) Shares issued (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Shares issued, value Unrecognized compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Granted, net of forfeitures (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Deferred Tax Assets Deferred Tax Assets, Gross [Abstract] Net operating loss carryforwards Stock-based compensations expense Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Deferred rent and other expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Deferred revenue Deferred Tax Assets, Deferred Income Patent costs/amortization Deferred Tax Assets, Goodwill and Intangible Assets Gross deferred tax assets Deferred Tax Assets, Gross Deferred Tax Liabilities Deferred Tax Liabilities, Gross [Abstract] Depreciation Deferred Tax Liabilities, Property, Plant and Equipment Gross deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax assets Deferred Tax Assets, Net Of Deferred Tax Liabilities Deferred Tax Assets, Net Of Deferred Tax Liabilities Valuation allowance Deferred Tax Assets, Valuation Allowance Net deferred tax assets Deferred Tax Assets, Net Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Laboratory and office space Laboratory And Office Space [Member] Represents information pertaining to laboratory and office space member. Letter of credit Letter of Credit [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Restricted cash and other assets Restricted Cash And Other Deposits [Member] Represents inforamtion pertaining to restricted cash and other deposits member. Accrued expenses Accounts Payable and Accrued Liabilities [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Tenant improvement allowance Payments for (Proceeds from) Tenant Allowance Letter of credit Area of additional office space leased Area of Real Estate Property Deferred rent and lease incentive liability Deferred Rent And Lease Incentive Liability This element represents both current and non current costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease and includes the deferred charge for an incentive or inducement granted by a lessor to a lessee, in order to motivate the lessee to enter the lease agreement, which incentive or inducement is to be recognized as a reduction of rental revenue over the lease term. Current portion of deferred rent and lease incentive liability (prior year less than) Rent expense Operating Leases, Rent Expense, Net Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Fair Value, Measurements, Recurring [Member] Money market funds Money Market Funds [Member] Corporate bonds Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] (Level 1) Fair Value, Inputs, Level 1 [Member] (Level 2) Fair Value, Inputs, Level 2 [Member] (Level 3) Fair Value, Inputs, Level 3 [Member] Total cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Total short-term investments Investments, Fair Value Disclosure Schedule of Authorized Shares of Common Stock for Future Issuance Schedule of Stock by Class [Table Text Block] Operating expenses Operating Expenses Remaining performance obligation, percentage Revenue, Remaining Performance Obligation, Percentage Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Remaining performance obligation, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Depreciation expense Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Authorized shares of Preferred Stock (in shares) Temporary Equity, Shares Authorized Preferred Stock, par value (in dollars per share) Temporary Equity, Par or Stated Value Per Share Temporary Equity, by Class of Stock [Table] Temporary Equity, by Class of Stock [Table] Series B Preferred Series D Preferred Stock [Member] Series D Preferred Stock [Member] Series E Preferred Stock [Member] Series E Preferred Stock [Member] Stock Conversion Description [Axis] Stock Conversion Description [Axis] Conversion of Stock, Name [Domain] Conversion of Stock, Name [Domain] Preferred stock automatically converted into common stock upon the closing of the IPO Preferred Stock Automatically Converted Into Common Stock Upon Closing Of Initial Public Offering [Member] Preferred Stock Automatically Converted Into Common Stock Upon Closing Of Initial Public Offering [Member] Preferred stock Temporary Equity [Line Items] Convertible preferred stock automatically converted into common stock (in shares) Conversion of Stock, Shares Converted Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Restricted Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Components of Accumulated Other Comprehensive Income (Loss), Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Stock Incentive Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Summary of Available-for-Sale Marketable Securities Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of Fair Values and Amortized Cost of Marketable Debt Securities by Contractual Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Nature of the Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Schedule of Property and Equipment Property, Plant and Equipment [Table Text Block] Selected Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Concentration Risk [Table] Concentration Risk [Table] Russian subsidiary Currency [Axis] Currency [Axis] All Currencies [Domain] All Currencies [Domain] U.S. dollars United States of America, Dollars Concentration Risk [Line Items] Concentration Risk [Line Items] Cash maintained in Russian bank accounts Cash Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Current Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Current Short-term deposits and investments Short-term Investments Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Property and equipment, net Restricted cash and other assets Restricted Cash and Investments, Noncurrent Total assets Assets Liabilities and stockholders’ equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued expenses Loan payable, current portion Loans Payable, Current Total current liabilities Liabilities, Current Non‑current liabilities: Other Liabilities, Noncurrent [Abstract] Deferred rent and lease incentive Deferred Rent Credit, Noncurrent Loan payable, net of current portion Loans Payable, Noncurrent Other long‑term liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 8) Commitments and Contingencies Stockholders’ (deficit) equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively Preferred Stock, Value, Issued Common stock, $0.0001 par value; 200,000,000 shares authorized; 22,471,776 and 22,343,254 shares issued and outstanding as of December 31, 2018 and December 31, 2017, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated deficit Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ (deficit) equity Total liabilities and stockholders’ equity Liabilities and Equity Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Initial Application Period Cumulative Effect Transition [Table] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Pro forma as if the previous accounting was in effect Calculated under Revenue Guidance in Effect before Topic 606 [Member] Adjustments due to ASU 2014-09 Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Common stock Receivable from stock option exercises Receivable from Shareholders or Affiliates for Issuance of Capital Stock Payment amount upon achievement of defined clinical milestones Payment Amount Upon Achievement Of Defined Clinical Milestones Represents information pertaining to payment amount upon achievement of defined clinical milestones. Contractual payments defined in the Exclusive Patent License agreement License And Option Agreement, Contractual Payments Made License And Option Agreement, Contractual Payments Made Statement of Comprehensive Income [Abstract] Operating expenses: Cost of Revenue [Abstract] Research and development Research and Development Expense General and administrative General and Administrative Expense Total operating expenses Loss from operations Operating Income (Loss) Investment income Investment Income, Net Loss on extinguishment of debt Foreign currency transaction gain (loss), net Foreign Currency Transaction Gain (Loss), before Tax Interest expense Other income (expense), net Other Nonoperating Income (Expense) Net loss Other comprehensive loss: Other Comprehensive Income (Loss), Tax [Abstract] Foreign currency translation adjustment Unrealized gain (loss) on securities Total comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Accretion of redeemable convertible preferred stock Net loss attributable to common stockholders Net loss per share: Earnings Per Share, Basic and Diluted [Abstract] Weighted average common shares outstanding: Basic and diluted (in shares) Related-Party Transactions Related Party Transactions Disclosure [Text Block] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Shares outstanding at December 31, 2017 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Grants in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Shares outstanding at December 31, 2018 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Shares outstanding at December 31, 2017 (in dollars per share) Grants in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Shares outstanding at December 31, 2018 (in dollars per share) Grants in period, amount Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants In Period, Amount Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants In Period, Amount Income Taxes Income Tax Disclosure [Text Block] Revenue Arrangements Revenue from Contract with Customer [Text Block]