All the blood tests we performed show that the teenager has been cured of sickle cell disease”
Dr. Marina Cavazzana, Necker Children’s Hospital in Paris, lead author of the study, Biotherapy Department.
We live in a world which is in a continuing development… In the center of all this, stands the human being, having the potential to make great discoveries in all the fields, thus improving the life quality in the society. Nowadays are well known advances in medicine and its disciplines for finding new ways in treating not only common diseases but also rare ones through gene therapy, that has shown clinical efficacy for several rare diseases, using different approaches and vectors.
But what is gene therapy?
Gene therapy, is an experimental technique that uses genes to treat rare genetic diseases; that consists in curing a single gene defect by introducing a 'correct' gene. It has been a long road to success of gene therapy to be approved since it started twenty years ago as a cure for everything from cancer to cystic fibrosis.
In 2012, Glybera® became the first gene therapy to be approved, for people with a rare disorder, that makes them unable to process dietary fat. It is designed to restore the LPL enzyme activity required to enable the processing, or clearance, of fat-carrying chylomicron particles formed in the intestine after a fat-containing meal.
Last year, the first commercial gene therapy that alters a person’s DNA was approved for children with a severe immune disorder. Gene therapies for rare forms of blindness are also showing promise. The evidences show that gene therapy is finally starting to fulfill its mission in treating rare genetic disorders.
Regarding this, the latest case study published, on 2 March 2017, in New England Journal Medicine, proves that gene therapy has cured sickle cell disease, in a 13 years old boy in Paris, France.
Before, explicating what the researchers did and what the results of the study were, let's get informed a little bit more about sickle cell disease.
The term sickle cell disease (SCD) describes a group of inherited red blood cell disorders. People with SCD have abnormal hemoglobin, called hemoglobin S or sickle hemoglobin, in their red blood cells. Abnormal versions of hemoglobin, the protein which carries the oxygen throughout the body, are due to a mutation in the gene that makes a subunit of hemoglobin, called beta-globin, localized on chromosome 11.
People who have SCD inherit two abnormal hemoglobin genes, one from each parent. In all forms of SCD, at least one of the two abnormal genes causes a person’s body to make hemoglobin S. When a person has two hemoglobin S genes, Hemoglobin SS, the disease is called sickle cell anemia. This is the most common and often most severe kind of SCD.
In a healthy person, red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons, because of abnormal shape of hemoglobin. These irregularly shaped cells can get stuck in small blood vessels, slow or block blood flow and oxygen to parts of the body.
The lack of tissue oxygen can cause attacks of sudden, severe pain known also as pain crises. These pain attacks can occur without warning, and a person often needs to go to the hospital for effective treatment. Over a lifetime, SCD can harm a person’s spleen, brain, eyes, lungs, liver, heart, kidneys, penis, joints, bones, or skin, ultimately resulting in diminishing life expectancy.
Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells blocking blood flow in a blood vessel. The inset image shows a cross-section of a sickle cell with abnormal (sickle) hemoglobin forming abnormal stiff rods.
Worldwide, more than 275,000 infants are born with sickle cell disease each year. In the United States, approximately 100,000 people, most of African ancestry or identifying as black, currently have it. About one in every 365 black children in the US is born with sickle cell disease, for which the life expectancy is now about 40 to 60 years, according to the U.S. National Heart, Lung, and Blood Institute.
There are treatments for sickle cell, such as some cancer drugs, but they can be difficult to manage and have side effects. People with the disorder are given blood transfusions to clear these painful blockages and prevent new ones. A potential treatment for sickle cell disease can be bone marrow transplant, but matching donors can only be found for around 10 per cent of people with the condition.
Recently, a team of researchers lead by Dr. Marina Cavazzana, Necker Children's Hospital's biotherapy department, in Paris, France, have developed a treatment that would work for everyone with the disorder. The research was focused on the mutated gene of beta hemoglobin . Here's where gene therapy fits.
Firstly, the researchers extracted a stem cell supply from a the bone marrow of a 13 years old boy, with the βS/βS genotype, before using chemotherapy to wipe out the remaining stem cells. Using a lentiviral vector, they transferred an anti-sickling gene into the patient’s stem cells (removed from the bone marrow). These lentiviral vectors produced by Bluebird Bio ,under the brand LentiGlobin BB305, were designed to make beta-globin, interfere with the boy’s faulty proteins, stopping them from clumping together. The modified stem cells were infused back into the patient.
After around three months, the boy showed a growing number of new blood cells, among them erythrocytes as well, containing normal hemoglobin . Before receiving treatment, the teen had terrible pain and needed blood transfusions, which required twice-yearly hospitalizations, whilst more than 15 months after transplantation, he had no pain crisis or hospitalizations and the antisickling protein remained high at approximately 50% . All the medicaments were stopped and he returned to his school activities.
The team concluded that their patient had complete clinical remission with correction of hemolysis and biologic hallmarks of the disease. The therapy converted the patient to sickle-cell trait — that is, a person who carries only one copy of the abnormal hemoglobin gene. Those individuals don't develop sickle cell disease. The tests, the researchers performed on the teenager's blood show that he has been cured of sickle cell disease.
That's exciting and encouraging for all the patients who suffer from sickle cell disease. Even though only one patient and 15 months is a short follow up, the benefits from the therapy will last, as Dr. Cavazzana, confidently said . The team has treated seven other patients, showing promising progress. If the treatment proves successful in larger trials, it could bring gene therapy into widespread use.
A new "door" is opened… There is hope … for every child who suffer from the devastating sickle cell disease.
COPYRIGHT: This article is property of We Speak Science, a non profit institution co-fonded by Dr. Detina Zalli (Harvard University) and Dr. Argita Zalli (Imperial College London). The article is written by Brisilda Pashaj (University of Plovdiv, "Paisii Hilendarski " Bulgaria ( Msc. Medical Biology).
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