Evaluation of the Efficacy and Safety of AVANZ® Phleum Pratense in Grass Pollen-induced Allergic Rhinitis During Controlled Exposure in an Environmental Challenge Chamber

Inclusion Criteria: * Written informed consent * Male or female aged 18 to 65 years * The subject fulfills one of the following criteria: * Male * Female, infertile * Female of child-bearing potential, with a negative pregnancy test * Moderate-to-severe grass pollen induced rhinoconjunctivitis * Positive skin prick test response (wheal diameter ≥ 3 mm) to Phleum pratense * Positive specific Immunoglobulin E (IgE) against Phleum pratense (≥ IgE Class 2; ≥0.70 kilo Unit/L) * Minimum level of rhinitis symptoms in an grass pollen challenge, defined as a total nasal symptom score of at least 6 (of 12) within the 3-hour grass pollen challenge at performed at the baseline ECC visit * The subject must be willing and able to comply with the trial protocol Exclusion Criteria: * Rhinoconjunctivitis caused by ragweed, mugwort or Alternaria alternate * Rhinoconjunctivitis caused by animal hair and dander, house dust mites and moulds * Clinical history of uncontrolled asthma within 3 months prior to screening * Subjects with reduced lung function forced expiratory volume in 1 second \<70% of the predicted value after adequate pharmacologic treatment * Subjects with asthma requiring treatment with inhaled corticosteroids outside the grass pollen seasons * Previous treatment with immunotherapy to a grass pollen allergen or a cross reacting allergen within the past 5 years * Ongoing treatment with any allergen-specific immunotherapy product * Symptoms of or treatment for upper respiratory tract infection, acute sinusitis, acute otitis media or other relevant infectious process at randomisation and at the baseline challenge * Clinically relevant nasal polyps * History of paranasal sinus surgery * History of surgery of nasal turbinates * History of anaphylaxis with cardiorespiratory symptoms (immunotherapy, exercise induced, food allergy, drugs or an idiopathic reaction) * History of recurrent (defined as 2 or more episodes) generalised urticaria during the last 2 years * History of drug-induced (including immunotherapy) facial angioedema or a family (parents and siblings) history of hereditary angioedema * Any clinically relevant chronic disease (≥3 months duration) (e.g. cystic fibrosis, malignancy, malabsorption or malnutrition, renal or hepatic abnormality, or any other diseases that in the opinion of the investigator would interfere with the trial evaluations or the safety of the subjects) * Systemic disease affecting the immune system (e.g. insulin-dependent diabetes, autoimmune disease, immune complex disease, or immune deficiency disease) * Immunosuppressive treatment (ATC code L04 or L01) within 3 months prior to the screening visit * Currently treated with tricyclic antidepressants, catecholamine-O * methyltransferase inhibitors and/or mono amine oxidase inhibitors * Treatment with antidepressant medication with antihistaminic effect (e.g. doxepin, mianserin) * Treatment with antipsychotic medications with antihistaminic effect (e.g. chlorpromazine, levomepromazine, clozapine, olanzapine, thioridazine) * Treatment with anti-IgE drugs (e.g. omalizumab) within 130 days/5 half-lives which ever longest * Treatment with systemic and/or topical β-blockers * Use of an investigational drug within 30 days/5 half-lives of the drug, which ever the longest, prior to screening * History of allergy, hypersensitivity or intolerance to an excipient the investigational drug (except Phleum pratense) * Being immediate family of the investigator or trial staff, defined as the investigator's/staff's spouse, parent, child, grandparent, or grandchild * History of alcohol or drug abuse