Spinal muscular atrophy (SMA) is a neurodegenerative disease due to a mutation resulting in low SMN protein levels. Three SMN-enhancing treatments are FDA approved, but there is limited real-world data describing provider intent when more than one treatment is prescribed. Treatment start/stop dates do not always give clear insight. This analysis aims to use clinician-entered data to describe providers’ intention for use when prescribing SMA treatments in a real-world population.
The SMA Clinical Data Registry contains clinician-entered data for 1,218 individuals across 25 care centers in the United States (U.S.). This analysis included treated U.S. individuals diagnosed with 5qSMA before 2 years of age and between 6/2019-6/2024 (when >1 SMA treatment was commercially available). Individuals treated via clinical trial were excluded. Prescriber’s intent was collected for each treatment utilized, and any treatments received after onasemnogene abeparvovec were considered concurrent.
The analysis included 202 individuals with a mean age of diagnosis and 1st treatment of 3.4 ± 6.2 and 4.1 ± 6.4 months, respectively. 75% were identified via prenatal and/or newborn screening, and the SMN2 copy number distribution was 49%, 39%, and 12% for 2, 3, and 4+ copies, respectively. Across groups, the intent of the 1st treatment was most commonly a single treatment not intended to be a bridge (71-88%). Bridge treatment was utilized for 18% of individuals; most were identified by screening (85%) and had 3 copies of SMN2 (54%). The median age at 1st treatment for bridge treatments was 28 days, compared to 39.5 days for non-bridge treatments. For individuals who received 2+ treatments (n=87), concurrent intent was reported for 49%, 22%, and 0% of individuals with 2, 3, and 4+ copies of SMN2. The median time from bridge to 2nd treatment initiation was 106 days. When the 1st treatment was not a bridge, the median time from 1st to 2nd treatment was higher when the 2nd treatment was intended to be concurrent (343 days, n=17) vs sequential (240 days, n=14).
This analysis describes the landscape of providers’ intended use when prescribing SMA treatments for children diagnosed under 2 years of age over the past 5 years. There may be a relationship between the prescriber’s treatment intent and the age at 1st treatment or time on treatment before switch/addition, but further analysis is warranted.