Evaluation of Safety and Efficacy of CTX001 in Pediatric Participants With Transfusion-Dependent β-Thalassemia (TDT)

Recruitment Status
ACTIVE, NOT RECRUITING
(See Contacts and Locations)Verified January 2026 by Vertex Pharmaceuticals Incorporated
Sponsor
Vertex Pharmaceuticals Incorporated
Information Provided by (Responsible Party)
Vertex Pharmaceuticals Incorporated
Clinicaltrials.gov Identifier
NCT05356195
Other Study ID Numbers:
VX21-CTX001-141
First Submitted
April 6, 2022
First Posted
May 1, 2022
Last Update Posted
March 2, 2026
Last Verified
January 2026

ClinicalTrials.gov processed this data on February 2026. Link to the current ClinicalTrials.gov record .

History of Changes

Study Details

Study Description

Condition or DiseaseIntervention/Treatment
Beta-ThalassemiaThalassemiaGenetic Diseases, InbornHematologic DiseasesHemoglobinopathies
Biological: CTX001

Study Design

Study TypeInterventional
Actual Enrollment16 participants
Design AllocationN/A
Interventional ModelSingle Group Assignment
MaskingNone (Open Label)
Primary PurposeTreatment
Official TitleA Phase 3 Study to Evaluate the Safety and Efficacy of a Single Dose of CTX001 in Pediatric Subjects With Transfusion-Dependent β-Thalassemia
Study Start DateMay 2, 2022
Actual Primary Completion DateMay 30, 2026
Actual Study Completion DateMay 30, 2026

Groups and Cohorts

Group/CohortIntervention/Treatment
CTX001
CTX001 (autologous CD34+ hHSPCs modified with CRISPR-Cas9 at the erythroid lineage-specific enhancer of the BCL11A gene). Participants will receive single infusion of CTX001 through central venous catheter.
Biological: CTX001
Administered by intravenous infusion following myeloablative conditioning with busulfan.

Outcome Measures

Primary Outcome Measures
  1. Proportion of Participants who Achieve Transfusion Independence for at Least 12 Consecutive Months (TI12)
Secondary Outcome Measures
  1. Proportion of Participants Achieving at Least 95 Percent (%), 90%, 85%, 75% and 50% Reduction in Annualized Transfusions
  2. Transfusion Free Duration for Participants who Achieve TI12
  3. Proportion of Alleles With Intended Genetic Modification Present in Peripheral Blood Over Time
  4. Proportion of Alleles With Intended Genetic Modification Present in CD34+ Cells of the Bone Marrow Over Time
  5. Change in Fetal Hemoglobin Concentration Over Time
  6. Change in Total Hemoglobin Concentration Over Time
  7. Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
  8. Proportion of Participants With Engraftment (First day of 3 Consecutive Measurements of Absolute Neutrophil Count [ANC] ≥500 per Microliter [mcgL] on 3 Different Days)
  9. Time to Engraftment
  10. Incidence of Transplant-related Mortality (TRM) Within 100 Days After CTX001 Infusion
  11. Incidence of TRM Within 12 Months After CTX001 Infusion
  12. Incidence of All-cause Mortality
  13. Relative Reduction in Annualized Volume and Episodes of RBC Transfusions starting Month 10 After CTX001 infusion

Eligibility Criteria

Ages Eligible for Study(Child)
Sexes Eligible for StudyAll
Accepts Healthy VolunteersNo
Inclusion Criteria
Diagnosis of TDT as defined by:
Documented homozygous or compound heterozygous β-thalassemia including β-thalassemia/hemoglobin E (HbE). Participants can be enrolled based on historical data, but a confirmation of the genotype using the study central laboratory will be required before busulfan conditioning
History of at least 100 mL/kilograms (kg)/year of packed RBC transfusions in the prior 24 months before signing of consent (or the last rescreening for patients going through repeat screening) or, for participants initiating transfusion therapy \<24 months before signing of consent, requirement for packed RBC transfusion at least every 3 to 4 weeks for ≥6 months
Eligible for autologous stem cell transplant as per investigator's judgment. Key
Exclusion Criteria
A willing and healthy 10/10 human leukocyte antigen (HLA)-matched related donor is available per investigator's judgement
Prior hematopoietic stem cell transplant (HSCT)
Participants with associated α-thalassemia and \>1 alpha deletion, or alpha multiplications
Participants with sickle cell β-thalassemia variant
Clinically significant and active bacterial, viral, fungal, or parasitic infection as determined by the investigator Other protocol defined Inclusion/Exclusion criteria may apply.

Contacts and Locations

Sponsors and CollaboratorsVertex Pharmaceuticals Incorporated
Locations
TriStar Medical Group Children's Specialists - Pediatric Oncology | Nashville Tennessee, United States, 37203Hospital for Sick Children - Hematology | Toronto , Canada, University Hospital Dusseldorf - Department of Pediatric Oncology, Hematology and Clinical Immunology | Düsseldorf , Germany, IRCSS Ospedale Pediatrico Bambino Gesu - Dipartimento di Onco-Ematologia e Terapia Cellulare e Genica | Rome , Italy, Great Ormond Street Hospital for Children | London , United Kingdom, St.Mary's Hospital - Children's Clinical Research Facility | London , United Kingdom,