Results of a clinical study of Nucala (mepolizumab) showed that severe asthma patients who are uncontrolled despite receiving Xolair (omalizumab) experienced improved asthma control when switched to Nucala, according to GlaxoSmithKline. GSK presented the results from the OSMO study at the American Academy of Allergy, Asthma & Immunology (AAAAI) and World Allergy Organization (WAO) Joint Congress in Orlando.

OSMO is an open-label, single-arm study which investigated whether patients who had been receiving Xolair, (a biologic targeting IgE in patients with allergic sensitization) for an average of 2.5 years and continued to have uncontrolled severe asthma, gained better asthma control following a switch to Nucala, (a biologic targeting IL-5 for patients with severe eosinophilic asthma).

In the study 145 patients, who were documented to have experienced at least two asthma exacerbations in the year prior to enrollment, were switched directly to Nucala without a wash-out period and followed for 32 weeks. In this study, Nucala data compared with baseline values prior to first dose, unless otherwise stated:


  • Met the primary endpoint of asthma control with clinically significant improvements, as evaluated by the Asthma Control Questionnaire (ACQ-5), with a mean change from baseline of -1.45 at week 32
  • Met all secondary endpoints and other key endpoints:
  • Rate of exacerbations requiring oral steroids reduced by 64% vs prior 12 months (3.26 to 1.18)
  • Rate of exacerbations requiring an ED visit or hospitalization reduced by 69% vs prior 12 months (0.63 to 0.19)
  • Improvement in lung function (pre-bronchodilator FEV1) of 159 mL vs baseline
  • Improvement in Quality of life as evaluated by the SGRQ (-19 units, compared with MCID -4.0) vs baseline
  • Reduction in blood eosinophils of approximately 80% by Week 4 (vs baseline), which was sustained until Week 32
  • Safety profile was consistent with the known profile of the treatment


“Patients participating in this study suffered burdensome day to day asthma symptoms and frequently required access to urgent care when their asthma symptoms significantly worsened,” said Ken Chapman, professor of Medicine, University of Toronto and an investigator in the OSMO study.

“Like many similar patients, they had both eosinophilic and allergic characteristics, making them eligible to receive treatment with either omalizumab or mepolizumab. OSMO showed us that when these patients remained uncontrolled on omalizumab and were then switched to mepolizumab, they experienced significant improvements – fewer symptoms, better lung function, improved asthma-related quality of life and fewer exacerbations. This study is a valuable addition to our understanding of how to manage patients with biologic therapies.”