A high‐dose, depigmented polymerized birch pollen extract for subcutaneous allergen immunotherapy has a favourable efficacy/safety ratio

BACKGROUND: Subcutaneous allergen immunotherapy (SCIT) with depigmented, polymerized (DPP) birch pollen extract has been marketed at doses of up to 1000 DPP units/mL since 2001. We sought to determine the dose‐dependent efficacy of a DPP birch pollen extract formulation in patients suffering from birch‐pollen‐induced allergic rhinitis or rhinoconjunctivitis with or without intermittent asthma. METHODS: A titrated conjunctival provocation test (CPT) was applied as a surrogate marker. This Phase II randomized, double‐blind, parallel‐group, dose‐ranging clinical trial was performed at 39 centres in Germany, Lithuania and Poland. After randomization to four dose‐level groups (100, 1000, 5000 and 10,000 DPP units/mL) and up‐dosing, participants received maintenance SCIT with five monthly subcutaneous injections. The primary endpoint was the proportion of patients in whom a higher concentration of birch pollen (vs. baseline) was needed to elicit a positive CPT. RESULTS: Three hundred forty‐three patients were included (mean (range) age: 42.6 (19–70)). The highest CPT responder rates were seen in the higher dose‐level groups. In the intention‐to‐treat analysis, the difference between the 100 and 10,000 groups was statistically significant (p = 0.0118). Although the proportion of patients with ≥1 treatment‐emergent adverse events increased with the dose, almost all these events were mild (65.6%) or moderate (18.5%). CONCLUSION: Judging by the results of a CPT, the efficacy/safety ratio in SCIT appears to be favourable for a high‐dose‐level preparation of a DPP birch pollen extract.