3. Patients must have failed a first-line chemotherapy regimen for nonresectable locally advanced or mCRC (first-line 5-FU-based therapies, including but not limited to FOLFOX, FOLFOX 4, mFOLFOX6, CapeOX, single-agent capecitabine, infusional 5-FU, or other chemotherapies. Bevacizumab, cetuximab, panitumumab, and EGFR inhibitors are allowed. Prior treatment with irinotecan or FOLFIRI is not allowed for Phase II). For Phase Ib only, up to 3 prior therapies are allowed (including non-irinotecan containing therapies and adjuvant therapy);