Emma Hitt, PhD

July 19, 2011

July 19, 2011 (Rome, Italy) — Raltegravir has similar safety and antiviral efficacy to tenofovir/emtricitabine when either is combined with ritonavir-boosted darunavir in antiretroviral-naive patients with HIV infection, new findings from the Resistance and Dosage Adapted Regimens (RADAR) study suggest.

Roger Bedimo, MD, FACP, associate professor of medicine at the University of Texas Southwestern Medical Center in Dallas, presented the findings here during a poster session at the 6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention.

"The RADAR study is the first study to explore the use of darunavir and raltegravir as a nucleoside-free regimen in treatment-naive patients," Dr. Bedimo told Medscape Medical News. According to him, previous studies on raltegravir in combination with darunavir have been conducted only in treatment-experienced patients.

"We think the use of raltegravir/darunavir in antiretroviral-naive patients is a viable alternative to conventional regimens," he suggested. He added that nucleoside reverse-transcriptase inhibitor (NRTI)-sparing regimens may avoid long-term mitochondrial, bone, and renal toxicities.

The RADAR trial is an open-label, 48-week pilot study designed to evaluate raltegravir compared with tenofovir/emtricitabine, both given in combination with ritonavir-boosted darunavir. Patients were previously untreated and had HIV-1 RNA levels of at least 5000 copies/mL at baseline.

The primary efficacy endpoint was the proportion of subjects with plasma HIV-1 RNA levels lower than 50 copies/mL at week 24. In the raltegravir group, 88.9% of patients achieved this endpoint compared with 81.0% in the tenofovir/emtricitabine group, which was not significantly different between treatment groups. The finding suggests that this NRTI-sparing regimen may be equally as effective as the tenofovir/emtricitabine combination.

Mean changes from baseline CD4+ cell count were not significantly different between groups. In addition, laboratory measures of total cholesterol, high-density lipoprotein cholesterol, triglycerides, and serum creatinine were comparable.

Dr. Bedimo notes that findings from the RADAR trials should be placed in context with those from the SPARTAN study, which evaluated atazanavir and raltegravir, and the PROGRESS trial, which evaluated lopinavir/ritonavir + raltegravir.

He also pointed out that a single-group study of raltegravir + darunavir, conducted by the AIDS Clinical Trials Group and presented at the Conference on Retroviruses and Opportunistic Infections 2011, raised concerns about a high rate of virologic failures and discontinuations, and that this finding needs further follow-up. No treatment-emergent resistance was reported in the current study. Three patients per group had discontinued by week 24.

Independent commentator Paul E. Sax, MD, clinical director of the division of infectious diseases and the HIV program at Brigham and Women's Hospital in Boston, Massachusetts, and associate professor of medicine at Harvard Medical School, also noted that the previous single-group study of raltegravir + darunavir "had an unacceptably high rate of virologic failure."

"A major limitation of this study is the small sample size, limiting its application to clinical practice," he told Medscape Medical News. "For now, clinicians should, in general, stick with initial regimens recommended in treatment guidelines and await the results of the ongoing fully powered trial of this regimen," he added.

The study was supported by Merck & Co and Tibotec Therapeutics (now Janssen Services). Dr. Bedimo has disclosed no relevant financial relationships. Dr. Sax reports being a consultant for Merck & Co and Jannsen Services.

6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention: Abstract MOPE214. Presented July 18, 2011.

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