Intratracheal administration: Non-invasive approach for liver-targeted siRNA-LNP delivery

Small interfering RNA (siRNA) has demonstrated significant success in treating hepatic diseases through intravenous (<em>i.v.</em>) or subcutaneous (<em>s.c.</em>) injection. In this study, we reported that siRNA encapsulated in lipid nanoparticles (termed RBP131) can effectively achieve gene silencing in the liver via the non-invasive intratracheal (<em>i.t.</em>) administration. Following a single <em>i.t.</em> dose, Apolipoprotein B (ApoB) gene silencing can be sustained for over three weeks, with a remarkably low ED₅₀ of 0.13 mg/kg. Multiple doses of 0.5 mg/kg administered twice a week can maintain long-term knockdown efficiency of around 90%. Further, in a hepatitis B virus (HBV) transgenic mouse model, significant x gene silencing (over 80%) was observed with treatment of 1 mg/kg siHBV-RBP131 formulation, comparable to the efficacy achieved through i.v. injection. Importantly, toxicity analysis indicated that the siRNA-RBP131 formulation was well tolerated in mice, even at a high dose of 10 mg/kg (over 70-times higher than ED₅₀). These findings open a new avenue for delivering siRNA-LNPs to the liver in a noninvasive strategy, providing a more patient-friendly approach that can be more easily translated into clinical practice.