Mexican Drug May Solve U.S. Antivenom Shortage

Part 2: Horses Key To Making Antivenom Up For FDA Approval

The last multimedia story in a series looking at the lack of antivenom to treat scorpion bites throughout the Southwest.

Toxicologists refer to the American southwest as the "Venom Belt". The region is home to thousands of venomous animals, some which can be extremely dangerous to humans.

Scorpion stings alone affect thousands of people each year but only one species, centruroides sculpturatus, or the bark scorpion, is dangerous to humans. It lives mainly in Arizona but has recently turned up in parts of New Mexico and southern Nevada. The VIPER Institute at the University of Arizona in Tucson estimates around 250 severe stings occur each year. Most of those are children, who, without treatment, can die from a bad sting.

The only way to treat a severe sting in the United States is in the intensive care unit. The bark scorpion's venom affects the nervous system by causing muscles to twitch uncontrollably. The venom can affect a person's lung muscles making it difficult to breathe. So people with bad stings are placed on ventilators and given high doses of sedatives to help with the muscle contractions.

The other option is to use antivenom. But the United States ran out of its supply seven years ago. The U.S. formula was made by immunologist Marilyn Bloom long before the existence of federal regulations. She retired in 1999 and left only a small supply of antivenom, which ran out in 2004.

At around the same time Bloom retired, an American pediatrician named Leslie Boyer was invited on a trip to Mexico by National Geographic television. They were going to film a documentary on venomous animals and asked Dr. Boyer along because she is also a toxicologist.

During that trip, Dr. Boyer witnessed a lab demonstration that would change the course of her professional life for the next 12 years.

“I watched as scorpion venom was injected by needle into a rodent,” she said. “And this little mouse got sick very fast... it frothed at the mouth, it was blue, it was pretty scary to watch.”

That mouse looked a lot like some of Dr. Boyer's worst scorpion sting patients. What happened next was a breakthrough for her.

“The professor in whose lab we were studying pulled up a syringe of a mysterious material, and injected that into the mouse,” she said. “And before my very eyes, in less than 15 minutes, that mouse transformed from a blue moribund twitching pile of fur to a happy mouse.”

Dr. Boyer had just witnessed the effects of a drug called Anascorp. It's just one of seven antivenoms made by the Mexican company Instituto Bioclon. Knowing that the United States faced a future without its own antivenom, Dr. Boyer made it her personal mission to bring the drug to the United States.

To do that she had to convince U.S. doctors of the effectiveness and safety of Anascorp and then file the necessary paperwork with the US Food and Drug Administration (FDA) to begin a clinical study of the drug. She also had to find sufficient funding to support the study and work around cumbersome international customs regulations.

Dr. Boyer finally launched a clinical trial of Anascorp in 2004, about two months before the American antivenom ran out . Twenty-seven hospitals in Arizona and one in Las Vegas participated. Hundreds of doctors and nurses volunteered their time while Instituto Bioclon donated bottles of Anascorp at no cost. Since then, nearly 2,000 Americans have received the drug. Now Anascorp is in the final evaluation phase by the US FDA.

(EDITOR'S NOTE: The antivenom has been approved by the FDA.)

“I was expecting a baby on that first trip to Mexico,” Dr. Boyer said. “My daughter is going to be twelve this August. She's told me that if this drug could be approved for her birthday it would be the best thing ever.”

The youngest American patient to receive the drug so far was only 25 days old when she was bitten by a scorpion in her crib. Her name is Ryleigh Wagly and is now four years old. The Wagly family lives in a rural village in eastern Arizona, more than two hours away from the nearest ICU.

Luckily, a small clinic in the nearby mining town of Morenci was part of the clinical study of Anascorp. Dr. Fred Fox was the physician who treated Ryleigh. He said the antivenom helped saved her life.

“(The drug) has been very successful for us,” Fox said. “It's allowed us to treat patients who either could have died or been seriously ill and would have been...sent to the intensive care unit. Now, we can treat them and actually send them home from here.”

Scorpion stings are just one part of a much larger problem. The World Health Organization (WHO) has said venomous animal bites and stings are a neglected public health issue.

In the United States alone, there is a severe shortage of rattlesnake and black widow spider antivenom. Texas and Florida are set to run out of antivenom for the dangerous coral snake this year. Also, there is no U.S. manufacturer for brown recluse spider bites.

The shortages are due to economics. Antivenom, like vaccines, is expensive to make and there simply aren't enough patients to guarantee a profit for a drug company.

Cynthia Lewis-Younger is the medical director of the Florida Poison Information Center in Tampa where coral snakes are a problem. She, like other toxicologists, has been waiting years for a stable source of good quality antivenoms to become available in the U.S.

“Around the world there is a huge need for good antivenoms,” she said. “We’re not the only country facing (shortages). There are many, many people across the world who die from significant envenomations. And antivenoms have saved many many lives.”