Researchers from Human Genome Sciences reported on Wednesday that they have managed to produce an experimental antibody treatment that helps rabbits and monkeys survive a normally lethal dose of anthrax bacteria.
Known as ABthrax or raxibacumab, the treatment works by inhibiting the deadly toxins released by anthrax cells from damaging and destroying healthy cells.
Researchers say the treatment has been designed to work in conjunction with existing antibiotic treatments in order to increase the chances of survival in people infected with anthrax.
“This adds an important new treatment to the arsenal of things we can use in treating anthrax,” said Sally Bolmer, a researcher with Human Genome Sciences whose study appears in the New England Journal of Medicine.
While anthrax is more commonly encountered in animals than in people, humans can also contract it by inhaling or ingesting bacterial spores. In recent years, public fears surrounding the disease have largely focused on its potential use as a biological weapon, particularly given that it can be transported easily and obtained relatively inexpensively on the black market.
If detected early enough, antibiotics are typically effective in treating anthrax infections. By the time most patients develop symptoms, however, the bacteria has already begun releasing toxins into the body, making it nearly impossible to treat. Historically, mortality rates have been as high as 92% for those who seek treatment after symptoms have already developed, a statistic that sinks to 45% when treated early.
While traditional treatments have focused on neutralizing the bacterial cells, the new ABthrax treatment has been engineered to bind to the chemical toxins themselves, rendering them innocuous.
“This is a different mechanism of action than antibiotics, which have been the mainstay of treatment,” Bolmer explained.
In their study, Bolmer and her research team reported that some 44 percent of rabbits and 64 percent of monkeys that received a single treatment of raxibacumab managed to survive anthrax exposure some 200 times more potent than the average lethal dose.
“That’s a very significant survival benefit. In other areas of medicine like cardiovascular disease, an improvement in mortality of 1 or 2 percent is considered medically important,” she said.
The study also gave the treatment to 300 healthy human subjects to test for possible side effects. While a few instances of headaches and soreness around the injection site were observed, no major side effects were detected.
Human Genome Sciences has already submitted the results of the study to the FDA. The company is the first to apply for approval under a new piece of legislation that allows pharmaceutical manufacturers to submit data from animal studies for infectious disease that are problematic to study with human patients.
Known as the “animal rule”, drug companies are required to demonstrate the effectiveness and safety of a new chemical on at least two species of animals.
Since 2006, Human Genome Sciences has been collaborating on their research with a special arm of the U.S. Department of Health and Human Services called the Biomedical Advanced Research and Development Authority.
The company has already supplied some 20,000 doses of ABthrax to the U.S. Strategic National Stockpile for emergency use in the event of an anthrax attack.
Significantly, eight years of research on the treatment began after the infamous 2001 anthrax attacks that took the lives of five U.S. citizens.
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Image Caption: Color-enhanced scanning electron micrograph shows splenic tissue from a monkey with inhalational anthrax; featured are rod-shaped bacilli (yellow) and an erythrocyte (red). Courtesy NIH
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