Unique Dual Targeting Of Thymidylate Synthase And Topoisomerase1 By Fdump[10] Results In High Efficacy Against Aml And Low Toxicity

Acute myeloid leukemia (AML) is an aggressive malignancy that leads to marrow failure and death. There is a desperate need for new therapies. The novel fluoropyrimidine, FdUMP[10], was highly active against both human AML cell lines, (IC50 values, 3.4nM-21.5nM) and murine lines (IC50 values, 123.8pM-131.4pM). In all cases, the IC50 of FdUMP[10] was lower than for cytarabine and similar to 1000 times lower than 5-fluorouracil (5-FU). FdUMP[10] remained effective against cells expressing the Flt3 internal tandem duplication, BCR-ABL, MN1, and an shRNA against p53. It had activity against patient samples at concentrations that did not affect normal hematopoietic cells. FdUMP[10] inhibited thymidylate synthase (TS) and trapped topoisomerase I cleavage complexes (Top1CCs), leading to DNA damage and apoptosis. All cell lines and nearly all primary AML samples examined expressed both TS and Top1. In vivo, FdUMP[10] was active against a syngeneic AML model with a survival advantage equivalent to doxorubicin plus cytarabine. 5-FU treatment was toxic and did not improve survival. FdUMP[10] was better tolerated than 5-FU or cytarabine plus doxorubicin and did not affect normal HSCs, while 5-FU dramatically impaired their ability to engraft. In summary, FdUMP[10] was highly efficacious and better tolerated than standard therapies. (Blood. 2012;119(15):3561-3570)