Randomized Phase 3 Clinical Trial with ADCETRIS Demonstrates Statistically Significant Improvement in Progression-Free Survival

Abstract Submitted to ASH for Presentation at the 2014 Annual Meeting; Regulatory Submissions Anticipated in 2015

BOTHELL, WA, USA & OSAKA, Japan I  September 29, 2014 I Seattle Genetics, Inc. (SGEN) and Takeda Pharmaceutical Company Limited (TSE:4502) today announced that patients with Hodgkin lymphoma (HL) who received ADCETRIS (brentuximab vedotin) as consolidation therapy immediately following an autologous stem cell transplantation (ASCT) lived significantly longer without disease progression compared to patients who received placebo. The phase 3 clinical trial, known as AETHERA, compared the use of single agent ADCETRIS to placebo in 329 patients with HL who were at risk of relapse. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, a defining marker of classical HL. ADCETRIS has been approved in more than 45 countries for the treatment of relapsed HL and systemic anaplastic large cell lymphoma (sALCL). ADCETRIS is not approved in the AETHERA treatment setting.

The AETHERA trial met its primary endpoint with ADCETRIS treatment resulting in a statistically significant improvement in progression-free survival (PFS) versus placebo as assessed by an independent central review committee (hazard ratio=0.57; p-value=0.001), which equates to a 75 percent improvement in PFS. PFS was assessed after a minimum of two years post initiation of treatment for all study patients. A pre-specified interim analysis of overall survival showed no statistically significant difference between the treatment arms. Patients on both study arms with progression of HL received a variety of subsequent therapies. Notably, most patients on the placebo arm received ADCETRIS after progression. A further analysis of overall survival is planned in 2016. The safety profile of ADCETRIS in the AETHERA trial was generally consistent with the existing prescribing information. An abstract was previously submitted for data presentation at the American Society of Hematology (ASH) annual meeting, December 6-9, 2014, in San Francisco, CA.

“Patients with Hodgkin lymphoma who relapse or are refractory to frontline therapy represent a significant unmet medical need. We believe the positive top-line results of the AETHERA trial demonstrate the ability of ADCETRIS to consolidate remissions and extend progression-free survival in patients with Hodgkin lymphoma who are at risk of relapse following an autologous transplant while having an acceptable safety profile,” said Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. “We anticipate reporting more complete AETHERA data at the ASH annual meeting in December and intend to submit a supplemental Biologics License Application to the FDA in 2015 for approval in this setting.”

“The AETHERA clinical trial results may support a new treatment paradigm for certain patients with Hodgkin lymphoma post autologous stem cell transplant,” said Michael Vasconcelles, M.D., Global Head, Oncology Therapeutic Area Unit, Takeda Pharmaceutical Company. “As the first randomized clinical trial of a comprehensive clinical development program with ADCETRIS, these data also provide important information to inform the entire ADCETRIS program. For these reasons, we are particularly grateful to the patients, in partnership with their families and the study investigators, for their participation in AETHERA. We look forward to submitting these data to regulatory agencies in our territories.”

Phase 3 AETHERA Clinical Trial Design
The AETHERA trial is a randomized, double-blind, placebo-controlled phase 3 study designed to evaluate the potential of ADCETRIS to extend PFS post-ASCT in patients with HL who have at least one risk factor for progression. In addition to the primary endpoint of PFS, secondary endpoints included overall survival, safety and tolerability. Patients must have risk factors for residual HL, defined as a history of refractory HL, those who relapse or progress within one year from receiving frontline chemotherapy and/or those who have disease outside of the lymph nodes at the time of pre-ASCT relapse. Patients received ADCETRIS or placebo every three weeks for up to approximately one year. This international multi-center trial is being conducted in the United States, Eastern and Western Europe and Russia.

Submission of safety data from the AETHERA trial to the FDA is a post-marketing requirement that Seattle Genetics will fulfill in its planned supplemental BLA. Takeda will provide safety data from the trial to the European Medicines Agency (EMA) as part of periodic safety reports required by the EMA’s conditional approval of ADCETRIS.

Please see Important Safety Information at the end of this press release.

