In vitro pharmacological characterization of vilanterol, a novel long-acting ß2-adrenoceptor agonist with 24-hour duration of action.

Vilanterol trifenatate (vilanterol) is a novel, long-acting ß(2)-adrenoceptor (ß(2)-AR) agonist with 24 h activity. In this study, we describe the preclinical pharmacological profile of vilanterol using radioligand binding and cAMP studies in recombinant assays as well as human and guinea pig tissue systems to characterize ß(2)-AR binding and functional properties. Vilanterol displayed a subnanomolar affinity for the ß(2)-AR that was comparable with that of salmeterol but higher than olodaterol, formoterol, and indacaterol. In cAMP functional activity studies, vilanterol demonstrated similar selectivity as salmeterol for ß(2)- over ß(1)-AR and ß(3)-AR, but a significantly improved selectivity profile than formoterol and indacaterol. Vilanterol also showed a level of intrinsic efficacy that was comparable to indacaterol but significantly greater than that of salmeterol. In cellular cAMP production and tissue-based studies measuring persistence and reassertion, vilanterol had a persistence of action comparable with indacaterol and longer than formoterol. In addition, vilanterol demonstrated reassertion activity in both cell and tissue systems that was comparable with salmeterol and indacaterol but longer than formoterol. In human airways, vilanterol was shown to have a faster onset and longer duration of action than salmeterol, exhibiting a significant level of bronchodilation 22 h after treatment. From these investigations, the data for vilanterol are consistent, showing that it is a novel, potent, and selective ß(2)-AR receptor agonist with a long duration of action. This pharmacological profile combined with clinical data is consistent with once a day dosing of vilanterol in the treatment of both asthma and chronic obstructive pulmonary disease (COPD).

Pharmacological characterization of indacaterol, a novel once daily inhaled 2 adrenoceptor agonist, on small airways in human and rat precision-cut lung slices.

Indacaterol is a novel once daily inhaled beta(2) adrenoceptor agonist in clinical development. This study compared the properties of indacaterol with salmeterol, formoterol, and albuterol on small airways in precision-cut lung slices from human and rat contracted with carbachol and serotonin, respectively. In human lung slices, the rank order of potency was formoterol >/= salmeterol > indacaterol > albuterol, respectively. Indacaterol had similar intrinsic efficacy to formoterol, followed by albuterol and salmeterol. The onset of action was fast for albuterol, formoterol, and indacaterol, whereas it was significantly slower for salmeterol. The duration of action ranking was indacaterol > salmeterol > formoterol > albuterol. When compared with human lung slices, in the rat lung slices, similar potency, intrinsic efficacy, and onset of action were observed for indacaterol, formoterol, and salmeterol. Albuterol had an increased potency when compared with human lung slices and a slower onset of action. In conclusion, our results show that the human lung slice system seems to be a good model to study the clinical properties of inhaled long-acting beta(2) adrenoceptor agonists and that caution is needed extrapolating from rat model to humans. Finally, using the human lung slice model, we have characterized indacaterol as a fast acting compound with a longer duration of action than salmeterol and formoterol.

A role for M(2) and M(3) muscarinic receptors in the contraction of rat and human small airways.

Large airway bronchoconstriction acts mainly through cholinergic pathways via muscarinic M3 receptors with some contribution from M2 receptors. By contrast, the mechanisms of small airway contraction are largely unknown. This study used precision cut lung slices to examine the role of muscarinic M2 and M3 receptors in the contractile response of rat and human small airways. In rat small airways, the M3 preferential antagonist, 4-DAMP, inhibited carbachol-mediated contraction (1×10(-6) M) more than that of the M2 selective antagonist, AF-DX116 (pIC50 values: 8.85±0.18 and 6.31±0.19, n=6-8 respectively). Tiotropium, inhibited the contractile response to carbachol with (pIC50: 9.86±0.07, n=6), but could not distinguish between M2 and M3 mediated effects. Similar experiments using human small airways with tiotropium and AF-DX116, gave a pIC50 of 10.35±0.05 and a pKB of 6.37±0.13, n=5 respectively. Therefore, M3 receptors play a key role in muscarinic contraction of small airways in both rats and humans but the effect of M2 receptors cannot be excluded. To investigate the role of M2 receptors, carbachol-induced contraction of small airways was performed in the presence and absence of a ß2-agonist in order to elevate intracellular cAMP levels prior to contraction. Isoproterenol-induced relaxation was significantly increased by AF-DX116 (P<0.001) in rat small airways and by AF-DX116 (P<0.01), gallamine (P<0.05) and pertussis toxin (P<0.05) in human small airways. Taken together, these data suggest that cholinergic antagonism of muscarinic receptors in human and rat small airways inhibits airway contraction via direct inhibition of contraction through M3 receptors, and by M2 receptor mediated inhibition of relaxation.