Sickle Cell Disease
Please talk to your health care provider about any curative therapy to see if it is an option for you or the person you are caring for.
Bone Marrow Transplant
A Bone Marrow Transplant (BMT) is a cure for SCD. However, the most successful BMTs occur when the patient has a donor who is a “full match” to their immune system. This is called an “HLA” match. HLA stands for Human leukocyte antigen. Usually this will be a full sibling (brother or sister) of the patient. Not many SCD patients have a full match which eliminates many SCD patients as being candidates for a BMT.
There is promising research using matches from non-related donors and donors who are a half HLA match to the patient. These experimental treatments are showing good results and could some day mean that a BMT will be available to many more SCD patients
A BMT is a procedure that replaces a patient’s bone marrow with the donor’s bone marrow. Our bone marrow produces blood cells. If a SCD patient has a successful BMT, they will start producing red blood cells that do not sickle and be cured of SCD.
Gene Therapy is an experimental process that is being studied to see if it can be used to cure or significantly improve SCD. There are several different types of gene therapy that are being studied. These include gene editing (turning off genes), gene addition (adding a gene) or gene correction (directly editing the sickle cell gene to create a new gene).
Many of the gene editing studies work by turning off a “suppressor gene”. At birth, a “suppressor gene” turns “off” the gene that produces fetal hemoglobin. By editing this suppressor gene, fetal hemoglobin production can be turned back on. This would allow the individual to produce significant amounts fetal hemoglobin to (hopefully) provide protection against many of the complications of SCD. Scientists use different types of tools called CRISPR, TALENS, Zinc Finger and PRIME to make those precise cuts or “edits” to the gene.
In gene addition therapies, a new gene is inserted into the stem cells (to see how this is done, click on the video below). If this is successful, people will produce equal amounts of healthy hemoglobin (usually hemoglobin A or hemoglobin F). It may even mean that people can produce more healthy hemoglobin than sickle hemoglobin similar to sickle cell trait so they would no longer have the complications of sickle cell disease.
Finally, the gene correction studies are using a combination of gene editing and gene addition. This process directly edits (cuts) the gene that causes the sickle cell mutation. At the same time, a new strand of DNA that makes healthy hemoglobin (hemoglobin A) is delivered like a missing piece into the space left behind. If successful, people should produce more healthy hemoglobin than sickle hemoglobin similar to sickle cell trait so they would no longer have the complications of sickle cell disease.
ALL of these gene therapies involve a similar process:
- First stem cells have to be collected from an individual with sickle cell disease using apheresis.
- The collected stem cells are sent to a lab where they go through the gene therapy and gene editing discussed above.
- Once these stem cells are ready, the patient is brought into the hospital to receive chemotherapy to empty out their bone marrow (remove the stem cells that currently have the gene for sickle cell disease) and make room for the new cells. The process of getting one’s own stem cells back is called an “autologous” stem cell (or bone marrow) transplant.
- After the transplant, people have to rest and recover for 90 days (sometimes up to 30 days in the hospital) and avoid being around other people as their immune system recovers.
At this time, we don’t know yet which gene therapy is the best as they are not all the same. However, they all have potential benefits for people with sickle cell disease. EVERYONE should talk to a sickle cell specialist if they are considering these therapies.
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