Two patients with chronic lymphocytic leukemia (CLL) who 10 years ago were among the first to receive groundbreaking chimeric antigen receptor T-cell therapy were still in remission a decade later, and they continued to show detectable levels of CAR T cells.
“We can now conclude that CAR T cells can actually cure patients with leukemia based on these results,” said senior author Carl H. June, MD, in a press briefing on the study published in Nature.
“The major finding from this paper is that, 10 years down the road, you can find these [CAR T] cells,” June, director of the Center for Cellular Immunotherapies, University of Pennsylvania, Philadelphia, added. “The cells have evolved, and that was a big surprise…but they are still able to kill leukemia cells 10 years after infusion.”
CAR T-cell therapy, in which patients’ own T cells are removed, reprogrammed in a lab to recognize and attack cancer cells, and then infused back into the patients, has transformed treatment of various blood cancers and shows often-remarkable results in achieving remissions.
While the treatment has become a routine therapy for certain leukemias, long-term results on the fate and function of the cells over time has been highly anticipated.
In the first published observations of a 10-year follow-up of patients treated with CAR T cells, June and colleagues described the findings for two patients, both with CLL, who back in 2010 were among the first to be treated with this groundbreaking therapy at the University of Pennsylvania.
A decade later, the CAR T cells are found to have remained detectable in both patients, who achieved complete remission in their first year of treatment, and both have sustained that remission.
Notably, the cells have evolved over the years — from initially being dominated by killer T cells to being dominated primarily by proliferative CD4-positive CAR T cells — with one of the patients exclusively having CD4-positive cells at year 9.3.
“The killer T cells did the initial heavy lifting of eliminating the tumor, ” first author J. Joseph Melenhorst, PhD, said in an interview.
“Once their job was done, those cells went down to very low levels, but the CD4-positive population persisted,” said Melenhorst, who established the lab at the University of Pennsylvania to follow patients treated with CAR T-cell therapy. “[This] delayed phase of immune response against cancer is a novel insight, and we were surprised to see it.”
Melenhorst noted that the clonal makeup of the CD4-positive cells importantly stabilized and became dominated by a small number of clones, suggesting further sustainability.
When one of the two patients, Doug Olson, who participated in the press conference, donated his cells back to the center after 9.3 years, the researchers found that his cells were still capable of destroying leukemia cells in the lab.
“Ten years [post infusion], we can’t find any of the leukemia cells and we still have the CAR T cells that are on patrol and on surveillance for residual leukemia,” June said.
One challenge of the otherwise desirable elimination of leukemia cells is that some aspects of sustaining CAR T-cell activity become problematic.
“The aspect of how the remission is maintained [is] very hard to study in a patient when there is no leukemia at all,” June explained. “It could be the last cell was gone within 3 weeks [of treatment], or it could be that the [cancer cells] are coming up like whack-a-moles, and they are killed because these CAR T cells are on patrol.”
Sadly, the other CLL patient, Bill Ludwig, who was first to receive the CAR T-cell treatment, died in 2021 from COVID-19.
Effects in Other Blood Diseases Similar?
CAR T-cell therapy is currently approved in the United States for several blood cancers, and whether similar long-term patterns of the cells may be observed in other patient and cancer types remains to be seen, Melenhorst said.
“I think in CLL we will see something similar, but in other diseases, we have yet to learn,” he said. “It may depend on issues including which domain has been engineered into the CAR.”
While the prospect of some patients being “cured” is exciting, responses to the therapy have generally been mixed. In CLL, for instance, full remissions have been observed to be maintained in about a quarter of patients, with higher rates observed in some lymphomas and pediatric ALL patients, Melenhorst explained.
The effects of CAR T-cell therapy in solid cancers have so far been more disappointing, with no research centers reproducing the kinds of results that have been seen with blood cancers.
“There appear to be a number of reasons, including that the [solid] tumor is more complex, and these solid cancers have ways to evade the immune system that need to be overcome,” June explained.
And despite the more encouraging findings in blood cancers, even with those, “the biggest disappointment is that CAR T-cell therapy doesn’t work all the time. It doesn’t work in every patient,” coauthor David Porter, MD, the University of Pennsylvania oncologist who treated the two patients, said in the press briefing.
“I think the importance of the Nature study is that we are starting to learn the mechanisms of why and how this works, so that we can start to get at how to make it work for more people,” Porter added. “But what we do see is that, when it works, it really is beyond what we expected 10 or 11 years ago.”
Speaking in the press briefing, Olson described how several weeks after his treatment in 2010, he became very ill with what has become known as the common, short-term side effect of cytokine release syndrome.
However, after Olson recovered a few days later, Porter gave him the remarkable news that “we cannot find a single cancer cell. You appear completely free of CLL.”
Olson reported that he has since lived a “full life,” kept working, and has even run some half-marathons.
June confided that the current 10-year results far exceed the team’s early expectations for CAR T-cell therapy. “After Doug [initially] signed his informed consent document for this, we thought that the cells would all be gone within a month or 2. The fact that they have survived for 10 years was a major surprise — and a happy one at that.”
June, Melenhorst, and Porter reported holding patents related to CAR T-cell manufacturing and biomarker discovery.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.