Smallpox drug tecovirimat appears safe and effective for monkeypox

Results from a small study suggest that the antiviral drug tecovirimat is safe and effective for the treatment of monkeypox.

The findings were published on August 26, 2022 in JAMA.

“In this preliminary study, oral tecovirimat was well tolerated by all patients with monkeypox infection, with minimal adverse effects. However, adverse effects could not always be differentiated from symptoms related to the infection,” the authors said.

As background, the authors noted that tecovirimat is an FDA-approved antiviral drug for the treatment of smallpox. Recently, the (US) Centers for Disease Control and Prevention (CDC) has permitted doctors to prescribe tecovirimat on a compassionate use basis to treat adults and children with monkeypox.

The 25 subjects enrolled in the study were referred to UC Davis – Health (Sacramento, California) between June 3, 2022, and August 13, 2022. All were male, and the median age was 40.7 years (range, 26-76).

They reported having symptoms or lesions for an average of 12 days before beginning treatment with tecovirimat. All had painful lesions. About half had less than a total of 10 lesions. And 92% had lesions in their genital or anal area.

Symptoms included fever (76% of subjects), fatigue (32%), sore throat (20%), chills (20%), backache (12%), muscle pain (8%), nausea (4%) and diarrhea (4%).

All subjects completed tecovirimat treatment for two weeks, and it was well tolerated. One subject was treated for 21 days.

By day 7 of tecovirimat treatment, 40% of the subjects had healed from their lesions. By day 21, 92% had healed from their lesions and were pain-free.

Most common adverse events reported on day 7 of therapy were fatigue (28%), headache (20%), nausea (16%), itching (8%) and diarrhea (8%).

The authors noted, “Limitations of the study include the small number of patients, lack of a control group, and selection bias. Additional large-scale studies are needed to elucidate antiviral efficacy, dosing, and adverse events.”