The Influence of Receptor Kinetics on the Onset and Duration of Action and the Therapeutic Index of NVA237 and Tiotropium

Abstract

Studies under nonphysiological conditions suggest that long receptor residency time is responsible for the 24-h duration of action of the long-acting muscarinic antagonist (LAMA) tiotropium. Our aim was to determine how clinically relevant dissociation rates under more physiological conditions influence the differences in onset of action between tiotropium and 3-[(cyclopentylhydroxyphenylacetyl oxy]-1,1-dimethyl-pyrrolidinium bromide (NVA237), a once-daily dry-powder formulation of the LAMA glycopyrronium bromide in development for chronic obstructive pulmonary disease. In addition, we have investigated kinetic selectivity at each of the muscarinic receptor subtypes to determine whether the improved cardiovascular therapeutic index obtained with NVA237 in animal models is attributable to differences in kinetic rate constants. The binding of radioligand [ 3 H]N-methyl-scopolamine was measured in the presence/absence of several concentrations of unlabeled competitors, and data were analyzed using a competition kinetic model to provide on/off rates for the competitor. We found shorter dissociation half-lives for NVA237 and tiotropium under physiological (11.4 and 46.2 min, respectively) versus nonphysiological conditions (173 and 462 min, respectively). NVA237 had a more rapid onset of action (3-4.8 times) versus tiotropium, determined in an vitro calcium and rat tracheal strip assay. Simulations suggested that the more rapid onset of NVA237 action could be explained by differences in kinetic parameters. NVA237 had greater equilibrium binding and kinetic selectivity for muscarinic type 3 (M 3 ) versus muscarinic type 2 (M 2 ) receptors, with a faster off rate from M 2 versus M 3 receptors than tiotropium, potentially affording it a more favorable therapeutic index. This study suggests that the 24-h duration of action of NVA237 and tiotropium is not solely the result of their slow dissociation from the M 3 receptor and highlights the importance of conducting in vitro experiments in conditions reflecting those in vivo.

Pharmacological Characterization of GSK573719 (Umeclidinium): A Novel, Long-Acting, Inhaled Antagonist of the Muscarinic Cholinergic Receptors for Treatment of Pulmonary Diseases

“…Within this group of compounds, the half-lives of ipratropium were the shortest. Recently, Sykes et al (2012) suggested that "physiological" assay conditions, in particular the sodium ion concentration of the incubation medium, can markedly reduce M3 mAChR residence times by as much as 10-fold, e.g., the half-life of tiotropium decreased from 462 minutes in the absence of sodium to 46 minutes in the presence of sodium. Nonetheless, the trends for M3 versus M2 mAChR dissociation seem to be a characteristic that is common to this group of pharmacophores.…”

Fevipiprant (QAW039), a Slowly Dissociating CRTh2 Antagonist with the Potential for Improved Clinical Efficacy

“…Previous studies designed to assess the kinetics of unlabeled CRTh2 antagonists have used nonphysiologic assay conditions, experiments being conducted at room temperature in the absence of salt (Gervais et al, 2011). Findings from these early kinetic studies are therefore likely to overestimate the receptor target coverage since it has been well documented that compound kinetics is highly dependent on temperature and sodium ion concentration (Sykes et al, 2012). This phenomenon was also apparent in the current study, with the off rates of QAW039 and OC-459 being up to 5-fold slower when measured at room temperature compared with 37°C.…”

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

“…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). However, other factors, particularly rebinding of the dissociated drug to receptors in the effect compartment, seem likely to contribute to the long duration of action of LAMAs in vivo (Sykes et al, 2012).…”

“…This problem also extends to data fitting procedures, because often researchers use very simple kinetic models to fit the data that do not account for such details (Motulsky and Mahan, 1984). Furthermore, radioligand binding assays are often conducted on ice and in nonphysiologic buffer conditions, and it has been shown that 10-fold shorter residence times of tiotropium at the M 3 acetylcholine receptor are obtained under physiologic conditions (Sykes et al, 2012). Label-free approaches (see next section) have also been used to study ligand protein interaction kinetics using purified proteins and immobilization strategies.…”