Seattle Genetics, Inc. and Astellas Pharma Inc. announced that data from the first cohort of a pivotal phase 2 clinical trial known as EV-201 demonstrated that the investigational agent enfortumab vedotin rapidly shrank tumors in most patients, resulting in an objective response rate (ORR) of 44% (55/125; 95% Confidence Interval (CI): 35.1-53.2). Complete responses (CR) were observed in 12% of patients (15/125). The median duration of tumor response was 7.6 months (range 0.95-11.3+).

This cohort was open to patients with locally advanced or metastatic urothelial cancer who had received previous treatment with a platinum-containing chemotherapy and a PD-1/L1 checkpoint inhibitor. Responses were similar in the subgroups of patients analyzed, including those who had the worst prognosis, such as patients who had three or more previous lines of therapy, patients with liver metastases, and those who had not responded to a PD-1/L1 inhibitor. Treatment-related adverse events that occurred in 40% or more of patients were fatigue, alopecia, rash, decreased appetite, taste distortion, and peripheral neuropathy.

The data will be featured in the official press program of the American Society of Clinical Oncology (ASCO) Annual Meeting and be presented as a Late-Breaking oral presentation (Abstract #LBA4505) and have been submitted for publication in a peer-reviewed journal. Despite recent advances in treatment, approximately 80% of people do not respond to PD-1/L1 inhibitors, which are the standard of care after platinum-containing therapy has failed as an initial treatment for advanced disease. 1,2,3 These patients have few treatment options and new therapies are urgently needed.