A Study to Evaluate the Efficacy and Safety of Fel d 1 Monoclonal Antibodies in Adult and Pediatric Participants With Allergic Conjunctivitis Due to Cat Allergy

A Randomized, Double-Masked, Placebo-Controlled, Phase 3 Study to Assess the Efficacy and Safety of Fel d 1 Monoclonal Antibodies in Participants With Allergic Conjunctivitis Due to Cat Allergy

This study is researching two experimental medicines, freneslerbart and mevonlerbart. Freneslerbart and mevonlerbart can be given alone or together. When given together, the medicine is called "REGN-2Cat". These medicines are also known as the "study drugs".

The aim of the study is to see what side effects freneslerbart, mevonlerbart, and REGN-2Cat may have and if they help reduce eye allergy symptoms caused by cat hair/dander compared with a placebo.

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

• 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)
• How long the study drug effect lasts

Study Overview

• Status: Recruiting
• Conditions: Allergic Conjunctivitis
• Intervention / Treatment: Drug: Placebo; Drug: REGN-2Cat; Drug: Freneslerbart; Drug: Mevonlerbart

• Study Type: Interventional
• Enrollment (Estimated): 570
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Clinical Trials Administrator; Phone Number: 844-734-6643; Email: clinicaltrials@regeneron.com

Study Locations

• United States
  • Massachusetts
    • Andover, Massachusetts, United States, 01810
      • Recruiting
      • Andover Eye Associates

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

1. Part A: adult participants aged 18 years and older. For part B: pediatric participants ≥8 years and <18 years, and adult participants aged 18 years and older.
2. Positive SPT to cat allergen extract
3. Positive specific Immunoglobulin E (sIgE) tests for cat and Fel d 1
4. Positive CAC criteria

Key Exclusion Criteria:

1. Significant and/or severe environmental allergies causing symptoms (eg, ocular itching, ocular redness, etc) outside of the challenge setting that are expected to coincide or may interfere with study assessments
2. Presence of any ophthalmic disease/ abnormality/ condition that may interfere with study assessments, affect the study outcomes or participant safety
3. A clinical history of asthma with treatment of asthma requiring systemic (oral or parenteral) corticosteroid treatment as defined in the protocol

Note: Other Protocol Defined Inclusion/ Exclusion Criteria Apply

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: REGN-2Cat; Part A and B	Drug: REGN-2Cat; Administered per the protocol; Other Names: REGN1908-REGN1909
Experimental: Freneslerbart; Part A and B	Drug: Freneslerbart; Administered per the protocol; Other Names: REGN1908
Experimental: Mevonlerbart; Part A	Drug: Mevonlerbart; Administered per the protocol; Other Names: REGN1909
Placebo Comparator: Matching placebo; Part A and B	Drug: Placebo; Administered per the protocol

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Ocular itch score in participants receiving REGN-2Cat as compared to placebo	At day 8, post-Conjunctival Allergen Challenge (CAC)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
1. Ocular itch score in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
2. Conjunctival redness score in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
3. Achievement of at least a 1-point reduction from baseline in ocular itch score for at least 2 out of 3 post-CAC time points in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
4. Achievement of at least a 1-point reduction from baseline in conjunctival redness score for at least 2 out of 3 post-CAC time points in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
5. Percent change from baseline in cat titrated Skin Prick Test (tSPT) in participants receiving REGN-2Cat as compared to placebo		Up to day 85
6. Ocular itch score in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
7. Conjunctival redness score in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
8. Achievement of at least a 1-point reduction from baseline in ocular itch score for at least 2 out of 3 post-CAC time points in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
9. Achievement of at least a 1-point reduction from baseline in conjunctival redness score for at least 2 out of 3 post-CAC time points in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
10. Percent change from baseline in cat tSPT in participants receiving freneslerbart as compared to placebo		Up to day 85
11. Ocular itch score in participants receiving mevonlerbart as compared to placebo	Part A	At day 8, post-CAC
12. Conjunctival redness score in participants receiving mevonlerbart as compared to placebo	Part A	At day 8, post-CAC
13. Achievement of at least a 1-point reduction from baseline in ocular itch score for at least 2 out of 3 post-CAC time points in participants receiving mevonlerbart as compared to placebo	Part A	At day 8, post-CAC
14. Achievement of at least a 1-point reduction from baseline in conjunctival redness score for at least 2 out of 3 post-CAC time points in participants receiving mevonlerbart as compared to placebo	Part A	At day 8, post-CAC
15. Ocular itch score in participants receiving REGN-2Cat as compared to mevonlerbart	Part A	At day 8, post-CAC
16. Ocular itch score in participants receiving REGN-2Cat as compared to freneslerbart		At day 8, post-CAC
17. Achievements of different degrees of clinical response, as measured by change from baseline in ocular itch score among participants receiving REGN-2Cat, freneslerbart, mevonlerbart or placebo		At day 8, post-CAC
18. Percent change from baseline in cat tSPT in participants receiving REGN-2Cat as compared to freneslerbart		At day 8
19. Percent change from baseline in cat tSPT in participants receiving REGN-2Cat as compared to mevonlerbart	Part A	At day 8
20. Ciliary redness score in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
21. Episcleral redness score in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
22. Total redness score in participants receiving REGN-2Cat as compared to placebo		Up to day 85, post-CAC
23. Ciliary redness score in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
24. Episcleral redness score in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
25. Total redness score in participants receiving freneslerbart as compared to placebo		Up to day 85, post-CAC
26. Percent change from baseline in cat tSPT in participants receiving mevonlerbart as compared to placebo	Part A	Up to day 85
27. Occurrence of Treatment Emergent Adverse Events (TEAEs)		Up to day 113
28. Severity of TEAEs		Up to day 113
29. Occurrence of Treatment Emergent-Serious Adverse Events (TE-SAEs)		Up to day 113
30. Concentrations of total freneslerbart in serum		Up to day 113
31. Concentrations of total mevonlerbart in serum		Up to day 113
32. Occurrence of Anti-Drug Antibodies (ADA) to freneslerbart		Up to day 113
33. Magnitude of ADA to freneslerbart		Up to day 113
34. Occurrence of ADA to mevonlerbart		Up to day 113
35. Magnitude of ADA to mevonlerbart		Up to day 113

Collaborators and Investigators

• Sponsor: Regeneron Pharmaceuticals
• Investigators: Study Director: Clinical Trial Management, Regeneron Pharmaceuticals

Study record dates

Study Major Dates

• Study Start (Actual): July 31, 2026
• Primary Completion (Estimated): May 31, 2029
• Study Completion (Estimated): September 20, 2029

Study Registration Dates

• First Submitted: June 23, 2026
• First Submitted That Met QC Criteria: June 23, 2026
• First Posted (Actual): June 30, 2026

Study Record Updates

• Last Update Posted (Actual): August 12, 2026
• Last Update Submitted That Met QC Criteria: August 10, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Cat allergy; Eye allergy; Cat-induced eye allergy; Ocular allergy signs/symptoms; Allergic conjunctivitis signs/symptoms
• Additional Relevant MeSH Terms: Immune System Diseases; Eye Diseases; Hypersensitivity, Immediate; Hypersensitivity; Conjunctivitis; Conjunctival Diseases; Conjunctivitis, Allergic
• Other Study ID Numbers: R1908-1909-ALG-2582

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.

IPD Sharing Time Frame

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 the study 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

• IPD Sharing Access Criteria: 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
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No