CHICAGO, June 6, 2016 /PRNewswire/ -- Polaris Group announced today that the phase III study of second line ADI-PEG 20 plus best supportive care versus placebo plus best supportive care in patients with advanced hepatocellular carcinoma (HCC) did not meet its primary endpoint of demonstrating overall survival (OS) benefits.  Median OS was 7.8 months for ADI-PEG 20 vs. 7.4 months for placebo (p = 0.884, HR=1.022 [95% CI: 0.847, 1.233]).  However, analysis of study data revealed that patients with arginine depletion for 7 weeks or longer had a median OS of 12.5 months, compared to 6.3 months (P < 0.0001) for patients with arginine depletion lasting less than 7 weeks. It is believed that treating patients with ADI-PEG 20 depletes circulating arginine, thus starving cancer cells of arginine, which is an essential amino acid for these cancers. This results in the starved cancer cells being unable to survive and grow while leaving the body's normal cells unharmed.  The statistically significant findings from the analysis of the study data appears to support this hypothesis. Additionally, sorafenib naïve patients appear to have benefited more than those who failed prior sorafenib treatment, suggesting that ADI-PEG 20 may be more efficacious in the first-line setting.

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The study also showed ADI-PEG 20 was well tolerated, with the most common side effects being fatigue and decrease of appetite.  The full study results were presented at a plenary session by the lead investigator, Dr. Ghassan K. Abou-Alfa from the Memorial Sloan Kettering Cancer Center, at the American Society of Clinical Oncology's 2016 annual meeting in Chicago.

"We are encouraged to see the overall survival benefit demonstrated by ADI-PEG 20 in the patient population with prolonged arginine depletion, which supports the theory that arginine depletion can be a safe way to extend life for these very ill patients," said John Bomalaski, M.D., Executive Vice President, Medical Affairs at Polaris Pharmaceuticals, Inc.  "We have already identified new combination therapy strategies that can significantly prolong arginine depletion and enable ADI-PEG 20 to synergize with current cancer treatments as shown in early stage clinical studies. We are making plans to move these combination therapies into late stage clinical development in the near future."

About ADI-PEG 20

ADI-PEG 20 is a biologic being developed by Polaris Group to treat cancers carrying a major metabolic defect that renders them unable to internally synthesize arginine. Because arginine is essential for protein synthesis and survival of cells, these cancer cells become dependent upon the external supply of arginine to survive and grow. ADI-PEG 20 is designed to deplete the external supply of arginine, causing arginine-dependent cancer cells to die while leaving the patient's normal cells unharmed.  Multiple cancers have been reported to have a high degree of arginine-dependency and can potentially be treated with ADI-PEG 20.

About Polaris Group

Polaris Group specializes in the research and development of protein drugs to treat cancer and other debilitating diseases. In addition to the ADI-PEG 20 program, Polaris Group is developing other biotherapeutic agents including a small molecule drug program that utilizes a rational structure-based approach to design novel compounds that inhibit the biological function of cancer-related protein targets.

For additional information please visit www.polarispharma.com

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SOURCE Polaris Group