A Multi-national, Randomized, Double-blind, Placebo-controlled, 3-period Crossover Study With GSK 573719 as Monotherapy in Adult Subjects With Asthma

This is a multi-national, randomized, double-blind, 3-period crossover, incomplete block design to evaluate 5 once-daily and 2 twice-daily doses of GSK573719 in combination with placebo. The study will explore the dose range of GSK573719 in asthmatic subjects who are currently using non-ICS controller medications. Subjects will participate in the study for up to a maximum of 14 weeks. At randomization subjects will be stratified by age to ensure adequate exposure to GSK573719 throughout the expected age range. The primary endpoint will be trough FEV1 obtained 24 hours after the last morning dose on Day 14 of each treatment sequence. A sub-group of subjects at selected sites (approximately 30% of the total population) will have additional serial assessments for spirometry, ECG and Holter, and pharmacokinetic sampling at the start and end of each treatment period. Safety assessments will include monitoring for adverse events, laboratory tests, asthma symptom assessments and twice daily PEF evaluation. Consenting subjects will have a blood sample taken for pharmacogenetic analysis.