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European Journal of Cell Biology Jun 2023Spinal muscular atrophy (SMA), the most common genetic cause of infantile death, is caused by a mutation in the survival of motor neuron 1 gene (SMN1), leading to the... (Review)
Review
Spinal muscular atrophy (SMA), the most common genetic cause of infantile death, is caused by a mutation in the survival of motor neuron 1 gene (SMN1), leading to the death of motor neurons and progressive muscle weakness. SMN1 normally produces an essential protein called SMN. Although humans possess a paralogous gene called SMN2, ∼90% of the SMN it produces is non-functional. This is due to a mutation in SMN2 that causes the skipping of a required exon during splicing of the pre-mRNA. The first treatment for SMA, nusinersen (brand name Spinraza), was approved by the FDA in 2016 and by the EMU in 2017. Nusinersen is an antisense oligonucleotide-based therapy that alters the splicing of SMN2 to make functional full-length SMN protein. Despite the recent advancements in antisense oligonucleotide therapy and SMA treatment development, nusinersen is faced with a multitude of challenges, such as intracellular and systemic delivery. In recent years, the use of peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) in antisense therapy has gained interest. These are antisense oligonucleotides conjugated to cell-penetrating peptides such as Pips and DG9, and they have the potential to address the challenges associated with delivery. This review focuses on the historic milestones, development, current challenges, and future perspectives of antisense therapy for SMA.
Topics: Humans; Oligonucleotides, Antisense; Muscular Atrophy, Spinal; Morpholinos; Motor Neurons; RNA Splicing
PubMed: 37295266
DOI: 10.1016/j.ejcb.2023.151326 -
Cells Oct 2023Antisense oligonucleotide-based (ASO) therapeutics have emerged as a promising strategy for the treatment of human disorders. Charge-neutral PMOs have promising... (Review)
Review
Antisense oligonucleotide-based (ASO) therapeutics have emerged as a promising strategy for the treatment of human disorders. Charge-neutral PMOs have promising biological and pharmacological properties for antisense applications. Despite their great potential, the efficient delivery of these therapeutic agents to target cells remains a major obstacle to their widespread use. Cellular uptake of naked PMO is poor. Cell-penetrating peptides (CPPs) appear as a possibility to increase the cellular uptake and intracellular delivery of oligonucleotide-based drugs. Among these, the DG9 peptide has been identified as a versatile CPP with remarkable potential for enhancing the delivery of ASO-based therapeutics due to its unique structural features. Notably, in the context of phosphorodiamidate morpholino oligomers (PMOs), DG9 has shown promise in enhancing delivery while maintaining a favorable toxicity profile. A few studies have highlighted the potential of DG9-conjugated PMOs in DMD (Duchenne Muscular Dystrophy) and SMA (Spinal Muscular Atrophy), displaying significant exon skipping/inclusion and functional improvements in animal models. The article provides an overview of a detailed understanding of the challenges that ASOs face prior to reaching their targets and continued advances in methods to improve their delivery to target sites and cellular uptake, focusing on DG9, which aims to harness ASOs' full potential in precision medicine.
Topics: Animals; Humans; Oligonucleotides, Antisense; Cell-Penetrating Peptides; Oligonucleotides; Morpholinos; Muscular Dystrophy, Duchenne; Muscular Atrophy, Spinal
PubMed: 37830609
DOI: 10.3390/cells12192395 -
Developmental Cell Oct 2015For over 15 years, antisense morpholino oligonucleotides (MOs) have allowed developmental biologists to make key discoveries regarding developmental mechanisms in... (Review)
Review
For over 15 years, antisense morpholino oligonucleotides (MOs) have allowed developmental biologists to make key discoveries regarding developmental mechanisms in numerous model organisms. Recently, serious concerns have been raised as to the specificity of MO effects, and it has been recommended to discontinue their usage, despite the long experience of the scientific community with the MO tool in thousands of studies. Reviewing the many advantages afforded by MOs, we conclude that adequately controlled MOs should continue to be accepted as generic loss-of-function approach, as otherwise progress in developmental biology will greatly suffer.
