Good morning, everyone, and welcome to the ProQR Therapeutics Virtual Investor and Analyst Educational Event. At this time, all attendees are in a listen-only mode, and a question and answer session will follow the formal presentations. To our analysts joining us live, please use the raise hand feature to indicate you have a question. As a reminder, this call is being recorded, and a replay will be made available on the ProQR website following the conclusion of the event. I'd now like to turn the call over to Sarah Kiely, Vice President of Investor Relations and Corporate Affairs at ProQR. Thank you all for joining us today. We're pleased to present our educational event, NTCP Modulation in Biliary Atresia via Liver-Targeted RNA Editing. During this presentation, we will make forward-looking statements, and actual results may differ materially from those described. Please refer to our SEC filings for a discussion of risks associated with an investment in ProQR. Let me now briefly walk you through today's agenda. We will start with opening remarks from our founder and CEO, Daniel de Boer. Next, Dr. Golnar Karimian, our Head of Hepatology, will discuss the rationale for NTCP modulation in biliary atresia and our recent target engagement clinical data with AX-0810. We are also pleased to be joined today by Dr. Gideon Hirschfield, a leading hepatologist and professor of gastroenterology and hepatology at the Toronto Centre for Liver Disease, who will provide perspective on this and the role of bile acids in cholestatic liver disease. Dr. Cristina López-López, our Chief Medical Officer, will then discuss the next steps for our NTCP programs, including our clinical development plans in biliary atresia and how we will evaluate the upcoming AX-0811 phase I data. Finally, we will conclude with a Q&A session featuring today's speakers. With that, it is my pleasure to hand things over to Daniel. Daniel? Thank you, Sarah. I'm Daniel de Boer, founder and CEO of ProQR, the leader in ADAR-mediated RNA editing. Through our Axiomer RNA editing platform, we are building a diversified pipeline across a range of diseases with multiple clinical data readouts expected over the next 12 months. Most recently, we reported the first clinical data from our wholly-owned program, AX-0810. These results represent an important milestone for ProQR, providing the first clinical validation of our Axiomer platform in humans and demonstrating dose-dependent target engagement of NTCP, the main hepatic transporter involved in bile acid uptake in the liver. Beyond NTCP, we are also advancing wholly-owned programs in MPS I Hurler syndrome and PNPLA3-related MASH. In addition, our strategic partnership with Eli Lilly and Company, as well as our AI-enabled discovery efforts and collaboration with Ginkgo Bioworks, accelerate the potential of the platform. Today, however, we are going to focus specifically on our NTCP programs and what the AX-0810 data tell us about the potential of this approach. AX-0810 has now demonstrated human target engagement of NTCP, and AX-0811, our next-generation AI-discovered NTCP program, is designed to build on that foundation with greater potency and durability. Earlier this month, we announced the AX-0811 phase I study is now underway, with initial data from the first two cohorts expected in early January 2027. These lead programs are being developed to address cholestatic liver disease, and our initial indication is biliary atresia, where we believe the biology of bile acid accumulation provides compelling rationale for NTCP modulation. The key question is how the human pharmacodynamics we have now observed with AX-0810 may translate into meaningful benefit for patients with biliary atresia. Dr. Golnar Karimian will now take you through that rationale and data in more detail. Golnar. Thank you, Daniel. Biliary atresia is a severe pediatric cholestatic disease that affects approximately 20,000 patients worldwide and is driven by toxic bile acid accumulation in the liver. There are currently no approved pharmacological therapies that alter the course of the disease, and recent late-stage trial results underscore the need for approaches that act directly on liver. The current standard of care is early surgical intervention with the Kasai portoenterostomy, which is intended to restore some bile flow. However, Kasai is often not sufficient, and most patients will continue to progress, with 60%-80% ultimately requiring liver transplantation in early childhood. This highlights both the severity of the disease and the urgent need for therapies that can modify disease progression. Our approach aims to selectively modulate NTCP to reduce toxic bile acid re-uptake into the liver, lowering bile acid burden to reduce intrahepatic cholestasis. Let's take a closer look at the normal enterohepatic cycle to understand the biology. In healthy individuals, bile acids are continuously recycled between the liver and the intestine, where they support digestion and absorption of lipids and fat-soluble vitamins. Approximately 95% of bile acids are reabsorbed from the intestine and return to the liver through blood circulation. NTCP is the main transporter responsible for recycling conjugated bile acids back into hepatocytes. In biliary atresia, however, this tightly regulated system is disrupted. Because bile flow is impaired, toxic bile acids accumulate in the liver and spill over into the circulation via increased activity of MRP3 and MRP4 transporters. This leads to an increase in conjugated and total bile acids in plasma. Persistent hepatic bile acid accumulation contributes to ongoing liver injury and intrahepatic cholestasis. Early in the disease, this leads to an increase in liver enzymes such as ALT, AST, and GGT, as well as negative impact on liver function as seen with an increase in plasma bilirubin and other fibrosis biomarkers. In biliary atresia, this is associated with worse outcomes, including progression and reduced native liver survival. By modulating NTCP activity via RNA editing, our therapeutic approach aims to decrease the amount of bile acid re-entering hepatocytes, increasing bile acid levels in the plasma, and in turn, excretion in the urine of these bile acids. This pharmacodynamic pattern of relieving the burden of toxic bile acids in the liver aims to improve liver health biomarkers and ultimately clinical outcomes. The distinction between plasma and hepatic bile acids is central to understanding both our mechanism and the clinical data I will review shortly. Our in vivo preclinical data set supports this approach. Starting on the left, in an advanced humanized mouse model, AX-0811 demonstrates a decrease in