Efficacy and Safety of Specific Immunotherapy with SQ Allergen Extract in Treatment-resistant Seasonal Allergic Rhinoconjunctivitis

Background: Specific immunotherapy is widely used to treat allergic rhinitis, but few large-scale clinical trials have been performed.

Objective: We sought to assess the efficacy and safety of specific immunotherapy with 2 doses of Alutard grass pollen in patients with moderately severe seasonal allergic rhinitis inadequately controlled with standard drug therapy.

Methods: We performed a double-blind, randomized, placebo-controlled study of 410 subjects (203 randomized to 100,000 standardized quality units [SQ-U] maintenance, 104 to 10,000 SQ-U, and 103 to placebo). Three hundred forty-seven (85%) completed treatment. Groups were well matched for demographics and symptoms.

Results: Across the whole pollen season, mean symptom and medication scores were 29% and 32% lower, respectively, in the 100,000-SQ-U group compared with those in the placebo group (both P < .001). Over the peak pollen season, mean symptom and medication scores were 32% and 41% lower, respectively, than those in the placebo group. The 10,000-SQ-U group had 22% less symptoms than the placebo group over the whole season (P < .01), but medication scores reduced by only 16% (P = .16). Quality-of-life measures confirmed the superiority of both doses to placebo. Local and delayed side effects were common but generally mild. Clinically significant early and delayed systemic side effects were confined to the 100,000-SQ-U group, but no life-threatening reactions occurred.

Conclusions: One season of immunotherapy with Alutard grass pollen reduced symptoms and medication use and improved the quality of life of subjects with moderately severe hay fever. The 100,000-SQ-U regimen was more effective, but the 10,000-SQ-U regimen caused fewer side effects.