Investigations into the Mechanisms of Pyridine Ring Cleavage in Vismodegib

Abstract

Vismodegib (Erivedge, GDC-0449) is a first-in-class, orally administered small-molecule Hedgehog pathway inhibitor that is approved for the treatment of advanced basal cell carcinoma. Previously, we reported results from preclinical and clinical radiolabeled mass balance studies in which we determined that metabolism is the main route of vismodegib elimination. The metabolites of vismodegib are primarily the result of oxidation followed by glucuronidation. The focus of the current work is to probe the mechanisms of formation of three pyridine ring-cleaved metabolites of vismodegib, mainly M9, M13, and M18, using in vitro, ex vivo liver perfusion and in vivo rat studies. The use of stable-labeled ( 13 C 2 , 15 N)vismodegib on the pyridine ring exhibited that the loss of carbon observed in both M9 and M13 was from the C-6 position of pyridine. Interestingly, the source of the nitrogen atom in the amide of M9 was from the pyridine. Evidence for the formation of aldehyde intermediates was observed using trapping agents as well as 18 O-water. Finally, we conclude that cytochrome P450 is involved in the formation of M9, M13, and M18 and that M3 (the major mono-oxidative metabolite) is not the precursor for the formation of these cleaved products; rather, M18 is the primary cleaved metabolite.

Microbial Degradation of Pyridine: a Complete Pathway inArthrobactersp. Strain 68b Deciphered

“…This gene organization allowed us to assume that the PyrA and PyrE proteins could comprise two-component monooxygenase. Earlier, it was supposed that pyridine degradation pathways might include reductive steps before ring cleavage (28); however, the latest data show that oxygenases are involved in the initial ring cleavage of some pyridine ring-containing compounds (19,24,29). Moreover, the aromatic N-heterocycle ring-cleaving monooxygenases (trigonelline monooxygenase [TgnB] and tetramethylpyrazine monooxygenase [TpdA]) clustered with PyrA in the same branch of the phylogenetic tree (Fig.…”

“…It has been proposed that a similar reaction takes place during chemical oxidation of 1-methyl-and 1-benzyl-3-carbamoylpyridinium in the presence of hydrogen peroxide (41). In addition, the P450-mediated epoxidation/peroxidation with a subsequent ring cleavage of the C-5-C-6 bond of the 2-substituted pyridine ring in vismodegib has been also anticipated (29). Moreover, 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase and 5-pyridoxic acid oxygenase, which cleave a C-C bond in the pyridine ring and which, initially, were assigned as dioxygenases, have been reclassified as flavindependent monooxygenases based on bioinformatics analysis, 18 O 2 experiments, and mechanistic investigations.…”

Rate-Determining and Rate-Limiting Steps in the Clearance and Excretion of a Potent and Selective p21-Activated Kinase Inhibitor: A Case Study of Rapid Hepatic Uptake and Slow Elimination in Rat

“…Isolated perfused liver experiment was carried as described in previous publications [23, 24]. Briefly, adult male Sprague-Dawley rats (350-400 g) were used as liver donors.…”

Synthesis, complex stability and small animal PET imaging of a novel 64Cu-labelled cryptand molecule

“…The determined distribution and clearance pattern in the case of [ 64 Cu]Cu-CryptTM is consistent with the known tendency of pyridine derivatives to be subject of metabolism in liver cells by N-methyltransferases as well as monooxygenase cytochrome P450. [27][28][29][30] Moreover, the predominantly hepatobiliary excretion pathway of [ 64 Cu]Cu-CryptTM also leads to exposure to liver enzyme superoxide dismutase as a potential site for transchelation of 64 Cu 2+ resulting in accumulation and retention of radioactivity in the liver over time. This observation is also consistent with the results of the challenge experiments in this work (see Table 2 molecules possessing a more favourable tri-pyridyl/tri-amine donor group set to allow formation of more kinetically inert 64 Cu-cryptates.…”