The basic pillars of cancer treatment have previously been limited to chemotherapy, radiation, and surgery. However, more targeted treatments have emerged over the last two decades. These drugs target specific cancer cells and have become standard treatments for many types of cancers. In addition, immunotherapy has emerged as an exciting and powerful cancer treatment. This type of treatment uses the patient's own immune system to battle challenging diseases.
One specific type of immunotherapy is called adoptive cell transfer (ACT), which involves engineering the patient's immune cells to recognize and attack the tumor. The responses to ACT have been remarkable in patients with advanced cancers, such as leukemia and lymphoma. In early-stage trials of ACT in patients with acute lymphoblastic leukemia (ALL) with minimal or no remaining treatment options, their cancers disappeared completely. The process of developing these therapies is quite innovative. First, the T cells are collected from the patient's blood and genetically engineered to produce special receptors called chimeric antigen receptors (CARs). These CARs allow the T cells to recognize specific proteins on tumor cells. Then, these T cells are replicated to billions in the lab and infused into the patient, and then the engineered cells kill the cancer cells.
The FDA approved two CAR T-cell therapies in 2017: Kymriah (tisagenlecleucel) suspension for intravenous infusion and Yescarta (axicabtagene ciloleucel). Kymriah is for the treatment of patients up to 25 years of age with B-cell precursor ALL that is refractory or in second or later relapse. It is a one-time treatment that uses the 4-1BB costimulatory domain in its CAR to enhance cellular expansion and persistence. Yescarta is a cell-based gene therapy used for treatment of adult patients with certain types of large B-cell lymphoma who have not responded to or who have relapsed after at least two other kinds of treatment.
Because of the risk of cytokine release syndrome (CRS) and neurologic toxicities, both Kymriah and Yescarta were approved with a risk evaluation and mitigation strategy (REMS). CRS is caused by a large, rapid release of cytokines into the blood from immune cells affected by the immunotherapy. CRS may result in fever, nausea, headache, rash, rapid heartbeat, low blood pressure and trouble breathing. Other potential side effects of CAR T-cell therapy include B-cell aplasia, tumor lysis syndrome, and cerebral edema.
CAR T-cell cancer treatment has had promising results so far. Some studies have shown up to 90 percent of children and adults with B-cell acute lymphoblastic leukemia who had either relapsed multiple times, or failed to respond to standard therapies, achieved remission after receiving CAR T-cell therapy. However, most participants in the trials have only been followed for a short time. In order to obtain information regarding the length of their responses, it will be necessary to follow the patients over the long term.
More research is needed to further explore this therapy as a standard treatment for leukemia and lymphoma. There are several ongoing trials in this area, and researchers are looking into further perfecting the CAR T-cells. Other cancers, such as solid tumors like pancreatic and brain, are being explored as additional therapeutic areas for CAR T-cell therapy.
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