Comparison of 1-(2-deoxy-2-fluoro-4-thio-beta-D-arabinofuranosyl)cytosine with gemcitabine in its antitumor activity.

The antitumor activity of a novel nucleoside, 1-(2-deoxy-2-fluoro-4-thio-beta-D arabinofuranosyl)cytosine (4'-thio-FAC) was compared with that of 2'-deoxy-2',2'-difluorocytidine (gemcitabine). 4'-Thio-FAC showed potent antitumor effects against various solid cancer cell lines in vitro. Also, gemcitabine showed remarkable in vitro antitumor effects, even more potent than 4'-thio-FAC. However, 4'-thio-FAC inhibited tumor growth more strongly than gemcitabine did at the same dose against human cancer cells implanted s.c. in nude mice. In addition, 4'-thio-FAC suppressed the tumor growth by oral administration. The toxicity of 4'-thio-FAC was weaker than that of gemcitabine in nude mice in both consecutive and intermittent administration. Accordingly, clinical usefulness of 4'-thio-FAC is expected.