Taysha Gene Therapies, Inc. (TSHA) Earnings Call Transcript & Summary

Good morning, and welcome to Taysha Gene Therapies Manufacturing Day. [Operator Instructions] Today, members of our management team will discuss our 3-pillar approach to manufacturing, the immunology of gene therapy and the regulatory landscape as it relates to manufacturing. Joining on the call today is R.A. Session, Taysha's President and Founder and CEO; Dr. Frederick Porter, Chief Technical Officer; Greg Gara, Senior Vice President of Manufacturing; and Dr. Suyash Prasad, Chief Medical Officer and Head of R&D. Next slide. Before we begin, please note that this presentation will include forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Please see Slide 2 of the company presentation and Taysha's SEC filings for important risk factors that could cause the company's actual performance and results to differ materially from those expressed or implied in these forward-looking statements. Taysha undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date of this conference call, except as may be required by applicable securities law. I'd now like to turn the call over to our President, Founder and CEO, R.A. Session II. R.A.?

Thank you, Kim. Good morning, and welcome, everyone, to our Manufacturing Day, which is the first of our Investor Mini Series. Next slide. We hope you find this very informative and look forward to joining our future Investor Days on CLN1 in August, Rett syndrome in September and Angelman syndrome in October. Next slide. Kicking the series off today, we are extremely excited to do a deep dive into our unique gene therapy manufacturing strategy here at Taysha. We will discuss how our approach is designed to overcome current challenges in AAV production and allow for rapid preclinical to clinical development using a flexible and scalable approach that integrates R&D and manufacturing early on. And we will review how this can derisk our overall portfolio and support consistent delivery of highly concentrated and pure products across our broad pipeline. We will also discuss recent key learnings in this space as well as relevant considerations like immunology of gene therapy and the regulatory landscape, as it relates to manufacturing. We believe these are all important topics that should be open for discussion to work collaboratively with others in the industry with the common goal of getting gene therapies approved efficiently and expeditiously to treat patients with debilitating and life-threatening diseases. Next slide. Today, you will hear from 3 members of our management team: Dr. Fred Porter, our Chief Technical Officer, who has over 25 years of manufacturing experience, including bridge -- including time at Bridge buy. We are also fortunate to have Fred as part of our team. He spent many years developing the gene therapy manufacturing process, which we are now using in our products. Which has allowed for a seamless transition to Taysha and a productive partnership with Catalent, UT South and UT Southwestern. Today, he will be discussing our 3-pillar approach to manufacturing. Greg Gara is our Senior Vice President of Manufacturing. He has over 25 years of experience in designing, constructing and starting up manufacturing facilities, most recently at Sarepta. Prior to that, he was at AveXis where he led the design, construction and start-up of the Liberty Bill facility and the new facilities in RTP North Carolina and Colorado. He also led the team focused on the facility expansion in North Carolina and the renovation of the Colorado site. Today, he will be discussing our commercial process. Dr. Suyash Prasad is our Chief Medical Officer and Head of R&D. He brings deep expertise in global drug development, and was previously the Chief Medical Officer at Audentes, where he led the development of its AAV8 program. Next slide. Our scientific approach is focused on the use of validated gene therapy technology, coupled with novel targeted payload design. We utilize AAV9 for its ability to effectively transduce cell types within the CNS, along with its well-validated safety and efficacy profile, as demonstrated in multiple preclinical and clinical programs. Our HEK293 triple transfection suspension process is highly scalable and offers yields in comparison to other methods currently utilized for recombinant AAV manufacturing. We believe this provides the right balance between scalability, yield and risk. In addition, our AAV manufacturing has been proven safe and effective across multiple serotypes in the clinic today. Importantly, we are confident that our process is not associated with some of the inherent toxicity related with other non-mammillian manufacturing systems, where there is always the risk of host cell DNA contamination and the final formulation of the drug, which can cause decreased transduction rates, increase in inflammation and ultimately impact efficacy and durability. The third part of our validated technology is the use of interthecal delivery as our chosen route of administration. Physicians have been administering intrathecal medicine for decades in an outpatient setting across multiple modalities. Intrathecal deliveries allows us to target CNS broadly, evade neutralizing antibodies by starting on the right side of the blood-brain barrier. Of course, the proof is in the data. It's been proven safe and effective when used in combination with AAV9. Intrathecal dosing has been studied extensively now across 4 clinical programs, including an SMA with Zolgensma in the STRONG trial; CLN6 Batten disease, CLN3 Batten disease and in our giant axonal neuropathy study with TSHA-120 which was the first intrathecally-dosed gene therapy trial in history. So by controlling for these key aspects, we believe we increase the probability of success and reduce the overall risk to our portfolio. Next slide. We view manufacturing as a strategic capability that distinguishes us from others in the field. Our integrated platform approach involving the full characterization of material from discovery through commercialization, allows the rapid development of multiple gene therapy candidates to the clinical stage. We depend on a reliable clinical and commercial supply, and we ensure that we have scalable commercial-ready manufacturer processes in place for each new candidate. We believe our approach derisks our portfolio and allows us to maintain time lines. It also allows for more favorable cost of goods sold, which Fred will dive in, too, shortly. Next slide. One of our core strategic advantages at Taysha is the partnership between R&D and CMC. Gene therapy manufacturing is highly complex and needs a full understanding of the underlying science. So it is important to have a Chief Technical Officer, who appreciates the scientific approach and has a strong foundation in scientific principles. In addition, the gene therapy field is rapidly evolving with respect to manufacturing. CMC analytics and bioanalytics requiring new techniques and expanded scientific thinking to be open into our approach to ensure that we continue to produce highly pure scalable products. This has reflected in the opinion of the regulators who are becoming increasingly focused on getting CMC production and analytics optimized much earlier in the development process. At Taysha, we are enhancing and expanding CMC and the research side of the R&D group in parallel, partnering early on and encouraging collaborative dialogue from inception. This is mirrored in the fact that the permanent R&D lab space -- our permanent R&D lab space is being built out next door to our 187,000 square foot GMP manufacturing facility in Durham, North Carolina. As CEO, I have been pleased to see the close respectful and highly engaged partnership between Fred and Suyash and their respective teams, in ensuring that we make gene therapy products expeditiously and of high quality to enable us to dose patients confidently. Next slide. Our manufacturing strategy allows for flexible and scalable manufacturing to support our broad pipeline. With such a deep portfolio, we never want to be capacity constrained. Next slide. Our 3-pillar approach to manufacturing includes our dedicated capacity at UT Southwestern here in Dallas, which currently runs a HEK293 triple plasma transfection suspension platform at 500-liter scale, soon to be 700-liter scale by the end of the year. This capacity is sufficient for early IND-enabling tox material as well as early clinical trial material, particularly for investigator-initiated studies. We couple that scale through our collaboration with the Paragon, subsidiary of Catalent, which Fred helped to essentially pioneer the gene therapy manufacturing process through our collaboration -- through our early collaboration at Taysha. We have significant dedicated capacity at Catalent, focused on early and late clinical-based material with the ability to augment that scale to commercial, once we reach that stage. Catalent is the only CDMO partner that is licensed to manufacture commercial AAV9. That takes us to our third pillar, which is our own internal manufacturing facility, which we are currently building in Durham, North Carolina. We recently broke ground on this 187,000 square foot facility, which will be 2,000 liters of scale with enough space to double that capacity to 4,000 liters worth of scale in the near future. We are very excited that this will be a multiproduct facility, meaning multiple production suites, but we'll also have full analytical capabilities, manufacturing process development, as well as product characterization and potency assay capabilities to release product within the facility. Now that I have provided you with an overview of the company. I will now turn the call over to Fred to discuss in detail our 3 pillar process. Fred?

