RESUMO
Background: In the ANRS 165 DARULIGHT study (NCT02384967) carried out in HIV-infected patients, the use of a darunavir/ritonavir-containing regimen with a switch to a reduced dose of darunavir maintained virological efficacy (≤50 copies/mL) for 48 weeks with a good safety profile. Objectives: To assess the total and unbound blood plasma pharmacokinetics of darunavir and associated antiretrovirals, and their penetration into semen before and after dose reduction. Patients and methods: Patients receiving a darunavir/ritonavir (800/100 mg q24h)-containing regimen for >6 months with plasma HIV-RNA ≤50 copies/mL for >12 months were switched to 400/100 mg darunavir/ritonavir q24h at week 0. A 24 h intensive pharmacokinetic blood sampling and a trough seminal sampling were performed before (week 0) and after (week 12) dose reduction. Individual pharmacokinetic parameter estimates were obtained using non-linear mixed-effect modelling for darunavir/ritonavir in blood plasma and used to test for bioequivalence, whereas darunavir/ritonavir in seminal plasma and NRTIs were analysed using a non-compartmental approach. Results and conclusions: Fifteen patients completed the intensive pharmacokinetic analysis. There was no significant decrease in total and unbound darunavir blood plasma exposure despite a 50% decrease in darunavir daily dose from 800 to 400 mg (AUC0-24 = 65â¯563 versus 52â¯518 ng·h/mL; P = 0.25). A decrease in apparent oral clearance (CL/F) of both darunavir and ritonavir at week 12 suggests a modification of the initial darunavir/ritonavir daily dose balance (800/100 to 400/100 mg), in favour of a reduced inducer effect of darunavir on cytochrome P450 and efflux transporters compared with the standard dose.