Well, good afternoon, everybody, it really is a pleasure to be here. Thank you to the session organizers, HRS and SADS, for putting together what I think is probably the best session of HRS sessions, and thank you all for being here. I have no conflicts of interest or disclosures. Everything I'm about to share is in the public domain. It is an exciting time for gene therapy, specifically for SADS conditions, specifically for cardiovascular disease. I think kind of what paints the picture best here is actually taking a step back and asking what's the landscape of gene therapy and cell therapy more broadly in the year 2025. This is a brief overview of that landscape. There are 33 gene therapies that have been approved, 35 RNA-based therapies that have been approved, 72 cell therapies that have been approved, and importantly for our conversation today, nearly all of these are for non-cardiac indications, cancer, skeletal myopathies, rare metabolic diseases, drive the bulk of these indications. The pipeline is flush. Over 4,000 gene and cell and RNA therapies are currently in the pipeline pre-FDA registration, 2,000 of them are gene therapies, 1,000 are for rare diseases, which again is pertinent to our conversation today, although most of them are for non-cardiac causes, and eight out of the top 10 are for cancer indications. One of the most interesting thing in this pipeline is the development of RNA therapies and the rapid expansion of multiple RNA therapy modalities in this development pipeline towards FDA registration, and this is just one graph of many you can find that shows the number of RNA therapies in this pipeline over time based on the modalities. So whether it's RNA interference, antisense therapies, all of them are increasing, and it's very exciting. Within this data, you can actually see among the indications, cardiovascular disease emerged, and so I think in the years ahead, we're going to see a lot more transition from gene replacement gene therapies to RNA-based therapies for cardiovascular disease. The American Heart Association has brought together individuals who have formed a scientific advisory statement on gene therapy for cardiovascular disease. Writing on behalf of the writing group, Yuri Kim from Boston, I think described gene therapy for cardiovascular disease very, very well. She said that gene therapy holds immense promise as a paradigm-shifting approach in the management of cardiovascular disease, offering the prospect of disease prevention, long-lasting cures, and alleviation of lifelong pharmacotherapy, and if you'd like access to the statement, I've created the QR code here, which according to my two teenage sons, is the most millennial thing I could possibly do, so if you would like, please scan it and justify my being a millennial. Thank you. In order to have a conversation about gene therapies, it's important to understand some of the mechanistic cause of cardiovascular disease that could be heritable, because this is the direct underpinning which requires knowledge of so that we can actually apply gene therapy. And as many in this room know, the mechanism oftentimes is of a single nucleotide variant in one of two copies of a gene. You need two copies of a gene to make the appropriate amount of messenger RNA to make the appropriate amount of protein, the central dogma for biology. If you have a single nucleotide variant that happens to land in the region on one of these copies and a loss-of-function mutation ensues, then you will not have the appropriate amount of messenger RNA, not the appropriate amount of the gene product, and that leads to a haploid insufficient amount of DNA product. And that's one very fundamental mechanism of heritable cardiac disease. The other is a dominant negative effect, where a similar mutation on one side of two alleles actually causes the protein to be made, and that protein is dysfunctional, somehow disrupting the normal copy that's also there. This dominant negative approach, as you might imagine, also critical for cardiovascular gene therapy, but would require a completely different mechanism to be able to treat this disease product. And so, for example, haploinsufficient disease, all you may have to do is actually deliver a copy of the normal allele, so-called replacement therapy, and this is done in what we'll see as the early phase clinical trials, replacement of that haploinsufficient allele. Conversely, on the dominant negative side, a different approach is needed, such as actually silencing of that abnormal protein so that that abnormal protein's not floating around the cardiac myocyte. And then in between is genome editing. You could actually change that DNA change back to a wild type or otherwise account for it, and both of those could be amenable, regardless of the mechanism. Gene therapy has, at its core, genome editing, and so the ability to make precise changes in the DNA underpins the very foundation of gene therapy. One very traditional approach is that of the classic CRISPR-Cas9 nuclease, where, if you are able to target a specific single nucleotide mutation that you want to change, and you can target it very precisely with a guide RNA, that guide RNA can then bring to it a nuclease, a DNA pair of scissors that cuts both sides of that allele and then allows for the DNA to kind of fray, and insertions or deletions of that nucleotides in that cut oftentimes knock out the gene product. And so with a very traditional approach to this, it's simply just knocking out that broken allele. Obviously, that doesn't work for everything, and so there's more sophisticated mechanisms of genome editing, including base editing, prime editing. These both are precipitated on a different kind of molecular scissors, a nickase, which cuts one side of that DNA strand. If you're a base editor, that then leads to a deaminase, which then converts that nucleotide from one type of nucleotide to another, a C to a T, an A to a G. If you're using the prime editing strategy, then a very specific guide RNA, a prime editing guide RNA, then introduces a very precise array of nucleotide changes. And so you can see how the advancement of CRISPR-Cas9 throughout these different mechanisms can actually allow for very specific changes directly to the DNA. This is the foundation of genome editing-based approach to gene therapy. Genome-free methodology is tremendously important. Right now, most of the therapies, as we'll see, are being delivered via a virus, adeno-associated virus AAV. This is not the only way you can deliver a gene therapy. There's also non-viral mediated delivery, most frequently lipid nanoparticles. And so these are engineered lipid envelopes that you can express proteins on the surface of that then target that cargo specifically to an organ. These work great for the liver, not so great for the heart. In fact, if anybody wants to make tons and tons of money, I would find a way to target lipid nanoparticles to the heart. You will be happy you did. And so these are two basic mechanisms to deliver that cargo once you have defined what that mechanism is that you want to treat. And so boiling this down, there are major themes for cardiovascular gene therapy in the year 2025. All of these tend to target