Non-natural peptide triazole antagonists of HIV-1 envelope gp120.

We investigated the derivation of non-natural peptide triazole dual receptor site antagonists of HIV-1 Env gp120 in order to establish a path for developing peptidomimetic antiviral agents. Previously, we found that the peptide triazole HNG-156 (R-I-N-N-I-X-W-S-E-A-M-M-CONH2, where X is ferrocenyltriazole-Pro (FtP)) had nanomolar binding affinity to gp120, inhibited gp120 binding to CD4 and the co-receptor surrogate mAb 17b and had potent antiviral activity in cell infection assays. Further, truncated variants of HNG-156, typified by UM-24 (Cit-N-N-I-X-W-S-CONH2) and containing the critical central stereospecific LX-LW cluster, retained the functional characteristics of the parent peptide triazole. In the current work, we examined the possibility to replace natural with unnatural residue components in UM-24 to the greatest extent possible. The analogue with the critical “hot spot” residue Trp 6 replaced with L-3-Benzothienylalanine (Bta) (KR-41), as well as a completely non-natural analogue containing D-amino acid substitutions outside the central cluster (KR-42, DCit-DN-DN-DI-X-Bta-DS-CONH2), retained the dual receptor site antagonism / antiviral activity signature. The results define differential functional roles of subdomains within the peptide triazole and provide a structural basis for designing metabolically stable peptidomimetic inhibitors of HIV-1 Env gp120.