Organization and Description of the Business	3 Months Ended
Mar. 31, 2026
Organization and Description of the Business [Abstract]
Organization and Description of the Business	1. Organization and Description of the Business *Organization* Abpro Holdings, Inc. and its subsidiaries, (the “Company”) is a biotechnology company headquartered in Burlington, Massachusetts, dedicated to developing next-generation antibody therapeutics to improve the lives of patients with severe and life-threatening diseases. The Company is focused on the development of novel antibodies using its proprietary discovery and engineering platforms, primarily in the areas of immuno-oncology, ophthalmology and infectious disease. On November 13, 2024 (the “Closing Date”), Abpro Corporation (“Legacy Abpro”) completed the merger with Atlantic Coastal Acquisition Corp. II (“ACAB”) (the “Merger”). At the Closing Date, ACAB changed its name to “Abpro Holdings, Inc.” *Reverse Stock Split* On October 16, 2025, the Company filed with the Delaware Secretary of State a Certificate of Amendment to the Certificate of Incorporation of the Company (the “Certificate of Amendment”), which became effective on October 31, 2025 (the “Effective Time”), to effect a one-for-thirty (1:30) reverse stock split (the “Reverse Stock Split”), of the shares of the Company’s common stock, par value $0.0001 per share. The Reverse Stock Split was approved by the Company’s stockholders at the 2025 annual meeting of the stockholders on October 10, 2025. The Company’s common stock began trading on a reverse stock split-adjusted basis upon market opening on November 3, 2025. As a result of the Reverse Stock Split, every 30 shares of issued and outstanding common stock were automatically combined into one (1) issued and outstanding share of common stock, without any change in the par value per share. No fractional shares were issued as a result of the Reverse Stock Split. Instead, stockholders who otherwise would have been entitled to receive fractional shares because they held a number of shares not evenly divisible by the Reverse Stock Split ratio will be entitled to receive an additional fraction of a share of common stock to round up to the next whole share. All of the Company’s historical share and per share information related to issued and outstanding common stock, restricted stock units, and options and warrants exercisable for common stock in these financial statements have been adjusted, on a retroactive basis, to reflect this 1:30 reverse stock split. *Risks and Uncertainties* The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of more advanced or effective therapies, dependence on key executives, protection of and dependence on proprietary technology, compliance with government regulations and ability to secure additional capital to fund operations. Programs currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure, and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. *Going Concern* The Company is required to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Through March 31, 2026, the Company has funded its operations mainly through equity and debt financings, including the proceeds from the issuance of shares under the SEPA (see Note 10), and to a lesser extent, payments received in connection with collaboration and license agreements. As of March 31, 2026 and December 31, 2025, the Company had an accumulated deficit of $120,023 and $118,995, respectively. The Company’s net loss was $1,028 and $3,887 for the three months ended March 31, 2026 and 2025, respectively. Substantially all of the Company’s net losses resulted from costs incurred in connection with the Company’s research and development programs and from general and administrative costs associated with the Company’s operations. The Company expects to incur substantial operating losses and negative cash flows from operations for the foreseeable future as the Company advances its product candidates. On April 2, 2025, the Company received written notice from the Listing Qualifications Department staff (the “Staff”) of the Nasdaq Stock Market (“Nasdaq”) notifying the Company that, based on the closing bid price of the Company’s common stock for the last 30 consecutive business days, the Company no longer complies with the minimum bid price requirement for continued listing on The Nasdaq Stock Market LLC. Nasdaq Listing Rule 5450(a)(1) requires listed securities to maintain a minimum bid price of $1.00 per share (the “Minimum Bid Price Requirement”), and Nasdaq Listing Rule 5810(c)(3)(A) provides that a failure to meet the Minimum Bid Price Requirement exists if the deficiency continues for a period of 30 consecutive business days. On February 18, 2026, the Company received written notification from the Panel stating that, due to the Company not having met the terms of the Panel’s November 10, 2025 decision that the Company demonstrate compliance with the minimum equity standard requirement under Nasdaq Listing Rule 5550(b)(1) by February 16, 2026, the Company’s securities were to be delisted from Nasdaq. The trading of the Company’s common stock was suspended at the open of trading on NASDAQ on February 23, 2026 and the Company’s securities now trade on the OTCQB, Pink Limited tier of the OTC Markets under the ticker symbol “ABPO”. The Company was provided fifteen (15) days from receipt of the aforementioned notice of the Panel’s decision to request that the Nasdaq Listing and Hearing Review Council (the “Council”) review the decision. The delisting does not affect the Company’s operations, but may have, among other material adverse effects, an adverse impact on the liquidity and market price of the Common Stock and on the Company’s ability to raise capital, including under the SEPA (see Note 10) and on favorable terms, if at all, in the future. On March 18, 2026, the Company formally appealed the delisting determination and is currently expecting the response in June 2026. As of March 31, 2026, the Company had cash of $5,398. Due to its current liabilities, the cash available to the Company will not be sufficient to allow the Company to operate for at least 12 months from the date these unaudited condensed consolidated financial statements are issued. The future viability of the Company is largely dependent on its ability to raise additional capital to finance its operations. The Company expects to seek additional funding through equity and debt financings, collaboration agreements and research grants. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. Accordingly, based on the considerations discussed above, management has concluded there is substantial doubt as to the Company’s ability to continue as a going concern within one year after the date these unaudited condensed consolidated financial statements are issued. The Company plans to continue to fundraise, as well as seek alternate revenues from collaboration and license agreements. If adequate funds are not available, the Company may be required to initiate steps to slow cash burn, extending the cash runway until financing can be secured. These unaudited condensed consolidated financial statements do not include any adjustments with respect to the carrying amounts of assets and liabilities and their classification that might result from the outcome of this uncertainty.

