Epetraborole, also known as GSK2251052 and AN3365, is a potent and selective leucyl-tRNA synthetase inhibitor. Epetraborole was in development for the treatment of infections caused by multidrug-resistant Gram-negative pathogens. GSK2251052 is a novel boron-containing antibiotic that inhibits bacterial leucyl tRNA synthetase. All Clostridium perfringens strains had GSK2251052 MICs of >32 μg/ml.