Identification of three new compounds that directly target human serine hydroxymethyltransferase 2.

Mitochondrial serine hydroxymethyltransferase 2 (SHMT2) is an important drug target in the one-carbon metabolic pathway, since its activity is critical for purine and pyrimidine biosynthesis. Additionally, it plays a prominent role during metabolic reprogramming of cancer cells, and SHMT2 inhibitors have proven useful as anticancer drugs. Compared to drugs targeting one-carbon metabolic enzymes (mainly dihydrofolate reductase and thymidylate synthase) that have been used for clinical treatment of cancer, efficient SHMT2-specific inhibitors are lacking. Therefore, we established a direct system for virtual screening, protein expression, and identification of inhibitors targeting SHMT2. First, 27 compounds qualifying as potential SHMT2 inhibitors were selected for biological activity verification through virtual screening of the 210 thousand compounds registered in the Specs database. Second, these 27 hits were subjected to quick screening by an in vitro non-competitive kinetic assay of SHMT2 single-enzyme catalysis. This allowed us to identify three compounds featuring medium-strength and non-competitive inhibition of SHMT2: AM-807/42004511 (IC50  = 14.52 ± 4.1665 μM), AM-807/40675298 (IC50  = 12.74 ± 5.8991 μM), and AM-807/42004633 (IC50  = 9.43 ± 0.5646 μM). We describe a quick screening method for the identification of inhibitors targeting SHMT2, providing a basis for subsequent identification and screening of new inhibitors.