Data from three Phase II clinical trials of PS-targeting antibody to be presented at 2010 ASCO Annual Meeting

May 21 2010

Peregrine's first-in-class PS-targeting antibodies reactivate immune responses and potentially work synergistically with multiple therapies; 2 new Phase IIb trials in refractory and front-line lung cancer patients to begin by mid-year

Peregrine Pharmaceuticals, Inc. (Nasdaq: PPHM), a clinical-stage biopharmaceutical company developing innovative monoclonal antibodies for the treatment of cancer and viral infections, will present data from three Phase II clinical trials highlighting the clinical potential of its unique phosphatidylserine (PS)-targeting antibody bavituximab for the treatment of solid tumors. PS-targeting antibodies represent an entirely new approach to treating cancer, using a novel immunomodulatory mechanism that enables the patient's own immune system to attack and destroy the tumor. Phase II data on the company's lead PS-targeting antibody bavituximab administered in combination with chemotherapy will be presented at the 2010 ASCO Annual Meeting.

"PS is a highly immunosuppressive molecule that inactivates the immune system and allows tumors to evade detection," commented Dr. Philip Thorpe, professor of pharmacology at the University of Texas Southwestern Medical Center, a scientific advisor to Peregrine and a pioneer in the development of PS-targeting therapies. "Supported by a growing body of research, PS-targeting antibodies appear to play a critical role in blocking this immunosuppressive molecule and reactivating the immune system's ability to mount a robust anti-tumor response. Since chemotherapy increases the exposure of PS on tumor blood vessels, bavituximab has even more of this immunosuppressive molecule to target, potentially offering a new synergistic approach for the treatment of cancer."

Based on the positive data reported to date, Peregrine plans to initiate a new randomized, placebo-controlled, double-blinded Phase II trial of bavituximab in combination with chemotherapy in refractory non-small cell lung cancer (NSCLC) patients. A new Phase II trial in front-line NSCLC patients is also expected to begin in by mid-year.

Usually located on the inside of healthy cell membranes, PS "flips" and becomes exposed on the outside of cells that line tumor blood vessels. PS also becomes exposed on virus-infected cells and enveloped viruses. A growing body of scientific evidence shows that this exposed PS inactivates the body's normal immune response.

The "flipped" PS molecules therefore create a specific target for anti-cancer and anti-viral treatments, leaving healthy cells unaffected. Peregrine's PS-targeting antibodies such as bavituximab target and block this immunosuppressive PS target, enabling the immune system to recognize the cancer cells as foreign and to reactivate the immune system to attack the tumor and inhibit its growth.

Clinical evidence supporting the PS-targeting approach will be discussed in three sessions at the 2010 ASCO Annual Meeting. Prior clinical data show that in combination with chemotherapy in advanced breast and lung cancer patients, Peregrine's first-in-class antibody bavituximab has achieved objective tumor response rates that compare favorably with chemotherapy alone. Bavituximab has also demonstrated a promising safety profile.

Of special interest, these prior clinical data also suggest that the PS-targeting mechanism may have additive therapeutic effects with other cancer treatments. This builds on preclinical studies that have previously shown that a number of FDA-approved anti-cancer treatments up-regulate the PS exposed on the tumor vasculature. Numerous preclinical studies have also demonstrated enhanced anti-tumor effects of PS-targeting antibodies when used in combination with a range of standard anti-cancer treatments, including radiation, chemotherapy, hormone depletion therapy and most recently, agents that induce apoptosis.

ASCO posters reporting bavituximab Phase II clinical results include:

Phase II study of bavituximab plus docetaxel in locally advanced or metastatic breast cancer (Abstract #1042), Author: David Tabagari, Poster Board 22C, S Hall A2

Phase II study of bavituximab plus paclitaxel and carboplatin in locally advanced or metastatic breast cancer: Interim results (Abstract #1062), Author: Minish Jain, Poster Board 22G, S Hall A2

Phase II study of bavituximab plus paclitaxel and carboplatin in untreated locally advanced or metastatic non-small cell lung cancer: Interim results (Abstract #7589), Author: Raghunadharao Digumarti, Poster Board 40H, S Hall A2

Source: BioCom Partners