• SEA-BCMA is a Novel Empowered Antibody Targeting BCMA for Multiple Myeloma
• Adds to Seattle Genetics’ Robust Clinical-Stage Development Pipeline across Multiple Hematologic and Solid Tumors

Bothell, WA (Press Release) – Seattle Genetics, Inc. (Nasdaq:SGEN) announced today dosing of the first patient in a phase 1 clin­i­cal trial eval­u­ating the safety and tolerability of SEA-BCMA for patients with re­lapsed or refractory multiple myeloma (MM). SEA-BCMA is an inves­ti­ga­tional anti­body empowered using Seattle Genetics’ pro­pri­e­tary Sugar Engineered Antibody (SEA) tech­nology designed to en­hance anti­body dependent cellular cyto­tox­icity. The target of SEA-BCMA, the cell surface protein B-cell maturation an­ti­gen (BCMA), is broadly ex­pressed on malignant plasma cells in multiple myeloma. SEA-BCMA has dem­onstrated en­cour­ag­ing antitumor activity in pre­clin­i­cal studies.

“Despite recent ad­vances in the treat­ment of multiple myeloma, it remains an incurable disease with a need for active and well-tolerated agents,” said Roger D. Dansey, M.D., Chief Medical Officer of Seattle Genetics. “BCMA is a val­i­dated thera­peutic target for multiple myeloma. SEA-BCMA rep­re­sents a novel empowered anti­body treat­ment ap­proach that has dem­onstrated antitumor activity and an acceptable safety profile in pre­clin­i­cal evaluation to date. We look for­ward to eval­u­ating SEA-BCMA through our clin­i­cal devel­op­ment pro­gram and hope to meaningfully im­prove out­comes for multiple myeloma patients.”

The phase 1 trial is an open-label, multi-center, dose-escalation and expansion clin­i­cal study designed to enroll approx­i­mately 65 patients with re­lapsed or refractory MM in the United States. The study is ex­pec­ted to be conducted in two parts, with a dose escalation cohort to eval­u­ate safety and tolerability and to de­ter­mine the maximum tolerated dose of SEA-BCMA, followed by an expansion cohort to obtain further data re­gard­ing safety and antitumor activity.

Data presented at the American Association for Cancer Research (AACR) Annual Meeting 2018 dem­onstrate that SEA-BCMA exhibits en­cour­ag­ing pre­clin­i­cal antitumor activity and has the poten­tial to be an active, tolerable and combinable agent.

For more in­for­ma­tion about the phase 1 study of SEA-BCMA for patients with multiple myeloma and enrolling centers, please visit www.clinicaltrials.gov (Identifier: NCT03582033).

About Multiple Myeloma

Multiple myeloma (MM) is an 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 United States. According to the American Cancer Society, more than 30,000 new cases of MM were ex­pec­ted in the U.S. in 2018, 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 SEA-BCMA

SEA-BCMA is a novel inves­ti­ga­tional anti­body empowered using Seattle Genetics’ pro­pri­e­tary Sugar Engineered Antibody (SEA) tech­nology that leads to en­hanced anti­body dependent cellular cyto­tox­icity. SEA-BCMA is a non-fucosylated BCMA-directed anti­body that is designed to block proliferative tumor cell signaling, mediate anti­body dependent cellular phago­cytosis and induce en­hanced cell lysis through anti­body dependent cellular cyto­tox­icity. The cell surface protein BCMA is ex­pressed on cells of several cancer types, in­­clud­ing multiple myeloma and other B-cell malig­nan­cies. BCMA is a val­i­dated thera­peutic target for multiple myeloma.

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 SEA-BCMA and its possible benefits and uses as mono­therapy and in com­bi­na­tion with other agents, 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 SEA-BCMA to show sufficient activity in the clin­i­cal setting referenced above and the risk of adverse events in connection with SEA-BCMA. 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 September 30, 2018 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.