Articles: oligonucleotides.
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Spinal muscular atrophy (SMA), a prominent genetic disease of infant mortality, is caused by low levels of survival motor neuron (SMN) protein owing to deletions or mutations of the SMN1 gene. SMN2, a nearly identical copy of SMN1 present in humans, cannot compensate for the loss of SMN1 because of predominant skipping of exon 7 during pre-mRNA splicing. With the recent US Food and Drug Administration approval of nusinersen (Spinraza), the potential for correction of SMN2 exon 7 splicing as an SMA therapy has been affirmed. ⋯ Here, we provide a historical account of events that led to the discovery of ISS-N1 and describe the impact of independent validations that raised the profile of ISS-N1 as one of the most potent antisense targets for the treatment of a genetic disease. Recent approval of nusinersen provides a much-needed boost for antisense technology that is just beginning to realize its potential. Beyond treating SMA, the ISS-N1 target offers myriad potentials for perfecting various aspects of the nucleic-acid-based technology for the amelioration of the countless number of pathological conditions.
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Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by degeneration of spinal motor neurons and poses significant adverse outcome in affected population. Survival motor neuron 1 (SMN1) protein encoded by SMN1 gene located on 5q13 is critical for survival and functioning of motor neurons. Almost identical gene SMN2, present on the same chromosome, produces a small truncated protein (SMN2) because of skipping of exon 7 from translation due to translation silent C6U substitution in exon 7 of SMN2 pre-mRNA transcript. ⋯ Major evidence of its efficacy came from a sham controlled phase 3 clinical study ENDEAR. The study was stopped early based on significantly favorable results in interim analysis and all the patients were transitioned to receive nusinersen in an ongoing open-label, phase 3 study, SHINE, which will evaluate the long-term efficacy, safety and tolerability of the drug. Nusinersen is globally the first drug approved (by the US FDA) for treatment of SMA in children and adults.
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Nusinersen is an antisense oligonucleotide intended for the treatment of spinal muscular atrophy. The pharmacokinetics of nusinersen, following intrathecal administrations, in the cerebrospinal fluid (CSF) and plasma of 72 pediatric patients (3 months to 17 years) with spinal muscular atrophy across 5 clinical trials was analyzed via population-based modeling. With sparse data in the CSF and profile data in the plasma, a linear 4-compartment model simultaneously described the time-concentration profiles in both matrices. ⋯ Simulations from the final model showed that age-based dosing in children under 2 years ensured a more comparable exposure (peak concentration and area under the concentration-time curve) across subjects in the population relative to a fixed dosing scheme. However, because no dose-limiting toxicity has been reported in any of the trials, a fixed-dose scheme (12 mg across all age groups) was recommended. The median terminal half-life of nusinersen in the CSF was determined from the model to be 163 days, which supported infrequent dosing, once every 4 to 6 months in pediatric patients with spinal muscular atrophy.
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Randomized Controlled Trial
Cardiovascular and Metabolic Effects of ANGPTL3 Antisense Oligonucleotides.
Epidemiologic and genomewide association studies have linked loss-of-function variants in ANGPTL3, encoding angiopoietin-like 3, with low levels of plasma lipoproteins. ⋯ Oligonucleotides targeting mouse Angptl3 retarded the progression of atherosclerosis and reduced levels of atherogenic lipoproteins in mice. Use of the same strategy to target human ANGPTL3 reduced levels of atherogenic lipoproteins in humans. (Funded by Ionis Pharmaceuticals; ClinicalTrials.gov number, NCT02709850 .).
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Review
Nusinersen: antisense oligonucleotide to increase SMN protein production in spinal muscular atrophy.
Patients with spinal muscular atrophy (SMA) have an autosomal recessive disease that limits their ability to produce survival motor neuron (SMN) protein in the CNS resulting in progressive wasting of voluntary muscles. Detailed studies over several years have demonstrated that phosphorothioate and 2'-O-methoxyethyl- modified antisense oligonucleotides (ASOs) targeting the ISS-N1 site increase SMN2 exon 7 inclusion, thus increasing levels of SMN protein in a dose- and time-dependent manner in liver, kidney and skeletal muscle, and CNS tissues only when administered intrathecally. On a dose basis, nusinersen was found to be the most potent ASO for SMN2 splicing correction in the CNS of adult mice. ⋯ In addition, there have been significant extensions in life expectancy. These findings led to the U. S. and European approval of nusinersen for use in SMA patients of all ages.