Precision BioSciences, Inc. (DTIL) Earnings Call Transcript & Summary

All right. Well, thanks, everyone, for being here and being here early. It's early hours for many people or maybe late hours depending on when you went to bed and when you flew. Thank you all for your presence. We're going to start on time in 1 minute. And so this is just a final thank you but also a reminder that if you have a cell phone, if you can turn it on to mute. And if you come to the panel discussions, if you can leave your cell phone at the chair just to avoid any interference. Okay. Any other questions before we begin? All right. It's going to be an awesome day. Thank you very much.

Good morning, and welcome to Precision BioSciences 2024 AASLD update on our lead clinical program, PBGENE-HBV, which has now reached the clinic, our ELIMINATE-B trial. My name is Michael Amoroso. For those of you who may not know me, I have the distinct pleasure of leading this wonderfully hard-working and talented Precision team. Today's agenda is exciting. We have a packed one for you. We're going to talk to you about our lead program, the situational landscape today, what patients are facing. We have some of our top thought leaders in the world with us today. We're going to talk to you about Precision's approach, the robust amount of animal data, proof-of-concept that we've put together to be the backbone and foundation of our regulatory packages around the world for this global trial, global where patients are with the highest of unmet need. And then we're going to talk to you a little bit about the clinical operations, exactly where we're at, what you can expect from us as we move forward. Before I take any further steps forward, I want to start with a gratitude, with thank you. I want to thank our investment community, many of whom in the room today or on the line. I want to thank our patient advocacy community also with us. I want to thank the teams, our clinical investigators, our Precision team members who make this all possible. And most importantly, I want to thank our patients for their trust in this trial. As a reminder, today's presentation contains forward-looking statements to the best beliefs we have today in our current thinking. Outcomes are never guaranteed. These statements are covered by the safe harbor provisions and the federal laws. And for any further debrief on this, please access our website at Precision Biosciences, our Investor Relations section. Now let me talk to you a little bit about Precision BioSciences, a company founded in '06 by a gentleman in the room here today, Dr. Jeff Smith, the creator of the proprietary ARCUS gene editing platform. The company went public in 2019 and a company with a very resolute, focused and specific message and mission. That is cure to go at the root cause of diseases and cure patients long term. Clinical development at Precision is guided by 3 core principles: patients with the highest unmet need. Using ARCUS, a differentiated gene editing platform in therapeutic areas where we believe the delivery and/or the unique characteristics of the cut, the gene edit will make the difference for the therapeutic index in such disease. And most importantly, we focus on operational excellence, speed to patient. We're talking about disease states where patients have the highest of unmet need. You'll see our pipeline slide today. First and foremost, the reason we're here, PBGENE-HBV for chronic hepatitis B. Super excited to say, clinic, we are back in the clinic. Moldova has been approved. Alina Jucov is with us today and I know we've already screened 2 patients in the last week. Alina, thank you. Chronic hepatitis B, an ARCUS-delivered LNP program to deliver for elimination of the viral genome, both cccDNA and integrated disease. Our second program, PBGENE-3243, a very different program for mitochondrial disorders, a debilitating terrible disease where patients cannot get out of bed in the morning and do normal daily activities because they have mutant attacked mitochondria that can't give them the energy reserves they need. That's our second wholly-owned program. Precision will file a CTA and/or INDs in 2025 and be in the clinic in '26. That program is a very unique program delivered to muscle through viral delivery, and it's the first of its kind, the first gene editing program not to edit the nuclear genome but to focus and edit the mitochondria within the cell. We'll talk more about that program in future updates. But today, the belle of the ball will be PBGENE-HBV for chronic hepatitis B. And our third program by our partners over at iECURE, spin-out out of Penn who are focused again on the highest of unmet need, they share our resolute goal. Patients with OTC deficiency, an unfortunately mortal disease for infants due to toxic ammonia levels. This is a program already in the clinic, approved CTAs in Australia and the U.K., IND in the U.S., and they're already treating patients. This is an AAV-directed gene insertion program using an ARCUS nucleus. Finally, Precision has a very healthy cash runway. It takes us well into 2026 the second half. And it enables us for data readout on PBGENE-HBV Phase I, data readout on PBGENE-3243 for mitochondrial disease; and of course, iECURE's data we will expect in '25 and they'll be funding operations. Now let's look at the chronic hepatitis B landscape. First and foremost, huge unmet need. I was at the Guggenheim conference last week and a question was asked of me: do these patients really need a cure? They have standard of care. Well, you see in this incredible visual that the prevalence, the global prevalence, hence our global trial, we will meet the patients where they are. The global prevalence of chronic hepatitis B, which does not have a cure, is larger than the entirety of combined clinical trials in the gene editing space today. Our responsibility is grand. These patients have a standard of care. Let's talk more about that. In the developed markets of the world where we have access to some therapies like nucleoside analogs, today's current standard of care, there are over 5 million patients being drug treated. It represents a multibillion-dollar market. And nucleoside analogs were a wonderful step forward from some of the people in this room, but it's not enough. Patients need more. The functional cure rate for patients who live on lifetime nucleoside analog therapy is 1% to 3%, 1% to 3%. Functional cure is defined as, to level set for all of us today, to reduce your viral markers to the point where you can discontinue therapy and have at least a 6-month interval of being disease-free. But that's not enough. We need a sterilizing cure. Unfortunately, even with the standard of care, we're still looking at many patients, many patients who will graduate to that unfortunate landscape of increased liver disease, late-stage cirrhosis, liver cancer. In fact, the 10-year cumulative risk in some of the published literature we've looked at is up to 30% for developing hepatocellular carcinoma. If you add late-stage liver disorders, late-stage cirrhosis, liver failure, it can be as high in some patient populations as 40%. That leads to over 1 million global deaths today. While we have a standard of care, we don't have a cure like we do for hepatitis C, and we need 1 urgently for patients. What we need is an approach that goes at root cause. There are 2 culprits that make this disease so difficult to overcome. First, the cccDNA, the replicating viral factory that continues to produce more virus and inundate the liver cells of our patients. Unfortunately, there's never been a therapy that can go at the root cause. All of the therapy today are downstream, and they look really at disrupting reverse transcription of that viral process. As you move forward and the disease matures, you'll become from what's known as an E-positive patient where you really have a tremendous amount of disease being produced from your cccDNA, the factory, to having integrated disease now in your hepatocytes in your genome. That's the integrated HBV DNA. So what we call it is there's 2 culprits or 2 heads of the dragon and they must be eradicated. To date, nothing has been able to go at root cause. I'm proud and glad and excited, palpable excitement to tell you, our ARCUS proof-of-concept data has shown the ability to target cccDNA as well as integrated disease. In fact, our preclinical models have shown the ability to eradicate a surrogate disease very similar to this cccDNA model as well as integrated disease. Dr. Cassie Gorsuch will take you through that today. Robust preclinical evidence is why we're so excited, but it's now time to move to the next step and that's obviously the clinic. I do want to highlight what Dr. Gorsuch will talk to you about today. I'm really proud to work with a company like Precision where we leave no stone unturned. What we have done to interrogate safety and potential efficacy for patients is second to none. Disease cell lines, mouse and gold standard nonhuman primate models, both episomal and diseased. And the ARCUS PBGENE clinical candidate has passed the test time and time again. Safety with our LNP-delivered product, with liver transaminase elevations, less than anything ever published. We spent a ton of time, and Cassie will talk to you about making sure we optimize our delivery, delivery, the greatest obstacle in any gene editing technology. We have shown in primates an ability to eliminate a surrogate for cccDNA. And we've used the transgenic models again to set the study design for starting with controlled nucleoside analogs, treating the transgenic models with a PBGENE-HBV and ultimately, being able to stop your nucleoside analog and retain that benefit of no viral load. This preponderance of evidence is why we're able to go to the global markets regulatory at the same time, simultaneous. We skipped no stone unturned. Genomic integrity, on and off-target editing, reproductive editing, PBGENE-HBV does not reproductive edit, and making sure your delivery vehicle, LNP is safe at representative doses. Finally, as you could see over my right shoulder, the show is really about to begin. But I do want to call out, if you build it, they will come. The excitement, the world leaders in this room are the greatest minds that have ever been around infectious disease and chronic hepatitis. We have built a world-class panel of investigators, experts and safety monitors. We have robust regulatory packages that I just talked to you about, the foundation being our preclinical evidence. We've gone out and got Dr. Murray Abramson, John Fry, Matt Wheeler, and some of the best clinical operations teams in the world. And ultimately, we have now gotten back into the clinic, where Dr. Alina Jucov in Moldova has screened patients starting this past week. So I'm excited to really ask the true investigators, where the rubber meets the road in front of the physicians -- in front of the patients, I'm sorry, the physicians who see them every day. What really does this landscape need? How excited and realistic is this therapy to come? Gentlemen?

