ASCO data highlight novel anti-cancer approach that exposes tumors to immune attack

TUSTIN, Calif., May 20, 2010 -- 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

Peregrine Pharmaceuticals, Inc. is a biopharmaceutical company with a portfolio of innovative monoclonal antibodies in clinical trials for the treatment of cancer and serious viral infections. The company is pursuing three separate clinical programs in cancer and HCV infection with its lead product candidates bavituximab and Cotara®. Peregrine also has in-house manufacturing capabilities through its wholly owned subsidiary Avid Bioservices, Inc. (www.avidbio.com), which provides development and biomanufacturing services for both Peregrine and outside customers. Additional information about Peregrine can be found at www.peregrineinc.com.

Safe Harbor Statement: Statements in this press release which are not purely historical, including statements regarding Peregrine Pharmaceuticals' intentions, hopes, beliefs, expectations, representations, projections, plans or predictions of the future are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The forward-looking statements involve risks and uncertainties including, but not limited to, the risk that results from larger clinical trials will not be consistent with results experienced in earlier clinical trials and preclinical studies, the risk that the company may experience delays in patient enrollment for the planned phase II clinical trials, and risk that results may not support registration filings with the U.S. Food and Drug Administration. Factors that could cause actual results to differ materially or otherwise adversely impact the company's ability to obtain regulatory approval for its product candidates include, but are not limited to, uncertainties associated with completing preclinical and clinical trials for our technologies; the early stage of product development; the significant costs to develop our products as all of our products are currently in development, preclinical studies or clinical trials; obtaining additional financing to support our operations and the development of our products; obtaining regulatory approval for our technologies; anticipated timing of regulatory filings and the potential success in gaining regulatory approval and complying with governmental regulations applicable to our business. Our business could be affected by a number of other factors, including the risk factors listed from time to time in the company's SEC reports including, but not limited to, the annual report on Form 10-K for the year ended April 30, 2009 and the quarterly report on Form 10-Q for the quarter ended January 31, 2010. The company cautions investors not to place undue reliance on the forward-looking statements contained in this press release. Peregrine Pharmaceuticals, Inc. disclaims any obligation, and does not undertake to update or revise any forward-looking statements in this press release.