Clonal Cytopenia of Undetermined Significance (CCUS)Phase 1NCT07753148
Safety and Tolerability of REGN17235 in Adult Participants With Clonal Cytopenia of Undetermined Significance and Low-Risk Myelodysplastic Syndrome With SF3B1 Mutation
A Phase 1 study testing REGN17235 in people with Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS), run by Regeneron Pharmaceuticals at 2 sites in Belgium.
Trial summary
This study will test a study drug called REGN17235 (the "study drug") to see if it can help treat Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS) with a specific genetic mutation (SF3B1 Mutation). Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Clonal Cytopenia of Undetermined Significance (CCUS), Low-Risk Myelodysplastic Syndrome (LR-MDS)
- What is being tested?
- REGN17235
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 52 participants
- Where
- 2 sitesBelgium
- Study dates
- 17 Sep 2026to 5 May 2031
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
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 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Presence of SF3B1 mutation in the bone marrow or peripheral blood AND diagnosis of low-risk MDS OR diagnosis of CCUS as defined by WHO 2022, 5th edition as described in the protocol
- Adequate bone marrow function as described in the protocol; red blood cell transfusion dependence is permitted
- Adequate hepatic and renal function as described in the protocol
Who cannot join
- Clinically significant anemia due to non-MDS or non-CCUS etiologies (eg, iron deficiency, vitamin B12 or folate deficiency, autoimmune or hereditary hemolysis, or hemorrhage) diagnosed or treated within the last 3 months prior to informed consent
- Recent or uncontrolled infections as described in the protocol
- Diagnosed or treated for malignancy other than MDS as described in the protocol
- Prior treatment with any systemic therapy for MDS or CCUS within 5 half-lives or within 14 days prior to first administration of study drug, whichever is shorter
- Allogeneic hematopoietic stem cell transplant within 100 days of enrollment or any signs or symptoms of ongoing Graft-Versus Host Disease (GVHD) as described in the protocol
- Note: Other protocol defined Inclusion/Exclusion Criteria apply
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Belgium2 sites, 2 recruiting
- Recruiting
Uz Ghent
Ghent, 9000
- Recruiting
Algemeen Ziekenhuis (AZ) Delta
Roeselare, 8800
About this study
Official title: An Open-Label, Multi-Center Phase I Study to Investigate the Safety and Tolerability of REGN17235 in Patients With Clonal Cytopenia of Undetermined Significance and Low-Risk Myelodysplastic Syndrome With SF3B1 Mutation
This study will test a study drug called REGN17235 (the "study drug") to see if it can help treat Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS) with a specific genetic mutation (SF3B1 Mutation).
The study is looking at:
- What side effects the study drug might cause
- How well the study drug works
- How much of the study drug is in the blood at different times
- If the body makes antibodies (proteins that attach to substances your body does not recognize) against the study drug; this may cause the study drug to not work as well.
- What is the best dose of the study drug to treat CCUS and LR-MDS
- Conditions
- Clonal Cytopenia of Undetermined Significance (CCUS), Low-Risk Myelodysplastic Syndrome (LR-MDS)
- Being tested
- REGN17235
- Keywords
- Blood cancer, First in human, Selective elimination of SF3B1-mutant cells
- Medical subject headings
- Hematologic Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
REGN17235Drug
Administered per the protocol
| Study group | Role | What they receive |
|---|---|---|
| Part 1 Dose Escalation | Experimental | Not described Receives: Drug: REGN17235 |
| Part 2 Safety Expansion | Experimental | Not described Receives: Drug: REGN17235 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Occurrence of Treatment Emergent Adverse Events (TEAEs)
Measured: Up to 5 years
Severity of TEAEs
Measured: Up to 5 years
Occurrence of Serious Adverse Events (SAEs)
Measured: Up to 5 years
Severity of SAEs
Measured: Up to 5 years
Secondary outcomes (4)
Hematologic improvement per International Working Group (IWG) 2018
Measured: Up to 5 years
Concentration of REGN17235 in serum
Measured: Up to 5 years
Occurrence of Anti-Drug Antibodies (ADA) to REGN17235 in serum
Measured: Up to 5 years
Magnitude of ADA to REGN17235 in serum
Measured: Up to 5 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted7 Aug 2026
- Study start17 Sep 2026
- Primary completion5 May 2031 (estimated)
- Study completion5 May 2031 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Clonal Cytopenia of Undetermined Significance (CCUS)Studies 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
- Non-randomised
- Intervention model
- Single group
- Model description
- Part 1 Single Part 2 Parallel
- Masking
- None (open label)
- Enrolment
- 52 participants (estimated)
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
- NCT07753148
- Sponsor's protocol ID
- R17235-HM-24125
- Other IDs
- 2026-525464-18-00
- Status last verified
- Oct 2026
- First submitted
- 3 Aug 2026
- Last updated
- 27 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- 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 27 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Open-Label, Multi-Center Phase I Study to Investigate the Safety and Tolerability of REGN17235 in Patients With Clonal Cytopenia of Undetermined Significance and Low-Risk Myelodysplastic Syndrome With SF3B1 Mutation
- ClinicalTrials.gov ID
- NCT07753148
- Acronym / sponsor ID
- R17235-HM-24125
- Conditions
- Clonal Cytopenia of Undetermined Significance (CCUS), Low-Risk Myelodysplastic Syndrome (LR-MDS)
- Keywords
- Blood cancer, First in human, Selective elimination of SF3B1-mutant cells
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 52 participants (estimated)
- Lead sponsor
- Regeneron PharmaceuticalsIndustry (pharma, biotech, devices)
- Study start
- 17 Sep 2026 (actual)
- Primary completion
- 5 May 2031 (estimated)
- Study completion
- 5 May 2031 (estimated)
- First posted
- 7 Aug 2026 (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.
