On August 30, the Food and Drug Administration (FDA) approved Kymriah, a gene therapy that targets a type of leukemia known as acute lymphoblastic leukemia (ALL). In a clinical trial involving 63 patients, 83 per cent of them went into remission within the first three months of treatment.

Specifically, this therapy is tailored to the form of ALL that starts in the B cells of the immune system, called B-cell ALL. The disease affects blood and bone marrow and causes a patient’s immune system to produce abnormal white blood cells.

In a healthy individual, two types of white blood cells, T cells and B cells, work together to fight infections. In patients with ALL, however, either T cells or B cells are produced at abnormally high levels, and the disease is classified as T-cell or B-cell ALL.

Kymriah is unique in that it is the first FDA-approved gene therapy. It offers hope for patients with relapsed or refractory ALL, forms of leukemia with limited treatment options.

In the clinical trial, Kymriah demonstrated promise in providing effective treatment within a year for B-cell ALL patients under 25 years old.

Kymriah is a specialized, cell-based gene therapy that works by modifying a patient’s own T cells into ones that contain a chimeric antigen receptor (CAR) protein. These ‘CAR-infused’ T cells can then be redirected to attack cancer cells that have a specific immune trigger, or antigen, on their surfaces. In this case, the antigen is known as CD19.

Because the treatment is different for every patient, a patient’s T cells are genetically manufactured at a certified hospital to contain CAR, and then the modified cells are incorporated into a transfusion specific to the patient.

This novel treatment was first developed by Dr. Carl June and his colleagues at the University of Pennsylvania in a collaboration with Novartis Pharmaceuticals Corporation in 2012.

The current go-to treatment options for ALL are chemotherapy and radiation therapy, which are long-term treatments that result in numerous complications and side effects. In addition, these treatments have a poor prognosis, or outcome, and less than 10 per cent of treated patients survive longer than five years. Chemotherapy and radiation therapy can also attack a patient’s healthy cells.

Kymriah also differs from traditional treatments because it is only administered once, via intravenous transfusion. Although this new therapy still comes with severe side effects, it opens the door to an alternative treatment route for ALL patients.

According to the Leukemia and Lymphoma Society of Canada, 55,900 Canadians were diagnosed with ALL in 2016.

Research and advancements in gene therapy in Canada are also in the works. Dr. Mark Minden, a Senior Scientist at the Princess Margaret Cancer Centre, noted that researchers are working on chimeric antigen receptor T cell (CAR-T) treatments that could combat a broader range of cancers.

A downfall of using CAR-T therapy is that, according to Minden, “it hits one protein on the leukemic cell and it can escape by modifying the cell.” Because CAR-T treatments are designed to target a single protein, their specificity makes it hard to modify treatment for patients with other variations of leukemia.

Several researchers in Toronto are working in this field, including Dr. Naoto Hirano, also a Senior Scientist at the Princess Margaret Cancer Centre. His team is working on a CAR-T therapy targeting different antigens, such as CD33, and modifying its signal to make it more efficient.

With regard to the future of gene therapy in Canada, Minden cited the need for more funding.

Kymriah is a unique therapy, providing hope to leukemia patients who have exhausted all other treatment routes. However, being the first of its kind in the US also means that there is an air of uncertainty around its long-term effects.

Novartis expects to certify Kymriah in 32 hospitals across the US by the end of the year and monitor eligible patients over a 15-year period for potential side effects and complications.

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