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SAN DIEGO, CA—The antiretroviral combination elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (the Quad) demonstrated comparable efficacy and favorable tolerability to efavirenz/emtricitabine/tenofovir disoproxil fumarate (Atripla) in treatment-naïve patients with HIV infection who were <95% and <90% adherent, according to a study presented at IDWeek 2012.
Historically, it is estimated that ≥95% adherence to antiretroviral therapy (eg, multiple tablet regimens containing protease inhibitors) is necessary to maintain HIV viral suppression and to prevent the emergence of drug resistance. A threshold of adherence to single tablet regimens has not been established.
A team of investigators led by Dr. Edwin DeJesus, MD, from the Orlando Immunology Center, Orlando, FL, and Dr. Peter Shalit, MD, from Tribal Med, Seattle, WA, sought to examine the virologic efficacy and safety of the Quad and Atripla in subjects with adherence rates <95% and <90% through a pre-planned adherence analysis using pill count methodology on all subjects randomized and treated in Study 102 (the Quad’s pivotal Phase 3 trial) at Week 48.
A high proportion of subjects (75%) had ≥95%single tablet adherence to both the Quad and Atripla at Week 48. Among those in the Quad arm, 86/346 patients (25%) had adherence <95% (23 [7%] of those <90%) and, in the Atripla arm, 89/349 (26%) had adherence <95% (36 [10%] of those <90%).
“The rates of virologic suppression (HIV-1 RNA <50 copies/mL) were high in Quad and Atripla and comparable between adherence groups, with 91% vs. 88% for adherence ≥95%,” Dr. DeJesus reported.
For subjects with suboptimal single tablet regimen adherence, virologic efficacy was numerically higher in the Quad arm. This includes patients with a <95% adherence rate (79% for the Quad vs. 75% for Atripla) and patients with a <90% adherence rate (70% for the Quad vs. 56% for Atripla).
Eight patients (2%) in each arm developed resistance. Among patients with adherence ≥95%, resistance developed in four patients who received the Quad vs. five patients who received Atripla. Among patients with adherence 90%–<95%, resistance developed in two patients who received the Quad vs. one patient who received Atripla. Among patients with adherence <90%, resistance developed in two patients in each arm.
“Quad may become an effective antiretroviral regimen with comparable efficacy to Atripla even in those with incomplete adherence,” noted Dr. DeJesus.
In future adherence studies, the authors noted that it may be useful to assess adherence by objective measures (eg, drug level analysis).
