Antibodies as drugs-a Keystone Symposia report.

Although antibodies have been used as molecularly targeted agents for difficult-to-treat diseases such as cancers, the high production costs associated with mammalian expression systems continue to be a drawback. In addition, the clinical efficacy of conventional IgG antibodies is limited. Several types of recombinant antibody (e.g. fused with anticancer drugs, multivalent, or multispecific) have been designed in efforts to develop next-generation antibodies with higher functionality. We used protein engineering to construct several anticancer recombinant antibodies by developing bispecific antibodies that induced specific antitumor effects against cancer cells through the recruitment of lymphocytes. We found that a humanized small bispecific antibody (Ex3) that targets epidermal growth factor receptor on tumor cells and CD3 on T lymphocytes had marked anticancer activity. Furthermore, the function of Ex3 was enhanced by fusion with the human Fc region, domain rearrangement, multimerization, and affinity maturation; a combination of these modifications showed at least additive cytotoxic effects. Interestingly, merely rearranging the domain order of Ex3 induced substantial cytotoxic enhancements, even though the structural format remained the same. Here, we describe our efforts to develop highly functional bispecific antibodies as next-generation therapeutic antibodies using protein engineering.

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases. Two monoclonal antibodies are available for treatment and other antibodies are currently being tested in multiple sclerosis (MS) patients. The purpose of the present review paper is to outline the antibody engineering technologies, the immunologic and pharmacologic concepts of mbs and the current status of treatment in MS with emphasis on clinical efficacy and safety. We conducted a through review of the scientific literature published until 31 December 2014 (print and electronic publications) concerning the production, applications and side effects of the use of Mabs. Sixty five articles were used in total (both original research and review papers). With the introduction of mAbs the treatment of MS has entered a new era, both with respect to efficacy and target specificity. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness, infection and other autoimmune diseases. In addition, unexpected consequences arise from our incomplete knowledge of the immune system. For example, natalizumab, a monoclonal antibody targeting α4-integrin on leukocytes increases the risk of developing progressive multifocal leukoencephalopathy, without causing notable immunosuppression. Further study on the use of mabs is required, both in vitro and in the clinical field, in order to increase our knowledge upon these new revolutionary therapeutic agents.

Background: GPRC5D is a G protein-coupled receptor that is expressed on multiple myeloma cells but absent from most healthy tissues. It is an attractive target for anti-tumor modalities including T cell-engaging bispecific antibodies. Recent clinical data demonstrate that combination therapy using T cell-engaging molecules, which individually target GPRC5D and BCMA on tumor cells, offers unprecedented therapeutic benefits for patients with relapsed/refractory multiple myeloma. A trispecific antibody that simultaneously engages these molecules while activating T cells is expected to provide comparable and additional benefits as a monotherapy. Methods: Multipass membrane proteins are valuable therapeutic targets but are largely inaccessible for antibody discovery due to structural complexity and high conservation. We developed an antibody discovery platform (MPS) tailored for membrane proteins that utilizes advanced immunization techniques including DNA, mRNA, and Lipoparticles (virus-like particles) and also utilizes evolutionarily divergent host species. From the parental antibodies isolated, we engineered panels of GPRC5DxCD3 bispecific and GPRC5DxBCMAxCD3 trispecific antibodies using multiple formats and CD3 arms that encompass different geometries and binding stoichiometries. GPRC5D multispecific antibodies were tested for target specificity using Integral Molecular’s Membrane Proteome Array (MPA). Both bispecific and trispecific antibodies were tested for in vitro potency and cytokine release using MM.1R and RPMI 8226 multiple myeloma cell lines. In vivo efficacy for a subset of antibodies was determined using xenograft models in humanized mice. Results: We immunized chickens with GPRC5D to obtain high-titer immune responses and configured resulting antibodies as T cell-engaging bispecific molecules with a CD3 binding arm. A subset of GPRC5DxCD3 bispecific antibodies displayed potent T cell-mediated cytotoxicity with picomolar potency on multiple myeloma cell lines. Antibody specificity profiling showed high specificity binding to its intended targets, and not to other proteins across the membrane proteome. Bispecific molecules were then re-engineered as trispecific antibodies with additional binding to BCMA, a well-validated multiple myeloma target. GPRC5DxBCMAxCD3 trispecific antibodies showed improved cytotoxic activity against multiple myeloma cells. Both bispecific and trispecific antibodies demonstrated a large window between cell killing and cytokine release. GPRC5D multispecific antibodies also showed robust tumor control against multiple myeloma xenografts in a humanized mouse model. Conclusions: GPRC5D multispecific antibodies hold promise as potent and safe therapeutics for multiple myeloma. Citation Format: Hayley Roth, Daniel Rogers, Ileine Sanchez, Breanna Tyrell, Amelia Snyder, Kyle Doolan, Benjamin Doranz, Ross Chambers, Joseph Rucker. GPRC5D multispecific antibodies with potent anti-tumor activity against multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3406.

