Emma Hitt, PhD

July 21, 2011

July 21, 2011 (Rome, Italy) — In a comparison of 2 nonnucleoside reverse-transcriptase inhibitors (NNRTIs), rilpivirine was as effective as efavirenz over 96 weeks in treatment-naïve patients with HIV infection, but was associated with a lower rate of adverse events, according to pooled findings from the ECHO and THRIVE trials.

Calvin J. Cohen, MD, director of research at the Community Research Initiative of New England, in Boston, Massachusetts, presented the findings during a poster session here at the 6th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention.

"This study summarizes the 2-year outcome comparing these 2 NNRTIs," Dr. Cohen told Medscape Medical News. "We learned from this analysis that there were no new safety concerns identified in this large cohort with 2 years of drug exposure, an essential aspect of new drug development. We also see few rebounds after viral suppression was established with rilpivirine, similar in degree to what is seen with the use of efavirenz, adding to the confidence in using this novel agent," he said.

Patients in the studies received once-daily rilpivirine 25 mg or once-daily efavirenz 600 mg, in combination with tenofovir/emtricitabine in the ECHO trial (n = 690), or in combination with tenofovir/emtricitabine, zidovudine/lamivudine, or abacavir/lamivudine in the THRIVE trial (n = 678).

A response rate (HIV-1 <50 copies/mL) of 78% was observed for both rilpivirine and efavirenz. However, significantly greater increases in lipid parameters were observed in the efavirenz group than in the rilpivirine group over the 96-week study period. In addition, grade 2 to 4 overall adverse events, rash, dizziness, abnormal dreams/nightmares, and adverse events leading to discontinuation, mostly rash and dizziness, were lower.

There was no difference between groups in total cholesterol levels or in high-density-lipoprotein cholesterol ratios. Minimal changes in creatinine were noted in both groups, and there were no discontinuations due to renal adverse events. There were no changes in QTc intervals in the 2 groups.

"Rilpivirine in the right patient provides a simple alternative that may be preferable for some patients, while maintaining the simplicity achieved with efavirenz/emtricitabine/tenofovir," Dr. Cohen said. "The main uncertainty, I believe, is that it is not clear how these agents would compare if studied as a single-tablet vs a single-tablet approach, since this study involved double blinding and twice-daily dosing of these regimens," he said. "Thus, the actual outcomes may be even better than what was observed here. That remains a key uncertainty, and is being addressed by another study that is underway."

"The results from this study are reassuring as they are similar to what was observed at week 48 and demonstrate no new safety concerns," said independent commentator Paul E. Sax, MD, clinical director of the division of infectious diseases and the HIV program at Brigham and Women's Hospital, and associate professor of medicine at Harvard Medical School, Boston.

"Overall, rilpivirine seems to be better tolerated than efavirenz, but is associated with a higher risk of virologic failure at high viral loads," he told Medscape Medical News. "It remains to be seen whether the same will be observed when the single-pill formulation of rilpivirine plus tenofovir plus emtricitabine is compared to the single-pill formulation of efavirenz plus tenofovir plus emtricitabine" he added.

The study was funded by Tibotec, the manufacturer of rilpivirine. Dr. Cohen reports serving on advisory boards for Tibotec. Dr. Sax reports acting as a consultant to and receivIng funding from Tibotec.

6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention: Abstract TULBPE032. Presented July 19, 2011.

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