RBx 343E48F0

**RBx 343E48F0** is a novel, potent, selective and long-acting muscarinic receptor antagonist developed by Ranbaxy Laboratories. It demonstrates high selectivity for the M3 muscarinic receptor with a pKi of 9.6 and 60-fold selectivity over the M2 receptor. The compound exhibits fast onset of action and long duration of activity (greater than 24 hours) with potential for use in treating Chronic Obstructive Pulmonary Disease (COPD). In preclinical studies, intratracheal administration showed dose-dependent inhibition of carbachol-induced bronchoconstriction with an ED50 value of 110 ng/kg. The drug incorporates gem-difluorocycloalkyl substituents and functions as a bronchodilator with superior lung retention properties.