EPO: A popular medicine for anemics holds promise for a range of other conditions, including stroke, heart attack and spinal cord injury
May 24, 2004
The Baltimore Sun
In 1987, neurologist Hannelore Ehrenreich noticed something odd in anemic patents being treated with a drug called erythropoietin. After taking the drug for just a few days, they seemed mentally sharper and more alert.
After several years studying the drug's effect on brain cells, she had an inspiration: Maybe the anemia drug could also heal brain damage caused by strokes.
Among colleagues, her theory was not a hit. "People laughed at me. They said I was crazy," remembers Ehrenreich, a researcher at the University of Gottingen in Germany. But 12 years later, her notion looks increasingly prophetic.
Erythropoietin, known as EPO, is showing promise not only for stroke, but also for a wide range of ailments including heart attack, multiple sclerosis, spinal cord injury, and nerve and intestinal problems. Some researchers think it could even prove helpful with schizophrenia and Alzheimer's disease.
EPO (pronounced EE-poe) seems to protect a variety of organs and tissues from harm, including the heart, the brain and nervous system.
"We're very excited about it because it has widespread and very potent activity," said neuroscientist Michael Brines, director of research at Warren Pharmaceuticals. The company is looking at EPO's ability to heal spinal cord and cardiac damage. Animals treated with the drug show "remarkable" recovery, Brines said.
EPO has been around for millions of years; it exists in a wide range of animals, including fish and humans. Three decades ago, in one of the first feats of genetic engineering, scientists created a synthetic version of the substance.
Since then, artificial EPO has become a popular medicine for increasing red blood cell levels in anemics. Because boosting these cells increases the amount of oxygen available to muscles and lungs, the drug has also been used by elite endurance athletes looking for an unfair advantage. Many national and international sports organizations have banned its use.
But in the past four years, researchers have realized that EPO can do much more. "It has a lot of potential in terms of preventing tissue death," said Johns Hopkins University cardiologist Gregg Semenza, who is studying EPO's effect on the heart. In studies of rats, it significantly decreased heart attack damage.
Another Johns Hopkins cardiologist, Joshua Hare, is studying EPO in pigs, whose hearts more closely resemble humans'. The data isn't in yet, but based on others' work and his own rat study, Hare has high hopes.
"It could greatly reduce the size of a heart attack, and the amount of damage," he said.
Surprisingly, some researchers say the two companies that make EPO seem less than enthusiastic about the drug's possible new uses. They accuse the companies, Amgen and Ortho Biotech, of showing little interest in funding new EPO research - possibly because new studies could uncover side effects that would endanger the drug's multibillion-dollar sales as an anemia drug. Both companies deny that.
Another possible reason for this alleged indifference: Recent studies looking at EPO as a cancer treatment found evidence that the drug may harm those patients.
Ironically, it is EPO's status as an approved drug that excites many researchers. Because it has been widely used for decades, researchers and regulators already know that it is relatively safe. "The beauty of EPO is that it's really well tolerated," said Ehrenreich, who is studying the drug as a stroke treatment.
She has found that patients given EPO injections within eight hours of a stroke did significantly better than those given a placebo. The EPO group had less brain damage and retained more functional ability: Only 14 percent ended up in nursing homes, compared with about half the placebo patients.
Ehrenreich recently started a larger study, which will examine more than 500 patients. If that trial goes well, EPO has a good chance of being approved in Germany, and perhaps the European Union, as a stroke treatment, she said.
In stroke and heart attack, EPO seems to work via the same mechanism, by blocking a process known as programmed cell death.
After many kinds of injury, cells around the damaged area destroy themselves in a misguided effort to promote healing. Ironically, this secondary suicide, called apoptosis, often causes more damage than the original injury. Somehow, Semenza says, EPO shuts off the cellular and genetic signals that trigger cell death.
Scientists have had little success in finding ways to stop apoptosis in humans. If EPO can do this, it would be a "huge deal, a new approach to tissue damage in general," says Hare.
Another promising area is spinal cord injury, which also involves programmed cell death. An Italian researcher reported that in rats with spinal cord injury, the drug markedly improved recovery. "It was one of the best effects we've ever seen," said University of Miami neuroscientist Dalton Dietrich, who is finishing a similar study funded by the National Institutes of Health. If the results of that study are positive, he likely will do a small human study next.
Protector of nerves
Even beyond blocking cell death, EPO seems to be a powerful protector of nerves, and researchers are studying it for use in patients with other neurological disorders. Johns Hopkins neurologists Sanjay Keswani and Ahmet Hoke are beginning an EPO study of people with transverse myelitis, an autoimmune disorder that damages the nervous system and often leads to paralysis.
Keswani believes the drug could treat a wide range of neurological diseases, including multiple sclerosis, a progressive paralysis that afflicts more than 350,000 Americans. "Any neurodegenerative disease, it's got potential," he said.
Others think EPO could be used to treat some chronic brain diseases. Ehrenreich, for example, is trying EPO on a group of 40 schizophrenics. In that illness, the cortex (the brain region responsible for logical thinking) gradually shrinks. EPO may thwart this neuronal loss, Ehrenreich says.
Neuroscientist Stuart Lipton is studying EPO's effect on HIV-related brain damage. In many cases, the disease causes mental problems, often to the point of a full-scale dementia resembling Alzheimer's.
Lipton, director of the Center for Neuroscience and Aging Research at the Burnham Institute in San Diego, says the early results look promising. He and others suspect that EPO could also be used to stave off Alzheimer's disease, the mysterious ailment that progressively kills neurons throughout the brain.
EPO does have limitations. For one, it can't be taken orally. Because it is a large protein that is broken down in the stomach, it must be injected. More importantly, in non-anemic patients it can raise red cell levels to the point that blood thickens and clots more easily, raising the risk of heart attack or stroke.
Particularly when EPO is used over months or years, as it would be in neurodegenerative disease, this effect might pose a serious hazard, researchers say.
To get around the problem, several companies, including Warren Pharmaceuticals, are working on versions of EPO that don't raise red cell levels. Lipton is also trying to combine EPO with other drugs, allowing doctors to use the hormone at lower doses.
He and others suspect that EPO isn't the only drug that will turn out to have benefits far beyond its original purpose. Many widely used compounds likely have hidden talents just waiting to be discovered, they say.
"There's a lot of stuff going on under our noses," said Hare, the Hopkins
cardiologist. "You've got to be looking for something to find it."
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