Smallpox Treatment TPOXX Benefits Outweigh Risks, says FDA

Smallpox is a naturally occurring, highly contagious, and sometimes fatal infectious disease.

The last case of wild smallpox occurred in Somalia in 1977.

Yet, it remains as one of the highest priority pathogens due to its potential as a biological weapon.

There is not a specific treatment for smallpox disease available today, but the Food and Drug Administration (FDA) is taking action to remove this shortcoming.

SIGA Technologies, Inc. announced a favorable outcome of the FDA Antimicrobial Drugs Advisory Committee meeting on oral TPOXX®, a small molecule antiviral treatment for smallpox.

TPOXX, also known as tecovirimat and ST-246®, an orally administered and IV formulation antiviral drug, that targets orthopoxvirus infections.

This FDA panel voted unanimously, 17 to 0, that the benefits of TPOXX outweigh its risks. The FDA had previously announced that its target final action date was August 8, 2018.

The U.S. government’s Biomedical Advanced Research and Development Authority (BARDA) funded the advanced development of oral TPOXX in partnership with SIGA.

Additionally, under Project Bioshield, BARDA has already acquired two million courses of oral TPOXX and such courses have been delivered to the Strategic National Stockpile.

Dr. Phil Gomez, Chief Executive Officer of SIGA Technologies said,  “We believe that safety and efficacy data support TPOXX’s future use as a medical counter-measure in response to a smallpox outbreak.”

Variola major is the severe form of smallpox, with a more extensive rash and higher fever. It is also the most common form of smallpox. Historically, variola major has a case-fatality rate of about 30 percent.

There are four types of variola major smallpox: ordinary (the most frequent); modified (mild and occurring in previously vaccinated persons); flat, and hemorrhagic.

And, the only smallpox prevention is vaccination, says the FDA.

Dryvax, a smallpox vaccine, originally licensed in 1944 was manufactured until the mid-1980s when the World Health Organization declared that smallpox had been eradicated.

Currently, there is one licensed smallpox vaccine; ACAM2000, which is based on the same strain of virus as Dryvax.

On May 2, 2005, CBER licensed Vaccinia Immune Globulin, Intravenous to treat rare serious complications of smallpox vaccination.

Recently, during February 2018, a biotechnology company announced positive results from a Phase 3 pivotal study of its investigational, non-replicating smallpox vaccine, IMVAMUNE®.

Additionally, IMVAMUNE recorded a statistically superior immune response (2x) and the majority of volunteers achieved primary vaccination, requiring no need for re-vaccination.

This clinical study demonstrated IMVAMUNE’s non-inferiority, which means not worse than ACAM2000, the current U.S. licensed, replicating smallpox vaccine.

For more information about SIGA, please visit www.siga.com.