TUSTIN, Calif., May 17, 2004 /PRNewswire-FirstCall via COMTEX/ -- Peregrine Pharmaceuticals (Nasdaq: PPHM) announced today that one of its scientific advisors and the inventor of its Vascular Targeting Agent platform technology, Dr. Philip E. Thorpe, presented a review of Vascular Targeting Agent (VTA) technologies at the Second International Conference on Vascular Targeting being held in Miami. The review was titled "Ligand-Based Vascular Targeting Agents as Cancer Therapeutics." Ligand-based VTAs are agents that bind specifically to tumor blood vessels and shut down blood flow to the tumor resulting in tumor cell death. Studies so far suggest there may be a number of advantages of VTAs over other cancer therapies including access of the target and mechanism of action. Peregrine has several core research programs focused on the identification and development of VTAs and other agents that affect tumor blood vessels.

Data was presented by Dr. Thorpe showing that the potential of vascular targeting as a cancer therapeutic approach has been firmly established in experimental studies. Treatment of tumors with VTAs lead to rapid reductions in tumor blood flow and death of tumor cells in the core of the tumor. VTAs are effective at treating both small and large tumors, and significant reduction of tumor mass is commonly seen in pre-clinical models. VTAs are attractive as a combination therapy with chemotherapeutic agents since the cells they are most effective at killing, the cells in the core of the tumor, are often spared during chemotherapy. Some examples of VTA and chemotherapy combination therapy have resulted in long lasting tumor regressions.

Peregrine has been active in the vascular targeting area since 1997 when it acquired the company that was developing Dr. Thorpe's technology. Peregrine currently has exclusive rights to over 190 U.S. and foreign patents and patent applications that broadly cover its vascular programs. The company has licensing agreements in place with Schering AG and Supergen to develop diagnostic and therapeutic agents under its technology platform and collaborations with other companies to develop and evaluate new VTAs.

About Vascular Targeting Agents

VTAs developed by Dr. Thorpe and his team represent the next generation of cancer therapy that works by a novel mechanism of action. Essentially, all detectable tumors rely on blood vessels to obtain oxygen and nutrients. Peregrine's VTAs localize within the tumor vasculature by selectively binding to the flat endothelial cells that line tumor blood vessels. Once the VTA binds to its target, it occludes the tumor vessels. Because blockage of a single capillary results in the destruction of thousands of tumor cells, only a small quantity of VTAs localized in the tumor's vascular system may cause an avalanche of tumor cell death.

There are thought to be a number of advantages of VTAs over other cancer therapies making them potentially powerful anti-cancer treatments. By targeting receptors unique to tumor cell vasculature, VTAs can kill tumors by cutting off oxygen and nutrients without causing damage to surrounding healthy tissue. Additionally, VTAs reduce the risk of potential side effects by operating at lower dosages than traditional cancer therapies because they do not need to penetrate the innermost part of a tumor to take effect. Lastly, while drug resistance caused by the instability and mutability of cancer cells is a significant problem with conventional therapies that target tumor cells, the cells targeted by VTAs do not mutate to become drug resistant. Peregrine believes that VTAs will be most effective when used in combination with existing anti-cancer therapies, providing a powerful "1-2 punch" for the effective treatment of various solid tumor cancers.

Two types of VTAs are currently being developed for cancer treatment: ligand-directed and small molecule VTAs. Ligand-directed VTAs use antibodies and peptides to selectively target toxins, pro-coagulants, and pro-apoptotic effectors specifically to tumor endothelium. Most small molecule VTAs do not specifically localize to tumor endothelium, but exploit pathophysiological differences between tumor and normal tissue endothelia to induce selective occlusion of tumor vessels. Both approaches have shown promise in pre-clinical animal testing. The key difference in the two technologies is that most ligand-directed VTAs (Peregrine's patented approach) require one or only a few doses to cause irreparable harm to the tumor blood vessel network, whereas, many small molecule-based VTAs require multiple or chronic dosing regimens to provide the same effect.

