REGN7257 in Adult Patients With Severe Aplastic Anemia That Is Refractory to or Relapsed on Immunosuppressive Therapy

A Phase 1/2 Study of REGN7257 (Anti-Interleukin 2 Receptor Subunit Gamma [IL2RG] Monoclonal Antibody) in Patients With Severe Aplastic Anemia That Is Refractory to or Relapsed on Immunosuppressive Therapy

This study is researching an experimental drug called REGN7257 (called "study drug"). The study is focused on patients who have severe aplastic anemia (SAA), a disease of the bone marrow resulting in an impairment of the production of blood cells.

The main purpose of this two-part study (Part A and Part B) is to test how safe and tolerable REGN7257 is in patients with SAA in which other Immunosuppressive therapies (ISTs) have not worked well.

The study is looking at several other research questions to better understand the following properties of REGN7257:

• Side effects that may be experienced by participants taking REGN7257
• How REGN7257 works in the body
• How much REGN7257 is present in blood after dosing
• If REGN7257 works to raise levels of certain blood counts after treatment
• How quickly REGN7257 works to raise levels of certain blood counts
• In patients for whom REGN7257 works to raise levels of certain blood counts after treatment, how many continue to show such a response throughout the study
• If REGN7257 works to lower the number of platelet and red blood cell transfusions needed
• How REGN7257 changes immune cell counts and composition
• How the body reacts to REGN7257 and if it produces proteins that bind to REGN7257 (this would be called the formation of anti-drug antibodies [ADA])

Study Overview

• Status: Terminated
• Conditions: Severe Aplastic Anemia (SAA)
• Intervention / Treatment: Drug: REGN7257

Detailed Description

The trial was intended to be a Phase 1/2 trial, but no participants were enrolled in Phase 2

• Study Type: Interventional
• Enrollment (Actual): 17
• Phase: Phase 1

Contacts and Locations

Study Locations

• France
  • Île-de-France Region
    • Paris, Île-de-France Region, France, 75010
      • Hôpital Saint-Louis - APHP
• South Korea
  • Gyeonggi-do
    • Incheon, Gyeonggi-do, South Korea, 21565
      • Gachon University Gil Hospital
  • Seoul Capital Area
    • Seoul, Seoul Capital Area, South Korea, 03080
      • Seoul National University Hospital
    • Seoul, Seoul Capital Area, South Korea, 06351
      • Samsung Medical Center
    • Seoul, Seoul Capital Area, South Korea, 06591
      • The Catholic University of Korea, Seoul St. Marys Hospital
    • Seoul, Seoul Capital Area, South Korea, 07985
      • Ewha Womans University Medical Centre
• United Kingdom
  • London, United Kingdom, SE5 9RS
    • King's College Hospital, London
  • West Yorkshire
    • Leeds, West Yorkshire, United Kingdom, LS97TF
      • St James's University Hospital
• United States
  • Ohio
    • Cleveland, Ohio, United States, 44195
      • Cleveland Clinic Foundation
  • Texas
    • Houston, Texas, United States, 77030
      • The University of Texas MD Anderson Cancer Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

1. Part A: SAA that is IST-refractory or IST-relapsed, as defined in the protocol
2. Part B: SAA that is IST-relapsed, as defined in the protocol
3. Hematopoietic stem cell transplantation (HSCT) is not available or suitable as a treatment option or has been refused by the patient
4. Adequate hepatic and renal function as defined in the protocol

Key Exclusion Criteria:

1. Diagnosis of Fanconi anemia or other congenital bone marrow failure syndrome as defined in the protocol
2. Evidence of myelodysplastic syndrome as defined in the protocol
3. Paroxysmal nocturnal hemoglobinuria (PNH) with evidence of clinically significant hemolysis (eg, treatment indicated) or history of PNH-associated thrombosis
4. Treatment with a T cell-depleting agent (eg, ATG or alemtuzumab) within 6 months prior to dosing
5. Treatment with a calcineurin inhibitor (eg, cyclosporine) within 4 weeks prior to dosing for patients enrolled in Part A
6. Treatment with eltrombopag or investigational thrombopoietin receptor agonist, Granulocyte Colony-Stimulating Factor (G-CSF), or an androgen (eg, danazol), within 2 weeks prior to dosing
7. HIV, hepatitis B or hepatitis C positive by serological testing at the screening visit as defined in the protocol
8. Active tuberculosis, latent tuberculosis infection (LTBI) or history incompletely-treated tuberculosis or LTBI
9. Active infection as defined in the protocol

