In Great Britain, a drug based on the Crispr genetic scissors technology has been approved for the first time in the world. This was announced by the medicines regulator MHRA (Medicines and Healthcare products Regulatory Agency).
The drug called “Casgevy” has been approved for the treatment of sickle cell disease and beta-thalassemia in patients aged twelve and over. Both genetic blood diseases are caused by errors in the gene for hemoglobin. This is an iron-containing protein complex that is found in red blood cells and is used to transport oxygen.
Long stays in the hospital are required
The so-called Crispr/Cas gene scissors can be specifically targeted at individual genes. The developers of the method, Emmanuelle Charpentier and Jennifer A. Doudna, received the Nobel Prize for this in 2020. "Casgevy" is used to change the faulty genes in patients' bone marrow stem cells so that they can produce functioning hemoglobin, the MHRA said in a statement. To do this, stem cells are taken from the bone marrow, processed in the laboratory and then reinserted into the patient. A hospital stay of several weeks is necessary for the therapy. But the result has the potential to last a lifetime, it said.
Both sickle cell disease and beta thalassemia are painful, lifelong conditions that in some cases can be fatal, said Julian Beach, interim executive director of the MHRA's Healthcare Quality and Access Department. He added: "Until now, a bone marrow transplant - which must come from a well-matched donor and carries the risk of rejection - has been the only permanent treatment option."
Sickle cell disease can cause severe attacks of pain, serious and life-threatening infections, and anemia, a lack of oxygen in the blood also known as anemia. Patients with beta thalassemia also suffer from anemia and often require blood transfusions at intervals of three to five weeks.
Free from severe pain attacks
Of 28 patients with sickle cell disease who were treated with the drug in a clinical trial, 97 percent were free from severe pain attacks for at least a year. In the clinical study with beta thalassemia patients who rely on blood transfusions, 93 percent (39 of 42 patients) did not need a red blood cell transfusion for at least twelve months. In the remaining three patients, at least a 70 percent reduction in blood transfusions was possible.
The drug is manufactured in a collaboration between Vertex and CRISPR Therapeutics, which are headquartered in the USA and Switzerland. According to a statement from the two companies, around 2,000 people in Great Britain are currently eligible for treatment with “Casgevy”. Vertex managing director Reshma Kewalramani spoke of a “historic day in science and medicine”. CRISPR Therapeutics boss Samarth Kulkarni said he hoped it was just the first of many applications of the method that could benefit people with serious illnesses, according to the statement.
Selim Corbacioglu from Regensburg University Hospital, who has already tested Crispr therapy himself, mentions some concerns. “We cannot be 100 percent sure that the gene scissors will not also change other DNA sections,” he said. “Crispr therapy cannot be carried out “just” either.” There are significant side effects and the therapy is very expensive.
According to Joachim Kunz from Heidelberg University Hospital, the therapy is "extremely complex, requires complex logistics and will probably not be infinitely scalable due to the resources required, but will only be available to a limited number of patients per year." The current clinical studies on Crispr therapy are promising, but even the patients who were initially treated were only followed up for about four years. "Even if there is no evidence of this yet, it could be that the effect of gene therapy diminishes over the years because, for example, the lifespan of the manipulated blood stem cells is shortened."