March 17, 2026 | T cell and immune cell engagement is gaining traction, but what makes it different from other therapies? Patrick Baeuerle, Ph.D., chief scientific advisor at Cullinan Therapeutics, and Jeffrey Miller, M.D., deputy director of Masonic Cancer Center, join The Chain to discuss the advantages, similarities, and differences of T cell and immune cell engagers, and how they compare to other modalities such as CAR T cells. Hosted by Laszlo Radvanyi, Ph.D., their conversation covers engineering recognition of multiple targets, prospects for peptide MHC engagers and NK cells engagers, and the application of these modalities to oncology and beyond.

GUEST BIOs

Patrick Baeuerle, Ph.D., Chief Scientific Advisor, Cullinan Therapeutics
Dr. Patrick Baeuerle is the cofounder of six MPM oncology portfolio companies, including Harpoon Therapeutics, iOmx Therapeutics, Maverick Therapeutics, TCR² Therapeutics, Werewolf Therapeutics, and Cullinan Oncology, where he is the acting CSO of Biologics. He is also an investment committee member of the UBS Oncology Impact Fund. Prior to joining MPM as an executive partner in 2015, Patrick served as vice president of research and general manager of Amgen Research Munich GmbH and as CSO for Micromet, where he was responsible for the development of BiTE antibody Blincyto. He was also professor and chairman of biochemistry and molecular biology at the Medical Faculty of Freiburg University, Germany.

Jeffrey Miller, M.D., Deputy Director, Masonic Cancer Center
Jeffrey Miller, M.D., received a bachelor’s degree from Northwestern University in Evanston, Illinois and received his master’s degree from Northwestern University School of Medicine. He completed an internship and residency in Internal Medicine at the University of Iowa in Iowa City. After completing a post-doctoral fellowship in hematology, oncology, and transplantation at the University of Minnesota, he joined the faculty in 1991. Dr. Miller is currently a professor of medicine at the University of Minnesota, Division of Hematology, Oncology, and Transplantation. He is the deputy director of the University of Minnesota Masonic Comprehensive Cancer Center. He is a member of numerous societies such as the American Society of Hematology, the American Association of Immunologists, a member of the American Society of Clinical Investigation since 1999.  He serves on the editorial board for Blood and is a reviewer for a number of journals and NIH grants.

HOST BIO

Laszlo Radvanyi, Ph.D., Professor of Immunology, University of Toronto
Dr. Laszlo Radvanyi has over 30 years of oncology research background in academia and leadership experience in leading a large cancer research institute, as well as leadership positions in international pharma and biotech. He is currently a professor in the immunology department at the University of Toronto where his research focuses on the role of non-coding regions, including retrotransposable elements and human endogenous retroviruses, in cancer development and as modulators of the immune response in cancer patients. Dr. Radvanyi served as president and scientific director of the Ontario Institute for Cancer Research from 2018 to 2024. Prior to this, Laszlo worked at EMD Serono (Merck KGaA) was senior vice president global head of the Immuno-Oncology Translational Innovation Platform and senior scientific advisor for immunology and immunotherapy. Laszlo was also a professor at the Department of Melanoma Medical Oncology at the University of Texas, MD Anderson Cancer Center in Houston from 2004 to 2014. He was also the founding chief scientific officer of Iovance Biotherapeutics (2014-2015), a pioneering company commercializing tumor-infiltrating lymphocyte adoptive cell therapies for melanoma and other cancers. Laszlo also sits on several national and international grant review panels and biotech advisory boards.

TRANSCRIPT

Welcome And Why Engagers Matter

Welcome to The Chain, the podcast exploring the lives, careers, research, and discoveries of protein engineers, scientists, and biotech professionals. We look at the impact their work is having on the field and where the industry is headed. Tune in to stay up to date on the newest advancements and to hear the stories that are impacting the world of biologics.

Meet The Guests And Their Work

Well, good morning, everybody, or good afternoon. I'm it's really a pleasure to host this CHI Chain podcast today on March 9th, 2026. The topic today is really exciting, a very exciting growing area, a very powerful area of immunotherapy, not only for oncology, but a growing area for other diseases such as autoimmunity, and that is the whole area of immune cell engagers. And my name is Laszlo Radvanyi. I'm past president scientific director of the Ontario Institute of Cancer Research in Toronto, Ontario. I'm currently a senior scientist at the Ottawa Hospital Research Institute Cancer Center, where I work on retrotransposable elements, but I've been involved in the cell therapy space for many years in the tumor for trading of the site field. And it's really exciting today to welcome two luminaries in the field of immune cell engagers, Dr. Patrick Baeuerle and Dr. Jeffrey Miller. I'll briefly introduce them to m Dr. Patrick Baeuerle is currently a co-founder of Cullinan Therapeutics, which is developing a really exciting engager for NK cells targeting Metane MICB. Many of you may know him that he was the chief scientific officer of Metro, sorry, Micromet, which developed the CD first CD19 CD3 byte that went into the clinic against lymphoma, which actually became a world leading product in the field. I think many of you know this product called Blue Saito. He's also co-founded eight biotechs throughout his career, including TCR Squared, et c. Another notable achievement or experience for him that he postdoc with Dave Baltimore, and he's won many, many awards. And so it's it's he's really a leader in the field and has written many articles in the field as well as the view articles.