Seattle Genetics Conference Call Details
Seattle Genetics’ management will host a conference call and webcast to discuss this announcement. The event will be held today at 5:30 a.m. Pacific Time (PT) / 8:30 a.m. Eastern Time (ET). The live event will be available from Seattle Genetics’ website at http://www.seattlegenetics.com, under the Investors and News section, or by calling 888-455-2263 (domestic) or 719-325-2464 (international). The access code is 9378967. A replay of the discussion will be available beginning at approximately 7:00 a.m. PT / 10:00 a.m. ET today from Seattle Genetics’ website or by calling 888-203-1112 (domestic) or 719-457-0820 (international), using access code 9378967. The telephone replay will be available until 8:30 a.m. PT / 11:30 a.m. ET October 1, 2014.

About ADCETRIS
ADCETRIS (brentuximab vedotin) is an ADC comprising an anti-CD30 monoclonal antibody attached by a protease-cleavable linker to a microtubule disrupting agent, monomethyl auristatin E (MMAE), utilizing Seattle Genetics’ proprietary technology. The ADC employs a linker system that is designed to be stable in the bloodstream but to release MMAE upon internalization into CD30-expressing tumor cells.

ADCETRIS for intravenous injection received accelerated approval from the U.S. Food and Drug Administration and approval with conditions from Health Canada for two indications: (1) the treatment of patients with HL after failure of ASCT or after failure of at least two prior multi-agent chemotherapy regimens in patients who are not ASCT candidates, and (2) the treatment of patients with sALCL after failure of at least one prior multi-agent chemotherapy regimen. The indications for ADCETRIS are based on response rate. There are no data available demonstrating improvement in patient-reported outcomes or survival with ADCETRIS.

ADCETRIS was granted conditional marketing authorization by the European Commission in October 2012 for two indications: (1) for the treatment of adult patients with relapsed or refractory CD30-positive HL following ASCT, or following at least two prior therapies when ASCT or multi-agent chemotherapy is not a treatment option, and (2) the treatment of adult patients with relapsed or refractory sALCL. ADCETRIS has received marketing authorization by regulatory authorities in 45 countries. See important safety information below.

Seattle Genetics and Takeda are jointly developing ADCETRIS. Under the terms of the collaboration agreement, Seattle Genetics has U.S. and Canadian commercialization rights and Takeda has rights to commercialize ADCETRIS in the rest of the world. Seattle Genetics and Takeda are funding joint development costs for ADCETRIS on a 50:50 basis, except in Japan where Takeda will be solely responsible for development costs.

About Hodgkin Lymphoma
Lymphoma is a general term for a group of cancers that originate in the lymphatic system. There are two major categories of lymphoma: HL and non-Hodgkin lymphoma. HL is distinguished from other types of lymphoma by the presence of one characteristic type of cell, known as the Reed-Sternberg cell. The Reed-Sternberg cell generally expresses CD30.

According to the American Cancer Society, approximately 9,200 cases of HL will be diagnosed in the United States during 2014 and more than 1,200 will die from the disease. Globally, there are more than 62,000 cases of HL diagnosed each year. Although frontline combination chemotherapy can result in durable response rates, up to 30 percent of these patients relapse or are refractory to frontline treatment and have few therapeutic options beyond ASCT.

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 Takeda Pharmaceutical Company Limited, is commercially available for two indications in more than 45 countries, including the U.S., Canada, Japan and members of the European Union. Additionally, ADCETRIS is being evaluated broadly in more than 30 ongoing clinical trials. Seattle Genetics is also advancing a robust pipeline of clinical-stage ADC programs, including SGN-CD19A, SGN-CD33A, SGN-LIV1A, SGN-CD70A, ASG-22ME 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.

About Takeda
Located in Osaka, Japan, Takeda is a research-based global company with its main focus on pharmaceuticals. As the largest pharmaceutical company in Japan and one of the global leaders of the industry, Takeda is committed to strive towards better health for people worldwide through leading innovation in medicine. Additional information about Takeda is available through its corporate website, www.takeda.com.

SOURCE: Seattle Genetics