When someone suffers a stroke, the cells at the center of the catastrophic brain damage may be too injured to be saved.
But scientists are striving to rescue the area that surrounds the wound using stem cells -- a new approach that offers hope that these supported cells can take over the work of their dead comrades.
There's no proof yet that this novel approach will work in humans. Carefully controlled studies of its effectiveness won't be complete for several years.
However, it shows signs of safety and effectiveness in animals, according to new data presented at a weekend conference on brain injury sponsored by the Santa Clara Valley Medical Center Rehabilitation Research Center.
No ill effects have been seen in the first dozen patients treated in a study at Stanford University and four other research hospitals, using a product called SB623. The Mountain View-based biotech company SanBio produces it from adult, not embryonic, stem cells culled from the bone marrow of healthy donors. The cells are genetically modified and given a booster that seems to improve their function.
Tests in mice show that symptoms improve, enabling the animals to eat and walk more normally over a six-month period.
In the lab, SB623 is proven to secrete chemicals that boost healing and reduce dangerous inflammation.
"It is going well," said SanBio researcher Casey Case, who presented the data at the Santa Clara Valley Brain Injury Conference, held in San Jose. "It is not cell replacement, but works through an indirect mechanism -- something that helps improve the tissue that remains," he said.
Many other biotech companies are trying a similar approach.
Stroke is the third largest cause of death and the single largest cause of adult disability in America, causing paralysis, impaired thinking, speech and motor control, according to the U.S. Centers for Disease Control and Prevention.
A stroke, sometimes called a brain attack, occurs when a clot blocks the blood supply to the brain or when a blood vessel in the brain bursts. This kills brain cells responsible for an array of physical and mental functions.
Most current therapies aim at limiting the damage within three hours of the attack.
This new approach could offer hope to those with chronic strokes, or who have had symptoms for months or even years. There is a huge unmet need for effective treatment in these patients. A successful clinical trial would have enormous implications.
Cell-based treatment for strokes is based on this concept: Brains try to heal themselves, but need help.
"Around the stroke, cells are still alive, but they're in a hostile environment," said Case. They retract from the threat. And their connections to adjacent cells, called synapses, are damaged. This makes rehabilitation more difficult because damage interrupts the internal communication needed to think, talk walk.
Cell-based therapies like SB623 seem to create a healing environment, reducing inflammation and exuding supportive growth chemicals. Brain cells adjacent to the damage extend themselves, Case explained, "and new synapses form."
The new cells don't replace the injured cells; in fact, they seem to disappear from the brain within a month. But their introduction seems to help, even after they're gone.
"Cell-based therapies are in their infancy. Every day is a learning experience," said Stephanie Kolakowsky-Hayner, director of rehabilitation research at Santa Clara Valley Medical Center and the chairwoman of the conference.
"The potential to regrow brain cells is very exciting," she said.
SB623 is built from adult, not embryonic, stem cells culled from the bone marrow of healthy donors. The cells are genetically modified, given a booster that seems to improve their function.
Between 2.5 million to 10 million cells are surgically injected directly into patients' brains at the site of the stroke.
Researchers are cautious, because more than 100 other drugs and agents have showed usefulness in animals, but have never successfully worked in humans. SanBio's Phase 1 safety study is expected to be completed by the end of the year. Even though it is just a safety study, the company also hopes to evaluate any improvement in motor function and cognition during the two years following implantation with the cells.
It must also compare outcome of test subjects with untreated people, because stroke victims sometimes improve on their own. If the U.S. Food and Drug Administration gives them the green light for further testing, the company will then move forward into Phase 2, which will involve 100 to 200 patients. Case said a final Phase 3 trial, required before marketing, would involve hundreds of patients and about five years."It's important because stroke can create lifelong disability," Kolakowsky-Hayner said. "It is not something that current medicine can fix."
Contact Lisa M. Krieger at 650-492-4098.