-Data Showcase Depth of Oncology Pipeline Using Seagen’s Innovative Technologies-

Seagen Inc. (Nasdaq: SGEN) today announced that preclinical data from its pipeline of novel targeted oncology drugs will be presented at the American Association for Cancer Research (AACR) Annual Meeting being held April 10-15, 2021. The oral and poster presentations will highlight several early-stage programs utilizing Seagen’s leading antibody-drug conjugate (ADC) technology as well as its proprietary sugar-engineered antibody (SEA) technology.

“Our research being presented at AACR describes intriguing preclinical data for three novel pipeline programs that are in ongoing clinical trials. This includes SEA-TGT, an anti-TIGIT antibody using our SEA technology, and two vedotin-based ADCs, SGN-B6A and SGN-STNV. We believe these three programs represent potential best-in-class or first-in-class targeted therapies for cancer,” said Roger Dansey, M.D., Chief Medical Officer at Seagen. “Among the findings, we will show the enhanced therapeutic effect in combining SEA-TGT with a checkpoint inhibitor or a vedotin-based ADC across different tumor models. In addition, we will report for the first time our preclinical data with SGN-STNV, a novel ADC targeting a carbohydrate antigen that may have broad applicability across solid tumors.”

Highlights of Seagen Programs Presented at AACR

SEA-TGT

Preclinical data will be presented for SEA-TGT, a novel investigational nonfucosylated human IgG1 TIGIT antibody, which utilizes Seagen’s proprietary SEA technology that enhances functionality by targeting key immune activating Fc receptors. TIGIT is an inhibitory immune checkpoint that has emerged as a clinically relevant immuno-oncology target. The monotherapy and combinatorial activity of SEA-TGT was assessed and compared to TIGIT monoclonal antibodies (mAbs) with inert, standard, or effector function modified backbones in vivo and in vitro. Key preclinical findings were as follows:

• the SEA-TGT backbone was distinct as it increased binding to activating FcγRIIIa with minimal binding to inhibitory FcγRIIb;
• the empowered backbone had superior therapeutic properties including enhanced depletion of TIGIT-positive regulatory T-cells and activation of antigen-presenting cells both of which are important in promoting antitumor activity;
• SEA-TGT demonstrated enhanced antitumor activity both as a single agent and in combination with anti-PD1 therapy; and,
• SEA-TGT produced an enhanced therapeutic effect when combined with an immunogenic tumor cell death-inducing vedotin ADC.

A phase 1 trial evaluating SEA-TGT alone and in combination with anti-PD-1 therapy in patients with advanced solid tumors and select lymphomas is ongoing.

SGN-B6A

Preclinical data will also be presented on SGN-B6A, an investigational ADC targeting integrin beta-6, which is overexpressed in numerous solid tumors and has been demonstrated to be a negative prognostic indicator across a diverse range of cancers, including non-small cell lung cancer (NSCLC). Data demonstrate SGN-B6A is active when dosed weekly in patient-derived xenograft models of NSCLC, representing both squamous and adenocarcinoma histology. A phase 1 trial evaluating monotherapy SGN-B6A in advanced solid tumors is ongoing.

SGN-STNV

SGN-STVN is an investigational ADC with a unique mechanism for targeting a carbohydrate antigen called Sialyl-Thomsen nouveau (STn), which is highly expressed on a variety of solid tumors including non-small cell lung, ovarian and gastric cancers. The preclinical data demonstrate SGN-STNV is highly specific for STn independent of protein identity, which could allow for the targeting of a range of tumor types that express different glycoproteins. In xenograft studies across key tumor types, the specificity and ability to target STn on multiple tumor-associated proteins led to durable tumor regressions. SGN-STNV was well-tolerated in in vivo studies and is being evaluated in an ongoing phase 1 study.

Additional Details of Seagen Presentations at AACR Annual Meeting 2021

All poster presentations will be available via on-demand view starting on April 10 at 8:30 a.m. Eastern Time. Oral symposium presentations will be available at the beginning of the session where the study is presented.

About Seagen

Seagen is a global biotechnology company that discovers, develops and commercializes transformative cancer medicines to make a meaningful difference in people’s lives. Seagen is headquartered in the Seattle, Washington area, and has locations in California, Canada, Switzerland and the European Union. For more information on the company’s marketed products and robust pipeline, visit www.seagen.com and follow @SeagenGlobal 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 potential of the Company’s SEA-TGT, SGN-B6A and SGN-STNV product candidates, the enhanced therapeutic effect in combining SEA-TGT with a checkpoint inhibitor or a vedotin-based ADC and the potential of the Company’s pipeline. 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 without limitation the difficulty and uncertainty of pharmaceutical product development, the risk of adverse events or safety signals, the inability to show sufficient efficacy in clinical trials and the possibility of adverse regulatory actions. More information about the risks and uncertainties faced by Seagen is contained under the caption “Risk Factors” included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission. Seagen 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 law.

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