Change in Certifying Accountants (Form 8-K)

Item 4.01. Changes in Registrant's Certifying Accountant.

Engagement of New Independent Registered Public Accounting Firm.

As previously reported in the Shuttle Pharmaceuticals Holdings, Inc. (the "Company") Current Report on Form 8-K filed with the Securities and Exchange Commission (the "SEC") on October 21, 2026, the Audit Committee (the "Audit Committee") of the Board of Directors (the "Board") of the Company", and the full Board, approved the dismissal of Forvis Mazars, LLP as the Company's independent registered public accounting firm, effective following the filing of the Company's Quarterly Report on Form 10-Q for the fiscal quarter ended September 30, 2026.

On November 2, 2026, the Company engaged Bush & Associates CPA LLC ("Bush & Associates") as the Company's new independent registered public accounting firm, upon the full execution of an engagement letter dated October 19, 2026. The engagement of Bush & Associates was approved by the Audit Committee in October 2026. Bush & Associates will audit the Company's financial statements as of and for the fiscal year ending December 31, 2026, and will review the Company's unaudited interim financial statements for the fiscal quarters ending March 31, 2027, June 30, 2027, and September 30, 2027.

During the fiscal years ended December 31, 2025 and December 31, 2024, and the subsequent interim period through November 2, 2026, neither the Company nor anyone acting on its behalf consulted with Bush & Associates regarding (i) the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on the Company's financial statements, and neither a written report nor oral advice was provided to the Company that Bush & Associates concluded was an important factor considered by the Company in reaching a decision as to any accounting, auditing, or financial reporting issue, or (ii) any matter that was either the subject of a disagreement (as defined in Item 304(a)(1)(iv) of Regulation S-K and the related instructions) or a reportable event (as defined in Item 304(a)(1)(v) of Regulation S-K).