NSC624206 is a ubiquitin E1 (UBA1) inhibitor with an IC50 of ~9 μM, specifically blocking ubiquitin-thioester formation without affecting ubiquitin adenylation. It prevents in vitro ubiquitination of p27 and induces p27 accumulation in HepG2 liver cancer cells, with a concentration-dependent reduction of ubiquitin-E1 thioesters (IC50 13 μM). It is used in life sciences research.