Entity Central Index Key Document And Entity Information [Abstract] Document And Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Trading Symbol Trading Symbol Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus In-process research and development Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Prepaid expenses Prepaid Expense Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Other assets: Other Assets [Abstract] Goodwill Goodwill In-process research and development Research Development In Process Other non-current assets Other Assets Noncurrent Total assets Assets Liabilities and Stockholders’ Equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued expenses Accrued Liabilities Current Total liabilities Liabilities Commitments Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock, no par value; authorized 10,000,000 shares; none issued and outstanding Preferred Stock Value Common stock, $0.01 par value; authorized 150,000,000 shares; 7,497,433 shares issued and outstanding at March 31, 2018 and December 31, 2017 Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders’ equity Stockholders Equity Total liabilities, and stockholders’ equity Liabilities And Stockholders Equity Preferred stock, no par value Preferred Stock No Par Value Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Income Statement [Abstract] 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 currency transaction loss Foreign Currency Transaction Gain Loss Before Tax Total other income (expense), net Other Nonoperating Income Expense Net loss Net Income Loss Net loss per 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 Write-off of deferred financing costs Deferred financing costs Accretion of issuance costs on Series A Convertible Redeemable Preferred stock Accretion of issuance costs on Series B Convertible Redeemable Preferred stock Statement Of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities Continuing Operations [Abstract] Net 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] Non-cash interest expense Amortization Of Financing Costs And Discounts Share-based compensation Share Based Compensation Depreciation Depreciation Write-off of deferred financing costs Write Off Of Deferred Financing Costs Changes in operating assets and liabilities Increase Decrease In Operating Capital [Abstract] Prepaid expenses Increase Decrease In Prepaid Expense Accounts payable Increase Decrease In Accounts Payable Accrued expenses Increase Decrease In Accrued Liabilities Other non-current assets Increase Decrease In Other Current Assets Net cash used in operating activities Net Cash Provided By Used In Operating Activities Continuing Operations Cash flows from investing activities: Net Cash Provided By Used In Investing Activities Continuing Operations [Abstract] Purchase 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 Continuing Operations Cash flows from financing activities: Net Cash Provided By Used In Financing Activities Continuing Operations [Abstract] Costs associated with the issuance of common stock Payments Of Stock Issuance Costs Deferred financing costs Deferred Financing Cost Proceeds from convertible notes payable Proceeds From Notes Payable Net cash (used in) provided by financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Net (decrease) increase in cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental non-cash financing transactions: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Accretion of issuance costs on Series A Convertible Redeemable Preferred stock Accretion Of Issuance Costs On Series A Convertible Redeemable Preferred Stock Accretion of issuance costs on Series B Convertible Redeemable Preferred stock Accretion Of Issuance Costs On Series B Convertible Redeemable Preferred Stock Organization Consolidation And Presentation Of Financial Statements [Abstract] Nature of Operations and Basis of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Polices Significant Accounting Policies [Text Block] Property And Equipment Property And Equipment [Abstract] Property and Equipment Property Plant And Equipment Disclosure [Text Block] Accounts Payable And Accrued Liabilities Current [Abstract] Accrued Expenses Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Current [Text Block] Commitments Commitments And Contingencies [Abstract] Commitments Commitments And Contingencies Disclosure [Text Block] Equity [Abstract] Stockholders' Equity Stockholders Equity Note Disclosure [Text Block] Earnings Per Share [Abstract] Net Loss Per Share Earnings Per Share [Text Block] Share-Based Compensation Share Based Compensation Option And Incentive Plans Policy Use of Estimates Use Of Estimates Basic and Diluted Net Loss per Common Share Earnings Per Share Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Schedule of Estimate Fair Value of Stock Options Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Table [Text Block] Property And Equipment Tables Property And Equipment Tables [Abstract] Property and Equipment Property Plant And Equipment [Text Block] Schedule of Accrued Expenses Schedule Of Accounts Payable And Accrued Liabilities Table [Text Block] Commitments And Contingencies Details Commitments And Contingencies Details [Abstract] Newton Lease Base Rent Operating Leases Of Lessee Disclosure [Text Block] Summary of Option Activity under 2010 Plan and 2013 Plan Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Summary of Warrant Activity Schedule Of Stockholders Equity Note Warrants Or Rights [Text Block] Common Stock Underlying Potentially Dilutive Securities Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Approximate number of patients impacted as there are no FDA-approved drugs for vEDS and MSUD. Organization, consolidation and presentation of financial statement. Organization, consolidation and presentation of financial statement. Organization Consolidation And Presentation Of Financial Statement [Table] Organization Consolidation And Presentation Of Financial Statement [Table] Business Acquisition Business Acquisition [Axis] Business Acquisition, Acquiree Business Acquisition Acquiree [Domain] Merger of Private Acer with Opexa Merger Sub incorporation. Merger of Private Acer with Opexa Merger Sub Incorporation Merger Of Private