Thanks, R.A. Welcome to all of our attendees for the manufacturing day today. I'm really excited to share with you, first, our 3-pillar approach to manufacturing, and we can dig in into a bit of a detail around what we're doing today and what we intend to do in terms of building a manufacturing facility for tomorrow. Next slide, please. But before I start with what we're doing today, I think it's probably important to reflect on how AAV manufacturing technology has evolved. And indeed, it is -- it's really evolved along with the science of gene therapy itself. When this technology was at its inception in the 1980s, we really used flat stock, low-volume tissue culture to propagate and produce AAV vectors. But as needs evolved along with the science with requirements for additionally -- additional lots and expanded volumes of product. The manufacturing technology is above, and that move towards roller bottle production onto cell factories. And in the 2010s into an adherent-based manufacturing-based processes like the ISLS bioreactor. But where we are today is moving that technology a bit further along towards industrialization. And what Taysha has invested in is a suspension-based process, which is scalable and efficiently utilizes our manufacturing space. So along with the production side of the technology, our purification approaches have evolved as well. In the early days of the basic science of AAV, we used centrifuge-based production, so clarifying [ supernation, considering ] our AAV particles first, and then separating our viral particles from other contaminants using centrifugation-based process disease. In the '90s through the 2000s, chromatography-based approaches were advanced, including ion exchange purification and then followed by affinity ligands who were specific for AAV. And today, we're seeing the evolution of multi-column approaches along with the traditional approach as to AAV purification being advanced for manufacturing. What we've invested in Taysha is trying to use the latest technology in production and purification to advance our programs to the clinic. So I'll now go into our 3-pillar approach to manufacturing and how we're using it to support our deep portfolio of programs at Taysha. Next slide, please. So as R.A. introduced in the introduction, we see our manufacturing approach as a 3-pillar strategy. First, partnering with our collaborators at UT Southwestern to produce early phase nonclinical and clinical vector. And this allows us to advance programs very quickly from a preclinical proof-of-concept to the clinic. They have scalable production at 50-liter tox scale and 500-liter GMP manufacturing in their pilot plant that we're utilizing to advance some of our early programs. Because our portfolio is so diverse, and we're advancing so many programs in parallel, we have been very proactive in partnering with leading CDMO partners to augment UT Southwestern's capacity. And one particular partner in this effort is Catalent. We are now -- they are a strategic partner for many of our programs where we're advancing multiple programs in parallel using our platform process to deliver on our clinical commitments for the year. Catalent also has large-scale capability in non-GMP in their GMP suites, where they're able to produce a 200 and 500-liter scale for nonclinical tox production as well as 800-liter and 1,000-liter commercial grade material. We're also leveraging the depth of expertise and analytical development in QC testing to support a full release panel for stability and characterization. So these are where we're investing our time today for our programs as they're advancing very rapidly out of our collaboration with UT Southwestern. But we know, based on our portfolio, we need to plan for the future. And so we've invested early in building manufacturing capacity of our own internally at Taysha. As I mentioned, we're utilizing 500-liter scale bioreactors scaled out in multiple trains at our new facility that we [ browned ] in Durham, North Carolina, which is a growing hub for gene therapy manufacturing. We broke around just a few months ago, and we expect our facility to be ready in 2023. And then I'll go into a little bit of detail about how we think about each of these pillars of our strategy, as we advance our portfolio programs. Next slide, please. So first, I'll start with UT Southwestern. As I mentioned on the slide before, we envision UT Southwestern as a key partner are rapidly advancing preclinical programs to the clinic. We're really focused on that innovation piece, from vector design to candidate development to early clinical manufacturing. And the team at UT Southwestern is really positioned to do this. So as we identify a candidate design, they'll evaluate it in their nonclinical vector core, then they'll be able to -- they are able to rapidly scale it up to a nonclinical batches that we use for pivotal nonclinical studies and then advance that same candidate to early manufacturing. And one of the key emerging themes in gene therapy is that comparability of early nonclinical lots with clinical material has become really critical. And this is really an advantage to us to have a partner like UT Southwestern to allow us to do that because we're using the same process for our nonclinical early clinical and other -- our outsourced programs. Shown here is their footprint where they have process development, QC and GMP capability within the facility and allows for that rapid transition out of the research laboratory into manufacturing. Next slide. So the second pillar of our approach, again, is Catalent and other CDMO partners. We know we have a deep portfolio, which really requires a partnership. And indeed, in the last 10 months, we've advanced 5 programs out of our portfolio into CDMO partners for manufacturing. Our intention is to build robust high productivity, high-quality asset with high-quality analytics to support advancing these programs very quickly from early clinical to pivotal programs. We've also invested in making sure this is a platform approach, aligned with what we've established at UT Southwestern to save time and identify cost efficiencies with our subsequent programs as they move to the clinic. This has helped us in terms of streamlined tech transfer, where our CDMO partners know the process we intend to use for each new candidate and abbreviated development time line where we've been able to compress that tech transfer phase of a process for any new candidate and to move it into manufacturing. We're trying to be mindful, upfront with this early clinical manufacturing about where we like our programs to be. And indeed, through these partnerships with Catalent and others, we're envisioning our path to what it would take to bring these programs to full commercial processes with assay qualification and validation to support BLAs. And then by building these relationships early, we're able to use the standing relationships to advance new programs or new strategies as we move our portfolio forward. Next slide, please. And finally, so we'll end up with -- end with our [ Taysha ] facility in RTP, and this was an early investment by the company supported by R.A. and the Board. Just to reiterate, again, as R.A. mentioned, this is a 187,000 square foot facility in Durham, North Carolina, with multiple production suites for upstream, downstream and fill finish. And we intend to use this facility to provide preclinical to commercial material field. In addition to the state of the art manufacturing facility design and process that we're using. We're also equipped with quality control labs to support the release of that product, which is critical to maintaining time lines for delivery. And indeed, in our facility design, that Greg will present in the next section of this talk, we have space for future expansion. We didn't utilize the entire facility in the first phase of growth. And we intend to flex that facility space as needed to support our pipeline. One of the other advantages, as R.A. mentioned, is that we've co-located this facility with our technical development group, which will be in the same building and our R&D labs, which will be just around the block to translate the latest science into products. As R.A. mentioned, we've had a really strong relationship between our research and development and technical development departments, and I think that benefits us immensely and trying to understand the products we make in feedback from manufacturing into the latest designs for new candidates. And all of this is located in the Research Triangle Park area, which has really become a hub for gene therapy talent in manufacturing as well as R&D. And we think that this early investment in manufacturing in the early months of our company's formation will really pay dividends because of our deep portfolio of multiple candidates but really high profitability of commercial success. And that's again why we've taken this 3-pillar approach to manufacturing. Next slide, please. And so again, why are we investing in internal manufacturing, it reduces supply risk and cost. We're happy to work with our partners at UC Southwestern for early clinical manufacturing and our CDMO partners. But by owning manufacturing, we're able to control all aspects of production release and supply chain, which really leads to ability to respond more rapidly to new programs, improve our processes and do it at a favorable cost. We do believe by investing in analytical capability and technical development, we can improve yields and increase robustness of our processes, which improves manufacturing success rate and consistency, which is also a really key attribute to success in gene therapy. And then also supply chain, we know that specifically due to all of our experiences during COVID this year, the supply chain matters, especially for gene therapy. And by controlling our supply chain risks and costs, we can favorably impact delivery of our product at a reasonable cost of goods. Next slide, please. So I think you're hearing a theme in our philosophy that leading with science and optimization and a good process really matters to us. And so this is something that we're baking into, how we think about gene therapy manufacturing. And then this really starts with the production process. So delivering a high-quality product of high yield, by a scalable approach, right out of the gate. And so we're fortunate that Dr. Stephen Gray, our partner at UT Southwestern, had the same vision that he invested in suspension-based production technologies in an academic setting. And so we're able to translate that nicely from early preclinical manufacturing on over. And so what we want to do is invest in continuing to be best-in-class in our production technology, which has been often been a focus in gene therapy because we have to make product to be able to maintain it throughout the process. Secondly, we're focusing on the downstream process and not only just to maintain high yield, but also quality and mitigate any safety issues that might arise. We know the agency is very focused on safety of gene therapy products and minimizing the presence of process residuals and contaminants is key. And so we're investing in building best-in-class downstream processes. Thirdly, we're focused on analytics, because we don't know for any process that we run, we can't understand it without a high-quality analytical panel with methods that are reliable and consistent. And so again, we're investing in this area in technical development in QC and R&D to make sure we're investing early. And I think this is one of our strategic strengths at Taysha that we're asking the questions early that we can have conversations about the quality attributes of our product and that we're investing in this for every batch we make essentially. And then it really gets down, so once we've done all that right distribution, making sure we have a thoughtful process of that distribution product, stability study, the supporting data and the processes to make sure we get our product to patients with a high quality and high potency. Next, please. So taking a step back, again, like I did in the first slide of this section, AAV manufacturing has evolved, and it's evolved from basic academic processes to the industrial processes we have today. But we still have a lot of diversity in the approaches that people are taking. Some of the early AAV by its name is adenovirus-associated virus . It was discovered because -- as a result of adenovirus co-infection in some of the earliest processes, used adenovirus as a helper virus for propagation. And these helper virus platforms are still in existence today. They are scalable and don't require a specific cell line that includes the complexity of a viral co-infection where these helper viruses need to be purified out. There's been investment in packaging cell lines, which are product-specific lines that minimize the need for helper viruses. But they have some complexity associated with them, meeting a new cell line for each product and still, again, have to mitigate the concerns about co-infection with an augmented virus. There's been a lot of discussion in the AAV field around baculovirus and SF9, and indeed, with optimization, they've shown to be of high yield and not require a product-specific cell line. But there's certainly some complexity and time involved in optimizing these processes and open questions about differences in post-translational modification and how they affect potency and immunogenicity. At Taysha, like as R.A. mentioned, we've invested in triple transfection in human embryonic kidney cells as our approach because it's, as R.A. mentioned, it strikes the right balance of good yield, rapid development and a harmonized platform process for every program. And at Taysha, with our large number of AAV9 programs. This makes sense for our needs of our portfolio, it's scalable and easy to implement for new programs. And so this is what we've invested in at Taysha. And so I'm happy to go through a few additional detailed slides about the platform that we've invested in. Next slide. And so our goal, like other gene therapy companies, is to produce high-yielding, high-quality AAV manufacturing processes. As we talked about earlier in the section, the first generation of this technology utilized attachment dependent systems that use serum. At small scale, this is executed in tissue culture flasks with cell factories and an industrial scale in attachment dependent bioreactors like the [ ISLS ] system, where Taysha and some others in the field have moved to is the suspension-based system, which is more standard for biologics production and utilizes standard off-the-shelf equipment that is easy to scale. And so what we've done is utilize that this platform process using flasks, crytovials of preserved cells to seeds [ shaped ] flasks and then wave bioreactors and then culminating in production in a stirred-tank bioreactor. This has been scaled up to 2,000 liters in the field and really represent kind of the latest technology advancement for a triple transformation process. And this is what we're utilizing at Taysha. Next slide. So we've also spoken a bit about purification technology and how that's evolved. Originally, academic processes use ultracentrifugation steps, and these are still in use today because they work. However, these processes are -- have risks associated with them when implemented in a manufacturing setting. There's a lot of open handling and manual manipulations that are difficult to control at scale. There's a risk because of them being open processes for microbial contamination and process variability and increase labor costs. Next slide. So at Taysha, we've tried to incorporate all these thoughts into our final process. And so again, we are using a human embryonic kidney triple transfection approach across platforms and sites, so we've implemented the same cell line, the same transfection process whether it's at UT Southwestern, at our CDMO partners or at our future facility in Durham, North Carolina. So we have access to a commercially available well-characterized HEK cell line. We have a paid up in royalty free license to that cell line for all of our products at Taysha. Because that we don't require serum or any animal components in media, it's more -- it's easy to scale and has a very clean advantageous agent profile. So that's something that's been -- that will be a benefit to us in the long term. In terms of our triple transfection platform, the way we think about this, this is the only thing that changes with a new candidate that comes out of our discovery work with UT Southwestern is a novel transgene payload and that is part of the diversity of programs at Taysha. We will innovate on payload design, whether it's a recombinant enzyme that's either unregulated promoter or under the control of different types of gene regulation and siRNA or others. And so this is something that as a manufacturing team, we need to be prepared to respond to. However, we use platform plasmids for the AAV replicates in AAV9 capsid. Again, all of our programs utilize our AAV9 capsid and the adenovirus helper elements, E4, E2A and VA elements that are required for replication. And so we continue to use this platform. And as we innovate on this platform, we've evaluated advanced transfection reagents which have helped increase yield and decrease empty capsids in our products. And so this is the platform we're using at a 500-liter scale across sites in our network. Next slide. So I mentioned the traditional downstream purification processes. What we've invested in Taysha is a universal column-based purification process, and that's scalable and it allows it to be operated as a [ closed ] system with consistent batch-to-batch performance and favorable yields. This involves an affinity capture step using AAV9 specific ligands that result in a high purity in concentration afforded in a single step. And we've invested in using ion exchange technology to enrich and full capsids in our final product, which results in a high yield and a high full particle ratio comparable to ultracentrifugation methods. We've also invested in and evaluate -- selecting and evaluating a stable product formulation that's favorable under all storage and handling conditions, including the clinic, and we're generating a great body of data on this formulation to support shelf life for all of our programs in the portfolio. And all of this is shown in the schematic below, again, so 2 key steps to the process of ultrafiltration and to a final formulation step and then sterile filtration steps to get us to drug product. Next slide, please. So I'll come back to the theme of analytics. And I -- and again, one of the other pillar -- the sub pillars of our 3-pillar approach is investing in analytical technology. So we know that robust analytical testing to characterize our product is important to demonstrate safety and efficacy. This is something that the regulators in the U.S. and EU have focused on in terms of specific guidance, and we'll get to some of the emerging themes in regulatory feel for gene therapy later in the talk. And that these analytical methods really play a pivotal role in understanding our processes and the attributes of our product that regulators and sponsors like us care about: strength; purity; safety; and potency. The interesting thing about AAV is, I feel like, it combines in terms of an analytical profile, some of the biophysical and biochemical methods that are used traditionally for protein biologics with advanced molecular assets. We need both of those to understand our product because of the AAV particle being a proteinaceous capsid and coding a gene of interest. And then together, we use this collection of assays as a -- a biochemical fingerprint that really defines the attributes of the product. And what we strive to do in the field in, at Taysha specifically, is to keep that consistent from batch to batch. And that's really our objective as a company is to use these analytical tools to inform our processes and inform our methods to deliver this for every batch of product [ that we make ]. Next slide, please. So now I'll go into some of the assays that we think about when we're thinking about quality attributes of gene therapies, Well, I thought I'd start with just defining these characteristics: strength; purity; integrity; potency; and safety. For AAV, strength really, it represents the amount of drug per dose. And this is something which I'll get to in the subsequent slides is really critical in AAV. Purity, which is not a surprising characteristic, but it's a measure of product versus contaminants. Again, when we're thinking about the safety of our product, a really critical attribute. Integrity, measure of our intact product. And I think in gene therapy and AAV that means intact particles and intact genome. So there's really 2 elements of the product that we care about here. Potency, that presents the functional activity of AAV vectors. And then safety, other attributes that are directly related to the safety of our product, such as sterility which we need -- we know we need to maintain for delivery [ reasons ]. Next slide. So now I'll try to get into how we think about what are some of the technologies and considerations for each of these attributes. So as we think -- as we define strength for AAV vectors, usually, most sponsors like us. Think about this by measuring the number of copies of the transgene cassette per patient. And so how do we measure that? We really measure that using molecular techniques using quantitative PCR. And now this is an area of molecular analytics that's evolved quite a bit over the last decade. In the '80s and '90s, PCR was just a qualitative technique where you can unload a certain amount of DNA on a gel and used densitometry. But the field has rapidly moved towards quantitative methods such as a real time PCR, which is the relative quantitative method where the amount of DNA and polymerase chain reaction is quantified versus a reference, based on the number of cycling that is required to get to the same signal. But now a new technology have emerged in the field using things such as Droplet Digital PCR, which is a uses a Poisson distribution of diluted PCR reactions to measure how many positive or negative droplets in a reaction are generated when it's subjected to a PCR cycle. And the benefit of this, it's really an absolute quantitation, not requiring a reference standard. And because of this, the amount of variability in the method has been used. And I think it's become the gold standard in gene therapy for a dose method. And so again, at Taysha, we've been investing in using best-in-class methods for defining dose because it really matters when we translate this from nonclinical experiments into clinical doses. Next slide. So then there's purity. So purity is also important. We want to reduce toxicity and potential immunogenicity of our products. We measure things such as aggregation, total protein purity and the amount of empty and/or a defective particles. So the kind of techniques that are -- as well as process residuals, including detergents, and other process components, plasma, ligands and the like that could result in a safety or immuno hypersensitivity risk. So again, we're investing in methods to measure this using, starting with gel electrophoresis and the figure on the right shows an example of a gel -- electrophoresis gel for multiple serotypes. And you can see some of the differences in pattern here. primarily based on serotype, but also you can see alternate bands that are there, which are really a reflection of purity. Aggregation is another important criteria because if we have an aggregated product that's not fully functional. And so we're using sizing technologies like size solution chromatography and light scattering to measure that. And of course, I think what's been an active discussion in the field measuring empty the [ full ] particles. So certainly, analytical ultra-centrifugation has been a leading method in the field as well as chromatography and electron microscopy. And you can see at the bottom of the figure on the right. The difference is in peaks, which really represent empty, intermediate and full particles for the preparations that were shown above and how important it is to measure these for every product. We're also thinking about safety and included in our release panel, sterility, endotoxin and measurement for adventitious agents, to make sure that we have a pure and safe product. Next slide, please. So this is integrity. So I think one of the other things that's important -- so we have a package piece of DNA, we ask the question, is that DNA a full length? Is our capsid of complete stoichiometry? And does it have full-length proteins? And we do that for our batches as well using sequencing. The current standard technology is [ syro ] sequencing, which is bulk sequencing. But we've been, again, invested into a deeper analysis using things like next-generation sequencing to better understand the products we're making. And we do the same for our capsid proteins, trying to ensure that we understand the quality of our products as we move. Next slide. So what we just talked about in the last few slides are really biophysical and molecular characteristics of our product. But what we really need to ensure at the end of the day is that it's -- has a functional biological activity. And the FDA considers this a really important attribute or gene therapy. And so we've invested our time and effort in building assays that can measure that. So the biologically relevant activity of our transgene product. For example, an in vitro enzyme activity for an AAV encoded enzyme is what we're investing time in. And so there are 2 general approaches for potency assay development in vitro methods, using a cell-based assay where we apply our gene therapy product that we allow it to transduce cells and then we look at the functional activity in an [enzyme] vitro setting. And so that's an area where the schematic shown at the right exemplifies where we use a tissue filter flask, transduce those cells and then measure it by logical activity of some kind. And every transgene or payload is different. And so we have to build bespoke functional activity -- enzymes activity assays for each of them. And another approach is to use [ NVivo ] method using a clinically relevant animal model of the disease, which is certainly possible, but really subject to the biological variability of an animal study. So that's another area of investment. Next step -- next slide, sorry. So what have we been doing? So we've been developing at Taysha, a panel of assays to measure these key attributes. We were thinking about the maturity of those methods and having a solid method to start with, so we can advance it to qualification -- validation to support BLA and MAA submissions, but we're also investing in things beyond just the release panel, deeper understanding of our product using advanced methods and that's a collaboration between R&D and technical development departments, I've already mentioned analytical ultra-centrifugation, next-generation sequencing, really developing best-in-class immune assays and reagents and utilizing mass spectrometry as a deeper characterization tool to inform future comparability studies. We've also invested early in potency assay development. We utilize a product independent infectivity method to get an early read of the functional activity of our products, but also our screening and building best-in-class AAV9 permissive cell lines as a basis for future potency assay development. And we're working on functional activity assays in the background to support our lead candidates as we advance them through the clinical development pipeline. Next slide. So in summary, I've described our 3-pillar approach and how it derisks our manufacturing for the portfolio. How -- we have -- are collaborating with UT Southwestern and industry-leading CDMOs to advance our early programs into the clinic. And indeed, we've invented 5 programs over the last 10 months that are in active GMP manufacturing. We are investing heavily and exclusively at Taysha and its commercial-ready HEK suspension process to derisk manufacturing demand from preclinical proof concept to pivotal studies and we've invested early and robust in analytical platform for release and characterization to inform our nonclinical and clinical studies and prepare for commercialization. So at this, I think that's the last slide of this section. And I would be -- if you want to advance to the next slide. And I'd be happy to take questions on this section.

Your first question comes from Laura Chico, Wedbush Securities. You mentioned your goal of winning capacity constraints in your commercial manufacturing platform. Could you talk a little more about the capacity at UT Southwestern, how that may impact program advancements?

Maybe I'll start, and then I can turn it over to Fred to provide some additional content. So when we initiated development and initiated work on the company, it was extremely important to kind of have a robust, validated manufacturing process and source for material. And this was extremely important as we were looking to rapidly advance multiple programs into the clinic early last year, and moving into this year and beyond. And we were fortunate that UT Southwestern had made significant investment along with Steve Gray around a commercially validated process that would be able to be transfer to ultimately a commercial scale facility and using that process early on in the translational research that he was initially doing and making sure that, that product was fully characterized understanding that this was becoming an area of regulatory scrutiny. And so we were pretty fortunate on that. Initially, UT Southwestern built out a GMP manufacturing suite running the HEK293 triple plasma transfection process and suspension culture at 500-liter scale, which is enough scale to initiate work on using intrathecal delivery, understanding that the amount of virus that you would need for intrathecal delivery is much, much less than you would need for an IV delivery or systemic delivery. Initially, they were running this at 500-liter scale, it would be enough to perform an initial clinical trial within the rare disease space using intrathecal route of administration. And so when you think about that, not only did they have the GMP suite, but they also had the process development suite that Fred mentioned before. That had the ability to initially run 50-liter scale which would ultimately support tox material and material that would ultimately go into IND-enabling studies, whether that was going to be in rodents or that was going to be in [ HPS ]. We've been fortunate to be able to augment that scale by an additional 150 liters to now run a total of 700 liters worth of capacity. 500 liters continue to be running the GMP suite and 200 liters in the non-GLP suite. And so we're pretty fortunate at that because, again, that gives us enough scale to not only be able to conduct early phase material -- early clinical phase material, but also tox material and have enough material left over for full product characterization, release testing and any type of profitability work that we would probably need to do down the line once we move from that facility into either our CDMO partner over at Catalent or in our commercial facility, which will come online in 2023. I'll stop there. But Fred, maybe you want to expand on that?

