Good afternoon, everyone. I'm Nicole Leber with Investor Relations at Lantern Pharma, and welcome to Lantern's Key Opinion Leader webinar on synthetic lethality, the unique and powerful mechanism of action behind Lantern's drug candidates, LP-184, LP-284, and LP-100. In oncology drug development, synthetic lethality has become a highly desired capability for small molecules as it promotes the selective antitumor toxicity of cancer cells while reducing potential side effects to normal cells. This mechanism of action can exploit vulnerabilities in cancer cells known as DNA damage repair deficiencies, which are common in 25%-30% of solid tumors. Using synthetic lethality, Lantern's drug candidate, LP-184, has demonstrated nanomolar potency across a comprehensive number of in vitro and in vivo preclinical models in solid tumors, as well as adult and pediatric central nervous system cancers. Based on its synthetic lethality mechanism of action and strong preclinical results, Lantern is targeting advancing LP-184 to a first in human phase I clinical trial in the first half of 2023. For today's KOL webinar, you'll be listening to Dr. Zoltan Szalasi, who is an expert on synthetic lethality in DNA damage repair deficient tumors. Dr. Szalasi serves joint appointments as group leader of the Translational Cancer Genomics department at DCRC and as faculty of the Computational Health Informatics Program, CHIP, and Assistant Professor of Pediatrics at Boston Children's Hospital, which are affiliated with Harvard Medical School. In today's webinar, you will hear Dr. Szalasi talk about a wide range of topics surrounding an introduction to synthetic lethality and how drugs with synthetic lethality can be used to treat tumors with DNA damage repair deficiency. You'll also hear how synthetic lethality can be leveraged to treat cancers with a subtype of DNA damage repair deficiency called nucleotide excision repair. Finally, you will hear him discuss the promising potential of LP-184's synthetic lethality for DNA damage repair deficient tumors, including how LP-184 could be combined with other FDA-approved agents to enhance its efficacy. With that, I'll now turn the webinar over to Dr. Szallasi. Dr. Szallasi, can you start us off by telling us about your lab and your lab's research focus? My lab at Boston Children's Hospital is interested in studying DNA repair deficiencies in solid tumors, various solid tumor types. We are particularly interested in developing methods that would use next-generation sequencing to detect and quantify individual DNA repair deficiencies in human tumor biopsies. That would allow us to prioritize patients that have a given DNA repair deficiency present in their tumors, and that would allow those patients to identify those patients that would most likely benefit from a treatment that would target that specific DNA repair deficiency. That's our main focus. We're mainly using next-generation sequencing, mainly somatic DNA, so the tumor DNA, both in the tumor DNA isolated from the tumor cells and also from cell-free DNA. That's our main research interest, and we are also trying to come up with strategies or, and identify molecular contexts in which these synthetic lethality-based therapies would be most efficiently used. Can you tell us about synthetic lethality in DNA damage repair deficient tumors and about some of the drugs that are being developed based upon synthetic lethality concepts? Synthetic lethality was mainly kind of proposed or created in the context of DNA repair deficiencies. The basic idea is that for most cancer therapy, the drugs are going to do some sort of a DNA damage that will prevent the replication of DNA. Of course, if DNA cannot be replicated, the cells cannot divide, the cells or the cancer cells will probably or obviously will die. Hopefully, this is the way you can eliminate the tumor. There are two parts of it mechanistically. One is that if a given DNA repair mechanism is missing, then hopefully there might be drugs that will be very efficient on that particular tumor type. The other part or the other arm of this treatment would be interfering with the checkpoints. In order to repair DNA damage, you need two things. You need a DNA repair mechanism, also you need to give some time to the cell to activate those mechanisms. Those are called the checkpoints. When DNA damage occurs, the cell senses the DNA damage. It slows down cell or stops replication, then the DNA repair mechanisms are activated and the DNA damage is corrected, then DNA replication and cell division can proceed. Basically, that's the idea that if you interfere with either of these arms when those are present in a given tumor type, then that will give you a potentially very efficient synthetic lethality-based strategy for treatment. For the PARP inhibitors were introduced in the context of homologous recombination deficiency. More recently, there have been several drugs in clinical trials that are interfering with the checkpoint. These are the mechanisms that are needed to give time for the cell to repair all that DNA damage. The idea is that if you block