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CASPER: Phase 1/2 Safety and Efficacy Study of CRISPR Cas9 Gene Editing in Patients with Severe Sickle Cell Disease

About this study

This is a clinical trial to learn about the safety and effects of CTX001 in patients with severe sickle cell disease (SCD). CTX001 is considered investigational, which means it has not been approved by the U.S. Food and Drug Administration (FDA). The goal of this study is to see if a single dose of CTX001 allows your body to increase the amount of a certain kind of hemoglobin called hemoglobin F (HbF) while decreasing the effects of SCD. Hemoglobin is a protein in red blood cells that carries oxygen to the body.

If you participate in this study, we will collect bone marrow cells (stem cells) from you and send them to a laboratory. Next, we will edit (change) the DNA in a specific gene in your cells to create the study product, CTX001. The technology we use to edit the DNA in the cell is called CRISPR/Cas9. It cuts the DNA like scissors. The blood stem cell then repairs the cut DNA using its natural repair tools. We hope this repair will help your body produce more hemoglobin F.

After we change your cells using CRISPR/Cas9, we will return them to you through your veins. This procedure is called an autologous bone marrow transplant and takes place in the hospital. You will take medicine to remove your own bone marrow cells and create “room” for the incoming edited cells. We will then infuse the modified cells into your vein.

Eligibility overview

  • 18 to 35 years old (Ages 18 to 25 at St. Jude)
  • Diagnosis of severe sickle cell disease

The above information is intended to provide only a basic description about a research protocol that may be currently active at St. Jude. The details made available here may not be the most up-to-date information on protocols used by St. Jude. To receive full details about a protocol and its status and or use at St. Jude, a physician must contact St. Jude directly.


Full title:

A Phase 1/2 Study to Evaluate the Safety and Efficacy of a Single Dose of Autologous CRISPR-Cas9 Modified CD34+ Human Hematopoietic Stem and Progenitor Cells (CTX001) in Subjects with Severe Sickle Cell Disease

Study goal:

The main goal of this study is to see if a single dose of CTX001 allows your body to increase the amount of hemoglobin F while reducing painful effects of sickle cell disease.


Sickle cell disease


18 to 25 years old

Clinical trials categories:

Blood Disorders Sickle Cell Disease

For physicians and researchers

Patients accepted to St. Jude must be referred by a physician or other qualified medical professional. Learn how St. Jude can partner with you to care for your patient.


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