This is a multicentre, open-label, Phase 1-2 study in patients with locally advanced and/or metastatic colorectal cancer (CRC) to investigate the effectiveness, safety and immunogenicity of the tumour multi-peptide vaccine IMA910 plus GM-CSF (1st cohort) given as monotherapy after successful (CR, PR or SD) completion of a 12 week first-line oxaliplatin-based standard chemotherapy (e.g. FOLFOX, XELOX). Safety, immunogenicity and effectiveness of IMA910 plus GM-CSF in combination with imiquimod will be investigated in a 2nd cohort of patients with locally advanced and/or metastatic colorectal cancer (CRC) after successful (CR, PR or SD) completion of a 12 week first-line oxaliplatin-based standard chemotherapy (e.g. FOLFOX, XELOX).