Thank you. Very excited to be working with these extraordinary clinical investigators. And indeed, let me introduce you to both of them. To your right is Mark Sulkowski. He is the Professor of Medicine at Johns Hopkins University. He is also the Director of the Division of Infectious Disease at Johns Hopkins Bayview Medical Center. And to his left is Jordan Feld. He's Section Head, Hepatology, Division of Gastroenterology, Hepatology and Director at the Toronto Center for Liver Disease in the University Health Network. Thank you so much for joining the panel. I'd like to start with you, Dr. Sulkowski, and that is with your extensive clinical experience, maybe you could share with us your view of the patient journey as they go through with chronic hepatitis B.

Sure. Well, first of all, happy to be here and really looking forward to walking through the natural history of hepatitis B. When we think about those 250 million to 300 million people with chronic hepatitis B, how does that start? What happens? Well, many are infected at a very young age, at birth around the world. And very quickly after the virus enters the human hepatocyte, it does 2 things. It establishes this cccDNA, which as you heard earlier, serves as the template, this mini chromosome for the production of new virions sustaining the infection. In addition, it integrates into the human genome. And this is something that happens throughout the lifespan of that patient as they progress through phases of chronic infection. Now among people infected at a very young age, most of them are unable to clear the virus. It establishes a chronic infection where the virus is constantly replicating, and the immune system is trying to eliminate it. I tell my patients, this is a battle, a lifelong battle of the virus and the immune system. And oftentimes, the virus is actually unable to be suppressed or eliminated. So this leads to challenges. We do fortunately have treatment. For the last 25 years, we've been able to use nucleoside, nucleotide analogs. These work at a very specific point. They work at reverse transcription. So this is where the new virion is produced and RNA is reverse-transcribed to DNA. They do not fundamentally impact the cccDNA, and they do not have any impact on the integrated hepatitis B DNA. Now they do suppress the virus, we'll talk more about that in a minute. And they do reduce the risk of outcomes but they very infrequently deliver what we call a functional cure. That is where the patient could come off therapy, have no evidence of DNA or S-antigen. And although it reduces the risk, these patients have a very large unmet medical need for a cure because they are at risk for cirrhosis and hepatocellular carcinoma. So I want to talk just a little bit about how we monitor patients in clinical practice. In clinical practice, we primarily measure DNA and S-antigen, but there are other markers. When I talked about how the virus starts its replication process, there is transcription of the cccDNA and the production of pregenomic hepatitis B RNA. This can actually be found in the blood of some patients. This is a direct marker of that transcriptional activity. And then as I suggested, the next step is for the assembly of a new virion. This occurs in the capsid with the core protein heavily involved and there is the reverse transcription that occurs. And this will ultimately produce new virions, and we can measure that in the blood with hep B DNA. This is the critical thing that we measure. But there are other markers as well. There is a hepatitis B core antigen and core-related antigen. These are viral products or proteins that are produced through this replication process. Many of them are not found in intact virions. They're found in empty particles and other forms in the blood. But the primary thing that we focus on is surface antigen. This is a critical part of the viral life cycle. And here, as we've talked about, you're seeing surface antigen from 2 sources. You're seeing it from cccDNA and you're seeing it as part of intact new virions. So we could certainly see S-antigen as part of viruses. But we also see it as a stand-alone particle that in subviral particles, and it's coming from 2 sources, ccc and integrated. The nucleoside-nucleotide analogs do not impact the production of this, and in most patients, it stays quite high. So now we think about what we're going to be able to measure and practice. And really, what we see with nucs is that the DNA can be suppressed at very low levels. It doesn't mean there's not viral replication in the liver. In fact, there is. But in the blood, we can't see the DNA. But for many patients, we still see markers of transcriptional activity. CccDNA is alive and well. We're also seeing S-antigen coming from the integrated, and that is something that fundamentally the nucs won't be able to control. So when we think about getting into a functional cure, that is the ability to stop the nuc, take the person off treatment, see no viral rebound, no production of new viruses and no surface antigen, we need to fundamentally control both sources, integrated and cccDNA. And that's a tough challenge and certainly happy to talk today about how we're going to approach that.

Thank you very much, Dr. Sulkowski. That was really quite enlightening. Switching gears a bit. Dr. Feld, you obviously have tremendous amount of experience in multiple modalities of treatment for chronic hepatitis B. You've seen where the marketplace is. You see what's coming up in development. Could you help orient me understanding where the PBGENE-HBV fits in all of this and what excites you about it?

Thanks, Murray. There's a lot of excitement in the hep B field. I think people have recognized this really clear unmet medical need, which Mark outlined, and we heard about earlier that patients are living with this chronic infection and despite our therapies are still at this persistent risk of end-stage liver disease and particularly liver cancer, which really is a devastating cancer. So we're struggling with trying to cure them, and people have looked at this very complicated viral life cycle and targeted it in many different ways. And so it is exciting that there's a lot of activity in this space, but it's also notable that because of the complicated viral life cycle, people have taken really different approaches to looking at this, and most targets are really looking pretty downstream. As Mark illustrated when we look at the current therapies, the nucleoside-nucleotide analogs, these are really in a very late stage in the viral life cycle, blocking that 1 step of converting pregenomic RNA to new HBV DNA. But even if you look at all of the other therapies that are in development, these are also all working at a relatively late stage in the viral life cycle. They're not going back to that root cause of targeting cccDNA and certainly nothing even thinking about targeting integrated DNA. So if you look at these, and I'm not going to go through them in great detail, but there are different targets across the viral life cycle, and this really leads to a wide variety of approaches. So if you look in the hep B field, you're going to see lots of different agents, lots of different agents being put together. But what brings -- what the commonality between them is, is that they're all targeting something relatively downstream. So furthest along, we have the antisense oligonucleotides, which are targeting the pregenomic RNA. Again, that's after cccDNA. Similarly, small interfering RNAs are doing the same thing. They're preventing the production of the protein, but they're not getting at the root cause and preventing the production of the RNA. And then you can even look further downstream where you look at things like nucleic acid polymers, which are actually blocking the production of these subviral particles that Mark mentioned. And that's leading somehow to an immune response, which to be honest, is not terribly well understood, which is leading to clearance in some cells. And then at the bottom, you see interferon. This is a therapy we've had for a very long time, decades. We still don't really understand entirely how it works other than to say that it's part of the innate antiviral immune response and is able to control viral replication and clear infected cells in some patients. But all of these have challenges because, first of all, they're working relatively far down in the life cycle of the virus, and they also potentially come with significant toxicities. And we also really fundamentally are not getting to the root cause of the infection. So the advantage of the PBGENE-HBV is really that it is going to this target, the key point of targeting covalently closed circular or cccDNA and also by proving to be active on integrated DNA. And this really obviates the need for all of those downstream products because if you get rid of the source, none of those other things that the other targets are targeting are actually necessary. So when you look at these markers that Mark went through nicely, of all of the things that we're measuring in the blood, if you think about how PBGENE-HBV could address these, you would expect to see that with elimination of cccDNA and elimination of integrated DNA, that those markers in the blood that are telling us about cccDNA transcriptional activity so things like hepatitis B RNA as well as the core-related antigen and the HBV DNA will all become undetectable. But importantly, also the surface antigen, which is coming from both sources of the DNA, the integrated and cccDNA has the chance and we hope to see that will also become undetectable in the blood but also not just in the blood but also in the liver, which is why we hope that patients will actually be able to come off therapy and truly have not just a functional cure but what we hope is a more complete cure. So when you look at the therapies that we're looking at currently, as Mark mentioned, with our current therapy, we're looking at very low rates of surface antigen loss. So these nucleoside analogs are safe, they're effective. They're well tolerated but people have to take them lifelong because you're looking at a probability of getting rid of surface antigen of about 1% to 3% per year. It's quite low. Interferon is a little better but interferon is really hard to take. It's got a lot of side effects. It's a finite therapy. But to be honest, the number of prescriptions for interferon for hepatitis B is almost 0 because -- in addition to patients are unwilling to go through interferon because of its difficult toxicity profile. And although it's exciting to see all these new agents and especially in antisense oligonucleotide entering Phase III clinical trials are ongoing, Phase III clinical trials, certainly exciting for the field, the expectation is that this is going to be incremental. This is going to move the field along but it's not going to get us to very high rates of cure. And what I think we're hoping is that when you move upstream in the viral life cycle, really target cccDNA and integrated DNA, that we can start to get to high levels of functional cure or even complete cure that we've not been able to see with the existing therapies.