No, I don't -- great question, and thanks, R.A., and I agree with all of that. And what I would probably highlight is we, again, we see UT Southwestern as 1 pillar of our strategy, right? And they are able to advance programs very rapidly. But we're also taking advantage of the scale of our CDMO partners. As you probably saw from my slide that we have 5 other programs that are moving at our external partners. So we're not limited by the capacity of UT Southwestern. They are certainly an element of our strategy, and we -- well, we're exploiting -- not exploiting -- we're taking advantage of those relationships with CDMOs to scale out in terms of capacity. So -- and I think we mentioned UT Southwestern preclinical capacity, and that's something we're investing in, in our own facility as well. So again, those tech development labs will serve a similar purpose providing nonclinical material as needed if we have more programs moving in parallel going forward.

Great. Thanks, Fred and R.A. Your next question comes from Gil Blum of Needham & Company. When in clinical development phase, are there used from both Catalent and other production facilities, which will eventually be involved in commercial production. The FDA has been requesting clinical assessments of batch-to-batch variation from different facilities.

Go ahead, Fred.

Yes. And so I think -- The way we're thinking about this now, we would -- we're rapidly moving with the construction of our facility. It's our intention is, as soon as our facility is up and running, we will transition those late-stage pivotal lots to our own internal facility. So that's our intention. However, if we have a fast-moving program, that requires a pivotal lot before we're ready to manufacture, we'll continue to use Catalent as that partner. And I think we've seen this really nicely in others in the field who have really diversified their strategy with internal and external capacity for pivotal lots. And so we'll continue to follow the clinical demands of our portfolio and do what's right to, again, maintain that pivotal lot manufacturing in the facility where we'll launch them.

Great. Your next question comes from Raju Prasad of William Blair. Is the production and purification process you're currently using at UT Southwestern and Catalent, the same as you plan to develop at your in-house manufacturing process?

Yes. Yes, it's the same. So we're using the same column steps and the same processes. And we'll -- again, we want to maintain that across sites. And that's one of the benefits of doing so, it's keeping things as similar as possible.

And maybe, Kim, I'll just add to what Fred mentioned. I think, again, this is a central thesis to our approach at Taysha in order to be able to take on such a large portfolio is basically achieved a number of economies of scale. One of this being, again, running the same type of processes between either our CDMO partners, our team at UT Southwestern, and ultimately, our internal manufacturing facility. And I think another important aspect to this is something that Fred mentioned, not only are we running the same upstream process but also the same downstream process, but we're controlling for things, again, that we know work well across the portfolio and across the platform. Again, using a single capsid, which allows us using the triple plasma transfection process to only swap out one plasmid within that process, and that's the payload plasmin, which we essentially optimized for each product, whether it's a regulated gene replacement therapy, plastic gene replacement therapy, vectorized short hairpin RNA, vectorized microRNA or whatever it is. And I think this is something that's extremely important. Also the fact that we're using intrathecal delivery. Again, it allows us to be able to do a lot more within our manufacturing capacity. Not only are we putting the drug exactly where we need to be within the CNS, but we're also limiting the amount of virus actually going into the patient ultimately reducing the risk of any type of systemic toxicity or exposure that could potentially happen. And so yes, we'll go through some of that as we talk about immunology. But these are things that are extremely important that allow us economies of scale and essentially read through from one product to the next, and we're not having to recreate the wheel, no matter if we're at UT Southwestern GMP, we're at Taysha GMP or we are at Catalent or other CDMO partners.

Thanks, R.A., and thanks, Fred. Raju Prasad of William Blair has another question. How many different clinical-grade products can you produce and support at once between facilities at UT Southwestern and Catalent?

I don't think we've reached our limit, right? So -- What Catalent has provided us, and I should acknowledge we're meeting with other CDMOs as well, is that as our needs have evolved, and we've shared our needs with Catalent, they've been able to uncork more capacity. They've been able to give us access to more nonclinical bioreactors or other programs. And indeed, we have programs that are literally within a month of each other advancing in parallel. Now if we actually hit a limitation, and we haven't yet, we're open to working with other partners that can continue to advance all these programs in parallel. So obviously, our CDMO partners have more capacity than UT Southwestern, but we do see them all as part of our strategy.

Yes. And again, I hate to kind of repeat myself, but I think it's an important question, Raj, that you asked. And I think, again, this really lends itself to our strategy, the fact that we're not using different serotypes for different products. The fact that we're not using different routes of administration for different products really allow us the flexibility to be able to use this platform approach and to move quickly. I think as Fred mentioned earlier in his presentation, that we're currently running 5 GMP runs. And as capacity starts to -- as capacity starts to come available, we ramp up a new run because of the large number of products within our portfolio that have achieved animal proof of concept. So we feel really comfortable being able to quickly move from one product to the next because again, it's all a single plasma chain. When you start to think about the supply chain constraints, again, the only thing that we're augmenting that we're not able to stockpile is the payload plasma. But from an AAV perspective, from a helper plasma perspective, we're able to kind of derisk the supply chain by being able to stockpile these, and this also allows greater flexibility. There was a question earlier that I think, Raj, that you asked that I did want to answer and it was one question. It may have been Gil. So my apologies if it wasn't you, Raj or Gil. But the question was really around variability between production facilities. And I do want to make a comment, particularly for our GAN program. It's important to try to derisk these programs early. And because where we actually acquired the GAN program or TSHA-120, it was with 5 years of clinical data, good material, made within the same process, which is the HEK293 triple plasma transfection suspension process. So the goal for that particular program, because it's moved so fast, and we already have really good data is really to produce a like-for-like process and ultimately derisk that program as much as we possibly can. So what does that mean to us? It means basically manufacturing that -- it basically means manufacturing that product within the same facility as the rest of our other products or as in the same facility that it was originally manufactured from a clinical development perspective. And we're going to look to try to do that every time in order to kind of derisk our portfolio.

Your next question comes from Joon Lee of Truist Securities. In terms of number of addressable patients assuming comparable dosing being used for GAN and GM2 programs, how many patients' worth of doses can you produce in each of the 3 facilities?

So I think right now, we're focused on ensuring we have the appropriate number of doses for clinical studies, right? So we're not running any of them at capacity. But I think we are confident that when we're operating our internal facility, and we've modeled this in our facility design that we'll be able to support the GAN, GM2 and CLN1 demand based on our productivity of our process. So we're envisioning that we run tens of batches a year for every line of our facility. Now our conversations with CDMOs at the moment are delivering a clinical batch, but we would pivot to a number of batches per year, which I believe they would propose somewhere around 12 to 15 batches year for any commercial products. So I don't think it's a concern, and that's something we actually modeled into our facility design with the programs that we knew were in that early wave.

Your next question comes from Yun Zhong of BTIG. What would be the ultimate manufacturing capacity at your facility in RTP? Do you think you'll need to be at that level if you're sticking to intrathecal delivery? And when do you think you'll be able to move away from the CDMO?

Again, I think we intend to move away from our CDMO as soon as our facility is online, at the end of 2023. That's our intention to pivot once our facility is GMP ready, we will start making clinical and commercial product in our facility. So 2023 is our goal. Again, we've modeled the demand for our programs that are entering the clinic now into our facility design. And as we add more programs into our clinical plans, we would continue to augment our capacity. But I think, again, with our current design with 2 by 2 -- 2,000 liters of capacity, we feel like for our first wave of programs, we have enough capacity. And again, if we're -- as we advance more programs, we can add more suites within the same facility, which is a real benefit to us.

Your next question comes from Silvan Tuerkcan of JMP Securities. Do you have any approaches towards decreasing empty capsids that may be different from other manufacturing approaches?

I wouldn't say it's different. I think we've invested heavily in making sure our empty to full separation is good and that we're developing and refining those processes. And I think what we've seen out of our non-clinical batches. And to date is that it's working. And I think it's -- we're seeing good separation of empty to full. We're seeing good productivity at the same time. And so I think as new technologies come to bear, and I think this is where we are as a field right now, is ultra-centrifugation and ion exchange chromatography are the tools we can use to separate. And we can use optimized cell culture conditions to reduce the number of empty capsids that are in the starting material. Those are the areas we're trying to exploit in the way we develop our processes. But I would acknowledge technical development is key to all of this, and that's why we're investing in that area to be able to evaluate and optimize all of our processes.

Great. And we have time for 1 more question from Joon Lee of Truist Securities. How are you planning to mitigate the plasma coal packaging and prevention of its punitive immune reaction.

Yes. I think in a couple of ways, and I think one is really optimizing our transfection conditions. One of the things we can't get around is AAV biology, right? So AAV does promiscuously package DNA. But what we want to do is minimize the amount of that DNA in our production systems. And then what agencies are asking is for us to characterize what is exactly packaged in those particles. And so I think that's what we're doing today. Certainly, open to next-generation technologies where we're looking at things like minimal DNA constructs to be able to minimize those effects. But right now, it's optimizing our processes, making sure that nothing outside of the particle is really being in the final product. And so we're evaluating that by a number of methods and then characterizing what we have there at this early point in time. So that's what we're doing today.

Thank you, Fred. And this wraps up our Q&A session. I'd like to turn the call back over to you, Fred, To discuss our approach to manufacturing.

Okay. Yes. Thanks, Kim. So now on to our manufacturing approach. So I've laid out the 3-pillar strategy and some of the kind of the guts of our platform and the way we think about it. But in this section, we'd like to talk about how we think about manufacturing specifically. And I'm really delighted to share this part of the agenda with Greg Gara, our Site Head and SVP of Manufacturing who will go through our commercial process and facility design. So next slide. So I'd like to start with our guiding principles. And I think -- I'm hoping this kind of resonate from the last section. The way we think about manufacturing is kind of focusing on a couple of key areas. And I wanted to start with the first, and this is really leading with science. So using the latest method to design and characterize our products from research through commercial lots. So by using that, those scientific -- asking scientific questions and using the best tools available, we feel like this puts us in a great position to advance program successfully to the clinic and beyond. Reverse process design, and I think this came up in the last section and then some of the questions. We want to build and refine the best manufacturing processes we can for our AAV9 constructs and leverage that know-how, and that's something that's been really exciting and interesting in the Taysha portfolio that we learn from each program. We learned from our first program through the portfolio -- pipeline, and then the second and third. And using those learnings to be best-in-class in AAV9-CNS-delivered gene therapies. The third is focusing on execution. And to me, that means embedding technical and scientific experts in execution, whether that happens in our internal facility at UT Southwestern or at CDMO and making sure we're putting the right minds around on the processes and methods and making sure they're executed to our expectation. I think the fourth is being proactive. We have a lot of great deep gene therapy experience on the team, and we're trying to leverage to anticipate and mitigate risk before they happen. And so there's a lot of learnings around the field, around the table on this team, Suyash's team and myself. And deep into our manufacturing team that we're trying to leverage to make sure we do it right the first time. Finally, the last 2, our active agency engagement. We know that regulators are asking great questions about -- and a lot of questions about manufacturing, and we're really seeking their feedback, and that we'll get to with that kind of last section of the talk today on our approach to make sure we're in step with what the expectations are to derisk any conversations about advancing to clinic and beyond. And I think the final one is hiring and developing the right talent. We want to build a team with a great culture with a can do ad with the right technical expertise to deliver on our mission. Next slide. So we have spent a lot of time talking about our technical processes in our manufacturing facility. But I wanted to just give a quick acknowledgment to quality systems as well. And we can't build a GMP facility without great quality systems. And that compliance is really critical to producing safe and efficacious products. So in parallel with the building of our facility and establishing these GMP methods externally, we've been building systems to support quality oversight for our CDMOs and our internal operations. Our facility design -- in our facility design, we really incorporated regulatory expectations of both EMA and FDA to make sure our facility is designed to be compliant from the start. And that we have -- that we leveraged these strong internal quality systems to ensure the consistent delivery and high-quality products. So this again, one of the foundational principles at Taysha is to focus on quality and technical excellence in what we do. Next slide. So again, back to this theme of a platform process and how and again, in this context for this section, how it enables sufficient engineering and design? So by using, we have our Taysha platform process, HEK suspension upstream, universal column base purification downstream and a harmonized analytical panel, and we intend to use that for all our programs across the portfolio. By doing that, having a consistent harmonized process, we can build a facility and process around it that we can make sure it's robust. And that means doing things like leveraging closed systems or single-use -- with a single-use disposable flow path throughout our process. And this is something that Greg can speak to in some of the facilities design as well. It really helps us simplify equipment selection. What we're doing really across the board between facilities and between small scale and large scale is using harmonized equipment, simplifying installation commissioning and operation and maximizing those off-the-shelf products really simplifies our commissioning and qualification. And by doing this, so as we think about advancing a new program into our existing manufacturing facility, simplifies that tech transfer, and we're already seeing benefits of that at our CDMO partners that once we have our platform processes in place as we advance the next program, if we're asking them to use the same platform process, really simplifies the tech transfer because the supply chain is the same, the processes are the same, materials are the same. And so that's been really helpful. And that we've designed our facility with an open ballroom concept to simplify labor the way we use are on the floor staff and simplify operations. And so that's what we've been doing across the board. And really, all of this has kind of been driven into our facility and operational design for our commercial facility. Next slide. I think we talked about the benefits of internal manufacturing in the first section. But again, the way we see it reduces our scale-up risk, and we really are scaling out. We've invested in 500-liter scale, at least for now for our indications as a terminal scale where we can stream together multiple 500-liter reactors to get a batch size that we need. It reduces our time line risk by being able to control everything from [ texture ], transfer, through release and reduce car cost of goods. So again, why we're investing early in internal manufacturing. Next slide. And again, I'd like to touch on the process design. So reliable processes really begin with a thoughtful internal process design. So we've intentionally focused on being in a process platform that's commercially ready, something that's easily scaled out and implemented for commercial manufacturing early in implementation, even from early nonclinical lots. So this helps us minimize changes that would region and comparability concerns later on. And that we're really evaluating the product quality of attributes of these batches to inform process performance and product quality early on. So really, we see this as a continuum from small-scale production from animal studies on to clinical and commercial scale batches. And so we think about this not as something that's required for GMP manufacturing, but something that we do as we understand our products early on. Next slide, please. So I think another element or a principle that's important for successful manufacturing is developing scale down models. And we've been evaluating our processes at small scale, at intermediate scale and production scale, to understand how it scales between the lab and the manufacturing plant. And that we've really applied traditionally, all of the typical bioprocess engineering principles to this, and that's the great thing about the suspension-based bioreactors are easily scalable but using those principles to make sure we can -- we know what we can expect out of a commercial manufacturing run. And then, that we are investing in technical development to build that know-how internally. And having that down scale model, those scientists co-located with our manufacturing team really helps support tech transfer and investigation on the manufacturing floor. And I think that's invaluable for complex biologics like gene therapy. And that having that team and that scale down model helps us troubleshoot things very quickly and mitigate risks as we implement commercial manufacturing processes. Next slide. So we've also focused on equipment. And so I talked about understanding our process and equipment. But I think this slide serves to highlight that we are using a scaled-down version of the same equipment in our technical development and pilot labs to support our manufacturing. And so having the same user interface and attributes really benefits us in terms of process design. So on the next slide. And all this culminates is once we collect all this knowledge around our processes, that tech transfer is the key to making sure we have a successful manufacturing campaign and that we can faithfully execute these processes that are designed in R&D or tech development lab in manufacturing. And this is a real joint effort where it starts with really writing up the technical description of the process, looking for any gaps or mitigations in our facility that we need to address in implementing the process and then making this a team effort where everyone's accountable from the development scientists through manufacturing and the quality team to make sure this successfully gets over the finish line, including supply chain. So this is kind of the way we think about our manufacturing process and how we set it up, both clinically and commercially. Next slide. And so I wanted to speak again briefly to cost of goods. I imagine this is a little bit already in our conversation today. We know this, that the cost of goods is directly related to all manufacturing materials, labor and supplies, including raw materials, direct labor and utilities and that by using an IT route of administration, it really reduces our burden in terms of a cost of goods, we're delivering this medicine to patients. We are striving to get the best yield we can out of our manufacturing processes to decrease our cost of goods and should really benefit our ability to deliver a medicine that has a good profit margin. Well, one of the other things we're thinking about in terms of internally establishing our facility that benefits us is we can manage the supplier cost, really excelling in execution, lowering our reject rate or lower badge costs, finding portfolio efficiencies with all of our AAV9 programs to find efficiencies in methodology between programs and control over our analytical testing and labor force. That really helps us optimize our cost of goods by internalizing our programs. Next slide. So at this point, so that's kind of the intro. And I'd like to -- I'm pleased to turn it around -- the presentation over to Greg Gara, who is our SVP of Manufacturing to go through our commercial manufacturing process and our facility that we're in the middle of constructing in Durham. So Greg, over to you.

