Novel Pathways of Ponatinib Disposition Catalyzed By CYP1A1 Involving Generation of Potentially Toxic Metabolites

Abstract

Ponatinib, a pan-BCR-ABL tyrosine kinase inhibitor for the treatment of chronic myeloid leukemia (CML), causes severe side effects including vascular occlusions, pancreatitis, and liver toxicity, although the underlying mechanisms remain unclear. Modifications of critical proteins through reactive metabolites are thought to be responsible for a number of adverse drug reactions. In vitro metabolite screening of ponatinib with human liver microsomes and glutathione revealed unambiguous signals of ponatinib-glutathione (P-GSH) adducts. Further profiling of human cytochrome P450 (P450) indicated that CYP1A1 was the predominant P450 enzyme driving this reaction. P-GSH conjugate formation paralleled the disappearance of hydroxylated ponatinib metabolites, suggesting the initial reaction was epoxide generation. Mouse glutathione S-transferase p1 (mGstp1) further enhanced P-GSH adduct formation in vitro. Ponatinib pharmacokinetics were determined in vivo in wild-type (WT) mice and mice humanized for CYP1A1/2 and treated with the CYP1A1 inducers 2,3,7,8-tetrachlorodibenzodioxin or 3-methylcholanthrene. Ponatinib exposure was significantly decreased in treated mice compared with controls (7.7- and 2.2-fold for WT and humanized CYP1A1/2, respectively). Interestingly, the P-GSH conjugate was only found in the feces of CYP1A1-induced mice, but not in control animals. Protein adducts were also identified by liquid chromatography–tandem mass spectrometry analysis of mGstp1 tryptic digests. These results indicate that not only could CYP1A1 be involved in ponatinib disposition, which has not been previously reported, but also that electrophilic intermediates resulting from CYP1A1 metabolism in normal tissues may contribute to ponatinib toxicity. These data are consistent with a recent report that CML patients who smoke are at greater risk of disease progression and premature death.

Role of Cytochrome P450 Enzymes in the Metabolic Activation of Tyrosine Kinase Inhibitors

“…Activation of AhR in wild-type mice resulted in increased clearance of ponatinib leading to 87% reduction in AUC and 62% decrease in half-life compared to untreated wild-type mice [22]. Ponatinib clearance was also increased in humanized CYP1A1/2 mice pretreated with 3-MC (54% reduction in AUC and 67% reduction in half-life) compared to untreated humanized mice.…”

The role of hepatic cytochrome P450s in the cytotoxicity of dronedarone

“…CYP1A1 is known to be responsible for the metabolism of pro-carcinogens such as polycyclic aromatic hydrocarbons (Moorthy et al 2015; Shimada 2006). The toxicological and clinical importance of CYP1A1 in drug metabolism warrants further investigation (Howard et al 2017; Lin et al 2017; Ma and Lu 2007) and our results suggest that precaution should be taken in patients with elevated CYP1A1 activity.…”

Identifying the reactive metabolites of tyrosine kinase inhibitors in a comprehensive approach: Implications for drug‐drug interactions and hepatotoxicity

“…GSH adduct formation was observed, with recombinant enzymes, in parallel to the disappearance of hydroxylated ponatinib metabolites, suggesting that the initial reaction was an epoxidation. Moreover, traces of GSH adduct were observed in fecal samples from CYP1A1‐humanized mice after CYP induction . Conversely, Kadi et al did not detect GSH adduct in RLM.…”

“…Ponatinib 68 biotransformation pathways primarily involve hydrolysis of the amide bond in plasma, hydroxylation, and piperazine N ‐demethylation . CYP1A1‐mediated aromatic hydroxylation of ponatinib was shown using recombinant enzyme incubations and mono‐ and dihydroxylated metabolites 69 and 70 were identified in humans (Figure ). GSH adduct formation was observed, with recombinant enzymes, in parallel to the disappearance of hydroxylated ponatinib metabolites, suggesting that the initial reaction was an epoxidation.…”

“…Conversely, Kadi et al did not detect GSH adduct in RLM. Moreover, protein adducts were also detected by LC‐MS, indicating that ponatinib RM are able to generate modified proteins and may contribute to ponatinib toxicity . Although ponatinib 68 contains an alkyne moiety, no evidence of oxirene or ketene generation has been observed.…”