Combination therapy with onasemnogene and risdiplam in spinal muscular atrophy type 1

Introduction/Aims There are currently three medications approved for spinal muscular atrophy (SMA), but the use of these medications in combination has not been well described. Methods This is a retrospective report of four cases of SMA treated with dual onasemnogene and risdiplam therapy at our institution. Results Following onasemnogene therapy, all four patients experienced a perceived plateau of therapeutic benefit, at which time daily risdiplam was started. Transient fatigue and weakness was seen in two patients following risdiplam initiation, but this resolved within 1 mo. One patient was hospitalized with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and post-viral pneumonia, weeks following risdiplam initiation. No other adverse effects related to onasemnogene and risdiplam combination therapy were identified and all patients experienced objective and subjective improvement. Discussion Combination therapy with onasemnogene and risdiplam in patients with SMA appears to be well-tolerated. Further large prospective trials are needed to determine whether dual therapy is more efficacious than monotherapy, and to identify rare adverse events that may occur with the use of combination therapy.