Parallel, Randomized, Double-Blind, Placebo-Controlled Trial in Adults for the Sublingual-Oral Immunotherapy (SLIT) of Allergic Rhinoconjunctivitis With or Without Asthma Caused By Ragweed Pollen

Specific allergen immunotherapy as currently practiced in the USA and described in product labeling comprises the subcutaneous injection of incrementally increasing doses to a targeted maintenance dose ("build-up") followed by maintenance injections of allergenic extract/vaccine. Up to 30-40 injections may be required during the build-up phase over a 3-6 month period. When adequate maintenance doses are reached, this form of immunotherapy (SCIT) has been shown to be highly effective and safe.

Standard practices recommend that the injections be given under the supervision of trained physicians and that the patient remain in the physician's office at least 20 to 30 minutes after an injection. The administration of immunotherapy injections are not recommended at home because of the risk of inadequate recognition and treatment of systemic reactions. The inconvenience and expense of traveling for allergy injections and the discomfort of the repeated injections is a disincentive to this form of treatment particularly in pediatric patients. For example, dropout rates exceeding 50% over a multi-year course of injection treatment have been reported.

Alternative routes for immunotherapy have been explored, especially in Europe in an attempt to improve patient compliance and to minimize the risk of serious adverse reactions. For example, sublingual-oral immunotherapy (SLIT), which is the administration of the allergenic extract/vaccine under the tongue for 1-2 minutes followed by swallowing, has been proven to be efficacious and safe in several double-blind, placebo-controlled studies. A recent Cochrane Review concluded, "SLIT is a safe treatment, which significantly reduces symptoms and medication requirements in allergic rhinitis."

Efficacy studies support the use of SLIT for the treatment of rhinitis or rhinitis and asthma. However, dosage schedules are highly variable and optimal maintenance doses have not yet been established. Thus, dosing studies should be designed to investigate not only the safety profile but to determine optimal doses for maintenance therapy of patients built-up by injection IT and for build-up regimens of previously untreated patients.

Much of the United States medical community's hesitation to embrace sublingual immunotherapy as a viable treatment option for allergy patients has stemmed from limited information using U.S. licensed allergenic extracts for this treatment route. Additionally, the cost-effectiveness of one form of therapy over the other has not been clearly evaluated and the third-party payers have not accepted SLIT for insurance coverage.