Abstract 142: Efferocytosis-stimulating Nanoparticles for Precision Atherosclerosis Therapy

Background: Our group recently established that the upregulation of the “don’t eat me” molecule, termed CD47, is a fundamental driver of the accumulation of diseased cells in the atherosclerotic plaque. This phenomenon renders vascular cells resistant to efferocytosis (programmed cell removal) and promotes lesion expansion. CD47-blocking antibodies restore this defect and dramatically reduce plaque burden. However, systemic blockade of CD47 is also associated with the off-target elimination of red blood cells, resulting in an anemia that limits the translational potential of systemic pro-efferocytic therapies. This study sought to develop a “precision” therapy which can 1. Reactivate efferocytosis specifically in the vessel wall; and 2. Do so without inducing any off-target toxicity. Methods and Results: Vascular-tropic nanoparticles (NPs) were prepared by loading carbon nanotubes with pro-efferocytic anti-CD47 therapies and a Cy5.5 molecular imaging fluorophore. In vitro cellular uptake and phagocytosis assays demonstrated that the NPs were rapidly taken up by macrophages (but not other vascular or immune cells) and potently stimulate phagocytosis of co-cultured apoptotic cells. To determine whether NPs home to lesional macrophages and specifically reactivate efferocytosis in vivo , angiotensin II-infused apoE -/- mice were treated with plain NPs or NPs conjugated to anti-CD47 therapy (NP-α-CD47). Flow cytometry revealed that the NPs accumulate in the atherosclerotic aortae, with near exclusive uptake by lesional Ly6-C hi monocytes and M1 macrophages (>70% cellular uptake). Compared to plain SWNT controls, NP-α-CD47 had a potent anti-atherosclerotic effect, decreasing lesion area, reducing the percentage of apoptotic debris within the necrotic core, and suppressing SHP-1 phosphorylation (indicating silencing of the anti-phagocytic pathway downstream of CD47). Safety profiling confirmed that NP-α-CD47 did not induce an anemia or significant adverse effects. Conclusions: Leveraging the knowledge that the “don’t eat me” signal CD47 is a novel translational target, these data reveal that precision-targeted nanotherapeutics can specifically and safely normalize efferocytosis in the atherosclerotic plaque.