Federal health regulators ordered the halt of a clinical trial for a cancer treatment developed by Juno Therapeutics after three leukemia patients reportedly died this year.

The United States Food and Drug Administration (FDA) placed a hold on the experimental cancer therapy called JCAR015 after the first patient died in May and two other patients died in late June.

The deaths of all three patients, who were in their 20s, were linked to swelling in the brain, Juno Therapeutics said.

According to Forbes, the cancellation is a blow for Juno Therapeutics, a biopharmaceutical startup valued at $4.3 billion. The company had its shares drop 30 percent to $28.50 on the Nasdaq after they closed at $40.82.

How JCAR015 Works

JCAR015, known as a chimeric antigen receptor T-cell or CART, involves genetically engineered white blood cells to treat adult leukemia. The treatment prompts engineered white blood cells or T-cells to attack B cells that turn malignant in different types of blood cancer.

More specifically, the treatment requires a meticulous and complex process of removing immune system T-cells from a patient, changing the T-cells' DNA to improve their ability to detect and kill cancer cells and infusing the altered T-cells back into the same patient.

According to Juno Therapeutics, the deaths occurred after the chemotherapy agent called fludarabine was added to the JCAR015 therapy. The company has proposed to the FDA that the clinical trial be continued using cyclophosphamide as a "pre-conditioning agent."

Early Results Of CART Trials

Leukemia patients who receive CART therapies usually receive doses of chemotherapy prior to the therapy itself in order to make the tumor more vulnerable to the CART cell.

In early stage clinical trials, CART therapies were found to eliminate all traces of lymphoma and leukemia in 40 percent to 90 percent of participants.

However, the experimental medicines can cause several side effects, including cytokine release syndrome and damage to healthy tissue. Cytokine release syndrome is the hazardous accumulation of toxic debris from killed tumor cells. The inflammation can be typically controlled with the help of steroids and other treatments.

What's Next For Juno Therapeutics

Juno's Chief Executive Officer Hans Bishop told Forbes that the FDA's decision is "a humbling experience."

"No doubt it is difficult for the physicians who are looking after these patients and their families," said Bishop.

He said the therapies are clearly potent, and that is why they provide the potential for cures.

"We're still learning to use them in the safest, most efficacious way," said Bishop.

Juno Therapeutics plans to submit a revised patient consent form, trial protocol, investigator brochure and a copy of the presentation to the FDA this week. The company will find out in the coming weeks the timing of the postponed trial. The development of its other products, including JCAR017, are not affected by the FDA's hold.

ⓒ 2021 TECHTIMES.com All rights reserved. Do not reproduce without permission.