Immunotherapy in MSS Colorectal Cancer: Dr. Fakih (2022)

Manju George 0:00
Hello everyone. I’m Dr Manju George. I’m the Scientific Director at PALTOWN Development Foundation, the nonprofit that supports COLONTOWN. Today we have with us Dr. Marwan Fakih. I’m sure that a lot of you already know him. He’s a professor of medical oncology and therapeutics research, a Judy and Bernard Briskin Distinguished Director of Clinical Research, Associate Director for Clinical Sciences, Medical Director of the Briskin Center for Clinical Research, Section Head of GI Medical Oncology, the City of Hope Comprehensive Cancer Center. We’re really excited to have you with us to talk to us about immunotherapy for MSS colorectal cancer.

Dr. Marwan Fakih 0:41
Thank you, Dr. George, and thank you for the invitation. Like many other physicians, we’ve all heard of COLONTOWN, and I have many patients actually, who participate in this forum, so it’s a pleasure to be here.

Dr. Marwan Fakih 1:01
I’m a medical oncologist, I treat colorectal cancer, and been doing so for the last 21 years. I’m very excited to see the field move forward. I know that we have a lot more work to do. Whatever progress we’ve made is good, but definitely not sufficient. So for those patients who are on the call, we feel you, we hear you, and I’m very hopeful that we will make more progress. So I’ve been asked today to talk about immunotherapy in microsatellite stable colorectal cancer. And this is an area that I certainly have a lot of interest in and I’ve seen some definite progress but I think it’s important that when we look at an area of research, to recognize where it’s working and also recognize where it’s not working. Defining a treatment is good, but it has to be the right treatment for the right patient. These treatments are not without side effects, and I think we have a lot more to learn, but I’m personally an advocate, and I think there are definitely patients who respond very well to immunotherapy with microsatellite stable colon cancer. I am personally treating many of those, and many of those have been on treatment for more than two years, but I’m also cognizant to the fact that not everybody responds. So when we start looking at immunotherapy, we have to ask ourselves, “what immunotherapy, and for whom”, and then try to understand how we can make it better. We all know that immunotherapy in colorectal cancer is approved for patients with microsatellite instability.

Dr. Marwan Fakih 3:09
What is micro satellite instability? I know that many of you have done a lot of your own research, are following the field of colorectal cancer very well, but, in a simplistic way, microsatellite instability – it means that there are errors in DNA within the tumor, and that the tumor cannot repair DNA damage, and that lack of ability to repair DNA damage is actually related to an error or a problem in the repair engine. And the repair engine here is what we call mismatch repair proteins, which simply are proteins that correct mismatches in the DNA. There’s two main reasons for mismatch repair protein loss. One is what we call Lynch syndrome, where one inherits a defective gene that is responsible for translation into one of those proteins: MLH1, MSH2, MSH6 and PMS2 are the four genes that we look for. And the other reason for mismatch repair deficiency or MSI-High, is silencing of those genes, which is more common in the elderly population, especially females, right sided colon cancer. And that’s really not a hereditary condition, but rather sporadic colon cancer, meaning colon cancer that we get without a hereditary predisposition. But both categories of patients who have this condition have the same issue, which is that they can’t repair the DNA damage, and therefore there is stacking of abnormal mutations in the genome of the tumor, which leads to a lot of abnormal proteins in the tumor per se, and now you suddenly have a tumor that has proteins that the body hasn’t seen before, and the body is able to recognize that tumor as, “Hey, you don’t belong here. You have proteins that are not part of my own normal makeup of protein and therefore I am going to unleash my immune system to attack this tumor”. And that’s why patients with mismatch repair abnormalities do a lot better when they have resected colon cancer than patients without mismatch repair abnormality.

Dr. Marwan Fakih 5:43
So if you look at patients with early stage disease, stage II and stage III who have MSI-High, they rarely relapse, and they have a better overall survival than patients who do not have MSI-High. And the main reason for that is that you have the immune system in the patients with MSI-High tumors, preventing metastases from happening, attacking the tumor before it develops micro metastatic disease, and therefore it gets a better overall survival. Indeed, if we look at the tumors from patients with mismatch repair deficient colon cancer, or otherwise known as microsatellite unstable or MSI-High – all is the same. You can see that these tumors have a lot of lymphocytes. These are CD8 positive cells. These brown dots are the lymphocytes at the tumor margin so it’s kind of preventing the tumor from expanding or attacking it where it is expanding. And so there are lots of what we call tumor infiltrating lymphocytes in the tumor, and the tumor is reacting back by trying to suppress these lymphocytes from killing it, and produces PD-L1. You can see the PD-L1 localizing at the sites of the CD8, and this PD-L1 is suppressing these lymphocytes. That’s simply why immunotherapy works so well, because when you give KEYTRUDA, you’re basically blocking PD-L1 from suppressing CD8s. Now these CD8s are happy, and they’re attacking the tumor and killing the cancer. And so either by using PD-L1 inhibitors, such as Atezolizumab or Nivolumab, or by using PD1 inhibitors where PD-L1 binds to, you can basically invigorate the immune response and stimulate these CD8 cells to attack the cancer.

