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Astellas, Seagen and Merck Announce Results of Clinical Trial Investigating Padcev With Keytruda and Padcev as Monotherapy in First-Line Advanced Urothelial Cancer

TOKYO and BOTHELL, Wash. and RAHWAY, N.J., Sept. 12, 2022. Astellas Pharma Inc. (TSE:4503, President and CEO: Kenji Yasukawa, Ph.D., "Astellas"), Seagen Inc. ( Nasdaq:SGEN) and Merck ( NYSE: MRK), known as MSD outside of the United States and Canada, today announced results from the phase 1b/2 EV-103 clinical trial (also known as KEYNOTE-869) Cohort K investigating PADCEV (enfortumab vedotin-ejfv) in combination with Merck's anti-PD-1 therapy KEYTRUDA (pembrolizumab) and PADCEV alone as first-line treatment in patients with unresectable locally advanced or metastatic urothelial cancer (la/mUC) who are ineligible to receive cisplatin-based chemotherapy. The findings were presented today at the European Society for Medical Oncology (ESMO) Congress as part of a late-breaking abstract presentation (Abstract #LBA73).

In patients treated with enfortumab vedotin and pembrolizumab (n=76), results demonstrated a 64.5% confirmed objective response rate (ORR) (95% CI: 52.7 to 75.1) per RECIST v1.1 by blinded independent central review (BICR), the primary endpoint of Cohort K, with 10.5% of patients experiencing a complete response and 53.9% of patients experiencing a partial response. The median duration of response (DOR) per BICR was not reached (95% CI: 10.25 months to NR). All-grade treatment-related adverse events (TRAEs) of special interest for enfortumab vedotin in combination with pembrolizumab were skin reactions (67.1%), peripheral neuropathy (60.5%), ocular disorders (dry eye, blurred vision, and corneal disorders) (26.3%), hyperglycemia (14.5%), and infusion-related reactions (3.9%). Pembrolizumab adverse events of special interest were consistent with previously observed safety data from monotherapy with the exception of severe skin reactions. Overall, the results were generally consistent with previously reported efficacy and safety results of the EV-103/KEYNOTE-869 dose-escalation cohort and expansion Cohort A.1

Please see Important Safety Information at the end of this press release for both drugs, including BOXED WARNING for enfortumab vedotin and immune-mediated adverse reactions for pembrolizumab.

Cohort K also included a monotherapy arm in which patients were treated with enfortumab vedotin alone (n=73), though this study was not designed to support a formal comparison between the two arms. Results showed a 45.2% confirmed ORR (95% CI: 33.5 to 57.3) per RECIST v1.1 by BICR, with 4.1% of patients experiencing a complete response and 41.1% of patients experiencing a partial response. The median DOR was 13.2 months (95% CI: 6.14 to 15.97) per RECIST v1.1 by BICR. All-grade TRAEs of special interest for enfortumab vedotin were peripheral neuropathy (54.8%), skin reactions (45.2%), ocular disorders (dry eye, blurred vision, and corneal disorders) (28.8%), hyperglycemia (11.0%), and infusion-related reactions (5.5%).

Additional secondary endpoints in the EV-103 Cohort K trial included progression-free survival (PFS) and overall survival (OS). Among patients treated with enfortumab vedotin and pembrolizumab, median PFS was not reached (95% CI: 8.31 months to NR). Median OS was 22.3 months (95% CI: 19.09 to NR). Among patients treated with enfortumab vedotin, median PFS was 8.0 months (95% CI: 6.05 to 10.35) and median OS was 21.7 months (95% CI: 15.21 to NR).

TRAEs of any grade that occurred in more than 20% of patients treated with enfortumab vedotin alone or in combination with pembrolizumab were fatigue, peripheral sensory neuropathy, alopecia, rash maculo-papular, pruritus, dysgeusia, weight decreased, diarrhea, decreased appetite, nausea, and dry eye.

"Results from EV-103/KEYNOTE-869 Cohort K support the ongoing investigation of enfortumab vedotin and pembrolizumab in cisplatin-ineligible patients with locally advanced or metastatic urothelial cancer who are in need of treatment options, and this combination may be an important therapeutic option for these patients," said Jonathan E. Rosenberg, M.D., Chief, Genitourinary Medical Oncology Service, Division of Solid Tumor Oncology, and Enno W. Ercklentz Chair, Memorial Sloan Kettering Cancer Center and EV-103/KEYNOTE-869 Cohort K primary investigator. Dr. Rosenberg has consulting relationships with Astellas, Seagen and Merck.

"We're encouraged by these positive findings from the combination of enfortumab vedotin and pembrolizumab in people with advanced urothelial cancer who historically have had limited treatment options in the first-line setting, and we intend to discuss these results with regulatory authorities," said Ahsan Arozullah, M.D., M.P.H., Senior Vice President and Head of Development Therapeutic Areas, Astellas.

"Nearly sixty-five percent of patients who were treated with enfortumab vedotin and pembrolizumab responded to the combination, with almost eleven percent showing no detectable cancer following treatment. These study results represent an encouraging finding for people with advanced urothelial cancer who are not eligible for cisplatin treatment," said Marjorie Green, Senior Vice President and Head of Late Stage Development, Seagen.

"We're pleased that this combination provided a meaningful benefit to this group of advanced bladder cancer patients in this study, and we will continue to investigate enfortumab vedotin plus pembrolizumab through our collaboration," said Dr. Eliav Barr, Senior Vice President, Head of Global Clinical Development and Chief Medical Officer, Merck Research Laboratories.

