ML323

ML323 is a potent, highly selective, and reversible small-molecule inhibitor of the Ubiquitin-Specific Protease 1 (USP1) and its essential cofactor, USP1-associated factor 1 (UAF1). USP1 is a deubiquitinating enzyme (DUB) that plays a pivotal role in DNA damage repair pathways, specifically the Fanconi anemia pathway and translesion synthesis, by regulating the ubiquitination status of FANCD2 and PCNA. ML323 binds to a cryptic allosteric site on USP1, inducing conformational changes that disrupt the enzyme's hydrophobic core and inhibit its catalytic activity. By preventing the deubiquitination of key substrates, ML323 sensitizes various cancer cells to DNA-damaging agents like cisplatin and PARP inhibitors. Beyond oncology, ML323 has been investigated for its ability to regulate metabolic processes such as adipogenesis, inhibit viral replication, and promote bone healing in nonunion fractures. It was originally developed as a chemical probe through the NIH Molecular Libraries Program.