Gene therapy with covalently closed-end AAV vector for spinal muscular atrophy

Covalently closed-end adeno-associated virus (cceAAV) vector is a new generation of self-complementary adeno-associated virus (scAAV) vector that does not utilize a mutant inverted terminal repeat (ITR) for vector production. Importantly, packaged genomes of these cceAAV vectors are markedly more intact than traditional scAAVs, which typically contain a large fraction of incomplete genomes, including many that lost their self-complementary configuration. Here, we report the first in-human experience with a cceAAV vector. High quality clinical grade cceAAV vector based on AAV serotype 9 (AAV9) was produced in 200 L of suspension 293 cells with a total yield of 4.3 × 10¹⁶ vector genomes (vg). Clinical trial in two spinal muscular atrophy (SMA) patients via intravenous injection at 12-24 months of age revealed no treatment-associated severe adverse events with a dose ranging from 6 × 10¹³ to 1.2 × 10¹⁴ vg/kg. Both patients showed rapid improvements in motor capabilities after gene therapy, as evidenced by substantial gains in motor function and electrophysiological parameters and capacity for independent mobility. Our strategy enabled us to perform gene therapy in older SMA patients who had received initial treatment with RNA-splicing modifying drug during infancy. These early data provide preliminary evidence for clinical use of cceAAV vectors, though further validation in larger cohorts is warranted.