Efficacy of the Anti-Bet v 1 Monoclonal Antibodies (Given Subcutaneously) to Reduce Allergic Rhinitis and Conjunctivitis Symptoms and Skin Test Reactivity Upon Exposure to Birch Allergen in Adult Participants

A Two-Part Randomized, Double-Blind, Placebo-Controlled Study to Assess the Efficacy of the Anti-Bet v 1 Monoclonal Antibodies to Reduce Allergic Rhinitis and Conjunctivitis Symptoms and Skin Test Reactivity Upon Exposure to Birch Allergen

Primary objective: To assess the efficacy of a single dose of the anti- Bet v 1 monoclonal antibodies (mAb(s ) in the reduction of allergic nasal symptoms during an out-of-season birch allergen environmental exposure unit (EEU) challenge in participants receiving REGN5713-5714-5715 versus placebo (Part A)

The study consists of Part A and Part B. All participants will be asked to complete both Part A and Part B of the study. The study lasts for a total duration of up to approximately 46 weeks (including up to a 10-week screening period). Part A of the study lasts up to approximately 28 weeks (including the screening period). Part B of the study starts after completion of Part A and lasts up to approximately 18 weeks (including an approximately 4-week follow-up period after end of birch pollen season (BPS)), dependent on the start and end times of the natural BPS.

Key Inclusion Criteria:

1. Documented or participant-reported history of birch tree pollen-triggered allergic-rhinitis (AR) symptoms with or without conjunctivitis (for at least 2 seasons)
2. Positive Skin prick test (SPT) with birch tree pollen extract (mean wheal diameter at least 5 mm greater than a negative control) in screening period
3. Positive allergen-specific immunoglobulin E (sIgE) tests for birch tree pollen and Bet v 1 (≥0.7 kUa/L) in screening period
4. Demonstrated TNSS ≥ 6 out of 12 on at least 2 time points during the birch EEU exposure challenge in screening period

Key Exclusion Criteria:

1. Participation in a prior REGN5713-5714-5715 clinical trial and received REGN5713-5714-5715 antibodies (receipt of placebo in a previous trial is allowed)
2. Significant rhinitis, sinusitis, significant and/or severe allergies not associated with the birch pollen season, or due to daily contact with other non-birch related allergens causing symptoms that are expected to coincide or potentially interfere with the study EEU assessments or with the birch pollen season, as assessed by the investigator
3. Participants who anticipate major changes in allergen exposure during the birch pollen season that are expected to coincide with study assessments or planned travel that is expected to interfere with the study assessments, as assessed by the investigator (eg. anticipated travel during planned EEU sessions or birch pollen season)
4. Persistent chronic or recurring acute infection requiring treatment with antibiotics, antivirals, or antifungals, or any untreated respiratory infections within 4 weeks prior to screening visit 1. Patients may be re-evaluated for eligibility after resolution of symptoms and specified duration.
5. History of significant, recurrent sinusitis, defined as at least 3 episodes requiring antibiotic treatment per year for the last 2 years
6. Abnormal lung function as judged by the investigator with Forced Expiratory Volume (FEV1) <75% of predicted at screening or randomization
7. A clinical history of moderate to severe asthma, uncontrolled asthma, global initiative for asthma [GINA] steps 3 to 5, history of life-threatening asthma, asthma exacerbations due to tree pollen allergy within 2 prior seasons, >2 asthma exacerbations requiring systemic steroids in past 12 months, asthma related emergency care or hospitalization within 12 months prior to screening, as defined in the protocol.
8. History of birch or other tree allergen immunotherapy in the 3 years prior to screening.
9. Use of anti-IgE or other biological therapy (including but not limited to anti IL-5, anti IL-4) that interferes with type 2 disease within 6 months prior to screening visit 1.
10. Allergen-specific immunotherapy with any allergen other than birch or other trees at screening.
11. History of clinically significant cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric, or neurological disease,
12. Any malignancy within the past 5 years, except for basal cell or squamous epithelial cell carcinomas of the skin or carcinoma in situ of the cervix or anus that have been resected, with no evidence of local recurrence or metastatic disease for 3 years.

NOTE: Other protocol defined Inclusion/Exclusion Criteria apply