BOTHELL - Seagen Inc. (Nasdaq: SGEN) and Astellas Pharma Inc. (TSE: 4503) today announced positive topline results from the Phase 3 EV-302 clinical trial (also known as KEYNOTE-A39) for PADCEV in combination with KEYTRUDA versus chemotherapy in patients with previously untreated locally advanced or metastatic urothelial cancer (la/mUC), a form of bladder cancer that has spread to surrounding organs or muscles, or other parts of the body.

The EV-302 trial enrolled patients with previously untreated la/mUC who were eligible for cisplatin- or carboplatin-containing chemotherapy regardless of PD-L1 status.

The EV-302 study met its dual primary endpoints of overall survival (OS) and progression-free survival (PFS), compared to chemotherapy. An Independent Data Monitoring Committee determined that OS crossed the pre-specified efficacy boundary at interim analysis. The safety results of the combination are consistent with those of enfortumab vedotin in combination with pembrolizumab previously reported in cisplatin-ineligible patients with la/mUC.

Roger Dansey, M.D., President, Research and Development, Seagen

'This study has the potential to be practice changing and offer a new standard of care for first-line metastatic bladder cancer. We look forward to presenting the results at an upcoming medical conference and discussing with regulators in order to get this medicine to patients as soon as possible.'

Ahsan Arozullah, M.D., M.P.H., Senior Vice President, Head of Oncology Development, Astellas

'We are thrilled that the topline results of the EV-302 study demonstrated that the combination of enfortumab vedotin and pembrolizumab improved the dual primary endpoints of OS and PFS. Patients living with metastatic urothelial cancer are in dire need of additional treatment options and this combination has the potential to advance the standard of care. We are extremely grateful to all of the patients who participated in this trial.'

Thomas Powles, M.R.C.P., M.D., Professor of Genitourinary Oncology at Queen Mary University of London; Director, Barts Cancer Center, London; EV-302 Primary Investigator

'Over two hundred thousand deaths from urothelial cancer are reported worldwide annually, making it a major cause of morbidity and mortality. The topline results from EV-302 are encouraging for patients with advanced-stage urothelial cancer, which is aggressive and associated with devastating outcomes.'

The EV-302 trial is an open-label, randomized, controlled Phase 3 study, evaluating enfortumab vedotin in combination with pembrolizumab versus chemotherapy in patients with previously untreated la/mUC. In this study, patients were randomized to receive either enfortumab vedotin in combination with pembrolizumab or chemotherapy. The dual primary endpoints of this trial are OS and PFS per RECIST v1.1 by blinded independent central review (BICR).

The EV-302 trial is intended to serve as the basis for global submissions and as the confirmatory trial for the U.S. accelerated approval of this combination. In April 2023, the U.S. Food and Drug Administration (FDA) granted an accelerated approval to PADCEV in combination with KEYTRUDA for the treatment of adult patients with la/mUC who are not eligible to receive cisplatin-containing chemotherapy based on the results from the EV-103 trial. The trial is part of an extensive program evaluating this combination in multiple stages of urothelial cancer.

About Bladder and Urothelial Cancer

Urothelial cancer, or bladder cancer, begins in the urothelial cells, which line the urethra, bladder, ureters, renal pelvis, and some other organs.1

If bladder cancer has spread to surrounding organs or muscles, it is called locally advanced disease. If the cancer has spread to other parts of the body, it is called metastatic disease. 2

Globally, approximately 573,000 new cases of bladder cancer and 212,000 deaths are reported annually.3

It is estimated that approximately 82,290 people in the U.S. will be diagnosed with bladder cancer in 2023.4

It is estimated that approximately 200,000 people in Europe and 24,000 people in Japan are diagnosed with bladder cancer annually. 5,6

Urothelial cancer accounts for 90% of all bladder cancers and can also be found in the renal pelvis, ureter, and urethra.2

Approximately 12% of cases are locally advanced or metastatic urothelial cancer at diagnosis.7

Ongoing Investigational Trials

The EV-302 trial (NCT04223856) is an open-label, randomized, controlled Phase 3 study, evaluating the impact of treatment with enfortumab vedotin in combination with pembrolizumab versus chemotherapy in patients with previously untreated locally advanced or metastatic urothelial cancer (la/mUC) who were eligible for cisplatin- or carboplatin-containing chemotherapy regardless of PD-L1 status.

The EV-103 trial (NCT03288545) is an ongoing, multi-cohort, open-label, multicenter Phase 1b/2 study investigating enfortumab vedotin alone or in combination with pembrolizumab and/or chemotherapy in first- or second-line settings in patients with la/mUC and in patients with muscle-invasive bladder cancer (MIBC).

