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SAN DIEGO--([ BUSINESS WIRE ])--Seattle Genetics, Inc. (Nasdaq: SGEN) today reported data demonstrating that prolonged treatment with ADCETRIS beyond 16 cycles of therapy was associated with clinically meaningful durations of response with a manageable safety profile. In addition, data were presented showing that ADCETRIS is a viable option for reducing tumor burden prior to allogeneic stem cell transplant. The data were presented at the 53^rd American Society of Hematology (ASH) Annual Meeting and Exposition being held December 10-13, 2011 in San Diego, CA. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30.

"Through both corporate and investigator trials, we are continuing to increase our knowledge about the activity and tolerability of ADCETRIS in patients with relapsed Hodgkin lymphoma or systemic anaplastic large cell lymphoma (sALCL)"

aThrough both corporate and investigator trials, we are continuing to increase our knowledge about the activity and tolerability of ADCETRIS in patients with relapsed Hodgkin lymphoma or systemic anaplastic large cell lymphoma (sALCL),a said Thomas C. Reynolds, M.D., Ph.D., Chief Medical Officer at Seattle Genetics. aThese ASH presentations describe data from patients receiving extended treatment with ADCETRIS, as well as the use of ADCETRIS prior to allogeneic transplant. There is also a preclinical report on the activity of ADCETRIS in primary effusion lymphoma, an aggressive type of non-Hodgkin lymphoma. We look forward to two other presentations that will take place later today and tomorrow at the ASH meeting, including one that will describe data from longer follow-up in our pivotal trial in systemic ALCL and another that will be the first report of data from our phase I front-line trial in Hodgkin lymphoma.a

Prolonged Treatment with Brentuximab Vedotin in Patients with Relapsed or Refractory Hodgkin Lymphoma (HL) or Systemic Anaplastic Large Cell Lymphoma (sALCL) (Abstract #3711)

Data were presented from a retrospective analysis of relapsed Hodgkin lymphoma and sALCL patients who received greater than 16 cycles of ADCETRIS in a treatment extension study. Seventeen patients were included in the analysis, and median duration of treatment was 17.3 months (approximately 24 cycles of every three week dosing). ADCETRIS is approved for treatment until a maximum of 16 cycles, disease progression or unacceptable toxicity. Key findings include:

• The overall objective response rate was 88 percent, including 76 percent complete remissions and 12 percent partial remissions.
• The median time to objective response was 2.5 months. Median duration of objective response has not been reached (range 8.3 to 23.2+ months).
• ADCETRIS was generally well-tolerated, with the most common adverse events being peripheral neuropathy (71 percent), upper respiratory infection (53 percent) and fatigue (47 percent).
• In this case series, prolonged treatment with ADCETRIS was associated with clinically meaningful durations of response without worsening of toxicity over time.

Allogeneic Transplant Following Brentuximab Vedotin Treatment in Patients with Relapsed or Refractory CD30+ Lymphomas (Abstract #3091)

Data were presented describing the outcome of 15 patients with relapsed Hodgkin lymphoma or sALCL who underwent an allogeneic stem cell transplant as their first subsequent therapy after participation in a pivotal trial of ADCETRIS. ADCETRIS is not indicated to enable a subsequent allogeneic stem cell transplant. Key findings include:

• Fifteen patients who achieved an objective response with ADCETRIS (12 patients with a complete remission and three patients with a partial remission) subsequently received an allogeneic transplant.
• Ten of 15 patients (67 percent) remained in remission following subsequent allogeneic transplant. Three patients progressed and two died.
• Median progression-free survival and overall survival have not been reached after a median duration of follow-up of approximately 20 months (range 8 to 24 months).
• The data demonstrate that ADCETRIS may be an option for reducing tumor burden in advance of an allogeneic stem cell transplant.

Preclinical Activity of Brentuximab Vedotin in Primary Effusion Lymphoma (PEL) (Abstract #3728)

In a poster session today, Dr. Shruti Bhatt from the University of Miami Miller School of Medicine describes preclinical data on the expression of CD30 in primary effusion lymphoma (PEL). PEL is an aggressive subtype of non-Hodgkin lymphoma that is commonly diagnosed in HIV-positive patients. The data demonstrate the expression of CD30 on PEL cell lines and primary tumor samples. ADCETRIS induced apoptosis in PEL cell lines and extended survival in a preclinical PEL model. ADCETRIS is not indicated for the treatment of PEL.

