Early results from two embryonic stem cell-based trials show promise

Yesterday, the company Advanced Cell Technology announced that two people in their clinical trials testing an embryonic stem cell-based therapy for forms of blindness is not only safe so far, but shows tentative early signs of restoring some vision in two patients. The work was published online January 23 in the journal The Lancet.

Of the two women discussed in the paper one had macular degeneration, the leading cause of blindness, and the other had the most common form of blindness in children, called Stargardt’s macular dystrophy. Both were participating in phase 1 trials testing cells derived from embryonic stem cells as a possible treatment for their blindness. All phase 1 trials are primarily designed to make sure a therapy is safe, but the researchers do also look for signs that the therapy might be effective. (We have more information about the phases of clinical trials on our website.)

The preliminary news that two women in these trials reported some improvements in vision warrants some cautious optimism. For those of us who have been following the field since the discovery of embryonic stem cells in 1998, this paper is a milestone. It’s the first published paper showing that—at least in this small number of patients for the first few months—the cells are safe.

However, two patients isn’t enough to show whether the therapy actually works. In fact, in a New York Times story Steven D. Schwartz, a professor of ophthalmalogy at UCLA's Jules Stein Eye Institute, who is leading the research, said there was evidence that at least one of the two patients might have experienced a placebo effect. Sorting out the real improvements from the placebos or short-term changes takes time, which is why clinical trials are set up to follow patients for several years. Only after many more people receive injections of the cells and are followed for several years will we know that the cells were effective.

A story by NPR quoted Schwartz:

Schwartz and his colleagues stressed that the findings are extremely preliminary and it's far too early to know anything for sure. The patients could continue to improve, or their vision could deteriorate again, he said. Many more patients will be needed to be treated for far longer to know whether the therapy is really safe and responsible for any improvement.

"My job is to decrease suffering, and if we overstate this and raise hopes falsely and then it doesn't work out, it will hurt people rather than help them," Schwartz said.

The Stanford University medical blog has more commentary on this trial from law professor Hank Greely. He's been following the field of embryonic stem cell research since the beginning and says the news is, "at least, a little exciting – and in a field that saw its first approved clinical trial stopped two months ago, even a little exciting news is very welcome." You can read more on their blog.

These are the only two trials currently underway testing an embryonic stem cell-based therapy. Along with the rest of the stem cell community we’ll be watching the results, and following the additional trials that are expected to start in the next few years. It’s through clinical trials such as these that safe and effective stem cell-based therapies will eventually reach patients.

A.A.