Abstract 2202: The combination of a mouse ortholog of ALKS 4230, a selective agonist of the intermediate affinity IL-2 receptor, and the angiogenesis inhibitor lucitanib enhances antitumor activity

ALKS 4230, an engineered cytokine designed for selective binding to the intermediate affinity interleukin-2 receptor (IL-2R), is being evaluated as a monotherapy and in combination with pembrolizumab in patients with advanced solid tumors. The selectivity of ALKS 4230 is achieved through stable fusion of circularly permuted IL-2 to IL-2Rα, with the goal of driving antitumor responses via selective activation of CD8+ T cells and NK cells, while avoiding activation of regulatory T cells (Tregs), which express the high affinity IL-2R. High levels of vascular endothelial growth factor (VEGF) are associated with an immunosuppressive tumor microenvironment and diminished response to high-dose IL-2. Lucitanib is an anti-angiogenic, multi-tyrosine kinase inhibitor targeting VEGFR1-3, PDGFRα/β, and FGFR1-3. We evaluated the antitumor efficacy and mechanism of the combination of RDB 1462, the mouse ortholog of ALKS 4230, and lucitanib in the MC38 mouse syngeneic tumor model. C57BL/6 mice were subcutaneously implanted with MC38 cells and treated with RDB 1462 (1.5 mg/kg and 3 mg/kg once every 3 days for 3 weeks), lucitanib (10 mg/kg daily for 28 days), or the combination of both molecules. After 11 days of treatment, lucitanib monotherapy resulted in 100% tumor growth inhibition (TGI), while 1.5 mg/kg and 3 mg/kg RDB 1462 monotherapy resulted in 25% and 51% TGI, respectively. Lucitanib monotherapy extended survival, with a mean survival time (MST) of 39 days compared to 15 days for vehicle, with no complete tumor regressions. MSTs were 18-22 days for RDB 1462 monotherapy groups, 60 days for the lower dose combination arm, and >60 days for the higher dose combination. Durable complete tumor regressions were observed in 1/20 mice treated with either dose of RDB 1462 monotherapy and 5/10 mice treated with the lower dose of RDB 1462 in combination with lucitanib. 10/10 mice treated with the higher dose of RDB 1462 in combination with lucitanib exhibited complete responses on Day 60. Flow cytometric analyses revealed that RDB 1462 treatment induced significant peripheral CD8+ T cell expansion compared to vehicle (p