Area of office space under sub-lease Area of Real Estate Property Award Type [Axis] Summary of Significant Accounting Policies [Abstract] Accounts payable Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Total Accrued expenses Accrued Liabilities, Current Accrued professional fees Additional Paid-in Capital [Member] Additional paid-in capital Additional Paid in Capital Stock-based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Stock-based compensation expense Share-based Payment Arrangement, Expense Antidilutive impact to EPS (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities, Name [Domain] ASSETS Assets [Abstract] Total assets Assets Total current assets Assets, Current Current assets: Assets, Current [Abstract] Unaudited Interim Financial Statements Summary of Significant Accounting Policies Business Acquisition [Line Items] Liquidity [Abstract] Business Combination, Consideration Transferred [Abstract] Cash and cash equivalents Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Supplemental Cash Flow Information Related to Operating Leases [Abstract] Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash Equivalents and Concentration of Cash Balance Cash and Cash Equivalents, Policy [Policy Text Block] Commitments and Contingencies Commitments and Contingencies [Abstract] Common stock reserved for issuance (in shares) Common Stock [Member] Common stock, par value (in dollars per share) Common stock, shares issued (in shares) Common stock, shares authorized (in shares) Common stock shares outstanding (in shares) Common stock, $0.00033 par value, 75,000,000 shares authorized at March 31, 2021 and December 31, 2020, 22,278,261 shares and 22,261,619 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively Common Stock, Value, Issued Retirement Plan [Abstract] Comprehensive loss Current income tax expense 401(k) employer contribution Stock-based 401K company common match Depreciation expense Depreciation Stock-Based Compensation [Abstract] Stock-Based Compensation Share-based Payment Arrangement [Text Block] Net Income (Loss) per Common Share [Abstract] Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Per share information: Net loss per share, basic (in dollars per share) Net Income (Loss) per Common Share Earnings Per Share, Policy [Policy Text Block] Net loss per share, diluted (in dollars per share) Federal statutory rate Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Unamortized Stock Compensation Expense [Abstract] Stock Options [Abstract] Share-based Payment Arrangement, Additional Disclosure [Abstract] Unamortized stock compensation expense Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Period for recognition Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Equity Component [Domain] Fair Value of Financial Instruments [Abstract] Fair Value, Net Asset (Liability) [Abstract] Transfers from Level 1 to Level 2 Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Transfers from Level 2 to Level 1 Fair Value, Assets, Level 2 to Level 1 Transfers, Amount Fair Value Transfers Between Levels [Abstract] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Transfers into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Fair Value of Financial Instruments [Abstract] Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value of Financial Instruments Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Quoted Prices in Active Markets (Level 1) [Member] Quoted Prices in Inactive Markets (Level 2) [Member] Significant Unobservable Inputs (Level 3) [Member] Grantee Status [Axis] Grantee Status [Domain] General and administrative expenses General and Administrative Expense General and Administrative [Member] Income Statement Location [Axis] Income Taxes [Abstract] Income Statement Location [Domain] Condensed Consolidated Statements of Operations and Comprehensive Loss [Abstract] Income Taxes Accrued interest and penalties Income tax benefit Restructuring reserve Increase (Decrease) in Restructuring Reserve Accounts payable Increase (Decrease) in Accounts Payable Accrued expenses Increase (Decrease) in Accrued Liabilities Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Increase (Decrease) in Stockholders' Equity [Roll Forward] Interest income Investment Income, Interest Issuance of common stock from equity transaction Term of sub-lease agreement Lessor, Operating Lease, Term of Contract Remaining lease term 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three Discount rate used to measure operating lease liability Lessee, Operating Lease, Discount Rate Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount 2021 (remaining nine months) Leases [Abstract] Lessee, Operating Lease, Description [Abstract] Total future minimum lease payments Lessee, Operating Lease, Liability, to be Paid Future Payments for Operating Lease Liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Leases 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Rent expense Leases [Abstract] LIABILITIES Liabilities [Abstract] Total liabilities and stockholders' equity Liabilities and Equity LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Total Liabilities Liabilities Noncurrent liability: Liabilities, Noncurrent [Abstract] Total current liabilities Liabilities, Current Current liabilities: Nature of Operations [Abstract] Long-term Commitment (Excluding Unconditional Purchase Obligation) [Abstract] Long-term Purchase Commitment [Line Items] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-term Purchase Commitment [Table] Category of Item Purchased [Axis] Committed funding to COVID-19 vaccine consortium Long-term Purchase Commitment, Amount Nature of Operations Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Net loss Net loss Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Over-Allotment Option [Member] Cash paid for operating lease liabilities Future Payments for Operating Lease Liabilities [Abstract] Lessee, Operating Lease, Liability, Payment, Due [Abstract] Operating lease liability Lease liability Operating Lease, Liability Operating lease obligation - long term Operating Lease, Liability, Noncurrent Operating lease obligation-short term Operating Lease, Liability, Current Total operating expenses Operating Expenses Right-of-use asset Operating lease right-to-use asset Operating expenses: Operating Expenses [Abstract] Operating