-Positive Phase 3 ECHELON-2 Clinical Trial Results to be Presented in Oral Session on Monday, December 3rd-

BOTHELL, Wash.--(BUSINESS WIRE)-- Seattle Genetics, Inc. (Nasdaq: SGEN) today announced that 31 abstracts featuring data from the broad ADCETRIS (brentuximab vedotin) development program have been accepted for presentation at the 60th American Society of Hematology (ASH) Annual Meeting and Exposition taking place from December 1-4, 2018 in San Diego, Calif. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, which is expressed on the surface of Hodgkin lymphoma (HL) cells and several types of non-Hodgkin lymphoma. ADCETRIS is being evaluated globally as the foundation of care for CD30-expressing lymphomas in more than 70 corporate- and investigator-sponsored clinical trials.

Data accepted for presentation at the ASH Annual Meeting include the following:

• Data from the phase 3 ECHELON-2 clinical trial evaluating ADCETRIS in combination with chemotherapy in previously untreated patients with CD30-expressing peripheral T-cell lymphoma (PTCL) patients will be presented in an oral presentation on Monday, December 3, 2018 at 6:15 p.m. PT. Seattle Genetics and its partner Takeda Pharmaceutical Company Limited�(Takeda) reported positive top-line results from the ECHELON-2 trial in October 2018. The trial demonstrated a statistically significant improvement in the primary endpoint of progression-free survival (PFS) of ADCETRIS in combination with CHP (cyclophosphamide, doxorubicin, prednisone) versus the control arm, CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone). The ADCETRIS plus CHP arm also demonstrated superior overall survival (OS), a key secondary endpoint, compared to CHOP. The ECHELON-2 trial is the first trial to demonstrate an OS advantage in this difficult to treat type of non-Hodgkin lymphoma. Seattle Genetics expects to submit in November 2018 a supplemental Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) for approval of ADCETRIS plus CHP in frontline CD30-expressing PTCL.
• Several analyses from the phase 3 ECHELON-1 clinical trial evaluating ADCETRIS in combination with chemotherapy in frontline Stage III or IV classical HL adult patients, which formed the basis of FDA approval in this indication in March 2018, will be presented. Data presentations include additional analyses from the ECHELON-1 study, including PFS per investigator and outcomes in younger patients (18-30 years of age). These analyses are consistent with the previously reported modified PFS data and demonstrate improved outcomes in the ADCETRIS plus AVD (doxorubicin, vinblastine, dacarbazine) arm versus ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine).
• Preliminary results from a phase 2 study of ADCETRIS in combination with Opdivo (nivolumab) among patients with relapsed or refractory primary mediastinal large B-cell lymphoma (CHECKMATE 436 trial), as well as updated results from an ongoing phase 1/2 study evaluating the combination therapy in relapsed or refractory HL.

“There will be more than 30 data presentations from both corporate- and investigator-sponsored studies presented at the 2018 ASH Annual Meeting evaluating ADCETRIS in a variety of CD30-expressing lymphoma settings. These presentations are reflective of a robust ADCETRIS clinical development program that we, in partnership with the oncology community, are conducting to improve the treatment outcomes for patients,” said Roger Dansey, M.D., Chief Medical Officer of Seattle Genetics. “Importantly, and in collaboration with our partner Takeda, the results of the phase 3 ECHELON-2 clinical trial evaluating ADCETRIS in combination with CHP chemotherapy in frontline CD30-expressing peripheral T-cell lymphoma patients will be presented in an oral presentation on Monday, December 3rd. These data are the basis for our planned supplemental Biologics License Application to the FDA requesting approval of ADCETRIS in this setting, which we intend to submit in November 2018.”

ADCETRIS is not currently approved for use in frontline PTCL or in combination with Opdivo.

