Background: GEC is the third leading cause of cancer mortality and the fifth most common malignancy worldwide. Fluoropyrimidine and platinum-based combinations are the most commonly used 1L treatment regimens. There are few standard treatment options after 1st line regimens. In the 3L+ GEC Keynote-059 trial, objective response rate (ORR) with Pembro was 15.5% in PD-L1(+) vs. 6.4% in PD-L1(-) tumors. While the responses were durable, the 6-months PFS (6-PFS) was only 14.1% and the median PFS was 2.0 mo. This highlights the remaining unmet need for the majority of patients who either are refractory or develop disease progression following treatment with PD-1 inhibitors in GEC. Cabo plus checkpoint inhibitors have shown clinical benefit in various cancers including hepatocellular, renal cell (RCC), urothelial and castration-resistant prostate cancers. In the CheckMate-9ER trial, Cabo+Nivolumab improved both OS and PFS vs sunitinib in 1L RCC. In patients with RCC who had progression on anti-PD1 inhibitor treatment, Cabo showed promising activity with an ORR of 33% and DCR of 79% (ESMO 2018, abstract 3793). Hypothesis: Based on preclinical and clinical observations, Cabo might contribute to overcoming primary or secondary resistance to PD-1 blockade in GEC. Methods: Prospective, open label, non-randomized phase 2 trial. Eligibility: Diagnosis of GEC, 2+ line of treatment including previous fluoropyrimidine/platinum, ECOG 0-2, adequate organ function, prior checkpoint inhibitor if tumor PD-L1 CPS≥10%. Treatment: Cabozantinib 40mg PO daily, Pembrolizumab 200 mg IV on day 1 of 21d cycle. Primary objective: Feasibility of the combination and estimate of efficacy. Primary endpoint:PFS-6. Secondary objectives: OS, ORR, adverse events. Total number of patients to be enrolled N = 27. Current enrollment (Sep 2020) N = 10. Statistics: If the PFS-6 is > 25%, the study would be regarded as positive, in which case it is planned to expand patient enrollment into a larger single arm phase 2 trial with additional sites to establish the efficacy of the regimen. Clinical trial information: NCT04164979