Seattle Genetics Highlights Five-Year Survival Results from Phase 1 Trial of ADCETRIS® (Brentuximab Vedotin) in Frontline Mature T-Cell Lymphoma at ASH Annual Meeting

Seattle Genetics, Inc. (Nasdaq: SGEN) today highlighted final five-year survival results from a phase 1 clinical trial evaluating ADCETRIS (brentuximab vedotin) in mature T-cell lymphoma (MTCL) at the 59^th American Society of Hematology (ASH) Annual Meeting and Exposition taking place in Atlanta, Georgia, December 9-12, 2017. The presentation highlighted durability data from a phase 1 clinical trial of ADCETRIS in combination with chemotherapy for the treatment of patients with newly diagnosed MTCL, also known as peripheral T-cell lymphoma (PTCL). ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, which is expressed on the surface of Hodgkin lymphoma cells and several types of non-Hodgkin lymphoma. ADCETRIS is currently not approved for the frontline treatment of MTCL.

“Approximately 4,000 patients are diagnosed with MTCL each year. The current standard of care for frontline MTCL treatment has not changed for several decades and there remains a significant need for improved therapeutic options. The results of this phase 1 trial support the ongoing phase 3 ECHELON-2 clinical trial and our goal to redefine frontline MTCL treatment with a novel ADCETRIS combination regimen,” said Jonathan Drachman, M.D., Chief Medical Officer and Executive Vice President, Research and Development at Seattle Genetics. “The final results from the phase 1 study were presented today, with five-year progression-free survival and overall survival rates of 52 and 80 percent, respectively. No patients have experienced any disease progression events since the three-year follow-up results. Importantly, after more than five years of follow-up, patients who remain in remission have the potential to be cured. These data continue to support the phase 3 ECHELON-2 trial, from which we anticipate reporting data in 2018.”

Five-Year Survival Results: Frontline Brentuximab Vedotin in Combination with CHP in Patients with CD30-Expressing Peripheral T-Cell Lymphomas (Abstract #2790, poster presentation on Sunday, December 10, 2017)

Data were reported from 26 frontline MTCL patients who received the combination regimen of ADCETRIS plus cyclophosphamide, doxorubicin and prednisone (CHP). Patients who achieved at least a partial remission with combination therapy following six cycles of ADCETRIS plus CHP were eligible to receive up to ten additional cycles of single-agent ADCETRIS treatment. The median age of patients was 56 years. Nineteen patients (73 percent) had a subtype of MTCL called systemic anaplastic large cell lymphoma (sALCL), including 16 patients with anaplastic lymphoma kinase (ALK)-negative disease, which is typically associated with a poor prognosis. Seven patients (27 percent) had a diagnosis of other types of MTCL. The majority of patients had advanced stage disease and were considered high risk. All patients on the trial achieved an objective response, including 92 percent with a complete response and eight percent with a partial response.