CAR T-cell therapy: How it works
T cells are immune system cells that play several key roles in the body’s fight against disease. They help the immune system respond to a disease and directly kill diseased cells.
Unfortunately, naturally occurring T cells are not good at recognizing and fighting cancer cells.
Chimeric Antigen Receptor (CAR) T-cell therapy is a type of immunotherapy that changes a patient’s own T cells so they are able to recognize and attack cancer.
CAR T-cell therapy has been extremely effective in many patients. In some cases, the treatment has eliminated all signs of cancer.
However, CAR T-cell therapy doesn’t work for every patient. Some have benefited for a short time before relapsing. Doctors are studying the reasons for these different responses.
How does CAR T-cell therapy work?
CAR T-cell therapy begins with apheresis, a special kind of blood draw where certain blood components are removed and the remaining blood is pumped back into the patient. In this case, the patient’s T cells are removed and then shipped to a lab.
There, scientists genetically modify the T cells so they produce a protein (called a receptor) that recognizes another protein (called an antigen) on the surface of cancer cells. This recognition allows the modified T cells to identify and attack the cancer.
The modified T cells are multiplied by the hundreds of millions and then infused back into the patient to fight the disease.
What cancers can be treated with CAR T-cell therapy?
After years of clinical trials, in 2017 the Food and Drug Administration approved the use of two CAR T-cell therapies. Both use genetically modified cells that recognize a protein (called CD-19) on the surface of cancerous B cells.
- Kymriah is for pediatric and young adult patients age 25 or younger with B-cell acute lymphoblastic leukemia. It has also been approved for adult patients with certain types of large B-cell non-Hodgkin's lymphoma who have relapsed on not responsed to standard treatments.
- Yescarta has been approved for patients with large B-cell non-Hodgkin's lymphoma that has relapsed or does not respond to standard treatments.
To be eligible for either treatment, patients must have been treated unsuccessfully with at least two other cancer therapies.
CAR T-cell therapy clinical trials are underway for several other cancers, including additional subtypes of leukemia and lymphoma.
What is CAR T-cell therapy like for patients?
After apheresis, modifying and expanding a patient’s T cell population usually takes a few weeks. Most people undergoing CAR T-cell therapy stay in the hospital as in-patients during this time.
When the CAR T cells are ready for use, they are sent back to the hospital for infusion. Before infusion, patients are usually given a short course of chemotherapy. This weakens their existing immune system, giving the engineered T cells a better chance of expanding and fighting the cancer.
The infusion of the modified T cells is quick, typically lasting less than an hour. Afterwards, patients must remain in the hospital for several days for monitoring. After they are discharged, patients must stay near the hospital for several weeks.
What are the side effects of CAR T-cell therapy?
CAR T-cell therapy’s side effects can be serious and even life-threatening, especially if left untreated.
One of the most serious is cytokine release syndrome. Cytokines are chemical messengers T cells produce to help organize the immune system’s fight against disease. In cytokine release syndrome, too many cytokines are produced. This can lead to a dangerously high fever, dangerously low blood pressure, difficulty breathing and organ failure. After infusion, doctors monitor for this condition and have effective treatments for patients who develop it.
CAR T-cell therapies can also have temporary but serious neurological effects, including confusion, slurred speech and seizures.
Other side effects include:
- low counts of red and white blood cells and platelets, another key blood component
- chills and shaking
- nausea, vomiting and diarrhea.
While these are the known side effects, CAR T-cell therapy is a new treatment and doctors continue monitoring patients to uncover any long-term impact on their bodies.
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