Parp-Inhibitors show promise in mesothelioma treatment

• Maja Belamaric
• Featured News, Mesothelioma, Treatments

At this year’s American Association for Cancer Research, investigators from the United Kingdom announced the positive results of a mesothelioma clinical trial testing a relatively new class of targeted drugs: the PARP inhibitors.

The study Niraparib Efficacy in Patients With Unresectable Mesothelioma (NERO) enrolled 88 patients randomized into two groups showed that those treated with niraparib extended the median progression-free survival by 1.5 months compared to the arm of patients who only received symptom management care.

Eligible patients had already undergone standard chemotherapy treatment for mesothelioma with success, but they relapsed with the cancer coming back or growing.

Currently, there are no proven therapies for mesothelioma beyond initial treatment and after recurrence. Data on the efficacy of chemotherapy are limited, and immunotherapy retreatment has been only a recent addition to the doctors’ treatment arsenal.

What are PARP inhibitors?

Simply put, PARP inhibitors are drugs that prevent the enzyme known as poly ADP ribose polymerase (PARP) from doing its job of repairing damaged DNA in cells. If not repaired, damaged cells, including cancer cells, die. Conversely, if repaired, even if the repair is erroneous, the cells go on to survive and replicate which can be problematic with cancerous cells. Typically, patients who responded to chemotherapy previously are more likely to see a benefit from this class of drugs. While this study did not require patients enrolled to have a somatic BAP1 deletion, other studies looking into this agent often do. Somatic mutations are those not passed down to offspring and are instead acquired in the cells over time. BAP1 is a tumor suppressor gene, therefore its deletion is understood as consequential in mesothelioma.

Clinical trials employing PARP inhibitors currently available in the United States

While this study took place in the United Kingdom, in the U.S. clinical studies utilizing PARP inhibitors have been available to mesothelioma patients who fit certain eligibility criteria. Currently, one of those studies is still open and enrolling.

Olaparib in Patients with HRD Malignant Mesothelioma is available at the University of Chicago Medicine to patients with the loss of BAP1 and/or a germline (passed down from parents) or somatic (acquired over lifetime) mutation that disrupts protein function in at least one of the patient’s genes.