Ashish Kamat: Hello and welcome again to UroToday's Bladder Cancer Center of Excellence. I'm Ashish Kamat, Professor of Urologic Oncology and Cancer Research at MD Anderson Cancer Center and it's a pleasure to have again to this forum a former guest of ours, someone that really everyone in the bladder cancer field knows nowadays, Dr. Amir Horowitz.

Today, we have the pleasure of congratulating Dr. Horowitz on his amazing award with BCAN, a translational clinical trial award and I'm not exaggerating when I say that this is a big deal. I've been involved with BCAN since its inception many years ago and over the years, BCAN has supported a lot of investigators in research that is truly groundbreaking. This is like the pinnacle of that research. This is something that is really, really going to be impactful for our patients.

Amir, thank you so much for taking time off to spend with us and just educating our audience briefly on your study.

Amir Horowitz: Thank you so much for the opportunity to meet with you today, Ashish, and thanks so much to UroToday for the kind invitation and, of course, to BCAN, which I'll get into in a moment.

So very briefly, the intention today is just to give a brief background on the study design and then a bit of the framework on the background that led into the design of this study, the rationale for it. So I'm going to share with you some information on this axis of HLA-E and NKG2A. It's being viewed very much as a traditional checkpoint inhibition pathway. There's far more in-depth biology surrounding natural killer cells.

We're very grateful to the Bladder Cancer Advocacy Network for this opportunity to fund this trial. This is actually a study that's based on biology for which I've been studying for nearly 20 years, obviously, not forever in the context of bladder cancer, but just delighted. I wanted to just give a shout-out to my two partners on this study, Dr. John Sfakianos, who's a urologic oncologist at Mount Sinai with us, who's a co-PI, and Dr. Matthew Galsky, who's a medical oncologist at Mount Sinai as well and the three of us work very closely folks in bladder cancer. Matt is acting as a study sponsor and we're working with the Hoosier Cancer Research Network to manage this trial. So really a huge, huge thanks and sense of gratitude to BCAN and to our partners.

All right. So this is the trial. It's a phase II single-arm trial called the ENHANCE Trial, clever or not, determined as this acronym right here. And just a very brief overview of this, we are starting with high-grade non-muscle-invasive bladder cancer patients having received and failed BCG.

This is a trial based on 60 patients broken into two cohorts. The first cohort is 40 patients that have carcinoma in situ high-grade disease only with a primary endpoint of complete response at six months and, of course, very closely monitoring safety.

Cohort B is based on a smaller number of patients and it's being driven more as a secondary endpoint exploratory arm while we're targeting papillary disease plus or minus CIS. This is really based on the principle that the signal that we have studying the mechanisms of resistance to standard of care BCG therapy is really showing a pretty profound preclinical effect in papillary disease as well. So we are defining a secondary endpoint of overall survival and event-free survival at 12 months, as well as cystectomy-free survival at 12 months.

Very important to the design of this study is in the event that we get what we hope in terms of the clinical signature, we will be profiling the primary tumors going into this combination checkpoint blockade using monalizumab, the NKG2A inhibitor, and durvalumab, the PD-L1 inhibitor, where we'll profile HLA-E expression on the primary tumors. I'll present just a tiny bit of data as background as to why we feel that this could potentially act as a important biomarker selection.

So in terms of just very briefly highlighting the framework underlying this study is that we believe we've identified some bonafide mechanisms of resistance to standard of care therapy and, essentially, what most urologists are very familiar with is that the original dosing of BCG therapy was defined somewhat arbitrarily based on receiving the six vials of BCG by Dr. Morales. It's a brilliant backstory I won't get into today, but the idea is that BCG therapy is extremely immunogenic. We find when you profile the blood and the urine longitudinally on therapy, that 100% of patients are mounting a very strong immune response to BCG. What we're finding when we look in more mechanistically at the cell-derived immune responses is, is that with each dose of BCG, you're increasing both this activation potential, but you're also increasing a potential to reach functional energy or what people refer to as exhaustion.

