Healthy VolunteerPhase 1NCT06665828
Phase 1 Safety and Tolerability Study of REGN9533 in Healthy Adults
A Phase 1 study testing REGN9533 in people with Healthy Volunteer, run by Regeneron Pharmaceuticals at 1 site in Belgium.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 to 55 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy Volunteer
- What is being tested?
- REGN9533
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 72 participants
- Where
- 1 siteBelgium
- Study dates
- 4 Mar 2025to 29 Jan 2026
- Phase
- Phase 1
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 55 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Has a body mass index between 18 and 32 kg/m2, inclusive
- 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
- Normal aPTT, normal PT, and normal platelet counts as described in the protocol
- Hemoglobin values at screening period and at day -1 as described in the protocol
- Negative Fecal Occult Blood Test (FOBT) during screening period
- Normal Bleeding Time Test (BTT) at day -1 as defined by the study site
Who cannot join
- 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
- 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
- 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)
- 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
- 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
- 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
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- 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
- 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
Trial locations and contacts
1 site in 1 country.
About this study
Official title: 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.
Read more
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
- Conditions
- Healthy Volunteer
- Being tested
- REGN9533, Matching Placebo
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
REGN9533Drug
Administered per the protocol
Matching PlaceboDrug
Administered per the protocol.
| Study group | Role | What they receive |
|---|---|---|
| REGN9533 | Experimental | Randomized as described in the protocol Escalating Cohorts including Optional Cohorts Receives: Drug: REGN9533 |
| Placebo | Experimental | Randomized as described in the protocol Receives: Drug: Matching Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence of Treatment Emergent Adverse Events (TEAEs)
Measured: Up to 100 days
Severity of TEAEs
Measured: Up to 100 days
Secondary outcomes (5)
Change in activated Partial Thromboplastin Time (aPTT)
Measured: Baseline up to 100 days
Change in Prothrombin Time (PT)
Measured: Baseline up to 100 days
Concentrations of REGN9533
Measured: Up to 100 days
Incidence of Anti-drug Antibodies (ADAs) to REGN9533
Measured: Up to 100 days
Titer of ADAs to REGN9533
Measured: Up to 100 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted30 Oct 2024
- Study start4 Mar 2025
- Primary completion29 Jan 2026
- Study completion29 Jan 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Healthy VolunteerStudies of the same condition, open and under way.
- More trials run by Regeneron PharmaceuticalsThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 72 participants (actual)
Sponsor and investigators
- Lead sponsor
- Regeneron Pharmaceuticals
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Clinical Trial Management, Study director, Regeneron Pharmaceuticals
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06665828
- Sponsor's protocol ID
- R9533-HV-2411
- Other IDs
- 2024-515285-14-00
- Status last verified
- Feb 2026
- First submitted
- 28 Oct 2024
- Last updated
- 6 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing
Study at a glance
From the registry record, last updated by the sponsor on 6 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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
- ClinicalTrials.gov ID
- NCT06665828
- Acronym / sponsor ID
- R9533-HV-2411
- Conditions
- Healthy Volunteer
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 72 participants (actual)
- Lead sponsor
- Regeneron PharmaceuticalsIndustry (pharma, biotech, devices)
- Study start
- 4 Mar 2025 (actual)
- Primary completion
- 29 Jan 2026 (actual)
- Study completion
- 29 Jan 2026 (actual)
- First posted
- 30 Oct 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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 design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| REGN9533 | Experimental | Drug: REGN9533Randomized as described in the protocol Escalating Cohorts including Optional Cohorts |
| Placebo | Experimental | Drug: Matching PlaceboRandomized as described in the protocol |
Who may qualify
- Ages
- 18 to 55 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- Has a body mass index between 18 and 32 kg/m2, inclusive
- 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
- Normal aPTT, normal PT, and normal platelet counts as described in the protocol
- Hemoglobin values at screening period and at day -1 as described in the protocol
- Negative Fecal Occult Blood Test (FOBT) during screening period
Key exclusion criteria (9 listed)
- 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
- 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
- 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)
- 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
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| REGN9533Administered per the protocol | Drug | REGN9533 |
| Matching PlaceboAdministered per the protocol. | Drug | Placebo |
Primary outcome
Incidence of Treatment Emergent Adverse Events (TEAEs)
Time frame: Up to 100 days
Severity of TEAEs
Time frame: Up to 100 days
5 secondary outcomes
Change in activated Partial Thromboplastin Time (aPTT)
Time frame: Baseline up to 100 days
Change in Prothrombin Time (PT)
Time frame: Baseline up to 100 days
Concentrations of REGN9533
Time frame: Up to 100 days
Incidence of Anti-drug Antibodies (ADAs) to REGN9533
Time frame: Up to 100 days
Titer of ADAs to REGN9533
Time frame: Up to 100 days
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 6 Feb 2026.
- Individual participant dataSharing planned: Yes. All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing
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Screening Protocol
Pain
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Clinical Trial Management study director
Regeneron Pharmaceuticals
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing REGN9533 in people with Healthy Volunteer, run by Regeneron Pharmaceuticals at 1 site in Belgium.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 6 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence of Treatment Emergent Adverse Events (TEAEs) (time frame: Up to 100 days). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 Feb 2026.