Mercaptopurine

Mercaptopurine (also known as 6-mercaptopurine or 6-MP) is an oral antimetabolite used in cancer chemotherapy. It belongs to the class of purine analogs and is primarily used in the treatment of certain leukemias. It interferes with DNA and RNA synthesis, thereby inhibiting the growth of rapidly dividing cancer cells.

Mechanism of Action

Mercaptopurine acts by:

• Converting into active metabolites (thioinosinic acid) inside cells
• Inhibiting purine nucleotide synthesis
• Incorporating into DNA and RNA, leading to faulty nucleic acid formation
• Suppressing proliferation of rapidly dividing cells, especially leukemic cells

Its metabolism is significantly affected by the enzyme thiopurine methyltransferase (TPMT).

Uses

Mercaptopurine is indicated for:

• Acute Lymphoblastic Leukemia (ALL) (mainly in maintenance therapy)
• Occasionally used in other hematological malignancies
• Also used (off-label) in some autoimmune conditions (e.g., inflammatory bowel disease)

Adverse Effects

Common Side Effects:

• Nausea and vomiting
• Loss of appetite
• Fatigue