Atlantic stal Acquisition II(ACAB) - Prospectus(update)

As filed with the U.S. Securities and Exchange Commission on November 28, 2025 Registration No. 333-291347 (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) Delaware 2834 87-1013956 (I.R.S. Employer Identification No.) UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Abpro Holdings, Inc. (Exact Name of Registrant as Specified in its ...