Phase 1 Safety and Tolerability Study of REGN9533 in Healthy Adults

A Phase 1, Randomized, Double-Blind, Placebo Controlled Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single Ascending Doses of REGN9533, a Monoclonal Antibody Against Factor XII, in Healthy Adults

The aim of this clinical trial is to see how safe and tolerable the clinical trial drug (REGN9533) is in healthy participants. This is the first time that REGN9533 will be given to humans.

After the clinical trial drug has been tested in healthy participants, future studies with REGN9533 will focus on participants with thromboembolic (blocking of blood vessels) diseases which include blood clots.

REGN9533 is a drug that is only used in clinical studies.

The clinical trial is looking at:

• The side effects REGN9533 might cause
• How much REGN9533 is in the blood at different times
• How the body reacts to REGN9533
• If the body makes antibodies to REGN9533 (unwanted immune response, which may cause REGN9533 to not work as well)
• What is the best dose of REGN9533

Study Overview

• Status: Completed
• Conditions: Healthy Volunteer
• Intervention / Treatment: Drug: REGN9533; Drug: Matching Placebo

• Study Type: Interventional
• Enrollment (Actual): 72
• Phase: Phase 1

Contacts and Locations

Study Locations

• Belgium
  • Antwerp
    • Edegem, Antwerp, Belgium, 2650
      • SGS Belgium NV_Edegem

Participation Criteria

Eligibility Criteria

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

Description

Key Inclusion Criteria:

1. Has a body mass index between 18 and 32 kg/m2, inclusive
2. Is judged by the investigator to be in good health based on medical history, physical examination, vital sign measurements, and electrocardiograms (ECGs) performed at screening and/or prior to administration of initial dose of study drug
3. Normal aPTT, normal PT, and normal platelet counts as described in the protocol
4. Hemoglobin values at screening period and at day -1 as described in the protocol
5. Negative Fecal Occult Blood Test (FOBT) during screening period
6. Normal Bleeding Time Test (BTT) at day -1 as defined by the study site

Key Exclusion Criteria:

1. History of any major surgical procedure or clinically significant physical trauma within the last 6 months that in the opinion of the investigator may pose a risk to the participant by study participation
2. History of clinically significant bleeding, requiring hospitalization or blood products within the last 6 months, that in the opinion of the investigator may pose a risk to the participant by study participation
3. History of bleeding diathesis (eg, including, but not limited to Hemophilia A or B, von Willebrand's Factor deficiency, fibrinogen deficiency, and other inherited or acquired bleeding disorders)
4. History of clinically significant cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric, or neurological disease, as assessed by the investigator, that may confound the results of the study or poses an additional risk to the participant by study participation
5. Is a current smoker including e-cigarettes or other nicotine-containing products; or is a former smoker including e-cigarettes or other nicotine-containing products which they have used at any time within 3 months prior to the screening visit
6. Has a confirmed positive drug test result at the screening visit and/or prior to randomization; or a history of recreational drug use (eg, marijuana) and/or drug or alcohol abuse within a year prior to the screening visit
7. Any malignancy, except for non-melanoma skin cancer or cervical/anus in-situ, that have been resected with no evidence of metastatic disease for 3 years prior to the screening visit
8. Has a history of significant multiple and/or severe allergies (eg, latex gloves), or has had an anaphylactic reaction to prescription or non-prescription drugs or food

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

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: REGN9533; Randomized as described in the protocol Escalating Cohorts including Optional Cohorts	Drug: REGN9533; Administered per the protocol
Experimental: Placebo; Randomized as described in the protocol	Drug: Matching Placebo; Administered per the protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Incidence of Treatment Emergent Adverse Events (TEAEs)	Up to 100 days
Severity of TEAEs	Up to 100 days

Secondary Outcome Measures

Outcome Measure	Time Frame
Change in activated Partial Thromboplastin Time (aPTT)	Baseline up to 100 days
Change in Prothrombin Time (PT)	Baseline up to 100 days
Concentrations of REGN9533	Up to 100 days
Incidence of Anti-drug Antibodies (ADAs) to REGN9533	Up to 100 days
Titer of ADAs to REGN9533	Up to 100 days

Collaborators and Investigators

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

Study record dates

Study Major Dates

• Study Start (Actual): March 4, 2025
• Primary Completion (Actual): January 29, 2026
• Study Completion (Actual): January 29, 2026

Study Registration Dates

• First Submitted: October 28, 2024
• First Submitted That Met QC Criteria: October 28, 2024
• First Posted (Actual): October 30, 2024

Study Record Updates

• Last Update Posted (Actual): February 6, 2026
• Last Update Submitted That Met QC Criteria: February 4, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: R9533-HV-2411; 2024-515285-14-00 (Ctis: EUCT Number)

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