US-based commercial-stage pharmaceutical company SIGA Technologies announced that its antiviral treatment Tepoxx (tecovirimat) has received regulatory approval in Japan.
Tepoxx, marketed as TPOXX in the US, is a highly targeted small-molecule antiviral that inhibits the activity of VP37, a protein that is found on the surface of all orthopoxviruses.
It slows the spread of the infection by preventing the virus from exiting infected cells, enabling the immune system to neutralise the virus.
The drug was approved by Japan’s Pharmaceuticals and Medical Devices Agency (PMDA), in collaboration with the Ministry of Health, Labour and Welfare (MHLW).
Tepoxx (200mg capsules) is indicated for smallpox, mpox, and cowpox, along with complications after smallpox vaccination in adults and children weighing at least 13kg.
SIGA, in partnership with Japan Biotechno Pharma, its exclusive distributor in Japan, delivered an order of Tepoxx to help build Japan’s strategic national stockpile.
SIGA Technologies CEO Diem Nguyen said: “The approval of Tepoxx in Japan marks another significant milestone in our mission to expand access to this critical antiviral treatment worldwide to support an effective response to an orthopoxvirus outbreak.
“We are grateful for the close collaboration with the Japanese regulatory authorities and strong partnership with Japan Biotechno Pharma that made this accomplishment possible.
“This approval highlights the importance of stockpiling effective antiviral therapies as a cornerstone of innovative solutions to safeguard public health against serious and potentially devastating infectious diseases, such as smallpox.”
The Japanese regulatory approval is based on data from 15 clinical trials of oral Tepoxx, including a repeat-dose Phase 1 pharmacokinetics (PK) trial in 20 participants in Japan.
In the studies, the antiviral drug showed no drug-related serious adverse events and quantifiable PK within efficacious dose ranges.
Four clinical trials in non-human primates (NHPs) and two in rabbits showed that Tepoxx significantly reduced both mortality and viral load.
The drug has also been studied in NHPs infected with the variola virus, where it showed improved survival and reduction in lesions.
Tpoxx is already approved in the US and Canada for smallpox, and in the European Union (EU) and the UK for smallpox, mpox, cowpox, and complications after smallpox vaccination.
SIGA Technologies chief scientific officer Dennis Hruby said: “Tepoxx was designed with a deep understanding of orthopoxviruses and has the potential to deliver an effective treatment option for managing these potentially devastating diseases.
“We are proud to see our work contribute to enhanced preparedness and public health resilience in Japan.”
