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Dr. Rebecca Gardner in her lab at Seattle Children’s Research Institute. (Seattle Children’s Photo)

When scientists at Seattle Children’s Research Institute began studying a new immunotherapy cancer treatment a few years ago, they found stunning results. More than 90 percent of children with leukemia who took the treatment went into remission.

But there was a troubling caveat to that success: Half of those children relapsed within a year, and when their cancer came back, the treatment no longer worked.

Now scientists at Children’s believe they have another shot at preventing those relapses. The institute launched a new clinical trial Thursday that will treat children with leukemia using a new kind of CAR T immunotherapy that targets two different cancer proteins instead of just one, potentially increasing a child’s chance at surviving the disease.

The approach is so new that only a few treatments like it have been tested, but the study’s lead investigator, Dr. Rebecca Gardner, is hopeful that it will hold the key to preventing relapses.

“It’s something that is just starting right now, but I think over the next year or two we’ll start to see more and more CAR T cell trials that are targeting two proteins at the same time,” Gardner told GeekWire.

CAR T immunotherapies work by genetically engineering a patient’s T-cells to recognize and destroy cancer cells. Most therapies being studied today do that by giving the T-cells receptors that lock onto CD19, a protein that is found on the surface of cancer cells.

The treatment is still cutting-edge, but it has shown incredible results in studies across the U.S. in the past few years. The first CAR T immunotherapy was approved for use by the FDA in August. It is also a treatment for children with leukemia, and more than 80 percent of patients who took it in clinical trials went into remission.

But relapse after immunotherapy treatments is still a huge problem, and it often happens because a patient’s cancer has found a way around their newly-powered T-cells.

“Of those who relapsed, half of them were relapsing because their leukemia evolved so that the T-cells could no longer recognize it,” Gardner said.

In other words, they no longer had that CD19 protein that let the T-cells lock onto them. About half of all patients who relapse after CAR T treatment experience that problem.

The new treatment takes CAR T immunotherapy up a notch: It equips T-cells with receptors for both CD19 and CD22, another protein found in leukemia cells. Gardner said the hope is that the cancer can’t evolve to get rid of both proteins, so even if it comes back, a patient’s immune system will be able to fight it off.

“The best case would be that all of [the patients] stay in remission,” Gardner said. “The reality is that’s probably unlikely to happen, but our hope would be that instead of having 50 percent of patients relapse, maybe only 20 percent of patients relapse.”

Seattle Children’s is making a big investment in leukemia research: The institute announced a $1 billion fundraising campaign Wednesday that includes plans for a new, 540,000-square-foot research center dedicated to immunotherapy.

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