The anti-IgE antibody Omalizumab has been approved for the treatment of perennial allergic asthma and dosing is adjusted according to total IgE levels and body weight, and a near complete suppression of free IgE is deemed to be necessary for optimal efficacy. As many asthmatics have additional sensitizations seasonal exposure may increase IgE levels and lead to an imbalance between IgE levels and omalizumab with possible impact on therapeutic outcome.
We studied serum total and specific (timothy grass) IgE levels in 17 rhinitis patients with or without asthma prior to and during the grass pollen season and calculated hypothetical doses of omalizumab.
During the pollen season, total IgE increased significantly from 89 (50-178) kU/l (geom. mean with 95% confidence interval) to 126 (63-251) kU/l (p=0.0006). Specific IgE increased from 11 (6.3-19) kU/l to 15.1 (8.3-29) kU/l (p=0.0013). Calculated doses of omalizumab based on pre-seasonal IgE levels were: no dosing: n=2; 150mg 4-weekly (wk): n=7; 300mg 4-wk: n=2; 225mg 2-wk: n=4; 300mg 2-wk: n=1; 375mg 2-wk: n=1. Based on seasonal IgE levels doses would have changed in 5/17 patients. Of these, two patients would have fallen out of the current dosing scheme.
A seasonal increase of serum total and specific IgE can be observed in patients with pollen allergy, although this would have no impact on omalizumab doses in the majority of patients. Individual variations, however, can be large and necessitate a dose correction. Therefore, therapeutic monitoring of free IgE levels during anti-IgE treatment appears as desirable tool.