Subcutaneous birch pollen allergen immunotherapy with a depigmented polymerized extract shows only sustained and long-term efficacy in a subgroup of monosensitized adults and adolescents with allergic rhinitis

Background Allergen immunotherapy (AIT) is an approved treatment for seasonal respiratory allergic diseases. A depigmented polymerized birch pollen extract for subcutaneous allergen immunotherapy (SCIT) has been demonstrated to be efficacious and safe in patients allergic to birch pollen and its homologous group. Objective To determine whether SCIT with a birch pollen formulation (5000 depigmented polymerized (DPP) units/mL) shows sustained and long-term efficacy in adults and adolescents with birch-pollen induced allergic rhinitis with or without intermittent asthma. Methods A multicentre (n = 66), double-blind, placebo-controlled Phase III clinical trial was performed in the Czech Republic, Finland, Germany, Latvia, Lithuania, Poland and Russia. Participants were randomized 2:1 to active treatment (birch 5000 DPP/ml) or placebo for three years of SCIT and followed up for two treatment-free years. The primary efficacy endpoint was the EAACI's combined symptom and medication score for rhinoconjunctivitis (CSMSEAACI). Results A total of 973 participants were screened and 649 were randomized (active treatment: n = 434; placebo: n = 215). The intention-to-treat analysis of the CSMSEAACI in the overall study population did not demonstrate statistically significant differences in years 1, 2 and 3. In a post-hoc analysis, among the subgroup of patients monosensitized to birch pollen allergen only (n = 200), we observed a statistically significant difference (active treatment vs. placebo) in the CSMSEAACI in year 2, 3 and 5. The AIT's safety profile was good. Conclusions SCIT with a depigmented polymerized birch pollen extract was safe. Sustained and long-term efficacy in years 2, 3 and 5 in monosensitized patients, but not in polysensitized patients was demonstrated. (EudraCT 2012-000414-11)