Evaluation of MGN1703 Maintenance Treatment in Patients With mCRC With Tumor Reduction During Induction Treatment

Inclusion Criteria:

* Signed written informed consent
* Male or female patient 18 years or older
* Histologically confirmed diagnosis of colorectal cancer presenting with unresectable stage IV (UICC) disease (primary tumor may be present)
* Complete or partial response, as assessed by local investigators according to RECIST 1.1, within 12-30 weeks from start of induction treatment with standard first-line chemotherapy with or without biological agents
* ECOG PS 0-1
* Haematology and biochemistry laboratory results within the limits normally expected for the patient population recovering after receiving induction treatment
* Male and female patients of childbearing potential (i.e. did not undergo surgical sterilization - hysterectomy, bilateral tubal ligation, or bilateral oophorectomy - and are not post-menopausal for at least 24 consecutive months) must use an effective method of contraception. Females of child bearing potential must have a negative serum pregnancy test

Exclusion Criteria:

* History of other malignant tumors within the last 5 years, except basal cell carcinoma or curatively excised cervical carcinoma in situ
* Known brain metastases (present or treated)
* Contraindication to receiving MGN1703 as per current investigator brochure
* Known hypersensitivity to any component of the study product
* Prior allogeneic stem cell transplantation or organ transplantation
* Active or uncontrolled infections or undiagnosed febrile condition
* Severe anemia requiring repeated blood cell transfusion
* Pre-existing autoimmune or antibody-mediated diseases or immune deficiency
* Chronic systemic immune therapy or immunosuppressant medication other than steroids within the last 6 weeks; continuous systemic steroid treatment within the last 2 weeks prior to start of study treatment
* Use of systemic antibiotic therapy within the last 2 weeks prior to start of study treatment
* Inadequate pulmonary function according to the Investigator's judgment, history of interstitial lung disease e.g. pneumonitis or pulmonary fibrosis or evidence of interstitial lung disease on baseline chest CT scan
* HIV seropositivity or active HBV/HCV infection
* Serious concomitant disease or medical condition that in the judgment of the investigator renders the patient at high risk of treatment complications
* Female patient who is pregnant or breast feeding
* Contraindication to receive the planned standard maintenance treatment according to applicable SmPC
* Treatment with any anti-cancer investigational drug within 12 months prior to study treatment or participation in another clinical study with other investigational drugs within 28 days prior to study treatment
* Vaccination within 1 months prior to start of study treatment
* Any medical, mental, psychological or psychiatric condition that in the opinion of the investigator would not permit the patient to complete the study or understand the patient information