Who was in charge of the trial for this type of experimental medicine? How does ‘base editing’ aid in the treatment of cancerous T-cells? What is the mechanism of the CRISPR-cas9 system? Was the treatment completely effective? Does base editing also treat blood disorders?
Scientists in the United Kingdom testing a new form of cancer therapy reported success in Alyssia, a teenage girl with T-cell acute lymphoblastic leukaemia.
What exactly happens in this sort of Cancer?
T-cells, white blood cells adapted to hunt and neutralize threats to the body, turn against the body in this type of blood cancer, eliminating good cells that ordinarily aid in immunity. The disease progresses quickly and is usually treated with chemotherapy and radiation therapy.
What exactly is ‘Base Editing?’
The genetic code of a person is made up of numerous permutations of four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Sequences of these bases, like letters in the alphabet, spell out genes, which are instructions for producing the wide range of proteins required for the body’s functions. In Alyssia’s case, her T-cells had become malignant, possibly due to a misalignment in the sequence of bases. A method to fix this misalignment could result in a stronger immune system.
A technology that allows genes to be tweaked and faults to be ‘corrected’ has enthralled the world of biomedical engineering during the last two decades. The CRISPR-cas9 technique has proven to be the most popular of these technologies.
The CRISPR-Cas 9 system is based on how certain bacteria defend themselves against viruses by snipping and storing portions of their genes. It comprises an enzyme that operates like molecular scissors. It can be designed to cut a portion of DNA at a certain spot, and a guide RNA can be used to insert a different genetic code at the incision locations.
While there are several methods for making such alterations, the CRISPR-cas9 system is thought to be the quickest and most adaptable. David Liu of the Broad Institute in Massachusetts has improved the CRISPR-cas9 system to directly change particular bases: for example, a C may be transformed into a G, and a T can be changed into an A.
While still a developing technology, base editing is said to be more effective at treating blood illnesses caused by single point mutations or where a single base pair change can cause terminal disease.
How did base editing help Alyssia with her therapy?
In the case of T-cell leukemia, the goal of gene therapy was to repair her immune system such that it stopped producing malignant T-cells. To begin, healthy T-cells were taken from a donor and subjected to a series of modifications.
The first base alteration disabled the T-cells’ targeting mechanism, causing them to stop attacking Alyssa’s body; the second deleted a chemical marking on all T-cells known as CD7, and the third stopped the cells from being killed by chemotherapy medication. Finally, the T-cells were instructed to attack all cells containing CD7, whether malignant or protective. After a month of remission, she received a second donor transplant to rebuild her immune system with healthy T-cells.
What was the efficacy of the Treatment?
Her cancer appeared to reappear three months following therapy, but the most current investigations show no traces of it.
Alyssia was one of ten people who took part in the trial and received the medication.
It’s been 1.5 years since she was first diagnosed with the condition, and it’s still unclear whether the medication has consistently and completely restored her immune system.