heritable cardiac disease. This tends to be monogenic Mendelian disease, where a single nucleotide variant causes a single protein to be abnormal. They have to have a defined genetic mechanism, because if you don't understand the gene mutation or the mechanism, you can't actually provide appropriate genome therapy or gene therapy. Most of these, for reasons we've talked about, are gene replacement strategies, where there's a haploinsufficient mechanism of disease, and the low-hanging fruit here is simply replacing that aberrant gene. Most of these are being delivered by AAV because of its tropism for the heart, and most of the trials are in early phase, phase I, phase II stages. So while there are many kinds of heritable cardiovascular disease, for our purposes, when we're going to talk about what's in early phase clinical trials, that world is quite small, and that's the world of primary diseases of the myocardium, cardiomyopathies. If one has PKP2-mediated arrhythmic cardiomyopathy, it's a very, very exciting time. So arrhythmic cardiomyopathy is defined as fiber-fatty replacement of the ventricular myocardium. The most common gene mutated in this disease process is PKP2, and it's a very simple loss-of-function, haploinsufficient mechanism. And gene replacement strategy is low-hanging fruit, and you can see that by the three companies that currently have phase I clinical trials to replace wild-type PKP2 in these individuals. And so as you can anticipate, the eligibility criteria for these trials is very straightforward. These associated PKP2 variants, you have to have that specific mechanism. These are for adults under the age of 66. You have to have an ICD. You have to have severe disease. You have to have ectopy, which might be one of the outcomes they're looking for. And you have to have low levels of antibodies, which can neutralize an AAV. That's very important for both the immune response that can occur, as well as preventing these antibodies from inhibiting the action of the virus. For myosin-binding protein C3, which is a haploinsufficient cause of hypertrophic cardiomyopathy, there is the MIPEQ trial looking for individuals in a phase Ib trial with myosin-binding protein C3 loss-of-function variants for C3 replacement gene therapy. This past fall was an exciting time. It saw the publication of this New England Journal article demonstrating that LAMP2 replacement in Danon syndrome is likely safe in this phase I trial. I mean, basically, with the same sort of haploinsufficient phenotype, this time due to an X-linked disease process, AAV9 loaded up with wild-type LAMP2 was given to individuals, biological boys in a phase I trial, and was found to be safe and a durable way of expressing that wild-type LAMP2 in the myocardium of these boys with Danon's disease. Interestingly, the enrollment for phase II is complete and looking forward to this trial beginning. Well, what about the reason that we're here, heart rhythm disorders and the SADS community? Right now, all the very promising gene therapies, they're there, but they're all in the preclinical phase. And so where are we right now? Well, there's a lot in this preclinical pipeline. I've just selected two examples here of in vivo proof-of-concept studies. There are many others, of course, in the literature. To your left is the suppression-replacement therapy for long QT syndrome type I, pioneered by Mike Ackerman, who you'll hear from in just a little bit, trying to address that dominant negative influence of the KCNQ1-mediated long QT syndrome, where suppression of the bad allele and then replacement with wild-type has been shown in this rabbit model to be an in vivo solution for these rabbits with long QT syndrome. And then to your right is an interesting study published quite recently for in vivo base editing. This is in vivo changes of a nucleotide in SCN5A, a major cause of long QT syndrome and Brigada syndrome, which in this mouse model corrected this mouse's arrhythmic phenotype. And so there are challenges in this way forward. Tremendous promise, but challenges. I think the scientific challenges revolve around target specificity. How do we target not only the specific tissue, the specific cells within that tissue, but the specific DNA sequence, or deliver a precise therapy is key. We need improved delivery and expanded delivery mechanisms. I think the value of AAV is central to all of this, but we need additional delivery vehicles. We have to minimize the immune response. That's central to keeping patients safe. We need better natural history studies, so we know how to properly ascertain what good phase one clinical trials would look like. We need to hear from the voice of our patients and their families, because quality of life cannot be silent in these phase one trials. We also have implementation challenges involving cost. We need to know the precise basis of individuals' genetic mechanism of disease, so if you don't know the genes for your hypertrophic cardiomyopathy, you cannot take advantage of HCM clinical trials. We need equity in the trials and access in the marketplace. At the end of the day, our patients need to remain our North Star. These are the individuals that we have to keep in mind as this field moves forward. This is Pablo, who had his cardiac arrest. You can tell he's feeling great because he's still able to text. They're in the hospital. People like JJ and people like Isabel are central to all of this. With this, my take home points for all of you is that the field of gene therapy is rapidly expanding. Gene therapies have arrived in the marketplace, primarily for non-cardiac indications. There's several early phase clinical trials for cardiomyopathies. Most cardiac channelopathy gene therapy approaches are in the preclinical stages, and gene therapy overall holds a tremendous promise for moving forward the care for these patients if we can balance risk with the benefits of treatment. So with that, thank you all very much. All right. Our next speaker is Dr. Michael Ackerman from the Mayo Clinic, and he's going to be speaking today about Don't Forget About Traditional Therapies, Recent Advances in the Management of SADS Conditions. Well, good afternoon, and I am the intermission between the current state of gene therapy that you heard from Dr. Landstrom and Dr. Webster on what physicians and caregivers need to know about gene therapy. So I'm the pause to say, until it's there in our world, don't forget about the traditional therapies, and we're going to take a look at a couple of them and how are we doing. So these are my conflicts of interest. You saw those. They're not going to affect our ability to where I'll detail three of those traditional therapies, and we'll focus on long QT syndrome and help you understand their place in our care of patients, even though they have not made it to guidelines yet. And we're not going to wait when we think of long QT syndrome and our treatment. Now, I would have loved to have been asked to tell you about the state of suppression replacement gene therapy, which you heard Dr. Landstrom mention, and I'm hoping that in one hour, is it one hour, Saranda? We're going to hear Dr. Nemani's name being the recipient of the Young Investigator Award