Combination SMA Therapy Shows Promise: Gene Therapy Plus Oral Drug Improves Outcomes
Real-world study of 20 children shows adding risdiplam after gene therapy improved motor, breathing, and swallowing function in spinal muscular atrophy.
Summary
A multicenter study of 20 children with spinal muscular atrophy (SMA) found that adding the oral drug risdiplam after gene therapy (onasemnogene abeparvovec) led to meaningful improvements. Most children (92%) showed stable or improved motor function, while 35% had better swallowing and 30% improved breathing. The combination was well-tolerated with no serious side effects. This real-world evidence suggests combination therapy may benefit SMA patients who plateau after initial gene therapy treatment.
Detailed Summary
Spinal muscular atrophy (SMA) is a devastating genetic disease that progressively weakens muscles, affecting movement, breathing, and swallowing. While three FDA-approved treatments have transformed outcomes, none provides a cure, leading families and doctors to explore combination therapies.
This retrospective study examined 20 children from six US medical centers who received onasemnogene abeparvovec (a one-time gene therapy) followed by risdiplam (a daily oral medication). Most patients had severe Type 1 SMA with two SMN2 gene copies. The average time between treatments was 15.2 months, with risdiplam started at a mean age of 24.9 months.
The results were encouraging across multiple domains. For motor function, 92% of children showed stability or improvement on standardized assessments after adding risdiplam. Swallowing function improved in 35% of patients - notably, three children with severe feeding difficulties were able to begin oral taste feeds. Respiratory function improved in 30%, with some children reducing their ventilator dependence from full-time to nighttime-only support.
Safety was reassuring, with no serious adverse events attributed to the combination therapy. Only one child discontinued risdiplam due to perceived lack of effectiveness. The most common reason for starting risdiplam was inadequate improvement or plateau after gene therapy (75% of cases).
These findings suggest combination therapy may help SMA patients who don't achieve optimal outcomes with gene therapy alone. However, this was a small, retrospective study without controls, and larger prospective trials are needed to confirm these promising results.
Key Findings
- 92% of children showed stable or improved motor function after adding risdiplam to gene therapy
- 35% had improved swallowing function, with some able to begin oral feeding
- 30% showed respiratory improvements, including reduced ventilator dependence
- No serious adverse events were observed with the combination therapy
- Most common reason for combination therapy was plateau after gene therapy alone
Methodology
Retrospective case series of 20 children from six US neuromuscular centers who received onasemnogene abeparvovec followed by risdiplam. Motor function assessed using CHOP-INTEND and HFMSE scales, with respiratory and swallowing outcomes evaluated clinically.
Study Limitations
Small sample size, retrospective design without control group, and variable follow-up periods limit generalizability. Larger prospective studies needed to confirm efficacy and establish optimal timing for combination therapy.
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