The Niemann-Pick C1 inhibitor NP3.47 enhances gene silencing potency of lipid nanoparticles containing siRNA

Haitang Wang, Yuen Yi C. Tam, Sam Chen, Josh Zaifman, Roy van der Meel, Marco A. Ciufolini, Pieter R. Cullis

Research output: Contribution to journalArticleAcademicpeer-review

32 Citations (SciVal)


The therapeutic applications of lipid nanoparticle (LNP) formulations of small interfering RNA (siRNA), are hampered by inefficient delivery of encapsulated siRNA to the cytoplasm following endocytosis. Recent work has shown that up to 70% of endocytosed LNP-siRNA particles are recycled to the extracellular medium and thus cannot contribute to gene silencing. Niemann-Pick type C1 (NPC1) is a late endosomal/lysosomal membrane protein required for efficient extracellular recycling of endosomal contents. Here we assess the influence of NP3.47, a putative small molecule inhibitor of NPC1, on the gene silencing potency of LNP-siRNA systems in vitro. Intracellular uptake and colocalization studies revealed that the presence of NP3.47 caused threefold or higher increases in accumulation of LNP-siRNA in late endosomes/lysosomes as compared with controls in a variety of cell lines. The gene silencing potency of LNP siRNA was enhanced up to fourfold in the presence of NP3.47. Mechanisms of action studies are consistent with the proposal that NP3.47 acts to inhibit NPC1. Our findings suggest that the pharmacological inhibition of NPC1 is an attractive strategy to enhance the therapeutic efficacy of LNP-siRNA by trapping LNP-siRNA in late endosomes, thereby increasing opportunities for endosomal escape.

Original languageEnglish
Pages (from-to)2100-2108
Number of pages9
JournalMolecular Therapy
Issue number12
Publication statusPublished - Dec 2016
Externally publishedYes


  • Animals
  • Carrier Proteins/antagonists & inhibitors
  • Cell Line, Tumor
  • Drug Synergism
  • Endosomes/chemistry
  • Gene Silencing
  • HeLa Cells
  • Humans
  • Lipids/chemistry
  • Membrane Glycoproteins/antagonists & inhibitors
  • Mice
  • NIH 3T3 Cells
  • Nanoparticles/chemistry
  • Proteins/antagonists & inhibitors
  • RAW 264.7 Cells
  • RNA, Small Interfering/pharmacology
  • Small Molecule Libraries/pharmacology


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