Note: Other protocol-defined inclusion/ exclusion criteria apply

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Sequential Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part A; Part A: Single ascending dose (SAD) escalation cohorts	Drug: REGN7257; Administered by intravenous (IV) infusion, in Part A and B.
Experimental: Part B; Part B: Multiple REGN7257 dosages.	Drug: REGN7257; Administered by intravenous (IV) infusion, in Part A and B.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of adverse events (AEs)	Part A	12 months post-treatment, approximately 52 weeks
Incidence of serious adverse events (SAEs)	Part A	12 months post-treatment, approximately 52 weeks
Incidence and severity of treatment-emergent adverse events (TEAEs)	Part A	12 months post-treatment, approximately 52 weeks
Incidence of serious adverse events (SAEs)	Part B	Through the end of study visit, approximately 78 weeks
Incidence and severity of treatment-emergent adverse events (TEAEs)	Part B	Through the end of study visit, approximately 78 weeks
Overall response rate (ORR)	Part B	At 6 months, approximately 26 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ORR	Parts A and B	At 3 months, approximately 12 weeks
Complete response (CR)	Parts A and B	At 3 months, approximately 12 weeks
Partial response (PR)	Parts A and B	At 3 months, approximately 12 weeks
Time to best response	Part A	Up to 12 months
Time to best response	Part B	Up to 18 months
Time to first response	Part A	Up to 12 months
Time to first response	Part B	Up to 18 months
Any clinical response	Part A	Until the end of study, approximately week 52
Any clinical response	Part B	Until the end of study, approximately week 78
Platelet transfusions per month over time	Part A	Up to 12 months
Platelet transfusions per month over time	Part B	Up to 18 months
Red blood cell transfusions per month over time	Part A	Up to 12 months
Red blood cell transfusions per month over time	Part B	Up to 18 months
Changes in lymphocyte cell counts	Part A	Up to 12 months
Changes in lymphocyte cell counts	Part B	Up to 18 months
Changes in neutrophil cell counts	Part A	Up to 12 months
Changes in neutrophil cell counts	Part B	Up to 18 months
Changes in hemoglobin cell counts	Part A	Up to 12 months
Changes in hemoglobin cell counts	Part B	Up to 18 months
Changes in reticulocyte cell counts	Part A	Up to 12 months
Changes in reticulocyte cell counts	Part B	Up to 18 months
Changes in platelet cell counts	Part A	Up to 12 months
Changes in platelet cell counts	Part B	Up to 18 months
Changes in the whole blood immune cell subsets (T cells)	Part A	Up to 12 months
Changes in the whole blood immune cell subsets (T cells)	Part B	Up to 18 months
Changes in the whole blood immune cell subsets (B cells)	Part A	Up to 12 months
Changes in the whole blood immune cell subsets (B cells)	Part B	Up to 18 months
Changes in the whole blood immune cell subsets [Natural killer (NK) cells]	Part A	Up to 12 months
Changes in the whole blood immune cell subsets (NK cells)	Part B	Up to 18 months
Drug concentrations in serum over time	Part A	Up to 12 months
Drug concentrations in serum over time	Part B	Up to 18 months
Incidence of treatment-emergent anti-drug antibody (ADA) over time	Part A	Up to 12 months
Incidence of treatment-emergent ADA over time	Part B	Up to 18 months

Collaborators and Investigators

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

Study record dates

Study Major Dates

• Study Start (Actual): January 13, 2021
• Primary Completion (Actual): October 17, 2024
• Study Completion (Actual): October 17, 2024

Study Registration Dates

• First Submitted: May 26, 2020
• First Submitted That Met QC Criteria: May 26, 2020
• First Posted (Actual): June 1, 2020

Study Record Updates

• Last Update Posted (Estimated): October 24, 2025
• Last Update Submitted That Met QC Criteria: October 22, 2025
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Keywords: Relapsed; Refractory; Immunosuppressive therapy (IST)
• Additional Relevant MeSH Terms: Bone Marrow Failure Disorders; Pathologic Processes; Disease Attributes; Hematologic Diseases; Bone Marrow Diseases; Anemia; Pathological Conditions, Signs and Symptoms; Hemic and Lymphatic Diseases; Recurrence; Anemia, Aplastic
• Other Study ID Numbers: R7257-RAA-1947; 2020-002031-29 (EudraCT Number); 2023-508601-24-00 (Registry Identifier: EU CT 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 may request access to anonymized patient level data or aggregate study data 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, has the legal authority to share the data, and has made the study results publicly available (eg, scientific publication, scientific conference, clinical trial registry).
• 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