Dulcie B. Schmidt

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

Activation of muscarinic subtype 3 (M3) muscarinic cholinergic receptors (mAChRs) increases airway tone, whereas its blockade improves lung function and quality of life in patients with pulmonary diseases. The present study evaluated the pharmacological properties of a novel mAChR antagonist, GSK573719 (4-[hydroxy(diphenyl)methyl]-1-{2-[(phenylmethyl)oxy]ethyl}-1-azoniabicyclo[2.2.2]octane; umeclidinium). The affinity (Ki) of GSK573719 for the cloned human M1–M5 mAChRs ranged from 0.05 to 0.16 nM. Dissociation of [3H]GSK573719 from the M3 mAChR was slower than that for the M2 mAChR [half-life (t1/2) values: 82 and 9 minutes, respectively]. In Chinese hamster ovary cells transfected with recombinant human M3 mAChRs, GSK573719 demonstrated picomolar potency (–log pA2 = 23.9 pM) in an acetylcholine (Ach)-mediated Ca2+ mobilization assay. Concentration-response curves indicate competitive antagonism with partial reversibility after drug washout. Using isolated human bronchial strips, GSK573719 was also potent and showed competitive antagonism (–log pA2 = 316 pM) versus carbachol, and was slowly reversible in a concentration-dependent manner (1–100 nM). The time to 50% restoration of contraction at 10 nM was about 381 minutes (versus 413 minutes for tiotropium bromide). In mice, the ED50 value was 0.02 μg/mouse intranasally. In conscious guinea pigs, intratracheal administration of GSK573719 dose dependently blocked Ach-induced bronchoconstriction with long duration of action, and was comparable to tiotropium; 2.5 μg elicited 50% bronchoprotection for >24 hours. Thus, GSK573719 is a potent anticholinergic agent that demonstrates slow functional reversibility at the human M3 mAChR and long duration of action in animal models. This pharmacological profile translated into a 24-hour duration of bronchodilation in vivo, which suggested umeclidinium will be a once-daily inhaled treatment of pulmonary diseases.

Nonpeptidic urotensin-II receptor antagonists I: in vitro pharmacological characterization of SB-706375

1 SB‐706375 potently inhibited [125I]hU‐II binding to both mammalian recombinant and ‘native’ UT receptors (Ki 4.7±1.5 to 20.7±3.6u2003nM at rodent, feline and primate recombinant UT receptors and Ki 5.4±0.4u2003nM at the endogenous UT receptor in SJRH30 cells). 2 Prior exposure to SB‐706375 (1u2003μM, 30u2003min) did not alter [125I]hU‐II binding affinity or density in recombinant cells (KD 3.1±0.4 vs 5.8±0.9u2003nM and Bmax 3.1±1.0 vs 2.8±0.8u2003pmolu2003mg−1) consistent with a reversible mode of action. 3 The novel, nonpeptidic radioligand [3H]SB‐657510, a close analogue of SB‐706375, bound to the monkey UT receptor (KD 2.6±0.4u2003nM, Bmax 0.86±0.12u2003pmolu2003mg−1) in a manner that was inhibited by both U‐II isopeptides and SB‐706375 (Ki 4.6±1.4 to 17.6±5.4u2003nM) consistent with the sulphonamides and native U‐II ligands sharing a common UT receptor binding domain. 4 SB‐706375 was a potent, competitive hU‐II antagonist across species with pKb 7.29–8.00 in HEK293‐UT receptor cells (inhibition of [Ca2+]i‐mobilization) and pKb 7.47 in rat isolated aorta (inhibition of contraction). SB‐706375 also reversed tone established in the rat aorta by prior exposure to hU‐II (Kapp∼20u2003nM). 5 SB‐706375 was a selective U‐II antagonist with 100‐fold selectivity for the human UT receptor compared to 86 distinct receptors, ion channels, enzymes, transporters and nuclear hormones (Ki/IC50>1u2003μM). Accordingly, the contractile responses induced in isolated aortae by KCl, phenylephrine, angiotensin II and endothelin‐1 were unaltered by SB‐706375 (1u2003μM). 6 In summary, SB‐706375 is a high‐affinity, surmountable, reversible and selective nonpeptide UT receptor antagonist with cross‐species activity that will assist in delineating the pathophysiological actions of U‐II in mammals.

