Clinical and economic consequences of switching from omalizumab to mepolizumab in uncontrolled severe eosinophilic asthma

Severe asthma is burdened by frequent exacerbations and use of oral corticosteroids (OCS), which worsen patients' health and increase healthcare spending. The aim of this study was to assess the clinical and economic impact of switching from omalizumab (OMA) to mepolizumab (MEP) in patients eligible for both biologics, but not optimally controlled by omalizumab. We retrospectively enrolled uncontrolled severe asthmatic patients who switched from OMA to MEP during the last two years. Information included blood eosinophil count, asthma control test (ACT), spirometry, serum IgE, fractional exhaled nitric oxide (FeNO), OCS intake, drugs, exacerbations/hospitalizations, visits and diagnostic exams. Within the perspective of Italian National Health System, a pre- and post-MEP 12-month standardized total cost per patient was calculated. 33 patients were enrolled: five males, mean age 57 years, disease onset 24 years. At OMA discontinuation, 88% were OCS-dependent with annual mean rate of 4.0 clinically significant exacerbations, 0.30 exacerbations needing emergency room visits or hospitalization; absenteeism due to disease was 10.4 days per patient. Switch to MEP improved all clinical outcomes, reducing total exacerbation rate (RR = 0.06, 95% CI 0.03-0.14), OCS-dependent patients (OR = 0.02, 95% CI 0.005-0.08), and number of lost working days (Δ = - 7.9, 95% CI - 11.2 to - 4.6). Pulmonary function improved, serum IgE, FeNO and eosinophils decreased. Mean annual costs were €12,239 for OMA and €12,639 for MEP (Δ = €400, 95% CI - 1588-2389); the increment due to drug therapy (+ €1,581) was almost offset by savings regarding all other cost items (- €1,181). Patients with severe eosinophilic asthma, not controlled by OMA, experienced comprehensive benefits by switching to MEP with only slight increases in economic costs.