 CAMBRIDGE, Mass., Feb. 05, 2021 GLOBE NEWSWIRE -- Spero Therapeutics, Inc. Nasdaq: SPRO, a multi-asset clinical-stage biopharmaceutical company focused on identifying, developing and commercializing treatments in high unmet need areas involving multi-drug resistant bacterial infections and rare diseases, today announced that the United States Food and Drug Administration FDA informed Spero that a clinical hold has been placed on its Phase 2a clinical trial of SPR720, Speros investigational oral antimicrobial agent being evaluated in patients with nontuberculous mycobacterial pulmonary disease NTM-PD. 