The clinical efficacy and safety of Maraviroc are derived from analyses of data from 3 trials in adult subjects infected with CCR5-tropic HIV-1: Trials A4001027 and A4001028 in antiretroviral treatment-experienced adult subjects and Trial A4001026 in treatment naive subjects. These trials were supported by a 48-week trial in antiretroviral treatment- experienced adult subjects infected with dual/mixed-tropic HIV-1, Trial A4001029.

Trials in CCR5-Tropic, Treatment-Experienced Subjects

Trials A4001027 and A4001028 were double-blind, randomized, placebo-controlled, multicenter trials in subjects infected with CCR5-tropic HIV-1. Subjects were required to have an HIV-1 RNA greater than 5,000 copies per mL despite at least 6 months of prior therapy with at least 1 agent from 3 of the 4 antiretroviral drug classes (greater than or equal to 1 NRTI, greater than or equal to 1 NNRTI, greater than or equal to 2 PIs, and/or enfuvirtide) or documented resistance to at least 1 member of each class. All subjects received an optimized background regimen consisting of 3 to 6 antiretroviral agents (excluding low-dose ritonavir) selected on the basis of the subjects prior treatment history and baseline genotypic and phenotypic viral resistance measurements. In addition to the optimized background regimen, subjects were then randomized in a 2:2:1 ratio to Maraviroc 300 mg once daily, Maraviroc 300 mg twice daily, or placebo. Doses were adjusted based on background therapy as described in Dosage and Administration (2), Table 1. 

In the pooled analysis for Trials A4001027 and A4001028, the demographics and baseline characteristics of the treatment groups were comparable (Table 16). Of the 1,043 subjects with a CCR5 tropism result at screening, 7.6% had a dual/mixed-tropism result at the baseline visit 4 to 6 weeks later. This illustrates the background change from CCR5- to dual/mixed-tropism result over time in this treatment-experienced population, prior to a change in antiretroviral regimen or administration of a CCR5 co-receptor antagonist.

The Week 48 results for the pooled Trials A4001027 and A4001028 are shown in Table 17.

After 48 weeks of therapy, the proportions of subjects with HIV-1 RNA less than 400 copies per mL receiving Maraviroc compared with placebo were 56% and 22%, respectively. The mean changes in plasma HIV-1 RNA from baseline to Week 48 were 1.84 log10 copies per mL for subjects receiving Maraviroc + OBT compared with 0.78 log10 copies per mL for subjects receiving OBT only. The mean increase in CD4+ cell count was higher on Maraviroc twice daily + OBT (124 cells per mm 3) than on placebo + OBT (60 cells per mm 3). 

Trial in Dual/Mixed-Tropic, Treatment-Experienced Subjects

Trial A4001029 was an exploratory, randomized, double-blind, multicenter trial to determine the safety and efficacy of Maraviroc in subjects infected with dual/mixed co- receptor tropic HIV-1. The inclusion/exclusion criteria were similar to those for Trials A4001027 and A4001028 above and the subjects were randomized in a 1:1:1 ratio to Maraviroc once daily, Maraviroc twice daily, or placebo. No increased risk of infection or HIV-1 disease progression was observed in the subjects who received Maraviroc. Use of Maraviroc was not associated with a significant decrease in HIV-1 RNA compared with placebo in these subjects and no adverse effect on CD4+ cell count was noted.

Trial in Treatment-Naive Subjects

Trial A4001026 was a randomized, double-blind, multicenter trial in subjects infected with CCR5-tropic HIV-1 classified by the original TROFILE tropism assay. Subjects were required to have plasma HIV-1 RNA greater than or equal to 2,000 copies per mL and could not have: 1) previously received any antiretroviral therapy for greater than 14 days, 2) an active or recent opportunistic infection or a suspected primary HIV-1 infection, or 3) phenotypic or genotypic resistance to zidovudine, lamivudine, or efavirenz. Subjects were randomized in a 1:1:1 ratio to Maraviroc 300 mg once daily, Maraviroc 300 mg twice daily, or efavirenz 600 mg once daily, each in combination with lamivudine/zidovudine. The efficacy and safety of Maraviroc are based on the comparison of Maraviroc twice daily versus efavirenz. In a pre-planned interim analysis at 16 weeks, Maraviroc 300 mg once daily failed to meet the pre-specified criteria for demonstrating non-inferiority and was discontinued.

The demographic and baseline characteristics of the maraviroc and efavirenz treatment groups were comparable (Table 18). Subjects were stratified by screening HIV-1 RNA levels and by geographic region. The median CD4+ cell counts and mean HIV-1 RNA at baseline were similar for both treatment groups.

The treatment outcomes at 96 weeks for Trial A4001026 are shown in Table 19. Treatment outcomes are based on reanalysis of the screening samples using a more sensitive tropism assay, enhanced sensitivity TROFILE HIV tropism assay, which became available after the Week 48 analysis; approximately 15% of the subjects identified as CCR5-tropic in the original analysis had dual/mixed- or CXCR4-tropic virus. Screening with enhanced sensitivity version of the TROFILE tropism assay reduced the number of maraviroc virologic failures with CXCR4- or dual/mixed-tropic virus at failure to 12 compared with 24 when screening with the original TROFILE HIV tropism assay.

The median increase from baseline in CD4+ cell counts at Week 96 was 184 cells per mm 3for the arm receiving Maraviroc compared with 155 cells per mm 3for the efavirenz arm.