Before the University of Pennsylvania team tweaked the process, clinical trials of the therapy yielded only modest results because the modified T cells “were very powerful in the short term but had almost no proliferative capacity” once they were infused back into the patient, Dr. Grupp explained.
“It does not matter how many cells you give to a patient, what matters is that the cells grow in the patient to the level needed to control the leukemia,” he said.
Dr. June’s team came up with what Dr. Grupp calls “the magic formula”: A bead-based manufacturing process that produced younger T-cell phenotypes with “enormous” proliferative capacity, and a lentiviral approach to the genetic modification, enabling prolonged expression of the CAR-T molecule.
“Was it rogue? Absolutely, positively not,” said Dr. Grupp, thinking back to the day he enrolled Emily in the trial. “Was it risky? Obviously ... we all dived into this pool without knowing what was under the water, so I would say, rogue, no, risky, yes. And I would say we didn’t know nearly enough about the risks.”
Cytokine storm
The gravest risk that Dr. Grupp and his team encountered was something they had not anticipated. At the time, they had no name for it.
The three adults with CLL who had received CAR T-cell therapy had experienced a mild version that the researchers referred to as “tumor lysis syndrome”.
But for Emily, on day 3 of her CAR T-cell infusion, there was a ferocious reaction storm that later came to be called cytokine release syndrome.
“The wheels just came off then,” said Mr. Whitehead. “I remember her blood pressure was 53 over 29. They took her to the ICU, induced a coma, and put her on a ventilator. It was brutal to watch. The oscillatory ventilator just pounds on you, and there was blood bubbling out around the hose in her mouth.
“I remember the third or fourth night, a doctor took me in the hallway and said, ‘There’s a one-in-a-thousand chance your daughter is alive when the sun comes up,’” Mr. Whitehead said in an interview. “And I said: ‘All right, I’ll see you at rounds tomorrow, because she’ll still be here.’ ”
“We had some vague notion of toxicity ... but it turned out not nearly enough,” said Dr. Grupp. The ICU “worked flat out” to save her life. “They had deployed everything they had to keep a human being alive and they had nothing more to add. At some point, you run out of things that you can do, and we had run out.”
On the fly
It was then that the team ran into some good luck. The first break was when they decided to look at her cytokines. “Our whole knowledge base came together in the moment, on the fly, at the exact moment when Emily was so very sick,” he recalled. “Could we get the result fast enough? The lab dropped everything to run the test.”
They ordered a broad cytokine panel that included 30 analytes. The results showed that a number of cytokines “were just unbelievably elevated,” he said. Among them was interleukin-6.
“IL-6 isn’t even made by T cells, so nobody in the world would have guessed that this would have mattered. If we’d ordered a smaller panel, it might not even have been on it. Yet this was the one cytokine we had a drug for – tocilizumab – so that was chance. And then, another chance was that the drug was at the hospital, because there are rheumatology patients who get it.
“So, we went from making the determination that IL-6 was high and figuring out there was a drug for it at 3:00 o’clock to giving the drug to her at 8:00 o’clock, and then her clinical situation turned around so quickly – I mean hours later.”
Emily woke up from a 14-day medically induced coma on her seventh birthday.
Eight days later, her bone marrow showed complete remission. “The doctors said, ‘We’ve never seen anyone this sick get better any faster,’ ” Mr. Whitehead said.
She had already been through a battery of treatments for her leukemia. “It was 22 months of failed, standard treatment, and then just 23 days after they gave her the first dose of CAR T-cells that she was cancer free,” he added.