E. S. Lee

Vicriviroc in Combination Therapy with an Optimized Regimen for Treatment-Experienced Subjects: 48-Week Results of the VICTOR-E1 Phase 2 Trial

BACKGROUND Agents that block the CCR5 coreceptor for human immunodeficiency virus (HIV) have demonstrated potent antiretroviral activity. In early clinical studies, the CCR5 antagonist vicriviroc proved to be a safe and effective component of combination antiretroviral therapy. METHODS This double-blind, dose-ranging, phase 2 trial randomized subjects to receive 30 mg or 20 mg of vicriviroc or placebo once daily plus re-optimized background therapy containing a protease inhibitor with ritonavir. Subjects were adults infected with CCR5-tropic HIV who were experiencing failure of triple antiretroviral regimens. The primary end point was mean change in baseline log(10) HIV RNA level at 48 weeks, based on an intent-to-treat analysis. RESULTS One hundred fourteen persons received vicriviroc at 30 mg (n = 39), vicriviroc at 20 mg (n =40), or placebo (n = 35). The mean change in baseline HIV RNA level at week 48 was -1.77 log(10) copies/mL for 30 mg of vicriviroc and -1.75 log(10) copies/mL for 20 mg of vicriviroc, compared with -0.79 log(10) copies/mL for placebo (P =.002 and P=.003, respectively, compared with placebo). Mean CD4 counts increased by 102, 136, and 63 cells/mm(3) for 30 mg vicriviroc, 20 mg vicriviroc, and placebo, respectively (P = .260 and P = .039, respectively, compared with placebo). Rates of adverse events (mostly mild-to-moderate) were 111.4, 112.5, and 147.4 events per 100 subject-years, respectively. CONCLUSIONS Vicriviroc administered with a protease inhibitor plus ritonavir-containing regimen shows potent antiretroviral and immunologic activity sustained over 48 weeks in treatment-experienced patients. CLINICAL TRIALS REGISTRATION NCT00243230 .

Mapping and characterization of vicriviroc resistance mutations from HIV-1 isolated from treatment-experienced subjects enrolled in a phase II study (VICTOR-E1).

Objectives: In the phase 2 VICTOR-E1 study, treatment-experienced subjects receiving 20 mg or 30 mg of the CCR5 antagonist vicriviroc (VCV), with a boosted protease containing optimized background regimen, experienced significantly greater reductions in HIV-1 viral load compared with control subjects. Among the 79 VCV-treated subjects, 15 experienced virologic failure, and of these 5 had VCV-resistant virus. This study investigated the molecular basis for the changes in susceptibility to VCV in these subjects. Methods: Sequence analysis and phenotypic susceptibility testing was performed on envelope clones from VCV-resistant virus. For select clones, an exchange of mutations in the V3 loop was performed between phenotypically resistant clones and the corresponding susceptible clones. Results: Phenotypic resistance was manifest by reductions in the maximum percent inhibition. Clonal analysis of envelopes from the 5 subjects identified multiple amino acid changes in gp160 that were exclusive to the resistant clones, however, none of the changes were conserved between subjects. Introduction of V3 loop substitutions from the resistant clones into the matched susceptible clones was not sufficient to reproduce the resistant phenotype. Likewise, changing the substitutions in the V3 loops from resistant clones to match susceptible clones only restored susceptibility in 1 clone. Conclusions: There were no clearly conserved patterns of mutations in gp160 associated with phenotypic resistance to VCV and mutations both within and outside of the V3 loop contributed to the resistance phenotype. These data suggest that genotypic tests for VCV susceptibility may require larger training sets and additional information beyond V3 sequences.