Pharmacokinetic and Safety Study of Raltegravir and Atazanavir in a Once Daily Dose Regimen in HIV-1 Infected Patients

The licensed dose of raltegravir is 400 mg twice daily with or without food. Raltegravir is metabolized predominantly through glucuronidation by UGT1A1. Atazanavir increases the plasma concentrations of raltegravir 400 mg twice daily by 72% due to inhibition of UGT 1A1. This suggests that combined use of atazanavir and a lower dose frequency of raltegravir, once daily for example, is possible. Another reason why raltegravir most likely can be applied is that its pharmacodynamic effect is not related to Cmin but to AUC which is expected to be similar for an 800mg QD dose when compared to 400mg BD. Phase III clinical trials evaluating QD dosing of raltegravir are currently ongoing and interim results are expected to be published in mid 2009. A regimen of atazanavir and raltegravir in combination with lamivudine or emtricitabine may be a well tolerated and effective NNRTI-, and ritonavir-sparing regimen that could be an attractive option for both first and second line (after NRTI/NNRTI failure) treatment regimens.