Immunotherapy has become a hot topic in the oncology space over the past decade. For many cancer patients, the traditional treatment options, like chemotherapy, radiation therapy, or targeted therapies like Gleevec or Herceptin, are ineffective in treating their disease. For these patients, immunotherapy, which uses the body’s own immune system to fight cancer, is offering an exciting new possibility for treatment, and maybe even one day a cure.
CAR T cell therapy is a particularly exciting sub-type of immunotherapy. There are hundreds of CAR T cell clinical trials currently being conducted in the US and around the world, and 2017 is projected to be the year we see the first CAR T therapy receive regulatory approval for use.
CAR T cell therapy works by taking a patient’s own T cells, which are part of the body’s natural immune system, and modifying them to express a Chimeric Antigen Receptor (CAR). CARs are proteins that allow T cells to recognize an antigen on targeted tumor cells. This creates artificial T cells which are genetically engineered to seek out cancer cells in the body and kill them.
The process begins by removing a patient’s blood and extracting the T cells through apheresis, a process used for the collection of blood components. The cells are then sent to the laboratory where they are reengineered to become CAR T cells and then multiplied so that there are millions of them. The cells are then infused back into the patient’s bloodstream where they further multiply in number. Once in the bloodstream, the CAR T cells find the areas where the cancer exists in the body and attach to the cancer cells in order to kill them. The CAR T cells can remain in the body for weeks, even months, after the initial infusion and guard against cancer recurrence.
Although this concept sounds promising, there can be some severe side effects involved which can be very dangerous for patients. The most troublesome side effect is cytokine-release syndrome. Cytokines are chemical messengers that help the reengineered T cells carry out their cancer killing duties. However, a rapid release of cytokines into the bloodstream can lead to extremely high fevers and dangerous drops in blood pressure.
B cell aplasia is another side effect which can be particularly worrisome for patients. Although CAR T cell therapy is designed to target and destroy cancerous B cells, there is not yet an effective mechanism to prevent normal B cells from being destroyed also. This can lead to patients having low numbers of healthy B cells, which lowers the body’s ability to produce the antibodies that protect against infection.
Scientists are currently working on finding ways to mitigate these side effects so that this therapy can become a viable treatment option for more patients.
Currently, CAR T therapy is only available to patients through clinical trials. Promising results have been reported in many trials treating patients with lymphoma and advanced acute lymphoma leukemia (ALL). However, these trials are small and, thus far, are only proof of principle studies. As such, lead investigators are optimistic at this stage, but have cautioned that further research is necessary before this can become a standard, routine treatment option for patients.
To find out more about the specifics of these clinical trials, and the outcomes for patients, visit the National Cancer Institute website.