Until recently, CRISPR, the gene-editing technology used by scientists Jennifer Doudna and Emmanuelle Charpentier to Nobel Prize in Chemistry 2020— sounded more like science fiction than medicine; lab-made molecular scissors are used to cut out problematic DNA sections in a patient’s cells to cure them of disease. But soon we were able to see regulators approve the first-ever treatment using this gene-editing technology in an effort to combat rare inherited blood disorders that affect millions of people around the world.
In a $900 million collaboration, rare disease specialist Vertex and CRISPR Therapeutics developed the therapy, called exa-cel (short for exagamlogenous autotemic cell). It has already gathered promising evidence that it may help patients with beta thalassemia and sickle cell disease (SCD), both genetic blood diseases that are relatively rare in the US but slightly more common hereditary disorders worldwide.
Beta thalassemia is characterized by damaged or missing genes that cause the body to produce less hemoglobin (an essential protein that carries oxygen), potentially leading to enlargement of the liver, spleen or heart, and misshapen or brittle bones. It is estimated to torment 1 in 100,000 people in the world, and regular blood transfusions are needed to avoid the most serious effects.
While the exact statistics are unknown, SCD is: estimated at 100,000 people in the US and millions around the world; it is attributed to a faulty gene that causes malformed hemoglobin that is stiff, sticky, and sickle-shaped (hence the name) and thus can prevent healthy blood cells from carrying oxygen around the body.
Exa-cell reportedly reduced the need for blood transfusions or the occurrence of serious, life-threatening medical events for months to years after patients received the treatment. New and impressive clinical research results were announced at a major international medical conference in June, bolstering the companies prospects of producing the first gene-editing therapy of its kind to reach the wider market and patients.
The drug makers say they plan to file exa-cel for regulatory approval in the US, UK and Europe by the end of this year, meaning the drug could receive a marketing authorization sometime in 2023. as more and more biopharmaceutical companies pursue new gene therapies.
Vertex and CRISPR Therapeutics’ therapy uses what is called an “ex-vivo” application of CRISPR gene editing (one that is done outside the actual body): the patient’s stem cells are extracted, the cellular DNA is extracted by exa-cell modified to produce a type of hemoglobin that the body does not usually make until childhood, and the modified cells are returned to the patient to stimulate healthy hemoglobin and red blood cell production.
The latest exa-cell clinical data, revealed at the 2022 European Hematology Association Congress in Switzerland, showed that all 75 patients with beta-thalassemia or SCD who received the gene-editing therapy had no or greatly reduced need for blood transfusions (in the case of beta-thalassemia) or cases of life-threatening blockages (in the case of SCD). All but 2 of the 44 patients with thalassemia did not require any blood transfusions in the 1- to 37-month follow-up after treatment administration, and the remaining 2 had 75% and 89% reductions in the amount of blood they needed. †
Equally impressive, all 31 patients with severe and life-threatening SCD experienced no vaso-occlusive crises (the life-threatening incidents where healthy blood is blocked from moving freely) in anywhere from 2 to 32 months after treatment. † Those same patients usually experienced an average of nearly four of these crises per year during the two years before receiving exa-cell.
CRISPR isn’t the only type of gene therapy that has been making waves in recent weeks. Earlier in June, a group of advisers to the Food and Drug Administration (FDA) gave unanimous recommendations for a few non-CRISPR-based gene therapies from Bluebird Bio. The treatments target genes linked to beta thalassemia and a rare condition that affects children called cerebral adrenoleukodystrophy (CALD). The latter is a disease that eat away white brain matter in children as young as 4 years of age, has few treatments and usually leads to death within 5 to 10 years.
Bluebird’s eli cell therapy has faced clinical setbacks due to its association with a higher risk of one type of cancer, but the independent consultants concluded that its benefits still outweighed the risks for some patients with few other options. The FDA is not required to follow the recommendations of its advisory panels, but it usually does.
There are about 20 cell and gene therapies (although not based on CRISPR gene editing) that have been approved by the FDA to date. According to MIT’s NEWDIGS drug development program, over 60 gene and cell therapies could be on the US market by 2030. That could lead to a transformation in how we think about incurable diseases, potentially using gene and cell therapies to treat everything from rare diseases to HIV. to heart disease†
Drug discovery is a long and unpredictable process. But the impact gene editing can have on drug development and how we think about disease is already clear. As Jon Moore, Chief Scientific Officer at biotechnology company Horizon Discovery, said in 2016, “The targets we find with CRISPR . † † will lead the drugs that will hit the market in the 2020s.”
The early potential of exa-cell just six years later would suggest this is a reasonable guess.
Sy Mukherjee has been reporting on healthcare for ten years. He is a consultant and communication architect at Idea Pharma.