RG7800, developed by Hoffmann-La Roche, was a molecule akin to risdiplam that has undergone phase I testing but was discontinued due to animal toxicity. Early leads also included sodium orthovanadate and aclarubicin.Morpholino-type antisense oligonucleotides, with the same cellular target as nusinersen, remain a subject of research in treating SMA and other single-gene diseases, including at the University College London and at the University of Oxford. SMN2 gene activation
This approach aims at increasing expression (activity) of the SMN2 gene, thus increasing the amount of full-length SMN protein available. Oral salbutamol (albuterol), a popular asthma medicine, showed therapeutic potential in SMA both in vitro and in three small-scale clinical trials involving patients with SMA types 2 and 3, besides offering respiratory benefits.A few compounds initially showed promise but failed to demonstrate efficacy in clinical trials. Butyrates (sodium butyrate and sodium phenylbutyrate) held some promise in in vitro studies but a clinical trial in symptomatic people did not confirm their efficacy. Another clinical trial in pre-symptomatic types 1–2 infants was completed in 2015 but no results have been published. Valproic acid (VPA) was used in SMA on an experimental basis in the 1990s and 2000s because in vitro research suggested its moderate effectiveness. However, it demonstrated no efficacy in achievable concentrations when subjected to a large clinical trial. It has also been proposed that it may be effective in a subset of people with SMA but its action may be suppressed by fatty acid translocase in others. Others argue it may actually aggravate SMA symptoms.
The American College of Obstetricians and Gynecologists recommends all people thinking of becoming pregnant be tested to see if they are a carrier. The carrier frequency of SMA is comparable to other disorders like thalassemia and in a north Indian cohort has been found to be 1 in 38. However, genetic testing will not be able to identify all individuals at risk since about 2% of cases are caused by de novo mutations and 5% of the normal population have two copies of SMN1 on the same chromosome, which makes it possible to be a carrier by having one chromosome with two copies and a second chromosome with zero copies. This situation will lead to a false negative result, as the carrier status will not be correctly detected by a traditional genetic test. Management
The management of SMA varies based upon the severity and type. In the most severe forms (types 0/1), individuals have the greatest muscle weakness requiring prompt intervention. Whereas the least severe form (type 4/adult onset), individuals may not seek the certain aspects of care until later (decades) in life. While types of SMA and individuals among each type may differ, therefore specific aspects of an individuals care can differ. Medication
Nusinersen (marketed as Spinraza) is used to treat spinal muscular atrophy. It is an antisense nucleotide that modifies the alternative splicing of the SMN2 gene. It is given directly to the central nervous system using an intrathecal injection. Nusinersen prolongs survival and improves motor function in infants with SMA.