Population Pharmacokinetic Analysis of Darunavir and Tenofovir Alafenamide in HIV-1-Infected Patients on the Darunavir/Cobicistat/Emtricitabine/Tenofovir Alafenamide Single-Tablet Regimen (AMBER and EMERALD Studies)

The single-tablet regimen darunavir/cobicistat/emtricitabine/tenofovir alafenamide (D/C/F/TAF) 800/150/200/10 mg has undergone phase III studies AMBER (NCT02431247) and EMERALD (NCT02269917) in HIV-infected patients. An existing population pharmacokinetic (PopPK) model for cobicistat-boosted darunavir (DRV) was updated to describe DRV PK in AMBER and EMERALD. For TAF, a PopPK model was developed using richly sampled phase I/II data and updated with sparsely sampled AMBER data. Individual exposure metrics for DRV and TAF in patients receiving D/C/F/TAF were derived (AMBER, n=356; EMERALD, n=750). The DRV PopPK model is a two-compartment model with sequential zero-order, first-order input. TAF PK is described by a one-compartment model with dual parallel input for absorption (slow and fast pathway). DRV covariates were α1-acid-glycoprotein and body weight. TAF covariates were lean body weight and α1-acid-glycoprotein. DRV and TAF PK were unaffected by age, race, or gender. Estimated DRV mean (SD) C0h and AUC24h, respectively, were 1899 (759) ng/mL and 87,909 (20,232) ng*h/mL in AMBER; 1813 (859) ng/mL and 85,972 (22,413) ng*h/mL in EMERALD. Estimated TAF mean (SD) AUC24h was 132 (41) ng*h/mL. These PK parameters were in line with historical data. No apparent relationships of DRV or TAF exposure with efficacy (virologic response) or safety (metabolic, cardiac, liver, gastrointestinal, skin, bone, renal, pancreas, lipid events) parameters were seen. Additionally, our findings demonstrate that in patients with low plasma concentrations, there is no risk of decreased virologic response or virologic rebound. This supports the use of a once-daily, single-tablet regimen of D/C/F/TAF 800/150/200/10 mg for the treatment of HIV-1-infected subjects.