STOMPing Out Mpox

Content From: Demetre Daskalakis, MD, MPH, National Monkeypox Response Deputy Coordinator, The White HousePublished: March 03, 20233 min read



Mpox cases continue to decline, but important scientific questions remain unanswered. Key among these: Does the investigational drug tecovirimat (TPOXX) actually work to treat mpox? 


In 2018, TPOXX was approved to treat smallpox by the United States Food and Drug Administration (FDA) under the “Animal Rule.” This rule allows findings from well-designed and well-conducted animal studies to support an FDA approval when human trials are not possible. Thankfully, since we don’t have smallpox circulating to test TPOXX against a real-world infection, the drug qualified for this rule and was approved to treat smallpox. The viruses that cause mpox and smallpox are similar, therefore antiviral drugs developed to protect against smallpox may be used to treat mpox. Since the 2018 approval did not include mpox, the CDC and FDA worked together in 2022 to establish an Expanded Access—Investigational New Drug (EA-IND) pathway for TPOXX so that it could be used to treat mpox in the event of an outbreak. 

Thousands of people were treated for mpox in the United States using this pathway during the current outbreak. Data from the EA-IND has taught us that TPOXX is safe, but it cannot tell us if the drug works to treat mpox. Since we have mpox virus circulating in the community, we have an opportunity to see if TPOXX works to treat mpox in a well-designed human study—the STOMP Trial. 

Study Design

STOMP has two randomized arms; participants are assigned, at random, to receive either TPOXX or an inactive placebo, which is a pill that looks like the active medication but has no active drug in it. This arm is very important because it allows scientists to compare the effect of TPOXX on mpox disease compared to no treatment with TPOXX. Neither study researchers nor the study participants know which arm they are enrolled in. This helps prevent bias when trying to measure if TPOXX works against mpox. People who get sicker while in the randomized placebo arm can join the open label arm and receive TPOXX.

The third arm is open label, meaning that both participants and study staff are aware they are receiving TPOXX. People with more severe mpox infection, people who have immune suppression, children, and pregnant people are in the open label arm.

How You Can Help

With cases low in the United States, it is hard to find people to participate in this important study. It is critical that we work to support the participation of people with mpox who are eligible so that we can learn if TPOXX can treat this disease. There are many ways to enter the study, including a phone number that a medical provider or a person with mpox can call to see if they are eligible. Learn more about the STOMP trial at STOMPTPOXX.orgExit Disclaimer or call (855) 876-9997 to connect to a study site.

People with mpox or suspected mpox are able to enroll in STOMP anywhere in the US. People who live near a study site have the option to participate onsite. If a site is not available, people can enroll remotely, which means they do not need to go to a study site to participate. For remote participants, all assessments are done through the phone or telemedicine. If you have mpox or are a provider taking care of a person with mpox, we need your help to get people in this study so we can learn how to use TPOXX for mpox infections around the world.