Monoclonal antibodies have recently started to deliver on their promise as highly specific and active drugs; however, a more effective, knowledge-based approach to the selection, design, and optimization of potential therapeutic antibodies is currently limited by the surprising lack of detailed structural information for complexes formed with target proteins. Here we show that complexes formed with minimal antigen binding single chain variable fragments (scFv) reliably reflect all the features of the binding interface present in larger Fab fragments, which are commonly used as therapeutics, and report the development of a robust, reliable, and relatively rapid approach to the determination of high resolution models for scFv-target protein complexes. This NMR spectroscopy-based approach combines experimental determination of the interaction surfaces and relative orientations of the scFv and target protein, with NMR restraint-driven, semiflexible docking of the proteins to produce a reliable and highly informative model of the complex. Experience with scFvs and Fabs targeted at a number of secreted regulatory proteins suggests that the approach will be applicable to many therapeutic antibodies targeted at proteins, and its application is illustrated for a potential therapeutic antibody targeted at the cytokine IL-1beta. The detailed structural information that can be obtained by this approach has the potential to have a major impact on the rational design and development of an increasingly important class of biological pharmaceuticals.

BackgroundInhibition of T cell activation and effector function via engagement of the co-inhibitory receptor PD-1 is a critical mechanism enabling tumors to evade host immunity. The two ligands for PD-1, PD-L1 and PD-L2, can be expressed by a variety of immunosuppressive stromal cells, particularly of the myeloid lineage, endothelial cells, and by tumors themselves. In addition to PD-1, PD-L1 engages B7-1 in an additional co-inhibitory interaction. Blocking only PD-1 or only PD-L1 thus does not relieve all inhibitory components of this pathway. We hypothesized that bispecific antibodies blocking both PD-L1 and PD-L2 could more fully restore tumor-specific T cell activation and potentiate anti-cancer immunotherapy. Furthermore, we speculated that enhancing the cytotoxic effector function of these antibodies might further enhance their efficacy through the depletion of tumor cells and supportive stroma.MethodsWe investigated the capacity of monoclonal antibodies capable of bivalent binding to both PD-L1 and PD-L2 to restore the function of PD-1-suppressed T cells in vitro. To assess the in vivo therapeutic efficiency of bispecific PD-Ligand antibodies with ADCC capacities, mouse IgG2a and modified human IgG1 versions were generated. We assessed their ADCC activity in vitro using a bioluminescent reporter assay, and their therapeutic efficiency in vivo in syngeneic or human-cell derived tumors.ResultsThe bispecific antibodies we generated restore the function of PD-1-suppressed T cells in vitro with equivalent efficiency to the FDA approved PD-1 antibody Pembrolizumab. Moreover, our modified human bispecific antibodies lead to significantly higher FcγRIIa activation than FDA-approved clinical human IgG1 PD-L1 antibodies in vitro. In vivo, ADCC-capable PD-Ligand bispecific antibodies suppress the growth of U2940 lymphoma in immunodeficient mice more efficiently than Rituximab, and in a syngeneic model of PD-L1/PD-L2 double positive colon carcinoma, these antibodies demonstrate superiority to PD-1 blocking antibodies to limit tumor growth and increase survival. Furthermore, treatment with our bispecific antibodies increases T cell proliferation and cytotoxicity and reduces density of immunosuppressive myeloid stroma in vivo.ConclusionsADCC-capable PD-Ligand bispecific antibodies display higher therapeutic potential than existing anti-PD-1 antibodies and represent a new class of PD-1 pathway therapeutics with significant potential for the treatment of a variety of human cancers.AcknowledgementsI would like to thank Anupallavi Srinivasamani, PhD student in Michael Curran’s lab, who performed a considerable amount of the work on this project before I joined.

