Press Releases

October 19, 2022

Mass General Brigham Sites Begin Phase 3 Trial Evaluating Mpox Treatment

Brigham and Women’s and Mass General Hospital part of national trial to assess effectiveness of antiviral tecovirimat (TPOXX) for the treatment of human Mpox infection

BOSTONMassachusetts General Hospital (MGH) and Brigham and Women’s Hospital (BWH), the founding members of Mass General Brigham, today announced their participation in STOMP (Study of Tecovirimat for Human Mpox Virus), a phase 3, randomized, placebo-controlled, double-blind trial evaluating the safety and efficacy of tecovirimat (TPOXX) for the treatment of human mpox. STOMP, which is being led by the AIDS Clinical Trials Group (ACTG), will gather data from a broad population of people with mpox to determine if participants receiving tecovirimat heal more quickly and have less pain compared with those taking placebo.

“We need studies like STOMP to know if a drug is working effectively and if it’s going to be the best treatment for our patients,” said MGH site principal investigator Elizabeth (Libby) Hohmann, MD, of the Infectious Diseases Division at MGH. “Randomized, double-blind clinical trials give us vital information to improve clinical care, and people living in the Boston area who have mpox have the opportunity to make a huge contribution by participating in this study.”

“This study will help us to understand if TPOXX is making a difference in a patient’s course of disease and what aspects of the disease it’s effective against,” said BWH site principal investigator Jennifer Manne-Goehler, MD, ScD, of the Division of Infectious Diseases at BWH. “Does it promote faster healing? Does it lead to less viral shedding? Does it decrease rare but serious complications of mpox? These are pressing questions that only a study like this one can help us answer.”

A global outbreak of mpox emerged in the spring of 2022 and has since spread throughout the world, with more than 56,000 cases in 103 countries and more than 21,000 cases in the United States, including 420 in Massachusetts.

Tecovirimat (manufactured by SIGA Technologies, Inc.) is approved by the U.S. Food and Drug Administration (FDA) to treat smallpox, but it is not yet known if it can effectively or safely treat mpox. The drug has been used to treat some patients during the current mpox outbreak under the investigational New Drug (EA-IND) protocol, sometimes referred to as “compassionate use.”

This multi-center trial will enroll more than 500 adults with mpox virus infection. Importantly, this trial will include people with severe disease and those at high risk of severe disease, including pregnant and breastfeeding people, children, and individuals with underlying immune deficiency and active inflammatory skin conditions. This high-risk group will all receive open-label tecovirimat. Study participants with symptomatic mpox virus infection, who do not meet the criteria for the open-label cohort, will be randomly assigned in a ratio of 2-to-1 to receive either tecovirimat or placebo orally for 14 days. Participants who are randomized in the double-blinded cohort of the study and later progress to severe disease will be offered the option to switch to open-label tecovirimat, as will participants who report persistent severe pain from mpox virus infection.

“This trial is designed to be centered on the needs of the patient — if an individual is progressing or suffering from more severe symptoms, we have the option to give them TPOXX without randomization,” said Manne-Goehler.

All participants in STOMP will be followed for at least eight weeks through a combination of virtual and in-person visits, as well as daily self-reports to determine if those receiving tecovirimat heal more quickly compared to those receiving placebo. STOMP will also provide critical data on the optimal dosing and safety of tecovirimat in children and people who are pregnant and breastfeeding.

Individuals who have presumptive or confirmed mpox infection (testing positive within seven days) and started experiencing symptoms within 13 days are eligible. Testing will be provided by the study. Participants with presumptive mpox virus infection who have not yet been tested are able to enroll as long as their study-provided test is positive. Participants must also have at least one active skin lesion that has not yet scabbed, a mouth lesion, or proctitis (inflammation in the lining of the rectum).

STOMP is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), which also funds the ACTG. A list of participating sites in the United States can be found here.

STOMP is led by Timothy Wilkin, M.D., M.P.H., Weill Cornell Medicine, William Fischer, M.D., University of North Carolina (UNC) and Jason Zucker, M.D., Columbia University (vice-chairs), and is supported by Judith Currier, MD, MSc, UCLA, and Joseph J. Eron, M.D., UNC (ACTG Co-Chair).

For more information about STOMP, please visit the ACTG website.

For information about enrolling in the trial at BWH or MGH, please click here.


About Mass General Brigham

Mass General Brigham is an integrated academic health care system, uniting great minds in medicine to make life-changing impact for patients in our communities and people around the world.

Mass General Brigham connects a full continuum of care across a system of academic medical centers, community and specialty hospitals, a health insurance plan, physician networks, community health centers, home care, and long-term care services.

Mass General Brigham is a non-profit organization that is committed to patient care, research, teaching, and service to the community. In addition, Mass General Brigham is one of the nation’s leading biomedical research organizations and a principal teaching affiliate of Harvard Medical School. For more information, please visit

About the ACTG

Founded in 1987, the AIDS Clinical Trials Group (ACTG) was the world’s first HIV research network. The ACTG conducts groundbreaking studies to improve the treatment of HIV and its complications, including tuberculosis and viral hepatitis; reduce new infections and HIV-related illness; and advance new approaches to prevent, treat, and ultimately cure HIV in adults and children. More recently, the ACTG has expanded its focus to include the evaluation of outpatient treatments for COVID-19. ACTG investigators and research units in 15 countries serve as major resources for HIV/AIDS research, treatment, care, and training/education in their communities. ACTG studies have helped establish current paradigms for managing HIV disease, and have informed HIV treatment guidelines, resulting in dramatic decreases in HIV-related mortality worldwide.