Dr. Marwan Fakih 7:45
So why does immunotherapy work for MSI-High and why doesn’t it work for MSS very well? It is because you don’t have lymphocytes infiltrating the tumor in patients with mismatch repair proficient colorectal cancer, MSS patients. There’s not enough CD8s, and there’s not enough CD8s because the tumor is not hypermutated. The tumor doesn’t have a lot of antigens. Why it doesn’t have a lot of neoantigens or a lot of abnormal proteins, is because you don’t have that mismatch repair problem. So we’re looking at two different populations, and you have to think about these checkpoint inhibitors as unleashing an existing immune response, and that’s why they work in MSI-High, and why they don’t work in MSS is that there’s no immune response to unleash of significance in these tumors. But that’s the simple explanation as to the difference between MSI-High and MSS as far as to why we’re seeing differences in responses. Now, this is another way to look at the checkpoint inhibitors and differences between MSS and MSI-High. MSS is the blue and MSI-High is red, and you can see that CTLA-4 is higher in MSI-High tumors, PD-L1 is higher, LAG-3 is higher. All of these are checkpoint inhibitors. And you can see that in all compartments, especially in the invasive front of the tumor, the margin of the tumor. So there are inherent differences between these two tumors, MSI-High and MSS and that’s why in MSI- High tumors, we use pembrolizumab up front in the first line setting because it works even better than chemo, as we have seen from a very large study that compared patients with stage IV colon cancer who have MSI-High. Half of them received chemotherapy, and half of them received KEYTRUDA (pembrolizumab). And you can see that with KEYTRUDA, these patients who are without progression at three years, pretty much these are the cured patients. These patients rarely ever relapse afterwards. And I would say a lot of these patients may have something on their CT, but it could be just that tumor fibrosed, and you can’t tell that it’s gone, because it leaves a mark. We have many patients now who are MSI-High who are absolutely cured with immunotherapy for three years and never relapse. And so definitely a big difference in outcome, and we don’t want to miss those patients because they respond beautifully to immunotherapy.

Dr. Marwan Fakih 10:22
It’s not that KEYTRUDA has not been tested in MSS patients, patients without microsatellite instability. This is a study that said, “I’m going to look at MSS patients, I’m going to look at colorectal cancer patients. I’m going to only enroll patients who have a high PD-L1”. And PD-L1 is a biomarker of response to KEYTRUDA. In lung cancer it indicates that you have an immunosuppressive effect of the tumor against the lymphocytes, and the higher the PD-L1 is, the more likely the response in certain tumor types, such as non-small cell lung cancer. So in this colorectal cancer study, they screened 138 patients, and out of those, 138 patients, only 33 patients were PD-L1 positive. 10 had other exclusion criteria. They ended up treating 23 patients and only one patient had a response. The definition of response is shrinkage by more than half, by the way. When we use these terms, stable disease means either slight increase or slight decrease, but a partial response means major decrease, more than 50% of the tumor disappearing. As you can see, only one patient did very well on this study, and everybody else progressed, although for some it took almost about eight months before progression. But the only patient who had a good shrinkage or partial response actually was MSI-High, and all the MSS patients here did not have an objective response. So even when you’re enriching for PD-L1 positivity in MSS colorectal cancer patients it is not likely that a drug like KEYTRUDA or a drug like OPDIVO on its own is going to make a difference. We’ve been involved in this study as well.

Dr. Marwan Fakih 12:20
This study was published a while ago, looking at atezolizumab, which is a PD-L1 inhibitor, and patients who have gone through a couple of lines of therapy, first line and second line. In this study the comparison arm was Regorafenib, or STIVARGA, and 1/3 of the patients got Atezolizumab alone, so a PD-L1 inhibitor alone. 1/3 got cobimetinib plus atezolizumab. Cobimetinib is a MEK inhibitor, and at that point it was thought that that makes the immunotherapy work better based on a small phase 2 trial. But the bottom line is, in these patients who received atezolizumab alone, or atezolizumab plus a MEK inhibitor, there wasn’t really much of a difference compared to STIVARGA alone. So again, this large trial of almost 250+ patients failed to show that we gain much by using immunotherapy in patients with colorectal cancer, especially in microsatellite stable colon cancer. The majority of these patients in the study – I think, were 97% or so – were microsatellite stable. On the other hand, there was a glimmer of hope from a trial done in Canada called the CO.26 trial. And in this study, they used a CTLA-4 inhibitor, so another checkpoint inhibitor, another immunotherapy that takes off the brakes from the lymphocytes against the cancer, along with the PD-L1 inhibitor. So a KEYTRUDA-like drug called durvalumab, and that combination was compared to no treatment at all and even though there were no major shrinkages and there was no difference in the time for progression, there was an effect on the overall survival. The red line is the patients who got the double immunotherapy. The blue line is patients treated with best supportive care, and it prolonged survival by 30% in these patients, but it wasn’t really a big difference in terms of duration of how many months of addition, but it did add some, suggesting that even in this population of microsatellite stable colon cancer, there may be something to immunotherapy, but the signal is not very, very strong, and maybe adding CTLA-4 does make a difference as well as most of the studies so far have not looked at the combination of PD1, CTLA-4.

