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cells could be just around the corner. The company says it spent
$45 million on amassing the evidence needed to persuade the U.S.
Food and Drug Administration to allow the first-of-a -kind human
trial to proceed—an effort that included animal tests it calls exhaus-
tive. “The agency told us our application was the largest they’d ever
received,” says Geron’s interim CEO, David Greenwood, sweeping
his hand over a double-length conference table that once creaked
under the weight of all 22,500 pages.
Geron’s success in getting the FDA to green-light the trial has
already triggered a small explosion of other embryonic-stem-cell
studies. Advanced Cell Technology, a smaller competitor in Marl-
borough, Massachusetts, has been cleared to begin two trials that
will involve replacing cells in the eyes of people going blind from
macular degeneration: lab workers will use stem cells to manufac-
ture a type of retinal pigment cell that the disease kills off. Next in
the pipeline is a startup company’s effort to transplant lab-grown
replacement nerves into infants with a fatal genetic disease called
spinal muscular atrophy. That trial is planned by California Stem
Cell, which has raised $10 million from wealthy donors and has
signed up Keirstead as its chief scientific advisor. Keirstead, bound-
ing through the still empty offices with a tape measure in hand,
says he is considering leaving his lab to join the company full time.
He thinks that with the Geron trial now under way, other human
studies can advance much more quickly and cheaply.
But that depends on what happens in the Geron trial. And
even some of stem cells’ most ardent advocates worry that things
may be moving too fast. Arthur Caplan, a bioethicist at the Uni-
versity of Pennsylvania and a defender of stem-cell research (see
Q&A, September/October 2006), calls the Geron study poorly
designed and says it should never have been allowed to proceed.
“ This is nuts and hugely risky,” says Caplan. “ The animal stud-
ies are not adequate to justify the trial.” Those studies provide
too little proof of safety, he contends, and Keirstead’s original
findings in rats offer thin evidence that people will be helped.
Looming large is the history of gene therapy, another advanced
biomedical technology, which badly misfired when a young volun-
teer named Jesse Gelsinger died in a safety study in 1999. Caplan,
who was close to those events, sees worrisome similarities (see
“The Glimmering Promise of Gene Therapy,” November/Decem-
ber 2006). “If they get an adverse event, there will be hell to
pay,” he says.
Spinal-cord injuries cause paralysis by killing off nerves that trans-
mit sensory impulses and leaving others stripped of their myelin
sheath, the layer of fatty insulating material that helps nerve signals
travel. Geron manufactures its treatment, known as GRNOPC1,
by coaxing embryonic stem cells to form what are known as oli-
godendrocyte precursor cells. Those cells are bottled and frozen,
and Geron scientists believe they may help restore some degree
of sensation and limb movement to patients if transplanted soon
after a spinal-cord injury. That is because oligodendrocyte cells
produce myelin and may serve other purposes as well, such as
encouraging new blood vessels to form. In Geron’s initial human
trial, designed to test the safety of the treatment, doctors plan to
inject two million cells each into the spines of 10 people whose
legs have been paralyzed in accidents.
Will the treatment be a cure? The odds are against it. In gen-
eral, most new treatments, never mind highly experimental ones,
bomb out early. What’s more, GRNOPC1 faces an uphill fight
against medical dogma, which says that it’s impossible to reverse
damage to either the brain or the human spinal cord. That means
few experts expect a miracle from GRNOPC1. Richard Fessler,
a surgeon at Northwestern Memorial Hospital in Chicago who
is leading patient recruitment for the Geron trial at seven U.S.
medical centers, calls the study a “rational” attempt to reverse
spinal-cord damage. But he cautions against expecting too much.
“We wouldn’t be doing this if we didn’t have hope, but I don’t want
to instill false hope,” Fessler said in a news conference in May,
after the second patient received the treatment. “I’m not going
to go to one of these patients and say, ‘We’re going to give you a
transplant and you’re going to walk.’”
Still, some patients are clamoring to join the Geron study, even
though only people with extremely recent injuries—the kind that
lab research suggests might be helped—are allowed to partici-
pate. A Dutch man offered Geron $1 million to treat his son, and
Keirstead says he received an even bigger offer from a paralyzed
Texas millionaire. “He said he’d pay me whatever millions it takes
looming large is the history of gene therapy, which badly misfired
when a young volunteer named Jesse gelsinger died in a safety
study in 1999. Arthur Caplan sees worrisome similarities. “if they
get an adverse event, there will be hell to pay,” he says.
July11 Feature Stem Cells.indd 54
6/8/11 10:04 AM
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