LIV-1 is Expressed in 92 Percent of Evaluated Breast Tumors

BOTHELL, WA, USA I October 21, 2013 I Seattle Genetics, Inc. (SGEN) today announced the initiation of a phase 1 clinical trial evaluating SGN-LIV1A for patients with LIV-1-positive metastatic breast cancer. SGN-LIV1A utilizes Seattle Genetics’ industry-leading antibody-drug conjugate (ADC) technology. The trial is designed to assess the safety and antitumor activity of SGN-LIV1A, an ADC targeted to LIV-1 (SLC39A6), a protein which is expressed in most subtypes of metastatic breast cancer.

“ADCs represent a novel treatment approach that have demonstrated activity in both hematologic and solid tumors. SGN-LIV1A is one of four ADCs that we are advancing into the clinic during 2013, demonstrating our significant investment in this approach for the treatment of cancer,” said Jonathan Drachman, M.D., Chief Medical Officer and Executive Vice President, Research and Development, at Seattle Genetics. “The target expression in breast cancer, preclinical antitumor activity, and need for novel therapeutic options for advanced breast cancer patients all support the clinical evaluation of SGN-LIV1A.”

ADCs are designed to harness the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity.

The study is a phase 1, open-label, dose-escalation clinical trial to evaluate the safety and antitumor activity of SGN-LIV1A in patients with LIV-1-positive metastatic breast cancer. The trial is enrolling patients with triple negative disease who have previously been treated with at least two prior cytotoxic regimens in the metastatic setting, or patients with ER-positive and/or PR-positive and HER2-negative disease who have previously been treated with at least two prior cytotoxic regimens in the metastatic setting, and at least three prior hormonal therapies. The primary endpoint of the trial is safety, with key secondary endpoints of objective response, duration of response and progression-free survival (PFS). The study is expected to enroll up to 70 patients at multiple centers in the United States.

“The treatment of cancer is changing with the introduction of more targeted agents and understanding disease-specific prognostic factors. Antibody-drug conjugates are an example of this evolving landscape, representing a rational approach to targeted drug delivery,” said Howard A. Burris, M.D., Chief Medical Officer, Executive Director of Drug Development at Sarah Cannon Research Institute and investigator for this phase 1 clinical trial. “We are eager to evaluate SGN-LIV1A in this phase 1 trial for advanced breast cancer.”

At the American Association of Cancer Research (AACR) Annual Meeting in April 2013, preclinical data demonstrated that up to 92 percent of breast tumors analyzed expressed LIV-1, with limited expression in normal tissue. SGN-LIV1A demonstrated significant antitumor activity in multiple preclinical models at well-tolerated doses (AACR 2013 Abstract 3962).

More information about the trial, including enrolling centers, will be available by visiting www.clinicaltrials.gov.

About SGN-LIV1A

SGN-LIV1A is an ADC comprised of an anti-LIV-1 monoclonal antibody linked to a synthetic cytotoxic cell-killing agent, monomethyl auristatin E (MMAE), using Seattle Genetics’ proprietary technology. The ADC is designed to be stable in the bloodstream, and to release its cytotoxic agent upon internalization into LIV-1-expressing tumor cells, which is expressed in most subtypes of metastatic breast cancer. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing the antitumor activity.

About Breast Cancer

October is recognized as Breast Cancer Awareness Month and, while there are several therapies available or in development, there remains a significant need to identify improved treatment options. Breast cancer is a disease where malignant (cancer) cells form in the tissue of the breast. Metastatic breast cancer occurs when the cancer has spread to other parts of the body. In the United States, breast cancer is the most commonly diagnosed cancer in women and one in eight women will be diagnosed with breast cancer in their lifetime. Breast cancer is the second leading cause of death among women. The American Cancer Society estimates that over 230,000 new cases of invasive breast cancer will be diagnosed in the United States during 2013, and approximately 40,000 people will die from the disease.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development and commercialization of innovative antibody-based therapies for the treatment of cancer. Seattle Genetics is leading the field in developing antibody-drug conjugates (ADCs), a technology designed to harness the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. The company’s lead product, ADCETRIS® (brentuximab vedotin), is an ADC that, in collaboration with Millennium: the Takeda Oncology Company, has been approved for two indications in 35 countries, including the U.S., European Union and Canada. Additionally, ADCETRIS is being evaluated broadly in more than 20 ongoing clinical trials. Seattle Genetics is also advancing a robust pipeline of clinical-stage ADC programs, including SGN-75, ASG-22ME, SGN-CD19A, SGN-CD33A, SGN-LIV1A and ASG-15ME. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including AbbVie, Agensys (an affiliate of Astellas), Bayer, Genentech, GlaxoSmithKline and Pfizer. More information can be found at www.seattlegenetics.com.

SOURCE: Seattle Genetics