for the KCNH2, our second proof of principle for gene therapy, which is working for KCNH2. It's really exciting, but I don't get to talk about that. Instead, we're going to talk about drugs, devices, or denervation and how we use these. And when we think of the traditional therapies, I need to remind us, because we're not doing very good at all. Most patients with long QT syndrome do not need and should not receive an ICD. We're still over-implanting these devices a lot. And when we look at the traditional therapies, Dr. Nivas looked at our program, and over the last 25 years of my practice, she tallied up to see that we have incorporated and implemented over 20 distinct therapies now among over 2,000 patients with long QT who have been treated at the Mayo Clinic. And when we tailor their therapy, and we personalize it, and we have it guided genotypically, we do very well in terms of eliminating, almost completely eliminating LQT-triggered breakthrough events. So right now in 2025, when we think of the state of therapy, the issue isn't preventing sudden death. A correctly diagnosed, well-wrist-stratified, well-treated patient, sudden death almost never happens in 2025. The challenge really is helping them live and thrive despite their diagnosis. And how are we doing with the living and thriving part? Not very well. If we're honest, and we peel back the curtain, and we actually ask our patients what they think about their current treatment configuration, this was pretty sobering to learn that over half of our patients have cited at least one major side effect of concern. Whether it's the beta blocker zombie, or the ICD-PTSD person, or the neuropathic pain post-denervation, there are real side effects of concern that drive us to find new therapies. And some of these aren't new. They're either rediscovery of old ways, or tweaks on the system. And I'm going to just illustrate three, I would say, atypical traditional therapies that we need to get better at. And the first is choosing not to treat, something we call INT for intentional non-therapy. Now it turns out, doesn't it, that INT is really hard for you all to do. To know they own a mutation, and you're saying we're not going to treat them. And we must figure this out, because we're over-treating patients. We're absolutely over-treating some patients. We grinded our teeth on this initial experience, and now I currently follow about 200 patients out of those 2,000 where we've chosen not to treat. We do QT preventative measures, but we're not going to commit them to prophylactic beta blocker therapy, or do a preemptive denervation, or install a defibrillator. What's quite striking to me, and a bit disturbing, is we are choosing non-therapy in people where we're removing their defibrillator. So when you have patients where we never would have put a defibrillator in the first place, and we're explanting them and moving to non-therapy, we have this incredible heterogeneity of practice, and we're going to need to figure out how to become comfortable and confident in the subset of patients who only need preventative measures, intentional non-therapy. Second one is, what about LCSD monotherapy, which we do a lot here at Mayo Clinic. And although the first denervation for long QT was published 50 years ago, 1975, it did not make it to guidelines until 2017. As a guideline-recommended or guided therapy. Now among these denervations, and I think we're now approaching 500, in 2017, the guidelines finally codified what we've been doing since 2005 for our patients, in terms of, if you had an appropriate shock, you could have denervation. If you hate your therapy, or you broke through your beta blocker, class one recommendation, and so forth. But what about denervation monotherapy? It's not in guidelines yet, and I would just encourage you to consider that, and we've started that. In fact, in our first 200 long QT patients that we encountered for denervation, one-third of them shifted to denervation solo therapy, and we now have about 150 patients where their only treatment for their long QT syndrome is their one-time left cardiac sympathetic denervation. Now what kind of patient, or what's the phenotype that is moving to denervation solo therapy? You probably have an idea. It's not a high-risk patient, because it's not a curative surgery. It's not a curative procedure. But I would basically put it as this. If you have a patient where you know they probably need therapy, you won't be comfortable doing intentional non-therapy, but they and you have chosen that life on beta blocker is not worth the living, and if they're LQT1, that's where denervation's anti-fibrillatory efficacy is absolutely the best. And this is our initial experience with that, and now it's continued with much longer follow-up and many more patients. So another traditional therapy that we're going to have to get comfortable with, and the challenge with this that I see out there is every program everywhere knows how to throw in defibrillators. And so since that tool is in the toolbox, it gets used. Now if that denervation option is not at your place, we all have a tendency to not reveal tools that are not in our toolbox. And I think we need to do a better job when we size up a risk assessment and we tailor our therapy to be able to say, I'm not sure that I have the right therapy or the right therapist or the right procedure for you, but maybe you would have an advantage elsewhere. That's gonna also be true, and Dr. Webster will probably comment on this, not every place is gonna be the appropriate place to deliver gene therapy. There are gonna be those gene therapy centers of excellence because there's gonna be a lot of issues surrounding the administration of that. And that should be okay with us because the patients deserve the best. The last is myxilatine. And you say, why is myxilatine here as a new one? It's actually kind of old, isn't it? In fact, it is, it's 30 years old, but I'm gonna show you a relatively new insight for myxilatine. 1995, Mark Keating discovered sodium channel-mediated long QT syndrome, published it in the journal Cell. That same year, Peter Schwartz took patients with sodium channel-mediated long QT syndrome and their mutant late-sodium-current-generating sodium channels and pharmacologically corrected it with the class II drug, the class IAB of myxilatine. And it's pretty incredible when you think about it that Peter Schwartz, I think I'm right, did the first genotype-directed therapy in all of cardiology when he used myxilatine to normalize the late-sodium-current-generating sodium channels. About 15 years ago, I started using it for patients not with LQT3, that was easy, but patients with LQT2, breakthrough cardiac events, long QT intervals, and we were like, wow, it's shortening the QT interval in them also. How can that be? It doesn't make sense, it shouldn't be working for LQT2. And from that initial experience that we published with Peter Schwartz and Leah Karate, we continued to expand that work to not a dozen patients, but 85 LQT2 patients, and then Leah Karate and our group published this last year in circulation. Not only in LQT2 patients does it shorten the QT interval, but those who are QT responders to myxilatine with