Response to Vicriviroc in Treatment-Experienced Subjects, as Determined by an Enhanced-Sensitivity Coreceptor Tropism Assay: Reanalysis of AIDS Clinical Trials Group A5211

The enhanced-sensitivity Trofile assay (Monogram Biosciences) was used to retest coreceptor use at both study screening and study entry for 118 treatment-experienced subjects in AIDS Clinical Trials Group A5211 who had CCR5-tropic (R5) virus detected by the original Trofile assay at study screening. Among 90 recipients of vicriviroc, a significantly (P<.001) greater mean reduction in HIV-1 RNA was observed in 72 subjects with R5 virus versus 15 subjects reclassified as having dual/mixed-tropic viruses at screening: - 1.11 versus -0.09 log 10 copies/mL at day 14 and -1.91 versus-0.57 log 10 copies/mL at week 24, respectively. Results suggest that the enhanced-sensitivity assay is a better screening tool for determining patient eligibility for CCR5 antagonist therapy.