A first-in-human phase I/IIa gene transfer clinical trial for Duchenne muscular dystrophy using rAAVrh74.MCK.GALGT2

<p>In a phase 1/2, open-label dose escalation trial, we delivered rAAVrh74.MCK.<em>GALGT2</em> (also <em>B4GALNT2</em>) bilaterally to the legs of two boys with Duchenne muscular dystrophy using intravascular limb infusion. Subject 1 (age 8.9 years at dosing) received 2.5 × 10¹³ vector genome (vg)/kg per leg (5 × 10¹³ vg/kg total) and subject 2 (age 6.9 years at dosing) received 5 × 10¹³ vg/kg per leg (1 × 10¹⁴ vg/kg total). No serious adverse events were observed. Muscle biopsy evaluated 3 or 4 months post treatment versus baseline showed evidence of <em>GALGT2</em> gene expression and <em>GALGT2</em>-induced muscle cell glycosylation. Functionally, subject 1 showed a decline in 6-min walk test (6MWT) distance; an increase in time to run 100 m, and a decline in North Star Ambulatory Assessment (NSAA) score until ambulation was lost at 24 months. Subject 2, treated at a younger age and at a higher dose, demonstrated an improvement over 24 months in NSAA score (from 20 to 23 points), an increase in 6MWT distance (from 405 to 478 m), and only a minimal increase in 100 m time (45.6-48.4 s). These data suggest preliminary safety at a dose of 1 × 10¹⁴ vg/kg and functional stabilization in one patient.</p>