Mayo Clinic, University of Minnesota develop 'robocop' stem cells to fight cancer

Researchers at the Mayo Clinic and the University of Minnesota say they're on the brink of a new era in cancer care — one in which doctors extract a patient's white blood cells, have them genetically engineered in a lab, and put them back to become personalized cancer-fighting machines.

The so-called CAR T cellular therapies are expected to receive federal approval this fall for certain rare blood cancers — B-cell forms of lymphoma and leukemia. But scientists at the Minnesota institutions hope that's just the first step that will lead to better treatment of solid tumor cancers as well.

"This is really the first approval of a genetically modified product for cancer therapy," said Dr. Jeffrey Miller, deputy director of the Masonic Cancer Center at the University of Minnesota. If the proof of concept works, he said, "we might be on the right track to get away from all of that toxic chemotherapy that people hate."

Participating in industry-funded clinical trials, the Minnesota researchers hoped to determine if patients with leukemia or lymphoma would be more likely to survive if their own stem cells were extracted to grow cancer-fighting T-cells that were then infused back into their bodies.

One analysis, involving trials by Kite Pharmaceuticals at Mayo and other institutions, found a sevenfold increase in lymphoma patients whose cancers disappeared when they received CAR T instead of traditional chemo-based treatment.

"I often tell patients that T-cells are like super robocops," said Dr. Yi Lin, a Mayo hematologist in Rochester. "We're now directing those cells to really target cancer."

The U.S. Food and Drug Administration is widely expected this fall to approve CAR T products made by Kite and Novartis, which genetically engineer T-cells to target so-called CD19 proteins found on the surface of leukemia and lymphoma cells.

The side effects can be harsh, because the T-cell infusions trigger an immune system response that can produce fever, weakness, racing heart and kidney problems. Short-term memory and cognitive problems also have occurred. Brain swelling led to five deaths of cancer patients who took part in a CAR T trial by Juno Pharmaceuticals. The trial was shut down as a result.

Lin said brain swelling appeared mostly in adults with leukemia. For now, she expects Kite's CAR T therapy to be approved for diffuse large B-cell lymphoma and the Novartis therapy to be approved for acute lymphoblastic leukemia in children. Federal regulations also might restrict CAR T for patients whose cancers survived traditional treatments.

Current practice to treat these cancers generally involves chemotherapy and radiation. Physicians then transplant stem cells, often from donor bone marrow, to regrow the patients' immune systems, which are weakened in the process of treatment.

CAR T differs in that patients will receive infusions of their own T-cells, genetically modified, which their bodies will be less likely to reject.

"It's individualized medicine," Lin said.

Before he tried CAR T at Mayo as part of a clinical trial, John Renze of Carroll, Iowa, had received two rounds of chemo, two rounds of radiation, and an experimental drug that did nothing to stop the spread of lymphoma.

"After you fail about four times, you start to wonder if anything is going to work," the 58-year-old said.

At first, there was no room for him in the Mayo trial — which has been a problem nationwide as desperate cancer patients have searched for treatment alternatives. But then he got the call one morning last summer while ordering coffee at his local cafe.

"Can you get up here by one?" the Mayo official asked.

"I'm on my way," Renze replied.

Even before federal approval comes through, researchers such as Miller are looking beyond the first-line CAR T therapies, and wondering if the approach can be used on solid tumors. Roughly 80,000 blood cancers occur each year in the U.S. that could be treated with CAR T, but the total number of cancers diagnosed each year is nearly 1.7 million.

The challenge is that solid tumors don't have the same protein targets as blood cancers. And T-cells would have to be more discriminating if infused to eliminate tumors in solid organs, Miller said. "If you destroy normal lung tissue (along with lung cancer), that's not going to work," he said.

Mayo researchers are studying whether CAR T can work against multiple myeloma, a cancer of the bone marrow, while U researchers are exploring ways to better control the CAR T-cells after they are infused in cancer patients.

Researchers also are trying to understand whether CAR T produces "memory" in the immune system, so it knows to react if cancers resurface.

In addition, Miller is studying whether NK cells, which also play a role in the human immune system, can be genetically modified and infused instead of T-cells to target cancer. The body doesn't reject NK cells from donors as much, he said. So NK cells from donor bone marrow or umbilical cord blood could be collected and mass produced to potentially provide faster and cheaper treatments.

Like many breakthrough therapies, CAR T will be expensive, with a price likely to exceed $200,000 per patient. How insurers plan to cover it remains unclear. Blue Cross and Blue Shield of Minnesota is evaluating evidence regarding CAR T's effectiveness, and will set a coverage policy after it receives FDA approval, said Dr. Glenn Pomerantz, Blue Cross' chief medical officer.

Mayo expects a surge of hundreds of cancer patients per year if CAR T is approved, because it will initially be provided by large medical centers that have experience with the therapy and its side effects. The Rochester hospital is planning to add staff and space dedicated to CAR T.

Miller said the U is developing advice for referring doctors and hospitals statewide, so they know what to do if CAR T patients show up with complex symptoms.

"They can be a bit delayed and you can't just keep people in the hospital to see if they develop these things," he said.

Renze's stem cells were taken last July, and his modified T-cells were put back a month later. He lost weight and felt sick for weeks, and had to drive three hours to Mayo for frequent checkups.

But as of last Aug. 31, the cancer had vanished.

Every three months, he returns to Mayo to make sure the cancer hasn't re-emerged. Then he returns to Carroll, where he owns farmland and car dealerships and dotes on his grandchildren.

"For people like me that have already failed a bunch of times, you're happy to try anything," he said. "I mean, what else would I have done?"

Jeremy Olson • 612-673-7744