FDA initially approves smallpox treatment of SIGA

The FDA approved the first treatment for smallpox. SIGA Technologies tested the drug in 359 healthy volunteers to demonstrate its safety and relied on animal data to demonstrate its efficacy.

Smallpox was eradicated in 1980, but the presence of the virus in US and Russian laboratories flasks on other sites, left some concern that it could be used as a biological weapon . These concerns fuel government demand for smallpox vaccines and have led SIGA to develop a drug to treat people infected with the virus.

The nature of smallpox means that the drug, an antiviral known as Tpoxx, has taken an unusual route. No case of smallpox occurs naturally, and it would be highly unethical to infect people for research purposes. As such, SIGA has never tested whether its treatment clears the virus in humans.

SIGA instead consulted the FDA with animal data infected with viruses similar to smallpox. These animal studies established a link between Tpoxx and a survival rate superior to that of placebo, which allowed SIGA to eliminate the bar of effectiveness established by the Rule on FDA animals. The rule allows drugs to obtain approval on the basis of well-controlled animal study data if it would be unethical or impossible to perform tests of effectiveness in humans.

SIGA evaluated the safety of Tpoxx in humans, however, administering the drug to 359 healthy volunteers. Some participants experienced headaches, nausea, and abdominal pain after receiving Tpoxx, but overall, the FDA found that the safety data was clear enough to warrant approval. The FDA's approval follows a unanimous recommendation from the agency's advisory board.

In return for his efforts, SIGA became the first company to receive a priority check certificate on the medical countermeasure. The salable good gives the holder a quick regulatory review for a future deposit. SIGA has a $ 472 million contract to supply the US government with Tpoxx. The US Department of Defense's involvement in the development and commercialization of the antiviral is one of the ways the government has supported SIGA to protect public health. "To counter the risk of bioterrorism, Congress has taken steps to allow the development and approval of countermeasures to counteract the pathogens that could be used as weapons," said Scott Gottlieb, MD, commissioner for the FDA. "The approval of today is an important step in these efforts, and this new treatment offers us an additional option if smallpox is used as a biological weapon."