Background: Lenvatinib, an anti-angiogenic multiple receptor tyrosine kinase inhibitor, in combination with the anti‒PD-1 antibody pembrolizumab, has demonstrated promising antitumor activity with manageable safety in the first- or second-line in a phase 2 trial of patients with advanced gastric cancer. LEAP-005 (NCT03797326) is a phase 2, multicohort, nonrandomized, open-label study evaluating efficacy and safety of lenvatinib plus pembrolizumab in patients with previously treated advanced solid tumors; here, we present findings from the gastric cancer cohort of LEAP-005. Methods: Eligible patients were aged ≥18 years with histologically or cytologically confirmed metastatic and/or unresectable gastric cancer, received at least 2 prior lines of therapy, had measurable disease per RECIST v1.1, ECOG PS of 0‒1, and provided a tissue sample evaluable for PD-L1 expression. Patients received lenvatinib 20 mg once daily plus pembrolizumab 200 mg Q3W for up to 35 cycles of pembrolizumab (approximately 2 years) or until confirmed disease progression, unacceptable toxicity, or withdrawal of consent. Treatment with lenvatinib could continue beyond 2 years in patients experiencing clinical benefit. Primary endpoints were ORR (per RECIST v1.1 by blinded independent central review) and safety. Secondary endpoints included disease control rate (DCR; comprising CR, PR, and SD), duration of response (DOR), PFS, and OS. Tumor imaging was performed Q9W from treatment initiation for 54 weeks, then Q12W to week 102, and Q24W thereafter. Results: 31 patients were enrolled in the gastric cancer cohort; 87% were male, 58% were aged < 65 years, and 71% had PD-L1 combined positive score (CPS) ≥1. Median time from first dose to data cutoff (April 10, 2020) was 7.0 months (range, 1.9‒11.9); 19 patients (61%) had discontinued treatment. ORR was 10% (95% CI, 2‒26); 1 patient had CR (3%), and 2 had a PR (6%). 12 patients (39%) had SD. Median DOR was not reached (range, 2.1+ to 2.3+ months). DCR was 48% (95% CI, 30‒67). Median PFS was 2.5 months (95% CI, 1.8‒4.2). Median OS was 5.9 months (95% CI, 2.6‒8.7). 28 patients (90%) had treatment-related AEs, including 13 patients (42%) with grade 3‒5 AEs. 1 patient had a treatment-related AE that led to death (hemorrhage). 8 patients (26%) had immune-mediated AEs: hypothyroidism (n = 5), hyperthyroidism (n = 2), and pneumonitis (n = 1). There were no infusion-related reactions. Conclusions: In patients with advanced gastric cancer who received 2 prior lines of therapy, lenvatinib plus pembrolizumab demonstrated promising antitumor activity and a manageable safety profile. Based on these data, enrollment in the gastric cancer cohort has been expanded to 100 patients. Clinical trial information: NCT03797326