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.

The preclinical pharmacological profile of 6-hydroxy-8-[(1R)-1-hydroxy-2-[[2-(4-methoxyphenyl)-1,1-dimethylethyl]amino]ethyl]-2H-1,4-benzoxazin-3(4H)-one monohydrochloride (olodaterol, previously known as BI 1744 CL), a novel, enantiomeric pure, inhaled human ␤ 2 -adrenoceptor (h␤ 2 -AR) agonist, was compared with marketed drugs, such as salmeterol and formoterol. In vitro, olodaterol showed a potent, nearly full agonistic response at the h␤ 2 -AR (EC 50 ϭ 0.1 nM; intrinsic activity ϭ 88% compared with isoprenaline) and a significant selectivity profile (219-and 1622-fold against the h␤ 1 -and h␤ 3 -ARs, respectively). Likewise, olodaterol was able to potently reverse contraction induced by different stimuli in isolated human bronchi. In vivo, antagonistic effects of single doses of olodaterol and formoterol were measured against acetylcholine challenges in anesthetized guinea pigs and dogs for up to 24 h by using the Respimat Soft Mist inhaler. Heart rate and metabolic parameters (serum potassium, lactate, and glucose) were monitored to evaluate systemic pharmacodynamic effects in the dog model. In both models, olodaterol provided bronchoprotection over 24 h. Formoterol applied at an equally effective dose did not retain efficacy over 24 h. In both models olodaterol showed a rapid onset of action comparable with formoterol. Taken together, the preclinical behavior of olodaterol suggests that this novel ␤ 2 -AR agonist has the profile for once-daily dosing in humans concomitant with a fast onset of action and a favorable systemic pharmacodynamic profile.Asthma and chronic obstructive pulmonary disease (COPD) are conditions characterized by airway obstruction, which is variable and reversible in asthma but is progressive in COPD (Guerra, 2009). Both diseases are very common, and their incidence is increasing globally, placing a growing burden on patients and health services in industrialized and developing countries (Pauwels and Rabe, 2004;Braman, 2006). ␤ 2 -Adrenoceptor (␤ 2 -AR) agonists are among the most potent and rapidly acting bronchodilators currently available for clinical use. In asthma, rapid-acting inhaled ␤ 2 -AR agonists are the therapy of choice as a reliever therapy for episodes of dyspnea and the pretreatment of exercise-induced bronchoconstriction (Bateman et al., 2008). In asthma patients with persistent symptoms long-acting ␤-agonists (LABAs), such as salmeterol and formoterol, are administered as an add-on controller therapy when the first-line treatment of medium dose-inhaled corticosteroids alone fails to achieve control of asthma (Bateman et al., 2008). Recently, formoterol has gained some recognition as an as needed controller therapy because of its fast onset of action. In addition, inhaled ␤ 2 -AR agonists provide major therapeutic benefits in the treatment of COPD, such as reduction in symptoms and exacerbations, increases in exercise capacity, and improvements of health-related quality of life (Gold, 2009).␤ 2 -AR agonists exert a bronchodilatory effect through activation of ...

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The spleen tyrosine kinase (Syk) is a key mediator of immunoreceptor signaling in immune cells. Thus, interfering with the function of Syk by genetic deletion or pharmacological inhibition might influence a variety of allergic and autoimmune processes. Since conventional Syk knockout mice are not viable, studies addressing the effect of Syk deletion in adult animals have been limited. To further explore functions of Syk in animal models of allergy and to shed light on the role of Syk in the in vivo migration of neutrophils and monocytes, we generated inducible Syk knockout mice. These mice harbor a floxed Syk gene and a tamoxifen-inducible Cre recombinase under the control of the ubiquitously active Rosa26-promoter. Thus, treatment of mice with tamoxifen leads to the deletion of Syk in all organs. Syk-deleted mice were analyzed in mast cell-dependent models and in models focusing on neutrophil and monocyte migration. We show that Syk deletion in adult mice reduces inflammatory responses in mast cell-driven animal models of allergy and asthma but has no effect on the migration of neutrophils and monocytes. Therefore, the inducible Syk knockout mice presented here provide a valuable tool to further explore the role of Syk in disease-related animal models.