LY2334737

LY2334737 is an orally available valproic acid ester of gemcitabine, a broad-spectrum antimetabolite with antineoplastic activity. LY2334737 is hydrolyzed by carboxylesterase 2 (CES2) and releases gemcitabine systemically over a period of time consistent with formation rate-limited kinetics. In turn, gemcitabine is converted into the active metabolites difluorodeoxycytidine diphosphate and triphosphate (dFdCDP and dFdCTP) by deoxycytidine kinase. dFdCDP inhibits ribonucleotide reductase, thereby decreasing the deoxynucleotide pool available for DNA replication; dFdCTP is incorporated into DNA, resulting in premature termination of DNA replication and eventually the induction of apoptosis. Compared to gemcitabine, this prodrug is able to avoid hydrolysis in enterocytes and the portal circulation thus avoiding first pass metabolism and increasing systemic gemcitabine availability. (In Vitro) :Five cell lines that express CES2 responded to LY2334737 treatment. LY2334737 is less cytotoxic to a SK-OV-3 CES2 knockdown than parental cells. The drug response of CES2-transfected HCT-116 cells correlated with CES2 expression level. Bystander studies show statistically greater PC-3-GFP growth inhibition by LY2334737 when cells are cocultured with CES2 and not mock transfectants. (In Vivo) :Oral treatment of xenograft models with 3.2 mg/kg LY2334737 once a day for 21 days shows greater tumor growth inhibition of CES2 transfectant than the mock transfectant.Metronomic LY2334737 administration causes increased blood flow in luciferase-tagged LM2-4 tumor xenografts, and this effect, readily measured using contrast micro-ultrasound, coincided with a relative increase in tumor bioluminescence.