Life-saving edit Sharon Lees/GOSH

In 2015, a little girl called Layla was treated with gene-edited immune cells that eliminated all signs of the leukaemia that was killing her. Layla’s treatment was a one-off, but by the end of 2017, the technique could have saved dozens of lives.

Gene editing involves altering or disabling existing genes, which used to be extremely difficult. It took many years to develop the gene-editing tool that saved Layla (pictured), but thanks to a revolutionary method known as CRISPR, this can now be done in just weeks.

In fact, CRISPR works so well that the first human trial involving the method has already begun. In China, it is being used to disable a gene called PD-1 in immune cells taken from individuals with cancer. The edited cells are then injected back into each person’s body. PD-1 codes for an “off switch” on the surface of immune cells, and many cancers evolve the ability to thwart immune attacks by flipping the PD-1 switch to “off”. On the edited immune cells there is no switch for cancer cells to flip.


A trial in the US due to start soon is far more ambitious. This involves adding an extra gene engineered to make the immune cells target tumours and then using CRISPR to disable PD-1 and two other genes. The addition of tumour-targeting genes has already produced very promising results in trials for cancers like leukaemia, but it has not worked well for solid tumours. The hope is that combining the two techniques will make treatments far more effective.

If these trials show that editing cells’ genomes is safe, it could soon be used to treat a much wider range of diseases, likely starting with eye disorders.

This article appeared in print under the headline “Gene editing starts to save lives”