Press Release

Seattle Genetics Initiates Phase 1 Trial of SGN-CD19B for Patients with B-cell Non-Hodgkin Lymphoma

-SGN-CD19B, A Novel Antibody-Drug Conjugate (ADC) Utilizing Seattle Genetics’ Newest ADC Technology, Demonstrated Strong Preclinical Antitumor Activity in B-cell Malignancies in Data Presented at the 2015 American Society of Hematology Annual Meeting-

BOTHELL, Wash.--(BUSINESS WIRE)--Feb. 25, 2016-- Seattle Genetics, Inc. (Nasdaq: SGEN) today announced initiation of a phase 1 clinical trial of SGN-CD19B for relapsed or refractory patients with two subtypes of B-cell non-Hodgkin lymphoma (NHL): diffuse large B-cell lymphoma (DLBCL) and grade 3 follicular lymphoma. About 85 percent of NHL is of B-cell lineage, and CD19 is broadly expressed across all subtypes of B-cell malignancies. SGN-CD19B is a novel antibody-drug conjugate (ADC) targeted to CD19 utilizing Seattle Genetics’ newest ADC technology. SGN-CD19B is composed of an anti-CD19 antibody attached to a highly potent cytotoxic DNA-crosslinking agent called a pyrrolobenzodiazepine (PBD) dimer, via a proprietary site-specific conjugation technology to a monoclonal antibody with engineered cysteines (EC-mAb). The trial is designed to assess the safety and antitumor activity of SGN-CD19B.

“B-cell malignancies are the most common type of non-Hodgkin lymphoma, or NHL. In the relapsed or refractory disease setting, B-cell NHL is difficult to treat, and there is an urgent need to identify more effective treatment options for these patients,” said Jonathan Drachman, M.D., Chief Medical Officer and Executive Vice President, Research and Development at Seattle Genetics. “With SGN-CD19A and SGN-CD19B, we are evaluating two clinical-stage ADCs directed against CD19 utilizing different ADC technologies with distinct mechanisms of action, which may result in differentiated clinical profiles and utility in NHL. Together with ADCETRIS, these programs are a part of our extensive efforts to improve outcomes for patients with lymphoma.”

The study is a phase 1, open-label, multi-center, dose-escalation clinical trial. The primary endpoints are the estimation of the maximum tolerated dose and evaluation of the safety of SGN-CD19B. In addition, the trial will evaluate antitumor activity, pharmacokinetics, objective response rate and progression-free survival. The study is designed to evaluate SGN-CD19B administered every four or six weeks and will enroll up to approximately 100 relapsed or refractory patients at multiple centers in the United States.

Preclinical data presented at the 2015 American Society of Hematology (ASH) Annual Meeting demonstrated that SGN-CD19B exhibits antitumor activity against a broad panel of CD19-expressing B-cell malignancies, inducing durable tumor regressions in multiple preclinical models of NHL and B-ALL.

With more than 15 years of experience and innovation, Seattle Genetics is the leader in developing ADCs. ADCs are monoclonal antibodies that are designed to selectively deliver cell-killing agents to tumor cells. This approach is intended to spare non-targeted cells and, thus, reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity.

For more information about the trial, including enrolling centers, please visit

About Non-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 (NHL). NHL is further categorized into indolent (low-grade) or aggressive lymphomas, including DLBCL and grade 3 follicular lymphoma. DLBCL is the most common type of NHL. According to the American Cancer Society, more than 72,000 cases of NHL will be diagnosed in the United States during 2016 and more than 20,000 people will die from the disease.

About SGN-CD19B

SGN-CD19B is a novel ADC targeted to CD19 utilizing Seattle Genetics’ newest ADC technology. CD19 is a protein expressed broadly on normal and malignant B-cells. SGN-CD19B is an antibody-drug conjugate (ADC) composed of an anti-CD19 antibody attached to two molecules of a highly potent DNA crosslinking agent called a pyrrolobenzodiazepine (PBD) dimer, using Seattle Genetics’ proprietary technology. PBD dimers are significantly more potent than systemic chemotherapeutic drugs, and site-specific conjugation technology (EC-mAb) allows uniform drug-loading of the cell-killing PBD dimer to the anti-CD19 antibody. The ADC is designed to be stable in the bloodstream and to release its potent DNA binding agent upon internalization into CD19-expressing cells. The ADC technology used in SGN-CD19B is the same as vadastuximab talirine (SGN-CD33A; 33A), an ADC in clinical development for myeloid malignancies.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development and commercialization of innovative antibody-based therapies for the treatment of cancer. Seattle Genetics is leading the field in developing antibody-drug conjugates (ADCs), a technology designed to harness the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. The company’s lead product, ADCETRIS® (brentuximab vedotin), is a CD30-targeted ADC that, in collaboration with Takeda Pharmaceutical Company Limited, is commercially available in 60 countries, including the U.S., Canada, Japan and members of the European Union. Additionally, ADCETRIS is being evaluated broadly in more than 70 ongoing clinical trials in CD30-expressing malignancies. Seattle Genetics is also advancing vadastuximab talirine (SGN-CD33A; 33A), an ADC that is expected to advance into a phase 3 trial for acute myeloid leukemia in 2016. Beyond ADCETRIS and 33A, the company is developing a robust pipeline of clinical-stage programs, including denintuzumab mafodotin (SGN-CD19A; 19A), SGN-LIV1A, ASG-15ME, ASG-22ME (enfortumab vedotin), SGN-CD70A, SEA-CD40 and SGN-CD19B. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including AbbVie, Agensys (an affiliate of Astellas), Bayer, Genentech, GlaxoSmithKline and Pfizer. More information can be found at

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the therapeutic potential of SGN-CD19B and anticipated clinical trials including potential patient and site enrollment. 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 inability to show sufficient activity in this recently initiated clinical trial and the risk of adverse events as SGN-CD19B advances in clinical trials and regulatory actions. More information about the risks and uncertainties faced by Seattle Genetics is contained under the caption “Risk Factors” included in the company’s Annual Report on Form 10-K for the year ended December 31, 2015 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.

Source: Seattle Genetics, Inc.

Seattle Genetics
Peggy Pinkston, 425-527-4160
Tricia Larson, 425-527-4180