Asthma symptom re-emergence after omalizumab withdrawal correlates well with increasing IgE and decreasing pharmacokinetic concentrations

Background: Physicians have questioned whether omalizumab can be discontinued or the dose reduced after clinical improvement is seen in patients with severe asthma. Objectives: To examine the relationships among omalizumab, free IgE, and clinical outcomes in a randomized, placebo-controlled trial in patients with severe persistent allergic asthma following a posology based on pretreatment total IgE and body weight. Methods: A pharmacokinetic-pharmacodynamic binding model was used to calculate free IgE, omalizumab, and total IgE concentrations during the 28-week treatment and 16-week follow-up of the INvestigation of Omalizumab in seVere Asthma TrEatment (INNOVATE) study. These were plotted against the mean changes in the total asthma symptom score, morning peak expiratory flow, and rescue medication use for physician-defined treatment responders and nonresponders. Results: The model accurately fitted omalizumab and free and total IgE, allowing reconstruction of the entire time course for each patient. Free IgE was rapidly suppressed below the 50 ng/mL (20.8 IU/mL) target, although there was a notable period before clinical measures stabilized. After treatment cessation, free IgE and omalizumab returned toward baseline and, after a delay, asthma symptoms re-emerged. Model-derived omalizumab and free IgE concentrations correlated well with changes in clinical outcomes, particularly in omalizumab-treated responders. Asthma symptoms exhibited different correlations during response onset compared with response offset (hysteresis), indicative of physiological time delays between changes in IgE levels and pulmonary function. Conclusion: Omalizumab and free IgE correlated well with clinical symptoms. Reducing omalizminab doses below those in the dosing table cannot be recommended; the resulting increase in free IgE would cause a deterioration in asthma control. (J Allergy Clin Immunol 2009;123:107-13.)