BRAF-mutated CRC updates: Dr. Corcoran (2022)

This is an automatically generated transcript.

Manju George 0:00
Hello everyone. I’m Dr Manju George, the scientific director of PALTOWN Development Foundation, the nonprofit that supports COLONTOWN. We have today with us, Dr. Ryan Corcoran, and he’s going to give us updates on BRAF, a mutated colorectal cancer slightly different from the format that we used to do before. We’ll start with asking Dr Corcoran how he got involved in GI oncology and to running these kind of trials.

Dr. Ryan Corcoran 0:32
Yeah. So, you know, I don’t know funny kind of long, roundabout story about I got here. So I I grew up in a family where nobody was in medicine or science. My both my mom and my dad were the first people in their families to go to a four year college and always liked science. And I think about my junior year of high school, my my high school at a fellowship that gave a couple, I mean, $1,000 maybe $2,000 to go to do something science related during the summer. And we would always go back to visit my grandparents, who were of my mom’s parents, who were Greek descent, who ran a diner and in New Jersey. And so we’d visit them for a month every summer. And so while I was there, I said, Well, there’s some drug companies in New Jersey. Maybe I’ll try to get a job there. And so through some Greek connections, got a unpaid internship at Merck, spent about four weeks there in chemistry, and just kind of completely was blown away. And started out actually on the chemistry side, and got very interested in the science. But when I started undergraduate at Princeton, I actually went back and worked at work every summer, but I ended up kind of getting more interested in biology. Worked with Arnie Levine, who was a person, one of the discoverers of P 53 and got very much interested in cancer biology. And then, really from the science, I got interested in medicine, went to medical school, did MD, PhD, PhD in cancer biology. And I think, you know, one of the things I’ve always been drawn to very difficult challenges. And, you know, I think that GI cancers as a whole are some of the hardest to treat and some of the deadliest cancers. I think, you know, colon cancer is the second leading cause of death, pancreatic cancer is the third leading cause of death, gastric, esophageal together, I think, are the fifth, fourth or fifth, so and very few, very little treatment. So I think I really got interested in, kind of going to where I thought science could really make a big difference. And so it’s a little bit, kind of what details the way I approach, you know, I approach what I do. So I obviously, I’m I do a lot of things. I do see patients. So I direct the GI cancer center, mgh, I see patients one morning a week and run some clinical trials, but I actually spend the majority of my time running a lab, and the lab is really focuses on understanding the mechanisms behind therapies, why they work, why they don’t work, and then figuring out how to how to use that knowledge to design better trials. And we’ve actually been fortunate to actually run those trials and use samples to then inform the next step. And so I think part of the story I’ll, I’ll tell you, kind of, you know, takes place over, over about 10 years, and really is kind of an example of how this, this process of of kind of going back and forth, can really be, can be productive?

Manju George 3:23
Wow, that’s, that’s quite the story. And I think that then, you know, we’re very fortunate that you’re working on something like BRaf, and, you know, now more into map, K pathway and all of that. I think your background and your interest to take on something challenging. That’s exactly what we need, right?

