Polaris Provides Early Evidence of Response to Arginine Depletion by ADI‑PEG 20 in Argininosuccinate Synthetase Deficient Thoracic Tumors

SAN DIEGO, April 20, 2017 – Polaris Group announced today that its lead therapeutic ADI‑PEG 20 (pegylated arginine deiminase) in combination with pemetrexed and cisplatin (ADIPemCis) demonstrated a good safety profile and a strong efficacy signal in argininosuccinate synthetase (ASS1) deficient malignant pleural mesothelioma (MPM) and non-small cell lung carcinoma (NSCLC), as reported in the Journal of Clinical Oncology. In the first nine patients (5 MPM, 4 NSCLC) enrolled in the dose escalation cohorts of this biomarker-directed phase 1 study, partial response was seen in 7 patients (4 MPM, 3 NSCLC). The study was led by Dr. Peter Szlosarek of Barts Cancer Center, Queen Mary University of London, and involved multiple sites in the United Kingdom.

The main goal of this phase 1 study is to determine the recommended phase 2 dose, safety and tolerability of ADIPemCis in patients with ASS1-deficient MPM and NSCLC. The nine enrolled patients were treated with fixed-dose pemetrexed and cisplatin (PemCis), the standard first-line chemotherapy for MPM and NSCLC, in combination with increasing doses of ADI‑PEG 20. The treatment appeared to be safe and well tolerated. Notably, three out of four MPM patients with a partial response had non-epithelioid tumor histology, which carries an unfavorable prognosis and historically responded poorly to chemotherapy.

“Based on the encouraging efficacy signal from these preliminary results, we have initiated a randomized, double blind, phase 2/3 trial comparing ADIPemCis with PemCis in patients with non-epithelioid MPM,” said John Bomalaski, M.D., Executive Vice President, Medical Affairs at Polaris Pharmaceuticals, Inc. “With ADIPemCis, 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.