Scientist Stories: E. John Wherry, T-cells and Cancer Immunotherapy

Hello and welcome to the Cancer Research Institute Cancer Immunotherapy and You patient education webinar series. I'm Dr. Arthur Brodsky, your host, and I'm the assistant director of scientific content at the Cancer Research Institute. And during today's webinar, we'll be focusing on cancer immunotherapy 2022 research and a look ahead. Over the next hour, we'll, we'll hear from a leading immunotherapy expert about the future of the field of cancer immunotherapy. In particular, we'll look at cutting-edge clinical immunotherapy treatments, biomarkers in cancer immunotherapy, technologies to accelerate advances, and the next frontiers in cancer immunotherapy. Toward the end, we'll also have some time to answer some audience questions, which you can enter via the Q&A box below. And before we begin, I would just like to quickly thank the generous sponsors of this webinar series, Bristol Myers Squibb and Lilly Oncology. And now it is my pleasure to introduce today's expert. Dr. John Wherry is currently the director of the Institute for Immunology, the chair of the Department of Systems Pharmacology and Translational Therapeutics, and the Richard and Barbara Shiffrin President's Distinguished Professor at the University of Pennsylvania Perelman School of Medicine. He is also a former CRI-funded postdoctoral fellow whose work during his fellowship was very very fundamental to the field of checkpoint immunotherapy and really helped kind of explain, help reveal the value of the PD-1/PD-L1 pathway. And Dr. Warey also now serves as an Associate Director of the CRI Scientific Advisory Council. So welcome, Dr. Warey, and thank you very much for joining us today.

Hi, Arthur. Thanks for having me. It's always a pleasure to be here with CRI.

It's great to have you. So let's jump right in. As far as novel treatments, new applications of existing therapies, especially in earlier stage cancers, and innovative clinical strategies, what are you most excited about in the coming year with respect to cancer immunotherapy?

Yeah, I think there are a couple different classes of things that are, that are really exciting and I'm looking forward to. The first, I'm gonna go through each of these and give an example or two, but the first is new checkpoint combinations and novel ways to apply checkpoints. The second, which may not sound like immunotherapy, but I think is exciting for the entire field, are new drugs targeting the oncogene RAS. KRAS in particular is mutated in a very high percentage of all cancers. And we now have some new drugs that seem to inhibit RAS very effectively. Using those drugs in combination with immunotherapy, I think, is something else that's gonna be very exciting. We also are making great progress in strategies for hard-to-treat cancers. And I'll talk about these as we go through, but in particular pancreatic cancer, glioblastoma, and multiple myeloma are areas where I expect that we'll see some advances over the next year. And then as you mentioned, moving into earlier stage cancers more and more as we understand how to use immunotherapy. So just one example, just in the past couple of days, we've seen a new report on the combination of targeting two checkpoints, one that we're very familiar with, PD-1, and a second checkpoint called LAG-3. A beautiful set of trials from Bristol Myers demonstrates how effectively you can target both of these pathways at the same time. Now, the idea of dual checkpoint targeting isn't necessarily something new, but this, this really is one of the few major advances in targeting two pathways at the same time since the original targeting, you know, using anti-CTLA-4 and anti-PD-1. This is now the second one where we see really, really good clinical activity. I think one of the things that was the ability to do this as a frontline treatment. And these patients were previously untreated, so we can now really reveal the effect of some of these novel combinations. But I see those combinations pushing even farther with combining checkpoints with ways to activate other parts of the immune system, particularly innate immune system. So the parts of the immune system that kind of get the B cells and T cells going. And also the ability to use combinations of checkpoint blockade with cytokines. So cytokines are kind of the growth factors for immune cells, to put it kind of simply. They're very specific to immune cells. They have really, really potent activities. And as it turns out, cytokines were our very first immunotherapy, immunotherapies done at the National Cancer Institute many, many years ago, but come with a lot of problems in how to use them effectively. Some second and third generation versions of some of these key cytokines now look quite promising. So I'm excited to see where that will go in 2022. I want to mention just briefly, I talked about the KRAS drugs in combination, but I want to skip over that and talk about these hard-to-treat cancers. We've seen some very exciting advances in the space of pancreatic cancer recently. In particular, the ability to combine multiple types of immunotherapy drugs in the same patient, which is a couple of years ago was something very difficult to do for a lot of logistical clinical trial reasons and also safety reasons. We now understand these drugs much better. We understand where and how to use them. We understand the kinetics of their responses that allows us to combine, in the case of pancreatic cancer, a drug that activates parts of the innate immune system to kick off the cascade and then come in a few days later and add a checkpoint blockade to make sure that the adaptive immune system, basically the second half of the handoff, continues to work properly. These things in hard-to-treat cancers are really going to change the landscape. Glioblastoma is the other place where I think we've seen major scientific advances over the past few years that are just creating a perfect foundation for major clinical advances. The last thing I'll mention on this topic is the idea of using cellular therapies. And in the space of multiple myeloma, that third hard-to-treat cancer, I expect that we're gonna see some important clinical advances, very likely using cellular therapies and, and probably what I will call next-generation cellular therapies. Where we can not only generate CAR T cells or engineer T cells to work the way we want, but we may also now be able to start endowing those T cells with very specific properties and perhaps even what we call logic gates to only turn on property X when they see a signal in the tumor microenvironment or a signal from a cancer cell. So those are some of the things that I'm excited about. Some of them just a couple of years ago would have seemed like science fiction, but the field is moving so fast that I do expect some of these things will be on our clinical are in this calendar year.