Multiple corporate and investigator presentations will be featured at ASH. Abstracts can be found at www.hematology.org and include the following:

Saturday, December 1, 2018

• Brentuximab Vedotin with Chemotherapy in Adolescents and Young Adults (AYA) with Stage III or IV Hodgkin Lymphoma: A Subgroup Analysis from the Phase 3 ECHELON-1 Study (Abstract #1647, poster presentation)
• Older Patients (pts) with Previously Untreated Classical Hodgkin Lymphoma (cHL): A Detailed Analysis from the Phase 3 ECHELON-1 Study (Abstract #1618, poster presentation)
• Phase 1/2 Study of Brentuximab Vedotin in Combination with Nivolumab in Patients with Relapsed or Refractory Classic Hodgkin lymphoma: Part 3 (Concurrent Dosing) Results and Updated Progression-Free Survival Results from Parts 1 and 2 (Staggered Dosing) (Abstract #1635, poster presentation)
• Phase 1 Study of MDR1 Inhibitor Plus Brentuximab Vedotin in Relapsed/Refractory Hodgkin Lymphoma (Abstract #1636, poster presentation)
• Real World Prevalence of Diagnostic Revision Among Patients with Peripheral T-cell Lymphomas (PTCL) in the US: Results of an Administrative Claims and Electronic Medical Record Analyses (Abstract #1633, poster presentation)
• Superior Clinical Benefit of Brentuximab Vedotin in Mycosis Fungoides Versus Physician's Choice Irrespective of CD30 Level of Large Cell Transformation Status in the Phase 3 ALCANZA Study (Abstract #1646, poster presentation)
• A Phase II Study of Brentuximab Vedotin plus Adriamycin and Dacarbazine without Radiation in Non-Bulky Limited Stage Classical Hodgkin Lymphoma (Abstract #1654, poster presentation)
• Treatment Patterns and Outcomes of Relapsed/Refractory Peripheral T-Cell Lymphoma (RR-PTCL) Patients Treated in the Community Oncology Setting (Abstract #1656, poster presentation)
• Nivolumab Combined with Brentuximab Vedotin for Relapsed/Refractory Primary Mediastinal Large B-Cell Lymphoma: Preliminary Results From the Phase 2 CheckMate 436 Trial (Abstract #1691, poster presentation)
• The Development and Validation of an Electronic Health Record (EHR)-Based Algorithm for Identifying Treatment Failure in Newly Diagnosed Hodgkin Lymphoma (HL) Treated in a US Community Oncology Setting (Abstract #2261, poster presentation)
• Real World Evidence in Relapsed/Refractory Classical Hodgkin Lymphoma Patients Who Are Ineligible for Stem Cell Transplant in the United States (US) (Abstract #2268, poster presentation)
• Toxicity Profile of Brentuximab Vedotin in Combination with Chemotherapy for Newly Diagnosed Patients with ALK+ ALCL: a Children's Oncology Group Study ANHL12P1 (Abstract #1625, poster presentation)
• Phase I Study of the Antibody-Drug Conjugate Brentuximab Vedotin Combined with Re-Induction Chemotherapy in Patients with CD30-Expressing Relapsed/Refractory Acute Myeloid Leukemia (Abstract #1431, poster presentation)
• Phase 1 Results from a Phase 1/2 Study to Assess the Safety, Tolerability and Recommended Phase 2 Dose (RP2D) of Brentuximab Vedotin Plus Doxorubicin, Vinblastine and Dacarbazine (A+AVD) in Pediatric Patients (Pts) with Advanced Stage Newly Diagnosed Classical Hodgkin Lymphoma (cHL) (Abstract #1644, poster presentation)

Sunday, December 2, 2018

• Brentuximab Vedotin Plus Chemotherapy in Patients with Advanced-Stage Classical Hodgkin Lymphoma (cHL): Evaluation of Modified Progression-Free Survival (mPFS) and Traditional PFS in the Phase 3 ECHELON-1 Study (Abstract #2904, poster presentation)
• Resolution of Peripheral Neuropathy (PN) in Patients Who Received A+AVD or ABVD in the Phase 3 ECHELON-1 Trial (Abstract #2921, poster presentation)
• Interim Analysis Results from an International, Multi-Centre, Non-Interventional Retrospective Study to Describe Treatment Pathways, Outcomes, and Resource Use in Patients with Classical Hodgkin Lymphoma: B-CD30+ Hodgkin Lymphoma International Multi-Centre Retrospective Study of Treatment Practices and Outcomes (B-HOLISTIC) (Abstract #2917, poster presentation)
• Combining Brentuximab Vedotin with DHAP as Salvage Treatment in Relapsed/Refractory Hodgkin Lymphoma: the Phase II HOVON/LLPC Transplant BRaVE Study (Abstract #2923, poster presentation)
• Peripheral T-Cell Lymphomas in Spain: Profiling Clinical, Phenotypic and Genetic Characteristics in Spanish Population (Abstract #2938, poster presentation)
• Primary Mediastinal B-Cell Lymphoma: Evaluation of Clinicopathologic Diagnosis Compared to Gene Expression Based Diagnosis in a Clinical Trial with CD30+ B-Cell Lymphomas (Abstract #2959, poster presentation)
• Utilization of a Novel Method of Detection of CD30 Expression in Diffuse Large B-cell Lymphoma (Abstract #2978, poster presentation)
• Health-Related Quality of Life (HRQL) Trajectories during Treatment for Advanced Stage Pediatric Hodgkin Lymphoma (HL) (Abstract #3587, poster presentation)

