Preclinical Evaluation of Long-Acting Muscarinic Antagonists: Comparison of Tiotropium and Investigational Drugs

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow limitation caused by persistent inflammatory processes in the airways. An increased cholinergic tone mediates different pathophysiological features of COPD, such as bronchoconstriction and mucus hypersecretion, mostly through activation of the human muscarinic M 3 receptor (hM 3 ) subtype. Tiotropium bromide (Spiriva) is a well established muscarinic antagonist in the pharmacological management of COPD with a once-daily posology. The rationale behind the sustained bronchodilation obtained with tiotropium consists in its slow dissociation from hM 3 receptors. In this study, we performed a comprehensive preclinical comparison of tiotropium with other long-acting muscarinic antagonists (LAMAs) currently in clinical development, namely aclidinium bromide and glycopyrrolate. The different muscarinic antagonists were characterized for their 1) affinity toward the different human muscarinic receptor subtypes expressed in Chinese hamster ovary cells and kinetics of receptor dissociation, 2) potency in inhibiting the agonist-induced activation of muscarinic receptors through measurement of second messengers, and 3) efficacy and duration of bronchoprotection, as tested in a model of acetylcholine-induced bronchoconstriction in anesthetized dogs over a period of 24 h. All of the tested LAMAs showed high affinity and potency toward the hM 3 receptor (tiotropium, pA 2 ϭ 10.4; aclidinium, pA 2 ϭ 9.6; and glycopyrrolate, pA 2 ϭ 9.7). However, dissociation half-lives of the LAMAs from the hM 3 receptor differed significantly (tiotropium, t 1 ⁄2 ϭ 27 h; aclidinium, t 1 ⁄2 ϭ 10.7 h; and glycopyrrolate, t 1 ⁄2 ϭ 6.1 h). In line with their kinetic properties at the hM 3 , the tested LAMAs provided different levels of bronchoprotection in the in vivo setting 24 h after administration (tiotropium ϭ 35%, aclidinium ϭ 21%, and glycopyrrolate ϭ 0% at 24 h) when applied at equieffective doses.

Comparative Characterization of Lung Muscarinic Receptor Binding After Intratracheal Administration of Tiotropium, Ipratropium, and Glycopyrrolate

“…The observed difference in the changes (extent, duration) in binding parameters (K d , B max ) after the intratracheal administration of tiotropium, ipratropium, and glycopyrrolate (Tables 3, 4) seems to coincide with the functional and in vitro receptor binding characteristics. In fact, Casarosa et al (37) showed that intratracheal tiotropium induced considerable bronchoprotection in anesthetized dogs lasting more than 24 h, significantly longer than glycopyrrolate. Both in the recovery of carbachol-induced contraction of the isolated guinea-pig tracheum and in the offset of the bronchodilator effects of anticholinergic agents in the isolated human bronchus, the glycopyrrolate-induced bronchodilation lasted longer than the ipratropium, but not tiotropium, -induced bronchodilation (36).…”

“…Furthermore, Haddad et al (19) showed that the inhibition by glycopyrrolate of electrical field stimulation-induced contraction of guinea-pig trachea and human airways was significantly more prolonged than that by ipratropium. In relation to the in vitro receptor binding kinetics, Casarosa et al (37) showed that the dissociation half-life (t 1/2 ) from the human M 3 receptor of tiotropium (27 h) was much longer than that of glycopyrrolate (6.1 h). Also, it was reported that glycopyrrolate compared with ipratropium dissociated more slowly from muscarinic receptors in human airway smooth muscle (19).…”

Ligand Residence Time at G-protein–Coupled Receptors—Why We Should Take Our Time To Study It

“…Although blocking M 1 /M 3 receptor subtypes would counteract airway limitation in chronic obstructive pulmonary disease patients, blocking presynaptic M 2 autoreceptors would be detrimental for this purpose and systemic M 2 antagonism would increase the risk of tachycardia as side effect. The difficulties in finding muscarinic receptor subtype-selective ligands were successfully overcome by the development of ipratropium, a shortacting muscarinic antagonist, and long-acting muscarinic antagonists (LAMAs) tiotropium (Disse et al, 1993) and the novel aclidinium (Gavaldà et al, 2009) and glycopyrronium (Casarosa et al, 2009) that are particularly indicated for maintenance therapy. All these drugs dissociate more rapidly from M 2 than from M 3 receptors.…”

“…All these drugs dissociate more rapidly from M 2 than from M 3 receptors. Apart from the advantageous kinetic subtype selectivity of these drugs, the duration of action of the LAMAs was suggested to be primarily related to their long residence time at M 3 receptors (Disse et al, 1993;Casarosa et al, 2009). Hence, it was shown that the duration of the bronchodilator action in vivo of different muscarinic antagonists resembles their residence times at M 3 receptors determined in vitro under nonphysiologic conditions (Gavaldà et al, 2014).…”

Van-e cardiovascularis mellékhatásuk az inhalációs antikolinerg szereknek?

“…Az M3-ról a disszociáció felezési ideje tiotropiumnál 27 óra, aclidiumnál 10,7 óra, glycopirrhoniumnál 6,1 óra. Az M2-ről a disszociáció felezési ideje tiotropiumnál 2,6 óra, aclidiniumnál 1,8 óra, glycopirrhoniumnál 0,37 óra [45,53,54,55,56,57].…”