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MesotheliomaJune 2021Summary reviewed August 2026

A Targeted Pill Stopped Mesothelioma Growth in 58% of Patients

Fifteen of 26 people with mesothelioma saw their cancer stop growing for at least 12 weeks after taking rucaparib, a pill that targets tumors with specific gene mutations. The treatment worked best in patients whose tumors had lost certain DNA repair proteins. Side effects were mostly mild — nausea and tiredness were most common.

What the trial was testing

The MIST1 enrolled 186 patients with mesothelioma. The study was sponsored by University of Leicester and tracked outcomes across the full group of patients who matched the trial's eligibility profile.

It was initial testing (phase 2). Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.

What the results showed

58% of patients with mesothelioma saw their cancer stop growing for at least 12 weeks on this targeted pill.

The Lancet. Respiratory medicine · 2021 · NCT03654833

These findings — that saw their cancer stop growing for at least 12 weeks — were published in the The Lancet. Respiratory medicine and represent the headline result of the study.

Researchers tracked outcomes across 186 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.

What this means for patients

For patients with mesothelioma, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.

What you can do now

This was an early-stage study and the treatment is not yet FDA-approved for mesothelioma. If you have mesothelioma that has grown after other treatments, ask your doctor about testing your tumor for BAP1 or BRCA1 mutations — this could help identify whether rucaparib or similar drugs might work for you in a clinical trial.

Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.