Symptomatic peritoneal carcinomatosis 10. Peritonitis 11. Serious, non- healing wounds, ulcers or bone fractures 12. Nephrotic syndrome 13. Arterial thromboembolisms or severe hemorrhages within 6 months before study enrolment (except bleeding tumor before tumor resection surgery) 14. Hemorrhagic diathesis or thrombotic tendency 15. Major surgery or radiotherapy within 12 weeks prior to the study treatment or anticipation of needing such procedure during the study period 16. Uncontrolled pleural effusion, pericardial effusion or ascites requiring repeated drainage more than once every 28 days 17. Participants with active malignancy (other than colorectal cancer [ CRC]) or a prior malignancy within the past 12 months 18. Participant with myocardial infarction within 6 months prior to enrollment or New York Heart Association Class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythm ias or electrocardiographic evidence of acute ischemia or active conduction system abnormalities. Prior to the first dose of study treatment, any electrocardiogram (ECG) abnormality at Screening must be documented by the investigator as not medically relev ant 19. Administration of a live, attenuated vaccine within 4 weeks before randomization or anticipation of a live attenuated vaccine will be required during the study 20. Participant has participated in another clinical study involving an investigational product (IP) or investigational device within 30 days prior to enrollment or is scheduled to participate in another clinical study involving an IP or investigational device during the course of this study 21. Known hypersensitivity to any component of the investigational drug 22. If female, participant is pregnant (exclusion confirmed with beta- human chorionic gonadotropin [ hCG] test) or lactating at the time of enrollment, or has plans to become pregnant or start breastfeeding during the study 23. Pre-existing alcohol or dru g abuse 24. Medical or mental impairments which make it impossible to obtain the patient’s consent or to conduct the study 25. A significant concomitant medical condition which the clinical investigator believes precludes the patient from enrolling in the study 26. Absent or limited legal competence Primary Endpoint : Occurrence of at least 1 ≥Grade 4 local adverse event (AE) or 1 ≥Grade 3 systemic AE and/or signs/symptoms, lab toxicities, and/or clinical events that is probably or definitely related to study treatment, any time from Day 1 until 21 days after administration of each dose of the vaccine . Criteria for Evaluation/Outcome Measures: Primary Outcome Measures: • The incidence and severity of all adverse events (AEs), related AEs, all serious adverse events (SAEs), related SAEs, and temporally -associated AEs according to the National Cancer Institute -Common Ter minology Criteria for Adverse Events (NCI- CTCAE) version 4.0 (v4.0) Treos Bio ZRT OBERTO -101 Amendment 3 Product: PolyPEPI 1018 Colorectal Cancer Vaccine Page 8 of 81 CONFIDENTIAL • Change from baseline in clinical laboratory safety parameters and vital signs • Number and proportion of subjects with any clinically significant change in vital signs (i.e., blood pressure, pulse rate, respiratory rate, body temperature) during the vaccine administration or within 60 minutes following administration Secondary Outcome Measure(s): • PEPIs as identified by the PEPI Test • Effector T cell response against 12 selected epitopes of PolyPEPI1018 as measured by interferon (IFN) -gamma Enzyme -Linked ImmunoSpot (ELISPOT ) assay for the following: o Number and proportion of subjects with 0, ≥1, ≥2, ≥3, ≥4, ≥5 effector T cell responses, respectively, detected at the Baseline Visits (Week -3 to -1 and Week 0) and at 3, 6 -, 9-, and 12-weeks after administration of the vaccine o For each subject, the number of effector T cell responses o For each subject, the time course of effector T cell response at Baseline Visits (Week -3 to -1 and Week 0) and at 3-, 6-, 9-, and 12-weeks after administration of the vaccine • Memory T cell response against 12 selected epitopes of PolyPEPI1018 as measured by the P recursors with High Proliferation Capacity (PHPC) assay for the following: o Number and proportion of subjects with 0, ≥1, ≥2, ≥3, ≥4, ≥5 memory T cell response, respectively, detected at the Baseline Visits (Week -3 to -1 and Week 0) and at 3 -, 6-, 9-, and 12-weeks after administration of the vaccine o For each subject, the number of positive memory T cell responses o For each subject, the time course of memory T cell response at Baseline Visits (Week -3 to -1 and Week 0) and at 3-, 6-, 9-, and 12-weeks after administration of the vaccine • Objective Response Rate (ORR) measured by CT scan at Screening Visit (Week -3 to -1), and at 6-, and 12-weeks after administration of each dose of the vaccine Exploratory Outcome Measures: • Correlation s between PEPIs identified by the PEPI Test and effector and memory T cell responses measured by ELISPOT and PHPC immunogenicity assays • Change in relative counts of tumor infiltrating lymphocytes (TILs) in accessible tumor biopsies at Baseline (Week -3 to -1) and at Week 12 as measured by immunohistochemistry • Correlation between PEPIs identified by the PEPI Test and infiltrating lymphocyte in tumor biopsies measured by immunohistochemistry • Correlations between T cell responses measured by ELISPOT and PHPC and infiltrating lymphocyte in tumor biopsies measured by immunohistochemistry • Correlation s between PEPIs identified by the PEPI Test and effector and ORR • Correlations between T cell responses measured by ELISPOT and PHPC and ORR Treos Bio ZRT OBERTO -101 Amendment 3 Product: PolyPEPI 1018 Colorectal Cancer Vaccine Page 9 of 81 CONFIDENTIAL Sample Size Justificatio n: Approximately 10 subjects will be enrolled in the study to receive three vaccination s. The study is not statistically powered to assess the primary or secondary outcomes measures.