This study will involve the use of a new compound, GW642444 that is being developed for the treatment of asthma and chronic obstructive pulmonary disease (COPD). It works by acting on cells in the lungs, causing some of the muscles around the lungs to relax and open up better (bronchodilation), making breathing easier. When a medicine is made into a form ready to be given to patients, the active ingredient is often prepared with another ingredient called a salt to help make it stable, and inactive ingredients are often added. Inactive ingredients might be used to help a medicine work better, to make it easier to produce the medicine, or to make it easier to get an accurate dose of medicine. In previous studies the study drug has been given as a dry powder containing either the "H" salt (with the inactive ingredient lactose), or containing the "M" salt (with the inactive ingredients lactose and cellobiose octaacetate). The "M" salt form of the study drug has been altered to contain lactose and a new inactive ingredient called magnesium stearate (instead of cellobiose octaacetate).

Participants in this study will receive both the "H" salt (GW642444H) and the new "M" salt (GW642444M) containing magnesium stearate. This study will be the first time the new "M" salt form of the study drug will be given to asthmatic patients.