A Study of a Patient-Specific Neoantigen Vaccine in Combination With Immune Checkpoint Blockade for Patients With Metastatic Colorectal Cancer

Inclusion Criteria: * Patients with histologically confirmed metastatic colorectal cancer (CRC) who are planned for, or have received \<30 days of first-line treatment in the metastatic setting with FOLFOX/bev, CAPEOX/bev, FOLFOXIRI/bev, or CAPOXIRI/bev per SOC * Measurable and unresectable metastatic disease according to RECIST v1.1 * Availability of formalin-fixed paraffin-embedded (FFPE) tumor specimens. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Patient has adequate organ function per defined criteria * If women of childbearing potential (WCBP), must be willing to undergo pregnancy testing and agrees to the use at least 1 highly effective contraceptive method during the study treatment period and for 150 days after last investigational study treatment. Exclusion Criteria: * Patients with deficient mismatch repair (dMMR) or microsatellite instability (MSI-H) phenotype * Patient has a known tumor mutation burden \<1 non-synonymous mutations/megabase * Known DNA Polymerase Epsilon mutations * Patients with known BRAFV600E mutations * Bleeding disorder or history of significant bruising or bleeding following IM injections or blood draws * Immunosuppression anticipated at time of study treatment * History of allogeneic tissue/solid organ transplant * Active or history of autoimmune disease or immune deficiency * Patient with symptomatic or actively progressing central nervous system (CNS) metastases, carcinomatous meningitis, or has been treated with whole brain radiation * History of other cancer within 2 years with the exception of neoplasm that has undergone potentially curative therapy * Any severe concurrent non-cancer disease that, in the judgment of the Investigator, would make the patient inappropriate for the current study * Active tuberculosis or recent (\<2 weeks) clinically significant infection, evidence of active hepatitis B or hepatitis C, or known history of positive test for HIV * History of pneumonitis requiring systemic steroids for treatment (with the exception of prior resolved in-field radiation pneumonitis) * Myocardial infarction within previous 3 months, unstable angina, serious uncontrolled cardiac arrhythmia, history of myocarditis, or congestive heart failure (Class III or IV). * Pregnant, planning to become pregnant, or nursing.