Beta-ThalassemiaPhase 3NCT05356195
Evaluation of Safety and Efficacy of CTX001 in Pediatric Participants With Transfusion-Dependent β-Thalassemia (TDT)
A Phase 3 study testing CTX001 in people with Beta-Thalassemia and Thalassemia, run by Vertex Pharmaceuticals Incorporated at 6 sites in 5 countries.
Trial summary
This is a single-dose, open-label study in pediatric participants with TDT. The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 modified CD34+ human hematopoietic stem and progenitor cells (hHSPCs) (CTX001). Read more about this study
- Who is it for?
- Ages 2 to 11 years
- Conditions the study is for
- Beta-Thalassemia, Thalassemia, Genetic Diseases, Inborn
- What is being tested?
- CTX001
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 16 participants
- Where
- 6 sitesin 5 countries
- Study dates
- 3 May 2022to 14 Nov 2027
- Phase
- Phase 3
- 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 2 to 11 years
- All sexes
- No healthy volunteers
- Child
Who may be able to join
- 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.
Who cannot join
- 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.
Trial locations and contacts
6 sites in 5 countries.
6 sites in 5 countries
United Kingdom2 sites
Great Ormond Street Hospital for Children
London
St.Mary's Hospital - Children's Clinical Research Facility
London
United States1 site
TriStar Medical Group Children's Specialists - Pediatric Oncology
Nashville, Tennessee, 37203
Germany1 site
University Hospital Dusseldorf - Department of Pediatric Oncology, Hematology and Clinical Immunology
Düsseldorf
Italy1 site
IRCSS Ospedale Pediatrico Bambino Gesu - Dipartimento di Onco-Ematologia e Terapia Cellulare e Genica
Rome
About this study
Official title: A Phase 3 Study to Evaluate the Safety and Efficacy of a Single Dose of CTX001 in Pediatric Subjects With Transfusion-Dependent β-Thalassemia
This is a single-dose, open-label study in pediatric participants with TDT. The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 modified CD34+ human hematopoietic stem and progenitor cells (hHSPCs) (CTX001).
- Conditions
- Beta-Thalassemia, Thalassemia, Genetic Diseases, Inborn, Hematologic Diseases, Hemoglobinopathies
- Being tested
- CTX001
- Medical subject headings
- beta-Thalassemia, Thalassemia, Genetic Diseases, Inborn, Hematologic Diseases, Hemoglobinopathies
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
CTX001Biological
Also called Exagamglogene autotemcel, Exa-cel
Administered by intravenous infusion following myeloablative conditioning with busulfan.
| Study group | Role | What they receive |
|---|---|---|
| CTX001 | Experimental | 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. Receives: Biological: CTX001 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Proportion of Participants who Achieve Transfusion Independence for at Least 12 Consecutive Months (TI12)
Measured: Up to 24 Months After CTX001 Infusion
Secondary outcomes (13)
Proportion of Participants Achieving at Least 95 Percent (%), 90%, 85%, 75% and 50% Reduction in Annualized Transfusions
Measured: From Baseline up to 24 Months After CTX001 Infusion
Transfusion Free Duration for Participants who Achieve TI12
Measured: Up to 24 Months After CTX001 Infusion
Proportion of Alleles With Intended Genetic Modification Present in Peripheral Blood Over Time
Measured: Up to 24 Months After CTX001 Infusion
Proportion of Alleles With Intended Genetic Modification Present in CD34+ Cells of the Bone Marrow Over Time
Measured: Up to 24 Months After CTX001 Infusion
Change in Fetal Hemoglobin Concentration Over Time
Measured: From Baseline (Pre-transfusion) up to 24 Months After CTX001 Infusion
Change in Total Hemoglobin Concentration Over Time
Measured: From Baseline (Pre-transfusion) up to 24 Months After CTX001 Infusion
Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
Measured: From Signing of Informed Consent up to 24 Months After CTX001 Infusion
Proportion of Participants With Engraftment (First day of 3 Consecutive Measurements of Absolute Neutrophil Count [ANC] ≥500 per Microliter [mcgL] on 3 Different Days)
Measured: Within 42 Days After CTX001 Infusion
Time to Engraftment
Measured: Up to 24 Months After CTX001 Infusion
Incidence of Transplant-related Mortality (TRM) Within 100 Days After CTX001 Infusion
Measured: Within 100 Days After CTX001 Infusion
Incidence of TRM Within 12 Months After CTX001 Infusion
Measured: Within 12 Months After Infusion
Incidence of All-cause Mortality
Measured: From Signing of Informed Consent up to 24 Months After CTX001 Infusion
Relative Reduction in Annualized Volume and Episodes of RBC Transfusions starting Month 10 After CTX001 infusion
Measured: From Baseline up to 24 Months After CTX001 Infusion
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted2 May 2022
- Study start3 May 2022
- Primary completion14 Nov 2027 (estimated)
- Study completion14 Nov 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Beta-ThalassemiaStudies of the same condition, open and under way.
- More trials run by Vertex Pharmaceuticals IncorporatedThe 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 3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 16 participants (actual)
Sponsor and investigators
- Lead sponsor
- Vertex Pharmaceuticals Incorporated
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- CRISPR Therapeutics
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05356195
- Sponsor's protocol ID
- VX21-CTX001-141
- Other IDs
- 2021-002172-39
- Status last verified
- Jun 2026
- First submitted
- 7 Apr 2022
- Last updated
- 1 Jul 2026
- Results posted
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: Details on Vertex data sharing criteria and process for requesting access can be found at: https://www.vrtx.com/independent-research/clinical-trial-data-sharing
Publications
Frangoul H, de la Fuente J, Chopra Y, Meisel R, Amrolia PJ, Algeri M, Sharma A, Cappellini MD, Corbacioglu S, Kattamis A, Lobitz S, de Montalembert M, Rondelli D, Sheth S, Steinberg MH, Walters MC, Boerner K, Liu T, Zairis S, Hobbs W, Grupp SA, Locatelli F; CLIMB THAL-141 and CLIMB SCD-151 Study Groups. Exa-cel in Children with Transfusion-Dependent beta-Thalassemia or Sickle Cell Disease. N Engl J Med. 2026 Jun 11. doi: 10.1056/NEJMoa2603387. Online ahead of print.
