Seattle Genetics Announces Updated Data of ADCETRIS® (Brentuximab Vedotin) in Combination with OPDIVO® (Nivolumab) in Frontline and Relapsed or Refractory Hodgkin Lymphoma at ASH Annual Meeting

– Additional Analysis in Phase 2 Trial of ADCETRIS plus OPDIVO in Patients with Frontline Hodgkin Lymphoma Aged 60 Years and Older –

– Two-Year Follow-up Results from Phase 1/2 Trial in Relapsed Hodgkin Lymphoma –

BOTHELL, Wash.–(BUSINESS WIRE)–Seattle Genetics, Inc. (Nasdaq:SGEN) today announced updated and long-term follow-up analyses from two clinical trials evaluating ADCETRIS (brentuximab vedotin) and OPDIVO^® (nivolumab) in frontline Hodgkin lymphoma (HL) patients aged 60 years and older and in relapsed or refractory classical HL. ADCETRIS is an antibody-drug conjugate (ADC) directed to CD30, a defining marker of classical HL. ADCETRIS and OPDIVO are not approved in combination for the treatment of HL. Results were presented today at the 61^st American Society of Hematology (ASH) Annual Meeting and Exposition taking place December 7-10 in Orlando, Fla.

“We continue to evaluate ADCETRIS in combination with novel therapies, such as checkpoint inhibitors, with the goal of identifying new options for CD30-expressing lymphomas where there is high unmet need,” said Roger Dansey, M.D., Chief Medical Officer at Seattle Genetics. “These data presentations at ASH reinforce our strong commitment to the ADCETRIS clinical development program, potentially moving into new patient populations and novel combination treatment strategies.”

Phase 2 Study of Frontline Brentuximab Vedotin Plus Nivolumab in Patients with Hodgkin Lymphoma Aged ≥ 60 Years (Abstract #237, oral presentation at 2:30 p.m. ET on Saturday, December 7, 2019)

Data were presented from an updated analysis from the phase 2 clinical trial evaluating ADCETRIS in combination with OPDIVO as frontline therapy for HL patients aged 60 years and older. Data were reported from 21 patients, and the median age was 72 years. The majority of patients (76 percent) had stage III/IV disease at the time of diagnosis. These results will be highlighted in an oral presentation by Christopher A. Yasenchak, M.D., Willamette Valley Cancer Institute and Research Center/US Oncology Research, Ore., and include:

• Of 19 response-evaluable patients, 18 patients (95 percent) had an objective response, including 13 patients (68 percent) with a complete response and five patients (26 percent) with a partial response. All response-evaluable patients experienced tumor reduction (complete response + partial response + stable disease) following treatment with ADCETRIS in combination with OPDIVO. Median duration of response was not yet reached and the maximum duration of response was 22 months and ongoing (95% CI: 7.06, -).
• The most common treatment-related adverse events of any grade occurring in at least 20 percent of patients were fatigue, diarrhea, pyrexia, infusion related reaction, peripheral motor neuropathy, peripheral sensory neuropathy and increase in lipase. One treatment-related serious adverse event was pyrexia. Fifty-seven percent of patients (12/21) had at least one treatment-related adverse event greater than or equal to Grade 3, most commonly increase in lipase (24 percent, 5/21), peripheral motor neuropathy and peripheral sensory neuropathy (each 14 percent, 3/21), and fatigue and hyponatremia (each 10 percent, 2/21).

Two-Year Follow-up Results from the Phase 1-2 Study of Brentuximab Vedotin in Combination with Nivolumab in Patients with Relapsed or Refractory Classical Hodgkin Lymphoma (Abstract #238, oral presentation at 2:45 p.m. ET on Saturday, December 7, 2019)

Data were reported from 93 patients with relapsed or refractory classical HL after failure of frontline therapy who received the combination regimen of ADCETRIS plus OPDIVO. After completion of the fourth cycle of treatment, patients were eligible to undergo an autologous stem cell transplant (ASCT). The median age of patients was 34 years. These results will be highlighted in an oral presentation by Alison J. Moskowitz, M.D., Memorial Sloan Kettering Cancer Center, NY, and include:

• Of the 91 treated patients, 85 percent (77/91) had an objective response, including 67 percent (61/91) with a complete response, 16 patients with a partial response and six patients had stable disease.
• Of the 91 treated patients, 67 patients received an ASCT per trial protocol with no additional salvage therapy.
• For all treated patients, the two-year progression-free survival (PFS) was 79 percent (95% CI: 68%, 87%). For the 67 patients who received an ASCT per trial protocol, the two-year PFS was 92 percent (95% CI: 80%, 97%). Median follow-up for all treated patients was 24.2 months (range 1.8-41.7) and the median PFS was not reached. Estimated overall survival at two years was 94 percent (95% CI: 85%, 97%) and median overall survival was not yet reached.
• Peripheral immune signatures were consistent with an activated T-cell response.
• Prior to ASCT, the most common adverse events of any grade occurring in more than 20 percent of patients were nausea, infusion related reaction, fatigue, diarrhea, pruritus, headache, vomiting and pyrexia. Other adverse events included peripheral neuropathy in 16 patients (18 percent) and neutropenia in six patients (7 percent). Two patients (2 percent) discontinued treatment due to adverse events, Grade 3 peripheral neuropathy and increased gamma-glutamyltransferase. Serious adverse events occurred in 14 patients (15 percent), including pneumonia, pneumonitis and pyrexia (two patients each); and Grade 3 Guillain-Barre syndrome (one patient).