hepatocytes bile acid levels by 67%, showing effective modulation of NTCP-mediated bile acid uptake. There were corresponding reductions in bile acid levels downstream in the bile ducts in the middle of the slide and in the portal vein on the middle right. On the far right of the slide, the same model was challenged with a DDC diet, which induces bile duct obstruction and mimics key features of cholestatic liver disease. In that setting, Axiomer-mediated NTCP modulation reduced histological cholestasis scores by 67%, as assessed by an independent external histopathologist. Together, these data provide compelling proof of concept for the therapeutic mechanism that reducing NTCP-mediated bile acid uptake via RNA editing can protect the liver from toxic bile acid accumulation and substantially reduce intrahepatic cholestasis. Turning now to the clinical data we reported earlier this year with AX-0810, the first in-human phase I study was designed to assess safety, tolerability, and pharmacokinetics, and to evaluate biomarker-based target engagement. Healthy volunteers received four weekly subcutaneous doses of AX-0810, and we assessed target engagement using three complementary biomarker approaches. First, we assessed clearance of orally administered TUDCA, which was intentionally selected because of its preferential NTCP-mediated hepatic uptake. Second, we assessed bile acids profile, including conjugated bile acids, which are specifically regulated through NTCP and provide a more direct assessment of the mechanism. Third, we measured total bile acids in plasma. With reduced NTCP-mediated hepatic uptake, we expected to see a concordant increase in bile acids in circulation. The current data set includes data from Cohorts 1 and 2, evaluating the 3 milligram and 6 milligram per kilogram dose levels respectively. Here are the baseline characteristics which show nice consistency across groups. Turning to safety and toler ability profile with Cohort 1 and 2 to date, there were no serious adverse events, and we observed no clinically significant changes in liver enzymes. In particular, we noted there was no occurrence of pruritus and no changes in hormone and vitamin D levels. We also saw no changes in bilirubin across cohorts, providing evidence that AX-0810 had no off-target effect on OATP, the main transporter of bilirubin, as expected with RNA editing. The pharmacokinetic profile was also consistent with our expectations, with the available data supporting an estimated half-life of eight weeks. Turning now to target engagement, we observed concordant, durable, statistically significant, and dose-dependent evidence of target engagement across all three independent biomarkers. The left and center panels demonstrate the specificity of our approach for NTCP rather than other hepatic transporters. Following an oral challenge, we observed a dose-dependent reduction in plasma TUDCA clearance, providing direct evidence of selective NTCP modulation. This specificity is further supported by the conjugated bile acids shown in the center panel. On the right, we observed up to an eightfold increase in serum total bile acids, consistent with the mechanism we described earlier, reduced hepatic uptake and retention of bile acids in plasma following NTCP modulation. The consistent dose-dependent responses across these three biomarkers strengthen our confidence in the robustness of the target engagement data and evidence that AX-0810 is engaging NTCP as intended. Looking more closely at the relationship between plasma and renal clearance, the urinary data show that these conjugated bile acids are eliminated through renal excretion in a manner that is directionally aligned with the increase in plasma bile acids. When we relate these findings back to the enterohepatic cycle, this is consistent with the pharmacology we would expect. Rather than accumulating within the hepatocytes, conjugated bile acids in the plasma are redirected toward urinary excretion. Together, these data support the proposed mechanism of action and demonstrate the potential of NTCP modulation with RNA editing to reduce intrahepatic cholestasis. The next question is how this may translate into benefit for patients with cholestatic disease. Continuing our examination of plasma conjugated bile acids. In the disease state, there is a toxic dynamic between bile acid levels in the liver and in plasma, as you can see in the middle graph. The red line shows the level at which accumulation of bile acids becomes toxic and leads to intrahepatic cholestasis. This is associated with deterioration of liver health biomarkers, disease severity, and worse clinical outcomes. By selectively reducing hepatic uptake through NTCP modulation, as shown on the right, RNA editing can prevent conjugated bile acids transport from the serum into the liver, protect the liver from toxic conjugated bile acids with the goal to prolong native liver health. For chronic treatment, it is also important that we can do this selectively while preserving other functions of NTCP, such as hormonal and drug transport. This, combined with the durability we are seeing with Axiomer, distinguishes our approach from broader NTCP inhibition and from therapies that act primarily in the intestine. To help put our findings into a broader clinical and disease context, I am very pleased to hand over to Professor Gideon Hirschfield, who will discuss in more detail the role of bile acids in the pathophysiology of cholestasis and why these changes in bile acids modulation are relevant as therapeutic approach. Professor Hirschfield is a world-renowned expert in the liver disease field, and his research focuses on advancing therapies for liver diseases to prevent the need for transplantation. Professor Hirschfield. Thank you, Golnar. My name's Gideon Hirschfield. It's a pleasure to be here today. What I'd like to do for the next 15 minutes or so is talk to you about the importance of bile acids and enterohepatic circulation in cholestatic diseases. When we think about cholestasis, we really need to take a mechanistic approach to understanding it, and we need to think beyond the fact that cholestasis is the presence of bile in blood and think about the etiologies and the site of the hepatobiliary injury. Cholestasis, in fact, is driven from the hepatocytes through the cholangiocytes into the large bile ducts, and we see hepatocellular injury, small bile duct injury, and large bile duct injury across the spectrum of cholestatic liver diseases that adults and children live with. When we think about the causes of cholestasis, we're therefore able to divide it into intrahepatic and extrahepatic. Here I demonstrate for you