Thanks, Fred. Good morning, everyone. So happy to be here, and a lot of talk about the facility. But before I actually get into the details behind the process and the building, I'm going to make you hold off a little bit longer. I have kind of a little analogies of how I look at things, and I know it is the Olympics, but I'm an NFL guy. And the way I look at Taysha is it's kind of an expansion team is how I look at Taysha, right? It's relatively new. It's been assembled, right, with very strong leadership starts at the top with R.A., right? You think about kind of a head coach then you've got Fred, right? I mean, wow, kind of the mastermind behind the offensive coordination, right? And then you got Suyash and his group, right, like a general manager, right, keep feeding the portfolio. You kind of put all that together, yes, we might be relatively new, right, as a group. But as far as the number of years in the GT space, right, there's a lot of years that are sitting here. So just kind of a way that I think about things moving forward before we dive into it. So next slide, please. So Fred's touched on this, right? But the way I think about this is kind of the top is the upstream, right, and the bottoms, the downstream. Questions I get asked a lot, right? Is the facility going to do from bullet to vial or cryovial, all the way through to drug product. The answer is, yes, right? So we will go ahead and we'll start at the top. We'll go ahead and pull out of the master of the working cell bank, a very small cryovial. We'll then go ahead through a series of passages or shake flasks. We'll go ahead and grow the media or the culture up. We'll look for a certain cell density. That's triggers that allows us to go ahead and expand the cells of the media, drop it on to a small wave bioreactor. This is all taken care of kind of in the inoculum space. And then we go ahead with the triple transfection. We are using the 500-liter Sartorius, also mirroring right, what's being done at the CDMOs. One thing I do want to mention before I kind of get to the downstream side is with other companies, I get, "Hey, Greg, let's go, build a facility." Right? We need to build a facility as fast as we can. And I say, "Okay. That sounds great, right? What would you like to build?" Well, we have some stuff, right? We get about some of this and some of that, I'm like, "Okay, that sounds great, right? It would be nice to have a little bit more focused. What do you actually need." And the theme, right, that R.A. and Fred have laid out throughout this entire first hour and 19 minutes has been platform. That makes my life a lot easier because when I show up with the facility, right, Fred says, we're going to run suspension, 500 liters, 2,000 in scale. Multiproduct, right, done. So I can go and move very, very quickly because the GT space moves on speed. And if we know exactly what we want, more importantly, what we need, I can go turn that into sticks and bricks as fast as I possibly can. When I have ambiguity, right, we don't know. Sometimes I might put a design together, right, that takes care of like 5 different things, but might not do one thing very, very well. So having a platform upfront knowing exactly what Taysha needs is a competitive advantage. It allows me to go ahead and build -- I'm not saying we're not going to build some flexibility into the facility but knowing exactly what we need is a very strong competitive advantage, which again, it's to the years in the GT space. So Fred talked to the bottom. We're running liquid-based chromatography, which is very standard nowadays. It has come a long way. I mean, I have been in the space now for coming up on 7 years, and it's changed dramatically just in a short period of time. but it is nice to see liquid chromatography across the board. You run into a small ultrafiltration or a tangential flow filtration. We then do a fill -- or a final fill formulation, which is the sterile filtration and then we'll go ahead and actually fill it into a vial with what we call as kind of a presentation. Next slide. Okay. I'm going to make you guys hold a little bit longer. So I'll give you a quick overview as far as the facility. You can see it there on the right. We are going to do a deep dive into it here in a second. So I have a fly through on a 3D model. But manufacturing is, obviously, the heart and soul of these plants, right? We run them. It is a modular design. A lot of people ask, are you going to go ahead and run kind of a stick in JeT built? Are you going to build it from scratch? Are you going to run a cleanroom modular design. We are moving forward with a modular design. There's a bunch of different companies that's out there. Lot of benefits, a little bit higher capital cost and running in as far as just putting up some studs and some dry walls, but highly recommended to look at a modular design. We've talked about the scale, right? So we've got multiples. We're at 2,000 with the 500s. We do have 2 upstreams kind of feeding a single harvest and then that harvest feeds the downstream. So the way to think about it is like a 2, 1 and 1. That's how the facility is going to be set up. And we do have fill finish. So again, it's kind of the bullet to vial mentality. Fred talked about it a lot. R.A. talked about it some right? We do have QCR analyticals inside the facility as you're looking to the picture on the right, it's the orange part. It's kind of nestled right in next to kind of that purple part of manufacturing to have full control over your QC lab, right, your environmental monitoring, your bioassays is very, very key. When you have to take a bunch of samples and ship these things out. You have to kind of track them, you might lose control. All of a sudden, they're not at the proper storage conditions. We have full testing in-house, which will be very beneficial. Something that somebody said to me a while back is control your own destiny. Having QC, right directly adjacent to manufacturing is very key here. The warehouse, the warehouse is sized to handle the trains, right? So we have 2,000 capacity. We have some push-through. We have some high-density type of racking and then you'll kind of your standard cold storage and reject and I'll get into more details here in a second. The second one is technical development, might not be a familiar term. Think about like research and development or think like MS&T. We call it technical development, TD for short. That is the Aquagreen kind of there around the corner. I will kind of walk through it. But like Fred just spoke about it, having that sitting inside the facility. So if you need to do preclinical or clinical or you need to go an improved yield or you have an investigation on the floor, we're really going to run a downsize scale model of what's sitting inside production. Utilities, you got to have utilities to run these plants. I'll get into that. That's kind of the goal part. There's kind of 2 parts. And then we're running a center utility building. And again, I'll walk you guys through it here in a second. The big one here that I really have not had the luxury in my career. So I do think kind of R.A. and Fred on this is we do have future expansion capability inside this facility. So relatively new in the space when we started based on my career, you go ahead and you start constructing these facilities and before you can actually even get through the design, right, R.A. or Fred are coming to me and they're saying, "Hey, Greg, I need you to expand the facility, right?" And if you don't have space within your walls and you have to go find somewhere else, right? And it might not be closed, and then you start worrying about how am I going to move materials from point A to point B. We're going to build out about 45% of this facility. R.A. touched on it. It is that open area that's up there on the right, you can kind of see the different columns that are holding up the roof, but we're at about 43% build. So as we go expand, I will show different areas. We have a whole lot of space going to the right, plus we've actually left space open within like the QC area as an example. Next slide. So we're going to go ahead and enroll the video for you guys because I know you've been anxiously sitting here, and you've heard a lot about it. So that right there is the actual front of the building. We've got some drone footage. So it's 187,500 square foot plant. It sits in an industrial park. So that was the drone footage that's now actually going to switch over to the 3D model. So we highlighted 2 buildings in this park. There's a total of 5 buildings. You see 4 of them. So if you go from top-down and then left to right, our building is the one on the right. So it's building 5 and then you've got building 4 below. The fifth building is south on the screen that you guys are currently looking at. That one is under construction. Building 1 is like a graphics warehouse, building 2 just below. It's like national warehouse. It's just a big warehouse building. The one that everybody kind of landmarks against our building is the building on the south, and that's KB biopharma. So they actually sit just to the south of the building. So if you can go ahead and enroll the video, please. Okay. So here's the front admin area. And again, you can kind of see the total square footage at the bottom. It's [86 1 ]. The building is [187 5 ]. So like I said, we're at about 43% capacity as far as built out. So as far as plan goes, just to kind of get some logistics out of the way, North is actually up on the screen that you guys are looking at. And then obviously, southwest is to your left and east is to your right. So that's the front admin area. We have about 100 seats set aside. We did show 200 capacity. So we do have some seating elsewhere. There is also a second floor that sits over the top of this, but I took that away just for clarity of the model. The way we set it up is the front entry is up there in the corner by the Taysha logos, that's where you actually enter the front of the building and then you'll have the front reception area. And then what we set up is like neighborhoods inside a city is kind of how we look at it. So the large amount of seating is directly south. You see kind of a bunch of rows. There's 8 of them. That's a large set of seating. We have a couple of private offices. The other thing I get asked is, are you guys running kind of what is your split with private offices versus seats. We're going with more seats versus private offices and then you kind of have your standard cafe and those types of things. So why should you go ahead and roll it to the next one. Okay. So QC, we've talked about QC a lot and having QC in-house, right, it pays huge dividends to Taysha. I've been on the other end of the spectrum where we've actually had to send out a bunch of our samples. And you worry about kind of chain of custody? Did they get stored correctly? Were the shipping conditions correct? And when you can actually have QC in-house. And when manufacturing roles, but that is the exit corridor right there kind of the right that buts-up to the green. Manufacturing will actually come out on the north and then they'll roll down to the south. We actually have a sample drop off right at the QC area. So the plan is, they'll be able to pull the samples inside the suites, swing back around on the exit and then go ahead and drop them right at QC. So the way QC is setup is up on the north on the right-hand corner, that's micro. So that's where EM for the facility will take place. And then just south of that is where we have freezer storage and supplies. So we're going to run a lot of kind of OE like compound, so they'll have their own little satellite area that they can go ahead and pull supplies and use them in the labs and then we'll have a company or internals that will go and actually stock it. And then we have the sample, we see area just below that. And then right to the south, which is kind of the bigger square, that's the bioassay. That's kind of the meat -- potatoes of QC. Then you can see at the very end on the south on the right and then everything that's on the left, that's future capacity. So I don't usually see that a lot in these new builds because square footage rate is expensive. And usually, you go ahead and kind of you squeeze everything down and you say, okay, we're just going to go ahead and build this and like I said, before I can get the design done, we're having to go expand it. And I've had to take very valuable like office space, it is the lowest cost per dollar. But when you only have 100 seats with 200 people, becomes a premium, we actually have future space inside QC to go ahead and expand and we have the adjacencies that we're looking for. So we have additional EM across the top and then we've got additional bioassay across the bottom. So go ahead and roll it. Okay. So this is the big one, this is very valuable to me. It is not only running the engineering side, but also the site head. Fred talked about it. Having technical development in-house is going to pay huge, huge dividends for us. So you can see they are not directly adjacent, but they sit kind of at the south end of this building. the way TD is set up is it's really it's a mini production. So you've got a small -- if I'm on the west, I'm going left to right. I've got a small little equipment of prepay across the top. I've got upstream, then I've got downstream and then I've got a small analytical area. So the plan here is to mirror off of and it kind of goes to that 3-pronged approach, right, UT and same thing with Catalent as we're going to model with kind of the equipment, right? We've already talked about like the ÄKTA, the Sartorius Bioreactors. You're not going to see anything different mine of scale sitting inside TD than what you're going to see inside production. That allows me to potentially produce tax lots. I can do preclinical, I can do clinical, right? And then I'm tech transferring to myself. It's a lot easier to technology transfer from Taysha to Taysha versus from somewhere else into our building. And then we've also left future expansion space and technical development. So kind of around the south, we do have -- we're showing a few of the benches, but that entire area on the south is there for future expansion for technical development. So not only do we have it on the east, we also have it within a few key areas. And this is, again, kind of back to that expansion team, right? It's like right the first time. We know the areas that are going to kind of grow and evolve, right? One's going to be actual QC, right, and the second one is going to be technical development. So go ahead and roll it. So the next one up to me is the heart and soul, right? So this is the heart. Everything else kind of supports the heart. This is manufacturing, so. It's a very large area. I'm going to kind of start with the little small square at the bottom. That's the IQ and the freezer room. One thing I've learned from the GT side of things is there's a heck of a lot of freezers that you need to go ahead and support the process. The rectangle, that's kind of like tetras. But the rectangle that's there on the left, that's the locker rooms. So you're going to come in, head through the locker rooms and then you're going to go ahead and enter into the entry airlock. So you'll go through the [ gonoroom ] just like anywhere else. And then as far as manufacturing goes, you have the entry hallway, which is right where manufacturing is at. Those are all your entry material airlocks and personal airlocks, we call them Maws & Paws. So the flow, if you think about it will be kind of through the [ gating ] room into those airlocks up into the production suites and then you have another set of airlocks. And what the airlocks do is they actually protect the environment, the manufacturing environment there that there to actually provide protection not to allow anything out or anything in that shouldn't be there. So the outer perimeter of manufacturing is what we refer to as the exit corridor, and then you've got the entry corridor. And as you can see, we have kind of some cold storage. We have the actual entry from the warehouse. So we have really good flow. And then please pay attention. We have kind of the corridor over on the right, the exit corridor, it will bend around. And once I actually show you the warehouse, we have a straight path with our waste back to the warehouse and out of the building. So we have really good adjacencies. And the other key point, too, Fred touched on it, is on the FDA and EMEA. We actually have people on retainer, and we've walked through our design multiple times. If we have any specific questions, we just -- we put it together, we sit down with them. and we have reviewed this multiple times, and they're very, very happy, no issues with the design that you guys are currently looking at. So go ahead and roll the slides. So warehouse, I know warehouses aren't fun, right, but it all starts with the warehouse. So the first thing that I have to bring up that everybody asked me for is, Greg, when can I have the warehouse? The reason you need the warehouse because you need to bring in your materials and materials need to be in a controlled environment, right, and they either feed like your QC areas, usually the first one that comes up when you're actually starting to develop your methods, then you have some noncontrolled materials that go to your technical development, but the big ones off to manufacturing. So we have standard -- we have cold storage that's sitting at kind of that square that sits off to the side on the left, then we've got different type of racking. So we've got push through. We've got high density, right? It's really -- it's a fairly small space. We sized it appropriately. It's 2,000 pallet count in order to support the production trains. And then on the south, you've got like your waste flows, so you can see how kind of the pink ties into the purple and then it goes directly out of the building. So we have really, really clean flows with the building. And then just to the left, that's shipping and receiving. So everything comes in on the left, right? It goes in and either goes into a rack or it goes into cold storage, comes out, gets kitted, gets moved into production. Obviously, we consume any of the waste we take back out and kind of down that east side down to the south and out of the building. Go ahead and roll it. And then last but not least, our utilities. So you need utilities to run these buildings. I'm going to start with kind of the gold box that sits outside the building. You see this a lot now. And the reason we do this, a couple of reasons. One is speed, right? I've mentioned that. I know that from the GT space as everybody is moving very, very fast. But we run what we call as a Century Utility building or a Century Utility plant. This is where your boilers and your chillers are sitting. If you do this off-line, you can move in parallel. So I can be performing construction inside the building, and I can also start spinning up these guys that actually make these prefab buildings and you see a lot of these, like the KBI building next door has done the exact same thing. And when you're actually building a Century Utility building inside the walls of your own facility, the craftsmanship is very, very high, right, versus having to build out in the field and combine multiple trades. And then what they do as they finish it, we're able to do site acceptance testing. Site acceptance testing, we put it on the back of a semi. We take it to the plant. We tie it into the building. We do a small checkout, and then we're up and running. So that's the advantage of the cup building. We have WFI, which sits kind of right above it, and then you've got kind of the restrooms, which are blocked into. And then over to the right is where our liquid biowaste still sit. Then we've got the fire pump room. And then just to the right of that is where the main switch gear where the building sits. And like I said, we also have a second floor mezzanine and some catwalks. That's where most of our mechanical for the building minus over kind of the part on the west. So if you go ahead enroll the video, I gave you guys kind of a quick flyover and it will actually take us back to the front of the building. I wish I could build it this fast. And this is what at the front of the building and the 3D rendering will look like. So you'll see the front entry way with the glass and then we have windows on the first and the second floor. So you've got manufacturing kind of rolling down to the left. And then you've got the office admin down the technical development, all the way down to the south side of the building. Okay. Let's go back to the slides, please. Okay. So now that we've actually looked at the building, right, what are the time lines? And we've heard 2023. There's also some check-in points along the way. So to give everybody an idea, right? Because it is all about speed. We onboarded our engineering contractor in February. It's been moving very, very fast. We then went to a business case in 2021. We did start demolition. So we do have the slab completely pulled up. We're actually starting to put spread footers in the ground. A spread footer is a hole that you dig in which actually will support the steel column, which will carry the weight of the second floor. Midyear 2023 is when we expect the construction to be complete. So right now, we've finished up business case in chartering phase and we're getting ready to move into the detailed design, and that's targeted to be kind of early to mid or fourth quarter of 2021. And then at the very back end, and we're leaving enough time because usually gets compressed. But as we're working through with the CDMOs, right, and also in our technical development, and we're using off-the-shelf right, versus customized equipment, the CTV or the commission qualification and validation should go very, very fast for us. So we're going to do a bunch of upfront testing, but we are leaving some time at the end, and that's when we'll actually come online, which will be late 2023 with a fully commissioned building ready to go. Next slide. I called this right the first time, right? So I talked about we are relatively new, right, as far as the team that's been together right? But we have years and years of experience. This is my fifth build doing this in a very short time. So it is lessons learned. I think about it right the first time. It's another way to kind of look at this side. The thing I found out going through this kind of trial in there in learnings has been the production lines. They drive everything. So again, back to the platform of what Fred said, right, in giving me this playbook, right? He says, I'm going to go ahead and I'm going to give you 500 , right? So we want 2,000, right 2 by 500, 2 suites, we're good to go. Then we run into a completely disposable process. Fred talked about that. It helps me with the capital. So I don't have to put any cleaning, any steaming right? All of that actually goes away to 100% disposable. The single use, again, it equals reduction in risk contamination. And the other thing it allows us to do is actually knock down our air handlers and our ISO classes, which is basically how to qualify our clean rooms. And if we do that, it's lower capital cost, and it's actually reduced operating expenses, which goes to the COGS that Fred talked about. The labor and the room sizing go together. There is a lot of labor because of minimal automation with these. And so you need to make sure you have proper spacing. Risk gives failure. So again, if you have a platform and you know what you need and what you want, you can actually go ahead and design in things like redundant utilities, right? So if something goes down, can you do an N plus 1 to make sure that you can keep the facility up and running because when you're down, you're not making money. And then the last one is, is put some hold steps in place, which the platform process is doing. It allows you to potentially pull your upstreams, the downstream or if all of a sudden, right, you have an issue or nonconformant, you need to perform an investigation, you can actually go ahead and hold the process. Next slide. And then just real quick, kind of just to close everything up, and I've seen this, right, in about the 4 or 5 years as far as the GT spaces, there's been serious evolution and a lot of it's been in the equipment, so Fred talked about it. But when I first started, right, the Pall Icellis was on its first generation. It's now on its fourth, and I'm sure they're probably working on their fifth. And this was the platform that everybody was after, right? I was using basically adherent. Now it's suspension, right? And the Sartorius is on their third, and I'm sure they're always -- they're working on their fourth. And you can kind of see the difference just in the pictures alone of the suspension to the adherence. And then as far as filling, fillings come a long way. You guys have probably heard like or rabs rigid air barrier, that was the fillers that people were putting into place. Now everybody is going into kind of a sterile isolator and it's more robotic, which means there's 0 human interaction, so reduced risk profile as far as the product goes. And then I guess -- the other one is talent growth, right? We really haven't talked about the people, but a lot of the reasons that we're in Durham, right, in RTP is about the talent, right? I need people, those are the most valuable assets, right? I can go buy a pump, I can go buy a filler, but it's the people who make the difference. And Taysha's really got a very, very strong team. And that's why I talked about the expansion from top-down, the team is extremely strong. Next slide. Okay. So just real quick as far as a summary. So R.A. talked about this, Fred has also spoken to it, right? We have decided to invest early on, right? So these things just don't pop up overnight and something that somebody said to me a long time ago, right, is control your own destiny. And so -- we've made the promise, right, as a strategic advantage to us to go ahead and build this facility and internalize as fast as we possibly can. The construction is underway, and it's going very, very well. We are on target for 2023. The modular design, it is going to be single use, and it is multiproduct, which is good. So we have enough capacity, and we have enough scale, plus we can run different vectors if we need to, the facility is set up for it. The big one is future space. I don't have to go anywhere. So R.A. comes to me tomorrow and says, Greg, I need you to go add another suite, right? I can do it. I don't have to say, well, let me go find a commercial real estate guy, and let me go down the street. And then the final one, right, is colocation. We're not -- by definition, we're not a campus, right? We don't have everything on a single piece of property. But I can tell you that translational sciences right? It's just down the street. It is literally like 2 miles away from the facility and everything else will be under one rough. So with that said, I'll turn this back over to you, Kim. Thank you.

