Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

Abstract

Treatment of HIV-infected patients coinfected with Mycobacterium tuberculosis is challenging due to drug-drug interactions (DDIs) between antiretrovirals (ARVs) and antituberculosis (anti-TB) drugs. The aim of this study was to quantify the effect of cobicistat (COBI) or ritonavir (RTV) in modulating DDIs between darunavir (DRV) and rifampin (RIF) in a human hepatocyte-based in vitro model. Human primary hepatocyte cultures were incubated with RIF alone or in combination with either COBI or RTV for 3 days, followed by coincubation with DRV for 1 h. The resultant DRV concentrations were quantified by high-performance liquid chromatography with UV detection, and the apparent intrinsic clearance (CLint.app.) of DRV was calculated. Both RTV and COBI lowered the RIF-induced increases in CLint.app. in a concentration-dependent manner. Linear regression analysis showed that log10 RTV and log10 COBI concentrations were associated with the percent inhibition of RIF-induced elevations in DRV CLint.app., where β was equal to -234 (95% confidence interval [CI] = -275 to -193; P < 0.0001) and -73 (95% CI = -89 to -57; P < 0.0001), respectively. RTV was more effective in lowering 10 μM RIF-induced elevations in DRV CLint.app. (half-maximal [50%] inhibitory concentration [IC50] = 0.025 μM) than COBI (IC50 = 0.223 μM). Incubation of either RTV or COBI in combination with RIF was sufficient to overcome RIF-induced elevations in DRV CLint.app., with RTV being more potent than COBI. These data provide the first in vitro experimental insight into DDIs between RIF and COBI-boosted or RTV-boosted DRV and will be useful to inform physiologically based pharmacokinetic (PBPK) models to aid in optimizing dosing regimens for the treatment of patients coinfected with HIV and M. tuberculosis.

Keywords: antiretroviral agents; cobicistat; darunavir; drug-drug interaction; human immunodeficiency virus; in vitro; rifampin; ritonavir.

Copyright © 2017 American Society for Microbiology.

Figures

FIG 1

Effects of rifampin alone or in combination with ritonavir on the mean DRV CLint.app. in primary human hepatocytes in vitro. Cryopreserved primary human hepatocytes were incubated with RIF alone (0.5 to 20 μM) (hatched bars) or with RIF (0.5 to 20 μM) together with RTV (0.01 to 10 μM) (gray bars) for 72 h. All cells were then incubated with RIF (0.5 to 20 μM) or RIF (0.5 to 20 μM) together with RTV (0.01 to 10 μM), as described above, together with DRV (5 μM) for 60 min. Control cells were treated with DRV (5 μM) alone for 60 min (black bar). The results shown represent the mean DRV CLint.app. from three biological replicates measured in hepatocytes from three independent donors (donors HU1399, HU1587, and HU1621). Error bars indicate SDs.

FIG 2

Effects of rifampin alone or in combination with cobicistat on the mean DRV CLint.app. in primary human hepatocytes in vitro. Cryopreserved primary human hepatocytes were incubated with RIF (0.5 to 20 μM) (hatched bars) or with COBI (0.13 to 12.76 μM) and RIF (0.5 to 20 μM) (gray bars) for 72 h. All cells were then incubated with RIF (0.5 to 20 μM) or RIF (0.5 to 20 μM) together with COBI (0.13 to 12.76 μM), as described above, together with DRV (5 μM) for 60 min. Control cells were treated with DRV (5 μM) alone for 60 min (black bar). The results shown represent the mean DRV CLint.app. from three biological replicates measured in hepatocytes from three independent donors (donors HU1399, HU1574, and HU1587). Error bars indicate SDs.

FIG 3

Comparative effectiveness of COBI and RTV at lowering the RIF-induced increase in the CLint.app. of DRV in human primary hepatocytes in vitro. The graph shows the relative effects of COBI and RTV on the inhibition of 10 μM RIF-induced elevations in DRV CLint.app. in cryopreserved primary human hepatocytes. Cells were coincubated with RTV (starting total concentrations, 0.1 to 10 μM; donors HU1399, HU1587, and HU1621) or COBI (starting total concentrations, 0.13 to 12.76 μM; donors HU1399, HU1574, and HU1587) in combination with RIF (10 μM) for 72 h prior to coincubation with DRV (5 μM) for 1 h. Each condition was tested in triplicate with cells from each donor. The concentrations of RTV and COBI plotted represent the unbound concentrations present in WME incubation medium following correction for protein binding. The untreated control (blank) was assigned a value of 0.001 μM in each case. Error bars indicate SEMs.