Methods: Relevant patients will be recruited from Respiratory Outpatient Wards. In total, 110 patients will be required. Visits will be performed at screening, at week 0, 4, 8, 12, 16, 26, 52. In the active arm, ICS dosage will be reduced to 50% at week 0 and removed at week 8. All visits include ACQ, FeNO, spirometry, blood eosinophils. S-periostin will be measured at screening and at week 8 and 16.