Azathioprine

Azathioprine is a pro-drug of 6-mercaptopurine (6-MP). 6-MP is inactive but acts as a purine antagonist and requires cellular uptake and intracellular anabolism to thioguanine nucleotides (TGNs) for immunosuppression. The TGNs and other metabolites (e.g. 6-methyl-mecaptopurine ribonucleotides) inhibit de novo purine synthesis and purine nucleotide interconversions.