It is, it is crazy to think of the amount of precision and customization we can do these days, and hopefully it will lead to great things. So, you know, as you alluded to, cancer immunotherapy has kind of successfully picked a lot of the lower-hanging fruit, so to speak. But as you mentioned, there's still a lot of other hard-to-treat cancers that don't respond to immunotherapies, and it's become clear that to cure the majority of patients, we will need novel approaches, including, as you just mentioned, combining immunotherapies not only with each other, but potentially also with traditional treatments like chemotherapy and radiation. However, there's a lot of option, a lot of potential treatment options, and determining the right combination for a particular person is, isn't easy. So to improve doctors' ability to tailor their treatments to individual patients, they're coming to rely on measurable factors known as biomarkers that can provide insight into someone's immune health as well as their cancer biology. This information can then help the doctors predict which therapy or combination of therapies might have the best chance of working for a particular person. And we already have some helpful biomarkers, as you know, PD-L1, MSI-HI, which stands for microsatellite instability high, and tumor mutational burden, otherwise known as TMB. But by themselves, they, they aren't really great predictors of patient responses, because they don't really reflect the entirety of the overall activity that's driving the cancer and the immune activity. So as we move forward, what are some promising clinical approaches that the field is pursuing as far as discovering, validating, and then using the biomarkers to improve cancer immunotherapy's effectiveness?

Yeah, thanks, Arthur. This is a really important question. And the simplest way to think about it is we don't all wear the same size clothes. So why would we think that a one-size-fits-all cancer treatment would make any more sense than all wearing the same size pants? It just doesn't work that way. We have a lot of information from really the past almost century of treating cancers to know that the tumor's genetics really matter and the exact details of what kind of tumor cell you have matters. But it matters just as much on the immune side. All of our immune systems differ from one another, and we can get into this more in, I think, the next question. But this has led to this idea that we need to also tailor our treatments to where our immune system is in the response to that tumor. And so this has led to the idea of, for the moment, let's call them sort of different immune types or immune fingerprints, we've started calling them. These are influenced by everything that's happened to you in your life as well as your genetics. So what we're starting to see is an idea that for a particular kind of cancer, let's just say melanoma because it's easy, because we know a lot about it, because we've been able to study it, we've been able to access the tumors because often they're superficial. We now know that if you look in the tumors, patients that all look largely the same outwardly can have many different flavors of pattern in the tumor environment. So there's a beautiful study from my friend Max Krummel at UCSF recently defining what he called tumor archetypes. So general patterns with which the tumor cell, the tumor microenvironment, and the immune system all interact. It's not that we're going to have an infinite number of these. Not every cancer patient is going to have its own unique pattern of this archetype, but rather they fall into large categories. Those categories now help us tailor different treatments that will be most likely to work in that particular patient. We can think about some of the existing biomarkers we have as being one axis in this idea of an archetype. If you are PD-L1 high, what this means is you have high amounts of the other half of the PD-1 pathway in your tumor, which means that the tumor has engaged this negative regulatory pathway to suppress the immune system. That also tells us that the, the tumor has some immune cells there, otherwise it wouldn't need to counteract that part of the response. But that only tells part of the story. We don't know how much the immune system has been suppressed. We don't know where those immune cells are in the tumor. We don't know what the other inflammatory environment is like in the tumor and whether there are growth factors that are driving the tumor to divide really fast, whether there are signals to generate fibrosis, which makes the tumor harder to treat. So we're now seeing the opportunity to actually create those biomarker maps in a much more clinically applicable fashion. This is great. You can do this in the research lab, and that's interesting, and we can discover mechanisms that way. But what we really want to do is to be able to work this into the clinical workflow So we can say, okay, this patient, while they have PD-L1, they really don't seem to have as many immune cells as they should have in the tumor. So that means that blocking that PD-1/PD-L1 pathway might not be the best strategy on its own. So can we actually combine PD-1 therapy with something that'll kickstart the immune system and get more immune cells in there? So we're looking at these biomarkers not in isolation anymore. And bringing that into the clinic has challenges because we need these to be highly reproducible, very easy very rapid turnaround kinds of tests. But I think what we're going to see in the next probably 12 to 18 months is a real advance in moving those biomarkers in. The second thing I'll say— there are two more points— the second thing I'll say is we're learning more and more about the overall immune fitness. And you mentioned this idea of immune health that we can get into in more detail, but really the idea that a patient's immune system isn't necessarily the same at baseline as a different patient. A 33-year-old melanoma patient is going to have a very different baseline immune system than an 87-year-old melanoma patient, especially if there are other differences, one being a smoker, the other a non-smoker, and different other backgrounds in their life history. That impacts how likely it is that the immune system will respond. This becomes more important even when we look at patients who've had several rounds of chemotherapy or other kinds of cancer therapies that can affect the immune system. So understanding what the potential is of the immune system when we're then going to ask the immune system to respond to immunotherapy is the other type of biomarker that we're starting to think about very carefully, especially in complex or hard-to-treat cancers. The third area for biomarkers that I think is going to really explode this year is the idea of a spatial analysis of the tumor. Where are the immune cells in the tumor? This matters a surprisingly large amount. If they're sort of randomly distributed throughout the tumor, not really organized in any fashion, kind of like dumping a bunch of BBs on the floor and they all spread out, that's not actually very good. You can have the same number of immune cells, but if they're actually coordinated and they're talking to each other and they cluster, especially around the edges of the tumor, where you have different types of immune cells all interacting with each other, that's a very positive prognostic indicator in a large number of cancer types and also may be the physical location where some of our immunotherapies are having their biggest effect. So I think the three things are understanding these sort of archetypes or immunotypes that distinguish one patient from another and categorizing them as they relate to treatment options. Two, understanding the overall immune fitness of a patient, what their immune system has the potential to do. 3, thinking about the spatial analysis and maybe even the temporal analysis of how things change over time in a particular tumor will likely be very important for biomarkers.

