Twice-daily amprenavir 1200 mg versus amprenavir 600 mg/ritonavir 100 mg, in combination with at least 2 other antiretroviral drugs, in HIV-1-infected patients

Low-dose ritonavir (RTV) boosts plasma amprenavir (APV) exposure. Little has been published on the efficacy, tolerability, and safety of APV 600 mg/RTV 100 mg (APV600/RTV) twice daily (BID) compared to APV 1200 mg BID (APV1200).

ESS40011 was a 24-week, multicenter, open-label, clinical trial in which antiretroviral therapy-naïve and -experienced HIV-1-infected adults were randomized 3:1 to receive either APV600/RTV BID or APV1200 BID, in combination with ≥ 2 non-protease inhibitor antiretroviral drugs. Non-inferiority of the APV600/RTV regimen to the APV1200 regimen was established if the 95% lower confidence limit for the difference in proportion of patients achieving HIV-1 RNA <200 copies/mL at week 24 with APV 600/RTV minus APV1200 was ≥-0.12. Late in the conduct of the trial, patients not yet completing 24 weeks of therapy were given the option of continuing treatment for an additional 24-week period.

211 patients were randomized, 158 to APV600/RTV and 53 to APV1200. At week 24, APV600/RTV was similar to or better than APV1200 (HIV-1 RNA <200 copies/mL in 62% [73/118] vs 53% [20/38] of patients; intent-to-treat: observed analysis). In the APV600/RTV arm, significantly more patients achieved HIV-1 RNA <50 copies/mL (48% [57/118] vs 29% [11/38] with APV1200, P = 0.04), and greater mean reduction from baseline in HIV-1 RNA was observed (-2.21 vs -1.59 log₁₀ copies/mL, P = 0.028). The two treatment arms were similar with respect to mean overall change from baseline in CD4+ count, frequency of drug-related grade 1–4 adverse events, and frequency of discontinuing treatment due to adverse events (most commonly nausea, diarrhea, vomiting or fatigue; 7% vs 8%), although a lower proportion of patients in the APV600/RTV arm experienced drug-related oral/perioral paresthesia (2% vs 8%). Eleven (73%) of 15 patients who had HIV-1 RNA <200 copies/mL at week 24 and chose to continue study treatment maintained this level of virologic suppression at follow-up 24 weeks later.

APV600 RTV BID was similar to or better than APV1200 BID in virologic response. Virologic results in a small number of patients who continued treatment for 24 weeks post-study suggest that virologic suppression with APV600 RTV BID is durable.