Dr. Ryan Corcoran 3:43
Good, yeah. So, so that’s, yeah, if there are any questions about that, but that’s, that’s, that’s a bit about me, and you know, if you want, we can go ahead and and get right into things. Okay, so, okay, so let me see here. All right. Okay. All right. Here we go. So we will. I was told people wanted to hear about BRAF mutant colorectal cancer today, so that’s what we’ll do. And what I really wanted to focus on is a little bit of, I’ll kind of pick up where my personal story stopped and talked a little bit about kind of, you know, kind of this interplay between science and the laboratory and and political trials and translational research over the last 10 years, and how it’s at least helped in some way, kind of move the the field forward. So, and then what I want to cover is really kind of where the field is, kind of what some of the interesting concepts and leads that we’re following, and really where I think the field is headed in this disease, or there’s just been a tremendous amount of progress over the last decade. So these are my, my financial disclosures. Um, so, so this is kind of how I like, actually, I this is a slide I used in my job talk. My first faculty position almost, probably 10 years ago now, and I’ve updated some of the technologies, like these sequencers didn’t exist 10 years ago, but I updated this. But this is still very much how I think about how to approach a clinical problem. And what this really suggests is there’s kind of a cyclical, iterative process where we really to accelerate discovery, we really need to kind of take mechanistic insights from the lab and use them to build the most rationally designed trials that we can but this can’t just be a unidirectional path like this, like it had been for many years. What we do need to do is, once we get those trials, is to understand how to collect critical samples from patients, whether they’re blood samples, tumor samples, and to really couple those, those critical specimens that tell us what’s going on in the patient and the patient actually receiving treatment, and really marry those with some of these incredible emerging technologies so that we can really get a better, better mechanistic understanding of what’s happening in people when we’re treating them with with the current therapy, and then we can bring that back to the lab model that mechanistically and develop new therapies. And interestingly, a lot, you know, if you go back 10-15, years, most things started at this point. They started with laboratory observations. And you would then kind of take things into the clinic and try to see what worked. More and more of what we’re doing now kind of originates at this point where we have a therapy that’s doing something, and we actually start by looking at what’s happening in the patient, and then using that to better guide our laboratory studies, so that we can continue this cycle and generate more and more impactful clinical trials. So what we’ll talk about today are is this yellow sliver of the pie. So colorectal cancer, as we as we get increasing knowledge of the molecular underpinnings, is increasingly classified by its mutational status. And you know, these are the key groups. Almost half of colorectal cancer is RAS mutated. The majority that are KRAS mutations, about five to 7% have NRAS mutations. And you know, we often just skip over this and talk about how this leads to resistance to EGFR antibodies and move on. But as I mentioned on a couple slides in my talk, this is an entire, entire different talk altogether. This is really starting to change. And I think you know, for those of you who were at ESMO or kind of been following some comments that there’s some, there’s some, there’s a coming wave of KRAS inhibitors now that I think is really going to revolutionize care for about half of patients with colorectal cancer. What we’re seeing with G12C inhibitors, which touches just a small sliver of this is really, I think, setting a roadmap for how we’re going to get to where we need to get with other you know, for example, G12D, KRAS. G12D selective inhibitors, or KRAS, selective inhibitors that hit KRAS but not the other RAS isoforms, HRAs and NRAs, so they hopefully will be tolerable. We really may have therapies that can very readily address this huge subset of patients that have really we’ve had nothing to offer for a very long time, but what we’ll talk about today are BRAF mutations. And, you know, I think one thing that that we we think about when we talk about RAS and BRAF mutations is they do drive resistance to other therapies like EGFR antibodies, but they also have prognostic effects. And BRAF V600 mutations, which is the majority of BRAF mutations in colorectal cancer, but not the only ones, and we’ll talk about that more in a second, are probably the worst player here. The prognosis for BRAF V600 mutations really is the worst of all molecular subtypes and NRAS and K RAS mutations, also in most studies, do confer some decreased overall survival. So we really do critically need better therapies for these groups. But this, this is, you know, one thing I’ll just start with, and then we’re going to focus on BRAF, V600 for the majority of the time, is this is becoming more and more of an important point that not all, and I would say a lot of physicians, don’t understand this either. Not all BRAF mutations are the same, and there’s really three classes of three functional classes and mutations in BRAF. And we really need to know about this. And I know that COLONTOWN does such an incredible job of informing patients and guiding them through this. This is something that I, I imagine you’re already doing, but certainly something that is really worth paying attention to, that a lot of times we you know, most oncologists, they see BRAF and they think BRAF. They just assume everything is behaves like BRAF V600. But that’s not the case. So BRAF V600 is basically the only thing that we consider class one. And the reason it’s unique is that not only is it an activating mutation, which doesn’t depend on signal from RAS upstream, but it actually can signal as a monomer, meaning just one protein. It doesn’t have to kind of dimerize with another RAF protein. And that is really unique in that. And the reason that the BRAF inhibitors we have are effective in this group is that they’re effective at inhibiting monomeric BRAF, but they run into problems when BRAF is dimerized, and so they’re not effective in any of these other. groups. Class two mutations are basically very similar, except they’re also activating. They don’t depend on RAS, but they require dimerization. That’s a signal. So they’re also oncogenic drivers. There’s a new there’s newer classes of what we call just RAF inhibitors, or type two RAF inhibitors, that are looking to show some, some, real promise here on class two point mutations, class two in frame, deletions and and BRAF fusions, which we also lump into class two. And finally, class three is really different. Class three mutations actually do the opposite. They actually either impair or inactivate the kinase function of BRAF. But what they do is they they cause BRAF to flip into a confirmation where, when it dimerizes with another RAF, either BRAF or CRAF, it, it transmits kind of a, kind of an activating conformational change to the other dimer partner, and then that dimer partner essentially can amplify any upstream signals. So we call these drivers, but we really think about these as amplifiers. And sometimes these are the only BRAF mutations in class three that you actually see co-occurs with with Ras mutations. These mutations are almost never seen together with Ras mutations. And also sometimes you’ll see them in the absence. And what they serve to do there is amplify upstream signals from receptor Cyrus and kinases like EGFR and so there’s a really nice review on this that Rona Yeager and I wrote a few years ago in cancer discovery. That is what I go back to to cheat and remember what, what point mutations actually class through class three, because it’s very hard to remember without that. But it also kind of walks through this. If anyone is interested, this is a good one to look up. So why is this relevant? Well, if you actually then break up the Braf group into BRAF v600 versus non v600, the effect on survival is very different. So obviously, see this kind of horrible effect on survival revival from mutations. But if anything, non these exciting mutations have a much better survival, or trending toward a strongly better survival than BRAF wild type patients. And so that’s an interesting component. But what’s even more interesting is that, as we know, we typically don’t give EGFR antibodies to patients with Ras mutations or BRAF mutations. But we need to be careful about this class one mutations. There’s definitely data that doesn’t work. Be refused center doesn’t work. But if you actually look at class two mutations, again, these drivers, it also doesn’t work. You get very few responses. 8% of patients respond to chemo and EGFR. But class three mutations, which again, amplify upstream signals, so they actually take EGFR and, you know, really propagate that signal. They actually have a 50% response rate. And so I see a lot of patients not getting EGFR antibodies because they have, sorry, my mouse seems very sensitive today because they have a BRAF mutation. But it’s really important that people check and, you know, I think as patient advocates, you know, if you see a non basic center mutation, definitely make sure, you know, try as much as you can to help that patient figure out what it is. Because, you know, a lot of patients miss out on the benefit of EGFR because they are misclassified. So with that, and again, if there’s any questions, feel free to stop and interrupt me. I’m happy to have this be a discussion. If there’s any questions on non , which is something I think we’re really trying to educate oncologists on more broadly now, let me know. Now, otherwise, I’ll move into the portion.

Manju George 13:43
Dr Corcoran, are there any trials specifically for the atypical BRAF mutations?

Dr. Ryan Corcoran 14:44
So there are. So most of those trials involve these type two RAF inhibitors, and so there are a handful of these. You know, the ones that are furthest in development are Alex h 254, from Novartis, although I don’t think that’s being pursued very heavily anymore. Velveranib from Genentech is is fairly advanced in clinical trials, both alone, in combination with a Mac inhibitor, and there have been some interesting responses seen, particularly in class two mutations, but mostly in melanoma and lung cancer. There’s another RAF inhibitor from a company called kymate, which is a company that I’m a scientific advisor for, that’s just finishing dose escalation again, specifically, really going after these non basic center mutations as their primary source. And while that that trial, I think, is having dedicated expansion cohorts in melanoma and lung, there are cohorts of that that allow colorectal so that that is where I think you know, and that molecule is also being done in combination with the Mac inhibitor. So those are the ones to think about in the setting of class two.

Manju George 14:57
Okay, and in those trials, do people have to like progress through first? Or two lines of therapy?