So it becomes a question of if and when tumors recur, they're met by a functional status of our immune system which, of course, will be heterogeneous across our patients. So one of the single strongest biomarkers, if you will, to come out of this study is that chronic activation of CD8-T cells and NK cells is driving seemingly constitutive production of interferon gamma systemically, as well as in the bladder microenvironment. And recurring tumors seem to be taking two fates. One is a highly activated phenotype in response to interferon gamma and it's driving HLA-E expression up and PD-L1 expression up. The chronic activation of NK cells and CD8-T cell is associating with increase in PD-1 and NKG2A, thereby making this sort of double-edged, this double-whammy inhibition that really might speak to the poor overall efficacy of traditional monotherapies.

So very briefly, we all know sort of the clinical regimen of standard of care BCG therapy. Just to highlight a high overview of what we were collecting, before start of therapy, we collected on everyone tumor, blood and urine and this is just an example of some of the analyses that we performed prospectively on everyone. So we're covering analysis stemming from DNA to RNA to protein, as well as into spatial analyses on a single-cell level so we can really start defining the microenvironment under a magnifying glass before, during and after therapy so that we can better understand why patients that are failing are failing.

I'm only going to show one piece of data just to highlight one salient point here. This is an example of what we call multi-chromogen immunohistochemistry and we profiled many more than just three markers, but profiling HLA-E and PD-L1, as well as CD3, just a marker for total T-cells, shown here on these images is one representative patient that went on to have tumor recurrence.

I use this example to show sort of an overview of the naive untreated microenvironment. There's plenty of tumor here, there's HLA-E expression, even PD-L1 to a degree. There's nothing special about it.

What was most striking to us is that this microenvironment actually seems somewhat immune-privileged in the untreated space. You find overall a paucity of immune cells shown here as just sort of the absence of CD3.

But what was really striking to us was in the recurring space is that every patient, for the most part, had actually massive immune infiltration in the tumors. In fact, when you profiled according to HLA-E, HLA-E bright tumor cells are aggregating as nests and the sort of normal expression of dim to negative-expressing tumor cells are also aggregating as nests and nearly a hundred percent concordant. We find that all of the T-cells and NK cells are going to these HLA-E brightness. So I'm not going to get into the data here because of just sake of time. This is sort of a reference where viewers can find bioarchived preprint online to look more in-depth.

But you're talking about tumor nests that are separated by hundreds to thousands of microns in the same piece of tumor tissue, and we're finding mechanistically that these HLA-E bright tumor nests are activated and they're actually secreting chemokines that are actively recruiting T cells and K cells, even T regs, specifically to them and so it seems like this is an active mechanism. I like to use the analogy of Homer's Odyssey and the Trojan horse. If you know what you're going to, suddenly we can arm immune system appropriately. So this really developed into the rationale for HLA-E and NKG2A as in axis.

This is the last piece of data to show, just to show that we can actually study proximity analyses. When you compare a summary plot of all untreated disease versus the BCG unresponsive space here, you just see a completely different picture like log orders, greater infiltration of T cells into the tumor period when you compare like 8,000 cells per square millimeter versus 80, but also the proximity. So anything left of the zero here means that the cells have actually infiltrated this boundary, like they're officially in the tumor nest.

Now, importantly as a companion diagnostics and all that, it was important to establish that these cells are indeed expressing NKG2A. This is just an example here to highlight in red where you have T cells, in green NKG2A, you actually see co-localization, as well as individual NKG2A-staining, suggesting not only do you have NK cells in this area, but you have this specialized subset of CD8-T cells that have actually acquired expression of NKG2A.

So importantly, we just published this study that's actually more focused than later stage disease, but it was really important for defining the framework of the study in BCG-resistant non-muscle-invasive cancer because what we find in later stage disease is that naturally HLA class I is lost on the tumors.

Importantly, NKG2A is strongly associating with better survival, like prognostically, but also even predicting response to PD-L1 inhibition monotherapy. This is really because what we find is that these CD8-T cells are actually able to react to HLA class I-deficient tumors. They are using TCR-independent mechanisms that are traditionally ascribed to NK cells. So what we found is that there's this subset of CD8-T cells that are highly inhibited by the presence of HLA-E, but in terms of targeting HLA-A, B, C, the classical class I, they're diverging from classical exhaustion. So we showed in vitro pre-clinically using our bladder cancer patients at Mount Sinai that using monalizumab leads to TCR-independent mechanisms of cytotoxicity by NK so this was very exciting.