What Keeps Patrick Up At Night

Jeff is a another luminary in the field. As Patrick, who's involved in T cell engagers and NK cell engagers, Jeffrey spent his entire career really devoted to the area of NK cells. He's a professor at the University of Minnesota. He's director of the Masonic Cancer Center at the University of Minnesota. He has over 20 years studying NK cells. Um and um he notably developed one of the first tri-specific engagers for NK cells, which he nicknamed TRICE or TRI-specific NK cell engagers for short. And he was one of the first to show that haplow NK transfer can and and persistence in clinical trials. And he was also one of the first to develop tri-specific NK cell engagers, which also activate the IL-15, IL-15 receptor pathways. So, welcome, gentlemen, welcome, and I appreciate you spending time with us today. So I'd like to start off with just you know a simple question to both of you. And Patrick, maybe I can go to you first. Just briefly, just tell us what keeps you up at night and what are you working on and what what's your key focus area now in the area of immune cell engagers? And then Jeffrey, I'll go to you too as well. What what what you're currently working on and what what is exciting you in the field right now?

So what's keeping me up at night is still T cell gauges after 28 years in the in the area at Cullinan, where I'm a chief scientific advisor. I'm currently developing CLN978 in the clinic as a next generation CD19 CD3 biospecific, so next gen plincido, if you wish. And this is entirely developed in autoimmune diseases, RA, SLE, Shogun's disease in global trials as we speak. Secondly, we have in the clinic a FLIP3, CD3 biospecific T cell engager called CLN049, with which we treat patients that have relapsed refractory AML. So that's currently the only FLIP3-specific T cell engager in clinical trials. Last not least, we have a BCMA CD3 biospecific T cell engager, which we inlicensed. And we will also entirely develop that in autoimmune diseases with SLE studies ongoing as we speak. This T cell engager has shown very high response rates in multiple myeloma patients that have extramedillary disease. I'm also a co-founder of Crossbow Therapeutics, clinical stage company that is focused on developing peptide MET-specific T cell engagers using TCR mimetic antibodies. The first product in the clinic is called CB250. It's a ketapsin G peptide MET CD3 biospecific T cell engager for AML. Then I'm currently advising about a half dozen small startups that develop next generation T cell engagers, exploring new targets, new indications, new technologies. And I'm still doing new company building with MPM Bioimpact, where I just started last year my ninth company with them.

Why Jeff Pushes NK Engagers

Wow, that's incredible. Is that all? It's incredible. No, it's really exciting. And I'll want to discuss more about the peptide MHC targeting with antibodies and and and and by tri-specifics. I think those are a really growing area. And also more on your, especially on your newer targets for AML and also your NK cell engagements. So, Jeff, what I mean, you've done so many things. You treated over 400 patients with NK cells over your career. You're really one of the amazing people in this field of NK cell engages and clinical trials. Can you tell me what sort of keeps you up at night and what you're working on currently?

Sure, Laszlo. Thanks. And Patrick, it's good to meet you this morning. I think, you know, as a very brief start, as outlined by Patrick already, one of the things that is keeping me up at night is that we still do not really have an NK cell therapeutic that's FDA approved. And I think the NK cell field is probably at least five to 10 years behind what's been going on with T cells. So just very briefly, Laszlo, as you pointed out, we started off really with NK cell therapeutic products. I think there's been different enthusiasm for cell therapies, as we're hearing with a bunch of different companies who have been at gung-ho with this strategy in mind, but it's still very difficult. It's hard to manufacture. There are a lot of barriers that I think we're learning about. And I think the T cell field has really paved the way based on the success of blendsido, as you already mentioned, that you really forming these molecular synapses in the body, in vivo, with the traditional protein therapeutic has a lot of advantages for exportability, for simplicity. So, so based on what we've learned with NK cells, and we do think some NK cell therapy has activity in a number of different diseases, especially acute myeloid leukemia, which we've studied for a number of different years. We're trying to make these immunologic synapses in vivo now with NK cell engagers. The one that we've studied very briefly is binding to CD16, which is the FC receptor on NK cells. And the rationale for binding this with an anti-CD16 sequence is that this will have higher affinity than the natural FC binding of the FC portion of a monoclone.

CD16A that you talk about.

CD16A, correct. Yep. And then we also bring wild type IL15 to the immunologic synapse and then a target Moiti. In the things that are in the clinic now, which we can talk about more, are a CD33 for targeting EML. And we could talk about our solid tumor targets as we get through the discussion. So the thing that's keeping me up at night before I retire, I have prompt that we need an FDA therapeutic, an FDA mediated therapy, FDA approved before I give out.

So, how soon are do you think we're away from that? I mean, there are multiple companies now.

Yeah, I think we're at least five years away. You know, that there's been a lot of entrance into the system. You know, we have innate pharma, we have Affimed. It's been a little bit discouraging that some of these things have been generated a huge amount of excitement and a little bit of tracking back, I think a little bit. And I think the most recent one is Affimed's, you know, really pulling out and filing for insolvency was a big disappointment to many. I think as monotherapy activity, there was some activity of Ephi Meds engagers, maybe even more excitement in combination with the cell therapy. But again, when you start doing these combinations and your drug development pathway is really dependent on another therapy, it is a difficult pathway to think about, I think.

So one of the areas that I think, you know, for non-efficientals and youth people to this field who are very interested in in immune cell engagers, they they also are cognizant of the fact that there's a whole plethora of immunotherapies out there, especially cell therapies like car T cells, TCRT cells. And many people are wondering, you know, like there's, you know, why why not car T cells? Why not TCRT cells? Why is this immune cell engager field still so exciting? And what advantages or disadvantages over CAR T cells and TCRT cells or an adoptive T cell therapy does it have? And in your view, like what are some of these advantages and what are some of the you know biological challenges for immune cell engagers that you can tell people that are sort of fixated on adoptive cell therapy to sort of listen to you guys and say, hey, wait a minute, you know, there's this other field that is showing really great promise. Patrick, you want to make some few comments about that?