Dr. Ryan Corcoran 15:02
Usually I don’t know the answer to that off top my head. A lot of times, trials like this will, will sometimes, sometimes they don’t specify, but I would probably recommend people get first line chemotherapy before doing this, and maybe even second line. Many of them will require progression on one line, but usually the the early signal finding trials are not as strict about limiting the specific lines of therapy. When you run a registrational trial, you have to be very clear that this is for third line. So we need patients who have who have progressed on first and second. These trials are probably a little more flexible. Okay. Okay, thank you, sure. So to move on to the portion of the talk. So you know this, this is really kind of right around when I finished my residency and clinical fellowship training, first year of fellowship, and I just entered the lab, I think in 2008 or 2009 and right around that time, mutations had had been discovered, and we had selected BRAF inhibitors entering the clinic, and really in 2010 some of the studies led by Keith Flaherty and colleagues showed this incredible response rate of 50 to 60% and almost half of melanoma patients that harbor mutations. And this was incredibly exciting, really kind of in the those early days of cognitive therapy and precision oncology and what we all as Cola, as VR cancer physicians thought was That’s fantastic, because the next biggest population of patients is colorectal cancer. About 10% of colorectal cancer patients same mutation, same drug. This is perfect. We’ll use it, and we’ll see all the same great things. Turns out that’s not the case. So Scott Kopetz, a great colleague and friend of mine, led this study, and right around when I joined the lab, these data came out, or joined I started as a post doc, these data came out and showed that there was a striking disparity in response where, I mean really, you can call this a 5% response rate, and you can see this patient barely hit that line, really negligible activity, same mutation, same same drug. What’s happening here? And so this immediately became very interesting to me, and I thought that this was really a place where understanding the mechanistic basis for this difference could really help us figure out what some of the shortcomings were in colorectal cancer and where we could go. And it’s interesting, because the prevailing hypothesis at the time was the reason for this is just that, you know, colorectal cancers must just be less dependent on BRAF. Maybe they don’t. They’re not as dependent on map kinase signaling as melanoma. And there must be other pathways in colorectal cancer, maybe the APC beta catenin pathway that’s mutated in almost every colorectal cancer, or the p(?) kynase pathway, something else is able to keep it alive in a redundant fashion, and whereas we can’t ever expect to get activity by targeting this pathway, although so we set out to really understand this and figure out if this was the case In the lab. And what we did was we took cell line models of melanoma, and also cell line models of colorectal cancer, and then we treated it, treated them with a BRAF inhibitor, in this case, membrane, the same inhibitor used in those two trials, and we saw what happened to signaling. This is phospho ERK. This is kind of the downstream output of the RAS BRAF pathway. And what we can see is that in melanoma, we can inhibit the pathway completely and keep the pathway off for extended periods of time, 40 hours or more. You did the same thing in colorectal cancer, you inhibit the pathway transiently, but it comes back on very rapidly within the first 24 to 72 hours, and really back to almost 50 to sometimes 100% of the starting level, even if you constantly replenish the drug. So it’s not that the colorectal cancer is chewing up the drug or spitting the drug out. The drug is only able to keep the pathway out for a little bit, and then something happens in the pathway comes back up. So this immediately was very surprising us to suggest, in an alternative hypothesis, that actually colorectal cancers may care just as much about the kinase pathway as the as melanomas. It’s just that we’re not actually inhibiting the pathway effectively in colorectal cancer. And this theme almost everywhere I’ve turned over the last 10 years, this theme keeps coming back. As you’ll see through the talk today, if there’s one thing that colorectal cancer tries to do is to keep this pathway on or turn it back on. And we still, with the drugs we have in hand, have not done as good a job as we can and should, turning the pathway off and keeping it off. And if we could achieve that, we really might. And as we’ve started to achieve that, we’ve seen the efficacy really, really start to move, but we may see it move even more in a direction. And right now, it’s the ability of this cancer to turn this pathway back on one way or another that causes a problem. So what we hypothesized at the time was, Well, maybe if we inhibited, um. This, this pathway with another agent, so BRAF and mechanisms together, you know, added some extra efficacy. And melanomas, we said maybe if we do that in colorectal cancer, we’ll keep the pathway off better, and we’ll have more activity. So this was actually fantastic. As a fellow, I was actually able to lead this trial into into kind of the first year or two of my faculty tenure and and what we found was that, well, maybe we did a little bit right? We went from a 5% response rate to a 12% response rate. And we had a few patients who did pretty well. This patient is actually a remarkable patient. I’ll come back to it a little bit, who I believe is somewhere in Texas, still in a complete response off of therapy. But, you know, moving the needle a little bit, but still not enough. And again, this, when a lot of people saw these data, they said, Well, Ryan, again, you’re wrong. This just proves, once again, that colorectal cancers don’t care about map kynase inhibition, one didn’t do it. Now, two didn’t do it. Clearly, that’s not the thing. But what was really important, and this is kind of coming back to how critical I think it is to understand what’s happening in the tumors of the patients who are getting this therapy. One thing we did with this trial, and credit to GSK, the company who was running this trial at the time, for supporting this, is what was we decided to get about 10 or 12 patients in the trial, we decided to get pre treatment and on treatment, biopsies on everyone, and we were successful maybe half of the time. But what we started to do is to say, Okay, how well are these drugs turning the pathway off? And when you look at melanoma with just a BRAF inhibitor, you can see that the vast majority are getting the pathways turning off by 80 to 90% a couple maybe aren’t, but most if you look at what’s happening in our colorectal cancer patients now with two drugs, BRAF and Mac, you see that the pathways being inhibited. It’s decreasing in everybody, but only by an average of about 30 to 40% and only rarely do you see kind of inhibition in a couple patients on the same level you’re doing now. So this, again, suggests to us that actually, wait a second, that hypothesis may be correct, that these cancers may care just as much about this cancer, about this pathway. It’s just that we’re not turning it off, even with these two drugs. So where do we go from here? So we went back to the lab again and said, let’s figure out what it is that’s that’s keeping this pathway back on. And what we started to do is just say, Okay, well, when we block BRAF, something must be coming in to turn the pathway back on. So we started to march our way upstream, and we found that, you know, other RAF members, like CRaf, were turning on as far as the pathway was turning back on and that RAS and activity was increasing. So we went upstream one more step and said, Well, maybe one of the receptor tyrosine kinases that signal into RAS may be accountable for this. And when we compared the expression levels of various receptor tyrosine kinases, or rtks, between colon and melanoma, both in cell models and in tissues, we found that one RTK in particular, EGFR was expressed ubiquitously at very high levels and very highly activated in colon, but not in melanoma. And it turned out that that pattern mostly held in patients too, where the majority of patients you can see the brown staining here is EGFR expression. Had high levels of EGFR, but not everyone, and this is important, whereas melanin, almost nobody did. And this suggests that EGFR and maybe other receptor tyrosine kinases were just feeding back in and turning this pathway back on after we were blocking BRAF. And so here’s how we put this model together that downstream of the RAS, BRAF, map kinase pathway, we know that ERP controls the expression of several really important what we call negative feedback regulators that actually prevent the normal activation of the pathway. So they prevent things like EGFR from engaging and activating RAS, and also feedback on other parts of the pathway. So, when BRAF is driving, all the signal – that’s in place and nothing else can really contribute. And as soon as you block BRAF, after about four to six hours, you know, you lose expression of these negative feedback signals. And now receptor tyrosine kinases like EGFR, which are there at these high and activated levels in colon, but not melanoma can just engage and reactivate the pathway. They can activate RAS, CRAF and come right around, turning the pathway back up. And this suggests this. Well, if this is what’s happening, maybe we can prevent this by either combining an EGFR inhibitor with a BRAF inhibitor, or maybe putting all three inhibitors together, MEK, EGFR and BRAF. And you know, when we looked at this clinically, we are, I’m sorry, pre-clinically, we found that when we combined a BRAF inhibitor and EGFR inhibitor, this is after 48 hours, you’re getting incomplete inhibition the pathway the BRAF inhibitor alone. But now you get complete inhibition, and you’re blocking this compensatory activation of RAS and CRAF that you see in the absence of an EGFR. And then if you look at mice, you get actually regressions of most of these tumors with a combination, whereas EGFR alone or BRAF alone didn’t do much on its own. And so these findings led us to actually pursue a series of iterative clinical trials looking at common either double or triple combinations of these agents. And over time, this led to this critical