WA-SEAGEN-INTERNATIONAL

Seagen International (Nasdaq:SGEN) today announced that the European Commission (EC) has granted marketing authorization for TUKYSA^® (tucatinib) in combination with trastuzumab and capecitabine for the treatment of adult patients with HER2-positive locally advanced or metastatic breast cancer who have received at least two prior anti-HER2 treatment regimens. TUKYSA is an oral, small molecule tyrosine kinase inhibitor (TKI) of HER2, a protein that contributes to cancer cell growth.^1,2

“This approval is a significant advancement for patients in Europe, who will for the first time have an approved medicine demonstrating a survival benefit for HER2-positive metastatic breast cancer after disease progression following two standard anti-HER2 treatment regimens,” said Prof. Dr. Med Volkmar Mueller, Deputy Director at the University Medical Center Hamburg-Eppendorf, Hamburg, Germany and investigator for the pivotal trial. “In the HER2CLIMB pivotal trial, the tucatinib combination regimen improved overall and progression-free survival compared to trastuzumab and capecitabine alone, including in patients with active, untreated or progressing brain metastases, a population with significant unmet need.”

“The TUKYSA combination is a landmark therapy for patients with HER2-positive metastatic breast cancer with or without brain metastases, extending overall survival in these patients after two prior anti-HER2-treatment regimens,” said Clay Siegall, Ph.D., Chief Executive Officer at Seagen. “We are pleased TUKYSA is now approved in Europe, and we look forward to further collaborating with individual countries to ensure it is available to patients.”

The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion for TUKYSA in December 2020. The approval of TUKYSA is valid in all countries of the European Union, as well as Norway, Liechtenstein, Iceland and Northern Ireland.

HER2CLIMB Efficacy and Safety

Patients who received TUKYSA in combination with trastuzumab and capecitabine in the pivotal trial had a 46 percent reduction in the risk of cancer progression or death (PFS), the primary endpoint, compared to patients who received trastuzumab and capecitabine alone (hazard ratio (HR)=0.54 [95% Confidence Interval (CI): 0.42, 0.71]; p<0.00001) and improved overall survival with a reduction in the risk of death by 34 percent (HR=0.66 [95% CI: 0.50, 0.87]; p=0.0048). The most common adverse reactions occurring in 20 percent or more of patients who received TUKYSA were diarrhea, nausea, vomiting, stomatitis, AST increase, ALT increase, and rash.¹

The pivotal trial, HER2CLIMB, is a randomized (2:1), double-blind, placebo-controlled, active comparator, global trial that enrolled 612 patients with HER2-positive unresectable locally advanced or metastatic breast cancer who had previously received, either separately or in combination, trastuzumab, pertuzumab, and trastuzumab emtansine (T-DM1 SmPC).

About HER2-Positive Breast Cancer

Patients with HER2-positive breast cancer have tumors with high levels of a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. In 2020, more than two million new cases of breast cancer were diagnosed worldwide, including 531,086 in Europe.³ Between 15 and 20 percent of breast cancer cases are HER2-positive.⁴ HER2-positive breast cancer tends to be more aggressive and more likely to recur than HER2-negative breast cancer.^4,5,6 Up to 50 percent of metastatic HER2-positive breast cancer patients develop brain metastases over time.^7,8,9

About TUKYSA (tucatinib)

TUKYSA is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein. In vitro (in lab studies), TUKYSA inhibited phosphorylation of HER2 and HER3, resulting in inhibition of downstream MAPK and AKT signaling and cell growth (proliferation), and showed anti-tumor activity in HER2-expressing tumor cells. In vivo (in living organisms), TUKYSA inhibited the growth of HER2-expressing tumors. The combination of TUKYSA and the anti-HER2 antibody trastuzumab showed increased anti-tumor activity in vitro and in vivo compared to either medicine alone.

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 statements made in this press release are forward looking, such as those, among others, relating to the therapeutic potential of TUKYSA including its efficacy, safety and therapeutic uses, and the potential to make TUKYSA available to patients in Europe. 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 possibilities that we may experience delays or setbacks in seeking pricing and reimbursement approvals or otherwise in commercializing TUKYSA in Europe; that adverse events or safety signals may occur; and that adverse regulatory actions may occur. More information about the risks and uncertainties faced by Seagen is contained under the caption “Risk Factors” included in the company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2020 and the company’s Current Report on Form 8-K dated December 30, 2020 filed with the U.S. 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.

1		Europeans Medicines Agency. TUKYSA Summary of Product Characteristics (SmPC).
2		Anita Kulukian, Patrice Lee, Janelle Taylor, et al. Preclinical Activity of HER2-Selective Tyrosine Kinase Inhibitor Tucatinib as a Single Agent or in Combination with Trastuzumab or Docetaxel in Solid Tumor ModelsMol Cancer Ther2020;19:976-987.
3		Breast. Globocan 2020. World Health Organization. 2020. https://gco.iarc.fr/today/data/factsheets/cancers/20-Breast-fact-sheet.pdf
4		Loibl S, Gianni L. HER2-positive breast cancer. Lancet. 2017; 389(10087): 2415-29.
5		Slamon D, Clark G, Wong S, et al. Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu onco­gene. Science. 1987; 235(4785): 177-82.
6		Breast Cancer HER2 Status. American Cancer Society website. https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-her2-status.html . Accessed March 9, 2020.
7		Freedman RA, Gelman RS, Anders CK, et al. TBCRC 022: a phase II trial of neratinib and capecitabine for patients with human epidermal growth factor receptor 2-positive breast cancer and brain metastases. J Clin Oncol. 2019;37:1081-1089.
8		Olson EM, Najita JS, Sohl J, et al. Clinical outcomes and treatment practice patterns of patients with HER2-positive metastatic breast cancer in the post-trastuzumab era. Breast. 2013;22:525-531.
9		Bendell JC, Domchek SM, Burstein HJ, et al. Central nervous system metastases in women who receive trastuzumab-based therapy for metastatic breast carcinoma. Cancer. 2003;97:2972-2977.

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