Partial Stem Cell Transplant for Sickle Cell Disease From Matched Donors

Matched Related Donor Non-myeloablative Hematopoietic Cell Transplantation With Alemtuzumab, 400 cGy TBI, and Abatacept for Sickle Cell Disease and Beta-Thalassemia

This is a non-ablative (partial) stem cell transplant for patients with severe sickle cell disease or beta-thalassemia requiring red cell transfusions. The intensity of the transplant is slightly increased from our previous transplant regimens. The goal is to aim for higher percentage of donor cells to stably remain in the recipients long term.

Study Overview

• Status: Recruiting
• Conditions: Sickle Cell Disease; Beta-thalassemia
• Intervention / Treatment: Other: Research blood draw; Radiation: Total Body Irradiation; Drug: Alemtuzumab; Drug: Abatacept

Detailed Description

Study Description:

Our prior non-myeloablative conditioning regimen (03H0170) included 1mg/kg of alemtuzumab divided over 5 days, 300 cGy total body irradiation (TBI), and sirolimus for immune suppression. Sickle disease-free survival (DFS) and overall survival (OS) were 85% and 94% respectively, graft failure 15%, no transplant related mortality (TRM), and acute or chronic GVHD <5%. A large proportion of patients achieved robust (>=95%) donor myeloid chimerism at day 30, but this proportion decreased quickly to 67.2% at 1, 64.9% at 2, and 60% at 3, and 56.9% at 4 years post-transplant.

A subsequent protocol (000539H) added briquilimab, an antibody targeting CD117 (c-Kit), to alem-300 cGy TBI regimen, but did not reduce the gradual decline in donor myeloid chimerism as originally hypothesized, leading to protocol closure. Rates of graft failure was 20%, no TRM, acute GVHD was 5%, and no chronic GVHD. We now propose to increase TBI to 400 cGy to further deplete host lymphoid and myeloid cells to achieve a higher percentage of donor leukocyte engraftment without substantially increasing toxicity. Since we will continue to use filgrastim to mobilize and collect donor hematopoietic cells, we also add abatacept to preserve the low rates of GVHD.

Objectives:

Primary Objective:

To reduce the proportion of patients with graft failure or donor myeloid chimerism <95%

Secondary Objectives:

• To compare CD14/15 and CD3 chimerism to prior MRD HCT protocols (03-H-0170, 14-H-0077, and 000539H)
• To assess the usual transplant related parameters, such as count recovery, transfusion support, rates of GVHD, viral/bacterial infections, rates of transplant related and overall mortality, and compare to prior MRD HCT protocols

Tertiary Objectives:

• To compare changes in organ function
• To examine neuropsychological functioning, wellbeing, and pain before and after HCT
• To obtain reproductive health related changes before and after HCT

Endpoints:

Primary Endpoint: proportion of participants with graft failure or myeloid chimerism <95% at 1 year post HCT

Secondary Endpoints:

• Percent myeloid (CD14/15) chimerism at day 30, 60, 100, 1 year, 2 years, and 3 years post HCT
• Percent T cell (CD3) chimerism at day 30, 60, 100, 1 year, 2 years, and 3 years post HCT
• Day of neutrophil engraftment per CIBMTR definition
• Day of platelet engraftment per CIBMTR definition
• Rates of viral reactivation or infection to day 100 post HCT
• Rates of acute and chronic GVHD at 1 and 2 years post HCT, respectively
• Rates of graft failure or myeloid chimerism <95% at 1 year post HCT
• Transplant related mortality at 1, 2, and 3 years post HCT
• Non-transplant related mortality at 1, 2 and 3 years post HCT

Exploratory Endpoints:

-Quality of life, neuropsychologic function, reproductive health questionnaires, serial testing or imaging of organ function/status

• Study Type: Interventional
• Enrollment (Estimated): 90
• Phase: Phase 2; Phase 1

Contacts and Locations

• Study Contact: Name: John F Tisdale, M.D.; Phone Number: (301) 402-6497; Email: johntis@mail.nih.gov
• Study Contact Backup: Name: Kelly S Norris, R.N.; Phone Number: (301) 529-7104; Email: kelly.norris@nih.gov

