A novel cancer drug that disables a protective enzyme in tumour cells controlled disease progression in 67% of patients with relapsed mesothelioma in a Phase I trial, according to research published in Nature Communications.
Mesothelioma is a rare but aggressive cancer typically caused by asbestos exposure, with approximately 30,000 people diagnosed worldwide each year. Current treatments offer limited benefit, with median survival around 12 months and five-year survival rates of approximately 10%.
Researchers at the University of Vermont and RS Oncology developed the drug RSO-021, based on a naturally occurring antibiotic called thiostrepton. The treatment targets peroxiredoxin 3 (PRX3), an antioxidant enzyme that tumour cells produce in elevated quantities to protect themselves from damaging reactive oxygen species generated by rapid metabolism.
By inhibiting PRX3, the drug causes hydrogen peroxide to accumulate in tumour cell mitochondria, triggering cell death. Because tumour cells generate more reactive oxygen species than normal cells, the drug shows selectivity for cancer cells over healthy tissue.
The Phase I trial, conducted in the United Kingdom between 2022 and 2023, enrolled 15 patients with relapsed mesothelioma. The drug was administered directly into the chest through an existing catheter, concentrating treatment at the tumour site. Progression-free survival averaged 4.2 months, comparable to current therapies, but overall survival exceeded what is typically seen with existing treatments.
The drug met safety and tolerability requirements, with no patient deaths attributed to treatment. Researchers confirmed the drug’s mechanism of action worked in human tumours, as observed in laboratory studies.
Phase II trial results are expected to be presented at a global oncology meeting this year. The team is also developing second-generation inhibitors that could potentially be delivered orally and applied to other cancer types.
Source: Medical Xpress / University of Vermont (Nature Communications, 2026)
