BASALIT trial: double‐blind placebo‐controlled allergen immunotherapy with rBet v 1‐FV in birch‐related soya allergy

Background Conflicting results exist on the effect of allergen immunotherapy (AIT) on pollen‐related food allergy. We aimed to investigate the efficacy of one‐year AIT with the folding variant (FV) of recombinant (r) Bet v 1 on birch‐related soya allergy. Methods Of 138 subjects with Bet v 1 sensitization, 82 were positive at double‐blind placebo‐controlled food challenge (DBPCFC) with soya. A total of 56 of 82 were randomized in the ratio of 2:1 (active: placebo). Per‐protocol population (PPP) had received ≥150 μg of allergen or placebo preparation. Outcome measures: lowest observed adverse effect levels (LOAEL), postinterventional occurrence of objective signs (objS) at any dose level, sIgE/IgG4 against Bet v 1 and Gly m 4. Between‐group changes were investigated (ancova, Mann–Whitney U‐test, Fisher exact test). Results Baseline characteristics including LOAELs were comparable in both groups with objS and subjS occurring in 82% and 95% of active (n = 38) vs 78% and 83% of placebo group (n = 18). After AIT, objS occurred in 24% and 47%, respectively. LOAEL group differences showed a beneficial tendency (P = 0.081) for LOAELobjective in PPP (30 active, 15 placebo). sIgG4 raised only in active group (Bet v 1: P = 0.054, Gly m 4: P = 0.037), and no relevant changes occurred for sIgE. Only 56% of the intended sample size was recruited. Conclusion For the first time, we present data on the effect of rBet v 1‐FV on birch‐related soya allergy. rBet v 1‐FV AIT induced significant immunogenic effects. Clinical assessment showed a tendency in favour of the active group but did not reach statistical significance.