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It's not hard to see how important this trial is. Everybody you talk to in the spinal-cord community worries about patients traveling overseas for risky, ambiguous cellular therapies, forking out tens of thousands of dollars and praying for a miracle. Kate Willette, whose husband was paralyzed in a skiing accident eight years ago, understands the desire to get better. Earlier this month she attended a gathering of researchers and the spinal-cord community where she watched Keirstead, dressed in jeans and an untucked white shirt, tell the crowd, "I can't promise you anything, but we're doing our damnedest." Willette, who moderates an online forum for families of people with spinal-cord injuries, says Keirstead is cautious, but exudes a welcome sense of confidence. "I can't tell you how exciting it is," she says of the Geron trial. "Either it's going to work or it's not, but we'll have something to hang our hats on." Of Keirstead, she says: "He's a rock star."
Keirstead's animal research was published in a peer-reviewed journal, but much of Geron's other preclinical documentation has been under wraps; only the company and the FDA know what it says. That leaves some researchers feeling unsettled. What's the precise mechanism of action? Could the cells prompt an immune response in patients? Or generate certain fibers that cause pain? Should Geron perform experiments in other types of animals before they go to humans? John Gearhart, a pioneering researcher whose early stem-cell work was funded by Geron and who is now director of the Institute for Regenerative Medicine at the University of Pennsylvania, says he wants the trial to succeed, but he constantly worries about safety. Gearhart wonders if there might not be some number of cells in Geron's therapy that don't behave as scientists want them to—they don't differentiate themselves into the desired cell type after they're injected. Research has shown that such cells may form tumors or interfere with normal function, and it is difficult to say for sure how many months or years later that might occur. For Larry Goldstein, director of the University of California, San Diego, stem-cell program, a key issue is risk versus benefit. While paraplegia is by no means easy to endure, people do adapt and can have fulfilling lives. What if the treatment causes harm? Ideally, Goldstein would have liked the first human embryonic-stem-cell therapy tested in a disease that leads inexorably to death, like ALS. "I'm nervous," he says. This first trial is "a high-wire act."