the wide variety of adult and children's diseases for which cholestasis is so important. You'll see that biliary atresia, as an example, has both extrahepatic and intrahepatic cholestasis as dominant features of the disease. Understanding the site and cause of cholestasis helps us as we think about better treatments for people living with these chronic inflammatory and fibrotic and symptomatic diseases. The helicopter view, however, is important to recognize the very close relationship between the liver and the bowel. Indeed, there's a very significant relationship between biliary secretion of conjugated bile acids into the bowel, modification of bile acids by the microbiome to create secondary bile acids, and then an exquisitely sensitive and controlled hepatic recirculation, going from the ileal lumen into the portal vein and then back into the liver, using a number of very important transporters. Bile acids are very important in liver and intestinal disease. This slide from the late Alan Hofmann, who really was the bile acid pioneer, just highlights for you some of the functions of bile acids and why they're so important. Cholesterol elimination, stimulation of bile flow itself, stimulation of biliary phosphocholine secretion, feedback inhibition of bile acid and cholesterol biosynthesis, and of course, lipid absorption, as well as stimulation of intestinal motility. We therefore have an exquisitely sensitive and important part of biology that, when injured, causes liver damage. But equally, we have the opportunity to use bile acids and bile acid transporters as therapies for our patients. Now, trying to understand these diseases has been challenging because frequently, we don't know the exact etiology. On the left, you can see a pictogram, which really applies to sclerosing cholangitis diseases, so that would include primary sclerosing cholangitis and biliary atresia, where you can see the importance of genes and environment, the importance of the immune system, the importance of normal biliary epithelial function to protect itself against acid, and then a crosstalk and a progressive fibrosis. Where we've landed is that we have recognized that toxic bile acid accumulation is very important as part of the injurious process. The failed metabolic homeostasis, because of different triggers, leads to cell stress and cell death, leads to inflammation, and leads to fibrosis. So this opens up opportunities for novel therapeutic strategies to stop the progressive biliary injury and help our patients have no further fibrosis and indeed, potentially reverse fibrosis alongside hopefully improving symptoms. Bile acid biology is not separate to immunology. We now recognize that bile acid metabolites, in fact, control immunoregulation, and we have a number of papers that show this in the gut. Gut bacteria are relevant as well, and the bile acids can inhibit Th17 cell function, which may be relevant to inflammatory disorders. This is also relevant in the liver itself and not just in the gut compartment. Finally, there is actually some very exciting data just published about how bile acid retention, and you will remember, that is a fundamental part of cholestatic injury in children and adults. But that bile acid retention, in fact, drives pro-inflammatory programs in macrophages. In this work, just published in "The Journal of Experimental Medicine," in models of primary sclerosing cholangitis, bile acid-laden apoptotic parenchymal cells are changing the program in macrophages, such that it drives a pro-inflammatory program, and that contributes to chronic hepatic inflammation. It speaks further to the important opportunity to reduce bile acid retention in the hepatic compartment. Bile acids are very, very complex chemicals, and they have very complex physiology, but equally complex potential toxicity. The primary bile acids, starting from cholesterol and conjugated in the liver, leading to secondary bile acids in the gut with a variety of different deconjugation, dehydroxylation, and again, repeat conjugation. Some of these bile acids are particularly toxic. In particular, the natural dihydroxy bile acids, chenodeoxycholic acid and deoxycholic acid, bind tightly to an absorbent as a measure of hydrophobicity and are highly cytotoxic. That is unlike ursodeoxycholic acid, which is considered to be devoid of cytotoxic properties, and cholic acid is an intermediate in terms of toxicity. This means that if we can reduce the toxic bile acids from the correct compartment, we should be able to improve inflammation. How is this system tightly regulated? The three major protein transporters for conjugated bile acids are NTCP, BSEP, and IBAT. You can see how this works in the enterohepatic circulation in this stylized picture, demonstrating the cycle of these conjugated bile acids into the liver, out of the liver, and then reabsorbed from the gut. Now, at a more microscopic and cellular level, you are then able to see on the left how this pathway is interacting with other pathways which we know to be anti-cholestatic and which we know have been used for therapies. On the left, you see the hepatocyte and the enterocyte. You see this enterohepatic circulation. You see the relationship to FXR and FGF19, and you understand that this is one of the homeostatic and then pathophysiological pathways of note in cholestatic diseases. On the right, you start to see the overlay with PPARs, which you will also know have been shown to be very effective therapies, particularly in adult cholestatic liver disease and particularly primary biliary cholangitis, where we have a number of ligands for PPAR receptors. This pathway is tightly regulated and is interacting with pathways of physiological and pathophysiological relevance. What happens if you have NTCP deficiency? This leads to conjugated hypercholanemia, but without a clinical phenotype. As you can see in this original paper of a number of patients with this very, very rare genetic deficiency, you can see that there is bile acid retention in the systemic circulation, but there is no pruritus because serum bile acids are not the pruritigen. The intrahepatic bile acid levels are low, and there's low bile acid levels in the small intestine. There is no significant liver injury. Here we have a very selective deficiency of a very key transporter in bile acid recirculation. If we want to then target intrahepatic cholestasis and be novel about our targeting, we then can think about a number of approaches. Clearly, we're going to focus on NTCP inhibition as a highly logical therapeutic target. Other people have talked about systemic IBAT inhibition in terms of the kidney axis, synthesis inhibition