13-year-old English girl cured of leukemia with genetically modified cells

A girl from the English city of Leicester was able to get rid of an aggressive form of leukemia after the world's first trial using cell therapy, according to NewScientist.

Last year, Alyssa was diagnosed with T-cell acute lymphoblastic leukemia (T-ALL). It is the most common type of cancer among children and young adults. Only 10% of those who survive a relapse of the disease survive. Alyssa was treated with chemotherapy and a bone marrow transplant, but this did not help. There was no other way to fight cancer, and the next step for the girl would have been palliative care if the doctors had not offered an experimental treatment with CAR-T cells.

Leukemia is caused by the uncontrolled reproduction of immune cells in the bone marrow. This is usually treated by destroying all bone marrow cells with chemotherapy and then replacing the bone marrow with a transplant. If this fails, CAR-T therapy can be used. Its essence lies in the fact that the patient receives an infusion of blood with immune T-cells from a healthy donor, which have been edited: a gene has been added to them that teaches them to track down and kill cancer T-cells without attacking each other.

To prevent T cells from destroying each other, the scientists turned off the receptor gene that identifies them as T cells. The creation of such CAR-T cells requires the simultaneous editing of four genes, which leads to another problem. Conventional gene editing involves cutting the DNA strands and using the cell's repair mechanism to join the ends. When many cuts are made at the same time, the cells sometimes die. Even if they survive, misconnected ends can lead to mutations that turn the cells cancerous.

In the case of Alyssa, the scientists instead used a modified form of the gene-editing protein CRISPR, which doesn't cut DNA but instead changes one DNA letter to another. Alyssa was the first person to ever be treated with CAR-T cells edited in this way.

Twenty-eight days after starting treatment, Alyssa went into remission and was able to undergo a second bone marrow transplant. So far, it is impossible to say with complete certainty that the girl has completely recovered, but now she is doing well, no cancer cells are found in her body.