Entity Central Index Key Document - Document and Entity Information [Abstract] Document Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Common Stock Shares Outstanding Entity Common Stock Shares Outstanding Entity Shell Company Entity Shell Company Entity Current Reporting Status Entity Current Reporting Status Entity File Number Entity File Number Entity Tax Identification Number Entity Tax Identification Number Entity Incorporation, State or Country Code Entity Incorporation State Country Code Entity Address, Address Line One Entity Address Address Line1 Entity Address, Address Line Two Entity Address Address Line2 Entity Address, City or Town Entity Address City Or Town Entity Address, State or Province Entity Address State Or Province Entity Address, Postal Zip Code Entity Address Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Security Exchange Name Security Exchange Name Title of 12(b) Security Security12b Title Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Entity Interactive Data Current Entity Interactive Data Current Accrued expenses and other current liabilities. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Restricted cash Restricted Cash Current Other receivable Other Receivables Net Current Prepaid expenses and other assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Operating lease right-of-use assets Operating Lease Right Of Use Asset Other assets Other Assets Noncurrent Total assets Assets Liabilities and stockholders' equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Current portion of long-term debt Long Term Debt Current Accounts payable Accounts Payable Current Accrued expenses and other current liabilities Accrued Expenses And Other Current Liabilities Total current liabilities Liabilities Current Long-term debt Long Term Debt Noncurrent Operating lease liabilities Operating Lease Liability Noncurrent Other long-term liabilities Other Liabilities Noncurrent Deferred rent Deferred Rent Credit Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2019 and December 31, 2018; zero shares issued and outstanding at September 30, 2019 and December 31, 2018 Preferred Stock Value Common stock, $0.001 par value; 200,000,000 shares authorized; 28,782,811 shares issued and 28,752,844 shares outstanding at September 30, 2019; 24,528,242 shares issued and 24,498,275 shares outstanding at December 31, 2018 Common Stock Value Treasury stock, at cost, 29,967 shares as of September 30, 2019 and December 31, 2018 Treasury Stock Value Additional paid-in capital Additional Paid In Capital Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders’ equity Stockholders Equity Total liabilities and stockholders' equity Liabilities And Stockholders Equity Preferred Stock, Par Value Preferred Stock Par Or Stated Value Per Share Preferred Stock, Shares Authorized Preferred Stock Shares Authorized Preferred Stock, Shares Issued Preferred Stock Shares Issued Preferred Stock, Shares Outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Treasury stock, shares Treasury Stock Shares Income Statement [Abstract] Statement [Table] Statement [Table] Product and Service Product Or Service [Axis] Product and Service Products And Services [Domain] Grant Revenue Grant [Member] Collaborative agreements. Collaborative Agreement Collaborative Agreements [Member] Statement [Line Items] Statement [Line Items] Revenue: Revenues [Abstract] Total revenue Revenue From Contract With Customer Excluding Assessed Tax Operating expenses: Operating Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income Loss Other income (expense): Other Nonoperating Income Expense [Abstract] Interest income Investment Income Interest Interest expense Interest Expense Foreign exchange gain (loss) Foreign Currency Transaction Gain Loss Before Tax Change in fair value of warrant liability Fair Value Adjustment Of Warrants Change in fair value of derivative liability Unrealized Gain Loss On Derivatives Total other income (expense) Other Nonoperating Income Expense Net loss Net Income Loss Net loss per common share, basic and diluted Earnings Per Share Basic And Diluted Weighted average common shares outstanding, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Temporary equity stock issued during period shares new issues. Temporary equity, stock issued during period shares conversion of convertible promissory notes. Temporary equity, stock issued during period value conversion of convertible promissory notes. Temporary equity stock issued during period shares exercise of warrants. Temporary equity stock issued during period value exercise of warrants. Statement Of Stockholders Equity [Abstract] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Redeemable Convertible Preferred Stock