what is car t-cell therapy? how immunotherapy is changing treatment options for cancer, diabetes and other autoimmune diseases
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in car t-cell therapy, t cells are taken from a person’s own body, tweaked in a lab to target diseased cells, and then re-introduced into the body intravenously.
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medical advancements continue to create new and exciting ways to tackle chronic and terminal diseases in a way that helps improve the quality of life and life expectancy of patients across the globe. while many treatments remain in the testing phase, others have solidified their place in the healthcare space because of their safety and efficacy.
one such therapy gaining traction in recent years is car t-cell therapy, a form of immunotherapy that has shown promise in treating many things, from autoimmune disease to solid-tumour cancers.
this therapy, which was first imagined in the late 1980s but not implemented in the medical world until 2017, is making waves as a viable and potentially life-changing treatment that could end up changing the course of human disease.
what is car t-cell therapy?
the body’s immune system is home to many different cells, each tasked with its own respective job to keep disease and illness at bay. t-cells are part of that system. they work by killing infected cells and assisting with the entire immune response. in car t-cell therapy, these cells are taken from a person’s own body, tweaked in a lab to target diseased cells, and then re-introduced into the body intravenously. they aren’t working alone, however.
when the cells are isolated outside of the body, medical scientists re-engineer them to produce a protein known as a chimeric antigen receptor, or car for short. once the car t-cell has been created, it is multiplied in a lab and infused back into a patient so it can continue to grow in numbers. these synthetic proteins can identify and bind to cancer cells, targeting the diseased cells it was created to destroy.
current uses of car t-cell therapy
since it was first introduced onto the scene in 2017, car t-cell therapy has made waves in the medical world for its viability in the treatment of various cancers, including:
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- b-cell acute lymphoblastic leukemia
- b-cell non-hodgkin lymphoma
- follicular lymphoma
- mantle cell lymphoma
- multiple myeloma
the u.s. food and drug administration approved six car t-cell therapies for these cancers.
in canada, however, the therapy has only been available to treat two cancers: mantle cell lymphoma and relapsed/refractory diffuse large b-cell lymphoma. the accessibility in the country is low, with only ontario, quebec, alberta, and nova scotia residents being able to access care using car t-cell therapy.
the effectiveness of a new therapy
when looking at its current uses and recent studies examining how it can be used in other ways, the efficacy of the therapy is promising but not perfect. according to research, each type of cancer treated has a different complete response rate, which is the percentage of people who saw success from the therapy with all signs of cancer disappearing. the number of patients seeing success based on their cancers include:
- 40 to 54 per cent for relapsed/refractory aggressive b-cell lymphomas
- 67 per cent of those with mantle cell lymphoma
- 69 to 74 per cent of those with indolent b-cell lymphomas
- 71 to 81 per cent of those with relapsed/refractory b-cell acute lymphoblastic leukemia
- 73 to 98 per cent of those with relapsed/refractory multiple myeloma
the research also mentions that “some of the responses were highly durable, suggesting that cd19-targeted car t-cells are able to cure certain patients.” since cure is such a significant word, medical researchers do not throw that out lightly.
that said, the results speak for themselves in some cases of car t-cell therapy and its ability to stomp out disease in people with specific types of cancers.
potential side effects and adverse events
just like any other treatment, car t-cell therapy does not come without downsides. there are various short- and long-term side effects that patients may have to contend with down the line when the therapies become more readily available.
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neurotoxicity, which is a risk if the car t-cells in the brain, is a possibility and can lead to symptoms including:
- confusion
- agitation
- lack of awareness
- headaches
- difficulties with written or spoken language
- anxiety
- occasional seizures
macrophage-activation syndrome can also develop, which causes the immune system to become inflamed. in a worst-case scenario, this side effect can cause multiple organ failure.
other possible side effects include:
- febrile neutropenia, which is when the white blood cells decrease abnormally in the body
- b-cell aplasia, when there are low or no b-cells in the body
- anemia, which is when the red blood cell counts fall well below what is typical
- thrombocytopenia, a decrease in blood platelets
- hypogammaglobulinemia, which is a reduction in gamma globulins (antibodies)
the most notable side effect of car t-cell therapy is cytokine release syndrome (crs). this syndrome occurs when the immune system becomes too overactive from a significantly high number of inflammatory cytokines in the blood. in some cases, crs can be mild, like the flu, but in others, it can be severe and lead to life-threatening events, such as multi-organ toxicity.
future directions for car t-cell therapy
recent studies have been investigating the therapy for other uses, and it has also shown promise in different areas of illness, including autoimmune disease and recurrent glioblastoma, an aggressive form of brain cancer.
a recent study published in the new england journal of medicine found car t-cell therapy to be effective at treating patients with three specific autoimmune diseases: systemic lupus erythematosus, idiopathic inflammatory myositis, and systemic sclerosis. the treatment worked on all three diseases to induce remission.
other research has also looked at the therapy’s effect on type 1 diabetes, and mice models show that it could help to both prevent the onset of diabetes as well as its progression once it has already developed.
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the results from a clinical trial using car t-cell therapy to treat recurrent glioblastoma were also recently released in the journal nature, showing that when the treatment was used in six patients, all six saw a reduction in the size of their tumours, lasting a minimum of several months of follow-up.
others working on car t-cell therapy for glioblastoma have seen similarly dramatic results. a clinical trial conducted by mass general cancer center combined car t-cell therapy with t-cell engaging antibody molecules (teams) to create another car t-cell approach, known as carv3-team-e t-cells, that’s viable enough to induce tumour regression in a matter of days following one single infusion of the targeted therapy. these results were also published in the new england journal of medicine.
this therapy is capable of targeting mixed cell populations within tumours, and all three participants in the trial ended up experiencing a rapid reduction in their tumour size, with one showing a near-complete tumour regression that lasted over the follow-up course of six months.
while these current studies and clinical trials are underway and not yet ready for public use, they show great promise in the future of treating various diseases simply by harnessing the power of the body’s own immune system.
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