Strategies for improving the specificity of siRNAs for enhanced therapeutic potential

ABSTRACT

Introduction: RNA interference has become a tool of choice in the development of drugs in various therapeutic areas of Post Transcriptional Gene Silencing (PTGS). The critical element in developing successful RNAi therapeutics lies in designing small interfering RNA (siRNA) using an efficient algorithm satisfying the designing criteria. Further, translation of siRNA from bench-side to bedside needs an efficient delivery system and/or chemical modification.

Areas covered: This review emphasizes the importance of dicer, the criteria for efficient siRNA design, the currently available algorithms and strategies to overcome off-target effects, immune stimulatory effects and endosomal trap.

Expert opinion: Specificity and stability are the primary concerns for siRNA therapeutics. The design criteria and algorithms should be chosen rationally to have a siRNA sequence that binds to the corresponding mRNA as it happens in the Watson and Crick base pairing. However, it must evade a few more hurdles (Endocytosis, Serum stability etc.) to be functional in the cytosol.

KEYWORDS:

• RNA interference
• siRNA
• strategies to overcome off-target effects
• immune stimulatory effects and endosomal trap

Article Highlights

• RNAi is an important mechanism that suppresses the expression of genes at the post-transcriptional level; thus, it is known as Post Transcriptional Gene Silencing (PTGS).

• Small interfering RNA (siRNA) is a tool to specifically target the mRNA of choice to degrade and prevent the translation process.

• Dicer based siRNA is a 25-27 nucleotide long asymmetric double-stranded RNA that degrades specific mRNA to prevent the translation process. Dicer based siRNA’s are cleaved to 21nt double-stranded RNA, which are then recognized and incorporated by the RNA Induced Silencing Complex (RISC) for the final degradation of the target mRNA. Recent studies have shown that Dicer based siRNAs are more potent than conventional synthetic siRNAs.

• The success of silencing depends on many factors including the design of siRNA, delivery approach, target cells and concentration of the siRNA, etc.

• Suitable siRNA delivery approaches need to be considered for efficient knockdown of the target gene through downregulation and improvement of the stability and half-life of the delivered siRNA.

This box summarizes key points contained in the article.

Acknowledgments

The authors acknowledge authorities from the Manipal Academy of High Education (MAHE) and Manipal Universal Press, Manipal, India for their language editing assistance.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

The authors gratefully were supported by the Nano Mission Council of the Department of Science and Technology, the Govt. of India, New Delhi (SR/NM/NS-1090/2012 (G)).