CMAB009 plus irinotecan versus irinotecan-only as second-line treatment after fluoropyrimidine and oxaliplatin failure in KRAS wild-type metastatic colorectal cancer patients: promising findings from a prospective, open-label, randomized, phase III trial

BACKGROUND: The 5-fluorouracil/leucovorin plus oxaliplatin (FOLFOX) regimen is the standard first-line treatment for metastatic colorectal cancer (mCRC), however, the optimal second-line regimen for KRAS wild-type mCRC patients is still investigational. In this study, we aimed to determine the clinical efficacy and safety of CMAB009 plus irinotecan compared to irinotecan-only as a second-line regimen for treating KRAS wild-type mCRC patients. METHODS: Patients with KRAS wild-type mCRC who had previously failed to respond to FOLFOX treatment were randomly assigned in a 2:1 ratio, to receive CMAB009 plus irinotecan or irinotecan-only. Patients receiving irinotecan-only were permitted to switch to CMAB009 therapy on disease progression and were grouped as the sequential-CMAB009 arm. The primary endpoints were overall response rate (ORR) and median progression-free survival (PFS). The secondary endpoints were median overall survival (OS), disease control rate (DCR), clinical benefit rate (CBR), and duration of response (DOR). RESULTS: The CMAB009 plus irinotecan arm demonstrated significantly improved ORR (33.2% vs. 12.8%; P < 0.001) and longer median PFS (169 days vs. 95 days; P < 0.001) as compared to the irinotecan-only arm. Patients receiving CMAB009 plus irinotecan also demonstrated improved DCR (80.1% vs. 65.2%, P < 0.001), CBR (30.0% vs. 14.6%, P < 0.001), and DOR (210 days vs. 109 days; P < 0.001) as compared to irinotecan-only. However, patients treated with CMAB009 had an increased risk of skin rash (66.9% vs. 5.5%, P < 0.001) and paronychia (9.8% vs. 0.0%, P < 0.001). Anti-drug antibodies (ADA) were detected in 3.6% of patients, and only 0.9% of patients who received CMAB009 experienced hypersensitivity reactions. In patients receiving sequential-CMAB009 therapy after failure with irinotecan, their median PFS was 84 days (95% CI 65 to 113 days). The median OS was 425 days for patients receiving CMAB009 plus irinotecan and 401 days for those with sequential-CMAB009 (P = 0.940). CONCLUSIONS: Treatment with CMAB009 plus irinotecan was found to be a superior second-line regimen in comparison to irinotecan-only in KRAS wild-type mCRC patients. Further, switching to CMAB009 can be considered as an efficient third-line of treatment after treatment failure with second-line irinotecan-only. Trial registration ClinicalTrials.gov: NCT01550055, retrospectively registered on March 9, 2012.