5-aza-4'-Thio-2'-Deoxycytidine (Aza-TdC) in People With Advanced Solid Tumors

Methylation-mediated silencing of genes is an epigenetic mechanism implicated in carcinogenesis; agents that inhibit this mechanism are of clinical interest because of their potential to re-activate silenced tumor suppressor genes. The nucleoside analog 5-aza-4'-thio-2'- deoxycytidine (Aza-TdC) is incorporated into DNA, where it engages the active site of DNA methyltransferase I (DNMT1), a maintenance methyltransferase that contributes to hypermethylation and silencing of tumor suppressor genes. Aza-TdC offers an improvement over traditional DNMT inhibitors via higher incorporation into DNA and lower cytotoxicity; Aza-TdC has greater antitumor activity than another recently developed DNMT1 inhibitor, TdCyd, in some solid tumor xenograft models. Treatment with Aza-TdC is anticipated to yield inhibition of tumor growth due to DNMT1 depletion at oral doses that are well tolerated in extended dosing schedules.