Hello everyone, and thank you for joining us. My name is Alex Chapman, and I'm the Head of Investor Relations and Corporate Communications here at Poseida. Before we begin, we'd like to remind listeners that today's call will include forward-looking statements that are based on current information, assumptions, and expectations that are subject to change. Actual results could differ materially from those stated or implied by our forward-looking statements due to potential risks and uncertainties that can be found in our press releases and latest SEC disclosure documents. These statements are made as of today's date, and the company undertakes no obligation to update these statements. During today's call, you are welcome to type questions into the chat window, which Poseida Management will address, as time allows, during the Q&A portion of the agenda. At the conclusion of the call, a recording of the program, including speakers and presentation slides, will be posted to the investor section of Poseida.com. With that, I'll turn it over to Dr. Kristin Yarema, President and CEO, to kick off today's program. Kristin? Thank you, Alex. It's my great pleasure to welcome you all to Poseida's first-ever R&D Day dedicated to our genetic engineering and delivery platform and rare disease pipeline, including non-viral gene insertion and gene editing programs. Today you will hear from Poseida scientists describing how the technology underlying our non-viral approach to genetic medicine is different and why we're excited. In addition to leading academic experts describing the significant unmet need that exists for patients in the disease areas we are targeting with our lead non-viral assets, we'll also share our latest advancements in genetic engineering and next-generation technologies with novel platforms and approaches that we believe represent the future of genetic medicines. Poseida is at its core a genetic medicine company with a powerful and proprietary set of tools that support us in our mission to pursue transformative new therapies with what we believe is the capacity to cure. Our tools enable us to develop allogeneic CAR-T programs that are distinctively rich in stemness, which has been shown to be important for efficacy. We believe we are quickly emerging as a leader in allogeneic cell therapy with three clinical-stage programs, impressive early data from our lead program in multiple myeloma, and our own GMP manufacturing. Our strategic investment from Astellas and our extensive partnership in hematological malignancies with Roche are further testaments to our approach. But today we are focusing on the other side of our business: non-viral approaches to gene delivery, gene editing, and gene insertion to permanently correct genetic defects that give rise to chronic rare disease. We believe this is the future of genetic medicines. While there is a lot of excitement around our cutting-edge allo cell therapy programs, you may be interested to know that Poseida was founded back in 2015 with gene therapies specifically in mind. Our founder, Dr. Eric Ostertag, was the first gene therapy PhD student to graduate from the University of Pennsylvania, and he recognized early on that available technologies like using viruses to insert genes, early editing systems like Zinc Fingers or TALEN, and delivery vehicles such as adeno-associated virus or AAV all had severe limitations that would likely mean these technologies could not realize the goal of developing therapies that could safely and essentially permanently correct genetic diseases. You see an overview of the challenges of these older technologies here, including safety problems, limited cargo size, very high cost and difficulty in manufacturing, inability to treat an array of patient types, and on and on. Starting in graduate school, Eric set a goal of creating the right fit-for-purpose set of tools for gene therapy, and he began to design and build the suite of distinctive and proprietary technologies that Poseida has today, all of which are now fully non-viral. Importantly, Poseida is far from alone in seeking ways to do things better and in believing non-viral approaches are the right choice. Look here at a comment made at a recent healthcare conference by Dr. Peter Marks, head of FDA's CBER division that oversees cell and gene therapy as well as other products such as vaccines. He says, "We are enthusiastic to see the development of non-viral vectors for gene therapy and look forward to working with sponsors on these programs as they work to achieve the necessary efficiency needed for effective gene transfer. There is real urgency around developing non-viral genetic medicines for patients in need, and we are encouraged that this type of approach is gaining traction with regulators. At Poseida, we have a bold vision to develop genetic medicines that are capable of treating medical problems at their root causes to provide corrective and transformational therapeutic benefit. This means not simply treating symptoms, but rather providing functional correction through insertion, deletion, or modification of genes. Importantly, these products also need to be safe, have durable efficacy, treat a wide spectrum of patient types with a single dose or short treatment course, and be able to be reliably manufactured at a scale and cost that means all patients that deserve to benefit from such therapies will be able to do so. For us, that means we need the ability to insert or edit whole genes while avoiding viral vectors. To meet this challenge, Poseida has developed a system of proprietary non-viral tools that can be used individually or together. For whole gene insertion without virus, we use a DNA transposon approach that can stably integrate even large genes. It has roughly 30-fold the cargo capacity of a virus and uses a simple cut-and-paste approach. For gene editing with exceptional fidelity, we use a novel double RNA-guided DNA nuclease that we believe is about 20-fold less error-prone than CRISPR-Cas9. For delivery, we use engineered lipid nanoparticles made from a library of Poseida proprietary lipids notable for their low immunogenicity, dose titration potential, and ability to be manufactured at scale and favorable cost. You will hear much more about the elements of the system over the course of the day. Our proprietary systems are highly versatile, and we have continued to add more innovation to them. As we build products using the core technologies I just described, we are incorporating further functional elements such as tissue targeting technologies, safety or modulation switches, and intracellular trafficking signals. This enables us to take a systems approach to genetic medicines, allowing for customization to address the underlying cause and complexity of various diseases. Stay tuned to hear specific applications as we discuss our individual pipeline programs. Many of you listening have heard much more about Poseida's clinical stage cell therapy programs than about our gene therapy side lately. So how does this all connect? Well, this simple figure illustrates just that. We can use Poseida's non-viral genetic engineering toolkit to both insert and edit genes with the advantages we have discussed in either ex vivo settings where we manipulate cells outside the body and then infuse them into a patient, or deliver those tools in vivo where they can work directly on a patient's own cells in their bodies. The ex vivo application, where we both insert CARs and edit T cells, is how we have built our allogeneic CAR-T portfolio. Our in vivo applications now include our lead gene editing program, P-KLKB1-101, and our lead gene insertion program, P-FVIII-101. I'd like to emphasize that this does represent a shift in our gene therapy focus, and this slide shows how we have evolved our pipeline over time. Previously, we have worked on programs such as our ornithine transcarbamylase or OTC program, which have used a hybrid AAV and lipid nanoparticle approach to reach higher activity levels than competitor technology can. While we are confident that approach works and those programs remain available for partnership or licensure, we are so excited about our advances in fully non-viral approaches that we are shifting and narrowing our internal focus to non-viral. We are currently moving forward toward INDs with our two lead fully non-viral programs, KLKB1 and Factor VIII. This refocusing is similar to what we have done previously on our cell therapy side, where we started efforts with autologous CAR-T but ultimately made a complete switch to allogeneic products, which we see as necessary to meet market needs in the long term. We learned from our autologous experience, then applied those learnings as we made the switch to allo, which we did without hesitation once we felt we had developed the right technology to enable our success in allo. Now we are at an analogous point in time with gene therapy. To conclude, I'd like to highlight that our two programs are both in rare genetic diseases with unmet medical need and substantial market opportunity for the right novel therapies. First, we will hear more about P-KLKB1-101 for Hereditary Angioedema or HAE, which is a disease affecting roughly 6,000 people in the U.S. alone, where unpredictable and potentially life-threatening tissue and airway swelling results from genetic defects in the vasodilation cascade. Although current therapies comprise a $2.6 billion market, they do not offer durable, reliable protection against attacks. We are using our gene editing approach to reduce kallikrein protein levels for what we believe could be lasting patient benefit. Second, we will look at P-FVIII-101, where we use our fully non-viral stable gene insertion technique to replace missing or defective Factor VIII protein to correct the defect that causes hemophilia A, which today affects 30,000 kids and adults in the U.S. Although the hemophilia market is already approaching $8 billion, we have yet to really offer a safe and effective gene therapy that can be used in patients of any age with durable results to control bleeds and avoid permanent joint damage and pain. As you learn about our efforts with these programs, our team will explain the exceptional science and technology that underpins these advances, including next-generation technologies such as site-specific gene insertion that will unlock future opportunities. We will set the stage for each of these programs with an overview of what these diseases mean for patients and why new therapeutic options are needed. We are delighted to have some true leaders in research and patient care with us today to do that. Dr. Steven Pipe from the University of Michigan will introduce us to hemophilia later on, but to start, I'd like to introduce Dr. Marc Riedl, who will give us an overview of Hereditary Angioedema. Dr. Riedl is Professor of Medicine and Clinical Director of the US HAEA Angioedema Center at the University of California, San Diego, where he also serves as Clinical Service Chief for Allergy Immunology. He is an active clinical trialist in angioedema and immunodeficiency conditions and