ASCO Education The Evolving Landscape of Bispecific Antibodies in Hematologic and Solid Tumors
Dr. Hope Rugo and Dr. Giuseppe Curigliano discuss recent developments in the field of bispecific antibodies for hematologic and solid tumors, including strategies to optimize the design and delivery of the immunotherapy.
TRANSCRIPT
Dr. Hope Rugo: Hello and welcome to By the Book, a podcast series from ASCO that features engaging conversations between editors and authors of the ASCO Educational Book. I am your host, Dr. Hope Rugo. I am the director of the Women's Cancers Program and division chief of breast medical oncology at the City of Hope Cancer Center. I am also the editor-in-chief of the Educational Book.
Bispecific antibodies represent an innovative and advanced therapeutic platform in hematologic and solid tumors. And today, I am delighted to be joined by Dr. Giuseppe Curigliano to discuss the current landscape of bispecific antibodies and their potential to reshape the future of precision oncology.
Dr. Curigliano was the last author of an ASCO Educational Book piece for 2025 titled, "Bispecific Antibodies in Hematologic and Solid Tumors: Current Landscape and Therapeutic Advances." Dr. Curigliano is a breast medical oncologist and the director of the Early Drug Development Division and chair of the Experimental Therapeutics Program at the European Institute of Oncology in Milan. He is also a full professor of medical oncology at the University of Milan.
You can find our disclosures in the transcript of this episode.
Dr. Curigliano, Giuseppe, welcome and thanks for being here.
Dr. Giuseppe Curigliano: Thanks a lot for the invitation.
Dr. Hope Rugo: Giuseppe, I would like to first ask you to provide some context for our listeners on how these novel therapeutics work. And then perhaps you could tell us about recent developments in the field of bispecific antibodies for oncology. We are at a time when antibody-drug conjugates (ADCs) are all the rage and, trying to improve on the targeting of specific antigens, proteins, receptors in the field of oncology is certainly a hot and emerging topic.
Dr. Giuseppe Curigliano: So, thanks a lot. I believe really it was very challenging to try to summarize all the bispecific antibodies that are under development in multiple solid tumors. So, the first thing that I would like to highlight is the context and the mechanism of action of bispecific antibodies.
Bispecific antibodies represent a groundbreaking advancement in cancer immunotherapy, because these engineered molecules have the unique ability to target and simultaneously bind to two distinct antigens. That is why we call them bispecific. So typically, one antigen is expressed on the tumor cell and the other one is expressed on the immune effectors, like T-cell or natural killer cells. So this dual targeting mechanism offers several key advantages over conventional monoclonal antibodies because you can target at the same time the tumor antigen, downregulating the pathway of proliferation, and you can activate the immune system. So the primary mechanism through which bispecific antibodies exert their therapeutic effects are: First, T-cell redirecting. I mean, many bispecific antibodies are designed to engage tumor-associated antigens like epidermal growth factor receptor, HER2, on the cancer cell and a costimulatory molecule on the surface of T-cell. A typical target antigen on T-cell is CD3. So what does it mean? That you activate the immune system, immune cells will reach the tumor bed, and you have a dual effect. One is downregulating cell proliferation, the other one is activation of the immune system. This is really important in hematological malignancies, where we have a lot of bispecifics already approved, like acute lymphoblastic leukemia or non-Hodgkin lymphoma.
The second, in fact, is the engagement of the tumor microenvironment. So, if you engage immune effector cells like NK cells or macrophages, usually the bispecific antibodies can exploit the immune system's ability to recognize and kill the immune cells, even if there is a lack of optimal antigen presentation.
And finally, the last mechanism of action, this may have a role in the future, maybe in the early cancer setting, is overcoming immune evasion. So bispecific antibodies can overcome some of the immune evasion mechanisms that we see in cancer. For example, bispecific antibodies can target immune checkpoint receptors, like PD-L1 and CTLA-4. Actually, there is a bispecific under development in breast cancer that has a dual targeting on vascular endothelial growth factor receptor and on PD-L1. So you have a dual effect at the same time.
