Exhibit 99.1 Spero Therapeutics Announces First Quarter 2024 Operating Results and Provides a Business Update CAMBRIDGE, Mass., May 15, 2024 — Spero Therapeutics, Inc. (Nasdaq: SPRO), a multi-asset clinical-stage biopharmaceutical company, focused on identifying and developing novel treatments for rare diseases and multi-drug resistant (MDR) bacterial infections, today announced financial and operational results for the quarter ended March 31, 2024. "We continued to make progress towards our stated goals ac ...