Reprogramming of macrophages into the inflammatory state (also known as M1) is currently considered as an effective way of eliminating cancer cells, but systemic deployment of this strategy is likely to induce dangerous autoimmune reactions. Consequently, converting immunosuppressive M2-type macrophages into M1 systemically is not a safe and effective therapeutic approach against cancer. Through cleavable covalent linking of curcumin to the chemotherapeutic agent Paclitaxel (Taxol), we have created a novel prodrug (STO-1) that, upon intravenous delivery, selectively reprograms tumor-associated microglia and macrophages (TAMs) and eliminates glioblastoma (GBM) without triggering autoimmunity. Demonstrating its therapeutic efficacy, prolonged treatment of six orthotopic GBM-bearing mice with STO-1 resulted in 67% long-term survival, with three surviving mice exhibiting complete tumor clearance and one displaying minimal residual disease, as confirmed by high-resolution ex vivo T2-weighted MRI 85 days after tumor inoculation. In contrast, the vehicle-treated mice displayed extensive intracranial tumors with edema and hemorrhage. Mechanistically, scRNA-seq analysis indicated induction of multiple M1-associated transcripts (ccrl2, cxcl9, ccr2, ccl5) consistent with robust TAMs reprogramming. In striking contrast to the M2⟶M1 reprogramming of TAMs, M1-type macrophages were suppressed in the spleens of STO-1-treated cancer-free mice. Therefore, STO-1 induces selective anti-tumor immunity and GBM elimination without triggering systemic autoimmune reactions.

Reprogramming of macrophages into the inflammatory state (also known as M1) is currently considered as an effective way of eliminating cancer cells, but, systemic deployment of this strategy is likely to induce dangerous autoimmune reactions. Consequently, converting immunosuppressive M2-type macrophages into M1 systemically is not a safe and effective therapeutic approach against cancer. Through cleavable covalent linking of curcumin to the chemotherapeutic agent Paclitaxel (Taxol), we have created a novel prodrug (STO-1) that, upon intravenous delivery, selectively reprograms tumor-associated microglia and macrophages (TAMs) and eliminates glioblastoma (GBM) without triggering autoimmunity. Demonstrating its therapeutic efficacy, prolonged treatment of six orthotopic GBM-bearing mice with STO-1 resulted in 67% long-term survival, with three surviving mice exhibiting complete tumor clearance and one displaying minimal residual disease, as confirmed by high-resolution ex vivo T2-weighted MRI 85 days after tumor inoculation. In contrast, the vehicle-treated mice displayed extensive intracranial tumors with edema and hemorrhage. Mechanistically, scRNA-seq analysis indicated induction of multiple M1-associated transcripts (ccrl2, cxcl9, ccr2, ccl5) consistent with robust TAMs reprogramming. In striking contrast to the M2M1 reprogramming of TAMs, M1-type macrophages were suppressed in the spleens of STO-1-treated cancer-free mice. Therefore, STO-1 induces selective anti-tumor immunity and GBM elimination without triggering systemic autoimmune reactions.

APG157DS is a multi-component investigational drug which is currently the subject of multiple cancer trials. It has shown promising efficacy in patients with head and neck cancer. We report its immuno-modulatory effect in a syngeneic mouse model of glioblastoma (GBM). Long-term treatment with APG157DS led to durable tumor remission in 50% of mice, while all vehicle-treated mice reached humane endpoints within 42 days. Mechanistically, the drug induced selective repolarization of tumor-associated macrophages (TAMs) from an immunosuppressive Arg1^high/iNOS^low phenotype to a tumoricidal Arg1^low/iNOS^high state, accompanied by increased intratumoral recruitment of activated (NKp46+) natural killer cells and CD8+ cytotoxic T-cells. APG157DS also suppressed vascular endothelial growth factor (VEGF) and Hypoxia-inducible factor 1-alpha (HIF-1α) expression in tumors, further impairing tumor growth. Notably, APG157DS did not elicit off-target macrophage activation in peripheral tissues such as the spleen, highlighting its selective immune targeting. These findings provide a mechanistic rationale for further clinical development of APG157DS in GBM and potentially other immune-evasive cancers.