So, what is really important, as a comment, is we need to focus first on the optimal format of the bispecific, the optimal half-life, the stability, because of course even if they are very efficient in inducing a response, they may give also a lot of toxicities. So in clinical trials already, we have several bispecifics approved. In solid tumors, very few, specifically amivantamab for non-small cell lung cancer, but we have a pipeline of almost 40 to 50 bispecifics under development in multiple solid tumors, and some of them are in the context of prospective randomized trials.
Dr. Hope Rugo: So this is really a fascinating area and it’s really exciting to see the expansion of the different targets for bispecific antibodies. One area that has intrigued me also is that some of the bispecifics actually will target different parts of the same receptor or the same protein, but presumably those will be used as a different strategy. It’s interesting because we have seen that, for example, in targeting HER2.
Dr. Giuseppe Curigliano: Oh, yes, of course. You may consider some bispecifics like margetuximab, I suppose, in which you can target specifically two different epitopes of the same antigen. This is really an example of how a bispecific can potentially be more active and downregulating, let us say, a pathway, by targeting two different domains of a specific target antigen. This is an important point.
Of course, not all the bispecifics work this way, because some of the target antigen may dimerize, and so you have a family of target antigen; an example is epidermal growth factor receptor, in which you have HER1, HER2, HER3, and HER4. So some of them can inhibit the dimerization between one target antigen and the other one, in order to exert a more antiproliferative effect. But to be honest, the new generation of them are more targeting two different antigens, one on the tumor and one on the microenvironment, because according to the clinical data, this is a more efficient way to reduce proliferation and to activate the immune system.
Dr. Hope Rugo: Really interesting, and I think it brings us to the next topic, which is really where bispecific antibodies have already shown success, and that is in hematologic malignancies where we have seen very interesting efficacy and these are being used in the clinic already. But the expansion of bispecific antibodies into solid tumors faces some key challenges. It’s interesting because the challenges come in different shapes and forms. Tell us about some of those challenges and strategies to optimize bispecific antibody design, delivery, patient selection, and how we are going to use these agents in the right kind of clinical trials.
Dr. Giuseppe Curigliano: This is really an excellent question because despite bispecific antibodies having shown a remarkable efficacy in hematological malignancies, their application in solid tumors may have some challenges. The first one is tumor heterogeneity. In hematological malignancy, you have a clear oncogene addiction. Let us say that 90% of the cells may express the same antigen. In solid tumors, it is not the same. Tumor heterogeneity is a typical characteristic of solid tumors, and you have high heterogeneity at the genetic, molecular, and phenotypic levels. So tumor cells can differ significantly from one another, even if within the same tumor. And this heterogeneity sometimes makes it difficult to identify a single target antigen that is universally expressed in an hematological malignancy. So furthermore, sometimes the antigen expressed on a tumor cell can be also present on the normal tissue. And so you may have a cross-targeting. So let’s say, if you have a bispecific against epidermal growth factor receptor, this will target the tumor but will target also the skin with a lot of toxicity.
The second challenge is the tumor microenvironment. The solid tumor microenvironment is really complex and often immunosuppressive. It is characterized by the presence of immunosuppressor cells like the T regulators, myeloid derived suppressor cells, and of course the extracellular matrix. All these factors hinder immune cell infiltration and also may reduce dramatically the effectiveness of bispecific antibodies. And as you know, there is also an hypoxic condition in the tumor.
The other challenge is related to the poor tumor penetration. As you know also with antibody-drug conjugate, only 1 to 3% of the drug will arrive in the tumor bed. Unlike hematological malignancies where tumor cells are dispersed in the blood and easily accessible, the solid tumors have a lot of barriers, and so it means that tumor penetration can be very low. Finally, the vascularity also of the tumor can be different across solid tumors. That is why some bispecifics have a vascular endothelial growth factor receptor or vascular endothelial growth factor as a target.
Of course, what do we have to do to overcome these challenges? First, we have to select the optimal antigen. So knowing very well the biology of cancer and the tumor-associated antigens can really select a subgroup of epitopes that are specifically overexpressed in cancer cells. And so we need to design bispecifics according to the tumor type. Second, optimize the antibody format. So there are numerous bispecific antibody formats. We can consider the dual variable domain immunoglobulin, we specified this in our paper. The single chain variable fragments, so FC variable fragments, and the diabodies that can enhance both binding affinity and stability. And finally, the last point, combination therapies. Because bispecific antibodies targeting immune checkpoint, we have many targeting PD-1 or PD-L1 or CTLA-4, combined eventually with other immune checkpoint inhibitors. And so you may have more immunostimulating effect.
