PEP03 is a new chemical entity developed as a highly selective, potent, and orally active 5-LO inhibitor. PEP03 exerts its action by blocking the generation of both cysteinyl LTs and LTB4. These LTs have been associated with the inflammatory response in the lung and with the clinical sequelae, including bronchospasm. Preclinical pharmacological in- vitro, ex-vivo and in-vivo testing indicates that PEP03 has multiple beneficial actions including prevention of bronchoconstriction, and reduction of vascular leakage, cellular infiltration, and bronchial hyperresponsiveness.