Dr. Marwan Fakih 14:56
Our group/myself had started looking at liver metastases and impact on response to immunotherapy, because we had many patients who would go on clinical trials receiving PD1 or PD-L1 targeting, who had MSS. What we would note is that some patients with lung metastases were having some shrinkage or prolonged stabilization, but everybody who has liver metastases, they tend to not do well at all on these studies. And I’ll show you some of the data that we generated, but some of the data that we published about four years ago after the REGONIVO data came from Japan also was substantiated by laboratory models. In this particular model, they treated mice by injecting colon cancer cell lines in their flank, and then they gave them immunotherapy with a PD-L1 inhibitor. And sure enough, the tumor in the flank shrunk. Now they got the same mice, the same tumor, and now they injected the tumor in the flank and the tumor in the liver, and let the tumor grow in the liver. And not only did the tumor in the liver not respond to PD-L1 therapy, but also the tumor in the flank of the mice did not respond to immunotherapy anymore, suggesting that when the colon cancer metastasizes to the liver, that that not only affects the response in the liver, but it may have a negative abscopal effect, a negative effect outside the liver on the response to immunotherapy. And there are many theories as to why that may be the case. Frankly, those theories come from mice models. They may not necessarily apply to humans fully. But one of the theories is that the tumors in the liver chew up the immune cells that are involved in attacking the cancer cells and therefore has a systemic impact on the overall response to immunotherapy.

Dr. Marwan Fakih 17:10
We looked at 95 patients who had microsatellite stable colon cancer, and those patients were treated with PD1 or PD-L1 therapy, and reported that data and in JAMA Network. What we did differently is we categorized patients according to their performance statuses. Are they: very weak/strong?; Do they have limitations in their physical activity? Is there any evidence of spread to the peritoneum? Any evidence of spread to the liver?; Any evidence of spread to the lung, lymph nodes, bone, brain? And then we also looked at tumor mutation burden in these tumors. And we looked at RAS mutation, BRAF mutation, APC and TP53. The thing that stood out the strongest here is that the liver was the biggest biomarker of resistance to immunotherapy. In this study, about 50-some patients with liver metastases were treated, and none of them had any major shrinkage. On the other hand, in the patients who did not have liver metastases, about 20% of those patients had major shrinkage, and you can see that the likelihood the impact on progression if patients had liver metastases – presence of liver mets, has a seven-fold increased risk of progression compared to non-liver metastases. We did see some other signs that are not very clear. The sidedness has a small impact on on on progression. The left did a little bit better than the right, so a higher chance of progression if they have right-sided tumor versus left-sided tumor. RAS mutation, there was slightly higher progression, like the progression of RAS mutation versus non-RAS mutation. I have to say, in other data sets that we have looked at we’re not as convinced on RAS, and that’s a story that needs to be unfolded some more. But APC mutation did not have a substantial impact. A lot of people report APC as a marker of resistance. – No. – You can have APC mutation with colon cancer, MSS, and still respond to therapy. So liver did come out as the biggest problem here, as far as response. And meanwhile, there had been some data suggesting that drugs that target what we call the vascular endothelial growth factor pathway, which is a pathway important in blood vessel formation that those inhibitors may substantiate or improve the response to immunotherapy. Particularly the drug STIVARGA, which is approved for refractory colon cancer, had been associated with decrease in macrophages or tumor-associated macrophages, especially the M2 phenotype, which associates with a poor outcome and switching it to the M1 phenotype, which are anti-cancer, that that may occur with STIVARGA, and that STIVARGA may also normalize the blood vessels, decrease the T-regs, the regulatory T-cells as well, which may also be important in reducing the immune resistance within the tumor microenvironment within the liver.

Dr. Marwan Fakih 20:43
I’m sure a lot of the folks on this forum had as much enthusiasm as I had about three years ago or more maybe, when this data from a Japanese group was reported at ASCO, I think it was three years plus now, looking at a small number of colon cancer patients, 24 patients, who had microsatellite stable colon cancer, I think, except one patient if I recollect right, and those patients were treated with STIVARGA (Regorafenib) plus Nivolumab (OPDIVO) and therefore the acronym “Rego” for Regorafenib; “Nivo” for Nivolumab. And the excitement was that these patients had progressed on standard of care, and when they were treated with this combination, almost half of those patients had not progressed at 7.9 months, or 8 months if we want to round it, and that approximately 1/3 of those patients had major response, – objective response, we call it. A majority had good disease control between stable disease and major shrinkage. And this data prompted many of us to consider offering this treatment on a compassionate basis, or rather than compassionate, the right term is “off-label”, even though this was not approved to offer this to patients with colorectal cancer. And to my surprise, when we were treating patients with this and we looked at our data in about 18 patients or so, initially we saw that 13 patients with liver mets, none of them responded, and that in the five patients without liver mets, maybe four of them had some minor shrinkages, not a major shrinkage, but were able to continue on treatment for a while and we reported that data.

