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

November 3, 2026 updated by: Regeneron Pharmaceuticals

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

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
570

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • California
      • Long Beach, California, United States, 90815
        • Recruiting
        • Ark Clinical Research, LLC
    • Massachusetts
      • Andover, Massachusetts, United States, 01810
        • Recruiting
        • Andover Eye Associates

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

8 years and older (Child, Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

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

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
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

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Ocular itch score in participants receiving REGN-2Cat as compared to placebo
Time Frame: At day 8, post-Conjunctival Allergen Challenge (CAC)
At day 8, post-Conjunctival Allergen Challenge (CAC)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
1. Ocular itch score in participants receiving REGN-2Cat as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
2. Conjunctival redness score in participants receiving REGN-2Cat as compared to placebo
Time Frame: Up to day 85, post-CAC
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
Time Frame: Up to day 85, post-CAC
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
Time Frame: Up to day 85, post-CAC
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
Time Frame: Up to day 85
Up to day 85
6. Ocular itch score in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
7. Conjunctival redness score in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85, post-CAC
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
Time Frame: Up to day 85, post-CAC
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
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
10. Percent change from baseline in cat tSPT in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85
Up to day 85
16. Ocular itch score in participants receiving REGN-2Cat as compared to freneslerbart
Time Frame: At day 8, post-CAC
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
Time Frame: At day 8, post-CAC
At day 8, post-CAC
18. Percent change from baseline in cat tSPT in participants receiving REGN-2Cat as compared to freneslerbart
Time Frame: At day 8
At day 8
20. Ciliary redness score in participants receiving REGN-2Cat as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
21. Episcleral redness score in participants receiving REGN-2Cat as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
22. Total redness score in participants receiving REGN-2Cat as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
23. Ciliary redness score in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
24. Episcleral redness score in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
25. Total redness score in participants receiving freneslerbart as compared to placebo
Time Frame: Up to day 85, post-CAC
Up to day 85, post-CAC
27. Occurrence of Treatment Emergent Adverse Events (TEAEs)
Time Frame: Up to day 113
Up to day 113
28. Severity of TEAEs
Time Frame: Up to day 113
Up to day 113
29. Occurrence of Treatment Emergent-Serious Adverse Events (TE-SAEs)
Time Frame: Up to day 113
Up to day 113
30. Concentrations of total freneslerbart in serum
Time Frame: Up to day 113
Up to day 113
31. Concentrations of total mevonlerbart in serum
Time Frame: Up to day 113
Up to day 113
32. Occurrence of Anti-Drug Antibodies (ADA) to freneslerbart
Time Frame: Up to day 113
Up to day 113
33. Magnitude of ADA to freneslerbart
Time Frame: Up to day 113
Up to day 113
34. Occurrence of ADA to mevonlerbart
Time Frame: Up to day 113
Up to day 113
35. Magnitude of ADA to mevonlerbart
Time Frame: Up to day 113
Up to day 113
11. Ocular itch score in participants receiving mevonlerbart as compared to placebo
Time Frame: At day 8, post-CAC

Part A
At day 8, post-CAC
12. Conjunctival redness score in participants receiving mevonlerbart as compared to placebo
Time Frame: At day 8, post-CAC

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
Time Frame: At day 8, post-CAC

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
Time Frame: At day 8, post-CAC

Part A
At day 8, post-CAC
15. Ocular itch score in participants receiving REGN-2Cat as compared to mevonlerbart
Time Frame: At day 8, post-CAC

Part A
At day 8, post-CAC
19. Percent change from baseline in cat tSPT in participants receiving REGN-2Cat as compared to mevonlerbart
Time Frame: At day 8

Part A
At day 8
26. Percent change from baseline in cat tSPT in participants receiving mevonlerbart as compared to placebo
Time Frame: Up to day 85

Part A
Up to day 85

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Regeneron Pharmaceuticals

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Clinical Trial Management, Regeneron Pharmaceuticals

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
July 31, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 31, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 20, 2029

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
June 23, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 23, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
June 30, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 5, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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