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Sickle Cell DiseasePhase 3NCT05329649

Evaluation of Safety and Efficacy of CTX001 in Pediatric Participants With Severe Sickle Cell Disease (SCD)

A Phase 3 study testing CTX001 in people with Sickle Cell Disease and Hydroxyurea Failure, run by Vertex Pharmaceuticals Incorporated at 7 sites in 4 countries.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
Search all trials

Trial summary

This is a single-dose, open-label study in pediatric participants with severe SCD and hydroxyurea (HU) failure or intolerance. 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
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
13 participants
Where
7 sitesin 4 countries
Study dates
2 May 2022to 6 Jun 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 severe SCD as defined by:
  • Documented SCD genotypes
  • History of at least two severe VOCs events per year for the previous two years prior to enrollment
  • Hydroxyurea (HU) failure unless HU intolerant
  • Eligible for autologous stem cell transplant as per investigators judgment

Who cannot join

  • A willing and healthy 10/10 human leukocyte antigen (HLA)-matched related donor
  • Prior hematopoietic stem cell transplant (HSCT).
  • Clinically significant and active bacterial, viral, fungal, or parasitic infection
  • Other protocol defined Inclusion/Exclusion criteria may apply.

Trial locations and contacts

7 sites in 4 countries.

7 sites in 4 countries

United States4 sites

  • Levine Children's Hospital - Hematology

    Charlotte, North Carolina, 28203

  • St. Jude Children's Research Hospital

    Memphis, Tennessee, 38105

  • TriStar Medical Group Children's Specialists - Pediatric Oncology

    Nashville, Tennessee, 37203

  • The Children's Hospital of Philadelphia - Hematology

    Philadelphia, Pennsylvania, 19104

Other trials in United States

Germany1 site

  • University Hospital Duesseldorf - Department of Pediatric Oncology, Hematology and Clinical Immunology

    Düsseldorf

Other trials in Germany

Italy1 site

  • IRCSS Ospedale Pediatrico Bambino Gesu - Dipartimento di Onco-Ematologia e Terapia Cellulare e Genica

    Rome

Other trials in Italy

United Kingdom1 site

  • St.Mary's Hospital - Haematology Dept

    London

Other trials in United Kingdom

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 Severe Sickle Cell Disease

This is a single-dose, open-label study in pediatric participants with severe SCD and hydroxyurea (HU) failure or intolerance. The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 modified CD34+ human hematopoietic stem and progenitor cells (hHSPCs) (CTX001).

Being tested
CTX001
Medical subject headings
Anemia, Sickle Cell, Hemoglobinopathies, Hematologic Diseases

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 groups in NCT05329649
Study groupRoleWhat they receive
CTX001ExperimentalCTX001 (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.

  1. Proportion of Participants who do not Have any Severe Vaso-occlusive Crises (VOCs) for at Least 12 Consecutive Months (VF12)

    Measured: Up to 24 Months After CTX001 Infusion

Secondary outcomes (30)

  1. Proportion of Participants Free from Inpatient Hospitalization for Severe VOCs for at Least 12 Months (HF12)

    Measured: Up to 24 Months After CTX001 Infusion

  2. Relative Reduction in Annualized Rate of Severe VOCs

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  3. Duration of Severe VOC Free in Participants who Have Achieved VF12

    Measured: Up to 24 Months After CTX001 Infusion

  4. Relative Reduction in Annualized Rate of Inpatient Hospitalizations for Severe VOCs

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  5. Proportion of Participants With Sustained Fetal Hemoglobin (HbF) ≥20 Percent (%) for at Least 3 Months

    Measured: Up to 24 Months After CTX001 Infusion

  6. Proportion of Participants With Sustained HbF ≥20% for at Least 6 Months

    Measured: Up to 24 Months After CTX001 Infusion

  7. Proportion of Participants With Sustained HbF ≥20% for at Least 12 Months

    Measured: Up to 24 Months After CTX001 Infusion

  8. Proportion of Alleles With Intended Genetic Modification Present in Peripheral Blood Over Time

    Measured: Up to 24 Months After CTX001 Infusion

  9. 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

  10. 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

  11. 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

  12. Time to Engraftment

    Measured: Up to 24 Months After CTX001 Infusion

  13. Incidence of Transplant-related Mortality (TRM) Within 100 Days After CTX001 Infusion

    Measured: Within 100 Days After CTX001 infusion

  14. Incidence of TRM Within 12 Months After CTX001 Infusion

    Measured: Within 12 Months After Infusion

  15. Incidence of All-cause Mortality

    Measured: From Signing of Informed Consent up to 24 Months After CTX001 Infusion

  16. Relative Reduction in Annualized Duration of Hospitalization for Severe VOCs

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  17. Proportion of Participants With Sustained HbF ≥30% for at Least 3 Months

    Measured: Up to 24 Months After CTX001 Infusion

  18. Proportion of Participants With Sustained HbF ≥30% for at Least 6 Months

    Measured: Up to 24 Months After CTX001 Infusion

  19. Proportion of Participants With Sustained HbF ≥30% for at Least 12 Months

    Measured: Up to 24 Months After CTX001 Infusion

  20. Time for Participants to Reach HbF ≥20%

    Measured: Up to 24 Months After CTX001 Infusion

  21. Time for Participants to Reach HbF ≥30%

    Measured: Up to 24 Months After CTX001 Infusion

  22. Relative Reduction from Baseline in Annualized Volume and Episodes of RBC Transfusions for SCD-related indications starting after Month 12 post-CTX001 infusion

    Measured: Up to 24 Months After CTX001 Infusion

  23. HbF Concentrations Over Time

    Measured: Up to 24 Months After CTX001 Infusion

  24. Hemoglobin (Hb) Concentrations Over Time

    Measured: Up to 24 Months After CTX001 Infusion

  25. Change in Reticulocyte Count Over Time

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  26. Change in Indirect Bilirubin Over Time

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  27. Change in Haptoglobin Over Time

    Measured: From Baseline up to 24 Months After CTX001 Infusion

  28. Proportion of Participants with Detectable Haptoglobin Over Time

    Measured: Up to 24 Months After CTX001 Infusion

  29. Change in Lactate Dehydrogenase (LDH) Over Time

    Measured: From Baseline (Pre-infusion) up to 24 Months After CTX001 Infusion

  30. Proportion of Participants with Normalized LDH Over Time

    Measured: 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.

  1. First posted15 Apr 2022
  2. Study start2 May 2022
  3. Primary completion6 Jun 2027 (estimated)
  4. Study completion6 Jun 2027 (estimated)

Resources

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
13 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05329649
Sponsor's protocol ID
VX21-CTX001-151
Other IDs
2021-002173-26
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

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing CTX001 in people with Sickle Cell Disease and Hydroxyurea Failure, run by Vertex Pharmaceuticals Incorporated at 7 sites in 4 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 5 inclusion and 4 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 7 sites in United States, Germany, Italy, United Kingdom. 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 do not Have any Severe Vaso-occlusive Crises (VOCs) for at Least 12 Consecutive Months (VF12) (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 NCT05329649, 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.

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