Snake venom delivers hope

15.05.2008 04:00 Health - Source: JS Online

If you talk to Del Lukaszewicz or Alma Cox, they are sure that snake venom was infused into their veins to treat their strokes.

Officially, neither they nor their doctors know whether they got simple saline or an experimental clear liquid derived from the venom of the Malayan pit viper. Both women were treated as part of an unusual clinical trial going on at two Milwaukee area hospitals.

It likely will be another year and a half before they find out what was used to treat them and, more importantly, whether it actually works.

But the drug has generated a buzz both here and nationally, in part because it could offer a sorely needed option for treating the vast majority of stroke patients who get to the hospital too late for the conventional treatment - a clot-busting drug that must be administered within three hours of the onset of symptoms.

The drug, known as Viprinex (ancrod), can be given by IV up to six hours after symptoms begin.

"Going from three hours to six hours . . . would allow a lot more people to be treated," said Gary Abrams, an associate professor of neurology at the University of California San Francisco. "That in itself would be a great advance."

However, the main concern with Viprinex, as has been the case with the only approved drug, t-PA, is the risk of bleeding in the brain, said Abrams, who is not a part of the study.

"It's tricky to use, to make the benefit greater than the risk," he said.

Viprinex is an enzyme that is obtained from the snake venom. It reduces levels of fibrinogen, a sticky coagulant in the blood that is the main protein involved in clotting.

The venom of the Malayan pit viper, a snake with long fangs, causes extensive bleeding.

It is believed that Viprinex improves blood flow to the brain in three ways:

It reduces fibrinogen levels, which inhibits growth of the clot. It reduces the thickness of blood, allowing it to flow more easily to blood-deprived areas of the brain. And it activates the body's natural clot-dissolving ability, which may help restore blood flow.

"This stuff is potent," said Warren Wasiewski, a neurologist and vice president and chief medical officer with Neurobiological Technologies, the California company that is funding the clinical trial of Viprinex.

Lower dose works better

Indeed, the drug may have been too effective, causing unacceptable rates of bleeding in the brain in earlier clinical trials.

On Wednesday the company presented research at a stroke conference in France suggesting that a new dosing regimen of the drug should improve its effectiveness and reduce the rate of bleeding in the brain.

The drug now is infused over a three-hour period rather than five to seven days.

"We found that a shorter infusion would do the trick," Wasiewski said.

The drug was close to proving it was beneficial several years ago, but because of problems with bleeding its development was temporarily halted, said Ralph Sacco, a professor and chairman of neurology at the University of Miami Miller School of Medicine.

Sacco, who is not a part of the study, said he was pleased to see that the company has revised the protocol for the clinical trial.

"In the past, we gave up on drugs when there was a glimmer of hope," he said.

Up to 1,300 stroke patients at hospitals around the country, including Aurora St. Luke's Medical Center and Froedtert Hospital, where Lukaszewicz and Cox, respectively, were treated, are expected to be enrolled in the trial.

In addition to using a drug derived from an unconventional source - snake venom - the trial is unusual in that two major hospitals in the area are taking part in the research. That means stroke patients from a large area could be offered the opportunity to be in the trial.

Venom or placebo?

Under the design of the trial, there is a 50/50 chance that patients will get the drug or a saline placebo.

Lukaszewicz, a 71-year-old south side resident, says she is certain she got the real thing.

On April 1 she was at home when she started feeling queasy. She sat down on a chair in her living room.

"That's all I remember," she said. "I lost three days."

During that time she was unable to move or speak.

Arvind Ahuja, a neurosurgeon at St. Luke's, told Lukaszewicz's husband, Paul, there were three options:

Do nothing, go into her brain through an artery with a device that could break up the clot, or enroll her in the Viprinex study.

Ahuja said that in patients with her kind of stroke there is about a 50% chance of dying in the first 30 days.

Since enrolling in the study, Lukaszewicz has recovered nearly all of her speech and a substantial amount of movement. She said she is hoping that with continued therapy she will be able to walk with a cane.

She said she is convinced that she got the drug because of her dramatic improvement.

The trial is double-blinded, meaning neither patients nor doctors know who gets the drug, but Ahuja said he has no reason to doubt her.

"She has really done well," he said. "If I had to guess, I would say, 'yes.' "

Likewise, Cox, who had her stroke in March 2007, said she believes she got the drug after she was taken to Froedtert Hospital.

Cox, 75, had lost a considerable amount of movement on the left side of her body. But three days after she was treated she was able to move normally, she said.

So far, the hospital has not had any cases of bleeding in the brain, said Michel Torbey, an associate professor of neurology and neurosurgery at the Medical College of Wisconsin who practices at Froedtert.

"In general, we've seen patients who have done very well, and we've seen patients who have stayed about the same," he said.

Because so few people get to the hospital early enough to get t-PA, another drug that can be administered by IV beyond six hours is needed, he said.

"As far as a quick (drug) therapy, there is nothing else out there," he said. "We definitely need to fill that gap."

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