Long-Acting RNAi Therapy for Atherosclerosis and Insulin Resistance

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ABSTRACT With the ability to silence individual genes and to drug the ‘undruggable’, RNA interference (RNAi) therapy has recently shown clinical success by delivering small interfering RNA (siRNA) to the liver for genetic diseases. However, new delivery strategies will be needed to expand the targeting possibilities of siRNA therapy beyond the liver for treatment of other diseases like atherosclerotic cardiovascular disease. We have therefore formed a team with complementary expertise in siRNA delivery and atherosclerosis, and developed a targeted siRNA delivery strategy to silence calcium/calmodulin-dependent kinase-IIγ (CaMKIIγ), a kinase that is activated in the macrophages of human and mouse advanced atherosclerotic lesions and promotes progression of clinically dangerous plaques. We showed that targeted siCamk2g treatment improved plaque stability by reducing necrotic core area and increasing fibrous cap thickness. Nevertheless, due to the transient nature of siRNA-mediated gene silencing, a critical challenge for siRNA therapy is the short duration of action. In this project, we propose to i) explore a novel siRNA delivery strategy that can dramatically extend the duration of CaMKIIγ silencing in atherosclerotic lesional macrophages; and ii) engineer the new siCamk2g platform for dual-cell targeting for integrated treatment of obesity-induced type 2 diabetes and atherosclerosis. Our new preliminary work has identified a distinct type of synthetic lipid-poly(ethylene glycol) (lipid-PEG) biomaterials that can markedly prolong siRNA silencing and its blood circulation. We thus hypothesize that the new lipid-PEG-mediated long-acting siCamk2g therapy could effectively target both atherosclerosis and insulin resistance with low dosing frequency. In Aim 1, we will synthesize a series of such distinct lipid-PEG biomaterials; systematically explore the lipid-PEG effects on the duration of action and pharmacokinetics of siRNA; and optimize the unique siRNA delivery platform in a mouse model with established atherosclerosis. The lead candidate with longest duration of macrophage CaMKIIγ silencing will be evaluated for efficacy in dampening atherosclerosis, with an emphasis on plaque necrosis, fibrous cap thickness, and efferocytosis and other inflammation resolution endpoints. In Aim 2, we will expand the long-acting siRNA therapy to dual-cell targeting for cardiometabolic disease, based upon the fact that CaMKIIγ is a common upstream target in both hepatocytes in obesity-induced insulin resistance and lesional macrophages in atherosclerosis. We will iteratively optimize the dual-targeting siCamk2g system in vitro and in vivo, including in a new mouse model with combined insulin resistance and atherosclerosis, in a manner to effectively improve type 2 diabetes and suppress atherosclerosis. We expect that successful completion of this project will lead to fundamental understanding of how the new lipid-PEG chemistry controls siRNA delivery and the development of a novel class of long-acting RNAi therapy for atherosclerosis and cardiometabolic disease.