also serves on numerous scientific committees as well as appointed expert panels for the FDA and NIH. Dr. Riedl, welcome, and over to you. Hello everyone, and thanks very much for the invitation to present to your group today. I'm very pleased to provide this presentation entitled Hereditary Angioedema: Where Are We Now? I'll just hope to provide you an overview of the current state of affairs with diagnosing and managing Hereditary Angioedema, but of course, have a look at the future and what work do we have left to do, at least from my perspective, in terms of improving the management of HAE. I'll begin just to level set an overview of the condition, the clinical features of HAE, which you may be very familiar with, but just a reminder that this condition causes fairly severe protracted angioedema events in the absence of urticaria. This has nothing to do with the allergy system. These are isolated angioedema events that tend to be very severe and often unpredictable. As you can see in the photos here on the slide, often affects the skin, the face, the extremities, but really anywhere on the skin can swell. Also very common are the gastrointestinal attacks, which again can affect any point in the GI tract, but usually the small intestinal swelling causes very severe and protracted abdominal pain. Then lastly, but most importantly, the airway attacks, which do have a significant risk of asphyxiation. Historical data shows that up to 40% of patients with airway attacks suffer life-threatening events if not accurately diagnosed, recognized, and treated effectively. Now, these attacks of HAE are protracted. They last up to two-four days in most cases and generally gradually become more severe over the first 24 hours. Very importantly, HAE attacks do not respond to allergy treatment. So the usual therapies given for allergic angioedema, antihistamines, corticosteroids, epinephrine, have no effect on HAE swelling, which is of course the reason that we're involved in developing very specific therapies for HAE. We do know of some triggers that cause HAE attacks. You see them listed here: trauma, stress, some medications such as estrogens or ACE inhibitors. But again, most attacks are quite unpredictable. And this is of course a genetic condition. Hereditary follows an autosomal dominant inheritance. This slide represents the common symptoms of HAE and was published by a group in Europe, a very large group of patients, over 220 patients, many years of observation with over 130,000 angioedema episodes. And you'll appreciate that most attacks, the vast majority, are either skin or gastrointestinal in nature, though over 50% of patients do experience these life-threatening airway events. Then you see a smattering of other various types of angioedema symptoms. Importantly, HAE prevalence is about one in 50,000. There's no clear ethnic predominance in terms of who's affected. We do know that while it's autosomal dominant and affects men and women equally, that women tend to be more severely affected. You can see the mean number of attacks here, about 24 a year in the female population and 20 in the male population. Now, this is the HAE mechanism or pathophysiology. First, you'll appreciate there's no involvement of the allergy system or cells here. This is of course swelling due to activation or dysregulation of the contact system or the kallikrein bradykinin system. You can see C1 inhibitor is represented by this red dot. If this is missing or dysfunctional, this contact system is dysregulated and you get excessive production of bradykinin due to overactivity of Factor XII and kallikrein. So very important at the heart of this is plasma kallikrein. It is the ultimate step that cleaves high molecular weight kininogen to bradykinin, then bradykinin acting on B2 receptors to cause increased vascular permeability and the symptoms that we see as angioedema, swelling of the skin, the GI tract, or the airway. Now, as you're probably aware, there's been tremendous clinical development in terms of HAE therapeutics over the last 10-15 years. I won't belabor the details, but recognize we had very little to manage HAE before 2009. We really relied heavily on the use of attenuated androgens to prevent attacks, which can be effective in some patients but lead to a slew of side effects and long-term adverse effect concerns. In recent years, we've seen three main strategies used for targeted therapies for HAE, replacing that C1 esterase inhibitor protein that's missing in the vast majority of patients with HAE, targeting kallikrein production or activity with various strategies at either blocking or inhibiting kallikrein activity or blocking the bradykinin B2 receptor, where of course you stop the effects of bradykinin on the vasculature. You may be familiar with some of these agents listed here, approved in the last 10-15 years to either prevent attacks or treat the attacks when they occur, so-called on-demand therapy. Which brings us to the strategies that we use in the clinical space to manage HAE. Listed here on the left, on-demand therapy, which is required for every patient that has Hereditary Angioedema. This is the first and most important step in managing patients, at least currently, to ensure they can stop an unpredictable and serious attack when it occurs. On the right-hand side is long-term prophylaxis, and we are increasingly using this to manage HAE due to the development of more effective, more tolerable long-term preventative treatments. This is of course a medicine given regularly on a scheduled basis to reduce or hopefully prevent attacks from occurring and also to prevent the severity or reduce the severity of those attacks. On-demand treatments for all patients, increasingly using long-term prophylaxis to manage patients. Depending on the survey that you look at in the United States, somewhere between 60%-80% of patients are on a long-term prophylactic therapy. I won't say much about short-term prophylaxis, but this is given prior to a surgery or procedure that has a high risk of triggering an HAE attack due to tissue trauma. At the bottom, very importantly, you'll see that all the current evidence-based guidelines recommend that we individualize this treatment plan, meaning that as we have options for treatment, we select those based on shared decision-making with the patient and really try to design the optimal treatment plan for a given individual. We do see variability in the efficacy of these agents from person to person. We see different side effects that may occur in patients. And so again, individualized therapy aimed at improving quality of life for that individual patient is really a high priority in the clinical space. Now, when we talk about treatments, we have to consider how does this impact patients? Much of our work, of course, is focused on the lower right here. What treatments do we have? Are those treatments accessible? Are they safe and tolerable for patients? We as clinicians spend a lot of time talking about attacks right above that. What types of attacks? What are the complications? How do they affect a patient during those episodes of swelling? But you can see here in this nice paper published by Aleena Banerji, it's much more complex than that. So we recognize there are aspects of quality of life that are very important to consider in HAE. High rates of depression and anxiety in these patients historically. The condition affects their social activities, their travel, their ability to work or go to school. And then of course, costs are important. Increasingly, we're under pressure to provide evidence that the costs are worth the benefits, and that can relate to both direct and very importantly indirect effects of a treatment or a condition. And we do see this again in the clinical space, a lot of pressure from payers to restrict access to these medications at times, which unfortunately does cause long-term problems for patients as we try to manage their condition. So I'll move towards the end and just talk about the goals of treatment. And we should keep this in mind as we think about therapies, about improving therapy for HAE. This is a Delphi initiative, this publication, 23 international experts, and you can see the consensus. The ultimate goal is to normalize a patient's life. All of the experts involved in this paper agreed that that should be the ultimate goal. Most of us agree that that means achieving total control of HAE, that people have no attacks, no symptoms of the condition on their treatment plan. Also important is that patients should have a lot of input in terms of is their HAE well controlled? Is their life normalized? And so there's work looking at tools to measure that, validated ways, as well as the discussions that we have in the clinic. We have room to improve in HAE therapies. That includes safer treatments that are highly effective, but also the burden of treatment, which is an issue, especially for long-term prophylaxis. These are medications that have to be given on a regular basis, often by injections or infusions. Some of them are given a couple of times a week, some given a couple of times a month. Over time with a chronic illness, there is a burden of treatment that we well recognize and we'd like to improve upon. Ultimately ensuring if we have effective treatments, are they accessible? At the end of the day, do they improve quality of life? I'll wrap up saying that we have accomplished a lot in HAE. We are now able to largely prevent death or mortality and excessive suffering from the condition with acute treatments. We can reduce hospitalization and disability for most or many patients, perhaps not all of them. We still have issues with the treatment burden, with the frequency of these chronically administered medications that is required. This does affect HAE and its interference with life. It's not just the symptoms, that's a big part of it, but it's also the treatment regimens that we need to use to manage the condition. So as you well know, there are many strategies still being looked at, investigated to improve treatment for HAE. That includes the work you all are doing with targeting the kallikrein gene with gene editing, other companies looking at gene editing or gene therapies designed as a sort of one and done treatment that might give long-term relief or protection from these attacks. There are interesting strategies looking at RNA targeted therapies that might have a longer duration of action with a single dose. Then interest in oral therapies. Patients are attracted to oral therapies if they have to take something chronically. The perceived burden of taking a pill is less. So we have targeted oral medications that are in development as well. So I think the future looks bright. I'm very excited to see what you all continue to work on as well as others in the space. And I think we have a great opportunity to further improve the lives of patients and families that are affected by Hereditary Angioedema. Thanks very much for the opportunity to present. I hope you enjoy the rest of your program. Thank you, Dr. Riedl, for that informative overview