Optimization of Cyclophilin B‑Targeted Tri-vector Inhibitors for Novel MASH Treatments

Cyclophilins have been implicated in the pathophysiology of metabolic dysfunction-associated steatohepatitis (MASH). Pharmacological inhibition of the cyclophilin B isoform has the potential to attenuate liver fibrosis in MASH, but current cyclophilin inhibitors in clinical trials lack isoform selectivity. We previously reported the novel tri-vector small-molecule inhibitor 1 that exhibited improved subtype selectivity by simultaneously engaging three pockets on the surface of cyclophilins. Here, we present structure–activity relationships that address genotoxicity concerns, enhance subtype selectivity, improve pharmaceutical properties, and demonstrate strong efficacy in a MASH cellular model. Lead compound 11 is a potent cyclophilin B inhibitor with an encouraging pharmacokinetic profile suitable for further development.