PubMed 42274009
Study at a glance
From the registry record, last updated by the sponsor on 1 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 3 Study to Evaluate the Safety and Efficacy of a Single Dose of CTX001 in Pediatric Subjects With Transfusion-Dependent β-Thalassemia
- ClinicalTrials.gov ID
- NCT05356195
- Acronym / sponsor ID
- VX21-CTX001-141
- Conditions
- Beta-Thalassemia, Thalassemia, Genetic Diseases, Inborn, Hematologic Diseases, Hemoglobinopathies
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 16 participants (actual)
- Lead sponsor
- Vertex Pharmaceuticals IncorporatedIndustry (pharma, biotech, devices)
- Collaborators
- CRISPR Therapeutics
- Study start
- 3 May 2022 (actual)
- Primary completion
- 14 Nov 2027 (estimated)
- Study completion
- 14 Nov 2027 (estimated)
- First posted
- 2 May 2022 (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 is a single-dose, open-label study in pediatric participants with TDT. The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 modified CD34+ human hematopoietic stem and progenitor cells (hHSPCs) (CTX001).
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| CTX001 | Experimental | Biological: CTX001CTX001 (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. |
Who may qualify
- Ages
- 2 to 11 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (4 listed)
- Diagnosis of TDT as defined by:
- Eligible for autologous stem cell transplant as per investigator's judgment.
Key exclusion criteria (6 listed)
- 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
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 |
|---|---|---|
| CTX001Also: Exagamglogene autotemcel, Exa-celAdministered by intravenous infusion following myeloablative conditioning with busulfan. | Biological | CTX001 |
Primary outcome
Proportion of Participants who Achieve Transfusion Independence for at Least 12 Consecutive Months (TI12)
Time frame: Up to 24 Months After CTX001 Infusion
13 secondary outcomes
Proportion of Participants Achieving at Least 95 Percent (%), 90%, 85%, 75% and 50% Reduction in Annualized Transfusions
Time frame: From Baseline up to 24 Months After CTX001 Infusion
Transfusion Free Duration for Participants who Achieve TI12
Time frame: Up to 24 Months After CTX001 Infusion
Proportion of Alleles With Intended Genetic Modification Present in Peripheral Blood Over Time
Time frame: Up to 24 Months After CTX001 Infusion
Proportion of Alleles With Intended Genetic Modification Present in CD34+ Cells of the Bone Marrow Over Time
Time frame: Up to 24 Months After CTX001 Infusion
Change in Fetal Hemoglobin Concentration Over Time
Time frame: From Baseline (Pre-transfusion) up to 24 Months After CTX001 Infusion
Change in Total Hemoglobin Concentration Over Time
Time frame: From Baseline (Pre-transfusion) up to 24 Months After CTX001 Infusion
Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
Time frame: From Signing of Informed Consent up to 24 Months After CTX001 Infusion
Proportion of Participants With Engraftment (First day of 3 Consecutive Measurements of Absolute Neutrophil Count [ANC] ≥500 per Microliter [mcgL] on 3 Different Days)
Time frame: Within 42 Days After CTX001 Infusion
Time to Engraftment
Time frame: Up to 24 Months After CTX001 Infusion
Incidence of Transplant-related Mortality (TRM) Within 100 Days After CTX001 Infusion
Time frame: Within 100 Days After CTX001 Infusion
Incidence of TRM Within 12 Months After CTX001 Infusion
Time frame: Within 12 Months After Infusion
Incidence of All-cause Mortality
Time frame: From Signing of Informed Consent up to 24 Months After CTX001 Infusion
Relative Reduction in Annualized Volume and Episodes of RBC Transfusions starting Month 10 After CTX001 infusion
Time frame: From Baseline up to 24 Months After CTX001 Infusion
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 1 Jul 2026.
- Derived from this study: PubMed 42274009Frangoul H, de la Fuente J, Chopra Y, Meisel R, Amrolia PJ, Algeri M, Sharma A, Cappellini MD, Corbacioglu S, Kattamis A, Lobitz S, de Montalembert M, Rondelli D, Sheth S, Steinberg MH, Walters MC, Boerner K, Liu T, Zairis S, Hobbs W, Grupp SA, Locatelli F; CLIMB THAL-141 and CLIMB SCD-151 Study Groups. Exa-cel in Children with Transfusion-Dependent beta-Thalassemia or Sickle Cell Disease. N Engl J Med. 2026 Jun 11. doi: 10.1056/NEJMoa2603387. Online ahead of print.
- Individual participant dataSharing planned: No. Details on Vertex data sharing criteria and process for requesting access can be found at: https://www.vrtx.com/independent-research/clinical-trial-data-sharing
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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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
6 sites in 5 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing CTX001 in people with Beta-Thalassemia and Thalassemia, run by Vertex Pharmaceuticals Incorporated at 6 sites in 5 countries.
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 4 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: under way, not looking for participants, as of the sponsor's last update on 1 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 6 sites in United Kingdom, United States, Canada, Germany, Italy. 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 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
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?
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?
Proportion of Participants who Achieve Transfusion Independence for at Least 12 Consecutive Months (TI12) (time frame: Up to 24 Months After CTX001 Infusion). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05356195, which also lists 1 linked publication.
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 1 Jul 2026.