Bispecific antibodies with natural architecture produced by co-culture of bacteria expressing two distinct half-antibodies

Targeting the Immune Microenvironment in Chronic Lymphocytic Leukemia: An Evolving Therapeutic Strategy

Although small molecule inhibitors that target the aberrant signaling pathways and molecular defects of chronic lymphocytic leukemia (CLL) result in improved survival benefits vs. traditional chemoimmunotherapy or chemotherapy, treatment resistance may result later, reflecting the intrinsic tumor heterogeneity, persistence of the leukemic clone, and presence of the tumor microenvironment, which supports the survival of the disease clone. Patients with CLL have immune-related abnormalities in T lymphocyte subset composition, immune synapse formation, and other immune dysregulations. Cellular interactions between the disease clone and its microenvironment provide therapeutic opportunities to target these tumor pathogenesis pathways, potentially improving the patient's immune functions and clinical outcomes of targeted therapies. At present, despite the lack of response of immune checkpoint inhibitors in CLL, they showed promising efficacy in patients with Richter transformation. Together with CD19-targeted chimeric antigen receptor-modified T cell (CAR-T) therapy, novel bispecific antibodies and other immunotherapies are being investigated to improve survival outcomes for patients with relapsed or refractory (R/R) CLL, as exemplified by epcoritamab, a bispecific antibody that recently demonstrated initial efficacy in R/R CLL and in patients in high-risk CLL subgroups, including those with TP53 aberrations and unmutated genes that encode immunoglobulin variable heavy chain region (IGHV). Furthermore, to address the immune escape of cancer cells and issues that impact the durability of single-targeted T cell-redirected therapies, novel strategies such as trispecific antibodies and combination therapies are being investigated to increase tumor specificity or immune cell activation. In summary, there is emerging evidence that immunotherapies may counteract the immunosuppressive microenvironment of CLL, improve clinical responses, decrease the risk of infection, and overcome treatment resistance.

Trends and challenges in bispecific antibody production

Bispecific antibodies (bsAbs) represent a rapidly growing field of therapeutic agents. More bsAbs are being approved worldwide and are in various stages of clinical trials. However, the discovery and production of novel bsAbs presents significant challenges due to their complex structure. Thus, precise control of assembly and stability is required, given the many formats developed. This review examines recent trends in bsAb production, focusing on advancements in engineering platforms, production strategies, and challenges in large-scale manufacturing. Key developments include improvements in modular antibody design, novel expression systems, and optimization of bioprocessing techniques to enhance stability, yield, and efficacy. Additionally, the article explores the future potential of bsAbs as next-generation therapeutics, underscoring the growing impact of these innovations on expanding treatment options for patients with unmet medical needs.

Mosunetuzumab for the treatment of follicular lymphoma

INTRODUCTION

Follicular lymphoma (FL) is an indolent non-Hodgkin lymphoma that shows a progressive increase in relapses and refractory in its natural history and a median survival of approximately 18-20 years. The advent of anti-CD20 monoclonal antibodies has changed the FL therapeutic algorithm, with an increase in progression-free survival. T-cell-dependent bispecific antibodies (BsAbs) represent an emerging drug class against FL.

AREAS COVERED

In this review, we selected papers from the principal databases (PubMed, Medline, Medscape, ASCO, ESMO) between January 2021 and June 2024, using the keywords 'mosunetuzumab' and 'follicular lymphoma' to provide an overview of mosunetuzumab-axgb, a pioneering BsAb. Its mechanism of action, efficacy, safety, and future perspectives were analyzed.

EXPERT OPINION

Mosunetuzumab grants a directing T-cell mediated cytotoxicity and allows a step-up dosing that reduces adverse events, such as cytokine release syndrome, with promising tolerability. At the same time, it improves outcomes in the evolving landscape of FL management, even in post-CAR-T FL patients. Prognostic factors and targetable mechanisms of resistance need to be explored.

NKG2D-bispecific enhances NK and CD8+ T cell antitumor immunity

BACKGROUND

Cancer immunotherapy approaches that elicit immune cell responses, including T and NK cells, have revolutionized the field of oncology. However, immunosuppressive mechanisms restrain immune cell activation within solid tumors so additional strategies to augment activity are required.

METHODS

We identified the co-stimulatory receptor NKG2D as a target based on its expression on a large proportion of CD8+ tumor infiltrating lymphocytes (TILs) from breast cancer patient samples. Human and murine surrogate NKG2D co-stimulatory receptor-bispecifics (CRB) that bind NKG2D on NK and CD8+ T cells as well as HER2 on breast cancer cells (HER2-CRB) were developed as a proof of concept for targeting this signaling axis in vitro and in vivo.

RESULTS

HER2-CRB enhanced NK cell activation and cytokine production when co-cultured with HER2 expressing breast cancer cell lines. HER2-CRB when combined with a T cell-dependent-bispecific (TDB) antibody that synthetically activates T cells by crosslinking CD3 to HER2 (HER2-TDB), enhanced T cell cytotoxicity, cytokine production and in vivo antitumor activity. A mouse surrogate HER2-CRB (mHER2-CRB) improved in vivo efficacy of HER2-TDB and augmented NK as well as T cell activation, cytokine production and effector CD8+ T cell differentiation.

CONCLUSION

We demonstrate that targeting NKG2D with bispecific antibodies (BsAbs) is an effective approach to augment NK and CD8+ T cell antitumor immune responses. Given the large number of ongoing clinical trials leveraging NK and T cells for cancer immunotherapy, NKG2D-bispecifics have broad combinatorial potential.