That makes a lot of sense. And I think you did a great job of explaining how complicated the situation is. It's not as simple as looking at one factor and it's a binary choice. Oh, it's either high or it's not, and that's how we treat. You have to kind of look at it holistically to some extent. And so related to that, a concept you alluded to a little bit earlier, but a concept that I've heard you mention a lot is immune health. And I understand that you led some important work that explored this concept in the context of COVID-19 patients. So I have kind of a multi-part question. First, explain, I guess, what do you mean by immune health? And then second, what did you learn from your COVID-19 studies? And how might you be able to apply some of those insights to cancer and immunotherapy?

Sure. Yeah. So I mean, and thanks, Arthur. This is something that we think a lot about these days. We think about it in the cancer immunotherapy space and also in the COVID COVID space. So what we mean by immune health, let me give sort of an example that I think will illustrate the point. If you go to your cardiologist and ask, how healthy is my heart? They're going to take your blood pressure. They're going to run some, you know, EEGs, EKGs to measure heart function, get cardiac output. And they'll be able to give you quantitative numbers, true measurements, and comparators to know how healthy your heart is compared to other people your age.. And then based on those measurements, they'll be able to recommend specific kinds of treatments to improve your heart health or to do preventative treatment to make sure your heart stays healthy. And this is true for neurology, you know, many other systems in the body. If you go ask that question of your primary care physician, because there is no clinician called an immunologist— there's an allergist, not really a clinical immunologist— if you go ask your primary care physician, how healthy is my immune system? We count white blood cells. It's basically a test that we've been using for about 100 years. If you go ask an immunologist who is a researcher running a research lab, we can measure millions of features of your immune system quite literally in an afternoon. So the idea of immune health is to figure out how to use that information about features of your immune system to diagnose treat and predict and prevent— predict future changes in health over time. The, the basis of immune health is the idea that really there's no tissue or cell in your body that doesn't interact with your immune system at some point. Most tissues in your body interact with your immune system all the time. Some of those immune cells end up back in the blood where we can actually listen to what those immune cells are telling us about how healthy the rest of your body is. So what we mean by this, immune health, is using the immune system to diagnose, treat, and prevent disease. What we also know about this, and why I think this is really important, is we know that the variation in your immune system from person to person is only partly contributed by genetics. This is not simply a genetic question, why your immune system is different from my immune system. It also And we know that the genetic contribution in identical twins is only about 30%. We know that your life history has a huge impact on your immune health. All the infections that you've had in your life, and we think about this a lot these days. This is not a foreign concept to anyone anymore about how your history of infection may impact your future responses to things. But we know this for a variety of different things. So we've been thinking about this a lot actually for cancer immunotherapy over the past maybe decade. And over the past maybe 5 to 7 years, we've built platforms to study this concept, particularly in melanoma, also in pancreatic cancer, where we've been asking, how does a patient's basic immune characteristics influence their ability to respond to therapies? As we've been doing this and we've published some of that work, a pandemic stumbled upon us. And we realized, one, that we had to do something to understand this disease early in March of 2020. And two, that we had the backbone of something that might make a real difference. We were seeing patients in the hospital that were really evolving down quite different clinical paths. Obviously, you know, I grew up studying viruses in the immune system. Viruses interact with the immune system and evoke very, very different patterns of responses depending on the host, depending on, on the virus. So we hypothesized that some of this variation clinically was a result of different patterns of the immune response. Very much like those archetypes that my friend Max at UCSF has defined in tumors, we hypothesized that in COVID we would see systemically— that is, we could see it in the peripheral blood— these different patterns of immune response that would be occurring. And it wouldn't be that every patient had its own unique path. Rather, there would be large general groups of patients that behave the same way. So we applied what was essentially an adapted immunotherapy immune profiling backbone to study COVID-19 patients. And what we found is there were really 3 major patterns of immune response in hospitalized, very sick COVID-19 patients. We had one group of patients where the immune response was essentially on hyperdrive. The B cells and T cells were more activated than we've seen in just about any other setting we've ever looked at in humans, and they were very imbalanced. This seemed to be one type of immune activation that was occurring. We had another set of patients where the immune response looked robust but actually looked kind of appropriate for a viral infection. It looked like those were patients where, yes, you would expect them to be sick, but it looked like the immune system was doing kind of what you would predict it should do. And then we had a third type of patients that looked like the immune system never got the message. There were— the immune system just wasn't activated, wasn't engaged, wasn't responding to the viral infection. Now, the value in knowing this in real time was that the first group of patients that I mentioned probably would have benefited, and we now know does benefit, from treating with steroids or immunosuppression. The third group of patients, treating them with steroids or immunosuppression actually is detrimental. Okay, again, we don't all wear the same size pants. So this was where, uh, returning that information to the clinic in real time gave us an ability to use an immune health metric to make treatment decisions. We're now moving this forward in the setting of COVID-19 vaccination to measure features of the immune system to know when some of our cancer patients and other immunosuppressed patients might need a fourth, possibly fifth booster dose, or when those boosters are unlikely to provoke a good immune response because of the immune system characteristics and where those patients might benefit from instead prophylactic monoclonal antibodies where we can get them. So our effort now is to actually be able to simplify some of these complex immune measurements so that we can put them back in the electronic medical record in a way that a physician can order a test and make a decision based on the results of that test returned in almost near real time. So hopefully immune health will move from this idea of describing how fit your immune system is to something that's actually actionable in the clinic where we can now order tests to say, how healthy is my immune system, at least initially, as it relates to SARS-CoV-2 vaccines? And then maybe in the future, which immunotherapies for cancer might, might work best in me compared to a different patient?