I will stop here just to sort of highlight the really brilliant work from the folks in the lab that drove this. These were all third and fourth-year medical students that I'm super proud. They've all recently matched at respective urology residences and just very, very grateful to John Sfakianos, Matthew Galsky, Nina Bhardwaj, and our whole team internally, as well as this really long list of important collaborators, both for contributing as sites to our clinical trial, but also just for the collaborative work.

Again, thank you so much, Ashish, and thank you so much to UroToday and especially to BCAN for this outstanding support. We're grateful. Thank you.

Ashish Kamat: Thanks, Amir. It's exciting to see all the work you've done over the years and I didn't realize you've been doing this for 25 years. I mean, you clearly know a lot about the subject and it's exciting to hear all the work that has gone into this. I would, of course, like to have you back on UroToday to talk more in-depth about your data and the science and everything that goes behind it and dig deep into it.

But right now, I want to focus again on congratulating you and congratulating BCAN for selecting this trial as a featured award, the translational clinical award, and let me ask you just three broad questions, if I might. When you look at this trial and where you think it's headed, what do you think this trial will mean for our patients once you answer the questions that you want to answer?

Amir Horowitz: You know, what I'm really proud of as well, very much through the lens of Matt Galsky, we got to interact with patients and patient advocates about this trial when we were designing it. So obviously, what I've been coming to appreciate most is just inherent toxicities associated with treatments and how that acts as just a general deterrence from patients willing to take on novel treatment strategies.

I think what is appearing most exciting to me is just how definitively correlated pre-clinically having higher HLA-E on tumors is to the sensitivity of blocking that interaction with NKG2A. And I don't know if this is exactly speaking to your question, Ashish, but I think where patients can appreciate the fact that there is a clinical trial out there right now that is fundamentally on the back of mechanistic science, there is so much in bladder cancer across other tumor types as well where trials are being designed and implemented based on observations from completely different tumor types and tumor settings. Or they're based on mouse studies, which are amazing, but they're not the same as truly studying it in your target population of patients.

So I hope that the patient population and the patient advocates can take out of this that our hope for this trial is that we believe we have a genuine biomarker potential of selection. So while we're not controlling for that in terms of the patient selection for this trial, we believe it's a powered study that will be able to extract that signature if it, indeed, holds up.

Ashish Kamat: Yeah. And again, it's very important that as we move the field forward across the spectrum of disease, we want to, on one hand, deescalate treatment for patients that might not need it and, on the other hand, amplify treatments or enhance the treatments for folks that need it. So having signatures such as these and ways in which we could, again, it's an overused term personalizing, but we really need to be able to use these to personalize treatment for our patients with bladder cancer.

Amir, last question. I know that a lot of the younger folks and me, too, of course, are interested in this advice that I'm going to ask you to give. What advice would you give to young investigators and people that are coming into the field of bladder cancer when it comes to research such as this and how to move forward and apply for awards such as these?

Amir Horowitz: That's a great question and I'm delighted to be able to answer it.

I owe so much of my success, but also I owe so much of my enjoyment on a daily basis, specifically to my collaborations with my surgical partners and medical oncologist partners. The team science approach that we take is that John Sfakianos and Matt Galsky, they're learning as much from me on the immunology, as I am learning from them, to really try and embrace this disease that I'm studying.

Before I got to Mount Sinai in 2017, of course, I was familiar with bladder cancer, but nothing at all on the true immunology of it or really just how the disease is treated. So it's that pairing of surgeon-scientist and physician-scientists that's not the same person. It's the commitment of somebody who's a card-carrying immunologist with a research program under their watch that's pairing, that's teaming up on the clinical side.

So if I had one piece of advice for people getting into bladder cancer, if you're clinical, find yourself a bonafide immunologist. And if you're an immunologist, I could not recommend more strongly bladder cancer as a disease of focus. I have never felt more welcomed into a community as an outsider. It was immediate for me. So I'm incredibly grateful not just to you, Ashish, and to BCAN and to UroToday, but really to everyone in the community that's embraced our research. That's my advice.

Ashish Kamat: Great piece of advice. And again, we all are on this for a common goal and that common goal gives us immense satisfaction and that's our patients.

Thank you, BCAN, for selecting such an amazing team to give this award to and thank you, UroToday, for allowing us to feature Dr. Horowitz on this platform. Thanks, again.

Amir Horowitz: Thank you all so much.