Personalized Peptide Vaccine in Treating Patients With Advanced Pancreatic Cancer or Colorectal Cancer

PRIMARY OBJECTIVES: I. Demonstrate that developing a custom vaccine for metastatic pancreatic ductal adenocarcinoma (PDA) and colorectal cancer (CRC) patients is feasible. (cohorts A and B) II. Show that a custom peptide-based vaccine in combination with imiquiomod, pembrolizumab, and/or sotigalimab (APX005M) is safe. (cohorts A and B and C and D) SECONDARY OBJECTIVES: I. Determine the clinical benefit of the peptide vaccine alone or combined with pembrolizumab or pembrolizumab and APX005M. (cohorts A and B and C and D) II. Demonstrate the antigenicity of each vaccine. (cohorts A and B and C and D) III. The change in neoantigen-specific T cell responses at 12 weeks after initiation of personalized peptide vaccination. (cohorts C and D) IV. Relapse-free survival and circulating tumor deoxyribonucleic acid (ctDNA) clearance rate. (cohorts C and D) OUTLINE: Patients are assigned to 1 of 3 cohorts. COHORT A: Patients receive personalized synthetic tumor-associated peptide vaccine therapy subcutaneously (SC) on day 1 of weeks 0, 1, 3, 4, 6, 12, and 24. Beginning 15 minutes after each vaccine is administered, patients then receive imiquimod cream topically in the absence of disease progression or unacceptable toxicity. Patients also undergo computed tomography (CT) or magnetic resonance imaging (MRI) scans at baseline and at weeks 0 and 6, then every 3 months, and at week 39. COHORT B: Patients receive personalized synthetic tumor-associated peptide vaccine therapy SC on day 1 of weeks 0, 1, 3, 4, 6, 12, and 24. Beginning 15 minutes after each vaccine is administered, patients receive imiquimod cream topically. Patients also receive pembrolizumab intravenously (IV) over 30 minutes every 3 weeks until week 24 in the absence of disease progression or unacceptable toxicity. Patients also undergo CT or MRI scans at baseline and at weeks 0 and 6, then every 3 months, and at week 39. COHORTS C AND D: Patients receive personalized synthetic tumor-associated peptide vaccine therapy SC on day 1 of weeks 0, 1, 3, 4, 6, 9, 12, 15, 18, 21, and 24. Beginning 15 minutes after each vaccine is administered, patients receive imiquimod cream topically. Patients also receive pembrolizumab IV over 30 minutes every 3 weeks until week 24 in the absence of disease progression or unacceptable toxicity. Beginning about 1 hour after each vaccine, patients also receive sotigalimab IV over 60 minutes on day 1 of weeks 0, 1, 3, 4, 6, 9, 12, 15, 18, 21, and 24 in the absence of disease progression or unacceptable toxicity. Patients also undergo CT or MRI scans at baseline and weeks 6,12, and 24, then every 3 months, and at week 39. After completion of study treatment, patients are followed for 6 months.