Optimisation of Next-Generation Polymyxins Leading to SPR206 as a Development Candidate Posted on June 24, 2019 at 3:18 pm.Written by Spero Therapeutics View Presentation Post navigation SPR741 in Combination with Minocycline Increases Antibacterial Efficacy In Vitro and In Vivo against XDR-Acinetobacter baumannii in a Pulmonary Model of InfectionMechanism of Action of SPR206, a Next-Generation Polymyxin Active against Gram-Negative Pathogens