Cancer Drug Controlled Disease in Phase 1 Trial
A clinical study of 15 patients found that the drug RSO-021 successfully controlled disease in 67 percent of participants.
Updated on Sept. 21, 2026 in Cancer
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In a phase 1 trial conducted between 2022 and 2023, the drug RSO-021 showed promise for treating mesothelioma. The treatment, which inhibits the PRX3 enzyme, resulted in disease control for 67% of the 15 patients involved after 12 weeks of therapy.
Why it matters
Mesothelioma is a rare cancer with limited treatment options, currently affecting approximately 3,000 Americans annually. By targeting the PRX3 enzyme, this drug offers a new approach to disrupting the chemical balance required for tumor cell survival.
The study administered RSO-021 at a weekly dose of 90 milligrams directly into the chest via catheter. Among the trial participants, no deaths were attributed to the drug during the study period.
The players
RS Oncology
This is the pharmaceutical organization that sponsored the phase 1 clinical trial for RSO-021.
University of Vermont
This academic institution served as the site for the initial research that led to the development of this drug.
The details
The drug RSO-021, a formulation of the antibiotic thiostrepton, works by binding to and blocking the PRX3 enzyme that tumor cells use to mitigate oxidative stress. Researchers are currently developing second-generation PRX3 inhibitors that could eventually be administered as a tablet rather than through a catheter.
Timeline
The phase 1 trial was conducted in the United Kingdom from 2022 to 2023.
The principal investigator presented the phase 1 findings in 2024.
The research paper regarding these results was published in July 2026.
Researchers expect to present phase 2 trial results later in 2026.
The Big Picture
This study advances the development of PRX3 inhibitors as a viable therapeutic strategy for oncology patients. The research provides critical clinical validation for the potential of targeting the PRX3 enzyme to disrupt tumor cell survival.
While the drug is not yet FDA-approved, this trial suggests a potential future treatment path for mesothelioma patients. Participants in the study required delivery of the medication directly into the chest, which remains a factor for future clinical accessibility.
The takeaway
This trial demonstrates that targeting the PRX3 enzyme is a scientifically sound method for inhibiting tumor cell growth in mesothelioma cases. Patients and their families should note that while early results are positive, the drug must still undergo larger, randomized trials before it becomes available.
What happens next
Researchers are scheduled to present the results from the phase 2 trial of RSO-021 at a global oncology meeting later in 2026.
Further reading
Learn more about the latest research and clinical developments in Cancer.
Source note: This article includes information reported by Medical Daily.
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