Third Coast Bancshares Received 4 Demand Letters Alleging Material Information Omissions Ahead Of Proposed Keystone Bank Merger Votes

As previously announced, on October 22, 2025, Third Coast Bancshares, Inc. (the "Company" or "Third Coast"), a Texas corporation and the parent company of Third Coast Bank ("Third Coast Bank"), a Texas banking association, entered into an Agreement and Plan of Reorganization (the "Agreement"), by and among the Company, Arch Merger Sub, Inc. ("Merger Sub"), a Texas corporation and a wholly owned subsidiary of the Company, and Keystone Bancshares, Inc. ("Keystone"), a Texas corporation and the parent company of Keystone Bank, SSB ("Keystone Bank"), a Texas state savings bank (collectively, the "Proposed Transaction").

In connection with the Proposed Transaction, Third Coast filed with the Securities and Exchange Commission (the "SEC") on November 26, 2025, a registration statement on Form S-4, File No. 333-291826, as amended on December 18, 2025, and which was declared effective by the SEC on December 19, 2025, containing a preliminary prospectus of Third Coast that also constituted a preliminary joint proxy statement of Third Coast and Keystone, and Third Coast filed a final prospectus with the SEC, dated December 19, 2025 (the "joint proxy statement/prospectus"), with respect to the special meeting of Third Coast shareholders scheduled to be held on January 23, 2026 and the special meeting of Keystone shareholders scheduled to be held on January 29, 2026. Third Coast and Keystone first mailed the joint proxy statement/prospectus to its respective shareholders on or about December 23, 2025.

In connection with the Proposed Transaction, from December 4, 2025, to January 16, 2026, Third Coast received four demand letters from purported Third Coast shareholders ("Demand Letters"), alleging that the joint proxy statement/prospectus omits material information in violation of federal securities laws and state law disclosure requirements and demanding that Third Coast provide additional disclosures in an amendment or supplement to the joint proxy statement/prospectus.