Main Inclusion Criteria:

          -  Histological documentation of adenocarcinoma of the colon or rectum.

          -  Progression or recurrence following prior irinotecan, oxaliplatin, 5-FU and anti-EGFR
             containing regimens for metastatic disease.

          -  Best response according to Response Evaluation Criteria in Solid Tumours criteria to
             the last anti-EGFR containing regimen of partial response or at least stable disease
             for 4 months.

          -  Measurable disease according to RECIST criteria.

          -  N-K-RAS (exons 2, 3 and 4) and BRAF wild-type and PIK3CA mutated.

          -  Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1.

        Main Exclusion Criteria:

          -  Previous treatment with PI3K inhibitor.

          -  Previous treatment with an anti-EGFR containing regimen for metastatic disease within
             6 months prior to inclusion into the study.

          -  Untreated brain metastases, unless treated > 4 weeks earlier and only if clinically
             stable and not receiving corticosteroids.

          -  NCI CTCAE v5.0 Grade ≥ 2 diarrhoea.

          -  History of significant, uncontrolled or active cardiovascular disease.

          -  Known active or uncontrolled pulmonary dysfunction.

          -  Uncontrolled diabetes mellitus (HbA1c > 7%) and fasting plasma glucose > 126 mg/dL.

          -  Known history of human immunodeficiency virus infection or active infection with
             hepatitis C virus or hepatitis B virus.

          -  Concurrent chronic immunosuppressive treatment either with steroids or other
             immunosuppressive agents.