Single-step purification of bispecific monoclonal antibodies for immunotherapeutic use by hydrophobic interaction chromatography

Bispecific antibodies can uniquely influence cellular responses, but selecting target combinations for optimal functional activity remains challenging. Here we describe a high-throughput, combinatorial, phenotypic screening approach using a new bispecific antibody target discovery format, allowing screening of hundreds of target combinations. Simple in vitro mixing of Fab-fusion proteins from a diverse library enables the generation of thousands of screen-ready bispecific antibodies for high-throughput, biologically relevant assays. We identified an obligate bispecific co-targeting CD79a/b and CD22 as a potent inhibitor of human B cell activation from a short-term flow cytometry signaling assay. A long-term, high-content imaging assay identified anti-integrin bispecific inhibitors of human cell matrix accumulation targeting integrins β1 and β6 or αV and β1. In all cases, functional activity was conserved from the bispecific screening format to a therapeutically relevant format. We also introduce a broader type of mechanistic screen whereby functional modulation of different cell subsets in peripheral blood mononuclear cells was evaluated simultaneously. We identified bispecific antibodies capable of activating different T cell subsets of potential interest for applications in oncology or infectious disease, as well as bispecifics abrogating T cell activity of potential interest to autoimmune or inflammatory disease. The bispecific target pair discovery technology described herein offers access to new target biology and unique bispecific therapeutic opportunities in diverse disease indications.

Antibodies, also called immunoglobulins, play a key role in the body’s immune response, binding to specific molecular targets. Of the five classes of antibodies, IgG has found the greatest clinical application. The article presents the mechanisms of antibody action, including interactions with FcR receptors on leukocytes, complement activation, and direct cytotoxic interactions, as well as the main methods of antibody production, which include hybridoma technology, phage display, and production using transgenic animals and their modifications, which allowed for the production of antibodies with reduced immunogenicity and increased their effectiveness and safety of use. It also characterizes various types of antibodies and presents the differences between them resulting from the structure and content of individual protein domains encoded by human genes and genes from other species. Antibodies are currently one of the most important groups of biological drugs used in the treatment of autoimmune, infectious, and neoplastic diseases. The properties of these large biomolecules and the achievements in the field of obtaining and modifying antibodies mean that they are currently the subject of many studies. New forms of antibodies, such as antibody–drug conjugates with highly potent cytotoxic agents, bispecific antibodies, and nanobodies, demonstrate an innovative approach to the treatment of cancer and autoimmune diseases. The dynamic development of the antibody market indicates its growing importance in modern pharmacy and medicine. Further research in this area may lead to the development of more effective and precise therapies, as well as to increase the safety of their use.

GBM (glioblastoma) is the most common and aggressive primary brain tumor in adults. Immunotherapy is an emerging and promising treatment modality for GBM. Unfortunately, most immunotherapy trials have provided only modest benefit to GBM patients thus far. A significant barrier that limits efficacy of immunotherapy in GBM is the paucity of tumor infiltrating lymphocytes and abundance of immune suppressive myeloid cells. A critical step in enhancing the efficacy of immunotherapy for GBM requires approaches that enhance T cell infiltration and reprogram the myeloid cells to a more pro-inflammatory state. S100A4 is a major regulator of stemness, epithelial-mesenchymal transition, and immunosuppression in glioma stem cells and a critical regulator of immune suppressive myeloid and T cell phenotypes in GBM. Targeting S100A4 in either glioma cells or stromal cells is sufficient to reprogram the tumor immune landscape and extend survival of glioma bearing mice, indicating that S100A4 is a promising immunotherapy target. Since S100A4 has both intracellular and extracellular function as well as cytokine-like function, we developed a S100A4 blocking antibody. While the anti-S100A4 antibody blocks breast cancer metastasis efficiently, it did not cross the BBB. Hence, we generated a bispecific S100A4-TfR antibody (BsA) that allows robust BBB penetration. Using ELISA, confocal immunofluorescent microscopy, and multiplexed flow cytometry, our preliminary results suggest that systemic administration of the S100A4-TfR BsA results in accumulation of BsA in the brain and glioma tissue, increased T cell infiltration and immune remodeling. Furthermore, the BsA is taken up by glioma cells and accumulates intracellularly, which is correlated with decreased nuclear SOX2 expression. These results suggest that S100A4-TfR BsA is a promising agent to treat GBM to reprogram the GBM immune landscape and reduce stemness. We are currently performing single cell RNA-sequencing to elucidate molecular and cellular changes induced by the bispecific antibody treatment in different cell types and performing long term survival analyses to evaluate its therapeutic potential. Citation Format: Thomas Wong, Jia-Shiun Leu, Xuejun Fan, Reece Kang, Nourhan Abdelfattah, Fransisca Leonard, Ningyan Zhang, Kyuson Yun. A novel bispecific antibody to reprogram the immune suppressive GBM TME [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2711.

