A phase II clinical trial of metformin combined with FOLFIRI plus bevacizumab as second-line therapy in patients with RAS-mutant metastatic colorectal cancer.

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3534 Background: Metastatic colorectal cancer (mCRC) patients with RAS mutations are confronted with limited novel targeted therapy. We previously reported that KRAS mutation mediated MATE1 down-regulation sensitizes colorectal cancer cells to metformin. Based on our preclinical research, we designed a study to explore whether metformin combined with FOLFIRI plus bevacizumab would improve efficacy in RAS mutant mCRC. Methods: This single-arm, multicenter trial (ChiCTR2000037943) recruited patients with RAS mutant mCRC that had failed to first-line bevacizumab plus an oxaliplatin-based regimen of systemic therapies. Patients received metformin 1000mg PO twice daily on day 1-14, plus irinotecan 180 mg/m² IV, calcium folinate 400 mg/m² IV, fluorouracil 400 mg/m² IV, and a 46-h CIV of fluorouracil 2400 mg/m², and bevacizumab 5 mg/kg IV, repeated every 14 days. We used Simon's two-stage design. The primary endpoint was objective response rate (ORR). The secondary endpoints were disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and safety. Results: One hundred sixteen patients were recruited between July 2020 and March 2023. KRAS codon 12 mutations were present in 81 cases (69.8%), codon 13 mutations in 17 cases (14.7%), codon 61 mutations in 6 cases (5.2%), and codon 146 mutations in 3 cases (2.6%). For the 81 patients with KRAS codon 12 mutation, 42 were with G12D (51.9%), 21 with G12V (25.9%), 7 with G12A (8.6%), and 6 with G12C (7.4%) mutation. The ORR was 21.6% (25/116), and DCR was 76.7% (89/116). The median PFS was 8.0 months, and patients without liver metastasis had longer PFS than those with liver metastasis (9.5 months vs. 5.6 months, P < 0.001). For the 45 patients without liver metastasis, the administration of metformin combined with FOLFIRI plus bevacizumab as second-line therapy resulted in significantly longer PFS than the first-line bevacizumab plus an oxaliplatin-based regimen (9.5 months vs. 7.9 months, P = 0.037). The median OS was not reached. The most common treatment-emergent adverse events (TEAEs) were neutropenia (73.7%), nausea (56.9%), anemia (54.3%) and diarrhea (49.1%). Grade 3 and above TEAEs occurred in 52 (44.8%) patients. No treatment-related mortality occurred. Conclusions: Metformin combined with FOLFIRI and bevacizumab had promising efficacy and tolerable toxicity in RAS mutant mCRC patients as second-line therapy. Further study in phase 3 trials is warranted. Clinical trial information: ChiCTR2000037943.