Exhibit 99.1 CAMBRIDGE, Mass., November 13, 2025 — Spero Therapeutics, Inc. (Nasdaq: SPRO), a clinical-stage biopharmaceutical company focused on identifying and developing novel treatments for rare diseases and multi-drug resistant (MDR) bacterial infections, today announced financial results for the third quarter ended September 30, 2025, and provided a business update. "We are pleased to have shared the Phase 3 PIVOT-PO study results for tebipenem HBr with the medical community at this year's IDWeek conf ...