Oligopeptide cyclophilin inhibitors: A reassessment

► We compare oligopeptides covering negative charges on the backbone for CypA inhibition. ► A high cis/trans ratio is found for the prolyl bond of WGP at pH 7.5. ► In line with other charged oligopeptides WGP is not an inhibitor for CypA. ► For CsA charge clustering in the side chain of the 1-position enhances the inhibitory potency of cyclosporin A.