Transcript-Targeted Therapy Based on RNA Interference and Antisense Oligonucleotides: Current Applications and Novel Molecular Targets

Abstract

The development of novel target therapies based on the use of RNA interference (RNAi) and antisense oligonucleotides (ASOs) is growing in an exponential way, challenging the chance for the treatment of the genetic diseases and cancer by hitting selectively targeted RNA in a sequence-dependent manner. Multiple opportunities are taking shape, able to remove defective protein by silencing RNA (e.g., Inclisiran targets mRNA of protein PCSK9, permitting a longer half-life of LDL receptors in heterozygous familial hypercholesteremia), by arresting mRNA translation (i.e., Fomivirsen that binds to UL123-RNA and blocks the translation into IE2 protein in CMV-retinitis), or by reactivating modified functional protein (e.g., Eteplirsen able to restore a functional shorter dystrophin by skipping the exon 51 in Duchenne muscular dystrophy) or a not very functional protein. In this last case, the use of ASOs permits modifying the expression of specific proteins by modulating splicing of specific pre-RNAs (e.g., Nusinersen acts on the splicing of exon 7 in SMN2 mRNA normally not expressed; it is used for spinal muscular atrophy) or by downregulation of transcript levels (e.g., Inotersen acts on the transthryretin mRNA to reduce its expression; it is prescribed for the treatment of hereditary transthyretin amyloidosis) in order to restore the biochemical/physiological condition and ameliorate quality of life. In the era of precision medicine, recently, an experimental splice-modulating antisense oligonucleotide, Milasen, was designed and used to treat an 8-year-old girl affected by a rare, fatal, progressive form of neurodegenerative disease leading to death during adolescence. In this review, we summarize the main transcriptional therapeutic drugs approved to date for the treatment of genetic diseases by principal regulatory government agencies and recent clinical trials aimed at the treatment of cancer. Their mechanism of action, chemical structure, administration, and biomedical performance are predominantly discussed.

Emerging Roles for the RNA-Binding Protein HuD (ELAVL4) in Nervous System Diseases

“…In parallel with these basic studies, we propose that strategies for modulating HuD levels (or activity) should be taken into account for developing new therapeutic approaches for neurodegenerative diseases. In this regard, an interesting opportunity is provided by recent pre-clinical and clinical studies based on the use of artificial oligonucleotides, such as aptamers or antisense oligonucleotides (ASOs) [ 66 , 67 ]. Aptamers are synthetic modified nucleic acids able to bind with high affinity a molecular target.…”

Alternative mRNA Splicing and Promising Therapies in Cancer

“…One is to employ targeted antisense oligonucleotides (ASOs), which involves designing short single-stranded DNA or RNA oligonucleotides (12–28 bases) that are reverse complements to specific RNA sequences and base pair to form DNA/RNA or RNA/RNA duplexes. DNA/RNA heteroduplexes can promote nuclear degradation of the RNA by RNase H, prevent the loading of the RNA onto ribosomes in the cytoplasm, or interfere with splicing mechanisms to promote the production of specific alternate splicing products [ 45 , 46 ]. RNA/RNA heteroduplexes may be used to interfere with splicing patterns specifically (see Figure 3 ).…”

Adding recombinant AAVs to the cancer therapeutics mix

“…ASOs are single-stranded RNA or DNA constructs designed to bind mRNA via complementary base pairing to regulate genes at the transcription level through physical steric blockade of producing mature mRNA or inducing RNase-H-mediated processing of the mRNA. 59 , 60 , 61 Typically, ASOs are 15–30 bps and contain chemically modified backbones to improve stability, protection from nucleases, and enhance efficacy. 59 In the context of cancer biology, ASOs have been tested with moderate success in oral squamous cell carcinoma, Kaposi’s sarcoma, and targeting a variety of angiogenic oncogenes; yet, no ASO is FDA approved to treat cancer to date.…”

“… 59 , 60 , 61 Typically, ASOs are 15–30 bps and contain chemically modified backbones to improve stability, protection from nucleases, and enhance efficacy. 59 In the context of cancer biology, ASOs have been tested with moderate success in oral squamous cell carcinoma, Kaposi’s sarcoma, and targeting a variety of angiogenic oncogenes; yet, no ASO is FDA approved to treat cancer to date. 60 Difficulties and concerns with RNAi therapies are mostly related to dosing, efficacy of vector, low delivery of RNA molecule, renal clearance, and off-target effects due to the selected carrier.…”

“… 60 Difficulties and concerns with RNAi therapies are mostly related to dosing, efficacy of vector, low delivery of RNA molecule, renal clearance, and off-target effects due to the selected carrier. 7 , 59 , 60 , 61 …”