Coadministration with lopinavir and ritonavir decreases exposure to BILR 355, a nonnucleoside reverse transcriptase inhibitor, in healthy volunteers.

The objective of this investigation was to evaluate the pharmacokinetic interaction of lopinavir/ritonavir (LPV/r) with BILR 355. In group A, 26 healthy participants were administered LPV/r (400mg/100mg) twice daily for 14 days, followed by coadministration of BILR 355, 150 mg twice daily for an additional 7 days. Pharmacokinetic assessments were performed on days 14 and 21. In group B, 8 healthy participants were given BILR 355/ritonavir (BILR 355/r, 150 mg/100mg) twice daily for 7 days. The pharmacokinetic data from group B (BILR 355/r-alone group) were also pooled with group B subjects from 3 similar phase I drug-drug interaction trials performed in parallel to this study. Coadministration with LPV/r resulted in a 51% decrease in steady-state area under plasma concentration-time curve from 0 to 12 hours (AUC(0-12,ss)) and steady-state maximum measured plasma concentration over a dosing interval (C(max,ss)) and a 50% decrease in steady-state plasma concentration 12 hours post last dosing (C(12,ss)) for BILR 355. Exposure to LPV was not changed after coadministration. BILR 355/r was well tolerated in this study. There was no evidence of increased risk of lopinavir or ritonavir toxicity upon coadministration with BILR 355.