study, again led by Scott Kopetz, that looked at the BEACON study, a BEACON regimen, which is now the combination of the BRAF inhibitor encorafenib and the EGFR antibody cetuximab. And when, when this arm was randomized against standard chemotherapy, there was a striking improvement in response rate, just 2% response rate for standard second line therapy, which is unbelievable to me. I think that was one of the more surprising things about this trial is how bad our standard treatments are for these patients, whereas the doublet therapy, BRAF EGFR had a 20% response rate and a nice benefit in survival. The surprising thing was, This also tested a regimen of BRAF EGFR and MEK, which was called the triplet. And when we had run a very equivalent trial with this a couple years before, using Gibrafenib and panetuzumab, we saw much more more, really kind of more substantial increase in activity when we added a MEK inhibitor to BRAF EGFR in this trial over the there was a jump in the response rate from 20% to 27% but there was really no difference in both progression free survival or overall survival. So the FDA ended up deciding that they were only going to approve this double therapy. And so this as of the last three years, is now, or two to three years, I guess, is now the FDA approved standard. But this is a huge advance. You know, for patients, as you can see, even though the response rate’s 20% lots of patients are benefiting, probably about three quarters of patients benefit. But there’s still some key issues. We need to do better than this, and we can do better this, the response rate’s low, only one out of five patients responds, and the durability is limited with only about a four month progression-free survival. So why is this, and where can we go from here? Well, again, one of the things we kept doing on the trials that we were running with BRAF map, BRAF EGFR, etc, was we kept getting these pair biopsies. And much like I showed you that BRAF mekalon, the pathway was inhibited in everyone, it didn’t quite reach this nice 80 to 90% average suppression that we saw in melanoma. Interestingly, with BRAF EGFR, we saw really a scattered pattern where we got nice inhibition in some patients, but no inhibition, and actually what we call paradoxical pathway activation, which can happen with BRAF inhibitors alone, sometimes in some patients, but when we started to put three drugs together now, we could see that we were really starting to get better and better suppression, maybe averaging about 60% now, but many more patients now with this kind of nice equivalent suppression, and this really is what we think is driving the improved response rate that we’re seeing amazingly, though, with three drugs, we’re still not getting as good a pathway suppression on average, than we are with one drug in melanoma, and that’s really the key problem. Now I’m gonna take a quick three-slide, perhaps digression from BRAF, to just talk about how this mechanism of adaptive pathway reactivation of colorectal cancer is, I think, one of the more critical challenges of treating colorectal cancer, and one that has relevance well beyond BRAF and I mentioned that we’re now seeing for the first time, K RAS inhibitors entering the clinic. This is a structural diagram of KRAS G12C inhibitors, which form a covalent bond to the mutant cysteine that see in the KRAS G 12 C mutation in colon cancer, these agents have entered the clinic and have shown great responses in lung cancer. This molecule Sotorasib has now been approved as a single agent in lung cancer. This molecule adagrasib from Murati will likely be approved in the next few months. But much like 10 years ago when we were looking at melanoma and colorectal cancer, the activity in colon cancer was not as good. Sotorasib with only a 12% response rate, and adagrasib updated at ESMO last week, with about a 19% response rate. So instead of 40% we’re now down in the teens so a little better than where we started in but what’s going on? Well, again, this same problem of adaptive pathway reactivation seems to be the key. And we’re really talented for postdoc my lab, Megan Ryan gathered a bunch of these models and showed that, again, not just in colon, even in some of the lung cancer models, that don’t respond, what you do is you get this very consistent pattern of, again, transient inhibition with a KRAS inhibitor, and then very rapid reactivation back to near complete baseline levels by just three days. And in colorectal cancers, again, this is predominantly driven by EGFR. And actually, I didn’t put the updated data in, but we just saw updated data from both of these trials last week at ESMO, and we’re now seeing, you know, just by adding EGFR antibodies again to KRAS, G12C, we’re seeing 30 to 45% response rates in this group, and this looks like it will, this will likely be the registrational path for colorectal cancer. So this same mechanism that we kind of discovered a decade ago for , looks like it’s going to be the critical component in, you know, maintaining and or achieving responses with some of these new KRAS inhibitors that are entering the clinic, and will hopefully help us take out that entire right half side of patients who really haven’t had a therapy. So so very, very exciting and very, very important. So to summarize this first part of the talk, you know, targeting adaptive feedback does lead to enhanced therapeutic advocacy in BRAF, these external colorectal cancer, and as we just saw on the last slide in the last few months, also in K RAS, G12, C colorectal cancer. But while EGFR brain played important role, this is this is critical. It appears to be absolutely critical only in a subset of patients. Maybe about 30 to 40% of patients are really dependant on EGFR and so that remainder of patient, patients who aren’t responding, we found that other receptor tyrosine kinases can step in and help reactivate the pathway even even in the setting of EGFR blockade. And so we’re starting to think a little bit about, is there a way to move beyond these single receptor tyrosine kinase strategies in order to block these EGFR independent mechanisms of adaptive feedback. One way to do that is to get kind of better downstream pathway inhibition. The MEK inhibitors that we used in the triple arm trials really didn’t do their job of keeping the pathway off. So there are some better downstream inhibitors now that we’ll talk about in a bit. But also, should we be targeting more conversion upstream nodes that intercept multiple R decays, like with things like shift two or using multiple antibodies or bispecific antibodies? These are questions we need to address. But before I talk more about that, I want to talk about kind of another issue that we face. So one is that, why aren’t more than 20% of patients responding? But the other question is, why are those patients responding for only four months? And this is where we come up to this kind of second flavor of resistance called secondary or acquired resistance. And unfortunately, even patients who have a phenomenal response, some clones, whether they’re pre existing or whether they arise during therapy, have some degree of resistance. Therapy and eventually grow out and drive treatment failure and disease progression. And you know, once we started getting some nice responses in these early trials of BRAF MEK and BRAF EGFR, we started to routinely biopsy patients before treatment and after treatment to understand what was changing these tumors to make them resistant. And our initial effort, which revealed the first clinical mechanisms of of of BRAF combination resistance and colorectal cancer that is published about seven years ago now, showed you know, initially, what looked like a disturbing pattern where almost every patient we looked at we saw a different thing. So we saw mutations or amplifications in KRAS, amplifications in BRAF. These occurred itself, mutations in MEK downstream of BRAF, and amplifications of receptor tynase and kinases Says. So initially it looked like this was just the big mess, and we weren’t sure how we would get around this. But then we started realizing, well, actually, look, everything is is clustering in this pathway, and once again, trying to keep this pathway or turn this pathway back on. And what we realized that actually that was the critical thing, again, supporting this hypothesis that this cancer cares a lot about the map kinase pathway, given the efforts that goes to turn it back on. And what we found is actually, while MEK inhibitors did not do a good job at preventing the pathway to be turned on with all these mutations, even though they were upstream, there’s just a funny quirk of that MEK inhibitors where it can’t keep the pathway off. In the setting of more and more signaling to MEK we found that one step downstream, prk inhibitors were much better at keeping the pathway off. Unfortunately, it’s taken a while to get good or erk numbers in the clinic, but I do believe we have them now in the last year or two. And so I’ll come back to this point in just a moment. It gets even more complicated than that and that, you know, sure, we can we, you know, we can biopsy one lesion and try to understand what’s happening with patient, but we have to understand that patients have multiple lesions. It’s almost like the Galapagos Islands, where cancer cells restricted to these lesions evolve independently and can come up with their own mechanisms resistance. And so what you can find actually, is this issue called tumor heterogeneity, where different lesions throughout the patient’s body can develop completely different resistance mechanisms that might respond to totally different therapies. And what makes it even more complicated, this is even within one of these lesions, you can find that different clones can arise that have independent mechanisms from ones right next to it. And so if you stick a biopsy needle into just one part of just one of many metastases, you might get a very limited view of what’s going on throughout that patient. And if you design your treatment to overcome resistance, just on this one biopsy, you know you really may kind of fail to anticipate several resistance mechanisms that may drive failure of that period. So one thing we started to turn to, to really understand the kind of the degree of the resistance problem we’re dealing with is something called circulating tumor DNA. And there was a lot of just, I know several of you watched the great debates and