of passive absorption, changing BSEP transport capacity, surgical diversion is already practiced. Then we already know a lot about IBAT inhibition, as we've seen that as a successful therapy for some other very rare liver diseases. Biliary atresia represents a highly logical target for NTCP inhibition. Biliary atresia is a destructive inflammatory process that affects intra- and extrahepatic bile ducts that leads to fibrosis and obliteration of the biliary tree and development of biliary cirrhosis. We don't have an etiology, but we fundamentally understand that it is a chronic, cholestatic, and progressive disease. We understand that there's a role for genes and environment, immune dysregulation. Importantly, there's clear injury and persistent and progressive cholestasis, including after Kasai enterostomy, where intrahepatic cholestasis bile acid retention is very important in driving further injury for these unfortunate children. There is a very high unmet medical need for people living with biliary atresia. It's a very rare disease. It's a pediatric disease. The patients are symptomatic, and they will progress to cirrhosis and portal hypertension. Standard of care is early Kasai as first-line therapy, but after that, there's a very high need for liver transplant in later life. Even though biliary obstruction is overcome with the Kasai, this does not change the progressive intrahepatic cholestasis and the progressive nature of this disease. That's why biliary atresia remains responsible for about 45% of all pediatric liver transplantation. Here you can see over a number of years that this number hasn't changed. The unmet need is real and important, and there is the opportunity to deliver new therapies. When you look under the microscope and you see what's happening, you can see this cholestatic process. There's expansion of the portal tract with stromal edema, there's prominent liver fibrosis, there's bile duct proliferation, and there are bile plugs. You can see some of this cholestasis. Therefore, this cholestatic liver disease is one where the unmet need aligns with new therapeutic opportunities to use our knowledge of bile acid recirculation to change intrahepatic bile acid retention as a potential therapy. When we look at mRNA expression of SLC10A1, which is NTCP, in biliary atresia, we see that it is significantly upregulated in response to this persistent cholestatic injury. NTCP expression is high in patients living with biliary atresia. We come to the fundamental hypothesis that accumulation of bile acids in the liver is a major factor in the pathophysiology of disease. In healthy individuals, we see that bile acid levels in each compartment are tightly regulated, whether that is the liver, the blood, the intestine, the kidney. In biliary atresia patients, we see consistent increases in bile acids in the liver and the serum. This is toxic bile acids which are associated with further liver injury. Therefore, NTCP modulation has the potential to lead to the opposite pattern of bile acids between liver and plasma. We can see that we will aim to reduce the bile acid retention in the liver, we will move the bile acids into serum and excrete them in the kidney, and we will reduce bile acids into the intestine or keep it at the same level. If we look at disease versus NTCP modulation in the disease state, the untreated biliary atresia patient, they have very high plasma bile acids, their liver bile acids are very high, and this toxic load is pro-fibrotic, and their expected outcome, unfortunately, without liver transplant, is mortality. NTCP modulation, editing therapy to change NTCP function will lead to high plasma bile acids, and we can already show in healthy volunteers target engagement. Liver bile acids will go down, and that has been shown in animal models, and that leads to the hypothesis, and there is a potential real opportunity to decrease negative outcomes. With that, I will now hand over to Cristina. Thank you, Professor Hirschfield. What you have just heard provides important clinical context for the AX-0810 data we reviewed earlier. In our first-in-human study of AX-0810, we have demonstrated clear dose-dependent target engagement across three predefined biomarkers, together with a favorable safety and tolerability profile to date. This data provide the first clinical validation of our RNA editing approach to NTCP modulation. This gives us an important anchor for our NTCP strategy. The next question is how far we can drive that pharmacology, and that is where AX-0811 comes in. Preclinically, AX-0811 demonstrates greater potency and longer durability than AX-0810. Using the same translational framework anchored by the AX-0810 human PK data, our modeling predicts approximately 40% editing at the 2 milligram per kilogram dose level and approximately 65% editing at the 4-milligram dose level. These projected levels of editing are achieved at lower doses than AX-0810. As such, we expect that AX-0811 has the potential for lower dose levels and less frequent dosing in the clinic, with a projected half-life greater than three months. AX-0811 is now in a first-in-human study. We announced the first participant dose earlier this month, and initial target engagement data are expected by early January 2027. AX-0810 provides us with evidence of human target engagement and a clear framework for evaluating AX-0811. We will use the same three target engagement measures with a particular emphasis. TUDCA will be our most sensitive measure for comparing pharmacodynamic effect given its specificity for NTCP and the controlled challenge conditions. Conjugated bile acid profile will be important for understanding translation into the disease setting. Total bile acids will remain an additional supportive measure of target engagement. We expect AX-0811 to outperform AX-0810 in all biomarkers across equivalent cohorts. Then we have a clear path to clinical translation. AX-0810 has shown that we can alter bile acid handling in humans, while our preclinical data show that reducing liver bile acid uptake can lower intrahepatic toxic bile acid burden and improve cholestasis. Our studies in biliary atresia will now test in patients how this can translate into measurable improvements in liver function with the ultimate goal of preservation of native liver health. An investigator-initiated trial in China will evaluate two dose levels in 10 patients aged 5 to 11 years post-Kasai with their native liver. The study will assess safety, PK, target engagement, and biomarkers of liver health, including measures such as ALT, AST, and GGT, liver function and fibrosis biomarkers, and liver stiffness by ultrasound elastography. We