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, Dr. 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, Dr. 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,” Dr. 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,” Dr. 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, Mr. 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 Mr. Olson recovered a few days later, Dr. Porter gave him the remarkable news that “we cannot find a single cancer cell. You appear completely free of CLL.”
Mr. Olson reported that he has since lived a “full life,” kept working, and has even run some half-marathons.
Dr. 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.”
Dr. June, Dr. Melenhorst, and Dr. Porter reported holding patents related to CAR T-cell manufacturing and biomarker discovery.