Preliminary Safety and Tolerability of a Novel Subcutaneous Intrathecal Catheter System for Repeated Outpatient Dosing of Nusinersen to Children and Adults With Spinal Muscular Atrophy

BACKGROUND: Many patients with spinal muscular atrophy (SMA) who might benefit from intrathecal antisense oligonucleotide (nusinersen) therapy have scoliosis or spinal fusion that precludes safe drug delivery. To circumvent spinal pathology, we designed a novel subcutaneous intrathecal catheter (SIC) system by connecting an intrathecal catheter to an implantable infusion port. METHODS: Device safety and tolerability were tested in 10 SMA patients (age, 5.4 to 30.5 y; 80% with 3 copies of SMN2); each received 3 sequential doses of nusinersen (n=30 doses). Pretreatment disease burden was evaluated using the Revised Hammersmith Scale, dynamometry, National Institutes of Health pegboard, pulmonary function testing, electromyography, and 2 health-related quality of life tools. RESULTS: Device implantation took ≤2 hours and was well tolerated. All outpatient nusinersen doses were successfully administered via SIC within 20 minutes on the first attempt, and required no regional or systemic analgesia, cognitive distraction, ultrasound guidance, respiratory precautions, or sedation. Cerebrospinal fluid withdrawn from the SIC had normal levels of glucose and protein; cerebrospinal fluid white blood cells were slightly elevated in 2 (22%) of 9 specimens (median, 1 cell/µL; range, 0 to 12 cells/µL) and red blood cells were detected in 7 (78%) specimens (median, 4; range, 0 to 2930 cells/µL). DISCUSSION: Preliminary observations reveal the SIC to be relatively safe and well tolerated in SMA patients with advanced disease and spinal fusion. The SIC warrants further study and, if proven effective in larger trials of longer duration, could double the number of patients able to receive nusinersen worldwide while reducing administration costs 5- to 10-fold.