Background: We have shown that autophagy, the regulated dissolution of cellular elements to maintain survival in adverse environmental conditions, is a determinant of resistance to chemotherapy in colorectal cancer models, and is reversed by chloroquine (Selvakumaran M, et al. Clin Cancer Res, 2013). A Phase I run-in demonstrated that full doses of mFOLFOX6/bevacizumab were tolerated with HCQ 600mg PO twice daily. Methods: We report a Phase II trial in previously-untreated patients with metastatic colorectal cancer. Patients were treated every two weeks with 5-FU (400mg/m2 bolus, then 2400 mg/m2 over 46h) together with leucovorin 200mg/m2, oxaliplatin 85mg/m2, bevacizumab 5mg/kg, all IV, repeated every two weeks, with HCQ as above. After 12 cycles, oxaliplatin was omitted and patients were continued on 5-FU, bevacizumab, and HCQ. Imaging was performed every 8 weeks. Results: Twenty-four patients (pts) have been accrued, of whom 23 are eligible: 10 female/13 Male; 19 Caucasian/3 Black/1 East-Asian. Toxicity has been generally tolerable. Grade 3 effects included neutropenia 9/23), diarrhea (1/23), and anorexia (1/23). There were two episodes of myocardial infarction, one fatal, one of atrial arrhythmia, and two of pulmonary embolism in the course of the trial. 20/23 patients were able to maintain full dose of HCQ. Patients evaluable for response include 19 (4 pts too early). There were 1 complete response (5%), 9 partial responses (47%), and 7 stable disease (37%). Four patients went off study for resection of metastatic disease after 3-25 months. Median progression-free and overall survival have not been reached. Autophagy biomarkers in peripheral mononuclear cells show autophagy inhibition in the majority of patients. Six of thirteen patients with genomic testing available had a TP53 mutation. Four of these six patients had a major response (1CR, 3 PR). Conclusions: The combination of FOLFOX/bevacizumab with HCQ is an active regimen in unselected patients with colorectal cancer. A randomized Phase II trial of the combination is in development. Clinical trial information: NCT01206530