The objective of this study was to explore the pharmacology of GSK961081, a bi-functional bronchodilator, in healthy volunteers.
Two randomized, double-blind, placebo-controlled studies were conducted. Following optimization of the propranolol dosing regimen (study 1), we conducted a five-period crossover study (study 2) in which subjects received the following treatments: dry powder inhaler (DPI) GSK961081 400 µg + oral placebo, DPI GSK961081 1,200 µg + oral placebo, DPI GSK961081 400 µg + oral propranolol 80 mg, DPI GSK961081 1,200 µg + oral propranolol 80 mg and DPI and oral placebo. GSK961081 (or inhaled placebo) was dosed at 0 h. Propranolol (or oral placebo) was dosed at −8, −2, 4, 10, and 16 h. The primary endpoint for both studies was bronchodilation, measured by specific airway conductance (sGaw), which was assessed at 0, 1, 4, 7, 12, 22, and 24 h in study 2. Tolerability and pharmacokinetics were secondary endpoints.
Studies 1 and 2 enrolled 18 and 23 subjects, respectively. In study 2, bronchodilation was seen for 24 h following GSK961081 400 and 1,200 μg. In the presence of β 2 blockade, GSK961081 1,200 μg demonstrated bronchodilation in the first 4 h after dosing (treatment difference from placebo at 1 h: 1.206; 90 % confidence interval [CI] 1.126–1.292; and at 4 h: 1.124; 90 % CI 1.078–1.173) but not at 7 h onwards. In the presence of β 2 blockade, GSK961081 400 μg demonstrated bronchodilation in the first 1 h after dosing (treatment difference from placebo: 1.193; 90 % CI 1.117–1.274), but not at 4 h onwards. Adverse events were reported for 21 (study 1) and 15 subjects (study 2); none were serious, and there were no deaths.
The duration of bronchodilation as a result of receiving the muscarinic antagonist component alone was shorter than that from the muscarinic antagonist β 2 agonist combination. Removing the β 2 agonist component may underestimate the contribution of the muscarinic antagonist component to the bronchodilation of the combination.