Frequency Therapeutics Inc Stock

Greetings. Welcome to Korro Bio's Analyst Day discussing KRRO-121, a potential first-in-class treatment for ammonia control.

[Operator Instructions]

Please note this conference is being recorded. This Analyst Day presentation will include forward-looking statements. Actual results could differ materially from these forward-looking statements. Please see Slide 2 of the accompanying presentation and our most recent annual and quarterly reports filed with the SEC for important risk factors that could cause actual results to differ materially from those expressed or implied in the forward-looking statements. We undertake no obligation to update or revise the information provided during the discussion or the accompanying presentation as a result of new information or future results or developments.

Our presentation will include preclinical data from Korro's development candidate, KRRO-121. These data may not be indicative of future data or results of the other ongoing or future preclinical studies or clinical trials. After our prepared remarks, we'll open the call for Q&A. I will now turn the call over to Ram Aiyar, CEO of Korro Bio.

Welcome, everybody. I'm Ram Aiyar, CEO and President of Korro Bio. We are a company that's publicly traded on NASDAQ. And for today, we're going to focus on our product candidate we call KRRO-121, a compound with the potential to treat patients with high ammonia across multiple diseases. I would like to introduce you to a couple of my colleagues today, Loïc Vincent, Chief Scientific Officer; Todd Chappell, our Chief Operating Officer; Michelle Dinon, among many things, a mother and a patient caregiver and finally, Dr. Bruce Scharschmidt, a physician scientist whose focus has been on hepatology.

More relevant to today, he's one of the clinical developers of a compound that has become the standard of care for urea cycle disorders, a set of genetic diseases where ammonia is a bad actor. My colleagues will be able to tell you much more about the patient need, starting with an interview style section between Todd and Michelle, the clinical perspective on the lack of ammonia control with Dr. Scharschmidt giving a clinical -- his clinical experience, Loic going through the scientific thesis to providing a better solution using a combination of genetic evidence and RNA editing, our platform; and finally, Todd, providing an overview of the market opportunity based on an immense amount of work that the team has done. In the end, we will then open it up for Q&A.

Just in the U.S., we have north of about 50,000 individuals that show up a year to the hospital with severe neurological conditions, despite having severe diet restrictions with a role that leads to very severe outcomes and eventually to mortality, all due to uncontrolled ammonia.

Let me just pause there for a second. We're talking about more than 50,000 individuals a year just in the U.S. Today, we will talk about an approach to controlling this ammonia in the human body in a very meaningful way. Any protein, its function is defined by its structure.

Through the lifetime of the protein as it undergoes many modifications, the function of the protein changes. These modifications give them an ability to either last longer, degrade faster and potentially alter its function based on context. Our technology platform OPERA, among many things and with many features is able to change the structure of a protein transiently for a certain period of time to modify its function.

We do this by changing a single alphabet on our RNA and using the body's machinery to create a version of the protein that is functionally more active. We can do this with high precision to lost transiently for a time where the protein provides benefit and then take it off all the while, without touching and without causing permanent changes. As we go through the scientific thesis today, it will become clear how our platform is applicable both in rare indications such as urea cycle disorders as well as in common diseases and the ability to use the body's existing machinery to "fix" itself.

This is just the beginning. As there are many other target disease pairs, we can go after using such an elegant approach, a small list of which is on our pipeline. Today, however, is only about KRRO-121. So let's get started as we have a jam-packed agenda. I am very excited to start. With that, I will turn it over to Michelle and Todd to share what it is to have a patient or a child living with urea cycle disorders.

Hi, everyone. I'm Todd Chappell. I'm the Chief Operating Officer here at Korro. We're here at the Korro office in Cambridge, Massachusetts, and I'm joined by our special guest, Michelle Dinon, who is a mother of a daughter who has been impacted by UCD. So I have a couple of questions for you. Thank you very much for joining us today.

Thanks for having me.

So maybe we can just start by kind of asking you a little bit about your daughter background in terms of when you first noticed symptoms, how she was diagnosed. We can start there.

Absolutely. So my daughter Sofia was born in 2008. We had a normal pregnancy, a normal delivery discharge from the hospital. Everything was typical, standard, what we would expect. The day after we were discharged, she was starting to get a little irritable. She was vomiting, but being a new mom, I didn't know the difference between normal vomiting, normal irritability and not normal vomiting and not normal irritability. So I was talking to my mother-in-law who has 6 children, and she was telling me this is completely normal. You're going to learn how to walk and just rock her and get her to sleep, we get her to calm down. This is all normal.

In the midst of that, we received your call this Friday evening around 09:00. We received a call from our pediatrician's office, and it was the physician on call, and he called to ask if Sophie was acting okay and went on to tell me that our newborn screening test had flagged a response for -- a result for a possible metabolic disorder.

It was something that he had always seen once in 40 years. We couldn't provide much more detail, told us that it could be life-threatening and that they would call us in the morning. We didn't get very much sleep that night. And they did call back in the morning, the state lab had rerun the test, and it was positive again.

So they had us go into NASH General. We did some blood work. And life changed pretty dramatically that day.

And so didn't you start treatment right away, the standard of care?

Yes. So they paged the metabolic physician at Mass General who came in and consulted and got her set up with what she needed. But they had to do some testing first, they had to do an ammonia test to test for ammonia levels. And they continue to do more, just generalized blood work, see if anything else was off and then started care pretty quickly after that.

And what did she start in terms of care?

She began on [indiscernible]. We were in the hospitals in intravenous [indiscernible], the standard medications for urea-cycle disorder so she was started on the IV version of that. She had to have blood draws very, very regularly, and we had to stop feeding her standard formula and start her on a prescription formula, it was [indiscernible] protein with balanced amino acids.

Right. And so how often would you have to go into the hospital to be tested and to visit the physicians?

At the beginning, we were there for a solid 2 weeks. I think that she spent the first week in the ICU and then we stepped down that we can learn how to manage medications and formula once she was stabilized. And then we would go in probably about every month at the beginning. And I would say we had many more proactive or -- yes, proactive ER visits that first year because we were told to watch for the symptoms of the irritability, vomiting, sleeping too much. Again, as a new mom, those are all [ stuff ] that any parent knows are difficult to assess whether or not it's abnormal.

Yes. I'm a father of 2 kids myself and imagining what that's like it's very difficult, I'm sure. So tell me a little bit about those emergency visits. What was -- what would happen that would prompt you to go to the emergency room and what would happen at the emergency room?

So the concern is always her ammonia level. The things that we learned eventually to watch for with increased or elevated ammonia levels were her eyes. Her eyes got very glassy and couldn't -- as she got older, past a couple of months old, she couldn't really hold that connection, eye contact, we would notice from that also vomiting if she was at sick otherwise, if there was not already something going on, so unexplained vomiting, diarrhea, anything that made her reduce what she was consuming or in a formula. So the diet was very regimented. And if she didn't hit her goals every day, then there's always a concern that her ammonia would increase if her body has began to catabolize if she wasn't consuming enough calories. So any of those instances could send us to the emergency room for ammonia check.

Right. And so we were talking earlier before we started this about how you'd have to weigh food and understand exactly how many calories she got and the protein. So can you talk a little bit about that?

Absolutely. We had spiral-bound notebooks. We still have them at home somewhere where we have an incredibly accurate food log. And anything that she had -- at the beginning, it was easy because it was formula. But once she started needing solid food or baby food even, anything that she didn't eat, we need in to weigh so that we could figure out how much she ate from that original container of babies, for example or the example that I've given you in banana, if she has a banana and we know it weigh 60 grams. And at the end, it weighs 20 grams, then we know she ate 40 grams and recalculate the protein in calories based on that.

Yes. So just overall, like what was the impact to your family to you and to your family.

It created an atmosphere of hypervigilance. I think that's probably the way that I would summarize it for myself, for my husband, for anybody that was helping with the care of Sofia, to lead us putting her into any kind of day care or shared child care situation. So we needed some accommodations their work and with our family, they had to learn how to track the food and protein. Our nanny had to learn how to track everything and watch for the signs of [ hyperammonia ].

Right. And so the daily medication that she would have to take was sodium phenylbutyrate, is that correct? And that's 3 times a day.

Yes. So she started on sodium benzoate and she went to [indiscernible]. The previous form of RAVICTI and then she was part of the clinical trial for RAVICTI. And yes, and then move her to RAVICTI. But yes, they were 3 times a day.

And that was probably pretty difficult. I can't get my son's brush his teeth every day. So I imagine it's probably pretty difficult to make sure that she's on schedule to take 3 times a day?

Yes. She takes medication twice a day now, and I don't know how we ever got her on schedule for 3 times a day or right back at that.

Yes. And so how is she doing now?

She is amazing. She is healthy. She's 17. She is everything you'd expect from a 17-year-old girl. She gives her parents a run for their money some days and she is a junior in high school. She's athletic. She snowboards. She is social, she's doing really well physically.

Yes. And the reason for that is that, as I understand it, 5 years old, you decided to get her liver transplant?

Yes. That's fair.

To talk a little bit about that process?

Absolutely so for us, at the time, about 10% of kids with the urea cycle disorders require liver transplants, the other people because of actual liver damage. The other patients who had liver transplants were more -- it was more of a decision to manage symptoms and the possible damage for Sofia was both. Her liver became enlarged at a very young age, and we watch that really closely. And in February of the year that she was transplanted, it was around that time that her liver started showing up on ultrasound is incredibly enlarged pushing against her other organs. Her liver enzymes begin to come back as much more elevated than they had over the past, and there was no real explanation. She wasn't sick for those enzymes to be elevated.

So we started talking about the possibility of doing a liver transplant before she became closer to liver failure or compromised liver.

Right. And that must be a difficult decision, just weighing the pros and cons for that? And then, I guess, trying to also just be interested to understand after the liver transplant, getting immunosuppressants and things like that can talk a little bit about that as well.

Yes. The decision-making process was incredibly difficult. At that point, not a lot of urea cycle disorder patients went through liver transplant. And it wasn't as though she was in liver failure, which would have made the decision for us. We be had to make the decision whether or not we would go do it at all, do it now, do it 5 years from now. And then once you go through that evaluation and are listed in your on call. However, it is long until you get that call.

Yes. And so for us, as we think about our research into urea cycle disorders, what do you wish you would have had at that time in terms of standard of care to treat Sofia?

I think that in Sofia's case, the liver transplant was inevitable because of the liver damage that she had. But I think the improved ammonia control would have been the ultimate factor in giving us some peace of mind. I think that the constant not knowing what her ammonia level was, having some type of in-home device to check ammonia levels, but it's been a miracle. That was always the piece that was the most unsettling.

Right. I mean having a medication. We have always thought that having a medication also that you're having to take 3 times a day especially for adolescents as well could really huge difference.

That's something I've seen a lot more since she's been a teenager that hesitation to want to comply with medication and requirements around that. I think that there's a natural rebellion when you become a teenager that makes you know a follow-up renewal. And I think the taking medication 3 times a day would be very stressful for a family.

Great. Thank you very much for your time. We really appreciate it. It's wonderful to hear firsthand when someone has gone through this, and I really appreciate it.