TL1A inhibition for inflammatory bowel disease treatment: From inflammation to fibrosis

The pivotal role of TL1A in modulating immune pathways crucial for inflammatory bowel disease (IBD) and intestinal fibrosis offers a promising therapeutic target. Phase 2 trials (TUSCANY and ARTEMIS-UC) evaluating an anti-TL1A antibody show progress in expanding IBD therapeutic options. First-in-human data reveal reduced expression of genes associated with extracellular matrix remodeling and fibrosis post-anti-TL1A treatment. Investigational drug TEV-48574, potentially exerting dual antifibrotic and anti-inflammatory effects, is undergoing a phase 2 basket study in both ulcerative colitis (UC) and Crohn disease (CD). Results are eagerly awaited, marking advancements in IBD therapeutics. This critical review comprehensively examines the existing literature, illuminating TL1A and the intricate role of DR3 in IBD, emphasizing the evolving therapeutic landscape and ongoing clinical trials, with potential implications for more effective IBD management.

Advancements in cancer immunotherapies targeting CD20: from pioneering monoclonal antibodies to chimeric antigen receptor-modified T cells

CD20 located predominantly on the B cells plays a crucial role in their development, differentiation, and activation, and serves as a key therapeutic target for the treatment of B-cell malignancies. The breakthrough of monoclonal antibodies directed against CD20, notably exemplified by rituximab, revolutionized the prognosis of B-cell malignancies. Rituximab, approved across various hematological malignancies, marked a paradigm shift in cancer treatment. In the current landscape, immunotherapies targeting CD20 continue to evolve rapidly. Beyond traditional mAbs, advancements include antibody-drug conjugates (ADCs), bispecific antibodies (BsAbs), and chimeric antigen receptor-modified (CAR) T cells. ADCs combine the precision of antibodies with the cytotoxic potential of drugs, presenting a promising avenue for enhanced therapeutic efficacy. BsAbs, particularly CD20xCD3 constructs, redirect cytotoxic T cells to eliminate cancer cells, thereby enhancing both precision and potency in their therapeutic action. CAR-T cells stand as a promising strategy for combatting hematological malignancies, representing one of the truly personalized therapeutic interventions. Many new therapies are currently being evaluated in clinical trials. This review serves as a comprehensive summary of CD20-targeted therapies, highlighting the progress and challenges that persist. Despite significant advancements, adverse events associated with these therapies and the development of resistance remain critical issues. Understanding and mitigating these challenges is paramount for the continued success of CD20-targeted immunotherapies.

A phage-displayed disulfide constrained peptide discovery platform yields novel human plasma protein binders

Disulfide constrained peptides (DCPs) show great potential as templates for drug discovery. They are characterized by conserved cysteine residues that form intramolecular disulfide bonds. Taking advantage of phage display technology, we designed and generated twenty-six DCP phage libraries with enriched molecular diversity to enable the discovery of ligands against disease-causing proteins of interest. The libraries were designed based on five DCP scaffolds, namely Momordica charantia 1 (Mch1), gurmarin, Asteropsin-A, antimicrobial peptide-1 (AMP-1), and potato carboxypeptidase inhibitor (CPI). We also report optimized workflows for screening and producing synthetic and recombinant DCPs. Examples of novel DCP binders identified against various protein targets are presented, including human IgG Fc, serum albumin, vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor (PDGF). We identified DCPs against human IgG Fc and serum albumin with sub-micromolar affinity from primary panning campaigns, providing alternative tools for potential half-life extension of peptides and small protein therapeutics. Overall, the molecular diversity of the DCP scaffolds included in the designed libraries, coupled with their distinct biochemical and biophysical properties, enables efficient and robust identification of de novo binders to drug targets of therapeutic relevance.

SpyMask enables combinatorial assembly of bispecific binders

Bispecific antibodies are a successful and expanding therapeutic class. Standard approaches to generate bispecifics are complicated by the need for disulfide reduction/oxidation or specialized formats. Here we present SpyMask, a modular approach to bispecifics using SpyTag/SpyCatcher spontaneous amidation. Two SpyTag-fused antigen-binding modules can be precisely conjugated onto DoubleCatcher, a tandem SpyCatcher where the second SpyCatcher is protease-activatable. We engineer a panel of structurally-distinct DoubleCatchers, from which binders project in different directions. We establish a generalized methodology for one-pot assembly and purification of bispecifics in 96-well plates. A panel of binders recognizing different HER2 epitopes were coupled to DoubleCatcher, revealing unexpected combinations with anti-proliferative or pro-proliferative activity on HER2-addicted cancer cells. Bispecific activity depended sensitively on both binder orientation and DoubleCatcher scaffold geometry. These findings support the need for straightforward assembly in different formats. SpyMask provides a scalable tool to discover synergy in bispecific activity, through modulating receptor organization and geometry.

An Engineered Mouse Model That Generates a Diverse Repertoire of Endogenous, High-Affinity Common Light Chain Antibodies

Bispecific antibodies have gained increasing popularity as therapeutics as they enable novel activities that cannot be achieved with monospecific antibodies. Some of the most popular bispecific formats are molecules in which two Fab arms with different antigen specificities are combined into one IgG-like molecule. One way to produce these bispecific molecules requires the discovery of antibodies against the two antigens of interest that share a common light chain. Here, we present the generation and characterization of a common light chain mouse model, in which the endogenous IGKJ cluster is replaced with a prearranged, modified murine IGKV10-96/IGKJ1 segment. We demonstrate that genetic modification does not impact B-cell development. Upon immunization with ovalbumin, the animals generate an antibody repertoire with VH gene segment usage of a similar diversity to wildtype mice, while the light chain diversity is restricted to antibodies derived from the prearranged IGKV10-96/IGKJ1 germline. We further show that the clonotype diversity of the common light chain immune repertoire matches the diversity of immune repertoire isolated from wildtype mice. Finally, the common light chain anti-ovalbumin antibodies have only slightly lower affinities than antibodies isolated from wildtype mice, demonstrating the suitability of these animals for antibody discovery for bispecific antibody generation.

