A groundbreaking new kind of therapy has successfully treated a teenage girl’s untreatable cancer for the first time.
For Alyssa’s leukemia, every previous treatment had failed. In order to create her a new live medication, physicians at Great Ormond Street Hospital performed a feat of biological engineering known as “base editing.”
Alyssa is still being watched in case the cancer recurs even though it is no longer evident six months later.
Alyssa, who is 13 and from Leicester, was diagnosed with T-cell acute lymphoblastic leukaemia in May last year.
T-cells are supposed to be the body’s guardians – seeking out and destroying threats – but for Alyssa they had become the danger and were growing out of control.
Her cancer spread quickly. The bone marrow transplant and subsequent chemotherapy treatments failed to remove it from her body.
The only alternative left without the experimental drug would have been to just keep Alyssa as comfortable as possible.
“Eventually I would have passed away,” said Alyssa.
Her mum, Kiona, said this time last year she had been dreading Christmas, “thinking this is our last with her”.
And then she “just cried” through her daughter’s 13th birthday in January.
Incredible developments in genetics have made what happened next feasible; it was inconceivable just a few years ago.
The team at Great Ormond Street used a technology called base editing, which was invented only six years ago.
Bases are the language of life. The four types of base – adenine (A), cytosine (C), guanine (G) and thymine (T) – are the building blocks of our genetic code.
Just as letters in the alphabet spell out words that carry meaning, the billions of bases in our DNA spell out the instruction manual for our body.
Base editing enables researchers to focus on a specific region of the genetic code, change the molecular composition of just one base, transform it into another, and modify the genetic instructions.
The vast group of medical professionals and researchers utilised this resource to create a brand-new variety of T-cell that could track down and eliminate Alyssa’s malignant T-cells.
They started with healthy T-cells that came from a donor and set about modifying them.
The first base edit disabled the T-cells targeting mechanism so they would not assault Alyssa’s body
The second removed a chemical marking, called CD7, which is on all T-cells
The third edit was an invisibility cloak that prevented the cells being killed by a chemotherapy
The T-cells were given instructions to search for anything in her body that had the CD7 marker so that they could all be destroyed, including the cancerous ones. This was the result of the final stage of genetic alteration.
That’s why this marking has to be removed from the therapy – otherwise it would just destroy itself.