REGOMUNE: A phase II study of regorafenib plus avelumab in solid tumors-Results of the oesophageal or gastric carcinoma (OGC) cohort.

4060 Background: Combination VEGF and PD-1/PD-L1 axis blockade has shown benefit in various tumors and is emerging as a promising combination strategy. Methods: This is a single-arm open-label multicentric phase II trial assessing the efficacy and safety of regorafenib (R) (160 mg QD 3weeks/4) + avelumab (A) (10 mg/kg every 2 weeks) combination in advanced or metastatic oesophageal or gastric carcinoma (OGC) patients (pts). The primary endpoint was the confirmed objective response rate, based on central review according to RECIST 1.1. Secondary endpoints included: 1-year progression free survival (PFS), 1-year overall survival (OS), and safety using NCI-CTCAE v5.0. Correlative studies were planned from pts tumor samples obtained at baseline. Results: Between Dec. 2018 and Mar. 2021, 49 pts were enrolled in 6 centers: 33 adenocarcinoma (ADK), 16 squamous cell carcinoma (SCC). Median age was 63.9 (range 33 – 80). Median follow-up was 14.5 months. Median number of previous treatment lines was: 2 (range 1 – 6). 29 (59.2%) pts experienced at least 1 dose modification or treatment interruption due to an adverse event related to treatment. The most common grade 3/4 adverse events were : Hypertension (12.2% of pts), palmar-plantar erythrodysesthesia syndrome (10.2%), and hypophosphatemia (8.2%). No death was related to the treatment. Among the 42 (29 ADK and 13 SCC) pts who had at least one imaging tumor assessment, 8 (19.1%) achieved a partial response, 5 (17.2%) and 3 (23.1%) in the ADK and SCC group respectively. 12 pts (28.6%) demonstrated stable disease and 22 pts (52.3%) had progressive disease. The median PFS and OS were 1.9 months (95%CI 1.8 – 3.5) and 7.5 months (95%CI 4.5 – 15.7) respectively. Conclusions: The R+A combination is associated with encouraging antitumor activity in patients with OGC. Full Biomarkers analyses will be presented at the meeting. Clinical trial information: NCT03475953.