Main idea: Although the primary endpoint was not reached for the Full Analysis Set, a significant and clinically relevant effect on Symptom Medication Score was clearly demonstrated for the subgroup of patients in the northeastern region of Europe, where birch is the predominant tree species. Proving efficacy of birch allergen subcutaneous immunotherapy is challenging due to the numerous factors influencing birch pollen allergen exposure in field studies.
Previous clinical trials with birch pollen subcutaneous immunotherapy have been conducted over a 1- to 2-year treatment period and involved mostly a single geographic location.
This study (EudraCT-Number: 2005-000025-35) intended to evaluate the effect of subcutaneous immunotherapy with high-dose hypoallergenic birch pollen allergoid in patients with confirmed moderate to severe seasonal allergic rhinitis/rhinoconjunctivitis over a 3-year course in 19 European centers.
Adults with confirmed birch pollen allergy (n = 253) were randomized to preseason placebo (n = 129) or active treatment (n = 124). The primary endpoint was a change in Symptom Medication Score after 2 years of treatment (2007).
Results: The change in allergy symptoms active- vs placebo-treated showed a positive trend, although significance was not achieved. The primary endpoint, assessed in 2007, coincided with the lowest pollination during the study period. In a subgroup analysis of patients in the north-eastern region (n = 102), where birch is the major tree and consequently patients’ exposure is higher, changes in Symptom Medication Score (32.7% reduction) and the median number of well days were highly significant in favor of the active group. Subcutaneous immunotherapy was well-tolerated and consistent with the known safety profile.