A functional lyoprotectant platform enables storage-stable, mucus-penetrating siRNA delivery to the lung.

Respiratory diseases remain a major global health concern, where pathological mucus accumulation and chronic inflammation severely compromise lung function. RNA therapeutics have emerged as a transformative modality to address underlying molecular pathologies beyond the capabilities of small-molecule drugs. However, effective delivery of RNA therapeutics to the lungs remains hindered by significant challenges. The instability of lipid nanoparticles (LNPs) in liquid formulations compromises their storage and cold-chain transport, while the pathological mucus hypersecretion characteristic of chronic airway diseases impedes nanoparticle penetration and delivery efficacy. Herein, we propose a functional lyoprotectant strategy that bridges formulation stability and biological functionality within a single design. Specifically, N-acetylcysteine (NAC), a clinically used mucolytic, was incorporated into a sucrose-based lyoprotectant matrix as a functional additive, enabling lyophilization while introducing mucus-modulating capability. The lyophilized LNPs preserved physicochemical integrity, maintained siRNA encapsulation, and achieved efficient mucus penetration and gene silencing in vitro and in vivo. In murine models of mucus-hypersecretory lung disease, a single-dose administration achieved enhanced therapeutic outcomes through a sequential and dual-action complementary mechanism, including extracellular NAC-mediated mucolysis and intracellular RNAi-mediated inflammation suppression. This work pioneers the concept of a functional lyoprotectant, offering a generalizable platform for storage-stable and biologically active inhaled RNA therapeutics.