Design and engineering of bispecific antibodies: insights and practical considerations

Bispecific antibodies (bsAbs) have attracted significant attention due to their dual binding activity, which permits simultaneous targeting of antigens and synergistic binding effects beyond what can be obtained even with combinations of conventional monospecific antibodies. Despite the tremendous therapeutic potential, the design and construction of bsAbs are often hampered by practical issues arising from the increased structural complexity as compared to conventional monospecific antibodies. The issues are diverse in nature, spanning from decreased biophysical stability from fusion of exogenous antigen-binding domains to antibody chain mispairing leading to formation of antibody-related impurities that are very difficult to remove. The added complexity requires judicious design considerations as well as extensive molecular engineering to ensure formation of high quality bsAbs with the intended mode of action and favorable drug-like qualities. In this review, we highlight and summarize some of the key considerations in design of bsAbs as well as state-of-the-art engineering principles that can be applied in efficient construction of bsAbs with diverse molecular formats.

i-shaped antibody engineering enables conformational tuning of biotherapeutic receptor agonists

The ability to leverage antibodies to agonize disease relevant biological pathways has tremendous potential for clinical investigation. Yet while antibodies have been successful as antagonists, immune mediators, and targeting agents, they are not readily effective at recapitulating the biology of natural ligands. Among the important determinants of antibody agonist activity is the geometry of target receptor engagement. Here, we describe an engineering approach inspired by a naturally occurring Fab-Fab homotypic interaction that constrains IgG in a unique i-shaped conformation. i-shaped antibody (iAb) engineering enables potent intrinsic agonism of five tumor necrosis factor receptor superfamily (TNFRSF) targets. When applied to bispecific antibodies against the heterodimeric IL-2 receptor pair, constrained bispecific IgG formats recapitulate IL-2 agonist activity. iAb engineering provides a tool to tune agonist antibody function and this work provides a framework for the development of intrinsic antibody agonists with the potential for generalization across broad receptor classes.

Exploring the biomarkers and potential therapeutic drugs for sepsis via integrated bioinformatic analysis

BACKGROUND

Sepsis is a life-threatening condition caused by an excessive inflammatory response to an infection, associated with high mortality. However, the regulatory mechanism of sepsis remains unclear.

RESULTS

In this study, bioinformatics analysis revealed the novel key biomarkers associated with sepsis and potential regulators. Three public datasets (GSE28750, GSE57065 and GSE95233) were employed to recognize the differentially expressed genes (DEGs). Taking the intersection of DEGs from these three datasets, GO and KEGG pathway enrichment analysis revealed 537 shared DEGs and their biological functions and pathways. These genes were mainly enriched in T cell activation, differentiation, lymphocyte differentiation, mononuclear cell differentiation, and regulation of T cell activation based on GO analysis. Further, pathway enrichment analysis revealed that these DEGs were significantly enriched in Th1, Th2 and Th17 cell differentiation. Additionally, five hub immune-related genes (CD3E, HLA-DRA, IL2RB, ITK and LAT) were identified from the protein-protein interaction network, and sepsis patients with higher expression of hub genes had a better prognosis. Besides, 14 drugs targeting these five hub related genes were revealed on the basis of the DrugBank database, which proved advantageous for treating immune-related diseases.

CONCLUSIONS

These results strengthen the new understanding of sepsis development and provide a fresh perspective into discriminating the candidate biomarkers for predicting sepsis as well as identifying new drugs for treating sepsis.

A novel conditional active biologic anti-EpCAM x anti-CD3 bispecific antibody with synergistic tumor selectivity for cancer immunotherapy

Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein that plays several roles in cancer biology. EpCAM is an attractive therapeutic target because of its expression in most solid tumors. However, targeting EpCAM has been challenging because it is also highly expressed in normal epithelial tissues. Initial attempts to develop EpCAM-specific T-cell engagers were unsuccessful due to severe cytokine release effects, as well as serious on-target, off-tumor drug-related toxicities. We developed novel, conditionally active biological (CAB) bispecific antibodies that bind to both EpCAM and CD3 in an acidic tumor microenvironment. In healthy tissues, binding to EpCAM and CD3 is greatly reduced by a novel, dual CAB selection, where each binding domain is independently blocked by the presence of physiological chemicals known as Protein-associated Chemical Switches (PaCS). The CAB anti-EpCAM T-cell engagers displayed the anticipated bispecific binding properties and mediated the potent lysis of EpCAM-positive cancer cell lines through the recruitment of T cells in the tumor microenvironment. Xenograft studies showed that the efficacy of CAB bispecific antibodies is similar to that of a non-CAB anti-EpCAM bispecific antibody, but they have markedly reduced toxicity in non-human primates, indicating an unprecedentedly widened therapeutic index of over 100-fold. These preclinical results indicate that the dual CAB bispecific antibody is potentially both a powerful and safe therapeutic platform and a promising T cell-engaging treatment for patients with EpCAM-expressing tumors.

Nonclinical immunogenicity risk assessment for knobs-into-holes bispecific IgG1 antibodies

Bispecific antibodies, including bispecific IgG, are emerging as an important new class of antibody therapeutics. As a result, we, as well as others, have developed engineering strategies designed to facilitate the efficient production of bispecific IgG for clinical development. For example, we have extensively used knobs-into-holes (KIH) mutations to facilitate the heterodimerization of antibody heavy chains and more recently Fab mutations to promote cognate heavy/light chain pairing for efficient in vivo assembly of bispecific IgG in single host cells. A panel of related monospecific and bispecific IgG1 antibodies was constructed and assessed for immunogenicity risk by comparison with benchmark antibodies with known low (Avastin and Herceptin) or high (bococizumab and ATR-107) clinical incidence of anti-drug antibodies. Assay methods used include dendritic cell internalization, T cell proliferation, and T cell epitope identification by in silico prediction and MHC-associated peptide proteomics. Data from each method were considered independently and then together for an overall integrated immunogenicity risk assessment. In toto, these data suggest that the KIH mutations and in vitro assembly of half antibodies do not represent a major risk for immunogenicity of bispecific IgG1, nor do the Fab mutations used for efficient in vivo assembly of bispecifics in single host cells. Comparable or slightly higher immunogenicity risk assessment data were obtained for research-grade preparations of trastuzumab and bevacizumab versus Herceptin and Avastin, respectively. These data provide experimental support for the common practice of using research-grade preparations of IgG1 as surrogates for immunogenicity risk assessment of their corresponding pharmaceutical counterparts.

