WEDNESDAY, July 8, 2009 (HealthDay News) -- Scientists report that experiments in animals show that a new, monoclonal antibody drug might safely cure anthrax poisoning in humans.
Although antibiotics can kill the anthrax bacteria, they are not effective in killing the toxins produced by the bacteria. The new drug, raxibacumab, specifically targets those toxins once they enter the bloodstream. After an anthrax attack, people may not know they are infected until the toxins are circulating in their blood, and it may be too late for antibiotics alone to be effective, the researchers explained.
"This drug strengthens America's arsenal against bioterrorism that would work in the face of antibiotic-resistant anthrax bacterium," said lead researcher Sally Bolmer, senior vice president of development and regulatory affairs at Human Genome Sciences Inc., the company that developed raxibacumab.
The drug works differently than antibiotics, Bolmer noted. "It [also] acts more quickly than vaccines. So, it is complementary to both of those," she said.
"If we administered it at the time the animals were exposed to anthrax or even waited until their symptoms developed, we could improve survival in rabbits and monkeys," she said.
The same doses of the drug were given to humans and the drug was well-tolerated, Bolmer added.
The report is published in the July 9 issue of the New England Journal of Medicine.
In the study, researchers showed that a single dose of raxibacumab was an effective treatment for inhalation anthrax in both rabbits and monkeys.
The drug provided a significant survival benefit to animals showing signs of the disease. The animals were exposed to a dose of anthrax approximately 200 times the lethal dose, the researchers said.
In addition, raxibacumab was safe when given to human volunteers and could be used in a clinical setting in cases of life-threatening inhalation anthrax disease, Bolmer said.
Under a contract with U.S. Biomedical Advanced Research and Development Authority, the company has delivered 20,000 doses of raxibacumab to the U.S. Strategic National Stockpile for emergency use. Approval of the drug by the U.S. Food and Drug Administration is pending, Bolmer said.
Mingtao Zeng, an assistant professor in the department of microbiology and immunology at the University of Rochester Medical Center, said this study has provided solid data to support raxibacumab as a new candidate drug for biodefense and public health.
"The most encouraging finding is that raxibacumab appeared to be safe and well-tolerated, with reasonably high doses in the phase 1 human clinical trial, which had 333 healthy human volunteers," Zeng said. "I anticipate that raxibacumab can be used as a short-term prophylactic agent for protection against anthrax or as a therapeutic drug in combination with antibiotics for effective treatment of anthrax."
Dr. Gary Nabel, director of the Vaccine Research Center at the U.S. National Institute of Allergy and Infectious Diseases and author of an accompanying journal editorial, said the paper shows that the antibody can block infection in animals and similar levels of the drug can be safely given to people.
"It therefore satisfies the criteria of the animal rule, a regulatory guideline used to approve drugs for diseases that can't be tested for efficacy in humans," Nabel said.
This antibody provides a new tool to control anthrax infection and "if approved, could be stockpiled as a countermeasure against this potential public health threat," he said.
"This paradigm of drug approval for biodefense agents provides a new way to address such threats, though questions remain about how and when to use such drugs and how to incentivize industry to produce them," Nabel said.
More information
For more on anthrax, visit the U.S. Centers for Disease Control and Prevention .