That's great to hear, and such an important step. And I think another important thing to point out, um, you kind of referred to as we were discussing biomarkers in the last question But there's, there's so much going on. And really, until recently, we didn't even— we needed technology to catch up in some ways for you to be able to do these, these deep dives. And not only— I mean, obviously, we've, we've done biopsies on tumors for a while, but, but even that kind of— there might be better ways for it. And so there, I want to turn to a study that you recently led, where you were applying a promising new technology to analyze immune activity with glioblastoma, which is an aggressive form of brain cancer. And here you showed that by measuring the patient's cell-free DNA in their blood, also known as a liquid biopsy or a blood biopsy, and this just took a simple blood draw, you found that you could learn about the immune activity within the brain tumors and in particular, which types of immune cells had infiltrated the tumors. So how might this approach, this liquid biopsy approach, help improve care for patients in the clinic? And what other technologies have the potential to help improve cancer immunotherapy's benefits moving forward.

Yeah, yeah, thanks. This study is a very interesting study, and there are a number of studies that have highlighted the ability to capture kind of bystander nucleic acid and to use that to sort of get a sense of what's happening elsewhere. And so this, this sort of fits with this idea that if we know what we're looking for in the blood, we can often find signals that tell us about some distal site. So this study in particular, we captured DNA in the blood. We were able to sequence that DNA in a way that revealed some of that DNA was coming from regions of the brain tumor and give us some sense of what might be happening there. Now it's not enough to really say like this is the sequence of the tumor cells, we know all the mutations. It's not quite enough to know, you know, which immune cells are there. But with basically the shadow of something happening at a distal site, we can infer a whole lot. What's really nice about this is you can do this longitudinally over time. So you get a kinetic picture of how well therapies are working, how much is that signal, whatever that signal is, changing over time. There would be great interest, I think, both clinically and experimentally to get serial biopsies in some of these more difficult to treat cancers. And some of this is starting to be done, but it's extremely taxing. It's very difficult on the patients. It's maybe not clinically indicated because of some risks associated with it. And actually, it's extremely expensive. If we can get a sliver of that information from the peripheral blood in a very easy way, or even cerebral spinal fluid in the case of glioblastoma, we can then get this picture over time. So we can learn a lot about the tumor. We can learn a lot about the immune system. On the larger scale, this illustrates this concept that the peripheral blood is a giant haystack. And buried in that haystack are these needles that tell us super important, sometimes really precise information. But we have to know what the needle looks like. And in many cases, we have to have a big enough magnet— that is the technology— to really find the needle. And in this case, the cell-free DNA, the magnet is the ability to sequence deeply enough and sequence the right DNA in the blood. We're now realizing that there are these little packets in the blood called exosomes. These are basically little pieces of cell membrane that get spit out. We don't fully understand why they get spit out and why certain cells do it a lot and others don't. And they can often also contain a lot of information. Tumor cells seem to make a lot of these. So do fibroblasts in the tumors. This gives us another needle that we can identify, read the language of, and understand what's happening in the tumor. So I think there are a lot of technologies. One of the things that we have these days on the scientific side is sort of an embarrassment of riches in the ability to measure things, especially on the DNA and RNA side. What I'm hopeful about for the next year is that some of that technological advance will also spill over into these imaging approaches. What I mentioned earlier about the spatial geography in the tumor, being able to measure more things there. But I think it's likely in this next year we'll see also some advances in being able to image things using radiological approaches clinically. So using tracers where we can— and for those of you that don't know, most of the time when you get a CT scan or a PET scan, most of what's being measured is the ability of tumor cells or cells of your body to take up glucose. So we're measuring basically the energy needs of the cells in your body. And of course, tumors have higher energy needs than other cells. But it's now possible to link basically tags onto some of these PET tracers. So instead of just asking who eats all the glucose we inject, you can say, where are my T cells? And image accumulation of T cells before and after immunotherapy.. And I think we're going to see more and more ability to image the immune response change or features related to the immune response change over time after immunotherapy. This is going to be incredibly important to understand, for example, how long does it take for a particular kind of immunotherapy to get the immune system on board. And that's important because we want to know if we're going to combine immunotherapies, we want to know when is the peak time to actually take advantage of this sort of synergistic effect that's at the heart of most of our combination immunotherapies. So I'm very excited about the technologies that are going to allow us to see deeper into the haystack, so to speak, and the magnets that will allow us to pull information out of the haystack. I'm also very excited in some of the advances in imaging, and I just gave two examples of imaging the tumor itself and then imaging based on these radiological approaches.

