The purpose of this study is to determine whether Ragweed-SPIRE is safe and effective at reducing allergy symptoms in people who suffer from allergy to Ragweed pollen

Inclusion Criteria:

• Male or female, aged 18-65 years.
• Reliable history consistent with moderate to severe rhinoconjunctivitis on exposure to ragweed for at least the previous two seasons.
• Minimum qualifying rhinoconjunctivitis symptom scores
• Ragweed-specific Immunoglobulin E (IgE) > 0.70 kU/L.

Exclusion Criteria:

• Subjects with a history of ragweed pollen induced asthma
• A history of anaphylaxis to ragweed allergen.
• FEV1 < 80 % of predicted.
• Subjects who cannot tolerate Baseline Challenge in the EEC.
• Subjects for whom administration of epinephrine is contraindicated (e.g. subjects with acute or chronic symptomatic coronary heart disease or severe hypertension).
• History of immunopathological diseases (e.g. multiple sclerosis) that in the opinion of the Investigator or the Sponsor could interfere with the results obtained from the study.
• A history of severe drug allergy, severe angioedema or anaphylactic reaction to food.
• A history of any significant disease or disorder (e.g. cardiovascular, pulmonary, gastrointestinal, liver, renal, neurological, musculoskeletal, endocrine, metabolic, neoplastic/malignant, psychiatric, major physical impairment)