Mercaptopurine (6-MP)

General information

Class/mechanism: Purine analog of adenine and hypoxanthine, antimetabolite that interferes with DNA synthesis. Mercaptopurine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is converted to thioinosinic acid (TIMP). TIMP inhibits reactions that typically involve inosinic acid (IMP), such as its conversion to xanthylic acid (XMP) and adenylic acid (AMP) via adenylosuccinate (SAMP). TIMP is also converted to 6-methylthioinosinate (MTIMP); TIMP and MTIMP have been observed to inhibit glutamine-5-phosphoribosylpyrophosphate amidotransferase, which is an early enzyme in the de novo pathway of purine ribonucleotide synthesis. Mercaptopurine is structurally and functionally similar to Thioguanine (Tabloid).
Route: PO
Extravasation: n/a

For conciseness and simplicity, HemOnc.org currently will focus on treatment regimens and not list information such as: renal/hepatic dose adjustments, metabolism (including CYP450), excretion, monitoring parameters (although this will be considered for checklists), or manufacturer. Instead, for the most current information, please refer to your preferred pharmacopeias such as Micromedex, Lexicomp, UpToDate (courtesy of Lexicomp), or the prescribing information.

Diseases for which it is used

• Acute myeloid leukemia
• Acute promyelocytic leukemia
• B-cell acute lymphoblastic leukemia
• CNS leukemia
• Langerhans cell histiocytosis
• T-cell acute lymphoblastic leukemia

Diseases for which it was used

• Gestational trophoblastic neoplasia

Patient drug information

• Mercaptopurine (Purinethol) patient drug information (Chemocare)
• Mercaptopurine (Purinethol) patient drug information (UpToDate)

History of changes in FDA indication

• 9/11/1953: Initial FDA approval
• 1/10/2003 (oldest label on [email protected]): Indicated for remission induction and maintenance therapy of acute lymphatic leukemia. (No supporting studies are cited)
• 4/28/2014: Purixan (mercaptopurine oral suspension formulation) FDA approved for the treatment of patients with acute lymphoblastic leukemia (ALL) as a component of a combination maintenance therapy regimen. (No supporting studies are cited)

Also known as

• Generic names: 6-MP, 6-Mercaptopurine
• Brand names: Purinethol, Purixan (oral suspension formulation)