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Updated: Jun 5, 2026
Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
Published on: July 26, 2017
Mechanistically probing lipid-siRNA nanoparticle-associated toxicities identifies Jak inhibitors effective in
Weikang Tao1, Xianzhi Mao, Joseph P Davide
1Department of RNA Therapeutics, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. weikang_tao@merck.com
Abstract:
A major hurdle for harnessing small interfering RNA (siRNA) for therapeutic application is an effective and safe delivery of siRNA to target tissues and cells via systemic administration. While lipid nanoparticles (LNPs) composed of a cationic lipid, poly-(ethylene glycol) lipid and cholesterol, are effective in delivering siRNA to hepatocytes via systemic administration, they may induce multi-faceted toxicities in a dose-dependent manner, independently of target silencing. To understand the underlying mechanism of toxicities, pharmacological probes including anti-inflammation drugs and specific inhibitors blocking different pathways of innate immunity were evaluated for their abilities to mitigate LNP-siRNA-induced toxicities in rodents. Three categories of rescue effects were observed: (i) pretreatment with a Janus kinase (Jak) inhibitor or dexamethasone abrogated LNP-siRNA-mediated lethality and toxicities including cytokine induction, organ impairments, thrombocytopenia and coagulopathy without affecting siRNA-mediated gene silencing; (ii) inhibitors of PI3K, mammalian target of rapamycin (mTOR), p38 and IκB kinase (IKK)1/2 exhibited a partial alleviative effect; (iii) FK506 and etoricoxib displayed no protection. Furthermore, knockout of Jak3, tumor necrosis factor receptors (Tnfr)p55/p75, interleukin 6 (IL-6) or interferon (IFN)-γ alone was insufficient to alleviate LNP-siRNA-associated toxicities in mice. These indicate that activation of innate immune response is a primary trigger of systemic toxicities and that multiple innate immune pathways and cytokines can mediate toxic responses. Jak inhibitors are effective in mitigating LNP-siRNA-induced toxicities.
Insights
Lipid nanoparticles (LNPs) deliver small interfering RNA (siRNA) but cause toxicities. Janus kinase (Jak) inhibitors effectively reduce LNP-siRNA toxicity without impacting gene silencing, offering a potential safety improvement.
Area of Science:
- Biomedical Science
- Pharmacology
- Immunology
Background:
- Systemic delivery of small interfering RNA (siRNA) therapeutics is challenging due to toxicity concerns associated with delivery vehicles like lipid nanoparticles (LNPs).
- LNPs, while effective for hepatocyte delivery, can induce dose-dependent toxicities independent of their therapeutic silencing effect.
Purpose of the Study:
- To investigate the mechanisms underlying LNP-siRNA-induced toxicities.
- To identify pharmacological interventions that can mitigate these adverse effects without compromising siRNA efficacy.
Main Methods:
- Evaluation of various pharmacological probes, including anti-inflammatory drugs and innate immunity pathway inhibitors, in rodent models.
- Assessment of the impact of these interventions on LNP-siRNA-mediated lethality, cytokine induction, organ damage, and hematological parameters.
- Analysis of gene silencing efficacy to ensure therapeutic activity was preserved.
Main Results:
- Janus kinase (Jak) inhibitors and dexamethasone completely abrogated LNP-siRNA toxicities, including lethality and organ impairment, without affecting gene silencing.
- Inhibitors of PI3K, mTOR, p38, and IKK1/2 provided partial protection.
- Genetic knockout of key immune mediators like Jak3, TNFR, IL-6, or IFN-γ alone did not alleviate the observed toxicities, suggesting a complex interplay of immune pathways.
Conclusions:
- Activation of the innate immune response is a primary driver of systemic LNP-siRNA toxicity.
- Multiple innate immune pathways and cytokines contribute to these toxic responses.
- Jak inhibitors represent a promising strategy for mitigating LNP-siRNA-induced toxicities, enhancing their therapeutic safety profile.
