Spinal muscular atrophy (SMA) is a debilitating genetic disorder that results in degeneration of muscle function. The rare disease, which usually appears in childhood, is typically treated with a drug called nusinersen, which is injected directly into the spinal canal.
A more streamlined method of administration has been developed for SMA. This method has just been evaluated for safety and efficacy in patients with advanced disease. The results of the evaluation were published in Muscle & Nerve.
Investigators evaluated the safety and effectiveness of nusinersen delivery via subcutaneous intrathecal catheter (SIC) system. The SIC system was developed specifically for use in SMA patients with spinal deformities or fusions, as traditional administration of nusinersen is known to have side effects in this particular class of patients.
Seventeen patients were included in the safety branch of the study, all of whom started nusinersen treatment between 2.7 and 31.5 years of age and received 9 to 12 doses of the drug via SIC. The efficacy branch of the study included 11 nonambulatory patients (patients who could not walk) who had never undergone treatment for their SMA.
The safety branch of the study saw 14 adverse events which occurred among 12 participants. The adverse events were all related to the SIC system and not the nusinersen drug itself. Four of the SICs suffered a malfunction and required surgical repair, while one became infected with bacterial meningitis and needed to be removed.
In the efficacy branch of the study, the results were more promising: patients who underwent a finger dexterity test called the nine-hole peg test showed a 15.9% and 19% improvement in both dominant and nondominant hands, respectively. Their grip strength also improved by 44.9%. However, no significant changes in motor scales, muscle force, pulmonary function, or SMA biomarkers were observed. All participants in the efficacy branch reported improvements in endurance, purposeful hand use, arm strength, head control, and/or speech.
Although the SIC system could lead to improvements in muscle function, it runs the risk of side effects not present in traditional nusinersen delivery. Further investigation into the pros and cons of SIC is certainly needed before considering this method of administration as a new mainstay of SMA therapy.
Written by Natan Rosenfeld