Thanks, Greg, and thanks, Fred. Really appreciate that. I'm now going to open the Q&A for questions. Your first question comes from Gil Blum, Needham & Company. Do you feel using CDMOs, which already produced commercial products and have been vetted by the FDA is derisking for Taysha's novel programs?

Kim, maybe I'll start. And then maybe, Fred and Greg want to chime in. I think, Gil, you've literally hit the nail on the head. I think through our history at our previous company at AveXis. I think this was extremely important as we were kind of embarking on kind of the first generation of industrial scale, gene therapy manufacturing, and we essentially were building the plane and flying it at the same time. As Greg and others were building out the liberty build facility, they were actually doing process development element at the same time with our partners over at Catalent. And this was extremely important in order to move this product in order to move Zolgensma forward in the speed in which we were able to do it essentially, you started with robust clinical data, and you were then trying to figure out how to reproduce that product in a reproducible, highly scalable and are unfortunate, we were able to do that both at the Libertyville facility that Greg built out and led, but also through our partners at Catalent. And partnering with the only commercial licensed AAV9 manufacturers is going to be extremely important and derisking to us. And again, because they have capacity that they're able to provide to us and in a meaningful -- and most of the time in a short period of time, this allows us to augment our scale. But at the same time, as I mentioned, we're doing the exact same thing with giant axonal neuropathy because, again, we're taking this product that is really at the point of embarking on regulatory discussions to make sure in order to derisk that BLA submission is essentially manufacturing that product with the same CDMO partner that manufacture the clinical product and making sure that, that's a like-for-like manufacturing process, it's starting from the cell line all the way through the upstream and all the way through the downstream and feel finish. In order to make sure that it's the same product characterization, same strength, purity, potency, all the things that Fred and Greg highlighted. And again, this is highly derisking to that product and ultimately, to the BLA in order to essentially try to lack onto a rocket ship that hopefully will be in the registration discussion here in the near term. term. So this is highly derisking to the portfolio. Greg, Fred, anything to add?

No. The only thing I would -- I totally agree, R.A.. And that's kind of the essence of our 3-pillar strategies, like the partners we chose were for that particular reason. So having a partner that has commercial gene therapy manufacturing experience, that's the logic, right? And the why is to derisk supply, right, whether it's clinical or commercial.

Your next question comes from Samantha Corwin of William Blair. Is the facility adaptable if or as the manufacturing process evolves and processes are standardized in the space?

You want me to take that?

Yes, please.

Yes. The answer is yes. I mean it is nice, right, to have the platform and know what we want and we need, right? But as I was talking and making mention, we will design it in some flexibility. I have -- if it really gets crazy if it, well, right, I can expand to the east, right? I have basically 50% of the building that's open to me. But we are designing in enough space for the flexibility it should something come in. So the way I look at it is you set up this platform, we do the tech transfer with a new product and it comes in, right, you can do kind of a quick paper exercise. And really, most of it should fit. There might be a few, that's your GAAP assessment. And then we need to take a look at that from a facility fit and figure out if I have a minor modification or a major modification? If it's major, right, how major is it? Does it require us to build out? Or can I go ahead and tweak what I have. We're running. We've got enough space around our bioreactors. We're running the appropriate power. We've got the right gases coming in. So should I need to change out a simple example. I need to pull a 500 out. I need to put 1,000 in, right? Because Fred says we need to move up as far as scale. That's not a problem with the facility.

Your next question comes from Nancy Winemaker of Jefferies. Exciting plans about the new facility. Generally is purification being scaled at the same rate as capacity plans for bioreactors. What is the rate limiting step in manufacturing process now and once in the internal facility?

Greg, why don't you go ahead and take that again? You thought about this a lot.

Yes. The rate limiting is the inoculum, right? That's the first rate limiting step. So I need to keep that room up and going. So I have multiple incubators. So going from cryovial through the different passages. I've got to keep that thing moving forward. So if for some reason, right, I lose a passage, right, from starting with a cryovial then I'm going to have go ahead and pull up. So once you get started with the first one, everything is going to cascade behind, and we're probably going to have just due to labor constraints, right? So we don't have major activities fall on the same day right? We're thinking about our labor and efficiencies is we'll probably have a 2- to 3-day stagger. So I will only lose a small amount of time. But today, my rate limiting, which will probably end up being tomorrow, is around the inoculum and then right behind that is the cell expansion suites. Purification runs very, very short. I can even say this across the GT space. It's somewhere around about 5 days and then once you actually hit the fill suite, it really takes longer to set up and fill out the paper than it does to actually fill the product. That's been the interesting part with the GT side of things. So yes, it would be the inoculum and into the cell expansion, but we will run on a cadence, and it will be about a 2- to 3-day delay, and we'll always have another lot or passage right behind it ready to go.

We only have time for 1 more question, unfortunately. It comes from Yun Zhong of BTIG. With your facility to -- with your own facility to reduce cost of providing capacity? Will you be exploring indications that will need systemic administration?

Suyash, do you want to take that question?

Sure. In terms of systemic administration versus intrathecal administration, well, I'm not -- I'll touch on this a little bit in my own section. In terms of the diseases we're treating. The vast, vast majority are going to be intrathecally dosed. And so in terms of the amount of product we will need is considerably less which has a whole set of implications, which I'll touch on. Fred's already touched on some of them. Of course, if we do feel that we can get the best efficacy and we'll deliver the drug safely, and we need to systemically administer a drug intravenously, then we will, of course, consider doing so, we'll model that in the animals and we'll take it for the clinical situation. There are a number of additional challenges when you go into systemic via systemic route of delivery, for example, we definitely need more product. And there are certain limitations when it comes to -- and I'll touch on this very point on my next section. There are some limitations when it comes to, for example, level of preexisting antibody that's available in the plasma. So there's a high level of antibody, you may not have to dose systemically, but you can dose intrathecally. In terms of the manufacturing side of things, and Fred can probably comment better on this. I don't think there's really any difference apart from the volume that you need of drugs. So clinically, if we need to co-administer systemically, we will. I think it's highly unlikely for the majority of our diseases, which are in neurological diseases. But I don't think there's going to be any additional modifications to the CMC plant of the manufacturer, if indeed, we need to do that. Fred?

Yes. Thanks, Suyash. And indeed, we don't anticipate any changes to the manufacturing process. And indeed, probably a little bit more -- It provides a little more flexibility about drug -- direct drug presentation because we're trying to deliver a very concentrated drug into a very small space in the CNS. So -- but again, I think, as Greg mentioned, we have room to scale if we happen upon an indication where IV in a systemic route of administration is the right thing to do. I think on the manufacturing side we're ready to respond.

Let's try to squeeze a couple more in, if we can. Next question comes from Kevin DeGeeter of Oppenheimer. For smaller markets such as GAN, how should we think about COGS from CDMO versus in-house manufacturing? Can some products for smaller markets be less expensive to produce at a CDMO?

And I'll just jump in here. Fred, you could tackle this question, but we won't speak specifically about our COGS.

Yes. No. And I think as -- when we think about this, certainly, we're thinking about speed and cost, right? So we have -- as R.A. said, we're on a rocket ship with GAN. We want to deliver pivotal material to be able to deliver that final product to patients. And while COGS is in the calculus, it's doing right by patients. And so that's what we're doing, our manufacturing strategy is to deliver this product, a licensed product that's available to all patients with GAN. Now I think we'll find the right balance in terms of making sure it's the right cost of goods, but that's the objective. And I think we can -- and if we did decide to advance GAN through a CDMO partner, well, we could still work on costs so good. So I think we would still put in the effort, and we'll have those conversations about yield and raw material costs, but I think it is the strategy we will use for certain programs.

Yes. I think just to add to what Fred said. I think we're inherently starting in a place that's a bit more beneficial than some of our colleagues that are working on systemic delivery products because essentially, just the volume of product that we're using across our portfolio is probably somewhere around 10% of what you would need from a systemic delivery. And that in itself, just because you need much less volume has a significant impact on cost of goods sold. So we're already starting from a place that is going to be a little bit more beneficial or favorable from a COGS perspective. But I think to Fred's point, ultimately, our goal is to deliver high-quality product to patients to ensure that the product is potency -- is potent enough in order to deliver the clinical results that we've seen to reproduce those clinical results that we've seen, not only in the clinic, but also in the commercial setting. And so 2 things that are important, particularly for GAN, speed and making sure that we have comparable material. And that's the reason why we're staying with the same CDMO partner. Once we ensure those 2 things, then I think to Fred's point, we'll start working on ways to optimize other aspects of the cost, particularly from a manufacturing perspective, but that could be done with further process development, but also making sure we're mitigating any risk from a supply chain perspective or a number of different ways and making sure that we ultimately have dual capacity. But in the short run, it's around making sure we can deliver highly comparable material in order to support a BLA filing and registration and ultimately to have high-quality reproducible potent material for patients.