In February 2020, the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy designation for enfortumab vedotin in combination with pembrolizumab for patients with unresectable la/mUC who are ineligible to receive cisplatin-based chemotherapy in the first-line setting. The designation is based on results from the dose-escalation cohort and expansion Cohort A of the phase 1b/2 trial, EV-103/KEYNOTE-869 (NCT03288545), evaluating patients with la/mUC who are ineligible to receive cisplatin-based chemotherapy treated in the first-line setting with enfortumab vedotin in combination with pembrolizumab.

Astellas, Seagen and Merck are further investigating enfortumab vedotin plus pembrolizumab in Phase 3 studies, including EV-302/KEYNOTE-A39 (NCT04223856), which is intended to confirm these results for the investigational treatment combination in previously untreated la/mUC and in muscle-invasive bladder cancer in EV-304/KEYNOTE-B15 (NCT04700124) and EV-303/KEYNOTE-905 (NCT03924895).

About Bladder and Urothelial Cancer
It is estimated that approximately 83,730 people in the U.S. were diagnosed with bladder cancer in 2021.2 Urothelial cancer accounts for 90% of all bladder cancers and can also be found in the renal pelvis, ureter and urethra.3 Globally, approximately 573,000 new cases of bladder cancer and 212,000 deaths are reported annually.4

About the EV-103/KEYNOTE-869 Trial (Cohort K)
The EV-103 trial (NCT03288545) is an ongoing, multi-cohort, open-label, multicenter phase 1b/2 trial of enfortumab vedotin alone or in combination with pembrolizumab and/or chemotherapy in first- or second-line settings in patients with locally advanced or metastatic urothelial cancer (la/mUC) and in patients with muscle-invasive bladder cancer.

Cohort K of the EV-103/KEYNOTE-869 trial is a randomized 1:1 cohort investigating enfortumab vedotin alone (n=73) or in combination with pembrolizumab (n=76) in adult patients with unresectable la/mUC who are ineligible for cisplatin-based chemotherapy and have received no prior treatment for la/mUC. The enfortumab vedotin monotherapy study arm is intended to characterize the activity of enfortumab vedotin alone in this patient population. The key outcome measure of EV-103/KEYNOTE-869 Cohort K is objective response rate (ORR) per blinded independent central review (BICR) using RECIST 1.1. Secondary endpoints include ORR per investigator assessment; duration of response (DOR), disease control rate (DCR) and progression-free survival (PFS) per BICR and investigator assessment; overall survival (OS); and assessment of safety.

About PADCEV
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.5 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).6

About KEYTRUDA
KEYTRUDA is an anti-programmed death receptor-1 (PD-1) therapy that works by increasing the ability of the body's immune system to help detect and fight tumor cells. KEYTRUDA is a humanized monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.

Merck has the industry's largest immuno-oncology clinical research program. There are currently more than 1,600 trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patient's likelihood of benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.

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 Seagen
Seagen Inc. 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.

Merck's focus on cancer
Our goal is to translate breakthrough science into innovative oncology medicines to help people with cancer worldwide. At Merck, the potential to bring new hope to people with cancer drives our purpose, and supporting accessibility to our cancer medicines is our commitment. As part of our focus on cancer, Merck is committed to exploring the potential of immuno-oncology with one of the largest development programs in the industry across more than 30 tumor types. We also continue to strengthen our portfolio through strategic acquisitions and are prioritizing the development of several promising oncology candidates with the potential to improve the treatment of advanced cancers.

About Merck
At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities.

About the Astellas, Seagen and Merck Collaboration
Astellas and Seagen entered a clinical collaboration agreement with Merck to evaluate the combination of Astellas' and Seagen's 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.

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.

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 PADCEV alone or in combination, including its possible efficacy, safety and therapeutic uses; plans to discuss Cohort K results with regulatory authorities; and clinical development plans, including planned and ongoing clinical trials. 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 the data from the EV-103 trial may not be sufficient to support any regulatory approval; the risk of adverse events, including the potential for newly-emerging safety signals; adverse regulatory actions; delays, setbacks or failures in clinical development activities, the submission of regulatory applications and the regulatory review process for a variety of reasons, including the inherent difficulty and uncertainty of pharmaceutical product development; possible required modifications to clinical trials; the inability to provide information and institute safety mitigation measures as may be required by the FDA or other regulatory authorities from time to time; 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, 2022 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.

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA
This news release of Merck & Co., Inc., Rahway, N.J., USA (the "company") includes "forward-looking statements" within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company's management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.

Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of the global outbreak of novel coronavirus disease (COVID-19); the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company's ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company's patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions.

The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company's Annual Report on Form 10-K for the year ended December 31, 2021 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site (www.sec.gov).

1 C.J. Hoimes, J.E. Rosenberg et.al. EV-103: Initial results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma. Annals of Oncology 2019; 30 (Supplement 5): v356–v402.
2 American Cancer Society. Cancer Facts & Figures. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2021/cancer-facts-and-figures-2021.pdf. Accessed September 10, 2022.
3 American Society of Clinical Oncology. Bladder Cancer: Introduction (9-20). https://www.cancer.net/cancer-types/bladder-cancer/introduction. Accessed September 10, 2022.
4 International Agency for Research on Cancer. Cancer Tomorrow: Bladder. http://gco.iarc.fr/tomorrow. Accessed September 10, 2022.
5 Challita-Eid P, Satpayev D, Yang P, et al. Enfortumab Vedotin Antibody-Drug Conjugate Targeting Nectin-4 Is a Highly Potent Therapeutic Agent in Multiple Preclinical Cancer Models. Cancer Res 2016;76(10):3003-13.
6 PADCEV [package insert]. Northbrook, IL: Astellas Pharma US, Inc.

SOURCE Astellas Pharma Inc.

Posted: September 2022

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