A Phase IIa Study of KHK4563

Inclusion Criteria: 1. Age 20 through 75 years at the time of Week -3 visit. 2. Written informed consent obtained from the subject prior to performing any protocol-related procedures, including screening evaluations. 3. Physician prescribed daily use of medium-dose or high-dose ICS plus LABA or any combination of sequential dosing of either medium-dose or high-dose ICS/LABA for at least 12 months prior to Week -3 visit. Dose must be stable for at least 30 days prior to Week -3 visit. 4. At least 2, but not more than 6, documented asthma exacerbations in the 12 months prior to Week -3 visit that required use of a systemic corticosteroid burst. Exclusion Criteria 1. Any condition (eg, any eosinophilic lower respiratory disease other than asthma, Churg-Strauss syndrome, hypereosinophilic syndrome, eosinophilic bronchitis, eosinophilic pneumonia, chronic obstructive pulmonary disease (COPD), bronchiectasis or cystic fibrosis (CF)) that, in the opinion of the investigator or Medical Expert, would interfere with evaluation of the investigational product or interpretation of subject safety or study results. 2. Any clinically relevant abnormal findings in physical examination, vital signs, hematology, clinical chemistry, or urinalysis during screening period, which in the opinion of the investigator, may put the subject at risk because of his/her participation in the study, or may influence the results of the study, or the subject's ability to participate in the study. 3. Acute upper or lower respiratory infections requiring antibiotics or antiviral medications within 30 days prior to Week -3 visit or during the screening period.