First Treatment for Smallpox Gains FDA Approval

The US Food and Drug Administration (FDA) has approved the first drug indicated for the treatment of smallpox.

Tecovirimat (TPOXX)—a drug developed in conjunction with the US Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA)—has been approved for the US market under the FDA’s Animal Rule, which allows for efficacy results from qualified animal studies to support a drug approval when human trials would be considered unethical.

FDA commissioner Scott Gottlieb, MD, said tecovirimat provides more assurance versus public concern of potential bioterrorism involving smallpox.

“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,” Gottlieb said in a statement. “Today’s approval provides an important milestone in these efforts.”

With its approval, tecovirimat became the first product to be awarded a Material Threat Medical Countermeasure priority review voucher, Gottlieb said. Its application was previously granted Fast Track and Priority Review designations, and an Orphan Drug designation with its approval.

As Contagion^® previously reported, the approval of tecovirimat for smallpox is largely based on the results of a recent study published in the New England Journal of Medicine, which revealed that twice-daily dosing of 600 mg of tecovirimat was safe in humans. Additionally, the investigators found that 10 mg/kg dose over 14 days was capable of achieving over 90% survival in a monkeypox/nonhuman primate model and a dose of 40 mg/kg for 14 days was found to be similarly efficacious in the rabbitpox/rabbit model.

In the human safety trials, the most frequently reported side effects were headache, nausea, and abdominal pain.

Smallpox is caused by the variola virus and is capable of spreading through direct contact between people. Symptoms include fever, exhaustion, headache, and backache within 10 to 14 days of infection, as well as a rash of small, pink bumps that could develop into sores.

Complications commonly associated with smallpox include encephalitis, corneal ulcerations, and blindness.

Though the World Health Organization (WHO) declared smallpox an eradicated disease in 1980, concern over its use as a bioweapon has persisted. Some of that concern may be quelled with tecovirimat’s approval.

“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,” Gottlieb said.