Study of DM-101PX in Adults With Birch Pollen Allergy

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 treatm…