Absorption, Metabolism, and Excretion of [14C]-Tolebrutinib After Oral Administration in Humans, Contribution of the Metabolites to Pharmacological Activity.

BACKGROUND AND OBJECTIVE: Tolebrutinib is a covalent inhibitor of Bruton's tyrosine kinase, an enzyme expressed in B lymphocytes and myeloid cells including microglia, which are thought to be major drivers of inflammation in multiple sclerosis. This excretion balance and metabolism study evaluated the metabolite profile of tolebrutinib in healthy male volunteers. METHODS: Six healthy volunteers received a 60-mg oral dose of [14C]-tolebrutinib, and metabolite profiling of 14C-labeled metabolites was performed using a combination of liquid chromatography, mass spectrometry, and radioactivity assay methods. RESULTS: Tolebrutinib was rapidly and completely absorbed from the gastrointestinal tract, followed by rapid and extensive metabolism. Excretion via feces was the major elimination pathway of the administered radioactivity (78%). Tolebrutinib was highly metabolized, with 19 metabolites identified in human plasma. Phase 1 biotransformations were primarily responsible for the circulating metabolites in plasma. Seven metabolites that achieved exposure in plasma similar to or higher than the parent compound were characterized biochemically for inhibition of Bruton's tyrosine kinase activity. Metabolite M8 exceeded the exposure threshold of 10% (18%) of the total radioactivity but had little if any pharmacological activity. Metabolite M2 (4% of circulating radioactivity) retained the ability to irreversibly and potently inhibit Bruton's tyrosine kinase in vitro, similar to the parent compound. Tolebrutinib and metabolite M2 had short (3.5-h) half-lives but durable pharmacodynamic effects as expected for an irreversible antagonist. CONCLUSIONS: Tolebrutinib was extensively metabolized to multiple metabolites. The hydroxylated metabolite M2 demonstrated similar inhibitory potency toward Bruton's tyrosine kinase as the parent compound. Both tolebrutinib and metabolite M2 likely contributed to pharmacological activity in vivo.

Preclinical in vitro and in vivo pharmacokinetic properties of danicamtiv, a new targeted myosin activator for the treatment of dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a disease of the myocardium defined by left ventricular enlargement and systolic dysfunction leading to heart failure. Danicamtiv, a new targeted myosin activator designed for the treatment of DCM, was characterised in in vitro and in vivo preclinical studies. Danicamtiv human hepatic clearance was predicted to be 0.5 mL/min/kg from in vitro metabolic stability studies in human hepatocytes. For human, plasma protein binding was moderate with a fraction unbound of 0.16, whole blood-to-plasma partitioning ratio was 0.8, and danicamtiv showed high permeability and no efflux in a Caco-2 cell line. Danicamtiv metabolism pathways in vitro included CYP-mediated amide-cleavage, N-demethylation, as well as isoxazole- and piperidine-ring-opening. Danicamtiv clearance in vivo was low across species with 15.5, 15.3, 1.6, and 5.7 mL/min/kg in mouse, rat, dog, and monkey, respectively. Volume of distribution ranged from 0.24 L/kg in mouse to 1.7 L/kg in rat. Oral bioavailability ranged from 26% in mouse to 108% in dog. Simple allometric scaling prediction of human plasma clearance, volume of distribution, and half-life was 0.64 mL/min/kg, 0.98 L/kg, and 17.7 h, respectively. Danicamtiv preclinical attributes and predicted human pharmacokinetics supported advancement toward clinical development.

In vitro and in vivo pharmacokinetic characterization of mavacamten, a first-in-class small molecule allosteric modulator of beta cardiac myosin.

Mavacamten is a small molecule modulator of cardiac myosin designed as an orally administered drug for the treatment of patients with hypertrophic cardiomyopathy. The current study objectives were to assess the preclinical pharmacokinetics of mavacamten for the prediction of human dosing and to establish the potential need for clinical pharmacokinetic studies characterizing drug-drug interaction potential. Mavacamten does not inhibit CYP enzymes, but at high concentrations relative to anticipated therapeutic concentrations induces CYP2B6 and CYP3A4 enzymes in vitro. Mavacamten showed high permeability and low efflux transport across Caco-2 cell membranes. In human hepatocytes, mavacamten was not a substrate for drug transporters OATP, OCT and NTCP. Mavacamten was determined to have minimal drug-drug interaction risk. In vitro mavacamten metabolite profiles included phase I- and phase II-mediated metabolism cross-species. Major pathways included aromatic hydroxylation (M1), aliphatic hydroxylation (M2); N-dealkylation (M6), and glucuronidation of the M1-metabolite (M4). Reaction phenotyping revealed CYPs 2C19 and 3A4/3A5 predominating. Mavacamten demonstrated low clearance, high volume of distribution, long terminal elimination half-life and excellent oral bioavailability cross-species. Simple four-species allometric scaling led to predicted plasma clearance, volume of distribution and half-life of 0.51 mL/min/kg, 9.5 L/kg and 9 days, respectively, in human.

IMI - oral biopharmaceutics tools project - evaluation of bottom-up PBPK prediction success part 1: Characterisation of the OrBiTo database of compounds.