Of course. Thanks for having me.

Our next guest is Dr. Scharschmidt, who will be giving a physician's perspective on UCD and hepatic encephalopathy.

Well, thank you, Todd, and good morning, everyone. I'd first like to thank Korro for including me and everybody for their interest. And I do hope you'll excuse my hoarseness and occasional cough. As someone blessed to have this young brand kids all having close, the occasional downside is getting exposed to virus that circulates among grade school kids here in San Francisco. And I might add that I'm delighted that this program includes the parent of the UCD patient, the perspective of UCD patients and families is critical, of course, bring a somewhat different perspective and look at recycle disorders through a somewhat different lens.

Now by way of introduction, I'm a liver specialist by training. In my academic past, I was Professor Medicine and Chief for GI at the University of California, San Francisco. [indiscernible] with my surgical colleagues helped launch the UCSF liver transplant program. During that time, I served as Editor in Chief of the Journal of Clinical Investigation and President of the parent organization. I was then recruited at clinical development at Chiron and I was first 2 [indiscernible] of biotechs and after its acquisition by Novartis, and a brief stay at Novartis and most relevant today, served as Chief Medical and Development Officer at Hyperion where we developed and launched glycerol phenylbutyrate which I'll refer to as GPB or RAVICTI for urea cycle disorders. We also conducted a large successful Phase II study of that same ammonia lowering drug for patients with decompensated cirrhosis and hepatic encephalopathy.

Now since Hyperion's 2015 acquisition, I've been doing other things and these are my disclosures. Now both UCDs and HE are all about ammonia. And when most people think of ammonia, they think of household cleaners, not something that our body makes or that circulates in our blood stream. So imagine, just imagine for a moment, either you or your child is diagnosed with UCD. So you or your child becomes severely and acutely ill. Your physician or pediatrician orders the blood ammonia test, refers to the metabolic geneticists to confirm the diagnosis of the UCD and advisers the following: the severely protein-restricted diet, perhaps to dietary supplements, short acting tablet or liquid taken up to several times per day, a warning that noncompliance with either drug can trigger a [indiscernible] crises, which may require hospitalization and cost permanent brain damage or even death and a caution that even if you do everything right, a crisis might still occur.

And by the way, here among the lucky ones, UCDs are rare. Many physicians have never seen a UCD patient and don't think to check blood ammonia [indiscernible] did. So hence, the title of this slide, UCDs are cruel. They can affect children starting early in life and they never let up and they're unforgiving. If we adults use blood pressure pills or stop adhering to a healthy diet, we may never suffer the consequences, not so for UCD patients.

Now bear with me for the next 2 slides where we dive into disease biology. The details are complex, but the concept is pretty straightforward. We Humans evolved as hunter-gatherers. Our ancestors didn't do when they find their next meals. Our bodies learned to store food. We start fat and adipose tissue and carbohydrates as glycogen in our liver and vessels, but we can't store protein. Dietary protein, which isn't incorporated into body tissues such as muscle or bone is broken down mainly in our intestines and ammonia is released as a byproduct. So this explains why we humans are constructed, [indiscernible] at all a blood from our testing flows first through our liver before it reaches the rest of the body.

As you can see at left, the liver triage its nutrients, includes ammonia and other gut-derived toxins. And as you can see at the right, [indiscernible] ammonia through a series of enzymatic steps called urea recycle, which when working normally, [indiscernible] ammonia in the form of urea that comes out of a urine and keep systemic ammonia levels low and protects the brain. So the 2 main causes of high blood ammonia therefore are liver disease and enzymatic defects in the urea cycle or UCDs. Patients with UCDs in whom the urea cycle is not working normally are often treated with what are called ammonia scavengers or alternate pathway drugs, so named because they provide an alternate pathway or ridding the body of ammonia.

The 2 approved drugs are sodium phenylbutyrate or Buphenyl and Glycerol phenylbutyrate aka GPB or RAVICTI. They're both products of phenylacetic acid which is converted to phenylacetyl glutamine, the urea surrogate that comes out in the urine. So the urea cycle that is a series of enzymatic steps which convert ammonia to urea. All UCDs are autosomal recessive disorders, except for OTC deficiency, which was x-linked. They're genetically very heterogeneous. Not only are there many different disease causing mutations, but due to the [indiscernible] of random x-chromosome activation is the female embryo develops, identical twin sisters conceived with the very same admirable gene exit dramatically different disease severity. Crises can occur with all UCDs but tend to be most common with effective enzymes early in the cycle, referred to as proximal disorders. The more severe the defect, the earlier the onset and severity is generally assessed clinically based on [indiscernible].

Ureagenesis can be measured directly using stable isotopes, but that is really done in clinical practice. It has so far been mainly a research tool. We don't have, for example, a readily measurable biomarker of disease severity or drug effect, such as Factor VIII levels for hemophilia A. Most UCD patients are not detected by newborn screening. And the best available data suggested the incidence is about 135,000 live births, which if all patients were diagnosed and live their normal lifespan, we mean a U.S. prevalence of around 10,000. But all patients are likely not diagnosed and some don't have a normal lifespan. So the true prevalence is uncertain.

In Hyperion's GPB trials, as you can see at lower right, we enrolled at approximately equal number of children and adults and the population was skewed towards females with OTC deficiency. Finally, UCD patients benefit from dedicated physician and patient advocacy groups with whom we work closely during development. And the IH sponsored UCD consortium has an ongoing longitudinal study, a valuable source of information, which I'll come back to later.

I think in development of the drug that's now RAVICTI with a lot of humility. Yes, I understood the biology of UCDs and had occasionally made the diagnosis correctly. Typically, in young women referred to our UCSF [indiscernible] clinic for what was thought to be unexplained hyperammonemia. These patients turned out typically to have OTC deficiency.

But I'm not a metabolic geneticist. This is why [indiscernible] by reading treatment guidelines, and they seem to make perfect sense and I quote, "The goal of treatment is to maintain normal levels of plasma ammonia through the use of a low protein diet, and medication while lowering per [indiscernible] growth." Now the first [indiscernible] for me was that there was no consensus among our investigators regarding ammonia control. Some really measured it. The reason it's a finicky blood test, which can yield spurious results, if not handled properly so that they've relied on their clinical judgment.

Other investigators were quite meticulous in keeping ammonia within normal limits. And the second surprise, not only to us at Hyperion, but also to our investigators came when we measured daily ammonia burden with round the clock levels as agreed to with FDA. We founded ammonia right dramatically throughout the day and often increased several fold after meal. So this begs the question, what's meant by keeping ammonia normal? Does it mean part of the time or all of the time and more importantly, do all the challenges associated with tight control really benefit patients?

So to answer this question, we are working with our [indiscernible] investigators did a post-hoc interrogation of our unique clinical trial and data set. The answer was an unambiguous yes. UCD patients do benefit from tight ammonia control. Based on the analysis of over 1,000 ammonia samples and over 100 patients with around-the-clock ammonia measurements. We found that the risk and frequency of hyperammonemic crises correlated directly with daily ammonia exposure.

Now round-the-clock ammonia measurements are, of course, impracticable in routine practice. We found that daily exposure correlated well with fasting morning levels, which are really doable. And you can see from the graphic, crises free survival decreased fasting morning ammonia level increased. Now those findings were presented at a plenary session and reviewed as quite important. But achieving that ammonia control is tough. And this is particularly true with school age children and adolescents who are no longer under their parents watch and want to fit in its goal, they want to eat a lunch, which looks like the other kids and not have to take drugs sometimes several times a day, a little long drugs, which can cause body odor.

And although GPB is better tolerated and has meaningful advantages over sodium phenylbutyrate, both drugs may need to be dosed several times a day. Both can decrease ammonia levels, branch gene immuno acids requiring monitoring and occasional supplementation and both have a neurotherapeutic index as high level [ phenylacetic ] acid can be toxic. So given these challenges facing UCD patients in their families, we explored the role of compliance and other factors as contributors to crises in our trials.

The table left catalogs what our investigators believe to have triggered crises among UCD patients in the year prior to enrollment in the GPB trials? Among 49 pediatric patients intercurrent illness or infections together accounted for about 40% of crises, a figure, which agrees reasonably well with the 33% reported from the UCDC sponsored longitudinal study. And compliance with [indiscernible] our drug together contributed to about 1/5 cases, but this likely understates the importance of noncompliance for several reasons.

It's likely underreported as patients and their families may understandably find it difficult to acknowledge noncompliance. More with the same illnesses, which trigger crises often cause nausea or vomiting, which makes it difficult for patients to take their drug. And the frequency of crises dropped by over half when patients enrolled in the GPB trials. Now when we felt GPB was a better drug and deserve some credit, it was also our job to ensure that patients comply with treatment while they were on trial. Both our data and the longitudinal study data indicate in most patients who experienced crises in fact, experience multiple. Finally and importantly, over 60% of patients are not prescribed drugs.

Our impression working with our study sites was that many of these patients and understand these are patients who have been diagnosed who are not taking drug and therefore, not in our trials, also experienced crises. These are, of course, patients who also might benefit from treatment. And that impression was borne out by unpublished data from the longitudinal study provided us by the consortium that was included in Hyperion's NDA.

Now these crises are the most dramatic manifestations of UCD and they may cause permanent brain damage or death. But the manifestations of urea cycle disorders comprise of spectrum. And I'll close with emerging information about OTC deficiency. Recall that OTC deficiency is the most common UCD subtype and is X-linked. It used to be believed that heterozygous females with OTC deficiency are asymptomatic because they have 1 normal x-chromosome. What's really elegant work done by Andrea Gropman, in particular, is showing that some of these patients exhibit subtle abnormalities and cognitive function and metabolic brain imaging. And a recent report pulling up over 100 such patients initially categorized as asymptomatic show that over 1/3 developed overt neuropsychiatric diagnoses usually in their late teens in 40% crisis. So I'd like to think there is still a lot we can do with these patients to help achieve better ammonia control and outcomes.

Well, I'd like to close with a few slides on what could be viewed as an additional important disease opportunity that is hepatic encephalopathy, which I will refer to as HG in patients with decompensated liver disease.

Now when the liver is badly scarred, for example, by chronic viral hepatitis for [indiscernible], I become scarred. We refer to scarring as cirrhosis. A cirrhotic liver not only failed to work properly, but the scarring [ impedes ] blood flow through the liver, which causes the pressure in the portal vein to go up. We call this portal hypertension, which results in blood flowing around the liver through newly formed collaterals, such as it reaches the systemic circulation and the brain unfiltered. HE is a major manifestation of decompensated cirrhosis. The only cure is liver transplantation but due to donor organ shortage, many patients may wait months or years for transplant or never get one at all.

HE manifestations range from confusion to coma or death. Regardless of the outcome, they're always frightening, and they're very expensive. The prevalence is probably greater than 200,000 and the pharmacoeconomics are strong.

