| Significant Accounting Policies (Policies) | 3 Months Ended | 12 Months Ended |
| Mar. 31, 2023 | Dec. 31, 2022 |
| Accounting Policies [Abstract] | | |
| Unaudited Interim Financial Statements [Policy Text Block] | Unaudited Interim Financial Information The unaudited interim consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP"), and in our opinion, include all adjustments of a normal recurring nature necessary for fair financial statement presentation. Interim results are not December 31, 2023. These unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2022 10 As a result of the merger in 2022, 1:0.102448 | |
| Consolidation, Policy [Policy Text Block] | Principles of Consolidation The unaudited condensed consolidated financial statements include the accounts of Apexigen and its wholly owned subsidiary. All significant inter-company transactions and balances have been eliminated in consolidation. | Principles of Consolidation The consolidated financial statements include the accounts of Apexigen and its wholly owned subsidiary. All significant inter-company transactions and balances have been eliminated in consolidation. |
| Emerging Growth Company [Policy Text Block] | Emerging Growth Company We are an “emerging growth company,” as defined in Section 2 2012 may not 102 1 not not 1934 not may | Emerging Growth Company We are an “emerging growth company,” as defined in Section 2 2012 may not 102 1 not not 1934 not may |
| Use of Estimates, Policy [Policy Text Block] | Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts expensed during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accruals for research and development costs, stock-based compensation, uncertain tax positions and fair values of common stock. We adjust such estimates and assumptions when facts and circumstances dictate. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the consolidated financial statements in future periods. As future events and their effects cannot be determined with precision, actual results could materially differ from those estimates and assumptions. | Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts expensed during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accruals for research and development costs, stock-based compensation, uncertain tax positions and fair values of common stock. We adjust such estimates and assumptions when facts and circumstances dictate. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the consolidated financial statements in future periods. As future events and their effects cannot be determined with precision, actual results could materially differ from those estimates and assumptions. |
| Segment Reporting, Policy [Policy Text Block] | Segment Reporting We have one operating segment, which is the business of researching, developing and commercializing antibody therapeutics for oncology. Our chief operating decision maker, our Chief Executive Officer, manages our operations on an aggregated basis for the purposes of allocating resources and evaluating financial performance. | Segment Reporting We have one operating segment, which is the business of researching, developing and commercializing antibody therapeutics for oncology. Our chief operating decision maker, Chief Executive Officer, manages our operations on an aggregated basis for the purposes of allocating resources and evaluating financial performance. |
| Cash and Cash Equivalents, Policy [Policy Text Block] | Cash and Cash Equivalents We consider all highly liquid investments purchased with original maturities of three | Cash and Cash Equivalents We consider all highly liquid investments purchased with original maturities of three |
| Investment, Policy [Policy Text Block] | Short-Term Investments Short-term investments consist of U.S. treasury securities with original maturities of greater than three one | Short-Term Investments Short-term investments consist of debt securities with original maturities of greater than three one |
| Fair Value Measurement, Policy [Policy Text Block] | Fair Value Measurements We apply fair value accounting to all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis. The carrying amount of our financial assets and liabilities, including accounts payable and accrued expenses, approximate their fair values due to their short-term maturities. | Fair Value Measurements We apply fair value accounting to all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis. The carrying amount of our financial assets and liabilities, including accounts payable and accrued expenses, approximate their fair values due to their short-term maturities. |
| Concentration Risk, Credit Risk, Policy [Policy Text Block] | Concentrations of Credit and Other Risks Financial instruments that potentially expose the Company to concentrations of credit risk consist principally of cash and cash equivalents on deposit with financial institutions, the balance of which frequently exceed federally insured limits. On March 10, 2023, may not March 31, 2023, We are subject to a number of risks similar to other early-stage biopharmaceutical companies, including the need to obtain adequate additional funding, possible failure of clinical trials, the need to obtain marketing approval for our product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of our products, and protection of proprietary technology. If we do not | Concentrations of Credit and Other Risks Financial instruments that potentially subject us to a concentration of credit risk consist primarily of cash and cash equivalents and short-term investments. We hold our bank deposits at accredited financial institutions and these deposits may not December 31, 2022 2021, We are subject to a number of risks similar to other early-stage biopharmaceutical companies, including the need to obtain adequate additional funding, possible failure of clinical trials, the need to obtain marketing approval for our product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of our products, and protection of proprietary technology. If we do not |
