Efficacy of amprenavir (APV) 600 mg plus low-dose ritonavir (RTV) in clinical practice

Treatment options for heavily pre-treated antiretroviral (ART) experienced patients are often limited by the development of resistance. Pharmacokinetic data suggest that PI combinations of APV 600 mg with low-dose RTV (100 mg or 200 mg) can achieve sufficient APV plasma levels to potentially overcome this increase in IC sub(50). We evaluated the clinical efficacy and safety of APV 600 mg/low-dose RTV ART regimens. Retrospective chart review. Patients were included if: (1) they were ART experienced; (2) they were receiving APV 600 mg plus RTV 100 mg or 200 mg and (3) they had a plasma HIV-1 RNA and CD4 measurement at both initiation and within 6 months of starting APV/RTV therapy. Given the varied time to follow-up, patients were categorized at every 3-month time points for evaluation. Data from 14 patients are presented (APV600/RTV100 n = 10; APV600/RTV200 n = 4). Patients had extensive ART exposures as evidenced by: (1) a mean of five prior ART regimens; (2) mean exposure to four prior PIs; (3) 11/14 were NNRTI experienced (79%); and (4) a mean (SD) years on ART of 6 (two). Thirteen of 14 patients were changed to APV/RTV for increasing VL measurements after a mean (SD) of 58 (52) weeks on their previous regimen. Median baseline CD4 and VL were 185 cells/mm super(3) and 140 089 cps/ml, respectively. Mean observed time on therapy (SD) was 31 (18) weeks. At 3 months and 6 months, the median VL change from baseline was a decrease of 105 176 cps/ml (n = 13; range: -2516 to -774 801 cps/ml) and 317 349 cps/ml (n = 7; range: -2516 to-774 950 cps/ml), respectively. Six of 14 patients at 3 months (43%) and 3 of 7 patients at 6 months (43%) had VL measurements less than 400 cps/ml. Documented adverse events related to APV/RTV were minimal with only one patient discontinuing therapy due to RTV-induced GI intolerance. No rashes were reported. These data suggest that combination ART regimens of APV 600 mg/low dose RTV appears promising for the treatment of antiretroviral experienced HIV-infected individuals. Prospective, multicenter trials evaluating APV600/RTV100 bid are currently underway.