Julie A. Parsons, MD Haberfield Endowed Chair in Pediatric Neuromuscular DisordersProfessor of Clinical Pediatrics and NeurologyUniversity of Colorado School of Medicine, Children's Hospital ColoradoAurora, CO, USAAs we talk about the gene transfer therapies and the modalities that we have to use, it's really interesting. Yesterday, with our keynote speaker, you could see this logarithmic growth of the use of gene transfer therapies for these disorders. If you look at the Venn diagram, you can see that really 27% almost of gene transfer therapies that are used are in musculoskeletal and neurology. For many of us as neurologists, we also take care of metabolic disorders.We really own right now this landscape, and of course, our two approved modalities are Onasemnogene and Delandistrogene. We're going to look at three different disorders, monogenic disorders, monogenic diseases, to typify what we look at in terms of some of the risks and benefits of these treatments. SMA, Duchenne, and X-linked myotubular myopathy are all rare disorders. They're all diseases that have a high unmet medical need and a significant disease burden.I think they're all good in terms of typifying where we are clinically with these disorders. The first question is, is it worth it? Are these effective treatments? We know from looking at the information about SMA that just looking early on, we know that if we treat kids early, that we do see a marked improvement in motor scores for kids that are treated early with Onasemnogene.In Duchenne, we have information that there is at least some improvement in the 4-5-year-olds in terms of motor skills treated with Delandistrogene. In terms of X-linked MTM, which was a very dramatic improvement, you could see that for boys who were basically traked, vented, and had no mobility, the bottom line, the blue line, is actually looking at ventilator dependence. Are they effective? Yeah, they're effective, but then we have to say, okay, what's the downside?The downside is that there's tremendous risk associated with treatment with these agents. If we really look at the sobering facts, we know that with SMA, there have been deaths, there have been fatalities related to thrombotic microangiopathy to patients who have liver failure, a couple of patients have died. With Onasemnogene, this is 4,000 plus doses that have so far been given. With Duchenne, unfortunately, many of us got the letter yesterday talking about an additional death in a patient treated with commercial Delandistrogene.We also know with some of the other agents, like fordadistrogene, patient died of heart failure, cardiac arrest, another patient who had acute respiratory syndrome with pulmonary edema. Again, we look at this and say this is significant. With X-linked MTM, as Alan said, there were some unanticipated deaths, four deaths from patients who ended up having cholestatic liver diseases that really wasn't anticipated prior to the patients being treated with the animal models and all that we had. Then many of you have heard about the patient with Rett syndrome who had a systemic hyperinflammatory syndrome. Again, these are rare disorders. They have a high disease burden, but the risk of treatment is significant.In the next part, Dr. Parsons discuss factors impacting safety and efficacy of AAV-mediated gene therapies.