Now we knew all this before embarking on Hyperion's Phase II trial. A big question for us and really the question for the field was about ammonia. It had been known for over a century that ammonia is elevated in HE patients, but was it a correlate or was high ammonia, in fact, a cause. The answer is that it's not just a correlate, but a cause. The result of a randomized double-blind, placebo-controlled study in 178 patients taught us that ammonia lowering decreases the risk and frequency of HE events as well as HE related hospitalizations.

Now this is a pretty big deal in the world of hepatology, but we took it 1 step further. Could ammonia lowering in the apparently beneficial drug effect be true, true, but unrelated, might the drug be doing something else. The answer turned out to be no. It's all about ammonia. Borrowing what we learned from UCD patients, we undertook the same type of post-hoc analysis with remarkably similar results. As you can see it right, lowering testing ammonia decreased the risk and frequency of HE events and the relationship between ammonia and HE events was in the same -- in the 2 treatment arms. But there was still another question we needed to answer.

Our Phase II study had been conducted at the same time as the rifaximin launch. Fast forward a couple of years, rifaximin has fully penetrated the market. We were considering Phase III I'm wondering if there was still an unmet need. So we do an observational study. We simply asked investigators to enroll patients who had experienced an HE event in the last month and follow them without any new intervention. Among 265 patients enrolled at 30 mostly U.S. centers and followed for an average of a little over 2 months, 27% experienced at least 1 additional on-study HE event and sometimes multiple. 85% of events resulted in hospitalization. 82% of patients who were on rifaximin at baseline. And as you can see it right, HE free survival didn't differ between patients who were or were not taking rifaximin at baseline. Now this, of course, doesn't mean that rifaximin doesn't work, but it does underscore a continuing unmet need. HE is not only hard on our patients, but it is expensive. The cost of HE related hospitalizations is almost early in the tens of thousands and the total cost to our health care system likely in the billions.

So some final thoughts. Why is HE still such a big problem? Well, in addition to compliance, we're getting better at treating other potentially lethal complications of cirrhosis and because HE per se doesn't increase transplant priority. We see more of it. It's also possible that ammonia may not be the only cause and/or the current treatment doesn't lower ammonia enough that we need something better, which I think is likely.

And finally, there is increasing interest in more subtle manifestations of HE called minimal or covert HE. This is conceptually analogous to the milder illness we talked about earlier in females with OTC deficiency. And like the OTC deficient patients, patients with COVERT HE have subtle cognitive and brain imaging abnormalities.

There is no professional consensus on whether or how to treat or test for it, and there is no approved treatment. There is a consensus, however, that it's a real problem and more common than avert. So as a hepatologist, I really do believe we can do more for these patients. Thanks very much for your attention.

Thank you, Dr. Scharschmidt, for going through the medical needs in hyperammonemic diseases. Hello, everyone. My name is Loic Vincent, and I am the Chief Scientific Officer at Korro Bio. Today, I am excited to present KRRO-121, our lead program targeting glutamine synthetase stabilization for the treatment of urea cycle disorders and hepatic encephalopathy. This represents a potentially first in class approach to ammonia control that could transform the lives of patients living with these high unmet medical conditions.

Let me start with the concepts underlying KRRO-121. glutamine synthetase, or GS, is a critical ammonia clearing mechanism in the liver. It complements the urea cycle and provides an alternative pathway for ammonia detoxification. The target validation comes from robust genetic evidence that uncovered the key amino-acid modification that can augment GS protein stability and this human genetic validation gave us confidence that stabilizing GS could be therapeutic.

The ammonia lowering benefits of enhanced GS activity may address substantial unmet need in patients with poor ammonia control, as described by Dr. Scharschmidt. This includes not only UCD patients, but also patients with HE.

KRRO-121 is designed to capitalize on this biology. It's a GalNAc-conjugated oligonucleotide, that edits GS messenger RNA to generate a stable de novo GS variant specifically in the liver that has increased stability and ammonia clearance capacity.

Our preclinical data that I'm going to run through today demonstrate that KRRO-121 has potential to trigger robust even clearance, supporting a timely UCD approach that may enable dietary liberalization as well as efficacy in other ammonia driven diseases such as hepatic encephalopathy. Finally, we are anticipating a regulatory submission for KRRO-121 in the second half of 2026. To understand our approach, it's important to recognize that the liver clears ammonia for 2 complementary pathways. The first is the urea cycle, which is expressed primarily in the liver. The second is glutamine synthetase expressed in many tissues, including liver, brain and muscles. The key insight is that GS clears ammonia and can bypass the urea cycle entirely. When the urea cycle is impaired, whether due to CPS1, OTC or any other enzyme deficiency, we can leverage this alternative pathway to clear ammonia.

And this is why targeting GS stabilization in the liver is such a compelling approach for OCD. Now let's understand why GS needs to be stabilized. GS protein levels are regulated by a glutamine independent feedback loop that causes degradation of GS when glutamine rises. When GS clears ammonia and [indiscernible] glutamine as shown on the left, rising glutamine levels trigger GS degradation. This creates a primatic cycle. When ammonia is high and you need more clearance capacity, GS starts to degrade, reducing ammonia clearance precisely when you needed most. The degradation mechanism involves a acetylation of key and terminal lysine residues shown on the right. At low glutamine levels, this rising residues are not acetylated and GS remains stable. However, at high glutamine levels, these lysines become acetylated which triggers a ubiquitination signal leading to protein degradation.

This feedback mechanism make biological sense in normal physiology, it prevents glutamine from accumulating to toxic levels. But in patients with hyperammonemia, this feedback loop becomes counterproductive. This is the vulnerability we are targeting with KRRO-121. The genetic evidence supporting our approach is company. We see validation from both sides, loss of function and gain of function. On the loss of function side, there is a published [indiscernible] report of 2 siblings with lysine 14 to asparagine mutation. This mutation mimics acetyl-lysine and make [indiscernible] GS prone to degradation resulting in GS deficiency on hyperammonemia. It shows that when we destabilize GS, you get elevated ammonia.

Even more exciting is the gain of function evidence. 9 patients have been identified with start-loss variants that stabilized GS due to the loss of the N-terminal lysine revenues which serve as the degradation [indiscernible]. These patients have increased GS stability, stable GS activity and importantly, lower ammonia levels. This human genetic data validates our hypothesis. If we can prevent GS degradation, we can enhance ammonia clearance. After understanding the degradation mechanism and seeing the genetic validation we form our therapeutic hypothesis, preventing GS degradation will stabilize the protein and enable increased ammonia clearance.

The slide shows our conceptual firework. If we can achieve liver-specific GS modification that prevents degradation, we hypothesize this will increase ammonia clearance capacity. The diagram illustrates the mechanism. Glutamate and ammonia are substrate for GS, which produces glutamine. In our modified GS variance, shown here with Arginine replacing one of the critical living residues, we prevent the degradation scene. The key is liver specificity.

We want to enhance GS activity in the liver where it can clear ammonia from the bloodstream without affecting GS in other tissues like the brand, which has different physiological roles. This hypothesis sets up our therapeutic approach.

Now let's say exactly what KRRO-121 does. On the left, KRRO-121 shown in red here, is a GalNac conjugated oligonucleotide, which ensures liver-specific RNA edit. The GalNac [indiscernible] binds to a [indiscernible] glycoprotein receptors that are highly expressed on hepatocytes providing exquisite liver selectivity. When KRRO-121 enters the hepatocyte, it binds to GS messenger RNA and recruits endogenous adenosine deaminase [indiscernible] RNA so-called EDA enzymes to make an A to I edit. [indiscernible] is read as a guanosine during translation effectively changing lysine [indiscernible] to an arginine [indiscernible].

The result shown on the right, is a de novo GS variant with arginine instead of lysine as a critical N-terminal position. This variant lacks the acetylation site, so it cannot be tagged for degradation and it can maintain consistent ammonia clearance capacity even when glutamine levels rise.

Now let's look at the data. This slide shows results from OTC-deficient human IPS-derived hepatocytes, which are the urea cycle defect carrying the D175D mutation in OTC. In [indiscernible] treated cells, without having a challenge, we see normal GS levels at [ 1.0 fold ], but when we add ammonia chloride to simulate high ammonia environment, GF levels dropped dramatically to 0.4 fold, which is a 60% reduction. This recapitulate the degradation mechanism we described earlier. However, when we treat with KRRO-121, GS levels remains stable at 0.9-fold even in the presence of high ammonia. Notably, only 20% to 25% RNA editing is required to maintain GS stability under ammonia stress. We have reached similar results in ASS1 deficient IPS-derived hepatocytes. This demonstrates that our approach may work across different CD genotypes supporting KRRO-121 span UCD potential.

Moving to in vivo studies. These are results from OTC deficient mice, which is a well-characterized UCD model. We dosed vehicle on most optimized oligonucleotides at 10-milligram per kilogram subcutaneously daily at day 0 to day 4, then measured outcomes on day 14 after the mice were challenged with ammonia simulating protein consumption. On the left panel, we see a dramatic reduction in ammonia levels. The human upper limit of normal is 75 micrograms per deciliter, which converts to approximately 450-micrometer in mice shown by the dashed line.

So we are bringing this mice much closer to normal ranges. Even during this metabolic stress, we see a nonsignificant change in plasma glutamine levels shown on the right panel, meaning glutamine level stays within manageable ranges. This slide demonstrates our mechanism of action using stable isotope [indiscernible]. We use N15-label glutamate as a target engagement tracer to directly measure GS activation. This is a powerful pharmacodynamic biomarker that allows us to track metabolic flux for the GS pathway. We dosed with [indiscernible], our most optimized oligonucleotide at 10-milligram per kilogram subcutaneously daily on day 0 for day 4. The challenge mice with 100-milligram per kilogram glutamine plus N-15 glutamate on day 11.

Three key findings validate our mechanism. On the left, we see increased plasma N-15 glutamine over time in treated animals with significantly higher under the curve. This directly demonstrates that GS is taking up N15 glutamate and ammonia to produce N-15 glutamine. In the middle panel, we see that the treatment decreased plasma ammonia throughout the time course with ammonia staying well below the 450 micromolar upper limit of normal even under this protein load challenge.

On the right, the treatment increased total liver GS concentration approximately 1.4 fold at peak. This shows that the stabilized variant accumulates in the liver over time, providing more enzymatic capacity. What's particularly elegant here is that we have demonstrated target engagement in OTC deficient mice.

But I should mention that we have observed similar results in wild-type mice which potentially validates that the mechanism of action provides disease-agnostic ammonia control. This slide shows data from CPS 1 deficient mice. The data reported here were generated by Dr. Brunetti-Pierri and Dr. Soria at IGEM, which is a well-recognized academic research group in Italy. They confirm our findings.

On the left, we see a significant reduction in nominal levels following ammonia challenge and on the right a nonsignificant change in plasma glutamine levels. This independent validation across a different UCD genotype in vivo strengthens our confidence in the panty applicability and diet liberalization potential of KRRO-121.

