The AIDS Clinical Trials Group (ACTG) presented data from the STOMP trial at the 2025 Conference on Retroviruses and Opportunistic Infections, revealing that tecovirimat did not improve mpox resolution. The phase 3 trial, which enrolled adults with mild to moderate clade II mpox, stopped early after an interim analysis showed the antiviral drug was ineffective in reducing lesion healing time or pain. While tecovirimat is FDA-approved for smallpox treatment, its efficacy against mpox remained unproven prior to this study.
This negative result underscores the critical need for effective mpox treatments. While the mpox outbreak may have waned, the virus continues to circulate globally, highlighting a persistent vulnerability. The lack of effective therapies leaves a significant gap in our ability to manage this disease and prevent future outbreaks. The findings also validate the importance of rigorous clinical trials to assess potential therapies, especially during public health emergencies.
The STOMP trial was a randomized, placebo-controlled, double-blind study involving 412 participants across 50 sites in seven countries. Participants received either tecovirimat or a placebo twice daily for 14 days. A separate open-label arm enrolled individuals with severe mpox or at risk for severe disease, all of whom received tecovirimat. The study found no safety concerns or deaths in either group. Further analysis of host and disease factors like age, HIV status, and vaccination status in the open-label arm did not identify predictors of mpox resolution.
The STOMP findings necessitate the exploration of alternative mpox treatments. While tecovirimat proved safe, its lack of efficacy prompts a renewed focus on research and development efforts. This includes investigating other antiviral candidates and exploring different therapeutic approaches. The ability to rapidly design and execute international clinical trials, as demonstrated by STOMP, will be essential in this ongoing pursuit.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
