Doctors are tapping an unlikely source to help stroke patients.

The venom of the Malaysian pit viper is the potent ingredient found in an experimental drug called Viprinex now being tested in hospitals. When given intravenously, Viprinex has been shown to help dissolve clots that plug arteries and cut off blood flow to the brain.

According to doctors, the major advantage of Viprinex, which also thins the blood, is that it may be effective as long as six hours after a stroke patient’s symptoms begin. That would double the window of the only government-approved clot-busting therapy, called tPA, which must be given within three hours.

The fact that fewer than 5 percent of stroke victims get to a hospital in time has greatly limited the use of tPA, or tissue plasminogen activator. In addition, some doctors are hesitant to use the drug, which has been available since 1996, because it causes bleeding in the brain in about six percent of patients.

“What many investigators have been looking for is something that can dissolve clots with less risk of bleeding,” said Martin Gizzi, the neurologist who heads the New Jersey Neuroscience Institute at JFK Medical Center in Edison, which is participating in a clinical trial of Viprinex.

Under the trial’s guidelines, some patients will receive Viprinex, while others get a placebo. Doctors won’t know who got the real thing until the research – which is being conducted at 200 sites worldwide – has been completed in 2009. Patients are followed for 90 days after receiving the drug so their level of recovery can be assessed.

The drug is derived from the venom of the Malaysian pit viper, an aggressive snake that inhabits forest edges across much of Southeast Asia and grows to about three feet in length. The venom is frozen before being purified and converted to a drug product, explained Warren Wasiewski, the scientist overseeing the trial for Neurobiological Technologies Inc., the company that makes the drug.

“We haven’t had too many people get upset about the fact this is a snake venom,” he said when asked how patients or their families have reacted.

There have been three prior studies conducted on the same drug under a different name. Data from one of those trials, published in the Journal of the American Medical Association in May of 2000, found that patients who received the drug – called ancrod – intravenously over a 72-hour period had regained more function after three months than patients who got a placebo. While ancrod caused a slightly higher rate of bleeding in the brain – 5.2 percent compared with 2 percent for the placebo group – it did not cause an increase in deaths.

In the Viprinex trial, a lower dose of the drug is being given and the infusion time is shorter – three hours compared with 72 hours, Wasiewski said.

Doctors involved in the Viprinex study said they are screening patients very carefully, excluding anyone with a prior history of hemorrhage.

“We’re very strict on prior history,” said Gerald Ferencz, a neurologist who directs the stroke center at Community Medical Center in Toms River, N.J.

This is not the first time researchers have turned to normally shunned creatures in hopes of helping stroke patients. Earlier research – which did not lead to an effective drug – involved the saliva of vampire bats, on the theory that it might also help break up blood clots.

Larry Goldstein, who is director of the stroke center at Duke University and is familiar with the bat study, said while Viprinex holds promise, the watchword is still caution.

“We’ve been down this road in the past and the proof requires a well-conducted and completed clinical trial,” said Goldstein, who is also a spokesman for the American Stroke Association. “Anything besides that and it’s pure conjecture and the lay public’s hopes are raised over and over again only to be dashed.”

JM END STEWART

(Angela Stewart writes about health care for The Star-Ledger of Newark, N.J. She can be contacted at astewart(at)starledger.com.)

2008-02-07-STROKE-SNAKEVENOM

AP-NY-02-07-08 1231EST


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