New Nucleotide-Competitive Non-Nucleoside Inhibitors of Terminal 2 Deoxynucleotidyl Transferase: Discovery, Characterization, and 3 Crystal Structure in Complex with the Target

Terminal deoxynucletidyl transferase (TdT) is overex-pressed in some cancer types, where it might compete with polμduringthe mutagenic repair of double strand breaks (DSBs) through the non-homologous end joining (NHEJ) pathway. Here we report the discoveryand characterization of pyrrolyl and indolyl diketo acids that specificallytarget TdT and behave as nucleotide-competitive inhibitors. These com-pounds show a selective toxicity toward MOLT-4 compared to HeLa cellsthat correlate well with in vitro selectivity for TdT. The binding site oftwo of these inhibitors was determined by cocrystallization with TdT, ex-plaining why these compounds are competitive inhibitors of the deoxy-nucleotide triphosphate (dNTP). In addition, because of the observeddual localization of the phenyl substituent, these studies open thepossibility of rationally designing more potent compounds