Sure. I lecture a lot about the difference between T cell engagers and CAR T cells and so done just a couple of weeks ago at AACR IO in in LA, and also learned from the organizer that CART T cells everyone can do in a lab, you know, you just need a stem cell therapy unit. And you you become an inventor of a new drug just inside your walls. Whereas for T cell engagers, it's much more complicated. You need anybody manufacturing, etc. So that most of the T-cell engager developments were done in industry. And so at the end, very few people are invited to these kind of meetings because there aren't any academic speakers to that topic. It's very evident that cow T cells are very difficult to make. T cell engagers are easier, faster, and cheaper to produce, or offer off-the-shelf availability, allow immediate start of treatment, have no need for lymphodepletion, have no black box warning for secondary malignancies, as may come from integration, can be given subcutaneously and can be given by repeat dosing. And there is a path for T cell engagers at least for outpatient use, which is very important for using them in autoimmune diseases. And there are now large meta-studies comparing the side effects of T cell engagers and CAR T cells. And is that it is evident that T cell engagers have far less grade 3 and higher CRS and neurotoxicity than CAR T cells. It's like a 2 to 8% difference. You also mentioned, Laszlo, that you want to talk about T cell exhaustion. So it's very obvious that T cell engagers that engage all the T cells in the body, including CD8, CD4s, NKTs, and gamma deltas, have a very large number of T cells which are very difficult to exhaust, right? Because only a small portion will start working on the target cells. In the case of cow T cells, you have a very small, very limited number of genetically engineered T cells that you really have to safeguard for. And their exhaustion is really an issue that you have to counter in some form, be it by suddenly.

Yeah, I know. I think of cargo therapeutics, CD22, where they're phase one at a five, seven, and nine-day, you know, manufacturing. And all and and we find that in some CAR T cell products, only a difference of four days of manufacturing can cause a huge shift from memory to effector to terminally differentiated cells, which which it's then, you know, the efficacy just drops dramatically. Yeah.

So I don't think exhaustion is a is a big problem for T cell engagers. It's probably also what people hear from CHEF for NK cells. You also asked about activation-induced cell death. I mean, obviously, after 12 approved T cell therapies, that can't be such an issue. And what we have observed for blincido is that effecto memory T cells actually get expanded in the patient, whereas other T cell populations stay the same. So I believe effective memories have no longer need for a secondary stimulus co-stimulation that may prevent exhaustion, but have a great go with just signal one provided by T cell engagers. Then also cold tumors can be obviously treated by T cell engagers. We have very good results with prostate cancer and with UVL melanoma, where we have even approved T cell engager in these code tumors. The size of T cell engagers may not matter much. We have with saluritamic, steep one, C D3 bi-specific from engine, essentially the largest T cell engager format there is, and it treats very well prostate cancer. So it seems not to be a problem to get in inside. For me, the biggest show stop was for T cell engagers, but likewise for CAR T cells and probably every other cell engaging therapy is actually the down regulation on loss of target, the heterogeneity of target expression. And I think going forward, multi-targeting could be a great way to eventually that.

So, Jeff, what do you what do you think about in terms of the NK cells and more than the cell engager field? What are the advantages you feel over? I mean, we we've heard a lot of hype and a lot of development now of NK cell therapies, doctor cell therapies, you know, car NK, especially for allogenaic, where they don't have you know all these toxicities associated with T cell-based cars. And but, you know, so that's sort of a competitive area. So it would be nice to hear what your thoughts are about NK car or NK cell adopter versus these immune cell engagers.

Yep. And actually I'm gonna start off, Patrick, by thanking you because I think you really set the stage. I think one of the things that got us motivated, and we've been working on these NK cell engagers now for the past 10 years, is really the comparison of T cell engagers with CAR T cell therapy. And, you know, there are at least a couple of studies that have crossed over from failing a CAR T cell therapy. Oh wait, from an NK cell from a T cell engager and vice versa. I think the biggest biggest advantage and the thing that keeps me going in the NK cell field, and we're also working on NK cars, is really the fundamental difference between NK cells and T cells. I think one of the advantages of NK cells is that they have as potent cytolytic machinery as does the T cell. The thing that's very, very different is the tuning of secondary cytokines. And you guys would be interested to know in our, you know, our last trike IND that we put in, the FDA made us do an exact comparison by making a lab-based T cell engager compared to an NK cell engager and looking at secondary IL-6 being produced by a peripheral blood mononose nuclear cell population. There's a huge, huge difference between the ability of an NK cell engager to mediate secondary cytokines compared to T cells. Now, so the the proof is in the pudding, of course, but we think that NK cells engagers and NK cell products compared to the equivalent on the T cell side will be safer. You know, we keep hearing from our community partners in the Minnesota area, especially those areas that are not associated or don't have, you know, secondary care for more complex patients, that sometimes even these T cell engagers are hard to implement in a community setting without very specific training. We think that NK cell engagers, if we prove that they can be equally effective, are going to be safer and maybe easier to administer.

The same thing, Laszlo, and we've talked about this in other venues. We think that off-the-shelf NK cells, because they can be allogenic and easier to produce, might be a little bit easier and safer than some of the T cell products. But there are other issues with NK cell therapies and barriers that need to be overcome. So what keeps me in the field is really this difference in safety profile. But again, I think we're three to five years behind the T cell field. The thing that I like the most, Patrick, in the T cell field is really the effectiveness of CAR T cell therapy and the effectiveness of bi-specific T cell engagers in different formats gives me some promise that we're going to be able to get some NK cell products out there.

