REGENXBIO Inc. Morgan Stanley 24th Annual Global Healthcare Conference

Sure. We have been in AAV gene therapy for 15 plus years at this point. Our base technology is based on AAV8 and AAV9 as the capsids that we have put into clinical studies over time. I think in the first few years, mainly did a lot of out-licensing of the technology, and that is one of the programs that came from that was Zolgensma, so a long lineage of success in scaling these technologies up. About 12 years ago, we decided to internalize programs and develop our own, and now we sit here today with a retina franchise that has got a significant partner with AbbVie and some late-stage data coming soon. Then the rare disease side, which I think our primary asset is the Duchenne program, RGX-202, alongside the Hunter program as well.

A lot going on, and I feel like we are just at the last edge of late-stage development, hopefully heading into commercialization next year.

Yeah, I think there are some significant differences. We went into the program several years back with the idea of a differentiated product. I think the primary, from a molecule standpoint, it is the addition of the C-terminus to the microdystrophin. The C-terminus, all the way back to Elevidys' AdCom, you can see FDA referencing that addition as making microdystrophin more like natural dystrophin. Our preclinical studies show a differentiation in basically muscle repair because of that C-terminus, and so that was incorporated. I think also two other key elements of it are a very modern manufacturing process. We can make very significant quantities of the product with a future low cost of goods, and most importantly, 80% full capsid, so very high purity as well. The last piece that Steve can certainly speak to later is the immune suppression regimen.

Right. That is what allows us to deliver the maximum dose safely and gives patients, we think, the best opportunity for benefit.

Yeah, I think we are showing a couple of areas of significant differentiation. Certainly, in patients that are, I would say 7 and older, we are seeing levels of microdystrophin 4 to 5 times greater than what was shown previously on Elevidys. I think on the consistency side, 80% of the patients have been measured to have 40% or more microdystrophin as a percentage of normal.

Right. We feel like the delivery and the methodology we're using is giving people the maximum chance and significant levels of biomarker.

One other aspect of that is very high vector copy number.

What do we think that's important for is long-term durability. Of course, that takes time to adjudicate and see if that manifests in the clinic, but we're really hoping that that leads to the ability to treat young patients and sustain that benefit longer.

Yeah, we're enrolling 1 and older. We've dosed patients that were 12 at the time of dosing, so we've got a really broad range. Interestingly, in the recruitment of the pivotal study, a pretty balanced level at each age group, so 1 to 4 to 7, and 7 and older, a nice balance across all three. So we can see, because there is an age dependency to the manifestation of the disease, we can see the clinical benefit more pronounced in the older children.