Synthesis of reversible PAD4 inhibitors via copper-catalyzed C−H arylation of benzimidazole

PAD4 is a promising epigenetic drug target for various cancers and immune diseases. In this work, we applied a Cu-catalyzed C–H arylation reaction of N-heteroarene to the synthesis of complex non-covalent PAD4 inhibitors bearing a bi-heteroaryl pharmacophore. This strategy allowed us to access various analogs of C2-aryl substituted benzimidazoles from a common benzimidazole core and easily accessible aryl iodides. Preliminary SAR studies revealed the indole motif of GSK-484 is critical to its activity. Replacing the N-cyclopropylmethyl group to N-benzyl group on the indole ring of GSK-484 resulted in more than 5-fold increase in cell killing efficacy against 4T1 cell line.