Monday, December 3, 2018

• The ECHELON-2 Trial: Results of a Randomized, Double-Blind, Active-Controlled Phase 3 Study of Brentuximab Vedotin and CHP (A+CHP) Versus CHOP in the Frontline Treatment of Patients with CD30+ Peripheral T-Cell Lymphomas (Abstract #997, oral presentation at 6:15 p.m. PT)
• Longitudinal Adverse Event Assessment of the Combination of Ipilimumab, Nivolumab And Brentuximab Vedotin in Relapsed/Refractory Hodgkin Lymphoma: A Trial of the ECOG-ACRIN Cancer Research Group (E4412: Arms A-F) (Abstract #623, oral presentation at 8:00 a.m. PT)
• A Phase I Study with an Expansion Cohort of the Combinations of Ipilimumab, Nivolumab and Brentuximab Vedotin in Patients with Relapsed/Refractory Hodgkin Lymphoma: A trial of the ECOG-ACRIN Research Group (E4412: Arms G-I) (Abstract #679, oral presentation at 10:30 a.m. PT)
• B-CAP (brentuximab vedotin, cyclophosphamide, doxorubicin and predniso(lo)Ne) in Older Patients with Advanced-Stage Hodgkin Lymphoma: Results of a Phase II Intergroup Trial By the German Hodgkin Study Group (GHSG) and the Nordic Lymphoma Group (NLG) (Abstract #926, oral presentation at 4:45 p.m. PT)
• Response-Adapted Therapy with Nivolumab and Brentuximab Vedotin (BV), Followed by BV and Bendamustine for Suboptimal Response, in Children, Adolescents, and Young Adults with Standard-Risk Relapsed/Refractory Classical Hodgkin Lymphoma (Abstract #927, oral presentation at 5:00 p.m. PT)
• Productivity Loss Among Parent Caregivers is Associated with Poor Health-Related Quality of Life (HRQL) at the Initial Diagnosis Of Pediatric Advanced Stage Hodgkin Lymphoma (HL) (Abstract #975, oral presentation at 5:00 p.m. PT)
• Baseline Tumor Transcriptome Characteristics Associated with the Response of Relapsed/Refractory Hodgkin Lymphoma Patients to Brentuximab Vedotin in Combination with Nivolumab (Abstract #2837, poster presentation)
• Patient and Physician Preferences for First-Line Treatment of Classical Hodgkin Lymphoma in the United States (Abstract #4786, poster presentation)
• Prolonged Overall Survival (OS) in a Subset of Responders to the Combination of Brentuximab Vedotin (Bv) and Bendamustine (B) in Heavily Treated Patients with Relapsed or Refractory Hodgkin Lymphoma (HL): Results of an International Multi-Center Phase I/II Experience (Abstract #2907, poster presentation)

About ADCETRIS (brentuximab vedotin)

ADCETRIS is being evaluated broadly in more than 70 clinical trials in CD30-expressing lymphomas. These include the recently completed phase 3 ECHELON-2 trial in frontline peripheral T-cell lymphomas (also known as mature T-cell lymphoma), the completed phase 3 ECHELON-1 trial in previously untreated Hodgkin lymphoma, the completed phase 3 ALCANZA trial in cutaneous T-cell lymphoma, and the ongoing CHECKMATE 812 trial of ADCETRIS in combination with Opdivo (nivolumab) for relapsed/refractory Hodgkin lymphoma.