of HAE. Hello, I'm Blair Madison, Chief Scientific Officer of Gene Therapy here at Poseida. I'm really excited to tell you about our new program using a high-fidelity approach to edit the KLKB1 gene. And we do this using our Cas-CLOVER nuclease, which is our first time using this technology for a therapeutic target. I'll first highlight how Cas-CLOVER is an ideal gene editing tool for the modulation of KLKB1 levels in HAE. Then after that, my colleague, Dr. Bonnie Jacques, will tell you about our exciting new in vivo data. For HAE, we're developing a precision-focused approach to edit the clinically validated target KLKB1. This is enabled using our site-specific Cas-CLOVER technology, which historically yields about 20 times higher fidelity than Cas9. The minimization of unintended edits is perhaps the single most critical goal for safe gene editing. At the same time, editing the KLKB1 gene and reduction of kallikrein activity in the blood will provide long-term relief and reduce the treatment burden and anxiety of chronic prophylaxis for patients. Our non-viral approach also enables additional follow-up treatment if ever needed. Let's recap some of the key biology relevant to KLKB1 and its role in the pathophysiology of HAE. In HAE, there is a fundamental deficiency in the C1 esterase inhibitor or C1-INH. This causes episodic activation of kallikrein and activation of the vasodilator called bradykinin. This leads to increased vascular permeability, swelling, and pain. As you heard from Dr. Riedl, this can be disfiguring, debilitating, and deadly when attacks affect the airway. By targeting and inactivating the prekallikrein gene KLKB1 through gene editing with our Cas-CLOVER nuclease, we can lower the levels of prekallikrein. This stops the episodic attacks to bring the pathway into balance and restore the vascular barrier, with this balance being readily evaluated by clear clinical biomarkers and key endpoints. So what is Cas-CLOVER and what is the mechanism behind its high fidelity? Let me first point out that Cas-CLOVER is a Poseida technology for our use in cell and gene therapy applications. Fidelity is key for minimizing unintended cutting when applying any nuclease technology, a criterion that has become standard in the field of precision gene editing. Structurally, Cas-CLOVER is a fusion between dCas9 and the nuclease domain from Clo51, shown here on the left. The feature underlying the high fidelity of Cas-CLOVER is that it requires dimerization to cut DNA. This dimerization is provided by two unique sequence-specific guide RNAs that position the nuclease in just the right spatial arrangement that allows cutting by the Clo51 nuclease domain. This contrasts with a typical RNA-guided approach like CRISPR-Cas9 diagrammed here to the right, which can frequently yield off-target cutting at sites with similar target sequences. With Cas-CLOVER, the dual-guide RNA approach increases the molecular specificity by 12 orders of magnitude. Think of this as a very precise GPS coordinate. For HAE, we harness this advantage for high-fidelity editing at KLKB1 with guide RNAs that are 100% primate conserved for ease of translation to higher species. So to recap, fidelity is enabled by a highly specific molecular address to bring together two halves of the nuclease, neither alone being able to cut without the other. This design is responsible for our excellent fidelity, which is about 20x better than Cas9, as you can see looking at all available data for Cas9 in primary cells, including multiple product candidates here shown to the right, compared to our results with Cas-CLOVER. There's no compromising with the on-target editing efficiency. As you can see from the graph to the far right, Cas-CLOVER editing rates meet or exceed the performance of Cas9. It provides the best of both worlds, both fidelity and efficiency. With Cas-CLOVER, it is also a proven workhorse for efficient gene editing in T cells in the context of our allogeneic CAR-T programs. One advantage we also recently unlocked was the internal development of an enhanced Clo51 nuclease domain, which executes the cutting function in Cas-CLOVER, as I mentioned. This provides enhanced activity, but with a full preservation, full preservation of fidelity. Let's dig into the fidelity we observe in the context of our KLKB1 target. For the KLKB1 target, we employ a single pair of guide RNAs to target precise editing at this gene. Now, to nominate candidate off-target sites, we conducted something called iGUIDE in liver-derived cell lines. This is an industry-accepted and FDA-recognized unbiased method for off-target discovery. After nomination, we then queried potential editing at these sites. Consistent with Cas-CLOVER's high-fidelity track record, we observed very low off-target edits as assessed here in primary human hepatocytes. Note here the high sensitivity of our assay, able to detect off-target edits down to a rate of 0.05%. Off-target editing was consistently below 0.1%, essentially at background levels, here shown in the shaded region at the bottom of this graph, with the vast majority of sites below our lower limit of detection. These off-target editing rates are much lower than that observed when using Cas9 in the liver, highlighting Cas-CLOVER's exceptional high fidelity. To recap, we see high fidelity for all of our previous studies and previous targets, and also high fidelity at the KLKB1 target. Well, what about increasing a cell's exposure to the Cas-CLOVER nuclease with much higher amounts of our lead candidate? Could this pose a challenge? Well, with other nucleases like Cas9, increasing the dose of the nuclease on human hepatocytes leads to escalating off-target effects and compromised fidelity. We conducted such a study with primary human hepatocytes in which they were incubated with progressively higher concentrations of our LNP candidate that delivers the Cas-CLOVER nuclease along with specific guide RNA pair. Results from this experiment are illustrated on the right. With Cas-CLOVER, dose escalation increases on-target editing as desired and as expected. However, in the context of LNP concentrations well above our EC50, where we see 90% editing at the KLKB1 target site, this dose escalation does not yield any appreciable increase in off-target editing, shown here in this box to the lower right. This allows for a wider index in which editing maintains our desired high fidelity. To recap, our nuclease provides high efficiency, high fidelity, with a specificity that is rock solid even in the context of high exposure. Okay, now to highlight the in vivo performance of our candidate, I'd like to introduce you to Dr. Bonnie Jacques, our Program Development Lead and Senior Director of Pharmacology, who will tell you more about the efficacy and tolerability of our LNP-mediated gene editing approach to HAE. Bonnie? Thank you, Blair. To continue building off those exciting platform advantages and the high fidelity offered by Cas-CLOVER, we sought to ask if we could actually apply this technology for the treatment of Hereditary Angioedema. As Dr. Riedl so compellingly spoke to earlier, there is a clear and critical unmet need for HAE patients to have stable relief from their symptoms while maintaining a best-in-class safety. In order to begin assessing the ability of our novel ionizable lipids and LNPs to deliver Cas-CLOVER in vivo, we conducted some proof-of-concept studies in mice. We were excited to see that not only do we get a clear reduction in protein kallikrein levels, but we also see stable and durable protein reduction. For HAE, it is critical that we reduce kallikrein levels, as this is the protein that mediates the significant vascular leakage and pain and swelling associated with HAE. It's been shown in the clinic that a 60% reduction in kallikrein levels is sufficient to provide full relief from HAE symptoms and attacks. Therefore, we define our minimal effective dose as the level at which kallikrein editing enables a targeted reduction in plasma kallikrein protein. As you can see on the right, when we map our level of editing to the level of protein reduction, we identify a very broad therapeutic window of opportunity. This could enable us to potentially dose patients and titrate to their individual level of correction needs. Having established the clear level of efficacy that we need, we next turned to our safety profiling. Blair walked us through the huge fidelity advantage that we get with Cas-CLOVER, as well as the minimal-to-no off-target editing. Our next step was to then assess the safety of our lipid LNPs. To do this, we conducted dose escalation studies in mice and found absolutely no significant levels of liver enzyme elevations, suggesting that we'll see no liver toxicity. We've obtained a dose range of up to 20x our minimal effective dose in safety. This is really huge a finding for gene therapy products, which have been classically characterized by having very narrow margins of safety. We believe one of the key drivers of the safety profile is the biodegradability of our lipid. You can see on the upper left that our Poseida lipid clears within 24 hours, whereas, for example, MC3, an FDA-approved lipid, has much slower clearance kinetics. Having established now this broad therapeutic window and therapeutic index showing both safety and efficacy, we're now set to move this program into potentially treating HAE patients. With a clear preclinical package in hand, we have now begun the path forward for moving P-KLKB1-101 towards HAE patients. On this path, we have already conducted a successful first interaction with the FDA and have been given a preliminary green light on both our treatment strategy as well as our patient population. We've also been initiating CMC activities, which include not only CDMO nomination, but also late-stage product development and analytical development, and have successfully initiated our first engineering runs. In preparation for our IND, we've been engaging key thought leaders and clinicians such as Dr. Riedl with significant experience working one-on-one with HAE patients. The goal here is to better understand how we can tailor our product to best match patient needs and expectations. Lastly, we've begun assessing clinical site readiness as well as our clinical protocols to hopefully speed the rapid development of P-KLKB1-101 and our Cas-CLOVER system into the clinic and beyond. Poseida is not only working on our Cas-CLOVER gene editing system, but we also have a fully non-viral gene insertion system. This is based on a novel and optimized transposon system delivered with our Poseida LNPs. Dr. Jack Rychak, our Vice President of gene therapy R&D, is now going to walk us through the really exciting advancements we've made in DNA delivery and how Poseida is now posed to address the needs of many patients with genetic diseases. Jack? Thanks, Bonnie. I'd like to start by describing what we believe the best-in-class platform for gene therapy would look like. Now, there are some diseases that can be corrected by simply inactivating a gene. Hereditary Angioedema is one great example, as Bonnie shared