Seattle Genetics Presents Data from Phase 1 Clinical Trial of Antibody-Drug Conjugate (ADC) SGN-CD19A in Non-Hodgkin Lymphoma at ASCO Annual Meeting

CHICAGO--(BUSINESS WIRE)--

Seattle Genetics, Inc. SGEN today will present interim phase 1 clinical data from SGN-CD19A, an antibody-drug conjugate (ADC) in development for the treatment of B-cell malignancies, at the American Society of Clinical Oncology (ASCO) 50^th Annual Meeting being held May 30 to June 3, 2014 in Chicago, IL. SGN-CD19A is an ADC targeting CD19, a protein expressed on B-cell malignancies.

“We continue to make strong progress advancing our proprietary pipeline programs, with SGN-CD19A representing one of five ADCs in clinical development. SGN-CD19A targets a promising cancer marker expressed in a variety of hematologic malignancies,” said Jonathan Drachman, M.D., Chief Medical Officer and Executive Vice President, Research and Development at Seattle Genetics. “These interim phase 1 data in aggressive non-Hodgkin lymphomas presented at ASCO, along with previous phase 1 data in acute lymphoblastic leukemia, demonstrate that SGN-CD19A has encouraging antitumor activity with multiple complete remissions in a patient population with significant unmet needs. The safety profile of SGN-CD19A is generally manageable with a notable absence of significant neuropathy or bone marrow suppression, which may enable future clinical trials with novel combination regimens. We look forward to final results from this ongoing phase 1 clinical trial to inform future SGN-CD19A program development plans.”

With over 16 years of experience and knowledge in ADC innovation, Seattle Genetics is the leader in developing ADCs, a technology designed to harness the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. Of the more than 30 ADC candidates in clinical development, greater than 20 utilize Seattle Genetics' proprietary ADC technology. Seattle Genetics and its collaborators, including Genentech, AbbVie and Progenics, have nine data presentations at ASCO that highlight the widespread evaluation of its ADC technology to potentially impact the way cancer is treated.

Interim analysis of a phase 1, open-label, dose-escalation study of SGN-CD19A in patients with relapsed or refractory B-lineage non-Hodgkin lymphoma (Abstract #8505, oral presentation Sunday, June 1^st at 9:48 a.m. Central Time)

Data were reported from 37 patients with relapsed or refractory aggressive B-cell non-Hodgkin lymphoma (NHL), including 32 patients with diffuse large B-cell lymphoma (DLBCL), four patients with mantle cell lymphoma (MCL) and one patient with Grade 3 follicular lymphoma. The median age of patients was 65 years and the median number of prior systemic therapies was two, with 10 patients (27 percent) having received a prior autologous stem cell transplant. Among enrolled patients, eight percent were primary refractory, 54 percent were refractory to their last treatment and 38 percent had relapsed following a response to their last treatment.

The primary endpoints of the ongoing clinical trial are to estimate the maximum tolerated dose and to evaluate the safety of SGN-CD19A. In addition, the trial is evaluating antitumor activity, pharmacokinetics, progression-free survival and overall survival. In this dose-escalation study, patients receive a single dose of SGN-CD19A on an every 3-week basis. Key findings included:

• No dose limiting toxicity was observed in the first cycle for any patients. Adverse events were observed in the 6 milligrams per kilogram (mg/kg) dosing regimen after the first cycle, therefore enrollment was discontinued. The 3, 4 and 5 mg/kg cohorts are being expanded, and the trial continues to enroll.
• At the time of data analysis, of the 37 patients treated across all dose levels, the objective response rate observed was 30 percent (11 patients). Six patients (16 percent) achieved a complete remission, five (14 percent) achieved a partial remission, 13 (35 percent) had stable disease and 13 (35 percent) had progressive disease as best response. The clinical trial is ongoing with nine of the 37 patients (24 percent) remaining on treatment and new patients continuing to be enrolled.
• The most common adverse events of any grade occurring in more than 30 percent of patients were blurred vision (51 percent), fatigue (38 percent), dry eye (35 percent), constipation (30 percent) and keratopathy (30 percent). Grade 3 or higher adverse events observed in two or more patients included blurred vision (six patients), keratopathy (three patients), low platelet count (three patients) and anemia (three patients).

More information about ongoing phase 1 SGN-CD19A clinical trials, including enrolling centers, is available by visiting www.clinicaltrials.gov.

About SGN-CD19A

SGN-CD19A is an ADC comprised of an anti-CD19 monoclonal antibody linked to a synthetic cytotoxic cell-killing agent, monomethyl auristatin F (MMAF), using Seattle Genetics' industry-leading proprietary technology. The ADC is designed to be stable in the bloodstream, and to release its cytotoxic agent upon internalization into CD19-expressing tumor cells. CD19 is expressed in B-cell ALL and NHL, including DLBCL. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing the antitumor activity.

Preclinical data presented at the 2011 American Association for Cancer Research Annual Meeting demonstrated that SGN-CD19A effectively binds to target cells, internalizes and induces potent cell-killing activity and durable tumor regressions at low doses in multiple preclinical cancer models. SGN-CD19A is being evaluated in two ongoing phase 1 clinical trials for patients with B-cell ALL and aggressive NHL.

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 an ADC that, in collaboration with Takeda Pharmaceutical Company Limited, is commercially available for two indications in 40 countries, including the U.S., Canada, Japan and members of the European Union. Additionally, ADCETRIS is being evaluated broadly in more than 30 ongoing clinical trials. Seattle Genetics is also advancing a robust pipeline of clinical-stage ADC programs, including SGN-CD19A, SGN-CD33A, SGN-LIV1A, ASG-22ME and ASG-15ME. 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 www.seattlegenetics.com.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the therapeutic potential of clinical product candidates. 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 risk of adverse events as these ADCs advance in other clinical trials. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company's 10-Q for the quarter ended March 31, 2014 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.