Dr. Hope Rugo: This is a fascinating field and it is certainly going to go far in the treatment of solid tumors. You know, I think there is some competition with what we have now for antibody-drug conjugates. Do you see that bispecifics will eventually become bispecific ADCs? Are we going to combine these bispecific antibodies with ADCs, with chemotherapy? What is the best combination strategy do you think looking forward?
Dr. Giuseppe Curigliano: So, yes, we have a bispecific ADC. We have actually some bispecifics that are conjugated with a payload of chemotherapy. Some others are conjugated with immunoactivation agents like IL-2. One of the most effective strategies for enhancing bispecific activity is the combination therapy. So which type of combination can we do? First, bispecific antibodies plus checkpoint inhibitors. If you combine a bispecific with an immune checkpoint, like anti-PD-1, anti-PD-L1, or anti-CTLA-4, you have more activity because you have activation of T-cells, reduction of immunosuppressive effect, and of course, the capability of this bispecific to potentiate the activity of the immune checkpoint inhibitor. So, in my opinion, in a non-small cell lung cancer with an expression of PD-L1 more than 50%, if you give pembrolizumab plus a bispecific targeting PD-L1, you can really improve both response rate and median progression-free survival.
Another combination is chemotherapy plus bispecific antibodies. Combining chemotherapy with bispecific can enhance the cytotoxic effect because chemotherapy induces immunogenic cell death, and then you boost with a bispecific in order to activate the immune system.
Bispecific and CAR T-cells, until now, we believe that these are in competition, but this is not correct. Because CAR T-cells are designed to deliver an activation of the immune system with the same lymphocytes engineered of the patients, with a long-term effect. So I really do not believe that bispecifics are in competition with CAR T-cells because when you have a complete remission induced by CAR T-cell, the effect of this complete remission can last for years. The activity of a bispecific is a little bit different. So there are some studies actually combining CAR T-cells with bispecifics. For example, bispecific antibodies can direct CAR T-cells in the tumor microenvironment, improving their specificity and enhancing their therapeutic effect.
And finally, monoclonal antibody plus bispecific is another next generation activity. Because if you use bispecific antibodies in combination with existing monoclonal antibodies like anti-HER2, you can potentially increase the immune response and enhance tumor cell targeting. In hematological malignancies, this has been already demonstrated and this approach has been particularly effective.
Dr. Hope Rugo: That’s just so fascinating, the whole idea that we have these monoclonal antibodies and now we are going to add them to bispecifics that we could maybe attach on different toxins to try and improve this, or even give them with different approaches. I suppose giving an ADC with a bispecific would sort of be similar to that idea of giving a monoclonal antibody with the bispecific. So it is certainly intriguing. We also will need to understand the toxicity and cost overall and how we are going to use these, the duration of treatment, the assessment of biomarkers. There are just so many different aspects that still need to be explored.
And then with that idea, can you look ahead five or ten years from now, and tell us how you think bispecific antibodies will shape our next generation cancer therapies, how they will be incorporated into precision oncology, and the new combinations and approaches as we move forward that will help us tailor treatment for patients both with solid tumors and hematologic malignancies? Are we going to be giving these in early-stage disease in solid tumors? So far, the studies are primarily focusing on the metastatic setting, but obviously one of the goals when we have successful treatments is to move them into the early stage setting as quickly as possible.
Dr. Giuseppe Curigliano: Let us try to look ahead five years rather than ten years, to be more realistic. So, personally I believe some bispecifics can potentially replace current approaches in specifically T-cell selected population. As we gather more data from ongoing clinical trials and we adopt a deeper understanding of the tumor immuno microenvironment, of course we may have potentially new achievement. A few days ago, we heard that bispecifics in triple negative breast cancer targeting VEGF and PD-L1 demonstrated an improvement in median progression-free survival.
So, how to improve and to impact on clinical practice both in the metastatic and in the early breast cancer setting or solid tumor setting? First, personalized antigen selection. So we need to have the ability to tailor bispecific antibody therapy to the unique tumor profile of individual patients. So the more we understand the biology of cancers, the more we will be able to better target.