Redeemable Convertible Preferred Stock [Member] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Treasury Stock Treasury Stock [Member] Additional Paid-in Capital Additional Paid In Capital [Member] Accumulated Deficit Retained Earnings [Member] Redeemable convertible preferred stock, beginning balance Temporary Equity Carrying Amount Attributable To Parent Redeemable convertible preferred stock, beginning balance, shares Temporary Equity Shares Outstanding Issuance of redeemable preferred stock Temporary Equity Stock Issued During Period Value New Issues Issuance of redeemable preferred stock, shares Temporary Equity Stock Issued During Period Shares New Issues Issuance of redeemable preferred stock upon conversion of promissory notes Temporary Equity Stock Issued During Period Value Conversion Of Convertible Promissory Notes Issuance of redeemable preferred stock upon conversion of promissory notes, shares Temporary Equity Stock Issued During Period Shares Conversion Of Convertible Promissory Notes Exercises of warrants Temporary Equity Stock Issued During Period Value Exercise Of Warrants Exercise of warrants, shares Temporary Equity Stock Issued During Period Shares Exercise Of Warrants Temporary equity, Accretion of redeemable preferred stock to redemption value Temporary Equity Accretion To Redemption Value Redeemable convertible preferred stock, ending balance Redeemable convertible preferred stock, ending balance, shares Beginning balance Beginning balance, shares Issuance of common stock warrants Adjustments To Additional Paid In Capital Warrant Issued Issuance of common stock in public offering, net Stock Issued During Period Value New Issues Issuance of common stock in public offering, net, shares Stock Issued During Period Shares New Issues Exercises of stock options Stock Issued During Period Value Stock Options Exercised Exercises of stock options, shares Stock Issued During Period Shares Stock Options Exercised Stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Accretion of redeemable preferred stock to redemption value Adjustments To Additional Paid In Capital Increase In Carrying Amount Of Redeemable Preferred Stock Net loss Ending balance Ending balance, shares Increase (decrease) in deferred rent. Accrued interest on term loan refinanced to principal. Debt refinanced with new term loan. Initial recognition of operating lease right-of-use assets and operating lease liabilities. Accretion of redeemable convertible preferred stock. Warrant liability converted to redeemable convertible preferred stock upon the exercise of warrants. Stock issuance costs incurred during non cash or partial non cash transaction. Statement Of Cash Flows [Abstract] Operating activities Net Cash Provided By Used In Operating Activities [Abstract] Net loss Profit Loss Adjustments to reconcile net loss to net cash used in operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization Depreciation And Amortization Stock-based compensation Share Based Compensation Non-cash interest expense Paid In Kind Interest Change in fair value warrant liability Change in fair value derivative liability Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Other receivable Increase Decrease In Other Receivables Prepaid expenses and other assets Increase Decrease In Prepaid Deferred Expense And Other Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses Increase Decrease In Accrued Liabilities Deferred rent Increase Decrease In Deferred Rent Net cash used in operating activities Net Cash Provided By Used In Operating Activities Investing activities Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Net cash used in investing activities Net Cash Provided By Used In Investing Activities Financing activities Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from issuance of redeemable convertible preferred stock, net Proceeds From Issuance Of Redeemable Convertible Preferred Stock Proceeds from issuance of common stock in public offering, net Proceeds From Issuance Initial Public Offering Long-term borrowings, net Proceeds From Issuance Of Long Term Debt Payments of initial public offering costs Payments Of Stock Issuance Costs Proceeds from exercise of stock options Proceeds From Stock Options Exercised Proceeds from exercise of warrants Proceeds From Warrant Exercises Repayments of long-term debt Repayments Of Long Term Debt Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net increase in cash and cash equivalents Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash, cash equivalents and restricted cash at the beginning of the period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash at the end of the period Supplemental disclosure for cash flow Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid Net Supplemental disclosure of non-cash investing and financing activities Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Accrued interest on term loan refinanced to principal Accrued Interest On Term Loan Refinanced To Principal Conversion of convertible promissory notes into redeemable convertible preferred stock Debt Conversion Converted Instrument Amount1 Issuance of warrants in conjunction with debt Conversion Of Stock Amount Converted1 Debt refinanced with new term loan Debt Refinanced With New Term Loan Initial recognition of operating lease right-of-use assets and operating lease liabilities Initial Recognition Of Operating Lease Right Of Use Assets And Operating Lease Liabilities Accretion of redeemable convertible preferred stock Accretion Of Redeemable Convertible Preferred Stock Warrant liability converted to redeemable convertible preferred stock upon the exercise of warrants Warrant Liability Converted To Redeemable Convertible Preferred Stock Upon Exercise Of Warrants Deferred initial public offering costs included in accounts payable and accrued expenses Stock Issuance Costs Incurred During Non Cash Or Partial Non Cash Transaction Purchases of property and equipment included in accounts payable Capital Expenditures Incurred But Not Yet Paid Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization and Description of Business Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurement Fair Value Disclosures [Text Block] Property Plant And Equipment [Abstract] Property and Equipment Property Plant And Equipment Disclosure [Text Block] Payables And Accruals [Abstract] Accrued Expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Leases [Abstract] Leases Lessee Operating Leases [Text Block] Stockholders Equity Note [Abstract] Stockholders’ Equity Stockholders Equity Note Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] License agreement. License agreements. License Agreements [Abstract] License Agreement License Agreement [Text Block] Revenue From Contract With Customer [Abstract] Revenue Revenue From Contract With Customer [Text Block] Related Party Transactions [Abstract] Related Party Transactions Related Party Transactions Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Use of Estimates Use Of Estimates Concentrations of Credit Risk Concentration Risk Credit Risk Cash and Cash Equivalents Cash And Cash Equivalents Unrestricted Cash And Cash Equivalents Policy Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Fair Value of Financial Instruments Fair Value Measurement Policy Policy [Text Block] Property and Equipment Property Plant And Equipment Policy [Text Block] Leases Lessee Leases Policy [Text Block] Long-Lived Assets Impairment Or Disposal Of Long Lived Assets Policy [Text Block] Preferred stock warrant liability. Preferred Stock Warrant Liability Preferred Stock Warrant Liability Policy [Text Block] Preclinical and clinical trial accruals. Preclinical and Clinical Trial Accruals Preclinical And Clinical Trial Accruals Policy [Text Block] Research and Development Expense Research And Development Expense Policy Stock-Based Compensation Compensation Related Costs Policy [Text Block] Income Taxes Income Tax Policy [Text Block] Grant revenue, revenue recognition policy. Grant Revenue Grant Revenue Revenue Recognition Policy Policy [Text Block] Revenue Under Collaborative Agreement Revenue From Contract With Customer Policy [Text Block] Net Loss Per Share Earnings Per Share Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Schedule Of Outstanding Potentially Dilutive Securities Excluded In Calculation Of Diluted Net Loss Per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Summary of Assets and Liabilities that Require Fair Value Measurements on a Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Composition of Property and Equipment, Net Property Plant And Equipment [Text Block] Schedule of Composition of Accrued Expenses Schedule Of Accrued Liabilities Table [Text Block] Lender Name Line Of Credit Facility [Axis] Line of Credit Facility, Lender Line Of Credit Facility Lender [Domain] Silicon Valley Bank and West River Innovation Lending Fund Member. SVB and WestRiver Silicon Valley Bank And West River Innovation Lending Fund [Member] Summary of Future Principal Payments Schedule Of Maturities Of Long Term Debt Table [Text Block] Schedule of Maturities of Operating Lease Liabilities Lessee Operating Lease Liability Maturity Table [Text Block] Stock-based Compensation Expense Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Organization and description of business. Organization and description of business. Organization And Description Of Business [Table] Organization And Description Of Business [Table] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Organization and Description of Business [Line Item] Organization And Description Of Business [Line Items] Reverse stock split description Stockholders Equity Reverse Stock Split Reverse stock split conversion ratio Stockholders Equity Note Stock Split Conversion Ratio1 Working capital. Cash and cash equivalents Working capital Working Capital Proceeds from borrowings under term loan Proceeds From Issuance Of Debt Significant accounting policies. Significant accounting policies. Significant Accounting Policies [Table] Significant Accounting Policies [Table] Statistical Measurement Range [Axis] Statistical Measurement Range [Member] Minimum Minimum [Member] Maximum Maximum [Member] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASU 2016-02 Accounting Standards Update201602 [Member] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Restricted cash Restricted Cash Property and equipment, estimated useful lives Property Plant And Equipment Useful Life Common stock options. Common Stock Options Common Stock Options [Member] Warrants to purchase common stock. Warrants to Purchase Common Stock Warrants To Purchase Common Stock [Member] Warrants to purchase redeemable convertible preferred tock. Warrants to Purchase Redeemable Convertible Preferred Stock Warrants To Purchase Redeemable Convertible Preferred Stock [Member] Outstanding potentially dilutive securities excluded in calculation of diluted net loss per share Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Right-of-use assets Operating lease, liability Operating Lease Liability Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Measurement Frequency Fair Value By Measurement Frequency [Axis] Measurement Frequency Fair Value Measurement Frequency [Domain] Fair Value Measurements on Recurring Basis Fair Value Measurements Recurring [Member] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level 1 Fair Value Inputs Level1 [Member] Level 2 Fair Value Inputs Level2 [Member] Level 3 Fair Value Inputs Level3 [Member] 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] Assets Assets Fair Value Disclosure [Abstract] Cash equivalents Cash And Cash Equivalents Fair Value Disclosure Schedule Of Property Plant And Equipment [Table] Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment, Type Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type Property Plant And Equipment Type [Domain] Lab Equipment Equipment [Member] Computer Hardware, Software and Telephone Office Equipment [Member] Furniture and Fixtures Furniture And Fixtures [Member] Leasehold Improvements Leasehold Improvements [Member] Construction in Progress Construction In Progress [Member] Property Plant And Equipment [Line Items] Property Plant And Equipment [Line Items] Property and equipment, gross Property Plant And Equipment Gross Less accumulated depreciation Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Property and equipment, net Accrued clinical and related costs Accrued Professional Fees Current Accrued compensation and related costs Employee Related Liabilities Current Accrued interest Interest Payable Current Operating lease liability, short-term Operating Lease Liability Current Accrued other Other Accrued Liabilities Current Accrued expenses and other current liabilities Debt Instrument [Table] Debt Instrument [Table] Short-term Debt, Type Short Term Debt Type [Axis] Short-term Debt, Type Short Term Debt Type [Domain] 2017 Notes Convertible Notes Payable [Member] Warrants Warrant [Member] Series D redeemable convertible preferred stock. Series D Redeemable Preferred Stock Series D Redeemable Convertible Preferred Stock [Member] Series C one redeemable convertible preferred stock. Series C-1 Series C One Redeemable Convertible Preferred Stock [Member] Debt Instrument Debt Instrument [Axis] Debt Instrument, Name Debt Instrument Name [Domain] Term loan. Term Loan Term Loan [Member] Silicon Valley Bank. Silicon Valley Bank Silicon Valley Bank [Member] Debt Instrument, Redemption, Period Debt Instrument Redemption Period [Axis] Debt Instrument, Redemption, Period Debt Instrument Redemption Period [Domain] Tranche A. Tranche A Tranche A [Member] Tranche B. Tranche B Tranche B [Member] Tranche C. Tranche C Tranche C [Member] Prepayment made prior to period first anniversary. Prepayment Made Prior To First Anniversary Prepayment Made Prior To Period First Anniversary [Member] Prepayment made by Period second anniversary. Prepayment Made By Second Anniversary Prepayment Made By Period Second Anniversary [Member] Prepayment made after period second anniversary. Prepayment Made After Second Anniversary Prepayment Made After Period Second Anniversary [Member] Long-term Debt, Type