Dr. Marwan Fakih 22:43
Before, we looked at the 95 patients. But this particular study from Japan has really triggered a plethora of trials looking at the same classes of drugs together, so a PD1 or PD-L1, plus what we call a “tyrosine kinase inhibitor”: pills that inhibit different enzymes and different proteins, including proteins that are important in the blood vessel activation process, what we call “vascular endothelial growth factor receptor inhibitors”. One such study is a study done in China. This is a tyrosine kinase inhibitor that is very similar to regorafenib, and this is a PD1 inhibitor, and 28 patients with microsatellite stability. Response rate was only 7%, but a lot of patients had stabilization and a good disease control so that’s not meaningless when you control the cancer in your patients more than six months. And so there are some signals, but not as strong as what’s been shown in the Japanese trial. This is a study that looked at STIVARGA plus pembrolizumab that was reported this meeting by a colleague of mine. Very discouraging is the fact that none of 73 patients had major shrinkages here. But when looking at the 16 patients who didn’t have any liver metastases, at least half of those patients were having ongoing benefit beyond the four months mark, while most of the patients had progressed at two months with liver metastases. That shows what we call the “progression-free survival curve”, the time to patients progressing. So those are the 16 patients in blue. And you can see that there are some patients who have more prolonged benefit, even at the one year, but that’s a small number of patients. Only two of the 16 probably were still deriving a benefit. So who are these two, and why and how can we identify them, is the big question. Who are those getting benefit beyond six months, right? Because, yes, liver metastases is a marker of resistance, but it doesn’t mean that everybody without liver metastases is going to benefit. Some will benefit more than others, and it does appear that those without liver metastases have a better survival. There are other studies we can go over and over, again. That’s another study of STIVARGA, plus another PD1 inhibitor and metastatic cancer. Again, microsatellite stable, and you can see, again, a big difference in response rates: patients without liver metastases – major shrinkage, more than 50% shrinkage, and 30% of patients stable disease, 20% here, major shrinkage with liver mets is only in 8% of patients. So again, showing a difference in time to progression in non-liver is better than liver. And this is a study presented… this meeting looking at bevacizumab, which is again a vascular endothelial growth factor inhibitor, plus KEYTRUDA (pembrolizumab), and they added what we call a MEK inhibitor, binimetinib to it. And here you see that about 1/3 of the patients had some form of shrinkage. And the patients who had major, major shrinkage – more than 50% shrinkage, are about 13% of patients. But a fair number of patients between mild increase and mild decrease. This is what we call stable disease. (That’s the yellow.) Again suggesting that there’s a signal here, but not too strong. And how can we identify those folks who benefit the most from this?

