DDEL-16. MICROMESH FOR REVAMPING THE ‘COLD’ TUMOR MICROENVIRONMENT IN GLIOBLASTOMA IMMUNOTHERAPY

Abstract

Abstract High-grade gliomas have poor prognoses with limited treatment options, typically maximal safe resection and adjuvant radiochemotherapy. Novel therapies often face challenges due to low brain penetrance and poor bioavailability. To address these issues, a conformable, compartmentalized polymeric implant called microMESH has been developed. microMESH provides localized, sustained release of drugs, small inhibitors, antibodies, and nanomedicines, enabling novel therapeutic combinations. When applied to the tumor margins, microMESH adheres to the tissue, releasing its therapeutic cargo over weeks and reducing systemic toxicity. Its biocompatibility, cytotoxicity, and anti-tumor efficacy were tested on murine cancer cells (CT-2A) and orthotopic glioblastoma syngeneic models. Exposing primary bone marrow-derived monocytes (BMDM) to CT-2A conditioned medium increased the expression of anti-inflammatory cytokines (IL-10 and IL-4) by 2 times without significantly affecting the pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), indicating that CT-2A cells tend to establish an immunosuppressive ‘cold’ tumor microenvironment. Next, the co-incubation of CT-2A cells with BMDM followed by the administration of the immune checkpoint inhibitor aCD47 resulted in a cancer cell viability drop by 50% already at 50 μg/ml aCD47 after 1 day. Additionally, pre-treatment with docetaxel (DTXL) further decreased cell viability, suggesting a synergism between aCD47 and the chemotherapeutic drug. Flow cytometry showed that 50 nM DTXL at 3 days post-incubation was responsible for a strong translocation of the ‘immunogenic dell death’ protein calreticulin on the cell membrane, potentially explaining the synergism. Over 2 months, the intracranially deployed microMESH biodegraded without inducing any toxic effect. In orthotopic CT-2A tumors, aCD47/DTXL–microMESH (0.75 mg/kg, single intracranial application) showed a 40-day survival compared to 22 days for iv DTXL (3 mg/kg qod), 24 days for ip aCD47 (5 mg/kg qod), and 18 days for untreated mice. microMESH helped identify and enabled novel combination therapies directly at the tumor bed, demonstrating superior efficacy over systemic therapies.