Longterm Debt Type [Axis] Long-term Debt, Type Longterm Debt Type [Domain] Loan and security agreement. Loan and Security Agreement Loan And Security Agreement [Member] Tranche B and C. Tranche B and C Tranche B And C [Member] Tranche one. Tranche 1 Tranche One [Member] Tranche two. Tranche 2 Tranche Two [Member] Tranche three. Tranche 3 Tranche Three [Member] Tranche One and Tranche Two. Tranche 1 and 2 Tranche One And Tranche Two [Member] Variable Rate Variable Rate [Axis] Variable Rate Variable Rate [Domain] Prime Rate Prime Rate [Member] Silicon Valley Bank, Silicon Valley Bank And West River Innovation Lending Fund. SVB, SVB and WestRiver Silicon Valley Bank Silicon Valley Bank And West River Innovation Lending Fund [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt instrument principal amount Debt Instrument Face Amount Interest rate Debt Instrument Interest Rate Stated Percentage Proceeds from sale of equity Proceeds From Issuance Or Sale Of Equity Debt instrument, Redemption price, percentage Debt Instrument Redemption Price Percentage Debt discount Debt Instrument Unamortized Discount Number of warrants issued Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Exercise price of warrant Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1 Warrants exercisable date Class Of Warrant Or Righst Date From Which Warrants Or Rights Exercisable Sale of stock Temporary Equity Shares Issued Sale of stock price per share Sale Of Stock Price Per Share Net proceeds from sale of shares Debt converted into shares Debt Conversion Converted Instrument Shares Issued1 Interest expense Interest Expense Debt Interest only period extended. Amortization period of payments of principal plus interest amounts. Line of credit facility, maximum borrowing capacity Line Of Credit Facility Maximum Borrowing Capacity Interest only period extended Interest Only Period Extended Amortization period of payments of principal plus interest amounts Amortization Period Of Payments Of Principal Plus Interest Amounts Percentage of aggregate principal amount Debt Instrument Redemption Price Percentage Of Principal Amount Redeemed Proceeds from lines of credit Proceeds From Lines Of Credit Debt instrument prepayment fee percentage. Prepayment fee percentage Debt Instrument Prepayment Fee Percentage Line of credit facility extended period. Line of credit facility, extended period Line Of Credit Facility Extended Period Debt instrument, maturity date Debt Instrument Maturity Date Percentage of final payment on principal amount of refinanced advances. Interest rate, terms Debt Instrument Interest Rate Terms Interest rate, percentage point added to reference rate Debt Instrument Basis Spread On Variable Rate1 Interest rate Debt Instrument Interest Rate During Period Percentage of final payment on principal amount of refinanced advances Percentage Of Final Payment On Principal Amount Of Refinanced Advances Long-term Debt, Gross Debt Instrument Carrying Amount 2019 (remaining three months) Long Term Debt Maturities Repayments Of Principal Remainder Of Fiscal Year 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 2023 Long Term Debt Maturities Repayments Of Principal In Year Five Thereafter Long Term Debt Maturities Repayments Of Principal After Year Five Total Long Term Debt Operating lease commencement date. Operating lease extended expiration date. Lessee operating lease option to extend additional period. Lessee Lease Description [Table] Lessee Lease Description [Table] Geographical Statement Geographical [Axis] Geographical Segment Geographical [Domain] Malvern, Pennsylvania PANAMA San Diego, California CALIFORNIA Lessee Lease Description [Line Items] Lessee Lease Description [Line Items] Lease commencement date Operating Lease Commencement Date Lease extended expiration date Operating Lease Extended Expiration Date Additional period option to extend the lease Lessee Operating Lease Option To Extend Additional Period Lessee, operating lease, option to extend description Lessee Operating Lease Option To Extend Lessee, operating lease, existence of option to extend [true false] Lessee Operating Lease Existence Of Option To Extend Lease expiration date Lease Expiration Date1 Weighted average remaining lease term Operating Lease Weighted Average Remaining Lease Term1 Weighted average discount rate used to determine the right-of-use assets and corresponding operating lease liabilities Operating Lease Weighted Average Discount Rate Percent Operating Lease Liabilities Payments Due [Abstract] 2019 (remaining three months) Lessee Operating Lease Liability Payments Remainder Of Fiscal Year 2020 Lessee Operating Lease Liability Payments Due Year Two 2021 Lessee Operating Lease Liability Payments Due Year Three 