On this slide, this is our most important preclinical data set because it uses the PXB mice, which have humanized livers. These mice retains zonal expression patterns making them highly relevant to human disease physiology. We dosed with vehicle our KRRO-121 at 50-milligram per kilogram subcutaneously under 0 and 14, which is an every 2 weeks dosing regime. Mice was then challenged with 350-milligram per kilogram ammonia on day 21. We have 4 key findings from left to right. First, we see stable de novo GS variant and normal total 14 levels in liver. This repeat Q2-weekly dosing at 50-milligram per kilogram dose produces an amount of the edited variant approximately 10% to 15% of total GS protein in the liver.

Second, statistically significant reduction in basel ammonia from over 100 micromolar in vehicle controls, down to about 70 micromolar with KRRO-121 treatment, served and some ammonia clearance during the challenge. Vehicle-treated animals spike to around 1,600 micromolar ammonia, well above the 500 micromolar upper limit of normal. But KRRO-121 treated animals stayed around 500 to 900 micromolar with the majority of animals remaining at or near normal limits. Finally, we have steady glutamine levels per challenge with no significant difference between vehicle and treated animals. This is important because it shows we are not causing problematic glutamine accumulation.

Now here are the critical mechanism insights. The potential ammonia lowering requires only a minimal amount of de novo GS. We are seeing dramatic efficacy with only 10% to 15% of total GS being the edited stabilized variant in the liver. This suggests that the de novo variant is substantially more active or stable than the white type GS, which makes sense given that it is protected from degradation. This humaized mouse model provides strong confidence that KRRO-121 enables stable level of GS, providing robust ammonia control in a system that closely mimics human hepatic physiology. This is the critical transactional bridge between rodent models and human clinical trials.

An important safety consideration for any ammonia lowering therapy is the potential impact on the central nervous system. Glutamine synthetase is expressed in brain astrocytes where it plays a critical role in neurotransmitter recycling and ammonia detoxification. So we needed to definitively address whether our KRRO-121, which is the brand of astrocyte populations. We dosed mice with vehicle and KRRO-121 at 10 or 20 milligrams per kilogram daily for 5 days. These are supra-therapeutic doses given the daily regimen. Here, you'll see immunohistochemistry staining for GFAP, which is a well-known and recognized astrocyte marker in brand section for OTC-deficient mice.

The top panel shows vehicle treated brain and the bottom shows KRRO-121 treated brain. These images more virtually identical. There is no increase in astrocytes relative to vehicle treatment indicating no astrocyte activation of gliosis. This data definitively demonstrates that KRRO-121 doesn't cross the blood brain barrier and does not have an effect on astrocytes in the CNS.

This is critical for the safety profile because it means we are enhancing ammonia clearance in the liver without the risk of disrupting the import on physiological functions of GS in the brand.

Now lets discussed the safety and the biodistribution profile. The data comes from our NHP repeat dose toxicology studies where we dose cynomolgus monkeys with KRRO-121, once weekly for 3 doses. Starting with biodistribution on the left. We see greater than 90% of COR121 delivered to the liver with only minimal distribution to kinase, spin and the injection site as expected, Critically we see less than 0.05 delivery to the bone marrow brand at Linz nos and losses.

These exclusive liver productivity is exactly what we want. It means we are targeting the therapeutic side while minimizing potential off-target effects. The middle panel shows immunofluorescence imaging confirming labor colocalization of KRRO-121 with Paris of GS. You can see the proper signal that sifilabelco121, colocalizing with the Tcena, which is GS1 Libre is happy staying on U.K. This beautiful collateration confirms that KRRO-121 is delivered to a patocyte in the percentile zone where GS is predominantly expressed.

On the right, we report nickel chemistry and hematology data at 6 hours plus the sub dose. As shown here, we see no changes in liver or kidney function. There is no impact on coagulation complement platelets or cytokines. Altogether, the safety data demonstrated liver restricted delivery with no CNS exposure, no evidence of off-target editing and a clean toxicology profile at doses well above the anticipated therapeutic range.

Let me summarize why we are excited about KRRO-121's potential. We have 3 key PCs of dividends. First, for preclinical efficacy, we have demonstrated a pan-neCD approach impacting multiple usage of types. We have robust ammonial control in both OTC and CPS 1 mice challenge with ammonia. And we have shown diarizationpotential, so having a reduction during porting change. Next for preclinical safety, we have seen no adverse safety signals in repeat dose when funding toxicology studies, no impact on coagulation, complement, platelet or cytokines.

And again, no increase in stasis pending in most brand tissue. This provides strong confidence in KRRO-121's safety play as we advance throughout the clinic. Finally we have demonstrated cancelation, producing a stable denovos GS variant, which increases harmonics and maintains normal butane levels. This came from mice to monkeys and shows Gana specific lever delivery.

Together, the strong preclinical data package demonstrates KRRO-121 first in-class potential for patients with peramonemia. Let's include my section with our development time lines. As you can see, we nominated KRRO-121 as our development candidate in the second half of 2025. Our next major milestone is regulatory filing for our first in-human trial, which we are expecting to submit in the second half of 2026.

I want to emphasize the statement at the bottom. We have a compelling product profile for controlling ammonia that we expect to drive strong patient engagement and equipment. Thank you. And now I'm passing the mic to Tod Chapel, who is going to cover the market opportunity for KRRO-121.

Hello again. As a reminder, I'm Todd Chapel, the Chief Operating Officer here at Korro. So 1 of my many roles here at Korro has been to develop the product positioning for our programs. So I'm excited to share with you today some of our thoughts on the unmet need for patients with elevated ammonia and the overall market opportunity for KRRO-121. Starting with the end in mind, we believe UCD and HE have significant unmet need for novel ammonia lowering therapies, which presents a substantial pipeline and a product opportunity.

If you look at each individually, UCB represents approximately 9,000 addressable patients in the U.S. and Europe are combined and with a $1.5 billion market opportunity. Additionally, hepatic encephalopathy represents over 200,000 addressable patients in the U.S. and Europe combined and over a $2 billion market opportunity. So what I'd like to do now is walk you through each 1 of these market opportunities and why we believe we can address the associated unmet medical need.

So I won't spend much time on this slide as Dr. Sharshman already mentioned the importance of novel therapeutics addressing reduction of ammonia. However, briefly, hyperammonemia, our high blood ammonia is caused by the livers and ability to process ammonia, often from liver diseases like cirrhosis, inherited metabolic disorders such as urea cycle defects, organic acidemias or certain medications like valproic acid, severe infections, got issues or turners like dehydration, trauma and diet changes can also lead to ammonia buildup that's toxic to the brain.

So what do ammonia levels that trigger these hyperammonemia episodes look like? Specifically in genetic diseases such as UCD and cirrhotic situations such as hepatic encephalopathy. Our data science team evaluated electronic medical records from participants across the United States to help us understand what levels trigger these events. In a cohort of genetically confirmed urea cycle disorder patients, mean ammonia was approximately 77 micromolar in the context of mean ammonia being 35 micromolar or below for healthy individuals.

And approximately 95% of these individuals had a measurement greater than 1.5x the upper limit of normal. As a result, ammonia control is highly challenging in UCD patients today, typically requiring nitrogen scavengers and a strict diet that can lead to malnutrition. We believe we can address the unmet need associated with UCD. While nitrogen scavengers have played a significant role in the lives of these patients, unmet need remains. RAVICTI has to be taken 3 times a day, which can be difficult for chronic diseases. RAVICTI is administered in the background of a strict diet and means still leaks to crisis due to elevated ammonia.

As Michelle clearly articulated, new therapies to address these unmet needs are needed. We believe KRRO-121 may offer a differentiated ammonia-lowering approach to potentially address all UCD patients and provide a convenient subcutaneous delivery administered on a weekly or monthly basis versus on a daily basis. Additionally, we believe KRRO-121 has the potential to result in further reduction of prices due to elevated ammonia and liberalized patient diet.

Lastly, for UCD, let's go down into the epidemiology in the U.S. and Europe. In the U.S. alone, genetic frequency analysis leads us to believe that there are approximately 6,500 UCD patients with approximately 4,200 having severe post neonatal onset. which is defined as symptomatic patients expected to benefit from pharmacological therapy. And then there are an additional 5,000 patients in Europe with ucd. Now switching over to the opportunity for KRRO-121 and hepatic encephalopathy. What we're showing in these rents is that ammonia measurement and uncontrolled AC patients are frequently above normal, which correlates to a higher AG risk. Dr. Sharsman already reviewed with us what's shown on the left-hand side. First, the HE events correlate with ammonia levels. And second, in a study with RAVICTI, those events decrease with ammonia levels that are lowered. Similar UCD and the bar graph in the middle and on the right-hand side, we're showing the electronic medical record data our team generated for severe recurring hepatic encephalopathy.

In the middle graph, you can see the median levels of ammonia are already elevated in these patients. well above 1.5x the upper limit of normal. On the right-hand side, we see that severe recurring HD represents 40% of the patient population. And of those patients, we estimate that nearly 75% have elevated ammonia. Lastly, available therapies do a poor job reducing ammonia in these patients, offering minimal reduction in demoting levels.

These elevated ammonia levels and HD patients result in increased health care resource utilization. Through our EMR analysis, we've shown that among severe recurring HE patients, the subset with high ammonia and stable mild scores have a greater than twofold increase in AC-related hospitalization compared to the broader severe recurring AG population.

We also see a nearly twofold increase in all-cause hospitalization for this high ammonia subgroup. This is important because of the cost of AC-related hospitalization can exceed $75,000 per visit. resulting in over $10 billion in pitching charges for HE in the U.S. each year. This underscores a strong pharmacoeconomic case for additional therapies in this space. Similar to UCB, we believe 121 has a compelling product profile to address HE patients with substantial unmet need for offering a differentiated ammonia-lowering approach. 1 that can directly lower ammonia thereby reducing the number of HE events.

And with GalNAc 121 will be admitted subcutaneously with improved dosing frequency compared to standard of care. ultimately leading to an overall improved quality of life and potential survival benefit. As stated earlier, we believe that the addressable patient population for recurring IG in the U.S. is approximately 80,000 and over 150,000 in Europe, resulting in nearly 230,000 total patients just in the U.S. and Europe.

We define addressable patient population as those with severe recurring HE events, high ammonia and with sufficient liver function. Finally, although it won't be our initial approach we also see an opportunity to expand to preventing initial HE events and patients at risk, similar to how rifaximin is being positioned in their current clinical trial. So with that, I'll turn it over to Ram for closing remarks.

Thank you, Todd, and thank you, everybody, today for being here with us. I want to end and leave you with 4 things. First, I hope you appreciate the need for controlling ammonia in humans. and the significant unmet need that still exists. You heard from a caregiver, you heard from a clinician, you heard from what the current standard of care is. In the case of urea cycle disorders, the current standard of care involves a need to have a high level of control of your diet in addition to taking a drug 3 times a day.

Despite that, the mortality in this patient population and the eventual malnutrition that exists is pretty severe. In the case of hepatic encephalopathy in a much larger patient population compared to UV cycle disorders. The current standard of care is highly ineffective in terms of preventing hospitalizations for those patients where ammonia control is challenging. So the new here, as you heard today, is extremely high. Two, the scientific evidence that our team has provided in utilizing a transient approach to stabilize neimmunesymphatas is elegant in and of itself.

