FDA Approves Tecovirimat, First Drug for Smallpox Treatment

Megan Brooks

July 13, 2018

The US Food and Drug Administration (FDA) has approved tecovirimat (TPOXX, SIGA Technologies), the first drug with an indication for treatment of smallpox, the agency announced today.

Although the World Health Organization (WHO) declared smallpox, a contagious and sometimes fatal infectious disease, eradicated in 1980, there is concern that smallpox could be used as a bioweapon.

"To address the risk of bioterrorism, Congress has taken steps to enable the development and approval of countermeasures to thwart pathogens that could be employed as weapons. Today's approval provides an important milestone in these efforts. This new treatment affords us an additional option should smallpox ever be used as a bioweapon," FDA Commissioner Scott Gottlieb, MD, said in a news release.

Tecovirimat is the first product to be awarded a material threat medical countermeasure priority review voucher, which provides additional incentives for certain medical products intended to treat or prevent harm from specific chemical, biological, radiologic, and nuclear threats.

"Today's action reflects the FDA's commitment to ensuring that the US is prepared for any public health emergency with timely, safe and effective medical products," said Gottlieb.

Smallpox is caused by the variola virus. Before its eradication, the virus was mainly spread by direct contact between people. Symptoms of smallpox typically begin 10 to 14 days after infection and include fever, exhaustion, headache, and backache. A rash initially consisting of small, pink bumps progresses to pus-filled sores before finally crusting over and scarring. Complications of smallpox may include encephalitis, corneal ulcerations, and blindness.

The effectiveness of tecovirimat against smallpox was shown in studies of animals infected with viruses closely related to the variola virus. More animals treated with tecovirimat lived than did animals treated with placebo, the FDA said.

Tecovirimat was approved under the FDA's animal rule, which allows findings from animal studies to support an FDA approval when it is not feasible or ethical to conduct efficacy trials in humans.

The safety of tecovirimat was demonstrated in 359 healthy human volunteers without a smallpox infection. The most commonly reported side effects were headache, nausea, and abdominal pain.

Tecovirimat had fast track and priority review status and orphan drug designation. It was developed in conjunction with the US Department of Health and Human Services' Biomedical Advanced Research and Development Authority (BARDA).

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