Acer With Opexa Merger Sub Incorporation [Member] Organization Consolidation and Presentation of Financial Statement [Line Items] Organization Consolidation And Presentation Of Financial Statement [Line Items] Number of patients impacted Number Of Patients Impacted Business combination date of completion Business Acquisition Effective Date Of Acquisition1 Business combination date of agreement Business Acquisition Date Of Acquisition Agreement1 Reverse stock split ratio Stockholders Equity Note Stock Split Conversion Ratio1 Options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Risk-free interest rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Expected life (years) Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 Volatility Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Dividend rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate Less: accumulated depreciation Property Plant And Equipment [Abstract] 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] Computer Hardware and Software Computer Equipment [Member] Leasehold Improvements Leasehold Improvements [Member] Furniture and Fixtures Furniture And Fixtures [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 Amortization And Impairment Charges Property and equipment, net Accrued legal fees current. Accrued pre-commercial costs current. Accrued license fees current. Accrued contract manufacturing costs current. Accrued contract research current. Accrued miscellaneous expenses current. Accrued legal Accrued Legal Fees Current Accrued pre-commercial costs Accrued Pre Commercial Costs Current Accrued consulting Accrued Professional Fees Current Accrued audit and tax Accrued Income Taxes Current Accrued license fees Accrued License Fees Current Accrued contract manufacturing Accrued Contract Manufacturing Costs Current Accrued contract research Accrued Contract Research Current Accrued miscellaneous expenses Accrued Miscellaneous Expenses Current Accrued expenses Loss contingency closing date. Financing aggregate consideration. Loss Contingencies [Table] Loss Contingencies [Table] Litigation Status Litigation Status [Axis] Litigation Status Litigation Status [Domain] Pending Litigation Pending Litigation [Member] Litigation Case Litigation Case [Axis] Litigation Case Litigation Case Type [Domain] Piper Jaffray & Co. v. Acer Therapeutics Inc.. Piper Jaffray & Co. Piper Jaffray Co V Acer Therapeutics Inc [Member] Legal Entity Legal Entity [Axis] Entity Entity [Domain] Private Acer. Private Acer Private Acer [Member] Lease Arrangement, Type Lease Arrangement Type [Axis] Lease Arrangement, Type Lease Arrangement Type [Domain] Newton lease. Newton Lease Newton Lease [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Loss contingency payable fees Loss Contingency Damages Sought Value Loss contingency closing date Loss Contingency Closing Date Financing aggregate consideration Financing Aggregate Consideration Reimbursement expenses Cost Of Reimbursable Expense Lease agreement date. Lease commencement date. Sublease expiration date. Sublease commencement date. Lease agreement date Lease Agreement Date Square feet of office space leased Area Of Land Lease commencement date Lease Commencement Date Lease expiration date Lease Expiration Date1 Sublease Commencement Date Sublease Commencement Date Sublease expiration date Sublease Expiration Date Operating leases monthly base rent year one. Operating leases monthly base rent year two. Operating leases monthly base rent year three. Month of Term Under Newton Lease, 1 to 12 Operating Leases Monthly Base Rent Year One Month of Term Under Newton Lease, 13 to 24 Operating Leases Monthly Base Rent Year Two Month of Term Under Newton Lease, 25 to 36 Operating Leases Monthly Base Rent Year Three Total commitment for rent Operating Lease Liability Security deposit Security Deposit Stockholders equity. Stockholders equity. Stockholders Equity [Table] Stockholders Equity [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] 2010 stock incentive plan. 2010 Stock Incentive Plan Two Thousand Ten Stock Incentive Plan [Member] Title of Individual Title Of Individual [Axis] Relationship to Entity Title Of Individual With Relationship To Entity [Domain] Executive officers and employees. Executive Officers and Employees Executive Officers And Employees [Member] Vesting Vesting [Axis] Vesting Vesting [Domain] One-year Anniversary of the Grant Date Share Based Compensation Award Tranche One [Member] Quarterly over Remaining Three Years Share Based Compensation Award Tranche Two [Member] Two thousand thirteen stock incentive plan. 2013 Stock Incentive Plan Two Thousand Thirteen Stock Incentive Plan [Member] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Research and Development Research And Development Expense [Member] General and Administrative General And Administrative Expense [Member] Class of Warrant or Right Class Of Warrant Or Right [Axis] Class of Warrant or Right Class Of Warrant Or Right [Domain] Series J warrants. Series J Warrants Series J Warrants [Member] Series K warrants. Series K Warrants Series K Warrants [Member] Stockholders Equity [Line Items] Stockholders Equity [Line Items] Number of common stock authorized for issuance Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Options contractual term Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period Share-based compensation arrangement by share-based payment award, stock options vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 Share-based compensation arrangement by share-based payment award, Vesting percentage Sharebased Compensation Arrangement By Sharebased Payment Award Award Vesting Rights Percentage Available for the grant of future awards Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Options Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward Number of Shares, Options outstanding at beginning of period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Number of Shares, Options granted Number of Shares, Options outstanding at end of period Number of Shares, Options exercisable at end of period Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Weighted Average Exercise Price, Options Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Rollforward Weighted