On July 13, 2018, the United States Food and Drug Administration (USFDA) approved TPOXX (tecovirimat), the first drug for treatment of smallpox1. Though the World Health Organization declared smallpox, a contagious and sometimes fatal infectious disease, eradicated in 1980, there have been longstanding concerns that smallpox could be used as a bioweapon.
The approval is based on data from 12 clinical trials of oral TPOXX in over 700 healthy human volunteers, which showed no drug-related serious adverse events. Four pivotal trials in non-human primates (NHPs) and two pivotal trials in rabbits demonstrated that TPOXX significantly reduced both mortality and viral load in NHP infected with monkeypox virus (MPXV) and in rabbits infected with rabbitpox virus2. TPOXX was approved under the FDA's Animal Rule, which allows efficacy findings from adequate and well-controlled animal studies to support an FDA approval when it is not feasible or ethical to conduct efficacy trials in humans.
The FDA granted approval of TPOXX to SIGA Technologies Inc. The FDA also granted Fast Track designation, priority review designations, and Orphan Drug designation to TPOXX.
TPOXX was developed in conjunction with the U.S. Department of Health and Human Services' Biomedical Advanced Research and Development Authority (BARDA). TPOXX will be available initially only through the U.S. Government's Strategic National Stockpile (SNS). SIGA has a $472 million procurement and development contract with BARDA, as part of which 2 million courses of oral TPOXX have been delivered to the SNS. Currently, there is a Request for Proposal outstanding for the maintenance of a smallpox antiviral stockpile within the SNS. SIGA intends to explore additional markets and potential indications for TPOXX in the United States and around the world.
About TPOXX (Tecovirimat)
TPOXX®, also known as tecovirimat and ST-246®, an orally administered and IV formulation antiviral drug for the treatment of human smallpox disease caused by variola virus. Tecovirimat inhibits an orthopoxviral protein that is required for the exit of enveloped virions from the infected cell; this block in virus release is sufficient to halt the spread of infection until the body's immune system can clear the virus. Tecovirimat is formulated as immediate release capsules to be taken at a dose of 600 mg twice daily with a meal for 14 days3.
About Smallpox
Smallpox is a contagious, disfiguring and often deadly disease that has affected humans for thousands of years. Naturally-occurring smallpox was eradicated worldwide by 1980, the result of an unprecedented global immunization campaign. Samples of smallpox virus have been kept for research purposes. This has led to concerns that smallpox could someday be used as a biological warfare agent. No cure or treatment for smallpox exists. A vaccine can prevent smallpox, but the risk of the vaccine's side effects is too high to justify routine vaccination for people at low risk of exposure to the smallpox virus.
Footnotes
1 https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm613496.htm
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