That's so fascinating, and I think the haystack is a wonderful analogy. I want to just kind of honing in on a point you mentioned I think is also really important. And talking about it in multiple responses now, but the immune system isn't something that's static. Not only is it different once someone starts to develop cancer potentially, but then when they're on treatment, the immune response changes. And, you know, in the past, we didn't really appreciate that. And like you mentioned, it would be very helpful for doctors to be able to kind of monitor the immune system over time. But having to to go in in an invasive way is obviously not ideal. So I think this could— technologies like these, whether it be the blood draw or the imaging, I think could be so helpful, you know, obviously from the doctors and the resources perspective, but most importantly from the people who have to undergo these procedures. And so, you know, one last question, I guess, from me before we open it up to the audience. So, you know, in addition to all these exciting avenues we've discussed, clearly there's still a lot more to the body's complex ecosystem that influences cancer. And the immune system and how patients will fare. Things like the microbiome, all the bacteria and fungi, viruses, bacteria, microscopic stuff within us, the relationship between the immune system and the nervous system, metabolism, among other things. And ultimately exploring these frontiers, I think, could help us unlock even more cures for more patients. So in your opinion, what are some of the most promising cutting-edge areas that are being investigated for their potential to transform cancer care?

Yeah, so this is, this is my favorite question, Arthur, and we can talk about this for an hour. But let me give just— I want to touch on 4 topics just very, very briefly. One that we've covered in other questions so far, and that's this idea of immune health. And so I won't be redundant, but I do want to sort of push the boundary on that a little bit. And so what I'm really excited about, and you touched on it a little bit, is asking how sort of larger things impact our immune health. I mentioned in passing this idea of life history, right? It's not just genetics. We know this is an incredibly impactful feature of immune health for influenza. The year you're born imprints you for the rest of your life in how you respond to every influenza infection or vaccine you get for the rest of your life based on the sequence of the strain of virus that you were exposed to the for the first time in your life. So that's an indelible mark on your immune system that now seems to actually carry with you for life. Neither good nor bad. Nobody worry about the year you're born. It's all fine. It shapes things in different ways. But if we take that further, we now know that certain other features really do have an immune component, but we're, we're barely scratching the surface of understanding, one, what the impacts are, and certainly far away from being able to harness this to make the immune system work better or worse. And I'll just mention very briefly and then talk about some areas that I think are exciting to think about for the future. The first is diet. And you mentioned the connection between the microbiome and metabolism. And it's very clear that diet impacts the immune system. Exactly how, we don't know. We are seeing benefits of high-fiber diet. We are seeing benefits of— in fact, there are clinical trials going on, very good, rigorously designed clinical trials, asking cancer patients to eat a lot of beans, when they're getting immunotherapy because of the high-fiber diet and the effects on microbiome. And I think they're going to be super exciting. They're going to reveal mechanisms and connections and biomarkers. But we need to learn more about this. We know that, that fasting, um, you know, intermittent fasting clearly has impacts on the immune system that we don't fully understand how they work. We don't know how to use them properly. Um, so there are many aspects of diet that need to be studied and integrated with the concept of immune health. Health. I'll add to that just two others where we know even far less. We know that sleep and circadian rhythm also impact the immune system. We know more about circadian rhythm effects on the innate immune system, but there are also hints that the circadian rhythm and sleep biology impact T cells and other things. How to harness it, how strong the effects are, we still don't really know. And then exercise clearly has immune rejuvenating effects. And that's probably the— of these three, that's the place where we probably even have the least rigorous data. But it's very clear going through life that exercise has an immune rejuvenating effect if done properly. And so how do we study this? It's very hard. I mean, you ask someone to self-report their diet and you might get an approximation of what's true. It turns out you ask people to report their exercise and they're probably even worse. Reporting sleep, it's the worst of the three. We all sleep less well than we think we do. And so there's studies using wearables and you can get an idea of the pattern of people sleeping and when people really think they're getting deep sleep, they're really not and so on. So the idea of using wearables or using continuous measurements of some of these things, I'm very excited about. Just three other areas quickly to mention. I know we wanna leave enough time for questions. One, you mentioned the neuroimmune connection. The nervous system and the immune system are our two major sensory systems of the body. Nervous system we think about as a sensory system very obviously because we touch, we see, we taste. But the immune system is sensing everything that's going on in our body all the time. It's attempting to return our tissues in our body to homeostasis all the time through fighting off infections, returning those wounds to homeostasis, and so on. And the connections between the nervous system and immune system are now very well established to the point that we're starting to see opportunities to manipulate one through the other. There have been some amazing studies recently showing that you could stimulate certain areas of the brain that are known to innervate— basically, the nerves lead down to the intestine. And if you stimulate that part of the brain, you can actually impact immune cells at that location in the intestine. So fascinating studies linking the two. I'll also put two other things on the radar. The first, which which, you know, is kind of obvious, and I hope it's obvious, is the opportunity for RNA technologies. For anyone in the audience who's not aware, our two mRNA COVID vaccines arose from cancer vaccines. The original purpose of the RNA platform for making vaccines was to make personalized cancer vaccines, because with that technology, you could make a personalized vaccine in 4 to 6 weeks. So let's not forget the power of that technology to impact cancer immunotherapy. And now, given all the interest, that technology has exploded exponentially in what it's capable of doing. There's a paper in Science last week showing that you could actually use RNA technology to inject RNA to make CAR T cells in vivo in an animal that would treat heart disease by attacking heart fibrosis. The possibilities here are endless. And then similarly, if you take that to the next logical extension, our ideas of nanotechnology or smart drugs that can actually change and adapt with the conditions. So I'll pause there, maybe with those sort of feeders that will provoke questions on some of those we could talk about.