Facilitating high throughput bispecific antibody production and potential applications within biopharmaceutical discovery workflows

A major driver for the recent investment surge in bispecific antibody (bsAb) platforms and products is the multitude of distinct mechanisms of action that bsAbs offer compared to a combination of two monoclonal antibodies. Four bsAb products were granted first regulatory approvals in the US or EU during 2023 and the biopharmaceutical industry pipeline is brimming with bsAb candidates across a broad range of therapeutic applications. In previously reported bsAb discovery campaigns, following a hypothesis-based choice of two specific target proteins, selections and screening activities have often been performed in mono-specific formats. The conversion to bispecific modalities has usually been positioned toward the end of the discovery process and has involved small numbers of lead molecules, largely due to challenges in expressing, purifying, and analyzing large numbers of bsAbs. In this review, we discuss emerging strategies to facilitate the production of expanded bsAb panels, focusing particularly upon combinatorial methods to generate bsAb matrices. Such technologies will enable screening in. bispecific formats at earlier stages of discovery campaigns, not only widening the accessible protein space to maximize chances of success, but also advancing empirical bi-target validation activities to assess initial target selection hypotheses.

Revolutionizing cancer immunotherapy: unleashing the potential of bispecific antibodies for targeted treatment

Recent progressions in immunotherapy have transformed cancer treatment, providing a promising strategy that activates the immune system of the patient to find and eliminate cancerous cells. Bispecific antibodies, which engage two separate antigens or one antigen with two distinct epitopes, are of tremendous concern in immunotherapy. The bi-targeting idea enabled by bispecific antibodies (BsAbs) is especially attractive from a medical standpoint since most diseases are complex, involving several receptors, ligands, and signaling pathways. Several research look into the processes in which BsAbs identify different cancer targets such angiogenesis, reproduction, metastasis, and immune regulation. By rerouting cells or altering other pathways, the bispecific proteins perform effector activities in addition to those of natural antibodies. This opens up a wide range of clinical applications and helps patients with resistant tumors respond better to medication. Yet, further study is necessary to identify the best conditions where to use these medications for treating tumor, their appropriate combination partners, and methods to reduce toxicity. In this review, we provide insights into the BsAb format classification based on their composition and symmetry, as well as the delivery mode, focus on the action mechanism of the molecule, and discuss the challenges and future perspectives in BsAb development.

High-Throughput Analyses of Therapeutic Antibodies Using High-Field Asymmetric Waveform Ion Mobility Spectrometry Combined with SampleStream and Intact Protein Mass Spectrometry

Intact protein mass spectrometry (MS) coupled with liquid chromatography was applied to characterize the pharmacokinetics and stability profiles of therapeutic proteins. However, limitations from chromatography, including throughput and carryover, result in challenges with handling large sample numbers. Here, we combined intact protein MS with multiple front-end separations, including affinity capture, SampleStream, and high-field asymmetric waveform ion mobility spectrometry (FAIMS), to perform high-throughput and specific mass measurements of a multivalent antibody with one antigen-binding fragment (Fab) fused to an immunoglobulin G1 (IgG1) antibody. Generic affinity capture ensures the retention of both intact species 1Fab-IgG1 and the tentative degradation product IgG1. Subsequently, the analytes were directly loaded into SampleStream, where each injection occurs within ∼30 s. By separating ions prior to MS detection, FAIMS further offered improvement in signal-overnoise by ∼30% for denatured protein MS via employing compensation voltages that were optimized for different antibody species. When enhanced FAIMS transmission of 1Fab-IgG1 was employed, a qualified assay was established for spiked-in serum samples between 0.1 and 25 μg/mL, resulting in ∼10% accuracy bias and precision coefficient of variation. Selective FAIMS transmission of IgG1 as the degradation surrogate product enabled more sensitive detection of clipped species for intact 1Fab-IgG1 at 5 μg/mL in serum, generating an assay to measure 1Fab-IgG1 truncation between 2.5 and 50% with accuracy and precision below 20% bias and coefficient of variation. Our results revealed that the SampleStream-FAIMS-MS platform affords high throughput, selectivity, and sensitivity for characterizing therapeutic antibodies from complex biomatrices qualitatively and quantitatively.

State-of-the-Art Approaches to Heterologous Expression of Bispecific Antibodies Targeting Solid Tumors

Bispecific antibodies (bsAbs) are some of the most promising biotherapeutics due to the versatility provided by their structure and functional features. bsAbs simultaneously bind two antigens or two epitopes on the same antigen. Moreover, they are capable of directing immune effector cells to cancer cells and delivering various compounds (radionuclides, toxins, and immunologic agents) to the target cells, thus offering a broad spectrum of clinical applications. Current review is focused on the technologies used in bsAb engineering, current progress and prospects of these antibodies, and selection of various heterologous expression systems for bsAb production. We also discuss the platforms development of bsAbs for the therapy of solid tumors.

Natural Killer Cell Engagers (NKCEs): a new frontier in cancer immunotherapy

Natural Killer (NK) cells are a type of innate lymphoid cells that play a crucial role in immunity by killing virally infected or tumor cells and secreting cytokines and chemokines. NK cell-mediated immunotherapy has emerged as a promising approach for cancer treatment due to its safety and effectiveness. NK cell engagers (NKCEs), such as BiKE (bispecific killer cell engager) or TriKE (trispecific killer cell engager), are a novel class of antibody-based therapeutics that exhibit several advantages over other cancer immunotherapies harnessing NK cells. By bridging NK and tumor cells, NKCEs activate NK cells and lead to tumor cell lysis. A growing number of NKCEs are currently undergoing development, with some already in clinical trials. However, there is a need for more comprehensive studies to determine how the molecular design of NKCEs affects their functionality and manufacturability, which are crucial for their development as off-the-shelf drugs for cancer treatment. In this review, we summarize current knowledge on NKCE development and discuss critical factors required for the production of effective NKCEs.