expect interim analysis in the first half of 2027, and these findings will help inform our subsequent phase II program. For the phase II program, the study is expected to enroll two cohorts of post-Kasai patients with their native liver. The study will assess improvements in liver health biomarkers as well as clinical outcomes. We are planning an interim analysis after 12 weeks, currently expected in mid-2028. We will provide additional detail regarding endpoints and the overall registration pathway at a later date and following regulatory interactions. Bringing this all together, I'd like to leave you with two key takeaways from today. First, we will use the same three target engagement biomarkers with AX-0811 with a defined biomarker framework to assess how greater potency and durability translates. Second, we have a clear path to test clinical translation from human NTCP target engagement to impact on liver health. AX-0810 has shown that we can alter bile acid handling in humans via RNA editing and modulation, and our preclinical data show that reducing hepatic bile acid uptake can lower liver bile acid burden and improve cholestasis. Our BA-IIT will assess how changes in bile acid handling translate into improvement in liver injury enzymes, function, fibrosis, and stiffness with the goal of prolonging native liver health. Beyond NTCP, our broader Axiomer pipeline is also advancing with multiple clinical catalysts ahead across our pipeline, including data from AX-0422 targeting MPS I Hurler syndrome and AX-2911 for PNPLA3-related MASH in the first half of 2027. We look forward to keeping you updated on our progress. Operator, we'll now take questions. Answer session with our speakers. To our analysts that are joining us live, we kindly ask that you limit your questions to one or two. Please hold for a brief moment while we poll for questions. Our first question comes from Steve Seedhouse at Cantor Fitzgerald. Please go ahead, Steve. Great. Thanks so much for hosting the event and for walking through all that. Maybe just real quick, I wanted to check if prior to the early January data update on AX-0811, if you would be sharing the highest dosed cohort data for 0810, just to look at the continued dose response there. Then maybe a more scientific question. Obviously, you showed the increase in urinary bile acid excretion. Wondering if there would be any expectation for side effects associated with that, analogous to the diarrhea that you see with IBAT inhibition when there's an increase in fecal bile acid excretion. On that point, I am curious if you actually had a chance to look at the fecal bile acid excretion in phase I, and if it changes at all, either up or down with NTCP inhibition and the corresponding changes you see in serum. Hey, Steve, this is Daniel. Thank you for the questions. I will take the first one. For AX-0810, as we have communicated before, we will share the full data on that study. So that includes the third cohort as well as the 12-week follow-up data on all three cohorts at a scientific or medical conference later this year. That will be ahead of the AX-0811 data, and that is on track. For your question with respect to the side effects, I will ask Golnar. Regarding, you had two questions. One was about the side effect on the kidney. Urinary excretion of the bile acids is something that happens also naturally in patients who have cholestasis. Based on the data that is currently available, cholestatic patients often do not suffer from a kidney disease. We don't expect to have side effects on the kidney, unlike the IBATs that cause diarrhea by excreting more bile acid through the feces. Just quick, have you looked at fecal bile acid excretion? I'm curious if it similarly goes up, and is a form of elimination from the serum or if it actually goes down because you're lowering the liver levels. Yeah. Steve, I don't think we've measured that, at least the data we don't have ready here. It also has to do with the site of the mechanism, right? The IBAT inhibitor blocks the uptake of the bile acids back into the blood from the intestine, and therefore the bile acids are cleared through the intestine and end up in feces. With the NTCP mechanism, they're cleared through the urine, as we have also seen in the target engagement study. Very helpful. All right. Thank you so much. Thanks, Steve. Yes. Thanks for the question, Steve. Our next question comes from Alec Stranahan at Bank of America. Please go ahead, Alec. Hey, guys. Thanks for taking our questions, and great to see the updates today. I guess two from me. Your AI-driven design system's projecting, I think, 40%-65% editing efficacy or efficiency versus AX-0810. Just trying to think through whether that gap will translate one to one to the human PK/PD data that you're expecting, and how might a big efficiency jump maybe change the dosing frequency you'd be targeting in a phase II? Then maybe one for Dr. Hirschfield, if he's still on the call. Any important treatment-related adverse events you'll be tracking that could arise from blocking some of the other functions of NTCP, maybe hormone transport for growth or drug transport for other medicines these kids may be taking? Just trying to think about additional data points that could validate the specificity of ProQR's approach. Thank you. Thanks, Alec, for the question. With respect to the AX-0811 molecule that's now in the clinic, the fast follower molecule for NTCP, that indeed in preclinical studies showed about six times higher editing efficiency. We do expect that to translate into human in a hopefully a similar way. We've seen that when we correlated the AX-10 data back from the clinic to the lab, to the animal models that were used, we saw a really good correlation of the PK, and linking that to the editing efficiency allowed us to then extrapolate what the editing efficiency in human would be for AX-0811. We do anticipate that at the lower doses, so the 2 milligram per kilogram and the 4 milligram per kilogram, the editing efficiency in human will be 40% and 65% respectively. We are looking forward to see what that will lead to in terms of biomarker responses. We have also shared earlier that AX-0811 has a significantly extended half-life compared to AX-0810. With that in mind, we do expect that molecule will have a less frequent dosing regimen. We currently anticipate that to be less frequent than once every quarter. For your second question, I will defer to Dr. Hirschfield. Well, thanks for the question. I think it is a good question. I suppose I frame it in a number of ways. One is that there are a few families, and they actually have a very benign clinical phenotype, which