2022 Lessee Operating Lease Liability Payments Due Year Four 2023 Lessee Operating Lease Liability Payments Due Year Five Thereafter Lessee Operating Lease Liability Payments Due After Year Five Total future lease payments Lessee Operating Lease Liability Payments Due Less: Present value adjustment Lessee Operating Lease Liability Undiscounted Excess Amount Rent expense Lease And Rental Expense Schedule Of Stock By Class [Table] Schedule Of Stock By Class [Table] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] Initial Public Offering I P O [Member] Underwritten public offering. Underwritten Public Offering Underwritten Public Offering [Member] Class Of Stock [Line Items] Class Of Stock [Line Items] Redeemable convertible preferred stock converted to aggregate of common stock Stock Issued During Period Shares Conversion Of Convertible Securities Common stock, shares, issued and sold Common stock, public offering price 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] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] General and Administrative General And Administrative Expense [Member] Research and Development Research And Development Expense [Member] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Total stock-based compensation Allocated Share Based Compensation Expense Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Award Type Award Type [Axis] Award Type Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Employee Stock Option Employee Stock Option [Member] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Unrecognized compensation expense Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Weighted-average period expected to be recognized Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 License agreement upfront payment. Potential milestones payment Reimbursement of costs incurred to Product storage costs. License Agreements. License agreements. License Agreements [Table] License Agreements [Table] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] MedImmune limited. MedImmune Limited Med Immune Limited [Member] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others By Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others Type [Domain] Achievement of clinical development and regulatory milestones. Achievement Of Clinical Development And Regulatory Milestones Achievement Of Clinical Development And Regulatory Milestones [Member] Commercial milestones. Commercial Milestones Commercial Milestones [Member] Counterparty Name Counterparty Name [Axis] Counterparty Name Repurchase Agreement Counterparty Name [Domain] Duke university. Duke University Duke University [Member] Wacker. Wacker Wacker [Member] License Agreements [Line Items] License Agreements [Line Items] License agreement upfront payment License Agreement Upfront Payment Potential milestones payment Potential Milestones Payment Research and development expense Reimbursement of costs incurred to product storage costs Reimbursement Of Costs Incurred To Product Storage Costs Sublicensable agreement expiration year. Sublicensable agreement expiration, year Sublicensable Agreement Expiration Year Sale of licensed products or services. Aggregate royalties payment Payments For Royalties Sale of licensed products or services Sale Of Licensed Products Or Services Nonroyalty payment received. Nonroyalty agreement term. Fees payment Payments For Fees Nonroyalty payment received Nonroyalty Payment Received Nonroyalty agreement term Nonroyalty Agreement Term Disaggregation Of Revenue [Table] Disaggregation Of Revenue [Table] Small business innovation research grants. SBIR Grants Small Business Innovation Research Grants [Member] Immuno forge company limited. ImmunoForge Immuno Forge Company Limited [Member] Collaborative Arrangement and Arrangement Other than Collaborative Type Of Arrangement [Axis] Collaborative Arrangement and Arrangement Other than Collaborative Arrangements And Nonarrangement Transactions [Member] Collaborative agreements payment receivable within one year of contract effective date. Collaborative Agreements Payment Receivable within One Year of Contract Effective Date Collaborative Agreements Payment Receivable Within One Year Of Contract Effective Date [Member] Disaggregation Of Revenue [Line Items] Disaggregation Of Revenue [Line Items] Revenue Grants from the National Institutes of Health Research And Development Arrangement Contract To Perform For Others Compensation Earned Collaborative arrangement upfront payment receivable Contract With Customer Liability Subsequent Event [Table] Subsequent Event [Table] Subsequent Event [Line Items] Subsequent Event [Line Items] Line of credit, payment terms Line Of Credit Facility Frequency Of Payment And Payment Terms