I haven't been in a clinical trial, but I also have asthma. Do you know all your triggers? Allergies are one of mine (somewhat indirectly - they led to sinus infections which led to flare-ups). Since being treated for allergies (shots and now weaned off daily allergy medicine except in certain situations) and taking environmental steps to limit exposure (primarily encasing all bedding/pillows in allergy covers), that portion of my asthma is well controlled. I still get the exercise induced asthma real bad though. :-(. Good luck.