Midostaurin drug interaction profile: a comprehensive assessment of CYP3A, CYP2B6, and CYP2C8 drug substrates, and oral contraceptives in healthy participants.

PURPOSE: Midostaurin, approved for treating FLT-3-mutated acute myeloid leukemia and advanced systemic mastocytosis, is metabolized by cytochrome P450 (CYP) 3A4 to two major metabolites, and may inhibit and/or induce CYP3A, CYP2B6, and CYP2C8. Two studies investigated the impact of midostaurin on CYP substrate drugs and oral contraceptives in healthy participants. METHODS: Using sentinel dosing for participants' safety, the effects of midostaurin at steady state following 25-day (Study 1) or 24-day (Study 2) dosing with 50 mg twice daily were evaluated on CYP substrates, midazolam (CYP3A4), bupropion (CYP2B6), and pioglitazone (CYP2C8) in Study 1; and monophasic oral contraceptives (containing ethinylestradiol [EES] and levonorgestrel [LVG]) in Study 2. RESULTS: In Study 1, midostaurin resulted in a 10% increase in midazolam peak plasma concentrations (Cmax), and 3-4% decrease in total exposures (AUC). Bupropion showed a 55% decrease in Cmax and 48-49% decrease in AUCs. Pioglitazone showed a 10% decrease in Cmax and 6% decrease in AUC. In Study 2, midostaurin resulted in a 26% increase in Cmax and 7-10% increase in AUC of EES; and a 19% increase in Cmax and 29-42% increase in AUC of LVG. Midostaurin 50 mg twice daily for 28 days ensured that steady-state concentrations of midostaurin and the active metabolites were achieved by the time of CYP substrate drugs or oral contraceptive dosing. No safety concerns were reported. CONCLUSION: Midostaurin neither inhibits nor induces CYP3A4 and CYP2C8, and weakly induces CYP2B6. Midostaurin at steady state has no clinically relevant PK interaction on hormonal contraceptives. All treatments were well tolerated.

A Conserved Allosteric Site on Drug-Metabolizing CYPs: A Systematic Computational Assessment.

Cytochrome P450 enzymes (CYPs) are the largest group of enzymes involved in human drug metabolism. Ligand tunnels connect their active site buried at the core of the membrane-anchored protein to the surrounding solvent environment. Recently, evidence of a superficial allosteric site, here denoted as hotspot 1 (H1), involved in the regulation of ligand access in a soluble prokaryotic CYP emerged. Here, we applied multi-scale computational modeling techniques to study the conservation and functionality of this allosteric site in the nine most relevant mammalian CYPs responsible for approximately 70% of drug metabolism. In total, we systematically analyzed over 44 µs of trajectories from conventional MD, cosolvent MD, and metadynamics simulations. Our bioinformatic analysis and simulations with organic probe molecules revealed the site to be well conserved in the CYP2 family with the exception of CYP2E1. In the presence of a ligand bound to the H1 site, we could observe an enlargement of a ligand tunnel in several members of the CYP2 family. Further, we could detect the facilitation of ligand translocation by H1 interactions with statistical significance in CYP2C8 and CYP2D6, even though all other enzymes except for CYP2C19, CYP2E1, and CYP3A4 presented a similar trend. As the detailed comprehension of ligand access and egress phenomena remains one of the most relevant challenges in the field, this work contributes to its elucidation and ultimately helps in estimating the selectivity of metabolic transformations using computational techniques.

Lack of inhibition of CYP2C8 by saroglitazar magnesium: In vivo assessment using montelukast, rosiglitazone, pioglitazone, repaglinide and paclitaxel as victim drugs in Wistar rats.

