Eye Study Is a Small but Crucial Advance for Stem-Cell Therapy
The results show that the treatment can be safe, but whether it can be effective is another question.
The first published clinical trial of stem-cell therapy is a tremendous boon to the company leading the experiment—but it’s only a small step forward for the field.
In a paper published this week in The Lancet, scientists from the David Geffen School of Medicine at the University of California, Los Angeles, and from Advanced Cell Technology, in Marlborough, Massachusetts, reported that two patients each safely received injections of embryonic stem cells into an eye.
Stem-cell research in patients suffered a major blow recently, when one leading company, Geron, pulled out of a pioneering spinal cord repair study. The new study is more limited in scope, focusing on treatment that is easier to study and less problematic.
The new study was written three months after treating the patients, both of whom have degenerative eye diseases and limited sight. Another three months has now passed, and Robert Lanza, chief scientific officer of Advanced Cell Technology, says both are still doing well, with no apparent side effects.
Lanza says Advanced Cell Technology would not commercialize the work itself, but would look to partner with a company that would.
The intent of the study was to show that the treatment is safe, not to look at its effectiveness. But Lanza, the paper, and a related commentary also published in The Lancet all cited the women’s reports of benefits from the procedure. One woman’s vision improved enough to see a hand waved in front of her face; the other climbed from 20/500 to 20/320 on an eye chart.
Kevin Eggan, an associate professor of stem cell and regenerative biology at Harvard University, says he’s surprised that The Lancet published such preliminary results, and that scientists are talking about the treatment’s effectiveness at such an early stage of research.
“I wouldn’t say the data is super convincing that these cells are doing much,” says Eggan, also a principal investigator with the Harvard Stem Cell Institute. Only two patients were studied, and in one of the patients, the cells appeared to have had no biological effect, despite her report of improvement. “For myself, I would have felt a lot more comfortable if I had several people telling the same story.”
This research is important, Eggan says, because it shows that at least some patients can safely receive cells derived from human embryonic stem cells. The implanted cells did not grow uncontrollably and did not trigger development of a teratoma—a benign tumor that contains other bodily tissues. “The cells are there, they’re surviving, and they’re persisting. They’re not growing out of control, and they’re not growing a teratoma.”
In the study, human embryonic stem cells were coaxed into becoming retinal pigment epithelium, or RPE cells. They were carefully examined for impurities or potential dangers, and then injected into one eye in each patient. The two received 50,000 RPE cells each. The next round of patients will receive 100,000 RPE cells, and later patients in the trial will be given 200,000 cells each.
Of the 24 people in the trial, half have dry, age-related macular degeneration—the most common cause of vision loss in older Americans—and half have Stargardt macular dystrophy, a far rarer disorder that strikes children and teenagers. There are no effective medical treatments for either condition. Lanza says the company will soon begin another round of research in the U.K. involving 24 patients with the same conditions.
The therapy is aimed at preventing loss of photoreceptors in the eye. Because the trial patients have already lost most of their receptors, they are less likely to benefit than people who have retained more vision, Lanza says.
The eye is a logical organ for testing stem-cell therapies because it is immunoprivileged, meaning it is unlikely to mount an immune response to foreign cells. The eye is also easy to see into, to check for progress and problems.
Ellen Feigal, senior vice president of research and development for the California Institute of Regenerative Medicine, describes the new study as “good for the field.”
“It’s a very good initial step in the process to evaluate a therapy for its safety and effectiveness,” she says.