Updated results from a phase Ib trial of regorafenib plus nivolumab in patients with advanced colorectal or gastric cancer (REGONIVO, EPOC1603).

Abstract

135 Background: In the phase 1 REGONIVO study, regorafenib of 80 mg/day plus nivolumab showed manageable safety profiles and encouraging anti-tumor activity for advanced colorectal cancer (CRC) or gastric cancer (GC) with objective response rate (ORR) of 36% in CRC and 44% in GC (Fukuoka, et al. ASCO 2019). Updated efficacy results are presented. Methods: Enrolled patients (pts) received regorafenib plus nivolumab in a dose-finding phase to estimate the maximum tolerated dose (MTD). Additional pts were enrolled in a dose-expansion phase. Regorafenib of 80 to 160 mg was administered once daily for 21 on 7 days off with nivolumab 3 mg/kg every 2 weeks. The primary endpoint was dose-limiting toxicity (DLT) during cycle one to estimate the MTD and the recommended dose. PD-L1 combined positive score (CPS) was assessed using the anti–PD-L1 28-8 antibody. Tumor mutation burden (TMB) was measured using Oncomine tumor mutation load assay. Results: Fifty pts were enrolled (25 CRC; 25 GC) until October 2018 with median prior treatment line of 3. Efficacy results were updated as of September 1st 2019. One CRC pt was with MSI-high but all other pts were with MSS or MMR-proficient. Among the 20 pts (9 CRC and 11 GC) with objective response (40%), responses are still ongoing in 13 pts (7 CRC and 6 GC) and the median duration of response was not reached (NR). Median progression free survival (PFS) was 7.8 months in CRC (95% CI, 2.8- NR) and 5.5 months (95% CI, 2.6-10.2 months) in GC. One-year PFS rate was 41.7% in CRC and 22.4% in GC. Median overall survival (OS) was not reached in CRC (95% CI, 9.7-NR) and 12.1 months (95% CI, 5.2-NR) in GC. One-year OS rate was 68% in CRC and 55.3% in GC. No significant difference of PFS and ORR was observed in CRC according to PD-L1 and TMB. Conclusions: Encouraging anti-tumor activity of the combination of regorafenib plus nivolumab had been maintained with long-term follow-up. A randomized study for MSS CRC is under planning. Clinical trial information: NCT03406871.