Mini-PBPK-Based Population Model and Covariate Analysis to Assess the Complex Pharmacokinetics and Pharmacodynamics of RO7449135, an Anti-KLK5/KLK7 Bispecific Antibody in Cynomolgus Monkeys

RO7449135, an anti-kallikrein (KLK)5/KLK7 bispecific antibody, is in development as a potential therapy against Netherton's syndrome (NS). In cynomolgus monkey studies, RO7449135 bound to KLK5 and KLK7, causing considerable accumulation of total KLKs, but with non-dose-proportional increase. To understand the complex PKPD, a population model with covariate analysis was developed accounting for target binding in skin and migration of bound targets from skin to blood. The covariate analysis suggested the animal batch as the categorical covariate impacting the different KLK5 synthesis rates between the repeat-dose study and single-dose study, and the dose as continuous covariate impacting the internalization rate of the binary and ternary complexes containing KLK7. To comprehend the mechanism underlying, we hypothesized that inhibition of KLK5 by RO7449135 prevented its cleavage of the pro-enzyme of KLK7 (pro-KLK7) and altered the proportion between pro-KLK7 and KLK7. Besides the pro-KLK7, RO7449135 can interact with other proteins like LEKTI through KLK7 connection in a dose-dependent manner. The different high-order complexes formed by RO7449135 interacting with pro-KLK7 or LEKTI-like proteins can be subject to faster internalization rate. Accounting for the dose and animal batch as covariates, the model-predicted free target suppression is well aligned with the visual target engagement check. The population PKPD model with covariate analysis provides the scientific input for the complex PKPD analysis, successfully predicts the target suppression in cynomolgus monkeys, and thereby can be used for the human dose projection of RO7449135.

Efficient production of bispecific antibody by FAST-IgTM and its application to NXT007 for the treatment of hemophilia A

Efficient production of bispecific antibodies (BsAbs) in single mammalian cells is essential for basic research and industrial manufacturing. However, preventing unwanted pairing of heavy chains (HCs) and light chains (LCs) is a challenging task. To address this, we created an engineering technology for preferential cognate HC/LC and HC/HC paring called FAST-Ig (Four-chain Assembly by electrostatic Steering Technology - Immunoglobulin), and applied it to NXT007, a BsAb for the treatment of hemophilia A. We introduced charged amino-acid substitutions at the HC/LC interface to facilitate the proper assembly for manufacturing a standard IgG-type BsAb. We generated CH1/CL interface-engineered antibody variants that achieved > 95% correct HC/LC pairing efficiency with favorable pharmacological properties and developability. Among these, we selected a design (C3) that allowed us to separate the mis-paired species with an unintended pharmacological profile using ion-exchange chromatography. Crystal structure analysis demonstrated that the C3 design did not affect the overall structure of both Fabs. To determine the final design for HCs-heterodimerization, we compared the stability of charge-based and knobs into hole-based Fc formats in acidic conditions and selected the more stable charge-based format. FAST-Ig was also applicable to stable CHO cell lines for industrial production and demonstrated robust chain pairing with different subclasses of parent BsAbs. Thus, it can be applied to a wide variety of BsAbs both preclinically and clinically.

Targeted Treatment of Relapsed or Refractory Follicular Lymphoma: Focus on the Therapeutic Potential of Mosunetuzumab

Follicular lymphoma is the most common indolent non-Hodgkin's lymphoma, and because of the incurable nature of this disorder, new therapies are constantly needed. The recently approved T-cell-dependent bispecific antibody mosunetuzumab showed promising results and manageable toxicities for patients with relapsed or refractory follicular lymphoma. Namely, as opposed to cellular immunotherapy options, this agent has the potential of being effective in patients with unfavorable features with a tolerable rate and severity of cytokine release syndrome, immune effector cell-associated neurotoxicity, and infectious complications. Given the recent withdrawal from the market of PI3K inhibitors and the practical challenges in utilizing with chimeric antigen receptor T-cells (CAR-T) for some patients, mosunetuzumab represents a "breath of fresh air" for both patients and hemato-oncologists. More data are required to better define the real potential of this molecule, either alone or in combination with other agents, including antibody drug conjugates, immunomodulators, and checkpoint inhibitors. Future studies will also shed light on the efficacy of mosunetuzumab compared with CAR-T, in well-designed registries or ideally in randomized controlled trials.

Preclinical development of ZED8, an 89Zr immuno-PET reagent for monitoring tumor CD8 status in patients undergoing cancer immunotherapy

BACKGROUND

ZED8 is a novel monovalent antibody labeled with zirconium-89 for the molecular imaging of CD8. This work describes nonclinical studies performed in part to provide rationale for and to inform expectations in the early clinical development of ZED8, such as in the studies outlined in clinical trial registry NCT04029181 [1].

METHODS

Surface plasmon resonance, X-ray crystallography, and flow cytometry were used to characterize the ZED8-CD8 binding interaction, its specificity, and its impact on T cell function. Immuno-PET with ZED8 was assessed in huCD8⁺ tumor-bearing mice and in non-human primates. Plasma antibody levels were measured by ELISA to determine pharmacokinetic parameters, and OLINDA 1.0 was used to estimate radiation dosimetry from image-derived biodistribution data.

RESULTS

ZED8 selectively binds to human CD8α at a binding site approximately 9 Å from that of MHCI making mutual interference unlikely. The equilibrium dissociation constant (K_D) is 5 nM. ZED8 binds to cynomolgus CD8 with reduced affinity (66 nM) but it has no measurable affinity for rat or mouse CD8. In a series of lymphoma xenografts, ZED8 imaging was able to identify different CD8 levels concordant with flow cytometry. In cynomolgus monkeys with tool compound ⁸⁹Zr-aCD8v17, lymph nodes were conspicuous by imaging 24 h post-injection, and the pharmacokinetics suggested a flat-fixed first-in-human dose of 4 mg per subject. The whole-body effective dose for an adult human was estimated to be 0.48 mSv/MBq, comparable to existing ⁸⁹Zr immuno-PET reagents.

