It’s a multi-step course of.

First, blood stem cells from a affected person’s bone marrow (the place all blood cells originate) are faraway from the physique.

Within the laboratory, a gene-editing instrument known as Crispr is used.

This permits a selected gene to be pinpointed and really exact enhancing to happen.

Nevertheless, as an alternative of immediately enhancing a defective gene, Casgevy as an alternative takes benefit of a course of that occurs when infants are within the womb, the place they make purple blood cells with foetal haemoglobin (a key protein that carries oxygen). This switches to the grownup kind as soon as they’re born.

Crucially foetal haemoglobin will not be affected by sickle cell illness, so Crispr acts by dampening down the “change” that makes the physique produce the grownup kind.

Sufferers must endure “conditioning” chemotherapy to ensure their our bodies are prepared to simply accept the edited stem cells.

Modified stem cells are then transfused again into the physique, the place they multiply and improve the manufacturing of secure, well-functioning purple cells.

The complete therapy should be thought-about fastidiously – it may contain prolonged stays in hospital and should have unintended effects, together with complications and bleeding issues.