New Drug Adds to Arsenal Against AIDS

The new HIV drug rilpivirine is safe and effective and has fewer side effects than efavirenz when used in combination therapy, two recent studies found.

Used in combination regimens, nevirapine and efavirenz (Sustiva) are equally effective in viral suppression, but they can cause severe side effects, which is why researchers are investigating possible substitutes. Like them, rilpivirine is a non-nucleoside reverse transcriptase inhibitor.

Marketed by Tibotec as Edurant, rilpivirine was compared with efavirenz in various regimens in two studies involving nearly 1,400 patients in 21 countries.

In the first study, initial response rates (viral load under 50 copies/mL, defined by intention-to-treat time to loss-of-virological-response algorithm [ITT-TLOVR]) were 86 percent for rilpivirine-based therapy and 82 percent for efavirenz-based therapy, and CD4 cell count increases were similar between the groups. Incidence of virological failure was slightly higher in the rilpivirine than efavirenz group (7 percent vs. 5 percent), though fewer discontinued treatment on rilpivirine than efavirenz due to adverse events (4 percent vs. 7 percent). Grade 2-4 treatment-related adverse events were less common with rilpivirine than efavirenz (16 percent vs. 31 percent), and lipid increases were significantly lower on rilpivirine than efavirenz (p
At 48 weeks, rilpivirine proved non-inferior in efficacy to efavirenz using a 12 percent margin on logistic regression analysis, the study found.

In the second study comparing rilpivirine-based with efavirenz-based therapy, response rates (less than 50 copies/mL ITT-TLOVR) were 83 percent for both confirmed at 48 weeks. Rilpivirine proved non-inferior in efficacy compared with efavirenz (also 12 percent margin), though incidence of virological failure was higher for rilpivirine (13 percent vs. 6 percent; 11 percent vs. 4 percent ITT-TLOVR). Grade 2-4 adverse events and discontinuations due to AEs were less common for rilpivirine than efavirenz (Grade 2-4: 16 percent vs. 31 percent; discontinuations: 2 percent vs. 8 percent).

Rilpivirine had a more favorable safety and tolerability profile than efavirenz, though a higher virological failure rate, and was non-inferior in efficacy, the study authors concluded.

The studies, "Rilpivirine Versus Efavirenz With Two Background Nucleoside or Nucleotide Reverse Transcriptase Inhibitors in Treatment-Naive Adults Infected with HIV-1 (THRIVE): A Phase 3, Randomized, Non-Inferiority Trial" and "Rilpivirine Versus Efavirenz with Tenofovir and Emtricitabine in Treatment-Naive Adults Infected With HIV-1 (ECHO): A Phase 3 Randomized Double-Blind Active-Controlled Trial," were published in Lancet (2011;378(9787):229-237 and 238-246, respectively).

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