Research on cancer therapies with genetically modified T cells, so-called CAR T cells (chimeric antigen receptor, short: CAR), has brought about extraordinary successes in recent years, although most of these were still associated with serious side effects. The method has so far proved to be particularly promising in the fight against leukemia, but research is also being conducted into the treatment of other types of cancer.

Under the name Kymriah, a therapy with CD19-specific CAR T cells by Novartis for the treatment of acute lymphocytic leukemia (ALL) was approved in the US in late August 2017. This was followed in October 2017 by authorization of a further therapy under the name Yescarta. The drug by the company Kite is intended for the treatment of certain forms of B-cell lymphomas. Both gene therapy medicinal products were also approved for the European market in 2018 by the European Medicines Agency (EMA). 

Treatment with such drugs involves filtering T cells from the patient's blood and genetically modifying them in the laboratory. The gene manipulation causes the cells to develop a CAR receptor on their surface, which enables them to recognize certain antigens - in this case the antigen CD19, which is expressed more strongly on leukemia cells. The CAR T cells are multiplied in the laboratory and administered to patients after two to three weeks by blood transfusion. When the CAR T cells in the blood encounter the cancer cells, they begin to multiply and destroy the cancer cells. Some patients have already been successfully cured of their leukemia thanks to this treatment. However, the therapy carries the risk of serious side effects. One example is a possible overreaction of the immune system, a so-called cytokine storm, which often takes a life-threatening course.