Improvement of the chemical inhibition phenotyping assay by cross-reactivity correction

Cytochrome P450 2B6 and UDP-Glucuronosyltransferase Enzyme-Mediated Clearance of Ciprofol (HSK3486) in Humans: The Role of Hepatic and Extrahepatic Metabolism

Ciprofol (HSK3486) is a novel intravenous agent for general anesthesia. In humans, HSK3486 mainly undergoes glucuronidation to form M4 [fraction of clearance (fCL): 62.6%], followed by the formation of monohydroxylated metabolites that further undergo glucuronidation and sulfation to produce M5-1, M5-2, M5-3, and M3 (summed fCL: 35.2%). However, the complete metabolic pathways of HSK3486 in humans remain unclear. In this study, by comparison with chemically synthesized reference standards, three monohydroxylated metabolites [M7-1, 4-hydroxylation with an unbound intrinsic clearance (CLint,u) of 2211 μl/min/mg; M7-2, ω-hydroxylation with a CLint,u of 600 μl/min/mg; and M7-3, (ω-1)-hydroxylation with a CLint,u of 78.4 μl/min/mg] were identified in human liver microsomes, and CYP2B6 primarily catalyzed their formation. In humans, M7-1 was shown to undergo glucuronidation at the 4-position and 1-position by multiple UDP-glucuronosyltransferases (UGTs) to produce M5-1 and M5-3, respectively, or was metabolized to M3 by cytosolic sulfotransferases. M7-2 was glucuronidated at the ω position by UGT1A9, 2B4, and 2B7 to form M5-2. UGT1A9 predominantly catalyzed the glucuronidation of HSK3486 (M4). The CLint,u values for M4 formation in human liver and kidney microsomes were 1028 and 3407 μl/min/mg, respectively. In vitro to in vivo extrapolation analysis suggested that renal glucuronidation contributed approximately 31.4% of the combined clearance. In addition to HSK3486 glucuronidation (M4), 4-hydroxylation (M7-1) was identified as another crucial oxidative metabolic pathway (fCL: 34.5%). Further attention should be paid to the impact of CYP2B6- and UGT1A9-mediated drug interactions and gene polymorphisms on the exposure and efficacy of HSK3486. SIGNIFICANCE STATEMENT: This research elucidates the major oxidative metabolic pathways of HSK3486 (the formation of three monohydroxylated metabolites: M7-1, M7-2, M7-3) as well as definitive structures and formation pathways of these monohydroxylated metabolites and their glucuronides or sulfate in humans. This research also identifies major metabolizing enzymes responsible for the glucuronidation (UGT1A9) and oxidation (CYP2B6) of HSK3486 and characterizes the mechanism of extrahepatic metabolism. The above information is helpful in guiding the safe use of HSK3486 in the clinic.

Evobrutinib pathway to its major metabolite M463-2 and insights from a biotransformation and DDI perspective

Evobrutinib is a highly selective, covalent, central nervous system-penetrant Bruton's tyrosine kinase (BTK) inhibitor, currently in Phase III trials for the treatment of relapsing multiple sclerosis. One major circulating metabolite of evobrutinib has been previously identified as the racemic dihydro-diol M463-2 (MSC2430422) in a Phase I human mass balance study.Phenotyping experiments were conducted to confirm the metabolic pathway of evobrutinib to M463-2. Ratio of the enantiomers was determined by enantioselective liquid chromatography with tandem mass spectrometry analysis of plasma samples from humans and preclinical species. Drug-drug interaction (DDI) characterisation, evaluation of pharmacological activity on BTK, and off-target screening experiments followed assessing safety of the metabolite.The biotransformation of evobrutinib to M463-2 was determined to be a two-step process with a CYP-mediated oxidation acting to form an epoxide intermediate, which was further hydrolysed by soluble and mitochondrial epoxide hydrolase. Only the (S)-enantiomer was determined to be a major metabolite, the (R)-enantiomer was minor. In vitro studies demonstrated the (S)-enantiomer lacked clinically relevant pharmacological activity, off-target effects and DDIs.The biotransformation of evobrutinib to its major metabolite has been elucidated, with the major (S)-enantiomer being shown to pose no on/off target or DDI risks.

Hepatic Enzymes Relevant to the Disposition of (-)-∆9-Tetrahydrocannabinol (THC) and Its Psychoactive Metabolite, 11-OH-THC

Marijuana use by pregnant women is increasing. To predict developmental risk to the fetus/neonate from such use, in utero fetal exposure to (-)-∆9-tetrahydrocannabinol (THC), the main psychoactive cannabinoid in marijuana and its active psychoactive metabolite, 11-hydroxy-∆9-tetrahydrocannabinol (11-OH-THC), needs to be determined. Since such measurement is not possible, physiologically based pharmacokinetic (PBPK) modeling and simulation can provide an alternative method to estimate fetal exposure to cannabinoids. To do so, pharmacokinetic parameters for the disposition of THC and 11-OH-THC need to be elucidated. Here, we report a first step to estimate these parameters, namely, those related to maternal metabolism of THC/11-OH-THC in human liver microsomes (HLMs) at plasma concentrations observed after smoking marijuana. Using recombinant cytochrome P450 (P450) and UDP-glucuronosyltransferase (UGT) enzymes, CYP1A1, 1A2, 2C9, 2C19, 2D6, 3A4, 3A5, 3A7, and UGT1A9 and UGT2B7 were found to be involved in the disposition of THC/11-OH-THC. Using pooled HLMs, the fraction metabolized (f m) by relevant enzymes was measured using selective enzyme inhibitors, and then adjusted for enzyme cross-inhibition. As previously reported, CYP2C9 was the major enzyme responsible for depletion of THC and formation of 11-OH-THC with f m values of 0.82 ± 0.08 and 0.99 ± 0.10, respectively (mean ± S.D.), while CYP2D6 and CYP2C19 were minor contributors. 11-OH-THC was depleted by UGT and P450 enzymes with f m values of 0.60 ± 0.05 and 0.40 ± 0.05, respectively (mean ± S.D.), with UGT2B7, UGT1A9, CYP2C9, and CYP3A4 as contributors. These mechanistic data represent the first set of drug-dependent parameters necessary to predict maternal-fetal cannabinoid exposure during pregnancy using PBPK modeling.