is reassuring, including no liver, renal injuries, and no itch. The mechanism here, of course, is meant to be selective, but I am sure the sponsor will be interested in following pruritus. I think given the role of bile acids, fat-soluble vitamin malabsorption in these patients, I think it will be relevant to be following fat-soluble vitamins. I am sure they will be interested to check there are not more urinary tract infections, and equally, no other hormonal or growth-related concerns. But I do not think that the study is going to be overly burdensome or complex in that regard. I think the concept is quite clear. Prevent intrahepatic toxicity from bile acids, move the toxicity from one compartment into a different compartment, and therefore preserve liver function. You would not predict, beyond what we have already talked about, any other predictable treatment adverse events. Great. Thanks for taking my questions. Thanks for the questions, Alec. Our next question comes from Kostas Biliouris. Please go ahead, Kostas. Thanks for taking our question and the helpful overview here. A couple of questions from us for Professor Hirschfield. The first one is, what would you like to see in the first readout in patients across the different liver function fibrosis and stiffness endpoints to feel comfortable with the drug effect here? Is there a specific biomarker or endpoint you are watching in patients to assess the effect? The second question is, from a physician perspective, can you talk a little bit about the potential advantages of a treatment that requires an infrequent injection compared to a treatment that requires daily pills in this pediatric population? Thank you. Yeah. Very good questions, Kostas. I think that in an early phase study beyond safety and the same pharmacokinetics that you've seen, we're going to be looking at liver enzymes, and in children, you're probably going to be focusing more on GGT and transaminases. ALP is complicated with growth. I think we'd like to see, as we've seen in other cholestatic liver disease trials, sometimes you can pick up changes in PRO-C3 fibrosis, and you can also pick up changes actually in the ELF test. So, I think there's enough in the simple part of the things that we measure in a clinical trial to get very early signals that effective protection of this hepatocyte that is being compartmentalized, damaged by the retention of toxic bile acids, does lead to changes in serum liver tests and fibrosis markers. I think that will then neatly dovetail with the reproduction of the phase I data in these kids when they get the drug. I don't actually think it's hard for patient sell to think about a drug that you took every two to three months. The biggest challenge is adherence in therapies, particularly in children, particularly as we transition them. Here you have the opportunity to have highly targeted rational therapy, in vivo adjustment of protein function, and then for the patient or the patient caregiver to only need to administer it every two to three months. That would be a massive step forward in biliary atresia, and ultimately in other cholestatic liver diseases, particularly if it's highly predictable and as at least the phase I data is really encouraging as to the science moving quite quickly into humans and into the clinic. Thank you. Great. Thanks for the questions, Kostas. Our next question comes from Gavin Clark-Gartner at Evercore. Please go ahead. Hi, this is Yixiong for Gavin. Thanks for the event. Super helpful. Two questions from me. One, I was wondering for the biliary atresia, this disease, how much of the ongoing disease can still happen after this Kasai procedure? That is still driven by this intracellular bile acid exposure, versus some other already happened inflammation or some duct injury. Because I thought of BA-IIT trial, the patients enrolled age are like 5 to 11. Just wondering at that age, how much fibrosis or other disease phenotype can be reversible through this bile acid unloading? The second question is also disease biology related. In the patients with this biliary atresia, is NTCP expression upregulated? Because we see previously in healthy volunteer, we've been targeting like a twofold increase in total bile acid as a relevant biomarker. If patients already see this upregulated NTCP expression, should we expecting to see a higher level of the bile acid change to anchor to the potential clinical benefit? Thanks. Well, I am happy to address the clinical question. I think the science can answer the second question. Remember that biliary atresia remains the leading cause of liver transplant despite Kasai portoenterostomy, and whilst of course, the timing of Kasai portoenterostomy is very important in outcome for kids with biliary atresia. The majority of these patients are ending up with a secondary biliary cirrhosis from progressive cholestatic injury over time, and that is why they end up needing a liver transplant, to prolong their life. I do not foresee that the concept that Kasai does not take away the cholestatic injury and does not change the fact that the hepatocytes in kids with biliary atresia are retaining too much bile acids, and we believe that that hepatocyte bile acid retention is driving some of the toxicity and the progression of the disease. You are right. There is always heterogeneity in all of these rare diseases. That would be something to be really thought about in later stage clinical trials. But in the early phase of moving into disease, I think you can be confident the patients are cholestatic, that they are retaining too much bile acids, and you should be able to get the early proof of concepts in terms of efficacy from the broad trial design that you have heard. Broadly for Axiomer or RNA editing, higher expression of the NTCP typically leads to better editing efficiency. Yes, we anticipate that higher expression of the NTCP in biliary atresia patients will be favorable for the editing efficiency. Golnar, can you comment on what effect that will have on the disease biology? Yes. In these patients, because already they have a high level of the bile acids in the serum due to their cholestatic situation, having at baseline higher NTCP expression means that they are exposed to also higher intrahepatic cholestasis. Now when we have a better target engagement because of the higher expression of the NTCP, we have also a better chance of reducing the intrahepatic cholestasis, specifically in biliary atresia. How we should look at it is not about looking how much we increase the bile acids in the serum compartment up, but how much we will reduce the intrahepatic cholestasis and how much we improve the liver health