Grass pollen allergens are recognised as a major cause of allergic diseases in humans and animals. Worldwide, at least 40% of allergic patients are sensitised to grass pollen allergens and between 50-90% of hayfever or seasonal allergy sufferers are allergic to grass pollen. ToleroMune Grass is a novel, synthetic, allergen-derived peptide desensitising vaccine, currently being developed for the treatment of grass allergy.

This study will look at the efficacy, safety and tolerability of three doses of ToleroMune Grass in grass allergic subjects following challenge with with grass in an Environmental Exposure Unit (EEU).

This study is designed as a randomised, double-blind, placebo-controlled, parallel group study to evaluate the safety and tolerability of ToleroMune Grass in grass allergic subjects with allergic rhinoconjunctivitis. The efficacy of ToleroMune Grass will be explored in subjects using an EEU (Environmental Exposure Unit).

The study will consist of 3 study periods. In Period 1, Screening will be performed up to a maximum of 16 weeks before randomisation and may consist of one or two visits to the clinic, at the Investigator's discretion. Baseline Challenge will consist of 4 visits to the EEU at least 3 days before randomisation.

In Period 2, subjects in each cohort complying with the inclusion/exclusion criteria will be randomised to one of four groups and will receive treatment every 2 weeks (±2 days) for 14 weeks.

In Period 3, Post Treatment Challenge will consist of 4 visits to the EEU about 25 weeks after the first administration in the treatment period and assessments will be performed identical to those at the baseline challenge. Follow-up will be conducted 3-10 days after PTC.

Inclusion criteria

• Male or female, aged 18-65 years.
• Minimum 2-year documented history of rhinoconjunctivitis on exposure to grass.
• Positive skin prick test to grass allergen.
• Minimum qualifying rhinoconjunctivitis symptom scores

Exclusion criteria

• History of asthma.
• A history of anaphylaxis to grassallergen.
• Subjects with an FEV1 <80% of predicted.
• Subjects who cannot tolerate baseline challenge in the EEU.
• Subjects for whom administration of epinephrine is contra-indicated (e.g. subjects with acute or chronic symptomatic coronary heart disease or severe hypertension).
• 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).