Mercaptopurine (6-MP) and Thioguanine (6-TG) nucleotide formation

To exert its antileukemic effect, 6-MP must penetrate target cells and be converted to the nucleotide analog, 6-MP-ribose phosphate (better known as 6-thioinosinic acid, or TIMP). The addition of the ribose phosphate is catalyzed by the salvage pathway enzyme, hypoxanthineguanine phosphoribosyl transferase (HGPRT).