Study Locations

• United States
  • Maryland
    • Bethesda, Maryland, United States, 20892
      • Recruiting
      • National Institutes of Health Clinical Center
      • Contact: NIH Clinical Center Office of Patient Recruitment (OPR); Phone Number: TTY dial 711 800-411-1222; Email: ccopr@nih.gov

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

• INCLUSION CRITERIA

RECIPIENT:

Participants must fulfill one disease category (1 or 2) and 3

1. Patients with sickle cell disease at high risk for disease related morbidity or mortality, defined by having an end-organ damage (A, B, C, D, OR E) or complication(s) not ameliorated by sickle cell-specific therapies (F):

   A. Stroke defined as a clinically significant neurologic event that is accompanied by an infarct on cerebral MRI ORb

   B. Abnormal trans-cranial Doppler examination (>=200 cm/s); OR

   C. Silent cerebral infarct defined as an infarct-like lesion based on an MRI signal abnormality at least 3 mm in one dimension and visible in two planes on FLAIR or T2- weighted images (or similar image with 3D imaging) and documented neurological examination performed by a neurologist demonstrating the participant has a normal neurologic examination, or an abnormality on examination that could not be explained by the location of the brain lesion(s); OR

   D. Sickle cell related renal insufficiency defined by a creatinine level >=1.5 times the upper limit of normal and kidney biopsy consistent with sickle cell nephropathy OR nephrotic syndrome OR creatinine clearance <60mL/min/1.73m2 for patients <16 years of age or <50mL/min for patients >16 years of age OR requiring peritoneal or hemodialysis; OR

   Age (Years): <= 5 / Upper limit of normal serum creatinine (mg/dl): 0.8

   Age (Years): 5 < age <= 10 / Upper limit of normal serum creatinine (mg/dl): 1.0

   Age (Years): 10 < age <= 15 / Upper limit of normal serum creatinine (mg/dl): 1.2

   Age (Years): > 15 / Upper limit of normal serum creatinine (mg/dl): 1.3

   E. Tricuspid regurgitant jet velocity (TRV) of >=2.5 m/s in patients at least 3 weeks after a vaso-occlusive crisis; OR

   F. Recurrent severe priapism defined as at least two episodes of an erection lasting >=4 hours requiring medical intervention (e.g. aspiration, injection of vasoconstrictor, prior penile surgery.); OR

   G. Sickle hepatopathy defined as EITHER ferritin >1000mcg/L OR direct bilirubin >0.4 mg/dL at baseline; OR

   H. Vaso-occlusive crises: more than 1 hospital admission per year while on a therapeutic dose of sickle cell treatment /medication; OR

   I. Acute chest syndrome (ACS): any ACS while on sickle cell treatment /medication

2. Patients with beta-thalassemia who have grade 2 or 3 iron overload, determined by the presence of 2 or more of the following:

   • Portal fibrosis by liver biopsy
   • Inadequate chelation history (defined as failure to maintain adequate compliance with chelation with deferoxamine initiated within 18 months of the first transfusion and administered at least 5 days each week)
   • Hepatomegaly of greater than 2 cm below the costochondral margin or by other imaging scans

3. Non disease specific

   • Ages >=4 years and less than 65 years old
   • Fully matched human leukocyte antigen (HLA) donors at A, B, C, and DR loci (8 of 8 or 10 of 10
   • Ability to comprehend and willing to sign an informed consent, assent obtained from minors when applicable. Negative serum or urine beta-HCG, when applicable

   • Agree to use birth control throughout the study and 3 months after abatacept or sirolimus administration.

     • Female subjects must agree to use a medically acceptable method of birth control such as oral contraceptive, intrauterine device, barrier and spermicide, or implant/injection from start of screening until immunosuppression is stopped.
     • Male subjects must agree to use effective contraception (including condoms) from start of screening until immunosuppression is stopped.

