Seattle Genetics Announces Presentations of New Clinical Data from Multiple Studies of Novel Targeted Therapies at the European Society for Medical Oncology (ESMO) 2019 Congress

– First Presentation of Initial Data from a Phase 1 Trial of Enfortumab Vedotin Plus Pembrolizumab in Locally Advanced or Metastatic Urothelial Cancer Featured in an Oral Session –

BOTHELL, Wash.–(BUSINESS WIRE)–Seattle Genetics, Inc. (Nasdaq:SGEN) today announced that new data from four of its investigational programs will be presented at the upcoming European Society for Medical Oncology (ESMO) 2019 Congress in Barcelona, Spain, from September 27 – October 1, 2019.

“We look forward to the presentation featuring antibody-drug conjugate enfortumab vedotin in combination with the immune therapy pembrolizumab in patients with previously untreated advanced urothelial cancer,” said Roger Dansey, M.D., Chief Medical Officer at Seattle Genetics. “We are also pleased to see initial results from an investigator-sponsored study called MOUNTAINEER examining the combination of our novel tyrosine kinase inhibitor tucatinib with trastuzumab for the treatment of HER2-amplified metastatic colorectal cancer. The development of these and other targeted medicines support our efforts toward becoming a multi-product oncology company.”

Details of the oral presentation:

EV-103: Initial results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma

Abstract: 901O

Presenter: C Hoimes, Case Western Reserve University, Cleveland, OH, USA

Session: Oral Presentation Proffered Paper Session – Genitourinary tumours, non-prostate

Date and Time: Saturday, September 28, 8:30-10:00 a.m. CEST

Location: Barcelona Auditorium, Hall 2

Details of company-sponsored presentations are as follows:

Systemic therapy in 2nd-line metastatic triple negative breast cancer (mTNBC): a systematic literature review (SLR) and meta-analysis (MA) of efficacy

Abstract: 360P

First Author: PA Kaufman, University of Vermont Cancer Center, Burlington, VT, USA

Session: Poster Presentation

Date and Time: Sunday, September 29, 12:00-1:00 p.m. CEST

Location: Barcelona Auditorium, Hall 4

Quality of life of metastatic urothelial cancer (mUC) patients treated with enfortumab vedotin (EV) following platinum-containing chemotherapy and a checkpoint inhibitor (CPI): data from EV-201 cohort 1

Abstract: 921P

First Author: B McGregor, Dana-Farber Cancer Institute, Boston, MA, USA

Session: Poster Presentation

Date and Time: Monday, September 30, 12:00-1:00 p.m. CEST

Location: Barcelona Auditorium, Hall 4

Phase 1/2 trial of tisotumab vedotin plus bevacizumab, pembrolizumab, or carboplatin in recurrent or metastatic cervical cancer (innovaTV 205/ENGOT-cx8)

Abstract: 1059TiP

First Author: I Vergote, Leuven Cancer Institute, Leuven, Belgium

Session: Poster Presentation

Date and Time: Sunday, September 29, 12:00-1:00 p.m. CEST

Location: Barcelona Auditorium, Hall 4

Details of select investigator-initiated trial presentation is as follows:

Trastuzumab and tucatinib for the treatment of HER2 amplified metastatic colorectal cancer (mCRC): Initial results from the MOUNTAINEER trial

Abstract: 527PD

First Author: JH Strickler, Duke University Medical Centre, Durham, NC, USA

Session: Poster Discussion Session – Gastrointestinal tumours, colorectal

Date and Time: Sunday, September 29, Poster Discussion: 3:00-3:15 p.m. CEST

Location: Cordoba Auditorium, Hall 7

For more information, including a complete list of abstract titles and presentation dates and times, visit the ESMO website at https://cslide.ctimeetingtech.com/esmo2019/attendee/confcal.

About Enfortumab Vedotin

Enfortumab vedotin is an investigational antibody-drug conjugate (ADC) composed of an anti-Nectin-4 monoclonal antibody attached to a microtubule-disrupting agent, MMAE, using Seattle Genetics’ proprietary linker technology. Enfortumab vedotin targets Nectin-4, a cell adhesion molecule that is expressed on many solid tumors, and that has been identified as an ADC target by Astellas. A Biologics License Application is currently under review by the U.S. Food and Drug Administration (FDA) for the treatment of patients with locally advanced or metastatic urothelial cancer who have received a PD-1/PD-L1 inhibitor and who have received a platinum-containing chemotherapy before (neoadjuvant) or after (adjuvant) surgery or in a locally advanced or metastatic setting. Enfortumab vedotin is being co-developed by Seattle Genetics and Astellas Pharma Inc.

The safety and efficacy of enfortumab vedotin are under investigation and have not been established. There is no guarantee that the agent will receive regulatory approval or become commercially available for the uses being investigated.

About Tisotumab Vedotin

Tisotumab vedotin is an antibody-drug conjugate (ADC) composed of Genmab’s human antibody that binds to Tissue Factor and Seattle Genetics’ ADC technology that utilizes a cleavable linker and the microtubule disrupting agent monomethyl auristatin E (MMAE). In cancer biology, Tissue Factor is a protein involved in tumor signaling and angiogenesis. The Tissue Factor antigen target is overexpressed in the vast majority of patients with cervical cancer and in many other solid tumors, including ovarian, lung, pancreatic, colorectal and head and neck. Based on its high expression on many solid tumors and its rapid internalization, Tissue Factor was selected as a target for an ADC approach. Tisotumab vedotin is being co-developed by Seattle Genetics and Genmab.

About Tucatinib

Tucatinib is an investigational, orally bioavailable, potent tyrosine kinase inhibitor that is highly selective for HER2 without significant inhibition of EGFR. Inhibition of EGFR has been associated with significant toxicities, including skin rash and diarrhea. Tucatinib has shown activity as a single agent and in combination with both chemotherapy and other HER2 directed agents such as trastuzumab.¹ Studies of tucatinib in these combinations have shown activity both systemically and in brain metastases. ¹ HER2 is a growth factor receptor that is overexpressed in multiple cancers, including breast, ovarian and gastric cancers. HER2 mediates cell growth, differentiation and survival. Tumors that overexpress HER2 are more aggressive and historically have been associated with poor overall survival compared with HER2-negative cancers. Tucatinib has been granted orphan drug designation by the FDA for the treatment of breast cancer patients with brain metastases.

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.

Forward Looking Statements

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the possible utility or application of the Company’s technologies to develop therapeutic agents, therapeutic potential of investigational agents, and future development activities including clinical trials. 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 difficulty and uncertainty of pharmaceutical product development, including the risks that Seattle Genetics may experience delays in its planned clinical trial initiations or otherwise experience failures or setbacks in its preclinical and clinical development programs due to the potential lack of efficacy or risk of adverse events or other factors. 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 June 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.

References:

1. Murthy, R. et al., Tucatinib with capecitabine and trastuzumab in advanced HER2-positive metastatic breast cancer with and without brain metastases: a non-randomised, open-label, phase 1b study. Lancet Oncol. 2018; May 2018.

Contacts

Media:

Monique Greer

(425) 527-4641

[email protected]

Investors:

Peggy Pinkston

(425) 527-4160

[email protected]