updates session yesterday, we had a whole kind of session on on circulating tumor DNA. But these are fragments of DNA shed from tumor cells into the bloodstream, and by a simple blood draw. Now we can collect and isolate these and these this DNA which is shed by lesions throughout the body. And in this way, we can get our full picture. Even though we can’t tell which lesion these are coming from, we at least know kind of everything that’s there that might be causing a problem that we need to overcome therapeutically. And when you do this in patients, you find that you see all these same resistance mechanisms that we saw in multiple patients. When we biopsy them one at a time, you see them all, sometimes in the same patient. This patient here has nine resistance mechanisms. Scott Kopetz gave a nice talk at ESMO looking at ctdna collected after progression and before treatment on the BEACON study and found that the same pattern emerges, basically, I think his in that study, about 60% of patients, or about two thirds of patients, developed some mutation within KRAS and RAS or MEK again, showing that this really is the way in which most patients progress on BRAF EGFR therapy is by essentially developing, or at least probably selecting out a clone that has a second mutation within this pathway that can keep the pathway on. So if we can figure out how to keep the pathway off in cells that hold these mutations, we actually can maybe prevent them from emerging. And this is something that we looked at setting out to study in the lab several years ago. And what we did was we took a cell line that was a cell line that was sensitive to BRAF EGFR, or BRAF MEK or BRAF MEK EGFR, and we engineered in every single mutation that we’d ever identified clinically in patients, one at a time into different models. But then we took those models and tried to really kind of replicate the situation where a patient has all these models inside them at once, all these resistance mechanisms at once. And so in a background of sensitive cells, we would add in roughly at 1% frequency each of these resistant clones, and then we would treat them, either in cell culture, or, as I’ll show in the next slide, in a mouse as an established tumor with different therapies. And we could see again, how well those therapies could inhibit growth, but also how well they could prevent the emergence of different resistant clones by looking at the change in frequency. And so we could actually chart this. And so just to kind of show you what’s happening here. If you just don’t give them any treatment, some of these, the resistant clones, will will have a little bit of a growth advantage. So you’ll see the frequency of each increase over time. But as soon as you put on a selective pressure, evolutionary pressure of therapy, BRAF MEK, or essentially the BEACON region of BRAF EGFR, you see that now the abundance of these clones relative to the overall population just shoots out. And now, just after two weeks of treatment, these resistant clones, which initially were about 7% of the population, are now three quarters of the population. You had a MEK inhibitor. Maybe it slows us down a little bit, but really doesn’t do much. But the amazing thing is, as soon as you just swap out a MEK inhibitor of ERK inhibitor, you can completely take away the selective advantage of these clones across the board, every single thing we’ve seen in patients. And this was really intriguing to us at the time. What was more intriguing is you can do the same thing, where you take these pools of clones and put them in a mouse and grow a tumor, and an untreated mouse will look like this, oops, where you know, the clones remain very small populations. But as soon as you treat with BRAF EGFR, BRAF mek, BRAF mek EGFR, these clones expand out, and they all, kind of, all these tumors grow through treatment over time. Interestingly, when we when we treated with BRAF EGFR and just changed the Mek out for erk inhibitor. Now, all of a sudden, we saw a very different picture. We could actually shrink these tumors, every single one of these tumors. Now, even though they had every resistance mechanism we’ve ever found in the patient, they shrink, and the abundance of the clones was completely unchanged from from no treatment, meaning that there was no selective pressure anymore imparted by these clones to this therapy. All we did was basically swap out the MEK for the ERK. So this is something that we are really excited about, and unfortunately, it took a long time to get to a point where we have good erk inhibitors in the clinic. We tried to do a trial with Lily with this erk inhibitor. Really not a potent enough ERK inhibitor, some other PK issues, but now we have two trials that are really interesting. One is called Hercules three. It is involves the base of the beacon regimen, plus what I think is one of the best erk inhibitors, called eras 007 this was previously called ASN 007 from a company called Asana. Full disclosure, I’m a scientific advisor for Araska as well, the company that runs this trial. But this is a very exciting trial. This trial enrolls patients who have not seen beacon before, and so this is an interesting option for people who are looking for, you know, beacon, but a little more and haven’t gotten it yet. But it yet, but it also, importantly, enrolls patients who have had prior beacon. And that’s something that I get emails about almost every week, is what do I do if I progressed on Beacon? So these are two trials here. This is a Novartis run trial where, right now there are multiple arms. They’re all based around kind of a BRAF, Erk, doublet, but they’re adding other agents as a triple combination, sometimes, PD, one, shift, two, Mac, various things. This is another one that accepts patients that are prior BRAF therapy. So we’re very excited to kind of see how this works against resistant clones, and with our ability to now track how each individual clone responds over time to these therapies, it will be really exciting to see if that could actually overcome many of these resistance mechanisms, like our preclinical data suggested a few years ago. So with that, I want to pivot slightly because so that’s one direction I see the field growing is kind of better inhibitors to keep the pathway off, we’re still not doing the job that we need to do, to just shut this pathway off and keep it off. But even if we do get better and better ways, the evolutionary potential of cancer is very humbling. And you know, targeted therapy may not be enough, but even if we divide the perfect way to turn the pathway off, you know, the cancer is going to find some way to get around almost any therapy. And while we hope we get more and more frequent responses and more and more durable responses, it’ll be nice if we get to a point where we can really get very long, durable responses or even eradicate some of these cancers. And you know, one interesting thing is that, you know, immunotherapy has certainly played a big role in many cancers. It hasn’t had a big role in colon cancer so far, but BRAF, V600 colorectal cancer actually overlaps very heavily with the hyper mutated or microsatellite unstable or mismatch repair deficient, as we sometimes call it, population. So this MSI population. There’s a big overlap between BRAF and MSI in the metastatic setting, which this graph is not. It’s probably about, maybe only 15% but much, much greater overlap in the early stagess. And one thing that we know is that if you know, if there is a population that responds well to immunotherapy, it is this MSI population, even though it’s unfortunately about 4% of metastatic colon cancer, those patients do phenomenally well with with immunotherapy, specifically PD one inhibition, and that now represents first line therapy for these patients. So what’s going on here? Well, you know, a very simple way of thinking about this is the response to immunotherapy is just kind of literally correlated with a number of mutations in a cancer cell. So things with really low mutational burden, like pancreatic cancer, with poor response, high mutational burden, like melanoma or mismatch repair deficient or MSI, colon cancer, good response, MSS colon cancer, microsatellite stable is kind of down here somewhere in the middle, and I’ll get back to this in a second. More mutations means more things that the immune system can recognize and potentially better response. But, I ask, is tissue mutational burning the whole story? I mean, this is a great graph put together by a team Hopkins, but you’ll notice that while everything lines up, there’s a few outlines, right? You’ve got some things. If you look particularly in this region right here, you’ll see that you’ve got lung cancer, Merkel cell that has about the same tumor mutation burden. That’s way up here. Then you’ve got a bunch of cancers like hepatocellular, esophageal, gastric, anal that actually and renal cell that respond very well to immunotherapy, all with the same mutational bird as colorectal cancer. But Colorectal cancer is way down here. This thing just fell off the line, and it does actually raise the question, is there more to it than just the mutational burden that’s preventing response? Is there some inherent signal within colorectal cancer that’s suppressing further and further a potential immune response? And when we think about kind of the hallmarks of cancer, over the years. You know, we often have thought about survival, I’m sorry, proliferation and survival, but, and that’s what we’ve always thought that the RAS not cranius pathway does, is it promotes these two things. It absolutely is. But would it be crazier out of the question, that one of the reasons that almost every cancer there is finds a way to activate this pathway one way or another, is that maybe this pathway actually blunts the immune recognition or immune response within that cancer. It actually makes the cancer cell less immunogenic to the tumor immune microbiome. Possible? Maybe a crazy idea, but we started to look back through patients from our prior trials, and what this graph shows these are patients who received BRAF EGFR or BRAF EGFR MEK on prior study. The red line is microsatellite stable patients, and the blue line are the patients who are MSI. What we notice is the MSS patients. Not a single patient stayed on for more than a year, but about a third of our MSI patients went on to have these incredibly durable responses, sometimes lasting several years or more. And