LQT2, we demonstrated significant therapeutic efficacy. Beyond that, we showed the why. Why does it work anyway for type II long QT syndrome? The mutation is in that KCNH2 encoded KV11.1 potassium channel responsible for IKR. That loss of function results in a prolongation of the action potential duration. But that's not the only reason why the APD lengthens. It turns out that secondarily, that loss of IKR causes the otherwise normal sodium channel. Amino acid one through amino acid 2016 is completely intact, and yet, that normal sodium channel acquires late sodium current properties to it, to which the use of myxilatine then pharmacologically targets and blocks that, thereby shortening the APD in LQT2 patients. In other words, patients with LQT2 are really LQT2 and acquired LQT3 hybrids, and that's probably why the most difficult to manage patients are our LQT2 patients. That's where the greatest unmet therapeutic need resides. And so with one minute on my counter, I'll leave you with these four take-home points to consider as the end of this intermission before we get back to the holy grail of gene therapy. First, new therapies for long QT syndrome are needed. The families have told us that. The patients have told us that. The status quo is not acceptable. We're not there yet. The guidelines second, essentially recommend universal beta-blocker therapy for all long QT syndrome. Class one, if the QTC is beyond this, class two, if it's less than that, and because of the universal beta-blocker therapy recommendation, we have been creating beta-blocker zombies. Not my term. The families have given that term to us to describe those in which the beta-blocker has not agreed with them. So we need to do better. Third, eventually the guidelines will recognize INT as a bona fide treatment strategy, and we'll need to get comfortable and confident with that. And they'll also recognize, probably in the next iteration, LCSD monotherapy as part of guideline-directed medical therapy. In the meantime, last, don't forget about myxilatine for patients with LQT2 and a QTC above 500 milliseconds. And you don't have to wait for the guidelines to catch up with that. It'll be there, but it might not be there for another five years. So our patients need it now appropriately. With that, just wanna thank those entities that have partnered with us, and I'm looking forward to the panel discussion at the end. Thanks a lot, everyone. Thank you. Thank you, Mike. Now I'm welcoming to the podium Dr. Gregory Webster, which will talk about what do doctors need to know. And we're looking forward to learning that. All right, we're gonna go back to gene therapy again. And those of you who've worked with me know my particular hobby horse. So instead of what do doctors need to know, I'm going to say what do clinicians need to know in order to implement gene therapy. So this is our case with disseminated inflammatory complications, the 14-year-old boy with an ultra-rare cardiomyopathy. Listed status two for transplant. Decided to enroll for gene therapy infusion under a research protocol using the AAV9 virus. Andrew taught us a little bit about what that is already, and I'll mention it more. And after infusion, his course was complicated by myocarditis, myositis, which is inflammation of the muscle, the skeletal muscle, thrombotic microangiopathy, which is small vessel capillary clot, causing aneuric renal failure, requiring dialysis, non-sustained VT that you see off to the right. This is only one example of several episodes of non-sustained VT, and seizures. He had a pericardial drain placement, a chest tube placement, and had no meaningful clinical efficacy, which was not expected at this stage of the therapy. But what we see is that we had real side effects from gene therapy, despite the fact that we didn't have an efficacious endpoint, which is where we are with gene therapy right now, and our community has to be ready for that. So what I'm gonna talk about a little bit over the next 12 minutes is why do these things happen, why are we doing them, and what do we have to be ready for as clinicians that are gonna be addressing gene therapy, whether we do it in our center, to Michael's point about whether or not it's gonna be at every center, or whether we're talking to our patients about this and saying, is this something you wanna consider at a center that does this? So the good news is, there is clinical efficacy in early studies, but there have been problems. There were 11 deaths in the first eight trials published by 2020. I've excluded the last five years because I didn't wanna partially count trials in progress. In particular, there were four deaths in the AT132 trial for myotubular myopathy. That was a serious kind of discussion in our community. And so far, about 30% of clinical trials with AAV vector have reported serious adverse events, and the AAV vector that Andrew mentioned, I'm gonna use this diagram to say adeno-associated virus, which is the packaging that gets gene therapy delivered. I'm gonna use this diagram to talk our way through it, so I'm just gonna orient you to this diagram. So on the left yellow side is viral delivery, both getting it into the bloodstream and then to the heart. Endocytosis, which gets it into the cytoplasm, delivers the capsid particle into the nucleus, whereas the first time the DNA is unpacked and allowed to have its therapeutic effects. After transcription, off to the right in the blue box, it undergoes the process that Andrew told us about, that central dogma of biology being translated, if necessary, into RNA. And then the cluster of blue dots is gonna represent the actual protein product. After it's done what it needs to do, it goes to a proteasome where it's broken down, and capsids are actually broken down in the same class of proteasome. And then transgene-encoded protein peptides and capsid peptides are eventually presented to the surface through the major histocompatibility complex, which all breakdown products are doing, not specifically the products that are transgene, but those transgene products get presented to the cell surface as well. So I'm gonna walk us through viral delivery, then talk about therapeutic effects, and then talk about why this matters. So as was alluded to earlier, 25% of people have pre-existing immunity to AAV vector. There is a high degree of homology between wild-type virus and the vector capsid that's used in gene transfer. And so if you've had prior contact with these adeno-associated viruses that are being used to package the gene therapy, you have pre-existing immunity, and neutralize the AAV before it can be delivered to the tissue of choice. And this lower right-hand corner shows the time course from hours to days to weeks to months. And if you have complement factor, complement protein, and pre-existing antibodies, you are going to inactivate your AAV in the first several hours, and the red bar shows this idea of clearing AAV out of the bloodstream. So you won't have successful delivery to your heart. Then if we think about getting it actually to the heart, so now we're in the heart or in other organs, you have to get endocytosis, and you have to actually get it into the cell. And in 36 trials of cardiovascular