Dr. Marwan Fakih 26:38
That’s another study presented at this meeting, a couple of days ago, with a PD1 inhibitor, plus, again, an angiogenesis inhibitor that is novel because it blocks two angiogenesis pathways, angiotensin 2 and VEGF. There’s more shrinkages than growth here and I think the exciting thing is, definitely there are patients who continue to benefit beyond the eight months mark. But the bottom line is, all these studies are not telling us: who are the patients with liver mets and who are the patients without liver mets? They’re not really reporting yet the characteristics of those patients. I do believe that it’s less likely that patients who are having great response here are liver mets patients, and it’s important for you to know that you’re going to have a lot of variations and responses and benefits dependent on what type of patients are going on the study. If it’s a patient who has only lung mets, that’s a patient who probably is going to be more likely to respond. But a study that uses the same regimen and enrolls 90% of the patients with liver metastases, the results of that study are going to be dismal. And so it is very hard to extrapolate from these 20, 30 patient trials into: “What is a better regimen for a patient?”. You may hear a little bit more in your forum about this study. So cabozantinib is a compound by a drug company called Exelixis Inc., and which is a drug that is approved for kidney cancer and liver cancer. They have a couple of reports this meeting on cabozantinib, plus a PD-L1 inhibitor. This is durvalumab, which is the PD-L1 inhibitor and plus cabozantinib. This is called the CAMILLA trial, and they looked at colorectal cancer here, 29 patients is reported as efficacy. And then they say, well, eight patients out of 29 had major shrinkage, 27.6% but in six out of the eight that response was sustainable, meaning on the next CT, the were still benefiting versus two out of the eight, the next CT that were progressing and you can see the median progression-free survival is 3.8, they don’t report on the characteristic by liver or non liver, but they do show that there is slightly better outcome for the RAS wild-type versus the RAS mutant. Again, something that we have seen on our multivariate analysis from a year ago. So the question is, should this be evaluated further in RAS wild-type? The problem is, they didn’t do the analysis here based on where the tumor spread. Could it be that the patients without RAS mutation were more more enriched in patients without liver mets here, and that’s why you’re seeing that signal? We don’t know. The other thing about this study is that they actually enrolled 36 patients, and seven patients actually didn’t reach the first CT scan, so they did not include them in the analysis. So the reality is that this study shows similar outcome as all the other studies in that the final confirmed responses, if we include the full sample of 36 patients, is 16.6%. So again, there are patients who benefit. This is very exciting. If you follow the 25 months mark, there are some patients at two years who are still benefiting. So who are they? And how do we identify them and offer them these strategies, and how do we make sure they don’t get diluted, and in the patient population sample who are not benefiting? And more importantly, how can we exclude patients who don’t benefit so that they can find other strategies to look into. Interestingly, this meeting from two days ago, looked at cabozantinib plus atezolizumab. Atezolizumab is not much different than durvalumab that it’s a PD-L1 inhibitor. And here again, they looked at 31 patients. The difference here is that the objective response rate is actually quite a bit lower than the previously presented study here. Only 3 out of 31 patients had major shrinkage. But then they report that most of these 3 were in the patients without RAS mutation. So again, something that needs to be explored further. Does RAS wild-type tumor, no RAS mutation, enrich for better likelihood of response? Could it be that patients without liver metastases and without RAS mutation could be the best patient population to look into – I think the challenge is, all of these are small studies, and you can’t do this kind of deep analysis on a small sample size, and I wish we could pull all these efforts from different investigators to answer that question, and it would require that all the sponsors agree to do so, which may not happen.

Dr. Marwan Fakih 32:03
Many of you have heard about the LEAP trial. This is KEYTRUDA plus lenvatinib, again, same concept, the tyrosine kinase inhibitor that at least partly targets VEGFR plus KEYTRUDA. And this study reported a 22% major shrinkage, and at six months, almost 1/3 of the patients had not progressed. This regimen actually moved on to a randomized phase 3 trial that is ongoing, so we will know soon. The good thing about that study is that they are stratifying by presence or absence of liver metastases so we’ll have a better idea as to the outcome in patients without liver mets. On the phase 2 study, which I am showing you here, the company did not report the outcome by liver and non-liver metastases. So finally, this is a study we reported last year on regorafenib, Nivolumab in microsatellite stable colorectal cancer, we enrolled 70 patients, 23 without liver metastases. You can see the response rate here. The major shrinkage is about one in five patients, but the stable disease is another 1/3 of the patients. Half of those patients still progressed by three and a half months. The liver metastases did not respond. What we reported at this meeting is that we know partly why liver meds don’t respond. If we look at biopsies from liver metastases versus no liver metastases, the liver metastases have less CD8 cells. These are lymphocytes that attack the tumor, and when we enrich further for granzyme B positivity, which is the substance that lymphocytes release when activated against the cancer. Again, we don’t see much of that in the liver. We see more of it in patients without liver mets and tumor biopsies that are not liver. The immune system is more robust in these non-liver metastases, which results in a higher regulatory T-cells in those tumors. You don’t see as much in the liver, and you see also more macrophages outside the liver. So basically, there’s more of an immune activation in tumors that spread outside the liver than in the liver. I don’t think it’s the same between lung, and peritoneum, and bone, and abdominal wall, and lymph node. I think there probably are differences. I think at the end of the day, the question is, which sites of disease may benefit the most: is there a biomarker of site of metastases, number of metastases, size of metastases, molecular biomarker? What type of mutations the tumor has, is there a special formula that we need to know about, that we need to come up with? I’m sure we’re not going to come up with the perfect one, but there are a lot of efforts being made to try to identify at least some form of biomarker that helps us further. So this is the same study we conducted. Now, you can see that patients without liver metastases: this is a good thing. You can see you have 1-2-3-4 patients out of 23 who had not progressed at the 40 week mark. And frankly, we’ve got two patients who’ve hit the two year mark without progression in our institute on this study. And so that’s not something you will achieve with STIVARGA alone. How much of this is from OPDIVO versus OPDIVO plus STIVARGA remains to be seen, but there’s probably some synergy between these two, but I don’t think it’s sufficient for the majority of patients versus liver- the majority had progressed by the 24 week mark. Very few patients continue beyond, and most of those eventually did progress. And you see the tumors. None of these tumors had sustained shrinkage below the 30% decline in tumor in the target lesions versus the non-liver mets, you have quite a few blue squares that go in the “PR” partial response category. So this is work we’ve done in our institute. When we stain the tumors of liver and we look at what we call the core of the tumor, you can see that the core of the tumor has very few lymphocytes that get into it versus lung, a lot of lymphocytes get into it. (That’s the blue here, is the lymphocytes) and so part of the problem with liver metastases is that the immune cells don’t get into it to attack and that’s been a challenge, frankly. I don’t think anybody has the definitive answer today, although a lot of efforts are being made to answer that or to overcome it, whether it’s viruses or other type of drugs. Finally, I want to say that the CTLA-4 question is not really done yet. This is a study that looked at a novel CTLA-4 inhibitor, plus a PD1 inhibitor in patients with colorectal cancer. Here at the upper right corner they enroll 20 patients. This is without regorafinib, this is just the CTLA-4, PD1, no TKI, no tyrosine kinase inhibitor, just the checkpoint inhibitors. And four out of the 20 patients here had major responses. And you can see a lot of these, some of these are quite durable. And again, they did not report in the poster if these were non-liver mets or not but I think that means something to me. Probably we do need a CTLA-4 inhibitor. And the question is, do we need the three drugs together or not? And so this is actually what we had proposed to SWOG. First of all, we’re pretty certain liver mets don’t respond to regoraphenib-nivolumab, so we think those patients should not be treated with this combination. And also, we have some data that peritoneal metastases are little bit more resistant and may not benefit that much from that combination. And so we’ve proposed a study looking at STIVARGA plus OPDIVO, REGONIVO compared with regorafenib, ipilimumab and nivolumab so, CTLA-4, PD1 plus regorafenib, we have already completed a study with REGONIVO IPI in our center. That data has not been reported yet, so I can’t go over it today but we think there’s enough to compare these two to see if there is a winner, and perhaps that can move forward to be compared to a standard of care in the future. I’m hoping that this will move forward. It’s too early yet, but that’s one way of approaching colorectal cancer with a microsatellite stability to recognize the patients who are more likely to benefit from a strategy and then explore it further, and then narrow down more the biomarkers so that you can identify even better who the potential super responders are. So what I summarize today is that microsatellite stable colorectal cancer is not all one disease, and especially with immunotherapy, it’s different than chemo. The site of metastases matters. And liver metastases are different than lung. They have biological differences in lymphocytic infiltration, antigen presenting cells, B cells, etc, that we are reporting on, and that the lung metastases have more active immune microenvironment that may contribute to the response to immunotherapy.

