Investigative Rilpivirine Maintains Efficacy Against Efavirenz at 96 Weeks: Presented at AIDS 2008

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Title: Investigative Rilpivirine Maintains Efficacy Against Efavirenz at 96 Weeks: Presented at AIDS 2008
URL: http://www.pslgroup.com/dg/227426.htm
Doctor's Guide
August 6, 2008

By Ed Susman

MEXICO CITY -- August 6, 2008 -- The experimental non-nucleoside reverse transcriptase inhibitor rilpivirine remains at least as effective as efavirenz in suppressing human immunodeficiency virus (HIV) to undetectable levels in the long term, possibly with a higher safety profile, according to research presented here at the 17th International AIDS Conference (AIDS 2008).

"[Rilpivirine] was generally well tolerated, with less increase in serum lipids and lower incidences of rash, nervous system, and psychiatric events, compared with efavirenz," said Mario Santoscoy, MD, Hospital Carlos Mac Gregor, Mexico City, Mexico, speaking here August 5 at an oral poster presentation where results from a 96-week extension trial were discussed.

Dr. Santoscoy and colleagues recruited 368 antiretroviral-naïve, HIV-infected individuals who were randomly assigned to 1 of 4 trial arms, with about 90 people in each group: a once-daily 25-mg rilpivirine arm; a once-daily 75-mg rilpivirine arm; a once-daily 150-mg rilpivirine arm; and a standard efavirenz regimen.

The extended trial data indicated that 76% of subjects on the 25-mg dose of rilpivirine achieved an undetectable viral load of less than 50 copies/mL, while 71% of patients on efavirenz achieved undetectable viral loads.

Since the low dose had similar efficacy to the higher doses in both the previously reported 48-week study and in the present 96-week extension, Dr. Santoscoy felt that the QTc issue with rilpivirine would not be a major factor.

Patients taking efavirenz continued on the same drug through 96 weeks for comparison purposes. Of those subjects receiving the 75-mg dose of rilpivirine, about 72% had undetectable viral loads at week 96. Of those patients receiving the 150-mg dose of rilpivirine, 71% achieved an undetectable viral load, illustrating the equivalence in efficacy for all the rilpivirine doses, said Dr. Santoscoy.

All patients received a background regimen of 2 nucleoside reverse transcriptase inhibitors -- either zidovudine and lamivudine (76%) or tenofovir and emtricitabine (24%).

Significant differences between adverse side-effect occurrences included the following: rash, 9% with rilpivirine (any dose) versus 21% of efavirenz patients (P = .01); nervous system events, 31% with rilpivirine (any dose) versus 48% with efavirenz (P = .01); abnormal dreams or nightmares, 3% with rilpivirine (any dose) versus 11% with efavirenz (P < .05).

The 25-mg dose of rilpivirine, the smallest dose investigated in this trial, was selected for use in future phase 3 studies because it appears to have the least impact on heart-rhythm abnormalities. At higher doses of rilpivirine, there is a lengthening of the QTc interval. Dr. Santoscoy noted that prolongation of the QTc interval did not appear to increase during the extension of the study. He suggested that the prolongation reaches a peak and then plateaus.

Funding for this study was provided by Tibotec Pharmaceuticals Limited, Cork, Ireland.

[Presentation title: TMC278 (Rilpivirine), a Next-Generation NNRTI, Demonstrates Long-Term Efficacy and Tolerability in ARV-Naïve Patients: 96-Week Results of Study C204. Abstract TUAB0103]

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