CONCLUSION

⁸⁹Zr immuno-PET with ZED8 appears to be a promising biomarker of tissue CD8 levels suitable for clinical evaluation in cancer patients eligible for immunotherapy.

Current landscape and future directions of bispecific antibodies in cancer immunotherapy

Recent advances in cancer immunotherapy using monoclonal antibodies have dramatically revolutionized the therapeutic strategy against advanced malignancies, inspiring the exploration of various types of therapeutic antibodies. Bispecific antibodies (BsAbs) are recombinant molecules containing two different antigens or epitopes identifying binding domains. Bispecific antibody-based tumor immunotherapy has gained broad potential in preclinical and clinical investigations in a variety of tumor types following regulatory approval of newly developed technologies involving bispecific and multispecific antibodies. Meanwhile, a series of challenges such as antibody immunogenicity, tumor heterogeneity, low response rate, treatment resistance, and systemic adverse effects hinder the application of BsAbs. In this review, we provide insights into the various architecture of BsAbs, focus on BsAbs' alternative different mechanisms of action and clinical progression, and discuss relevant approaches to overcome existing challenges in BsAbs clinical application.

A novel IgG fc by computer-aided design enhances heavy-chain heterodimerization in bi- or tri-specific antibodies

Background

The classical “Knob-into-holes” (KIH) strategy (knob(T366Y)/hole (Y407T)) has successfully enhanced the heterodimerization of a bispecific antibody (BsAb) resulting in heterodimer formation up to 92% of protein A (ProA)-purified protein pool. However, it does not show high efficiency for every BsAb.

Methods

KIH was initially applied to a CD20/CD3 BsAb. After in-silico modeling, two additional new mutations, S354Y in knob-heavy chain (HC) and Q347E in hole-HC, together with KIH named “ETYY”, were introduced in the Fc. Functional and physicochemical assays were performed to assess the BsAb.

Results

The CD20/CD3 BsAb hybrid only represented ~ 50% of the ProA-purified protein pool when KIH was applied. With ETYY, the percentage of CD20/CD3 hybrid increased to 93.8% in the ProA-purified protein pool and facilitated the second purification via ion-exchange chromatography. S354Y in the knob-HC introduced a hydrophobic interaction with Y349 on the hole-HC, and Q347E on the hole-HC introduced an ionic interaction with K360 on the knob-HC. CD20/CD3-v4b (containing ETYY) retains the original activity of the BsAb at both Fab and Fc regions. Its melting temperature is > 65 °C and aggregation temperatures (Tagg)266 and Tagg473 are both > 70 °C, indicating high thermostability. The dynamic light scattering (DLS) assay shows only one peak with the size of an IgG molecule with PDI of 0.121, indicating low aggregation potential of the BsAb.

Conclusions

This computer-aided novel ETYY design of BsAb Fc facilitates enhanced heterodimerization while retaining functional and physicochemical properties. This has the potential to improve the development of next-generation BsAbs with higher yields and simpler purification.

The mosaic puzzle of the therapeutic monoclonal antibodies and antibody fragments - A modular transition from full-length immunoglobulins to antibody mimetics

The use of monoclonal antibodies represents an important and efficient diagnostic and therapeutic tool in disease management and modern science but remains limited by several factors including the uneven distribution in diseased tissues as well as undesired activation of side immune reactions. Major scientific advancements including Recombinant DNA Technology, Hybridoma Technology, and Polymerase Chain Reaction have considerably impacted the use of monoclonal antibodies providing technical and effective solutions to overcome the shortcomings encountered with conventional antibodies. Initially, the introduction of antibody fragments allowed a more uniform and deeper penetration of the targeted tissue and reduced unwanted activation of Fc-mediated immune reactions. On another level, the immunogenicity of murine-derived antibodies was overcome by humanizing their encoding genes with specific sequences of human origin andtransgenic mice able to synthesize fully human antibodies were successfully created. Moreover, the advancement of genetic engineering techniques supported by the modular structure of antibody coding genes paved the way for the development of a new generation of antibody fragments with a wide spectrum of monospecific and bispecific agents. These later could be monovalent, bivalent, or multivalent, and either expressed as a single chain, assembled in multimeric forms or stringed in tandem. This has conferred improved affinity, stability, and solubility to antibody targetting. Lately, a new array of monoclonal antibody fragments was introduced with the engineering of nanobody and antibody mimetics as non-immunoglobulin-derived fragments with promising diagnostic and therapeutic applications. In this review, we decipher the molecular basis of monoclonal antibody engineering with a detailed screening of the antibody derivatives that provides new perspectives to expand the use of monoclonal fragments into previously unexplored fields.

Assessing four subdomain-specific affinity resins' capability to separate half-antibody from intact bispecific antibody

Half-antibody is a frequent byproduct associated with the recombinant production of many asymmetric bispecific antibodies (bsAbs). Although this byproduct can be largely removed by post-capture polishing steps, it is ideal to have it partially cleared at the capture step to achieve a more robust downstream process. Previously we showed that Protein A affinity chromatography possesses the capability to separate half-antibody. In this study, we assessed the half-antibody separation capability of four less commonly used subdomain-specific affinity resins. The data suggest that these resins exhibit different capabilities for separating half-antibody from the corresponding bsAb. In specific, whereas Protein A affinity resin can always provide partial separation under typical conditions, the separation efficiency of three subdomain-specific affinity resins (i.e., Capto L, CaptureSelect CH1-XL and CaptureSelect FcXP) heavily relies on the property of the two parental monospecific antibodies from which the bsAb is derived, which may range from complete separation to no separation at all. This novel information provides more options for half-antibody clearance at the capture step.

