Grade 3-5 adverse events (AEs) were seen in 88.3% of patients receiving onartuzumab and in 78.3% of patients receiving placebo, with serious AEs in 55% and 40%, respectively.The addition of onartuzumab to mFOLFOX6 in gastric cancer did not improve efficacy in an unselected population or in a MET immunohistochemistry-positive population.The YO28252 study demonstrated that the addition of the anti-MET agent onartuzumab to mFOLFOX6 for treatment of gastric cancer did not improve efficacy in an overall study population or those selected for positive MET status by immunohistochemistry.