Immunotherapy drug pembrolizumab (Keytruda) continues to show ground-breaking effectiveness in the treatment of malignant pleural mesothelioma, according to the latest published study.
Mesothelioma specialist Dr. Evan Alley detailed the results earlier this month in The Lancet Oncology.
Alley, chief of hematology and medical oncology at Penn Presbyterian Medical Center, believes pembrolizumab could become an accepted second-line treatment for pleural mesothelioma.
Pembrolizumab is marketed as Keytruda by pharmaceutical giant Merck & Co.
Alley cited the ongoing clinical trial involving 13 research sites covering six countries. The trial, which includes the Abramson Cancer Center at Penn Medicine, evaluates the effectiveness of pembrolizumab for patients with several different advanced malignancies.
The study includes 25 pleural mesothelioma patients.
“This study provides evidence that some patients [with mesothelioma] can have long-term disease control with this drug, which we haven’t seen before,” Alley said in a press release. “This drug appears to be well tolerated.”
Standard first-line therapy for mesothelioma includes a combination of chemotherapy, radiation and surgery, but it remains relatively ineffective as a long-term solution.
Alley believes pembrolizumab, classified as a checkpoint inhibitor drug, can provide a needed advancement in treatment.
Checkpoint inhibitors allow the immune system to fight the cancer by negating the PD-L1 protein, which normally prevents the immune response.
“There have been a lot of studies looking at different drugs, but researchers have not seen positive results,” Alley said. “We’ve found this new class of drugs that seems to be more effective than what’s been available in the past.”
Mesothelioma is a rare and aggressive cancer caused by exposure to toxic asbestos fibers. It is diagnosed in an estimated 3,000 people in the U.S. each year. There is no definitive cure.
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The 25 mesothelioma patients in the trial received the drug every two weeks for up to two years, unless the disease progressed or an unacceptable side effect occurred.
All patients had previously received chemotherapy and were experiencing disease progression when they joined the trial.
Fourteen of the 25 mesothelioma patients experienced initial tumor reduction during treatment. Average time before disease progression was six months.
The average overall survival was 18 months. Four of the patients lived — or are still living — more than two years after the trial began.
“Most patients who receive a second-line therapy have a life expectancy of about six or seven months,” Alley said. “So to have four patients still ongoing at two years is very encouraging.”
Mesothelioma patient Walter Merth, who is not participating in the ongoing clinical trial, has done especially well with pembrolizumab.
Merth receives the drug at the Abramson Cancer Center as part of the Merck Access Program, which offers co-pay assistance and insurance coverage for eligible patients.
He started taking the drug in early 2016 when his cancer started growing again, only two months after aggressive surgery attempted to remove it. Merth credits the drug for a dramatic turnaround.
“The therapy has given me a new window. It’s like getting my life back,” Merth told Asbestos.com in September 2016.
The U.S. Food and Drug Administration already approved pembrolizumab for the treatment of other cancers, including melanoma, certain head and neck cancers, and metastatic non-small cell lung cancer with tumors that express the PD-L1 protein.
Mesothelioma patients also reported only minimal side effects, including dry mouth, loss of appetite, fatigue and nausea.
“One great sign in this study is that none of the patients had to stop treatment because of side effects,” Alley said. “Some had temporary stoppages, but they were able to continue.”
There are more than 90 active clinical trials across the country today involving pembrolizumab and various cancers.
Alley said two new trials involving pembrolizumab and mesothelioma will begin later this year.
Each will include the drug in combination with other therapies.
Former President Jimmy Carter brought considerable attention to pembrolizumab in 2015 when he credited the drug for stopping the melanoma cancer that had spread to his brain.
“We need to better understand what we can do next to make immunotherapy more effective for more patients,” Alley said.