earlier. However, genetic diseases that can be corrected by simple gene inactivation are the exception. In most cases, we'll need to restore the mutated gene to its functional state. Inserting the full wild-type form of the gene into the patient's genome would enable us to address genetic disease at its root cause in the genome. This could give us the potential to resolve the disease and render a durable functional cure. Now, as genetic diseases come in a variety of severities, we should not expect a one-size-fits-all dosing approach to work for all patients. Rather, we would want to be able to start each patient on a low dose and titrate up with additional doses to get each patient to the appropriate degree of genomic correction. This requires, of course, a drug product that is amenable to repeat dosing. So what are the tools that we need to enable this? First, we need a molecular platform, something that is able to take a whole gene's worth of DNA and insert it into the patient's genome. Second, we need a delivery system, something that is able to deliver both our corrective gene and the molecular platform to the intended cells, and which also can be repeatedly dosed. As I'll show you, we've developed both here at Poseida, a powerful gene-inserting molecular platform that we call SPB, and a best-in-class nanoparticle delivery system. Before digging in on our two platforms, I'd like to briefly discuss the value of inserting whole genes. As you may know, genetic mutations come in a variety of flavors. The loss of function disease can be caused by any of a number of mutations in the affected gene, and patients may carry unique mutations that all cause the same disease. One therapeutic approach could be to correct each patient's unique mutation individually, basically edit the mutated gene back to the wild-type form. This approach is generally referred to as gene editing or base editing. However, the challenge with the editing approach is that it must be bespoke. We need to create a new drug product for each specific mutation and would potentially need to manufacture and navigate multiple drug products through the regulatory process. If, instead of correcting the mutation, we instead introduce a functional copy of the entire gene, we can have a single product that could potentially address all mutations causing a specific disease with one product, and thereby enabling a much more equitable and cost-effective product. All right, let's start talking about our platform technologies. This is where it gets good. So I'll start with our molecular platform. This system is based on a proprietary transposon type system called Super PiggyBac, which I'll refer to here as SPB for brevity. This system has two components shown on the left here on the slide: the DNA cargo and the SPB transposase. The cargo is basically our corrective transgene along with the additional transposon backbone elements. The transposase is the enzyme that is responsible for cutting our corrective transgene out of the backbone and pasting it into the genome. This is a cut-and-paste system. This platform gives us some amazing versatility. We can use SPB, a single molecular platform, to insert any gene into the genome and potentially treat multiple diseases. Additionally, transposons like SPB are professional DNA inserters, evolved and optimized for high efficiency. Now, let me switch gears and introduce the second platform that we need, which is the delivery system. For in vivo gene therapy, viral delivery systems such as the AAV have dominated the field, though at Poseida, we are investing in non-viral delivery technologies. So I'll start with a question: why are we pursuing non-viral delivery? The simple answer is that we believe this is the right approach to truly unlock the prompts of what gene therapy can do. Non-viral delivery platforms can free us from cargo capacity constraints of traditional AAV-type vectors. This is, of course, critical if we want to deliver whole gene-sized cargoes of DNA along with the associated molecular platform required for genomic integration. If we're relying on AAVs as our delivery system, we just run out of space very quickly of what we can fit in an AAV. Separately, unlike viral vectors, nanoparticles can be readily engineered to be non-immunogenic. This means that we could potentially administer each patient multiple doses. This would enable us to titrate individual patients to efficacy without risking overshoot. Finally, while AAVs are biological vectors, nanoparticles are built on chemistry, which provides us some advantages in terms of manufacturing cost and efficiency of platformization. Overall, we view non-viral delivery as not only the right approach to treat rare genetic disease, but also as a foundation upon which to expand genetic medicine as a modality to treat multiple disease types. The lipid nanoparticle, or LNP, has emerged as a transformative non-viral delivery platform. Now, the conventional LNP is just fantastic for liver-directed mRNA delivery. It is highly efficient and can be manufactured at large scale. But these conventional LNPs do have some significant shortcomings if we try to deploy them for delivery of DNA and other very large payloads. In particular, there are two hurdles to enabling delivery of gene-sized DNA payloads with the conventional LNP. The first relates to transduction efficiency: how many cells are we able to productively get our DNA cargo into? These images on the left are from mouse liver after administration of a conventional, off-the-shelf LNP delivering either mRNA or DNA, coding for the same transgene and at the same dose. You can see that for mRNA, we just get amazing expression. Most of the cells are expressing our payload, as shown in the red color here. In contrast, we see very infrequent expression when we're delivering DNA. There's a couple of red spots you can see here and there, but most of the cells here just are not converting the DNA that we've delivered into functional protein. Separately, DNA as a payload exhibits safety challenges that are significantly greater in magnitude than those found for mRNA and other smaller types of nucleic acids. In the graph on the far right, I'm showing you the serum cytokine concentration, excuse me, the serum concentration of IL-6, a pro-inflammatory cytokine that we can use here as a proxy for unwanted activation of the immune system. You can see that dose for dose, the DNA LNP produces significantly greater IL-6 than the mRNA LNP. Now, this immune activation with DNA can cause toxicity, including unwanted damage to the liver. The high immune sensitivity to a DNA payload, coupled with the inherently low transduction efficiency, makes deploying conventional LNP platforms for DNA delivery a nonstarter. The platform just doesn't work very well for DNA. The LNP, though, does have some great advantages. We just need to build on them, build on the LNP, keep what it does good, to get it a viable delivery vehicle for DNA-based gene insertion therapies. Now, at Poseida, our non-viral platform work has been laser-focused on developing technologies meant to address the immunotoxicity and efficiency barriers that I outlined on the previous slide. Our approach has been to view the LNP as a starting place, again, really a foundation, upon which we can stack the additional technologies needed to enable delivery of DNA and other large genetic payloads. We want to preserve the good aspects of the LNP that we need: liver tropism, manufacturability, interspecies translatability, while adding in new functionalities. We start with what's noted in the middle here as our core technology suite. These are the ionizable lipids and our molecular platforms for gene insertion and genome editing. Stacked on top of our foundational technologies are what we call innovation elements. These are platforms that we've invented and engineered specifically to solve the challenges that we had identified for non-viral delivery of DNA. As shown in the bottom here, we've grouped these into technologies that can address safety or efficacy, as well as some unique options that we can add in based on the requirements of individual programs. I'll focus the remainder of my talk on describing how we've combined these various technology elements together and some of the very impressive results that they're now generating. I'll start with our work on safety. Now, as I mentioned, the primary issue with which we're concerned is unwanted activation of the immune system. Now, it turns out that one thing we can do to avoid activation in the immune system is simply to prevent our nanoparticles from being taken up by the immune cells in the first place. Now, we've accomplished this by some careful and clever engineering of the surface architecture of the nanoparticle depicted on the left as our targeting construct. The bar graph on the right shows ALT levels as a measurement of liver toxicity. You can see with the red bar, we have pretty high elevations when we're using a standard DNA LNP. These are much higher than what we would see if we were deploying mRNA instead of DNA. In light blue is the same LNP, same dose, but now with our targeting construct, which, as you can see, leads to a significant reduction in hepatotoxicity. It's about a factor of 10. However, we're still not quite where we want to be, which is the dotted line representing the upper limit of normal for this enzyme. To remedy this, we've added in what we call our armoring platform, which is delivered by our nanoparticle and serves to temporarily shield hepatocytes from unwanted pro-inflammatory signals. Going back to the bar graph, you can see that when we stack our targeting and armoring platforms, we are able to reach our target for safety. Now, I'll move on from safety and start talking about efficacy. As I mentioned, non-viral DNA delivery with conventional LNPs is just inherently inefficient, owing in part to the need for DNA to traffic through the intracellular space to the nucleus. This is a problem that can be thought of as distinct from that of DNA toxicity, and we've attacked it using a different set of tools. We started by rethinking the foundational components of the LNP, in particular the ionizable lipid. We identified, through in-house synthetic chemistry effort coupled with powerful in vivo screening campaigns, a number of structural features that specifically aid in DNA delivery. This has resulted in seven Poseida-owned patent families comprising ionizable lipids with unique encapsulation and delivery capabilities for DNA and other large genetic payloads. Now, we are really excited about our novel lipids, and if you'd like to learn more about them, we plan to have an abstract at upcoming technical meetings. However, today I want to focus on a separate platform component that we call the intracellular trafficking agent, and this one is really exciting. Now, the ICTA is a novel family of polymers that we've engineered to protect and shepherd DNA on its intracellular journey once it reaches its target cell. Adding our ICTA into an LNP serves to boost the activity from DNA, and it has an astounding