Cobicistat is a new pharmacokinetic enhancer or booster of the HIV protease inhibitor darunavir. Cobicistat is distinct from the conventional booster ritonavir in that cobicistat presents a more selective inhibition of the enzymes metabolizing drugs. In addition, cobicistat is a weaker inhibitor of the efflux drug transporters expressed at the level of the blood-brain barrier (i.e. P-glycoprotein (P-gp) and breast cancer resistance Protein (BCRP)). A weaker inhibition of these efflux transporters could possibly result in less darunavir entering the brain when boosted by cobicistat as compared to a boosting by ritonavir. Such a difference could potentially be critical in patients with HIV-associated neurocognitive disorders as sufficient drug levels are needed to efficiently inhibit HIV replication inside the brain.~The aim of this study is to determine whether the boosting of darunavir by cobicistat results effectively in lower darunavir concentrations in the CSF as compared to a boosting by ritonavir. The study will be performed in HIV infected patients presenting HIV associated neurocognitive disorders (HAND) and requiring a lumbar puncture for clinical reasons. In addition, the patients will be only eligible if the are treated or if they qualify for a darunavir/ritonavir (800/100 mg once daily) containing regimen. Darunavir concentrations will be measured simultaneously in the CSF and plasma (CSF/plasma ratio) first with the ritonavir boosting and subsequently with the cobicistat boosting.
The purpose of this study is to assess whether a boosting by cobicistat results in similar concentrations of darunavir in the brain compared to a boosting by ritonavir.