6-Mercaptopurine (hydrate)

6-Mercaptopurine (6-MP) is an inhibitor of purine synthesis and interconversion.{36297} It is rapidly converted to 6-mercaptopurine ribonucleoside-5'-monophosphate, which inhibits phosphoribosyl pyrophosphate (PRPP) amidotransferase, the rate-limiting enzyme in purine synthesis. It also inhibits the conversion of IMP to adenylosuccinic acid and xanthylic acid and blocks AMP formation in vitro. 6-MP (30 mg/kg) inhibits growth of sarcoma 180, adenocarcinoma E 0771, and adenocarcinoma 755 tumors and reduces the size of leukemia L1210 subcutaneous growths in mice.{36298} It also decreases delayed-type hypersensitivity and thyroid inflammation in a guinea pig model of thyroiditis when administered pre- or post-disease onset.{36299} Formulations containing mercaptopurine have been used for maintenance therapy in patients with acute lymphoblastic leukemia.{36300}