effect size. The images on the right are bioluminescence produced in immunocompetent mice following a single intravenous administration of a DNA LNP. On the left is what we see from a conventional DNA LNP. On the right is what we get when we add in the ICTA to the same LNP composition. The effect here, again, is pretty eye-popping. It's over 100-fold greater activity coming off of the same dose of DNA. Combining our proprietary ionizable lipids, targeting construct, and ICTA has paid remarkable dividends for applications with secreted transgenes, and we have moved these elements actively into our hemophilia A program. On the right, I'm showing you how our platform innovations, novel lipids, ICTA targeting, and so on, have translated to increasing Factor VIII levels. The gray bar represents our starting place with this program. This is where we were using off-the-shelf lipids, standard LNP format. We're getting definite Factor VIII activity. It's there, though not quite at the level that we think we need to be at for a viable gene therapy product for hemophilia. Moving to the right, the blue bars represent sequential additions of Poseida platform elements, which, as you can see, result in really significant improvements to Factor VIII activity. Now, I'll note that we don't intend to express a thousandfold of normal Factor VIII levels in a clinical product. Our target's actually 50%, right where that dotted line is. Rather, I'd encourage you to interpret this data as representative of the capability and the power of our non-viral delivery platform. As I mentioned earlier, resolution of some diseases requires inserting the corrective gene into a threshold proportion of liver cells. For some diseases, not one or two cells, but we got to control how many we're getting in is really the defining feature. Metabolic diseases are an example of this. Now, our platform was designed to enable us to control the frequency of cells transducing and producing functional protein. On the left, I'm showing you data using our non-viral delivery platform in the context of propionic acidemia, an inborn error of metabolism that manifests early in childhood with life-threatening consequences. The bar graph demonstrates an approximately 30-fold increase in protein expression with the Poseida platform relative to conventional LNP. Importantly, this increase is not due to a small number of cells just expressing more protein. That wouldn't help us solve this particular disease. But rather, what we're getting is expression of the transgene in more cells distributed throughout the liver, as you can see in the immunostaining images here. On the far right, I'm showing you representative examples of how our non-viral platform behaves with two other transgenes relevant for inborn errors of metabolism: the PAH sequence for phenylketonuria and ARG1 for arginase deficiency. You can see that in both cases, we're observing broad transduction across the liver in these juvenile mice, demonstrating that what we have here is a true platform able to be deployed across multiple disease applications. I'll finish by circling back to our recent strategic review in which we decided to discontinue investment in AAV for our internal programs. The data on this slide is, in part, what prompted that decision. On the left is data from our formerly partnered PKU program, in which we were using an AAV to deliver the PAH transgene. Now, as we disclosed in our R&D presentation last year, we were able to fully resolve the PKU disease phenotype with a single dose, bringing phenylalanine levels down to wild type. On the left is the representative immunostaining showing the distribution of the corrective PAH protein that led to full resolution of the disease. This is the degree of expression that we got using an AAV for DNA delivery. On the right is the same transgene, this time, though formulated non-virally using our nanoparticle platform and delivered as a single dose. You can see that it's achieving essentially the same distribution as what we got with AAV, which has gotten us very excited. Now, we, of course, have some work to do as we advance our non-viral platform into the clinic. What we're doing here is novel, but the data here underpins our conviction that we've got the platform aimed in the right direction to support the potential for a powerful and highly differentiated set of genetic therapy products. Before concluding, I'd like to circle back on how our approach is different from the various other gene therapy modalities in active development. I'll start from the left with what we can call the first-generation gene therapy products. This is AAV, plasmid DNA, and mRNA delivered in LNP, these types of therapeutics. Each of them can deliver whole genes, and therefore they have the potential to treat loss of function genetic disease. However, none of these modalities address disease at the genomic level and generally are unable to confer lifelong durability. Moving to the table on the right, we have three types of genetic medicine. Genome editing (for example, base editing, prime editing) can repair mutations, though, of course, we need to create a new product for each specific mutation. The key challenge with the editing modality is in the efficiency of productization. Next, we have nucleases such as CRISPR-Cas9. These are professional DNA cutters. With these platforms, we can knock in whole genes. This does give us the versatility that editing lacks, which is great. The disadvantage, though, is that nucleases are just terrible at gene insertion. They're cutters, not DNA inserters. The efficiency of insertion is just very, very low, which makes repeat dosing and non-viral formulation almost impossible to implement. Poseida's transposon platform, on the other hand, is a professional DNA inserter, and the high enzymatic efficiency and compact size of the transposase enzyme makes non-viral formulation and repeat dosing possible. Now, all the tools on the slide are great in their own way, and they absolutely have their place in patient care. However, we believe the approach that we have selected, a transposon molecular platform coupled with a non-viral delivery system, offers the greatest potential, the greatest benefit in treating genetic disease. I'll close by summarizing and noting our anticipated next steps with this platform. Delivery of DNA, particularly large gene-sized bits of DNA, is hard because of immunotoxicity and transduction efficiency limitations that are just inherent to DNA as a cargo. We're using the LNP as a foundation for building our non-viral delivery platform, preserving the good elements of the LNP (manufacturability, translatability, and so on), preserving those good elements while engineering in additional technologies to solve DNA-specific challenges. As I showed you, these additional platforms play very nicely with the LNP and so have put us on the path to being able to deliver DNA with developable safety and transduction efficiencies. Our long-term strategy of engineering a better delivery system than AAV is starting to pay off. Moving forward, we're all in on our non-viral platform to support our internal and future gene therapy gene insertion programs. We're currently working toward nominating a development candidate to support our Hem A program. Now, with that, I will thank you very much for your attention. We'll now transition to updates on our P-FVIII-101 program addressing hemophilia A, starting with Dr. Steven Pipe. Dr. Pipe is a professor of pediatrics and pathology at the University of Michigan, Ann Arbor and medical director of the Pediatric Hemophilia and Coagulation Disorders Program and of the Special Coagulation Laboratory. Dr. Pipe has been actively involved in clinical trials with novel therapeutics for hemophilia, including gene therapies. His passion for hemophilia patients is demonstrable, as he was the 2015 recipient of the Leadership and Research Award from the National Hemophilia Foundation. He has served on the boards of directors for the Hemostasis and Thrombosis Research Society and the American Thrombosis and Hemostasis Network, and is currently chair of the Medical and Scientific Advisory Committee to the National Hemophilia Foundation. Dr. Pipe, over to you. Well, thanks, Jack, and welcome to everyone. Today I'm going to introduce you to the treatment landscape for the rare bleeding disorder hemophilia A, with a focus on available therapies and unmet needs. Hemophilia A is an X-chromosome-linked bleeding disorder due to deficiency or dysfunction of clotting Factor VIII, and it's characterized by recurrent bleeding primarily into joints that can lead to a debilitating arthropathy. There are just over 30,000 patients with hemophilia in the U.S., 85% with hemophilia A or Factor VIII deficiency and 15% with hemophilia B, which is due to Factor IX deficiency and carries a similar bleeding phenotype. But globally, there are over 400,000 patients with hemophilia, but more than 80% of these have no access to any treatment products. Factor VIII is measured as a percentage of the plasma level that would normally be present, and in patients with hemophilia, plasma levels of Factor VIII correlate well with the severity and frequency of bleeding episodes. So hemophilia is then subdivided into three bleeding phenotypes. Mild hemophilia occurs in 30%-40% of patients, with factor activity levels that are greater than 5% up to about 40%. Bleeding episodes are uncommon, with major trauma or surgery the usual cause. Moderate hemophilia occurs in approximately 10% of patients and is defined by a factor activity level between 1%-5%. And patients with moderate hemophilia typically experience 4-6 bleeding episodes per year, with episodes that are precipitated by surgery or even minor or moderate trauma. But severe hemophilia occurs in approximately half of all patients, and it's characterized by factor activity levels of less than 1%. Patients with severe hemophilia manifest recurrent hemorrhages that are either spontaneous or follow only minimal trauma, with an expectation of 2-4 bleeding episodes per month if they weren't on some form of prophylactic therapy. So compared to mild or moderate hemophilia, severe hemophilia A has a higher propensity for bleeds, greater risk for joint bleeds, greater restriction on their activities due to the risk of bleeding, prior joint damage, as well as ongoing pain, and a higher level of uncertainty about their future as it relates to career choices, education, and overall psychosocial impact. Now, bleeding into a joint, or a hemarthrosis as we call it, is the primary manifestation of hemophilia. Even a single joint bleed can result in joint disease later in life, but the risk of joint disease increases with each subsequent hemarthrosis. Initial acute bleeding has marked clinical manifestations of pain, swelling, loss of range of motion, but the blood in the joint leads to inflammatory changes in the joint lining, the synovium, and that leads to synovial hypertrophy and neovascularization, which leads to even more propensity for bleeding. Ultimately, this inflammatory synovitis leads to