Discovery of potent measles virus fusion inhibitor peptides via structure-guided derivatization†

Fusion inhibitor peptide (FIP), a short peptide known as a measles virus (MeV) infection inhibitor, inhibits membrane fusion between the viral envelope of MeV and the host cell membrane. Therefore, FIP is potentially useful as a drug candidate for treating MeV infection, but improvement of inhibitory activity is desirable. In this study, we conducted a structure–activity relationship study of FIP and, based on the result and the previously reported crystal structure of the complex, we designed FIP derivatives. From a series of derivatives, we discovered an FIP derivative with a strong inhibitory activity (IC₅₀ = 210 nM) derived from the enhanced binding affinity (K_D = 6.6 nM) to the MeV fusion protein.