First-in-Human Trial to Assess REGN20423 in Healthy Adult Participants and Adult Participants With Atopic Dermatitis (AURA-AD)

A Two-Part Phase 1, Randomized, Double-Blind, Placebo-Controlled First-in-Human Study to Assess the Safety, Tolerability, Pharmacokinetics, and Immunogenicity of REGN20423 in Adult Healthy Participants and Adult Participants With Atopic Dermatitis

This clinical trial will evaluate REGN20423, an investigational medicine that has not previously been studied in humans and is used only in clinical studies. The study will assess the safety, how the body processes the medicine, and the dose levels that may work best. It will also test whether REGN20423 can help treat adults with atopic dermatitis.

This is a two-part study:

Part A includes healthy adult participants. Part B includes adults with atopic dermatitis.

The Study is Looking at:

• What side effects REGN20423 might cause
• How much REGN20423 is in the blood at different times
• How well REGN20423 works in adults with atopic dermatitis
• Whether the body makes antibodies against REGN20423
• How the body changes after having REGN20423, which can help researchers understand why REGN20423 works better in some people than others
• What the best dose of REGN20423 is

Study Overview

• Status: Not yet recruiting
• Conditions: Atopic Dermatitis; Healthy Volunteer
• Intervention / Treatment: Other: Placebo; Drug: REGN20423

• Study Type: Interventional
• Enrollment (Estimated): 136
• Phase: Phase 1

Contacts and Locations

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

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Part A: Enrolls healthy participants Part B: Enrolls participants with atopic dermatitis

Key Inclusion Criteria:

Part A:

1. Is judged by the investigator to be in good health based on medical history, physical examination, vital signs, Electrocardiograms (ECGs), and laboratory safety testing at screening and prior to initial dose of study intervention

2. Has a BMI within 18 to 31 kg/m² (inclusive) at the screening visit

   Part B:

3. Has a history of AD for at least 6 months at screening
4. Has EASI score ≥5 at both the screening and baseline visits
5. Has IGA score ≥2 at both the screening and baseline visits

Key Exclusion Criteria

Part A:

1. Hospitalized (>24 hours) for any reason within 30 days prior to the screening visit
2. Hypersensitivity to the study treatment or any of its excipients
3. History of clinical parasite infection, except treated trichomoniasis
4. Received a live attenuated vaccine within 1 month prior to the first screening visit or anticipates need for a live attenuated vaccine during the study

5. History of alcohol or drug abuse as determined by the investigator

   Part B:

6. Known or suspected history of immunosuppression
7. Presence of skin comorbidities at screening that may interfere with study assessments
8. Inability to discontinue medications and treatments prior to baseline and during the study per the Excluded Medications and Treatments list
9. Uncontrolled chronic disease that might require bursts of oral corticosteroids during the study

Note: Other protocol defined Inclusion/ Exclusion criteria apply

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part A	Other: Placebo; Administered per the protocol; Drug: REGN20423; Administered per the protocol
Experimental: Part B	Other: Placebo; Administered per the protocol; Drug: REGN20423; Administered per the protocol

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Severity of TEAEs	Up to 52 weeks
Occurrence of Treatment Emergent Adverse Events (TEAEs)	Up to 52 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Concentrations of REGN20423 in serum		Up to 52 weeks
Absolute values from baseline of total Interleukin 13 (IL-13)		Up to 52 weeks
Absolute values from baseline of total Immunoglobulin E (IgE)		Up to 52 weeks
Absolute values from baseline of total eosinophil counts in blood		Up to 52 weeks
Absolute values from baseline of total periostin		Up to 52 weeks
Absolute values from baseline of total Thymus and Activation-Regulated Chemokine (TARC)		Up to 52 weeks
Percent change from baseline of total IL-13		Up to 52 weeks
Percent change from baseline of total IgE		Up to 52 weeks
Percent change from baseline of total eosinophil counts in blood		Up to 52 weeks
Percent change from baseline of total periostin		Up to 52 weeks
Percent change from baseline of total TARC		Up to 52 weeks
Occurrence of Anti-Drug Antibodies (ADA) to REGN20423		Up to 52 weeks
Magnitude of ADA to REGN20423		Up to 52 weeks
Absolute change from baseline in Eczema Area and Severity Index (EASI) score	Part B EASI is a validated measure used to assess the severity and extent as a percentage by body area of head, trunk, arms and legs, and converted to a score of 0 to 6. Higher scores indicate higher improvement. Also, AD disease characteristics will be assessed for severity by the investigator or designee on a scale of "0" (absent) through "3" (severe)	Up to 52 weeks
Percent change from baseline in EASI score	Part B	Up to 52 weeks
Achievement of EASI-50	Part B	Up to 52 weeks
Achievement of EASI-75	Part B	Up to 52 weeks
Achievement of EASI-90	Part B	Up to 52 weeks
Achievement of Investigator's Global Assessment (IGA) 0-1	Part B IGA is a frequently used clinician-reported instrument in clinical studies for rapid and easy assessment of disease severity of AD globally. It is based on a 5-point scale with range from "0" (clear) to "4" (severe), with higher scores indicating more severe disease	Up to 52 weeks
Achievement of IGA 0-1 with reduction in IGA score by ≥2	Part B	Up to 52 weeks
Achievement of a reduction in IGA score by ≥2	Part B	Up to 52 weeks
Absolute change in % Body Surface Area (BSA)	Part B	From baseline up to 52 weeks
Absolute change in EASI	Part B	From baseline up to 52 weeks
Percent change in % BSA	Part B	From baseline up to 52 weeks
Percent change in EASI	Part B	From baseline up to 52 weeks

Collaborators and Investigators

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

Study record dates

Study Major Dates

• Study Start (Estimated): May 4, 2026
• Primary Completion (Estimated): June 9, 2028
• Study Completion (Estimated): June 9, 2028

Study Registration Dates

• First Submitted: April 7, 2026
• First Submitted That Met QC Criteria: April 7, 2026
• First Posted (Actual): April 14, 2026

Study Record Updates

• Last Update Posted (Actual): April 14, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Eczema; Inflammatory skin disease
• Additional Relevant MeSH Terms: Genetic Diseases, Inborn; Immune System Diseases; Hypersensitivity, Immediate; Hypersensitivity; Skin Diseases; Skin Diseases, Genetic; Skin Diseases, Eczematous; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Skin and Connective Tissue Diseases; Dermatitis, Atopic; Dermatitis; Eczema
• Other Study ID Numbers: R20423-HV-2555; 2025-524205-32-00 (Ctis)

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
• product manufactured in and exported from the U.S.: Yes