Pfizer Inc. /zigman2/quotes/202877789/composite PFE +0.74% and German-based Merck KGaA /zigman2/quotes/200605022/delayed DE:MRK +0.37% said Tuesday a phase 3 trial of a cancer treatment did not meet its primary endpoint of superior overall survival. Pfizer's stock slipped 0.9% in premarket trade. The trial tested avelumab as a third-line treatment for unresectable, recurrent or metastatic gastric adenocarcinoma patients whose disease progressed following two prior therapeutic regiments. The safety profile was consistent with that observed in the overall clinical development program. The companies said this was the first trial conducted with a checkpoint inhibitor compared with an active chemotherapy comparator rather than placebo. "Data from this study will provide valuable information for physicians treating this late stage disease," said Luciano Rossetti, global head of R&D at Merck. "We remain committed to our ongoing gastric cancer program with avelumab including the JAVELIN Gastric 100 study in the first-line switch maintenance setting." Pfizer's stock had gained 9.3% year to date through Monday, while the SPDR Health Care Select Sector ETF /zigman2/quotes/205918244/composite XLV +0.59% has run up 18.7% and the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA +0.45% has rallied 19.3%.