Seattle Genetics Announces Presentations of New Clinical Data from Multiple Studies of Novel Targeted Therapies at the American Society of Clinical Oncology (ASCO) Annual Meeting

First Presentation of Data from EV-201 Pivotal Trial of Enfortumab
Vedotin in Locally Advanced or Metastatic Urothelial Cancer Featured in
an Oral Session on Monday, June 3
rd

BOTHELL, Wash.–(BUSINESS WIRE)–Seattle
Genetics, Inc.
(Nasdaq:SGEN) today announced data from six of its
proprietary programs will be presented at the upcoming American Society
of Clinical Oncology (ASCO) 2019 Annual Meeting taking place May 31 to
June 4, 2019 in Chicago. More than 10 sessions at the meeting will
feature Seattle Genetics’ approved or investigational therapies,
including an oral presentation of the results from the enfortumab
vedotin pivotal trial. The abstracts published in advance of the ASCO
meeting were made available today on the ASCO website at www.asco.org.

“Data to be presented on our approved or investigational targeted
medicines support our efforts toward becoming a multi-product oncology
company,” said Roger Dansey, M.D., Chief Medical Officer at Seattle
Genetics. “Importantly, the oral presentation of the results from the
EV-201 pivotal trial of enfortumab vedotin in patients with locally
advanced or metastatic urothelial cancer is our first solid tumor
late-stage development program. We are also presenting updated analyses
from the ECHELON-1 and ECHELON-2 frontline phase 3 trials of ADCETRIS®
(brentuximab vedotin) that is approved for several types of lymphomas.”

Details of the oral presentation:

Abstract Title: EV-201: Results of Enfortumab Vedotin Monotherapy for
Locally Advanced or Metastatic Urothelial Cancer Previously Treated with
Platinum and Immune Checkpoint Inhibitors

Abstract: #LBA4505

Presenter: Daniel P. Petrylak, M.D., Yale School of Medicine

Date and Time: Monday, June 3, 9:24-9:36 a.m. CDT

Location: Arie Crown Theater

Details of select company- or
investigator-sponsored presentations are as follows:

Brentuximab Vedotin with Chemotherapy for Stage 3/4 Classical Hodgkin
Lymphoma: Three-year Update of the ECHELON-1 Study (Abstract #7532)

Date and Time: Monday, June 3, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #286

Response to A+CHP by CD30 Expression in the ECHELON-2 Trial (Abstract
#7538)

Date and Time: Monday, June 3, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #292

Response to Brentuximab Vedotin by CD30 Expression: Results from Five
Trials in PTCL, CTCL, and B-cell Lymphomas (Abstract #7543)

Date and Time: Monday, June 3, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #297

Tucatinib, Palbociclib, and Letrozole in HR+/HER2+ Metastatic Breast
Cancer: Report of Phase IB Safety Cohort (Abstract #1029)

Date and Time: Sunday, June 2, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #110

Performance of FACT-GOG-Ntx to Assess Chemotherapy-Induced Peripheral
Neuropathy (CIPN) in Pediatric Hodgkin lymphoma (HL) Patients (Abstract
#10064)

Date and Time: Saturday, June 1, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #446

Details of company-sponsored trials in progress
presentations are as follows:

SGNTV-001: Open Label Phase 2 Study of Tisotumab Vedotin for Locally
Advanced or Metastatic Disease in Solid Tumors (Abstract #TPS3160)

Date and Time: Saturday, June 1, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #145a

Phase 2 Trial of Tisotumab Vedotin in Platinum-Resistant Ovarian
Cancer (innovaTV 208) (Abstract #TPS5602)

Date and Time: Saturday, June 1, 1:15 p.m.-4:15 p.m. CDT

Location: Hall A, Poster Board #421a

SGNLVA-002: Single-Arm, Open Label Phase IB/II Study of Ladiratuzumab
Vedotin (LV) in Combination with Pembrolizumab for First-Line Treatment
of Patients with Unresectable Locally Advanced or Metastatic
Triple-Negative Breast Cancer (Abstract #TPS1110)

Date and Time: Sunday, June 2, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #186a

SGNBCMA-001: A Phase 1 Study of SEA-BCMA, a Non-Fucosylated
Monoclonal Antibody, in Subjects with Relapsed or Refractory Multiple
Myeloma (Abstract #TPS8054)

Date and Time: Monday, June 3, 8:00 a.m.-11:00 a.m. CDT

Location: Hall A, Poster Board #379a

EV-103: Enfortumab Vedotin Plus Pembrolizumab and/or Chemotherapy for
Locally Advanced or Metastatic Urothelial Cancer (Abstract #TPS4593)

Date and Time: Monday, June 3, 1:15 p.m.-4:15 p.m. CDT

Location: Hall A, Poster Board #415b

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 March 31, 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.

Contacts

Media:
Monique Greer
(425) 527-4641
mgreer@seagen.com

Investors:
Peggy Pinkston
(425) 527-4160
ppinkston@seagen.com