this checkpoint, then the cell will not have enough time to repair the DNA damage. In combination with the DNA-damaging drug, the cells will basically die. There are several clinical trials right now in progress. ATR inhibitor is one example. berzosertib would be a good example of drug. VRK1 inhibitors are in clinical trials in combination, for example, with PARP inhibitors. That would be adavosertib or CHK1 inhibitor, that's another checkpoint protein, as prexasertib. Basically, these are relatively advanced stages of other lethality-based strategies. What has the clinical experience been with PARP inhibitors, and what are some of the lessons that have been learned? In general, the experience with PARP inhibitors has been very positive. Initially it was thought or it was hoped that PARP inhibitors would work out really well in homologous recombination deficient cancer types, especially those that have inactivating or pathological mutations of the BRCA1 and BRCA2 genes. Those tumor types would be mainly or predominantly ovarian cancer, to a lesser extent, breast cancer, and to some extent prostate cancer. The clinical trials have been completed on tumor types, and in general, the experience has been very positive. Progression-free survival was very significantly increased with various schedules or various forms of PARP inhibitor therapy. Now the overall survival data are also coming in, and those also look very promising. In general, this whole concept of using synthetic lethality, connecting homologous recombination deficiency mainly as determined as BRCA1 and BRCA2 mutations and PARP inhibitors have been a very successful strategy. In general, patients have benefited a lot from this overall treatment strategy. We have, of course, learned a lot during these clinical trials and the associated research processes or projects. There was a relatively simple idea or mechanism how we thought PARP inhibitors might be working. Obviously, as always in biology, the situation is much more complicated, much more complex. We just started to understand these more complicated interactions between PARP inhibitors and the mechanism by which PARP inhibitors work. We are still working on that, and obviously we still have a lot to learn about, for example, combination of various treatment options. For example, PARP inhibitors and immune checkpoint inhibitor therapy may have some very efficient combinations. Understanding the mechanism, it's a very long process. What genes are often involved and dysfunctional to make tumors nucleotide excision repair deficient, and what are these tumor types? Nucleotide excision repair is, well, like everything else in biology, it is extremely beautiful, extremely complex process with many, many, many players. A few things should be kind of stated for clarity. One is that the DNA damage in nucleotide excision repair can be sensed in two different ways. One is that if you have a DNA damage, a bulky adduct, so something that's sitting on the DNA like a large, you know, chemical moiety, and that's kind of distorting the DNA, the structure, that could be detected anywhere in the genome, and that's called global nucleotide excision repair. The other sensory arm is related to transcription. When you're transcribing DNA into RNA, it's a very complicated, very complex process, and obviously if there is some sort of a bulky adduct sitting on the DNA, then the RNA polymerase, the RNA transcribing machinery cannot proceed, and that could be sensed as well. Both of those sensory mechanisms are going to feed into the same common pathway, and that will use the same bring the same biological process to remove that part of the DNA that has been damaged and it fix it, and fix it, and then just kind of correct that part of DNA that was damaged. There are many important players on that. Usually, those genes are named something called ERCC genes. ERCC2, ERCC3, ERCC4, ERCC5, ERCC6 are the key players that play very important role in this individual part of nucleotide excision repair. The interesting or the important part in these names is that in some cancer types, some of these genes are quite frequently and recurrently mutated. As I mentioned, in bladder cancer, for example, it is well known that about 10-15% of bladder cancer cases have an inactivating mutations in ERCC2. That sort of suggested that there might be something going on at, for example, in bladder cancer in terms of NER deficiency. These are the genes that one would want to look at in terms of either inactivating mutations or down-regulations or suppression if one is looking for nucleotide excision repair deficiency. Expanding on that last question, could you explain how nucleotide excision repair deficiencies could be leveraged to develop drug strategies to specifically kill tumor cells? Nucleotide excision repair deficiency has a very interesting history. We have known about nucleotide excision repair in general for many, many decades. Those guys that received the Nobel Prize a couple of years ago showing or kind of discovering and describing the various DNA repair mechanisms, described