FLT-PET Scan Provides Early Evidence of Response to Arginine Depletion by ADI-PEG 20 in Argininosuccinate Synthetase Deficient Thoracic Tumors

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CHICAGO, June 6, 2016 /PRNewswire/ -- Polaris Group announced today that FLT-PET scan provided early evidence of response to arginine depletion by its lead therapeutic ADI-PEG 20 (pegylated arginine deiminase) in argininosuccinate synthetase (ASS1) deficient thoracic tumors.  The results were generated during analysis of an ongoing phase 1 study that tests combining ADI-PEG 20 with the standard first-line chemotherapy cisplatin + pemetrexed (ADIPEMCIS) in ASS1-deficient malignant pleural mesothelioma (MPM) and non-squamous non-small cell lung carcinoma (NSCLC) and presented at the American Society of Clinical Oncology's 2016 annual meeting in Chicago.

The investigators used [18F]-fluoro-L-thymidine–positron emission tomography (FLT-PET) scan to image thymidine intake by tumors at baseline and during treatment cycles, thereby establishing a longitudinal pattern of metabolic response to the treatment.  Data from 11 patients (8 MPM and 3 NSCLC) showed that partial metabolic response could be seen as early as 24 hours post ADI-PEG 20 treatment.  This demonstrates that ADI-PEG 20 can have a significant effect on a tumor after only one dose. The metabolic response rate increased as patients completed additional cycles of ADIPEMCIS treatment, and was consistent with partial response rate as assessed by RECIST1.1 using computerized axial tomography (CAT) scanning. 

"This FLT-PET scanning technique shows that arginine starvation in the tumor can occur after only one dose of ADI-PEG 20," said John Bomalaski, M.D., Executive Vice President, Medical Affairs at Polaris Pharmaceuticals, Inc.  "The increase of the metabolic response rate, as well as the response rate using two dimensional RECIST 1.1 imaging with CAT scans with more completed cycles of ADIPEMCIS treatment further supports the notion that arginine depletion by ADI-PEG 20 can be combined with pemetrexed and cisplatin for effective disease control for these patients."

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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