Seattle Genetics, Inc. Release: FDA Accepts Supplemental BLA And Grants Priority Review For ADCETRIS (Brentuximab Vedotin) In The AETHERA Setting For The Post-Transplant Consolidation Treatment Of Hodgkin Lymphoma Patients At High Risk Of Relapse

-PDUFA Action Date August 18, 2015-

-Submission of Supplemental BLA Based on Positive Phase 3 AETHERA Clinical Trial Results Recently Published in The Lancet-

BOTHELL, Wash.--(BUSINESS WIRE)--Seattle Genetics, Inc. (Nasdaq: SGEN) announced today that the U.S. Food and Drug Administration (FDA) has accepted for filing a supplemental Biologics License Application (BLA) for ADCETRIS (brentuximab vedotin) in the AETHERA setting for the post-transplant consolidation treatment of Hodgkin lymphoma (HL) patients at high risk of relapse or progression. The FDA granted Priority Review for the application and the Prescription Drug User Fee Act (PDUFA) target action date is August 18, 2015. The submission of the supplemental BLA is based on positive results from a phase 3 clinical trial called AETHERA that was designed to determine if 16 cycles of ADCETRIS as consolidation therapy immediately following an autologous stem cell transplant (ASCT) could extend progression-free survival (PFS) in HL patients at high risk of relapse or progression. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, which is expressed in classical HL and systemic anaplastic large cell lymphoma (sALCL), as well as other lymphoma subtypes. ADCETRIS is approved in relapsed HL and sALCL but is currently not approved for consolidation therapy in HL patients immediately after ASCT.

“The phase 3 AETHERA trial demonstrated that using ADCETRIS in this setting significantly improved progression-free survival with a manageable safety profile. We look forward to working with the FDA during their review of our application for approval of this additional indication for ADCETRIS.”

Globally, there are more than 65,000 cases of HL diagnosed each year. Although frontline combination chemotherapy can result in durable responses, up to 30 percent of these patients relapse or are refractory to frontline treatment. The standard for these patients is to proceed to an ASCT but approximately half of all HL patients who undergo an ASCT experience subsequent disease relapse.

“The FDA’s filing of our supplemental BLA and priority review designation for ADCETRIS as consolidation therapy represents a significant milestone towards our goal of making ADCETRIS available to high risk HL patients immediately following an autologous stem cell transplant who currently have no therapeutic options to prevent progression,” said Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. “The phase 3 AETHERA trial demonstrated that using ADCETRIS in this setting significantly improved progression-free survival with a manageable safety profile. We look forward to working with the FDA during their review of our application for approval of this additional indication for ADCETRIS.”

The positive results from the phase 3 AETHERA trial were published in The Lancet in March 2015 and were presented at the 56^th American Society of Hematology (ASH) Annual Meeting in December 2014. Results from the AETHERA trial in 329 HL patients at high risk of relapse following ASCT included:

• The trial achieved its primary endpoint and demonstrated a significant increase in PFS per independent review facility, with a hazard ratio of 0.57 and a p-value of 0.001. Median PFS was 43 months for patients who received ADCETRIS versus 24 months for patients who received placebo. The two-year PFS rate was 63 percent in the ADCETRIS arm compared to 51 percent in the placebo arm.
• The PFS benefit was consistent across all pre-specified subgroups, including primary refractory patients, patients who relapsed within twelve months of frontline therapy and patients who relapsed after twelve months with extranodal disease.
• ADCETRIS-treated patients received a median of 15 treatment cycles and 48 percent received the maximum of 16 cycles, indicating generally acceptable tolerability and a manageable adverse reaction profile.
• The most common adverse events in the ADCETRIS arm were peripheral sensory neuropathy (56 percent), neutropenia (35 percent), upper respiratory tract infection (26 percent), fatigue (24 percent) and peripheral motor neuropathy (23 percent). The most common adverse events in the placebo arm were upper respiratory tract infection (23 percent), fatigue (18 percent) peripheral sensory neuropathy (16 percent), cough (16 percent) and neutropenia (12 percent). Eighty-five percent of patients with peripheral neuropathy on the ADCETRIS arm had resolution or improvement in symptoms with a median time to improvement of 23.4 weeks.

Submission of safety data from the AETHERA trial to the FDA is a post-marketing requirement.

