Hello. My name is Naval Daver, I’m a faculty and we’re here at the iwAL meeting. And I have the pleasure of having with me great colleagues and friends, Paresh Vyas, Alexander Pearl and Dr Carsten Müller. And we’ll be discussing some of the topics that were discussed this morning. So I’m going to turn it over here to our panel. So we had a really exciting session discussing different mechanisms of resistance to various targeted therapies, as well as epigenetic modulations that are being seen.

And one of the questions that came up that I think is very obvious but actually doesn’t come up as much is even though we have these patients with really low allelic burden mutations, whether it’s FLT3 or IDH, we see responses in a number of them, 5%, 10%. And so, what are potential other mechanisms of response that are occurring? And maybe what can we do in the scientific aspect, to try to understand these mechanisms a little better? And maybe Paresh, I’ll start with you, and then we’ll go down.

Thank you very much Naval. In the IDH-1 and 2 mutant AML field, and Sasha and my colleague Carsten will speak to FLT3 mutant, and indeed, FLT3 wild type. We find that patients who have small clones, maybe five or 10% respond to these inhibitors and achieve a complete remission. And it’s always been a puzzle Why this happens. And we speculated that there will be a non cell intrinsic effects of the mutant leukemia on other clones. So the FLT3 mutant or the IDH mutant would impact non-mutant cells. And there may also be impacts on wild type signaling. So that was the basis of the discussion today. And maybe my colleagues would like to comment. Maybe Sasha.

Sure.

I mean, I think in the IDH inhibitor realm, you can imagine some of this could be confirmed by 2-HG, which is a metabolic byproduct of mutated cells… It’s cell permeable, and it can work on the cells that don’t carry the mutation. Perhaps that has something to do with it, but we don’t know the analogous situation with FLT3. We know that patients who relapse sometimes are captured early in their relapse and they only have a small number of blasts that might explain the low allele burden. And yet that’s the growing clone and the one that you’re targeting.

But why we see the entire leukemic population stay quiescent and not expand under the pressure of a FLT3 inhibitor, it’s not entirely known. Wild type FLT3 may have something to do with the growth of the leukemia, but when we’ve tried to treat patients with relapsed wild type, wild type FLT3 with these inhibitors, the response rates have been, you know, dismally low. So I don’t think we have a great understanding of that,

Um, but presumably there’s some either, cell extrinsic mechanism by which this happens, or perhaps cell to cell contact that happens from the mutated cells that’s modulated in the presence of the inhibitor or even something secreted by the cell, protein translation that’s down regulated by the inhibitor, perhaps.

I think that’s an interesting question in general, but I think here, if your combination therapy, it might really be that these drugs work together in a certain way, especially for gilteritinib, I think that it has multiple functions and FLT3 wild type might also be of importance and in the way that this data out from Maria Konopleva but also from our lab that really gilteritinib, especially in combination with ven, might really down-regulate MCL-1. And that might be one reason why with gil-ven combination you could see shrinking of clones, which are of wild type. And I think that is obviously then on target effect, which is unexpected. But I think unexpected in the way that even the wild type AML cells might respond. And I think this gives a lot of implications for further development.

Yeah, I think it’s fascinating, right? The whole MCL-1 story in the last four or five years, and we initially thought it was very much venetoclax relevant. But now I think, you know, FLT3 inhibitors are bringing new angle, and now maybe it’s not only relevant for FLT3-mutated. It could cascade, and then I think you know the obvious elephant in the room, so to say, is the immune system right? And with sorafenib, we’re starting to see some glimpses that post-transplant, there was CD8 activation, expansion. Very nice data published in Nature, lead to a trial using maintenance sorafenib, and we still don’t know how much of this was from FLT3 versus immune. I think it’s going to be really fascinating and important to see what happens with the gilteritinib randomized study. Obviously, if we think it’s heavily FLT3 mutated, which I still do, then it should be clearly positive. But if it’s immune system, we’ll have to see. And maybe there is immune modulation, gilteritinib, so I think really interesting stuff.

Maybe turn back to Paresh. So you showed some very fascinating data Paresh, with the LMPP population having very early detection of a FLT3 mutation in IDH patients who didn’t have it previously. So do you think this is something, I know we’re far away, but let’s say 5, 10 years down the line. If we could do this in real time quickly. Is there any clinical application or is there a way we can use this to tailor molecular targeted therapies?

Sure. So the data I showed today really speaks to very, very early modulation of the leukemia by therapy. So even after one cycle, I suspect, we showed it after three cycles of the venetoclax with ivosidenib, or venetoclax, ivosidenib and AZA, The whole leukemia is re-modulated, but you have to look really in the very early compartments, the stem progenitor compartments to see this modulation and all the resistant clones are selected very, very quickly, and then they take time to develop and expand. And so what Naval’s asking, really, is if, after a cycle or two, we were in a routine manner able to look at that very early compartment, could we predict long term responders versus responders who say, after 12 months, were going to relapse?