hemophilic arthropathy due to osteochondral damage, with chronic pain, functional limitations, and severe negative impact on quality of life. This vicious circle of bleeding, inflammation, and joint destruction is only interrupted by prevention of joint bleeding through prophylactic replacement therapy. Now, there were no effective therapeutic options for patients until the 1960s with the development of plasma-based products. By the 1970s, highly purified, lyophilized plasma-derived clotting factors enabled widespread prophylaxis and home infusions, dramatically improving the health and well-being of patients, but only to tragically result in 90% of those with severe disease acquiring bloodborne transfusion-associated viral infections like HIV and hepatitis. The cloning of the genes for Factor VIII and Factor IX ushered in the recombinant era, and we now have multiple recombinant factor products, some with bioengineered properties primarily to extend their plasma half-life. But in the most recent decade, we have the first non-factor therapy, emicizumab, which is a bispecific monoclonal antibody that substitutes for Factor VIII and has enhanced the effectiveness and reduced the burden of prophylaxis. The recombinant era has also ushered in the gene therapy era, and gene therapy through gene editing has now been approved and can lead to stable expression of plasma Factor VIII and Factor IX, such that patients can discontinue routine prophylaxis with an expectation for a marked reduction in bleeds and overall factor usage. But despite these advances, not all joint bleeding has been eliminated, and joint disease is still observed as persons with hemophilia age. Clotting factor concentrates are required to be given by IV administration. Peak levels are achieved immediately after infusion, but then they fall quickly over time. The levels at any particular time of day may not be adequate for all the activities that a person with hemophilia is engaged in. In addition, non-factor therapies such as emicizumab show a ceiling effect of correction only into the mild hemophilia range. So the requirement for adherence to prophylaxis and the risk of continued episodic bleeding contributes to a continued adverse impact on overall quality of life. Several studies have suggested that factor levels may need to be sustained above 15% in order to prevent spontaneous bleeding, or even above 35% in order to prevent all traumatic bleeds. Unmet needs remain. There are barriers to the adoption of prophylaxis. Patients still struggle with adherence to these prophylactic regimens. We still see recurrent bleeds despite prophylaxis, and there are tremendous health inequities, particularly on a global scale. The community's expectations for better care are for prophylaxis that will be available for all patients who have a relevant bleeding phenotype, innovations that will improve adherence to treatment, and the goal is to achieve zero bleeds, particularly joint bleeds, so that there will be no joint damage over the long term. We're really striving to enable persons with hemophilia to live active lives similar to their non-hemophilic individuals in the community. Now, this slide depicts the hemophilia landscape as it has evolved over the last several decades, moving from replacement therapy to non-factor therapies and then viral vector-delivered gene therapy. We have an ever-expanding toolbox of therapies whose efficacy has to be balanced with known safety issues. The current gene therapy era has utilized recombinant adeno-associated virus, or AAV vectors, to deliver new gene copies to the liver, but with inconsistent efficacy and some important safety concerns. Therefore, the community is looking to new technologies, particularly non-viral delivery techniques, in order to improve the risk-benefit profile of this potentially transformative treatment. The goals of gene therapy for hemophilia are to increase factor levels. This allows patients to come off their clotting factor concentrate prophylaxis, reduce their annualized bleeding rates, reduce the burden of their care, as well as improve their quality of life, aiming for a hemophilia-free mindset. However, potential safety issues have remained. These include liver toxicity thought to be related to an immune response to the viral vector, the need for immunosuppressive therapy after treatment, complications of lack of control of factor expression, including development of thrombosis, and at least a theoretical risk of oncogenesis related to gene integration events that's going to require lifetime monitoring. To summarize the current state of gene therapy, viral gene therapy can be delivered as a single infusion event, liberating patients from the burden of prophylaxis with reduced annual costs and achieving steady-state hemostasis with effective bleed control and improved quality of life. But the drawbacks are that not all patients are eligible for this treatment. This is not yet available for children. It's not available for most with preexisting neutralizing antibodies to the AAV vectors or those with a history of inhibitor antibodies directed against Factor VIII, which occurs in about 30%-40% of all individuals with severe disease. There are known and potentially unknown risks related to the liver toxicity and the need for the immunosuppressive therapy. There also are main questions about long-term safety and durability of this platform of therapy, and there is a high initial cost for this treatment. So the ideal genetic therapy would be suitable for pediatric through-adult patients. There should be opportunity to individualize the delivery of this treatment through titration and the opportunity for repeat administration, which is just not possible with current technologies with the AAV platform. Non-viral strategies may eliminate the challenges of the immune reaction and liver toxicity. So we're looking to improve both acute and long-term safety, achieve predictable and durable treatment response at a lower cost than current strategies. And so I'm excited about the technologies that you're going to hear more about today. So thank you very much. Thank you, Dr. Pipe, for that informative look at the treatment landscape for hemophilia A. Undoubtedly, there are key unmet needs for hemophilia patients. I just want to review some of the key challenges of a viral and episomal gene therapy approach that Jack raised earlier and how this is relevant for hemophilia A. On this table, you can see that there are multiple critical limitations of AAV strategies that are likely underlying its poor uptake. Perhaps most of all, preexisting immunity takes AAV completely off the table for many patients. Alternative approaches with episomal DNA, shown in the center of this table, address only a few of these challenges, whereas our non-viral approach has the potential to address many more. You just heard Jack review some key advances we have made for our non-viral system, many just in the past six months. But let me jump into some key advantages specific to hemophilia A treatment. Looking back at Dr. Pipe's emphasis around an ideal approach, our goal is to address each of these challenges with some of the key aspects summarized here in the center. A non-viral LNP approach avoids the immunogenicity inherent to a viral approach like AAV. This would allow greater access and the ability to redose so that more patients from a range of needs can receive the therapy. One key advantage with our approach is that transposition into the genome locks in the therapeutic transgene long-term, providing perhaps years of durable factory production. What about younger patients? Well, in data I'm about to share, transposition into growing hepatocytes works very efficiently. This is exciting as it could open up early intervention options for adolescent patients. Finally, one really exciting option is the opportunity to back off, titrate down, or swap out therapies with an off-switch if needed. This is enabled by our large cargo capacity, which easily accommodates both an off-switch to modulate expression and an optimized Factor VIII transgene. So how do we get DNA into the genome to lock in long-term expression? Well, at the core of our non-viral system is the piggyBac DNA transposon, which Jack highlighted earlier. Unlike nucleases such as Cas9, which has an array of disadvantages, our system is a simple cut-and-paste transposon that inserts DNA into the genome without double-strand breaks. With our enhancements to the transposase, this is a very efficient process. One additional key advantage is the large transposon cargo capacity, having long been known as a key advantage of piggyBac over other technologies such as lentivirus and the Sleeping Beauty transposon. This allows one to deliver a much wider array of gene and cargo sizes. Because our transposon system is also redosable and reversible, one can potentially titrate to efficacy or back off through our modulator or off-switch. Now, as I mentioned, the large cargo capacity of our transposon system gives us the ability to accommodate larger genes. This capability also allows us to plug in an array of versatile components from our vector toolkit. This is powerful because this is the DNA that is going to be providing factory expression for the patient long after the initial administration. Here on the left, insulators provide additional durability by preventing transgene silencing. Our off-switch here in the center allows us to remove transposed cells to reduce or turn off expression. And lastly, on the right here, we can easily accommodate the necessary factory open reading frame for full correction of hemophilia A. Now, optimizing all these components of the transgene through an iterative engineering of the transposon, we maximize factory production. Here on the left, you can see the factory production at each of these stages of transposon optimization. Okay, so how do we get this highly optimized transposon into the genome so that it can get to work producing Factor VIII? Well, the workhorse that drives the insertion of our versatile DNA transposon is our fourth-generation Super PiggyBac transposase, or SPB for short. Like the transposon, we include multiple functional elements within the SPB mRNA to provide high functionality, with the progressive activity from each of these versions shown here on the right. Through all of these elements, by screening for both optimal DNA and mRNA function, we maximize the efficiency of transposon insertion for robust factory production. So the end goal is to efficiently insert the functional DNA transposon, or vector, into the genome. Expression of this DNA then restores factor levels for hemophilia patients. But how much vector insertion or copy number is required to yield that necessary therapeutic level of Factor VIII? Well, we observed that editing less than 5% of liver cells is more than sufficient to provide the 30%-35% target Factor VIII level mentioned by Dr. Pipe that would fully restore hemostasis and also protect against long-term joint damage. But what does 5% mean? How does this compare to other natural sources of genome