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Pancreatic Cancer Vaccine Enters Mid-Stage Trial

Researchers evaluate genetically modified bacterium

Medical investigators at the Virginia G. Piper Cancer Center in Scottsdale, Arizona, are studying a new cancer immunotherapy to see whether it can help patients with advanced pancreatic cancer.

Participants in the phase IIb Efficacy of Combination Listeria/GVAX Immunotherapy in the Pancreatic Cancer SEtting (ECLIPSE) trial will be randomly assigned to receive the CRS-207 vaccine alone or the CRS-207 vaccine combined with the GVAX Pancreas vaccine and low-dose cyclophosphamide. A third group of patients will receive standard chemotherapy. A total of 240 patients are expected to be treated at more than 20 sites in North America.

Both investigational vaccines were developed by Aduro BioTech.

The CRS-207 vaccine is a weakened form of the bacterium Listeria monocytogenes that has been genetically modified to be safe for human use while retaining its ability to stimulate the immune system. Specifically, CRS-207 has been engineered to stimulate an immune response against the tumor-associated antigen mesothelin, which is present at high levels on pancreatic cancer cells.

The GVAX vaccine is composed of genetically modified, inactivated pancreatic cancer cells, which have been shown to stimulate the immune system’s anticancer activity. The vaccine is administered with low-dose cyclophosphamide to boost the vaccine’s effectiveness.

In a recent phase IIa trial involving 90 patients with advanced pancreatic cancer, survival was improved in patients who received the combination regimen of CRS-207, GVAX, and cyclophosphamide compared with those given GVAX and cyclophosphamide.

After a median follow-up period of 7.8 months, median overall survival (OS) was significantly improved in patients treated with CRS-207, GVAX, and cyclophosphamide compared with those treated with GVAX and cyclophosphamide (6.1 months vs. 3.9 months, respectively; hazard ratio [HR], 0.54; P = 0.011).

The treatment effect was particularly evident in patients who received two or more prior regimens for metastatic pancreatic cancer, with a median OS of 5.1 months versus 3.7 months for the two treatments, respectively (HR, 0.34; P = 0.001).

Both immunotherapies were well-tolerated, with no serious treatment-related adverse side effects. Toxicities included transient fever, rigor, and lymphopenia after the administration of CRS-207, and local injection-site reactions after the administration of GVAX.

Pancreatic cancer is difficult to treat and is the fourth leading cause of cancer-related death in the U.S. Tumors may grow in the pancreas without early symptoms, which means that the disease is often in an advanced stage when it is diagnosed, and survival remains poor.

Sources: TGEN; June 12, 2014; and ASCO; January 2014.

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