(USA TODAY) Researchers have had early success with a new therapy for leukemia that trains the body's own immune system to fight cancer, a small study shows.

Doctors at Memorial Sloan Kettering Cancer Center in New York focused on a fast-growing blood cancer called B-cell acute lymphoblastic leukemia, which affects a type of white blood cell that makes antibodies. All of the patients in the study had relapsed after being treated with chemotherapy, according to the study, published today inScience Translational Medicine.

Patients like these have few good options left, says Renier Brentjens, one of the study's senior authors and director of cellular therapeutics at Sloan Kettering. Only about 30% of these respond to additional chemotherapy. Their best hope is to undergo a bone-marrow transplant, the only therapy known to offer a chance of cure. However, patients with active cancer aren't eligible for these procedures, he says. Only patients whose cancer is in remission are eligible for a transplant.

Doctors are turning to experimental immune therapies as a "bridge" to transplant, Brentjens says.

For decades, scientists have wondered if the body could do a better job fighting cancer than chemo does. While the immune system provides a strong defense against foreign invaders, such as bacteria and viruses, it doesn't always recognize cancer cells as dangerous, partly because they arise from the body's own tissues.

Along with doctors at Sloan Kettering, the University of Pennsylvania's Stephen Grupp and other researchers have been trying to train specialized immune cells to recognize leukemia cells and kill them. They do this by drawing blood, isolating "hunter cells" called T-cells, then genetically modifying them, so they seek out tell-tale proteins found on cancerous cells, says Lee Greenberger, chief scientific officer at the Leukemia and Lymphoma Society.

"We hope the T-cells will go through the blood, find the cancer cells and kill them," Brentjens says.

In the new study, 14 of the 16 adults who received the cell therapy experienced a "complete remission," with no detectable leukemia cells left, and seven were healthy enough to undergo a bone-marrow transplant, the study says.

"The effects of this innovative immunotherapy are quite striking," says Marshall Lichtman, a professor at the University of Rochester School of Medicine and Dentistry, who wasn't involved in the new study. "Certainly this is a step forward for patients facing death."

Because this was an early-phase study, researchers didn't include a comparison group of patients receiving other therapy, Lichtman says. Historically, however, standard chemotherapy or transplantation has failed to help these patients.

The therapy has serious risks. Revving up the immune system can be dangerous, leading to serious side effects, Brentjens says. Because doctors have developed ways to help predict which patients will suffer these complications, they're able to monitor and keep patients from becoming too ill, Greenberger says.

Bone-marrow transplants themselves are risky, and two patients died from transplant-related complications, the study says. And Brentjens noted that his study was a small, "phase 1" study, which is the earliest stage of research in humans. He hopes to conduct larger studies.

But it's encouraging to see progress in an otherwise deadly disease, especially at multiple institutions, says Linda Burns, president of the American Society of Hematology. Doctors from the University of Pennsylvania also presented positive results from a study of 59 patients at the society's annual meeting in December.

Scientists are testing similar approaches in other types of leukemia and lymphomas, she says.

Brentjens is a co-holder of a patent on the technology used in this study, which was licensed to Juno Therapeutics last year.

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