Public health company the US Food and Drug Administration stated on Friday that it has authorised the marketing of the first drug TPOXX (tecovirimat) for treatment of smallpox.

This US FDA approval of TPOXX was awarded to SIGA Technologies Inc under the former's fast track, priority review and orphan drug designations. The drug was developed in conjunction with the US Department of Health and Human Services' Biomedical Advanced Research and Development Authority.

Although the World Health Organisation declared in 1980 that smallpox, a contagious and sometimes fatal infectious disease, was eradicated, there have been longstanding concerns that smallpox could be used as a bioweapon. Complications of smallpox could include encephalitis (inflammation of the brain), corneal ulcerations (an open sore on the clear, front surface of the eye) and blindness.

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

Additionally, the safety of the company's TPOXX was evaluated in 359 healthy human volunteers without a smallpox infection. The most frequently reported side effects were headache, nausea and abdominal pain.