Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8⁺ T and NK cells, with minimal expansion of regulatory T cells. Inherently active, nemvaleukin neither requires metabolic/proteolytic conversion nor degrades into native IL-2. Preclinical characterization confirmed receptor selectivity and antitumor activity of nemvaleukin alone and with checkpoint inhibitors (CPIs) and informed dose selection for the first-in-human study ARTISTRY-1; other combination regimens are ongoing evaluation. In ARTISTRY-1, responses with nemvaleukin in combination with pembrolizumab were observed in a variety of tumors, including GI. In addition to the clinical outcomes of these patients (pts), we describe preclinical evaluation of nemvaleukin with tyrosine kinase inhibitors (TKIs)—a drug class indicated for some GI cancers. Methods: Pts with GI cancers who had progressed on prior therapy were enrolled into cohorts of mixed tumor types in ARTISTRY-1 (NCT02799095) and received IV nemvaleukin (3 µg/kg) and pembrolizumab (200 mg). Outcomes presented include antitumor activity and safety as of August 2021. Combinations of nemvaleukin with TKIs were evaluated in mouse tumor models, including colorectal adenocarcinoma (MC38). Results: Clinically, 26 pts with GI cancer (colon/colorectal, n = 14; esophageal, n = 5; hepatocellular, n = 3; pancreatic, n = 3; gastric, n = 1) received nemvaleukin + pembrolizumab (median 3 cycles [range: 1-24]). Median age was 55 y (range: 26-82), ECOG performance status was 0 (n = 6) or 1 (n = 20), and median prior lines of therapy was 3 (range: 1-6). Four pts had a partial response, 2 with esophageal, 1 with MSI-H colorectal, and 1 with pancreatic cancer, with target lesion decreases of 37% to 63%. Six pts had stable disease. Two responders remain on treatment (> 36 and > 80 wks for colorectal and esophageal cancer, respectively). Frequent (> 25%) nemvaleukin-related adverse events (AEs) among all pts receiving nemvaleukin combination (n = 156) were chills (58%), pyrexia (53%), nausea (29%), and fatigue (29%). Grade ≥3 nemvaleukin-related AEs (≥8%) were reported in 48%, including anemia (12%), neutrophil count decreased (10%), and neutropenia (8%). In mice, the combination of the mouse ortholog of nemvaleukin with VEGF TKIs showed improved antitumor activity and survival, along with increased immune activation and angiogenesis blockade in the tumor microenvironment compared with any compound alone. Conclusions: Emerging clinical data show responses in GI tumors may be achieved with nemvaleukin/pembrolizumab with manageable safety. Preclinical evidence of antitumor activity of nemvaleukin with CPIs or TKIs warrants further exploration of nemvaleukin in new combinations for pts with GI cancers. Clinical trial information: NCT02799095.