nucleotide excision repair several decades ago. Implicitly, we knew or we thought that nucleotide excision repair should be damaged in cancer types as well, in various solid tumors as well, we didn't really have much evidence for that. It's not that trivial to detect, A, given DNA repair deficiency in a real human cancer biopsy, in a real human patient. Since platinum treatment has been around for many decades since the eighties, that means close to 40 years now. Since we knew how platinum works, introducing various forms of DNA damage, either cross-linking between DNA strands, but more frequently within the same DNA strand. We knew that platinum, based on its mechanism, should be very effective against a tumor or any sort of cell that has damaged nucleotide excision repair. Since platinum is a very efficient drug, if you just think about Lance Armstrong, right? He was treated with platinum, and he had very advanced cancer, but one can find many other examples. In some cases, platinum is an extremely efficient drug to treat or to eliminate cancer cells. We sort of expected that nucleotide excision repair deficiency should be present in cancer, but we didn't really have hardcore evidence that it is actually present in the real human tumor cases. Recently, two years ago, Kent Mouw's lab or laboratory showed that this is actually in fact the case. He basically looked at a particular gene, it's called ERCC2, which is very often mutated in bladder cancer, and this is one of the key enzymes of nucleotide excision repair. He just simply showed that if you take these mutations that are frequently present in bladder cancer and you take cell lines, and if you introduce those mutations into those cell lines, then you're actually making those cancer cases nucleotide excision repair deficient. Basically, this was the first evidence that nucleotide excision repair, nucleotide excision repair deficiency is in fact present in human tumor cases. Therefore, it should be exploitable therapeutically, if by nothing else, than by the administration of platinum, which would be a very efficient drug to treat nucleotide excision repair deficient cells. Shifting now to Lantern's drug candidate LP-184, could you tell us how LP-184 works in tumors with nucleotide excision repair deficiencies? LP-184 or its like earlier incarnation, which is irinotecan, At least irinotecan has been around for now almost 30 years or so, or even more. It will bind to DNA. It's an alkylating agent. It will form bulky adduct. It's not a huge molecule, but it's a relatively large molecule. It's going to bind DNA, it shouldn't be there. If, for example, RNA polymerase in transcription wants to proceed along DNA, it will kind of hit it. Unless it's removed, it just cannot proceed, the transcription is going to be blocked. There have been a couple of very nice papers in the early 2000s when a Dutch institute, Hoeijmakers' group, showed very clearly that transcription-coupled repair very efficiently remove this drug. This is kind of interesting. We are not quite sure we understand why it is so efficiently removed by transcription-coupled repair, but that's kind of the advantage of this drug as well. Because if in normal cells, non-cancer cells, transcription-coupled repair works really well. That means that most normal cells in our body that are not cancerous, that do have transcription-coupled repair, will be able to remove this drug very efficiently, or these bulky adduct, these DNA damages very efficiently. That's what LP-184 or irinotecan does. It just binds the DNA. It is removed by transcription-coupled repair. If nucleotide excision repair is damaged, so if either the transcription-coupled repair sensing arm or the common pathway, which, you know, that is the effector that actually fixes the DNA damage, then that's going to be lethal for the cell because it cannot remove this DNA damage and DNA replication or transcription is completely blocked, and the cell will die. That's what these experiments show. These very early experiments showed very clearly, and just to give some impressive numbers here, if... Just kind of going back very briefly to PARP inhibitors and homologous recombination deficiency, if you remove BRCA1 or BRCA2 from a cell, so you have a normal cell and you have a normal cell, or you have a cell with BRCA1 activity, and you remove the key homologous recombination gene, BRCA1, that cell will become 100 to 1,000-fold more sensitive to PARP inhibitors. That's extremely. That is a huge therapeutic window there. There's a very similar therapeutic window for LP-184 in the context of nucleotide excision repair deficiency. If you have a control cell, a normal cell, and another cell with the only difference is that you remove one of the key nucleotide excision repair enzymes, let's say ERCC2, then that cell will become several orders of magnitude more sensitive to irinotecan relative to the normal cell. That's a huge difference. That gives a very convenient therapeutic window when the doctor or when in the, we'll know that the drug will not kill, at a given concentration, will not kill the normal