Pharmaceutical company SIGA Technologies has secured the US Food and Drug Administration’s (FDA) approval for the use of its TPOXX (tecovirimat) to treat smallpox during an outbreak.

TPOXX is the first drug approved for this indication. It is an oral small-molecule antiviral therapy developed in partnership with the Biomedical Advanced Research and Development Authority (BARDA).

The drug also obtained fast track and priority review designations from the US regulatory agency, which granted a seven-year expiry for TPOXX.

Based on the extended shelf-life, SIGA plans to ask BARDA to ask for a $50m payment under an existing contract. The contract stipulates that SIGA is eligible to receive a $41m hold back payment for the FDA approval.

SIGA Technologies CEO Phil Gomez said: “The FDA approval of TPOXX achieves an important objective for both SIGA and our lead partner in the US Government, the BARDA.

“The approval validates this novel therapy as an important medical countermeasure in response to a potential outbreak.”

“The approval validates this novel smallpox therapy as an important medical countermeasure in response to a potential smallpox outbreak.”

The FDA decision comes after review of results obtained during 12 clinical trials conducted to evaluate oral TPOXX in a total of more than 700 healthy volunteers. Data is said to have revealed no drug-related serious adverse events, with most frequent side effects being headache, nausea and abdominal pain.

Additional studies in non-human primates (NHPs) with monkeypox virus and rabbits infected with rabbitpox virus showed TPOXX can lead to a significant decrease in mortality, as well as viral load.

Smallpox is a contagious infectious disease that was eradicated in 1980 but is considered as a bioweapon threat.

Initially, TPOXX is set to be available for the treatment of the disease through the government’s Strategic National Stockpile (SNS).

According to a $472m procurement and development contract with BARDA, SIGA has delivered two million courses of oral TPOXX to the SNS. The company intends to further extend potential indications and markets for the drug.