Co-Stimulation And Combination Strategies

Wow, this is fantastic. This just got me thinking about a whole bunch, whole bunch of different questions. You know, I mean, you know, persistence has always been an issue, of course, with adoptive T cell therapies. I mean, I've been in the chill field, that's a good thing that's been always a huge issue. Generating and and and maintaining memory T cells, you know, to persist for recognition against cancer, especially antigens. And that really, you know, separates, you know, you know, durable from non-durable responses. And so I guess my next question is since we're on the topic of, you know, more than one target and how to, you know, engineer recognition of multiple targets is is are there possibilities and what are the possibilities of you know engaging co-stimulation or other signaling pathways in addition to antigen recognition and then antigen, you know, activating receptor activation? Are there prospects for activating co-stimulatory receptors and other receptors that can actually induce memory T cell population that maybe actually can persist and recognize antigen for long, longer periods of time that you can actually then re-engage with a different type of immune cell engager later on, because that's one of the advantages, of course, of immune cell engagers that you can technically infuse them or subcutaneously inject them multiple times. And that is a distinct advantage over adoptive cell therapy. So I was just wondering using your brain both on T cells and then K cells, Patrick, maybe you can start. But what are the sort of new horizons in sort of triggering other signaling pathways to generate memory and better efficacy?

Yeah, definitely in the industry there's quite some effort to introduce co-stimulatory signals into T cell engagers, be it physically into one molecule or separately as a separate bi-specific, which is pursued by Roche. It's now a long time that people have produced nice in veto data, and now the first data from Roche came out combining a CD28 co-stimulator with a T cell engager in targeting CEA CA Camp 5. I just saw the results and I wasn't really overly excited to see them. I don't know how how well the improvement was over just the CA Camp 5 engager. We have now key learnings from approved T cell engagers, and one of the things is that all of them just provide signal one. All of them have compelling single agent activity.

Is that enough? I mean, do we need to enough?

And what other ways than co-stimulation are there to get you to way higher response rates? And my simple solution would be look at what first results are there with combination of T cell engagers with standard of care. It's absolutely amazing. And that has also prompted phase three studies now in first line, combining T cell engagers with whatever there is: ADCs, monoclone antibodies, polychemotherapy, imits, TKIs, and anti-PD1 antibodies. And in all cases, you can augment automatically the efficacy. I think that is the easier path to take than now come in with co-stimulatory molecules that you have to fumble into a T cell engager so that the T cell engager does not kill a T cell that has the co-stimulatory molecule expressed, right? That's probably you have to do by bringing CD3 and co-stimulatory binder very close together so that there's a mutually exclusive engagement.

IL-15 Trikes And NK Receptors

Well, that's a very good, yeah. I mean, I was really reading some of your review articles too, Patrick, and I was very intrigued by the by the relative success of combining chemotherapy even concomitantly with with T cell engagement. And so this is actually a really a growing area, and also the chance of antigen release and epitope spreading, antigen spreading by the targeting specific antigen and then the endogenous T cells coming in so so in the NK area there are other receptors NKPRs NKG2D C D16. I guess Jeff like what's the optimal receptor to target or yeah I there are actually dual specifics that target C D16 and NKG2D should be going after those or is a single one enough and what sort of signaling pathways because some NK cell engagers also you know use IL 15 as you know you you you're a huge fan and a huge proponent of that area can you just tell us a little bit about what you're thinking about there yeah let us yeah so I think you're right the one thing that's really unique about the trike engagers is really that co-stimulatory, you know, bringing this wild type IL-15 to the immune complex.

It's you know the the biology behind this is really intriguing. I think we published I think about 10 years ago now that if you give constant IL-15 stimulation at least to an NK cell I think there's probably some truth to T cells as well you can induce cytokine induced exhaustion. So we found that giving tonic stimulation at least in the assays that we used, you know, when we gave three days on, three days off three days on, the function of the cells at the end of the day was much better than giving a continuous nine day exposure to IL-15. So what's unique about the IL-15 in our engagers is that when you flank a wild type IL-15 molecule with these engager sequences, you actually attenuate the activity of IL-15 on a micromolar basis compared to recombinant human IL-15. So we think one of the keys is to downratch it that cytokine signal is at the same time that you work through activating receptors. So I think you know that the the triche molecule that we use really ligates agonistically CD16 and that's a really commonality CD16 is the most potent activating receptor on NK cells and you mentioned the other co-stimulatory molecules. So our engager is we're working with a small biotech company called GT Biopharma who is currently doing the clinical manufacturing through a CRO that they're working with.

As you know innate FEMED at least worked through a CD16A engager that was a little bit different than ours in a tetrameric I think structure innate pharma has a molecule that co-stimulates NKP46 and Dragonfly co-stimulates through NKG2D all of them have in common CD16 stimulation either with an anti-CD16 sequence or through an IgG that natural but naturally binds the FC receptor. So just getting back to one critical point in our thinking when we set up exhaustion models in hypoxia or unfavorable metabolic circumstances we find that IL15 is the only other co-stimulatory molecule that can somewhat overcome those signals. And at least in our hands with our laboratory based you know co-stimulation of NKG2D or NKP46, we find that IL15 really has unique properties in addition to being expanding the effector to target ratio. You know we all know that relative to the number of NK cells that physiologically circulates through tumors or through the blood, the T cells are much, much, much greater than NK cells. But when you give this IL15 signal you can expand the effector to target ratio in vivo and we think that that's part of the mechanism why these NK cell engagers may work. And at least the trike is really really different from the other engagers that do not expand the logic response in vivo.

So what about IL21 IL21 is also a cytopine that activates NK cells has not been and we know that IL21 can help expand NK cells for adoptive cell therapy. We have the data from Dean Lee and others is that being looked at just briefly if you need to comment on that.

