Prostate
Prostate-specific Membrane Antigen Emerging as an Important Therapeutic Target to Deal with Prostate Cancer
By Seattle Genetics, Inc. & PSMA Development Company LLC (PDC)
Jun 21, 2005 - 10:50:00 AM

Seattle Genetics, Inc. (Nasdaq:SGEN) and PSMA Development Company LLC (PDC), a joint venture between Progenics Pharmaceuticals, Inc. (Nasdaq:PGNX) and Cytogen Corporation (Nasdaq:CYTO), announced today that Seattle Genetics has licensed its proprietary antibody-drug conjugate (ADC) technology to PDC.

The license provides PDC with rights to utilize the ADC technology to link cell-killing drug payloads to PDC's fully human monoclonal antibodies that target prostate-specific membrane antigen (PSMA), which is highly expressed on both primary and metastatic prostate cancer cells.

"PSMA is emerging as an important therapeutic target because of its strong expression on prostate cancer and tumor vasculature and its limited presence on normal tissues, making it ideal for use as an ADC therapy," commented Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. "Our industry-leading ADC technology can link synthetic, cell-killing auristatin payloads to the PSMA-targeted antibodies developed by PDC, resulting in compounds that are designed to be more potent and effective in treating prostate cancer."

PSMA is a protein abundantly expressed on the surface of prostate cancer cells, with an increased expression in high-grade cancers, metastatic disease and hormone-refractory prostate cancer. PSMA is also present at high levels on the newly formed blood vessels, or neovasculature, needed for the growth and survival of many solid tumors. In contrast to other prostate-related antigens such as prostate-specific antigen (PSA), prostatic acid phosphatase (PAP) and prostate secretory protein, PSMA is a membrane glycoprotein that is not secreted. This unique expression pattern makes PSMA an excellent antigenic target for monoclonal antibody diagnostic and therapeutic options.

"We are encouraged by preclinical data demonstrating that PSMA can be effectively targeted by antibodies developed through PDC in combination with Seattle Genetics' ADC technology," said Michael D. Becker, Cytogen's President and Chief Executive Officer. "In addition to major ADC collaborations and licenses, Seattle Genetics has itself demonstrated the potential of this technology by advancing multiple ADC compounds into development. As we continue to advance PSMA programs through preclinical development and initiate clinical trials for our first fully human monoclonal antibody, we are building important clinical momentum which will set the stage for additional drugs coming from our unique PSMA technologies."

Under the terms of the multi-year agreement, PDC will pay Seattle Genetics a $2.0 million upfront fee for access to the technology for use with antibodies targeting the PSMA antigen. PDC has also agreed to make progress-dependent milestone payments and pay royalties on net sales of resulting ADC products. PDC is responsible for research, product development, manufacturing and commercialization of all products under the collaboration. Seattle Genetics will receive material supply and annual maintenance fees as well as research support payments for any assistance provided to PDC in developing ADC products.

About ADCs

ADCs utilize the targeting ability of monoclonal antibodies to deliver potent, cell-killing payloads to specific cells. Seattle Genetics has developed improved ADC technology employing synthetic, highly potent drugs that can be attached to antibodies through proprietary linker systems. The linkers are stable in the bloodstream and release the drug payload once inside target cells. ADCs can increase the therapeutic potential of the many antibodies with targeting ability but limited or no inherent cell-killing activity.

About Prostate Cancer

Prostate cancer is the most common type of cancer found in American men, other than skin cancer. The American Cancer Society estimates that there will be about 232,090 new cases of prostate cancer in the United States in the year 2005 and that about 30,350 men will die of this disease. Prostate cancer is the second leading cause of cancer death in men, exceeded only by lung cancer.

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