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 Geneticsa 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.

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

ADCETRIS was granted accelerated approval by the U.S. Food and Drug Administration in August 2011 for two indications: (1) the treatment of patients with Hodgkin lymphoma after failure of autologous stem cell transplant (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 is not approved for use outside the United States. The marketing authorization application for ADCETRIS in relapsed or refractory Hodgkin lymphoma and systemic ALCL, filed by Takeda Global Research & Development Centre (Europe), was accepted by the European Medicines Agency in June 2011.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development and commercialization of monoclonal antibody-based therapies for the treatment of cancer. ADCETRIS was approved by the FDA on August 19, 2011 for two indications. ADCETRIS is being developed in collaboration with Millennium: The Takeda Oncology Company. In addition, Seattle Genetics has three other clinical-stage ADC programs: SGN-75, ASG-5ME and ASG-22ME. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Abbott, Bayer, Celldex Therapeutics, Daiichi Sankyo, Genentech, GlaxoSmithKline, Millennium, Pfizer and Progenics, as well as ADC co-development agreements with Agensys, an affiliate of Astellas, and Genmab. More information can be found at [ www.seattlegenetics.com ].

U.S. Important Safety Information

Warnings and Precautions:

• Peripheral neuropathy: ADCETRIS treatment causes a peripheral neuropathy that is predominantly sensory. Cases of peripheral motor neuropathy have also been reported. ADCETRIS-induced peripheral neuropathy is cumulative. Treating physicians should monitor patients for symptoms of neuropathy, such as hypoesthesia, hyperesthesia, paresthesia, discomfort, a burning sensation, neuropathic pain or weakness and institute dose modifications accordingly.
• Infusion reactions: Infusion-related reactions, including anaphylaxis, have occurred with ADCETRIS. Monitor patients during infusion. If an infusion reaction occurs, the infusion should be interrupted and appropriate medical management instituted. If anaphylaxis occurs, the infusion should be immediately and permanently discontinued and appropriate medical management instituted.
• Neutropenia: Monitor complete blood counts prior to each dose of ADCETRIS and consider more frequent monitoring for patients with Grade 3 or 4 neutropenia. If Grade 3 or 4 neutropenia develops, manage by dose delays, reductions or discontinuation. Prolonged (a1 week) severe neutropenia can occur with ADCETRIS.
• Tumor lysis syndrome: Patients with rapidly proliferating tumor and high tumor burden are at risk of tumor lysis syndrome and these patients should be monitored closely and appropriate measures taken.
• Stevens-Johnson syndrome: Stevens-Johnson syndrome has been reported with ADCETRIS. If Stevens-Johnson syndrome occurs, discontinue ADCETRIS and administer appropriate medical therapy.
• Progressive multifocal leukoencephalopathy (PML): A fatal case of PML has been reported in a patient who received four chemotherapy regimens prior to receiving ADCETRIS.
• Use in pregnancy: Fetal harm can occur. Pregnant women should be advised of the potential hazard to the fetus.

Adverse Reactions:

ADCETRIS was studied as monotherapy in 160 patients in two phase 2 trials. Across both trials, the most common adverse reactions (a20%), regardless of causality, were neutropenia, peripheral sensory neuropathy, fatigue, nausea, anemia, upper respiratory tract infection, diarrhea, pyrexia, rash, thrombocytopenia, cough and vomiting.

Drug Interactions:

Patients who are receiving strong CYP3A4 inhibitors concomitantly with ADCETRIS should be closely monitored for adverse reactions.

For additional important safety information, please see the full U.S. prescribing information for ADCETRIS at [ www.seattlegenetics.com ] or [ www.ADCETRIS.com ].

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the therapeutic potential of ADCETRIS. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Factors that may cause such a difference include the inability to show sufficient activity in future clinical trials and the risk of adverse events as ADCETRIS advances in clinical trials. In addition, data from our clinical trials, including our pivotal trials which were the basis for FDA accelerated approval, may not necessarily be indicative of subsequent clinical trial results. More information about the risks and uncertainties faced by Seattle Genetics is contained in the companyas 10-Q for the quarter ended September 30, 2011 filed with the Securities and Exchange Commission. Seattle Genetics disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.