NIH

Tecovirimat ineffective against clade II mpox despite safety

March 13, 2025

The NIH-sponsored Study of Tecovirimat for Mpox (STOMP) concluded that tecovirimat, an antiviral drug initially approved for smallpox, is safe but ineffective in treating clade II mpox. The international clinical trial, which began in September 2022, enrolled participants from multiple countries affected by the global mpox outbreak. Interim analysis revealed that tecovirimat didn’t reduce the time to clinical resolution of mpox lesions or improve pain control among adults. Participants in the study reported mpox symptoms for a median of eight days before entry and had a median of nine lesions. By day 29, clinical resolution was achieved by 83% of those receiving tecovirimat and 84% of those on placebo, showing no significant difference. Improvements in pain and viral DNA clearance rates were also similar between the two groups, with no statistically significant differences observed. Consequently, the trial's Data Safety and Monitoring Board recommended halting further enrollment.

Source:

(2025, March 12). NIH. Tecovirimat is safe but ineffective as treatment for clade II mpox. https://www.nih.gov/news-events/news-releases/tecovirimat-safe-ineffective-treatment-clade-ii-mpox