C13 - Design and synthesis of itaconate polyesters enables metabolite delivery via microparticles that drive anti-inflammatory outcomes

Introduction: : Inflammatory autoimmune diseases occur when the immune system mistakenly attacks healthy tissues, leading to severe and debilitating outcomes. Existing therapies are non-curative and require life-long treatment, emphasizing the need for new treatments that target novel pathways to achieve potent efficacy. One emerging strategy for controlling inflammation is altering immune cell function using metabolites. Itaconate (ITA) – a derivative of a tricarboxylic acid cycle intermediate – has been shown to exert anti-inflammatory effects in several models of autoimmunity. However, efficacy is dependent on systemic, daily, high dose treatments due to ITA’s poor membrane permeability. While encapsulation in polymer matrices could overcome barriers to uptake, effective loading of ITA is further hindered by low molecular weight and hydrophilicity. Here, we synthesized ITA-based polymers to enable particle assembly entirely from polymeric ITA. This work advances a biomaterials-based strategy to deliver ITA directly to the intracellular compartment of innate cells, overcoming hurdles to metabolite delivery and expanding opportunities for disease intervention.

Materials and

Methods: : ITA polyesters were synthesized from itaconic acid and diols in a 1:1 ratio with a tin(II) octoate catalyst at 130°C. Microparticles (MPs) were assembled from ITA polyesters by the single emulsion synthesis method and characterized using scanning electron microscopy (SEM) (morphology), laser diffraction analysis (size), and electrophoretic light scattering (zeta potential). Microscopy and flow cytometry were used to evaluate MP uptake, cell viability, and inflammatory cytokine production by bone marrow-derived dendritic cells (BMDCs). Co-cultures were employed to assay effects of ITA MP treatment on T cell polarization.

Results, Conclusions, and Discussions:: ITA polyester synthesis generated a high molecular weight polymer with ITA repeat units that facilitated successful generation of MPs entirely from polymerized ITA. MPs measured ~3um in size, exhibited distinct morphologies (Fig. 1A), and were readily engulfed by BMDCs (Fig. 1B) without cytotoxic effects. Importantly, MP treatment reduced IL-6 secretion (Fig. 1C) – an inflammatory driver of autoimmunity; this effect was not observed with dose-matched, soluble ITA. These data support our hypothesis that ITA MPs enhance metabolite transport to the intracellular compartment of cells. Of note, ITA MPs also inhibited polarization of inflammatory (TH17) and promoted regulatory T cells (Tregs) (Fig. 1D). Thus, in addition to modulating innate signaling, ITA MPs could further direct adaptive immunity for treatment of autoimmune diseases.

ITA’s unique role in controlling inflammation through metabo-regulatory, transcriptional, and post-translational mechanisms make it an attractive candidate for tackling autoimmunity. This work presents a novel strategy for ITA-based therapies with the potential to overcome limitations of soluble treatment that require high and frequent dosing due to poor uptake by immune cells. Ongoing studies are examining if hydrolytically-driven controlled release of ITA can be further achieved by tuning the molecular weight of polyesters to modulate cytokine secretion over distinct time scales. Additional work will test therapeutic efficacy of ITA MPs in models of autoimmunity.

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