This study is being conducted in order determine whether IMA910 as single agent with GM-CSF as adjuvant following pre-treatment with low-dose cyclophosphamide is safe and shows sufficient anti-tumour effectiveness in patients with advanced CRC to warrant further development. Secondary objectives of this study are investigation of immunological parameters and additional effectiveness endpoints. Furthermore, safety, immunological parameters and effectiveness of IMA910 as single agent with GM-CSF in combination with imiquimod following pre-treatment with low-dose cyclophosphamide will be investigated in a 2nd cohort of patients.