Inclusion Criteria:
* Participant of either sex and any race, aged 18 to 65 years inclusive.
* Documented clinical history of birch pollen-induced allergic rhinitis or rhinoconjunctivitis with symptoms that interfere with daily activities or sleep and remain bothersome despite the use of relevant symptomatic medication, and have been present over, at least, 2 previous allergy seasons.
* Bet v 1 specific serum IgE ≥ 0.7 kAU/L.
* Positive Skin Prick Test to birch pollen allergen, with a wheal diameter ≥ 5 mm.
* Body weight ≥ 50 kg and body mass index (BMI) within the range 18-35 kg/m2 inclusive.
Exclusion Criteria:
* History or findings on physical examination at screening visit of any significant disease or disorder which, in the opinion of the Investigator, could put the participant at risk because of participation in the study, influence the results of the study or the participant's ability to participate in the study.
* History of significant rhinitis, sinusitis, and/or presence of significant symptoms of respiratory allergy due to regular contact with other allergens, not associated with the birch pollen season, that are expected to coincide or potentially interfere with the study allergen challenge assessments, as assessed by the Investigator.
* History of nasal polyps or other nasal oropharyngeal conditions that in the judgement of the Investigator may interfere with study outcome assessments.
* History of chronic obstructive pulmonary disease requiring regular treatment.
* Current diagnosis of uncontrolled, partially controlled or persistent asthma requiring regular (\> 6 weeks per year) maintenance use of inhaled corticosteroids. History of severe asthma during the pollen season. History of asthma deterioration that resulted in emergency treatment or hospitalization in the 12 months before screening, or a life-threatening asthma attack at any time in the past.
* Forced Expiratory Volume in one second (FEV1) \< 75% of predicted. History of severe drug allergy, severe angioedema or systemic allergic reaction of Grade 3 or greater, according to the World Allergy Organization (WAO) scale, due to any cause.
* History of intolerance to the Investigational Product, rescue medications used for systemic allergic reactions (i.e., adrenaline, antihistamine, glucocorticoids, and beta-2 agonists such as salbutamol), or their excipients.
* History of acute hypersensitivity and/or anaphylaxis to protein therapeutics or components of formulation.
