Background: NIVACOR trial is an open-label, multicentric Italian phase II trial of FOLFOXIRI/bevacizumab in association with an anti-PD1 antibody, nivolumab, in patients (pts) with metastatic colorectal cancer (mCRC). We report preliminary safety analysis by an Independent Monitoring Committee. Methods: Pts with mCRC RAS or BRAF mutated, regardless microsatellite status and eligible to receive a first line treatment will be enrolled. FOLFOXIRI/bevacizumab (BEV) in association with nivolumab (NIV) was administered every 2 weeks for 8 cycles (induction) followed by BEV plus NIV every 2 weeks (maintenance) until PD or unacceptable toxicities. BEV was administered intravenously at dose of 5 mg/kg and NIV intravenously as a flat dose of 240 mg every 2 weeks. The primary endpoint was the ORR. The safety is assessed after the inclusion of the 10^th patient, receiving ≥1 dose. Results: As of September 20, 2020, 25/70 pts are enrolled. The first 10 pts were evaluated for preliminary safety analysis. Median age was 58 years (32-66), 60% of pts were male, median cycles of treatment was 5.5 (1-9). 100% were KRAS G12D mut and BRAF wild type, respectively, and 2% MSI-H/dMMR. 7/10 pts experienced at least one AE related to FOLFOXIRI/BEV and 2/10 related to NIV. The most frequent grade 1-2 AEs related to FOLFOXIRI/BEV were nausea and vomiting 4(57%), fatigue 5(71%), and diarrhea 5(71%); 3(43%) pts had grade 3-4 neutropenia, and 1(14%) febrile neutropenia. Only 2 pts developed grade 1-2 AEs related to NIV represented by rash (50%) and salivary gland infection (50%); no grade 3-4 was reported. One of pts with dose delay because of serious AES (proteinuria) BEV related, and one patient discontinued due to serious AEs (ileo-urethral fistula) not related to NIV. Conclusions: Combination of FOLFOXIRI/BEV and NIV was generally well tolerated and showed an acceptable toxicity profile. The final analysis will be scheduled at the end of enrollment. Clinical trial information: NCT04072198