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Early virologic rebound in a pilot trial of ritonavir-boosted atazanavir as maintenance monotherapy.

Karlström O, Josephson F, Sönnerborg A

Department of Infectious Diseases, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden. ollekarlstrom@ki.se

OBJECTIVE: To investigate the feasibility of ritonavir-boosted atazanavir monotherapy in HIV-1-infected patients with stable antiretroviral therapy (ART). DESIGN: Single-armed single-center pilot trial. METHODS: Adult HIV-1-infected patients, without protease inhibitor (PI) experience, were eligible if they had maintained a viral load <20 copies/mL for a minimum of 12 months on conventional ART. The trial regimen was atazanavir/ritonavir at a dose of 300/100 mg once daily. The atazanavir dose could be adjusted if plasma concentrations showed a low exposure. The study was intended to recruit 30 patients to be followed over 72 weeks. If 5 cases of virologic failure occurred during this period, the study was to be terminated. RESULTS: The study was terminated according to protocol when 15 of the planned 30 patients had been recruited, because 5 cases of virologic failure had occurred. In patients failing therapy, viral rebound was seen at weeks 12 through 16. Plasma atazanavir concentrations were not associated with the outcome. The median serum bilirubin concentration was significantly lower in the patients failing therapy, however. No PI resistance was found in samples from patients failing therapy. CONCLUSIONS: Ritonavir-boosted atazanavir as maintenance monotherapy in HIV-1 infection might not be as potent as conventional ART. Serum bilirubin should be further studied as a biomarker of adequate atazanavir exposure.

Published 13 March 2007 in J Acquir Immune Defic Syndr, 44(4): 417-22.
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