A Study in Advanced or Metastatic Gastrointestinal Cancers Exploring Treatment Combinations With Pelareorep and Atezolizumab

The overall aim is to assess safety, predictive biomarkers, and preliminary efficacy as assessed by tumor response criteria at week 16 for cohorts1, 2, 3, and 4, and best overall response rate and OS in Cohort 5. If a cohort shows a promising ORR in Stage 1 of the Simon two-stage design, that cohort may be expanded to enroll additional patients (up to 50 patients in Cohorts 1 and 3 , up to 28 patients in Cohort 4, and up to 64 patients in Cohort 5) in an extension phase per predetermined statistical conditions. In addition, either or both arms of Cohort 5 may expand if the data collected in Stage 1 suggest that expansion may help in assessing the potential survival benefit of the investigational therapy(ies). In this study, we hypothesize that treatment with pelareorep will prime the tumor microenvironment (TME) for checkpoint blockade therapy, thereby increasing PD-L1 expression and the number of new T cell clones within the tumor, both of which are associated with increased response to checkpoint blockade.