A study released a long-term comparative analysis of AAV9-mediated gene replacement therapies in murine spinal muscular atrophy (SMA) models. It compares engineered gene therapy versions over extended time horizons, with the goal of understanding durability and performance across approaches. For SMA programs, long-term data is a central hurdle because AAV-delivered therapies must sustain motor function benefits and avoid late-onset complications. The study’s comparative design adds context for selecting vector and expression strategies for translation. While the report is in animal models, the focus on longevity strengthens the evidence base for AAV9 approaches and informs what durability targets future clinical follow-up should capture.