The peptidic urotensin-II receptor ligand GSK248451 possesses less intrinsic activity than the low-efficacy partial agonists SB-710411 and urantide in native mammalian tissues and recombinant cell systems

1 Several peptidic urotensin‐II (UT) receptor antagonists exert ‘paradoxical’ agonist activity in recombinant cell‐ and tissue‐based bioassay systems, likely the result of differential urotensin‐II receptor (UT receptor) signal transduction/coupling efficiency between assays. The present study has examined this phenomenon in mammalian arteries and recombinant UT‐HEK (human embryonic kidney) cells. 2 BacMam‐mediated recombinant UT receptor upregulation in HEK cells augmented agonist activity for all four peptidic UT ligands studied. The nominal rank order of relative intrinsic efficacy was U‐II>urantide ([Pen5‐DTrp7‐Orn8]hU‐II4–11)>SB‐710411 (Cpa‐c[DCys‐Pal‐DTrp‐Lys‐Val‐Cys]‐Cpa‐amide)≫GSK248451 (Cin‐c[DCys‐Pal‐DTrp‐Orn‐Val‐Cys]‐His‐amide) (the relative coupling efficiency of recombinant HEK cells was cat>human≫rat UT receptor). 3 The present study further demonstrated that the use of high signal transduction/coupling efficiency isolated blood vessel assays (primate>cat arteries) is required in order to characterize UT receptor antagonism thoroughly. This cannot be attained simply by using the rat isolated aorta, an artery with low signal transduction/coupling efficiency in which low‐efficacy agonists appear to function as antagonists. 4 In contrast to the ‘low‐efficacy agonists’ urantide and SB‐710411, GSK248451 functioned as a potent UT receptor antagonist in all native isolated tissues studied (UT receptor selectivity was confirmed in the rat aorta). Further, GSK248451 exhibited an extremely low level of relative intrinsic activity in recombinant HEK cells (4–5‐fold less than seen with urantide). Since GSK248451 (1u2003mgu2003kg−1, i.v.) blocked the systemic pressor actions of exogenous U‐II in the anaesthetized cat, it represents a suitable peptidic tool antagonist for delineating the role of U‐II in the aetiology of mammalian cardiometabolic diseases.

Camphor sulfonamide derivatives as novel, potent and selective CXCR3 antagonists.

A series of N-arylpiperazine camphor sulfonamides was discovered as novel CXCR3 antagonists. The synthesis, structure-activity relationships, and optimization of the initial hit that resulted in the identification of potent and selective CXCR3 antagonists are described.

Discovery of (3-endo)-3-(2-cyano-2,2-diphenylethyl)-8,8-dimethyl-8-azoniabicyclo[3.2.1 ]octane bromide as an efficacious inhaled muscarinic acetylcholine receptor antagonist for the treatment of COPD

Design and syntheses of a novel series of muscarinic antagonists are reported. These efforts have culminated in the discovery of (3-endo)-3-(2-cyano-2,2-diphenylethyl)-8,8-dimethyl-8-azoniabicyclo[3.2.1]octane bromide (4a) as a potent and pan-active muscarinic antagonist as well as a functionally active compound in a murine model of bronchoconstriction. The compound has also displayed pharmacokinetic characteristics suitable for inhaled delivery.

Design, synthesis and structure–activity relationship of N-substituted tropane muscarinic acetylcholine receptor antagonists

A novel series of N-substituted tropane derivatives was characterized as potent muscarinic acetylcholine receptor antagonists (mAChRs). Kinetic washout studies showed that the N-endosubstituted analog 24 displayed much slower reversibility at mAChRs than the methyl-substituted parent molecule darotropium. In addition, it was shown that this characteristic appeared to translate into enhanced which duration of action in a mouse model of bronchonstriction.

Tyrosine urea muscarinic acetylcholine receptor antagonists: Achiral quaternary ammonium groups

Tyrosine ureas had been identified as potent muscarinic receptor antagonists with promising in vivo activity. Controlling the stereochemistry of the chiral quaternary ammonium center had proved to be a serious issue for this series, however. Herein we describe the preparation and SAR of tyrosine urea antagonists containing achiral quaternary ammonium centers. The most successful such moiety was the 2-methylimidazo[2,1-b][1,3]thiazol-7-ium group which yielded highly potent antagonists with long duration of action in an inhaled animal model of bronchoconstriction.