Nusinersen for the treatment of spinal muscular atrophy

INTRODUCTION

Spinal muscular atrophy (SMA) is an autosomal recessive degenerative neuromuscular disorder characterized by loss of spinal motor neurons leading to muscle weakness. This review article focuses on a novel antisense oligonucleotide treatment, first ever approved for SMA (nusinersen, Spinraza^TM) and describes the exciting journey from early ASO clinical trials to regulatory approval of the first ever known effective treatment for SMA. Areas covered: This article reviews the results of the published open label nusinersen studies in infants and children, and briefly covers the preliminary findings of the recently completed but as yet unpublished nusinersen-sham controlled trials, as well as the presymptomatic nusinersen trial known as Nurture. Clinical use of nusinersen is also reviewed. Expert commentary: Collectively, the studies show improvement in motor function across SMA of all types, including SMA type 3. Best motor response was observed with early treatment; presymptomatic treatment prevented disease manifestations. Nusinersen was found to be safe and well tolerated across all age groups studied. Nusinersen has irrevocably altered the natural history of SMA and allowed for the first time children to transition between SMA types. Nusinersen should be considered as standard of care for the treatment of SMA of all types.

Molecular inversion probes equipped with discontinuous rolling cycle amplification for targeting nucleotide variants: Determining SMN1 and SMN2 genes in diagnosis of spinal muscular atrophy

The novel techniques of molecular inversion probes (MIPs) combined with discontinuous rolling cycle amplification (DRCA) was developed for determination of the multi-nucleotide variants at single base. The different-length MIPs, a padlock-probe based technology, are designed to simultaneously recognize the identical nucleotide variants. After ligation and DRCA, the different-length genetic products representing the certain genotypes could be simply determined by the short-end capillary electrophoresis (CE) method. By using MIPs-DRCA method, the various gene dosages of SMN1 and SMN2 genes in homologous or heterologous subjects were successfully quantified for diagnosis of spinal muscular atrophy (SMA). The length of the MIP for SMN1 gene was 106 bp, and for SMN2 gene was 86 bp. After method optimization, the MIP products of SMN1 and SMN2 were well separated with the resolution of 1.13 ± 0.17 (n = 3) within 10 min. There were total of 56 DNA blind samples analyzed by this strategy, including 38 wild types, 12 carriers and 6 SMA patients, and the data of gene dosages was corresponding to those analyzed by conformation sensitive CE and denatured high performance liquid chromatography (DHPLC) methods. This MIPs-DRCA method which could be applied to simultaneously genotype multi nucleotide variants at single base, such as K-ras gene, was very feasible for determination of genetic diseases in clinical.

Universal fluorescent tri-probe ligation equipped with capillary electrophoresis for targeting SMN1 and SMN2 genes in diagnosis of spinal muscular atrophy

This is the first ligase chain reaction used for diagnosis of spinal muscular atrophy (SMA). Universal fluorescent tri-probe ligation (UFTPL), a novel strategy used for distinguishing the multi-nucleotide alternations at single base, is developed to quantitatively analyze the SMN1/SMN2 genes in diagnosis of SMA. Ligase chain reaction was performed by adding three probes including universal fluorescent probe, connecting probe and recognizing probe to differentiate single nucleotide polymorphisms in UFTPL. Our approach was based on the two UFTPL products of survival motor neuron 1 (SMN1) and SMN2 genes (the difference of 9 mer) and analyzed by capillary electrophoresis (CE). We successfully determined various gene dosages of SMN1 and SMN2 genes in homologous or heterologous subjects. By using the UFTPL-CE method, the SMN1 and SMN2 genes were fully resolved with the resolution of 2.16±0.37 (n=3). The r values of SMN1 and SMN2 regression curves over a range of 1-4 copies were above 0.9944. Of the 48 DNA samples, the data of gene dosages were corresponding to that analyzed by conformation sensitive CE and denatured high-performance liquid chromatography (DHPLC). This technique was found to be a good methodology for quantification or determination of the relative genes having multi-nucleotide variants at single base.