Saroglitazar, a PPAR αÒ® agonist, is currently undergoing global development for the treatment of NASH and other indications. Saroglitazar showed CYP2C8 inhibition in human liver microsomes (IC50: 2.9 µM). The aim was to carry out drug-drug interaction (DDI) studies in Wistar rats using saroglitazar (perpetrator drug) with five CYP2C8 substrates. Also, the in vitro CYP2C8 inhibitory potential of saroglitazar in rat liver microsomes (RLM) was evaluated to justify use of preclinical model. The oral pharmacokinetics of various CYP2C8 substrates; montelukast, rosiglitazone, pioglitazone, repaglinide and intravenous pharmacokinetics of paclitaxel was assessed in the presence/absence of oral saroglitazar (4 mg/kg) in Wistar rats. A separate study was performed to assess the oral pharmacokinetics of saroglitazar. Serial blood samples were collected from all studies and the harvested plasma were stored frozen until bioanalysis. LC-MS/MS was used for the analysis of various analytes; concentration data was subjected to noncompartmental pharmacokinetic analysis. Statistical tests (unpaired t-test) were employed to judge the level of DDI. Generally, the pharmacokinetics of CYP2C8 substrates was not affected by the concomitant intake of saroglitazar as judged by the overall exposure (AUC0-last and AUC0-inf) and elimination half-life. The CYP2C8 IC50 of 4.5 µM in RLM for saroglitazar, supported the use of rats for this DDI study. In conclusion, pharmacokinetic data of diverse CYP2C8 substrates suggested that coadministration of saroglitazar did not cause clinically relevant DDI.

Prediction of inter-individual variability on the pharmacokinetics of CYP2C8 substrates in human.

Inter-individual variability in pharmacokinetics can lead to unexpected side effects and treatment failure, and is therefore an important factor in drug development. CYP2C8 is a major drug-metabolizing enzyme known to be involved in the metabolism of over 100 drugs. In this study, we predicted the inter-individual variability in AUC/Dose of CYP2C8 substrates in healthy volunteers using the Monte Carlo simulation. Inter-individual variability in the hepatic intrinsic clearance of CYP2C8 substrates (CLint,h,2C8) was estimated from the inter-individual variability in pharmacokinetics of pioglitazone, which is a major CYP2C8 substrate. The coefficient of variation (CV) of CLint,h,2C8 was estimated to be 40%. Using this value, the CVs of AUC/Dose of other major CYP2C8 substrates, rosiglitazone and amodiaquine, were predicted to validate the estimated CV of CLint,h,2C8. As a result, the reported CVs of both substrates were within the 2.5-97.5 percentile range of the predicted CVs. Furthermore, the CVs of AUC/Dose of the CYP2C8 substrates loperamide and chloroquine, which are affected by renal clearance, were also successfully predicted. Combining this value with previously reported CVs of other CYPs, we were able to successfully predict the inter-individual variability in pharmacokinetics of various drugs in clinical.

Functional characterization of 12 allelic variants of CYP2C8 by assessment of paclitaxel 6α-hydroxylation and amodiaquine N-deethylation.

Cytochrome P450 2C8 (CYP2C8) is one of the enzymes primarily responsible for the metabolism of many drugs, including paclitaxel and amodiaquine. CYP2C8 genetic variants contribute to interindividual variations in the therapeutic efficacy and toxicity of paclitaxel. Although it is difficult to investigate the enzymatic function of most CYP2C8 variants in vivo, this can be investigated in vitro using recombinant CYP2C8 protein variants. The present study used paclitaxel to evaluate 6α-hydroxylase activity and amodiaquine for the N-deethylase activity of wild-type and 11 CYP2C8 variants resulting in amino acid substitutions in vitro. The wild-type and variant CYP2C8 proteins were heterologously expressed in COS-7 cells. Paclitaxel 6α-hydroxylation and amodiaquine N-deethylation activities were determined by measuring the concentrations of 6α-hydroxypaclitaxel and N-desethylamodiaquine, respectively, and the kinetic parameters were calculated. Compared to the wild-type enzyme (CYP2C8.1), CYP2C8.11 and CYP2C8.14 showed little or no activity with either substrate. In addition, the intrinsic clearance values of CYP2C8.8 and CYP2C8.13 for paclitaxel were 68% and 67% that of CYP2C8.1, respectively. In contrast, the CLint values of CYP2C8.2 and CYP2C8.12 were 1.4 and 1.9 times higher than that of CYP2C8.1. These comprehensive findings could inform for further genotype-phenotype studies on interindividual differences in CYP2C8-mediated drug metabolism.