A 68-year-old woman with GOLD stage 3 COPD (FEV1 40% predicted) continues to have two to three moderate exacerbations per year despite dual long-acting bronchodilator therapy (LAMA/LABA). Blood eosinophils are 420 cells/µL. According to the 2023 Canadian Thoracic Society COPD pharmacotherapy guideline, what is the next best step?