OC 53.4 - An siRNA gene therapy to modulate circulating plasminogen activator inhibitor 1

Background: Plasminogen activator inhibitor-1 (PAI-1) plays a role in many pathologies including thrombosis, diet-induced obesity, and age-associated diseases such as diabetes, cancer, and Alzheimer’s disease. Circulating PAI-1 levels are significantly high in these diseases as PAI-1 has a crucial role in fibrinolysis, in the metabolic syndrome and in cell aging. Decreasing circulating PAI-1 levels has both experimental and therapeutic value, although no clinically relevant approach is available to inhibit or knockdown PAI-1 long-term. RNA gene therapy is a strategy to regulate the levels of target proteins that are not amenable to traditional small-molecule or protein-based therapies.

Aims: To develop an siRNA- lipid nanoparticle (LNP) agent which knocks down PAI-1 in the liver to modulate its circulating levels long-term.

Methods: Encapsulating siRNA agents in LNPs allows delivery to the liver with the advantage of being long-acting and highly specific for its target. We first identified siRNA sequences targeting mouse PAI-1 mRNA in silico and then tested them in vivo. Knockdown was analyzed based on plasma antigen and mRNA expression levels in the liver.

Results: A dose of siRNA-LNP resulted in a 90% knockdown of PAI-1 plasma protein, starting from 3 days post-administration and lasting 14 days. Liver PAI-1 mRNA expression was found to be >10-times greater in diet-induced obese mice compared to healthy mice. Liver PAI-1 mRNA expression was exponentially correlated with mouse body weight. A dose of siRNA-LNP in obese mice resulted in a 70% knockdown in PAI-1 plasma protein 7 days post-administration.

Conclusion(s): A single injection of siRNA encapsulated in LNPs can potently knockdown PAI-1 in plasma for multiple weeks. The therapeutic potential of this agent in PAI-1 associated diseases will be assessed which may provide a tool to reduce the risk of morbidity and mortality.