 Shares of Seagen Inc. SGEN, 0.71 gained 2.5 in premarket trading on Tuesday after the company said an early-stage clinical trial evaluating its investigational treatment for urothelial cancer in combination with Merck Co. Inc.s MRK, 0.47 Keytruda met its primary endpoint. Seagen is developing the therapy, enfortumab vedotin, with Astellas Pharma Inc. jp:TSE:4503 ; it received a Breakthrough Therapy designation in early 2020. 