Background: Capecitabine (Cap) is a standard first-line maintenance treatment option for colorectal cancer. Fuquinitinib (Fru) is a highly selective small molecule tyrosine kinase inhibitor that inhibits VEGFR1/2/3, which has been approved by the U.S. Food and Drug Administration (FDA) for adults with mCRC who have been previously treated with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy and has recommended by NCCN guidelines as a standard treatment. Preliminary research results found that adding Fru to Cap as maintenance treatment was safe and improved progression-free survival (PFS, primary endpoint) for mCRC patients (pts). Methods: Eligible pts had been confirmed mCRC who achieved disease control (including CR/PR and SD) after at least six cycles of first-line standard chemotherapy. During phase Ib, pts received Fru (4 mg p.o. qd, 3 weeks on/1 week off, q4w]) plus Cap (850 mg/m², p.o. bid, d1-7 and d15-21, q4w). In phase II, pts were randomized in a 1:1 ratio to receive either Fru (RP2D, 3mg, 3 weeks on/1 week off) plus Cap or Cap alone. The primary outcome was PFS 1 (defined as time from randomization to disease progression or death). Secondary were PFS 2 (defined as time from first time receiving 1L treatment to disease progression or death), ORR and DCR. Results: At data cutoff (Jan 23, 2024), 46 pts were enrolled and 38 pts who had at least one tumor assessment post treatment were randomly assigned in Fru plus Cap arm (n=20) and Cap arm (n=18). Of these pts, the median age was 59.5 (39-78) and 58.5 (32-75) years, 11 (55.0%) and 10 (55.6%) had left-sided tumors, respectively. Most pts had previously received bevacizumab therapy (65.0% /66.7%) or cetuximab (30% /22.2%). The median cycles of first-line treatment were 8 (5-12) and 8 (4-13), 8 (40.0%) and 8 (44.4%) achieved PR in the pts who had received first-line therapy, respectively. The median PFS 1 was 9.2 mo in Fru plus Cap arm and 3.1 mo in Cap arm (HR=0.385 [95% CI: 0.163 - 0.906], p=0.024). And PFS 2 was also significantly prolonged in Fru plus Cap vs Cap (16.8 vs 8.5 mo, HR=0.314 [95% CI: 0.125 - 0.788], p=0.0098). Consistently, ORR (15.0% vs 5.6%) and DCR (80% vs 55.6%) were improved in Fru plus Cap arm. The safety was similar to the previous results without new safety signals appearing. Conclusions: PFS was significantly prolonged and ORR was improved in mCRC pts treated with Fru plus Cap as first-line maintenance treatment. This trial is ongoing and updated data will be presented in the future. Clinical trial information: NCT05451719.