gene therapy that have been registered on clinicaltrials.gov, 33 of them use AAV, so that's what I'm gonna focus on. I'm gonna leave the lipid nanoparticles, the lentivirus aside. And there are 12 occurring types of this virus with different tissue tropisms. And you have to deliver a lot. So we're talking about one times 10 to the ninth, to three times 10 to the 14th viral particles that are being injected into your body. Compare that kind of intellectually to the idea of getting sneezed on, right? That's how we deliver viral particles otherwise. And that's necessary for efficacy, but also because in current manufacturing processes, and it's getting better, only about 30% of these capsids are being correctly and totally loaded so that they're at their maximum efficacy. So you've got to give a lot of this. And the side effects are in the liver, the kidneys, the lungs, the brain, and then the thrombocytopenia and the thrombotic microangiopathy. And I'm gonna give you some examples of why this happens or where this happens. So hepatotoxicity happens in between 25 and 90%, some of which is subclinical, but associated with elevations in your AST and ALT. That's because there's high hepatic tropism of AAV. AAV likes to go to the liver. In addition, the liver is highly vascularized, so a ton of blood goes to it. And there are fenestrated sinusoidal endothelial cells as they pass through the liver, which allows the contents of the blood to get to the liver cells quickly. Thrombocytopenia happens in up to 90% of patients. Some of this is because of the immune process I'm gonna mention briefly, but some of it is direct activated of platelets by AAV. And thrombotic microangiopathy, which is what the patient I told you about at the very beginning of this talk actually had, is due to activation of this process. And I'm showing you a diagram from this Schwartzer article which explains how much I'm under-representing the complexity of the immunologic process that's happening here. This is not simply a one-time problem. It is multiple pathways of immunoresistance that are reacting to the virid capsule. Now, I'm gonna show you in one slide something in particular, but notice that there's complement complex in here that I'm gonna elude in the next slide. And then dorsal root ganglion pathology, which is a rare but important complication, is due to direct neuronal and axonal viral toxicity. So there's a lot of ways that dumping an enormous amount of virus into someone might be bad for you. And that's what we're seeing in a small percentage of the people that undergo gene therapy. So what do we do about it? So here we are, we're physicians and other practitioners that are gonna actually give gene therapy. How do we prevent this? So you may remember from your training that there is this pathway of B cells and T cells. And you get a dendritic cell, and it presents to either naive CD4 cells or naive CD8 cells. The naive CD4 cells control with helper T cells and then activate the B cell response, whereas CD8 positive T cells are effector T cells. What we have discovered as a community immunology is that you can block this process, tacrolimus, corticosteroids, and rituximab. And most gene therapy is currently giving some combination of serolimus, rituximab, and cyclosporins in order to, or steroids in general, in order to decrease this response. And I mentioned the complement pathway as well. That's the third angle, but I didn't have a good diagram to show it in a simple way. These are what are causing those side effects, this huge immune response. And that's why we are immunosuppressing people during the acute phase of delivering viral particles. All right, so I showed you this viral delivery process. So why are we doing it? Of course, we have therapeutic effects, and that's why we're doing this. I don't wanna stand up here and say, what do MDs need to know? It's only terrible things. Actually, this is the future. I agree with everybody who's sitting up here. And in fact, reproducible early data shows clinical efficacy in more than a dozen diseases. There are 84 cardiac gene trial therapies initiated, ongoing, or completed in the US. Five of those are in children. This is not what we usually do. We usually let the adults do it and then later apply it to children. Here, these are diseases that are pediatric-centered that we're doing cardiac trophism in. And so this is the future of what we need to do. We will continue to move forward on many of the problems that I've brought. None of those are entirely unsolvable issues. The good news is I deeply believe that we will be able to treat new diseases with this. And Andrew gave us a sense of how many are coming. Do you stay treated? That's the next question. What happens later? Do you stay treated? So this is Luke Coombs, and Coombs and his song, they say nothing lasts forever. The idea of gene therapy is that you deliver this DNA, it becomes a little circle in the nucleus and pumps out protein. And that does happen. Unfortunately, there's not a ton of data in hearts, but these are data from various other gene therapy products. And all you need to know is that the gray bars represent places where the efficacy is declining. And that happens for a couple reasons. One is something called vector dilution. And vector dilution means that you deliver the vector where you want it, but then the cells continue to divide. And every time you divide, you only get half the amount of DNA that you got the first time. And so you start diluting the gene product. Fortunately, cardiac cells, fortunately for our patients, cardiac cells don't divide very much. So vector dilution is less of a problem for us. But what is a risk for us is that intrinsically those proteins that you're introducing eventually get broken down, both the capsid and the transgene encoded protein particles, and they get presented to the exterior of the cell. And effector CD8 positive T cells will eventually get rid of some of the cells that you have most effectively delivered by viral particles to. That doesn't mean it won't work. It doesn't mean that all of it will go away. But there is reason to think that gene therapy doesn't have to be durable every single time we do it. And it's another piece of what we're going to have to address as a group. And as we talk to patients and say, what do you expect? We need to address the fact that there's no guarantee that gene therapy will be an indefinite part of the solution. So I was asked to say, what do clinicians need to know? And I hope what I've done here is explain why these complications happen. I told you about our 12-year-old, our 14-year-old now, who had meaningful complications of immune activation and microthermotic events. And that's largely because of viral load, which I think we will get better at, and multi-organ inflammation that we're treating with immunosuppression. I don't think we are going to be dealing with these problems forever, but we are right now. But there's good news, which is there is efficacy. There has been effectiveness in early trials. Not all of them are cardiac. And importantly, we are highly responsive to pathology. We're actually treating the problem in the cell as opposed to treating the symptoms that result