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Background

Birch, alder, hazel, and oak are members of the birch homologous group based on cross-reactivity toward the birch pollen allergen Betula verrucosa 1. Theoretically, allergy to these tree pollens may be treated by immunotherapy with one representative allergen extract.

Objective

To evaluate post hoc whether treatment of birch pollen–induced allergic rhinoconjunctivitis with a standardized tree sublingual immunotherapy (SLIT)-tablet containing birch pollen extract reduces symptoms and symptom-relieving medication use during the oak pollen season (OPS).

Methods

In a randomized, multinational, double-blind trial (EudraCT-2015-004821-15), 634 participants (ages 12-65 years) received daily tree SLIT-tablet (12 SQ-Bet) or placebo before and during tree pollen season (alder/hazel plus birch pollen season [BPS]). Symptom-relieving medication was allowed. The primary end point was the average total combined score (sum of rhinoconjunctivitis daily symptom score and daily medication score) during BPS. Outcomes during the OPS (excluding overlapping BPS days) were analyzed post hoc.

Results

Relative improvements in average total combined score, daily symptom score, and daily medication score with the tree SLIT-tablet versus placebo during the OPS were 25%, 22%, and 32%, respectively (all P < .001). Significant correlations were observed between birch and oak serum immunoglobulin E (sIgE) at baseline (r = 0.86) and between birch and oak IgG4 after treatment (r = 0.72). Oak sIgE and IgG4 kinetics in response to tree SLIT-tablet treatment were similar to birch.

Conclusions

The tree SLIT-tablet leads to significant improvement of rhinoconjunctivitis outcomes during the OPS, supporting the clinical relevance of immunological cross-reactivity toward birch and oak allergens.