Free-IgE as a Predictor of Responsiveness to Omalizumab in Oral Corticosteroid-Dependent Asthma Patients

To date, no biomarkers have been found that are able to predict the clinical response to omalizumab. The aim of this study was to assess whether blood concentration of free Immunoglobulin E (IgE) can predict response to treatment with this monoclonal antibody. In a group of patients who were candidates for omalizumab treatment, forced spirometry and blood IgE were measured at entry and at each six-month visit, and free-IgE blood concentrations were measured at month 6. At month 18, the OMADORE protocol was applied. The complete follow-up lasted 30 months. Patients were considered responders if they met at least one of the following criteria: increase in forced expiratory volume in one second (FEV₁) at the follow-up visit compared to baseline; reduction in corticosteroid dose at the last visit compared to baseline; reduction in omalizumab dose at the follow-up visit; a positive score on the composite index combining all three criteria. The biomarker used to predict treatment response was the free IgE value and the percentage of free IgE to total IgE measured at visit 1, after six months of omalizumab treatment. The percentage of responders varied according to the parameter used (FEV₁, omalizumab, corticosteroid dose, and the composite index; 45.2%, 64.5%, 48.4%, and 77.4%, respectively). IgE blockade was around 97% both for the group as a whole and for the subgroups. There were no differences in free IgE values nor in the ratio of free IgE to total IgE between responders and non-responders. These results confirm that there is a group of patients who may benefit from the reduction/withdrawal of omalizumab. Determination of free IgE six months after initiation of omalizumab treatment does not discriminate between responders and non-responders.