November 5, 2009

No Heart Rhythm Problem With 25 mg of Rilpivirine

People taking a 25 mg once-daily dose of rilpivirine (TMC278) had no signs of trouble with their heart rhythm, according to a study presented November 1 at the Infectious Disease Society of America conference in Philadelphia and reported by the National AIDS Treatment Advocacy Project (NATAP). These study results are encouraging, as this is the dose being explored for use in people starting HIV treatment for the first time.

Ripilvirine, a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) being developed by Tibotec, initially showed promise in treating HIV resistant to first-generation NNRTIs. Unfortunately, the doses likely needed to effectively suppress drug-resistant virus were associated with QT interval abnormalities—problems with the natural movement of electrical impulses through the chambers of the heart.  

The low 25 mg dose, which showed evidence of being effective in a Phase II study involving first-time treatment takers, did not appear to cause QT interval abnormalities. To explore this further, Simon Vanveggel, PhD, and his colleagues at Tibotec in Antwerp, Belgium, compared rilpivirine with Sustiva (efavirenz) and a placebo over 11 days in 120 HIV-negative participants.

According to his team’s presentation at the Philadelphia conference, Vanveggel reported that rilpivirine had absolutely no significant impact on the QT interval in the study participants. In the previous Phase IIb study, Sustiva actually showed some impact on QT interval, though not enough to raise serious concerns. In this study, Sustiva also had no impact on the QT interval.

Rilpivirine, combined with Truvada (tenofovir plus emtricitabine), is currently in Phase III studies involving treatment-naive individuals. A single pill that would combine rilpivirine with Truvada is also being studied.

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