Topics: Animals; Developmental Biology; Humans; Morpholinos; Oligonucleotides, Antisense; Zebrafish
PubMed: 26506304
DOI: 10.1016/j.devcel.2015.09.017 -
Journal of Biosciences 2023Duchenne muscular dystrophy (DMD) is an X-linked genetic disease primarily affecting boys causing loss of the dystrophin protein, ultimately leading to muscle wastage... (Review)
Review
Duchenne muscular dystrophy (DMD) is an X-linked genetic disease primarily affecting boys causing loss of the dystrophin protein, ultimately leading to muscle wastage and death by cardiac or respiratory failure. The genetic mutation involved can be overcome with antisense oligonucleotides which bind to a pre-mRNA and results in reading frame restoration by exon skipping. Phosphorodiamidate morpholino oligonucleotides (PMOs) are a class of antisense agents with a neutral backbone derived from RNA which can induce effective exon skipping. In this review, the evolution of PMOs in exon skipping therapy for the last two decades has been detailed with the gradual structural and functional advancements. Even though the success rate of PMObased therapy has been high with four FDA approved drugs, several key challenges are yet to overcome, one being the dystrophin restoration in cardiac muscle. The current scenario in further improvement of PMOs has been discussed along with the future perspectives that have the potential to revolutionize the therapeutic benefits in DMD.
Topics: Male; Humans; Morpholinos; Dystrophin; Muscular Dystrophy, Duchenne; Oligonucleotides, Antisense; Exons
PubMed: 37846020
DOI: No ID Found -
Drug Design, Development and Therapy 2017Duchenne muscular dystrophy is a fatal neuromuscular disorder affecting around one in 3,500-5,000 male births that is characterized by progressive muscular... (Review)
Review
Duchenne muscular dystrophy is a fatal neuromuscular disorder affecting around one in 3,500-5,000 male births that is characterized by progressive muscular deterioration. It is inherited in an X-linked recessive fashion and is caused by loss-of-function mutations in the gene coding for dystrophin, a cytoskeletal protein that stabilizes the plasma membrane of muscle fibers. In September 2016, the US Food and Drug Administration granted accelerated approval for eteplirsen (or Exondys 51), a drug that acts to promote dystrophin production by restoring the translational reading frame of through specific skipping of exon 51 in defective gene variants. Eteplirsen is applicable for approximately 14% of patients with mutations. This article extensively reviews and discusses the available information on eteplirsen to date, focusing on pharmacological, efficacy, safety, and tolerability data from preclinical and clinical trials. Issues faced by eteplirsen, particularly those relating to its efficacy, will be identified. Finally, the place of eteplirsen and exon skipping as a general therapeutic strategy in Duchenne muscular dystrophy treatment will be discussed.
Topics: Animals; Humans; Morpholinos; Muscular Dystrophy, Duchenne
PubMed: 28280301
DOI: 10.2147/DDDT.S97635 -
Neuromuscular Disorders : NMD Jun 2023Eteplirsen is FDA-approved for the treatment of Duchenne muscular dystrophy (DMD) in exon 51 skip-amenable patients. Previous studies in boys > 4 years of age indicate...
Eteplirsen is FDA-approved for the treatment of Duchenne muscular dystrophy (DMD) in exon 51 skip-amenable patients. Previous studies in boys > 4 years of age indicate eteplirsen is well tolerated and attenuates pulmonary and ambulatory decline compared with matched natural history cohorts. Here the safety, tolerability and pharmacokinetics of eteplirsen in boys aged 6-48 months is evaluated. In this open-label, multicenter, dose-escalation study (NCT03218995), boys with a confirmed mutation of the DMD gene amenable to exon 51 skipping (Cohort 1: aged 24-48 months, n = 9; Cohort 2: aged 6 to < 24 months, n = 6) received ascending doses (2, 4, 10, 20, 30 mg/kg) of once-weekly eteplirsen intravenously over 10 weeks, continuing at 30 mg/kg up to 96 weeks. Endpoints included safety (primary) and pharmacokinetics (secondary). All 15 participants completed the study. Eteplirsen was well tolerated with no treatment-related discontinuations, deaths or evidence of kidney toxicity. Most treatment-emergent adverse events were mild; most common were pyrexia, cough, nasopharyngitis, vomiting, and diarrhea. Eteplirsen pharmacokinetics were consistent between both cohorts and with previous clinical experience in boys with DMD > 4 years of age. These data support the safety and tolerability of eteplirsen at the approved 30-mg/kg dose in boys as young as 6 months old.