from the disease. And children are in early trials. And then we'll have to address durability, both long-term immune recognition and then vector dilution, which is fortunately less critical in cardiomyocytes. Like everybody up here, I am excited about where we're going. I don't think we are entirely done yet. And those of us who are clinicians get to stand up and say we are living through some of the most exciting times, and we will deal with these issues together. But the first step is for all of us to recognize what they are and why our patients are having the symptoms that they're having. I want to thank you for inviting me, and thank you very much. All right, for our final speaker for this afternoon, we've got Dr. Patrick Eleanor from Mass General, and the title of his talk is Looking to the Future, Where Will We Be in 2035? Thanks, Marty. What a great set of talks. You guys are tough acts to follow. So we'll try and stumble my way through it. I would agree with Dr. Landstrom that we're in the midst of an absolutely transformative time for gene therapies in cardiovascular disease and in diseases in general. If you just look at the last couple of years for sickle cell, we've had gene editing described in two back-to-back papers for CRISPR-Cas9-based editing to try and treat sickle cell. For any of those who trained in our generation, this is a devastating disease. Watching young folks come in with sickle cell crises, die in their 30s and 40s, and having the promise to give them a therapy with a single shot to try to restore it is incredibly humbling. And I think that type of promise is exactly what we hope to see in the cardiovascular field in the years to come. The same is happening in lipids. This is a slide I stole from my friend, Seth Catherason. I don't have any financial interest in the company VIRV, but this particular trial was actually stopped. It shows both the promise and the peril, but targeting a base editing strategy to disrupt PCSK9, it's a single base variant edit, lowers cholesterol and lowers it dramatically. The problem, this particular trial was stopped because of hepatotoxicity in six of the patients. They've gone on to a second round therapy, which they hope will be more promising. But the point is, is that you can quickly, effectively, and sustainably reduce lipids with a single base edit. It's been shown in mice for genetic cardiomyopathies, and as Dr. Ackerman and his team have shown for long QT syndrome, a single base edit for MYH7 can, in mice and a couple of different lines, reduce fibrosis and hypertrophy. So what are some of the potential advantages? Obviously, it's an on-target therapy. If you're studying genetics, you have your causative gene, there's a potential for a single therapy, or maybe at most two, as opposed to a lifetime of treatment. Reduced healthcare utilization, coming to see us is expensive, whether we admit to it or not, over one's lifetime, it's incredibly expensive. And hopefully, improve quality of life, getting folks back to that life we want them to lead. And if you had a common platform or approach, we talked about a handful of diseases. This is a panel from one of the companies. There are many, many different cardiovascular conditions, some common, some rare. What are some of the challenges we face? We touched on a number of them today. One, choosing the right target and target therapy. Really the field's still in its infancy. I mean, we're early days compared to some of the other areas that we're looking at. Safety, we've heard about in a number of different things, mentioned one with VIRV and others. The delivery mechanism, I think, is going to be the single greatest challenge. We know the genes to target. It really comes down to delivery and payload. And that delivery, if we get safer and effective ways, that will close a lot of the gap that we face. There are certainly going to be ethical concerns. You heard from Mike that some patients choose not to treat. I would expect that even with malignant cases, some will choose to treat, some will choose not to treat. There's going to be limited availability inherently with any therapy like this, and it's certainly going to cost a fortune. These are not going to be cheap therapies because most of them are going to be boutique therapies. The rarer the disease, the more boutique the therapy will be. It'll get a rare disease designation and therefore almost certainly a high price. We don't really know the long-term effects for some of the therapies. Are they sustained as one? Are they off-target effects? And are there deleterious effects are certainly another major concern. There have been deaths. Obviously, this case was high profile. You heard about some of them from Dr. Webster a moment ago. But a young patient with Duchenne's muscular dystrophy died after AAV infusion therapy. There have been others, and we'll certainly see this. I think that does give us some pause. On the promising side, when you look at the genes that are involved, we are at a very interesting time. In the last two decades, the genetics of most common diseases and rare diseases has largely been solved. I'm going to show you two slides on AFib. You may ask why I'm going to talk about AFib in a SADS session. The reason is not just because I do it. That's not the point. I'm going to bring it back to the diseases in general. To just make this, this is a Manhattan plot that came out earlier this year for AFib. We've gotten to saturation level for common diseases of understanding the common basis of genetic diseases. It's important to remember you can swap in a plot for dilated cardiomyopathy, hypertrophic cardiomyopathy, QT interval. You'll get the same type of Manhattan plot. When you sum up these genetic variants, people at the top 1%, 2%, and 5% are going to carry the same risk as a rare causative Mendelian mutation that we're used to looking at. The challenge is you're not really going to be able to target these very easily. We could try and target a pathway, maybe for Brugada syndrome where you have one large spike in this Manhattan plot, or maybe for AFib where you have one large spike. You could try to alter something at that highest level of risk. But largely, you're just not going to be able to tackle these in the years to come. I don't expect a huge amount of progress in this type of polygenic risk and base editing those types of diseases. We're just going to not be able to fix those in 2035. The primary focus will be really around sequence-based ascertainment of individual variants or mutations. This has been done for AFib. I'll skip all the details other than to say that the top five things associated with AFib. Number one is Titan. Obviously, it affects a lot of different cardiomyopathies. The reason I illustrate it here is, again, not the point about AFib, but it's because 1 in 250 people in the world have a terminating variant in Titan. If you want to fix two genetic conditions in heart disease, you should fix lipids and you should fix Titanopathies. They both have the same frequency, and you can take every other cardiovascular disease that we have, or every other rare disease, wrap it up, and you'll get the same frequency as the number of people walking around with Titan