ABCB1 allele polymorphism is associated with virological efficacy in naïve HIV-infected patients on HAART containing nonboosted PIs but not boosted PIs.

Objective: To assess the effect of the multidrug resistance-1 single nucleotide polymorphism (ABCB1 SNP) C3435T in exon 26 on the virological responses to first-line protease inhibitor (PI)-containing HAART regimens. Method: A cohort of 182 HIV-infected patients with a PI-containing HAART regimen initiated from 1997 to 2004 was enrolled. Time to the first indetectable viral load (VL) was determined in patients with the CC, CT, or TT genotype. Results: There were 37%, 44%, and 19% of patients who had the CC, CT and TT genotypes, respectively. The median estimated times to VL indetectability in the CC, CT, and TT groups were respectively 5.9, 3.9, and 4.8 months (p = .06). In patients on a non-boosted PI regimen, ABCB1 genotype was associated with time to VL indetectability that was shorter in patients with the CT than CC genotype (CT vs. CC, hazard ratio [HR] = 0.62, p = .02; TT vs. CC, HR = 0.72, p = .21). This association was not found in patients with first-generation boosted PI-containing regimens and especially not with second-generation boosted PI-containing regimens. Conclusion: Our results show that the ABCB1 SNP in exon 26 is associated with virological efficacy in HIV-infected patients treated with nonboosted PI-containing regimens but not with those containing boosted PIs, particularly of the second generation.