We'll squeeze one more in here. Silvan Tuerkcan from JMP Securities. What will be the critical steps for the different lead assets and moving manufacturing from CDMOs to the Jerome plant once it's operational?

So I think -- what are the key steps. So I think the way I see it today is really establishing a process that we feel good about, and that's what we're in the middle of doing today. So I think more all of our programs, establishing this process at either UT Southwestern and the bulk of them, quite honestly, are at Catalent because they have more capacity is feeling good about that process as a basis line in building that analytical toolkit. So I think once we have that in place, what that allows us to do is to compare the analytical quality of the material during facility, and well, so move that process design, sorry, I should start there, faithfully into our facility and then use the analytical panel that we have that we're building and add thing to all the time to be able to make the case that it's comparable and representing. Do we anticipate a massive overall changes in our process design? We do not. I think we got a scalable process. We know what the critical raw materials are. We know our operational steps. We have a really good panel for release and additional characterization test. So those are the key things. And then it goes back to the last -- this last section of our presentation, faithfully transfer in that process in those methods to our facility. That's kind of the way we think about it start with the end in the mine, collect that data. And then I think the last piece is we retain reference materials, so you can do that comparability study in a way that the agency would like to see. And maybe the last bit I keep thinking of things as we go, have that discussion with the agency about our plans. So I think getting this in front of them, telling them this is our plan and discussing the strategy ahead of doing it are probably the key elements of doing that successfully.

Great. Thank you, Fred. Thank you, Greg, for all this. I'd now like to close the section, and I'll turn the call over to Dr. Suyash Prasad, who will talk about the immunology of gene therapy. Suyash?

Well, thank you, Kim. Thank you, R.A., Fred, and Greg. I'm very excited to be part of this discussion actually. I think it's a really special thing to be able to talk about our approach to manufacturing. And part of what we want to talk about within this discussion on the manufacturing of gene therapies, the immunology of gene therapy. It's a topic that we get asked a lot of questions about and it's a topic that is a lot discussed about in the gene therapy press, and it's something we talk with the regulators about. And there is clear relationship between some of the immunological issues that happen in the clinical setting, the preclinical setting within the context of CMC and product quality. So we feel it's an appropriate time to touch on this -- in this particular session. Next slide, please. So Fred already talked about and R.A. has talked about the really nice partnership that occurs between myself and my group and friend and his group. And it really is a great partnership. We're both -- are scientists at heart, Fred and myself. And so we have a lot of scientific discussion. We speak about all aspects of gene therapy. In fact, Fred not only having a nice discussion just about early spot assays yesterday. And it's just nice to have a partner who heads up manufacturing that I can work with and my team can work with. And I think it's a core strength of what we do here at Taysha. Now when you think about immunology, we've bucketed -- if you look at this slide, things have bucketed into four areas. You look at the preclinical and CMC considerations. We've touched on some of the CMC considerations already, and I'm going to touch on some of the preclinical issues. It's important to understand how to detect adverse events that are immunological in nature and within any adverse event in the clinical trial where the train sites have to do it properly. And it's also appropriate to be able to treat adverse events and think about how you're going to treat them before they even occur. So for example, most gene therapies now have some kind of in suppressive regime in place as we start the clinical trial. We indeed have our own and I'm going to talk you through in some detail. But you sometimes get breakthrough immunological consequences. It's always best to think about what happens before that actually happens and how you might address. And then, of course, the fourth bucket is clinical prophylaxis for related adverse events. So how are you going to mitigate any adverse events immunological in nature before they will recur. So just taking a step back and look at this slide in a bit more detail. On the preclinical side, of course, it's very hard actually translating immunobiology from animals into humans. And there is this one area but it's really difficult to translate. The FDA stands out there, they appreciate that. And NHP models a large animal model such as dogs are the best, but you're still unable to predict everything. So there's been many, many cases where you see it not for confidence in the human and there was no sign whatsoever, any preclinical studies, even though the preclinical studies have been robust and comprehensive. So there's always a degree of unpredictability when it comes to the immune system. CMC considerations, we've already touched on the fact that product quality is key, matters such as the empty-full capsid ratio is really, really critical, trying to minimize empty capsids as much as possible. And our intent is always to have less than 10% empty capsid and the rest full capsid. That's what we're always aiming for because the more empty capsids you have, essentially, empty capsid is contaminate. It adds our loads and it becomes a greater immunological trigger of events. Contaminants, of course, can be in the journey. And of course, there's a lot written about CPG motives, specifically unmethylated CPG motives. And I can touch on that a lot more of this presentation goes on. In terms of detecting AEs, you've got to be -- you have to make sure the protocol safety monitoring plans are written appropriately and is in frequent testing on an ongoing basis with function test for some kind of T cell-mediated reaction, troponin to look at cardiac inflammation, early spot to look at other T cell media interactions to the transgene as opposed to capturing the impact. And there's a lot of pragmatic issues to pragmatic considerations, especially when you're doing studies in children as many of our programs are because there are a limited amount of blood volume we can take. So you've got to think very carefully about what you take from when a clinical relevance is. In terms of treating AEs, if you get a breakthrough immunological event, usually the best thing to do is to increase the dose of steroids as a general immunosuppressive. But you all have to understand what's gone mechanistically because it could be that some other targeted immunosuppressive or antiinflammatory would be more appropriate. And you have to set up a data monitoring committee with the right people on it, and they have to be actively involved in the setup of the study and set up of the safety monitoring plan and ongoing monitoring. And from our perspective on the DMC, we like to have at least one disease expert, one genotherapy expert and one immunologist on every one of our DMCs for each program, and that seems to work very nicely. And then in terms of prophylaxis, I'm going to talk about our approach, which is essentially using prednisolone and sirolimus or also known as rapamycin for a period of time. I'll go through that in detail in a couple of slides time. Next slide, please. So when you think about immunological responses to gene therapy, there are at least 4 big obstacles. There are more, but these are the 4 ones that people really think about most. The first is preexisting neutralizing antibodies or IgG. And that may do 2 things. It may make the patient more likely have some kind of immunological reaction from a safety perspective. But actually, more importantly, may impede back to transduction because if you infuse AAV into a patient. And there are previously antibodies to AAV before the AAV catered has a chance to enter a cell and transfuse a cell, it will be metabolized away by the preexisting antibody. So there's a risk that it will notify or dampen down efficacy. In addition to that, transduced cells may be eradicated by anti-AAV captive T cells, is a T cell-mediated cellular immunological reaction. And we see this frequently. We often see LFTs going up, especially with liver directed gene therapies, for example, in hemophilia, and that's because a transduced cell suddenly becomes vulnerable to an immunological attack by T cells, which destroys the cell and causes inflammation in, liver function test horizon. The best way of treating that usually is with some steroids. You may also get an immune response to the transgene product. So an immunotransific capsid, AAV8, AAV9, whatever seratonin you're using or the protein is produced, and this is more likely to happen if the patient you are treating is a No Patient i.e. they have no existing protein whatsoever. And then as the gene therapy produces new protein that's missing, the body recognizes that as foreign because it's not been exposed to that protein even though it's a natural normally occurring protein and the patient may develop an immune response to that transgene product. It's less common, but it does happen and it's important just to keep an eye out for it. And then there's a group of other associated toxicities that are in the news at the moment. So DRG inflammation, just a little people talk about TMA, the thrombotic microangiopathy is another thing that people are talking about at the moment. So you will have your mind on and sort of the plan ready for all of these different potential immunological responses to gene therapy. Next slide, please. Now our approach at Taysha and at a high level, as R.A. has already mentioned and you've heard from us before many times, as AV on serotype HTK293 and its intrathecal dosing. Our approach as a standard does mitigate many immunological concerns. So for example, because we're giving the drug intrathecally, which is an immune privileged space, there is much reduced exposure, so systemic circulation. Even though you do get some leakage out of the blood-brain barrier through the systemic circulation, it is an immune privileged space. So we actually don't need to stream for antibodies to AAV9 before we dose. We do take antibody levels, but even if patients have high levels of AAV9 antibodies, we will still go ahead and dose patients. And I'll show some data from agents on neuropathy study that shows we've successfully dosed patients in the presence of significant amount of AAV9 antibodies. That's the first point. The second one, which has already been touched on in the previous Q&A session, is this. And that is we are giving far, far, much viral load, far reduced viral load, is probably 10% to 15% of what would be given systemically. Now we give a high dose target to the brain and spinal cord, but we give a low edition compared to systemic gene therapies. And that's because with dose you must always look at how patients are being dosed in a gene therapy study and look at the units, if it's total VG, then it means that's the total amount of viral loads that low the patient is receiving. If this is VG per kilo, which is how you does a systemic administered gene therapy, then you have to multiply by the VG by the weight of the child, okay? And for a 6-year-old boy who weighs 20 kilos, who's receiving a Duchenne product today at 2e14 VG per kilo. You multiply 2e14 by 20 because the child weighs 20 kilos. So you're approaching a 1e16 total VG. For us, we're starting at the 5e14 total VG and we may go to 1e15 total VG and some of our clinical trajectory studies. So it's a lot fold less than the systemic administrated gene therapy. And that's probably the biggest single factor why we're much less likely to precipitate any kind of immunological consequence for adverse events. And once again, registration of specific data in relation to this from our giant axonal neuropathy clinical trial. So we're giving a much reduced dose. It's a privileged space, in a privileged space. preexisting antibodies are not going to be concerned, and that we cover with transient imosuppression, so steroid and Sirolimus, also known as rapamycin. Next slide, please. So there's a few general immunological principles I want to just touch on. And this session is really going to be looking at things at a high level and what can practically do from an immunological perspective. We're not going to spend time getting to depth of this pathway or that path. It's just, okay, these are the kinds of situations that might encounter, how do we manage it and how do we mitigate those kinds of issues prior to even coming across an adverse event. So it's a very practical pragmatic approach to immunosuppression and immunological management within gene therapy. But there's still a few high-level principles I want to understand. There is this concept of innate immunity versus adaptive immunity. Innate basically is the first line of defense between -- to any foreign turns encountered adapted is a specific defense that's mounted. It's a bit longer to mount, but specific defense has mounted against the particular foreign material. So it's where you get a specific antibody response to AAV9, for example, or a T-cell mediate reaction to a specific transgene promise. It's long-lasted and it's highly specific. You also got to think about T cell responses versus B cell responses, T cell is cell-mediated, B-cell is antibody. In reality, they're not fully separate. There is quite a lot of interlocking into even between the 2, but it's sometimes useful conceptually to think about them separately. Complement is a big -- is an increasingly emerging hot topic in the arrow gene there. We've seen some specific side effects that are complement-mediated. And complement is a group of proteins that float around in the blood produced by the liver. They're generally inactive but then get activated and create this immunological cascade of events that help encourage phagocytosis of any foreign material. And the role of complement is complex, which is not fully elucidated yet, but it clearly has impact both on B-cell function and T-cell function. And is an important mediator of innate immunity. And then we've touched on product characteristics already, but just to reemphasize the fact that the purity of the product, i.e. removing a much host cell protein, host-cell-contaminated DNA is important. The role of unmethylated CpG motifs and reducing CpGs as much as possible, in principle, is an important thing. It may not be as relevant for us because we're just giving a much lower dose, but it's still an important principle to bear in mind. And then this matter of empty versus full capsid and really seeing anti-capsids as a contaminant. They're just add unnecessarily to viral load and can precipitate an immunological consequence and just really focusing on making sure those full capsids are what we're delivering to the patient. And I think, as a general principle, as Fred and Greg have already emphasized, the fact we're thinking about these product characteristics and characterizing the CMC side of things very early in trying to move into tox studies and clinical studies as quickly as possible with our final product is a really critical part of our strategic approach in terms of planning for the longer-term BLA filings and actual approval and commercialization. Next slide, please. So it's also important to note that there are both host-specific factors and treatment-specific factors of that, can drive immunogenicity. These are -- this is once again a conceptual slide. This was published by Federico Mingozzi. It's a very nice review article a couple of years ago about AAV vector immunogenicity. And he talked specifically about some of these host-specific matters and treatment-specific matters. I won't go through all of them. But for example, in terms of a host-specific factor, if a disease has, as part of its process, underlying inflammation, then the likelihood of immunological response is higher. So for example, Duchenne, where you have an ongoing progressive destruction of muscle tissue and associated inflammation, they're more likely to have an immunological consequence because the body is already primed for an immunological response. Whereas something like Rett syndrome, where we're giving the drug intrathecally, there's no inflammation going on in the brain. Of course, there are some other pathological matters, but there's no inflammatory process going on, which means that I think it's much less likely to see an immunological event in that particular setting. So there's a few other host-specific factors that really need to be thought of that are outlined in this slide, on this paper, which I'm not going to go through in detail. But then there's also treatment-specific factors and we touched on route administration already, but things like if the transgene -- if the protein product is intracellular versus secreted, it's more likely to be -- it's more likely to trigger a immunological consequence. In a secreted protein -- in a secreted -- this is where the protein is secreted and then a disease situation, if a small amount of protein is present and it gets secreted, the body does get used to it. So for example, with diseases like GM2 or CLN1, where the protein is secreted, there is some appreciation by the body's immune system that this protein is native. And so when you give more of it by inducing gene therapy to produce the transgene product, then it's less likely to cause an immunological consequence. So there's also treatment-specific factors that need to be taken in consideration. And all of these, you can spend a long time talking about various matters on this slide, but essentially, think -- you got to think about host-specific as well as treatment-specific factors when you consider how you're going to manage immunological response, and it's different from disease to disease. Next slide, please. So we've touched on delivery of drug already, but I wanted to show these diagrams because we often get asked the question about what exactly is intrathecal delivery versus ICM versus IT versus IV. And you can see in the column on the left-hand side, the [ dark ] on the left, this is intrathecal delivery, where you lay the patient on the side. You pop a needle in into the lower spine, so usually L3-L4 or L5 -- L4-L5. You slowly slide the needle in. You take out the needle, leave the catheter in, tie some tube in after draining off a few ml of CSF and then slowly inject a drug into the intrathecal space. You then lay the patient on the back, tilt the head down and the drug pools around the brain and the spinal cord. Now as I've already mentioned, the intrathecal cavity is immuno-privileged. And if you look at the other 2 diagrams, giving the drug into the ICV, this is the lateral ventricles and the ICM, which is the back of the brainstem, they're also immuno-privileged and also need lower volumes. But there's much more technical challenge in using those 2 routes of delivery. You need a neuroradiological suite, neurosurgeons to deliver the drug. Intrathecal delivery is minimally invasive, much lower risk. And doctors have been doing this few years. I've given intrathecal drug myself many, many times. Now the intrathecal space in an adult or, in fact, in a child over the age of about 3 is about 130 ml, which is very different to the systemic circulation, where you can have several pints of blood circulating in the body. And so the amount of drug you need is much, much reduced. So we're guessing around [ a log far lesser ], about 10% of the systemic dose. And once again, that really does help mitigate the risk of any kind of immunological or other adverse events. Next slide, please. So one of the things we try to emphasize throughout this whole presentation is just the partnership between myself and Fred and Greg and the partnership between our groups in R&D and CMC, and it is absolutely essential to ensure high product quality. Capsid immunogenicity is a concern. So reducing empty capsids is important. And the FDA has seen -- a few years ago, it was much harder to remove empty capsids. We're better at it now. And as Fred has already emphasized, we're spending lots of time and energy in enhancing our process to make sure it's pristine and removing as much anti-capsid as possible. But you can have products, which are up to 90% anti-capsid. And from my perspective, that's really adding way, way too much unnecessary contaminant and adding viral load, which could precipitate a side effect, either secondary to an immunological event or just secondary to the high viral load. And the other thing I think that we're doing well is we're doing all this early because with a lot of companies, they are evolving the platform in parallel to running development programs, whereas we're trying to get the platform right to start off very early on development programs. The more you switch platforms or developed program goes along, it can result in changes in product quality attributes such as, for example, the full-to-empty capsid ratio. So once again, doing things early is going to be much, much better. Removing process waste and impurities is important. Capsid impurities is important. Greg talked about the upstream and downstream processes, and we really touched on the fact that animal models are not really that predictive of immunological consequence. And Fred also talked about the need to really have accurate assays from being able to ensure that how much you're actually giving what you think you're giving to the patient and giving what you think you're giving in the preclinical packages. And once again, spending time early getting this right, having that partnership between translational R&D and CMC and quality, we're all located in the same place is critical and make sure we do that properly. Next slide, please. Okay. Let me touch on, very practically, what we're going to be doing the prophylactic immunosuppression across all our programs, and we've done a lot of learning from our GAN program, which, as you know, started dosing patients in 2015. So I'm going to share a little bit of the information from that program here. Next slide, please. So with giant axonal neuropathy, we have the construct in the middle. We've got the human full-length gigaxonin gene and gigaxonin is a protein that's missing in giant axonal neuropathy. It's part of the ubiquitin-proteasome system, which have -- breakdown waste, old denatured proteins. In the absence of gigaxonin, you're going to build up all these [ abnormal ] proteins causing reduced [indiscernible] chemical transmission down a neuron and the clinical features of giant axonal neuropathy. So we're replacing the gigaxonin gene. We're using a small synthetic promotor, JeT, which is moderate in strength and wrapping it up on a sub-complementary AAV9 capsid. We've given the drug intrathecally. I've already talked about how we do that. And you can see there's 4 dose cohorts at 3.5e13 total vg, 1.2x -- 1.2e14 total vg, 1.8e14 total vg and [ 3.5e14 ] total vg. We've shared data on the first 3 cohorts. We have data from the highest dose cohort to share later this year, and 14 patients have been dosed thus far with a very, very safe, safe profile. Now you'll note that the immunosuppression regime in the bottom left-hand corner of this slide is prednisolone and rapamycin. And in the first couple of patients, short-course steroid was given. But after noticing some asymptomatic inflammatory episodes, specifically an elevation of the white cell count in the cerebrospinal fluid, which is fully asymptomatic, the principal investigator, Carsten Bonnemann, at the NIH in conjunction with Steve Gray our partner, decided to elongate the steroid regime and add in rapamycin as a T-cell modulator. And that -- on that regimen, it's been a very, very safe drug. Next slide, please. The other important point is that given that the drug is being intrathecally, we can actually dose in the presence of antibodies to AAV9, which is very unusual. Most gene therapy programs will actually preclude patients who have high levels of a particular antibody titer, which actually precludes maybe 30% of population who have antibodies to AAV9 or AAV8 or whatever serotype it is. But you can see in the diagram on the left-hand side that about half the patients that have been dosed were seronegative. About 1/4 were seropositive, so the greater than 1 in 50 levels of antibody, and about 1/4 were borderline, between 1 in 5 and 1 in 50 levels of antibody. And in the graph on the -- in the diagram on the right-hand side, you can see that 10 of the patients dosed were [ positive ] had a little bit of the preexisting gigaxonin and 4 were [ negative ], so have 2 nonmutations, have no gigaxonin, whatsoever. And those patients have a greater risk of having an immunological event to the transgene product because these patients have never seen gigaxonin before. Next slide, please. So this is the actual regimen. The steroid has been given for a year. So if you look at the time line scale at the top, the gray is a week before gene transfer. So start patients on steroids 1 milligram per kilogram just before gene transfer. The green is week 0 when we give the gene transfer, and then the dark blue is 3 months of 1 milligram per kilogram per day of oral prednisolone. At day 90, we check test set of bloods. And then surely thereafter, if the bloods are all fine by chemistry, hematology, et cetera, we then start to take down the steroid slowly over the next 2 to 3 months, usually about 8 weeks, usually by about 15% per week, but there is some investigator discretion in how rapidly they drop that dose of steroid. If there is any kind of breakthrough immunological event during the [ light blue ] period when the steroids are being reduced, one options is just to go back up on the steroids. That hasn't really been needed to be done in the GAN study. And the patient should then be off the steroid by the weak 24, the day 180 visit when we have our 6-month time point on the -- from an efficacy and safety perspective. Next slide, please. So that's the steroid. Essentially, 3 to 4 months or 1 mg per kg followed by a taper over 8 weeks or so. Now sirolimus, also known as rapamycin, once again, we start sirolimus 1 week prior to gene transfer, and then we keep the sirolimus going for over -- for a year, so there's a longer period of time than the steroid. And as you know, sirolimus is a -- it's a very well-known immunosuppressive agent. It's a T-cell mediator. It's been used in solid organ transplant. I've used on the pediatric intensive care in as many times. So it's a well-known drug and the side effects are well known. And we know how to monitor for it and how to make sure we keep serum levels of sirolimus in the right range to enhance its immunosuppressive effect but not cause too much immunosuppression or any of the side effects associated with it. So we start the drug 1 week prior to gene transfer. We give 0.8 milligram per meter square twice daily. We'll keep it going for about 9 months to the day 270 visit. And we measure levels of sirolimus on an ongoing basis, and we tailor the sirolimus that's given based on those levels. So we're being very precise about the dose we give. At the day 270 visit, if the lab test's normal, we start to wean down the sirolimus. We wean it down over a course of 4, [ 6, 8 weeks ], somewhat an investigator discretion, but make sure the patient is off in the day 360 visit or the 1-year visit. So by the time we hit the 1-year time point, the patient should be off both immunosuppressive drugs, steroid for 6 months and rapamycin for a year. Next slide, please. And that steroid, sirolimus regime has been used in the vast majority of the GAN patients after the first couple and reflect back on the slide I showed dosing the presence of antibodies. Given those antibodies, given the regime, the immunosuppression, you can actually see when you look at the safety findings of it being -- is clinically well tolerated. There's some evidence in the earlier patients before we [ even started ] the longer immunosuppression regime of asymptomatic cerebrospinal fluid pleocytosis. Pleocytosis means -- basically means some white cells in CSF. There's no dose-limiting toxicity, no liver inflammation, no transaminase whatsoever. [ On the study ] we've done on an ongoing basis, there was no evidence of inflammation or enhancement, no evidence of any acute or subacute inflammation, no neurological signs or symptoms, no sudden sensory changes. Obviously, DRG inflammation is something that the FDA and others are concerned about the moment, but there's no sensory change whatsoever and [ over this, the ] thrombocytopenia or the TMA has been discussed. So really, very, very reassuring safety profile within the context of really stunning clinical efficacy data. You'll remember from previous discussions at the MFM32, the key end point is declining 8 points a year, the clinical meaningful change on the [indiscernible] is 4 points a year. And after dosing at the medium low, medium high dose, that stabilizes out. So a significant clinical [ element ] change in efficacy. And in addition to that, a very nice safety profile and yet we have the high dose to come. So really very positive findings from this giant axonal neuropathy study. Next slide, please. So I think in summary, our approach to managing immunological consequence in the gene therapy study really lowers any kind of immunological risk. We've got a much reduced particle load via dose and route administration. You've heard from Frank and Greg how they're producing high-quality, high-purity clinical product from very, very early on, minimizing host cell residuals, reducing empty capsids and designing constructs to minimize immune stimulation and truncated transgene products. And Fred and I work closely and talk about this all the time. We use a standard HEK293 mammalian cell processor from the mammalian itself and very well used, very well recognized, more experience commercially with this process than any other process. And we're using appropriate immunosuppression with the administration of prednisolone and sirolimus. The other things I can recall that sometimes not really thought about enough or talked about enough is that you need to have a very diligent and written clinical protocols. You're going to have a good safety monitoring plan, a good safety management plan, i.e., you got to teach the investigators what to look out for in terms of an adverse event, make sure you -- then they have to pick it up early, make sure there's a plan in place now to treat some kind of immunologic consequence if indeed we need to and then have a good way of looking back and learning from that and informing the rest of the study. Having said that, with our regime of sirolimus and prednisolone, I don't anticipate there being many, especially within the context of giving a low dose of drug. And importantly, you've got to have good physicians at Taysha who know what they're doing and are on top of everything, but they've got to work closely with a very, very highly expert, enthused, motivated data monitoring committee. And as I already mentioned, we make sure that we have on our DMC [ study ] program a gene therapy expert, disease expert and an immunological expert. And we make sure they're highly engaged. We talk with them frequently. On that note, I think that's my last slide. So I will just -- would like, once again, just to thank the team, thank Fred and Greg for their partnership and RA for his support. And I'll hand over back to Kim to answer any questions.

