Sickle cell disease gene therapy FAQ

Eligibility criteria may be different for each available gene therapies, including clinical trials. However, there are a few general criteria across all therapies, including your age, your sickle disease genotype, other treatments you are taking, your response to other treatments and your general health. To determine your eligibility, you may have to undergo certain tests as part of the screening process.

If you are eligible and decide to receive  gene therapy, your clinical team and healthcare providers will make a plan for the treatments you are taking for your sickle cell disease. For example, if you are taking hydroxyurea, you may have to stop taking it two to three months before the stem cell collection process for gene therapy. You may undergo blood transfusions for this period to replace your hydroxyurea or other medications. 

Gene therapy involves a series of steps over a long period of time, some of which will include long hospital stays. It is important to obtain specific information about the clinical trial or therapy you are considering. These are the general steps:  

• You will first prepare for stem cell collection.  
• Two to three months later you will have your stem cells collected.  
• Your stem cells will take seven to 10 weeks to be manufactured and processed in a lab.  
• If the modified stem cells meet certain criteria, you will go through chemotherapy for conditioning. 
• A few days later, the modified stem cells will be infused back into your body.  
• After this, you will remain in the hospital as an inpatient for a long period and monitored closely. This period will approximately last four to six weeks.
• After this inpatient period, you will transition to monthly outpatient visits.

Learn more about each of these steps in the Navigating sickle cell disease gene therapy infographic.

Receiving gene therapy clinical trial can be a difficult process for many reasons, such as the risks of the procedure, difficulty of conditioning process and a long-term hospital stay. It may also be difficult to manage your hopes, expectations and emotions.   

 After living with sickle cell disease for most of your life, you may struggle with taking on a new identity after the procedure. We created a fact sheet on mental health and sickle cell disease gene therapy participation to answer some of your questions. 

Gene therapy has the potential to significantly improve the health and quality of life for individuals with sickle cell disease. Talk to your doctor to determine if gene therapy could be right for you.

Gene therapy should be provided at Qualified Treatment Centers throughout the United States. These institutions should provide multi-disciplinary care. You should ask if the following types of care and services are available:  

• Established sickle cell center 
• Ability to do apheresis and collect stem cells 
• Blood bank 
• Fertility preservation 
• Mental health program 
• Local housing 
• Ability to follow patients for at least 15 years 

You may hear that gene therapy is being called “transformative” or “curative” or even, a “cure”. The meanings behind “curative” and “cure” for sickle cell disease can be deeply personal. For now, gene therapy is considered “transformative,”, meaning people will experience a change.  

Researchers will use your data (and the data of others) to determine if gene therapy can be considered “curative” or a “cure” for sickle cell disease.

Gene therapy is a treatment that may improve the health of people with sickle cell disease. The treatment may stop the sickling of cells and improve the lifespan of red blood cells. It may reduce complications of sickled cells blocking blood flow and depriving tissues of oxygen (called vaso-occlusive crises), pain and tiredness. Researchers do not know how gene therapy will affect people who have pre-existing organ damage in the long term. 

Every person’s experience may be different. Studies show that people who receive gene therapy for sickle cell disease have different benefits, such as decreased pain and lower levels of sickled hemoglobin. Any conditions or types of organ damage from sickle cell disease that happened before receiving the therapy may not improve or change after gene therapy.   

Clinical trials showed that those who participate in gene therapy have less sickled hemoglobin, less hemolysis and little to no vaso-occlusive pain events. Those who participate in gene therapy may also have improved health-related quality of life, including improved emotional and psychosocial well-being, general health and less bodily pain. 

You will be under the care of your clinical trial’s team and physicians for about two to three years. During that time, you will be in the hospital for a period about four to six weeks. After you complete the gene therapy trial, you will continue to have outpatient clinic visits. You should receive regular follow-up care related to your gene therapy from your clinical trial’s team. You should also seek care for your general health from your primary care providers (including your hematologist) after gene therapy. Your research team and general health care providers should work together to care for your health and well-being. 

Experts recommend that you are followed for 15 years after your gene therapy treatment as part of the clinical trial. This will allow researchers to study the gene therapy treatment over time and to detect and treat long-term risks. These follow-up clinical studies are intended to help researchers detect all long-term effects over time. 

Across the different gene therapy approaches, the goal of gene therapy is to decrease the amount of sickled hemoglobin in every red blood cell. The clinical trial team will know if the gene therapy worked if the amount of sickled hemoglobin has lowered enough at certain checkpoints after the gene-modified stem cells are returned to your body. If the team can lower the sickled hemoglobin enough, the cells will not be fragile, sticky or even sickle. This can decrease the complications and treat or prevent the symptoms of sickle cell disease.

The gene therapy process may not work for a few reasons: 

• Although there may be several attempts to collect your stem cells, the clinical trial team may fail to collect enough cells to modify for gene therapy.  
• Once the collected stem cells are gene-modified, the team may find that the cells are unsafe to return to your body.

In both instances, you would be removed from the study.  

After the process, gene therapy may not have successfully lowered the amount of sickled hemoglobin in your blood. If this happens, your clinical trial doctor and general provider will talk to you about next steps for your long-term care.