Predicting oral bioavailability (Foral) is of importance for estimating systemic exposure of orally administered drugs. Physiologically-based pharmacokinetic (PBPK) modelling and simulation have been applied extensively in biopharmaceutics recently. The Oral Biopharmaceutical Tools (OrBiTo) project (Innovative Medicines Initiative) aims to develop and improve upon biopharmaceutical tools, including PBPK absorption models. A large-scale evaluation of PBPK models may be considered the first step. Here we characterise the OrBiTo active pharmaceutical ingredient (API) database for use in a large-scale simulation study. The OrBiTo database comprised 83 APIs and 1475 study arms. The database displayed a median logP of 3.60 (2.40-4.58), human blood-to-plasma ratio of 0.62 (0.57-0.71), and fraction unbound in plasma of 0.05 (0.01-0.17). The database mainly consisted of basic compounds (48.19%) and Biopharmaceutics Classification System class II compounds (55.81%). Median human intravenous clearance was 16.9L/h (interquartile range: 11.6-43.6L/h; n=23), volume of distribution was 80.8L (54.5-239L; n=23). The majority of oral formulations were immediate release (IR: 87.6%). Human Foral displayed a median of 0.415 (0.203-0.724; n=22) for IR formulations. The OrBiTo database was found to be largely representative of previously published datasets. 43 of the APIs were found to satisfy the minimum inclusion criteria for the simulation exercise, and many of these have significant gaps of other key parameters, which could potentially impact the interpretability of the simulation outcome. However, the OrBiTo simulation exercise represents a unique opportunity to perform a large-scale evaluation of the PBPK approach to predicting oral biopharmaceutics.

Oral delivery of diabetes peptides - Comparing standard formulations incorporating functional excipients and nanotechnologies in the translational context.

While some orally delivered diabetes peptides are moving to late development with standard formulations incorporating functional excipients, the demonstration of the value of nanotechnology in clinic is still at an early stage. The goal of this review is to compare these two drug delivery approaches from a physico-chemical and a biopharmaceutical standpoint in an attempt to define how nanotechnology-based products can be differentiated from standard oral dosage forms for oral bioavailability of diabetes peptides. Points to consider in a translational approach are outlined to seize the opportunities offered by a better understanding of both the intestinal barrier and of nano-carriers designed for oral delivery.

PBPK modeling of irbesartan: incorporation of hepatic uptake.

Physiological based pharmacokinetic (PBPK) modeling is now commonly used in drug development to integrate human or animal physiological data in order to predict pharmacokinetic profiles. The aim of this work was to construct and refine a PBPK model of irbesartan taking into account its active uptake via OATP1B1/B3 in order to predict more accurately its pharmacokinetic profile using Simcyp(®). The activity and expression of the human hepatocyte transporters OATP1B1 and OATP1B3 were studied. The relative activity factors (RAFs) for OATP1B1 and OATP1B3 transporters were calculated from intrinsic clearances obtained by concentration dependent uptake experiments in human hepatocytes and HEK overexpressing cells: RAF1B1 using estrone-3-sulfate and pitavastatine clearances, and RAF1B3 using cholecystokinine octapeptide (CCK-8) clearances. The relative expression factor (REF) was calculated by comparing immunoblotting of hepatocytes (REFHH ) or tissues (REFtissue) with those of overexpressing HEK cells for each transporter. These scaling factors were applied in a PBPK model of irbesartan using the Simcyp® simulator. Pharmacokinetic simulation using REFHH (1.82 for OATP1B1, 8.03 for OATP1B3) as an extrapolation factor was the closest to the human clinical pharmacokinetic profile of irbesartan. These investigations show the importance of integrating the contribution of the active uptake of a drug in the liver to improve PBPK modeling.

Identification of metabolic pathways and enzyme systems involved in the in vitro human hepatic metabolism of dronedarone, a potent new oral antiarrhythmic drug.

The in vitro metabolism of dronedarone and its major metabolites has been studied in human liver microsomes and cryopreserved hepatocytes in primary culture through the use of specific or total cytochrome P450 (CYP) and monoamine oxidase (MAO) inhibitors. The identification of the main metabolites and enzymes participating in their metabolism was also elucidated by using rhCYP, rhMAO, flavin monooxygenases (rhFMO) and UDP-glucuronosyltransferases (rhUGT) and liquid chromatography/tandem mass spectrometry (LC/MS-MS) analysis. Dronedarone was extensively metabolized in human hepatocytes with a metabolic clearance being almost completely inhibited (98 ± 2%) by 1-aminobenzotriazole. Ketoconazole also inhibited dronedarone metabolism by 89 ± 7%, demonstrating the crucial role of CYP3A in its metabolism. CYP3A isoforms mostly contributed to N-debutylation while hydroxylation on the butyl-benzofuran moiety was catalyzed by CYP2D6. However, hydroxylation on the dibutylamine moiety did not appear to be CYP-dependent. N-debutyl-dronedarone was less rapidly metabolized than dronedarone, the major metabolic pathway being catalyzed by MAO-A to form propanoic acid-dronedarone and phenol-dronedarone. Propanoic acid-dronedarone was metabolized at a similar rate to that of N-debutyl-dronedarone and was predominantly hydroxylated by CYP2C8 and CYP1A1. Phenol-dronedarone was extensively glucuronidated while C-dealkyl-dronedarone was metabolized at a slow rate. The evaluation of the systemic clearance of each metabolic process together with the identification of both the major metabolites and predominant enzyme systems and isoforms involved in the formation and subsequent metabolism of these metabolites has enhanced the overall understanding of metabolism of dronedarone in humans.