Polaris Lead Therapeutic ADI‑PEG 20 in Combination with First Line Chemotherapy Is Active in Argininosuccinate Synthetase Deficient Mesothelioma

SAN DIEGO, June 5, 2017 – Polaris Group announced today that its lead therapeutic ADI‑PEG 20 (pegylated arginine deiminase) in combination with pemetrexed and cisplatin (ADIPemCis) is active in argininosuccinate synthetase (ASS1) deficient malignant pleural mesothelioma (MPM), including non-epithelioid MPM, which carries an unfavorable prognosis and historically responds poorly to chemotherapy. The results were generated from a phase 1b dose escalation and expansion study (TRAP), led by Dr. Peter Szlosarek of Barts Cancer Center, Queen Mary University of London, and presented at the American Society of Clinical Oncology’s 2017 annual meeting.

Thirty one (31) MPM patients (11 epithelioid and 20 non-epithelioid) were enrolled and treated with fixed-dose pemetrexed and cisplatin (PemCis), the standard first-line chemotherapy for MPM, in combination with increasing doses of ADI‑PEG 20. The treatment appeared to be safe and well tolerated. The partial response rate was 35.5% (95% CI 19.2%-54.6%) with a disease control rate of 93.5% (95% CI 78.6%-99.2%). Median progression free survival was 5.6 months (95% CI 4-6) and median overall survival was 10.1 months (95% CI 6.7-17.7).

“Based on the encouraging efficacy signal from the TRAP study, we have initiated a randomized, double blind, phase 2/3 trial comparing ADI‑PEG 20+PemCis with PemCis in patients with non-epithelioid MPM,” said John Bomalaski, M.D., Executive Vice President, Medical Affairs at Polaris Pharmaceuticals, Inc. “With ADI‑PEG 20+PemCis, we hope to bring an effective treatment to this subset of MPM patients, who have a dire need for medical intervention.”

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.