modification? Well, to put this in perspective, this is nearly 1,000-fold lower than the annual background internal organ mutation rate, including the liver, documented to normally occur in all humans. Additionally, for reference, the vector copy number we observe is about 1 million-fold lower than the mutation rate occurring in cells of sun-exposed skin every year. This low level of vector copy is a testament to the maximal efficiency of factory production from each copy of transposon integrated into the genome. Okay, so we see that low vector copy number is sufficient to yield therapeutic levels of Factor VIII. Where do these vectors insert in the genome? We and others have observed that 50%-60% of insertions occur within intergenic regions, between genes, with the minimal requirement of a TTAA sequence for DNA integration. There's additional preference for the TTTAAA sequence, a motif found at only about 1 in 2,000 genomic positions, or about 0.05% of all sites. Fortuitously, transposition also occurs within regions of the genome that support robust transgene expression for efficient production of Factor VIII. This is a well-known feature of piggyBac. How does this integration profile, though, affect safety? Well, in our preclinical mouse models, we observed no lesions associated with transposition among over 200 animals, which is also consistent with published studies. In fact, in a tumor-prone model, we see a decreased trend in lesions in animals with vector integration in the liver. Additionally, piggyBac is routinely used for CAR T transgene delivery to produce our CAR T cells. In over 100 patients receiving these CAR T cells, we have not observed any signs of clonal expansion, with about 42 billion cells administered in our autologous CAR T clinical trials. Okay, so what I just reviewed regarding our transposon technology is relevant to the long-term genetic toxicity, or genotoxicity. But what about shorter-term tolerability? Well, to deliver transposon and transposase nucleic acids to liver cells, we've carefully engineered our lipid nanoparticle technology to avoid immunogenicity. As you can see here in these four plots on the left, they are depicting ALT, AST, IL-6, and interferon gamma levels. It's clear that liver enzymes and pro-inflammatory cytokines are greatly reduced with our approach compared to a conventional LNP. The transposon tools are delivered efficiently, resulting in insertion and robust factory production, as you can see here on the top-right graph, which we observed in both mouse and rat efficacy studies. In some, our LNPs provide high tolerability without compromising on efficacy. Now, I want to turn your attention to one of the most important and salient advantages of our gene insertion technology, and that is durability. After cargo insertion with our transposase technology, the transgene can do its job producing Factor VIII. But for how long? Well, in this study, in adult mice with hemophilia, shown by the blue line, the transgene continues producing Factor VIII, being steadily detectable in the bloodstream of these mice for the entire duration of the 13-month study. These mice are also tolerized to Factor VIII, meaning that their immune system does not mount an adaptive immune response against Factor VIII. And this enables us to accurately assess this durability over a long period of time. This yellow line here is the expression that would be attained from a plasmid episome alone. And we've done this experiment here with an inactive or dead transposase that cannot integrate cargo. In this case, factor levels begin low and decline over time, indicating that insertion is key to durability. With integration, the clotting efficacy is restored to normal levels in these animals, measured here at 13 months to the right. At the end of the study, a careful examination of livers from these animals also revealed no lesions or gross liver pathology. Now, I want to get to one of the other highly advantageous features of our technology, and that is repeat dosing. Titrating to efficacy and repeat dosing would realize a key advantage of a non-viral gene therapy approach to hemophilia A, as also raised by Dr. Pipe. Needs will vary patient to patient, and the option to provide additional doses helps to address specific needs. Although waning expression is highly unlikely given the durability we observe, an option of repeat dosing would enable providers to top off expression should the need arise. In tolerized hemophilia A mice, we can do this. We can stepwise titrate up to the desired levels of Factor VIII. And that data is shown here to the left. This is exciting because of the opportunity for new expression with each subsequent dose, an option that would be very difficult with any Cas9 or nuclease-based approach, and simply not feasible with an AAV approach. But what about topping off expression long after an initial dose? Well, remember in the 13-month study, the control mice expressed very low levels of Factor VIII, as expected. For these animals, a rescue dose of transposon plus transposase restores Factor VIII expression via transposon cargo integration. And because both our engineered LNP and nucleic acids possess key immune evasion properties, this prior exposure to the cargo and transposase does not pose a barrier to the redosing strategy. Okay, all this data I've shown you thus far involves LNP and vector delivery to the adult liver. What about the possibility of treating younger patients? As you heard from Dr. Pipe, early intervention is key, and with sufficient levels of hemostasis, one can likely prevent permanent joint damage. Unfortunately, gene therapy options are currently nonexistent for younger patients. This is partly due to the technical challenges posed by normal body growth in younger individuals. The dividing cells of the growing liver render an AAV, or episomal approach, unrealistic because of the rapid dilution that would occur to the vector as the cells multiply. With our transposase system, however, integration locks in the vector, and expression continues throughout liver growth, providing durable Factor VIII expression. This is because there is no dilution of the vector. On the right here in data, it's readily apparent in this experiment in neonatal mice that expression is maintained following our non-viral approach, here shown by the blue line. However, without integration using a catalytically dead transposase, here in the yellow line for our control animals, the episomal-derived expression of Factor VIII is rapidly lost. We're very excited about the efficiency we see in the juvenile liver, and we're very hopeful at the prospect of treating younger patients with our non-viral approach. Lastly, one very unique option I want to discuss is the concept of the off-switch. This switch allows small molecule-induced reduction for either a complete shutoff or, alternatively, a dial down of Factor VIII levels. Now, why would you ever want to use such a switch and turn off the therapy? With repeat dosing, we have the ability to titrate up the levels of Factor VIII. Conversely, if Factor VIII levels are ever too high, in which thrombosis might be a concern, we can dial levels back down with the off-switch. Additionally, any modification of a cell's genome, whether one uses CRISPR-Cas9, transposons, or viruses, carries some very small risk of cellular transformation. This is unavoidable. And the off-switch provides a fail-safe to eliminate cells exhibiting any signs of clonal expansion, quickly and efficiently. Okay, so how does this work? Well, in a single vector, we have both the off-switch and the Factor VIII gene. Thus, any cell that we remove with the off-switch impacts only those cells initially modified, which, I remind you, is also a very small proportion of hepatocytes. Our approach contrasts greatly with existing viral strategies, which lack both the cargo capacity and restricted transduction that our non-viral system possesses. These options to titrate up, titrate down, and shut off are unique to our non-viral integrating approach. Ultimately, this speaks to our goal to provide a versatile and flexible treatment option for hemophilia A patients, as described by Dr. Pipe. Just to recap, our approach to hemophilia A seeks to widen accessibility, provide long-term durability, maximize expression, and enable needed flexibility. We're very excited about the advancement of our hemophilia A program enabled by these strategies, having established proof of principle in rodents. The next key step involves the final optimization of our delivery modality, followed by validation in higher-order species. Early interactions with regulatory agencies are in preparation, and we look forward to meeting the enthusiasm of providers and the FDA. Looking towards the clinic, we will continue to engage with key thought leaders, including Dr. Pipe, as we assess clinical feasibility. We've marked a significant milestone in our journey towards a future where the burden of hemophilia is no longer a foregone conclusion but a challenge we are well equipped to overcome. Next up, I will give you an update on our up-and-coming site-specific transposon technology. Now, I'd like to turn your attention to one of our rapidly evolving technologies for targeted gene insertion, the site-specific DNA integration system. I'm really excited to give you an update on our recent advances here. We believe the site-specific piggyBac transposase has the potential to treat a broad array of diseases through a highly unique gene insertion approach. It could literally be a game changer. To design such a system, we first thought about the ideal traits you would want for a site-specific gene insertion platform. Fundamentally, it must deliver efficient, high-fidelity integration of the transgene cargo at the desired genomic site. Next, aiming for simplicity ensures ease of manufacturing and implementation, improving the odds of success through development. Reprogrammability adds greatly to the versatility of the system, providing gene integration at chosen genomic target sites and tailored to the needs of each indication. Furthermore, a reprogrammable platform would enable simultaneous knockout and knock-in of a replacement cassette or a promoterless approach to perfectly match endogenous expression levels. With site-specific integration comes not only versatility but also new levels of control. Reproducible integration patterns are more likely to lead to uniform expression levels of integrated cargo since expression is provided by an identical genomic context. With this added control come some of the most sought-after traits of a gene therapy platform: reduced variability and increased predictability. Site-specific gene insertion brings us one step closer to realizing a genetic medicine approach that can safely address a broad array of diseases. As I'm sure you are aware, there are a lot of site-specific gene insertion platforms currently in development. A tremendous amount of effort has also been made to adapt nucleases, such as CRISPR-Cas9, to also fill this role. However, nucleases like Cas9 only cut DNA and