SPIRIT: switching to emtricitabine/rilpivirine/tenofovir DF single-tablet regimen from boosted protease inhibitor maintains HIV suppression at week 48

Antiretroviral regimen simplification improves quality of life and medication adherence while reducing the risk of HIV virologic failure (VF) and long-term drug-related toxicities. Emtricitabine/rilpivirine/tenofovir disoproxil fumarate (FTC/RPV/TDF) is a well-tolerated and efficacious once-daily single-tablet regimen (STR) treatment option. Here we report the Week 48 safety and efficacy results of SPIRIT, the first study to evaluate switching from boosted protease inhibitor (PI+RTV)-based HAART to a simplified regimen of FTC/RPV/TDF STR. SPIRIT is a phase 3b, randomized, open-label, multi-center, international, 48-week study to evaluate the safety and efficacy of switching from PI+RTV regimens to FTC/RPV/TDF in virologically-suppressed HIV-1 infected participants. Participants were randomized 2:1 to switch to FTC/RPV/TDF at baseline or maintain their current PI+RTV regimen with a delayed switch to FTC/RPV/TDF at Week 24. The primary endpoint was non-inferiority (12% margin) of FTC/RPV/TDF relative to PI+RTV regimens in maintaining plasma HIV-1 RNA <50 copies/mL at Week 24 by FDA snapshot analysis. Plasma HIV-1 RNA levels were assessed at screening, baseline, and at Weeks 4, 8, 12, 24, (28 and 32 for delayed switch participants), 36, and 48 or early termination. A total of 476 participants were randomized and received at least 1 dose of study drug (317 FTC/RPV/TDF; 159 PI+RTV+2NRTIs). Baseline characteristics were similar across treatment arms. The primary endpoint of non-inferiority at Week 24 was met (HIV-1 RNA <50 copies/mL by FDA snapshot analysis 93.7% FTC/RPV/TDF vs. 89.9% PI+RTV+2NRTIs; difference 3.8%, 95% CI: -1.6 to 9.1]). Through Week 48, 88.3% of subjects switching to FTC/RPV/TDF at baseline maintained virologic suppression (HIV-1 RNA <50 copies/mL by FDA snapshot analysis). The rate of virologic suppression at Week 48 for the 152 participants who switched to FTC/RPV/TDF at Week 24 was comparable to the rate of virologic suppression at Week 24 for those who switched to FTC/RPV/TDF at baseline (delayed switch to FTC/RPV/TDF 92.1%; baseline switch to FTC/RPV/TDF 93.7%). In the Week 48 analysis of SPIRIT, the first study to evaluate switching to FTC/RPV/TDF STR from a PI+RTV-based regimen in virologically-suppressed, HIV-1-infected participants, virologic suppression was maintained regardless of whether participants switched to FTC/RPV/TDF at baseline or at Week 24. (Published: 11 November 2012) Citation: Abstracts of the Eleventh International Congress on Drug Therapy in HIV Infection Fisher M et al. Journal of the International AIDS Society 2012, 15 (Suppl 4):18275 http://www.jiasociety.org/index.php/jias/article/view/18275 | http://dx.doi.org/10.7448/IAS.15.6.18275