cells because those are very efficiently dealing with the DNA damage as opposed to the cancer cells that do not have the mechanism to remove the drug. That's basically the concept of synthetic lethality, and that's basically the concept of LP-184 efficacy. There is one other important factor here that one needs to remember, which makes the use of LP-184 a bit more complicated than, you know, a general other targeted agent, is that LP-184, in its form that it's in the vial, is an inactive drug. It needs to be activated. The enzyme that's activating is called prostaglandin reductase, PTGR, PTGR1. There are different isoforms of that as well. That enzyme needs to be present in order to activate the drug. It has its advantages and disadvantages. One advantage is that white blood cells do not express PTGR1. In general, LP-184 or irinotecan are not toxic for white blood cells, which is a very important consideration in determining side effects or toxicity. The downside is that if PTGR1 for some reason is not expressed in that cancer, then the drug will not work. For LP-184 to work, you need to consider two factors or two issues. One, the cell needs to be NER deficient, nucleotide excision repair deficient. The second one, the cell will also need to express this activating enzyme, PTGR1. Adding on to that, what tumors could be targeted using LP-184? As I already mentioned, the for a long time, we didn't necessarily know whether nucleotide excision repair deficiency exists in solid tumor types. The first tumor type in which we, I mean, the research community obtained hard evidence, hardcore evidence, that actually it's present in solid tumor types, is bladder cancer. The reason for that was that a one of the key nucleotide excision repair enzymes, ERCC1, ERCC2, has inactivating mutations in 10%, 15% of the cases. By definition, one would think that bladder cancer would be a good target for LP-184 or irinotecan therapy, which is in fact the case as we have shown and others shown in preclinical studies. In general, one would think that any tumor types that have an inactivation of any of the key players of NER, nucleotide excision repair, should be sensitive to the drug, provided PTGR1 expression is also present. This kind of takes us back to the agnostic concept that I mentioned in context of immune checkpoint inhibitors and microsatellite unstable tumors. We kind of hope that in any solid tumor types where we can have evidence that nucleotide excision repair deficient repair is deficient or damaged, we are probably good candidates for LP-184 therapy. The tumor types for which we have at least some preclinical evidence that there might be good candidates are in addition to bladder cancer, which is probably our strongest candidate right now. We do have evidence that breast cancer, a subset of breast cancer, we do not know exactly what percentage. We are not talking about the overwhelming majority. We are talking about 5%-10%. We have evidence that a subset of breast cancer is nucleotide excision repair deficient. The reason we actually, we know it, that probably these are the cases that are very sensitive to platinum treatment, platinum therapy. We also have evidence based on preclinical models that gastric adenocarcinoma cases are nucleotide excision repair deficient. These are tumor types. That's probably a good indicator always that if a given tumor type occasionally gives you very good response to platinum, then probably that's a good indicator that NER, nucleotide excision repair deficiency might be present. A very interesting recent set of results we have recently produced suggest that kidney cancer, a subset of kidney cancer cases are somehow nucleotide excision repair deficient. How or why we are still working on it is there seems to be some sort of hypoxia normoxia regulation, but it's very clear that a subset of kidney cancer cases are also LP-184 sensitive. Ken Offit's lab, that was a lab working in parallel with us about a couple of years ago on irinotecan sensitivity and NER deficiency, produced an overall estimate, just looking at all of the tumor types they characterized at Sloan Kettering with the Impact panel when they look at the mutational profile or the inactivating mutations in about 500 genes. Based on that, he found that for most solid tumor types, the number or the possible proportion of NER deficiency will vary between a few percent up to 15%-20%, depending on the solid tumor type. What I hope will be the case, because I think this is a promising drug, is that we will be able to establish some sort of a tumor agnostic diagnostic for NER deficiency. Those patients that have strong indications of an NER deficiency and PTGR expression, independent of the tumor type or the histology, will benefit from this treatment. Would you expect drugs like LP-184 to be used in combination with other synthetic lethal agents? Like everything in biology, everything is connected. Always there are very deep interaction between different mechanisms. Obviously, because nature keeps reusing the same mechanism, the same tricks, and it just ensures robustness for