Great. Thank you, Suyash. We'll take a couple of questions here. First question comes from Salveen Richter of Goldman Sachs. Could you discuss the impact to the potential addressable population that doses -- that dosing regardless of preexisting antibodies could lead to?

Yes, I can. So there's quite a lot of nice epidemiological data that shows that for AAV9 in the adult population, it's about 30% to 35% of individuals are seropositive. So what that means is if we have to preclude patients with seropositive, we reduce the eligible population of the clinical trial and commercialization by about 30%. Now there is an age association with that. So when a baby is born, they will inherit maternal antibody, which is passively acquired. So newborn babies will also be -- 30% of them will be seropositive. They lose that maternally inherited antibody by the time of about 6 months, and so we've got a window from the age of about 6 months to 2 or 3 years where most children are -- the vast majority are seronegative. By the age of about 3 or 4 years, children start to be exposed to AAV9 in their community and start to bring out the -- start to seroconvert to be seropositive. So probably 15% of teenagers are seropositive. By the time they reach adulthood or early 20, it's about 30% of patients are seropositive. So the fact that we can dose in the presence of antibody with our low -- high dose tox in the brain or spinal cord but low dose systemically in combination with the sirolimus-steroid combination means that, that full 100% of population would be eligible, and nobody would be excluded from an antibody perspective.

Great. Thank you, Suyash. Your next question comes from Gil Blum of Needham & Company. In this upcoming Advisory Committee discussion on safety of AAVs on September 2, 3, do you believe the FDA will provide you guidance regarding safety requirements? Should we expect improved clarity regarding those guidelines and how they would reflect -- how would they reflect mutations on programs?

It's a great question, and I think it's -- I'm looking forward to that meeting actually. So the -- it's kind of mentioned a couple of days ago. I think it was the first I heard was about 2 or 3 days ago. And it looks as though there's 5 topics that the FDA is going to focus on at that meeting. They're going to talk about better integration oncogenicity risks. They're going to talk about [ how high are ] the toxicity issues. They're going to talk about thrombotic microangiopathy and then nonclinical findings of neurotoxicity, especially related to DRG inflammation but also on a separate topic, actually clinical findings of neurotoxicity based on brain magnetic resonance imaging studies. Now I think the reason for the meeting -- and it's a timely meeting. We've seen, in the past year, 1.5 years, 2 years, a number of clinical holes, and the clinical holes tend to be both simply kind of CMC issues or safety issues. So on the safety side, you've got better integration. There was some thought about this happening with a [ Unicure ] product about 6 months ago. Product's now on old. Pathotoxicity issues, we know that there's liver inflammation associated with a number of -- with many, many gene therapies. And there were the 3 very sad, very unfortunate deaths in the X-linked myotubular myopathy program that were due to liver issues, preexisting liver issues that children have. TMA is known -- this is the association of thrombocytopenia with renal dysfunction that is thought to be either related to viral load or immune mediated. And of course, DRG has been talked about a lot. So I think there's going to be a deep discussion around these safety maps. What I'm hoping to see is some guidance on what we do in terms of monitoring for such things and preventing such things in the clinical setting. But every one these matters, we at Taysha have a very good idea of what we need to do, and we have repeated discussions with regulatory agencies. We always talk to our safety monitoring plans, and they seem happy with what we do. For example, with DRG, we make sure that even though the risk is extremely low and we don't think it's an issue, really much of an issue, we make sure that we do clinical examination and nerve conduction studies over time. And the regulator seems satisfied with that. So I think the meeting is going to be a great discussion. I'm looking forward to it. I'm hoping there will be some clearer guidance. But from our perspective, we have a good handle on these 5 kind of topics and how we plan to manage them and mitigate them in the clinical program.

Great. Thanks, Suyash. Sami Corwin of William Blair had a follow-up to that, is -- are there any other particular discussion points that you'd like to hear about at this FDA meeting?

The one thing that I hope is talked about in detail is, at a higher level, it's conceptually the balance of risks and benefits because there are all these safety issues that people get very concerned about and appropriately so. We want to avoid causing any kind of harm to children in clinical studies, in particular, severe harm or death. But that discussion has to be taken into consideration within the context of the severity of disease we're trying to treat. So for example, for GM2, these children die at age of 3 or 4. So if they have a bit of inflammation of DRGs that results in a sensory loss, that's actually neither here nor there. For giant axonal neuropathy, you're seeing children relentlessly progress on -- into wheelchairs at the age of 10, on the ventilator by 15 and die by the age of 20. And if their platelet count drops by a bit but they're still within the normal range, still functions well, just keep an eye on it. So I think I really hope this discussion is -- the FDA is less scaremongering and more here are the safety issues. Let's think about them sensibly within the context of each disease and the balance of risks and benefits. I think it will be, but I really hope that that's how the discussion occurs at that meeting.

Thanks, Suyash. Next question comes from Gil Blum of Needham & Company. Is adaptive immunity or T cell in any relation to existing neutralizing antibodies?

Yes, it's a good question, and it's -- I didn't touch on a lot of theoretical or complex mechanisms. And I made the point earlier. Think about B-cell reactivity and T-cell reactivity. B-cell humoral response is really antibody mediated. You can have an antibody response to capsid. You can have it in transgene product. And you can measure by measuring IgG on an ongoing basis. T-cell-mediated immunity, you can have, once again, to capsid or you can have it to transgene product. And as the T-cell response that is what results in the liver inflammation generally that we've seen. You can measure it by ELISpot tests. There's a whole different discussion on ELISpot on how that's valuable and how interpretable they are, but that's the best we have at the moment of teasing out whether something's T-cell mediated or not. There is definitely some kind of interaction between the presence of neutralizing antibody, which is a B-cell response and a T-cell-mediated response because there are just -- there's interweaving between the 2. You can't think of both responses being separate. And in fact, rapamycin, sirolimus is generally T cell mediated, but it also has an impact on B-cell triggering as well. So it does also nullify an antibody response to a degree. What I will say is if neutralizing antibodies are present in a patient, there is a greater likelihood of seeing a T-cell-mediated reaction. But I think from our perspective, with the lower doses we've given in comparison to systemic gene therapies and the fact we're coverings with rapamycin and steroid, I think, we should be fine there. But it's definitely something to keep an eye on.

