CAR T-Cell Therapy Turns 10 and Finally Earns the Word 'Cure'

Kate Johnson

July 21, 2022

Ten years ago, Stephan Grupp, MD, PhD, plunged into an unexplored area of pediatric cancer treatment with a 6-year-old patient for whom every treatment available for her acute lymphoblastic leukemia (ALL) had been exhausted.

Dr Stephan Grupp

Grupp, a pioneer in cellular immunotherapy at Children's Hospital of Philadelphia (CHOP), had just got the green light to launch the first phase 1 trial of chimeric antigen receptor (CAR) T-cell therapy for children.

"The trial opened at the absolute last possible moment that it could have been helpful to her," he told Medscape Medical News. "There was nothing else to do to temporize her further.... It had to open then or never."

The patient was Emily Whitehead, who has since become a poster girl for the dramatic results that can be achieved with these novel therapies. After that one CAR T-cell treatment back in 2012, she has been free of her leukemia and has remained in remission for more than 10 years.

Grupp says that he is, at last, starting to use the "cure" word.

"I'm not just a doctor, I'm a scientist — and one case isn't enough to have confidence about anything," he said. "We wanted more patients to be out longer to be able to say that thing which we have for a long time called the 'c word.'

"CAR T-cell therapy has now been given to hundreds of patients at CHOP, and ― we are unique in this ― we have a couple dozen patients who are 5, 6, 7, 9 years out or more without further therapy. That feels like a cure to me," he commented.

First Patient With ALL

Emily was the first patient with ALL to receive the novel treatment, and also the first child.

There was a precedent, however. After having been "stuck" for decades, the CAR T-cell field had recently made a breakthrough, thanks to research by Grupp's colleague Carl June and his team at the University of Pennsylvania. By tweaking two key steps in the genetic modification of T cells, June's team had successfully treated three adults with chronic lymphocytic leukemia (CLL), two of whom were in complete remission.

But using the treatment for a child and for a different type of leukemia was a daunting prospect. Grupp recalls that he was candid with Emily's parents, Tom and Kari Whitehead, emphasizing that there are no guarantees in cancer treatment, particularly in a phase 1 trial.

But the Whiteheads had no time to waste and nowhere else to turn. Her father, Tom, recalls saying: "This is something outside the box, this is going to give her a chance."

Grupp, who describes himself as being "on the cowboy end" of oncology care, was ready to take the plunge.

Little did any of them know that the treatment would make Emily even sicker than she already was, putting her in intensive care. But thanks to a combination of several lucky breaks and a lot of brain power, she would make a breathtakingly rapid recovery.

The "Magic Formula"

CAR T-cell therapy involves harvesting a patient's T cells and modifying them in the lab with a chimeric antigen receptor to target CD19, a protein found on the surface of ALL cancer cells.

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, 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.

June's team came up with what 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 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 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" (N Engl J Med. 2011;365:725-33).

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 (CRS).

"The wheels just came off then," said Tom. "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,' " Tom told Medscape Medical News. "And I said, 'Alright, 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 Grupp. The ICU "worked flat out" to save her life, he recalls. "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 recalls. "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).

"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,' " said Tom.

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.

Talking About "Cure"

Now that Emily, 17, has remained in remission for 10 years, Grupp is finally willing to use the word "cure" ― but it has taken him a long time.

Now, he says, the challenge from the bedside is to keep parents' and patients' expectations realistic about what they see as a miracle cure.

"It's not a miracle. We can get patients into remission 90-plus percent of the time — but some patients do relapse — and then there are the risks [of the cytokine storm, which can be life-threatening].

"Right now, our experience is that about 12% of patients end up in the ICU, but they hardly ever end up as sick as Emily...because now we're giving the tocilizumab much earlier," Grupp said.

Hearing Whispers

Since their daughter's recovery, Tom and Kari Whitehead have dedicated much of their time to spreading the word about the treatment that saved Emily's life. Tom testified at the US Food and Drug Administration's advisory committee meeting in 2017 when approval was being considered for the CAR T-cell product that Emily received. The product was tisagenlecleucel-T (Novartis); at that meeting, there was a unanimous vote to recommend approval. This was the first CAR T cell to reach the market.

As co-founders of the Emily Whitehead Foundation, Tom and Karis have helped raise more than $2 million to support research in the field, and they travel around the world telling their story to "move this revolution forward."

Despite their fierce belief in the science that saved Emily, they also acknowledge there was luck — and faith. Early in their journey, when Emily experienced relapse after her initial treatments, Tom drew comfort from two visions, which he calls "whispers," that guided them through several forks in the road and through tough decisions about Emily's treatment.

Several times he and Kari refused treatment that was offered to Emily, and once they had her discharged against medical advice. "I told Kari she's definitely going to beat her cancer ― I saw it. I don't know how it's going to happen, but we're going to be in the bone marrow transplant hallway [at CHOP] teaching her to walk again. I know a lot of doctors don't want to hear anything about 'a sign,' or what guided us, but I don't think you have to separate faith and science, I think it takes everything to make something like this to happen."

Enduring Effect

The key to the CAR T-cell breakthrough that gave rise to Emily's therapy was cell proliferation, and the effect is enduring, beyond all expectations, said Grupp. The modified T cells are still detectable in Emily and other patients in long-term remission.

"The fundamental question is, are the cells still working, or are the patients cured and they don't need them?" said Grupp. "I think it's the latter. The data that we have from several large datasets that we developed with Novartis are that if you get to a year and your minimal residual disease testing both by flow and by next-generation sequencing is negative and you still have B-cell aplasia, the relapse risk is close to zero at that point."

While it's still not clear if and when that risk will ever get to zero, Emily and Grupp have successfully closed the chapter.

"Oncologists have different notions of what the word 'cure' means. If your attitude is you're not cured until you've basically reached the end of your life and you haven't relapsed, well, that's an impossible bar to hit. My attitude is, if your likelihood of having a disease recurrence is lower than the other risks in your life, like getting into your car and driving to your appointment, then that's what a functional cure looks like," he said.

"I'm probably the doctor that still sees her the most, but honestly, the whole conversation is not about leukemia at all. She has B-cell aplasia, so we have to treat that, and then it's about making sure there's no long-term side effects from the totality of her treatment. Generally, for a patient who's gotten a moderate amount of chemotherapy and CAR T, that should not interfere with fertility. Has any patient in the history of the world ever relapsed more than 5 years out from their therapy? Of course. Is that incredibly rare? Yes, it is. You can be paralyzed by that, or you can compartmentalize it."

Tom, Emily, and Kate Whitehead

As for the Whiteheads, they are focused on Emily's college applications, her new driver's license, and her project to co-write a film about her story with a Hollywood filmmaker.

Tom says the one thing he hopes clinicians take away from their story is that sometimes a parent's instinct transcends science.

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.

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