| Property, Plant and Equipment, Policy [Policy Text Block] | Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. The estimated useful life of laboratory equipment, furniture and fixtures, office equipment, and software ranges from two five | Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. The estimated useful life of laboratory equipment, furniture and fixtures, office equipment, and software ranges from two five |
| Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] | Impairment of Long-Lived Assets Our long-lived assets are comprised principally of our property and equipment and right-of-use lease assets. We periodically evaluate our long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets or group of assets may not three March 31, 2023 2022. | Impairment of Long-Lived Assets Our long-lived assets are comprised principally of our property and equipment and right-of-use lease assets. We periodically evaluate our long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets or group of assets may not December 31, 2022. |
| Deferred Charges, Policy [Policy Text Block] | Deferred Financing Costs Deferred financing costs consist of direct costs and commitment fees directly attributable to the commencement of the equity line agreement with Lincoln Park upon the closing of the merger in July 2022. 24 March 31, 2023, three March 31, 2023. | Deferred Transaction Costs Deferred transaction costs consist of direct legal, accounting, filing and other fees and costs directly attributable to the merger (see Note 3 December 31, 2021. 2021, 2022 3 Deferred Financing Costs Deferred financing costs consist of direct costs and commitment fees directly attributable to the commencement of the equity line of credit from Lincoln Park Capital Fund, LLC upon closing of the Business Combination (see Note 7 24 December 31, 2022, December 31, 2022. |
| Revenue from Contract with Customer [Policy Text Block] | Revenue Recognition Under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers not not March 31, 2023. We may not October 2019, one may March 31, 2023 December 31, 2022, | Revenue Recognition Under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers not not December 31, 2022. We may not October 2019, one may December 31, 2022 2021, |
| Lessee, Leases [Policy Text Block] | Lease We determine if an arrangement is a lease at inception and if so, we determine whether the lease qualifies as an operating or a finance lease. We previously leased our principal facility under a non-cancelable operating lease agreement with a lease term ended in March 2023. six March 2023. March 31, 2023 December 31, 2022, three March 31, 2023 2022, | Lease We determine if an arrangement is a lease at inception and if so, we determine whether the lease qualifies as an operating or a finance lease. We include operating lease in operating lease right-of-use (“ROU”) assets and lease liabilities in our consolidated balance sheets. We did not December 31, 2022 2021. not may 12 not We lease our facility under a non-cancelable operating lease agreement and recognize related rent expense on a straight-line basis over the terms of the leases. As an implicit interest rate is not |
| Research and Development Expense, Policy [Policy Text Block] | Research and Development Expenses Research and development costs are expensed as incurred. Research and development expenses are primarily for the development of sotiga, our lead product candidate, as well as APX601 We estimate external research and development expenses based on the services performed, pursuant to contracts with commercial and academic institutions that conduct and manage research and development services on our behalf. We record the costs of research and development activities based upon the estimated amount of services provided but not third not may Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are capitalized and then expensed as the related goods are delivered or the services are performed. We evaluate such payments for current or long-term classification based on when they will be realized. | Research and Development Expenses Research and development costs are expensed as incurred. Research and development expenses are primarily for the development of sotiga, our lead product candidate, as well as APX601 We estimate external research and development expenses based on the services performed, pursuant to contracts with commercial and academic institutions that conduct and manage research and development services on our behalf. We record the costs of research and development activities based upon the estimated amount of services provided but not third not may Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are capitalized and then expensed as the related goods are delivered or the services are performed. We evaluate such payments for current or long-term classification based on when they will be realized. |
| Transaction Costs [Policy Text Block] | Transaction Costs Transaction costs consist of direct legal, accounting, filing and other fees and costs directly attributable to our exploration of strategic alternatives. We expense transaction costs in the period in which the costs are incurred and the services are received. Transaction costs were $0.2 million for the three March 31, 2023 | |
| Stockholders' Equity, Policy [Policy Text Block] | Common Stock Warrant We record at fair value freestanding puttable or redeemable warrants, or warrants which are not December 31, 2021. July 2022, March 31, 2023. Public Warrants The public warrants, issued in connection with the BCAC's initial public offering prior to the merger and the private offering transactions completed in July 2022 January 2023, 7 | Common Stock Warrant We record at fair value freestanding puttable or redeemable warrants, or warrants which are not December 31, 2021. 3 December 31, 2022. Public Warrants The public warrants, issued in connection with the BCAC's initial public offering prior to the merger and the PIPE transaction completed in July 2022, 8 |
