Seattle Genetics Announces ADCETRIS® (Brentuximab Vedotin) Approval in Japan for the Treatment of Relapsed or Refractory Hodgkin Lymphoma and Anaplastic Large Cell Lymphoma

BOTHELL, Wash.

Seattle Genetics, Inc. (Nasdaq: SGEN) today announced that its collaborator, Takeda Pharmaceutical Company Limited (Takeda), has received approval of ADCETRIS (brentuximab vedotin) from the Japanese Ministry of Health, Labour and Welfare (MHLW) for the treatment of patients with CD30-positive relapsed or refractory Hodgkin lymphoma (HL) and anaplastic large cell lymphoma (ALCL). As a result, Seattle Genetics will receive two milestone payments from Takeda totaling $9 million upon final pricing agreement in Japan. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, a defining marker of classical HL and known to be expressed in some types of non-Hodgkin lymphoma, including ALCL.

“Until now, patients in Japan with relapsed or refractory Hodgkin lymphoma or ALCL had few therapeutic treatment options, and the approval of ADCETRIS represents a significant milestone in making this innovative targeted therapy available to these patients in need,” said Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. “ADCETRIS is now approved in 39 countries, and we continue to work with our collaborator, Takeda, to expand regulatory approvals globally. Through both our regulatory activities and robust clinical development program, our goal is to establish ADCETRIS as the foundation of therapy worldwide for patients with CD30-positive malignancies.”

The approval of the new drug application was based on two global pivotal phase 2 clinical trials of ADCETRIS, as well as a phase 1/2 clinical trial conducted in Japan, for patients with relapsed or refractory CD30-positive HL and ALCL. In March 2012, the Japanese MHLW granted ADCETRIS orphan drug designation for the treatment of patients with HL and ALCL, which triggered priority review in Japan.

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 (FDA) and approval with conditions from Health Canada for two indications: (1) the treatment of patients with HL 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 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 autologous stem cell transplant (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 more than 35 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. Seattle Genetics is entitled to royalties based on a percentage of Takeda’s net sales in its territory at rates that range from the mid-teens to the mid-twenties based on sales volume, subject to offsets for royalties paid by Takeda to third parties.

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, has been approved for two indications in more than 35 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, 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.

ADCETRIS (brentuximab vedotin) U.S. Important Safety Information

BOXED WARNING

Progressive multifocal leukoencephalopathy (PML): JC virus infection resulting in PML and death can occur in patients receiving ADCETRIS.

Contraindication:

Concomitant use of ADCETRIS and bleomycin is contraindicated due to pulmonary toxicity.

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. 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, interrupt the infusion. If anaphylaxis occurs, immediately and permanently discontinue the infusion.
• Hematologic toxicities: Grade 3 or 4 anemia, thrombocytopenia and prolonged (≥1 week) severe neutropenia can occur with ADCETRIS. Febrile neutropenia has been reported with ADCETRIS. Monitor complete blood counts prior to each dose of ADCETRIS and consider more frequent monitoring for patients with Grade 3 or 4 neutropenia. Closely monitor patients for fever. If Grade 3 or 4 neutropenia develops, manage by G-CSF support, dose delays, reductions or discontinuation.
• Serious infections and opportunistic infections: Infections such as pneumonia, bacteremia and sepsis/septic shock (including fatal outcomes) have been reported in patients treated with ADCETRIS. Closely monitor patients during treatment for the emergence of possible bacterial, fungal or viral infections.
• Tumor lysis syndrome: Closely monitor patients with rapidly proliferating tumor and high tumor burden.
• Progressive multifocal leukoencephalopathy (PML): JC virus infection resulting in PML and death has been reported in ADCETRIS-treated patients. In addition to ADCETRIS therapy, other possible contributory factors include prior therapies and underlying disease that may cause immunosuppression. Consider the diagnosis of PML in any patient presenting with new-onset signs and symptoms of central nervous system abnormalities. Evaluation of PML includes, but is not limited to, consultation with a neurologist, brain MRI, and lumbar puncture or brain biopsy. Hold ADCETRIS if PML is suspected and discontinue ADCETRIS if PML is confirmed.
• Stevens-Johnson syndrome (SJS): SJS has been reported with ADCETRIS. If SJS occurs, discontinue ADCETRIS and administer appropriate medical therapy.
• Embryo-fetal toxicity: Fetal harm can occur. Advise pregnant women 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 (≥20%), regardless of causality, were neutropenia, peripheral sensory neuropathy, fatigue, nausea, anemia, upper respiratory tract infection, diarrhea, pyrexia, rash, thrombocytopenia, cough and vomiting.

Drug Interactions:

Concomitant use of strong CYP3A4 inhibitors or inducers, or P-gp inhibitors, has the potential to affect the exposure to MMAE.

Use in Specific Populations:

MMAE exposure is increased in patients with hepatic impairment and severe renal impairment.

For additional important safety information, including Boxed WARNING, 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 potential commercial opportunity for ADCETRIS in Japan and the potential for approval of ADCETRIS in other countries. 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 risks that ADCETRIS will not be widely adopted by physicians in Japan or reimbursement may be difficult to secure. In addition, data from the pivotal clinical trials may not support marketing approval for submitted indications in other countries despite approval in the U.S. and E.U. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company’s 10-Q for the quarter ended September 30, 2013 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.