SANTA MONICA, Calif. & BOTHELL, Wash.–(BUSINESS WIRE)–

Agensys, Inc., an affiliate of Tokyo-based Astellas Pharma Inc., and Seattle Genetics, Inc. (SGEN) today announced interim data from a phase I clinical trial evaluating ASG-5ME for the treatment of castration-resistant prostate cancer (CRPC). ASG-5ME is an antibody-drug conjugate (ADC) targeting the SLC44A4 antigen that is being co-developed by both companies for the treatment of solid tumors. The data are being presented at the American Society of Clinical Oncology (ASCO) annual meeting being held June 1-5, 2012 in Chicago, IL.

SLC44A4 is an attractive target in prostate cancer and is present in the majority of patients with both localized and metastatic disease, said Leonard Reyno, M.D., Senior Vice President and Chief Medical Officer of Agensys. The current Phase I data demonstrates the tolerability of this antibody drug conjugate and further evaluation of safety and antitumor activity in patients with castration resistant prostate cancer is ongoing.

It is encouraging to observe these preliminary data with ASG-5ME in prostate cancer, a disease for which late-stage patients need additional therapeutic options, said Jonathan Drachman, M.D., Senior Vice President, Research and Translational Medicine of Seattle Genetics. In addition to prostate cancer, our two companies are continuing to evaluate the potential use of ASG-5ME in other solid tumor indications. In parallel, we are collaborating with Agensys to co-develop ASG-22ME, an ADC targeting Nectin-4 for solid tumors.

Phase 1 trial of ASG-5ME in metastatic castration-resistant prostate cancer (CRPC) (Abstract #4568) ASG-5ME is being evaluated in a single-agent phase I clinical trial to determine the maximum tolerated dose (MTD) and to assess the safety, pharmacokinetic profile and antitumor activity of escalating doses of ASG-5ME. At the time of data analysis, 26 patients were enrolled. The median age of the patients was 69.5 years and the median baseline prostate-specific antigen (PSA) level was 82.25.

Key findings, presented by Dr. Michael Morris from Memorial Sloan Kettering Cancer Center in New York, NY, and clinical investigator on the study include:

The phase I trial is ongoing, with enrollment to two expansion cohorts in chemotherapy nave and chemotherapy exposed CRPC patients planned.

Seattle Genetics and Agensys recently completed enrollment in a phase I pancreatic cancer trial of ASG-5ME dosed weekly. The companies plan to evaluate ASG-5ME in patients with gastric cancer based on preclinical expression data.

About ASG-5ME ASG-5ME is an ADC composed of a fully human antibody directed to SLC44A4, a solute carrier antigen family member identified by Agensys to be overexpressed in epithelial cancers, including more than 80 percent of samples derived from patients with prostate, pancreatic and gastric cancers. The antibody is attached to monomethyl auristatin E (MMAE) via an enzyme-cleavable linker using Seattle Genetics proprietary technology. The ADC is designed to be stable in the bloodstream, but to release MMAE upon internalization into SLC44A4-expressing tumor cells, resulting in targeted cell-killing.

Seattle Genetics and Agensys are co-developing and will globally co-commercialize and share profits on a 50:50 basis for ASG-5ME and ASG-22ME. Seattle Genetics also has an option for 50:50 cost and profit-sharing of a third ADC program at the time of investigational new drug submission.

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