Preclinical development of siRNA therapeutics: Towards the match between fundamental science and engineered systems

The non-viral delivery of small RNA molecules like siRNAs still poses a major bottleneck for their successful application in vivo. This is particularly true with regard to crossing physiological barriers upon systemic administration. We have previously established polyethylenimine (PEI)-based complexes for therapeutic RNA formulation. These nanoplexes mediate full RNA protection against nucleolytic degradation, delivery to target tissues as well as cellular uptake, intracellular release and therapeutic efficacy in preclinical in vivo models. We herein present data on different polyplex modifications for the defined improvement of physicochemical and biological nanoparticle properties and for targeted delivery. (i) By non-covalent modifications of PEI polyplexes with phospholipid liposomes, ternary complexes ("lipopolyplexes") are obtained that combine the favorable features of PEI and lipid systems. Decreased cytotoxicity and highly efficient delivery of siRNA is achieved. Some lipopolyplexes also allow prolonged storage, thus providing formulations with higher stability. (ii) Novel tyrosine modifications of low molecular weight PEI offer further improvement of stability, biocompatibility, and knockdown efficacy of resulting nanoparticles. (iii) For ligand-mediated uptake, the shielding of surface charges is a critical requirement. This is achieved by PEI grafting with polyethylene glycol (PEG), prior to covalent coupling of anti-HER1 antibodies (Erbitux®) as ligand for targeted delivery and uptake. Beyond tumor cell culture, analyses are extended towards tumor slice cultures from tumor xenograft tissues which reflect more realistically the in vivo situation. The determination of siRNA-mediated knockdown of endogenous target genes, i.e., the oncogenic survival factor survivin and the oncogenic receptor tyrosine kinase HER2, reveals nanoparticle penetration and biological efficacy also under intact tissue and stroma conditions.

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“…insufficient lysosomal release. So far, these issues still pose major hurdles for translating siRNA into the clinic [1,2].…”

Section: Introductionmentioning

confidence: 99%

Optimized polyethylenimine (PEI)-based nanoparticles for siRNA delivery, analyzed in vitro and in an ex vivo tumor tissue slice culture model

Ewe

Höbel

Heine

et al. 2016

Drug Deliv. and Transl. Res.

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“…It was found that chemically synthesized 21-mer RNA duplexes with 2-nt 3′ overhangs at both ends, which directly mimic the products produced by Dicer, efficiently suppressed gene expression in mammalian cells [4,26]. These duplexes, referred to as canonical siRNAs, are widely used in biomedical research [11]. Later, it was found that RNA duplexes, smaller than 30 nt in length but longer than siRNAs, were significantly more efficient than canonical siRNAs and did not induce interferon response in a variety of cell lines [15].…”

Section: Dicer Substrate Interfering Rnasmentioning

confidence: 99%

“…Synthetic small-interfering RNAs have become an advanced and powerful tool for specific gene silencing and could be considered as promising class of therapeutics for the treatment of diseases associated with overexpression of specific genes [10][11][12]. However, therapeutic applications of canonical non-modified siRNAs are limited by their sensitivity to ribonucleases, possibility of unfavorable guide strand selection, and activation of innate immune system by siRNA containing immunostimulatory motives in the sequence, which can lead to poor gene silencing efficiency [13,14].…”

Section: Introductionmentioning

confidence: 99%

Noncanonical Synthetic RNAi Inducers

Gvozdeva¹,

Chernolovskaya²

2016

RNA Interference

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This review focuses on current strategies of development of noncanonical synthetic RNA interference (RNAi) inducers with structural modifications for promoting better gene silencing with low risk of side effects. A particular focus is on longer RNA duplexes 25-30 nucleotides (nt) in length that mimic Dicer substrates to improve interaction of RNAi inducers with RNAi machinery. Various design strategies of efficient Dicer substrate smallinterfering RNA (siRNA) are described. It was found that the length, chemical modifications, and overhang structure influence the gene silencing activity and RNA-induced silencing complex (RISC) assembly. Special attention is paid to the long doublestranded RNA duplexes that induce effective gene silencing in Dicer-dependent or Dicerindependent mode. Some structural variants of shorter siRNAs, including hairpin and dumbbell siRNAs and fork-siRNA (fsiRNA) with several nucleotide substitutions at the 3′ end of the sense strand, are also analyzed. These structural modifications provide efficiently increased gene silencing of targets with unfavorable duplex thermodynamic asymmetry. Recent data remove the length and structure limits for the design of RNAi effectors, and add another example in the list of novel RNAi-inducing molecules differing from the classical siRNA, which is discussed in this chapter.

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“…Concerning nucleic acid delivery towards cancer treatment, work previously done showed that the effective regulation of tumour unregulated protein expression is defi nitely a powerful tool, since theoretically any gene could be elected as a RNAi target, opening up the possibility for biomedical research to truly solve unmet clinical challenges (Videira et al 2013 ;Pecot et al 2011 ;Bader et al 2011 ;Oh and Park 2009 ). More impactful, different tumour stages, from cell differentiation, progression or resistance to tumour-host interaction, could be targeted eliciting a new class of RNAs-based therapeutics (Croce 2009 ).…”

Section: Nanomedicinal Oncological Products Intended For Clinical Pramentioning

confidence: 99%

“…In fact, currently RNAi-based nanomedicines under preclinical and clinical evaluation are mainly based on lipid or polymeric materials (Videira et al 2013 ).…”

Section: Nanomedicinal Oncological Products Intended For Clinical Pramentioning

confidence: 99%

Regulatory Aspects of Oncologicals: Nanosystems Main Challenges

et al. 2014

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Preclinical development of siRNA therapeutics: Towards the match between fundamental science and engineered systems

Cited by 50 publications

References 133 publications

Optimized polyethylenimine (PEI)-based nanoparticles for siRNA delivery, analyzed in vitro and in an ex vivo tumor tissue slice culture model

Optimized polyethylenimine (PEI)-based nanoparticles for siRNA delivery, analyzed in vitro and in an ex vivo tumor tissue slice culture model

Noncanonical Synthetic RNAi Inducers

Regulatory Aspects of Oncologicals: Nanosystems Main Challenges

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