Evaluation of species differences in the metabolism of the selective NaV1.7 inhibitor DS-1971a, a mixed substrate of cytochrome P450 and aldehyde oxidase.

Nonclinical metabolite profiling of DS-1971a, a potent selective NaV1.7 inhibitor, was performed to predict human metabolites.After the oral administration of radiolabelled DS-1971a, the predominant metabolite in mouse plasma was M4, a monoxide at the pyrimidine ring, while the major metabolites with the first and second highest exposure in monkey plasma were M2, a monoxide at the cyclohexane ring, and M11, a demethylated pyrazole metabolite.Incubation studies with liver cytosolic and microsomal fractions in the absence or presence of NADPH indicated that the metabolising enzyme responsible for M4 formation was aldehyde oxidase (AO), while cytochrome P450s (P450s) were responsible for M2 and M11 formation. These results suggest that DS-1971a is a substrate for both AO and P450.When DS-1971a was incubated with liver S9 fractions and NADPH, the most abundant metabolites were M4 in mice, and M2 and M11 in monkeys, indicating that the results of in vitro incubation studies could provide information reflecting the in vivo plasma metabolite profiles in mice and monkeys. The results obtained from the incubation with the human liver S9 fraction and NADPH suggested that a major circulating metabolite in humans is M1, a regioisomer of M2.

SAR inspired by aldehyde oxidase (AO) metabolism: Discovery of novel, CNS penetrant tricyclic M4 PAMs.

This letter describes progress towards an M4 PAM preclinical candidate inspired by an unexpected aldehyde oxidase (AO) metabolite of a novel, CNS penetrant thieno[2,3-c]pyridine core to an equipotent, non-CNS penetrant thieno[2,3-c]pyrdin-7(6H)-one core. Medicinal chemistry design efforts yielded two novel tricyclic cores that enhanced M4 PAM potency, regained CNS penetration, displayed favorable DMPK properties and afforded robust in vivo efficacy in reversing amphetamine-induced hyperlocomotion in rats.

Identification and human exposure prediction of two aldehyde oxidase-mediated metabolites of a methylquinoline-containing drug candidate.

1. Aldehyde oxidase (AO enzymes)-mediated oxidation predominantly occurs at a carbon atom adjacent to the nitrogen on aromatic azaheterocycles. In the current report, we identified that AO enzymes oxidation took place at both the C-2 and C-4 positions of the methylquinoline moiety of Compound A based on data from mass spectrometric analysis, AO enzymes "litmus" test, and comparison with authentic standards. 2. To assess the potential for inadequate coverage for these two AO enzyme-mediated metabolites in nonclinical safety studies, given concerns due to differences in AO enzymes expression between preclinical species and humans, the human circulating levels of the two AO enzyme-mediated metabolites were predicted prospectively using in vitro and in vivo models. Both formation clearance and elimination clearance of the two metabolites were predicted based on in vitro to in vivo correlation and comparison with in vivo data from rats. 3. The result showed that the 4-OH metabolite of Compound A would account for less than 3% of the total drug-related exposure in human plasma, while the exposure to the 2-oxo metabolite would be relatively high (∼70%). 4. The predicted human exposure levels for the two metabolites are in similar ranges as those observed in monkeys. These data taken together support the advancement to clinical development of Compound A.

Molybdenum's Role as an Essential Element in Enzymes Catabolizing Redox Reactions: A Review.

Molybdenum (Mo) is an essential element for human life, acting as a cofactor in various enzymes crucial for metabolic homeostasis. This review provides a comprehensive insight into the latest advances in research on molybdenum-containing enzymes and their clinical significance. One of these enzymes is xanthine oxidase (XO), which plays a pivotal role in purine catabolism, generating reactive oxygen species (ROS) capable of inducing oxidative stress and subsequent organ dysfunction. Elevated XO activity is associated with liver pathologies such as non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC). Aldehyde oxidases (AOs) are also molybdenum-containing enzymes that, similar to XO, participate in drug metabolism, with notable roles in the oxidation of various substrates. However, beneath its apparent efficacy, AOs' inhibition may impact drug effectiveness and contribute to liver damage induced by hepatotoxins. Another notable molybdenum-enzyme is sulfite oxidase (SOX), which catalyzes the conversion of sulfite to sulfate, crucial for the degradation of sulfur-containing amino acids. Recent research highlights SOX's potential as a diagnostic marker for HCC, offering promising sensitivity and specificity in distinguishing cancerous lesions. The newest member of molybdenum-containing enzymes is mitochondrial amidoxime-reducing component (mARC), involved in drug metabolism and detoxification reactions. Emerging evidence suggests its involvement in liver pathologies such as HCC and NAFLD, indicating its potential as a therapeutic target. Overall, understanding the roles of molybdenum-containing enzymes in human physiology and disease pathology is essential for advancing diagnostic and therapeutic strategies for various health conditions, particularly those related to liver dysfunction. Further research into the molecular mechanisms underlying these enzymes' functions could lead to novel treatments and improved patient outcomes.

Metabolism of xenobiotics by aldehyde oxidase.

Aldehyde oxidase (AO) is a cytosolic molybdoflavoprotein whose contribution to the metabolism and clearance of xenobiotics-containing heterocyclic rings has attracted increased interest in recent years. This unit details methods for identification and confirmation of AO as a metabolic pathway as well as a method for estimating clearance of compounds that are AO substrates.

Changes in the abscisic acid levels and related gene expression during fruit development and ripening in bilberry (Vaccinium myrtillus L.).

Abscisic acid (ABA) is a natural plant hormone playing an important role in many physiological processes including fruit ripening and is also recently found to be potential for biomedical applications. This study was aimed to measure ABA levels and its biosynthesis in bilberry (Vaccinium myrtillus L.), which is one of the best sources of anthocyanins. Five ABA biosynthetic genes were isolated from bilberry and their expression profiles were studied in bilberry tissues, particularly during berry development. The level of ABA highly increased at the onset of bilberry fruit ripening, at the stage when expression of anthocyanin biosynthetic genes, chalcone synthase (VmCHS) and anthocyanidin synthase (VmANS), also increased. In fully ripe berries and leaves, ABA levels were lower but none was detected in bilberry stem or rhizome. The expression of 9-cis-epoxycarotenoid dioxygenase (VmNCED1) and putative neoxanthin synthase (VmNSY) was high in berry tissues and their expression increased markedly at the onset of berry ripening along with the accumulation of ABA. In contrast, the expression of zeaxanthin epoxidase (VmZEP), short-chain dehydrogenase/reductase (VmSDR/ABA2) and aldehyde oxidase (VmAO) were most highly associated with leaf tissues with no obvious relation to ABA content during berry development. The obtained results indicate that the ABA biosynthesis may play an important role in the regulation of ripening of non-climacteric bilberry fruits through transcriptional regulation of key ABA biosynthetic genes.