On May 1^st, 2018 the Antimicrobial Drugs Advisory Committee reviewed the new drug application (NDA) 208627 for SIGA Technologies’ tecovirimat, proposed for the treatment of smallpox caused by the variola virus, in pediatrics and adults.  The drug inhibits the production of extracellular viral forms responsible for the spread of infection within the body. Although smallpox was considered eradicated in 1980 due to widespread vaccination, the US population may currently be susceptible due to the halt in routine vaccinations. In the case of an outbreak, tecovirimat, may be useful in preventing the spread of the virus.

SIGA discussed the potential to use smallpox as a bioweapon and the importance of having a treatment to combat it. The proposed dosing for the oral tablet was 600 mg, twice daily, to achieve safe and efficacious levels in humans.

Efficacy trials were conducted in animals as a substitute for human clinical trials. Six animal model studies were used to assess efficacy, 4 in non-human primates (NHP)s and 2 in rabbits. All cases discussed showed nearly complete protection from death and reduced morbidity. Twelve human safety studies were conducted and showed that tecovirimat was generally well-tolerated. Adverse events were reported  in 37% of Tecovirimat patients and 33% in the control group, with the most common AEs being headaches, nausea and abdominal pain.

Panelists were asked to vote on whether the risk-benefit profile of tecovirimat supports its use for the treatment of human smallpox. The panel unanimously voted  towards approval of tecovirimat (17 Yes, 0 No). The committee praised the appropriate use of the animal rule by the sponsor. Members noted that tecovirimat fills an unmet need – an effective drug for a disease to which there was no currently approved treatment.

The agency is not obligated to follow its panel’s recommendation, but normally does so. On July 13^th  the FDA approved TPOXX (tecovirimat) as the first drug indicated for smallpox.

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This post was authored by Sami Mourad. Sami is a summer intern at ISS and a 3rd year pharmacy student at the Rutgers University Ernest Mario School of Pharmacy