biomarkers. That is, I think, the results of this higher chance of target engagement. Great. Thank you for the questions. Our next question comes from Catherine Novack at Jones Trading. Please go ahead, Catherine. Hi. Thank you for taking my question. I have one for Dr. Hirschfield again on biliary atresia. Just curious about the etiology of biliary atresia with regard to the BA-IIT, which I believe is going to be conducted ex-U.S. Are there any geographic differences in causes and triggers of BA that we should be aware of that might complicate the translation of ex-U.S. data to U.S. patients or European patients? Any color you can give on geographic differences would be helpful. I think the simple answer is no. I think the complex answer is, of course, this is a combination of genes and environment, and there's been lots of different hypotheses about which is dominant. But we've never really come up with a conclusion about where is this window of exposure, probably for the babies in utero, that triggers what then becomes a progressive fibroobliterative cholangiopathy. I think clinically, the patients are behaving the same once they've got the clinical diagnosis of biliary atresia. So long as the sponsor, which I'm sure they will, is working with the appropriate expertise in pediatric hepatology to make the diagnosis correctly and exclude the other cholestatic liver diseases, which is not easy to do, but is very doable and there's a very clear structure to diagnosing biliary atresia as opposed to, say, Alagille or other genetic cholestasis or other concerns. Then I think the clinical phenotype is consistent between the U.S. and ex-U.S. But it's a good question. Got it. Thanks. Thanks for the question, Catherine. Our next question comes from Susheela Hernandez at Kempen. Please go ahead, Susheela. Thank you so much for the event. Very insightful. We were just wondering whether you can give more color on continuing either AX-0810 or AX-0811. Also, considering your expectations of AX-0811, and which factors or data might impact that decision. Hi, Susheela. Thank you for the question. Yes, we are expecting the AX-0811 initial data readouts, the first two cohorts of target engagement data in early January. That data will finalize the decision if it will be AX-0810 or AX-0811 that we will use in the BA-IIT, that we will run in biliary atresia. And then likely that same molecule we will take forwards into the phase II in biliary atresia. That will be driven by that data readout. Having that said, based on the preclinical data, we see that AX-0811 is much more potent. Our expectation is that AX-0811 will move forward into those next steps. Perfect. Thanks. If you could also give some color on how that would inform, or the Chinese investigator-initiated trial, how that would inform a subsequent phase II design, or how you see its role alongside the development. Happy to. I will have Cristina López-López, our Chief Medical Officer, address that. Thank you so much for the question. As we presented, we have two-step approach. On one side, we have the investigator- initiated trial where we are moving from healthy volunteers into a children pediatric indication, 5 to 11 years. This will give us a lot of information regarding PK, PD, safety, and tolerability, and this will totally inform the phase II that we are planning to do. In the slide that I presented, I mentioned that we have two groups, two cohorts. We are planning to go to infants below two years old, and we are discussing with regulators how this study could look like to ensure that we have meaningful outcomes moving forward. In terms of the endpoints that we are going to be looking at, we are going to really look at the liver health combined with biochemical biomarkers, imaging biomarkers, and also hard clinical outcomes. Perfect. Thanks. Thanks for the question, Susheela. Our next question comes from Ryan Deschner at Raymond James. Please go ahead, Ryan. Thanks for the question for Dr. Hirschfield. After the Kasai procedure is done in your patients, in cases where it's successful, do you consider the cholangiopathy component to be largely solved? In other words, what does the ceiling look like in terms of what an effective NTCP inhibitor could theoretically deliver to a BA patient? Also, was curious specifically why bulevirtide, for example, as an NTCP inhibitor, hasn't been used off-label in biliary atresia patients. Is it more of a therapeutic window issue or something more specific to its interaction with NTCP versus AX-0810, AX-0811's mechanism? Thanks. Well, I'll answer it backwards. Clearly, there are many people thinking about NTCP in cholestatic liver disease. This approach is more unique and more targeted and more transformational. But there are other sponsors who've thought exactly as to your point about what would be the role in different cholestatic liver diseases. I think bulevirtide is just not accessible, so no one's actually realistically given it. To give it to a child, I think would be very difficult when it's not really used in children. We don't use it for Hepatitis D, which is treated in adults. I think you're then alluding to, and I'm an adult physician, not a pediatric physician, so I don't claim to have all knowledge about biliary atresia. But I think what you're saying is can we predict who does badly after Kasai? There are features biochemically and sort of liver stiffness and growth and bile acid levels that can be used to identify the patients who are not going to get the best outcome from a Kasai. But is it possible in any of these rare diseases to get rid of heterogeneity? No, of course not, because there's a window when you make the diagnosis and then get the kid to have the Kasai portoenterostomy, and so that must be an area of heterogeneity. That must contribute to why some kids rapidly progress despite the Kasai, and other kids are living into their teens, but then running into end-stage biliary cirrhosis and needing a liver transplant late. So, it's fair to say that going beyond the proof of concept will require extra attention to that heterogeneity. I don't think it's particularly relevant in the early phase of proof of concept, but as with any sort of complex rare disease, the next steps will require careful sort of alignment of patient phenotyping to really choose the bigger population to prove your ultimate efficacy. Thank you very much. Thanks for the questions, Ryan. Our next question comes from Jon Wolleben at Citizens. Please go ahead, John. Hey, thanks for taking the question. Along the same lines, I was hoping for a comment from Dr. Hirschfield in management. How are you thinking about a potential registrational