A Study of the Safety, Pharmacokinetics, and Therapeutic Activity of RO6958688 in Combination With Atezolizumab in Participants With Locally Advanced and/or Metastatic Carcinoembryonic Antigen (CEA)-Positive Solid Tumors

This is an open-label, multicenter, dose-escalation and expansion Phase Ib clinical study of RO6958688 in combination with atezolizumab. Part I of the study is subdivided into parts IA and IB. Part IA is dose escalation with a starting dose of 5 mg of RO6958688 given QW (once a week) and a fixed, flat dose of 1200 mg given Q3W (every 3 weeks) of atezolizumab, to evaluate the safety and determine the MTD of RO6958688 in combination with atezolizumab. Part IB is a dose/schedule finding part that will explore different administration schedules of RO6958688 in combination with atezolizumab (1200 mg Q3W) to establish the appropriate dose/schedule of RO6958688 in combination with atezolizumab.