Having the ability to stabilize an intracellular protein using a mechanism the body understands and leveraging it to activate utimunesipitase is novel and yet has the potential to provide benefit that has never been seen before. all inspired from genetics. Over the last 2 years, this team has accelerated the development of this therapy in a very short period of time and is a testament to the improvements in the platform as it pertains to both potency and delivery that we have demonstrated today.

Third, KRRO-121 has the potential to modify the standard of care, going from a therapy that's 3 times a day oral to something that's likely once in 2 weeks or more infrequent depending on what the clinical studies are to show. That is just the beginning. The convenience of taking the medication, even if it were as good as the current standard of care to improve significantly compliance is highly beneficial for patients. On top of that, 121 has the ability or the potential to let adolescents who suffer from urea cycle disorders have a semi-normal life in terms of protein consumption.

The next time you have a cheeseburger, you will remember these kits and the potential benefit you're providing them. This drug, in addition to improving quality of life, has the potential to prevent hospitalization in urea cycle disorder patients and mean that's very high. And hopefully, we can demonstrate that in the clinical studies that we intend to run. Let me just pause there for a second. The ability to have an impact on ammonia in both these patient populations is tremendous, both from a caregiver standpoint, as you heard today as well as from a patient perspective.

You will hear more about the next steps and the additional guidance we will provide later this year as to what are the clinical inflection points that you will see. As you heard from Lloyd, we intended to have a regulatory clearance through a regulatory application in the second half of this year. Once we have guidance in terms of what those clinical studies will look like, based on alignment and the multiple regulatory authorities, we will provide more clarity as to what the next steps are.

Our initial intent with the clinical studies is to show that we have a profound ammonia lowering effect in either 1 or both of these patient operations. Finally, I'd like to end with a little insight into what the possibilities of our Opera platform look like. Today, I hope it gives you a window of how we, at KRRO are approaching product market fit with RNA editing therapies. We've been able to demonstrate this with Korro especially how it's different from DNA editing.

How creating a transient protein variant is very different than going after a mendelian disease with a pathogenic vary. I hope you can see how this opens up the possibility of us affecting biology in very meaningful ways, not just in rare genetic diseases, but also in much larger patient populations. We've shown that learning from genetics, we can affect a similar change in a transient action where you probably don't want to edit a certain transcript or modify a certain protein in a permanent fashion.

In the case of 121 where ammonia and glutamine control is going to be very important in various physiological situations, a permanent DNA modification is not feasible. This is an exciting day for me and for the company, and we've been working on specifically KRRO-121 over the last few years. Hopefully, you share the same excitement that we have in terms of having a meaningful impact on these patients, where ammonia is a bad actor and potential for the ability to control it across multiple patient populations to not just improve outcomes, but also the quality of life of these patients.

With that, I'd like to thank our speakers, Dr. Scharschmidt, Michel, Lou, Todd, and we'll be happy to open it up for questions.

[Operator Instructions] First question today is coming from Yasmeen Rahimi from Piper Sandler.

Congrats on excellent presentation connecting the dots of unmet need market opportunity, mechanistic rationale and really strong preclinical data that you shared with us. I guess my question is, I know, Ron, you noted you can give us more color once the regulatory filing is taking place. But I would love to hear from our KOLs, how do you think about -- how has the regulatory path evolved? Is ammonia still a good POC biomarker? Or should we be looking at Gudemade? So it doesn't mean that you're focusing on those, but if we could just maybe help understand what are the key biomarkers to assess in a clinical study and how the regulatory path could have evolved in this space that would really graceful. And again, congrats on a very thoughtful and meticulous presentation to us this morning.

This is Todd Chapel. So I'm going to be directing traffic here for these questions. And so I think for this first question, we'll have Dr. Sharma response.

Yes, that's a very good question, thanks. I mean, I think nothing has changed with respect to ammonia and urea recycle disorder, it's still absolutely the driver but your question about codamine is a very good one. And I think the short answer is that with respect to hyperammonemic crises. ammonia is the horse included minas the current. So what do I mean by that? Well, glutamine is the body's most abundant tomato acid so in a situation where the body can't get rid of waste nitrogen, for example, in inadequately treated UCD patients would mean become elevated as a consequence.

However, and we looked at this really quite closely and published our findings. Elevate glutamine has no predictive value for crisis once ammonia is taken into account. So unlike current therapy and by that, I mean, tidalocetic acid prodrugs were in elevatedglutamine could be a marker of adequate control or patients at risk. Now in the case of the Coral product, Elevated glutamine if it occurs, and you heard from all adopt has observed, which suggests to me at least that the drug is doing its same.

It's working. and include mine is replacing urea as a vehicle for waste nitrogen suasion. I hope that answers your question.

Our next question today is coming from Steve Seedhouse from Kantar.

I have 3 questions. I'll just take 1 by one, if I could. First, I guess, is just how fast do you think you can get to proof of concept pharmacodynamic data, namely, obviously, clinically relevant impact on ammonia levels. And are you planning to start the first study of a therapeutic dose and in patients?

We'll have Ram respond to that.

Steve, thank you for joining. As I mentioned, we are gaining alignment from the different regulatory bodies as you can imagine, for a rare disease, you want to go farm wide as quickly as possible. And so I would say stay tuned, I will come back to you or we will come back to you later this year in terms of when that is likely going to be. The intent, however, is exactly as you described it, which is the first goal is to show a reduction in ammonia.

It's just unclear at this point in time, specifically how we're guiding to in which patient population.

Second question is just -- I mean, a little preamble here. First of all, I think 1 of the keys to RNA editing right now is finding targets were less than complete editing will confirm that's more clinical benefit. And you were talking about we could show 20% to 25% editing is all that's required to rescue the phenotype in hepatocytes and maybe even less than that in the mice. So do you think that's a sweet spot? Or is that leaving efficacy on the table if you could get more editing than that. What would happen if you got more editing than that? Could it be harmful? And what's your conviction that you can get to that editing level in humans?

And for this one, I'll have a Loic to response.

It's a very thoughtful question. So you're correct. Now what I've demonstrated for this program is 20% to 25% editing sufficient to at entities and in particular to increase the size of our targets. whether we can increase the editing, we have some data where we can go up to 40% of editing and pet incentives, and this translates into the similar activity in terms of the toxification of ammonia in our clinical models, whether increased 18% could have detrimental impact of safety issue in human, this is fairly unknown at this point of time.

Well, I mean the key message here is that you're correcting a mutation. You don't need to have like now 90% editing was much lower. Anything you can really correct pathway. and you can rest on normal expansion. So whether there feels ending into that direction. I truly believe that modulating targets is going to be a big path forward as we are going to advance several programs with this type of strategy in the near future.

Okay. Great. Last question for me. Just obviously, this is a GalNAc conjugate so there's a limited read-through from the AATD program in terms of the mode of delivery and how much editing you therefore expect. I'm wondering though, separately about the target itself. So glutamine synthetase how does this expression level in the liver compared to something like Serpina One or other targets you've tested? And how would the expression level of the target itself affect editing efficiency that you'd expect in humans. Just thinking about how to handicap the variables that would be predictive of editing efficiency in humans once we get to the clinical trial.

And we'll continue with Loic on that one.

Yes. So I mean if you compare Sanand wines, there are fundamental different targets. For the earlier you try to correct this tenuation. For the later, you try to improve the function by changing the -- restoring the biology and increasing the air size. It's going to translate into the clinic, we're using conjugated delivery.

We have exclusive delivery of our ASO to the hepatocytes. And what we intend to do is now we are generating data, safety, but also we will be doing arosteric modeling and using PK/PD modeling to define the dose that is going to be strategic in the clinic. I think on the -- the data we have generated in preclinical setting. We have a large body of evidence demonstrating that at least it incentives the level of editing we are reaching and the correction of ammonia detoxification is really element, and we aim to be at those that are efficient when we get into patients.

I'd like to add to what as Luis said, Steve, to complement a couple of points. First thing earlier this year, we shared our data on a SERFA1-editing that is in vivo, we're close to 100% almost, okay? So it shows you the amount of progress that we've made from an editing standpoint of where the platform has come through. Second, I think that the reason why this -- the speed at which we have made this progress is because of the potency improvements we've seen on our GalNAc conjugate. And so just to put that in context, the current 121 program is a couple of logs fold more potent than what we had taken to the clinic earlier with GalNac delivery.

And so build a lot of confidence in terms of how we are evolving the platform. and build a lot of confidence in terms of the amount of editing that we need to see in humans at a dose that's going to be relatively safe.

Your next question today is coming from Luca Issi from RBC Capital Markets.

Congrats on preclinical and upcoming record for progresses on 121. And we have a follow-up question for Dr. Benson on the endpoint. This is CationorLuka, by the way. Is there a glutamine level and ammonia threshold that you'll be targeting with your first cum study from -- we're just thinking from the regulatory perspective, do you think this will be compared to the Finabutarige, just like ATD uses augmentation therapy to set the bar. And down the road is actually crisis very going to be required for an approval and maybe Dr. Shashi.

Yes. First, let's have Dr. Sharma respond to that.

Good receptor question. No, I think we would anticipate something similar to what was the case for RAVICTI. Alon, the approval was based on favorable ammonia control and of course, the regulators also wanted to see the hyperimmunes were at least directionally favorable.

I think it's unlikely that given the frequency that a statistically significant change in prices would be needed. But again, I would anticipate that approval would be based given precedents and favorable benefit with respect to ammonia with other things question sorry.

This is Erik. Yes, so a very thoughtful question. I mean from a clinical perspective, what we have been able to demonstrate with an contributed oligonucleotide as a decrease of ammonia with effective ossification, bringing the levels below the acolyte of normal or 1 is -- so I think when we think about the translation and as mentioned by gos, will we be targeting the same impact.

It also has a benefit to potentially trigger uberization as you have seen in our studies, whenever we have done challenges, we have been able to control and detoxify ammonia and this could have life-changing consequences for patients, we do see from a diode perspective.

Our next question is coming from in Desnofrom from Raymond James line.

First 1 for -- first 1 for Dr. Schar Schmidt. Do you think preventing GS degradation could reasonably enable enough ammonia clearance to allow patients to return to a completely normal diet and maybe for LOC, do you have a rough expectation for how often you expect to dose UCD patients with 121.

Dr. Shash smith.

I'll refer to Loic sort of on the frequency of dosing. That's typically something that would be defined in early clinical trials at Mad. I think the advantages of 121 should be substantial. I mean, just perhaps to reiterate or put some color about what I said earlier. and perhaps the most obvious advantage is compared with very short half-life PAA prodrugs is durable around-the-clock coverage.

We should benefit all patients, even those with good compliance, for example, where they sleep or if they're too sick to take their amounts. There isn't another theoretical advantage, which I think could turn out to be important and that is in the case of PA prodrugs. And when removal is really a byproduct of PAA detoxification and conjugation with glutamate in to form general acetabutamine.