remember that one patient I pointed to on the original BRAF mek trial, who I said, I think I believe, is still alive somewhere in Texas, this patient had a complete response on a very suboptimal, targeted therapy regimen, BRAF mek, and stated this response for at least four or five years, came off therapy, and as far as I know, is potentially curative or disease. We sequenced this tumor up and down, nothing different from any other BRAF tumor retreated, other than the fact that this patient was MSI. So this led us to think maybe, maybe, maybe by blocking the Braf pathway, only because, again, there’s no immunotherapy happening here by blocking the Braf pathway, maybe we’re, we’re, uh, kind of creating some change in the tumor cell that allows an already present immune response that’s happening in this MSI population to then accelerate and to and to actually have pretty dramatic and durable anti tumor effects. What if that’s the case? What if we could harness that and and, you know, take that benefit into into all BRAF patients, including the microsatellite, like stable patients. So we looked more carefully at this. These are all the biopsies we we had about 60 biopsies from patients on BRAF, EGFR BRaf, EGFR MEK, and what we found was that going from day one to day 15 of treatment are basically pre treatment, and two weeks of treatment, we saw that just with targeted therapy, with BRAF targeted therapy, we saw an increase in T-cell and proficient tumor and an increase in the CD positive cytotoxic T cells, the ones that we believe do most of the cell counting. So this suggests that just again, blocking BRAF signaling, can actually, you know, increase immune cell recruitment into the cancer. You know, again, supporting this hypothesis, we developed an immune competent mouse model that we can actually put a BRAF V600 tumor into in the setting that intact immune system, and show that, again, while an immunotherapy opinion, one never on its own, has very little effect on this very low mutational burden model. BRAF, MEK, also very minimal, maybe a tiny improvement over over, no treatment. But when you put the two together, you get this profound benefit with actually, many of these tumors actually regressing, and you also again see an increase in the amount of T cell infiltration into the tumor just with targeted therapy load. So this really made us hypothesize that by blocking BRAF, maybe we’re doing something that can help engage the immune response. And this led us to initiate this clinical trial, which is the first clinical trial to combine BRAF targeted therapy with immunotherapy. Now, we developed this concept about five or six years ago, and anytime you know the first version of an idea, it takes longer to convince drug companies to do it. You have to kind of make concessions. So we were able to get Novartis to support this, but only if we could use BRAF MEK, because they had safety data from BRAF meK and PD one for melanoma patients. So even though we knew this was not the best way to target this pathway, it had a, I said, a 12% response rate, but really only a 7% confirmed response rate. We said, okay, at least we can prove the concept. We’ll be able to if this works, we’ll see a nice improvement over the 7% in fact, if you we just updated these data as Mugi in Barcelona, if you just look at the NSS populations, this trial is now completed enrollment. We still have spots for two NSI patients, but all the MSS slots are full in 28 patients, we now saw a 25% response rate. So three to four times the response rate that we saw would be RAF mek alone. And more importantly, the responses were very durable. So this is the historical progression free survival for BRAF MEK about three and a half months. The median progression free survival we saw in this population was six months, and about 20% of our patients stayed on for a year or more, whereas zero patients stayed on for over a year with the BRAF directed therapy alone. So this really does suggest that there’s some really intriguing interaction between BRAF targeting and immunotherapy. And one of the things we did with this study, this is again, where I was talking earlier about merging these critical patient samples that you know are the key to answering these questions, and merging them with these with these important emerging technologies that really allow you to ask new questions. So one of the things we did this time on our pre treatment (_?_) is we actually performed single cell RNA sequencing work where we actually can isolate single cells, tumor cells, immune cells, and sequence the RNA in that cell so that we can get an idea of what type of cell that is from its RNA profile, or also how the gene expression those cells changes from before to after treatment. And what we found is in that patients who did well, who had a progression free survival of more than six months, almost all the genes that were most highly upregulated in these patients after two weeks of treatment relative to baseline, were immune. They involved in andr-?- presentation within the cell, interferon response, or even involved chemokines that recruit T cells, whereas in patients who didn’t do well, we didn’t see the cell regulation. The other thing we saw was that in the in the patients who did well, we saw high level down regulation of the MAP kinase pathway, our old nemesis, and the patients where we didn’t see it didn’t do well, we weren’t inhibiting the pathway. And that made us think, are those two things, you know, true, true and unrelated, or are they actually causally related? Maybe it’s the fact that we’re down regulating the pathway to a high degree in some of these patients, that’s actually causing the immune genes to go up, whereas the lack of failure to do that with this kind of crude, you know, outdated BRAF core, BRAF MEK is the reason why some patients aren’t doing it. And so we were able to take what are called Patient derived forgoing models, these kind of cool 3d organ like systems that we were able to develop from the pretreatment biopsy of many patients. And so now we can actually match the model to the patient based on how they did. And so we’re lining these up based on each of these patients, how long they were on therapy. And you can see that when you treat these models with BRAF Mek, the ones that did the best, you get better inhibition the pathway. So bluer means better inhibition of (_?_) pathway signaling, and redder means higher up regulation of the immune immune programs. But we know this is not the best way to inhibit the pathway, so we then moved to a BRAF perp core, which we which, as you can see, was able to effectively inhibit the pathway across all the models from patients, whether they did well or not. Amazing thing now is that you see every single patient now up regulates these immune programs. So if, if we could actually achieve high level Pathway inhibition in all of our patients, maybe now all those patients will go on to benefit. And that’s kind of shown a different way here, where, again, with BRAF mek, you’re not getting upregulation immune systems, these immune programs in the patients who didn’t do well, but you are the BRAF (_?_), and so this is, this suggests that kind of a more optimal core, you know, may actually extend this. And so, you know, Scott Kepetz and Van Morris and colleagues started this trial, you know, a couple of years ago that looked at adding PD one inhibition into the beacon regimen, or I think is a better BRAF targeting core. And while we know that the response rate with beacon is about 20% they saw a similar induction of response rate to 50% and again, some some nice evidence of durability. So we really think this is a real thing, this kind of mechanistic interaction, and interestingly, I’ve said one more non BRAF. We’ve actually now started to look at this with KRAS G 12 C inhibitors and a similar mouse model of KRAS G 12 C muting colon cancer. We find that K RAS G12 C inhibitor treatment also induces all these same immune programs and has a very nice synergistic effect with a KRAS G 12 C number, suggesting that the same kind of concept, maybe KRAS G 12 C, EGFR, PD, one kind of or wherever KRAS inhibitor comes, G 12 D, or KRAS pan, KRAS selective that we can actually hopefully harness the same interaction with the immune system. So, you know, I’m getting towards I think the last slide to the talk. But you just to kind of share with you, these are the trials that I’m aware of that have that involve PD, one and BRAF combinations. This is kind of the follow up to Scott Kopetz and Dan Morris trial. Swag, 2107 which, I’m sorry I meant to put that, that name in here. This trial, as far as I know, does not allow prior BRAF, and it randomizes to get people to standard beacon to Beacon plus PD one. This is the entity number. And then this Novartis trial I mentioned earlier, that uses a B RAF or core, has at least one arm that that that combines BRAF prk with PD one. And this does allow prior. It accepts people who do who don’t, but it allows you to do it. So this is, these are just options, I think, will be great for you to know about and share with your patients. And so I’ll end there. I think, you know, understanding the resistance mechanisms, really, I think can help guide and accelerate the development of effective treatment strategies. And I think, you know, in a span of about five years, we saw the response rate in colon cancer go from Colon cancer go from 5% to 20 to 30% by understanding the underpinnings of resistance here, I think all the data for information, one thing that the MAP kinase pathway really does represent a critical dependence in colon cancer, probably in KRAS colon cancer as well. And optimizing the inhibition that pathway can improve efficacy. Unfortunately, diverse mechanism resistance, kind of all you may arise in these patients, and they all seem to, fortunately converge on one event, which is to turn the map kinase pathway back on. And if we can focus on a way to interrupt that, so, for example, by targeting ERP, we might be able to actually prevent the output of this resistance. And ultimately, I think there’s a lot of promise in integrating other therapy my knowledge, particularly immunotherapy, to try to really pull the immune the immune system, into play, to try to eradicate whatever resistance that we can’t deal with with targeted therapies alone for a more durable response or maybe even cure without a stop and take any questions you have in the remaining time.

