Siga (SIGA - Get Report) soared 159% early Wednesday after the micro-cap biotech claimed its lead drug became "the first drug ever to demonstrate 100% protection against human smallpox virus in a primate trial conducted at the federal Centers for Disease Control and Prevention."

"This test in non-human primates is as close as anyone can get to the real thing because there has not been any natural occurrence of smallpox since 1977," Siga said.

The New York-based company said the Department of Homeland Security has designated smallpox a "material threat" to national security, so Siga-246 "will be eligible for purchase for the Strategic National Stockpile under Project Bioshield."

Shares rose $3.13 to $5.10.