Third Coast Bancshares, Inc.

proxy statement of Great Plains and Third Coast that also constitutes a prospectus of Third Coast, and Third Coast will file other documents regarding the proposed transaction with the SEC. A definitive joint proxy statement/prospectus will also be sent to Great Plains’ and Third Coast’s shareholders seeking the required shareholder approvals of the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT ON FORM S-4 AND THE JOINT PROXY STATEMENT/PROSPECTUS INCLUDED WITHIN THE REGISTRATION STATEMENT ON FORM S-4 WHEN THEY BECOME AVAILABLE, AS WELL AS ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC IN CONNECTION WITH THE TRANSACTION OR INCORPORATED BY REFERENCE INTO THE REGISTRATION STATEMENT ON FORM S-4 AND THE JOINT PROXY STATEMENT/PROSPECTUS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION REGARDING THIRD COAST, GREAT PLAINS, THE TRANSACTION AND RELATED MATTERS. The documents filed by Third Coast with the SEC may be obtained free of charge at the SEC’s website at www.sec.gov. In addition, the documents filed by Third Coast may be obtained free of charge at its website at https://ir.thirdcoast.bank/financials/sec-filings/. Alternatively, these documents, when available, can be obtained free of charge from Third Coast upon written request to Third Coast Bancshares, Inc., Attn: Investor Relations, 1800 West Loop South, Suite 875, Houston, TX 77027, or by calling (713) 960-1300. Participants in this Transaction Third Coast, Great Plains, their respective directors and executive officers and certain of their other members of management and employees may be deemed to be participants in the solicitation of proxies from Great Plains’ shareholders and Third Coast’s shareholders in connection with the proposed transaction. Information about the directors and executive officers of Third Coast may be found in Third Coast’s Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the SEC on March 4, 2026 and in Third Coast’s proxy statement for its 2026