So the timing and the amount of ammonia removed is not driven by high ammonia per se, the retripnbuy as well as limited by the timing and amount of PA, which needs to be metabolized and could be safely delivered. By contrast, the more robust would mean synthetase created by KRRO-121 should operate based on conventional enzymkinetics can be specifically responsive to high ammonia. So a treatment, if you will, which is there when the patients need it. I mean given the preclinical findings, which -- look described, I can only imagine sort of good things, if you will, yes, patients would be allow it to live a more normal life, perhaps decrease their drug requirements, have a diet, which doesn't require a dietary supplements comes something closer to the roll. So yes, that's my quick pick on things.

Look from a treatment perspective and dosing regimen. So what we have done in the preclinical setting, we're still generating data in our IND studies from a safety and PK perspective. We would intend to use every auto week or frequent administration, subcu to patients.

Next question today is coming from Cosmos Boris from Oppenheimer.

This is Kostas for Andreas. Congratulations on the progress and the great data here. A couple of questions from me. The first 1 is around diagnosis. It seems that these diseases are under diagnosed. Do you expect the diagnosis rate to increase in the future potential with newborn screening or other approaches. And the second question is on the translation from mice and nonhuman primate data, how well those data have been translated to humans for the approved drugs? And congrats again on the progress.

I will have Dr. Sharma respond to the diagnostics question.

Again, it's a really good question, particularly for disorders such as area cycle disorders where only a minority are picked up by newborn screening. Historically, as you allude to when there's an effective treatment available the diagnosis rate tends to increase. And certainly, that could be the case here. I would just also add that the patients who were severely -- sufficiently severely affected to come to medical attention to the ones who tend to be diagnosed.

So if anything, diagnosis right biolubut the patients in gracious need, for the most part, probably already identified.

Lake is going to respond to the translation question.

Yes. From a transition from milestone NHPs and to human, so in working with Norgine contributed alone usually the translation from small cases to human is relatively straightforward. I think for time sisters in particular, I start with the target. The target expression in UCD patients is consistent. There is no change. And there's no impairment in test in the legal.

So from a delivery perspective, we don't expect any issue. In our preclinical city, we use very stringent ammonia change where we use that very high concentration to the test the potency of KRRO-121 in generating de novo van for these interface, and we have been able to generate consistent data. I think the most critical data that in our data set is the PXP Humanized liver mouse studies.

Well, here, we're using a mass model but with Juniper. And we have been able to demonstrate the generation of our de novo variance and also, we have been able to report a very significant decrease in ammonia after change. So -- and we would expect translation from preclinical to the clinic, assuming that we will be in a therapeutic range from a safety and efficacy perspective.

Our next question today is from Ken Kay from Cardin.

A question for Mike. Just trying to get an understanding of 2 things. One, I guess, how fast the car can go. Can you tell us what kind of editing efficiencies you're able to achieve here?

Editing efficiencies, where we are reporting is that 20% to 25%. In different maleic studies, we are able to go up to 40% so we are in a range where no editing is sufficient to generate the item in entities that have improved half life in our clinical setting.

And what is the correlation with the editing inefficiency -- the amount of editing and the reduction in ammonia. Is that linear? What does that graph look like?

Yes. No. From a correction perspective, it's a very good question. It's clear when we reach at least 20% this translates into the increase in the retail incentives. So maybe to go into a little bit deeper into the mechanism of action we are editing utilizing, and we are editing and rising into angina. So we are removing 1 of the recitation site that is going to trigger degradation of the proteins for the proteasome. So by doing that, we increased the active significantly.

To give you some perspective, the native got incentives are price in human is about 1 to 2 days. And in the presence of excess of glutamine, the half life is decreasing down to 6 to 12 hours. With editing, we are doing, and again, we have a, say, 20% to 30% editing. The half life of the glutamine centers as variant we agonize in based on the preclinical studies is about 14 days. so 2 weeks.

So the half life of the end product, which is the reticent variance is significantly improved and this is the sustained ammonia detoxification that is now kicking in with our KRRO-121 treatment.

Next question is coming from Myles Minter from William Banner.

First, just if you looked at any sort of downstream markers on metabolism, I assuming UCDs like these patients, most of them are going to be OTC deficient. So like I just shunting this more towards a problem of a buildup of a carbon mile phosphate or heroic acid and you're just pushing this disease down the chain because the underlying urea cycle is sort is still there. That's the first one. And the second one, maybe for Dr. Sham, there's been a lot of talk about lack of enrollment cadence in UCD trials, been a ton of sponsors out there doing some work and just taking exceptional long periods of time to get patients into trials.

Just any sort of comment on expected enrollment cadence in this 1 for KRRO products?

Great. We'll have Lloyd respond to the first question.

Yes. So just for clarification. So in the cycle now Air were using modest system where we have enzymes that are deficient but we have demonstrated is that multiple on decisions like OTC SSI, the cycle is defective. Here what we are activating is the mutants. It's a complementary pathway. It has nothing to do with the cycle nurseries. It's a separate pathway that complements the ammonia detoxification.

And Dr. Sharen, maybe you can respond to the next question.

Sure, happy to. I mean enrollment is never easy with an ultra-orphan disease. But just to give you some context in that period over the 4 years that I was there, we completed 5 clinical trials in patients with urea-cycle disorders in addition to the pivotal. There were 3 or 4 supporting studies in different age groups. These enrolled exclusively in North America. So the U.S. sites plus 6 children's in Toronto. And I think the 1 point I would make is really the importance, and it's difficult for me to overstate this, but the importance of working closely with the patient adequacy group, the national re recycle disorder foundation and also the anti-sponsored physician group, the UCD consortium.

So it was really an effective partnership that enabled on-time enrollment of this rare patient population.

Next question is coming from Mitra from H.C. Wainright.

I just wanted to ask a little bit more on IDEAL trial design that you would envision with the, obviously, caveat that you have to follow up with FDA. Just thinking about like what would be clinically meaningful here on a duration of follow-up basis what would be required to definitively show benefit in HE? Is it something that would be weeks, months or longer? And then separately, would you seek to enroll ideally stable HE patients or those with recent HE events at a high risk of recurrence and would you think about hospitalization rate or something else in terms of what would invest physicians as well as patients that this therapy would be meaningful to them.

We'll have Ram respond first and then follow up with Dr. Owen.

Thanks, Mitch. I'm sure the same questions are on everybody's mind on this call in terms of what the next steps are. I think if I could just take 1 -- take it 1 level a buck. Our goal for us is to show that mechanistically, we can reduce ammonia. There are a couple of ways in which we can show that in different populations, we can show that. So that will be the first study in which we didn't show impact that the mechanism works, the target is engaged and is active.

What that study exactly looks like, we will come back to you shortly, but that's the goal first. The second, once we've established that would be to understand dosing schedule in each of the different patient population. So it is likely that it's going to be different in UCD patients or recycle patients versus what it is in hepatology patients. And so that will likely be the next step. And then finally, as you alluded to, what are going to be hard outcomes, how you think about showing benefit in UCD, whether it's die liberalization or a reduction in the crisis.

I think that those are things that we still need to get buy-in from regulators either pre or post approval. So I know these questions are relevant and I understand the reason to understand them. But once we have more clarity on what the full development plan looks like and the alignment with regulators, I think we'd be in a much better position to respond to that.

Based on our preclinical studies and based on what we are seeing in human cells, that shouldn't take very long. Now the contingent component there is that a GalNac-conjugated ASO will take time to get the hepatocyte, more time to edit and then have impact. And so we don't know what that PD really looks like. but it shouldn't be months is our expectation.

Dr. Sharman, any follow-up details?

Just happy to add a little color perhaps about what an AG trial hypothetically might look like. I think 1 of your questions pertain to the patient population. And yes, as you're question suggested, I think we would do something rather similar to what Salix did than we did at a period we would enroll patients in between events were clinically stable or qualified based on past HE events in the Lapa study that I quoted, it was a recent A event in the Phase II study which have been accepted by FDA supporting we did a look back for 6 months.

And I think that would be the patient population. Yes, hospitalizations, I think, would be important. Reading through all of this is very strong pharmacoeconomics. In the Phase II study, ROCE at all, with glycerol hitobuterate, about 50% of the patients were hospitalized and hospitalizations were significantly reduced with treatment. If I remember correctly, I think your third question pertaining to what we'd be looking at in the study, I would anticipate the patient benefit, we need to be in the form of a decrease in over 80 events, which would be defined as Grade 2 or higher.

I can spend a lot of time on this, but just to give you sort of a short version, we spent quite a bit of time with FDA preparing for what would have been a Phase III trial that never executed before we were acquired, we developed an AG rating instrument because the onsale used by Salix was criticized. I think there is also the potential for greater power and smaller sample sizes because it's very likely that patients experiencing more subtle HE events. For example, manifested by transient confusion, which occurs at all are being missed.

So I think it all has implications for what the next trial might look like and how we could use what we've done in the past to inform the next trial around.

[Operator Instructions] Our next question is coming from Katherine Novet from Jones Research.

Just as you're thinking about PD biomarkers for target engagement, does this -- would be a de novo added that you're making? Can you demonstrate in vivo editing capabilities in healthy volunteers. What are your thoughts on initial readouts?

Thanks, Katherine. It's a very thoughtful question. So I mean, to your question about can we demonstrate your engagement or any endpoint in root where we can comment to that is the data we have generated in preclinical setting. As you have noticed in the PXD mice, when we look at ammonia level before change. We have seen a 20% to 30% reduction in baseload and in the studies that we have done with the Nutmeg, which is target engagement, of course, we have seen in a wild-type Letalien engagement as well. So as we are creating a de novo ban, it's possible that in SC Volunteer, we could see some effects.

At this point of time, I cannot really say yes or no. This is something we will be monitoring, of course, but now from the preclinical setting, there's an impact.

And then just wanted to get your thoughts. Does this strategy potentially shift the burden of ammonia clearance from liver to other organs such as kidneys. What are the long-term risks of relying on GS to clear ammonia from the liver?

So maybe I'll start and maybe Bruce can add on this. So as we discussed now, we are activating this complementary pasta. It's like a synthetic risk sale is defective and then you are activating the glutamine incentives that will restore normal ammonia detoxification. The impact of KRRO-121 is happening in the liver through the Ghana conjugation it's exclusive delivery to deliver and has minimal ammonia detoxification in the local for instance. So likely, the site of action for a drug is going to be in the liver.

Again, we are not editing both likely in the terminal domain of the finance entities. So at some point, the de novo variance is going to be degraded by the proteasome. This is happening at a much later time form as compared to the native detente. And again, our therapy is tangent. We aim to treat the patients. Now every other week or less frequently.

But now if we stop the treatment, clearly, we're not generating any new de novo variance. So that would be a strategy where we can fine-tune the traffic now patent to retain BT and Cetip. Bruce, you want to add on this?

I guess just a comment, maybe to rephrase the question, is there some potential downside or perhaps injurious consequence of -- the approach has been outlined. I think my take would be probably no. I might add that the biology of ammonia and nitrogen metabolism is quite complex, but the final pathway for getting rid of the ammonia is discretion of urea in the urine.