This study will test a study drug called REGN17235 (the "study drug") to see if it can help treat Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS) with a specific genetic mutation (SF3B1 Mutation).
The study is looking at:
- What side effects the study drug might cause
- How well the study drug works
- How much of the study drug is in the blood at different times
- If the body makes antibodies (proteins that attach to substances your body does not recognize) against the study drug; this may cause the study drug to not work as well.
- What is the best dose of the study drug to treat CCUS and LR-MDS
Study design
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Part 1 Single Part 2 Parallel
| Arm | Type | Receives |
|---|---|---|
| Part 1 Dose Escalation | Experimental | Drug: REGN17235 |
| Part 2 Safety Expansion | Experimental | Drug: REGN17235 |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Presence of SF3B1 mutation in the bone marrow or peripheral blood AND diagnosis of low-risk MDS OR diagnosis of CCUS as defined by WHO 2022, 5th edition as described in the protocol
- Adequate bone marrow function as described in the protocol; red blood cell transfusion dependence is permitted
- Adequate hepatic and renal function as described in the protocol
Key exclusion criteria (6 listed)
- Clinically significant anemia due to non-MDS or non-CCUS etiologies (eg, iron deficiency, vitamin B12 or folate deficiency, autoimmune or hereditary hemolysis, or hemorrhage) diagnosed or treated within the last 3 months prior to informed consent
- Recent or uncontrolled infections as described in the protocol
- Diagnosed or treated for malignancy other than MDS as described in the protocol
- Prior treatment with any systemic therapy for MDS or CCUS within 5 half-lives or within 14 days prior to first administration of study drug, whichever is shorter
- Allogeneic hematopoietic stem cell transplant within 100 days of enrollment or any signs or symptoms of ongoing Graft-Versus Host Disease (GVHD) as described in the protocol
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 |
|---|---|---|
| REGN17235Administered per the protocol | Drug | Part 1 Dose Escalation, Part 2 Safety Expansion |
Primary outcome
Occurrence of Treatment Emergent Adverse Events (TEAEs)
Time frame: Up to 5 years
Severity of TEAEs
Time frame: Up to 5 years
Occurrence of Serious Adverse Events (SAEs)
Time frame: Up to 5 years
Severity of SAEs
Time frame: Up to 5 years
4 secondary outcomes
Hematologic improvement per International Working Group (IWG) 2018
Time frame: Up to 5 years
Concentration of REGN17235 in serum
Time frame: Up to 5 years
Occurrence of Anti-Drug Antibodies (ADA) to REGN17235 in serum
Time frame: Up to 5 years
Magnitude of ADA to REGN17235 in serum
Time frame: Up to 5 years
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Oct 2026.
- Individual participant dataSharing planned: Yes. All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing
Related trials for Clonal Cytopenia of Undetermined Significance (CCUS)
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Ascorbic Acid and Chemotherapy for the Treatment of Relapsed or Refractory Lymphoma, CCUS, and Chronic Myelomonocytic Leukemia
Clonal Cytopenia of Undetermined Significance, High Grade B-Cell Lymphoma With MYC and BCL2 or BCL6 Rearrangements
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CHIP/CCUS Natural History Protocol
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CHIP in Health and Disease
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Dresden MDS Registry With an Accompanying Biomaterial Collection
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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.
Clinical Trial Management study director
Regeneron Pharmaceuticals
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing REGN17235 in people with Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS), run by Regeneron Pharmaceuticals at 2 sites 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 3 inclusion and 6 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: looking for participants now, as of the sponsor's last update on 27 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites 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?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Clinical Trials Administrator (844-734-6643, clinicaltrials@regeneron.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Occurrence of Treatment Emergent Adverse Events (TEAEs) (time frame: Up to 5 years). The study lists 4 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 27 Oct 2026.