Pharmacokinetics and metabolism of mirogabalin, a novel α2δ ligand, in rats and monkeys.

The purpose of this study was to investigate the pharmacokinetic behaviour of mirogabalin in rats and monkeys.Pharmacokinetic parameters of mirogabalin after its oral and intravenous administration were determined. Distribution study, mass balance study, and metabolite identification were also conducted after the oral administration of [14C]mirogabalin.Plasma exposure (Cmax and AUCinf) increased dose-proportionally after the oral administration of mirogabalin at 1, 3, and 10 mg/kg to rats and monkeys. Mean total body clearance (CLtot) after intravenous administration at 3 mg/kg was 13.5 mL/min/kg in rats and 9.02 mL/min/kg in monkeys, and absolute bioavailability at 3 mg/kg was 97.6% in rats and 85.2% in monkeys. There was a greater recovery of radioactivity in urine than that in faeces after the oral administration of [14C]mirogabalin. The main radioactive component in the plasma, urine, and faeces was mirogabalin. A204-4455 (lactam form), an oxidised metabolite of mirogabalin, mirogabalin N-glucuronide and O-glucuronide of oxidised A204-4455 were detected as minor components in monkeys and rats.Mirogabalin administered orally was almost completely eliminated via urinary excretion. A small part of the orally administered dose of mirogabalin was metabolised via glucuronidation at the amine and carboxylic acid moiety and oxidation as the primary metabolic pathway.

Estimation of fraction of drug metabolism by a single UDP-glucuronosyl transferase enzyme using relative expression factor.

The estimation of the contributions of UDP-glucuronosyl transferase (UGT) isoforms to the overall metabolism still suffers from technical difficulties due to limited information on enzyme levels in recombinant systems and specific inhibitors, unlike the case for cytochrome P450s (CYPs). The protein expression levels of UGT in both recombinant system microsomes (RM) and human liver microsomes (HLM) were quantified using liquid chromatography-tandem mass spectrometry, and the relative expression factor (REF) value of HLM to recombinant microsomes was estimated to evaluate the fractions of drug metabolism by a single UGT enzyme (fmUGT) of UGT substrates. The REF values of UGT1A1, UGT1A3, UGT1A9, UGT2B4, UGT2B7, and UGT2B17 were 0.228, 0.0714, 0.0665, 0.420, 0.118, and 0.0442, respectively. fmUGTs in HLM were estimated for several typical UGT substrates utilizing these values and metabolic clearances in RM. These values were comparable to the reported values estimated by various methods. This study provided useful information on REF values, which promote a robust estimation of fmUGT values for UGT substrates when evaluating the contribution of UGT isoforms to total metabolic clearance.

Bioactivation of loxoprofen to a pharmacologically active metabolite and its disposition kinetics in human skin.

Loxoprofen (LX) is a prodrug-type non-steroidal anti-inflammatory drug which is used not only as an oral drug but also as a transdermal formulation. As a pharmacologically active metabolite, the trans-alcohol form of LX (trans-OH form) is generated after oral administration to humans. The objectives of this study were to evaluate the generation of the trans-OH form in human in vitro skin and to identify the predominant enzyme for its generation. In the permeation and metabolism study using human in vitro skin, both the permeation of LX and the formation of the trans-OH form increased in a time- and dose-dependent manner after the application of LX gel to the skin. In addition, the characteristics of permeation and metabolism of both LX and the trans-OH form were examined by a mathematical pharmacokinetic model. The Km value was calculated to be 10.3 mm in the human in vitro skin. The predominant enzyme which generates the trans-OH form in human whole skin was identified to be carbonyl reductase 1 (CBR1) by immunodepletion using the anti-human CBR1 antibody. The results of the enzyme kinetic study using the recombinant human CBR1 protein demonstrated that the Km and Vmax values were 7.30 mm and 402 nmol/min/mg protein, respectively. In addition, it was found that no unknown metabolites were generated in the human in vitro skin. This is the first report in which LX is bioactivated to the trans-OH form in human skin by CBR1. Copyright © 2015 John Wiley & Sons, Ltd.

Raludotatug Deruxtecan, a CDH6-Targeting Antibody-Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models.

Cadherin-6 (CDH6) is expressed in several cancer types, but no CDH6-targeted therapy is currently clinically available. Here, we generated raludotatug deruxtecan (R-DXd; DS-6000), a novel CDH6-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and evaluated its properties, pharmacologic activities, and safety profile. In vitro pharmacologic activities and the mechanisms of action of R-DXd were assessed in serous-type ovarian cancer and renal cell carcinoma cell lines. In vivo pharmacologic activities were evaluated with several human cancer cell lines and patient-derived xenograft mouse models. The safety profile in cynomolgus monkeys was also assessed. R-DXd exhibited CDH6 expression-dependent cell growth-inhibitory activity and induced tumor regression in xenograft models. In this process, R-DXd specifically bound to CDH6, was internalized into cancer cells, and then translocated to the lysosome. The DXd released from R-DXd induced the phosphorylation of Chk1, a DNA damage marker, and cleaved caspase-3, an apoptosis marker, in cancer cells. It was also confirmed that the DXd payload had a bystander effect, passing through the cell membrane and impacting surrounding cells. The safety profile of R-DXd was favorable and the highest non-severely toxic dose was 30 mg/kg in cynomolgus monkeys. R-DXd demonstrated potent antitumor activity against CDH6-expressing tumors in mice and an acceptable safety profile in monkeys. These findings indicate the potential of R-DXd as a new treatment option for patients with CDH6-expressing serous-type ovarian cancer and renal cell carcinoma in a clinical setting.

