Paper # 555|
S/GSK1349572 Is a Potent Next Generation HIV Integrase Inhibitor and Demonstrates a Superior Resistance Profile Substantiated with 60 Integrase Mutant Molecular Clones
Takahiro Seki*1, M Kobayashi1, C Wakasa-Morimoto1, T Yoshinaga1, A Sato1, T Fujiwara1, M Underwood2, E Garvey2, and B Johns2
1Shionogi & Co, Ltd, Osaka, Japan and 2GlaxoSmithKline, Research Triangle Park, NC, US
Background: S/GSK134957 is a potent once-daily
unboosted integrase inhibitor (INI) under clinical development. Previous
studies with a subset of clinically relevant integrase mutant virus
demonstrated limited cross resistance to other integrase inhibitors in vitro. When
virus was passaged in the presence of S/GSK134957, highly resistant mutants
were not isolated, but mutations that conferred low-fold change (maximum fold
change=4.1) were identified within and around the integrase active site. Herein,
we demonstrate S/GSK134957 profile against a large panel of clinically relevant
Methods: Seventy integrase inhibitor-resistance
associated site-directed molecular clones (SDM) were constructed from the
wild-type molecular clone pNL432. Viral fitness was assessed with replication
in PBMCs and/or with a HeLa-CD4 cell single round infection assay. Mutations
assessed were primarily those associated with raltegravir (RAL) and
elvitegravir (ELV)-resistant viruses (RVs) observed in clinical trials, and
included double mutations in the 3 RAL resistance pathways (Y143C/H/R,
Q148H/K/R and N155H). Novel triple-quintuple mutations identified during
passage of Q148H/K/R clones in the presence of S/GSK134957 were also included.
Ten site-directed molecular clones replicated poorly, and the fold change (FC)
in susceptibility against the remaining 60 site-directed molecular clones was
determined with a HeLa-CD4 cell assay.
Results: In RAL-related resistant viruses, all 143
and 155 pathway viruses were still sensitive (FC<5) to S/GSK134957.
G140S/Q148H, a significant RAL-RV in the Q148 pathway, was still sensitive to S/GSK134957.
S/GSK134957 showed reduced activity against E138K/Q148K (fold change =19) and
G140S/Q148R (fold change =8.4). Addition of T97A, M154I, or V201I, to
G140S/Q148H increased S/GSK134957 resistance. Among ELV-related RVs, all
viruses remained sensitive to S/GSK134957. For the 28 single mutant site-directed
molecular clones, S/GSK134957 demonstrated low fold change (<5). For the 28
double mutant site-directed molecular clones, S/GSK134957 demonstrated low fold
change (<5) in activity against all except E138K/Q148K, G140S/Q148R, and
Q148R/N155H. These integrase inhibitor-resistant viruses had relatively low
replication rates compared to wild-type virus.
Conclusions: S/GSK134957 has a markedly different
resistance profile, as evidenced by limited cross-resistance to RAL-resistant site-directed
molecular clones. All single mutant and 25/28 double mutants did not alter fold
change activity to S/GSK134957 >5. These data show that S/GSK134957 has a
resistance profile distinct from RAL and ELV, and demonstrates the potential
for S/GSK134957 to have a higher genetic barrier to resistance.