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STANFORD, Calif.—Approximately 800,000 people have a stroke annually in the United States, and roughly 85 percent of those strokes are ischemic—that is, they occur when a clot forms in a blood vessel and cuts off blood to part of the brain. Intensive damage usually results from these strokes, ranging from loss of motor function to loss of speech, depending on the magnitude of the stroke and where in the brain it happens. And while there are some approved therapies for ischemic stroke, they require application within a few hours of the stroke, which means few patients benefit during the acute phase of stroke. While some functionality can return, it is often limited, and it is generally believed that any recovery that will take place happens within six months after the incident.
But based on the results of a recent study led by the Stanford University School of Medicine, that might not be the case.
A small clinical study meant to test the safety of a stem cell treatment for stroke sufferers aptly demonstrated its safety and more, with unexpected positive results in the study participants.
The study consisted of 18 individuals who had suffered a single stroke, with the average age of 61. All of the participants had suffered strokes in the brain's outermost cortex, resulting in severely diminished motor function, and their strokes took place between six months and three years before the trial. The treatment consisted of drilling a small hole in the skull to facilitate direct administration of adult human mesenchymal stem cells (known as SB623 cells) to several spots at the periphery of the stroke-damaged area. These stem cells were derived from the bone marrow of two donors, then modified to alter their ability to restore neurological function. They were provided by biotechnology company SanBio Inc., which also funded and helped to design the trial.
Mesenchymal stem cells represent one of the more ideal subtypes of stem cells, for a variety of reasons: they have not been found to have a propensity for forming tumors, they don't appear to trigger immune reactions even when coming from unrelated donors and they are easily harvested from bone marrow.
Following treatment, patients were monitored through blood tests, clinical evaluation and brain imaging. Participants saw no side effects attributable to the stem cells, nor any life-threatening adverse effects linked to the treatment procedure. While the implanted cells do not survive long in the brain—preclinical studies show that they begin to disappear after one month and are gone two months post-procedure—patients demonstrated significant recovery within a month after treatment and continued improving for several months afterward, sustaining the improvements at six and 12 months post-surgery.
Specifically, there was an overall 11.4-point improvement on the motor-function component of the Fugl-Meyer test, which measures patients' movement deficits. One patient, who suffered a stroke in May 2011, had little use of her right arm after her stroke, and her right leg faced similar issues, leading her to depend heavily on a wheelchair. Following the treatment, she said her right arm and leg “woke up.”
Though the results are very encouraging, Dr. Gary Steinberg, professor and chair of neurosurgery at Standford and lead and senior author for the paper, is not getting carried away just yet.
“This was just a single trial, and a small one,” he pointed out. “It was designed primarily to test the procedure’s safety. But patients improved by several standard measures, and their improvement was not only statistically significant, but clinically meaningful. Their ability to move around has recovered visibly. That’s unprecedented. At six months out from a stroke, you don’t expect to see any further recovery.”
Still, a particularly promising result was the fact that the improvements seen were independent of patient age or their condition at the beginning of the trial.
“Older people tend not to respond to treatment as well, but here we see 70-year-olds recovering substantially,” Steinberg said. He is the Bernard and Ronni Lacroute-William Randolph Hearst Professor in Neurosurgery and Neurosciences at Stanford. “This could revolutionize our concept of what happens after not only stroke, but traumatic brain injury and even neurodegenerative disorders. The notion was that once the brain is injured, it doesn’t recover—you’re stuck with it. But if we can figure out how to jump-start these damaged brain circuits, we can change the whole effect. We thought those brain circuits were dead. And we’ve learned that they’re not.”
Another trial is now underway to further test these results, with Steinberg as the principal investigator. The randomized, double-blinded multicenter Phase 2b trial is actively enrolling participants, with a goal of 156 chronic stroke patients.
“There are close to 7 million chronic stroke patients in the United States,” Steinberg remarked. “If this treatment really works for that huge population, it has great potential.”