Oral smallpox treatment proves effective in animal trials

An oral smallpox treatment developed by SIGA Technologies, Inc. has proven effective through human safety and animal efficacy studies published in the New England Journal of Medicine this month.

Known as tecovirimat, or TPOXX, the efficacy of the oral formulation was tested in lethal monkeypox and rabbitpox models that coincide with the Food and Drug Administration’s (FDA) “Animal Rule.” A minimum dose of 10 milligrams per kilogram for monkeypox and 40 milligrams per kilogram for rabbitpox over 14 days achieved 90 percent survival rates, the company reports.

“Smallpox is both highly contagious and highly lethal, and there is growing concern that smallpox could be used as a potential bioweapon,” SIGA CEO Phil Gomez said. “A smallpox bioterror attack could be especially damaging because the majority of today’s population is not immune to the virus, as routine vaccination ended in the 1970s. Rapid spread from person-to-person can occur through speaking, breathing or touching, and smallpox also can be transmitted by direct contact with infected fluids and contaminated objects. These factors underscore the need for an effective smallpox antiviral therapy, and we believe that TPOXX can address this need.”

In May, FDA’s Antimicrobial Drugs Advisory Committee granted a favorable outcome to a new drug application for oral TPOXX filed by SIGA in December. The 17-member panel voted unanimously that the treatment’s benefits outweighed its risks.

“The human safety and animal efficacy data reported in the New England Journal of Medicine are a large part of the TPOXX New Drug Application and support the use of this novel antiviral agent,” SIGA Chief Scientific Officer Dennis Hruby said. “The absence of drug-related serious adverse events in the human safety trial coupled with a high survival rate in TPOXX-treated non-human primates receiving a lethal challenge dose of monkeypox virus establish a compelling risk-benefit profile for TPOXX in the treatment of smallpox.”

The Biomedical Advanced Research and Development Authority (BARDA) funded development of oral TPOXX under Project Bioshield.