Pembrolizumab was safe, tolerable, and yielded robust anti-tumour responses in patients with malignant pleural mesothelioma, according to data from the phase Ib KEYNOTE-028 clinical trial presented at the AACR Annual Meeting 2015, April 18-22.

“Malignant pleural mesothelioma is a rare form of cancer that arises in the outer lining of the lungs and internal chest wall. With a median survival of only about one year, there is a clear need for new treatment options,” said Evan W. Alley, MD, PhD, clinical associate professor, co- director of the Penn Mesothelioma and Pleural Program, and chief of the Hematology/Oncology Division at Penn Presbyterian Medical Center in Philadelphia.

“One of the main goals of our study was to establish whether the PD-1 inhibitor pembrolizumab was safe and tolerable for patients with this disease,” continued Alley. “None of our patients experienced any unexpected side effects and all adverse events could be managed without discontinuing treatment, so the primary study endpoints of safety and tolerability were met.”

“Somewhat more exciting was the fact that our preliminary analysis shows signs of clinical benefit,” he added. “We don’t have survival data yet, but the 76 percent disease-control rate that we observed among patients with advanced malignant pleural mesothelioma who had disease that had progressed after standard therapy or who were unable to receive standard therapy is very promising. There are no FDA [Food and Drug Administration]-approved treatments for malignant pleural mesothelioma that has progressed after standard therapy and response rates to second-line chemotherapy are usually less than 10 percent.”

KEYNOTE-028 is a phase Ib clinical trial that is evaluating pembrolizumab as a potential treatment for a variety of advanced solid tumours.

Only patients who have tumours that are positive for the protein PD-L1 are eligible for enrolment in the trial.

According to Alley, these data on the malignant pleural mesothelioma patient cohort are the first results of KEYNOTE-028 to be reported.

The preliminary data, which have been updated since the abstract was submitted, showed that among the 25 patients with malignant pleural mesothelioma that screened positive for PD-L1 and who were assigned pembrolizumab, seven experienced a partial response and 12 had stable disease.

At the time of analysis, two patients had not been assessed for response and 13 patients were still receiving pembrolizumab through the trial.

Alley explained that the researchers are hoping to have updated results to present at the AACR Annual Meeting 2015, including insight into whether tumour histology—that is, the cellular and tissue characteristics of the tumour—are associated with response.

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Source: AACR