Dr. Marwan Fakih 40:17
So where do we go from here? I think there are a lot of studies across the nation and across the globe trying to look beyond checkpoint inhibitors, beyond STIVARGA and tyrosine kinase inhibitors. There’s a lot of studies looking at what we call bispecific antibodies, which typically target tumor-specific antigen and CD3. There are cellular therapeutics going on, including tumor infiltrating lymphocyte infusions, but you have to harvest the tumor here, grow the lymphocytes infiltrating the tumor. It’s a long process, and then grow these lymphocytes into the billions and then re-inject them in the patient and hope that they infiltrate the tumor and attack it. There’s some data that that is effective in non-small cell lung cancer and melanoma, and there are some efforts in colorectal cancer. There’s no data yet if that is effective or not, but that’s what those studies are doing. There are studies called neoTCR, where you basically take a biopsy, identify cancer specific antigens, and then clone receptors to those antigens, and then engineer the lymphocytes of that patient to express those receptors and then re-infuse those lymphocytes. There are CAR T in early development. CAR T in solids have been much harder than CAR T in liquid tumors, and because these engineered T-cells have more difficulty infiltrating within the solid tumor. But certainly it is an area of interest and should be evaluated. But where CAR T is going to be, we still don’t know. There are some studies looking at combinations of neoantigens and vaccines plus checkpoint inhibitors. Certainly there are other studies that have integrated immuno-checkpoint inhibitors, like nivo plus FOLFOX early on, and those studies should be maturing soon. Whether one should also engage with CTLA-4, PD1 plus chemo early on, is another question. But those are other directions. So I hope this is a little helpful, and I think we can open it up for discussion.

Manju George 42:48
Okay, thank you, Dr Fakih, that was awesome. I have one question, and then we will look at the chat and look through all the questions. So in the mouse model that you mentioned when they had the tumor also implanted in the liver, in addition to the flank tumor, the animal did not respond to immunotherapy. Did they do an experiment where they then remove the liver tumor and then try to see if the animal was again sensitive to –

Dr. Marwan Fakih 43:10
–They did not. But we have clinical data that shows that with regonivo and others, that hepatectomy patients will respond. So there are data that our group/myself have generated that show that if you have a hepatectomy, and now the patient, six months later, has lung-only metastases, that those patients could respond, and some of them for a very long period of time. Whether it is as robust as patients with never liver metastases our data shows a little bit less robust, maybe, but some surprisingly, very protracted benefits. Once you don’t have active disease it’s a little bit different story. It’s important to note that all of these are associations that we are describing. So the question becomes, is an association, a cause-effect? Is it or not? Is it the biology of the cancer that leads to liver metastases that makes it more immune resistant? If that is the case, you wouldn’t expect that the surgery would fix that problem, right? Or is it also possible that the biology that is favorable enough that a patient can undergo liver surgery means that they are also a little bit more immune sensitive. It’s possible, but association is important enough in your patient selection, right? Even if you cannot prove a cause effect, if you have an association of lack of response, at least it helps you on how you define your patient population is to benefit from a specific strategy.

