New York ? An experimental drug helped monkeys and rabbits survive anthrax in a series of studies, suggesting it could be useful in case of another anthrax attack.

In 2001, five people died after inhaling anthrax germs they’d gotten through the U.S. mail.

Doctors now use antibiotics to prevent or treat anthrax, and there is also an anthrax vaccine. The experimental drug works a different way — by blocking deadly anthrax toxin from entering cells. Researchers say it could be combined with antibiotics.

The company that developed the experimental drug under federal contract has already delivered 20,000 doses to the government for emergency use. It has also asked the Food and Drug Administration to approve the drug — called ABthrax — under a rule that lets animal studies substitute for human studies when it’s not feasible to test a drug in people.