Now in the case of penalistatic acid prodrugs, urea is replaced by what's essentially a foreign compound. That will also feel good to me, but I'm really not aware of any real consequences of VA prodrugs. I mean, if anything, the KRRO-121 should be more patient friendly, if you will, because the vehicle for it is being shifted from urea to glutamine, which is a normal body constituent and amino acid.

So it's hard for me to envision any sort of real downside, if you will, the approach being outlined.

Your next question today is coming from Bill Man from Clear Street.

So I have sort of a multi-parter that has to do with therapeutic window. Given you're looking at sort of an ending efficiency that needs to be tuned rather than maximized. What can we expect in terms of intra-patient variability of editing? And in the case that's something that a patient does have editing above and beyond the intended range, what are the theoretical issues that could arise in terms of adverse events? And how serious versus transient might those be?

Thank you for the questions. When it comes to treating patients, 1 may think that we will see some viability of course patients. Then it comes down to the potency and the specificity of our work, what we have done, now we have generated an optimized Ghana contributed or gone petite that consistently induce relevant editing in all our poplinical settings, should be in vitro and in vivo while we can expect in patients with aging, we may have some viability in terms of anything ranging from 20% to 40%. likely we have enough to generate the return incentives.

To think about the specificity of our well, we have done all off target prediction in terms of initial looking in vitro, in primary manepathocides or in vivo in the humanized liver from the PHP mice. We have not seen any off-target whatsoever. So if you think about if large editing is happening, then this should transfer into meaningful production of the glutamine synthetase variance, but because we have not seen any off-target passenger any transcript level, we don't expect any downside of having editing in patients.

We reach the end of our question-and-answer session. I'd like to turn the floor back over to Rob for any further closing comments.

Well, thank you, everybody, for listening in for this almost 2-hour session. Really appreciate the time this morning. As you've seen, we've been very thoughtful in terms of laying out the clinical need, the scientific basis of our potential therapy, the market opportunity here that is relatively large and underserved across the 2 patient populations and the speed with which we can generate a reasonable data set to show that our drug is working in the near term. I wanted to thank Dr. Scharschmidt, for being here with us, for Michelle, for spending time with us at KRRO and talking through her story with Sofia and really looking forward to the next update that we would give with 121, which will likely be during the time of our regulatory filing, which we have guided to as the second half of this year.

Everyone. Good morning. Thank you all for joining us today. My name is Henry Jiang. I'm with the banking team here at JPMorgan, and it's my pleasure to be introducing Korro Bio today. Joining us on stage and presenting will be Ram Aiyar, President and CEO of Korro Bio. Just a quick note, we'll have some time after the presentation for questions, so please wait until then. But without further ado, I'll pass it over to you, Ram.

Also, thank you for the JPMorgan Healthcare team for giving us the opportunity to present here today. It's great to see this amazing crowd here. So thank you for being here. Really appreciate it. Hopefully, we'll tell you a little bit about what we do at Korro.

Here are my customary forward-looking statements, you can always go to the SEC to find our most latest filings. So what do we do at Korro? At Korro, our vision is to develop transformative medicines for both rare as well as highly prevalent indications. And so we do that primarily by activating biological pathways. It's a very hard thing to do. Most modalities are focused on knocking down proteins or knocking down certain areas. Gene therapy is the only one where you can add another protein or activate signals. In this case, we use a simple chemically modified oligonucleotide or RNA to go and effect the change, okay? So we do that to make a single base change from an adenosine to inosine by editing RNA, not touching DNA at all to really impact the protein structure and sequence. We have an ability to deliver very modularly. So based on cell types, based on tissue types, we can conjugate with different chemical entities to really be very precise and target the right cell type.

And then lastly, here's where I think that this takes a lot from gene therapy, where we learn with the genetics and are able to influence the similar sort of outcomes that you could see, but in a very transient fashion and nothing permanent. And so knowing that you can have predictable outcomes or biological impact, I think that's going to be important. Just wanted to set the stage so that we're all on the same page in terms of what the technology is, what we're trying to do and what the base case assumption is.

So today, I want to leave you with three things, okay? The first thing is that I don't believe that RNA editing as a modality has really been articulated in a way that people understand where its benefits are. So today, with our pipeline, which is very focused, we'll be able to share with you how we can alter biology in very meaningful ways. So that's the first thing. The second thing I want to leave you with is we have a program called KRRO-121. It will be in the clinic in the latter half of this year. It is a very unique program that highlights where the benefit of RNA editing is going to be. I will give you a snippet of information in terms of what that looks like. We'll have a larger Analyst Day or an education session on January 27, watch out for that. And you'll learn a lot more about both the patient need, how we're going to approach it from a market perspective, what the clinical development considerations are and with even a caregiver of a patient being there, talking us a little bit about that indication.

And then finally, 2025 was an amazing year for us. It epitomized what biotech is all about. It was the first time we took a clinical program with an RNA editing compound within 2 years into the clinic and generated data within about a 9-month period. The flip side to the biotech roller coaster is that the data that came out was not as anticipated, did not meet our expectations. So we pivoted. And so we'll give you a little bit of learnings that we have from that program, how we have incorporated it into our other programs moving forward. And hopefully, you'll be able to see that we have removed the question of can RNA editing get to close to 100% or not.

So bear with me, I'll walk you through all three of them. OPERA is a platform that we use. It was built on four different pillars. When you think about understanding how ADAR works and how you can leverage it, that is the first pillar of our knowledge base that has helped to build this platform. The second pillar, when you think about oligonucleotides, it's all about chemistry, whether it's novel chemistry or whether it's fit for purpose or it's utilizing the existing chemistry that we have, that has been applied to other oligonucleotide therapies. We leverage all of those. The key is around how we design these constructs.

You can't talk about oligos without talking about delivery. So that's our third sort of pillar. We leverage existing delivery. And as these therapies get better, we would get more and more access to clinically validated technologies that can take us to different tissue types. And finally, since 2021, we have been using machine learning to both design and identify targets within the organization. So those are the four pillars that make up our platform OPERA.

Again, just to set the stage, so where can you apply them? When you think about the ability to change a single alphabet, in this case, an adenosine to inosine, we can do that in multiple ways. We can go in the pre-mRNA stage post DNA transcription and actually affect a change where you can change gene expression, either up or down. That's not our current focus. Or the other place you can have an impact is really thinking about changing protein structure by altering amino acids.

And I'll tell you a little bit about what we mean by that. So on the left-hand side is how we utilize this technology to repair a protein that is a pathogenic variant. So if you have a disease, let's just take alpha -1 as an example, alpha-1 antitrypsin deficiency. There's a single G-to-A pathogenic variant in the gene called SERPINA1. That's in DNA that gets transcribed into RNA and that creates a pathogenic variant. We can step in, in the RNA and make that change and correct that protein. So we can convert that A back to a G and therefore, returning the amino acid that was not a mutant that is a wild type and therefore, repairing a protein. So that's the example of what you can do with the repair.

That is not where we think the main primary focus of this platform is. There are many ways to go after those pathogenic variants. You can alter DNA, you can alter the protein. Even though that we have a single program in that space, our primary focus moving forward is on the right-hand side. And this is where it gets very exciting in terms of all the things you can do with biology that haven't been able to be done before. For example, what do I mean by that? On the right-hand side, we have the ability to modulate proteins and therefore, activate biological pathways. And again, as I said, we do this by creating a single adenosine modification to guanosine. And therefore, we can change 12 amino acids in the final protein.

So there are many ways we can go after biology where that just a single change can really activate a pathway. So that's what our pipeline is really focused on. As you can see, our lead program right now with KRRO-121, we're focused on stabilizing an intracellular protein. It is a GalNAc-conjugated liver-focused program, primarily indicated for reducing ammonia in multiple indications. I'll tell you a little bit about it very shortly. We anticipate a regulatory filing in the second half of this year and then entering the clinic and data very shortly.

We have -- as I mentioned, we have a teach-in session on the 27th, if you're available, please do make it. It will be 2 hours of scintillating conversation around why ammonia is bad and what the patients go through and how we think we have a best-in-class compound to help them and help the patients. The second program here, as I said, we repair a pathogenic variant in alpha-1. I'm going to use that as a test case to show that we can get close to 100% editing, which has never been shown before. We anticipate getting to a development candidate in the first half of this year and entering the clinic, and we'll give you guidance as we move forward.

The last 2 programs are, again, a very solid indicator of how we are approaching biology. And I'm going to give you later in the talk small snippets of data where people have tried to go after both of these proteins for these indications and have not been successful, and we've been able to show that. You don't see KRRO-110 on this pipeline. It was our lead program last year. Based off of the evidence that we have and the information I'm going to share, we're terminating the study. We have a lot of learnings here. We've kept the patient community up to date in terms of what we're doing. They're excited about our next-generation program that we're bringing forward, but we are not progressing with KRRO-110 moving forward.

All right. So let's take a step back now. That was part one of what I wanted to share with you in terms of where RNA editing is best suited. As you saw, it is not in genetic diseases necessarily, but it's slowly moving towards more prevalent indications. So today, I'll start with 121, which is our first step into going into prevalent indications where gene therapy cannot really be applied, and you need a transient way to go after it. So every time we have a diet, we generate waste. And so one of those waste products is ammonia. And when ammonia increases in serum, typically, it gets cleared by clearance mechanisms, both in muscle as well as in the liver, but primarily through the liver because that's if your master regulator and metabolic stabilizer. When you have no issues, ammonia gets secreted out or excreted out.

When you do have liver failure, cirrhosis, mutations in this urea cycle processing mechanism across all of the 8 enzymes, you end up with an increased level of ammonia. That increased level of ammonia causes many different things, causes neurological and cognitive challenges, causes frequent hospitalizations, causes you to not eat and have a highly restricted diet. PiZZ is out of the question, steak is out of the question. We're talking about very, very minimal protein consumption. It also increases your risk of infection. And so they all compound into you showing up in the hospital more often and with a very high mortality depending on the indication. And so having a modality that's transient, that is an injectable that's subcu that has the potential to go once a month, is pretty amazing for the current patient population where either they have no opportunity in one of these indications and another indication, you're fighting against a one -- three times a day oral therapy.

So what's our solution? Our solution is a GalNAc-conjugated oligonucleotide going after the specific RNA, where we are changing an amino acid and therefore, changing the actual function of the protein. You may have heard of molecular glues, you may have heard of E3 ligase as molecular degraders. But what we are doing is removing the substrate where E3 ligase can actually bind that. So by removing a lysine and converting it in an arginine, you can't degrade this protein. And so it's more stable, sticks it down intracellularly longer and has a higher capacity to clear ammonia. It is not in the urea cycle pathway, so it can actually go after and treat patients across all urea cycle disorders.

So when you think about the market, not just focus on specific genetic mutations or specific subsets of urea cycle disorders, we're actually going after all of them. And so it's -- in the U.S., there's a prevalence of about 4,500 patients across all of the mutations. There is an equal number in Europe and U.K. These patients, liver transplant is the only way they can get out of it early in life. If they are detected late onset, they actually have tremendous malnutrition. And so providing a way to help these patients is actually going to be very, very meaningful by providing a subcu therapy that they can inject and the caregivers don't need to worry about these patients.

