FDA Approves First Gene Therapy Treatment for Leukemia

We can now reprogram our bodies


The FDA has approved gene therapy treatment for the first time—a historic move in the annals of medicine. The new treatment—Kymriah (tisagenlecleucel)—uses modified T-cells to battle leukemia.

The approval of Kymriah serves as a harbinger for the approval of other forms of gene therapy that will battle cancer and other serious illnesses using a novel and exciting approach: reprogramming the body through artificial means.

Cell-Based Gene Therapy

Cell-based gene therapy refers to the practice of introducing new genetic material into a specific cell population and then re-introducing these modified cells into the body. Once in the body, these new cells can produce proteins that help fight cancer or other serious diseases.

Kymriah involves the introduction of genetically modified T-cells—a type of lymphocyte, or white blood cell—into the body. These modified T-cells recognize and attack leukemia cells.

Gene therapy is preferable to chemotherapy because gene therapies are less toxic. Chemotherapy affects the whole body and causes body-wide adverse effects. With cell-based gene therapy, re-engineered cells are infused locally and fight tumors specifically.

In addition to being a form of gene therapy, Kymriah is also an immunotherapeutic agent. Immunotherapy leverages the power of the immune system to treat disease.

Kymriah Explained

In technical terms, Novartis’s Kymriah is an experimental chimeric antigen receptor (CAR) T-cell therapy used to treat relapsed or refractory (i.e., resistant to treatment) B-cell acute lymphoblastic leukemia. 

Kymriah is a customized form of immunotherapy wherein a patient’s own T-cells are first collected and then sent to a manufacturing center.

The T-cells are harvested using a procedure called leukapharesis.

At the manufacturing center, these T-cells are modified to include a gene that codes for CAR expression. These modified cells are then infused back into the patient. Once in the body, CARs target a specific antigen called CD19 that is located on the surface of leukemia cells and kill these cancerous cells. Once in the blood, these modified T-cells grow and expand to eradicate cancer within two or three weeks.

Experts at the FDA based their approval of Kymriah on a single arm of a phase II clinical trial in which 63 children, adolescents, and young adults with relapsed or refractory B-cell acute lymphoblastic leukemia received a single dose of the treatment. Of these participants, 83 percent went into remission after three months. Furthermore, 75 percent remained free of disease after six months. Importantly, Kymriah was granted Priority Review and Breakthrough Therapy designations by the FDA.

Acute lymphoblastic leukemia is a cancer of the bone marrow and blood. It causes the body to make abnormal lymphocytes. These abnormal blood cells quickly crowd out healthy blood cells in the bone marrow. We need our blood cells to survive.

When the number of normal blood cells dramatically decreases, death can ensue.

Although older adults can develop ALL, it is primarily a disease of children. About 90 percent of children with ALL go into remission after treatment. Kymriah is approved for use in patients who are younger than 25 years old and have either cancer that has recurred or cancer that is resistant to treatment.

Concerns About Kymriah

One concerning negative side effect of any type of monoclonal antibody therapy is cytokine release syndrome, an infusion reaction which is also called cytokine storm. Cytokines are small proteins that are secreted by cells and have effects on other cells.

In most people, symptoms of cytokine release syndrome are mild or moderate and can be easily treated. These symptoms include:

  • low blood pressure
  • fatigue
  • tachycardia
  • headache
  • fever
  • nausea
  • chills
  • rash
  • scratchy throat
  • trouble breathing

However, patients who have blood cancers—like ALL—are at higher risk of developing severe cytokine storm with life-threatening symptoms. For this reason, infusions need to take place at high-volume centers with specialists trained to manage serious complications like cytokine storm.

Finally, Kymriah is expected to cost around $500,000. Nevertheless, treatment with Kymriah is still cheaper than a bone marrow transplant, which is commonly used in the treatment of leukemia.

A Word From Verywell

Refractory or relapsing ALL is a deadly disease. The approval of Kymriah provides hope for a few hundred young people in the United States who have no treatment options left. It has proven effective in clinical trials. However, the clinical trials were limited in duration, and it remains to be seen whether Kymriah can induce lifelong remissions.

In sweeping terms, the approval by the FDA of a form of gene therapy for the first time ushers in a new age of medicine: an age where we can reprogram our cells to fight cancer and other deadly diseases.


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Colwell J. Panel OKs CAR T Therapy for Leukemia. Cancer Discovery. July 27, 2017.

FDA News Release. FDA approval brings first gene therapy to the United States. August 30, 2017.

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