5-aza-2′,2′-difluoro deoxycytidine (nuc013): a novel nucleoside dna methyl transferase inhibitor and ribonucleotide reductase inhibitor for the treatment of cancer

Tumor suppressor genes can be silenced genetically as well as epigenetically. One approach to reversing epigenetic suppression of tumor suppressor genes is to inhibit DNA methyl transferase. 5-aza-2′,2′-difluorodeoxycytidine (NUC013) is a novel DNA methyl transferase and ribonucleotide reductase inhibitor that is a more potent inhibitor of growth than decitabine in the NCI 60 cancer cell line panel. NUC013 is more active than decitabine against p53-null/mutant cancer cell lines (p = 0.027) but is even more so against p53 wild-type (WT) cell lines (p = 0.0025). The maximum tolerated dose in mice of NUC013 is greater than 120 mg/kg administered intravenously for three consecutive days a week for three weeks. With this regimen and a dose of 20 mg/kg in a human leukemia HL-60 (p53-null) NCr-nu/nu mouse xenograft model (n = 10/group), NUC013 demonstrated a survival benefit (saline median survival (MS) = 26.5 days, NUC013 MS = 32 days and hazard ratio (HR) = 0.26 (p = 0.032)). In a colon cancer LoVo (TP53 WT) xenograft, mice treated with decitabine at 5 mg/kg had worse survival than saline controls (decitabine MS = 31 days, saline MS > 60 days and HR = 26.89 (p < 0.0001)). At a dose of 20 mg/kg NUC013, mean tumor volume in the LoVo xenografts was lower than controls by 50.9% and at 40 mg/kg by 53.7% (both p < 0.0001).