Yeah so it's on the list of things that we're going to make we did make an IL12 NK cell engager and it's a little bit different but IL-12 as you know is great for inducing an interferon gamma costimulus if you think that that's the dominant receptor for anti-tumor response. But what we found out is it doesn't compare at all to the IL-15 in vivo proliferative effects. So IL-21 is interesting it worries me a little bit that some IL-21 studies when they were given as cytokines were not safe but again maybe this attenuating the signal being flanked by two immunologic engagers might make that so we are thinking about creating one of those you know the one thing is Patrick mentioned about these engagers they're somewhat modular. You know you could swap out different domains you can switch the order and I think the key is going to be making bigger complexes for dual targeting. I think we all know what happens with T car therapy and antigen escape. So our approach right now is to put on a second arm to the standard trike to target a second molecule or like Patrick mentioned to add in a domain that would induce checkpoint blockade at the same time. For NK cells we're very interested in NKG2A you know there is an antibody out there called monoluzimab that is I think still going through clinical testing and at least all NK cells that get activated highly upregulate NKG2A. So if I were to pick one just based on the frequency of expression that is one of the ones that we're targeting at the same time we're doing antigen target to interrupt that checkpoint pathway as well.

And there's also a problem with shedding obviously through proteases, atoms, matrix and calopodase that release, for example, make a subunits like alpha three that has been an issue with NKG2Ds are you enjoying the conversation?

We'd love to hear from you. Please subscribe to the podcast and give us a rating it helps other people find and join the conversation. If you've got speaker or topic ideas we'd love to hear those too you can send them in a podcast review.

So Patrick this is actually an interesting question because or an area that the Jeff brought into the area kind of or brought up toxicity and so there's now also newer biologics that are being made in the checkpoint field and the cytokine engagement field that are sort of conditionally activated molecules that supposedly get activated by proteases or acidic pHs into a microenvironment. What's happening in that area is this a promising area or is this just you know just a pie in the sky to be based on some other you know cytomics you know that really kind of didn't that kind of fell through do you think these engagers will be able to conditionally activate them and make them safer and also then dual target two two or more antigens to actually then make it more tumor cell specific?

Very good question, Laszlo. I started actually two companies developing conditional T cell engagers that use releasable masks one was Maverick which was sold to Takeda and the other one was Harpoon which then got sold to Merck. Currently we have quite some excitement with a company called VirBio. They have a conditional T cell engager that targets PSMA and remarkably and as expected the activation of that T cell engager solely in the tumor microenvironment really is good on safety. There is no grade three observed and it's very good on efficacy where some patients even have a greater 90% PSA reduction or greater 50% PSA reduction. And this is a very interesting molecule where the mask actually is a polyethylene glycol like polypeptide attached to both ends of the bite antibody that wraps up the entire molecule and masks it until it comes off in in the tumor microenvironment. So yes we need conditional T cell engages simply for the reason that there is a scarcity of targets for solid tumors. There are many that are so clean that you don't have an issue with normal tissue expressing just a few hundred copies of the target. That is easily managed with monoclonals or with ADCs but this kind of an expression difference cannot be easily managed with T cell engages because of that exquisite sensitivity to very low target levels.

So you need 50 copies and you you get a kill. So and that leaves us with very few targets in solid tumors the situation obviously is different for hemonc where you have all these nice lineage markers for one and you can uplate an entire B cell compartment alongside the tumors without um much consequence the B cells will grow back. But with solid tumors you have very few targets to play with most recently and most excitingly we have now interesting prostate cancer targets steep 1, steep 2 KLK2. PSMA is considered dirty and we have only a success here now when we use it in a conditional T cell engager. Other promising targets I see in solid tumors is glodin'6, Clipic III, glodin 18.2 then AMG is going after a logic gated mesothelin CDH3 type pair which also promises a better safety than you see with mesotheline targeting alone. And these conditional T cell engagers that you mentioned Laslo are just a way to unlock dirty targets and to make them usable. I mentioned PSMA but think about EPCAM EGFR PER2 B783 Nectin4. They're all wonderful targets that work for AVCs but really cannot be worked with T cell engagers unless you have a tumor resident activation and you make definitely two key approaches here one are the masks that you can cleave off and the other one are the pH sensitive ones which also in my view have great promise but lack this kind of a clinical validation that we now see with the masks.

Right right so Jeff do you think this is an important area or NK cells because they're don't cause CRS and other toxicities and but again engaging them specifically in the tumor microenvironment is this is this a is this a problem with the NK cells and that would require these conditional activators or do you think that's not important in the field of NK cell engagement?

Yeah that's a great question. I actually think the you know the more we delve in a microenvironment I think we're going to find many parallels between NK cells and T cells. So I think a lot of our efforts have been really interested in Patrick thank you for at least mentioning B7H3 it it at least in the work that we've been doing and we have papers already out there in prostate cancer in in head and neck tumors we have a paper under review now in glioblastoma the B7H3 is really amazingly and ubiquitously expressed in solid tumors and in multiple myeloma which is under review right now it's a very odd target it seems to correlate with aggressiveness of disease it is very it seems to be a great target and you already mentioned the ADC data that's out there with a B7H3 ADC. So what we're finding Lessio is if it if you could target an antigen in the tumor microenvironment we've been interested in things like B7H3 because they seem to be not only present on the tumor but some components of the microenvironment we know that MDFCs can be targeted by B7H3 engagers. So the more we look I think the more interested we're into some of these combinations again building the complex to target B7H3 and something else like mesothelin or even EGFR, which we have tested at least in a preclinical model can be very interesting. And again all of these over signals, you know, IL15 is still remarkably successful in inducing at least NK cell activation where other signals might exhaust cells.

