Mercaptopurine

Mercaptopurine is an oral purine antimetabolite that disrupts nucleotide synthesis and function. It is used mainly in maintenance treatment of acute lymphoblastic leukemia and in some autoimmune diseases.

Thiopurine metabolism: The enzymatic conversion of thiopurine drugs into active and inactive metabolites. Mercaptopurine’s clinical effects depend on competing metabolic routes that produce active nucleotides or deactivate the drug.
Acute lymphoblastic leukemia: A cancer of immature lymphoid cells that accumulate in the bone marrow and blood. Mercaptopurine is a standard component of prolonged maintenance therapy for this leukemia.
Purine: A nitrogen-containing molecular framework found in nucleic acids and many cellular metabolites. Mercaptopurine is structurally related to purines, the molecules it mimics.
Thioguanine: A thiopurine antimetabolite used in some leukemia regimens that forms active thioguanine nucleotides. It shares active metabolites with mercaptopurine but differs in metabolism, dosing, and toxicity profile.
Thioguanine nucleotides: Nucleotide metabolites of thiopurines that can disrupt DNA and RNA synthesis and signaling. These metabolites are among the main intracellular products responsible for mercaptopurine’s antileukemic action.
Maintenance therapy: Long-term, lower-intensity treatment given to keep a disease in remission or prevent its return. Daily mercaptopurine helps sustain remission during the maintenance phase of leukemia treatment.
Nucleotide: A molecular unit composed of a nitrogenous base, a sugar, and one or more phosphate groups. Mercaptopurine’s active metabolites resemble purine nucleotides used in DNA and RNA.
Methotrexate: An antifolate drug that inhibits dihydrofolate reductase and other folate-dependent enzymes. It is commonly paired with mercaptopurine in leukemia maintenance but blocks a different metabolic pathway.
Thiopurine S-methyltransferase: An enzyme that methylates thiopurine drugs and metabolites, influencing their activity and toxicity. Its activity changes how much mercaptopurine enters competing metabolic pathways.
Inflammatory bowel disease: A group of chronic inflammatory disorders of the digestive tract, chiefly Crohn’s disease and ulcerative colitis. Mercaptopurine has been used as an immunosuppressant in selected cases, though onset is slow.

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Gertrude B. ElionBroader topic: Elion and George Hitchings developed this early leukemia treatment by targeting purine metabolism.