Children with Spinal Muscular Atrophy May Benefit from Increased Access to Second Therapies

Individuals with spinal muscular atrophy (SMA) who have a suboptimal response to initial gene transfer therapy may benefit from subsequent treatment with a different agent, according to data presented at the 2024 MDA conference. However, meeting the criteria for insurance coverage for a second therapy remains an elusive quest for many patients with SMA who may not respond to the initial intervention, said Stephanie Acord, MD, a pediatric neurologist at Cook Children's Medical Center in Fort Worth, Texas.

Acord and her team shared their real-world experience of treating seven patients with SMA that received onasemnogene abeparvovec (OA) as an initial therapy and were subsequently given either nusinersen or risdiplam when they reached plateaus in motor function gains. Six patients had 2 copies of the SMN2 gene and one patient had 3 copies of the SMN2 gene.

All seven children experienced significant improvement in motor function after receiving additional, ongoing treatment. The patients with type 1 SMA had improvements of 5 to 17 points on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) scale between 2 and 23 months after adding a second therapy. Four of those patients registered additional gains, measured with the Revised Hammersmith scale, within 5 to 13 months. The patient with type 2 SMA improved by 4 points on the Revised Hammersmith scale within 7 months.

Since the initial evaluations, all patients have had additional gains in clinical examination assessments, motor development scales, motor milestones, and quality of life. The authors said that the improvement in the scores can be attributed to the additional treatments rather than the continued effects of the initial OA therapy.

“Based on our experience, we feel that all patients with spinal muscular atrophy should have accessibility to additional treatments to promote additional gains,” Acord said. However, identifying which patients will have suboptimal response to initial therapy and obtaining coverage for additional treatment is no easy task, the author explained.

The approval of secondary treatment for patients with suboptimal response to initial therapy is subject to inconsistent processes across insurance policies. Some insurance companies require results of tests that measure disease progression, such as a 6-minute or 2-minute walk test, to approve the continuation of treatment. Acord’s team is experimenting with sensor-based tools for assessing motor function. Children with SMA often have arm weakness, which results in limited independence and challenges. Wearable sensors may be able to capture spontaneous movements that reflect meaningful improvement in the range of motion, such as the ability to feed independently. “There are limitations within the scales, “ Acord stressed. “Insurance companies rely solely on the scales, but we have to convince [them] that there is so much more to [assess] in terms of quality of life.”