-Data Presentations Highlight Continued Advances in Research for
Treating Blood Cancers-

BOTHELL, Wash.–(BUSINESS WIRE)–Seattle
Genetics, Inc. (Nasdaq:SGEN) today announced data from its ADCETRIS^®
(brentuximab vedotin) clinical development program at the 24^th
Annual Congress of the European Hematology Association (EHA) taking
place June 13-16 in Amsterdam; and the International Conference on
Malignant Lymphoma (ICML) from June 18-22 in Lugano. Updated analyses
from clinical trials evaluating ADCETRIS in combination with Opdivo^®
(nivolumab), as well as encore analyses from the phase 3 ECHELON-1,
ECHELON-2 and ALCANZA clinical trials, will be highlighted in 12
presentations at EHA and ICML. ADCETRIS is an antibody-drug conjugate
(ADC) directed to CD30, a defining marker of classical Hodgkin lymphoma
(HL) and expressed on the surface of several types of peripheral T-cell
lymphomas. Opdivo is a programmed death-1 (PD-1) immune
checkpoint inhibitor that is designed to harness the body’s own immune
system to help restore anti-tumor immune response. ADCETRIS and Opdivo
are not approved in combination for the treatment of relapsed or
refractory primary mediastinal large B-cell lymphoma (PMBL), HL,
pediatric HL or for other indications. ADCETRIS in combination with
bendamustine is not approved for HL.

“This year at the EHA and ICML meetings, key ADCETRIS data will be
featured that continue to support our goal of further expanding our
clinical development program beyond the six ADCETRIS approved
indications,” said Roger Dansey, M.D., Chief Medical Officer at Seattle
Genetics. “We are excited about several ADCETRIS-related presentations
including encore oral presentations from the ECHELON-1 and ECHELON-2
phase 3 trials, as well as clinical research updates on ADCETRIS
combination treatment strategies.”

Details of oral and poster presentations
featured at EHA include:

Abstract Title: Frontline Brentuximab Vedotin with Chemotherapy for
Stage 3/4 Classical Hodgkin Lymphoma: 3-Year Update of the ECHELON-1
Study (Abstract #S820)
Oral Presentation Date and Time: Saturday,
June 15, 12:00-12:15 p.m. CEST
Location: Hall 5

Abstract Title: Nivolumab and Brentuximab Vedotin-based,
Response-adapted Treatment in Primary Refractory and in Pediatric
Patients with Relapsed/Refractory Classical Hodgkin Lymphoma in
Checkmate 744 (Abstract #S822)
Oral Presentation Date and
Time: Saturday, June 15, 12:30-12:45 p.m. CEST
Location:
Hall 5

Abstract Title: The ECHELON-2 Trial: Results of a Randomized,
Double-blind Phase 3 Study of Brentuximab Vedotin and CHP (A+CHP) versus
CHOP in Frontline Treatment of Patients with CD30+ Peripheral T-cell
Lymphomas (Abstract #PS1070)
Poster Presentation Date and
Time: Saturday, June 15, 5:30-7:00 p.m. CEST
Location:
Poster Area

Abstract Title: Nivolumab Combined with Brentuximab Vedotin for
Relapsed/Refractory Primary Mediastinal Large B-cell Lymphoma: Efficacy
and Safety Results from the Phase 2 Checkmate 436 Study (Abstract #S1601)
Oral
Presentation Date and Time: Sunday, June 16, 9:00-9:15 a.m. CEST
Location:
Hall 5

Details of oral and poster presentations
featured at ICML include:

Abstract Title: Safety and Response after 2 Cycles of Brentuximab
Vedotin Substituting Vincristine in the OEPA/COPDAC Regimen for High
Risk Pediatric Hodgkin Lymphoma (HL) (Abstract #025)
Oral
Presentation Date and Time: Wednesday, June 19, 5:25 p.m. CEST
Location:
Cinema Corso

