A phase Ib/II study to evaluate surufatinib combined with camrelizumab and chemotherapy in the second-line treatment of advanced colorectal cancer: Phase Ib results

3555 Background: Surufatinib is a novel small-molecule kinase inhibitor targeting VEGFR1-3, FGFR and CSF-1R with confirmed efficacy in epNET and pNET. Preclinical studies have demonstrated that surufatinib combined with immune checkpoint inhibitors (ICIs) have synergistic antitumor effects by modulating tumor immune microenvironment. Additionally, surufatinib plus toripalimab (anti-PD-1) has showed preliminary anti-tumor activity in multiple solid tumors, including colorectal cancer (CRC). This study aimed to evaluate the efficacy and safety of surufatinib plus camrelizumab (anti-PD-1), irinotecan and GM-CSF as second-line treatment in advanced CRC. Here we reported the results of the phase Ib study. Methods: This ongoing phase Ib/II, open-label trial (NCT04929652) enrolled patients (pts) aged 18-75 years old with pathologically confirmed locally advanced or metastatic CRC who have progressed on/been intolerant to the standard first-line therapy. In the Ib dose escalation/de-escalation phase, pts received surufatinib at 250mg once daily (QD) as starting dose, in combination with fixed dose of camrelizumab (200 mg, d1), irinotecan (200 mg/m 2 , d1) and GM-CSF (5ug/kg, d2-d7), every 3 weeks (Q3W). Based on DLTs, the dose of surufatinib should escalate to 300 mg or de-escalate to 200 mg. The primary objective of the phase Ib study was to determine the safety and DLT in first treatment cycle defining the recommended phase 2 dose (PR2D). Additional 36 pts were enrolled in the phase II dose expansion stage using RP2D. Primary endpoint of phase II was ORR as per RECIST 1.1. Secondary endpoints included PFS, DCR, OS and safety. Results: Enrollment opened in Nov 2021 and data cutoff in Dec 2022. 12 pts (median age 54) were treated in Phase Ib study (surufatinib 250 mg: N = 6; surufatinib 300 mg: N = 6). 75% were male and 17% had ECOG PS 1. 11/12 (92%) pts were positive for KRAS, NRAS or BRAF mutations. No DLT was observed in the starting dose cohort (surufatinib 250 mg), and one patient in the surufatinib 300 mg cohort experienced DLT (Grade [G] 3 vomiting). Surufatinib 300 mg QD was defined as the RP2D. Other G3 treatment related adverse events (TRAEs) were hypertension (1/12; 8.3%) and diarrhea (1/12; 8.3%). All other TRAEs were grade 1-2, and the most common (≥40%) were diarrhea (75%), fatigue (58%), vomiting (58%), nausea (50%), hypertension (42%), proteinuria (42%) and alopecia (42%). Of the 12 pts evaluable for tumor response, 3 pts achieved PR, 9 pts achieved SD. The ORR was 25% (3/12), the DCR was 100% (12/12) and median PFS was 7.2 months (95%CI 3.7-10.7). Conclusions: Surufatinib plus camrelizumab, irinotecan and GM-CSF was well tolerated, with a manageable safety profile, and showed preliminary anti-tumor activity in patients with advanced CRC. The dose-expansion phase is ongoing. Clinical trial information: NCT04929652 .