Manju George 44:43
Okay, thank you. So we will go through the questions. Annie has a question, “Can you comment on the KISIMA-01, combo approach with the vaccine, where Dr. Kopetz has indicated there has been response in liver mets?”.

Dr. Marwan Fakih 45:02
No, I can’t comment on that. I don’t have additional information.

Manju George 45:06
Okay, then other than liver mets and RAS status is tumor burden a factor determining efficacy of IO and MSS?

Dr. Marwan Fakih 45:17
Yes and no. If, for example, and I didn’t present that data, I think we reported the first case of Pol E mutation responding to immunotherapy. So about 0.5% of patients will have Pol E mutations, which is polymerase E, which is important. Those patients are MSS, but they have what we call an ultra mutated colorectal cancer. Their tumor mutation burden is more than 200. They respond as well as MSI-High, if not better. Those are one in 200 patients. You don’t want to miss them. You identify them by the super high TMB, and they definitely should get immunotherapy, even though there’s no indication for immunotherapy for those patients, yet (-official indication). Then you have what we call intermediate TMB. They’re not MSI high, but their tumor mutation burden is 14, 12, 16. I think some of these patients, may respond somewhat to immunotherapy. I don’t think they respond as well as the MSI high. They usually are more stable disease or less durable responses. There’s been case reports of such cases responding to pembrolizumab. It’s important to note that the keynote 158, that we reported that led to the approval of pembrolizumab in the TMB of more than 10. Actually, that study did not include colorectal cancer patients, so it’s hard to extrapolate as to the benefit, but even in that particular study, there was a correlation between the level of TMB and response, and even though it’s not in the paper. Merck, the sponsor of that trial, had reported that if you look at those patients who had a TMB of 10 to 15, the objective response rate, the major shrinkage rate, was less than 15%. The overall population was 29% but if you look at the 10 to 15, they didn’t do that well. And therefore immunotherapy in patients who have a TMB of more than 10, but less than 20 should not be first line and should not be second line, in my opinion, because the benefit is not clear, but they should not be excluded from from getting KEYTRUDA. In the MSS patients that we looked at in our center, we didn’t see a correlation between TMB in response to regonivo or other PD1 inhibitors. And we have many patients who had an objective response or durable, stable disease with a TMB of one and two. So those patients that you see that have the tail of the curve with ongoing benefits were not intermediate TMB, you know. So, the bottom line, yes, there are patients with very low TMB that respond to immunotherapy, but not liver mets.

Manju George 48:06
The second part of the question is, is there any evidence that in low burden or low tumor burden settings radiation treatment previous or concomitant to IO could increase IO efficacy? Can it make the tumors more immunogenic?

Dr. Marwan Fakih 48:22
I personally, I doubt. I think the data has been extremely thin. We had done a study of Y90 followed by a PD1 and CTLA-4 inhibitor. Unfortunately, we had to close the study because we had nine patients, and none of them responded, whether in the liver or outside the liver, to the immunotherapy. I think there’s been some reports about SBRT plus immunotherapy. Those data have been extremely mixed, and the benefit was slim, and it’s not really clear if it’s attributed to the SBRT or not, so I don’t think so. I am aware that the recent study, and I think everybody should take that with a grain of salt, that the REGONIVO that was reported at this GI ASCO has said the patients with prior radiation did better, but there’s two reasons to give prior radiation. One is rectal cancer, which tends to have more lung mets. So when you say prior radiation is… they had chemo radiation for their primary rectal cancer before surgery, and then they develop probably lung mets. So it’s enriching lung mets. The second is SBRT, right? And who gets SBRT? -The patients who don’t have diffuse disease, the patients who have only few metastases. And who are the patients who have only few metastases? -Those who have a robust immune response against their cancer. So here, the prior radiation therapy is likely enriching a patient population that would have responded to immunotherapy whether they got radiation or not, by selecting patients who have a better immunoscore. So a lot more to be learned. But I think the radiation concept had been tested for a very long time now, and the data should be still evaluated in a research setting, but I don’t think clinically there’s any reason to believe that we should be radiating to induce a response at this point. I think we need to evaluate it further.

Manju George 50:29
Okay, so the next part of the question, I think it’s very important to address that, how should, when patients are considering immunotherapy – you just mentioned TMB. What are the other ways to find the PD1, PD-L1, CPS scoring or TPS scoring? What do you comment about that?