Organization and Description of the Business

3 Months Ended

Mar. 31, 2026

Organization and Description of the Business [Abstract]

Organization and Description of the Business

1. Organization and Description of the Business

Organization

Abpro Holdings, Inc. and its subsidiaries, (the “Company”) is a biotechnology company headquartered in Burlington, Massachusetts, dedicated to developing next-generation antibody therapeutics to improve the lives of patients with severe and life-threatening diseases. The Company is focused on the development of novel antibodies using its proprietary discovery and engineering platforms, primarily in the areas of immuno-oncology, ophthalmology and infectious disease.

On November 13, 2024 (the “Closing Date”), Abpro Corporation (“Legacy Abpro”) completed the merger with Atlantic Coastal Acquisition Corp. II (“ACAB”) (the “Merger”). At the Closing Date, ACAB changed its name to “Abpro Holdings, Inc.”

Reverse Stock Split

On October 16, 2025, the Company filed with the Delaware Secretary of State a Certificate of Amendment to the Certificate of Incorporation of the Company (the “Certificate of Amendment”), which became effective on October 31, 2025 (the “Effective Time”), to effect a one-for-thirty (1:30) reverse stock split (the “Reverse Stock Split”), of the shares of the Company’s common stock, par value $0.0001 per share. The Reverse Stock Split was approved by the Company’s stockholders at the 2025 annual meeting of the stockholders on October 10, 2025. The Company’s common stock began trading on a reverse stock split-adjusted basis upon market opening on November 3, 2025.

As a result of the Reverse Stock Split, every 30 shares of issued and outstanding common stock were automatically combined into one (1) issued and outstanding share of common stock, without any change in the par value per share. No fractional shares were issued as a result of the Reverse Stock Split. Instead, stockholders who otherwise would have been entitled to receive fractional shares because they held a number of shares not evenly divisible by the Reverse Stock Split ratio will be entitled to receive an additional fraction of a share of common stock to round up to the next whole share.

All of the Company’s historical share and per share information related to issued and outstanding common stock, restricted stock units, and options and warrants exercisable for common stock in these financial statements have been adjusted, on a retroactive basis, to reflect this 1:30 reverse stock split.

Risks and Uncertainties

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of more advanced or effective therapies, dependence on key executives, protection of and dependence on proprietary technology, compliance with government regulations and ability to secure additional capital to fund operations. Programs currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure, and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Going Concern

The Company is required to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Through March 31, 2026, the Company has funded its operations mainly through equity and debt financings, including the proceeds from the issuance of shares under the SEPA (see Note 10), and to a lesser extent, payments received in connection with collaboration and license agreements.

As of March 31, 2026 and December 31, 2025, the Company had an accumulated deficit of $120,023 and $118,995, respectively. The Company’s net loss was $1,028 and $3,887 for the three months ended March 31, 2026 and 2025, respectively. Substantially all of the Company’s net losses resulted from costs incurred in connection with the Company’s research and development programs and from general and administrative costs associated with the Company’s operations. The Company expects to incur substantial operating losses and negative cash flows from operations for the foreseeable future as the Company advances its product candidates.

On April 2, 2025, the Company received written notice from the Listing Qualifications Department staff (the “Staff”) of the Nasdaq Stock Market (“Nasdaq”) notifying the Company that, based on the closing bid price of the Company’s common stock for the last 30 consecutive business days, the Company no longer complies with the minimum bid price requirement for continued listing on The Nasdaq Stock Market LLC. Nasdaq Listing Rule 5450(a)(1) requires listed securities to maintain a minimum bid price of $1.00 per share (the “Minimum Bid Price Requirement”), and Nasdaq Listing Rule 5810(c)(3)(A) provides that a failure to meet the Minimum Bid Price Requirement exists if the deficiency continues for a period of 30 consecutive business days.

On February 18, 2026, the Company received written notification from the Panel stating that, due to the Company not having met the terms of the Panel’s November 10, 2025 decision that the Company demonstrate compliance with the minimum equity standard requirement under Nasdaq Listing Rule 5550(b)(1) by February 16, 2026, the Company’s securities were to be delisted from Nasdaq. The trading of the Company’s common stock was suspended at the open of trading on NASDAQ on February 23, 2026 and the Company’s securities now trade on the OTCQB, Pink Limited tier of the OTC Markets under the ticker symbol “ABPO”. The Company was provided fifteen (15) days from receipt of the aforementioned notice of the Panel’s decision to request that the Nasdaq Listing and Hearing Review Council (the “Council”) review the decision. The delisting does not affect the Company’s operations, but may have, among other material adverse effects, an adverse impact on the liquidity and market price of the Common Stock and on the Company’s ability to raise capital, including under the SEPA (see Note 10) and on favorable terms, if at all, in the future.

On March 18, 2026, the Company formally appealed the delisting determination and is currently expecting the response in June 2026.

As of March 31, 2026, the Company had cash of $5,398. Due to its current liabilities, the cash available to the Company will not be sufficient to allow the Company to operate for at least 12 months from the date these unaudited condensed consolidated financial statements are issued. The future viability of the Company is largely dependent on its ability to raise additional capital to finance its operations. The Company expects to seek additional funding through equity and debt financings, collaboration agreements and research grants. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects.

Accordingly, based on the considerations discussed above, management has concluded there is substantial doubt as to the Company’s ability to continue as a going concern within one year after the date these unaudited condensed consolidated financial statements are issued. The Company plans to continue to fundraise, as well as seek alternate revenues from collaboration and license agreements. If adequate funds are not available, the Company may be required to initiate steps to slow cash burn, extending the cash runway until financing can be secured. These unaudited condensed consolidated financial statements do not include any adjustments with respect to the carrying amounts of assets and liabilities and their classification that might result from the outcome of this uncertainty.