Orphan Drug Improves Mesothelioma Survival in Phase II Trial

T. Researchers with the National Cancer Institute report that, when administered along with the traditional chemotherapy, amatuximab appears to be able to enhance the effectiveness of treatment and extend survival.

Amatuximab is a monoclonal antibody that targets the glycoprotein mesothelin. Many types of cancer overexpress this protein, including pleural mesothelioma. Studies have found that mesothelin plays a role in cell adhesion which allows tumors to take hold and ‘seed’ new tumors in other parts of the body. By binding to the mesothelin on the surface of mesothelioma cells, amatuximab prevents this adhesion and triggers an immune response against tumors. It was granted orphan drug status in the U.S. in 2012 for its potential to improve mesothelioma treatment. It received the same designation in Europe in 2013.

The newly-completed phase II study, headed by Raffit Hassan, MD, of the National Cancer Institute, involved 89 pleural mesothelioma patients from 26 centers. These patients received 5 mg/kg of amatuximab along with their pemetrexed and cisplatin on days one and eight of their 21-day treatment cycles. Patients who had some response to the drug were given amatuximab for “maintenance” after all of their chemotherapy cycles were finished.

The good news is that, not only was the treatment well tolerated, but imaging studies showed that it either shrank mesothelioma tumors or stopped their growth in 90% of patients. Forty percent of patients experienced a partial response while more than half experienced stable disease.

Although the treatment did not significantly extend progression-free survival in these patients, overall survival was better than standard treatments. Median overall survival among mesothelioma patients on the combination treatment with amatuximab was 14.8 months, with a third of patients still alive and 5 still on amatuximab for maintenance when the tests were concluded. With standard therapy, mesothelioma survival is often less than 12 months.

Mesothelioma is an aggressive asbestos-linked cancer of internal membranes. New drugs designed to treat it may be eligible for orphan drug status because the disease is so rare, claiming the lives of about 2,500 Americans annually. By forgoing certain regulations and fees, orphan drugs like amatuximab can be brought to market faster and potentially benefit more people with diseases like mesothelioma.

Source:

Hassan, R et al, “Phase II clinical trial of amatuximab, a chimeric anti-mesothelin antibody with pemetrexed and cisplatin in advanced unresectable pleural mesothelioma”, September 17, 2014, Clinical Cancer Research, Epub ahead of print