A Study to Assess the Potential for Airway Sensitivity Reactions With Propellants HFA-152a (Test) and HFA-134a (Reference) Administered Via Pressurized Inhalers in Adults With Mild Asthma

The purpose of the study is to assess the propellants,1 - Difluoroethane \[HFA-152a\] (Test) and 1,1,1,2-Tetrafluoroethane \[HFA-134a\] (Reference) for their potential to cause the airways to tighten when delivered through pressurized metered dose inhalers (pMDI). The rationale for this study is to develop a low carbon footprint alternative propellant, HFA-152a, which will have a lower impact on global warming.