New mesothelioma drug turns cancer’s own defenses against it — SkimNews
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- RSO-021 controlled disease progression in 67% of mesothelioma patients in a Phase 1 trial of 15 relapsed patients sponsored by RS Oncology, with post-treatment tissue confirming the drug hit its intended PRX3 target in human tumors.
- The drug uses thiostrepton, a naturally occurring antibiotic reformulated for oncology, to disable peroxiredoxin 3 (PRX3) inside cancer cell mitochondria, causing hydrogen peroxide to accumulate until cell death occurs.
- RS Oncology was spun out of the University of Vermont around 2015 to commercialize the lab discoveries, with UVM pathology professor Brian Cunniff serving as the company's chief science officer and Victoria Gibson as lead author of the Nature Communications study.
- Phase 1 results showed average progression-free survival of 4.2 months, no patient deaths attributed to the drug at the 90-milligram dose, and overall survival that Cunniff called 'better than what is typically seen with currently available therapies.'
- The treatment is delivered directly into the chest cavity through a catheter already in place to drain pleural effusions, a complication affecting roughly 90% of mesothelioma patients, which concentrates the drug near the tumor.
- Researchers report RSO-021 also modulates the immune environment around tumors, giving the drug what Cunniff described as 'both cytotoxic activity' and 'immunomodulatory capacity.'
- Phase 2 has been completed and results are expected at a global oncology meeting later in 2026, while UVM and collaborators at the University of Leicester are developing second-generation PRX3 inhibitors, potentially as oral tablets, and exploring thiostrepton in gastric and other gastrointestinal cancers.
Why it matters: Mesothelioma carries a median survival of roughly 12 months and a five-year survival rate near 10%, with no effective standard of care for relapsed patients. A Phase 1 disease-control rate of 67% and above-standard overall survival in 15 critically ill patients gives RS Oncology a credible clinical signal to expand the PRX3-targeting strategy into peritoneal, gastric, and other gastrointestinal cancers where the same mitochondrial vulnerability may apply.
Ask SkimNews