So you know as I try to teach the students all the time you know your models are only as good as the complexity of a physiologic microinfoamin't you got to migrate through and we've been studying pancreatic cancer which is incredibly difficult to get through that spyprotic area around the tissue you know if you manage to get through that you got to migrate through the tissue and create immunologic synapses through that crawling. If you don't migrate through the tissue any defect at any step of the way is going to cause a problem. And again IL-15 really induces this migratory speed in this serial killing or the repeat touching between different tumor targets. So I think we've learned that you know biopsing tumors in these clinical trials is really critically important. I think Patrick to troubleshoot where we want to go next if we can identify which step is a limitation for our therapeutic effect.

Yeah so Patrick you mentioned and and you know this is a hot new area now car T cells tooth or solid tumors because of the heterogeneity and then you know car or whatever an antigated car gets one or two it's not going to cut it right because of you know antigen escape, etc. So now there's you mentioned you know for example ImmunoCore made the first engager for you know GP100 for uvial melanoma so what is the prospect for peptide MHC engagers you know for not T cell but then you know Jeff is there any prospect to engage in K cells to to to to this you know recognition system too as well I mean that might be some really innovative new approach there Patrick what is this what what do you think the prospects of this area are and maybe you can also you know make a comment about the car T cell theory too because it seems to be a hike now as you know going to be the solution to solid tumors now make all these PMHC antibodies and yeah away we go it comes Laszlo all from the the scarcity of solid tumor targets for engages and at crossbow as I said we have we are not using TCRs soluble TCRs as Immunocord did for their first product but we use antibodies because we know how to engineer them and how to isolate them.

There will be no clonal selection against finding high affinity antibodies in in the first go whereas TCRs are typically selected for not be of high affinity as long as they do not target tumor specific peptides so there there are advantages to that approach but I think the the single most important thing is to find peptide MHC complexes that are abundant just have the 515 copies but have 500 or a thousand copies. And that is also why it cost we focused on catapsene G, which in AML is is highly expressed to at least a thousand copies or higher. And that is really important if you want to go out of that target class, which opens up essentially every antigen in the cell be it in the nucleus in the mitochondria be it's secreted sitting in the membrane wherever there is a peptide that ultimately gets presented by an MHC, you have a new target that can dramatically expand the target space.

In oncology you also may be able to find tumor specific peptides let's say derived from a Rust mutant from a PI3 kinase mutant from a Q53 mutant. The downside really of targeting peptide MHC is HLA restriction that is is also not liked in the industry just to start out with only 30-40% of your patients and among those you only have a 20% response rate that at the end of the day gives you single digit responses. This is really the major drawback here on the other hand you know you have exquisitely tumor specific targets if you think about a REST mutant peptide or anything like that that promises exquisite safety what about NK cell do you think this is something engaging a PMHC with an antibody then coupled to an NK cell engager is this is this or this is a crazy idea I mean can that add another element or another flavor to the NK cell activation appeal?

It's not a crazy idea, Patrick I completely agree with what you said. So we haven't tried the NK cell engagers with any of these TCR like either antibodies or mimics but it certainly allows you I you may be aware of some of the work going on at MD Anderson where they're making TCR cars really analogous to what's going on in the T cell field. I think our approach is because of the you know MHD restriction is not going to that area because we can do dual targeting and other manipulations I would say I I just want to highlight one advantage of NK cells in general when you activate them sufficiently is they have high levels of NKG2D which recognize these stress logins. So remember besides this specific targeting through CD16, you know NK cells have natural cytotoxicity and they really overcome one of the problems in tumors which is this downregulation of MHC. In fact that makes killing more favorable in NK cells that have downregulated MHC molecules. And if you do that with additional targeting it is one of the theoretic advantages especially those tumors that upregulate stress ligands like MICE B. You know there are even car structures that are trying to target with higher affinity MICE B in the ULB proteins. So we have a lot of interesting biology I think to figure it out we haven't done these specific TCR like approaches just because it narrows the field rather than broadening it, which has kind of been our goal.

MRD And Earlier Line Treatment

No, this is fantastic. I got a few more questions but this is such an amazing conversation I wish I can continue it on for another two hours but I guess some other more you know interesting questions I had or potentially interesting questions is so currently a lot of you know T cell and NK cell indices are used for recurrent disease metastatic disease but you know there's a new upsurge now in interest especially in immunotherapy you've seen the successes with neoadjuvant and adjuvant phase immunotherapy so neoadjuvant therapies are now very very important and in fact I'm a big proponent of you know neoadjuvant immunotherapy before standard care surgery or others to sort of activate that immune response is there a prospect for using safe immune cell engagers, T cell NK cell engagers in sort of a neo adjuvant setting to you know activate that T cell response together with a combination with checkpoint or or other modalities? Is this a is this a growing area or an area that's being developed, Patrick?

It's certainly an area that is I find extremely exciting because you put the T cell engagement into a situation where there's low tumor cell load and where there's an unencumbered T cell environment from not taking C in chemo and whatnot. But I I think that the the more important trend I see right now is to use T cell engagers in minimal residual disease which you can bring about just by initial chemotherapy for instance because again you have very few tumor cells left that just need to be mopped up by the T cell engager. That comes with very little side effects because there isn't much T cell activation associated with that. And the first results are just amazing. Think about the inside now being approved in firstline ALL in combination with polychemotherapy that gives you an 85% overall survival after four years. This is is comes close to a cure of that disease. And I believe we have to put T cell engagers way more into combination trials and move them first line upfront. And the initial proof of concept studies in smaller trials are just really amazing and have prompted now a lot of phase three studies of T cell engagers in first line in DLBCL, follicular lymphoma, etc, in combination with standard of care. And unfortunately there aren't yet such experiments with solid tumors but I can imagine also there is a great benefit by combining with orthogonal modalities.

