On Friday, July 13th, FDA approved TPOXX (tecovirimat) for the treatment of smallpox. According to the World Health Organization (WHO), smallpox was eradicated in 1980; however, since eradication almost forty years ago, there have been concerns that the variola virus could be used as a bioweapon.
What is smallpox?
Smallpox is a highly contagious infectious disease with no specific treatment. Vaccination can protect against some, but not all forms of smallpox. There are two clinical forms of smallpox: variola major and variola minor. Variola minor is a less serious and less common version of the virus with a 1% fatality rate. Variola major is more serious and has a 30% fatality rate. Variola major is broken down into four main types, which include:
- Ordinary—most common type of smallpox
- Modified—mild, can occur even if vaccinated
- Flat—uncommon, often fatal
- Hemorrhagic—uncommon, often fatal
FDA Approves TPOXX for the Treatment of Smallpox
SIGA Technologies’ TPOXX was approved by the FDA as a precautionary measure to ensure that the United States would be prepared for a potential public health emergency related to smallpox. According to a statement from Scott Gottlieb, M.D., Commissioner of the FDA, “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 action reflects the FDA’s commitment to ensuring that the U.S. is prepared for any public health emergency with timely, safe and effective medical products.”
TPOXX was approved using data from well-controlled animal studies because there are currently no naturally occurring cases of smallpox in the world. Under FDA’s Animal Rule, sponsors may use efficacy findings from animal studies when it is not feasible or ethical to conduct efficacy trials in humans. Although efficacy trials could not be performed in humans, SIGA did conduct safety trials on 359 healthy volunteers. Based on this study, common side-effects of the drug include headache, nausea, and abdominal pain.
The TPOXX application was granted Fast Track, Priority Review, and Orphan Drug designations. In addition, TPOXX was the first drug to receive a Material Threat Countermeasure Priority Review Voucher, which “provides additional incentives for certain medical products intended to treat or prevent harm from specific chemical, biological, radiological and nuclear threats.”