the living cell. The different DNA repair pathways are also very intimately interconnected. BRC function, homologous recombination, the Fanconi pathway, and nucleotide excision repair has very profound mechanistic interactions. This has been known, this is kind of pretty well mapped out. It wouldn't be very surprising that there is some evidence, experimental evidence, only pre-clinically, that probably PARP inhibitors and drugs targeting NER deficiency would be a good combination. This has been raised before. It wasn't investigated in sufficient depth, but since platinum is a very good drug to target, nucleotide excision repair deficient cells, it was suggested that PARP inhibitors should be combined with platinum. The problem was that it wasn't really clear, it wasn't very well-defined which tumor cases or what sort of molecular background would make a cell very sensitive to this combination. We do not really have strong clinical evidence or directions how we should be applying it. The same applies, in the case of, you know, LP-184 as well, that combination of PARP inhibitors with LP-184 should be explored, preferably in a mechanistically justified and mechanistically informed manner that would tell you that this is the molecular mechanism would very profoundly impact both NER, nucleotide excision repair, and homologous recombination. Those links or those mechanisms probably exist. We know that they exist. We need to see how often they are present in tumors, and those cases are probably good candidates for this combination therapy. We in fact have some very preliminary preclinical model-based evidence that this is might be a good strategy. The nice thing about this thing is that while I do not want to understate or underestimate side effects or secondary malignancies and, you know, in general the side effects or toxicity of PARP inhibitors and LP-184, but these drugs are probably relatively less toxic, definitely less toxic than, for example, an intensive platinum therapy. It might be actually a viable strategy to target those specific tumors with this combination, especially in an advanced setting in, you know, stage 3 or stage 4 setting, highly metastatic tumor cases. One thing I forgot to mention about PARP inhibitors at the beginning when we were just talking about success about PARP inhibitors, that it is very impressive how well PARP inhibitors perform in advanced cancer cases as well. I really want to emphasize here that these synthetic lethality-based therapies may really provide a significant benefit in those cases with very advanced, highly metastatic stage 3, stage 4 cases as well. What about LP-184 in combination with spironolactone? That's a good question. The idea with spironolactone is that, we know for a fact that without suppressing nucleotide excision repair activity, these drugs will not work. That's very clear from all the preclinical models and even for PDX models. That was a kind of fortuitous observation. It's actually very interesting. It was shown, it was seen that spironolactone, which is a quite commonly used drug in cardiovascular diseases, suppresses ERCC3, which is one of the key enzymes of NER. ERCC2 and ERCC3 are helicases, and they are actually unwinding the DNA that allows kind of cutting out the damaged part and then kind of, filling in the part that was removed. ERCC3 is a key NER enzyme. Spironolactone definitely suppresses expression. In preclinical models, it's certainly the case that suppressing ERCC3 using spironolactone will make a cell LP-184 sensitive. That's very clear. In a human being, we do know that spironolactone doesn't cause too much problem in the therapeutic concentrations because people take these drugs, and they benefit a lot in cardiovascular diseases, and they do not have toxicities at least related to suppression of protein production. One needs to see... That needs to be done, you know, experimentally or in a human clinical trial setting, that if you use the therapeutically justified conservation of spironolactone, to what extent is that going to change the expression of protein level of ERCC3 in normal and in cancer cells? If you say that I could just simply target cancer cells at very high doses of spironolactone, yes, that will make cells NER deficient and LP-184 sensitive. How will that play out in a clinical setting? That's a question that's certainly worth asking. That's a very, you know, interesting and worthy endeavor. We should probably get answers for that as soon as possible. That may make NER proficient cells NER deficient, so that may be helping the treatment. Let's not forget that PTGR expression also needs to be present. That it would certainly increase the number of potentially sensitive to more cases to LP-184. Then again, we need more data on that. Thank you for joining us today, Dr. Szallasi, and for your fascinating insights on synthetic lethality and Lantern's drug candidate, LP-184. I'd also like to thank the audience today for tuning in. If you enjoyed this webinar, please visit Lantern's website to download this or any of our past key opinion leader webinars. Thank you.