CAR T-Cell Therapy

Chimeric antigen receptor (CAR) T-cell therapy is one of the latest treatment advances for some forms of blood cancer, including certain types of acute lymphocytic leukemia (ALL) and certain types of large-B-cell lymphoma.^1,2 Additionally, research is underway to study the use of CAR T-cell therapy in people with multiple myeloma and other blood cancers.³

CAR T-cell therapy is a type of immunotherapy, treatments that boost the immune system’s ability to fight cancer. It is also classified as a type of adoptive cell transfer, as it uses the patient’s own immune cells to treat their cancer. In CAR T-cell therapy, the patient’s T-cells are removed from their body and changed in the laboratory to attack cancer cells.⁴

About T-cells

T-cells are a type of white blood cell. Acting as a key component of the immune system, T-cells fight infections and cancer cells in the body. However, cancer cells can continue to change and may stop or slow the normal T-cell response.⁴

How CAR T-cell therapy works

In CAR T-cell therapy, the patient’s own T-cells are removed from the blood, and using an inactive virus, the T-cells are modified to produce a specific receptor on the surface of their cells, called a chimeric antigen receptor (CAR). This receptor recognizes and attaches to a specific protein found on the blood cancer’s cells. The modified T-cells are then replicated in the laboratory to create hundreds of millions of copies. The engineered T-cells are then infused into the patient, where they find and kill the cancer cells in the body.⁴

Creating the modified T-cells may take approximately 3-4 weeks. Before receiving the CAR T-cell therapy, patients may receive chemotherapy to reduce the number of cancer cells circulating in the body. The infusion of the CAR T-cell therapy generally takes less than an hour. Patients are advised to stay close to the hospital where they received treatment for at least four weeks in case of serious side effects.⁵

Figure 1. CAR T-cell therapy procedure

Approved products

The first two CAR T-cell therapies approved by the Food and Drug Administration (FDA) are tisagenlecleucel (brand name: Kymriah™) and axicabtagene ciloleucel (brand name: Yescarta™).^1,2

Tisagenlecleucel is approved for the treatment of acute lymphocytic leukemia (ALL) in certain patients up to 25 years of age whose cancer is in second or more relapse (the cancer went into remission but came back two or more times) or refractory (the cancer never went into remission despite treatment). The patient’s own T-cells are modified to attack cells with CD19 receptor present – CD19 is a protein found on the surface of certain cancer cells. In clinical trials, 83% of patients who received tisagenlecleucel experienced a remission of their ALL.^1,5,6 As of May 2018, the U.S. Food and Drug Administration (FDA) expanded the approval of tisagenlecleucel to include adults with certain types of relapsed or refractory large B-cell lymphoma following at least two forms of systemic treatment.⁷

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Axicabtagene ciloleucel is approved for the treatment of adults with certain types of relapsed or refractory large B-cell lymphoma following at least two forms of systemic treatment, such as chemotherapy or stem cell transplant. The patient’s own T-cells are modified to attack cells with CD19 receptor present.^8,9 In a clinical trial, approximately half of the patients who received axicabtagene ciloleucel had a complete response – their cancer was undetectable – and nearly 30% of patients had a partial response. For those who had a complete response, the effects seem to be lasting with most patients continuing to show no signs of their cancer for at least 6 months after treatment. For those who experienced a partial response, many saw the benefits of the treatment decrease after 6 months.²

Possible side effects of CAR T-cell therapy

CAR T-cell therapy can cause serious side effects, and some of these side effects can be life-threatening. The infusion of the modified T-cells may lead to a serious inflammatory side effect called cytokine release syndrome (CRS). If CRS is not quickly treated, it can cause death. The symptoms of CRS include fever, chills, difficulty breathing, dizziness or lightheadedness, nausea, vomiting, diarrhea, a fast or irregular heartbeat, and severe fatigue or weakness. Patients who experience any of these symptoms should immediately seek medical care.^1,6,8

Another potential serious side effect of CAR T-cell therapy is neurological events, including confusion, swelling of the brain, and seizures. Some of these may be life-threatening.^4,6,8

CAR T-cell therapy can increase the risk of serious infections, and some infections can be life-threatening. CAR T-cell therapy can also lower blood cell counts, including red blood cells, white blood cells, and platelets.^6,8

These are not all the possible side effects of CAR T-cell therapy. Patients should talk to their doctor about potential side effects, as well as telling their doctor about all other conditions they may have (such as problems with the heart, lung, kidney, liver, or neurological problems) and all medications they are taking.^6,8

Challenges of CAR T-cell therapy

Because current CAR T-cell therapies are a personalized therapy, they cannot be mass-produced. Some critics have said the price of therapy is unaffordable. Some small, early trials are testing out an off-the-shelf CAR T-cell therapy which uses T-cells from healthy donors rather than the individual patient.^4,10

The potential life-threatening side effects are also a challenge of CAR T-cell therapy. Most side effects can be managed if identified and treated early.⁴