mutations. So you can't ignore that one, whether it causes heart failure, cardiodyelated myopathy, AFib, restrictive myopathy, or others. The problem, I think, is illustrative. This is a cartoon of Titan. This came from one of our earlier papers. There are thousands of loss-of-function variants in Titan. On the top was AFib. You can swap in DCM, HCM. They're all interchangeable. The variants are everywhere throughout the protein. They cause, they have a large number of mutations, and we're not going to be able to fix all of them. You could try. I think with base or prime editing, it's a brute force thing. You could just make every single guide that's out there. You'd probably get the 60% that you could efficiently target, but they would all be custom rearrangements. So even if you had a common delivery mechanism, you would have to have an off-the-shelf approach to packaging. We heard from Dr. Landstrom, if it was as simple as replacing the protein, I think we'll make more progress there. And then you could think about targeting a related pathway to try and correct this disease in many thousands of individuals. So we heard about, from Dr. Landstrom, base and prime editing and all of their associated flavors to go and individually replace those variants. I think the problem is obvious when you look at the Titanopathies, that that's going to be a challenge. The other is delivery is really, I think, the major challenge in our area. The dependency that we have on AAVs, I think it should generate a lot of excitement. They're what we have. They're really cool. They have increasing specificity, but they're not going to be what ultimately gets us there. I think it's unlikely. I think we will see lipid nanoparticles, virus-like particles, and bispecific antibodies that will get us there in the future. And we really need cell type and organ-specific targeting to have the least toxicity and the greatest efficacy. And I think we'll see some other options. Another approach, if you have thousands of mutations for Titan, is to try to restore it by altering other potential pathways. And that's something we haven't touched on. Essentially to do reversion screens, where you start with the disease state over here, in red, and then you're trying to disrupt individual genes or pathways that then revert you towards normal. And I think that will be a complementary approach. We've been doing this for the last couple of years, where you produce large-scale, you know, pick Titan or your favorite gene. You can swap in BAG3, 1QT, or anything else. You grow the cells at scale. You plate them. You perturb them with hundreds, if not thousands, of either chemical compounds, genetic perturbations. With high-content imaging, you look for things that go from the disease state to the wild type state, and then you follow it up with functional evaluation. I'll show you one. This paper was out online in BioRxiv. I should have put the reference in there, but it was Chopra and colleagues. A control cardiomyocyte, a Titan knockout, where the sarcomeres are essentially ablated, another gene related to it. But interestingly, we found this one that basically restored sarcomere structure, both in wild type cells and in Titan knockout cells. When we then went and just brought them back into engineered heart tissues, we had the controls, the Titan, obviously, with reduced force, and then this gene, HSPP7, that restored contractile function. Obviously, just in an engineered heart tissue and not in a human, but it's a conceptual approach that I think is interesting. We're now taking a rather brute force approach to this, essentially going through every gene in the genome, as well as many thousands of compounds to take and say, can we find other genes that would potentially help us to restore gene function for a gene like Titan or others? You can just swap in any of your favorite genes and do this type of reversion screening. Where do I think we are in 2025? Really exciting time. I mean, if I was graduating medical school now, I'd probably go into a biotech company or join one of these guys' labs to try and work on a targeted therapy. I think there's great promise, but as we heard a moment ago from Mike, I think our EP labs, ICDs, beta walkers, and current therapies are safe for now. What do I expect in 2035? We're going to have safe, effective organ and cell type specific delivery tools. I think those are not far away. There are a lot of biotech companies. That is their sole mission in life, and they've made a lot of progress. We'll have multiple replacement therapies, so that overexpression that you heard about from Dr. Landstrom, we're going to have those for a number of different diseases. I think they will have advanced in the next decade. We'll have a limited number of options. I think if you have a founder mutation in a large number of individuals, then base or prime editing makes sense. Go to those individuals. You just can't apply that at scale across thousands of different individual mutations. I think we'll start to see some therapies emerging targeting disease pathways and looking for reversion type screening. Those will be available or starting to be in about the next decade. Thanks very much. I get to work with a really talented team, both at MG, Mass General Brigham and the Broad, and happy to join the panel discussion. Thank you, Patrick, and thank you to all the speakers for really an incredible quality of the talks. We have about 10 to 12 minutes for discussions. Yes, there is a QR code, but there is also a very full room, and I will invite people to the podium and maybe ask first in person. Let's not give to the teenagers, kids of Andy, too much satisfactions about the use of the remote coding. Please come to the podium and ask questions. While we're waiting for people to come to the podium or to the microphone for the question, I'd just like to bring up a point for the panel to discuss. There's two big features. Number one is we want to be part of the gene therapy future, and so we need to be trained to participate in that, but at the same time, at our center, we may already be doing gene therapy, and we need to be ready as cardiologists to deal with the aftermath. Like Dr. Webster showed, we also had a patient at the University of Utah that died, a muscular dystrophy boy, within five days of his infusion with overwhelming cardiac dysfunction, and he went from having this dilated ventricle to this incredibly hypertrophied ventricle. That was all inflammation, and as we went through kind of like the root cause analysis, I was thinking, well, maybe we should have put him on ECMO, got him through this immune process. Maybe we could have saved him, and then spoke to some other people where they tried that, and it didn't work, so a lot of complicating things here. If people are doing gene therapy at your center, you've got to have a plan of action for how you're going to manage these kids and how you're going to get them into clinic or the ICU really, really quickly, but I just wanted to open this up for others to talk about. I think there's a couple points. I think there will be cases where ECMO will work. I mean, I do think there are times that there's direct systolic dysfunction as part of the