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Horses Key To Making Antivenom Up For FDA Approval

Dr. Alejandro Alagon teaches biochemistry at Mexico's Autonomous National University. He is also a consultant to the Mexican company Instituto Bioclon.
Mónica Ortiz Uribe
Dr. Alejandro Alagon teaches biochemistry at Mexico's Autonomous National University. He is also a consultant to the Mexican company Instituto Bioclon.
How Horses Help Make Antivenom In Mexico

MEXICO CITY – In the past seven years, about 2,000 Americans stung by dangerous scorpions in the southwest have been treated with antivenom made in Mexico. The drug is called Anascorp and it's in final evaluation phase before the Food and Drug Administration (FDA), which is evaluating the drug for use in the United States.

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

Worldwide there is a severe shortage of all kinds of antivenom, partially, because there is little economic incentive for companies to produce it. Despite the expense and challenge, one company in Mexico has proved itself to be a leader in the production of anti-venom.


In Mexico, scorpion stings are a true public health dilemma. As recently as 20 years ago, hundreds of people across the country would die from severe stings. At one Red Cross clinic in Leon, in the state of Guanajuato, there can be up to fifty scorpion sting patients a night. That amount of traffic makes it hard for doctors to provide supportive care like in the United States where patients are put on ventilators and given a high does of sedatives. Instead the more practical solution was to come up with a quality antivenom that could be administered by via IV.

How Horses Make Antivenom
How Horses Make Antivenom

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

Instituto Bioclon, based out of Mexico City, began production of antivenom in the early 1990's. The products it developed and distributed around the country helped drop the death rate from severe scorpion stings to about 30 per year from the hundreds just a generation ago.

Dr. Alejandro Alagon started working as a consultant and researcher for Bioclon 15 years ago. He is also a professor of biochemistry at Mexico's Autonomous National University (UNAM). His office is located in a lab in the city of Cuernavaca, just south of Mexico City. Dr. Alagon, who loves to go spider hunting, needs to look no further than the outer pane of his office window where black widows nurse yellow egg sacks.

His fascination with venomous animals began when he was a kid growing up on his grandfather's ranch. One day one of his grandfather’s ranch hands was bitten by a vicious viper.


“You can imagine being a 6, 7-year-old kid, looking at that terrible wound with necrosis and tissue destruction,” Dr. Alagon said, recalling the snake bite. “His gums bled for hours and hours. He almost died.”

Today, his grandfather's ranch is actually helping cure people like the ranch hand who was bitten.

The 80-year-old Alagon ranch sits on 444-acres of verdant landscape in the south central state of Puebla. The air is sweet with the smell of ripe mangos and peeking out beneath the mossy soil are ancient Totonacan ruins. The ranch is home to 59 horses that belong to Instituto Bioclon. The horses are the source of the life-saving anti-venom.

Dr. Alagon's younger brother, Andres Alagon, oversees the horse ranch. The younger Alagon is a pediatrician that practices in the nearby city of Poza Rica, in the neighboring state of Veracruz.

To make anti-venom, the horses are progressively injected with a variety of animal venom over the course of four to six months.

For scorpion venom, the horses start off by getting a dose equivalent to half a sting. After six months, they will be injected with the equivalent of 100 stings. The horse's immune system responds by making antibodies against the venom. It's the way any mammal's immune system works. Instituto Bioclon uses horses because they are relatively healthy animals and easy to work with.

Once the horses are producing a sufficient level of antibodies ranch hands draw their blood. The plasma is separated out and eventually processed in Bioclon's labs for human use.

Because anti-venom comes from animal plasma, it often cause allergies in humans. But Bioclon uses a technology called fabotherapeutics, a process that removes the parts of molecules that cause allergies while leaving in the parts that are effective against the venom. In U.S. trials patients who were given Anascorp showed signs of recovery within two hours.

Dr. David Warrell, a professor of tropical medicine at the University of Oxford in the United Kingdom, has spent the past 40 years studying anti-venom treatments, including the drugs made by Bioclon. Anascorp, he said, is one of few anti-venoms that have been put through rigorous clinical trials.

“The results I think were quite clear cut,” he said. “They demonstrated the effectiveness and safety of this antivenom newly being considered for use in the United States.”

Bioclon is currently supplying antivenom in parts of South America and sub-Saharan Africa. The company is also in negotiations with the Moroccan government about supplying antivenom for the particular scorpion species native to that country.

Anascorp is currently in the final evaluation phase by the FDA, which could make a decision sometime this month. With antivenom vanishing off American hospital shelves, experts say the need for new products grows greater with each passing day.