A Study of MLN0264 in Participants With Cancer of the Stomach or Gastroesophageal Junction

The drug being tested in this study is called MLN0264. MLN0264 is being tested to treat tumors in people who have metastatic or recurrent gastric or gastroesophageal junction malignancies expressing guanylyl cyclase C (GCC). Participants will be analyzed in cohorts based on GCC expression: low=combined H-score 10-109, intermediate=combined H-score 110-249, high=combined IHC H-score \>250. This study will assess tumor size reduction in patients who are administered MLN0264. The study enrolled 38 patients. All participants will be administered MLN0264 at 1.8 mg/kg as a single, 30-minute, intravenous (IV) infusion on Day 1 of each 3-week treatment cycle, followed by a rest period of 20 days. Participants will continue to receive MLN0264 for up to 1 year or until disease progression or unacceptable toxicity occurs. This multi-centre trial will be conducted worldwide. The overall time to participate in this study is approximately 19 months. Participants will make 3 to 6 visits to the clinic per treatment cycle, an end-of-treatment visit 30 days after the last dose of study medication, and follow-up assessments every 12 weeks until death or 6 months after the last patient completes treatment - whichever occurs first.