are really the wrong fit for gene insertion. Cas9 lacks the ability to directly affect gene integration. Instead, one must use Cas9-induced double-strand breaks to stimulate the cell's natural DNA repair machinery, which may or may not be sufficiently active, often depending on whether the cell is proliferating or not. Additionally, many of the double-strand breaks do not lead to an insertion but rather unintended mutations and even chromosomal translocations, which can pose a significant genotoxicity risk. These unintended mutations also render such sites unavailable to edit again, meaning that you get just one shot to generate your desired mutation. Naturally, there has been a shift in the genome editing field over the last few years towards the creation of novel double-strand break-free site-specific gene insertion tools. Unfortunately, none of these has yet to emerge as a clearly feasible technology fit for gene therapies. Instead, they're complex multi-component or multi-step systems that suffer from undesirable byproduct edits, limited cargo capacity, or a lack of reprogrammability. Some still require nuclease or nickase activity, thus only partially addressing genotoxicity concerns. Finally, many display low efficiency in human cells, making them ineffective for therapeutic applications. Seeking to overcome such drawbacks, we view our site-specific system as a simple solution for a direct double-strand break-free gene insertion technology. So how did we set about to do this? First, we wanted to build upon the key advantages already inherent to our transposon platform. That is, an efficient gene insertion tool that has demonstrated high efficiency in human cells time and time again. Additionally, such a system accommodates large cargo in a redosable, reversible, and scarless manner. The simple cut-and-paste mechanism, mediated entirely by the piggyBac transposase, ensures that there are no copying errors or truncated products integrated into the genome. To retain these traits, we simply added one new feature to the workhorse that is our Super PiggyBac transposase. That is the ability to find the desired genomic site before pasting the cargo DNA into the genome. These new finding modules are easily swappable, allowing reprogrammability to unique sites in the genome. The payoffs of starting with a well-established system like piggyBac are clear. Here we are looking at in vivo site-specific integration of a transposon cargo in the mouse liver. This early-generation site-specific piggyBac yields on-target integration that is easily detectable and quantifiable by a digital PCR assay. In contrast, a non-targeted variant called PBX resulted in no integration at the genomic site targeted, as expected. To our knowledge, in vivo editing has not yet been achieved by competing double-strand break-free site-specific platforms, which speaks to the potential of our technology. Building upon this early generation of our site-specific technology, we needed to further improve upon the efficiency. To do this, we took a multi-pronged approach to enhance activity. We focused on the DNA binding domain, or binding module, the linker that attaches that module to the transposase, the inverted terminal repeat, or ITR, sequence that the transposase binds on the transposon, and lastly, the transposase itself that catalyzes the insertion. Here on the bottom left, you can see that after several rounds of molecular evolution, we improved site-specific integration by over 30-fold. From this work, we now have a system with site-specific activity comparable to that provided by a Cas9 knock-in approach. On the right here is data from an experiment where we targeted a single copy site in the B2M gene and Hep G2 cells. You can see the comparable activity. However, the key difference here is that our site-specific system integrates DNA without creating double-strand breaks or mutations. I want to emphasize a key challenge here. That is that integration at single copy target sites, like the one here, is very challenging for any technology. It's a classic needle-in-the-haystack problem where the tool is forced to search for a single site hidden among millions of possible positions. In contrast to a single site in the entire genome, what if we were to target a sequence that occurs, say, hundreds or thousands of times throughout the genome? Wouldn't this make it easier to improve editing efficiency? It seems likely. So then why does the field limit itself to single copy targets? Well, the answer is clear for nuclease-based gene integration approaches. For those using any nuclease for knock-in integration of DNA cargo, they have no option but to focus on single copy genomic sites because double-strand DNA breaks are toxic to cells. Now, cells can handle and repair one or two double-strand breaks, but when there are hundreds or thousands, the cells are likely to die. And even if they do survive, they are highly prone to deleterious chromosomal translocations and genome instability. Here we see that when we target a single copy gene with the site-specific piggyBac technology, we can successfully integrate DNA cargo at a subset of cellular genomes in this plot to the right. However, targeting DNA to a sequence that occurs hundreds or thousands of times throughout the genome, we now easily achieve multiple integration events per genome, up to 50 per genome, at a rate that exceeds even the theoretical maximum of a perfectly efficient system that targets a single copy, here illustrated by this dotted red line. These are representative data showing the efficiency we can achieve using site-specific piggyBac at such repetitive multi-copy sites in cell lines. The advantage is clear when targeting such sites. Okay, so targeting repetitive sites might increase efficiency, but is it really practical? Well, by swapping out the finding modules, we programmed integration of cargo at two different sites in repetitive DNA. Here, making use of these sites, we want to highlight a few key traits of site-specific piggyBac: predictable, reproducible, site-specific integration with high efficiency and high fidelity. At both sites, about 2-6 on-target site-specific integrations are observed per haploid genome in these cell lines. Finally, the key to any site-specific gene integration system is that it is actually site-specific. Here on the right, we are mapping the genomic location of all integration events, both on and off-target sites in HepG2 cells. Along the X-axis are plotted all genomic positions. As a reminder, there are millions of possible sites where cargo could integrate. This plotted data on the right here might look a little odd, but you can see that two events clearly stand out. These are the sites where site-specific piggyBac was programmed to integrate, with more than 90% of integration events found here at the desired on-target site with very few insertions found elsewhere. What's encouraging is that these are early results with early technology prior to any efforts to optimize on-target fidelity and increase this specificity even higher. We have multiple lines of investigation ongoing to further augment this fidelity, and I look forward to sharing more on this in the future. In conclusion, site-specific piggyBac adds to Poseida's genome editing toolkit with a simple system for site-specific double-strand break-free gene insertion. Building on the advantages of piggyBac, especially considering its efficiency and cargo capacity, we believe this technology could literally be a game changer in genetic medicines. Our recent molecular evolution has already improved efficiency 30-fold, resulting in a system capable of efficient site-specific integration at single copy target sites on par with Cas9 knock-in approaches. But the double-strand break-free nature of site-specific piggyBac opens up new possibilities of DNA cargo insertion at multi-copy sites, which simply isn't feasible with a nuclease. It's already clear that this offers real benefits to efficiency. We continue to maintain focus on improving the fidelity past 90% and optimizing and deploying the system in vivo using our non-viral LNP, as well as identifying additional repetitive safe harbor sites to unlock the full potential of site-specific piggyBac. Thank you for joining me to hear about our recent milestones with the site-specific transposon technology. I'm always thrilled to share our progress on one of our most exciting technologies. I will now turn things back over to our CEO, Kristin Yarema, for closing remarks. Thank you again. Thanks, Blair. Thanks to all of you who have joined us today. I hope you've enjoyed and learned from what we have shared here. But most of all, I hope you are taking away the same conviction we have at Poseida that patients deserve better genetic medicine options that have the capacity to cure a wide range of diseases, and also the same sense of urgency that patients are waiting now. Returning to more recent comments from Dr. Peter Marks of the FDA, we can see in his top quote, "If we don't lean into accelerated approval, we're going to leave a lot of patients behind," that FDA understands the urgency and is thinking about how transformational genetic medicines might move quickly through clinical development and approval. I find his bottom quote even more striking and inspiring. I think the possibility of genome editing could be an incredible game changer, not just for rare diseases, but for more common diseases. Dr. Marks, we think so too, if we can find approaches that can be safe, effective, durable, and accessible to patients. At Poseida, while we are emphasizing discipline and focus in our portfolio choices and strong operational execution across our programs today, we also believe we have the non-viral toolkit that justifies us dreaming big in the longer term. Ex vivo, we are already poised to extend allogeneic cell therapy beyond oncology into other indications, including autoimmune disease and beyond. Looking to in vivo applications, while we are confident in our allogeneic cell therapy platform and excited by our early clinical results there, in vivo CAR-T is another potential future direction. Further, with our whole gene insertion and editing capabilities, and let's not forget site specificity, we envision someday treating not only other rare genetic diseases but potentially prevalent diseases as well. In conclusion, Poseida has developed a broad and proprietary suite of fully non-viral differentiated genetic engineering technologies, including stable, potentially site-specific insertion of whole genes, high fidelity gene editing, and strength in delivery systems, including lipid nanoparticles. We believe this makes us uniquely positioned in the industry to deliver on the promise of genetic medicines, bringing the kinds of therapies patients and physicians are looking for from just a hope to reality. We enthusiastically welcome discussions with investors and biopharma industry partners who share our vision and commitment to the journey to make life better for the patients who are waiting. With that, I'd like to thank you for joining us once again today.