Topics: Male; Humans; Child, Preschool; Infant; Muscular Dystrophy, Duchenne; Morpholinos; Exons; Mutation; Dystrophin
PubMed: 37207382
DOI: 10.1016/j.nmd.2023.03.008 -
Clinical Pharmacology and Therapeutics Jan 2016The development of genetic and molecular biology tools permitting the connection of specific genes to their functions has accelerated our understanding of molecular... (Review)
Review
The development of genetic and molecular biology tools permitting the connection of specific genes to their functions has accelerated our understanding of molecular pathways underlying health and disease. The resulting gains in knowledge have propelled gene targeting to the forefront of promising therapeutic strategies. Here we discuss the uniquely powerful and adaptable approach of morpholino-driven modification of normal and mutant gene expression as a pathway to health.
Topics: Animals; Disease; Drug Carriers; Gene Expression; Gene Targeting; Genetic Engineering; Humans; Models, Genetic; Morpholinos; Preventive Medicine
PubMed: 26474085
DOI: 10.1002/cpt.276 -
Nucleic Acid Therapeutics Jun 2018RNA interference (RNAi) is a fundamental cellular process for the posttranscriptional regulation of gene expression. RNAi can exogenously be modulated by small RNA... (Review)
Review
RNA interference (RNAi) is a fundamental cellular process for the posttranscriptional regulation of gene expression. RNAi can exogenously be modulated by small RNA oligonucleotides, such as microRNAs (miRNAs) and small interfering RNAs (siRNAs), or by antisense oligonucleotides. These small oligonucleotides provided the scientific community with powerful and versatile tools to turn off the expression of genes of interest, and hold out the promise of new therapeutic solutions against a wide range of gene-associated pathologies. However, unmodified nucleic acids are highly instable in biological systems, and their weak interaction with plasma proteins confers an unfavorable pharmacokinetics. In this review, we first provide an overview of the most efficient chemical strategies that, over the past 30 years, have been used to significantly improve the therapeutic potential of oligonucleotides. Oligonucleotides targeting and delivery technologies are then presented, including covalent conjugates between oligonucleotides and targeting ligand, and noncovalent association with lipid or polymer nanoparticles. Finally, we specifically focus on the endosomal escape step, which represents a major stumbling block for the effective use of oligonucleotides as therapeutic agents. The need for approaches to quantitatively measure endosomal escape and cytosolic arrival of biomolecules is discussed in the context of the development of efficient oligonucleotide targeting and delivery vectors.
Topics: Amyloidosis; Animals; Biological Transport; Cell-Penetrating Peptides; Cytosol; Endosomes; Gene Transfer Techniques; Genetic Therapy; Humans; Lipids; MicroRNAs; Morpholinos; Nanoparticles; Neoplasms; Oligonucleotides; Oligonucleotides, Antisense; Peptide Nucleic Acids; Phosphorothioate Oligonucleotides; RNA, Small Interfering
PubMed: 29883296
DOI: 10.1089/nat.2017.0716 -
Journal of Visualized Experiments : JoVE Aug 2022The morpholino oligomer-based knockdown system has been used to identify the function of various gene products through loss or reduced expression. Morpholinos (MOs) have...
