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7-Methoxy-4-trifluoromethylcoumarin (MFC) has been used extensively in high-throughput screens for the identification of potential CYP2C9 interactions. More recently, additional probes from Invitrogen have been used. Vivid 2C9 Green is the [...]

Research has been conducted on the cytochrome P450cam. The ability of this cytochrome to catalyze the 2-ethylhexanoic acid formation from the 2-ethylexanol has been investigated.

Research was conducted to investigate the detritylation of ethers using iodine-alcohol reagents through an acid-catalyzed reaction. Results demonstrate that 1% solutions of iodine in methanol readily removed trityl and dimethoxytrityl ether groups in good yield and selectively. Trityl groups were transformed to trityl methyl ether and triphenylmethane but triphenylmethanol is also formed when the methanol is wet.

Sotorasib is a first-in-class, targeted covalent inhibitor of Kirsten rat sarcoma viral oncogene homolog (KRAS) G12C approved by the FDA to treat patients with locally advanced or metastatic non-small cell lung cancer with the KRAS G12C mutation. The mass balance, excretion, and metabolism of [ 14 C]-sotorasib was characterized in rats and dogs after a single dose of 60 or 500 mg/kg, respectively. Mean recovery was >90% for both species. Excretion of unchanged sotorasib was a minor pathway in rats, accounting for <4% of administered dose in urine and <7% of administered dose in feces. Approximately 66% of administered dose was recovered in the bile from bile duct cannulated rats as metabolites. Excretion of unchanged sotorasib was the major excretion pathway in dogs, likely caused by solubility-limited absorption. Major pathways of sotorasib biotransformation included glutathione conjugation and oxidative metabolism. In vitro experiments demonstrated that nonenzymatic conjugation (Michael addition) was the primary mechanism of the reaction with glutathione. Extended radioactivity profiles in blood and plasma were observed in rats, but not dogs, after dosing with [ 14 C]-sotorasib. In vitro experiments demonstrated that sotorasib-protein adducts were observed with both rat hemoglobin and serum albumin, explaining the extended radioactivity profile. SIGNIFICANCE STATEMENT: This study characterized the mass balance, excretion, and metabolism of [ 14 C]-sotorasib, a covalent Kirsten rat sarcoma viral oncogene homolog G12C inhibitor, in rats and dogs. Rapid absorption and extensive metabolism of sotorasib was observed in rats, while sotorasib was primarily excreted unchanged in dog feces, likely due to solubility-limited absorption. Protein adducts with rat hemoglobin and serum albumin were characterized, explaining observed extended blood and plasma radioactivity profiles. The primary biotransformation pathway, glutathione conjugation, was mediated through nonenzymatic conjugation., (Copyright © 2022 by The American Society for Pharmacology and Experimental Therapeutics.)

Advances in drug interaction screening have resulted in reduced compound attrition rates due to unfavorable CYP-mediated drug interactions in clinical trials and improved patient safety. A major driver for the success in predicting drug interactions is a better understanding of the biological, chemical or mechanical factors that can impact the prediction of drug interactions in vitro. The enzyme source, probe substrate, accessory proteins and pharmacogenetics can all have profound effects upon the robustness and relevance of data generated with in vitro drug-drug interaction assays. Furthermore, the use of in silico techniques can potentially afford a priori knowledge of drug interaction potential, thus reducing the time and cost associated with drug interaction screening. This review will focus on recent advances in in vitro, in silico and bioanalytical techniques and demonstrate how these tools are currently used to provide effective CYP drug interaction screening in a discovery setting.

Over the past 15 years, a concerted effort has been undertaken by the pharmaceutical industry to reduce the attrition of clinical candidates resulting from undesirable ADME characteristics. Increasing regulatory and competitive pressures demand that pharmaceutical products brought to the market possess pristine safety and drug co-administration profiles for most therapeutic areas. The high-profile withdrawal of drugs such as mibefradil from the market because of unfavorable drug-drug interaction profiles has focused efforts on screening for cytochrome P450 (CYP)-mediated drug interactions early in the discovery paradigm and on predicting the impact of inhibition on the in vivo situation. This paper discusses current practices used to screen for CYP-mediated drug-drug interactions in vitro (inhibition and induction) and how these data are being used to predict whether a clinically relevant drug-drug interaction is likely to occur in vivo.

Studies were designed to investigate the possible mechanisms associated with the kinetic observation of CYP2C9 activation by dapsone and its phase I metabolite, N-hydroxydapsone. Kinetic studies suggested that dapsone activated CYP2C9-mediated flurbiprofen 4(')-hydroxylation by decreasing the K(m) (alpha=0.2) and increasing the V(max) (beta=1.9). Interestingly, N-hydroxydapsone also activated flurbiprofen 4(')-hydroxylation by increasing V(max) (beta=1.5) but had no effect on K(m) (alpha=0.98). To study the effects of these modulators on the binding affinity of flurbiprofen, spectral binding studies were performed. In the presence of dapsone, the spectral binding constant (K(s)) for flurbiprofen was reduced from 14.1 to 2.1 microM, while in the presence of N-hydroxydapsone, the K(s) remained unchanged (14.0 microM), which suggests that dapsone causes an increase in the affinity of flurbiprofen for CYP2C9, whereas N-hydroxydapsone does not. Additionally, stoichiometry measurements under activation conditions in the presence of dapsone resulted in a doubling of both NADPH and oxygen consumption for flurbiprofen 4(')-hydroxylation, with an overall increase in metabolite formation and a decrease in formation of peroxide and excess water. Interestingly, the presence of N-hydroxydapsone generally caused the same effects on stoichiometry as those of flurbiprofen 4(')-hydroxylation but failed to reduce excess water formation, which suggests that, while N-hydroxydapsone activates CYP2C9, it does so less efficiently and possibly through a mechanism different from that of dapsone.