FDA Approves SIGA's Small Pox Therapy

(RTTNews) - The U.S. Food and Drug Administration Friday said it has approved SIGA Technologies Inc.'s (SIGA) TPOXX, the first-ever smallpox therapy. Shares of SIGA closed Friday's trading up 17 percent.

TPOXX (tecovirimat) is the first drug with an indication for treatment of smallpox. Though the World Health Organization declared smallpox, a contagious and sometimes fatal infectious disease, eradicated in 1980, there have been longstanding concerns that smallpox could be used as a bioweapon.

"To address the risk of bioterrorism, Congress has taken steps to enable the development and approval of countermeasures to thwart pathogens that could be employed as weapons. Today's approval provides an important milestone in these efforts. This new treatment affords us an additional option should smallpox ever be used as a bioweapon," said FDA Commissioner Scott Gottlieb, M.D.

TPOXX is is the first product to be awarded a "Material Threat Medical Countermeasure" priority review voucher.

Smallpox, one of the most deadly diseases known to humanity, is caused by Variola virus, a member of the genus Orthopoxvirus. The last known natural case of smallpox was reported in Somalia in 1977, and it was declared eradicated in 1980.

Only two labs in the world have been permitted to store the smallpox virus for research - the Centers for Disease Control and Prevention (CDC) in the United States, and the Russian State Centre for Research on Virology and Biotechnology in the Russian Federation. There have been concerns that some countries could employ smallpox in a bioterrorism attack.

There is one FDA-approved vaccine by the name ACAM2000 to prevent smallpox. Until 1972, this vaccine was given routinely in the United States, after which the practice was stopped.

Most people born in the United States after 1972 have not been vaccinated against the disease. Some people have been vaccinated through the military or because they were part of Smallpox Response Teams that were formed after the 9/11 terrorist attacks. But this vaccine is associated with significant adverse events - some of which are life-threatening.

TPOXX's effectiveness against smallpox was established by studies conducted in animals infected with viruses that are closely related to the virus that causes smallpox, and was based on measuring survival at the end of the studies. More animals treated with TPOXX lived compared to the animals treated with placebo. TPOXX was approved under the FDA's Animal Rule, which allows efficacy findings from adequate and well-controlled animal studies to support an FDA approval when it is not feasible or ethical to conduct efficacy trials in humans.