ADCETRIS 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 injection for intravenous infusion has received FDA approval for five indications in adult patients with: (1) previously untreated Stage III or IV classical Hodgkin lymphoma (cHL), in combination with chemotherapy, (2) cHL at high risk of relapse or progression as post-autologous hematopoietic stem cell transplantation (auto-HSCT) consolidation, (3) cHL after failure of auto-HSCT or failure of at least two prior multi-agent chemotherapy regimens in patients who are not auto-HSCT candidates, (4) sALCL after failure of at least one prior multi-agent chemotherapy regimen, and (5) primary cutaneous anaplastic large cell lymphoma (pcALCL) or CD30-expressing mycosis fungoides (MF) who have received prior systemic therapy.

Health Canada granted ADCETRIS approval with conditions for relapsed or refractory Hodgkin lymphoma and sALCL in 2013, and non-conditional approval for post-autologous stem cell transplantation (ASCT) consolidation treatment of Hodgkin lymphoma patients at increased risk of relapse or progression.

ADCETRIS received conditional marketing authorization from the European Commission in October 2012. The approved indications in Europe are: (1) for the treatment of adult patients with relapsed or refractory CD30-positive Hodgkin lymphoma following ASCT, or following at least two prior therapies when ASCT or multi-agent chemotherapy is not a treatment option, (2) the treatment of adult patients with relapsed or refractory sALCL, (3) for the treatment of adult patients with CD30-positive Hodgkin lymphoma at increased risk of relapse or progression following ASCT, and (4) for the treatment of adult patients with CD30-positive cutaneous T-cell lymphoma (CTCL) after at least one prior systemic therapy.

ADCETRIS has received marketing authorization by regulatory authorities in 72 countries for relapsed or refractory Hodgkin lymphoma and sALCL. See select important safety information, including Boxed Warning, 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 is solely responsible for development costs.

About Seattle Genetics

Seattle Genetics, Inc. is an emerging multi-product, global biotechnology company that develops and commercializes transformative therapies targeting cancer to make a meaningful difference in people’s lives. ADCETRIS® (brentuximab vedotin) utilizes the company’s industry-leading antibody-drug conjugate (ADC) technology and is currently approved for the treatment of multiple CD30-expressing lymphomas. Beyond ADCETRIS, the company has established a pipeline of novel targeted therapies at various stages of clinical testing, including three in ongoing pivotal trials for solid tumors. Enfortumab vedotin for metastatic urothelial cancer and tisotumab vedotin for metastatic cervical cancer utilize our proprietary ADC technology. Tucatinib, a small molecule tyrosine kinase inhibitor, is in a pivotal trial for HER2-positive metastatic breast cancer. In addition, we are leveraging our expertise in empowered antibodies to build a portfolio of proprietary immuno-oncology agents in clinical trials targeting hematologic malignancies and solid tumors. The company is headquartered in Bothell, Washington, and has a European office in Switzerland. For more information on our robust pipeline, visit www.seattlegenetics.com and follow @SeattleGenetics on Twitter.

ADCETRIS (brentuximab vedotin) Important Safety Information

BOXED WARNING: PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML):

JC virus infection resulting in PML and death can occur in ADCETRIS-treated patients.

