Treating Human Monkeypox Viral Infection with Tecovirimat
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Reviewed & Translated by Dat Tien Nguyen, B.A, ScM.
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Posted on March 23rd, 2026
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In recent years, the human monkeypox virus has posed a significant public health challenge. Being a relative of the eliminated smallpox virus, there had been interest in utilizing smallpox therapy for monkeypox. A study recently published in the New England Journal of Medicine that tested the effectiveness of tecovirimat in treating human monkeypox virus infection.
Funding Source(s): US National Institutes of Health
The phase 3 clinical trial included 344 participants with a median age of 34 years old who had been diagnosed with symptomatic monkeypox infection. Symptoms of this infection had persisted for a median of 8 days. The participants reported a subjective median pain score of 5 out of 10, and each individual has on average 9 sites of skin lesion. 35% of these patients are being infected with HIV, and 23% of them had received at least one dose of smallpox or monkeypox vaccine.
The patients were randomly assigned to be treated with either placebo or tecovirimat, the specific dosage is not stated in the study’s protocol. After 29 days of treatment, the researchers found that there is no significant difference in resolution of skin lesion or pain between patients treated with tecovirimat or placebo. The usage of tecovirimat also does not increase the rate of viral DNA clearance. The lack of observable effect is not due to the mechanism of tecovirimat, as the orthopoxvirus VP37 envelope-wrapping protein targeted by the medication is conserved between smallpox and monkeypox virus. But, the researchers hypothesize that the dose level was insufficient to elicit adequate antiviral effect.
Funding Source(s): US National Institutes of Health
The phase 3 clinical trial included 344 participants with a median age of 34 years old who had been diagnosed with symptomatic monkeypox infection. Symptoms of this infection had persisted for a median of 8 days. The participants reported a subjective median pain score of 5 out of 10, and each individual has on average 9 sites of skin lesion. 35% of these patients are being infected with HIV, and 23% of them had received at least one dose of smallpox or monkeypox vaccine.
The patients were randomly assigned to be treated with either placebo or tecovirimat, the specific dosage is not stated in the study’s protocol. After 29 days of treatment, the researchers found that there is no significant difference in resolution of skin lesion or pain between patients treated with tecovirimat or placebo. The usage of tecovirimat also does not increase the rate of viral DNA clearance. The lack of observable effect is not due to the mechanism of tecovirimat, as the orthopoxvirus VP37 envelope-wrapping protein targeted by the medication is conserved between smallpox and monkeypox virus. But, the researchers hypothesize that the dose level was insufficient to elicit adequate antiviral effect.