CD-sens and clinical changes during withdrawal of Xolair after 6 years of treatment

Background: Many clinical trials with omalizumab, Xolair, have been reported but the treatment period has always been short, i.e. < 12 months. After withdrawal, the clinical symptoms tend to return. A group of patients who stopped treatment after approx. 6 years allowed studies of the long-term effects of Xolair. Methods: The patient's cat or mite allergen sensitivity was quantitated as basophil allergen threshold sensitivity, CD-sens, and immunoglobulin E (IgE) and IgE- and IgG4-antibodies were determined before start and during treatment withdrawal. Asthma severity was evaluated from forced expiratory volume (FEV), peak expiratory flow (PEF) and a questionnaire. Results: At 6-14 months without Xolair 13 of the 18 cat and mite allergic asthmatics had either improved or remained the same as on treatment. Most of the patients were in a stable clinical condition reporting high quality of life, no increased nightly asthma attacks, no emergency visits as well as little or no increase in medication. The CD-sens to cat showed a peak 4 months after withdrawal but then decreased to levels below those of untreated patients with allergic asthma and at 12 months six of 14 had nonreactive basophils. Cat IgG4 antibody levels were higher than in cat allergics in general. Conclusion: Most of the patients 12-14 months had, after closing of 6-year Xolair treatment, a surprisingly mild asthma. Interestingly, and probably contributing to the clinical results, a downregulation of basophil, and presumably also mast cell, reactivity, was seen.