These values are comparable to, or slightly better than, the overall efficacy that we observed with the peptide triazoles against subtype C viruses. == Inhibition of replication-competent HIV-1. of HIV-1 was also observed with HNG-156. We found that HNG-156 had a greater than predicted effect when combined with several other entry inhibitors or the reverse transcriptase inhibitor tenofovir. Overall, we find that HNG-156 is noncytotoxic, has a broad inhibition profile, and provides a positive combination with several inhibitors of the HIV-1 life cycle. These results support the pursuit of efficacy and toxicity analyses in more advanced cell and animal models to develop peptide triazole Clopidogrel family inhibitors of HIV-1 into antagonists of HIV-1 infection. == INTRODUCTION == The global spread of human immunodeficiency virus type 1 (HIV-1), with an annual incidence of 2.6 million cases in 2009 2009, continues to be a serious public health problem and a daunting challenge for the discovery of interventions that can be effective across all human cultures. Among the populations of greatest occurrence and spread, in Africa and Asia, therapeutic drugs such as reverse transcriptase (RT), protease, and integrase inhibitors represent costly options. Currently, only 50% of those medically eligible have access to effective treatment. A vaccine, which PLA2G4C would provide an ideal strategy, is not yet available. In the light of these limitations, novel preventatives, such as a topical microbicide or an oral preexposure prophylactic (PrEP), are an urgent goal (13,37,51). HIV-1 entry into host cells has Clopidogrel been proposed as an appealing drug target (50). HIV-1 infects macrophages and T cells by fusion of the viral membrane with the target cell membrane (4,19). The fusion process is mediated by the viral envelope glycoprotein, which is derived from the proteolytic cleavage of a gp160 precursor into the gp120 surface protein and the gp41 transmembrane protein (26,33,34,38). The initial step of cell entry is initiated by the interaction of gp120 with the T-cell antigen receptor CD4 (2,15,44). CD4 induces conformational changes in gp120 that are postulated to promote subsequent steps in cell-virus fusion, such as binding to the chemokine coreceptor CCR5 or CXCR4 and the exposure of heptad repeat 1 on gp41 (48,49). The latter transitions into a gp41 six-helix bundle, ultimately resulting in membrane fusion (6,28,36,55). Interviral contents, including capsid protein p24 and reverse transcriptase, are released into infected cells after fusion. Recently, a new group of entry inhibitors that allosterically block gp120 interactions has been developed. One such inhibitor is the small peptide 12p1, which antagonizes gp120 interactions with both CD4 and the coreceptor (5,17,23,24). A peptide triazole derivative of 12p1, HNG-156, contains a ferrocenyl triazole-substituted conjugate and binds to monomeric gp120 with an equilibrium dissociation constant (KD) of 7 nM, in contrast to the 2 2,600 nMKDvalue of 12p1 (22,52). Both enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) analyses revealed that HNG-156 retained the ability to inhibit the interaction of gp120 with both CD4 and the coreceptor and inhibited HIV-1BaLentry with a nanomolar 50% effective concentration (EC50) (22). Additionally, a sequence-minimized form of the peptide was found to retain much of its antiviral potency at a substantially reduced size (52). In this study, we explored the antiviral breadth and combination potential of the peptide triazoles. We tested HNG-156 and a smaller derivative against a panel of subtype B and C isolates of HIV-1 and found that HNG-156 was able to inhibit the majority of the viruses tested, as well as replication-competent clinical isolates. The smaller peptide was also able to inhibit most of the isolates tested, albeit at higher concentrations. Because the most effective treatment for HIV-1 is the use Clopidogrel of a cocktail of multiple drugs targeting the virus, we combined HNG-156 with other entry inhibitors as well as with the RT inhibitor tenofovir. We demonstrated that HNG-156 can be paired with any candidate and that it can be favorably combined with many entry inhibitors at the higher concentrations likely to be used as treatment. Overall,.