polymerase resulted in the formation of CNddC nucleotide at the 3 terminus of the primer. Subsequently, Hanaoka et al. employed large stress
liquid chromatography and mass spectrometry to demonstrate the presence of CNddC in hydrolysates 
of DNA isolated from cells after CNDAC treatment, indicating that B elimination occurs in intact cells. Eventually, it was demonstrated that all detectable CNddC was at the 3 terminus, delivering evidence of the self strand breaking action of CNDAC nucleotide following incorporation into DNA. Hence, the mechanism of action of CNDAC is distinct from other clinically energetic nucleosides. To obtain oral bioavailability, CNDAC was derivatized with a palmitoyl group at the N4 exocyclic amine this was designated as CS 682 by Sankyo Co. , Ltd. , Tokyo, Japan, the original pharmaceutical sponsor. The fatty acid side chain on the N4 group of the cytosine moiety improves oral bioavailability and reduces inactivation by deamination.
Subsequently, after Cyclacel Pharmaceuticals, Berkeley Heights, NJ, USA, assumed clinical development of the compound in 2003, this was re designated at first as small molecule library， and hts screening subsequently as sapacitabine. Thus, all the names indicate the same chemical entity, but determine the respective sources of compound. As is the case with other deoxycytidine analogs, for example, ara C, gemcitabine, research in cell lines demonstrated that is phosphorylated to the monophosphate by deoxycytidine kinase, albeit with comparatively poor performance compared with dCyd or the other analogs. Cells lacking this enzyme were drastically resistant to the analog. Also, CNDAC is a substrate for deamination by cytidine deaminase, which generates the inactive uracil derivative CNDAU. The triphosphate accumulates in a concentration dependent manner, and competes with dCTP for incorporation into DNA.
CNDAC was demonstrated to have strong antitumor activity in preclinical studies. The antiproliferative results of CNDAC in terms of IC50 values had been more strong than those observed with ara C. The analog showed broad spectrum activity against tumor cell lines and also in the P388 leukemia mouse model. CNDAC was far more productive than cytarabine in some human tumor cell lines derived from lung, stomach and osteosarcoma and showed superb activity against tumor cell lines refractory to cytarabine. However, the orally administered prodrug was more powerful against human tumor xenografts than CNDAC or 5 fluorouracil. It was also efficient against several human organ tumor xenografts over a wider dose array and with fewer toxicities.
CS 682 was also successful against P388 human leukemia cells resistant to a selection of other agents which includes mitomycin C, antigen peptide, 5 fluorouracil and cisplatin in syngeneic mice. Utilizing highresolution magnetic imaging, LY364947 Wu et al. demonstrated that CS 682 delayed the growth of orthotopically implanted AX3488 liver tumors, and also delayed their meta static conduct. The metastatic behavior of an orthotopic model of pancreatic carcinoma was delayed, and overall survival of the mice was prolonged by CS 682. A liposomal formulation of CNDAC showed activity against Meth A sarcoma bearing mice when injected intravenously. The antitumor activity of the liposomally encapsulated formulation was a lot more powerful than that of the parent drug suggesting that the liposomal preparation improved therapeutic efficacy although at the very same time lowering toxicity.
Sapacitabine in combination with histone deacetylase inhibitors induced an improve in apoptosis and demonstrated substantial benefit compared with the single agent treatment options the two in vitro and in xenografts of the MV4 11 myeloid leukemia.