Seagen and Astellas Announce Positive Topline Results For PADCEV® (enfortumab vedotin-ejfv) with KEYTRUDA® (pembrolizumab) as First-Line Treatment for Advanced Urothelial Cancer

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BOTHELL, Wash. & TOKYO– Seagen Inc. (Nasdaq:SGEN) and Astellas Pharma Inc. (TSE:4503, President and CEO: Kenji Yasukawa, Ph.D., “Astellas”) today announced positive topline results from the phase 1b/2 EV-103 clinical trial (also known as KEYNOTE-869) Cohort K evaluating PADCEV® (enfortumab vedotin-ejfv) in combination with Merck’s anti-PD-1 therapy KEYTRUDA® (pembrolizumab) as first-line treatment in patients with unresectable locally advanced or metastatic urothelial cancer (la/mUC) who are ineligible to receive cisplatin-based chemotherapy. Merck is known as MSD outside the United States and Canada.

In patients treated with enfortumab vedotin and pembrolizumab, results demonstrated a 64.5% confirmed objective response rate (ORR) (95% CI: 52.7 to 75.1) per blinded independent central review (BICR), the primary endpoint of Cohort K. The median duration of response (DOR) per BICR was not reached. The most frequently reported treatment-emergent adverse events Grade 3 or greater that occurred in more than 5% of patients were rash maculo-papular, anemia, lipase increased, urinary tract infection, hyperglycemia, fatigue, neutropenia, hematuria, diarrhea, acute kidney injury, hyponatremia, chronic kidney disease, weight decreased, syncope, hypophosphatemia, pneumonitis, sepsis, and alanine aminotransferase increased. Overall, the results are generally consistent with previously reported efficacy and safety results of the EV-103 dose-escalation cohort and expansion Cohort A.1 Additional Cohort K results will be reported at an upcoming scientific congress.

EV-103 Cohort K is a randomized cohort investigating enfortumab vedotin alone or in combination with pembrolizumab as first-line treatment in patients with unresectable la/mUC who are ineligible to receive cisplatin-based chemotherapy. Secondary endpoints include ORR per investigator assessment; DOR, disease control rate and progression-free survival per BICR and investigator assessment; overall survival; and assessment of safety.

Please see Important Safety Information at the end of this press release, including BOXED WARNING for enfortumab vedotin.

“We are encouraged by the positive topline results of Cohort K for the combination of enfortumab vedotin and pembrolizumab in first-line locally advanced or metastatic urothelial cancer, and we look forward to sharing results at an upcoming medical meeting,” said Roger Dansey, M.D., interim CEO and Chief Medical Officer, Seagen.

“Approximately half of patients with advanced urothelial carcinoma are ineligible for cisplatin-based chemotherapy,” said Ahsan Arozullah, M.D., M.P.H., Senior Vice President and Head of Development Therapeutic Areas, Astellas. “We intend to discuss Cohort K results with regulatory authorities as we seek to develop a new first-line treatment combination for these patients.”

Seagen, Astellas and Merck are investigating enfortumab vedotin plus pembrolizumab as part of an extensive collaboration, which also includes three Phase 3 studies: the EV-302/KEYNOTE-A39 trial intended to confirm these results, as well as EV-304/KEYNOTE-B15 and EV-303/KEYNOTE-905 in muscle-invasive bladder cancer.

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 (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.