Tecovirimat is safe but ineffective as treatment for clade II mpox
March 12, 2025
A landmark clinical trial funded by the NIH has concluded that tecovirimat (TPOXX) monotherapy does not accelerate the resolution of clade II mpox lesions or improve pain management. The STOMP study, conducted across multiple countries, found no significant difference in recovery rates between those receiving tecovirimat and those given a placebo. These findings align with results from the PALM007 study in the Democratic Republic of Congo. The trial underscores the urgent need for alternative mpox treatments and improved understanding of disease progression. Future research should focus on combination therapies and factors influencing clinical outcomes to guide more effective treatment strategies.
The NIH-sponsored STOMP trial has delivered a crucial insight into mpox treatment, determining that tecovirimat (TPOXX) monotherapy does not significantly enhance recovery for clade II mpox patients. Conducted across Argentina, Brazil, Japan, Mexico, Peru, Thailand, and the United States, the study found that 83% of tecovirimat recipients achieved clinical resolution by day 29—statistically identical to the 84% recovery rate observed in the placebo group. These results align with the PALM007 study in the Democratic Republic of Congo, reinforcing doubts about the drug’s efficacy as a standalone treatment.
Participants entered the trial a median of eight days after symptom onset, with a median of nine mpox lesions. Despite high pain levels reported at baseline, pain reductions were nearly identical between the treatment and placebo groups. Additionally, while initial viral DNA clearance rates were slightly higher in the tecovirimat group, the advantage disappeared by day 15, further questioning the drug’s therapeutic benefit.
An exploratory analysis of STOMP’s open-label arm suggested that younger age and HIV-negative status correlated with faster recovery, but no definitive predictors of disease progression emerged. This underscores the urgent need to refine mpox treatment strategies, particularly for immunocompromised patients.
With mpox still circulating globally, particularly in Africa where clade I outbreaks continue, the findings highlight an unmet need for alternative therapeutics. Future research must explore combination therapies and investigate the underlying factors influencing mpox severity and recovery. While tecovirimat remains FDA-approved for smallpox, these results indicate that monotherapy is not a viable solution for mpox, emphasizing the necessity of targeted drug development efforts to better manage current and future outbreaks.