| Derivatives, Policy [Policy Text Block] | Derivative Warrant Liabilities We account for the private placement warrants (see Note 7 815, Derivative and Hedging may March 31, 2023 December 31, 2022, not three March 31, 2023. | Derivative Warrant Liabilities We account for the private placement warrants (see Note 8 815, Derivative and Hedging may December 31, 2022, December 31, 2022. |
| Share-Based Payment Arrangement [Policy Text Block] | Stock-Based Compensation We measure all equity awards granted to employees and non-employees based on the estimated grant date fair value. For awards subject to service-based vesting conditions, we recognize stock-based compensation expense on a straight-line basis over the requisite service period, which is generally the vesting term. For awards subject to performance-based vesting conditions, we recognize stock-based compensation expense using the accelerated attribution method when it is probable that the performance condition will be achieved. We recognize forfeitures as they occur. We use the Black-Scholes option-pricing model to estimate the fair value of equity awards and recognize expense using the straight-line attribution approach. The Black-Scholes option-pricing model requires assumptions to be made related to the expected term of the awards, expected stock priced volatility, risk-free rate for a period that approximates the expected term of the awards and the expected dividend yield. | Stock-Based Compensation We measure all equity awards granted to employees and non-employees based on the estimated grant date fair value. For awards subject to service-based vesting conditions, we recognize stock-based compensation expense on a straight-line basis over the requisite service period, which is generally the vesting term. For awards subject to performance-based vesting conditions, we recognize stock-based compensation expense using the accelerated attribution method when it is probable that the performance condition will be achieved. We recognize forfeitures as they occur. We use the Black-Scholes option-pricing model to estimate the fair value of equity awards and recognize expense using the straight-line attribution approach. The Black-Scholes option-pricing model requires assumptions to be made related to the expected term of the awards, expected stock priced volatility, risk-free rate for a period that approximates the expected term of the awards and the expected dividend yield. |
| Income Tax, Policy [Policy Text Block] | Income Taxes We account for income taxes under the asset and liability method. Under this method, we recognize deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. We measure deferred tax assets and liabilities using enacted tax rates applied to taxable income in the years in which we expect to realize those temporary differences. We recognize the effect on deferred tax assets and liabilities of a change in tax rates as income or loss in the period that includes the enactment date. We establish a valuation allowance, when necessary, to reduce deferred tax assets to the amount we expect to realize. We recognize the financial statement effects of uncertain tax positions when it is more-likely-than- not, no | Income Taxes We account for income taxes under the asset and liability method. Under this method, we recognize deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. We measure deferred tax assets and liabilities using enacted tax rates applied to taxable income in the years in which we expect to realize those temporary differences. We recognize the effect on deferred tax assets and liabilities of a change in tax rates as income or loss in the period that includes the enactment date. We establish a valuation allowance, when necessary, to reduce deferred tax assets to the amount we expect to realize. We recognize the financial statement effects of uncertain tax positions when it is more-likely-than- not, no |
| Comprehensive Income, Policy [Policy Text Block] | Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized gains or losses on our marketable securities. | Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity that are excluded from net loss, primarily unrealized gains or losses on our marketable securities. |
| Earnings Per Share, Policy [Policy Text Block] | Net Loss per Share We calculate basic net loss per share by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for each period presented, since the effects of potentially dilutive securities are antidilutive given our net loss. | Net Loss per Share We calculate basic net loss per share by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is the same as basic net loss per share for each period presented, since the effects of potentially dilutive securities are antidilutive given our net loss. |
| Major Vendor [Policy Text Block] | Major Vendor We had a major vendor that accounted for approximately 15.0% and 42.1% of the research and development expenses for the three March 31, 2023 2022, March 31, 2023 December 31, 2022, March 31, 2023 December 31, 2022, not three March 31, 2023 2022. We had additional two three March 31, 2023, not March 31, 2023. | Major Vendor We had a major vendor that accounted for approximately 39.9% and 23.2% of the research and development expenses for the years ended December 31, 2022 2021, December 31, 2022 2021, December 31, 2022 2021, not December 31, 2022 2021. We had an additional vendor in 2021 December 31, 2021. not December 31, 2021. |
| Basis of Accounting, Policy [Policy Text Block] | | Basis of Presentation We prepare our consolidated financial statements and accompanying notes in accordance with accounting principles generally accepted in the United States of America (“GAAP”). |
| New Accounting Pronouncements, Policy [Policy Text Block] | | Recently Adopted Accounting Pronouncements In August 2020, No. 2020 06, 470 20 815 40 January 1, 2022. not In October 2020, No. 2020 10, January 1, 2022. not Recent Accounting Pronouncements In June 2016, No. 2016 13, Financial Instruments Credit Losses (Topic 326 January 1, 2023. not |