Average Exercise Price, Options outstanding at beginning of period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Weighted Average Exercise Price, Options granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Weighted Average Exercise Price, Options outstanding at end of period Weighted Average Exercise Price, Options exercisable at end of period Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Weighted Average Remaining Contract Term, Options Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract] Weighted Average Remaining Contractual Term, Options outstanding at beginning of period Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Weighted Average Remaining Contractual Term, Options exercisable at end of period Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 Aggregate Intrinsic Value, Options outstanding at beginning of period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Aggregate Intrinsic Value, Options outstanding at end of period Aggregate Intrinsic Value, Options excersiable at end of period Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 Unrecognized compensation expense Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options Share based compensation arrangement by share based payment award, Average remaining vesting period Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Weighted average grant date fair value of options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Stock based compensation expense Allocated Share Based Compensation Expense Stockholders equity warrants or rights forfeited in period number of underlying shares Stockholders equity warrants or rights outstanding number of underlying shares. Stockholders equity warrants or rights exercisable number of underlying shares. Class Of Warrant Or Right [Table] Class Of Warrant Or Right [Table] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Warrants Warrant [Member] Class Of Warrant Or Right [Line Items] Class Of Warrant Or Right [Line Items] Number of Shares, Outstanding at beginning of period Stockholders Equity Warrants Or Rights Outstanding Number Of Underlying Shares Number of Shares, Exercisable at beginning of period Stockholders Equity Warrants Or Rights Exercisable Number Of Underlying Shares Number of Shares, Options Caneled/forfeited Stockholders Equity Warrants Or Rights Forfeited In Period Number Of Underlying Shares Number of Shares, Outstanding at end of period Number of Shares, Exercisable at end of period Stockholders equity warrants or rights forfeited and cancelled in period weighted average exercise price of underlying shares. Stockholders equity warrants or rights weighted average exercise price. Stockholders equity warrants or rights outstanding weighted average exercise price of underlying shares. Stockholders equity warrants or rights outstanding weighted average exercise price of exercisable underlying shares. Weighted Average Exercise Price, Warrants Stockholders Equity Warrants Or Rights Weighted Average Exercise Price [Abstract] Weighted Average Exercise Price, Outstanding at beginning of period Stockholders Equity Warrants Or Rights Outstanding Weighted Average Exercise Price Of Underlying Shares Weighted Average Exercise Price, Exercisable at beginning of period Stockholders Equity Warrants Or Rights Outstanding Weighted Average Exercise Price Of Exercisable Underlying Shares Weighted Average Exercise Price, Options Canceled/forfeited Stockholders Equity Warrants Or Rights Forfeited And Cancelled In Period Weighted Average Exercise Price Of Underlying Shares Weighted Average Exercise Price, Outstanding at end of period Weighted Average Exercise Price, Exercisable at end of period Stockholders equity warrants or rights outstanding weighted average remaining contractual term in years. Stockholders equity warrants or rights outstanding weighted average remaining contractual term in years end. Stockholders equity warrants or rights weighted average remaining contractual term. Stockholders equity warrants or rights exercisable outstanding weighted average remaining contractual term in years. Weighted Average Remaining Contract Term, Warrants Stockholders Equity Warrants Or Rights Weighted Average Remaining Contractual Term [Abstract] Weighted Average Remaining Contract Term, Outstanding at beginning of period Stockholders Equity Warrants Or Rights Outstanding Weighted Average Remaining Contractual Term In Years Weighted Average Remaining Contract Term, Exercisable at beginning of period Stockholders Equity Warrants Or Rights Exercisable Outstanding Weighted Average Remaining Contractual Term In Years Weighted Average Remaining Contract Term, Outstanding at end of period Stockholders Equity Warrants Or Rights Outstanding Weighted Average Remaining Contractual Term In Years End Stockholders equity warrants or rights weighted average intrinsic value. Stockholders equity warrants or rights outstanding intrinsic value. Stockholders equity warrants or rights exercisable intrinsic value. Intrinsic Value, Warrants Stockholders Equity Warrants Or Rights Weighted Average Intrinsic Value [Abstract] Intrinsic Value, Outstanding at beginning of period Stockholders Equity Warrants Or Rights Outstanding Intrinsic Value Intrinsic Value, Exercisable at beginning of period Stockholders Equity Warrants Or Rights Exercisable Intrinsic Value Intrinsic Value, Outstanding at end of period Intrinsic Value, Exercisable at end of period Stockholders equity warrants or rights expired in period number of underlying shares. Warants expired for aggregate share of common stock to purrchase Stockholders Equity Warrants Or Rights Expired In Period Number Of Underlying Shares Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Options to purchase common stock. Options to purchase common stock Options To Purchase Common Stock [Member] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Convertible redeemable preferred stock Redeemable Convertible Preferred Stock [Member] Short-term Debt, Type Short Term Debt Type [Axis] Short-term Debt, Type Short Term Debt Type [Domain] Convertible Promissory Notes Convertible Notes Payable [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Common stock dilutive securities Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount