Delavirdine Shown to Enhance HIV Protease Inhibitor Therapy

July 12, 2000

New York (MedscapeWire) Jul 12 — Results from studies evaluating safety and efficacy of delavirdine (Rescriptor, Agouron Pharmaceuticals), a nonnucleoside reverse transcriptase inhibitor (NNRTI), as part of combination therapy containing HIV protease inhibitors (PIs) for the treatment of HIV infection were reported at the XIII International AIDS Conference in Durban, South Africa. Delavirdine appeared to enhance HIV PI-containing combination therapy by reducing plasma HIV RNA levels and increasing CD4 cell counts in a small study of people failing antiretroviral therapy who had never previously received NNRTIs.

In an additional report, combination therapy containing delavirdine and a reduced dose of indinavir lowered the rate of nephrolithiasis compared with full-dose indinavir without delavirdine.

In a retrospective study conducted at the California Pacific Medical Center in San Francisco, California, 13 NNRTI-naive HIV-infected individuals in an urban private practice who were failing antiretroviral treatment received delavirdine as part of second-line therapy in combination with either a new single PI or dual PI regimen.

At study entry, the median plasma HIV RNA level was 25,650 copies/mL, and the CD4 count was 176 cells/mm 3. After 24 months of treatment, 11 (84%) of 13 patients had attained HIV RNA levels less than 500 copies/mL, and the median CD4 count was 410 cells/mm 3.

"NNRTIs as a class of drugs may have an impact on subsequent therapy. In designing strategies for antiretroviral therapy, consideration can be given to using Rescriptor for subsequent regimens," said W. F. Owen, Jr, MD, lead investigator of the study.

In preliminary studies conducted by Joseph Eron, MD, at the University of North Carolina, Chapel Hill, the coadministration of delavirdine with a regimen including a reduced dose of indinavir was shown to result in an incidence of nephrolithiasis of 1% (2 of 199 patients); for patients receiving a regimen including full-dose indinavir without delavirdine, the incidence was approximately 9.9% (7 of 71 patients).

In 2 open-label clinical studies a total of 270 HIV-infected patients were randomized to receive regimens including 400 mg delavirdine 3 times daily plus a reduced dose of indinavir (600 mg or 400 mg) 3 times daily, or a control regimen including the full dose of indinavir (800 mg) 3 times daily without delavirdine. In this study, delavirdine was shown to boost the minimum concentration of indinavir in the body after administration while minimally affecting the maximum concentration (peak concentration).

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