lease expense Loss from operations Operating Income (Loss) Nature of Operations [Abstract] Other income Other Income and Expenses [Abstract] Accrued Expenses [Abstract] Retirement Plan Plan Name [Axis] Plan Name [Domain] Prepaid expenses and other Prepaid Expense and Other Assets, Current Proceeds from exercise of warrants Proceeds from issuance of shares Proceeds from issuance of common stock, net of issuance costs Property and equipment, net Property, Plant and Equipment, Net Right-of use assets recorded in exchange for lease obligations Research and development expenses Research and Development Expense Research and Development Research and Development Expense, Policy [Policy Text Block] Clinical Development and Commercialization of COVID-19 Vaccine [Member] Research and Development Arrangement [Member] Research and Development [Member] Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated Deficit [Member] Liquidity Substantial Doubt about Going Concern [Text Block] Exercisable, weighted average remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Term of option Vested and expected to vest, weighted average remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Expected term Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Exercisable, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Options outstanding, weighted average remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Proceeds from issuance of shares, net of underwriting discounts and commissions Sale of Stock, Consideration Received on Transaction Sale of Stock [Domain] Assumptions Used to Value Stock Options and Warrants Granted Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Stock Option Activity Accrued Expenses and Other Liabilities Schedule of Accrued Liabilities [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Business Acquisitions, by Acquisition [Table] Antidilutive Securities Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Stock-Based Compensation Expense Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Patent Costs Selling, General and Administrative Expenses, Policy [Policy Text Block] Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Weighted Average Exercise Price [Roll Forward] Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Expired (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Nonemployee Consultants [Member] Share-based Payment Arrangement, Nonemployee [Member] Stock-Based Compensation [Abstract] Share-based Payment Arrangement, Noncash Expense [Abstract] Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Share price (in dollars per share) Share Price Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Dividend rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Assumptions Used in Determining Fair Value of Stock Options Granted [Abstract] Stock-Based Compensation [Abstract] Fair value of option on grant date (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Shares available for grant (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Number of shares authorized for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Exercisable (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Vested and expected to vest, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Equity Award [Domain] Stock-Based Compensation Share-based Payment Arrangement [Policy Text Block] Options outstanding, beginning balance (in shares) Options outstanding, ending balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Options outstanding, beginning balance (in dollars per share) Options outstanding, ending balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Options outstanding, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Number of Shares [Roll Forward] Vested and expected to vest (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number 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 Balance (in shares) Balance (in shares) Shares, Outstanding Sales price (in dollars per share) Shares Issued, Price Per Share Condensed Consolidated Balance Sheets [Abstract] Statement [Table] Statement [Line Items] Condensed Consolidated Statements of Cash Flows [Abstract] Equity Components [Axis] Condensed Consolidated Statements of Changes in Stockholders' Equity [Abstract] Issuance of common stock from 401K match (in shares) Stock Issued During Period, Shares, Employee Benefit Plan Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of common stock from 401K match Stock Issued During Period, Value, Employee Benefit Plan Issuance of common stock (in shares) Issuance of common stock, net of issuance costs (in shares) Issuance of common stock, net of issuance costs Options granted Reverse stock split ratio Total stockholders' equity Balance Balance Stockholders' Equity Attributable to Parent STOCKHOLDERS' EQUITY STOCKHOLDERS' EQUITY Subsequent Events Subsequent Events [Abstract] Sale of Stock [Axis] Unrecognized tax benefits Use of Estimates Use of Estimates, Policy [Policy Text Block] Warrants to Purchase Common Stock [Member] Warrant [Member] Weighted average common shares outstanding, basic (in shares) Weighted average common shares outstanding, diluted (in shares) Accrued compensation Maximum [Member] Minimum [Member] Statistical Measurement [Axis] Statistical Measurement [Domain] Cover [Abstract] Amendment Flag Current Fiscal Year End Date Document Period End Date Entity [Domain] Entity Address, State or Province Entity Current Reporting Status Entity Filer Category Entity Registrant Name Entity Central Index Key Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Legal Entity [Axis] Document Type Entity Interactive Data Current Entity Shell Company Entity Emerging Growth Company Entity Small Business Term the Plan shall continue to remain effective, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Share-based Compensation Arrangement by Share-based Payment Award, Term of Plan Term of plan Number of equity-based compensation plans. Number of Equity-Based Compensation Plans Number of equity compensation plans Refers to the percentage of stock outstanding as of the immediately preceding December 31st used to determine the annual increase in the Plan limit for authorized shares that may be granted as qualified and nonqualified options. Percentage of Common Stock outstanding Percentage of Common Stock outstanding used to determine annual increase in the plan limit Represents the 2018 Equity Incentive Plan. Equity Incentive Plan 2018 [Member] 2018 Equity Incentive Plan [Member] Represents the 2014 Equity Incentive Plan. Equity Incentive Plan 2014 [Member] 2014 Equity Incentive Plan [Member] The 2019 Inducement Plan provides for the grant of non-qualified stock options. Inducement Plan 2019 [Member] 2019 Inducement Plan [Member] Represents the 2010 Equity Incentive Plan, the 2012 Equity Incentive Plan, and the 2014 Equity Incentive Plan (the Plans). Equity Compensation Plans [Member] The Plans [Member] Non-qualified stock options (NQs) under the equity compensation plans that may be granted to service providers. Nonqualified Stock Options [Member] Nonqualified Options [Member] Incentive stock options (ISOs) under the equity compensation plans that may be granted only to employees. Incentive Stock Options [Member] Incentive Stock Options [Member] Disclosure of accounting policy for significant risks and uncertainties. Significant Risks and Uncertainties, Policy [Policy Text Block] Significant Risks and Uncertainties The amount of securities included in a shelf registration statement filed with the Securities and Exchange Commission (the "2020 Shelf Registration Statement") for the issuance of common stock, preferred stock, warrants, rights, debt securities and units (collectively, the "Shelf Securities") that are available for future sale. Shelf Registration Statement, Available for future sale Registered securities in Shelf Registration Statement available for future sale Aggregate number of shares of company's outstanding shares that can be sold under a common stock purchase agreement without shareholder approval. Common Stock Purchase Agreement, Shares that can be sold, Shares Shares of common stock that can be sold without shareholder approval (in shares) Aggregate amount of shares to be purchased under a common stock purchase agreement. Common Stock Purchase Agreement, Shares to be purchased, Value Common stock to be purchased under common stock purchase agreement Number of shares issued during the period as consideration for equity transaction. Stock Issued During Period, Shares, Equity Transaction Issuance of common stock from equity transaction (in shares) Percentage of the company's outstanding shares that can be sold under a common stock purchase agreement without stockholder approval. Common Stock Purchase Agreement, Shares that can be sold, Percentage Percentage of shares of common stock that can be sold without shareholder approval Cumulative number of shares purchased under a common stock purchase agreement. Common Stock Purchase Agreement, Cumulative shares sold Shares sold under common stock purchase agreement (in shares) Securities that remain available for future sale under a shelf registration statement, or 2020 Shelf Registration Statement, filed with the SEC in July 2020, for the issuance of common stock, preferred stock, warrants, rights, debt securities and units, collectively the "Shelf Securities." Shelf securities available for sale Shelf securities available for sale Number of shares to be purchased under a common stock purchase agreement. Common Stock Purchase Agreement, Shares to be purchased, Shares Shares of common stock to be purchased (in shares) Number of shares of stock issued from exercise of warrants during the current period. Stock Issued During Period, Shares, Warrants Exercised Issuance of common stock for warrant exercise (in shares) Value of stock issued as a result of the exercise of warrants. Stock Issued During Period, Value, Warrants Exercised Issuance of common stock for warrant exercise Liquidity [Abstract] Tabular disclosure of supplemental cash flow information related to lessee's operating leases and right-of-use assets and lease liabilities. Lessee, Operating Lease, Supplemental Cash Flow Information Related to Operating Lease [Table Text Block] Supplemental Cash Flow Information Related to Operating Leases Incentive stock options (ISOs) that may be granted only to employees and non-qualified stock options (NQs) that may be granted to service providers under the equity compensation plans. Qualified and Nonqualified Stock Options [Member] Stock Options [Member] Stock Options to Purchase Common Stock [Member] The total current and noncurrent amount recognized for uncertain tax positions as of the balance sheet date. Liability for Uncertain Tax Positions Uncertain tax positions Amount of increase (decrease) in obligation for operating lease. Increase (Decrease) in Operating Lease Liability Operating lease liabilities Carrying value as of the balance sheet date of obligations incurred through that date and payable for research and development costs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Research and Development Costs, Current Accrued research and development costs Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year and thereafter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Lessee, Operating Lease, Liability, to be Paid, Year Four and Thereafter 2025 and after The percentage of remaining payments that required to be paid in order to terminate an operating lease agreement. Operating Lease, Percentage of remaining payments required to be paid to terminate lease Percentage of remaining payments required to be paid to terminate lease Number of installments in which the remaining lease payments need to be made in order to terminate the operating lease agreement. Operating Lease, Number of Installments for Remaining Lease Payment Number of installments for remaining lease payment Amount of remaining lease payments under the operating lease agreement. Operating Lease, Remaining lease payments Remaining lease payments The number of planned clinical trials that have been delayed, specifically as a result of the adverse impact the COVID-19 Pandemic has had on clinical trial operations for cancer indications in the United States. Number of planned clinical trials delayed Number of planned clinical trials delayed The number of planned clinical trials. Number of planned clinical trials The civilian cabinet organization which coordinates science, technology, and innovation activities in Brazil. Ministry of Science, Technology and Innovation of Brazil [Member] Ministry of Science, Technology and Innovation of Brazil [Member]