Manju George 56:26
Okay, thank you so much. We don’t have too much time.

Dr. Ryan Corcoran 56:28
Okay, I thought I was doing better on time. I’m so sorry.

Manju George 56:31
No worries. The question that I have is that you showed that with your ERK inhibition and the BRAF inhibition you had like the heat map, showed that there was a lot of suppression of the MAP kinase pathway, and then, you know, and all the immune genes getting activated, right? So following the Novartis trial, are you planning to do something similar, like what Dr van Morris is doing, but instead, with the B RAF inhibition plus ERK inhibition plus nivolumab, are you planning something like that possible?

Dr. Ryan Corcoran 57:00
I mean, I think the Novartis trial will be the first version of that, you know, I think that there’s a lot of question now, you know, what do you do now ? Do you do BRAF ERK and PD one? Do you do BRAF, EGFR, erk and PD one? I mean, you know. So I think the Hercules three trial will, I think, be helpful to show, if you know, really show I think whether adding or is helpful, and I think that trial probably will answer that question, I hope in one way or another. And depending on what that shows, we can try to then bring this parallel effort that’s happening of just adding PD, one alone, and decide if we should merge those effects. So that will be interesting. I’m looking at the chat. There’s a bunch of questions here. I can try to go through a couple of these quickly, and maybe I might have a minute or two to go over here. I’ll jump into my next, next meeting, because I thought we had about 10 minutes left, and I must have lost track of time at the end there.

