Engineering next-generation cellular therapies for solid tumors

Marco Davila
Hey, my name is Marco Davila.

Kedar Kirtane
I’m Kedar Kirtane from the Moffitt Cancer Center.

Marco Davila
And we were the co-chairs of a session focused on solid tumor cellular therapy here at IWCAR-T, and really excited to talk about some of our presentations and I think some of the implications of the work that we presented. My name is Marco Davila. I’m from the Roswell Park Comprehensive Cancer Center in Buffalo, New York.

Kedar Kirtane
I’m gonna let Dr. Welty go.

Nathan Welty
Yeah. I’m Nathan Welty. I’m from the University of Pennsylvania.

Eric Smith
Eric Smith, Dana-Farber Cancer Institute.

Sebastian Kobold
Sebastian Kobold, LMU in Munich.

Yihan Zuo
I’m Yihan Zuo. I come from Roswell Park Comprehensive Cancer Center.

Marco Davila
Great. So I’m going to give a very quick summary of my presentation. So what I just discussed was a MUC16 IL-18 CAR T-cell that has been developed in collaboration with other investigators at Roswell Park, as well as an AI protein or generative biology protein company. We discussed the development of a novel MUC16 binder that paired to IL-18 and demonstrated its in vitro and in vivo efficacy. We have recently applied to the FDA and were awarded an IND to develop this into a phase one trial for patients with relapsed refractory epithelial ovarian cancer. We plan to open this trial at Roswell Park over the summer after we complete our clinical trial development.

Nathan Welty
So I’m Nathan from UPenn, and my work has been developing novel engineering strategies for myeloid cells. And what I presented today was a new engineering strategy to engineer hematopoietic stem cells for a more durable myeloid cell that could target solid tumors and showed enhanced efficacy when these cells are given together with CAR T cells in the solid tumor microenvironment and the way that these cells can modify the tumor microenvironment to enable enhanced T-cell functions. And I think this was really important preclinical work to demonstrate the cooperation of myeloid cells and immune responses and the fact that we can potentially engineer them for future therapies and hopefully lay the groundwork for more things to come in the future with new engineering perspectives around myeloid cells.

Eric Smith
Hey, my name’s Eric Smith from Dana-Farber Cancer Institute. I shared work that was led by Cedric Louvet in our group, also looking at engineering the hematopoietic stem cell in such a way where the chimeric antigen receptor only is expressed after that HSC differentiates into the immune effector cell type of choice. In our case, we focused on NK cells, and our strategy was also unique in that we engineered the regulatory elements of a lentivirus so that the HSCs can be transduced, but again, that the CAR doesn’t express until after the daughter cells have become NK cells. And we confirmed the specificity of this approach after screening a large library of potential regulatory element combinations and also the potency. This is really a long-lived therapy and we think a safe one that could be transformative to really increase the durability of responses for both blood cancers, but also solid tumors.

Sebastian Kobold
So my name is Sebastian Kobold. I’m from the LMU in Munich, Germany. My lab is interested in generating add-ons to cellular therapies to make them work in solid tumors specifically. And today I introduced a strategy where we engineer cytokine receptors to turn suppression into stimulation and also how we could actually transform heterodimeric signaling into homodimeric signaling to provide a broad range of different effector signals to T cells to transform the phenotype. And by doing so, we would endure the activity over prolonged periods of time against chosen cancer cells for as long as the cytokines supporting that activity would be present. And we could demonstrate the principle of this strategy, both in vitro and in vivo, in a range of models. And we believe that this could become a transformative way of enhancing different cell products in pancreatic ductal adenocarcinoma, breast cancer, and other diseases. We’re looking forward to translating this work.

Yihan Zuo
Hello, I’m Yihan Zuo, and I come from Roswell Park Comprehensive Cancer Center. Our study is focused on next-generation CAR-cell therapy for solid tumors using an armoring strategy. And our study demonstrates how IL-36 gamma armored CAR cells reprogram neutrophils and induce endogenous antitumor immunity. Our study indicates that we use an armoring strategy which can further enhance CAR-cell efficacy in solid tumors in the absence of lymphodepletion. And it also demonstrates that IL-36 gamma armored CAR cells can activate the cancer immunity cycle and induce endogenous antigen-specific T cells with long-lasting antitumor efficacy. This is achieved by mobilizing neutrophils with antigen-presenting cells and also tumor-killing effects.