Yeah, it's incredible. And, you know, a big part of science too is trying to focus, trying to measure one variable kind of in isolation and see how just that one affects it. But, you know, when you talk about how we live our lives, it's hard to, you know, how do you tease apart the sleep from the exercise from the diet? It's definitely, definitely some challenges in how we'll structure those experiments. So we have one question, or our first question from the audience was, goes back to our biomarker question, specifically the PD-L1 and the MSI-high and the high tumor mutational burden. And specifically, their question is about colorectal cancer. I think that's one of the really interesting types where, again, that the biomarkers aren't perfect, but patients who do have some of those biomarkers are much more likely to respond, and patients that don't probably won't respond. And so the patient's question is, are there any other biomarkers potentially on the horizon? Or maybe even like, I guess, you know, as you're referring to kind of a panel of biomarkers.

Yeah, there are some. I think You know, these are the 3 best so far. There are lots of companion biomarkers for individual drugs. I think the one— and you bring up colorectal cancer, it's a very interesting one, and it's actually a challenge. MSI-high colorectal cancer responds very well to immunotherapy. We still have room to do there. Not every MSI-high colorectal patient responds to immunotherapy the way we want. But on the flip side, the non-MSI-high colorectal cancer, there's still a huge unmet need What's clear there from older studies is this idea of the immune aggregates seems to play an important role. The exact context of immune cells in the tumor is a prognostic marker that seems to matter. I'm optimistic that as we get, to be quite literal, more colors in our tissue imaging on tumor histology into clinical workflows, we're going to be able to use these complex patterns more easily. The, what we call lymphoid aggregates in the tumor, seem to have a lot of potential as a biomarker. They're difficult because they require multiplex imaging in a clinical workflow. But there's a lot of effort to move that forward.

So we have two more questions that are kind of related. So I'm going to try to combine them. They both have to do with the circulating, the cell-free DNA, one component of which, you know, as as you mentioned, there's lots of DNA in our blood, some from the tumor, some from the immune cells. And these questions relate to, one, do you expect that these liquid biopsies will be specific or precise enough to determine tumor immune profiles to such an extent that they would actually be able to dictate— not dictate treatment, but guide treatment? And then second, will they be able to— will advances in these blood-based biopsy tests Would they also be able to help physicians monitor the responses as a patient's continuing treatment?

Yeah, so, so the answer to both is yes. Really getting the tumor-immune interactions, we still require a little bit of work there. But what we're already doing in some cancers, not as much in glioblastoma yet, but for example, in lung cancer, we can actually see which mutations the tumor has by using DNA in the blood. So in lung cancer, we can tell if it's a KRAS mutation or one of the other mutations that's common in lung cancer. We can see that in the blood, and based on that, we can decide whether a KRAS inhibitor or another inhibitor would benefit that patient. And to the second question, we can then monitor those mutations in the blood over time, so we can actually see a surrogate of tumor burden go down. What's important there is we can also see escape from that mechanism occurring before it occurs clinically. So if you treat a lung cancer patient with an inhibitor of KRAS, for example, you can see the KRAS mutant signature in the blood go down. What you can also see sometimes, unfortunately, is that tumor cells with a different mutation then start arising. So in other words, there was a small subclone in the tumor that had a different driver mutation or different mutational profile that then was not susceptible to the first drug. That gives you a much more rapid ability to react and to hopefully address that second tumor clone that's emerging before the tumor burden gets too high, before the disease gets too cumbersome to treat. So the answer to both questions is absolutely yes. There are opportunities to use circulating tumor DNA to make treatment decisions and to monitor treatment response. Great.

I've got, I've got a question that you're really going to like. If you thought the next frontiers one was good, So our next question relates with T-cell exhaustion. And fortunately, we have one of the world's foremost experts in T-cell exhaustion with us. So how does— I guess, could you maybe just start out by explaining what T-cell exhaustion is for those who don't know? And then the other part of the question, specifically what our audience member was interested in, is how do clinicians detect when T-cell exhaustion occurs?

