Introduction

In a significant yet surprising revelation at the 2025 Conference on Retroviruses and Opportunistic Infections (CROI) held in San Francisco, the AIDS Clinical Trials Group (ACTG) presented crucial findings from its STOMP study, showing that tecovirimat, an antiviral medication, failed to enhance the resolution of mpox (formerly known as monkeypox) in affected individuals.

STOMP Study Overview

The STOMP trial, officially known as the Study of Tecovirimat for Mpox (A5418), concluded its participant enrollment in December 2024 after an interim analysis indicated the treatment did not lead to quicker recovery time for skin lesions or alleviate pain in adults with mild to moderate Clade II mpox. This news is particularly disheartening as tecovirimat, developed by SIGA Technologies, had hope riding on its potential to combat this rising global health concern that was prompting extensive outbreaks.

Clinical Implications

Dr. Judith Currier, Past ACTG Chair, emphasized the importance of such rigorous clinical trials during health crises, stating, “There was considerable hope that tecovirimat would be an effective mpox treatment, and it was only through this rigorously designed trial that we were able to conclusively demonstrate its ineffectiveness in speeding time to resolution.”

Study Details

The STOMP trial was a phase 3, randomized, placebo-controlled study that enlisted 412 participants from 50 sites across seven different countries. Participants with symptoms for less than 14 days were either administered 600 mg of tecovirimat or a placebo twice daily over a two-week span. Significantly, 33% of individuals enrolled were also living with HIV, while 22% had taken at least one dose of the mpox vaccine.

Findings

The findings presented by ACTG were notable; although no major safety issues were reported, the data demonstrated that tecovirimat did not significantly alter the clinical course of mpox lesions or associated discomfort in participants, who were predominantly male (98%) and ethnically diverse (53% White, 11% Black, 45% Hispanic).

Secondary Analysis

Moreover, a secondary analysis aimed at understanding the various host and disease factors that might correlate with clinical resolution failed to identify any significant predictors. Researchers noted a trend wherein younger age associated with lower levels of mpox DNA led to quicker clinical resolution, but these observations lacked statistical backing in their modeling analyses.

Future Directions

Dr. Timothy Wilkin, the Protocol Chair, expressed optimism regarding the efficiency of conducting international clinical trials in the midst of a pandemic, and underscored the need to explore alternative treatments for mpox and other orthopoxviruses, as tecovirimat’s role was effectively dashed by these findings.

Conclusion

As mpox continues to pose a threat globally, researchers are calling for more investigation into effective therapeutic options for this virus. The conclusions drawn from the STOMP study mark a crucial step forward in understanding mpox disease management, urging the scientific community to pivot towards finding new solutions.

With mpox cases still surfacing in various regions, including the United States, the need for effective treatment has never been more pressing. The results from this prominent study serve as a catalyst for further exploration and innovation in addressing mpox and potentially other infectious diseases in the future.

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