The first gene editing clinical trial sponsored by US companies has released data to STAT news showing promising results using a CRISPR based therapy. Sickle cell anaemia and beta thalassemia patients required no further treatments after one appointment.

CRISPR Therapeutics and Vertex Pharmaceuticals have published data on their CTX001 treatment which demonstrates the curative potential of CRISPR-Cas9 – unlike a previous study into HIV.

The treatment reactivated foetal haemoglobin for patients suffering from sickle cell anaemia and beta thalassemia. Foetal haemoglobin is different from adult haemoglobin and is not affected by the mutations that cause the inherited blood disorders. CRISPR-Cas9 is used to reactivate the production of foetal haemoglobin by removing the repression on the gene, rather than by directly editing the faulty DNA.

Sickle cell anaemia causes ‘sickling’ of the red blood cells, morphing the shape and making the cells rigid. This rigidity causes the cells to get stuck in the blood vessels leading to organ damage and severe pain. Beta thalassemia is the result of too little haemoglobin being produced – leading to lack of oxygen, organ damage and anaemia. These blood disorders are currently treated by multiple blood transfusions and pain-relief.

Blood stem cells were isolated from each patient for editing by CRISPR-Cas9. The patient’s bone marrow was treated to remove any mutation carrying blood cells then the edited blood stem cells were put back into the bloodstream. Replacing the stem cell population led to a successful reactivation of foetal haemoglobin. The proportion of haemoglobin in the beta-thalassemia patient that was foetal instead of adult nine months after treatment was 99.8%. Similar results were seen in the sickle cell anaemia case with 47% of the haemoglobin being foetal – above 25% is deemed sufficient to alleviate symptoms.

This trial involved only two patients but already more have been recruited and are expected to receive treatment soon. More data must be collected before broader conclusions can be drawn on the benefits of CRISPR-Cas9 based therapies for patients as off-target mutations are a possibility. These off-target cuts may cause unintentional gene edits that could lead to cancer or other diseases.

Nevertheless, this first sponsored trial is an exciting milestone for CRISPR-Cas9 therapies and with many more trials on the horizon, gene therapy may soon be commonplace.

For the full story, click here for STAT News.