Monitoring multiple quality attributes of a complex Fc-fusion protein during cell culture production processes by mD-LC-MS peptide mapping

Fc-fusion proteins represent a successful class of biopharmaceutical products. They are considered highly heterogeneous products due to the common degradation of amino acids that occurs during their production in upstream and downstream processes (e.g., oxidation and deamidation) and, above all, their complex glycosylation profile. Multi-dimensional liquid chromatography-mass spectrometry (mD-LC-MS) has recently gained much interest for process analytical technology, enabling the integration of this analytical technology in production and purification environments. In this study, an online mD-LC-MS/MS peptide mapping method was developed for monitoring multiple quality attributes, including the N-glycosylation state of a complex Fc-fusion protein, which is made by combining two heavily glycosylated cytokines with an Fc domain. This fully automated workflow includes sample purification, reduction, digestion, peptide mapping, and subsequent mass spectrometric analysis. Two immobilized enzyme cartridges based on trypsin and Lys-C protease were employed to generate a detailed glycosylation mapping, as trypsin allowed the identification of only one of four glycosylation sites, while Lys-C was more informative for two other sites. Site-specific glycosylation information such as antennarity, sialyation, and core fucosylation state was also determined. In addition to glycans, other post-translational modifications could be monitored simultaneously during the cell culture production processes by the mD-LC-MS/MS approach. In summary, the generated data demonstrate the applicability of mD-LC-MS for the monitoring and trending of multiple attributes for complex antibody formats over production processes in an automated and fast manner, compared to the complex and time-consuming traditional offline assays.

Nonclinical Pharmacokinetics and Pharmacodynamics Characterization of Anti-CD79b/CD3 T Cell-Dependent Bispecific Antibody Using a Surrogate Molecule: A Potential Therapeutic Agent for B Cell Malignancies

The T cell-dependent bispecific (TDB) antibody, anti-CD79b/CD3, targets CD79b and CD3 cell-surface receptors expressed on B cells and T cells, respectively. Since the anti-CD79b arm of this TDB binds only to human CD79b, a surrogate TDB that binds to cynomolgus monkey CD79b (cyCD79b) was used for preclinical characterization. To evaluate the impact of CD3 binding affinity on the TDB pharmacokinetics (PK), we utilized non-tumor-targeting bispecific anti-gD/CD3 antibodies composed of a low/high CD3 affinity arm along with a monospecific anti-gD arm as controls in monkeys and mice. An integrated PKPD model was developed to characterize PK and pharmacodynamics (PD). This study revealed the impact of CD3 binding affinity on anti-cyCD79b/CD3 PK. The surrogate anti-cyCD79b/CD3 TDB was highly effective in killing CD79b-expressing B cells and exhibited nonlinear PK in monkeys, consistent with target-mediated clearance. A dose-dependent decrease in B cell counts in peripheral blood was observed, as expected. Modeling indicated that anti-cyCD79b/CD3 TDB’s rapid and target-mediated clearance may be attributed to faster internalization of CD79b, in addition to enhanced CD3 binding. The model yielded unbiased and precise curve fits. These findings highlight the complex interaction between TDBs and their targets and may be applicable to the development of other biotherapeutics.

Design of a Novel Fab-Like Antibody Fragment with Enhanced Stability and Affinity for Clinical use

With increasing interest in applying recombinant monoclonal antibodies (mAbs) in human medicine, engineered mAb fragments with reduced size and improved stability are in demand to overcome current limitations in clinical use. Herein, a novel Fab-like antibody fragment generated via an in silico-based engineering approach where the CH1 and CL domains of Fab are replaced by the IgG1 CH3 domains is described. This construct, designated as FabCH3, maintains the natural N-terminus and C-terminus of IgG antibody, can be expressed at a high level in bacterial cells and, importantly, exhibits much higher stability and affinity than the parental Fab when tested in a mesothelin-specific Fab m912, as well as a vascular endothelial growth factor A (VEGFA)-specific Fab Ranibizumab (in vivo). The high-resolution crystal structures of m912 FabCH3 and m912 Fab are determined, and the comparative analysis reveals more rigid structures in both constant domains and complementarity-determining regions of FabCH3, explaining its enhanced stability and affinity. Overall, the stabilized FabCH3 described in this report provides a versatile platform for engineering Fab-like antibody fragments with higher stability and antigen-binding affinity that can be used as a distinct class of antibody therapeutics.

Development of T-cell engagers selective for cells co-expressing two antigens

T cell-engaging bispecific antibodies (TCEs) are clinically effective treatments for hematological cancers. While the utility of TCEs in solid malignancies is being explored, toxicities arising from antigen expression on normal tissues have slowed or halted several clinical trials. Here, we describe the development of TCEs that preferentially drive T cell-mediated death against target cells co-expressing two tumor-associated antigens. We show that Ly6E and B7-H4 are simultaneously expressed on approximately 50% of breast cancers, whereas normal tissue expression is limited and mostly orthogonal. Traditional bispecific TCEs targeting a singular antigen, either Ly6E or B7-H4, are active when paired with high-affinity CD3-engagers, but normal tissue expression presents a toxicity risk. Treatment with a murine cross-reactive B7-H4-TCE results in rapid and severe weight loss in mice along with damage to B7-H4-expressing tissues. To overcome on-target toxicity, we designed trispecific antibodies co-targeting Ly6E, B7-H4, and CD3 and characterized the impact of dual-antigen binding and the relative placement of each binding domain on tumor killing in vitro and in vivo. In vitro killing of tumor cells co-expressing both antigens correlates to the placement of the higher affinity B7-H4 binding domain, with only modest enhancements seen upon addition of Ly6E binding. In xenograft models, avid binding of appropriately designed trispecific TCEs enables tumor growth inhibition while evading the poor tolerability seen with active bispecific TCEs. Collectively these data highlight the potential for dual-antigen targeting to improve safety and efficacy, and expand the scope of tumors that may effectively be treated by TCEs.