path here in BA? Do you think outcomes will be necessary, or are you going to be proposing some composite biomarker endpoints? For Dr. Hirschfield, if it's not outcomes, what would you want to see that would be most convincing, either singularly or in a composite? Dr. Hirschfield, if you could go ahead to address the question, and then the second part for Cristina, please. It is a great question, and you know we are highly vexed of it in the adult world. I think there is a little bit more leeway in the pediatric world for these ultra-rare diseases where clearly the regulators recognize the incredible obstacles to doing outcome studies, which will take a long time and are very nearly impossible. Clearly would be impossible to do sort of placebo-controlled without access to registry data. I would imagine that there will be a lot of opportunity to look at registry data, to look at real-world data, and comparators. Whilst of course we would like to show liver transplant-free survival, I think other things such as stabilization of bilirubin, stabilization of liver stiffness, growth trajectories for children, frequency of clinical try and overcome, as you point out, what is a complex regulatory pathway for ultra-rare diseases with slow progression, heterogeneity, inability to do placebo. I think there will be a willingness from regulators, particularly in the pediatric setting, to take that on collaboratively. We will learn a lot when other sponsors publish their data on their efforts in biliary atresia. Although we are aware that an IBAT was tried in biliary atresia, what we are not aware of is all the data that will come from that study, which I think will inform the community to do a better study. It may not have worked for that drug, but it may actually still help the field as a whole. Yeah. I would like just to echo what our colleague, Gideon, just mentioned. This is exactly the path that we would like to move forward in partnership with the regulators. At the moment, obviously, we are thinking about the hard clinical outcomes, but based on the clinical outcomes, we know that it may take a long time, et cetera. We are really looking at many different outputs that go at three levels. A, clinical outcomes that relate to health resource utilization, meaning native liver survival, portal hypertension. We are thinking about imaging biomarkers or ultrasound biomarkers when we are thinking about fibrosis, or we are thinking about liver stiffness. We are also looking about biochemical biomarkers when we are thinking about liver health. Our current conversations that we're going to do with health authorities across the three different regions, U.S., Europe, and also Asia, will rely potentially on a composite to ensure that we can capture the entire value of this drug. I think that is very much aligned with our colleague that just presented today. Thanks for the color. Thanks for the questions, Jon. Our next question comes from Keay Nakae at Chardan. Please go ahead. Hi, thank you. With respect to AX-0422 for Hurler and AX-2911 for PNPLA3, when you report that initial data, can you give us a little more color on what you might report for each of those? Hey, Keay, thanks for the questions. AX-0422 for MPS I, we have earlier said that we expect initial clinical data by mid next year. That is on track. There are no changes to that guidance, and that will be the usual endpoints for MPS I. So it is typically GAG reductions as a biomarker after subcutaneous administration of AX-0422 in the first cohort. AX-2911 is targeting PNPLA3, which is a genetic driver in certain subgroups of MASH, particularly lean MASH. There we will look at a whole range of different liver health biomarkers and imaging. More detail on that is to come. We have earlier said that that program will start clinical studies in the first half of next year, and that guidance is still on track. All right. Thanks. Thanks for the questions. Our final question comes from Ananda Ghosh at H.C. Wainwright. Please go ahead. Hey. Hi. Thanks, team. One question for Dr. Hirschfield. I just wanted to dig more deep into his comment on the heterogeneity issue and how would he think a potential design might include the variability issue with the heterogeneity in a phase II study? It's a good question. Again, I don't claim to be a pediatrician, but I think what pediatricians are looking for is what's happening to the patient's bile acid levels, what's happening to their serum liver tests, and what's happening to them then clinically. I think it'll be important in the design of the investigator-initiated to only have patients who've got active cholestasis, because clearly that'll be very important. At the same time, not to have patients who've crossed the line to too advanced disease with deep jaundice, and are too sick to benefit because the liver's failed. Therefore, you don't have the opportunity to use your compartmentalized approach to treatment. So I think that's how it's going to be tackled at a practical level. I think so long as it's tackled that way and the patients enter with active cholestasis, then you're going to get the information that you want very quickly because of the encouraging phase I data suggesting very effective target engagement as to whether or not adjusting NTCP functions selectively, as this therapy does, it drives down the cholestatic injury, one would predict very quickly. Great. Thanks. Maybe one follow-up question. Given BOLD missed on native liver survival despite bilirubin being accepted prognostic bridge, do you still consider bilirubin as an adequate surrogate for BA? Yeah. But of course it's an adequate surrogate. I think what BOLD teaches us is that there is some unrealism from the regulators. But equally, you have to have a drug that's very effective. So one of the challenges in all of these discussions that we have is that when we do suddenly bring in really targeted, highly effective, rational therapies, then some of the challenges that we face with drugs of less efficacy will disappear. I think it's just the fact that any outcome study in liver disease and any outcome study of rare liver disease, and any outcome study of rare pediatric liver disease is an incredibly high threshold for the regulators to be looking for. Many of you will know that even in PBC and PSC in the adult world, it causes us lots of angst and discussion and disconnect between the investigators and the regulators. Great. Very helpful. Thank you, Dr. Hirschfield. Thank you for the questions, Ananda. This concludes the Q&A session for today, and also the virtual investor and analyst educational event. We thank you all for joining, and you may now disconnect.