An experimental drug called raxibacumab protected monkeys and rabbits against inhaled anthrax and could presumably be used to protect humans in the event of a terrorist attack, researchers reported today in the New England Journal of Medicine. Anthrax can be killed with antibiotics, but the death of the anthrax organisms releases a deadly flood of toxin. Raxibacumab is a monoclonal antibody, produced in animals, that binds to the toxin and removes it from the blood stream, preventing its lethal effects.
A vaccine against anthrax is available and is given to laboratory workers and some soldiers, but its use has been controversial because of the high incidence of side effects. The new research provides "an important addition to the existing arsenal" against anthrax, Dr. Gary G. Nable, director of vaccine research at the National Institute of Allergy and Infectious Diseases wrote in an editorial in the same issue of the journal.
The antibody, called ABthrax, was developed by Human Genome Sciences of Rockville, Md., under a contract from the government's Biomedical Advanced Research and Development Authority following the 2001 attacks in which anthrax-containing letters were sent to journalists and politicians, killing five people. The company has already delivered 20,000 doses of the drug to the U.S. Strategic National Stockpile for emergency use.
In one experiment, monkeys got a single dose of ABthrax or a placebo two days before receiving a lethal dose of anthrax. Those receiving a placebo all died within six days, while nine of the 10 receiving the highest dose survived. In a similar experiment, monkeys were given the drug after inhaling a powder of anthrax 200 times the lethal dose. Nine of 14 monkeys receiving the highest dose survived. Similar results were obtained with rabbits.
The drug cannot ethically be tested against anthrax in humans, but studies in 333 healthy people showed that it produced no adverse side effects. The company has applied to the Food and Drug Administration for approval under a rule that lets animal studies substitute for human ones in cases where human testing is not feasible.
-- Thomas H. Maugh II