Updated phase III clinical trials indicate that a combination of two immunotherapy drugs can improve prognosis in patients with non-removable mesothelioma tumors, according to scientists from the Netherlands Cancer Institute.

The trial, called checkmate 743, is a combination of drugs nivolumab and ipilimumab. Nivolumab is a cell checkpoint inhibitor, which means that the drug “shuts off” the inhibitors in T-cells that keep the cells from attacking tumors. In other words, it causes T-cells to attack tumors. Ipilimumab is an antibody that activates the immune system.

Nivolumab is already a cancer treatment under the brand name Opdivo. Ipilimumab, brand name Yervoy is a common melanoma treatment.

The experiment involved about 600 people with unresectable mesothelioma. Half of the patients received the experimental drug combination and the other half received normal chemotherapy. One of the two treatments would be their first line of therapy. Researchers examined the progress of patients for two years.

According to researcher Dr. Paul Baas, in the experimental group, 41% of patients showed significant tumor shrinkage while 2% of those patients showed complete tumor reduction. Forty-four percent of patients in the chemotherapy group showed partial tumor shrinkage. Even though the percentage of shrinkage is similar, the impact is much greater in the immunotherapy group.

Baas explained his research in the virtual The International Association for the Study of Lung Cancer conference video here.

The trial is still in phase III, meaning that scientists are still learning about the side-effects of the treatment. Thirty percent of patients experienced severe side-effects. About 15% of the patients were in the experimental group and exited the treatment prematurely.

Baas recommended making immunotherapy the first treatment for those with inoperable tumors. He said that the treatment could provide a longer survival rate for someone with mesothelioma, which already has a normally-poor prognosis.

“CheckMate 743 met its primary endpoint of statistically improved OS with nivolumab + ipilimumab vs standard of care chemotherapy in first-line treatment of patients with mesothelioma," Baas said. "These clinically meaningful data represent the first positive phase 3 trial of immunotherapy in first-line (malignant pleural mesothelioma) and should be considered as a new standard of care."

The phase II reports for this clinical trial were published in an article from The Lancet in March of 2019. Anna Bibby and Nick Maxwell, experts on mesothelioma commented about the substantial impact of immune checkpoint inhibitors on the future of mesothelioma treatment. Bibby said in a podcast that this treatment would bring hope to people with this type of cancer.

It is estimated that phase III will conclude in April 2022.

Read more about treatment options for Mesothelioma here.

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