Background Real-world effectiveness of mepolizumab as add-on therapy for severe asthma (SA) with eosinophilic phenotype has been demonstrated in observational studies, mainly in North America and Europe. The NUCALA Effectiveness Study (NEST) (GSK 213475) is assessing the effectiveness of mepolizumab in Latin America (Argentina, Chile, Colombia), Arab Gulf countries (Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates) and Asia (Turkey, India).

Aims and objectives To describe the rate ratio of clinically significant asthma exacerbations (CSE) in the 12-months pre- and post-mepolizumab treatment.

Methods NEST is a self-controlled cohort of patients with SA treated with add-on mepolizumab in clinical practice. This was an interim analysis (IA) of patients who received at least one dose, and have complete 12-months pre- and post-mepolizumab initiation historical record. CSE was defined as deterioration in asthma requiring (1) use of systemic corticosteroids for ?3 days and/or (2) ER visit and/or hospital admission.

Results A total of 235 patients were included in the IA (mean age 49 years; 73.2% female). CSE was reported by 128 (59.0%) patients 12-months pre- and 52 (23.1%) patients post-mepolizumab initiation. The mean (SD) number of CSE was 3.6 (3.5) and 1.5 (0.9) episodes per patient pre- and post-mepolizumab, respectively.  Rate ratio of CSE showed a 61% (95% CI: 53?68%) reduction in the 12-month post-mepolizumab initiation.

Conclusion This interim analysis demonstrates the effectiveness of mepolizumab in patients with SA with eosinophilic phenotype in different countries.

Funding GSK (Study ID: 213475)