Background:

Raltitrexed is an inhibitor of thymidylate synthase (Ki = 62 nM).[1] It inhibits the growth of L1210 mouse lymphocytic leukemia cells in vitro (IC50 = 8 nM) as well as reduces thymidylate synthase activity and completely eliminates tumors in a mouse L1210:ICR ascitic tumor model when administered at a dose of 4 mg/kg, effects that can be reversed by administration of thymidine. It also reduces tumor growth and the number of metastases in an HCT116-luc mouse xenograft model.[2] Formulations containing raltitrexed have been used in the treatment of advanced colorectal cancers.
Reference:
[1]. Jackman, A.L., Taylor, G.A., Gibson, W., et al. ICI D1694, a quinazoline antifolate thymidylate synthase inhibitor that is a potent inhibitor of L1210 tumor cell growth in vitro and in vivo: A new agent for clinical study. Cancer Res. 51(20), 5579-5586 (1991).
[2]. Qiu, C., Li, Y., Liang, X., et al. A study of peritoneal metastatic xenograft model of colorectal cancer in the treatment of hyperthermic intraperitoneal chemotherapy with Raltitrexed. Biomed Pharmacother. 92, 149-156 (2017).