Thank you very much. This has been a really great conversation. And I want to thank you very much for your participation. I also want to kind of pivot to say that PBGENE-HBV is designed to meet the needs of the patient. And when you speak to the foundation, Hepatitis B Foundation and you ask the question, what's the ideal treatment look like? We want it to be safe, tolerable, no long-term complications. We want finite treatment, not chronic lifelong treatment. We want to be able to work in all patients across the globe and across the different genotypes. We want to be able to restore the immune system to help fight the hepatitis B virus. And of course, we want to reduce the risk of death due to liver disease. These are all really important questions, and I'm very excited to introduce Dr. Cassie Gorsuch who's the Head of Gene Therapy. She will be taking the mic and talk to you about the preclinical data, setting us up for the clinical trial to get those very different points that I've just made.

Thank you, Murray.

Thank you.

Hello, everyone. I'm Cassie Gorsuch, and it's really a pleasure and a privilege to be here to share with you on behalf of the Precision team really the excitement behind our preclinical data and why this is such an important moment for us as we head back into the clinic with PBGENE-HBV. So we've spent a little time this morning talking about that the unmet need in chronic hepatitis B patients is high. You've heard that patients want a cure. We've seen that we're not getting there today with the standard of care. Reducing or silencing various components of the viral life cycle aren't getting us there. So how do we get there? I think if you look across literature, in various publications in the hepatitis B space, if you speak with our KOLs, our leading investigators, anyone who's been in this space, everyone agrees if you eliminate cccDNA, you will cure hepatitis B. There's not a question to that. If you eliminate cccDNA, you will cure hepatitis B. And now we think we finally have an approach to use an ARCUS gene editing strategy to directly target and eliminate cccDNA and inactivate integrated HBV DNA. So how is that possible? So ARCUS today is really the only clinical-stage gene editor designed to eliminate cccDNA. And we think that this is really feasible because of some unique features that the ARCUS platform is built on. We've talked about these before, but as a reminder, these really come down to 3 key components that are unique to ARCUS proteins: the cut, the way in which ARCUS cuts the DNA; the simplicity, as we call it, and here, what we mean by that is the single component nature of ARCUS gene editors; and then finally, the small size of ARCUS nucleases. So when we talk about this simplicity and size for PBGENE-HBV, I think it's really important to kind of drill down, how do we see those as important for hepatitis B? I mentioned ARCUS is a single component nuclease. What that means is that we can design the protein to recognize a DNA sequence of our choice, in this case within the hepatitis B viral genome. And that same protein can also cut the DNA so 1 protein that binds and cuts. Many of the other gene editing platforms are built on multiple components, a guide RNA that has to get into the space between the 2 strands of DNA, and then a nuclease or an effector protein that has to actually elicit the outcome. ARCUS is 1 protein that does both so it's a really elegant system. Size also matters here, and we often think about size of nuclease as being really important for delivery. That's true even in the case of an LNP like PBGENE-HBV. The size of the ARCUS mRNA is about 1/5 of the size of the Cas9 and even smaller compared to things like epigenetic editors or base or prime editors. It's extremely small. Why that matters is the length of your mRNA directly correlates with how much RNA you can make, the quality of that RNA, how you characterize it. And the quality of the RNA, as I'll show you in a little bit, is directly related to the safety of the LNP product. So we really think that ARCUS is uniquely situated to provide a functional cure for hepatitis B patients based on these unique features of the platform. So I'm going to talk a little bit about our preclinical data today, and I'm not going to talk about all of our preclinical data because there's a lot. We'll be here all day. What I want to emphasize here is that one of the challenges in the preclinical space for hepatitis B is there's not 1 great preclinical model that fully recapitulates the viral life cycle and that we can use PBGENE-HBV in. And so at Precision, what our approach has been to assemble a matrix of models, and we've looked high and low, assembled as many models as we can to really demonstrate robust safety and efficacy of PBGENE-HBV. So this includes using things like human cell lines, primary human hepatocytes that are infected with HBV. We think that system is really as close as you can get to the patient liver scenario as you can in the lab. We've also used episomal AAV mouse models, a transgenic mouse model, and we even developed our own nonhuman primate model. I'm going to talk a little bit about how all of these fit into the preclinical package that we've assembled to demonstrate safety and efficacy. So let's dig in. I'm going to start with safety, first and foremost. Thinking about this as a Phase I trial, safety is on everyone's mind. As you can see in the slide here, we have utilized this matrix approach, multiple different models to triangulate safety across the various different considerations. Michael told you earlier that the things that you really need to think about for gene editing in terms of safety are really in 3 buckets. One is the specificity of the nuclease. We'll go through a little bit of that. One is the ability -- well, the biodistribution of your product. Once you administer PBGENE in vivo, where does it go? It's essential it does not distribute to germ cells, those cells that contribute to reproductive editing. And finally, we used a comprehensive approach to study the overall tolerability. So how well is the drug product tolerated? And at Precision, we put a high emphasis, high -- we really prioritized nonhuman primates for the study to evaluate the safety of the product because nonhuman primates are as close as we can get to the human setting before we get to humans. So I want to start actually with the last one I touched on is the nonhuman primate safety data. This here is some of our data from one of our GLP toxicology studies. In this particular study, nonhuman primates were administered 2-dose administrations of PBGENE-HBV, 1 on day 1 and 1 on day 29. And this multi-dose study was really designed to evaluate the safety of giving multiple administrations of PBGENE-HBV as we consider a multi-dosing strategy in the clinic. What you're looking at here is liver transaminase as well as bilirubin. And as you'd expect after an LNP administration, you do see a transient elevation in ALT and AST directly after the LNP infusion. It's really important to note that in this particular dose, which is actually our highest dose in this study, we did not exceed 3x the upper limit of normal, which represents minor elevation, very well-tolerated profile in primates. It's also worth noting that both ALT and AST elevations came down after a transient elevation without any intervention. These animals were not premedicated on steroids. And so I think whenever you start to look across the landscape, this is a really favorable overall safety profile. And it's worth noting additionally that no change in bilirubin was associated with these transaminate elevations. So that's, we think, a really critical piece of our preclinical safety package as we think about how it relates to the multi-dosing clinical trial that we've designed. I mentioned there's a couple of other buckets of safety that are top of mind for a gene editor. The first one I mentioned was specificity. I'm really proud of the work that we've done at Precision to build a robust, very thorough comprehensive genome-wide analysis to interrogate the specificity of the nuclease. In our view, the only way to eliminate cccDNA is to cut cccDNA. That means you have to cut the cccDNA. And that means that you can't cut anywhere else in the genome. That's really important. And so at Precision, we've put a lot of effort into interrogating this, optimizing the nucleus for safety and specificity, and PBGENE-HBV demonstrates a very high degree of specificity and importantly, no risk of translocations, no additional HBV integrations were observed after editing. I mentioned earlier that a second category of safety when thinking about gene editing is the biodistribution in vivo of the product. And so we studied this in nonhuman primates. And we found that PBGENE-HBV does not distribute to germ cells so the egg, sperm, the cells that are especially important when considering reproductive editing. And then finally, I just want to reiterate, based on the data that we just looked at, that PBGENE-HBV has been well tolerated through multiple dose administrations consistently across nonhuman primate studies. Every time we've given a dose of PBGENE-HBV, we see the PK of the infusion looks consistent with each administration, so there's no cumulative toxicities. There's no change in how the drug is metabolized in vivo after each administration. And so this really gives us a lot of confidence as we head into this multi-dosing study that we'll talk about a little bit more here in a minute. And the last thing I just want to note as we're thinking about how PBGENE-HBV was designed and optimized, I think it's really worth calling out that not all LNP products are the same. The mRNA, as I mentioned earlier, is the internal parts of the lipid nanoparticle. And the way in which you make and characterize, purify your mRNA really contributes to the overall safety profile. And our team, really proud of the work that our team has done at Precision to optimize the mRNA, the way we make it, the way we characterize it, the way we package it into the lipid nanoparticle, and all of that work is absolutely contributing to the overall safety profile of PBGENE-HBV. Now I'd like to switch to talking about efficacy. This is where I get really excited. We talked this morning about how this is a novel approach to treat chronic hepatitis B going after root cause. PBGENE-HBV, as we've talked about, is really designed to do 2 things. One is to eliminate cccDNA, the other is to inactivate integrated HBV DNA. When we think about how to study those preclinically, we tend to think about them as separate so that you can really demonstrate efficacy against each target, cccDNA and integrated HBV DNA. And so first, I'd like to talk about the models that we've utilized to demonstrate efficacy against cccDNA. We've previously shared data demonstrating dose-dependent effects in HBV-infected primary human hepatocytes with dose-dependent cccDNA elimination and associated reductions of viral markers. We've also used an episomal mouse model to demonstrate really impressive dose deescalation really in efficacy and reductions in S-antigen durable long after all of the drug components are gone in that model. And then the last one, and I'm actually going to talk through this data is in our nonhuman primate model. I mentioned this is a model that we developed at Precision to really be able to demonstrate this efficacy in a large animal. So one of the challenges I mentioned earlier is that hepatitis B is fairly species-specific. Nonhuman primates don't get hep B which is good for them, hard for us. And so what we did is that we took a different virus and encoded part of the HBV genome in a different virus and then infected the nonhuman primates. That surrogate virus we used has a lot of similar features to chronic hepatitis B. It infects hepatocytes, it forms a mini-genome sitting in hepatocytes of the liver, very similar to cccDNA. So it allows us to establish an infection in this large animal and monitor editing against our target site using our drug against a viral DNA species that looks like cccDNA. So we developed this model. In this particular study, we administered 2-dose administrations of our LNP carrying an ARCUS nuclease. What you see is that this highest dose, we achieved 99% viral editing, and that was with 2 dose administrations. What's not really fully represented on this slide but worth mentioning is that at each of these dose levels, we tested, we got about 50%, half of the editing that we achieved in that first dose, and the rest of the editing was achieved through the second dose. So what that tells you is that you can continue to push efficacy through giving additional subsequent dose administrations. And this is really the basis on how we designed our clinical trial. This study used 2-dose administrations. You'll see how we're thinking about our clinical trial will allow up to 3-dose administrations should we need to continue to push efficacy forward. So how do we achieve this level of editing? It really comes down to delivery and potency of your ARCUS nuclease. What you're looking at here is actually biodistribution from one of our nonhuman primate studies in the liver. In the top left hand, this small picture is a section, a piece of the liver from a nonhuman primate taken down whenever the peak mRNA expression would occur in the liver, peak mRNA delivery would occur in the liver. The brown staining, all of those brown dots represent ARCUS mRNA within the liver. And so you can see in the small image that we've got really nice broad distribution of the mRNA throughout the liver. It doesn't accumulate in certain areas within the liver, nice broad distribution, which is going to be important to eliminate all of the cccDNA. You've got to get to all the cells. When you zoom in and actually look at what's going on in the hepatocytes, you can see ARCUS mRNA in every hepatocyte. And when we calculate how much ARCUS mRNA is actually present, it works out to about 10,000 mRNA molecules per cell, extremely efficient delivery. So this gives us a lot of hope and excitement as we think about translating this into humans. We know the bar is high. cccDNA elimination is a tall task. We think our preclinical data really supports that we could achieve that. The last side of the preclinical efficacy piece is really thinking about efficacy against integrated HBV DNA. So we've talked through cccDNA. I mentioned that we think about our models sort of separately between cccDNA and integrated DNA. And so as you can see here, we've assembled again kind of a matrix approach of different models that all have integrated HBV DNA only. We've used human cell lines in the lab with varying numbers of integrations. And I think really excited is the transgenic mouse data and I'll talk through that now. So this transgenic mouse model is a little bit unique in that every cell in the mouse has an HBV integration. We used this model because we wanted to demonstrate efficacy, specifically against integrated HBV DNA in vivo. And so this model allowed us to do that. What we did is we took a cohort of mice shown here in the orange line and put them on nucleoside analogs for 14 days. These mice because they have a full-length integrated HBV DNA do express HBV DNA secreted into the serum so that's what we're measuring here. You can see when you withdraw a nucleoside analog, as you'd expect if you did this in patients, you see a rebound in HBV DNA in this model. That line goes back up to where the saline control animals are. We also took a group of animals and put them on nucleoside analogs for 14 days and gave them 2-dose administrations of PBGENE-HBV at day 0 and day 14 so a finite course of treatment. And then we withdrew the nucleoside analog on day 14. What we were extremely excited to see is that HBV DNA went to below limit of quantitation in this assay, and it remains there for the entirety of the study. There was no viral rebound. And so this is really proof of principle that you could achieve a functional cure, something like this as we think about removing a nucleoside analog. If you get enough editing of cccDNA and integrated HBV DNA, there is hope that you could remove a nucleoside analog and remain virally suppressed. So I hope you can see at Precision, we've taken a really comprehensive look at this in our preclinical models. We, as Michael likes to say, we've left no stone unturned. We looked at every single model that we could to really evaluate both the safety and efficacy of PBGENE-HBV. We've demonstrated today safety in our nonhuman primate studies, but we've also collected the safety alongside the germline editing and specificity analysis. We've assembled a really robust matrix of models demonstrating the ability to eliminate cccDNA and to inactivate integrated HBV DNA. And it's really this comprehensive data set that gives us so much excitement as we head into the clinic. I'm excited to share the data with you. I'm excited to hand it back off to Murray to tell you more about our clinical study.

Thank you. So as Cassie said, there's a lot of excitement right now. And there's no question that we are at a pivotal part of an inflection point not only for our company but also within the space of chronic hepatitis B. [Technical Difficulty] Other non-hepatitis B ideologies anytime. No signs of hepatocellular carcinoma. And basically, we also want to avoid people who have been on prior investigational drugs within 6 months, with the exception of the siRNA individuals who need to be off therapy in their investigational drug for over a year. This is a Phase I study design. It's a classic design and it's built for speed and the potential for rapid evaluation of safety and efficacy that we'll report out over the course over the next year. Keep in mind that in this particular case, the standard design is a multiple ascending dose escalation. It's at 3 dose levels starting with the lowest, moving potentially up to the highest, standard 3+3 design. Each patient can receive up to 3-dose administrations. That's going to be contingent upon how they perform, both on a clinical outcomes as well as biomarkers. Now assuming that we have the data and that we've reached our maximal dose that we feel is effective based on the data and the clinical findings, we're going to then proceed to gather even more data in the part 2, the dose expansion part. There, when you could add part 1 and part 2, we have up to 45 individuals total enrolled in the entire study. I want to point out, again, during this dose expansion, we're going to be collecting a lot of data. We will be at the dose that we feel is the most efficacious for multiple reasons. And importantly, it's the go-forward dose. It's a finite treatment, and so these patients who received it may actually show evidence of cure, functional cure using a finite dose therapy. Specific to this, why are we choosing to dose up to 3? Well, Dr. Gorsuch already indicated in the preclinical model, there's good evidence that this increases the cumulative editing of the viral DNA. Dose 1, we will evaluate them carefully, safety parameters, biomarker parameters. And then over the course of the next 8 weeks, depending on those outcomes, they could potentially get a second dose. Again, repeat clinical evaluations, biomarkers, depending on how they do, depending if they -- I mean, at this point, they could potentially stop because of their success or they may need to be re-dosed again and that would happen again within this 8-month -- 8-week period subsequent to that. Now how are we going to be measuring? There's a lot of data on this slide. I'd like to walk you through a little bit of it. Indeed, the Phase I study goal is to demonstrate both safety and efficacy. This is primarily a safety study as a Phase I. We're looking at the frequency and the severity of dose-limiting toxicities or DLTs. On the efficacy side, the antiviral activity is going to be looked upon through the usual clinical study biomarkers. Dr. Sulkowski earlier went through a number of them so I won't do it again, but you can see them on the right side of your slide. We're going to be monitoring multiple biomarkers, but what we'll be looking for is a reduction or negativity in the hepatitis B surface antigen, looking for a change in baseline at this level and maybe even the presence and development of anti-hepatitis B antibodies. So the proportion of patients with undetectable surface antigen levels will be measured at each study visit. We also would expect, as I said, that the hepatitis B DNA will remain negative and that will be sustained. But what we will look for is a reduction in the RNA levels and this will be very important because if we start to see these sort of phenomena occurring in these patients, we would actually hope to stop the standard of care, nucleoside analogs, and we would measure that the proportion of patients who can discontinue nuc therapy. Our ultimate goal during this period of time would be functional cure. And that's going to be defined as a sustained seroclearance of the surface antigen, whether or not there is a presence of antibodies to surface antigen and continued viral DNA suppression that has existed for over 6 months. So with that, you have a little taste of the protocol, a lot more to discuss at eventual time in the future. But I'm very thankful that I have an opportunity to have some very distinguished experts within the clinical investigation space globally. There's no question that I'm super grateful for you to join the panel. And I'd like to be able to introduce each one of them to you now and have a little bit of time to ask them some questions. Now Alina Jucov. Dr. Jucov is the principal investigator for Arincia Research Clinical in Chisinau, Moldova. She's also the Assistant Professor of Department of Gastroneurology at the State University of Medicine and Pharmacy. Thank you. Dr. Ed Gane is a Professor of Medicine at the University of Auckland. He's also the Deputy Director of New Zealand Liver Transplant Unit and the Chief Medical Adviser for the New Zealand Clinical Research Organization. Thank you, Dr. Gane. Dr. MF Yuen is Chair of the Professor of Gastroneurology and Hepatology at the Li Shu Fan Medical Foundation. He's also Professor of Medicine at the University of Hong Kong; and Dr. Kosh Agarwal. He's a hepatologist and transplant physician at the Institute of Liver Studies, King's College Hospital, NHS Foundation Trust in London. So to all of you, welcome very much. And thank you. Now if each of you will allow me, I'd like to kind of pick your brains, given that you're experts in your field to learn a little bit about your practice, learn about your thoughts on the exciting gene therapy but also a little bit about what you're thinking about the future. And if Dr. Jucov, if you don't mind, I'll start with you. You work and are proficient in doing clinical trials in Moldova. You see a lot of patients, and your patients within the clinical scene really has given you some great insights. So I wanted to have you share a little bit about what that means and what that means for the clinical trial that you're participating in.

So thank you very much for the question. My name is Alina. I'm a Board-certified gastroenterologist and internist. I'm also passionate about advanced clinical research in areas like gastroenterology, hepatology, and the internal medicine. The prevalence for hepatitis B in Moldova is very high. Among the general adult population, the prevalence rate of HBS antigen is estimated to be around 10%, categorizing Moldova as a high endemic region. While significant progress have been made in managing HBV, a curative treatment still remains crucial. So however, there are some promising drugs in development, a functional cure that removes the need for long-life treatment duration and, of course, minimalize liver-related complications still remain vital. And let's hope that gene therapy will make it in the near future. So having the experience of more than 10 years in my early phase clinical research, having a high prevalence under availability of a patient, and unfortunately, curative treatment is lacking in this indication. This motivates our patients to come into a clinical trial. Thank you.

Thank you very much. Dr. Gane, I want to switch to you. You obviously have tremendous amount of experience. You live in New Zealand but you're a pioneer in hepatitis treatments, more recently, gene editing therapies. So given that experience in that perspective, what is your level of enthusiasm for the PBGENE-HBV gene clinical trial?

Thanks, Murray, and thanks for inviting me to this, a very important symposium. I think this is an incredibly important study. I've been fortunate enough to be involved in hepatitis B cure research for the last 5 years, I guess. We've made little steps but we're still at the stage where we cannot offer a finite cure which will be successful in a significant number of patients. As you mentioned, I have also been involved in the pioneering first in-vivo gene editing studies in hereditary amyloidosis and hereditary angioedema. And I've seen what marvelous step forward it has been and the treatment of what are lethal conditions. You have a finite treatment which really revolutionizes people's lives. Now hepatitis B is also a lethal disease. We do have good oral treatments but the biggest issue for us and our clinics are treating significant numbers of people, and people do stop their treatments and that comes with a risk. And we also know that our current treatments reduce but don't eliminate the risk of liver cancer. I think this is -- could be a paradigm shift in the way we manage hepatitis B, that a finite course of treatment could cure somebody's hepatitis B and reduce significantly the risks of complications. And I think we can't forget also that this has the potential to make people surface antigen negative. And I think for the patient and for the patient's family, this is incredibly important, given the stigma that associates hepatitis B infection.

Thank you. There's no question that this disease is a global disease. This panel demonstrates this very clearly. I'm going to move to Dr. Yuen and ask you, given that you were really a prolific researcher of extraordinary size within the space of hepatitis B clinical research, and given that your clinic is very large and in Hong Kong, maybe you could share with me a little bit of your insight about what this trial, the clinical trial will mean to your patients and maybe the space of hepatitis B.

Thank you. First of all, I would like to let you know that in Hong Kong, we are now still having 6% of the population living with chronic hepatitis B infection. And in fact, every year, we have at least 1,400 new cases of liver cancer because of hepatitis B. And in Hong Kong, this liver cancer related to mortality ranked third in cancer mortality. And I have been involved in many clinical trials for hepatitis B. And we -- although we still -- I mean, we now have standard treatment to, I mean, reduce the risk of liver cancer, but there are still patients coming up to my clinic presenting with liver cancer. And in fact, the patients always ask me, "Dr. Yuen, since you are involved in so many novel drug therapy for hepatitis B, can you tell me or can you give me a medication or drug that can eliminate the virus from my body?" And I told them, we have new drugs to reduce the viral activities further, to reduce liver cancer further. But now we don't have novel therapy that can eliminate the virus. And today, I'm very happy to know that this may become possible. We now have a potential one that can eliminate the virus from the body. And I'm very happy, I hope I can tell them, there's a potential one coming up in Hong Kong. And I'm very excited to tell you that this trial will be run in Hong Kong, and that will change the hepatitis B treatment field in the near future.

Yes, yes. No, it's a very exciting time and I can feel for the needs of your patient. I want to continue our global journey, if I may, for a second. We're going to just go to the U.K. now. Obviously, Dr. Agarwal, you have and you head an institution that's known for hepatitis B. You have both basic research and clinical activities at our top level. I want to kind of take what Dr. Yuen said about the patient and their needs and go to you and ask, what are patients asking you? What are they looking for from you? And where does PBGENE-HBV fit in that space?

Thank you, Murray, and thank you for the invite to come and talk and be a part of this study. I think it is truly a very exciting time, and we're delighted at Kings to be involved in this study. It's hard to follow on from my colleagues but I want to emphasize that our patients in our clinic, and it's a big clinic, really are aware and it's really important for the community. We remind everyone that hep B is an oncological virus. It causes cancer. So the therapies we have are moderately effective, small steps, but we really need to be more pioneering. And as Michael alluded to, it's not just the rubber on the road, we need to put skin in the game. So the clinical side of this and the patient side of this critically is all about discussing these issues with the patients, having our own patient groups involved. And again, it's a delight to work within this environment from not only the investigators, the science but also the safety side of things. So this is going to be a very carefully conducted study. But lastly, to come back to your point, we've really taken a time at Kings where we, in London, have the global representation of hepatitis B, a population of 12 million. Finding a lot of hepatitis B, rich diversity to really address the patients issues and concerns. They all want a cure. We tell our patients in clinic, we need to get you to a cure. And actually, our preliminary discussions, really talking about these sorts of modes of therapies or this platform, that they are very keen, 70% of our patients, we did a study in just talking to our patients, 200 of them, just very generally talking about what would you think about this sort of potential, and 70% of them were very keen to hear more about it. So we mustn't forget the patients, and I think that's to the credit of Precision Bio. I think the science is exciting. It's great to work with wonderful PIs who I really admire. And we're really keen to put skin in the game, but we really need to remind ourselves that we have to put the bar higher for our patients who are getting the complications of liver disease from hepatitis B.

Thank you, thank you. We've taken a whirlwind around the world. It's really quite incredible. We've covered a lot of different topics. The prevalence in the different diseases, the level of enthusiasm, the focus on being different for a functional cure and the hope that it provides. Did I miss any questions? I just want to ask the panel. You basically had a squeeze your career within 60 seconds, 90 seconds. I want to thank you very much for participating and really appreciate the time you've spent with us on the panel today. I'm going to move really to the summary part, if I may, have some closing thoughts on what we've just heard both from a preclinical but also the clinical side. What we've seen is the goal of sterilization cure with initial target of functional cure. We've seen the right clinical design that's been based on robust preclinical data that Dr. Gorsuch presented and alignment on the regulatory side. We've seen a global Phase I study up to 5 countries and the largest real-world opportunity locations. And you've had the opportunity to meet the panel, to meet many of the clinical investigators. Very honored to be working with these experts and the experience in gene editing, hepatology and infectious diseases. And of course, the clinical programs and the execution guided by the leading investigators and advisers were on track for clinical data readouts in the next year, 2025. So with that, I'd like to now move on back to our CEO, who will provide some of his own closing thoughts.

Thank you, Murray. Wonderful. Thank you. So before I bring our colleagues, a few colleagues of mine up and we sit and take the questions and answers from our live audience as well as the line, I think I'll preempt probably the biggest question. So when? So when, Michael? I hear that question all the time. As we've talked about, we are clinically operational as we speak. Moldova is our first open site. We'll continue to announce the other 4 to 5 countries as they come on board and get their regulatory approvals. Many of those packages are submitted, and we're waiting through the distinct processes. We're working with those regulatory agencies. We've also worked to be at the contract level, making sure we have our sites identified. We can move through IRBs and get to patients as soon as possible. We'll continue to look for first data readout in 2025. 2025 will be a steady pulsed year. Now that you understand the design a bit more that Murray took you through, you can see whether it be dose level 1 or dose level 2 or 3, we'll have a steady pulse of data throughout the year. We'll be smart about when it makes sense to come out and talk to you. Safety will be the first and most important thing and we want to get that information out as soon as we can. And then we'll make sure we collect the representative amount of evidence as we assess the different dose and schedule because please remember, we're looking at dose and schedule. And later in the year, second half of '25, what the vision and target would be, I hope to be able to say we have found a dosing schedule where we've gotten the S-antigen to a negative nondetectable level, we could stop nucleoside analogs and start tracking patients, of course, again for the safety but also to see if the viral load remains gone. So 2025 will be a steady year and we will communicate with you at a premium and let you know at subsequent meetings. That being said, I want to thank you. I hope the presentation was as wonderful to you folks as it is for us in the room to see the palpable energy, and I'm going to ask some of my colleagues to join me as we open up to any of your questions. Thanks again, and thank you to all the panelists.

I think Alex Kelly, our CFO, is going to help facilitate.

I have the microphone. If there are questions in the room, I'd be happy to -- I'd like to ask them first and then we'll go to the phones. Please introduce yourself, too, for the panel.

[indiscernible] at Goldman Sachs. Thank you for the time today. Just a couple of questions here. Firstly, a little bit more on the data disclosures. How are your team thinking about the extent and frequency of data exposures? Would you consider sharing maybe some more data after a certain number of patients are treated or after a certain amount of follow-up time? And then secondly, on the trial itself, how are you thinking about the treatment regimens across geographies so potential for variability? And how do you intend to control for that in subsequent analyses?

Yes, I'll start off with the data and then I'll ask some of our clinicians who are going to be part of the trial and part of the safety monitoring to speak a little bit about the standards of care across the globe if that works. I wish I could tell you more robustly exactly when -- you see this is a nascent approach. You see these 3 escalating dose levels, and we'll be looking at that cumulative editing. So I think we're just going to be smart in what makes sense. And we're going to come out and look to tell you probably sooner than later that we feel good about the safety of this product, that it mimics what Cassie has shown you that we've done in nonhuman primates and beyond. We don't have a -- obviously, the key liver meetings, you want to have something exciting to talk about. That would be a goal. We're working and thinking about intelligent publication plans. So we'll work with, depending on the veracity of the data and the excitement, we'll be working with certain publications. But I think for me, I'm a believer in communicating at a premium. I think you can think about a steady cadence through '25. And I do feel we're going to accrue this trial in '25. And I think we're going to have good data. If you think about how this comes in pieces, after each dose of administration, about 4- to 5- to 6-week window, you will know your safety from an LNP. That's a pretty short period of time. At the same amount of time, you have first efficacy readings of your serology like S-antigen. Mark took us through that today. Murray, okay? And then ultimately, I think it takes a little longer to say, do we get the S-antigen knocked down after cumulative administrations? Do we have 2 consecutive periods of time, 4-week intervals, where the serology shows negative or undetectable S-antigen? And is it now time to stop the nucleoside analogs? So I would be guessing to say if the first dose level is going to accomplish that or the second or third dose level. So I think there'll be a steady pulse. We don't have a plan more concrete than that, but I promise we'll communicate with you and the investor community at a premium as those plans form. The second question was about the different geographies, I believe, correct me if I'm wrong, and how that standard of care that you have to have some level of unison to perform a global trial of what that standard approach is. So Alina, Mark, would you guys speak a little bit too, and Murray feel free to chime in, to the presence of all these patients real world? Do you have them on nucleoside controlled? Maybe talk a little bit about better than 200 IUs and no cap, please.

Thank you very much for the question. Actually, we have available entecavir and tenofovir in our country. This is the first opportunity for our patients because they refuse, they are not too wild to receive interferons. So we have possibility of identifying patient on standard of care with maintenance period for a long period so it's not an issue at all. Having a negative HBV DNA with available HBS antigen per entry criteria so it's not an issue. By the way, it's not about Eastern Europe. It's also about -- it's a worldwide situation. But entecavir and tenofovir is the first option for HBV patients.

Mark?

And I'll just emphasize that last point because I think it's important. There is absolute consensus among the Asia Pacific, American, and European guidelines that the nucleoside/nucleotide analogs of choice or tenofovir and entecavir, and we've been using them for well over a decade. So there is, I think, great homogeneity in terms of how those patients will be treated entering into the clinical trial.

And I'll just follow it up very briefly by saying the design of the trial is taking advantage of standard of cure. At the same point, given the mechanism of action of our study drug, it's getting to the root of the problem, the cccDNA. So using regardless of whatever standard nucleoside that's being used in the region of the world, there's going to be a reason to think that it should be very effective and similar across the groups.

Thank you. I would like to add, in addition this is a standard measurement in relation with for a virally suppressed patient to enter on stable medication with entecavir and tenofovir, it's not an issue at all. It doesn't matter for age and demographics.

Thank you, Alina.

Are there other questions coming from the room? Okay. Naresh, can we see if there are questions coming in on the phone line, please?

[Operator Instructions] Our first question comes from the line of Kostas Biliouris with BMO.

This is [ Phil ] for Kostas. Congrats on the progress. So we have a couple of questions. So this first one, in a clinical trial, how are you thinking about because you're not discussing about specific dose levels. We're just wondering how do you think about the dose levels of humans, especially given the comparison versus other gene editing therapies? Currently, you can see doses ranging from 0.1 to 1 mg per kg range in clinical trials. And the second question is on your preclinical data. So in your NHP model, have you ever tried to sort of basically detect like what is the viral load or like pretreatment hepatitis S-antigen level compared to that in human patients? And so have you tried to look at also editing efficiency while using different kind of AAV levels in NNP? So if you have a look at it, have you ever observed any variability in terms of the editing efficiency there when you give the NHP like high dose versus low dose AAV?

Yes, I'll start off, and I'll ask Cassie to join me a little bit about, I think the question started off a little bit about the different dose levels, and have we taken into account across disease states, gene editing approaches of LNP delivery. That's the first question I think I heard there. And second, really the NHP models and the proxy for viral loads so Cassie will come to you in a moment. I think it's a great question. I think it's a fair question. The short answer is, yes, of course, we've taken into account all of the data that we see with gene editing delivered with LNPs. As we talk about these toxicology studies are absolutely acute toxicology studies. They are looking mostly at the delivery vehicle. But I want to caution everybody, and I think Cassie did a great job in our presentation today to compare 1 LNP to another at a given dose, I think that's a dangerous thing to do. I think if you really examine the data that Cassie showed you today from some of the tox data at 1.5 mg per kg, you will see, for example, in a nonhuman primate, not diseased, the similar as other companies would be using across other diseases for their tox models. The transaminase levels, for example, most important to us because we're talking liver disease are markedly different. And Cassie has talked to you about all LNPs are not the same. What you put inside of that LNP and the quality and optimization of mRNA make all the difference. So I think when you can take a step back and say nonhuman primates are a proxy that are great for liver toxicity, they're great for your blood count, specifically looking at platelets, a bigger challenge in cardiovascular disease. But what the primate can't account for is infusion reactions, injection reactions. We know we can premedicate that. We know what that looks like. So I think we have an idea of what the doses for LNPs will be. But I think you got to be very careful to compare it 1 study to the next. And you really have to think about the underlying disease of the patient. For example, we're hyper-focused on a patient's liver. We're in liver disease. But if I was in cardiovascular disease, Ed's talked about some of the other trials before, I understand why thrombocytes are a major area of focus. By the way, we didn't see any of those issues in our CBCs. Cassie, I think the second part of the question was more about really the proxy of the nonhuman primate to the human with viral load, if I heard that correctly, please?

Yes. So I mentioned that we established this nonhuman primate model. And the way that we did that was to use an AAV, which is a different type of virus to infect livers, to establish a surrogate virus for hepatitis B since primates don't get hepatitis B. So the way in which that we did that model is we actually established a very high viral infection. AAV can be immunogenic in primates as it can be in humans, and primates can mount an immune response against a viral infection, as you'd expect. We did premedicate the monkeys to try to prevent that, but they still are able to mount some level of an immune response. So we actually gave them a high viral infection to make sure that through the course of the entire study, they had a viral infection but they didn't clear it on their own, that there was something present for us to edit and measure in the liver. And so when you think about how does that relate to the human setting, the number of AAV copies on average in that -- in the liver of those animals was about 100 copies per cell. That's on the very, very, very high end of what -- there's a huge range of cccDNA levels that I reported. I think, typically, most are in the 10-ish range or lower. And so actually, the viral infection in primates is much greater than what we would expect to see at a per-cell basis in humans, which we think actually sets the bar for editing higher. And so I think as you think about that data, it's a useful model to evaluate the biodistribution of the LNP, the ability of the mRNA to translate into the ARCUS protein. The ability of the ARCUS protein to cut and degrade viral DNA and the ability to evaluate subsequent dose administrations like we did in that study. It's not the human setting. It is time to test this in the human setting and see how that works. But we think it is, as you relate to the human scenario, potentially even a higher bar than what we'd expect to see in terms of viral load in patients.

Excellent, Cassie. Thank you. And thank you for the questions. For the next questions, Alex, if we could just ask the phone lines, we're in a bit of a big room so please try to speak up and really project your voice. It's tough for us. We're leaning in to try to make sure we could hear the questions. Please, next questions.

Our next question comes from the line of Maury Raycroft with Jefferies.

Congrats on the progress. Maybe I'll just start with 1, just for exploratory biomarkers. Will you assess immune function at baseline and posttreatment in patients to see if by reducing the S-antigen, you're enabling some immune system restoration that could give you additional confidence about stopping nucs?

Yes. Murray, do you want to start with that?

The simple answer is we're intrigued by this as well, and so we will be looking at certain markers but also biobanking a good bit of material that will allow us to do further analysis as we get more data and the study progresses. Thank you for the question.

Thank you. Maury, did you have another?

Sure. Yes, I'll do 1 more quick one. So just based on the last question in response, it sounds like in the models, there's a higher total amount of cccDNA versus what you see in infected humans. But I'm just wondering if in infected humans there could be reservoirs of cccDNA. And this could -- this variability could affect how PBGENE-HBV works. Or would you anticipate that just by getting to that third dose in the clinical study, you're going to eliminate all the cccDNA? Just asking about like reservoirs that could be an issue?

It's a great, great question, Maury.

Yes. Yes, great question, Maury. Thanks for asking it. Certainly, there are different types, if you want to call it that, of cccDNA reservoirs within the liver of infected patients. Some of the cccDNA molecules may be more transcriptionally active than other molecules. And so if you want to think about that as sort of different sources, you can. At the end of the day, they're both cccDNA and they all have the target site for PBGENE-HBV nuclease. And so as long as the target site is present, we have no reason to believe that the transcriptional activity of cccDNA or any other really aspect of the way that the cccDNA may be present in the cells would affect the ability to edit it. And I think that's really borne out and is replicated in the HBV-infected primary human hepatocytes. In that particular model, I mentioned this in my mind, is really the gold standard model because it's human cells with HBV infection so we can measure editing directly against the actual HBV genome in the context of a human cell. And you would expect that, that model could fully recapitulate the spectrum of cccDNA molecules that you might find in a patient. And so I think we have looked at that. We have not observed any differences in terms of different capabilities of editing cccDNA based on different parameters like that. And our PHH studies have really demonstrated very robust and dose-dependent cccDNA elimination after treating with PBGENE-HBV. So I think it's a good question, an important question. And I think we have high confidence that we have that one covered.

Awesome. Okay. Next question.

Our next question comes from the line of Soumit Roy with Jones Research.

One question on the enrollment criteria, given the co-infection rates of the other patients, what do you expect the screen failure rate to be? And the second one is dovetailing on the prior question. The life cycle of the virus, does integrated DNA turn into cccDNA also? And if ARCUS system has activity against the integrated DNA also.

Yes. So let's start off with our key clinicians here who do this every day. So Mark, Alina, would you weigh in a little bit about the inclusion criteria about the co-infections? And if you see that as any challenge to enrollment? And then what we'll do is we'll come back to Cassie to make sure we're really, really clear on what the target is of PBGENE-HBV from a cccDNA and integrated standpoint. Mark, Alina, would you please?

Thank you very much for this question. Actually, from my experience, screen failure rates in virally suppressed patients, it's around 20%. But because we are performing prescreening activity, so this means you have available information about historical co-infection. We try somehow to avoid. So at my unit we are mitigating screen failure rates in order to reduce and not to provide the hope for the patient who actually is not eligible.

And I'll just add to that. I don't anticipate around the world at the sites that you saw earlier. We're going to see very high rates of co-infection with HIV, hepatitis d, or hepatitis C, although I'll comment that those are really important subpopulations that we would like to see elimination of hepatitis B in those groups as well because they have worse liver disease and greater poor outcomes. But I don't anticipate to affect the Phase I study you heard about today.

Thank you, team. And Soumit, a very practical question. I'm a practical man. We talk a lot. So I would just say to you, if you just think about what we showed today, just the United States for a minute coming off Mark, 300,000 patients controlled on nucs, 80% e-negative. You hear the prescreening and the potential screening failure rates, I think there's plenty of patients. And I want to reiterate, this is a real-world trial. We built this trial with the top leaders in the world of who's in the greatest need and let's get to them. So Cassie, could you help clear up the integrated versus cccDNA and what PBGENE-HBV actually does?

Yes. So just to answer the first question of do integrins produce cccDNA? The answer is no. So in the viral life cycle, after a hepatocyte is infected, cccDNA sets up shop in the nucleus and then fragments of the virus, so not full-length genomes, just pieces of the viral DNA get randomly integrated into the host genome. Because it's not full-length HBV DNA, those integrations actually cannot produce active virions. And so there are really 2 distinct viral reservoirs, if you will, cccDNA is solely responsible for producing HBV DNA and active infectious virions, and integrated HBV DNA really only produces S-antigen. However, to achieve a functional cure, you have to eliminate cccDNA to reduce HBV DNA and you have to inactivate integrated HBV DNA in order to bring S-antigen down. So it is essential, if your goal is functional cure, to target cccDNA and integrated HBV DNA, and PBGENE-HBV is absolutely designed to do that. The target sequence that the nucleus recognizes is present in cccDNA and integrated HBV DNA. And I think through our preclinical data, we've really demonstrated that when you cut cccDNA at that target site, it primarily leads to degradation or loss elimination of that molecule. And when you cut and inactivate integrated HBV DNA, that will shut down expression of S-antigen from the integrins. So they are quite distinct. They're both really important when you think about providing a functional cure option for patients and PBGENE-HBV is designed to do both.

Awesome. Thank you, Soumit. Next questions?

Our next question comes from the line of Andrea Newkirk with Goldman Sachs.

I was just wondering if you could speak on the considerations that drive the decision to redose within this study.

Yes, Andrea, I'll start off, and then I'm going to really come back to Cassie again on this and ask the clinicians to feel free to weigh in because again, think about the nascent approach, Andrea. I think if you look at the modeling here, and we know I'm not the infectious disease expert in this room. But when it looks to a nascent approach like gene editing, you must -- again, Cassie started the presentation off, why we believe the only chance at cure. And we talk functional cure because it's a step to sterilizing cure. But why we believe that we believe you have to eliminate, extinguish the factory that is producing replicating virus, cccDNA, then you go take out the rest of the bad guys, so to speak, that have set up shop in the integrated disease. Because of the fact that if you follow our proof-of-concept models, where we try to model this out as perfectly as humanly possible, you can only deliver an LNP to a certain safe level, and we want to do that. And that delivers your PBGENE, and you're going to cut out an X or Y amount of virus. We knew that in order to get to the 99% that we showed in the nonhuman primates of cutting out the cccDNA, that was 2 administrations. Cassie said earlier, the first administration gave you about half of that mission, 50%. So that's why we've set up a trial following the preclinical evidence that allows up to 3 because our intent, make no mistake about it, is to cut out 100% of the cccDNA. We believe that is the foundation for cure. What we might find out -- so remember, it's dose level and it's administration. We're looking for the right dose and schedule here. And the second half of the question?

Yes, I can take it. At first, I just want to say, I'm so excited about how this trial is designed because it really allows us to test 2 hypotheses: one is, can you get there with fewer doses by increasing the dose? That's one side of how we've designed this trial. The other one is, can you get there through multiple administrations at a lower dose. I think if you look at the LNP gene editing space, it's clear that there is an upper limit on the amount of LNP that you can give to a patient safely. And so that's an important consideration. The second is we know, as Michael just said, to cure hepatitis B, you need to eliminate cccDNA and that's a tall task. We take it seriously. And so what we did is we really spent a lot of time optimizing for safety, which I think is really borne out in our safety data. We think we're going to be able to dose escalate as good or better than any of the LNP type approaches today. But we also wanted to give ourselves, following the preclinical data, the ability to continue to redose. And so that was a design element in our safety studies that is going to allow us to translate that into the clinic. And so if you think about that from just a scientific perspective, it's a really exciting trial design to be able to answer sort of this way and this way of how are we going to get there for a cure for patients. And so I think, Andrea, really the trial design, why consider multi-dosing, it's really -- the goal is to provide a functional cure. And we can get there going this way or we can get there going this way. This gives us 2 shots at that.

And I just want to put the final stamp on that to say, but it is a finite course of treatment. While this is nothing mechanistically like SOVALDI, the goal is to treat for a finite course to get to cure, functional cure step on. Mark, Alina, Murray, is there anything you want to add there?

The only thing I might emphasize we're using the term functional cure, which in general means when other action talk about that you're leaving behind some cccDNA, but the immune system is controlling it. I think the really important point here in this discussion is we actually have the ability to potentially eliminate hep B removing the word functional from the definition.

Mark, I loved that you said that. We do this functional cure is a word that has been developed because of the tools we've had through regulators. But what Mark is saying is the goal of this mechanism is a sterilizing cure, of course. Mark, that's an awesome point. Alina, did you have anything on, Murray?

I think everything was added. But here in additional liver biopsy will be the gold standard, which will show actually.

Yes. So to Alina's point, really important to show where -- remember, you can reduce S from the cccDNA or integrate it, and that the biopsy will be part of the protocol. Thank you. Alex?

Yes. So I think we have no more questions on the phone line. Sorry, there is 1 more question, getting the signal from Naresh.

Okay. Let's take 1 more.

We have no further questions over the phone. I will now hand off to Alex Kelly for questions via e-mail.

Thank you, operator. Appreciate that. So 2 questions before closing. I think that there is -- I'm getting some questions via e-mail, 1 for Alina since Moldova is the first site to approve CTA. There is interest in knowing, number one, what's the reception so far from your patients. And when are you going to dose the first patient?

It's a question for $1 million so I'm pleased to inform that this week, first, the patient was screened at my unit. Thank you for my team for doing this. It's too early to estimate the first dosing because of a screening period, we are still screening period, and we are still waiting for our lab results to check the entry criteria. But absolutely, I think Precision Bio will come with updates in relation with the first dosing plant. Thank you so much.

Thank you so much. Next question is about the U.S. So Michael, the question is you talked about IND. What role do you think the U.S. is going to play in the Phase I clinical trial?

Yes, really important. And I'd ask my U.S. physicians in the room, feel free to speak up as I -- so the U.S., very important what Precision did here is. We picked the top -- we talked about building a center of excellence for infectious disease for hepatitis. We went to where the top thought leaders in the world are, where the patients are for the feasibility of the trial. The goal here is to get to data. And then and only then, we said, okay, we're a new mechanism. We're going to work with regulators to get them comfortable. So the U.S. classical, if you look at big pharma and the studies that have come through infectious disease, these are all sites in the room we've talked about, the countries we've talked about. The U.S., and Mark, correct me if I'm wrong, usually waits in Phase I. They're usually more of a Phase II site or later on in development. And I think what's incredibly exciting to me and Mark, I'm going to go out on a limb here, I've got top U.S. investigators last night sitting up here with me right now, pre-patient 1 Phase I. And I think there's a palpable excitement of all eyes are on the first approach to possibly go to cure. So the U.S. is part of our 4- to 5-country plan. It will not be our first operational site, as you've seen. We are ready. Our IND package is finalized, okay? And we're working with regulators around the world, and we'll tell you when that approval happens. Right now, whether or not the U.S. is part of part 1, that first 3, 6, 9 patients are part of the expansion phase to be determined once we're through the IRB and we have the site open. But of course, I promise you, I'll be the first to tell you when the sites in the U.S. are up and running. Mark, is that a fair characterization of the U.S.?

Yes, Michael, I actually think it is. I think it's a very fair characterization. And today's discussion reminding me of sofosbuvir, which started in New Zealand with Professor Gane. And we were itching in the U.S. to get access to those now were known curative DAAs and the same has played out with other mechanism of action or drugs for hepatitis B. So this is really unique and really exciting for the U.S. patients and U.S. clinicians.

Awesome. Well, look, I want to thank our physicians who are in the room, Jordan, MF., Ed, I mean the people up here today, Alina, Mark, I mean, just an unbelievable job that's been done by the team. Someone once told me that if you really want to be successful, you surround yourself with people who are smarter than you are, and I think we've done that. So the reality here is now there's only 1 thing left to do, go treat patients. So we thank you for your energy. We thank you for your time today, to our community, and we look forward to continuing to communicate along the journey here as the ELIMINATE-B trial commences and starts generating data.