In the dose escalation part of the study, four groups of patients with the following tumor types will be enrolled: recurrent GBM, metastatic breast cancer, metastatic CRC and advanced pancreatic adenocarcinoma. It is anticipated that approximately 45 patients will be enrolled in the dose escalation part. Approximately 15 GBM patients (maximum of 2 patients per dose level) will be enrolled to previously well-tolerated doses during dose escalation if no slot is available in a cohort under active testing. In the dose expansion part of the study, five groups of patients (approximately 15 patients per group) with the following tumor types will be enrolled: recurrent GBM, triple negative metastatic breast cancer, hormone receptor positive (ER+/PR+, and Her2-) metastatic breast cancer, gastric/gastroesophageal junction cancer, and a combined maximum of 15 patients with metastatic CRC or advanced pancreatic adenocarcinoma. The dose expansion will enroll approximately 75 patients. Accounting for patients who may withdraw or who may not meet the eligibility criteria, it is expected that this study will enroll approximately 120 patients.