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 Gene Therapy; Hope And A Joker To The Sickle Cell Puzzle

Sickle cell disease, a group of inherited blood disorder that affects the red blood cell, sickle cell anemia being the most common condition. This disorder occurs due to the mutation in a protein in hemoglobin which aid the transport of oxygen in red blood cells. The red blood cells that normally should be biconcave and squeeze easily through small capillaries, become inflexible and sickle shaped and eventually get stuck, resulting in pains characterized by the disease.

Several scientific research have been on the move over the past decades to develop curative treatments for this disease that affects millions of people around the world, with a greater proportion from Africa, part of the middle East and Southern Asia. Bone marrow transplant is the only treatment that offers a cure to sickle cell currently, but accompanied with great risk.

According to recent researches, gene therapy seems to be a hope of treatment. It helps repair genetic mutations by replacing defective genes with healthy ones, through specific genetic modifications. One of its positive prospect is that, unlike bone marrow transplant that requires a donor(matched sibling) with a healthy red blood cells, whose key white blood cell proteins must match that of the recipient. 

Gene therapy makes use of the patient's cells.

The choice of gene therapy over bone marrow transplant despite the fact that both requires chemotherapy is because, patients with bone marrow transplant need immunosuppressive drugs which is not needed in gene therapy.

One of the research teams lead by Pediatrician Erica Esrick is testing gene therapy. Their work is in the clinical trial phase and takes advantage of continuous fetal hemoglobin production which is a healthy type of hemoglobin produced by fetuses and young babies. The process involves collecting cells(arising from the bone marrow) intravenously from the patient, and taken to the laboratory where the main genetic modification takes place. The patient is usually admitted for about three days for the cells to be collected, which may be repeated if required.

A virus is used as a vector to insert the desired gene in the cells collected from the patient. This gene blocks the protein that stops the production of the fetal hemoglobin, hence there is continuous production of the healthy hemoglobin by the modified cells.

The cells are then returned to the patient again, and chemotherapy is administered for about a month to enhance the modified cells to take over the healthy cell production in the bone marrow.

A major concern and threat to previous gene therapy trials is cancer, and it's also a major point to be considered in this new trials. A clinical trial carried out by a company with the name, Bluebird bio, made it known that a  participant in the trial developed leukemia. It was then unveiled that the leukemia was not related to the gene transferred, but as a result of the chemotherapy. 

The Esrick's lead clinical trial has recorded no leukemia as at the current stage they are in their trial. Their gene therapy trial has treated nine patients, while more positive developments are anticipated.

A lot of families and parents' hopes are raised high as the gene therapy is promising a curative treatment to the disorder. The fact that more options aside bone marrow transplant would be possible, keeps the researchers excited and ready to put do more.