The present work offers a snapshot of the state-of-the-art of crystallographic, analytical, and computational methods used in modern drug design and development. Topics discussed include: drug design against complex systems (membrane proteins, cell surface receptors, epigenetic targets, and ribosomes); modulation of protein-protein interactions; the impact of small molecule structures in drug discovery and the application of concepts such as molecular geometry, conformation, and flexibility to drug design; methodologies for understanding and characterizing protein states and protein-ligand interactions during the drug design process; and monoclonal antibody therapies. These methods are illustrated through their application to problems of medical and biological significance, such as viral and bacterial infections, diabetes, autoimmune disease, and CNS diseases. As approaches to drug discovery have changed over time, so have the methodologies used to solve the varied, new, and difficult problems encountered in drug discovery. In recent years we have seen great progress in the fields of genetics, biology, chemistry, and medicine, but there are still many unmet medical needs, from bacterial infections to cancer to chronic maladies, that require novel, different, or better therapies. This work will be of interest to researchers and policy makers interested in the latest developments in drug design

Thanks to advances in research, it may soon be easier to diagnose autoimmune diseases earlier, but therapy remains a tricky problem

Therapeutic antibodies have been used since the end of nineteenth century, but their use is progressively increased and recently, with the availability of monoclonal antibodies, they are successfully employed in a large disease spectrum, which transversally covers different fields of medicine. Hyperimmune polyclonal immune globulin has been used against infectious diseases, in a period in which anti-microbial drugs were not yet available, and it still maintains a relevant place in prophylaxis/therapy. Although immune globulin should be considered life-saving as replacement therapy in humoral immunodeficiencies, its place in the immune-modulating treatment is not usually first-choice, but it should be considered as support to standard approved treatments. Despite therapeutic monoclonal antibodies have been lastly introduced in therapy, their extreme potentiality is reflected by the large number of approved molecules, addressed toward different immunological targets and able to heavily influence the prognosis and quality of life of a wide range of different diseases.

Bispecific antibodies are in clinical and preclinical development for the treatment of various cancers and life-threatening infectious diseases. Designed to direct and enhance the body’s immune response to specific tumours and pathogens, bispecific antibodies have shown promising results in Phase I and Phase II clinical trials, leading in some cases to complete or partial responses in cancer patients. These bispecific antibodies consist of a ‘targeting’ domain, typically a fragment of a monoclonal antibody that binds to a tumour, linked to a ‘triggering’ arm that is specific for a molecule capable of mediating a phagocytic or lytic response by macrophages, natural killer cells, T-cells or other effector cells. By mediating an immune assault on tumours or pathogens, bispecific antibodies may also lead to antigen presentation and a vaccine-like response in patients. Over the next few years, we expect several bispecific antibodies to enter the late stages of clinical trials and ultimately emerge as new pharmaceutical products.

Objective: Bispecific antibodies (BsAbs) have demonstrated significant therapeutic impacts for the treatment of a broad spectrum of diseases that include oncology, auto-immune, and infectious diseases. However, the large-scale production of clinical batches of bispecific antibodies still has many challenges that include having low yield, poor stability, and laborious downstream purification processes. To address such challenges, we describe the optimization of the controlled Fab arm exchange (cFAE) process for the efficient generation of BsAbs. Methods: The process optimization of a large-scale good manufacturing practice (GMP) cFAE strategy to prepare BsAbs was based on screening the parameters of temperature, reduction, oxidation, and buffer exchange. We include critical quality standards for the reducing agent cysteamine hydrochloride. Results: This large-scale production protocol enabled the generation of bispecific antibodies with >90% exchange yield and at >95% purity. The subsequent downstream processing could use typical mAb procedures. Furthermore, we demonstrated that the bispecific generation protocol can be scaled up to ∼60L reaction scale using parental monoclonal antibodies that were expressed in a 200L bioreactor. Conclusion: We presented a robust development strategy for the cFAE process that can be used for a larger scale GMP BsAb production.

Engineered Fc-lacking bispecific antibodies have shown an exceptionally high potency for recruiting lymphocyte effector cells and enhancing antitumor activity, which is under evaluation in several clinical trials. However, current treatment regimens raise some issues that should be considered, such as the high cost of clinical-grade bispecific antibodies and the achievement of sustained therapeutic plasma levels. The use of gene transfer methods may circumvent problems related to large-scale production and purification, and result in sustained therapeutic plasma concentrations of the Fc-lacking bispecific antibodies. In fact, terminally differentiated cells and non-terminally differentiated cells can be genetically modified to secrete functionally active bispecific antibodies exerting clear anti-tumor effects. This review highlights the relevance of different promising strategies for in vivo delivery of therapeutic bispecific antibodies.