Marco Davila
So I really enjoyed this session. I think that while they’re all very different talks, they were organized around one theme: how do we overcome the barriers that are present within solid tumor malignancies? And the strategies involved manipulating cytokines, either providing the cytokines through the CAR T cells or reversing a negative signal that’s provided from cytokines, or using novel production systems. So I want to kind of hit on some of those topics for a deeper discussion. So, Kedar, do you want to start?

Kedar Kirtane
Yeah, and maybe this is not the right forum, but it’s still a good question, I think. You guys all described really fascinating scientific technologies to overcome these barriers. Can you comment on the potential scalability as manufacturing complexity increases? As you know, we’ve had some issues with manufacturing for certain FDA-approved products here. I’m curious whether you’ve thought about that long term.

Marco Davila
Probably relevant for Nathan and Eric.

Nathan Welty
Yeah, so I can talk about that a little bit. We’ve had a lot of experience at our center with engineered HSC products using CRISPR editing technology, which is what I use to generate my cells. And I think from the get-go, we’ve been very intentional about trying to use the same sorts of GCSF-mobilized normal donor cells that we would use if we were to translate this into a regular system. So we’ve tried to maximize translatability from the beginning. I think there are a lot of unanswered questions in the field about number, quality, et cetera, in the engineered HSC space in particular, and there are going to be a lot of probably regulatory issues around that when you’re engineering new cells, either with viruses or with CRISPR-based technologies that we have to anticipate. I think we can learn from what we’ve done with CAR T cells, but I think there are going to be some unique factors that are specific to HSCs. And those parameters, clinically, will have to be developed as we think about getting these closer to translation.

Eric Smith
Yeah, I can briefly add to that. This is a super exciting time to be doing gene and cell therapies, as you know, and there are now FDA-approved HSC-modified cells, not in cancer immunotherapy, but for sickle cell disease and hemoglobinopathies. So we really want to leverage that experience. We think for our cancer patients, mobilizing and collecting HSCs, if this was done ex vivo, is certainly possible. We do that for autotransplants. We think the numbers of cells that are needed are reasonable to obtain. But ultimately, the goal of going direct in vivo and mobilizing HSCs, targeting HSCs, while still needing some development clinically, is certainly feasible with the tools that we have today.

Marco Davila
So now I wanted to talk a little bit about the cytokine talks. So I presented on IL-18, Yihan on IL-36 gamma, Sebastian on some features of cytokine receptors in general. So there are obviously lots of great cytokines that have impacts on the immune system, T cells, the microenvironment: IL-2, IL-7, IL-12, IL-15, IL-36, IL-18. What are the defining features that we should look at as designers of CARs to say these are really the important features to combine with a CAR T cell, specifically when attacking a solid tumor? So I’ll kind of pitch that to you all. Sebastian?

Sebastian Kobold
Yeah, sure. To me at least, or to us, I think a key feature is the response. Because I think that was also the reason why we chose to pivot more to the receptors than to the cytokines, which we do too, simply because although the topic of being able to reprogram the tumor microenvironment is very compelling, I’m not sure that we really understand how much is enough and how much is too much. And in that sense, it makes it really difficult to say, okay, is it IL-18? There’s great data already out there for IL-18, or is it maybe another one that would be better? And if so, when should we stop doing that? So I think that’s a little bit of the challenge. Whereas if you’re seeing just a cell-autonomous system, where the thing that’s being fed is just the T cell, that becomes maybe a bit more controllable in terms of understanding how much the tumor already has and is producing constantly as a function of the cells that are there. But I think the question is open, and obviously in your data it looks different too, right?

Yihan Zuo
Yeah, and in terms of the translational study, actually the cytokine-armored CAR cells function through immunomodulatory effects beyond killing ability. Because we all know lymphodepletion is a very important step for CAR T-cell preparation. But in our study, we found that lymphodepletion can also disrupt the interaction between the immunomodulatory effects and the cytokine-armored CAR cells. So whether the role of lymphodepletion is important or not needs to be investigated. And the beauty of armored CAR T cells is that they rely on the endogenous T-cell response rather than CAR T-cell persistency.

