The Japan Ministry of Health, Labour and Welfare has granted regulatory approval to SIGA Technologies' TEPOXX (tecovirimat 200 mg capsules) for the treatment of smallpox, mpox, cowpox, and complications arising from smallpox vaccination in both adult and pediatric patients (weighing at least 13 kg). This decision marks a significant milestone as TEPOXX becomes the first antiviral therapy approved in Japan for addressing orthopoxvirus infections.
Regulatory Milestone and Strategic Stockpiling
The Pharmaceuticals and Medical Devices Agency (PMDA), in collaboration with the Ministry of Health, Labour and Welfare, approved TEPOXX based on comprehensive data. SIGA Technologies, in partnership with its exclusive distributor Japan Biotechno Pharma, has already delivered an initial order of TEPOXX to bolster Japan's strategic national stockpile. Diem Nguyen, CEO of SIGA Technologies, emphasized the importance of this approval in expanding global access to this critical antiviral treatment, especially in time-sensitive emergencies.
Clinical Evidence and Safety Profile
The approval is supported by data derived from 15 clinical trials involving over 800 healthy volunteers. These trials included a pivotal repeat-dose phase 1 pharmacokinetics (PK) study conducted in Japan, which demonstrated a favorable safety profile with no drug-related serious adverse events and quantifiable PK within efficacious dose ranges. Furthermore, four pivotal studies in non-human primates and two pivotal studies in rabbits demonstrated that TEPOXX significantly reduced mortality and viral load. Studies involving non-human primates infected with the variola virus (the causative agent of smallpox) also showed improved survival and a reduction in lesion counts.
Mechanism of Action
TEPOXX is a highly targeted small-molecule antiviral that functions by inhibiting the VP37 protein, which is present on the surface of all orthopoxviruses. By preventing the virus from exiting infected cells, TEPOXX effectively slows the spread of the infection, allowing the immune system to clear the virus more efficiently.
Global Approvals and Availability
TPOXX is already approved in the United States and Canada for the treatment of smallpox. In the European Union and the United Kingdom, where it is marketed as Tecovirimat-SIGA, the drug is approved for the treatment of smallpox, mpox, cowpox, and complications following smallpox vaccination.
Impact on Public Health
Dennis Hruby, Ph.D., Chief Scientific Officer at SIGA Technologies, highlighted that TEPOXX was designed with a deep understanding of orthopoxviruses, offering an effective treatment option for managing these potentially devastating diseases and enhancing public health resilience in Japan.
