This study is researching 2 experimental drugs, REGN5713 and REGN5715, which are called REGN5713-5715 when mixed together (called "study drug") to reduce eye allergy signs and symptoms due to birch tree pollen allergy.

The aim of the study is to see how safe and effective the study drug is at lowering allergic eye signs and symptoms compared with placebo. A placebo looks like a treatment but does not contain any real medicine.

The study is looking at several other research questions, including:

• What side effects may happen from taking the study drug
• How much study drug is in the blood at different times
• Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects).

Key Inclusion Criteria:

1. Documented or participant-reported history of moderate to severe birch pollen allergy for at least 2 years with bothersome ocular symptoms during the birch season
2. Positive SPT to birch allergen extract, as described in the protocol
3. Positive allergen specific immunoglobulin E (sIgE) tests for birch and Bet v 1 (≥0.7 kUa/L) at screening visit 1
4. Must be able to complete birch screening CACs and meet the criteria, as described in the protocol

Key Exclusion Criteria:

1. Participation in a prior clinical study and received either REGN5713-5714-5715, REGN5713-5715, or REGN5715 antibodies, as described in the protocol
2. Inability to complete or termination of the screening or confirmatory CACs due to a safety concern (eg, anaphylaxis) per Principal Investigator (PI) judgement
3. Significant and/or severe allergies causing symptoms that are expected to coincide or potentially interfere with the study CAC assessments, as assessed by the investigator, as described in the protocol
4. Persistent chronic or recurring acute infection requiring treatment with systemic antibiotics, antivirals, or antifungals, or any untreated respiratory infections within 4 weeks prior to screening visit 1, as described in the protocol
5. The presence of an active ocular infection (bacterial, viral, or fungal) or diagnosis by a physician within 30 days prior to screening visit 1, as described in the protocol

Note: Other protocol defined Inclusion/Exclusion criteria apply.

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.

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, or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made results publicly available (e.g., scientific publication, scientific conference, clinical trial registry),
• the legal authority to share the data, and
• ensured the ability to protect participant privacy.

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf