Good morning and welcome to the first annual H.C. Wainwright Virtual Liver Disease Conference. I'm Luis Santos, Senior Equity Research Associate, Healthcare and Biotechnology at H.C. Wainwright, and this year, for the first time, we are combining our viral hepatitis and MASH Conferences. This way, we expand the scope to also include liver cancer, and we are very pleased to be hosting some of the most innovative biotech companies in the world, alongside key opinion leaders in the areas of Hepatitis B virus, Hepatitis Delta virus, MASH treatments, and hepatocellular carcinoma treatments, and with that, I want to introduce our next speaker, Cassie Gorsuch, Chief Scientific Officer of Precision BioSciences, a clinical stage biotech company pioneering the ARCUS gene editing platform to develop in vivo gene editing therapies that target the root cause of genetic and infectious diseases. Cassie, welcome. It's a pleasure to have you. Thank you so much for having us. Happy to be here. So for this fireside chat, we are going over the usual suspects. We're going to start with an introduction to your platform, ARCUS, going through the mechanism of action of your lead in HBV, the scientific rationale for that, the data you've generated, and how do you see this going forward. So can you give us a brief introduction on your ARCUS platform and how is this different than other gene editing technologies? Yeah, I'd be happy to. So at Precision BioSciences, we have a proprietary gene editing platform that we call ARCUS. And so we developed this gene editing platform, and it has some pretty distinct features that we think make it a really great basis for therapeutic gene editing. And it's quite different than a lot of the other gene editing technologies that others may be familiar with, like CRISPR-Cas9 technology. So our ARCUS platform, the nuclease, is actually derived from a protein that occurs in nature. It occurs in a green algae. And our founders really spent, you know, the better part of about 10 years really determining how to take that protein that occurs in nature and adapt it and engineer it to be able to recognize a target sequence of our choice and really hone the specificity through protein engineering. And so, as I mentioned, it has some unique features that I'm sure we'll get into here in a minute. But really, we at Precision think this technology has the potential to be leveraged in a number of different therapeutic applications to provide differentiated types of editing outcomes that really matter when you think about using gene editing therapeutically. And so that's our platform. We own the ARCUS technology. We develop those nucleases. And that's sort of the consistent thread across all of our portfolio is the use of an ARCUS nuclease for in vivo gene editing. How unique, how exactly does it differentiate from other platforms, especially in vivo gene editing? There's a unique cut size and also the compact size. Can you tell us more about that? Of course. Yeah. So these are those features that I had just mentioned. We think of them as the cut, the size, and the simplicity. And so when we talk about the cut, what we mean is the way in which the ARCUS nuclease actually cuts the DNA. When an ARCUS nuclease cuts DNA, it creates a four- base pair, three prime overhang. And this very unique signature matters in particular therapeutic contexts. One example of this would be for gene insertion. And you can really see that using a nuclease that has that overhang cut allows for higher efficiency, higher fidelity gene insertion. And that's being really demonstrated in the hands of our partner at iECURE through their OTC deficiency program, which is in the clinic now, leveraging an ARCUS nuclease for gene insertion in vivo. So that's the cut. Next is the size. So ARCUS is the smallest gene editor. It's about 1,000 bases of sequence, so significantly smaller than any other nuclease that's out there. And that really gives us a lot of flexibility when we think about delivery. If you ask anybody in the gene editing space, one of the biggest challenges for developing gene editing therapeutically is delivery. And so having a small nuclease actually allows us to leverage LNP technology, like in our HBV program, as well as AAV technology, like in our DMD program. And I think size is obvious how it matters in the context of AAV, where the packaging capacity is very limited. But I think it also matters in the size. And the size matters in the context of LNP as well, where you have to make that mRNA. You want to make that mRNA that goes into the lipid nanoparticle and very high quality. The mRNA can provide some of the toxicity that's associated with different lipid nanoparticle formulations. Some of that comes from the mRNA. And so having good quality mRNA is really essential for overall safety of an LNP product. Having a shorter sequence within that mRNA actually allows for better, higher quality mRNA production. And so I think size really matters in the context of both LNP and AAV. Then the last piece is simplicity. What we mean by this is that ARCUS is one protein. We can engineer it to recognize DNA, and it has the catalytic domain to cut the DNA. So it's all one protein that recognizes and cuts DNA. And that contrasts to any CRISPR-based system where you need a guide RNA that actually is your GPS signal for where it goes in the genome. And then you have your nuclease that then cuts or base edits or prime edits. And so having these multiple components systems can really make things a little bit more complicated. All of those different components have to work in concert together to actually achieve the edit, which may decrease efficiency. So having one protein that binds the DNA and cuts the DNA, we think, is a really elegant approach for gene editing. Absolutely. Thank you for that overview. So why liver? So your lead is PBGENE, your lead program is PBGENE-HBV. So why did you prioritize this program and why HBV? Yeah. So at Precision, when we think about our technology, I just talked about all these unique features and how they can be leveraged in different ways. And so when I think about it, there's a lot of opportunity. There's a lot of things you could do with our platform. And so for us, when we think about what should we do, first and foremost is unmet need. We think about what diseases need a differentiated gene editing approach. And here, I think HBV is an obvious one. There's really not a way for patients to achieve a cure today. The functional cure rate in HBV on standard of care is about 1% to 2%. And so there's a huge unmet need. These patients go on to progress to late-stage liver disease, hepatocellular carcinoma, cirrhosis. And really, I think it's an obvious unmet need area where a gene editing approach has the potential to really provide a differentiated approach that's never been tried. And so first, it's unmet need. And then we think about, does our technology have any unique features that may make it better at that particular gene editing application compared to other gene editing technologies? And so that's when the differentiators of our platform come into play. Are those going to matter in the context, the therapeutic context we're talking about? And so for HBV, we think the small size of the nuclease matters because we're using LNP. We just talked about that. And we also think the simplicity of the system may matter for HBV, where you're targeting covalently closed circular DNA, ccc DNA, which is a very compactly wound DNA molecule. And so, having a small protein that in itself binds the DNA and cuts the DNA, we think that has the potential to be really advantageous over other gene editing platforms, particularly for HBV. And so it's the unmet need, and then it's the differentiation of our technology. Can it matter in that disease indication? And for those reasons, we thought HBV was a really excellent first clinical trial using our technology for our wholly owned internal programs to really demonstrate the potential of the technology. So going into that mechanism of targeting ccc DNA and integrated DNA, your goal is to achieve a true cure versus other approaches which are going for functional cure. Can you give us a little bit more color on that nuance? Yeah, absolutely. And so I think I'll start with describing functional cure. This is something many people are probably familiar with in this audience. So functional cure in Hepatitis B is defined as S-antigen loss off treatment, six months off treatment, right? So you have to achieve S-antigen loss. You have to be HBV DNA negative, which indicates that your viral infection is under control, S-antigen loss for at least six months off treatment. And when you think about what that means in the context of Hepatitis B patients, what's really going on there is ccc DNA is the source of the viral infection. That's the DNA molecule that sits in hepatocytes forever. In the context of functional cure, what the goal is, is to achieve really immune control of the infection. And so the ccc DNA doesn't really go away. It just gets suppressed. And so you achieve off treatment viral suppression. But you always have this ccc DNA present, and you always are at risk of viral reactivation. And so I think that's always the concern for therapies striving for functional cure would be viral relapse. In the case of our program for HBV, our goal is actually to cut and eliminate ccc DNA and cut and inactivate integrated HBV DNA. And so if you remove the viral source, if you remove ccc DNA entirely, you actually are now achieving not a functional cure, but a complete cure because it's not about maintaining viral suppression. It's about clearing the viral infection. And in that case, you really have no risk of reactivation. You have no increased risk long term of other types of liver complications. And so we think it's worth striving for that. It's a tall task, of course, but we think it's worth shooting for that North Star. Absolutely. And would this be on top of background therapy with nucleoside analogs? How did you design