Abstract 2172: Tumor IL1RAP levels and reduction in serum biomarkers correlate with response in PDAC patients treated with nadunolimab, an anti-IL1RAP monoclonal antibody, in combination with gemcitabine and nab-paclitaxel

Background: Interleukin-1 Receptor Accessory Protein (IL1RAP) is expressed on cancer and stromal cells in pancreatic ductal adenocarcinoma (PDAC), and high tumor IL1RAP RNA expression is a negative prognostic marker1. Dimerization between IL1RAP and the IL-1 receptor is required for IL-1 signaling, and the IL-1 axis has been implicated in the tumor microenvironment and immune response to PDAC. Nadunolimab (CAN04), a fully humanized ADCC-enhanced IgG1 anti-IL1RAP antibody, blocks IL-1α and IL-1β signaling. Preliminary efficacy from the clinical phase 1/2a trial CANFOUR, where PDAC patients (n=73) received nadunolimab with gemcitabine and nab-paclitaxel (GN), show median iPFS of 7.2 months (iRECIST; 95% CI 5.2-8.5), median OS of 12.7 months (10.0-19.1) with 59% of patients alive, and 1-year survival of 57%2. Methods: Patients with previously untreated, locally advanced or metastatic PDAC received nadunolimab at doses from 1 to 7.5 mg/kg, in combination with GN. The exploratory objective was to measure serum and tumor biomarkers related to treatment outcome. Pre-treatment tumor biopsies were assessed for IL1RAP expression by immunohistochemistry. Serum from all patients was analyzed for biomarkers by Meso Scale Discovery (MSD) and Olink. Results: IL1RAP was expressed on tumor and stromal cells in all biopsies analysed and IL1RAP-positive infiltrating immune cells were detected in biopsies from 94% of patients (n=38). The level of IL1RAP on tumor cells was associated with response (PR vs SD and PD; p=0.082). Patients with PR had a median IL1RAP H-score of 200, while patients with SD or PD as best response had a median H-score of 110. The data suggest a relationship between high IL1RAP expression and increased iPFS and OS. Reductions in serum biomarkers downstream of IL-1, detected by MSD, were also associated with response. Patients with the largest treatment-related decreases in IL-6 displayed a prolonged iPFS (p