Patricia Inacio, PhD, science writer —

Young children with spinal muscular atrophy show improvements in motor function after six-months of treatment with Spinraza, a German study shows. The response to Spinraza strongly correlated with the age when treatment began, with children treated before seven months of age responding better to the therapy. These findings support the need for early detection of SMA by screening newborns, study authors emphasized. Spinraza, developed by Biogen, is the first FDA-approved drug for SMA. SMA arises due to mutations in the survival motor neuron 1 (SMN1) gene, which is key to the function and survival of the nerves that control muscles. Some patients, however, maintain a copy of a gene called SMN2, a gene nearly identical to SMN1 that can give rise to a shorter version of the SMN protein. Spinraza boosts the amount of the SMN protein by increasing the levels of full-length messenger RNA (mRNA), the mediator between gene and protein, generated by the SMN2 gene. Spinraza is administered via intrathecal injection — directly to the cerebrospinal fluid around the spinal cord, where motor neurons of SMA individuals degenerate due to insufficient levels of SMN protein. The therapy was approved in the U.S. in December 2016 to treat SMA types 1–3 in children and adults, and learned approval in Europe in June 2017. Prior to the EU’s approval, a group of children in Germany with SMA type 1 was given access to Spinraza for seven months, under an Expanded Access Program (EAP). The children had different ages and were at different stages of the disease, representing a more heterogenous group than those in previous trials. Researchers analyzed data from 61 children treated with Spinraza in seven centers under the EAP. Children enrolled in the study developed the first symptoms of SMA before the age of 6 months and had no ability to sit independently. Moreover, 38 children had less than two copies of the SMN2 gene, and 20 children had more than three copies. In three children, the SMN2 copy number was unknown. Previous studies showed that a higher number of SMN2 correlates with longer survival and inversely with disease severity. Administration of Spinraza was performed on days 1, 15, 30, 60 and 180. Researchers measured the treatment outcomes by assessing primarily the changes from the beginning of the study in the score of the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders, also known as (CHOP INTEND), which measures motor function. The CHOP-INTEND scores range from 0 to 64 points and previous studies have reported that children with SMA type 1 have a mean value of 21.4 points. The test was performed at the beginning of the study, then after 60 days, and at the end of treatment. Additionally, they assessed changes in scores in section 2 of the Hammersmith Infant Neurological Examination (HINE) scale, another test measuring motor function, whose scores range between zero and 26. The HINE-2 was performed routinely at every patient visit. At baseline, children’s mean CHOP INTEND score was 22.3 and after six months of treatment the mean score improved to 31.2, which was an increase of nine points. Specifically, eight children improved by one to four points, and 17 children improved by five to nine points. Sixteen children improved by more than 10 points (between 10 and 14 points), and 11 children underwent an increase on the CHOP INTEND by more than 15 points. Children with less than two copies of the SMN2 gene had lower scores in the CHOP INTEND at the beginning of the trial. The changes in scores after treatment were comparable to children with more than three SMN2 copies, scores of 8.1 and 8.2, respectively. Treatment was more effective in younger children (aged below 7 months) compared to older ones — an improvement of 14.4 vs. 7.0, respectively. These results suggest there is a “critical therapeutic time window for delivery of SMN-targeted therapies. The implementation of newborn screening for SMA is crucial to allow pre-symptomatic diagnosis." Regarding the motor response, 19 children improved by more than two points in HINE-2 motor milestones —  15 children increased their score by two to four points, and four children by more than five points. Four children (6.6%) achieved full head control, and 2 children (3.3%) were able to sit independently. After six months of treatment, the parents of 28 children reported a marked improvement in motor function, while three parents noticed no benefit, and one a slight worsening. Respiratory function was improved in 16 children, with a marked improvement in four of them. Overall, these findings “indicate that even in advanced stages of the disease, Spinraza can lead to improvement of motor function as measured by CHOP INTEND. Moreover, the results support early diagnosis and access to Spinraza as early as possible as a key factor to improve the outcomes of children with SMA. Researchers now will evaluate whether increasing the treatment period with Spinraza enhances the therapy’s benefits and patients' quality of life. The data will be collected within the SMArtCARE project, a “real-world data” registry of SMA patients.

