Atazanavir: a new protease inhibitor to treat HIV infection.

PURPOSE: The pharmacology, pharmacokinetics, and clinical trials of and drug interactions and formulary considerations associated with atazanavir, the newest protease inhibitor (PI) to treat human immunodeficiency virus (HIV) infection, are evaluated.
SUMMARY: Clinical and pharmacokinetic trials were identified through a MEDLINE search. In addition, all available literature citations and meeting abstracts were obtained from the drug's manufacturer. All articles identified from the data sources were evaluated, and all information deemed relevant was included in this review. Data on atazanavir for the treatment of HIV infection are limited to several phase II and III trials, one of which is still ongoing. Atazanavir has shown efficacy comparable with other PIs and the nonnucleoside reverse-transcriptase inhibitor efavirenz in reducing HIV RNA levels, increasing CD4+ lymphocyte counts, and increasing the percentage of patients achieving clinically undetectable HIV RNA levels when given as the sole PI in treatment-naive patients, in combination with saquinavir in treatment-experienced patients, and with ritonavir-boosting regimens in highly treatment-experienced patients. Treatment-naive patients receiving atazanavir commonly develop a protease enzyme mutation on codon 50, which decreases HIV's susceptibility to atazanavir but may increase the susceptibility of the virus to other PIs. When atazanavir is given to patients with preexisting PI-related mutations, the virus's susceptibility to atazanavir is greatly reduced. The occurrence of lipid abnormalities, which has been a major concern with previous PIs, has not been shown to be troublesome in patients receiving atazanavir.
CONCLUSION: Atazanavir may be used alone as a first-line PI, with saquinavir in treatment-experienced patients, or in combination with a ritonavir-boosting regimen in highly treatment-experienced patients as part of a salvage regimen.