Clinical trials of an experimental treatment for adults with leukemia were abruptly stalled by the Food and Drug Administration after two patients died of complications from neurotoxicity last week.
Juno Therapeutics, a development-stage biotechnology company, has been experimenting with treatments that use immune cells, or T-cells, engineered to attack cancerous acute lymphoblastic leukemia cells in the body. However, two patients in the most advanced stages of treatment experienced significant swelling of the brain and died last week. Another patient died under similar circumstances back in May.
The FDA has issued a clinical hold on the trials, meaning that no new patients will be enrolled and no existing patients will be given additional doses until the treatment plan is properly revised for safety.
The researchers, however, believe that the deaths are less a result of the T-cell therapy than they are from a toxic reaction with certain types of chemotherapy drugs involved with the affected patients. The FDA is expected to approve further treatments without the chemotherapy.
“The last week has been difficult and humbling for everyone involved, in particular, of course, the physicians and the patients’ families,” said Juno CEO Hans Bishop. “Neurotoxicity as an adverse event is well-cataloged, but [this] was a real surprise.”
Despite the very serious setbacks, researchers say they can use the information learned to improve treatments and make further advancements in combating leukemia. Some three-quarters of all medical visits involve varied types of drug therapy, and clinical experimentation is an essential part of the learning curve for developing safe and effective treatments.
“This sort of thing is incredibly common in new drug development. It’s unfortunate, but I don’t know how you avoid it,” said Dr. Otis Brawley, a chief medical officer at the American Cancer Society.
“These are relatively rare events,” said Dr. Jae Park, one of the physicians conducting Juno’s trials at Memorial Sloan Kettering Cancer Center in New York. “I don’t think it changes the fundamental promise or the long-term plan here.”
