Enhanced intratumoral delivery of immunomodulator MPLA via hyperbranched polyglycerol-coated biodegradable nanoparticles.

Immunomodulatory agents (IMA) have significant potential to enhance cancer treatment but have demonstrated limited efficacy beyond the preclinical setting due to poor pharmacokinetics and toxicity associated with systemic administration. On the other hand, when locally delivered, IMAs require repeated administration to optimize immune stimulation. To overcome these challenges, we encapsulated the toll-like receptor (TLR)4 agonist monophosphoryl lipid A (MPLA) within hyperbranched polyglycerol (HPG)-coated biodegradable nanoparticles (NP) engineered for gradual drug release from the nanoparticle core, resulting in a more persistent stimulation of anti-tumor immune responses while minimizing systemic side effects. In a model of malignant melanoma, we demonstrate that HPG-NP encapsulation significantly improves the antitumor efficacy of MPLA by enhancing its ability to remodel the tumor microenvironment (TME). Compared to free MPLA, HPG-NP-MPLA significantly increased the natural killer cell and cytotoxic T cell mediated antitumor immune response and tuned the tumor draining lymph nodes towards a T helper (Th)1 response. Furthermore, when combined with local delivery of a chemotherapeutic agent, HPG-NP-MPLA induces the conversion of an immunosuppressive TME to immunogenic TME and significantly improves survival.