According to scientists, new research on ALS may shed light on the mechanisms underlying spinal muscular atrophy. Two RNA binding proteins, TDP-43 and hnRNP A1, are abnormal in certain cases of ALS.  This leads to their accumulation in ALS patients' nerve cells associated with movement. As the name suggests, RNA binding proteins have the capacity to bind with RNA molecules, limiting their ability to become proteins. University of Montreal researchers wanted to understand what happened to movement nerve cells when they removed TDP-43 from the cells' nucleus. Depleting the binding protein TDP-43 led to changes in the processing, or splicing, of messenger RNA in the cell. Because TDP-43 binds with RNA, and can change how it is spliced, depleting it in the cell nucleus led to alterations to another RNA binding protein, hnRNP A1. This protein can get spliced into two variations, both regulated by TDP-43. Changes in hnRNP A1 messenger RNA also resulted in protein aggregation and were toxic to cells. Importantly, hnRNP A1 controls splicing of the SMN gene, the underlying cause of SMA. Researchers don’t know how the hnRNP A1-triggered SMN splice variation affects the function of the SMN gene. But they noted that Spinraza, a therapy recently approved for SMA, targets the hnRNP A1 protein's splicing of the gene. Spinraza was derived from this same type of research.

Researchers have uncovered the gene network regulating the transition of progenitor cells into motor neurons during the development of embryos, using chicken and mice as models. The study also sheds light on why these neurons develop faster in the embryo compared to other nerve cells. The findings may help researchers…

Scholar Rock’s SRK-015 prevented additional atrophy in mice with muscle wasting and increased healthy animals’ muscle mass and function, a study reports. The biotech company’s therapy targets the precursor to the growth factor myostatin, whose over-activation is linked to muscle atrophy. The study’s findings support SRK-015’s potential as a treatment for muscle…

Researchers have shown that the technology called antisense oligonucleotides, used in the only FDA-approved therapy for SMA, Spinraza (nusinersen), can be improved upon. They designed two new sequences that significantly increased SMN production in human cells and in a mouse model of SMA when administered alone or combined. The…

Envisagenics has raised a total of $2.35 million to continue working to discover RNA-based therapies for diseases linked to RNA splicing errors, such as spinal muscular atrophy. The company uses an innovative platform that couples RNA splicing analysis with artificial intelligence. The biotechnology company's drug discovery platform, called SpliceCore, aims to develop therapeutics that correct splicing errors in RNA — the molecule that, along with DNA, gives the instructions to make all the proteins required for our cells to function. Errors in RNA splicing — a natural process cells use to generate a variety of RNA molecules by simply arranging the building blocks that compose the RNA molecule in different ways — are the cause of more than 300 genetic diseases, including SMA. With RNA splicing analysis, researchers are able to analyze millions of RNA sequence codings and identify RNA splicing errors. The most plausible and likely targets for treatments, after being validated in experiments using patients’ data, are then identified by artificial intelligence. With a target identified, researchers can then design a tailored drug and investigate its action, or how well it might work, using the SpliceCore's modular platform. The money was raised in what is called seed capital round, in which an investor funds a company in exchange for an equity stake in it.

Preimplantation genetic diagnosis may help couples prevent the risk of having a child with spinal muscular atrophy (SMA). The case report “The clinical application of preimplantation genetic diagnosis to prevent spinal muscular atrophy in a Chinese family: A case report” was published in the Journal of the Neurological…

Defects in our cells’ natural cleaning system — called autophagy — may be a trigger for the development of motor neuron diseases such as spinal muscular atrophy (SMA), researchers at the University of Würzburg, Germany, suggest. Their study, “Plekhg5-regulated autophagy of synaptic vesicles reveals a pathogenic mechanism in…

Invitae presented data that supports combining genetic sequencing with platforms that detect copy number variant (CNV) as a way of diagnosing neuromuscular disorders — such as spinal muscular atrophy — and one superior to genetic sequencing alone. The results were in one of the 15 posters Invitae, a genetic information…

Human urine cells grown in a lab could help scientists test spinal muscular atrophy treatments, a Chinese study reports. The SMA patients from whom they were collected have a gene mutation associated with the disease, the researchers said. The study, “Application of urine cells in drug intervention for spinal muscular…