Etoposide metabolic enzymes (CYP3A4/UGT1A1)

Etoposide metabolic enzymes are a group of proteins responsible for the biotransformation and elimination of the chemotherapeutic agent etoposide. The primary enzymes involved in its phase I metabolism are Cytochrome P450 3A4 (CYP3A4) and 3A5 (CYP3A5), which catalyze the O-demethylation of etoposide to form its catechol metabolite (Wen et al., 2012, PubMed: 22403123). This catechol can be further oxidized by enzymes such as myeloperoxidase (MPO) and prostaglandin H synthase into reactive quinone species, which are highly electrophilic and capable of causing the DNA damage associated with therapy-related secondary leukemias (Zhuo et al., 2004, PubMed: 15155820). Phase II metabolism is primarily handled by UDP-glucuronosyltransferase 1-1 (UGT1A1), which conjugates etoposide and its catechol with glucuronic acid to facilitate biliary and renal excretion (Wen et al., 2007, PubMed: 17565008). Because these enzymes dictate the balance between detoxification and the formation of toxic intermediates, their activity—influenced by genetic polymorphisms and drug-drug interactions—is a major determinant of etoposide's safety and efficacy profile.

Other names

Etoposide-metabolizing enzymesCytochrome P450 3A4UDP-glucuronosyltransferase 1-1Cytochrome P450 3A5Etoposide catechol-forming enzymes

These enzymes facilitate the biotransformation of etoposide through oxidative and conjugative pathways. CYP3A4 and CYP3A5 convert etoposide to a catechol metabolite, which can be further activated to reactive quinones, while UGT1A1 mediates the glucuronidation of etoposide and its metabolites to facilitate excretion.