What is gene therapy?

Gene therapy is a treatment that changes the genetic material in some of your cells, to treat a disease. It does not change every cell in your body. For sickle cell disease and beta thalassaemia, the cells that are changed are your own blood stem cells.

The treatment used on the NHS in England is called Casgevy. Blood stem cells are taken from your body, edited in a laboratory using a method called CRISPR, and then put back through a drip. You also need chemotherapy first, so that the edited cells can settle in the bone marrow and start making blood.

Where CRISPR came from

CRISPR is not something scientists invented from scratch. Bacteria already use a CRISPR system as part of how they defend themselves against viruses. In 2012, Emmanuelle Charpentier and Jennifer Doudna showed that this system could be turned into a tool that cuts DNA at a place you choose. They were awarded the Nobel Prize in Chemistry for that work in 2020.

NHS England describes Casgevy as the first approved therapy to use that Nobel Prize-winning CRISPR method.

When it became available here

The UK medicines regulator, the MHRA, authorised Casgevy in November 2023. It described it as a world-first gene therapy that aims to treat sickle cell disease and transfusion-dependent beta thalassaemia.

NHS England has since made it available in England, for some people aged 12 and over: for transfusion-dependent beta thalassaemia from August 2024, and for severe sickle cell disease from January 2025. Whether it is an option for you personally is a question only your own haematology team can answer.

This page is a short introduction written from published sources. It is general information, not advice about your own care. Arrangements in Scotland, Wales and Northern Ireland are decided separately and are not covered here.