235 IL-4/13 Blocking Peptide (KROS-401) Inhibits M2 Macrophage Polarization in vitro and Demonstrates Anti-tumor Activity in a Murine Model of Glioblastoma

INTRODUCTION: Glioblastoma (GBM) is the most aggressive primary brain malignancy with a median survival of 14 months. Tumor-associated macrophages (TAMs) comprise up to 40% of the GBM tumor mass and are significant enablers of an immunosuppressive tumor microenvironment (TME), limiting immunotherapeutic efficacy. TAMs are generally classified as M2 macrophages that demonstrate a pro-tumor phenotype and increased CD206 surface marker expression. Reducing the M2 macrophage population in tumors has shown benefit in preclinical studies across various cancers. Interleukins (IL)-4 and -13 both play a role in polarizing macrophages to an M2 state. We developed a peptide inhibitor (KROS-401) that targets the shared IL-4Ra subunit of the IL-4 and -13 receptor complex to inhibit macrophage polarization to an M2 phenotype and reprogram the immunosuppressive TME. METHODS: Human peripheral blood mononuclear cell (PBMC)-derived macrophages were isolated and treated with KROS-401 in the presence of IL-4 and IL-13 cytokines. M2 (CD206) surface markers were assessed by flow cytometry. The efficacy of KROS-401 peptide was examined using an intracranially implanted syngeneic murine model with luciferase-expressing GL261, a glioma cell line. Mice were inspected daily for survival and tumor growth was tracked by non-invasive in vivo bioluminescent imaging (BLI). RESULTS: Human PBMC-derived macrophages treated with KROS-401 displayed a dose-dependent decrease in M2 (CD206) cell surface markers. KROS-401 peptide inhibitor demonstrated anti-tumor activity in GL261 glioma-bearing mice with a significantly increased probability of survival compared to control (p = 0.0046) with a median survival of >40 days versus 27 days, respectively. CONCLUSIONS: KROS-401 inhibits M2 polarization of human macrophages in vitro and tumor growth in vivo. These findings highlight this IL-4/IL-13 peptide inhibitor as a potential immunomodulator of the TME for the treatment of GBM.