Great. Thank you, Suyash. Yun Zhong of BTIG has the next question. What's the cutoff titer for preexisting neutralizing antibodies? Are you exploring methods to allow patients with preexisting neutralizing antibodies to be eligible for gene therapy?

Sure. So there is no cutoff for antibodies in our particular study. We have dosed patients in the presence of antibodies. I showed a slide earlier where we dosed patients with antibodies greater than 1 in 50 in giant axonal neuropathy study without any consequences. And I think it's a point that bears in mind repeating. I don't think there's any other companies dosing patients in the presence of antibody-specific serotype. We're able to do that because we give the drug intrathecally, and we're covering with a moderate immunosuppressive regime of sirolimus and steroids. So from our perspective, there is no level of antibody that we would preclude a patient being dosed. Having said that, if we see a patient who has been dosed, who has very high levels of antibody, we will just keep a close -- slightly closer eye on them. We've made sure the principal investigator is involved, and we'd see if there's any triggering of an immunological event. But from our GAN study, it doesn't look as though there's a relationship between preexisting antibody and adverse consequence.

Great. Thank you, Suyash. Maybe time for one more question from Raju Prasad of William Blair. Do patients who have preexisting anti-AAV9 antibodies have any unique findings and side effects or efficacy as compared to patients without neutralizing antibodies?

Sorry, the question was basically, if they have antibodies, are they more likely to have some kind of immunological consequence. Yes. So at the moment, we don't think that's the case. Theoretically, I think it probably is the case. If a patient has preexisting antibody, then it means they've seen the AAV9 serotype before. So their immune system is somewhat primed to that. And theoretically, they would then be likely to have -- more likely to have a T-cell-mediated response. Having said that, we didn't see any evidence of that in our GAN study, but it was only 14 patients, so may not be quite enough patients to really tease out any kind of relationship. So as I say, I think we're happy dosing patients in the presence of antibody. We've been able to do that nicely in the preclinical work. We've been able to do it nicely in the GAN study, and we'll have to wait and see what happens. We will be collecting total antibody, neutralizing antibody at baseline and on an ongoing basis. And if there is any relationship between preexisting antibody and adverse consequence later on, then we will be able to tease that out and determine that.

Great. Thank you, Suyash. We're at time now, and I'd like to turn the call over to Fred Porter to talk about the regulatory landscape. Fred?

Thanks, Kim. So we're on to the last section of our conversation today, and I'll kick this off and go through the slides. And then I'll ask Suyash to also join me in kind of reflecting on some of this as well. So let's get on to the next slide. So we spent a lot of today talking about how the gene therapy field and specifically the manufacturing in gene therapy has evolved. And a lot of this is just advancing the technology that we have available to us, but also, much of what we're doing is motivated by keeping up with regulatory expectations. And indeed, the regulatory expectations for gene therapy manufacturing and actually perhaps the whole field has evolved over the last few years. And I think the best -- this is best reflected in a number of new guidances that have come out to help specify our -- the expectations of sponsors like Taysha around CMC clinical and nonclinical expectations. And so what we've shown on this slide is just kind of highlighting some of those new guidances, and you can see many of them have really come out in the last year, 1 year, 1.5 years, including a very specific guidance from FDA around neurodegenerative guidances that was issued in January of 2021. And this is not exclusive to FDA. EMA has shared a recent guidance on advanced therapies, including gene therapy that really guide the work that we do and how we think about bringing these programs forward for FDA and EMA review. And so we're responding to this very specific feedback because we know the intention is to make this helpful for us in advancing programs to the clinic and beyond. So next slide. So to speak specifically around CMC or manufacturing considerations for neurodegenerative diseases, one of -- these are some of the themes that are emerging from some of this advice that's been issued for us. And one is to think about making manufacturing process decisions early in development, and that's something that I hope came through in our conversation with you today around defining our processes, the critical quality attributes and critical process parameters to make sure we have a process that looks an awful lot like our commercial processor lead development. Really taking innovative strategies, I think the agencies have acknowledged that for rare diseases like the neurodegenerative diseases we're trying to tackle at Taysha, we need to take different approach, not just making one large lot of product and then treating all the patients with it but rather using knowledge that we generate over -- by generating multiple small lots to really establish the baseline of quality attributes for our product. And that we should be focusing on, especially for licensure process control in that critical quality attributes need to be defined. And I think we always acknowledge biologics -- for biologics that processes the product, but I would say, in particular for gene therapy, this is of the utmost consideration in our philosophy that the process that we define really dictates the quality of the product that we have at the end of the day and that we need to measure these attributes to demonstrate that. And finally here, I mentioned this earlier in the conversation that when we're delivering a advanced product like gene therapy for a CNS indication, we needed to be very thoughtful about the formulation of that product to make sure it's compatible with the small volumes of the target area that's being the brand and spinal cord and making sure we have as clean a product as possible. And so I'm hoping these themes came through in our conversation already today. But that's just reemphasizing these are the things pulled right out of recent guidance for us in the field. So if you don't mind advancing to the next slide. So what are some of the specifics for us? And so these are a few bullets that I pulled out. So I think one thing that's on our minds is making sure we mitigate any immune -- inflammatory immune response or any other safety issues that might be presented by our product. And I think that was very relevant to the FDA advisory board that's upcoming. This is a topic of immediate discussion and on the minds of regulators and that we should be focused on product-related impurities, making sure we have good control over empty particles or residuals -- or empty particles, so these are product-related impurities, anti-particles, incomplete particles. And then the next bullet, process-related impurities. And I know I spoke about the methods that we're establishing to measure these earlier in the talk today. We've talked about there's an emphasis on making sure we have good ID test, knowing that the product we make is correct and that -- I think this is the agency acknowledging that, for small patient populations, we're making these in multi-product facilities, and we need a good ID test to confirm the identity of our product. And we talked about potency, that suitable functional activity assays are important. And the agencies are asking us to have these qualified for pivotal studies and validated by the time we have our BLA ready to go. And we spoke a bit about strength, measuring the strength of our products, using assays like digital PCR to make sure we can translate nonclinical dosing studies into dosing plans for patients. So I think all in all, collectively, this highlights how important as analytical testing and assay development is for our regulatory conversations with agencies. And that's why we're investing so much effort and time and collaborative effort between R&D and technical development and manufacturing in this area. Next slide, please. So finally, there's a couple of other points to make here. I think there's a focus on manufacturing process changes and defining CQAs, and we're, again, trying to be very intentional in this area, minimizing the amount of process change to minimize those kind of analyses being required. I think -- and then finally, device compatibility. We've been -- there's been a lot of focus in the field on manufacturing the right product. But now that's -- it's being extended to making sure we have evaluated how it's getting delivered to the patient in CNS, delivered gene therapy. It involves a particular set of tubing and perhaps other devices. And the agencies are asking for us to evaluate that thoroughly. And again, reemphasizing that they would like a dialogue between sponsors and regulators to make sure we all have a clear expectation of what needs to be done to advance these program -- products to patients as quickly as possible. So next slide. So I think taking all this together, what -- our Taysha approach is have those regulatory conversations early, specifically around manufacturing, highlighting our overall manufacturing approach, focus on release and characterization methods, potency assay strategy and stability plans. And we've been doing this already over the last few months for our first collection of programs with FDA, EMA, MHRA and PI, and we're already benefiting from that by incorporating this feedback early into our manufacturing and our clinical plans to make sure we're -- and introducing our Taysha platform approach to manufacturing to these agencies, which has been met with really positive feedback. And how do we see this benefiting us, and this is where I'll ask Suyash to comment as well, is I think this helps us align with regulators on our manufacturing strategy. This will be increasingly critical for pivotal programs like GAN, where we're really seeking approval for BLA approval, and I think that's going to be instrumental to our overall manufacturing and commercial plan. As our facility comes online, Greg mentioned we've been using advisers to comment on our facility plan, but we certainly intend to put our facility design in front of regulators and making sure they're aligned with our quality plans and commissioning approach for the facility. So I think this is all in all kind of the manufacturing side of how we're thinking about our regulatory strategy. And I'll invite Suyash and RA to comment if you like. Maybe Suyash first.

Sure. Thanks, Fred. I think you outlined that very nicely, but I'll make a couple of general comments. You mentioned the guidance that was published by the FDA earlier in the year, the -- it was gene therapy for rare neurodegenerative diseases and came, I think, January, February of this year. And it really nicely written guidance, actually quite pragmatic, quite helpful. We were very, very reassured to see it because when we read through it, actually, we were basically doing everything that they've asked for. And they're really focused on 3 pieces. One is CMC characterization, which really what Fred has focused on, what today's discussion has been focused on. The second is preclinical studies and how we make the most of those to learn to inform the clinical studies. And the third piece is around clinical studies and in particular on natural history studies to inform clinical development. So I think on the product quality side of things, the CMC attributes you've heard already that there's 2 things I think we're doing that are important. The first is we have a team that knows what they're doing, and we've all done it before. You heard that, for Greg, this is his fifth rodeo. So he knows how to build a manufacturing plant. Fred's done this plenty of times. I've done this plenty of times, so we know what to do. And the most important thing is that we're doing it early and high quality and investing now. Fred's outlined our 3-pillar approach, and I think that's very helpful. That all came through in this guidance. Focus on product quality, focus on it early, get it into preclinical tests, get it in the clinic early, that's exactly what we're doing. On the preclinical side of things, we are -- we have a very robust approach. We've talked before about our approach to IND-enabling toxicology where we do not 1, not 2 but 3 species of animals. We do chronic mouse tox over a long period of time. We do rat, and we do NHPs. And I think getting product into those 3 species early is really important, really valuable. We even, in some of our preclinical studies, actually not only dosed with gene therapy but adding some concomitant immunosuppressant just to try and model what might happen from an immunological perspective. Now I've already made the point that translating immunobiology is very, very complex, so it's somewhat exploratory when we're adding some immunosuppressives into our preclinical studies, but it may give us some useful information. But we're thinking about it. So I think these are some of the things that really -- that come out of this regulatory guidance document that already we're thinking about doing and doing well. I guess the final comment I'd make would be more of a qualitative comment in that our strategy is to take every one of our programs to multiple regulatory agencies. We speak to the FDA, the U.K., Germany, Canada. Several other countries, we're thinking of as well. And that means we have 3 or 4 regulatory interactions for every 1 of our programs. And we're in the midst of those at the moment. We've had several of them now. And now the pandemic's -- well, it's not over, but people are traveling a little more. So myself and Fred and other members of the team fly to Dallas and sit in a room. We have these regulatory meetings, and they go very, very well. The people who talked most on this meeting are myself, Fred and Steve Gray, who's our partner in UTSW, and the tone of the meeting is collegial. They appreciate everything we're doing. They learn from us. We learn from them. And I think, as a company, we've made a really good first impression with all of the agencies we've interacted with, and we've actually had more than one interaction with a couple of the agencies already, and they're always happy to see us again. And in the fact, in the last meeting for one of the agencies, they said to us we look forward to seeing you next time. So I think the guidance is one thing as the rules and regulations we'll have to do, but there's a qualitative aspect of these regulatory interactions. And so far, from my perspective, and I'm sure Fred would agree, they've gone very, very nicely. All right. I'll stop there. I know -- I'm sure that RA has a couple of final comments, but let me stop there.

I think we're going to take one question. We're almost at time. But Kim, I think we have time for one question.

Okay. Sure. So Suyash, this question comes from Yun Zhong of BTIG. From your experience, what do you think could be the biggest safety concern from intrathecal delivery of AAV gene therapy?

That's a good question. There's -- I think that there's a couple of nuances for intrathecal gene therapy over and above systemic gene therapy in terms of side effect, but they're pretty minor. So I've given lots of intrathecal drug myself in my pediatric practice, not gene therapy but oncology drug and anesthetic drug. And the one thing that sometimes happens with children and adults is that they have a headache after the infusion of the drug, after injection of the drug. And that just gets covered with a bit of Tylenol. And if you lay a patient on their back head down, which, once again, helps distribute drug around the brain and spinal cord but also somehow helps the post-lumbar puncture headache. That is a very well, very established reaction. But there's not really -- I've never seen any major side effects just from intrathecal dosing side. From the gene therapy side, I don't think there's anything over and above what you might expect for standard gene therapy. And in fact, I think it's going to be far safer because you're giving much less drug. I think the consequences that you have to watch out for are things such as liver inflammation, cardiac inflammation from any drug that leaks out systemically; and then, of course, any kind of white cell count elevation that suggests there may be some kind of an inflammatory process going on in the brain, but we've not seen that. We've seen the white cell count changes in the first couple of patients in the GAN study, but that actually was not on the head by this steroids and rapamycin cover. But it's still something to watch out for. So we are going to do CSF samples on 3 monthly basis, and we're going to do MRI scans on a regular basis to see if there's any white matter changes. But I don't anticipate seeing any major side effects specifically related to intrathecal dosing apart from those related specifically to the actual intrathecal administration itself. And in fact, from our preclinical package, the tox profile or safety profile looks very, very good. So I don't really anticipate anything specifically related to an intrathecal administration of drug.

Right. Thank you, Suyash. And thanks to all who put in questions, very thoughtful questions for us. I'd now like to turn the call over to RA for his closing remarks.

Sure. Maybe we can go to the next slide. Again, we want to thank everyone for joining us today. Our goal really was to really demonstrate kind of how we think about manufacturing. We think about it early. We think about it often, but also as a field, we think it's important to be able to share some of the best practices that we've been able to gain over years and years in the space, whether that is at previous companies that we've been a part of in kind of helping to pioneer gene therapy from a manufacturing perspective but also some of the learnings that we've achieved through our collaboration with our collaborators over at UT Southwestern, Dr. Steven Gray as well as bringing on some additional expertise from a gene therapy perspective. And so hopefully, we were able to demonstrate our knowledge but also the fact of how we think about manufacturing and the aspects of how we think about it from early discovery through the translational development cycle into the clinic and ultimately once we get there, to commercial scale. We have multiple product -- multiple value inflection points from our products that we plan to achieve on over the next 18 months that we've made a significant transition this year into a pivotal stage gene therapy company with TSHA-120 program in giant axonal neuropathy. And we expect to provide an update on that program, both from a clinical perspective with the release of the high-dose data as well as our regulatory interactions around what a development and approval pathway could potentially look like for that program by the end of the year. Furthermore, we remain on track to report first-in-human biomarker data in our TSHA-101 program in GM2 gangliosidosis as well as dose the first patient under our currently open IND for TSHA-118 in CLN1 Batten disease. Again, we expect to open up our clinical development and our clinical trials for Rett syndrome and SURF1-associated Leigh syndrome by the end of the year. Lastly, I would really like to give a special thanks to Fred and Greg from our manufacturing group; Suyash, who's our CMO and Head of R&D, for participating in the event and sharing their insights. Again, we appreciate all that who joined and the great questions that came over from the analyst community. And we look forward to seeing you at our next investor meeting series, which will be coming up next month, and that'll be a focus on CLN1 infantile Batten disease. In September, we plan to focus on our Rett syndrome program. And in October, we just announced that we'll be doing an investor meeting series on our Angelman program. So again, we appreciate everyone's attendance today, and have a great day and great rest of the week. Thanks.