The morpholino oligomer-based knockdown system has been used to identify the function of various gene products through loss or reduced expression. Morpholinos (MOs) have the advantage in biological stability over DNA oligos because they are not susceptible to enzymatic degradation. For optimal effectiveness, MOs are injected into 1-4 cell stage embryos. The temporal efficacy of knockdown is variable, but MOs are believed to lose their effects due to dilution eventually. Morpholino dilution and injection amount should be closely controlled to minimize the occurrence of off-target effects while maintaining on-target efficacy. Additional complementary tools, such as CRISPR/Cas9 should be performed against the target gene of interest to generate mutant lines and to confirm the morphant phenotype with these lines. This article will demonstrate how to design, prepare, and microinject a translation-blocking morpholino against hand2 into the yolk of 1-4 cell stage zebrafish embryos to knockdown hand2 function and rescue these "morphants" by co-injection of mRNA encoding the corresponding cDNA. Subsequently, the efficacy of the morpholino microinjections is assessed by first verifying the presence of morpholino in the yolk (co-injected with phenol red) and then by phenotypic analysis. Moreover, cardiac functional analysis to test for knockdown efficacy will be discussed. Finally, assessing the effect of morpholino-induced blockage of gene translation via western blotting will be explained.
Topics: Animals; Embryo, Nonmammalian; Gene Knockdown Techniques; Morpholinos; Oligonucleotides, Antisense; Phenotype; RNA, Messenger; Zebrafish; Zebrafish Proteins
PubMed: 36036621
DOI: 10.3791/63324 -
Skeletal Muscle Nov 2023The lack of functional dystrophin protein in Duchenne muscular dystrophy (DMD) causes chronic skeletal muscle inflammation and degeneration. Therefore, the restoration...
BACKGROUND
The lack of functional dystrophin protein in Duchenne muscular dystrophy (DMD) causes chronic skeletal muscle inflammation and degeneration. Therefore, the restoration of functional dystrophin levels is a fundamental approach for DMD therapy. Electrical impedance myography (EIM) is an emerging tool that provides noninvasive monitoring of muscle conditions and has been suggested as a treatment response biomarker in diverse indications. Although magnetic resonance imaging (MRI) of skeletal muscles has become a standard measurement in clinical trials for DMD, EIM offers distinct advantages, such as portability, user-friendliness, and reduced cost, allowing for remote monitoring of disease progression or response to therapy. To investigate the potential of EIM as a biomarker for DMD, we compared longitudinal EIM data with MRI/histopathological data from an X-linked muscular dystrophy (mdx) mouse model of DMD. In addition, we investigated whether EIM could detect dystrophin-related changes in muscles using antisense-mediated exon skipping in mdx mice.
METHODS
The MRI data for muscle T2, the magnetic resonance spectroscopy (MRS) data for fat fraction, and three EIM parameters with histopathology were longitudinally obtained from the hindlimb muscles of wild-type (WT) and mdx mice. In the EIM study, a cell-penetrating peptide (Pip9b2) conjugated antisense phosphorodiamidate morpholino oligomer (PPMO), designed to induce exon-skipping and restore functional dystrophin production, was administered intravenously to mdx mice.
RESULTS
MRI imaging in mdx mice showed higher T2 intensity at 6 weeks of age in hindlimb muscles compared to WT mice, which decreased at ≥ 9 weeks of age. In contrast, EIM reactance began to decline at 12 weeks of age, with peak reduction at 18 weeks of age in mdx mice. This decline was associated with myofiber atrophy and connective tissue infiltration in the skeletal muscles. Repeated dosing of PPMO (10 mg/kg, 4 times every 2 weeks) in mdx mice led to an increase in muscular dystrophin protein and reversed the decrease in EIM reactance.
CONCLUSIONS
These findings suggest that muscle T2 MRI is sensitive to the early inflammatory response associated with dystrophin deficiency, whereas EIM provides a valuable biomarker for the noninvasive monitoring of subsequent changes in skeletal muscle composition. Furthermore, EIM reactance has the potential to monitor dystrophin-deficient muscle abnormalities and their recovery in response to antisense-mediated exon skipping.
Topics: Mice; Animals; Dystrophin; Mice, Inbred mdx; Electric Impedance; Mice, Inbred C57BL; Muscular Dystrophy, Duchenne; Muscle, Skeletal; Morpholinos; Myography; Biomarkers
PubMed: 37980539
DOI: 10.1186/s13395-023-00331-1