Background: Nivolumab in combination with chemotherapy has been approved in the first-line treatment of PD-L1-positive metastatic gastric cancer (GC). Fibroblast growth factor receptor 2 (FGFR2) is overexpressed in 30% of patients with GC and is a potential new target for targeted therapy with monoclonal antibodies¹ or allosteric extracellular inhibitors.² The aim of the NIVOFGFR2 study was to evaluate the preliminary efficacy of nivolumab in metastatic GC co-expressing PD-L1 and FGFR2. Methods: In this single-arm, multi-center, phase 2 study, eligible patients had metastatic untreated HER2-negative gastric adenocarcinoma with centrally confirmed expression of PD-L1 (CPS≥5; DAKO 28-8) and FGFR2 (moderate (2+) and strong (3+) membranous staining in more than 1% of tumor cells; Abсam EPR24075-418). Patients received nivolumab 360 mg with CapeOX (capecitabine and oxaliplatin) every 3 weeks. The primary endpoint was 1-year progression-free survival (PFS). Secondary endpoints included median PFS and overall survival (OS), objective response rate (ORR) and Grade ≥3 adverse events rate. Results: Seventy-four HER2-negative patients were screened and23 (31%) patients were enrolled (median age 61 years, men 74%, Caucasian 91%, ECOG PS 1-2 78%, organs with ≥2 metastases 78%; CPS (5-9) 22%, (≥10) 78%). 1-year PFS rate was 30,4%. The median PFS was 6.2 months (95% CI 4.4-7.6). The ORR was 21.7% with 1 complete response. With a median follow-up of 11.8 months at data cutoff, the median OS was not reached. Grade ≥3 treatment-related adverse events were reported in 9 (39.1%) patients. Conclusions: An interim analysis demonstrates modest efficacy and an acceptable safety profile of nivolumab in combination with chemotherapy in patients with FGFR2-positive, PD-L1-positive metastatic GC. Further follow-up is ongoing. 1. Wainberg, Lancet Oncol. 2022. 2. Tsimafeyeu, Invest New Drugs. 2023. Clinical trial information: NCT05859477.