Abstract Title: Response-Adapted Treatment with Nivolumab and
Brentuximab Vedotin in Young Patients with Relapsed/Refractory Classical
Hodgkin Lymphoma: Checkmate 744 Subgroup Analyses (Abstract #026)
Oral
Presentation Date and Time: Wednesday, June 19, 5:35 p.m. CEST
Location:
Cinema Corso

Abstract Title: Extended Follow-up a Phase 1 Study of Ipilimumab,
Nivolumab and Brentuximab Vedotin in Patients with Relapsed/Refractory
Hodgkin Lymphoma: A Trial of the ECOG-ACRIN Research Group (E4412: Arms
A-I) (Abstract #077)
Oral Presentation Date and Time: Thursday,
June 20, 5:45 p.m. CEST
Location: Cinema Corso

Abstract Title: Nivolumab Combined with Brentuximab Vedotin for
Relapsed/Refractory Primary Mediastinal Large B-cell Lymphoma: Efficacy
and Safety Results from the Phase 2 Checkmate 436 Study (Abstract #108)
Oral
Presentation Date and Time: Friday, June 21, 2:15 p.m. CEST
Location:
Room B, Palazzo dei Congressi

Abstract Title: Response to A+CHP by CD30 Expression in the ECHELON-2
Trial (Abstract #228)
Poster Presentation Date and Time: Wednesday-Friday,
June 19-21, 12:00-5:00 p.m., 9:00 a.m.-5:00 p.m. and 9:00 a.m.-6:30 p.m.
respectively, CEST
Location: Marquee Parco Ciani

Abstract Title: Exploratory Biomarker Analysis in the Phase 3
ECHELON-1 Study: Worse Outcome with ABVD in Patients with Elevated
Baseline Levels of sCD30 and TARC (Abstract #235)
Poster
Presentation Date and Time: Wednesday-Friday, June 19-21, 12:00-5:00
p.m., 9:00 a.m.-5:00 p.m. and 9:00 a.m.-6:30 p.m. respectively, CEST
Location:
Marquee Parco Ciani

Abstract Title: Brentuximab Vedotin and Bendamustine is a Feasible
and Effective Drug Combination as First-line Treatment of Hodgkin
Lymphoma in the Elderly (HALO trial) (Abstract #237)
Poster
Presentation Date and Time: Wednesday-Friday, June 19-21, 12:00-5:00
p.m., 9:00 a.m.-5:00 p.m. and 9:00 a.m.-6:30 p.m. respectively, CEST
Location:
Marquee Parco Ciani

Abstract Title: Final Data from the Phase 3 ALCANZA Study:
Brentuximab Vedotin (BV) vs Physician’s Choice (PC) in Patients (pts)
with CD30-positive (CD30+) Cutaneous T-cell Lymphoma (CTCL) (Abstract
#232)
Poster Presentation Date and Time: Wednesday-Friday,
June 19-21, 12:00-5:00 p.m., 9:00 a.m.-5:00 p.m. and 9:00 a.m.-6:30 p.m.
respectively, CEST
Location: Marquee Parco Ciani

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 therapeutic
potential of ADCETRIS, including the combination of ADCETRIS with OPDIVO
or other agents, the potential expansion of the company’s ADCETRIS
clinical development program and the potential for additional approved
indications of ADCETRIS. 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 or its collaborators may
experience delays in planned clinical trial initiations or otherwise
experience failures or setbacks in clinical development due to lack of
efficacy, adverse events or other factors. Seattle Genetics or its
collaborators may also be delayed or unsuccessful in regulatory
submissions and in obtaining regulatory approvals for a variety of
reasons including the difficulty and uncertainty of pharmaceutical
product development, negative or disappointing clinical trial results,
unexpected adverse events, adverse regulatory actions and the inherent
uncertainty associated with the regulatory approval process. 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, except as required by law.

SOURCE: Seattle Genetics, Inc.

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