DONOR:

• Fully matched human leukocyte antigen (HLA) donors at A, B, C, and DR loci (8 of 8 or 10 of 10) are intended for this study.
• Donors age 4 or older and >=15 kg (or weight deemed acceptable by IR for line placement, DTM for apheresis, and pediatric consult service) eligible to donate hematopoietic stem cells, are eligible for this study.
• Donors will be evaluated in accordance with existing Standard NIH Policies and Procedures for determination of eligibility and suitability for clinical donation. Donors will sign on a separate protocol, 20-H-0099 NHLBI standard of care protocol for the mobilization and collection of HSCs. Note that participation in this study is offered to all eligible donors, but is not required for a donor to make a stem cell donation, so it is possible that not all donors will enroll onto this study.

EXCLUSION CRITERIA

RECIPIENT:

• Karnofsky or Lanksy performance status of <40
• Diffusion capacity of carbon monoxide (DLCO) <35% predicted (corrected for hemoglobin and alveolar volume). This criterion may be omitted in young children (e.g. near age 5) or other individuals who may have difficulty understanding or complying with instructions of testing.
• Baseline oxygen saturation of <85% or PaO2 <70
• Left ventricular ejection fraction: <35% estimated by ECHO
• Transaminases >5x upper limit of normal for age
• Evidence of uncontrolled bacterial, viral, or fungal infections (currently taking medication and progression of clinical symptoms) within one month prior to starting the conditioning regimen
• Major anticipated illness or organ failure incompatible with survival from HCT
• Pregnant or breastfeeding

DONOR:

• Pregnant or breastfeeding
• Cognitively impaired subjects

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
Other: Matched related donors; Donors for patients	Other: Research blood draw; About 5 tablespoons of blood will be collected from donors for research purposes.
Experimental: Transplant recipients; Patients with symptomatic sickle cell disease or beta-thalassemia	Other: Research blood draw; About 5 tablespoons of blood will be collected from donors for research purposes.; Radiation: Total Body Irradiation; Total Body Irradiation 400 cGy; Drug: Alemtuzumab; 1 mg/kg; Drug: Abatacept; 10 mg/kg x 6

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Donor myeloid chimerism	percentage of donor myeloid chimerism	1 year

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Donor CD3 chimerism	percentage of donor myeloid chimerism	1 year
Overall survival	percentage of patients surviving at 1 year	1 year
Acute Graft versus Host Disease	percentage of patients with Grade 2-4 acute GVHD	1 year

Collaborators and Investigators

• Sponsor: National Heart, Lung, and Blood Institute (NHLBI)
• Investigators: Principal Investigator: John F Tisdale, M.D., National Heart, Lung, and Blood Institute (NHLBI)

Publications and helpful links

Helpful Links

• NIH Clinical Center Detailed Web Page

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 30, 2032
• Study Completion (Estimated): June 30, 2035

Study Registration Dates

• First Submitted: May 16, 2026
• First Submitted That Met QC Criteria: May 16, 2026
• First Posted (Actual): May 20, 2026

Study Record Updates

• Last Update Posted (Actual): May 20, 2026
• Last Update Submitted That Met QC Criteria: May 16, 2026
• Last Verified: May 15, 2026

More Information

Terms related to this study

• Keywords: Sickle Cell Disease; Stem Cell Transplant; Chimerism; Beta-Thalassemia
• Additional Relevant MeSH Terms: Genetic Diseases, Inborn; Hematologic Diseases; Anemia, Hemolytic, Congenital; Anemia, Hemolytic; Anemia; Hemoglobinopathies; Thalassemia; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Hemic and Lymphatic Diseases; Anemia, Sickle Cell; beta-Thalassemia; Immunoconjugates; Amino Acids, Peptides, and Proteins; Proteins; Investigative Techniques; Therapeutics; Antibodies, Monoclonal, Humanized; Antibodies, Monoclonal; Antibodies; Immunoglobulins; Immunoproteins; Blood Proteins; Serum Globulins; Globulins; Radiotherapy; Abatacept; Alemtuzumab; Whole-Body Irradiation
• Other Study ID Numbers: 10002545; 002545-H

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: We are planning to collect and report data as a group.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No