In the early days of transplantation research, doctors didn’t even realize GVHD could happen, Flowers said. In some of the first transplants performed, researchers saw that patients who’d received donor cells from an identical twin had fewer side effects after the transplant than those who’d gotten a transplant from a non-twin sibling or from an unrelated donor — but those with twin transplants were also much more likely to relapse.
Researchers eventually realized those “side effects,” which they first termed secondary disease and later GVHD, were due to the donor cells attacking healthy tissue. But for a while, they didn’t realize the two attacks — against cancer cells and against the normal cells — could be separated. For many years, doctors told their patients a little GVHD was good, that it meant the transplant was working. Like yin and yang, GVHD went hand-in-hand with an effective transplant — or so the thinking went at the time.
Recently, though, that dogma is shifting. Researchers and physicians are realizing they can divorce the powerful graft-vs.-tumor effect, which rids patients of cancer cells, from the damaging and sometimes deadly effects of GVHD. Again, those efforts come back to quality of life for survivors, said Lee.
“When I started in this field 20 years ago, most people were focused on just getting their patients through transplant,” Lee said. “Now, we do want it all. We want them to have good quality of life in addition to not having their disease comes back, and a lot of that hinges on whether they get chronic GVHD or not.”
Preventing chronic GVHD
Several research efforts are aimed at preventing GVHD before it even crops up, Lee said. At the Hutch, clinical researcher Dr. Marie Bleakley is leading studies that separate out some immune cells from the donor blood or bone marrow before the transplant. Those clinical trials are based on a growing body of research that has sifted out the specific cells and molecules responsible for triggering GVHD. Bleakley’s studies have shown promising initial results in preventing chronic GVHD, dropping the rates of transplant patients who develop the condition from about 40 percent to less than 10 percent.
Researchers have observed that cord blood transplants, using blood cells from donated umbilical cords rather than blood stem cells from adult donors, result in lower levels of moderate to severe chronic GVHD — about 10 to 20 percent vs. 40 percent. Other studies have also found that giving patients the immune system-suppressing drug cyclophosphamide as a preventive measure drops the risk of chronic GVHD by about 50 percent. Flowers and her colleagues recently found that in addition to lower rates of chronic GVHD, the disease was shorter in recipients of cord blood transplant and in those who had received cyclophosphamide.
Hill’s clinical work also focuses on GVHD prevention, building off the preclinical studies he and others led identifying the specific cells that drive the disease.
“What I’m really interested in is trying to develop prevention strategies for GVHD that involve much more targeted therapies,” he said. “That’s where I see the field moving, away from broadly immune-suppressive drugs and more toward targeted immune suppression that don’t have the same side effects.”
The next phase — getting even more targeted
Researchers are also coming to understand that different patients’ diseases may be even more distinct from each other than they’d previously realized.
“The real question now is, ‘Is all chronic GVHD the same?’ and it’s probably not,” Hill said. “So one treatment’s probably not going to fit all in chronic GVHD.”
Understanding the differences will entail identifying specific proteins and cells that are active in an individual patient, and tailoring that patient’s treatments accordingly. That will involve new blood tests to predict which treatment a given patient is likely to respond to, Hill said. But in parallel, researchers are also trying to identify targeted treatments that may work better for specific organs affected by GVHD, Lee said.
She and her colleagues at the Hutch are poised to launch a number of clinical trials testing therapies specifically for patients with just one form of chronic GVHD, such as scleroderma or lung GVHD.
In the coming years, “I think we’ll see even more targeting of specific kinds of chronic GVHD,” Lee said. “We won’t just treat all people with chronic GVHD the same. Instead, we’ll use markers in their blood and what organs are involved to intelligently select a treatment based on the kind of chronic GVHD they have.”
Those differences are likely part of the reason that combatting chronic GVHD has proven so difficult, Lee said.
“Recent years have been exciting but I wish I could point to a breakthrough that will work for most people. It’s just a very hard disease,” she said. “But there’s been a lot that’s happened the last couple years that makes me hopeful we’ll have better treatments ahead.”