A phase ib trial of assessing the safety and preliminary efficacy of a combination therapy of geptanolimab (GB 226) plus fruquintinib in patients with metastatic colorectal cancer (mCRC).

e15551 Background: A combination of anti-vascular endothelial growth factor receptor(anti-VEGFR) and anti-programmed cell death-1/ligand 1 (PD-1/L1) may synergize with each other and lead to better anti-tumor efficacy. We aimed to assess the safety and preliminary efficacy of combination therapy with geptanolimab (GB226, a highly selective, fully human monoclonal antibody PD-1 mAb) plus fruquintinib (a VEGFR inhibitor) in previously treated metastatic colorectal cancer (mCRC) patients. Methods: In this phase Ib trial, we enrolled mCRC patients who had failed one or two standard therapies. Patients were given geptanolimab (3mg/kg every 2 weeks) and fruquintinib (once daily for 21 days on/7 days off with planned dose cohorts of 3mg, 4mg, and 5mg) on a 28-day cycle. A standard 3+3 design was employed to determine the primary endpoints of the maximum tolerated dose (MTD) and/or the recommended phase 2 dose (RP2D) based on dose-limiting toxicities (DLT). Secondary endpoints included objective response rate (ORR), duration of response (DOR), disease control rate (DCR), progression free survival (PFS), and overall survival (OS). Results: By December 15, 2020, 15 patients were enrolled: 1 with MSI-H, 12 with MSS, and 2 with MS unknown. Ten out of 15 patients (66.7%) had received ≥2 previous lines of treatment including chemotherapy in combination with anti-EGFR (33.3%) or anti-VEGF (53.3%). Seven patients (46.7%) were found to have the PD-L1 combined positive score (CPS)≥1. Two DLTs (one patient with grade 3 ALT and AST elevation and one patient with grade 3 proteinuria) were identified in fruqintinib 5mg cohort (6 patients enrolled). No DLT was observed in either 3mg (3 patients enrolled) or 4mg (6 patients enrolled) cohorts. RP2D of this combination was identified as geptanolimab (3mg/kg, every 2 weeks) and fruquintinib (4mg, once daily for 21 days on/7 days off). In all evaluable patients, the overall ORR was 26.7% (4/15, 3 confirmed PR, 1 unconfirmed PR), and the ORR was 33.3% (2/6) in the RP2D group. The DCR for all evaluable patients was 80%, and the median PFS (mPFS) was 7.33 months (95% CI: 1.91 – NE). The median DOR and median OS was not reached at the data cut-off date. Among 12 patients with MSS, the ORR was 25.0% (3/12, 2 confirmed PR, 1 unconfirmed PR), DCR was 75% and mPFS was 5.45 months (95% CI: 1.84-9.66). All patients had at least 1 treatment related AE (TRAE). The common TRAE were proteinuria (46.7%), hypertension (46.7%), and elevated aspartate aminotransferase (40.0%). Grade 3 AEs were observed in 46.7% of patients and the most common grade 3 AE was hypertension (20.0%). No grade 4 and 5 TRAE was observed. Conclusions: The combination of geptanolimab and fruquintinib had manageable safety profiles and encouraging anti-tumor activity in mCRC patients. Clinical trial information: NCT03977090.