So Jeff I mean we know based on you know cancer biology, I mean of course you know solid tumors versus liquid tumors Heme tumors. We know that NK cells are important for preventing metastasis and they sort of are able to target micrometastasis. So there's plenty of evidence for that. Do you think that NK cell engages in the minimal residual disease adjuvant phase setting are something we should be developing and adjourned activity in this area?

Yeah. I think Laszlo, I and I agree, Patrick, with everything you said. I'm a big believer at a physiologic effector to target ratio. So, you know, there's two ways to overcome that. You either expand and make more NK cells to increase the ET ratio, or you apply it in a setting where it's likely to work better, which is a minimal residual disease setting. I think, you know, innate pharma in collaboration with Sanafi started to at least think about combinations of NK cell engagers, at least in the AML space with hypomethylating agents and phenatoclax. And I think it makes a lot of good sense. The thing that worries me is that if you make your combinatorial partner a chemotherapy, that it's going to lower the immune system, that you may somehow do that in detriment. The one thing that's very clear, even with the CD33 engager that's being tested in the clinic now, that even in blatantly relapsed acute myeloid leukemia, the IO-15 is still powerful enough to expand those NK cells in vivo in every single patient. So I do really think that these combinational partners, especially with the IO-15 co-stimulation, have really a lot of attractiveness. You know, I'm still a hematologist. I attend on the bone marrow transplant unit five weeks a year.

The setting that's really rich for this testing is to have a safe biologic that could be used in the setting of minimal residual disease used after an allergenic transplant in AML. As you know, the immune system is really complicated in that setting. But if you target the IL-15 mainly to NK cells with this CD16 binder, we see very little of cross-activity to T cells. So we think that this would be a perfect setting, at least for reduced intensity transplant relapse rates, can be as high as 40% in the first two years. Applying an engager in a minimal residual disease setting is going to be really the perfect setting, but we got to get beyond the safety testing and we got to get a monotherapy signal and more advanced disease before we I think you're absolutely right.

In Vivo mRNA Delivery Prospects

I'm a huge fan of that. You know, I remember during the development of some of these macrophage ADCP like C D47 and Circum Alpha, I was always arguing you have to use it in a minimal residual setting, and there was a lot of promise there. But I don't know what happened to that. It kind of, you know, wasn't really followed up. You know, this minimal residual disease application. No, that's fantastic. I guess one other question that came up, and Dan had pointed this out to me, Dan Barry at CHI, is, you know, of course, now there's the development of in vivo nanoparticle antiviral-based cars. And I know that there's been some activity of encoding these immune cell engagers by specifics in in sort of nanoparticles using RNA. Where do you think this is gonna go? Is this is this where the field of immune cell engagers is gonna go? Or or do you do you think you know we should, you know, there's still a lot of room for just manufacturing in and biologics? So what do you guys think about the in vivo mRNA space in terms of encoding these? What do you think the future is there and the prospects for that and the opportunities there?

Patrick, you can you know it's probably the ultimate savior for CAR T cell technology because all the autologous stuff is just too expensive and and not readily available, particularly now that folks moving to autoimmune diseases. Promises of these in VOCA T cells is really that they are available off the shelf, that the development times for making them are much reduced compared, let's say, to a monoclonal antibody. And they promise a one-and-done treatment or eventually also a repeat treatment, and they definitely leverage the super high activity of CAR T cells. They don't require lymphodepletion, otherwise, you would take away the T cells that you want to transfect. Don't know whether that is really an advantage. I always viewed authoricus T cells as a combination therapy of a lymphodepletion plus a CAR T. And when you use mRNA, there is certainly no risk of secondary malignancies. The challenges, however, are what we have now seen from a study recently published in the New England Journal in SLE in Lupus is very inconsistent CAR T cell levels that were all over the place. Not a very impressive target B cell elimination. And you wonder also about the path to an outpatient use of this technology. My conclusion is it's still very early days for that technology, years away from a first approval. And by that time, there are first approvals, we will have multiple T cell engagers already approved in autoimmune diseases.

Yeah, I mean the issue there is in many of these cases you have to infuse these mRNAs to get into places like the liquid that can you know manufacture and spool out these things, versus even now a really exciting area, of course, a subcutaneous application of immune cell engagers. So I think that's you know for out out outpatient use. And and still it's the manufacturing for mRNAs is still a huge area, it's still complicated. And then the cold chain, etc. So, I mean, are you Jeff, are you guys thinking of in vivo encoded mRNA encoded NK cell engagers?

Or is this something that's no, it's I think it's really at the discussion stage right now, and again, it's incredibly early. I think the fact that mRNAs have been able to express T cell engagers, we have not tried it for NK cell engagers, but we are thinking about it as a way of half-life extension. You know, at least the NK cell engagers, the same thing with the T cell products, have assured half-life. You know, blend Cito, we mimic our administration first as continuous infusion. Our B7H3 trike was FDA. You know, we got approval to proceed to start the trial in the next two months with subcutaneous injection. And, you know, mRNA might be a way of half-life extension without changing the actual molecule. But again, we haven't tested it. The only other thing, in addition, Lazio, and this gets even more complicated, but you can make an NK cell or a T cell express a trike as a way of delivering that and really getting some of the benefit of where the cell therapies might track. But it is a little bit, it's getting more complicated than we even are. So I think the mRNA strategy is certainly a little bit easier. And again, thinking about exportability. And as I got many COVID mRNA vaccines, we know that they could be given safely and they can be effective in those settings. So I think it's a great area to think about.