Yeah, great question. So yeah, so as Arthur knows, we've been working on T-cell exhaustion actually since the CRI funded me as a, as a trainee 20 years ago. So T-cell exhaustion is what happens when T cells of the immune system get chronically stimulated. The immune system evolved to deal with infections where typically you get a period of immune activation, you control the infection, and then the immune system gets rest and the immune system gets to sort of rejuvenate itself because it's not being stimulated. Under conditions where the immune system is continuously activated, T cells in particular undergo something called exhaustion, where their functional properties get attenuated. And they go into sort of a state where they end up basically in a stalemate between a chronic infection and the immune system or a tumor and the immune system. And this is a balance, this is a very delicate sort of evolutionary balance. If the tumor starts growing more, the T cell exhaustion will get worse. But if the T cells start getting better, they'll push the tumor down. And this happens continuously over time. What we've learned about exhaustion is that if you take away some of the negative regulatory pathways holding those T cells in check, you can give them the advantage, and then they kill off the tumor more. This is the whole basis of checkpoint blockade, at least PD-1 blockade. So the question is, how do we know that that's happening clinically? Well, a number of years ago now, Alex Huang, when he was in my lab, was really the first to show— we'd known how PD-1 blockade was working, but Alex was the first to really show that the major cell type responding in melanoma patients was an exhausted T cell. He used a series of biomarkers in the blood to examine which T cells were responding, how they were responding, what were their transcriptional circuits that they were using. Now, we can do all that in the research lab, and we can know that for small cohorts of patients. The question is, how does a physician, you know, at a community practice know that when they put their patient on anti-PD-1? The answer is we don't most of the time. We trust from the biology that we've studied in small numbers of patients at high resolution that we can infer what's happening from the clinical patterns of a large number of patients where we have low-dimensional data. What it turns out is that in most cases where tumors have a lot of mutations, these MSI-high tumors, tumors where we know there's been a mutagen— smoking, UV from sunlight for melanoma, in the case of head and neck cancer, often a viral infection— where the tumors can be recognized by the immune system very effectively, but then you reach some stalemate. In many or most of those cases, exhausted T cells are playing at least some, sometimes a major role. So we sort of infer most of the time. When we see these treatments failing, that's when we need to look more carefully to see if maybe T cell exhaustion wasn't overcome. And that's where we're starting to develop some of these immune health measures that we hope to put into the clinic to answer exactly the question that the audience member brought up. But right now we sort of take it on faith and we're hoping to do better than that in the future. Gotcha.

So we have our next question. You know, we've been kind of discussing the whole time about, I guess, the easy-to-treat tumors, the ones that were the most— that have been the most responsive to immunotherapy. I guess melanoma, lung cancer, bladder, kidney, a couple others are what we normally characterize. Most of the time they're called hot tumors, meaning that the immune system has kind of already started the battle within them. But then there's, you know, a lot of tumors. I think the majority of tumors are considered cold in that the— I guess there's several different ways it could happen, but essentially in all of them, the immune system is not able to respond against maybe they're held at bay, maybe they're— maybe they can't even detect it at all, whatever it may be. And this is kind of, I guess, the main, you know, what we've been talking about with these combinations and new strategies is to try to figure out how to turn these cold tumors hot. So what are some of the promising approaches there?

Yeah, this is great because this, this is the place where we need a lot of work. So there are different ways that the immune system is kept at bay, and these cold tumors are cold. One major way is that there are very few mutations in these cold tumors, so there's nothing for the immune system to grab onto. You can think about this like a, you know, a rock climber on a sheer rock face. There's nothing to grab onto for the immune system to really sort of recognize and cling to the tumor. We need to be thinking about other ways to generate immune reactivity. There's some very creative approaches out there that provoke changes in the tumors that make them more recognizable by the immune system. I won't go into some of the mechanistic approaches for that, but there are drugs now to provoke better immune recognition in the tumors. The other way tumors can stay cold, and these are not mutually exclusive, is tumors basically exclude immune cells. They exclude immune cells by building up a fibrotic shield around them. This is often what we think about for pancreatic cancer, where the immune cells just don't get in. If they get in, they're in a really inhospitable environment. So remember those BBs on the floor? They just— the immune system can't talk to each other in the tumor microenvironment. They end up sort of as isolated soldiers, sort of behind enemy lines. So the approaches being thought about there are to make the tumor environment more hospitable, that is, somehow activate the immune system to degrade sort of the fibrous nature of the tumor and, and to get immune cells talking to each other in the tumor microenvironment. The third way is that the tumor set up a very negative regulatory environment. And we see this in glioblastoma, where in the brain you don't want the immune system getting activated too much. So the natural tendency of that tissue is to keep the immune system quiet, even if there are things to recognize there, you know. So you get a viral infection in your brain, maybe you can purge it quickly, but if you can't, you're better off trying to live with it than having your immune system destroy you and kill you. So in the brain, you're dealing with another flavor of that don't activate the immune system set of signals. So what we're learning is that each of these have various sort of levers and control panel switches that we can turn on and off to get the innate immune system involved, which means we can kickstart the right kind of inflammation to bring cells into the tumor, make the tumor cells more recognizable, or switch the inflammatory environment to make it more hospitable for immune cells. We're seeing lots of drugs in this class. We're seeing innate immune activators. We're seeing oncolytic viruses. In the case of pancreatic cancer, we're seeing a drug called anti-CD40, which is a particular switch on innate immune cells that seems to give them the ability to talk to T cells in the adaptive immune system. So there's a lot of science in this space, and our knowledge base on how to activate the innate immune system in the context of tumors has really, you know, generated an enormous number of tools that are in the immunotherapy pipeline at early and some at intermediate stages of testing in humans.