Similarly, for patients with hepatic encephalopathy, again, not a small patient population just in the U.S., we're talking about 80,000 or so individuals that have high ammonia as well as hepatic encephalopathy. There is no therapy that has been proven to work, except for a nitrogen degrader to remove the -- reduce the ammonia and therefore, improve its benefit. So in both of these patient populations, we think that we have enough genetic evidence to suggest that we can have a benefit as well as clinical evidence to suggest that we are going to be successful in doing this. Again, not small patient numbers and not small market opportunities.

So again, I just want to recap. 121, we're not correcting a mutation. We are creating a de novo variant of a protein that's more stabilized. It's a very unique way of going using RNA editing from a modality standpoint. We intend to treat patients across multiple indications that have elevated ammonia. They have both large unmet medical needs in clinical studies. In the first clinical study, we will know whether you can reduce ammonia or not in a very rapid fashion in both of those patient populations. And as I mentioned, we'll have a workshop on the 27th to give you a little bit more insight.

We anticipate filing from a regulatory standpoint in the second half of this year. That to me is exciting, never been done before, right? And so -- there are many other such protein modifications we can make. And hopefully, we'll have the opportunity to take you through each one of them. The second piece I want to -- the last piece I wanted to connect with you on is what we have learned in alpha-1 antitrypsin deficiency, our experience through KRRO-110 and what we have generated moving forward. So to set the stage, KRRO-110 was a -- we have started the REWRITE study. REWRITE was a 2-part study, a single ascending dose part that had both healthy volunteers as well as alpha-1 patients and a Part 2 that was a multi-dose study to do once in 3 weeks or once in 4 weeks.

We stopped after the first part. We took the drug in a single dose into patients, dose escalated up to 1.2 mg per kg, which is very high for 110, which is a lipid nanoparticle encapsulating a single-stranded oligonucleotide. The only issue we saw, which was resolved within 10 hours was an infusion reaction in 2 of those individuals that were treated with ibuprofen. So we think that the profile was really good when we took it into humans and healthy participants.

When we went into patients, we saw 2 things. The first thing was the 7 patients that we treated that had alpha-1 antitrypsin deficiency, every single one of them had an increase in M protein. They went from not having any protein at all to seeing a level of protein in circulation, and that happened very rapidly. So we know that when the oligo gets into the system, it can go and edit. The unfortunate situation is that we did not see the M protein at levels that we thought would be competitive moving forward.

The reason we didn't see that is we saw differences in PK in the healthy volunteers versus alpha-1. And then when we dug in a little bit deeper in terms of root cause analysis, we saw that the structural integrity of the KRRO-110 as a product changed. We did cryo-EM. We saw that these products were spherical in healthy volunteer serum. They look like a football, not the European kind, the U.S. kind in serum ex vivo from patients. And so we don't exactly understand the mechanism, but we know that the morphology has changed, that changed the PK, and we believe that, that has changed the exposure for these patients. That's the reason -- that's one reason to terminate and not move forward with 110.

The other reason why we decided not to do that is that we made a ton of progress on our next-generation alpha-1 product. I don't think till date, anybody has shown greater than 90% editing in an in vivo model for a target that is meaningful. From a potency standpoint, this is almost 3 logs more than 110 in and of itself. And we've been able to achieve this in about 6 months. So the platform has evolved significantly for us to learn from what we've done in the past to get to a very potent compound in a very short period of time. We have now the ability to provide an option for these patients that's going to be as good as gene replacement in a transient fashion, which has never been done before. So we are pretty excited about this and gives us a lot of optionality in terms of moving forward.

As I said, we're close to a development candidate. Over the next couple of months or a few months, we'll be able to nominate that, and we'll -- we have guided towards a first half development candidate nomination. As you see on the slide, on the left-hand side, you see it's in two different animal models, we're achieving similar levels of editing, which is very exciting.

All right. I'm going to leave you with two targets that have been close to us and have taken a little bit of time, but we really have made a ton of progress. AMPK gamma 1 is an isoform-specific energy pathway modulator. It's involved in lipogenesis. I think Merck, Pfizer, Lilly and others have been trying to use a small molecule activator for, I want to say, 3 decades, and they have not been very successful in terms of showing a compound with high selectivity, high specificity and low toxicity. The biggest issue for this compound or this target is that when you activate it systemically, you end up with CARDIOTOX because the isoform specificity doesn't exist. So we've been able to create a highly selective gamma 1 isoform-specific activator just targeting the liver that removes some of the toxicity profile that can be seen.

So what does that look like? We -- as we develop this program, it's one of the first steps towards longevity if you've seen a target that has been implicated and longevity through metabolic stabilization. So on the left -- so we took this compound with a GalNAc-conjugated oligo to target AMPK gamma 1 to activate it in a diabetic -- in a diet-induced obese model. And on the left-hand side, we show that we have normalized the liver health. We only show ASCLT here. But if you look at all the other parameters, you will see such a normalization occur.

On the right-hand side, we show that within a week, we're able to see a differential between body weight. It's not tremendous. It's not intended to be that way, but the food intake that's being taken is very similar in these mice. So if you put those 3 pieces together, where you see normalization of the liver, reduction in body weight, despite food intake, now you can start to see where this program can come in, specifically in the spectrum of MASH. And again, as we progress this asset later this year, we'll give you more insight into where it will fit on that spectrum relative to the approved therapies that will be out there.

The biggest thing here is we only need 20% editing. We don't need more than that, which is a huge advantage as we think about moving forward, knowing that we can achieve a 100-plus percent editing or close to 100% editing with alpha-1, we feel very confident that we can get here in a very rapid fashion. Again, a very unique way to go after a target that has been traditionally undruggable and to provide a subcu therapy with infrequent dosing in a patient population that people have been trying to go after.

And the last one I'll leave you with is our program in ALS, which is restoring function. TDP-43 is a protein that has been very, very hard to go after as it has 3 different pathologies implicated. You need to have signaling that is lost in ALS because of aggregation of this protein. You have aggregation of the protein in the cytoplasm that leads to cell death. And then you have a mislocalization of this protein that enables both of those functions. And so you need a therapy that can bring everything together, keep the protein inside, keep it functional and prevent the aggregation.

We presented this poster very recently in December that we can do all 3 of those things, never been done before, right? You can only do 1 or 2 of -- 1 of any one of those things. So on the left-hand side, we induced iPSC motor neurons with a chemical stress inducer that pushed the protein outside the nucleus into the cytoplasm and created aggregates. We then when we treated with an oligonucleotide to edit a specific site, we were able to not only keep the protein inside the nucleus, but on the right-hand side, we can show that we continued signaling in 2 different downstream signaling pathways, STMN2 at the bottom, POLDIP3 at the top. Both of those, again, very hard to do by themselves, to do both of them by themselves. And so we are demonstrating here that in a very unique way, we're using RNA editing where no other gene therapy can be utilized.

So recapping everything that I just said, the 3 things that I wanted to leave you with. Hopefully, I've laid out for you what RNA editing can do in a very unique fashion. It's like going to the moon or going to Mars, baby steps to sort of get there, and we're starting to take those steps. So that's the first one. The second one, hopefully, I gave you an indication of where KRRO-121 is going to be and the milestones that we anticipate in 2026 and how exciting that product is going to be for these patients. And then the last one, hopefully, you have seen the learnings that we have at KRRO-110 and how we've translated that by moving away from a lipid nanoparticle, focusing on a GalNAc construct for all of our pipeline programs targeting the liver and then expanding from the liver into the CNS. We have a cash runway into the second half of '27. We believe that we can achieve a lot of these milestones in a very rapid fashion. And it's going to be an exciting year for us. And hopefully, we can share that with you. And happy to take any questions.

The first question is that what is the general safety problem of RNA editing comparing to DNA editing?

So RNA editing is the enzyme itself that makes the single edit is very specific. When you think about window size from gene editing to RNA editing using ADAR, it's a single base. So the likelihood of off targets is very, very low. We didn't see anything in KRRO-110. When we even went into humans, we didn't see anything that we saw in the preclinical studies ex vivo in human cells. So the specificity of making that edit is actually very, very high. We, in fact, look for 110, we looked across the transcriptome and didn't see any other place where it could actually have an impact. So that's on the RNA side.

On the protein side, we go after targets that have been genetically validated. So you know that what the mechanism exists, whether when we create a novel protein, we know what it's going to likely do. And we have ways to test it out in vitro as well as in silico. And so in this case, when you go after intracellular proteins, you have a little bit more privilege in terms of making these changes that is not going to have an impact on the immune response. And so when you add all of that together, using a GalNAc-conjugate that has been now in approved products, we feel very confident that the safety profile is going to be very, very good for these products.

Okay. The second question is about the GalNAc-conjugate. When you conjugate GalNAc with -- to the ASO, are you decreasing the dosage of it?

So let's just make sure I understand the question. So relate -- increase the dosage relative to our LNP product. Is that the question? I think we have to see in humans what that actually looks like, right? So traditional ASOs have been able to show somewhere between 200 and 400 mg fixed dose, you can have tremendous impact. siRNAs and ASOs have taken about 15 years to sort of get potency up. With the construct that we showed for alpha-1, that is a sub-nanomolar ED50, which has never been shown before. It's very close to an ASO gapmer. And so that's why we feel very confident that we can get to both durability as well as dosing and achieving close to 100% editing for those constructs.

I have a question, Ram. So you've obviously demonstrated that RNA editing can achieve similar profiles, DNA editing. To what extent do you think that it's possible to achieve this with targets other than AATD?

Yes. I think that we have spent a long time on alpha-1, and we have understood both what the structure of the RNA is and what chemical modifications are needed to make those changes. When we started with alpha-1 for 110, it took us 2 years to get to a development candidate because it was novel biology. When we did 121, it took us 12 months to sort of get there from a potency standpoint. For this asset, it's going to take us close to 7 months to get to that context. So I think that whether we can achieve it or not, that's not the question. We can definitely achieve it. The question is how long would it take to get there. And we've built out our platform such that we have enough diversity of targets and chemistry that we can actually get there pretty rapidly. So proof is in the pudding, right? We have to get to humans and show that this works at a high level. And so that's been really our focus.

Ram, congratulations for all these like progress in the early pipeline. So I'm just curious like what are the sort of principle of disease that you are selecting for this RNA editing that your platform is uniquely advantaged compared to directly delivering mRNA gene editing or AAV-based therapies?

So I'll use 121 as a perfect example, right? Or even AMPK gamma1 is a perfect example. You don't want to constitutively upregulate these pathways because they are energy management, they utilize and burn and create more mitochondria. If you make that edit, it's going to leave a permanent challenge in terms of having that pathway always on. That's problematic. But when you -- Yes, but your dosing frequency is going to be much, much longer, right? So when you think about a chronic indication with an mRNA, I don't think you want to do once a week, right? Even when you take an OTC, we're talking about once in a month, once in 3 months, depending on the potency of the construct. And so the goal for us has always been, as I said, in prevalent indications. And so the safety bar increases tremendously as you go higher in population.

Great. Well, I think that concludes our session today. Thank you so much for being here, Ram and thank you all for joining us.