Biggest Challenges And What Comes Next

It's been a fantastic conversation. I mean, I've learned so much, and I think our listeners who listen to this amazing podcast are going to just get a comprehensive 101 lesson on immune cell engagers and where they're going. What are the advantages and disadvantages? I guess my also I'm very excited at the prospect. I don't know if anybody's thinking about this, but combining different types of immune cell engagers, right in sequences, like a T cell engager with an NK cell engager afterwards as we understand more of the biology and you know what targets to hit, you know, like, you know, I think that that is, I don't know if anybody's looking at that, but that's perhaps an area to, again, clinically, it's it's all about getting these things into the clinic. It's just maybe you know, a minute or so, can you just you know just summarize what you think are the current challenges and what should we be prioritizing in the field of intakes and T cell engagers in the future, like what we should be focusing on to get more of these things into the clinic past the finish line to really help our patients. So, so Patrick, maybe you want to go first and then you know we'll we'll get Jeff to give his final thoughts.

Happy to do so. So no surprise, I agree to favor combination of T cell engagers with standard of care for enhancing efficacy, moving them to first line and eventually spare chemotherapy for the patient. Use T cell engagers in MRD, further to lower incidences of grade 3, grade 2, CRS, and ICANNs by conditional activation, logic gating, by combining step up dosing, anti-S6 steroids, etc., what whatever we have. SAQ administration, very important in that aspect, can lower C max values upon start of infusion and use in MRD. Multitargeting of T cell engagers, very important to overcome target loss, target heterogeneity, etc. And we see that already developing. Just mentioned BCMA, GPC for GPCR5D, dual targeting T cell engager in multiple myeloma GNJs developing, that led to a 100% response rate in relapse effector patient.

Just proof of concept that dual targeting is is is is really the way I mean even with cars, the you know, the 1922 and even the triple cars, right, for B cell and the polemas.

Then, as I mentioned, new T cell target discovery, particularly for solid tumors, is important. And last not least, new indications. And here we want to see many more autoimmune diseases being treated with B cell depleting T cell engagers, and these next generation T cell engagers in autoimmune diseases may have to strive for optimal safety, convenience, and outpatient use so that they can reach a large market population.

Agreed. I think the autoimmune disease, you know, based on some of the data that's coming out with the car T cells by Nobartis and others, I mean the SLE effects are just remarkable. And I can I can see immune cell engagers, T cell engagers, you know, targeting B cells could be hugely effective and very clinically applicable, much more practical. So, Jeff, what are your thoughts in terms of the what should we prioritizing the NK immune cell engagers area in the next few years?

Yep. And Patrick, as you said, I think you know everything you said about T cell engagers is applicable to NK cell engagers. There's a couple of things I wanted to highlight about the combinations. You know, there there's been a big push. There has been dozens of NK cell companies. That number is shrinking down a little bit. I think some of the most promising data with an NK cell product was in combination with AFEMA's anti-CD30 antibody and Hodgkin's disease, which really gave very unique responses in combining an NK cell engagement with. I think it was quite remarkable. Yep. So I think the the things that we need to think about is in autoimmune disease, you know, we've made a CD19 trike that's quite effective in eliminating allergenic B cells in vitro and in an animal model. I think about NK cell therapy for autoimmune disease is perhaps perfect. You know, T cells can give some activation that could be really worrisome in that setting. There's not been an NK cell engager tested in that setting. Patrick, I think blincito has been used in rheumatoid arthritis in a nature medicine paper.

Many autoimmune diseases. Just New England Journal paper a couple of days ago showed an ITP patient. Oh, yeah. Very effectively treated with blincito.

So I think this might be a real way to think about for NK cell therapeutics in those settings where the global systemic immune activation might be a little bit less with NK cells. But again, we have to go through in these relapse refractory patients. We have to move it up into other settings and combinations that can be used. And I guess the burden I feel upon me now is we have to get a really concrete efficacy signal in both, you know, the hemolignancy that we're working on, and at least in some settings of a solid tumor. If we don't, it's not gonna get to the bar of trying these combinations. So you have to, in my opinion, see some monotherapy activity, even the most advanced diseases, even if that might not be the optimal way to test it for the future. So I guess I have a lot of hope that we're gonna get there. And again, I think the time frame has got to be in the next three to five years. As therapies go up and down, we don't want to see it go down further. So we need to see some really bona fide, believable clinical success. That's the goal.

Wow, this has been fantastic. But I think you I'm a believer, and you know, I you know have been in my career an adopter T cell aficionado. I mean, I've mostly worked on tumor for training lymphocytes, as you may well know. You know, working at Lion Biotechnologies as a CSO and and initially, and then you know, which became Iovance. And but I've always sort of looked at the T cell engager field as sort of a very viable, very important alternative that, you know, people have been sort of thinking about, but because of the hype of the adoptive T cell therapies, of course, the car T cell therapies for heme malignancy is kind of a lot of the public has not been really as well informed about the advantages of of these really novel and really effective biologics in terms of the practicality, dosing, safety, efficacy, et c. So I really think that I hope that many, many people listen to this podcast and really, you know, get a really thorough knowledge about this. And of course, there's so many new targets that are possible, you know, in this area. So I'd like to thank both of you, Patrick and Jeff, for coming on and spending the hour or so with us here and really sharing your expertise and your knowledge in this area. And I'd like to thank also CHI and The Chain podcast for hosting and for sponsoring this event. So with that said, thank you very much, everybody, and have a nice rest of the day or evening, wherever you may be. Thank you.

Thank you guys. Take care.