A cancer pill noted for its effectiveness in stopping leukemia in some patients can also help delay the deadliest effects of a pox virus in mice — offering the prospect of using similar drugs to treat or prevent smallpox, scientists said on Monday.

Tests of Gleevec, Swiss drug giant Novartis AG’s successful leukemia pill, showed it could save the lives of mice infected with vaccinia — a close relative of smallpox.

The drug, known generically as imatinib or STI-571, also prevented infection in the mice and slowed the spread of the virus in the body when given after infection.

“We propose the use of STI-571, a drug developed to treat cancer without substantial side effects, as a therapeutic for infections caused by pox viruses,” the researchers write in this week’s issue of the journal Nature Medicine.

Other drugs being developed in the same class may be even more useful against not only smallpox but other germs that infect cells in similar ways, the researchers, led by Daniel Kalman of Emory University School of Medicine in Atlanta, said.

Smallpox, caused by a virus called variola, was declared eliminated in 1980 after a global vaccination campaign. It no longer exists in nature, but experts fear terrorists or governments could use samples to launch biological attacks.

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