Dr. Marwan Fakih 50:45
I think it’s important to note that not all tumors are the same, and I think we have to really look at the data within colon cancer. So far, the PD1 story has not panned out that much in colorectal cancer and we’ve had patients with a CPS score of 20, 30 with liver mets that we got excited about with them on immunotherapy, and we don’t see a response. And so I don’t think that we have a biomarker today of a response to immunotherapy in somebody with a low TMB, with the exception of saying that liver is a biomarker of high level of resistance, and frankly, everything else is still under investigation. I wish I would say otherwise, but there’s no definitive answer yet, and there’s a lot of conflicting data from different sets of studies.

Manju George 50:45
Okay, thank you. So maybe some kind of composite score where they look at the location of the mets, maybe CPS, maybe TMB, or all of that together?

Dr. Marwan Fakih 51:50
Yeah. I mean, eventually that would be the hope, right? It’s coming up with a formula that takes into consideration the host, the tumor, and the clinical presentation. So a molecular score, right? Patient score, it could be ECOG as well. We’ve seen ECOG 2’s don’t do as well with immunotherapy than ECOG zero likely, and site of metastatic disease. And also from my personal experience, somebody who has 1000 lung mets what we call “miliary disease” in the lungs, we don’t see them respond to immunotherapy, and partly because probably the tumor has escaped/there’s no immune system to prevent it from exploding in a diffuse process. Versus somebody with well defined 15 spots in the liver may respond to immunotherapy. So you cannot come up with such a score unless you have prospectively collected data sets that are very large, treated in a homogeneous manner, and the data is collected prospectively on all these variables. To my knowledge, that data set is not there.

Manju George 53:01
Okay, thank you. So another question is about the microbiome. Do you have any thoughts on whether the diet, gut microbiome – Does it have any effect in MSS CRC?

Speaker 1 53:13
I don’t have any data myself. I think the microbiome story is still evolving on some of the data with fecal transplantation had been intriguing in couple cases with melanoma. I think the disheartening thing is that that data came out three, four years ago and you would expect that somebody could have validated it already. There’s been so many trials that have included capsules that have different bacteria, etc, to try to answer that question. And I hope it’s true. I think it needs to be validated in probably non-small cell lung cancer and melanoma first. But today I don’t have any special diet that I prescribe to my patients. I’m not against them trying. I’m very open about that, but the evidence is not there.

Manju George 54:12
Okay, there’s one question about efficacy of IO and MSS patients with isolated lymph node mets, the rationale being that lymph nodes have a high concentration of the immune cells.

Dr. Marwan Fakih 54:21
They do very well. In our experience, lymph-only metastasis, not all of them respond. But I think if you ask me today, based on my observation and what we have seen, the two sites that benefit the most are lung and lymph node.

Speaker 1 54:39
Okay. And then there was this other question about sequencing. Dr. Barzi had reported that subsequent treatment with TAS-102, the responses were higher after people were on radiation. What do you think about it?

Dr. Marwan Fakih 54:54
I think one has to be very careful and anecdotal evidence from subgroup analysis, from studies. It seems to me that if you give immunotherapy, you change the course of the disease after immunotherapy. It’s not necessarily making TAS-102 work better. You’ve seen the data with the Canadian trial. There was no difference in progression, but the curve separated for overall survival. So even when patients do progress, we do see that not all the tumors necessarily progress after IO and so you’re dealing with a little bit different biology after immunotherapy. It doesn’t mean that because you gave immunotherapy, it’s going to make the chemotherapy… – It could be that those patients, even without TAS-102, may have had a more indolent course. So those are only hypothesis-generating questions and need to be validated. Of course, I would rather use a regimen of IO that has a 30% chance of keeping 1/3 of patients without progression at eight months than using Lonsurf. And hey, if Lonsurf works better afterwards, that’s great, but we need more work on biomarkers.

Manju George 56:07
Okay, so basically, what you’re saying is that – there is this talk in COLONTOWN too – that if you get immunotherapy, and then people who have gone back on chemo, they are responding better. And what you’re saying is that that might be because the immunotherapy affected the progression without actually responding to chemo, right?

Dr. Marwan Fakih 56:25
The disease may become a little bit more indolent in some patients. There are a lot of patients who, prior to IO, when they go and study you have 20, 30, tumors progressing. They have stable disease, and then only five tumors are growing, and the other 15 are still regressed, but they meet the guidelines of progressive disease, and they come off study and and now their immune system has been conditioned to attack those 15 tumors, but the other five have escape mechanisms. And even when they have escape mechanisms, they may not be growing at the same pace that they did before going on IO. It doesn’t mean that every patient that gets IO will have that benefit. That’s very important to note. You know, there’s even some thoughts of hyperprogressors with IO, where the disease is progressing more quickly. I haven’t seen liver metastases change course that much after IO for example.

Manju George 57:28
Looks like there are no more questions. Thank you, Dr Fakih for that very interesting and informative talk. Thank you all for attending. The video of the talk will be available soon at the Lecture Hall in COLONTOWN University.