New Mesothelioma Drug Turns Cancer’s Own Defenses Against It

Mesothelioma isn’t a word most people toss around in everyday conversation, but for the few thousand folks diagnosed each year it’s a life‑changing reality. The disease is stubborn, linked to inhaled asbestos fibers that sit in the lungs for decades before sparking chronic inflammation and, eventually, a deadly tumor.

Globally, about 30,000 new cases pop up annually, and the therapeutic toolbox is painfully thin. Chemotherapy and the newer immunotherapies help a handful, yet the median survival hovers around 12 months and only roughly one in ten patients lives five years after diagnosis.

“We’re looking at a disease that desperately needs better options,” says Brian Cunniff, a professor at the University of Vermont (UVM). His team, together with research scientist Victoria Gibson and collaborators worldwide, decided to flip the script on a classic cancer‑fighting idea.

Instead of flooding tumors with antioxidants—a strategy that, in past trials, often fed the cancer’s fire—they asked, “What if we yank away the tumor’s own antioxidant shield?” Their target? Peroxiredoxin 3, or PRX3, a mitochondria‑resident enzyme that helps cancer cells mop up the reactive oxygen species (ROS) they churn out as a by‑product of their frenzied metabolism.

When PRX3 is blocked, ROS accumulate, and the tumor’s internal machinery essentially overloads itself. To pull off this molecular sabotage the researchers turned to thiostrepton, an old‑school antibiotic discovered decades ago. By tweaking it into a formulation called RSO‑021, they created a drug that latches onto PRX3 and disables it.

Pre‑clinical work was promising. Knocking out PRX3 in mesothelioma cell lines caused the mitochondria to falter, slowed cell division, and prevented tumor formation in mice. Even more reassuring, mice engineered to lack PRX3 altogether showed no obvious health problems—suggesting the enzyme can be targeted without wrecking normal tissue.

The real test came in a Phase I trial run by RS Oncology, a spin‑out company founded to shepherd the UVM discovery into the clinic. Thirty‑something patients with relapsed mesothelioma, many already fitted with chest catheters for fluid buildup, received RSO‑021 directly into the pleural space. The results? Disease progression was halted in 67 % of participants, some tumors actually shrank, and the drug was generally well tolerated.

Those numbers sound like a small beacon in a very dark field, but they sparked a genuine buzz. Patients lived longer than historical controls treated with standard care, and the safety profile was encouraging enough that researchers are already planning larger studies.

“People will come up to us at conferences and say you can’t mess with mitochondria—they’re too essential,” Gibson remarks with a smile. Yet the data from both mice and humans are quietly saying otherwise, opening a door to a therapeutic concept that could extend beyond mesothelioma to any cancer that leans heavily on PRX3.

While it’s still early days, the work illustrates how revisiting old drugs with fresh eyes can uncover unexpected weapons against stubborn cancers. If the upcoming trials confirm these findings, we may finally have a treatment that turns a tumor’s own survival trick against it, offering hope to the men and women who have been fighting mesothelioma for far too long.