Tumor cells extensively utilize the pentose phosphate pathway for the synthesis of ribose. Transketolase is a key enzyme in this pathway and has been suggested as a target for inhibition in the treatment of cancer. In a pharmacodynamic study, nude mice with xenografted HCT-116 tumors were dosed with 1 ('N3′-pyridyl thiamine'; 3-(6-methyl-2- amino-pyridin-3-ylmethyl)-5-(2-hydroxy-ethyl)-4-methyl-thiazol-3-ium chloride ...