Background: Ramucirumab, a humanized monoclonal antibody targeting VEGFR2, is used for treatment of metastatic gastroesophageal adenocarcinoma after disease progression on first-line chemotherapy. Superior survival outcome is expected when combined with paclitaxel. However, many patients suffer from chemotherapy-induced peripheral neuropathy after oxaliplatin-containing first-line treatment and are unable to tolerate paclitaxel. Irinotecan has shown survival benefit as a single agent or in combination with other agents for treating gastroesophageal cancer, but has not been evaluated with ramucirumab. We hypothesized that the combination regimen of irinotecan and ramucirumab administered as second-line treatment for advanced gastroesophageal adenocarcinoma will be better tolerated than ramucirumab and paclitaxel with similar clinical efficacy. Methods: The primary objective of this multi-institutional, single-arm phase 2 clinical trial is to determine the progression-free survival (PFS) after disease progression on up to one line of cytotoxic chemotherapy. Secondary objectives include objective response rate, overall survival, time to progression, and clinical benefit; and to evaluate toxicity and tolerability. Patient-derived xenograft and organoid models generated in a subgroup of patients. Investigation of blood-based angiome profiling and cell-free DNA are planned. Patients received 8 mg/kg ramucirumab with 180 mg/m² irinotecan IV every 14 days. A sample of 40 achieves 85.7% power at a one-sided significance level of 5% to detect a median PFS of 4 months compared to historic control of 2.5 months assuming the accrual time of 12 months and additional follow-up of 12 months and using a one-sample log rank test. NCT03141034. Results: Forty patients were enrolled from four institutions from December 2017 through May 2021. All patients received platinum-based chemotherapy prior to enrollment, 8 patients had HER2 positive disease, and 6 patients had received an immune checkpoint inhibitor. As of September 2021, median follow up time was 7.7 months. Median PFS was 4.6 months (95% CI 2.7 – 5.4). Of 31 patients evaluable for response, 9 patients (29%) had objective responses (1 complete response, 8 partial responses) and 5 patients (16%) had stable disease greater than 6 months. Diarrhea, nausea, vomiting, and neutropenia were common adverse events; no G3/4 neuropathy was reported. Patient-derived organoid and xenograft models were generated from 9 patient samples, treated in vitro to correlate with each patient’s disease response. Conclusions: Ramucirumab and irinotecan appears to be effective and well-tolerated in patients with previously treated gastroesophageal adenocarcinoma. This regimen is now part of standard guidelines and could be a preferred option for patients after disease progression on first-line chemotherapy. Clinical trial information: NCT03141034.