Q&A: How mpox research is helping scientists prepare for a new pandemic
June 4, 2025
The mpox outbreak of 2022 devastated communities across the U.S., including San Francisco. Yet the widely used antiviral TPOXX failed to speed recovery in clinical trials led by UC San Francisco and the Democratic Republic of the Congo. While the drug was safe, results showed no significant benefit—underscoring the urgency of developing more effective therapeutics. The inclusion of pregnant women and children in open-label study arms marked an ethical advancement in clinical trial design. This experience demonstrates why real-time, equitable trials are essential during health emergencies to ensure that treatment strategies are both evidence-based and inclusive from the outset.
The 2022 mpox outbreak brought over 20,000 cases and nearly 70 deaths in the United States, with San Francisco among the hardest hit. In the absence of approved treatments, physicians widely prescribed tecovirimat (TPOXX), an antiviral effective against smallpox. However, a global clinical trial—led by UC San Francisco in coordination with the Democratic Republic of the Congo—has found that while TPOXX is safe, it does not accelerate mpox recovery time. These results, though disappointing, are a critical step forward.
The study's ethical design set a new standard by including vulnerable populations—pregnant women, children, and immunocompromised patients—in an open-label arm. Too often, these groups are excluded from early trials, resulting in years-long delays before lifesaving drugs become accessible to them. This trial ensured they received standard care while contributing vital data to future treatment guidance.
The findings also stress the importance of understanding the limitations of animal model extrapolations and the necessity of rigorous human trials during health crises. While TPOXX showed promise in smallpox animal studies, it did not yield the same benefit for mpox in human populations.
Looking forward, attention turns to alternative treatments such as brincidofovir and monoclonal antibodies. These emerging options require similar robust clinical evaluations, especially as Clade I and Clade II strains of mpox continue to circulate globally.
The TPOXX trial reinforces the vital role of equitable, real-time clinical research in public health emergencies. In a future marked by emerging infectious threats, the ability to launch well-designed, inclusive trials rapidly will be key to protecting all populations—not just the healthiest—from the next epidemic. The scientific community must prioritize preparedness, agility, and equity in outbreak research to ensure timely access to safe and effective interventions.