Investigation of Efficacy and Safety of Ragweed MATAMPL, Pollinex-R and Placebo in Patients With Ragweed Allergy

Allergic rhinitis is a nasal inflammatory disorder initiated by an immunoglobulin-E (IgE) mediated hypersensitivity to allergens. This condition is characterized by sneezing, rhinorrhea, nasal itching and congestion. When a patient is exposed to an allergen to which they are sensitive, the allergen cross-links with the Ig E antibody, which is bound to the surface of tissue mast cells. This cross-linking then triggers the release of proinflammatory substances, such as histamine and eicosanoids, and is known as the early response. In a skin prick test, this reaction produces a wheal-and-flare response. Normally, systemic exposure to an allergen also leads to the more prolonged late reaction, in which eosinophils, basophils, and activated T cells are recruited to the site of exposure. The recruited T cells also secrete inflammatory cytokines, such as interleukin-4 (IL-4) and IL-5, typically associated with helper T cells type 2 (TH2), which further propagate the inflammatory cascade. Typically, the early response occurs within 15 to 30 minutes (but as quickly as a few seconds) and usually resolves within 1 to 3 hours, and the late response occurs within 6 to 12 hours and resolves in 24 hours.

Allergic vaccination (AV), also referred to as immunotherapy or allergen-specific immunotherapy (SIT), is a curative approach that is available for allergic diseases, which directly treats the underlying disease. AV is the practice of administering gradually increasing quantities of an allergen extract to an allergic patient to ameliorate the symptoms associated with the subsequent exposure to the causative allergen. AV is believed to exert its beneficial effects on the immune system, at least in part, by modifying the T-lymphocyte response to subsequent natural allergen exposure. AV has been shown to inhibit both early and late responses to allergen exposure. AV acts on T cells to modify peripheral and mucosal TH2 responses to allergen in favor of helper T cell type 1 (TH1) responses. One of the hallmarks of successful AV is the redressing of a "healthy" TH1/TH2-balance.

Although efficacious, immunotherapy is generally considered a long-term disease modifying measure that requires months to years of treatment, entails multiple injection regimens and involves some risk for adverse immune reactions.

Recent improvements, such as optimal dosing, allergen modification (to reduce allergenicity while maintaining immunogenicity), adjuvant adsorption (to control release) and adjuvant activity (to assist immunomodulatory action) are being explored to reduce the risk of anaphylaxis and decrease the commitment to multiple injections.

A novel allergy vaccine (Ragweed MATAMPL) has been developed for the prevention or relief of allergic symptoms caused by a variety of pollens. Ragweed MATAMPL, which contains the allergens of ragweed (chemically modified by glutaraldehyde) adsorbed onto L-tyrosine with the addition of the adjuvant monophosphoryl lipid A (MPL), is being evaluated for the specific treatment of ragweed seasonally induced allergic rhinitis. Ragweed MATAMPL is intended for use as a pre-seasonal therapeutic allergy vaccine in patients with proven seasonal allergic rhinitis and conjunctivitis due to IgE mediated allergy to ragweed. This novel vaccine formulation is designed to provide a vaccine that will be efficacious with only four escalating dose injections, in contrast to the longer schedules currently in use.

This placebo-controlled clinical trial is designed to evaluate the safety and efficacy of Ragweed MATAMPL as determined by patient symptomatic response to pollen and patient quality of life in an environmental exposure chamber (EEC) that reproduces the clinical setting. The development of the EEC, which delivers a controlled pollen challenge over time and allows evaluation of a patient's response at any time point throughout the challenge process, provides the opportunity to examine various aspects of efficacy of anti-allergic treatments within a single center at various times of the year. The EEC affords a more controlled environment than natural pollen exposure in which variables such as unpredictable pollen levels, varying weather conditions during the study period, and varying levels of pollen exposure within the patient population are eliminated. Furthermore, the question of patient compliance is largely eliminated because the patients are scrutinized closely while they are recording symptoms. In addition, an EEC study is an acceptable study model for determining the dose response for an allergic rhinitis drug as outlined in the draft U.S. Food and Drug Administration (FDA) guidelines "Allergic Rhinitis Clinical Development Programs for Drug Products," April 2000.