Seattle Genetics’ Antibody-Drug Conjugate Technology Utilized in Genentech’s Polivy, Now Approved by FDA

-Approval Triggers Milestone Payment and Royalties on Worldwide Net
Sales-

BOTHELL, Wash.–(BUSINESS WIRE)–Seattle Genetics, Inc. (Nasdaq:SGEN) today announced U.S. Food and Drug
Administration (FDA) approval of Polivy™ (polatuzumab vedotin-piiq),
which is an antibody-drug conjugate (ADC) targeting CD79b that utilizes
Seattle Genetics’ technology. Polivy was developed and will be
commercialized by Genentech, a member of the Roche Group. It was
approved in combination with bendamustine plus Rituxan^®
(rituximab) (BR) for the treatment of adults with relapsed or refractory
(R/R) diffuse large B-cell lymphoma (DLBCL), who have received at least
two prior therapies. Polivy previously received FDA Breakthrough Therapy
Designation, and was approved more than two months ahead of the
Prescription Drug User Fee Act (PDUFA) action date of August 19, 2019.

“The approval of Polivy under our collaboration with Genentech is an
important milestone for Seattle Genetics as it extends the reach of our
technology to more patients with significant unmet medical needs,” said
Clay Siegall, Ph.D., President and Chief Executive Officer of Seattle
Genetics. “This approval, along with our own internal ADCs in
development and those of other collaborators, such as GlaxoSmithKline,
highlights that ADCs continue to grow as an important therapeutic
approach to treating both hematologic malignancies and solid tumors.”

Polivy was granted PRIME (PRIority MEdicines) designation by the
European Medicines Agency (EMA) for the treatment of patients with R/R
DLBCL. PRIME is a designation implemented by the EMA to support data
generation and development plans for promising medicines, providing a
pathway for accelerated evaluation by the agency. Polivy is also being
investigated by Genentech in several ongoing clinical trials for the
treatment of non-Hodgkin lymphoma (NHL), including frontline DLBCL.

Seattle Genetics’ ADC technology combines the specificity of monoclonal
antibodies, innovative linker systems and potent cell-killing agents to
treat cancer. The technology has been licensed to several companies,
including Genentech and GlaxoSmithKline. Under the terms of these
agreements, each company has rights to use the technology with
antibodies against selected targets. The licensee is responsible for
research, product development, manufacturing and commercialization.
Seattle Genetics is entitled to receive fees, progress-dependent
milestone payments and royalties on worldwide net sales of any resulting
ADC products.

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 company’s
transition into a multi-product global oncology company, the therapeutic
importance of ADCs, the commercial potential of Polivy including the
potential for its approval for use in the European Economic Area for the
treatment of R/R DLBCL and the potential for its approval in the United
States and other territories in additional indications, the potential
for Genentech and GlaxoSmithKline to pay the company milestones and
royalties, as well as other statements that are not historical facts.
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 risks and uncertainties
associated with commercializing Polivy due to competition, unexpected
adverse events, regulatory action, reimbursement, market adoption by
physicians or other factors. Genentech may also be delayed or
unsuccessful in its planned clinical trial initiations, the enrollment
in and conduct of its clinical trials, obtaining data from clinical
trials, planned regulatory submissions, and regulatory approvals in each
case for a variety of reasons including the difficulty and uncertainty
of pharmaceutical product development, negative or disappointing
clinical trial results, unexpected adverse events or regulatory
discussions or 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” 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
applicable law.

Contacts

Investors:
Peggy Pinkston
(425) 527-4160
[email protected]

Media:
Monique Greer
(425) 527-4641
[email protected]