The experimental non-nucleoside reverse transcriptase inhibitor (NNRTI) rilpivirine, also known as TMC-278, is comparable to Sustiva in terms of reducing viral loads and increasing CD4 counts over 48 weeks in people taking antiretroviral treatment for the first time, according to data presented at the 11th European AIDS Conference (EACS).

Study C204 is a 96-week study comparing three once-daily doses of rilpivirine to Sustiva, all in combination with Truvada (tenofovir/emtricitabine) or Combivir (zidovudine/lamivudine). The 48-week data were presented at EACS by Patrick Yeni of the Hôpital Bichat in Paris and his colleagues.  

A total of 368 patients are participating in the study. Ninety-three patients have been randomized to the 25 mg rilpivirine group, 95 to the 75 mg group, 91 to the 150 mg, and 89 to Sustiva. All patients in the study were treatment-naïve upon entering, meaning that they had not taken any other HIV medications in the past.

The demographics of those participating are similar between those taking rilpivirine and those taking Sustiva. Roughly one third of the participants in all three groups are women, and about 45 percent are white. Participants started the study with viral loads of approximately 70,000 copies and CD4 counts of approximately 200 cells.

The proportion of people who had undetectable viral loads after 48 weeks of treatment were nearly identical, regardless of whether they took rilpivirine—at any dose—or Sustiva. Eighty-one percent of people taking Sustiva had a viral load of less than 50 copies after 48 weeks, while 81 percent of those taking 25mg of rilpivirine, 80 percent of those taking 75 mg, and 77 percent of those taking 150 mg had undetectable virus at the same time point.

CD4 count changes did not differ significantly between the groups; average increases of 125 to 145 cells after 48 weeks of treatment were reported.

Of particular interest was the safety profile of rilpivirine compared with Sustiva. According to data presented at EACS, and previously at the fourth IAS Conference on HIV Pathogenesis, Treatment and Prevention in Sydney, people taking rilpivirine were much less likely to experience the majority of side effects that are common with Sustiva, including rash, dizziness and abnormal dreams. The incidence of psychiatric disorders such as depression and insomnia were similar between those taking rilpivirine and those taking Sustiva.

There are also reasons to expect, though it is too early to tell, that rilpivirine may be safer that Sustiva for use by HIV-positive pregnant women.

Based on these results, Tibotec is moving forward with further development of rilpivirine using the 75 mg dose. Provided that larger studies confirm the efficacy and favorable side effect profile of the drug, rilpivirine will likely become a useful tool for people who are considering starting antiretroviral therapy.