Evaluation of Efficacy and Safety of a Single Dose of CTX001 in Participants With Transfusion-Dependent β-Thalassemia and Severe Sickle Cell Disease

A Phase 3b Study to Evaluate Efficacy and Safety of a Single Dose of Autologous CRISPR Cas9 Modified CD34+ Human Hematopoietic Stem and Progenitor Cells (CTX001) in Subjects With Transfusion-Dependent β-Thalassemia or Severe Sickle Cell Disease

Evaluation of Efficacy and Safety of a Single Dose of CTX001 in Participants With Transfusion-Dependent β-Thalassemia and Severe Sickle Cell Disease (NCT05477563) is a Phase 3 interventional studying Beta-Thalassemia and Thalassemia, sponsored by Vertex Pharmaceuticals Incorporated. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

About This Trial

What Stage of Research Is This?

Phase 3 trials confirm efficacy and safety in large patient groups (often 300–3,000+) and form the evidence base for an FDA approval submission. For Beta-Thalassemia, Phase 3 studies typically randomize participants between the investigational treatment and either a placebo or current standard of care. A successful Phase 3 result is the threshold most treatments need to clear before regulatory approval.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

With a target enrollment of 26 participants, this is a small study — typical of early-phase research, rare-disease trials, or pilot studies designed to generate preliminary signal before a larger study is launched.

Who May Be Eligible (Plain English)

Key Who May Qualify: - Participants with TDT and SCD: - Eligible for autologous stem cell transplant as per investigator's judgment. - Participants with TDT: - Diagnosis of TDT as defined by: - Documented homozygous β-thalassemia 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 milliliter (mL)/kilograms (kg)/year or 10 units/year of packed red blood cells (RBC) transfusions in the prior 2 years before signing the consent or the last rescreening for patients going through re-screening - Participants with SCD: - 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 Key Who Should NOT Join This Trial: - Participants with TDT and SCD: - 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) - Clinically significant and active bacterial, viral, fungal, or parasitic infection as determined by the investigator - Participants with TDT: - Participants with associated α-thalassemia and \>1 alpha deletion, or alpha multiplications - Participants with sickle cell β-thalassemia variant - Participants with SCD: - History of untreated moyamoya syndrome or presence of moyamoya syndrome at screening Other protocol defined Inclusion/Exclusion criteria may apply. Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language

Key Inclusion Criteria: * Participants with TDT and SCD: * Eligible for autologous stem cell transplant as per investigator's judgment. * Participants with TDT: * Diagnosis of TDT as defined by: * Documented homozygous β-thalassemia 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 milliliter (mL)/kilograms (kg)/year or 10 units/year of packed red blood cells (RBC) transfusions in the prior 2 years before signing the consent or the last rescreening for patients going through re-screening * Participants with SCD: * 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 Key Exclusion Criteria: * Participants with TDT and SCD: * 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) * Clinically significant and active bacterial, viral, fungal, or parasitic infection as determined by the investigator * Participants with TDT: * Participants with associated α-thalassemia and \>1 alpha deletion, or alpha multiplications * Participants with sickle cell β-thalassemia variant * Participants with SCD: * History of untreated moyamoya syndrome or presence of moyamoya syndrome at screening Other protocol defined Inclusion/Exclusion criteria may apply.

Treatments Being Tested

BIOLOGICAL

CTX001

Administered by intravenous (IV) infusion following myeloablative conditioning with busulfan

Locations (6)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

New York Presbyterian Hospital - Morgan Stanley Children's Hospital

New York, New York, United States

Levine Children's Hospital - Hematology

Charlotte, North Carolina, United States

TriStar Medical Group Children's Specialists - Pediatric Oncology

Nashville, Tennessee, United States

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

King Faisal Specialist Hospital & Research Centre - Riyadh - Hematology

Al Mathar Ash Shamali, Saudi Arabia

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT05477563), the sponsor (Vertex Pharmaceuticals Incorporated), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT05477563 clinical trial studying?

This is a single-dose, open-label study in participants with transfusion-dependent β-thalassemia (TDT) or severe sickle cell disease (SCD). The study will evaluate the safety and efficacy of autologous CRISPR-Cas9 modified CD34+ human hematopoietic stem and progenitor cells (hHSPCs) using CTX001. The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.

Who can participate in NCT05477563?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT05477563?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT05477563. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT05477563. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-05-08 · Data from ClinicalTrials.gov.