By Bunmi Yekini
The antiviral drug tecovirimat (TPOXX) has been found ineffective in reducing lesion resolution time or alleviating pain in adults with mild to moderate clade II mpox, according to interim findings from the Study of Tecovirimat for Mpox (STOMP). The clinical trial, sponsored by the National Institutes of Health’s (NIH) National Institute of Allergy and Infectious Diseases (NIAID), revealed no significant safety concerns but failed to demonstrate the drug’s efficacy.
Based on these results, the study’s Data Safety and Monitoring Board (DSMB) recommended halting further participant enrollment. NIAID accepted this recommendation, also closing an open-label arm designed for participants at elevated risk of severe mpox.
“The initial STOMP findings provide valuable insight to inform clade II mpox medical countermeasures and underscore the critical importance of conducting well-designed randomized clinical trials during infectious disease outbreaks,” said NIAID Director Jeanne Marrazzo, M.D., M.P.H.
STOMP, which began in September 2022, randomized participants in seven countries, including the U.S., to receive either tecovirimat or a placebo. An interim analysis conducted when 75% of the target enrollment was reached found less than a 1% chance of demonstrating the drug’s effectiveness with further study.
“STOMP was a banner study for its speed of startup, inclusiveness, and collaboration across governments and public health authorities,” said study chair Timothy Wilkin, M.D., M.P.H., from the University of California, San Diego. “This study may serve as a model for outbreak response, delivering essential scientific evidence while also enabling equitable treatment access.”
Mpox, caused by a virus primarily spread through close contact, has seen global outbreaks in recent years. While tecovirimat was originally approved by the FDA to treat smallpox, its efficacy against mpox remains unproven.
NIAID emphasized the ongoing need for systematic evaluation of existing and novel mpox treatments and announced further analyses of STOMP data. Additionally, the CDC continues to provide tecovirimat under an expanded access protocol for patients with severe cases or elevated risks.