Systemic 6-mercaptopurine (6-MP) pharmacokinetic pathway (6-MP PK pathway)

The systemic 6-mercaptopurine (6-MP) pharmacokinetic pathway is the metabolic network responsible for the biotransformation of the thiopurine prodrug 6-MP into its active and inactive metabolites. 6-MP is primarily used in the treatment of acute lymphoblastic leukemia and inflammatory bowel diseases, where it acts as a purine antimetabolite. The pathway involves the activation of 6-MP by hypoxanthine-guanine phosphoribosyltransferase (HPRT1) into thioguanine nucleotides (TGNs), which exert cytotoxic effects by incorporating into DNA and RNA, leading to cell cycle arrest and apoptosis (StatPearls, 2023). Parallel catabolic pathways involve the inactivation of 6-MP by thiopurine S-methyltransferase (TPMT) and xanthine oxidase (XDH), which produce 6-methylmercaptopurine and 6-thiouric acid, respectively (PharmGKB, 2021). Genetic polymorphisms in enzymes like TPMT and NUDT15 are critical clinical factors, as they significantly alter the balance between active and toxic metabolites, potentially leading to life-threatening myelosuppression (PubMed, 2020). Consequently, therapeutic drug monitoring of TGN and 6-MMP levels, along with pharmacogenetic testing, is standard practice to optimize dosing and minimize systemic toxicity (FDA, 2022).

Other names

6-mercaptopurine metabolism pathwayThiopurine metabolic pathway6-MP metabolic pathwayAzathioprine/6-mercaptopurine pathway

6-mercaptopurine is a purine analog that acts as an antimetabolite; it is converted into thioguanine nucleotides (TGNs) which incorporate into DNA and RNA, causing strand breaks and inhibiting de novo purine synthesis (StatPearls, 2023).