About ADCETRIS

ADCETRIS is being evaluated broadly in more than 30 ongoing clinical trials, including four phase 3 studies, in earlier lines of its approved HL and sALCL indications as well as in many additional types of CD30-positive malignancies, including cutaneous T-cell lymphoma, B-cell lymphomas and mature T-cell lymphomas.

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 FDA 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 approved under accelerated approval based on overall response rate. An improvement in patient-reported outcomes or survival has not been established. Continued approval for these indications may be contingent upon verification and description of clinical benefit in confirmatory trials.

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 more than 50 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 and is the most common type of blood cancer. 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 9,050 cases of HL will be diagnosed in the United States during 2015 and more than 1,150 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 a CD30-targeted ADC that, in collaboration with Takeda Pharmaceutical Company Limited, is commercially available for two indications in more than 50 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 in CD30-expressing malignancies. Seattle Genetics is also advancing a robust pipeline of clinical-stage programs, including SGN-CD19A, SGN-CD33A, SGN-LIV1A, SGN-CD70A, ASG-22ME, ASG-15ME and SEA-CD40. 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:

ADCETRIS is contraindicated with concomitant bleomycin due to pulmonary toxicity (e.g., interstitial infiltration and/or inflammation).

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.
• Anaphylaxis and infusion reactions: Infusion-related reactions, including anaphylaxis, have occurred with ADCETRIS. Monitor patients during infusion. If an infusion-related reaction occurs, interrupt the infusion and institute appropriate medical management. If anaphylaxis occurs, immediately and permanently discontinue the infusion and administer appropriate medical therapy.
• Hematologic toxicities: Prolonged (=1 week) severe neutropenia and Grade 3 or 4 thrombocytopenia or anemia 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. Monitor patients for fever. If Grade 3 or 4 neutropenia develops, consider dose delays, reductions, discontinuation, or G-CSF prophylaxis with subsequent doses.
• Serious infections and opportunistic infections: Infections such as pneumonia, bacteremia, and sepsis or 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.
• Increased toxicity in the presence of severe renal impairment: The frequency of =Grade 3 adverse reactions and deaths was greater in patients with severe renal impairment (creatinine clearance less than 30 mL/min) compared to patients with normal renal function. Avoid the use of ADCETRIS in patients with severe renal impairment.
• Increased toxicity in the presence of moderate or severe hepatic impairment: The frequency of =Grade 3 adverse reactions and deaths was greater in patients with moderate (Child-Pugh B) or severe hepatic (Child-Pugh C) impairment compared to patients with normal hepatic function. Avoid the use of ADCETRIS in patients with moderate or severe hepatic impairment.
• Hepatotoxicity: Serious cases of hepatotoxicity, including fatal outcomes, have occurred with ADCETRIS. Cases were consistent with hepatocellular injury, including elevations of transaminases and/or bilirubin, and occurred after the first dose of ADCETRIS or rechallenge. Preexisting liver disease, elevated baseline liver enzymes, and concomitant medications may also increase the risk. Monitor liver enzymes and bilirubin. Patients experiencing new, worsening, or recurrent hepatotoxicity may require a delay, change in dose, or discontinuation of ADCETRIS.
• 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. Hold ADCETRIS if PML is suspected and discontinue ADCETRIS if PML is confirmed.
• Serious dermatologic reactions: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), including fatal outcomes, have been reported with ADCETRIS. If SJS or TEN 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 monomethyl auristatin E (MMAE).

Use in Specific Populations:

MMAE exposure and adverse reactions are increased in patients with moderate or severe hepatic impairment or severe renal impairment. Avoid use.

For additional important safety information, including Boxed WARNING, please see the full U.S. prescribing information for ADCETRIS at www.seattlegenetics.com.

Forward-Looking Statement

Certain of the statements made in this press release are forward-looking, such as those, among others, relating to the therapeutic potential of ADCETRIS and the possibility that ADCETRIS may receive approval of a new indication from the FDA based on the submitted supplemental BLA. 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 safety and/or efficacy results of the AETHERA trial in at risk, post-ASCT Hodgkin lymphoma will not be sufficient to gain marketing approval in the United States or any other country for the indication sought in the sBLA, that we will be required to generate additional data or amend our submission for marketing approval. In addition, our regulatory plans may change as a result of further consultation with the FDA. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company’s Annual Report on Form 10-K for the year ended December 31, 2014 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.

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