Spinal Muscular Atrophy Clinical Trial Landscape

The SMA trial landscape in 2026

Spinal muscular atrophy is the rare disease success story of the decade. Three approved therapies transformed what was once uniformly fatal in its most severe form: onasemnogene abeparvovec (Zolgensma, Novartis), nusinersen (Spinraza, Biogen), and risdiplam (Evrysdi, Roche). Each mechanism works differently — gene replacement, antisense oligonucleotide splicing correction, and oral small molecule splicing correction — and each has a different administration route, cost, and durability profile.

The current clinical development focus has shifted to two underserved populations: (1) patients who were treated with one approved therapy and need to know if switching or adding a second agent is beneficial, and (2) older patients with SMA Types 2 and 3 who were not treated in infancy and have substantial motor neuron loss that gene therapy alone cannot reverse.

Key SMA program categories to monitor:

• Next-generation SMN2 splicing: Higher-potency or CNS-penetrant small molecule splicing correctors beyond risdiplam
• Combination therapy: Risdiplam or nusinersen plus onasemnogene in previously untreated or re-treatment populations
• Adult SMA: Programs specifically addressing SMA Types 2 and 3 in adolescent and adult patients, including muscle-targeted approaches
• Neuroprotection: Agents targeting motor neuron health independent of SMN levels — for patients with irreversible loss
• Gene therapy follow-on: Long-term follow-up studies of onasemnogene cohorts, re-dosing studies, and next-generation AAV9 constructs
• SMA with respiratory compromise: Specialized programs in ventilator-dependent SMA patients

Who uses SMA trial monitoring

Rare disease BD teams

Biogen (nusinersen), Roche (risdiplam), and Novartis (onasemnogene) dominate SMA — but the combination therapy space and adult SMA are open for in-licensing. Academic programs and smaller biotechs developing neuroprotective agents, next-generation SMN2 modulators, or muscle-targeted approaches are active licensing targets for any company seeking to expand their SMA franchise.

Neuromuscular disease investors

The SMA market is one of the best-validated rare disease markets by payer acceptance for high-cost therapies. Analysts watch combination therapy trials closely — if risdiplam plus onasemnogene significantly outperforms either alone, that drives new trial designs and potential label expansions across both franchises.

Patient foundation-engaged professionals

Cure SMA and SMA Europe engage actively in clinical trial design. Companies developing in SMA benefit from tracking all active trials to understand the competitive landscape for patient enrollment — a critical constraint given the relatively small patient population (approximately 10,000 SMA patients in the US).

Frequently asked questions