A Rice University bioengineering team is working on a new gene therapy against sickle cell anemia. If the findings were confirmed, we would be able to correct the mutation causing the disease already in the womb. One of the available therapies against sickle cell anemia is stem cell transplantation. Unfortunately, only 15% of patients find a compatible donor between relatives and volunteers.
The authors of the study have developed an alternative more compatible with the organism and available to all. The therapy uses CRISPR-Cas9 to repair the patients' hematopoietic stem cells. What is therapy? Doctors isolate the patient's bone marrow cells and correct them with genetic editing. At this point they use chemotherapy to eliminate part of the sick stem cells, so as to make room for healthy ones.
Then they implant the edited cells into the patient and wait for them to reproduce. Repairing stem cells instead of replacing them eliminates the risk of rejection, cutting most of the problems associated with transplantation. At first, the team tested guinea pig therapy using stem cells from 5 sick patients.
The edited cells multiplied and continued to function for about 4 months. In a second phase, the researchers used a more recent and precise version of the CRISPR-Cas9. This change has led to less unexpected changes. Genetic editing has corrected 40% of the cells. 50% of the stem cells cut the wrong DNA without correcting it. 10% continued to produce the sick version of hemoglobin.