Nature Communications | New Immunotherapy Strategy for Glioblastoma: Co-delivery of Macrophage Engager mRNA and PD-L1 Antibody via mRNA Nanoparticles

This study presents an innovative nanoplatform design to address delivery challenges and the immunosuppressive microenvironment in glioblastoma immunotherapy, offering significant insights for targeted delivery of mRNA therapeutics and combinatorial immune activation strategies in cancer immunology.

 

Literature Overview

The article titled 'Co-delivering macrophage engager mRNA and PD-L1 antibody via tumor-responsive nanoparticles for glioblastoma immunotherapy,' published in Nature Communications, systematically explores how multifunctional lipid nanoparticles (LNPs) can enable synergistic delivery of mRNA-encoded bispecific macrophage engagers (BiME) and PD-L1 antibodies to overcome blood-brain barrier (BBB) penetration barriers and the immunosuppressive tumor microenvironment in glioblastoma (GBM). The research team developed the PL@mBiME platform, achieving brain tumor targeting, acid-responsive charge reversal, glutathione (GSH)-triggered antibody release, and sustained in vivo BiME expression, significantly enhancing antitumor immune responses.

Background Knowledge

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, with a five-year survival rate of less than 7%. Its treatment faces three major challenges: the blood-brain barrier (BBB) limiting drug delivery, a highly immunosuppressive tumor microenvironment (TME), and insufficient T-cell infiltration. Tumor-associated macrophages (TAMs) constitute 30–50% of immune cells within GBM and predominantly exhibit an M2-like phenotype, promoting immune evasion and tumor progression. Current PD-1/PD-L1 checkpoint inhibitors show limited efficacy in GBM, primarily due to poor BBB penetration and lack of T-cell infiltration in the TME. Therefore, researchers have turned to the innate immune system, particularly reprogramming TAMs into antitumor M1 phenotypes. HER2 (ErbB2) is frequently overexpressed in GBM and represents a potential tumor antigen target. CD206 is a marker receptor for M2-like macrophages, and the RP-182 peptide can bind CD206 and induce M2-to-M1 conversion. Based on this, bispecific macrophage engagers (BiMEs) targeting HER2 and CD206 bridge tumor cells and macrophages, forming a breakthrough strategy. However, BiME proteins have short half-lives, struggle to cross the BBB, and systemic delivery may cause toxicity. mRNA technology enables localized, sustained expression of complex proteins, but efficient delivery to brain tumors remains a major bottleneck. Thus, developing nanocarriers with BBB-penetrating, tumor-responsive, and immune-coactivating capabilities became the focus of this study.

 

 

Research Methods and Experiments

The study employed multiple murine GBM models, including GL261-Luc and CT-2A-Luc syngeneic models, to evaluate the in vivo efficacy of PL@mBiME. Nanoparticles were administered systemically via tail vein injection, with tumor growth dynamically monitored using bioluminescence imaging (BLI) and magnetic resonance imaging (MRI). To assess BBB penetration, an in vitro BBB model was established using bEnd.3 and GL261 co-cultures, and transwell assays were performed using Cy5/Cy7-labeled nanoparticles. In vivo biodistribution was confirmed via near-infrared fluorescence imaging and ex vivo organ analysis. Mechanistic investigations included flow cytometry to analyze phenotypes of tumor-infiltrating immune cells, immunofluorescence staining to evaluate TAM polarization, and ELISA to measure cytokine secretion. To examine immune memory, long-term surviving mice were rechallenged with tumor cells on day 45, and CD8⁺ T-cell responses were monitored.

Key Conclusions and Perspectives

• PL@mBiME achieves charge reversal in the acidic TME (from −8.15 mV at pH 7.4 to +17.65 mV at pH 5.0), enhancing tumor cell uptake and endosomal escape, thereby significantly improving mRNA transfection efficiency. This finding provides clear physicochemical rationale for designing responsive nanocarriers, guiding future drug delivery systems to optimize pKa values to match the weakly acidic TME.
• In the GL261 model, PL@mBiME treatment led to complete tumor regression in 80% of mice, significantly extending survival, with superior efficacy compared to mBiME or aPD-L1 alone. This indicates that coordinated activation of innate and adaptive immunity is crucial, suggesting that future immunotherapies should prioritize multi-mechanistic combination strategies.
• BiME successfully bridges HER2⁺ tumor cells and CD206⁺ macrophages, inducing M2-to-M1 reprogramming, enhancing phagocytosis and antigen presentation. Flow cytometry shows a significant increase in the M1/M2 ratio, along with decreased SIRPα⁺ cells and increased MHCII⁺ cells, demonstrating effective macrophage activation and supporting the rationale of targeting CD206 for reprogramming.
• PL@mBiME selectively releases PD-L1 antibodies within tumors, avoiding systemic exposure and reducing toxicity risk. The GSH-responsive linker releases approximately 50% of the antibody under 4 mM GSH, simulating the tumor microenvironment, suggesting that future antibody-drug conjugates (ADCs) or bifunctional nanomedicines should exploit the reductive TME for precise release.
• Upon rechallenge, long-term surviving mice effectively controlled tumor growth, accompanied by expansion of CD44⁺CD8⁺ T cells and elevated IL-15 levels, indicating that PL@mBiME induces durable immune memory. This finding emphasizes that therapeutic vaccine strategies can be realized through mRNA platforms, advancing personalized immunotherapy toward curative outcomes.

Research Significance and Prospects

This study provides a translational nanoplatform for mRNA-based immunotherapy in GBM, addressing both delivery and immune activation challenges. Its acid-responsive and GSH-triggered release mechanisms can be widely applied to targeted therapies for other solid tumors. Future work may explore different tumor antigen combinations, extend to HER2-low tumors, or combine with CAR-M therapy to further enhance macrophage function.

From a drug development perspective, PL@mBiME demonstrates the synergistic advantages of co-delivering mRNA and antibodies, supporting the development of multifunctional nanomedicines for refractory cancers. Its favorable biocompatibility and lack of significant toxicity lay a safe foundation for clinical translation, potentially advancing mRNA therapies into the field of brain tumor treatment.

 

 

Conclusion

The PL@mBiME nanoplatform developed in this study represents a significant advancement in glioblastoma immunotherapy. By integrating mRNA-encoded bispecific macrophage engagers with PD-L1 antibodies, the system achieves brain-targeted delivery, tumor microenvironment-responsive activation, and immune checkpoint blockade in a synergistic manner. The platform demonstrated potent antitumor efficacy across multiple GBM models, including significantly prolonged survival, induction of complete remission, and establishment of durable immune memory. Mechanistically, PL@mBiME successfully reprograms TAMs toward an M1 phenotype, enhances phagocytosis and antigen presentation, and activates T-cell responses, reshaping the immunosuppressive microenvironment. This strategy not only overcomes the two major clinical hurdles—BBB penetration and immunosuppression—but also exhibits excellent safety, with no significant weight loss or organ toxicity. From bench to bedside, this platform offers new therapeutic hope for GBM patients and provides a replicable paradigm for mRNA-based combination immunotherapy in other refractory solid tumors. Future studies should focus on validation in humanized models and GMP-compliant manufacturing to accelerate clinical translation, potentially establishing this approach as a new cornerstone in comprehensive GBM treatment.

 

Haoge Zhang, Jia Miao, Lin Gao, Yini Zhu, and Jinbing Xie. Co-delivering macrophage engager mRNA and PD-L1 antibody via tumor-responsive nanoparticles for glioblastoma immunotherapy. Nature Communications.