your trial, ELIMINATE-B, that is now ongoing? Our ELIMINATE-B is a Phase 1 study. What we are doing in this study is really testing the ability of PBGENE-HBV to provide a safe antiviral response in patients who are on nucleoside analogs. And so our population that we're starting in are e antigen negative patients controlled on nucleoside analogs. And the thought process there is that our preclinical data really clearly demonstrate that by giving repeat administrations of PBGENE-HBV, you can continue to increase efficacy. You achieve cumulative editing with subsequent dose administrations, and you can continue to drive the antiviral response downward. And so based on that preclinical data, we wanted to set the clinical study up for success. And so from the beginning, we designed it as a repeat administration study. So ELIMINATE-B patients who enroll in it will receive three administrations of PBGENE-HBV. And while they're receiving those administrations, they stay on their background nucleoside analog. And we think that's important because if you think about what's going on in the liver during the course of treatment with PBGENE-HBV, what we're doing is we're eliminating viral DNA. And so by keeping patients on nucleoside analogs, we prevent reactivation or reinfection from any persistent viral DNA that isn't eliminated on first administration or second administration. And so by keeping them on background NUCs, we can maintain the progress that we've made with each administration of PBGENE-HBV until we achieve complete viral clearance, until we achieve S-antigen loss, which we would interpret as eliminating ccc DNA in the liver. And once we achieve S-antigen loss, then we'll really test for that complete cure by taking patients off nucleoside analogs. That's, of course, the long-term goal is to have patients off all therapy, so we'll take patients off nucleoside analogs and test for S-antigen and HBV DNA to ensure no reactivation, ensure we've cleared the virus completely, but that's really the goal for ELIMINATE-B and the goal for PBGENE-HBV. Great. And right now you have Cohorts 1 and 2, and you're planning on a Cohort 3. So you have data from Cohorts 1 and 2, drug doses, the 0.2 mg per kg, 0.4 mg per kg respectively. And how's the safety so far, and what do you expect from Cohort 3? Yeah, great question. So we released data in early August on Cohort 1. That was after completing all three patients, all three administrations with a couple of months follow-up on those patients. And so what we demonstrated in Cohort 1, keep in mind, this is a Phase 1 dose escalation study. So this was our lowest dose level. So we were excited to see good tolerability across all three individuals, all three dose administrations. And this was important because this is really the first time, one, that gene editing has been used in HBV, and two, that a gene editing study was really set up from the beginning as a multi-dose regimen. And so I think there were a lot of questions about what will the safety of repeat administration with a gene editor look like. And so in Cohort 1, it was really important to set that foundation that you can continue to administer repeat dosing, even in the context of liver infection, with a gene editor and demonstrate safety. So no greater than Grade 2 AEs were observed in any of the participants with any of the administrations in Cohort 1. All of the AEs that were reported were consistent with what you'd expect for IV/ LNP administration and infusion-related reactions. They were transient, resolved very quickly. Transaminases and platelets all looked good in those patients. And so overall, I think safety for Cohort 1 was really quite good. And that was that 0.2 mg per kg dose, as you mentioned. Excitedly, we also demonstrated antiviral activity in all three participants in that cohort. So all subjects demonstrated substantial S-antigen reductions, somewhere between about 45% to almost 70% S-antigen reduction during their course of treatment. And for our lowest dose level, I think we were all really excited to see a consistent antiviral response across patients, even at that lowest dose level. We shared in the press release in early August. One of those participants is actually sustaining about a 50% reduction in S-antigen now seven months post-treatment. And so I think that really demonstrates sort of the durable nature of a gene editing approach in treating Hepatitis B. We also have presented some initial safety data from our next cohort. So this is Cohort 2, 0.4 milligrams per kilogram. And really, I think very similar story on the safety side for patients who've received their full dose administrations, multiple dose administrations. Again, we're seeing very good tolerability. Infusion-related reactions are the most common type of AE that we're observing. Transaminases, platelets all look good. And that's with repeat administration as well. And so we haven't put out efficacy data for Cohort 2 yet. Our plan is really to complete all three administrations for all three