A Study to Demonstrate How Well REGN1908-1909 Works in Reducing Ocular Allergy Signs and Symptoms in Adult Participants With Cat Allergy

Key Inclusion Criteria:

1. Documented or participant-reported history of moderate to severe cat allergy for atleast 2 years with bothersome ocular symptoms being near cat(s)

2. Positive SPT with cat allergen extract (mean wheal diameter at least 5 mm greaterthan the negative control) at screening visit 1

3. Positive Allergen-specific Immunoglobulin E (sIgE) tests for cat allergen and Fel d 1 (both ≥0.7 kUa/L) at screening visit 1

4. Must be able to complete the screening CACs to confirm moderate to severe catallergen-induced allergic conjunctivitis as described in the protocol

5. Must not have lived with a cat(s) in the home for the past 3 years and must bewilling to have no exposure to cat(s) at home throughout the study duration asdescribed in the protocol

Key Exclusion Criteria:

1. Participation in a prior clinical study and received either REGN1908-1909, REGN1908,or REGN1909 antibodies as described in the protocol

2. Inability to complete or termination of the screening or confirmatory CAC (whereapplicable) due to a safety concern (eg, anaphylaxis), per PI judgement

3. Significant and/or severe allergies, ocular, nasal, or systemic disease causingsymptoms (eg, ocular itching, ocular redness, etc) that are expected to coincide orpotentially interfere with the study CAC assessments, as described in the protocol

4. Persistent chronic or recurring acute infection requiring treatment with systemicantibiotics, antivirals, or antifungals, or any untreated respiratory infectionswithin 4 weeks prior to screening visit 1 as described in the protocol

5. Presence of ocular conditions associated with acute or chronic vision loss, or anyother ophthalmic disease or abnormality that may affect the study outcomes orparticipant safety, per Principal Investigator (PI) judgement as described in theprotocol

6. Uncontrolled asthma or on Global Initiative for Asthma (GINA) steps 4 to 5 asdescribed in the protocol

7. Abnormal lung function as judged by the investigator with Forced expiratory volumein 1 second (FEV1) <70% of predicted at screening

8. History of cat immunotherapy (eg, subcutaneous immunotherapy or any other route) inthe 3 years prior to screening visit 1

9. Ongoing Allergen immunotherapy (AIT) with any allergen other than cat at screeningvisit 1 as described in the protocol

Note: Other Protocol Defined Inclusion/ Exclusion Criteria Apply