An inhibitor of thymidylate synthase (Ki = 62 nM); inhibits the growth of L1210 mouse lymphocytic leukemia cells in vitro (IC50 = 8 nM); reduces thymidylate synthase activity and completely eliminates tumors in a mouse L1210:ICR ascitic tumor model at 4 mg/kg; reduces tumor growth and the number of metastases in an HCT116-luc mouse xenograft model