participants within a cohort before really talking through efficacy data. But we'll be excited to share that data, hopefully, in the near future here. And as you mentioned, we have also initiated Cohort 3. We haven't disclosed the dose level for Cohort 3 just yet. I expect that'll come out here in the next several weeks or months. But we've initiated Cohort 3. So that's one of the interesting parts of our study design is it actually allows us to just escalate into our next cohort while we're completing those repeat administrations in the previous cohort. So Cohort 3 is underway. The protocol allows us for additional dosing cohorts if we decide we'd like to do that, if the data were to suggest we could or should continue to look at dose escalation. I think there's other levers within the protocol that we may explore here soon as well, including dosing interval, so yeah, there's a lot of exciting things going on right now within the ELIMINATE-B study so far, the safety data has been really impressive, and I think we really felt good going into the clinical study based on the preclinical safety data, and I'm really pleased to see that that continued to hold as we're continuing to dose escalate now in our clinical study. You did mention the interval, the dosing interval. How should we think about that? How are you thinking about that? And what would trigger that? At what point in the trial would that be disclosed or that lever will be used? Yeah. So right now, the way that the trial is designed is participants receive subsequent administrations eight weeks after their prior administration, and so they'll get their first dose, wait eight weeks, get their second dose, wait eight weeks, and get their third dose, and when we designed that interval, we really thought about the window of safety for LNPs. That's typically a matter of days or weeks where you may see some things like infusion-related reactions, transaminase elevations. Other people have reported transient platelet declines, and so we wanted to make sure that we were outside of that LNP window for those types of events prior to dosing their next LNP administration. The other consideration for that interval was really, in some of the HBV trials, we've seen an efficacy-related transaminase flare a couple of weeks after dosing. This would be an ALT elevation that's really, I think, the field's assuming a good elevation, a good ALT flare associated with antiviral response in the liver. That can occur anywhere from maybe six to eight weeks post an antiviral response. We wanted to be cautious for the first-in-human study design and set that interval at about eight weeks. Now with safety data in hand and those transaminase curves are public, you can see within a matter of the first couple of weeks, they're really quite flat back down to baseline, not seeing much in that later time frame. It looks like based on the data that we've collected so far, we certainly would have the ability to bring in that interval and administer those in closer succession. And that really, I think, a couple of things that scientifically is interesting to test to see if you can continue to drive antiviral responses down faster. Maybe that has an effect on the immune system or on other antiviral responses within the liver. But I think also from just a patient perspective, shortening the course of treatment may be beneficial as well. And so I think it's something we're interested in exploring. We haven't opened that cohort just yet, but I think that's something that we'll be looking at in the near future. That's very helpful. And you do plan to get biopsy data at the end. What insights do you expect to extract from that? Anything on DNA editing and transcript suppression? Anything else? Yeah. So if you think about the mechanism here, what we're really doing is affecting ccc DNA, integrated DNA within the liver. Our primary biomarker is S-antigen expression in the plasma. And that's what everybody's using. HBV DNA is undetectable because these patients are on nucleoside analogs. We will be looking at some novel biomarkers like HBV RNA and core-related antigen, but those aren't expressed in the majority of E negative patients. And so when they're there, I think they're useful tools for understanding activity specifically on ccc DNA, but we don't expect them to be present in most of our patients. And so really that leaves you with S-antigen. The challenge with S-antigen as a readout is that it is produced from both integrated HBV DNA and ccc DNA. And if you think about really the disease biology here, while we are targeting both integrated and ccc DNA, I think ccc DNA is asymmetrically more important than integrated DNA because only ccc DNA can produce new infectious particles. And so in my mind, I would put more emphasis on activity against ccc DNA. To be clear, our preclinical data suggest we target both. We are effective on both. But you can't really demonstrate on S-antigen alone where the effect comes from in the liver. Is it on integrated DNA? Is it on ccc