Image source: CI Photos/shutterstock.com
It’s new, unique and very potent
Common cancer treatments include radiation and chemotherapy. However, these therapies do not always work effectively for all, with many patients facing high rates of recurrence. For these sufferers, the new type of drug might provide some hope. It is a highly personalized treatment, in which immune cells from the patient’s body are modified in a way which causes them to attack cancer cells. It is called Chimeric Antigen Receptor (CAR) T-cell therapy.
The human’s immune system protects the body from infections and cancer and is made up of billions of immune cells. Lymphocytes are a subtype of blood cells and represent a major portion of such immune system cells. While B-lymphocytes make antibodies to fight infections, T-lymphocytes and natural killer cells directly kill infected or cancerous cells. T-lymphocytes, or T-cells for short, also communicate with and attract other cells within the immune system via peptides called cytokines. The CAR T-cell therapy takes advantage of the body’s own natural defense system to fight the cancer cells.
Cancer is devious
Obviously, the immune system is not able to kill all cancerous cells on its own. Cancer cells have strategies to escape our defense system, therefore making the disease difficult to cure at present. In a process called immune-editing, the cancer cells constantly change their phenotype until they appear like normal cells. In this way, they become invisible for the immune system. A second strategy of cancer cells is immune evasion, whereby cancer cells send out inhibiting factors to block the immune cells. The CAR T-cell therapy creates a form of lymphocytes which never previously existed. CAR T-cells can unmask and target cancer cells. They can stay in the body and replicate for months or even years.
How it works
CAR T-cell therapy is developed from the patient’s own immune system in a process which takes about three weeks.
In a first step a doctor removes white blood cells from the patient and extracts T-cells. These cells are taken to a manufacturing facility and are genetically reengineered to detect cancer cells and destroy them. From this point onward the cells are known as CAR T-cells. The reengineered cells are multiplied in the laboratory until there are many millions of them. Finally, the cells are injected into the patient.
The results of CAR-T cell treatments are impressive. The newly approved Kymriah drug can cure pediatric acute lymphoblastic leukemia. Twelve-year-old Emily Whitehead, for example, was near death at an age of six as a result of leukemia. She was the first child to have received the experimental cancer medicine. Emily fully recovered and has now been free from leukemia for the last five years. Lots of other success stories have also been documented.
However, there are more aspects to consider: the new and effective therapy can also have dangerous side effects. Cytokine-release syndrome occurs as a positive response of T-cell activation and is therefore an indication that the therapy is working. However, it can also be life-threatening. It may cause high fevers, low blood pressure and poor lung function. Neurotoxicity effects, organ failure and other serious complications have also been reported. Patients have even died during a couple of clinical trials for different CAR T-cell therapies.
Finally, the therapy must also be cost effective. A Kymriah treatment will cost about 470.000 Dollars in the US – for just a single dose. Of course, it will be a special treatment for patients who have lost their last hope after intensive chemotherapy or stem cell transplant have failed. However, somehow the health care systems must be able to deal with these high costs.
Much research is still needed
CAR T-cell therapy is still in its infancy. Today, this mechanism works exclusively for acute lymphoblastic leukemia. However, there are several promising studies concerning other types of blood cancer as well as approaches for solid types of tumor within the brain, lung, skin or pancreas, although the outcomes of these remain uncertain.