The checkpoint inhibitor pembrolizumab appears to be well tolerated and may have antitumor activity in patients with PD-L1-positive malignant pleural mesothelioma, according to a study published in The Lancet Oncology. Pembrolizumab is approved to treat melanoma, non-small cell lung cancer, and head and neck cancers. This is the first study to show a positive impact from a checkpoint inhibitor immunotherapy in this disease.1

In this trial, 25 patients were given a dose of pembrolizumab every 2 weeks for 24 months. They found that the cancer reduced in size in 14 of those patients. On average, patients went approximately 6 months without their disease progressing, and overall survival (OS) was approximately 18 months. Fourteen patients passed away during the study and 4 were still undergoing treatment at the time of analysis.

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The researchers report that most patients with malignant pleural mesothelioma who receive a second-line therapy have a life expectancy of approximately 6 or 7 months. In a news release, the researchers said that to have four patients still ongoing at 2 years is very encouraging.2 The most common side effects reported were fatigue, nausea, loss of appetite, and dry mouth. The investigators noted that none of the patients had to stop treatment because of side effects.

The team evaluated results from an ongoing, nonrandomized, open-label, phase 1b trial involving 13 research sites in 6 countries. Malignant pleural mesothelioma is a rare and aggressive cancer primarily caused by the inhalation of asbestos. Most patients survive less than 1 year. The standard first-line therapy treatment involves chemotherapy and currently there is no approved second-line therapy. 


1. Alley EW, Lopez J, Santoro A, et al. Clinical safety and activity of pembrolizumab in patients with malignant pleural mesothelioma (KEYNOTE-028): preliminary results from a non-randomised, open-label, phase 1b trial. Lancet Oncol. 2017 Mar 10. doi: 10.1016/S1470-2045(17)30169-9 [Epub ahead of print]

2. Pembrolizumab shows promise in treatment of mesothelioma. Philadelphia, PA: University of Pennsylvania School of Medicine; March 20, 2017. EurekAlert! website. Accessed April 3, 2017.