So our next audience question actually segues nicely from that. You mentioned oncolytic viruses. What are, what are some promising— I know already they're approved for melanoma because, as you mentioned, they're superficial, so it's relatively easier to get the virus in. But what is there Are there any promising trials involving oncolytic viruses to kind of heat up tumors?

Yeah, there are a number, and there are a number of companies in this space, and I'm not familiar with all of the early-stage clinical trials in this space, but certainly this has been talked about for a long time in glioblastoma as well, where you might think of glioblastoma to be at the opposite end of the spectrum to melanoma in terms of accessibility, but it turns out that for glioblastoma, as many of the audience members may know, there's a lot of intracranial operation, intracranial accessibility in glioblastoma for palliative reasons and treatment reasons. So getting oncolytic viruses into glioblastoma is something that is high on the priority list for a variety of reasons. There are also companies working on systemic delivery of oncolytic viruses, and this is something that's been thought about for a long time, but it's been harder to understand how we could enact that. And they're a little bit earlier on, how they home to the tumor preferentially is only partially understood at this stage. But yes, I think you could classify mostly the tumors where oncolytic viruses have a lot of future activity, at least in the short term, to be those that there's a lot of accessibility. So melanoma, skin cancers, head and neck, glioblastoma paradoxically, and a few others.

Great. So now for our last question, I mentioned earlier about the mRNA vaccines and that they were initially developed for to fight cancer. And then there they, they were, they were developing the personalized neoantigen vaccines. Neoantigen meaning, you know, it's an antigen, the marker that the immune system would actually target. Neo would just mean that it's one that doesn't belong there. It's whether it's from a mutation or a virus or whatever. And then, and so with that, we can tell the immune system with these neoantigen vaccines, you can kind of tell the immune system exactly what the cancer looks like. It can go in Ideally, it would be able to go in and then eliminate it without accidentally attacking any other cells. So what is the state of these personalized neoantigen vaccines and trials right now?

Yeah, so there are a number of them, and they're, they're being done different ways. Different platforms are being used. So there's the mRNA platform, and there's what we call long peptide vaccines, which is basically just making the short piece of protein and mixing them with some Well, actually even injecting them by themselves or mixing them with some mild immune stimulant. And so this has been done in glioblastoma, some wonderful work out of Boston. It's been done in a couple of other cancers with some very good data that the immune system can be engaged. We're still awaiting really the good data on efficacy, that this is actually having a major impact on outcomes for cancer. Now, for all of the amazing things that happened because of mRNA vaccines during the pandemic, because we had to, you know, maybe a mild downside is that most of the energy in the mRNA vaccine field was at least temporarily turned to battling the pandemic. So there have been a lot of consequences for cancer patients, cancer treatments, because of the pandemic. And maybe one is that the mRNA approach has slowed down a little bit with the efforts going into the clinic. It is so readily accessible and so easy to do this. And for those of you that don't know, from the time that the sequence of the SARS-CoV-2 virus was made public, actually 2 years ago on January 10th, to the time that the vaccine construct was sent to Moderna was 3 days. The time from the very first sequence of the virus being available to the first patient injected with the first SARS-CoV-2 COVID-2 vaccine was 66 days. So when we get back to all of our efforts being focused on cancer vaccines, cancer immunotherapy, the turnaround time and the things we've learned in the mRNA vaccine field will make this happen very quickly. But the other thing that's happened in this space, Arthur, just to sort of finish out the thoughts, is we've gotten much better at predicting what are the neoantigens that we should be targeting. A lot of really wonderful work from London, from Charlie Swanton's group, has really defined classes of neoantigens, how they work, at least in lung cancer. And there are many other ways that we're starting to understand how to categorize the targets that T cells should recognize in tumors. And they're not all equally good, and we're still learning the rules of that. So that's the other place where there's been a lot of advancement in the last couple of years.

That's awesome to hear. So that is all the time we have for today. I apologize, I know there were a lot of questions from our audience and we weren't able to get to all of them. We'll try to do a follow-up to address as many as we can. So thank you so much, Dr. Warey, for sharing your insights and expertise with us today. For more of our webinars and the additional resources we have for patients and caregivers as part of CRI's Answer to Cancer educational programs, we encourage you to check out our website at cancerresearch.org/patients. Here you can read and watch stories shared by others who have received immunotherapy across a wide variety of cancer types. You can browse our library of past webinars and immunotherapy patient summits featuring the world's leading immunotherapy experts. You can access information on other resources including treatment, emotional support, and financial assistance. And you can find— you can get help finding an immunotherapy clinical trial. So I'd also like to thank our sponsors, Bristol Myers Squibb and Lilly Oncology, one last time for making this webinar series possible. And thank you all for your attention today. I hope you found today's webinar interesting and informative. And again, you can watch this and all of our other webinars on our website at cancerresearch.org/webinars or our YouTube channel to learn more about the immunotherapy options in a number of cancer types. Finally, Dr. Wehry, I'd like to thank you again so much for helping to highlight the exciting future of the this field of cancer immunotherapy, as well as the amazing work that you're doing to help patients. We wish you the best of luck.

Thanks, Arthur, and thanks to CRI.

Thank you, guys.