Antifolates are a group of antimetabolite agents, which block the functions of folic acid. Folic acid is a cofactor to different kinds of methyltransferases. The latter are related to serine, methionine, thymidine and purine biosynthesis. Thus, antifolates are able to inhibit cell division, DNA/RNA synthesis and repair as well as protein synthesis.

AICARFT (aminoimidazole-4-carboxamide ribonucleotide formyltransferase) is an enzyme in purine biosynthesis. Cancer calls for DNA and RNA to proliferate. Purines are necessary for cell division. Therefore, AICARFT inhibitors have the potential in the treatment of cancer.

Kevin R. Fales, et al produced a series of compounds in their research. As a result, Compound 28a (LSN 3213128) exhibits most potent activity among all the products.

LSN 3213128 is a selective, nonclassical, orally active antifolate, potently and specifically inhibits AICARFT. It occupys AICARFT binding pocket and interacts with the protein. The inhibitor also exhibits low IC50 values of 16 nM in cell-free assay and 19 nM in cell assay. LSN 3213128 has no obvious effect on other upstream enzymes, with IC50s of >100 μM.

According to the excellent potency of LSN 3213128, researchers carried out some biological assays to identify its bioactivity.

Above all, LSN 3213128 is a folate competitive inhibitor, displays potent inhibitory effect on AICARFT. Besides, it elevates ZMP with high antiproliferative properity in MDA-MB-231 cells.

In addition, LSN 3213128 shows potent activity in animal assay. It markedly enhances ZMP levels in nude mice bearing H460 cells. In MDA-MB-231met2 xenografts mice model, LSN 3213128 significantly inhibits tumor growth after oral administration.

1. Fales KR, et al. Med Chem. 2017 Dec 14;60(23):9599-9616.