6-Thioguanosine-5'-O-triphosphate (sodium salt)

6-Thioguanosine-5’-O-triphosphate (6-thio-GTP) is an active metabolite of the purine analog 6-thioguanine and the immunosuppressive purine analog azathioprine .^1,2 It is formed from 6-thioguanine via 6-thio-GMP and 6-thio-GDP intermediates by phosphorylation and from azathioprine via 6-mercaptopurine , 6-thio-GMP, and 6-thio-GDP intermediates by a non-enzymatic process and several enzymatic reactions. 6-thio-GTP binds to a variety of GTPases, including Rac, Ras, Cdc42, and RhoA but selectively inhibits activation of Rac1 and Rac2 over Cdc42 in primary human CD4⁺ T cells stimulated with anti-CD3 and anti-CD28 antibodies.^3,4 It inhibits T cell receptor-stimulated proliferation of T cells and reduces CD28-dependent T cell survival in vitro in isolated mouse splenocytes.⁵ 6-Thio-GTP (0.5 mg/kg) increases survival in a mouse model of heart transplantation.