Species differences between rats and primates (humans and monkeys) in complex cleavage pathways of DS-8500a characterized by 14C-ADME studies in humans and monkeys after administration of two radiolabeled compounds and in vitro studies.

Our previous study in rats demonstrated that the metabolic pathways of DS-8500a, a novel GPR119 agonist, include cleavage pathways: reductive cleavage of the oxadiazole ring in the liver and hydrolysis of the amide side chain. In the present study, in vivo metabolic profiling in humans and monkeys after the oral administration of two 14C-labeled compounds was performed to investigate species differences of the cleavage pathways. In monkeys, the oxadiazole ring-cleaved metabolites were mainly detected in feces, but not observed in bile, unlike in rats, suggesting that the reductive ring-opening metabolism occurs in the gastrointestinal tract. In vitro incubation with enterobacterial culture media demonstrated that the reductive cleavage of the oxadiazole ring in humans and monkeys was considerably faster than that in rats. The other cleavage metabolite (M20), produced via hydrolysis of the amide side chain, was detected as the major plasma metabolite in humans and monkeys, and its subsequent metabolite (M21) was excreted in feces, whereas M21 was not a major component in rats, indicating a notable species difference in the amide hydrolysis. In conclusion, this study comprehensively revealed the pronounced species difference of the cleavage pathways: reductive ring-opening by intestinal microflora and liver, and amide hydrolysis.

Datopotamab Deruxtecan, a Novel TROP2-directed Antibody-drug Conjugate, Demonstrates Potent Antitumor Activity by Efficient Drug Delivery to Tumor Cells.

Trophoblast cell surface antigen 2 (TROP2) is highly expressed on various epithelial tumors and correlates with poor prognosis. We developed the novel TROP2-directed antibody-drug conjugate (ADC), datopotamab deruxtecan (Dato-DXd, DS-1062a), with a potent DNA topoisomerase I inhibitor (DXd), and evaluated its antitumor activity and safety profiles in preclinical models.The pharmacologic activity and mechanism of action of Dato-DXd were investigated in several human cancer cell lines and xenograft mouse models including patient-derived xenograft (PDX) models. Safety profiles were also assessed in rats and cynomolgus monkeys.Dato-DXd bound specifically to TROP2 and was internalized into tumor cells followed by intracellular trafficking to lysosome and DXd release, which induced DNA damage and apoptosis in TROP2-expressing tumor cells in vitro. Dato-DXd exhibited in vivo antitumor activity with DNA damage induced by the accumulated DXd in TROP2-expressing xenograft tumors, but neither isotype control IgG-ADC nor anti-TROP2 antibody had this effect. Dato-DXd also showed potent antitumor activity with tumor regression in several TROP2-expressing xenograft tumors including NSCLC PDX models. Safety profiles of Dato-DXd in rats and cynomolgus monkeys were acceptable.Dato-DXd demonstrated potent antitumor activity against TROP2-expressing tumors by efficient payload delivery into tumors and acceptable safety profiles in preclinical models. These results suggest Dato-DXd could be a valuable treatment option for patients with TROP2-expressing tumors in the clinical setting.

CYP2D6-Mediated metabolism of a novel acyl coenzyme A:cholesterol acyltransferase inhibitor, pactimibe, and its unique plasma metabolite, R-125528.

Pactimibe sulfate is a novel acyl coenzyme A:cholesterol acyltransferase inhibitor. We conducted metabolic studies of pactimibe and its plasma metabolite, R-125528. Pactimibe had multiple metabolic pathways including indolin oxidation to form R-125528, omega-1 oxidation, N-dealkylation, and glucuronidation. Among them, the indolin oxidation and the omega-1 oxidation were dominant and were mainly catalyzed by CYP3A4 and CYP2D6, respectively. The intrinsic clearance (CL(int)) values for these pathways in human hepatic microsomes were 0.63 and 0.76 microl/min/mg-protein, respectively. On the other hand, the metabolic reaction for R-125528 was restricted. It was demonstrated that omega-1 oxidation was the only pathway that could eliminate R-125528 from the systemic circulation. To our surprise, only CYP2D6-expressing microsomes could catalyze the reaction, and omega-1 oxidation was strongly correlated with the CYP2D6 marker reaction, dextromethorphan O-demethylation (r(2) = 0.90), in human hepatic microsomes. Although R-125528 is an atypical substrate for CYP2D6 because of its acidity, the K(m) value was 1.8 microM for the reaction in human hepatic microsomes and the CL(int) value was as high as 75.0 microl/min/mg-protein. These results suggested that the systemic clearance of R-125528 was highly dependent on CYP2D6 activity and that several studies with CYP2D6 including drug-drug interaction and polymorphism sensitivity should be performed during development from the viewpoint of metabolite safety assessment. The finding that R-125528, an acidic compound devoid of basic nitrogen, was a good substrate for CYP2D6 raised a question about previously reported CYP2D6 models based on a critical electrostatic interaction with Asp(301) and/or Glu(216).