Unable and/or unlikely to comprehend how to use the investigational device in this study or to follow study instructions Change in asthma therapeutic regimen from Screening through visit 5 Exacerbation of asthma within 8 weeks prior to Screening History of diabetes mellitus Previous exposure to any inhaled insulin product other than TI inhalation Powder or similar formulation Inability to perform PFT maneuvers meeting recommended American Thoracic Society (ATS) standards of acceptability and repeatability criteria Any clinically important pulmonary disease Major organ system diseases including seizures, heart failure, uncontrolled hypertension, cancer within the past 5 years, aneurysm, liver disease, anemia or autoimmune disorder Clinically significant abnormalities on screening laboratory evaluation Female subjects who are pregnant, lactating, or planning to become pregnant during the clinical trial period or not practicing adequate birth control