Mpox drug Tpoxx didn't speed lesion healing in clade 1 patients, trial shows
April 17, 2025
A landmark clinical trial in the Democratic Republic of the Congo found that tecovirimat (Tpoxx), widely distributed for mpox treatment, was ineffective in accelerating healing or reducing pain for patients infected with clade 1 mpox. Published in the New England Journal of Medicine, the PALM007 study revealed no statistically significant differences in recovery time or mortality between patients treated with Tpoxx and those given a placebo. Researchers are now calling for the urgent development of alternative therapies, including combination antivirals and monoclonal antibodies, especially as severe outcomes remain high in under-resourced regions battling clade 1 mpox.
The most comprehensive study to date on tecovirimat (Tpoxx) for clade 1 mpox has delivered sobering results: the antiviral drug showed no significant benefit in speeding lesion healing or reducing pain in infected patients. The PALM007 trial, conducted across hospitals in the Democratic Republic of the Congo from 2022 to 2024, involved 597 hospitalized patients—most of whom were children or had severe disease. Results, published in the New England Journal of Medicine, confirmed that Tpoxx and placebo recipients had similar recovery trajectories, with lesion clearance taking about a week in both groups and no significant difference in mortality or recurrence.
Though the study confirmed the drug's safety, it raised concerns about the inconsistency between human clinical data and the promising animal models that led to tecovirimat’s emergency approvals. These findings echo the recently halted STOMP trial for clade II mpox and underscore the need for new therapeutic options. Alternative antivirals like brincidofovir and monoclonal antibodies are now being proposed as future candidates for mpox treatment—particularly as public health experts warn of bioterrorism risks tied to related viruses like smallpox.
A related meta-analysis of mpox cases in the DRC from 1970 to 2024 revealed stark disparities in disease severity and fatality, with significantly higher mortality in community settings compared to hospitals. Regions with weak healthcare infrastructure had fatality rates over 11%, compared to less than 1% in well-supported areas. Researchers stress that without access to effective treatments, vaccines, and diagnostics, endemic mpox will continue to take a deadly toll, especially among children and immunocompromised populations.
Taken together, these studies highlight a critical gap in the global mpox response: the absence of effective, accessible therapies for the most dangerous viral clade. The research community and global health agencies must pivot rapidly to find and test new solutions.