The primary objective of the study is to evaluate the safety and tolerability of REGN5713-5714-5715 in healthy adult participants.

The secondary objectives of the study are:

In Part A and Part B:

• To characterize the concentration time profile of single doses of REGN5713-5714-5715 in healthy adults
• To assess the immunogenicity of single dose of REGN5713-5714-5715.

In Part B:

• To assess the inhibition of allergic symptoms as measured by total nasal symptom score (TNSS) provoked by a birch allergen nasal allergen challenge (NAC) in birch-sensitized allergic subjects after a single subcutaneous (SC) dose of REGN5713-5714-5715
• To assess the skin test reactivity provoked by a skin prick test (SPT) with serial birch allergen titration after a single SC dose of REGN5713-5714-5715.

Key Inclusion Criteria:

• Participant is judged by the investigator to be in good health based on medical history, physical examination, vital sign measurements, and ECG performed prior to study drug dosing
• Participant is in good health based on laboratory safety testing obtained at the screening prior to study drug dosing
• Part B: Has a medical history of birch tree pollen-triggered allergic rhinitis (AR) symptoms with or without conjunctivitis (for at least 2 seasons) based on participant's recall
• Part B: Has positive skin prick test (SPT) with birch tree pollen extract (mean wheal diameter ≥5 mm greater than a negative control) in screening period

Key Exclusion Criteria:

• History of clinically significant cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric, or neurological disease, as assessed by the investigator that may confound the results of the study or pose an additional risk to the participant by study participation
• Has any physical examination findings and/or history of any illness that, in the opinion of the study investigator, might confound the results of the study or pose an additional risk to the participant by study participation
• Participation in any clinical research study evaluating another investigational drug or therapy within 90 days or at least 5 half-lives (whichever is longer) for an investigational biologic drug, or at least 28 days for other investigational products, or within 6 months for immunotherapy prior to the screening visit of the current trial
• Pregnant or breastfeeding women
• Part B: Receipt of study drug REGN5713-5714-5715 in Part A
• Part B: Significant rhinitis or sinusitis outside of the birch pollen season or due to daily contact with other allergens causing symptoms, that is expected to coincide with the study NAC assessments as assessed by the investigator
• Part B: A clinical history of asthma requiring chronic medication such as regular, inhaled corticosteroids for >6 months per year
• Part B: History of birch allergy immunotherapy (SCIT, sublingual immunotherapy, or oral immunotherapy) in the 5 years prior to screening

NOTE: Other protocol defined inclusion/exclusion criteria apply.

All individual participant data (IPD) that underlie publicly available results will be considered for sharing

Individual anonymized participant data will be considered for sharing once the indication has been approved by a regulatory body, if there is legal authority to share the data and there is not a reasonable likelihood of participant re-identification.

Qualified researchers may request access to anonymized patient level data or aggregate study data when Regeneron has received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc) for the product and indication, has the legal authority to share the data, and has made the study results publicly available (eg, scientific publication, scientific conference, clinical trial registry).