(719b) Metabolite Delivery to Antigen-Presenting Cells Using Targeted Layer-By-Layer Nanoparticles for Immunomodulatory Cancer Therapy

Immunotherapy offers an alternative approach to prime a patient’s immune system to attack cancer cells and develop long-lived immune memory. However, immunosuppressive—or “cold”—tumor environments limit the efficacy of promising immunotherapies such as immune checkpoint blockade, so alternative strategies are needed to transform the tumors to an inflamed, immune-infiltrated phenotype. Nanoparticles that facilitate the targeted delivery of potent immune modulating agents to specific immune cells in the tumor or lymphoid tissues have the potential to address this need and improve disease outcomes.

In a collaboration with the labs of Timothy Padera, PhD (MGH) and Matthew Vander Heiden, MD, PhD (MIT/KI), we have identified that the metabolite L-arginine plays a critical role in supporting DC function but is depleted in tumor-draining lymph nodes (tdLNs). Arginine deprivation results in reduced DC metabolism, antigen processing and presentation, and expression of costimulatory molecules when DCs are stimulated, hereby showing impaired immune response. We hypothesized that delivery of arginine specifically to DCs in the tdLN would enhance their function, resulting in improved T cell priming and more robust anti-cancer response to immunotherapies.

The modular nature of Layer-by-Layer NPs enables us to separately optimize the targeting and trafficking of the NPs—by modulating the outer layer for cell targeting and the stiffness of the core to promote NP internalization—as well as the loading of a variety of therapeutic agents. In this work, we determine physiochemical properties—specifically, surface chemistry and core composition—that facilitate NP delivery to antigen-presenting cells (APCs). We apply these optimized properties to develop an APC-directed therapeutic NPs encapsulating the agonist MPLA and metabolite L-arginine to augment immune cell function to promote anti-cancer immunity.

To identify an APC-targeting NP formulation, LbL NPs formulated with soft and rigid liposomal cores and varying surface chemistries—including polypeptides, synthetic polymers, and native polysaccharides—were screened on APC populations to identify candidates with high NP-cell association. This revealed that dextran sulfate enhanced NP association with APCs and the soft liposomal cores enhanced intracellular accumulation.

We then developed a NP loaded with L-arginine and targeted using the DXS surface chemistry and soft liposomal core to facilitate intracellular delivery. The LbL-Arginine NP had higher association with DCs compared to cancer cells, protected arginine from arginase degradation, and in arginine deprivation conditions it restored intracellular arginine levels of DCs and improved DC activation upon stimulation with LPS. In the 4T1-OVA breast cancer model, we found improved survival response to a cancer vaccine (LPS+OVA) co-administered with LbL-Arginine versus the vehicle control (LbL NP without arginine). In the B16F10-OVA melanoma model, LbL-Arginine increases circulating tumor-reactive T cells and survival upon tumor rechallenge compared to the LbL-vehicle. Given the promising results of incorporating arginine delivery with immunotherapies, we engineered the LbL-arginine NP to contain the adjuvant MPLA for co-delivery of the metabolite arginine and the immune agonist to enhance DC function further. B16F10-OVA mice treated with the LbL-Arginine-MPLA NP showed significantly enhanced survival over the LbL-Vehicle-MPLA NP, highlighting the more robust response with incorporating the adjuvant directly into the NP system.

This work demonstrates the targeted delivery of immunotherapeutic agents using LbL NPs with optimized physiochemical properties can dramatically improve the delivery of immune agonists and metabolites to APCs for a more specific and effective immunotherapeutic treatment strategy.