About Classical 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: Hodgkin lymphoma and non-Hodgkin lymphoma. Classical Hodgkin lymphoma 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 expresses CD30.

According to the American Cancer Society, approximately 8,110 cases of Hodgkin lymphoma will be diagnosed in the United States during 2019 and 1,000 will die from the disease. Approximately half of all newly diagnosed Hodgkin lymphoma patients have Stage III/IV disease. According to the Lymphoma Coalition, over 62,000 people worldwide are diagnosed with Hodgkin lymphoma each year and approximately 25,000 people die each year from this cancer.

About ADCETRIS

ADCETRIS is being evaluated broadly in more than 70 clinical trials in CD30-expressing lymphomas. These include three completed phase 3 trials: ECHELON-2 trial in frontline peripheral T-cell lymphomas, ECHELON-1 in previously untreated Hodgkin lymphoma, and ALCANZA in cutaneous T-cell 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 six indications in adult patients with: (1) previously untreated systemic anaplastic large cell lymphoma (sALCL) or other CD30-expressing peripheral T-cell lymphomas (PTCL), including angioimmunoblastic T-cell lymphoma and PTCL not otherwise specified, in combination with cyclophosphamide, doxorubicin, and prednisone, (2) previously untreated Stage III or IV classical Hodgkin lymphoma (cHL), in combination with doxorubicin, vinblastine, and dacarbazine, (3) cHL at high risk of relapse or progression as post-autologous hematopoietic stem cell transplantation (auto-HSCT) consolidation, (4) 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, (5) sALCL after failure of at least one prior multi-agent chemotherapy regimen, and (6) 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 in 2013 for patients with (1) HL after failure of autologous stem cell transplant (ASCT) or after failure of at least two multi-agent chemotherapy regimens in patients who are not ASCT candidates and (2) sALCL after failure of at least one multi-agent chemotherapy regimen. Non-conditional approval was granted for (3) post-ASCT consolidation treatment of patients with HL at increased risk of relapse or progression in 2017, (4) adult patients with pcALCL or CD30-expressing MF who have received prior systemic therapy in 2018, (5) for previously untreated patients with Stage IV HL in combination with doxorubicin, vinblastine, and dacarbazine in 2019, and (6) for previously untreated adult patients with sALCL, peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS) or angioimmunoblastic T-cell lymphoma (AITL), whose tumors express CD30, in combination with cyclophosphamide, doxorubicin, prednisone in 2019.

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) for 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, (4) for the treatment of adult patients with CD30-positive cutaneous T-cell lymphoma (CTCL) after at least one prior systemic therapy and (5) for the treatment of adult patients with previously untreated CD30-positive Stage IV Hodgkin lymphoma in combination with AVD (Adriamycin^®, vinblastine and dacarbazine).

ADCETRIS has received marketing authorization by regulatory authorities in 73 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 a late-stage pipeline including enfortumab vedotin for metastatic urothelial cancer, currently being reviewed for approval by the FDA, and tisotumab vedotin in clinical trials for metastatic cervical cancer, which utilize our proprietary ADC technology. In addition, tucatinib, a small molecule tyrosine kinase inhibitor, is in late-stage development for HER2-positive metastatic breast cancer and in clinical development for metastatic colorectal cancer. We are also 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) U.S. 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 beginning with Cycle 1 for patients who receive ADCETRIS in combination with chemotherapy for previously untreated Stage III/IV cHL or previously untreated PTCL. Monitor complete blood counts prior to each ADCETRIS dose. Monitor more frequently 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 wasgreater 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. In addition to ADCETRIS therapy, other possible contributory factors 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, including severe abdominal pain, perform a prompt diagnostic evaluation and treat appropriately.
• Hyperglycemia: Serious cases, such as new-onset hyperglycemia, exacerbation of preexisting diabetes mellitus, and ketoacidosis (including fatal outcomes) have been reported with ADCETRIS. Hyperglycemia occurred more frequently in patients with high body mass index or diabetes. Monitor serum glucose and if hyperglycemia develops, administer antihyperglycemic medications as clinically indicated.
• 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% in any study) Adverse Reactions: Peripheral neuropathy, fatigue, nausea, diarrhea, neutropenia, upper respiratory tract infection, pyrexia, constipation, vomiting, alopecia, decreased weight, abdominal pain, anemia, stomatitis, lymphopenia and mucositis.

Drug Interactions

Concomitant use of strong CYP3A4 inhibitors or inducers 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.

Please see the full Prescribing Information, including BOXED WARNING, for ADCETRIS here.

Forward Looking Statements

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the potential uses and benefits of ADCETRIS (brentuximab vedotin) in combination with OPDIVO^® (nivolumab) in frontline Hodgkin lymphoma (HL) patients age 60 years or older and in relapsed or refractory classical HL under staggered and concurrent dosing schedules, the therapeutic potential of ADCETRIS in these indications and the company’s clinical development plans. 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 potential lack of efficacy or risk of adverse events associated with the use of ADCETRIS in certain clinical settings and the difficulty and uncertainty of pharmaceutical product development. 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, 2019 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, except as required by law.

Opdivo^® is a registered trademark of Bristol-Myers Squibb Company.

Contacts

Media:

Monique Greer

(425) 527-4641

mgreer@seagen.com

Investors:

Peggy Pinkston

(425) 527-4160

ppinkston@seagen.com