In vitro assessment of the potential for dolutegravir to affect hepatic clearance of levonorgestrel

OBJECTIVES: The World Health Organization recommends that all countries adopt dolutegravir-based antiretroviral therapy as the preferred regimen for all individuals living with HIV. Levonorgestrel is a commonly used hormonal contraceptive, which undergoes drug–drug interactions with some antiretrovirals, but the potential interaction between dolutegravir and levonorgestrel has not been examined. We aimed to evaluate cytochrome P450 (CYP)-mediated levonorgestrel metabolism and quantify the effects of dolutegravir on levonorgestrel apparent intrinsic clearance (CL(int.app.)) and CYP gene expression. METHODS: In vitro CYP-mediated CL(int.app.) of levonorgestrel was quantified using a recombinant human CYP (rhCYP) enzyme system. A primary human hepatocyte model of drug metabolism was used to assess the effects of dolutegravir on (1) levonorgestrel CL(int.app.), using liquid chromatography-tandem mass spectrometry, and (2) the expression of specific CYP enzymes, using quantitative real-time polymerase chain reaction. RESULTS: Levonorgestrel clearance was mediated by multiple rhCYPs, including rhCYP3A4. Under control conditions, levonorgestrel CL(int.app.) was 22.4 ± 5.0 μL/min/10(6) hepatocytes. Incubation with 43.1 nM of unbound dolutegravir elevated levonorgestrel CL(int.app.) to 31.4 ± 7.8 μL/min/10(6) hepatocytes (P = 0.168), while 142.23 nM increased levonorgestrel CL(int.app.) to 37.0 ± 2.9 μL/min/10(6) hepatocytes (P = 0.012). Unbound dolutegravir ≥ 431 nM induced expression of CYP3A4 (≥ two-fold) in a dose-dependent manner, while 1.44 μM of unbound dolutegravir induced CYP2B6 expression 2.2 ± 0.3-fold (P = 0.0004). CONCLUSIONS: In summary, this in vitro study suggests that dolutegravir has the potential to increase hepatic clearance of levonorgestrel by inducing both CYP3A and non-CYP3A enzymes. The observed in vitro dolutegravir–levonorgestrel drug–drug interaction should be further examined in clinical studies.