Manju George 57:57
I think most of them are like comments. So I’m seeing, yeah, I think some of them, you know, as you answered, I think as you went through your talk, many of them were answered. So there is one question in the literature. It seems that targeting TGF beta pathways interesting for CMS four, but the results of the clinical trials are rather disappointed. Do you know why?

Dr. Ryan Corcoran 58:18
We don’t know why. And you know, I think that TGF beta, you know, may, may have some interaction really, with the immune response. But, you know, these CMS criteria, they haven’t really, we haven’t really figured out and merge them with new therapeutic strategies. Well, you know, I see this other comment here, and again, I agree that the Novartis phase one trial, there’s lots of different you know, this is commenting on a BRAF, MEK, ERP only afforded a stability of about five or six months. You know, a lot of these arms aren’t up at full dose yet. And, you know, I’m not sure BRAF MEK and ARK is necessarily what I would – I think BRAF ERK is the key core. So some of these arms I’m more excited about than others, but we have to test them out. I think what the trial is doing, which is good, is it’s going to answer the question, and the answer won’t be great, won’t always be good in every single arm, but we’re getting there. But I think that the BRAF, erk, PD, one arm on this trial, I think will be really interesting. There’s also a shp2 arm too, so we’ll have to just let those get up to full dose and and they’re still in dose escalation. (Reading the next question – ) Is there a way to receive immunotherapy, regardless of MSS or MSI? So the one way to that you can actually kind of qualify for immunotherapy is if your tumor mutational burden is above 10, that alone is probably enough to get it doesn’t colorectal cancer patients with TMB above 10 don’t respond very well immunotherapy, but sometimes patients can use that to help get access to immunotherapy, if they try to create this, probably the best thing would be to try to get on one of these trials. So if you haven’t had BRAF, or someone hasn’t had BRAF, try to get on swab 2107, if someone has then the Novartis trial, and hopefully future trials will, will, will come and then (Reads the next question – ))we’d really happy to hear opinion on the beacon input. Okay, so I think maybe I hopefully someone asked that question before I addressed it. But yes, we talked about this where that pattern of resistance really did seem to be predominantly again, like what we’ve always seen, emergence of KRAS and MAP kinase -?- mutations, probably about two thirds of patients. That was a really cool presentation, and good to see it.

Manju George 1:00:22
Dr Corcoran, how does the olix search (?), and if the biomed Valley ERK inhibitor compare with the EVAs 007?

Dr. Ryan Corcoran 1:00:33
It’s far less potent, so it’s probably about 30 to 100 fold less potent. And while I think it was one of the better earlier erk inhibitors, probably not as good as some of the newer kind inhibitors. And I think, you know, the I’m hoping we’ll be able to answer this question, right? That that that now that we have agents that are actually kind of do what they designed to do.

Manju George 1:00:56
Okay. I think so I got through as many of these questions I could.

Dr. Ryan Corcoran 1:01:01
Feel free to email me if there are other burning questions, you can pull the questions or email me individually. And it was a pleasure talking all today.

Manju George 1:01:09
thank you so much for your time. Great to have you. Okay. Bye, bye.

Dr. Ryan Corcoran 1:01:16
Thank you very much. Bye, bye. You.