I think there will need to be some technological developments, but I suspect they will happen, and I don’t think they’ll be difficult to do. I think the adaptation of these technological developments has to be done in the context of clinical trials. We have uniform treatment and uniform patient data sets, and then you would be able to develop a companion diagnostics that could be more readily used across the local labs throughout the world. But I see that coming.

I think it’s very fascinating because, you could also postulate, and ALL is leading the way, right? that the lower your disease burden, you have a healthy immune system you can bring in immunotherapies where you have, 99% active T cells versus not. The question is, would this be the time when you know, in three months, six months something’s going to happen? Bring in whatever it may be, bispecifics, CD47, where your immune system is on your side and that could be, you know, 10 years away. But it’s very interesting.

So Sacha, you know, the FLT3 as we know, a lot of mechanical resistance, but I think from a very clinical practical point of view, what are your thoughts on the need for testing for FLT3 relapse for everybody, and I think we’re seeing more and more that we’re going to see maybe non-FLT3 resistance. So what do you do at the U Penn for testing? Do you do it at every single time point? What would you recommend to practicing community doctors?

Well, there’s a couple different ways you can test. One is by PCR, which gives you a quick answer for the FLT3-ITD presence and the most common FLT3-TKD, which is a D835. So you get that back very rapidly, and we test every patient at relapse because it can change. You can go from not having a FLT3 mutation to having a FLT3 mutation that’s detected at relapse. And if you presented initially with FLT3 mutation, it can be lost at relapse. So that’s important to know. For example, gilteritinib, it really is only active at relapse in a patient who has a FLT3 mutation then, not from initial diagnosis. So you need to know at the time you’re treating the patient.

The issue that you bring up is, as we’ve incorporated FLT3 inhibitors to frontline therapy seven and three and midostaurin, less frequently we’re seeing patients who had the FLT3 mutation, particularly FLT3-ITD at initial diagnosis, who, when they relapse, still have the FLT3-ITD. It happens, but it used to happen in nearly every patient, more than 80% of patients and now the data would suggest with midostaurin, it’s probably about 50%, and more limited data for second generation drugs. But the crenolanib data would say, maybe it’s only about a quarter of those patients who have a FLT3 mutation at relapse, so that’s a big change in the natural history. And there’s a similar study looking at sorafenib, which are the same. So I think it’s very important in a patient who has a relapse, who had a history of a FLT3 mutation to say it’s still there and if they didn’t, to say, has shown up because now you have a therapeutic target for which we have a drug that in a randomized study that’s shown improved survival compared to alternatives. So that’s an important difference.

Yeah, I think it’s… I mean, and without giving too much of what will be shown at ASH, You know, you’ll see some of the data with the ven-gilt, AZA-ven-gilt combos and I think very similar to blina-ponatinib or others in ALL. You’re almost completely eradicating the target clone and you’re in completely different mechanisms, right? So it’s really fascinating. The problem in AML is that those competing clones come much, much more quickly than in ALL where it may take years or never. And so, you know, I think we need immunotherapies even more and Carsten, to you… Epigenetics, I think, is one of the next major frontiers along with the immune system. So in clinical trials, I mean, I would say we have had very limited ability to do epigenetic sequencing on a routine basis. So what are some of the things you think you know, we can start doing into trials or what are you doing on on going trials to really look at the epigenome? I mean, it’s the most complicated one right now for us. So, tricky question. So I mean, if you have a therapy on which you think you had an epigenetic target in this therapy, then you look at this. So, for example, we are doing a trial where we do.. we have published a study a couple of years ago where we know that EZH2 is quite important in the way that if you lose it, you have a therapy resistance towards a lot of things, including FLT3 inhibitors.

But what we are doing that we know that with proteasome inhibition you can increase the H2. And now we’re doing a clinical trial, which will finish enrolment at the end of the year. And then we’ll particularly look whether EZH2 and especially the histone modification pattern can be re-established and whether this is then related. And I think it’s really important to do this on a specific basis. So we know that with AZA and decitabine, there’s no real correlation, and this a lot has to do with when you do AZA treatment and you do get a decrease in DNA methylation very soon. And at the time you harvest again the cells plus, let’s say, after 15 days, then lots of the methylation has emerged. This is a problem, and I think since no one really knows where to look at so far, I think there’s no real established things there.

What I think it’s particularly interesting in the future is that AZA also has effects on the immune system in the way that you have a different shape of probably immune surveillance. You have different things of expressed things in the cell and of dying cells, what kind of peptides there are. And that might make a difference. But so far, I’m not aware of anyone who has really pinpointed the one AZA specific immune target.

Great. So the more we know, the more we need to know, right? We’re learning more and more. So that’s great. So I think with that I will thank you all very much. Carsten, Sasha and Paresh. And it was a great session. And thank you very much for joining.

Thank you. Thank you.