In a primate trial conducted at the federal Centers for Disease Control and Prevention SIGA-246 protected cynomolgus monkeys from smallpox disease following intravenous high dosing with the smallpox virus.
The drug prevented symptoms of disease whether delivered at the same time as the virus or 24 hours later, supporting the drug's use for both post-exposure prophylaxis and treatment. SIGA-246 completely prevented lesion formation and showed no obvious toxicity.
“We are particularly pleased because the amount of virus used in this study is equivalent to the level present in late-stage disease in humans, which we believe signals that SIGA-246 can be used to prevent disease in humans,” said Dr Dennis Hruby, Chief Scientific Officer of Siga. “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.”
Smallpox is considered one of the most significant biowarfare threats. Smallpox is readily transmitted between humans, it has significant mortality rates and the population is no longer vaccinated against it. At this time, there is also no approved treatment for smallpox.
Siga previously announced that SIGA-246 has been shown to be safe to administer to humans as a once-a-day pill. In December 2005, the FDA granted “fast-track” status to SIGA-246.