Contraindication

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

Warnings and Precautions

• Peripheral neuropathy (PN): ADCETRIS causes PN that is predominantly sensory. Cases of motor PN have also been reported. ADCETRIS-induced PN is cumulative. Monitor for symptoms such as hypoesthesia, hyperesthesia, paresthesia, discomfort, a burning sensation, neuropathic pain, or weakness. Institute dose modifications accordingly.
• Anaphylaxis and infusion reactions: Infusion-related reactions (IRR), including anaphylaxis, have occurred with ADCETRIS. Monitor patients during infusion. If an IRR occurs, interrupt the infusion and institute appropriate medical management. If anaphylaxis occurs, immediately and permanently discontinue the infusion and administer appropriate medical therapy. Premedicate patients with a prior IRR before subsequent infusions. Premedication may include acetaminophen, an antihistamine, and a corticosteroid.
• Hematologic toxicities: Fatal and serious cases of febrile neutropenia have been reported with ADCETRIS. Prolonged (≥1 week) severe neutropenia and Grade 3 or 4 thrombocytopenia or anemia can occur with ADCETRIS. Administer G-CSF primary prophylaxis starting with Cycle 1 for previously untreated patients who receive ADCETRIS in combination with chemotherapy for Stage III or IV classical HL. Monitor complete blood counts prior to each ADCETRIS dose. 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 ADCETRIS-treated patients. Closely monitor patients during treatment for 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 compared to patients with normal renal function. Avoid use 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 or severe hepatic impairment compared to patients with normal hepatic function. Avoid use in patients with moderate or severe hepatic impairment.
• Hepatotoxicity: Fatal and serious cases have occurred in ADCETRIS-treated patients. Cases were consistent with hepatocellular injury, including elevations of transaminases and/or bilirubin, and occurred after the first ADCETRIS dose or rechallenge. Preexisting liver disease, elevated baseline liver enzymes, and concomitant medications may increase the risk. Monitor liver enzymes and bilirubin. Patients with new, worsening, or recurrent hepatotoxicity may require a delay, change in dose, or discontinuation of ADCETRIS.
• PML: Fatal cases of JC virus infection resulting in PML and death have been reported in ADCETRIS-treated patients. First onset of symptoms occurred at various times from initiation of ADCETRIS therapy, with some cases occurring within 3 months of initial exposure. Other possible contributory factors other than ADCETRIS include prior therapies and underlying disease that may cause immunosuppression. Consider PML diagnosis in patients with new-onset signs and symptoms of central nervous system abnormalities. Hold ADCETRIS if PML is suspected and discontinue ADCETRIS if PML is confirmed.
• Pulmonary toxicity: Fatal and serious events of noninfectious pulmonary toxicity including pneumonitis, interstitial lung disease, and acute respiratory distress syndrome have been reported. Monitor patients for signs and symptoms, including cough and dyspnea. In the event of new or worsening pulmonary symptoms, hold ADCETRIS dosing during evaluation and until symptomatic improvement.
• Serious dermatologic reactions: Fatal and serious cases of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported with ADCETRIS. If SJS or TEN occurs, discontinue ADCETRIS and administer appropriate medical therapy.
• Gastrointestinal (GI) complications: Fatal and serious cases of acute pancreatitis have been reported. Other fatal and serious GI complications include perforation, hemorrhage, erosion, ulcer, intestinal obstruction, enterocolitis, neutropenic colitis, and ileus. Lymphoma with preexisting GI involvement may increase the risk of perforation. In the event of new or worsening GI symptoms, perform a prompt diagnostic evaluation and treat appropriately.
• Embryo-fetal toxicity: Based on the mechanism of action and animal studies, ADCETRIS can cause fetal harm. Advise females of reproductive potential of the potential risk to the fetus, and to avoid pregnancy during ADCETRIS treatment and for at least 6 months after the final dose of ADCETRIS.

Most Common (≥20%) Adverse Reactions: Neutropenia, anemia, peripheral sensory neuropathy, nausea, fatigue, constipation, diarrhea, vomiting, and pyrexia.

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

Moderate or severe hepatic impairment or severe renal impairment: MMAE exposure and adverse reactions are increased. Avoid use.

Advise males with female sexual partners of reproductive potential to use effective contraception during ADCETRIS treatment and for at least 6 months after the final dose of ADCETRIS.

Advise patients to report pregnancy immediately and avoid breastfeeding while receiving ADCETRIS.

For additional Important Safety Information, including BOXED WARNING, please see the full Prescribing Information for ADCETRIS at www.seattlegenetics.com or http://www.adcetris.com.

Forward Looking Statements

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the submission of a supplemental Biologics License Application (BLA) to the FDA for approval of ADCETRIS in frontline CD30-expressing PTCL in November 2018, the publication of data relating to ADCETRIS at ASH 2018, and the utilization of ADCETRIS for uses that are not yet approved. Actual results or developments may differ materially from those projected or implied in these forward-looking statements due to factors such that the company may be unable to expand ADCETRIS’ labeled indications due to unexpected, negative or delayed regulatory action, and that supplemental BLA submission based on�ECHELON-2�may not be submitted to, accepted for filing by, or ultimately approved by, the FDA in a timely manner or at all or with the requested label. More information about the risks and uncertainties faced by Seattle Genetics is contained under the caption “Risk Factors” included in the company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2018 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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Seattle Genetics, Inc.

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