Management Change/Compensation (Form 8-K)

(b) On January 30, 2026, Ankit Mahadevia, MD notified the Board of Directors (the "Board") of Spero Therapeutics, Inc. (the "Company") of his intention to resign from the Board, including from his service on the Development Committee of the Board and from all officer and director positions he holds with any and all subsidiaries of the Company, effective as of January 30, 2026. Dr. Mahadevia's resignation is as a result of his other professional commitments and not the result of any dispute or disagreement with the Company or the Board on any matter relating to the Company's operations, policies or practices. The Company thanks Dr. Mahadevia for his years of service since the inception of the Company. The Company and Dr. Mahadevia intend to enter into a consulting agreement, pursuant to which Dr. Mahadevia will be available to provide support to the Company's management.

On January 20, 2026, the Company received a letter (the "Letter") from the U.S. Securities and Exchange Commission (the "SEC") advising the Company that the SEC has concluded its investigation into the Company and that, based on the information as of the date of the Letter, the SEC does not intend to recommend an enforcement action against the Company at this time. The Letter was provided under the guidelines set out in the final paragraph of Securities Act Release No. 5310. The investigation was previously disclosed by the Company in its periodic reports under the Securities Exchange Act of 1934, as amended.