Enfortumab vedotin in combination with pembrolizumab is being investigated in an extensive program in multiple stages of urothelial cancer, including two Phase 3 clinical trials in MIBC in EV-304 (NCT04700124, also known as KEYNOTE-B15) and EV-303 (NCT03924895, also known as KEYNOTE-905). The use of enfortumab vedotin in combination with pembrolizumab in second-line urothelial cancer and in MIBC has not been proven safe or effective.

About PADCEV (enfortumab vedotin-ejfv)

PADCEV (enfortumab vedotin-ejfv) is a first-in-class antibody-drug conjugate (ADC) that is directed against Nectin-4, a protein located on the surface of cells and highly expressed in bladder cancer.8 Nonclinical data suggest the anticancer activity of PADCEV is due to its binding to Nectin-4-expressing cells, followed by the internalization and release of the anti-tumor agent monomethyl auristatin E (MMAE) into the cell, which result in the cell not reproducing (cell cycle arrest) and in programmed cell death (apoptosis).9

About Seagen

Founded 25 years ago, Seagen Inc. is a global biotechnology company that discovers, develops, manufactures and commercializes targeted cancer therapeutics, with antibody-drug conjugates (ADCs) at our core. Our colleagues work together with urgency to improve and extend the lives of people living with cancer. An ADC technology trailblazer, approximately one-third of FDA-approved and marketed ADCs use Seagen technology. Seagen is headquartered in Bothell, Washington and has locations in California, Canada, Switzerland and across Europe.

About Astellas

Astellas Pharma Inc. is a pharmaceutical company conducting business in more than 70 countries around the world. We are promoting the Focus Area Approach that is designed to identify opportunities for the continuous creation of new drugs to address diseases with high unmet medical needs by focusing on Biology and Modality. Furthermore, we are also looking beyond our foundational Rx focus to create Rx+ healthcare solutions that combine our expertise and knowledge with cutting-edge technology in different fields of external partners. Through these efforts, Astellas stands on the forefront of healthcare change to turn innovative science into VALUE for patients.

About the Seagen, Astellas and Merck Collaboration

Seagen and Astellas entered a clinical collaboration agreement with Merck to evaluate the combination of Seagen's and Astellas' PADCEV (enfortumab vedotin-ejfv) and Merck's KEYTRUDA (pembrolizumab) in patients with previously untreated metastatic urothelial cancer. KEYTRUDA is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

Seagen Forward-Looking Statements

Certain statements made in this press release are forward-looking, such as those, among others, relating to the therapeutic potential of enfortumab vedotin, alone or in combination, and its possible efficacy, safety and therapeutic uses; the potential for results from the EV-302 trial to change practice, offer a new standard of care, or serve as the basis for global submissions and as the confirmatory trial for the U.S. accelerated approval of the combination of enfortumab vedotin and pembrolizumab; plans to present results at an upcoming medical conference, discuss the results with regulators and deliver medicine to patients; planned and ongoing clinical trials and the development program for enfortumab vedotin. 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 possibility that data from the EV-302 trial may not be sufficient to support any regulatory approvals or to convert accelerated approval in the U.S. to regular approval; adverse events and newly-emerging safety signals; adverse regulatory actions; delays, setbacks or failures in product development activities, the submission of regulatory applications and the regulatory review process for a variety of reasons, including, without limitation, the inherent difficulty and uncertainty of pharmaceutical product development; possible required modifications to clinical trials; failure to properly conduct or manage clinical trials and failure of clinical results to support continued development or regulatory approvals. 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 June 30, 2023 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.

Astellas Cautionary Notes

In this press release, statements made with respect to current plans, estimates, strategies and beliefs and other statements that are not historical facts are forward-looking statements about the future performance of Astellas. These statements are based on management's current assumptions and beliefs in light of the information currently available to it and involve known and unknown risks and uncertainties. A number of factors could cause actual results to differ materially from those discussed in the forward-looking statements. Such factors include, but are not limited to: (i) changes in general economic conditions and in laws and regulations, relating to pharmaceutical markets, (ii) currency exchange rate fluctuations, (iii) delays in new product launches, (iv) the inability of Astellas to market existing and new products effectively, (v) the inability of Astellas to continue to effectively research and develop products accepted by customers in highly competitive markets, and (vi) infringements of Astellas' intellectual property rights by third parties.

Information about pharmaceutical products (including products currently in development), which is included in this press release, is not intended to constitute an advertisement or medical advice.

Contact:

David Caouette

Tel: (310) 430-3476

Email: dcaouette@seagen.com

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