Antibody-Drug Conjugate (ADC) SGN-CD48A Being Evaluated as Monotherapy, With Innovative Linker Technology That Highlights Continued Industry Leadership in ADCs

BOTHELL, Wash.--(BUSINESS WIRE)-- Seattle Genetics, Inc. (NASDAQ: SGEN) today announced dosing of the first patient in a phase 1 clinical trial evaluating the safety and tolerability of SGN-CD48A for patients with relapsed or refractory multiple myeloma (MM). SGN-CD48A is an investigational ADC targeted to the protein CD48, which is highly expressed on MM cells. SGN-CD48A uses the company’s latest ADC technology advancement, a PEGylated glucuronide linker that improves stability, reduces off-target uptake, and enables conjugation of more molecules of the microtubule-disrupting cytotoxic agent monomethyl auristatin E (MMAE) per antibody. With this novel linker, SGN-CD48A has demonstrated promising antitumor activity in preclinical studies.

“Multiple myeloma is the second most common blood cancer in the US and remains an incurable disease despite recent medical advances. Patients are in need of new targeted treatment options that increase durable remissions,” said Robert Lechleider, M.D., Senior Vice President, Clinical Development at Seattle Genetics. “SGN-CD48A uses our latest ADC technology, and the initiation of this phase 1 trial in relapsed or refractory multiple myeloma highlights our continued leadership in ADCs as we address this challenging disease.”

The phase 1 study is a multicenter open-label dose-escalation trial designed to enroll approximately 75 patients with relapsed or refractory MM. SGN-CD48A will be administered at an initial dosing interval of every three weeks. The primary objectives of the trial are to evaluate the safety and tolerability of SGN-CD48A and to identify the maximum tolerated dose (MTD). Key secondary objectives include assessing the antitumor activity and identifying the recommended single-agent dose and schedule.

For more information about the phase 1 clinical trial (NCT03379584), please visit www.clinicaltrials.gov.

About Multiple Myeloma

Multiple myeloma (MM) is a rare and aggressive cancer that forms in white blood cells called plasma cells. Cancerous plasma cells can crowd out healthy blood cells, impair bone strength and weaken the immune system. MM is the second most common blood cancer in the US. According to the American Cancer Society, more than 30,000 new cases of MM were expected in the US in 2017, with over 12,500 deaths. Despite recent medical advances, MM still remains an incurable disease. It is managed with sequential lines of treatment that typically yield shorter durations of disease control with each subsequent relapse, and some patients receive more than four lines of treatment over the course of their disease.

About SGN-CD48A

SGN-CD48A is a novel investigational ADC targeted to CD48, a cell surface protein highly expressed in multiple myeloma. The ADC uses Seattle Genetics’ latest technology innovation, a next generation PEGylated glucuronide linker that enables conjugation of eight molecules of the microtubule-disrupting cytotoxic agent monomethyl auristatin E (MMAE) to a CD48-targeted monoclonal antibody. SGN-CD48A is designed to be highly stable in circulation and release an increased amount of MMAE upon internalization into CD48-expressing cells, producing greater antitumor activity in preclinical studies.

About Seattle Genetics

Seattle Genetics is an innovative biotechnology company dedicated to improving the lives of people with cancer through novel antibody-based therapies. The company’s industry-leading antibody-drug conjugate (ADC) technology harnesses the targeting ability of antibodies to deliver cell-killing agents directly to cancer cells. Seattle Genetics commercializes ADCETRIS® (brentuximab vedotin) for the treatment of several types of CD30-expressing lymphomas. The company is also advancing a robust pipeline of novel therapies for solid tumors and blood-related cancers designed to address significant unmet medical needs and improve treatment outcomes for patients. More information can be found at 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 SGN-CD48A and its possible benefits and uses as monotherapy, and anticipated clinical trial, patient enrollment target, and intended endpoints. 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 of SGN-CD48A to show sufficient activity in the clinical setting referenced above and the risk of adverse events of SGN-CD48A. 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, 2017 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.

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Seattle Genetics, Inc.

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Source: Seattle Genetics, Inc.

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