side-effect of gene therapy, but a lot of it is microvascular, and if you're talking about microvascular occlusion and small vessel deterioration in multiple organs, that's not what ECMO does best. The good news is, and I think several people got this across, but most recently in the last talk, I think we're in an interim phase where we need to be ready to do this for the next five to seven years, but my hope is that we will not have, I think we'll have better trophism as time goes on. I also think that a little bit our colleagues in transplant medicine have learned immunosuppression without necessarily having to learn every bit of immunology that affects the heart, and I think that's going to happen for us, too, is that we're going to need to know practical immunology and practical immunosuppression to help gene therapy in the very short run, but we are not going to need to be basic science experts about immunotherapy. We're going to have to consult our colleagues who are and develop plans of care to be able to rapidly intervene for folks who are decompensating quickly, because I think it's going to be immune therapy as much as kind of our traditional cardiovascular support therapy. Go ahead, Patrick. Yeah, I mean, I guess I agree. It's just a transitional state, because anything that's going to rely long-term on any immune therapy is just never going to be scalable, right? I mean, not in an era where we have RNAs. Like, if you look at VIRV and targeting lipids with a single shot, there's an appeal, because you can knock it out with a single shot, but they're not using an AAV mechanism, right? I mean, that will allow you to get the scale, but you already have an RNA-based therapy with Inquisirin that's on the market and available, and it's once every six months is not so bad for dosing, but I think it's naturally going to limit our market, and so it'll force us to get quickly to non-AAV mechanisms, yeah. Well, there are questions from the iPad, so I think this is mostly for Mike and for everyone else in the panel. Why not using a flecainide in LongQT2? Mike, you want to take this one? So the question of, for flecainide in LQT2, that's pretty easy. It doesn't work. So for flecainide, flecainide is not a class 1B drug, so it has very little particular activity on the late sodium current. It's a peak sodium current blocker, so where flecainide has worked great for CPVT and other lesions where you get effectively reactivated sodium channels for which the flecainide is then blocking, but that's why there's actually in LQT3 even, the vast majority of mutations are myxilatine sensitive, but every once in a while, if you have a LQT3 mutation where that mutation's biophysical properties is reactivation of the sodium channel, then flecainide is actually better than myxilatine, but there's no reason in LQT2 where all of those effectively result in late sodium current generation why you need a class 1B type agent like myxilatine. Before, sorry, I have a question again on the LongQT syndrome that I think is like, we are discussing gene therapy and we will have the problem of finding the sweet spot of patients that will benefit the most, and certainly in the PKP2ACM trials, that has been a quest to identify. Now for LongQT syndrome, based on what you presented, where do you see the sweet spot of the candidate patients for gene therapy, considering that you are the first one that says we defeated in a way sudden cardiac death in managing LongQT patients well, and there is a lot of alternative, including the non-treatment in some cases. Yeah, no, I think that's a great point. I think it will be an evolution of what is the definition of unmet therapeutic need. So we, just for full disclosure, our LQT1 gene therapy was way further along than our LQT2. We were ready for an IND-enabling LQT1 trial. We've already shown the LQT1 in rabbit therapeutic efficacy trial. We and our corporate partner paused it. It was first paused and actually axed by Pfizer when we had licensed our IP to Pfizer. They axed the development, gave it back to us. And why did they ax it? They said, you know, we're not ready for the primary definition of unmet therapeutic need to be I hate my beta blocker. So for LQT1, when the greatest issue is I hate my beta blocker, that's gonna be a difficult first order. And so whereas in LQT2, that is our priority lesion within the long QT syndrome space, there is actually unmet need. There are more breakthroughs. So you're gonna envision LQT2 patients on therapy who still have shocks. And there are those. And then eventually, once you establish that, I can envision that five years from now, LQT1 will be brought into the queue. Because while cost is ginormous in the beginning, it won't be five to 10 years from now type thing. And then you will have the opportunity where to not have to be on beta blocker therapy in LQT1 to be a potential bona fide option. And I kind of pushed back at that when we were making that decision or when they, the industry made it for me. But I get it. It makes sense. And I think that was probably the wise, and if I had a do-over, I would have started our discovery program with KCNH2, LQT2. Because we always knew there was a differential in unmet need. We're gonna take one more question from the chat, but we recognize we're at the time. And if anyone needs to get up to another conference, please feel free to do so. But just one of the questions in the chat that I'd like to direct to Dr. Landstrom. Someone asked, will we have cardiovascular genomics advanced fellowships in 2025? And what might that look like? I do love the question. I guess the answer is I wish we will. I don't know if there'll be formal pathways. In fact, if the timeframe is 2025, there will be no formal pathway. I think, though, that maybe perhaps we've heard today is one reason why we need to consider moving forward with a formal pathway. I think the ability for all of us to care for these patients hinges more and more on understanding the genetic cause. And I think the uptake of gene testing for disease states where gene testing is standard of care is embarrassingly low. I think we collectively have more work to do to become more fluent in what it means to see these patients. And I don't think you have to be a card-carrying cardiovascular genetics specialist because these individuals are everywhere. I think we heard from Dr. Elnor that all these diseases, common, rare, congenital, acquired, all of them have a genetic basis, all of them. And I think it just highlights, again, that we have to be able to account for it formally in our educational process to be able to say, if you're seeing these patients, that you need to have a certain sort of foundation of knowledge. And what that means, I think, is up for debate. But I think we need something there formally in place. This was a fantastic session. In the interest of time and the sessions ahead of us, we need to close. And I just wish to really thank all the four speakers for an incredible quality and thanks for organizing these sessions. Thank you.

gene therapy

cardiovascular diseases

SADS conditions

CRISPR-Cas9

RNA therapies

genome editing

immune reactions

long QT syndrome

therapeutic approaches

clinical integration