Inhibition of the growth of human hepatocellular carcinoma in vitro and in athymic mice by a quinazoline inhibitor of thymidylate synthase, CB3717.

Two human primary liver cancer cell-lines, PLC/PRF/5 and Hep 3B, grown both in vitro and as xenografts in nude mice were used to evaluate the chemotherapeutic potential of a new quinazoline antifolate CB3717. Xenograft growth rate was followed both by serial serum alphafoetoprotein (AFP) measurement and direct volume estimation. A dose regime of 200 mg CB3717 kg-1 body wt day-1 for 5 days caused a significant reduction in growth rate, as measured by relative serum AFP, of both xenografts; PLC/PRF/5 derived xenograft growth was also inhibited by 125 mg CB 3717 kg-1 day-1 for 5 days. Cell culture experiments showed that the ID50 for the cell lines fell within the range of serum CB3717 concentration achieved by a dose of 300 mg m-2 given to patients. Treatment with CB3717 stimulated the incorporation of exogenous thymidine into DNA by the tumour cells, presumably because of inhibition of the de novo pathway and reduction of endogenous thymidine triphosphate pools. These results suggest that CB3717 may be a useful new therapeutic agent in human primary liver cell carcinoma and that blocking the salvage pathway may further increase efficacy.