FDA approves first drug designed to treat smallpox
- The Food and Drug Administration announced Friday approval of the oral antiviral TPOXX, the first drug with a primary indication for the smallpox virus.
- The World Health Organization declared smallpox eradicated in 1980, but there are concerns that the virus could be used as a weapon in a bioterrorism attack. It’s anticipated that TPOXX is only the first drug among a string of medications that could be approved to reduce the risks of bioterrorism.
- The product was also awarded a Material Threat Medical Countermeasure priority review voucher. The PRV program typically applies to drugs approved for rare tropical diseases or rare pediatric diseases. These vouchers allow a company to get a "fast-pass" to approval for another compound. They can also be sold; and many have gone for high prices.
While circulating smallpox is no longer a threat, there are concerns that the virus could be used to threaten health and safety through bioterrorism. Two heavily-guarded stores of the smallpox virus still exist — one at the Centers for Disease Control and Prevention in Atlanta, and the other in Russia. Terrorism experts, however, fear that there may be other sources of the smallpox virus, or that a terrorist lab or individual could use gene editing to recreate it.
Given that smallpox vaccination was halted after 1980, most people under the age of 40 are unprotected against the disease. The smallpox vaccine is routinely given only to military personnel, lab workers or others likely to come into contact with the virus during an attack. Smallpox kills almost a third of people who are infected with it, and infants, pregnant women and anyone with HIV or immunosuppressive condition are particularly at risk.
Siga Technologies of Corvallis, Ore. developed TPOXX (tecovirimat) under a federal biomedical defense contract, and the FDA provided it with fast-track and priority review designations. Researchers are now working on producing another antiviral treatment for smallpox. An intravenous version of TPOXX is also in the works. Research suggests that TPOXX can be effective in animals and humans, and works by inhibiting the action of a protein known as P37, which infected cells need to release the smallpox virus so that it can spread.
Research on a treatment for smallpox began at the National Institute of Allergy and Infectious Diseases after the Sept. 11 terrorist attacks. At the same time, scientists worked to safely dilute the U.S. national stockpile of smallpox vaccines. It was developed through a collaboration with the Biomedical Advanced Research and Development Authority (BARDA). SIGA has a $472 million procurement and development contract with the agency to deliver 2 million courses of TPOXX to the stockpile.
Smallpox has devastating effects, which begin 10 to 14 days after infection with symptoms of fever, exhaustion and headache. The pus-filled sores that result from smallpox can eventually lead to permanent scarring, and the disease can also cause loss of large areas of skin, encephalitis (inflammation of the brain) and blindness.
TPOXX’s efficacy was tested on non-human primates and rabbits infected with viruses similar to smallpox—monkeypox and rabbitpox, two potentially lethal infections. The medicine was also evaluated in 359 healthy humans without smallpox. In humans, the most common side effects of the drug were headache, nausea and abdominal pain, according to the FDA.