6-Thio-GTP is a metabolite of Azathioprine, a drug used in the therapy of chronic inflammatory and auto-immune diseases. The immunosuppressive properties of Azathioprine are very likely caused by binding of 6-Thio-GTP to the GTPase Rac.
6-Methylthio-Guanosine, 6-Methylthio-Inosine and 6-Mercaptopurine-riboside nucleotides are structurally related to 6-Thio-GTP. 6-Mercaptopurine-riboside, a sulfhydryl analog of inosine, inhibits nucleoside transport across erythrocyte plasma membranes, and also has immunosuppressive properties. It has been used similarly to mercaptopurine in the treatment of leukemia.