Second, bispecific antibodies should be combined. I can see in the future a potential trial in which you combine a bispecific anti-PD-L1 and VEGF with immune checkpoint inhibitor selected also to the level of expression of PD-L1, because integration of antibody bispecific with a range of immunotherapies, and this cannot be only immune checkpoint inhibitors, but can be CAR T-cells, oncolytic viruses, also targeted therapy, will likely be a dominant theme in the coming years. This combination will be based on the specific molecular and immuno feature of the cancer of the patient.
Then we need an enhanced delivery system. This is really important because you know now we have a next generation antibody. An example are the bicyclic. So you use FC fragment that are very short, with a low molecular weight, and this short fragment can be bispecific, so can target at the same time a target antigen and improving the immune system. And so the development of this novel delivery system, including also nanoparticles or engineered viral vectors, can enhance the penetration in the tumor bed and the bioavailability of bispecific antibodies.
Importantly, we need to reduce toxicity. Until now, bispecifics are very toxic. So the more we are efficient in delivering in the tumor bed, the more we will reduce the risk of toxicity. So it will be mandatory to reduce off-target effects and to minimize toxicity.
And finally, the expansion in new indication. So I really believe you raised an excellent point. We need to design studies in the neoadjuvant setting in order to better understand with multiple biopsies which is the effect on the tumor microenvironment and the tumor itself, and to generate hypotheses for potential trials or in the neoadjuvant setting or in those patients with residual disease.
So, in my opinion, as we refine design, optimize patient selection, and explore new combination, in the future we will have more opportunity to integrate bispecifics in the standard of care.
Dr. Hope Rugo: I think it is particularly helpful to hear what we are going to be looking for as we move forward to try and improve efficacy and reduce toxicity. And the ability to engineer these new antibodies and to more specifically target the right proteins and immune effectors is going to be critical, of course, moving forward, as well as individualizing therapy based on a specific tumor biology.
Hearing your insights has been great, and it really has opened up a whole area of insight into the field of bispecifics, together with your excellent contribution to the ASCO Educational Book. Thank you so much for sharing your thoughts and background, as well as what we might see in the future on this podcast today.
Dr. Giuseppe Curigliano: Thank you very much for the invitation and for this excellent interview.
Dr. Hope Rugo: And thanks to our listeners for joining us today. You will find a link to the Ed Book article we discussed today in the transcript of this episode. It is also, of course, on the ASCO website, as well as on PubMed. Please join us again next month on By the Book for more insightful views on the key issues and innovations that are shaping modern oncology.
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The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions. Guests on this podcast express their own opinions, experience and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product, service, organization, activity or therapy should not be construed as an ASCO endorsement.
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Disclosures:
Dr. Hope Rugo:
Honoraria: Mylan/Viatris, Chugai Pharma
Consulting/Advisory Role: Napo Pharmaceuticals, Sanofi, Bristol Myer
Research Funding (Inst.): OBI Pharma, Pfizer, Novartis, Lilly, Merck, Daiichi Sankyo, AstraZeneca, Gilead Sciences, Hoffman La-Roche AG/Genentech, In., Stemline Therapeutics, Ambryx
Dr. Giuseppe Curigliano:
Leadership: European Society for Medical Oncology, European Society of Breast Cancer Specialists, ESMO Open, European Society for Medical Oncology
Honoraria: Ellipses Pharma
Consulting or Advisory Role: Roche/Genentech, Pfizer, Novartis, Lilly, Foundation Medicine, Bristol-Myers Squibb, Samsung, AstraZeneca, Daiichi-Sankyo, Boerigher, GSK, Seattle Genetics, Guardant Health, Veracyte, Celcuity, Hengrui Therapeutics, Menarini, Merck, Exact Sciences, Blueprint Medicines, Gilead Sciences
Speakers’ Bureau: Roche/Genentech, Novartis, Pfizer, Lilly, Foundation Medicine, Samsung, Daiichi Sankyo, Seagen, Menarini, Gilead Sciences, Exact Sciences
Research Funding: Merck
Travel, Accommodations, Expenses: Roche/Genentech, Pfizer, Daiichi Sankyo, AstraZeneca