Discovery of Novel Quaternary Ammonium Derivatives of (3R)-Quinuclidinol Esters as Potent and Long-Acting Muscarinic Antagonists with Potential for Minimal Systemic Exposure after Inhaled Administration: Identification of (3R)-3-{[Hydroxy(di-2-thienyl)acetyl]oxy}-1-(3-phenoxypropyl)-1-azoniabicyclo[2.2.2]octane Bromide (Aclidinium Bromide)

Abstract

The objective of this work was to discover a novel, long-acting muscarinic M(3) antagonist for the inhaled treatment of chronic obstructive pulmonary disease (COPD), with a potentially improved risk-benefit profile compared with current antimuscarinic agents. A series of novel quaternary ammonium derivatives of (3R)-quinuclidinol esters were synthesized and evaluated. On the basis of its overall profile, (3R)-3-{[hydroxy(di-2-thienyl)acetyl]oxy}-1-(3-phenoxypropyl)-1-azoniabicyclo[2.2.2]octane bromide (aclidinium bromide) emerged as a candidate for once-daily maintenance treatment of COPD. This compound is a potent muscarinic antagonist, with long duration of action in vivo, and was found to have a rapid hydrolysis in human plasma, minimizing the potential to induce class-related systemic side effects. Aclidinium bromide is currently in phase III development for maintenance treatment of patients with COPD.