Sublingual-swallow immunotherapy with standardized 3-grass pollen extract: a double-blind, placebo-controlled study

Sublingual immunotherapy (SLIT) is accepted as a safe and effective route for the treatment of grass pollen allergy, but clarification of its clinical and biological efficacy requires more study.

To evaluate the efficacy, safety, and compliance of SLIT with a standardized 3-grass pollen extract in patients with grass pollen seasonal allergic rhinoconjunctivitis, with or without mild asthma.

This multicenter, randomized, double-blind study included 127 patients (aged 12-41 years; mean age, 24.9 years) with grass pollen seasonal allergic rhinoconjunctivitis, with or without mild asthma. They received either SLIT with a high-dose, standardized, 3-grass pollen extract or placebo for 10 months before and during the grass pollen season. The efficacy evaluation compared weekly clinical scores (defined as the sum of the symptom score and rescue medication score) to measure rhinoconjunctivitis and asthma for the first 8 weeks of the pollen season. We also evaluated safety and compliance and measured changes in anti-Dactylis specific IgG4 antibody levels.

There was a trend in favor of the study group in the mean adjusted clinical score. The groups were not comparable on inclusion (P = .02): the SLIT group included more subjects with asthma and had a higher mean IgG4 serum level. Additional exploration according to subgroups with and without asthma found that among the patients without asthma, the SLIT group had a significantly better clinical score (P = .045). Anti-Dactylis specific IgG4 levels increased significantly in the SLIT group.

SLIT with a standardized, high-dose, 3-grass pollen extract is safe and significantly improves the clinical score in patients with hay fever and without asthma during the pollen season.