Selection of T1249-Resistant Human Immunodeficiency Virus Type 1 Variants

Abstract

Human immunodeficiency virus type 1 (HIV-1) entry is an attractive target for therapeutic intervention. Two drugs that inhibit this process have been approved: the fusion inhibitor T20 (enfuvirtide [Fuzeon]) and, more recently, the CCR5 blocker maraviroc (Selzentry). T1249 is a second-generation fusion inhibitor with improved antiviral potency compared to the first-generation peptide T20. We selected T1249-resistant HIV-1 variants in vitro by serial virus passage in the presence of increasing T1249 doses after passage with wild-type and T20-resistant variants. Sequence analysis revealed the acquisition of substitutions within the HR1 region of the gp41 ectodomain. The virus acquired mutations of residue V38 to either E or R in 10 of 19 cultures. Both E and R at position 38 were confirmed to cause resistance to T1249, as well as cross-resistance to T20 and C34, but not to the third-generation fusion inhibitor T2635. We also observed substitutions at residues 79 and 90 (Q79E and K90E), which provide modest resistance to T1249 and, interestingly, T2635. Thus, the gp41 amino acid position implicated in T20 resistance (V38 replaced by A, G, or W) is also responsible for T1249 resistance (V38 replaced by E, R, or K). These results indicate that T20 and T1249 exhibit very similar inhibition modes that call for similar but not identical resistance mutations. All T1249-resistant viruses with changes at position 38 are cross resistant to T20, but not vice versa. Furthermore, substitutions at position 38 do not provide resistance to the third-generation inhibitor T2635, while substitution at positions 79 and 90 do, suggesting different resistance mechanisms.

Potent HIV fusion inhibitors against Enfuvirtide-resistant HIV-1 strains

“…T1249, a second generation HIV fusion inhibitor, contains all three functional domains, including pocket-, HR-and lipid-binding sequences. However, it functions more like T20 (25). Therefore, T20-resistant strains with GIV mutations are also insensitive to T1249 (27).…”

“…T20 contains the HR-and lipid-binding domains. It inhibits HIV fusion by binding to the HR sequences in NHR, including the GIV motif, through its N-terminal HR-binding domain and interacting with the lipid membrane on the target cell, via its C-terminal lipid-binding domain (25). Mutations of the conserved GIV motif may affect the binding of T20 to the HR sequence in NHR, resulting in significant reduction of T20-mediated inhibitory activity on HIV fusion and entry.…”

Resistance Profiles of Novel Electrostatically Constrained HIV-1 Fusion Inhibitors

“…Nearly all the individual selected mutations had little impact on the susceptibility to T-1249. However, V38D/E conferred high-level resistance to T-1249 (30-fold) and T-20 (more than 200-fold), but not to another fusion inhibitor, T-2635 (42,43), suggesting that there is potential cross-resistance between T-20 and T-1249. In contrast, T-2635 was hardly affected by such single mutations except for Q79E and K90E with a mild resistance of 4-and 7-fold, respectively (42), indicating that T-2635 had a preferential resistance pattern similar to SC34 and SC34EK, because these inhibitors were essentially effective against all variants with single mutations.…”

“…However, V38D/E conferred high-level resistance to T-1249 (30-fold) and T-20 (more than 200-fold), but not to another fusion inhibitor, T-2635 (42,43), suggesting that there is potential cross-resistance between T-20 and T-1249. In contrast, T-2635 was hardly affected by such single mutations except for Q79E and K90E with a mild resistance of 4-and 7-fold, respectively (42), indicating that T-2635 had a preferential resistance pattern similar to SC34 and SC34EK, because these inhibitors were essentially effective against all variants with single mutations. Interestingly, although HIV-1 SC34(P-122) and HIV-1 SC34EK(P-120) showed mild (7.3-fold) and moderate resistance (21-fold) to C34, respectively, we observed significant differences in resistance against T-2410, another next generation fusion inhibitor, which differed from C34 by only two added amino acids at each of the N and C termini (13).…”

“…Resistance profiles of these next generation fusion inhibitors with physicochemical modifications are expected to be different from those of the native sequence peptide fusion inhibitors, although only those of T-1249 and T-2635 were examined (42,43). T-1249, one of the first next generation fusion inhibitors, showed potent anti-HIV-1 activity in HIV-1-infected patients that failed to respond to T-20 treatment (12).…”