Both types of VTAs have produced a characteristic pattern of necrosis after administration to mice and rats with solid tumors. They cause a widespread central necrosis that can extend to as much as 95% of the tumor. A thin rim of viable tumor cells usually survives at the periphery of the tumor at which point the tumor cells obtain nutrients from unaffected blood vessels in the surrounding normal tissues. These tumor cells at the periphery of the solid tumor can usually be treated effectively with existing chemotherapy agents.

Peregrine's VTA patent estate includes more than 190 issued or pending patents and patent applications. Peregrine's business development philosophy in the VTA field is to grant access to companies interested in actively developing VTAs. The company has entered into both exclusive and non-exclusive licenses for different targets and/or effectors to meet the needs of our licensees.

About Peregrine Pharmaceuticals, Inc.

Peregrine's research and development efforts focus on discovering and developing products that affect blood flow to tumors. Peregrine's vascular research programs fall under several different proprietary platforms including Anti-Phospholipid Therapy (APT), Vascular Targeting Agents (VTAs), anti-Angiogenesis and Vasopermeation Enhancement Agents (VEAs). The company has research collaborations with pharmaceutical and biotechnology companies to develop its VTA platform for therapeutic and diagnostic applications and expects to enter its first APT compound into clinical trials for cancer therapy during calendar year 2004.

Peregrine's vascular agents may also have applications in other angiogenesis-dependent diseases besides cancer such as diabetes, arthritis, skin disorders and eye diseases. Peregrine currently has exclusive rights to over 190 U.S. and foreign patents and patent applications that broadly cover its vascular programs. In addition, the company is currently evaluating its proprietary technology for use in treating non-angiogenesis dependent diseases such as viral infections. The company believes that the pre-clinical data generated by the company and the broad nature of its intellectual property may provide many opportunities for product development, partnering and licensing.

Peregrine's most clinically advanced therapeutic program is based on a targeting platform outside vascular biology. This technology platform is known as Tumor Necrosis Therapy (TNT) and targets dead or dying tumor cells that are common to the majority of different tumor types. Cotara™, the most clinically advanced TNT program, is currently in a Phase I clinical trial for the treatment of colorectal carcinoma at Stanford University Medical Center. In addition, we have received protocol approval from the U.S. Food and Drug Administration ("FDA") to initiate a registration clinical study for the treatment of brain cancer. The company is currently seeking a development or funding partner to move the brain cancer program forward. The company believes that continuing the clinical development of Cotara™ in tumor types other than brain cancer will add significant value to the program. The company has a research collaboration to develop immunocytokines based on the TNT platform and a TNT-based agent has been developed and approved for the treatment of lung cancer in China under a licensing agreement.

The company also operates a cGMP contract manufacturing facility for monoclonal antibodies and recombinant proteins through its wholly owned subsidiary Avid Bioservices, Inc. (www.avidbio.com). Avid produces clinical trial materials to support phase I through phase III clinical trials for biotechnology companies including Peregrine. Copies of Peregrine press releases, SEC filings, current price quotes and other valuable information for investors may be found on the website www.peregrineinc.com.

Safe Harbor Statement: This release may contain certain forward-looking statements that are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Actual events or results may differ from the company's expectations as a result of risk factors discussed in Peregrine's reports on file with the U.S. Securities and Exchange Commission, including, but not limited to, Peregrine's report on Form 10-Q for the quarter ended January 31, 2004 and on Form 10-K for the year ended April 30, 2003.

     Peregrine Investor Relations
     Frank Hawkins and Julie Marshall
     Hawk Associates, Inc.
     (800) 987-8256 or
     info@hawkassociates.com

SOURCE Peregrine Pharmaceuticals, Inc.

Frank Hawkins and Julie Marshall, both of Hawk Associates,
Inc., +1-800-987-8256, or info@hawkassociates.com, for Peregrine

http://www.peregrineinc.com