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Novel leukemia therapy aims to treat sick kids before time runs out

Highly personalized treatments for aggressive pediatric leukemia are available and have proved effective for those who can wait for them. What about those who can't?

A decade ago, CAR T cell therapy changed the world of cancer treatment, offering a personalized approach to patients with blood cancers like leukemia

But getting that specialized treatment to patients is costly and time consuming. It can take up to two months to harvest a patient's T cells and reprogram them into cancer-fighters — a nonstarter for many young patients with aggressive cancer.

These patients "don't have months or years to live," said Dr. Mohamed Kharfan-Dabaja, director of Blood and Marrow Transplantation and Cellular Therapies at the Mayo Clinic in Florida. "They have weeks." Kharfan-Dabaja was not part of the new research.

A novel approach to CAR T (chimeric antigen receptor T cell) therapy aims to cut down that turnaround time significantly. Instead of reprogramming each patient's cells, researchers are testing the safety of using universal, or "off the shelf," CAR T cells from other patients, preprogrammed to fight cancer. These cells are then tweaked further using another gene-modifying technology — CRISPR — to ensure they are not rejected by the patient's own immune system.

Scientists at University College London in the United Kingdom tested the safety of the experimental approach in six children — mostly toddlers — with advanced leukemia. The research was published Wednesday in the journal Science Translational Medicine.

Conventional treatments, like chemotherapy, had already failed in the six children in the study, a phase 1 clinical trial. The goal was to determine whether the new approach was safe. The scientists will determine whether it is effective in future, larger studies.  

"These are very difficult children to treat," said Waseem Qasim, a study author and professor of cell and gene therapy at Great Ormond Street Hospital for Children in London. 

The goal of the new treatment approach isn't necessarily curative; instead, it's to get patients into remission so that they are well enough for a bone marrow stem cell transplant. 

The new approach is a "bridge to transplant," said Dr. Stephen Gottschalk, head of the Department of Bone Marrow Transplantation and Cellular Therapy at St. Jude Children's Research Hospital in Memphis. "If they're not in remission before transplant, their likelihood of relapse is probably 80%."

Gottschalk, who was not involved with the trial, called the new research "exciting."

Modifying the harvested T cells with CRISPR — a genetic tool that can cut and paste bits of DNA — and then preparing them for use can take about 12 days, Qasim said. For most patients, the wait may be even shorter — just the time needed to thaw the prepared frozen T cells.  

"If we want to make these treatments available worldwide, off the shelf is going to be the way to provide them," Qasim said. 

The "off the shelf" approach also ensures that there are enough T cells for the treatment. "These young children are so small that it's very difficult actually to collect cells," Gottschalk said.

None of the children in the trial experienced dangerous side effects from the experimental treatment. One particular side effect associated with CAR T therapy is called a cytokine storm, and it can be deadly. It occurs when the body's immune system goes haywire in response to the therapy.

Four of the children ultimately died — not from the treatment or a cytokine storm, but from their cancer. Two entered remission and remain alive and well, Qasim said, 9 and 18 months following treatment. 

Dr. Kris Mahadeo, an associate professor in the department of Pediatrics Patient Care at the University of Texas MD Anderson Cancer Center in Houston, said the early results were encouraging.

"The idea is to get all of these children to live full lives," said Mahadeo, who was not involved with the study. "That's the promise of what we're working toward."

CORRECTION (Nov. 3, 2022, 8:05 a.m. ET): A previous version of this article misspelled the first name of a study author. He is Waseem Qasim, not Wassim.

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