DNA? And so those liver biopsies are really essential for looking in the liver to say, where did PBGENE-HBV have an effect that had this downstream decrease on S-antigen? And so I think we are during this Part 1 of our Phase 1 study, liver biopsies are optional for our participants. We are working with our investigators to try to identify individuals who are willing to undergo, it's really two liver biopsies because you need a paired biopsy, one at baseline, yeah, one post-treatment, exactly, so you need to be able to compare ccc DNA levels at baseline, ccc DNA levels post-treatment. We can look at transcript expression from ccc DNA versus integrated DNA. I think really interesting, you can look at pgRNA, which is only produced from ccc DNA. It actually may be a more sensitive marker for ccc DNA compared to looking directly at ccc DNA, and so there's a number of endpoints that we can look at within biopsies to really understand our mechanism of what's going on in the liver that's accountable for the S-antigen reductions in the serum. That's great. And with just the couple of minutes that we have left from a broader HBV field point of view, how do you see the bar for functional cure and for total cure, that true cure that you're pursuing? And how does that fit the treatment, the current treatment landscape for gene editing in such a large indication? Yeah. So if you look at the treatment landscape for HBV today, I think everyone would agree it's been a challenge. I think we haven't seen a real winner in terms of achieving functional cure or complete cure for a huge number of patients. I mentioned earlier the standard of care today on nucleoside analogs is 1%-2% functional cure rate. I think sort of best of what we're seeing right now is maybe up to 10% functional cure rate. That's with Bepi. And that's obviously looking at potentially combining with a lot of other types of antivirals or immune modulators. And so I think if you really look at the field today, it's been underwhelming. It's been disappointing. And I think in my mind, one of the reasons that that may be is that we've never really been able to target the root source of the infection. All of these different modalities target downstream components of the viral life cycle with the goal of allowing for the host immune system to regain control of the viral infection and achieve that functional cure state where ccc DNA is still present but is suppressed. And so I think, unfortunately, that hypothesis of interfering with downstream markers within the viral life cycle in order to achieve viral control just really hasn't been supported in the clinical data that we've seen. And so I'm super excited that we now have PBGENE-HBV, which goes directly at the root source, eliminates ccc DNA, inactivates integrated DNA. And I think that that really poses a very differentiated approach for achieving a complete cure for HBV. I think when we talk with others in the field, people are clearly very excited about this approach. One thing we haven't touched on is we actually have a late-breaker oral presentation for this program at the Liver Meeting hosted by AASLD here in the next couple of weeks. And so what we were excited about is it says very clearly on the website, they won't consider Phase 1 studies for an oral presentation for late-breakers. And yet we have an oral presentation as a late-breaker. And so I think that really tells you the field's excited for a differentiated approach, excited to see what's coming out of our study. And so I think it really has the potential to really change how we think about treatment for chronic infections like Hepatitis B. Excellent, Cassie. Very, very briefly, the next 12, 18 months, can you tell us what are the key milestones we should be keeping our eye open? Yeah, so I just mentioned we have a presentation at the Liver M eeting at AASLD. That'll be happening here in the next couple of weeks. Additional data to be shared there. We need to continue to complete Cohort 2, complete Cohort 3. We mentioned the next potentially looking at dosing interval cohorts, so those could be in the next few months, really, as we think about when we could consider those, and so over the next several weeks to months, I think we're going to be continuing to gain a lot of really valuable data. We'll have some biopsy data, hopefully, within that time frame as well from initial patients in Part 1, and the goal will, of course, continue to be to identify the best path towards S-antigen loss using things like dosing interval, dose level, number of administrations. We're really trying to optimize that dosing schedule in order to move into Part 2 of this study that will take that dosing paradigm into a larger number of patients. And all of those patients will undergo those paired liver biopsies. So a lot of information to come from those as well. Excellent. And again, thank you so much for sharing this overview and the details. Exciting story. Well, thank you for being here. And thank you for attending. Thanks very much, Luis.