Marco Davila
Well, I love the fact when you kind of highlighted translation of some of these ideas in cell therapies, because ultimately that’s probably the most important thing that has to happen with anything that we do. We have to put this into patients and find out what the toxicities are, what the potential benefits are, and whether we can improve on this in an iterative fashion. There have already been publications of clinical trials using IL-18, so that information is very valuable and gives us things we can build on.

Another topic I wanted to talk about, although we didn’t necessarily present this directly, is in vivo gene therapy. I almost feel like if there’s a cell and gene therapy discussion, you always have to include in vivo gene therapy. That’s kind of hot right now. Industry is moving toward that, academic labs are around that. I want to hear people’s general ideas involving in vivo gene therapy. Is this something that is ready for prime time? Is this really going to replace adaptive cell therapy? What are people’s thoughts on this? Partly I just want to know for myself so I can steal good ideas. Sebastian?

Sebastian Kobold
Yeah, I think we can all agree that if that would work, it would be a game changer in everything we do because of scaling, because of cost, et cetera. To me, one of the biggest questions that still needs to be answered is to what level we can get such a strategy to help us get away from the need for non-myeloablative chemotherapy or preconditioning. Because I think it’s very clear in all the autologous and allogeneic studies that we’ve seen that you need that. Everyone that had cohorts without it did not see activity and then closed the cohort and went on to the one where it was included. There have been a few myeloma patients that look good, but the follow-up is short. So I don’t know, especially in solid tumors, to what level you can get away without that.

Nathan Welty
I think also when it comes to in vivo, a big challenge that the field is going to have to address is cell number. When you manufacture an ex vivo product, you’re giving a defined cell number typically in our clinical trials, and there are manufacturing release criteria for all of the commercial cell therapy products. And you probably don’t need as many T cells as we’re giving people, but how do you quantify that when you’re giving this in an in vivo manufacturing system? And I think that becomes an even bigger question when you’re moving outside of T cells, because as I talked about, the CAR is going to expand your T-cell population naturally in vivo, but that doesn’t happen with some of the other immune cell types we’re talking about engineering in vivo.

So then you have to think about whether there is an expansion strategy for those cells or whether there is a selectable marker that we can induce. One of the things I didn’t talk about with my strategy is that by knocking out and knocking in at the same time, we’ve introduced a naturally selectable marker because only our knocked-out, knocked-in cells will be knocked out for the gene. So you can give an anti-CD33 antibody, for instance, deplete all of the CD33-positive cells, and enrich for the engineered cells we’re trying to generate. So I think employing strategies like that for other cell types might become important as well when we think about moving to an in vivo setting.

Marco Davila
Eric, I want to ask you as well, because your system is very adaptable to in vivo, but it requires lentivirus because you can’t really do it with RNA if you want persistent gene engineering. But RNA is attractive from a safety perspective. So how do you think about lentivirus versus RNA for in vivo?

Eric Smith
Yeah, I can preface that by talking about the field in general. I’ve been very impressed with the data we have so far, even with all the caveats, just a few patients and a few months of follow-up. But the fact that we’re seeing deep responses in nearly all these patients without lymphodepletion is very encouraging. And then to your question, lentivirus versus RNA, I think there will be different indications for both. RNA, of course, doesn’t give you persistence, but you have added safety that may work really well if there is a way to target minimal residual disease or certainly autoimmunity, or if repeat dosing is required similar to a T-cell engager. Whereas the lentivirus approach, certainly through targeting HSCs as we’re doing, is still a one-time treatment where you’re going to have very long-term production of these modified immune effector cells. And even with these cells, if there’s massive expansion, that could potentially overcome that limitation.

Marco Davila
So at this point, great discussion. I think that’s one of the great aspects of this meeting, being able to talk with our colleagues about great research and things that have implications within the field of cell and gene therapy. But I’d like to close out the session now. On behalf of my co-chair, Kedar Kirtane, and my co-panelists, I want to thank everyone for taking their time and listening to this discussion.