Lometrexol (DDATHF), an antipurine antifolate, can inhibit the activity of glycinamide ribonucleotide formyltransferase (GARFT) but do not induce detectable levels of DNA strand breaks. Lometrexol can further inhibit de novo purine synthesis, causing abnormal cell proliferation and apoptosis, even cell cycle arrest. Lometrexol has anticancer activity. Lometrexol also is a potent human Serine hydroxymethyltransferase1/2 (hSHMT1/2) inhibitor.