An experimental cell therapy treatment that grafts cancer-fighting traits onto a person’s immune system cells has found some success in a small pool of leukemia patients who did not respond to chemotherapy.

Leukemia is never an easy disease to beat back, but adults with relapsed B cell acute lymphoblastic leukemia, or B-ALL, have especially grim prospects. This particular kind of blood cancer progresses quickly and has only a 30 to 40 percent cure rate in adults. Chemotherapy drugs can sometimes clear out the cancer the first time around, but some patients relapse, requiring another round of chemotherapy, then a bone marrow transplant. But this second round can sometimes fail, because the recurring leukemia proves resistant to the drugs.

Now, in a paper published Wednesday in the journal Science Translational Medicine, scientists have successfully treated B-ALL patients by inserting new genetic material into some of their T cells. The cell therapy allows the patients’ immune systems to find and destroy the places where the blood cancer is hiding out.

In one case, the treatment cleared up a patient’s leukemia in a little more than a week.

“We had hoped but couldn’t have predicted that the response would be so profound and rapid,” Memorial Sloan-Kettering Cancer Center researcher Renier J. Brentjens told the New York Times.

Brentjens and his colleagues treated five B-ALL patients with some of their own T cells, which were genetically programmed to recognize a particular protein on the surface of B cells, the immune system cells that are affected by this kind of leukemia. The reengineered T cells then lay waste to all of the patient’s B cells, healthy and cancerous alike (the loss of healthy B cells can be treated later).

“We’re creating living drugs,” senior author Michel Sadelain told the New York Times. “It’s an exciting story that’s just beginning.”

Still, the treatment is far from 100 percent perfect. Three of the five patients in the study have been in remission for anywhere between five months and two years. Another patient died of a blood clot after going into remission, and another relapsed again -- possibly because a steroid treatment meant to control a side effect of the cell therapy may have wiped out the souped-up T cells before they could attack the B cells. The three survivors may yet relapse again.

And there are risks associated with the cell therapy. The T cells’ offensive onslaught can create what’s called a “cytokine storm,” a potentially fatal immune chain reaction that usually induces an extremely high fever.

"This is very early in development," University of Pennsylvania researcher David Porter, who was not involved with the study, told U.S. News & World Report. "We are just starting to learn about the short-term side effects, and we don't know about the long-term effectiveness or safety."

At the moment, this kind of cell therapy is being used as a lead-in to a bone marrow transplant. But in the future, doctors may be able to just use immunotherapy by itself.

"This is still an experimental therapy," Brentjens told USNWR. "But it's a promising therapy."

SOURCE: Brentjens et al. “CD19-Targeted T Cells Rapidly Induce Molecular Remissions in Adults with Chemotherapy-Refractory Acute Lymphoblastic Leukemia.” Science Translational Medicine 5: 177ra38, 20 March 2013.