Abbreviations: Chimeric antigen receptor T cells (CAR-Ts), dual-antigen targeted T cell engagers (DAT-TCE), Fragment antigen-binding (Fab), Hematoxylin and eosin (H&E), Institutional Animal Care and Use Committee (IACUC), Immunoglobulin G (IgG), immunohistochemistry (IHC), NOD SCID gamma (NSG), peripheral blood mononuclear cells (PBMCs), surface plasmon resonance (SPR), T cell-engagers (TCEs)

Full-length recombinant antibodies from Escherichia coli: production, characterization, effector function (Fc) engineering, and clinical evaluation

Although several antibody fragments and antibody fragment-fusion proteins produced in Escherichia coli (E. coli) are approved as therapeutics for various human diseases, a full-length monoclonal or a bispecific antibody produced in E. coli has not yet been approved. The past decade witnessed substantial progress in expression of full-length antibodies in the E. coli cytoplasm and periplasm, as well as in cell-free expression systems. The equivalency of E. coli-produced aglycosylated antibodies and their mammalian cell-produced counterparts, with respect to biochemical and biophysical properties, including antigen binding, in vitro and in vivo serum stability, pharmacokinetics, and in vivo serum half-life, has been demonstrated. Extensive engineering of the Fc domain of aglycosylated antibodies enables recruitment of various effector functions, despite the lack of N-linked glycans. This review summarizes recent research, preclinical advancements, and clinical development of E. coli-produced aglycosylated therapeutic antibodies as monoclonal, bispecific, and antibody-drug conjugates for use in autoimmune, oncology, and immuno-oncology areas.Abbreviations: ADA Anti-drug antibody; ADCC Antibody-dependent cellular cytotoxicity; ADCP Antibody-dependent cellular phagocytosis; ADC Antibody-drug conjugate; aFc Aglycosylated Fc; AMD Age-related macular degeneration aTTP Acquired thrombotic thrombocytopenic purpura; BCMA B-cell maturation antigen; BLA Biologics license application; BsAb Bispecific antibody; C1q Complement protein C1q; CDC Complement-dependent cytotoxicity; CDCC Complement-dependent cellular cytotoxicity; CDCP Complement-dependent cellular phagocytosis; CEX Cation exchange chromatography; CFPS Cell-free protein expression; CHO Chinese Hamster Ovary; CH1-3 Constant heavy chain 1-3; CL Constant light chain; DLBCL Diffuse large B-cell lymphoma; DAR Drug antibody ratio; DC Dendritic cell; dsFv Disulfide-stabilized Fv; EU European Union; EGFR Epidermal growth factor receptor; E. coli Escherichia coli; EpCAM Epithelial cell adhesion molecule; Fab Fragment antigen binding; FACS Fluorescence activated cell sorting; Fc Fragment crystallizable; FcRn Neonatal Fc receptor; FcɣRs Fc gamma receptors; FDA Food and Drug Administration; FL-IgG Full-length immunoglobulin; Fv Fragment variable; FolRαa Folate receptor alpha; gFc Glycosylated Fc; GM-CSF Granulocyte macrophage-colony stimulating factor; GPx7 Human peroxidase 7; HCL Hairy cell leukemia; HIV Human immunodeficiency virusl; HER2 Human epidermal growth factor receptor 2; HGF Hepatocyte growth factor; HIC Hydrophobic interaction chromatography; HLA Human leukocyte antigen; IBs Inclusion bodies; IgG1-4 Immunoglobulin 1-4; IP Intraperitoneal; ITC Isothermal titration calorimetry; ITP Immune thrombocytopenia; IV Intravenous; kDa Kilodalton; KiH Knob-into-Hole; mAb Monoclonal antibody; MAC Membrane-attack complex; mCRC Metastatic colorectal cancer; MM Multipl myeloma; MOA Mechanism of action; MS Mass spectrometry; MUC1 Mucin 1; MG Myasthenia gravis; NB Nanobody; NK Natural killer; nsAA Nonstandard amino acid; NSCLC Non-small cell lung cancer; P. aeruginosa Pseudomonas aeruginosa; PD-1 Programmed cell death 1; PD-L1 Programmed cell death-ligand 1; PDI Protein disulfide isomerase; PECS Periplasmic expression cytometric screening; PK Pharmacokinetics; P. pastoris Pichia pastoris; PTM Post-translational modification; Rg Radius of gyration; RA Rheumatoid arthritis; RT-PCR Reverse transcription polymerase chain reaction; SAXS Small angle X-ray scattering; scF Single chain Fv; SCLC Small cell lung cancer; SDS-PAGE Sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SEC Size exclusion chromatography; SEED Strand-exchange engineered domain; sRNA Small regulatory RNA; SRP Signal recognition particle; T1/2 Half-life; Tagg Aggregation temperature; TCR T cell receptor; TDB T cell-dependent bispecific; TF Tissue factor; TIR Translation initiation region; Tm Melting temperature; TNBC Triple-negative breast cancer; TNF Tumor necrosis factor; TPO Thrombopoietin; VEGF Vascular endothelial growth factor; vH Variable heavy chain; vL Variable light chain; vWF von Willebrand factor; WT Wild type.

Kinetics study of the natural split Npu DnaE intein in the generation of bispecific IgG antibodies

Rapid and efficient bispecific antibody (BsAb) production for industrial applications is still facing many challenges. We reported a technology platform for generating bispecific IgG antibodies, "Bispecific Antibody by Protein Trans-splicing (BAPTS)." While the "BAPTS" method has shown potential in high-throughput screening of BsAbs, further understanding and optimizing the methodology is desirable. A large number of BsAbs were selected to illustrate the conversion efficiency and kinetics parameters. The temperature of reaction makes no significant influence in conversion efficiency, which can reach more than 70% within 2 h, and CD3 × HER2 BsAb can reach 90%. By fitting trans-splicing reaction to single-component exponential decay curves, the apparent first-order rate constants at a series of temperatures were determined. The rate constant ranges from 0.02 to 0.11 min^-1 at 37 °C, which is a high rate reported for the protein trans-splicing reaction (PTS). The reaction process is activated rapidly with activation energy of 8.9 kcal·mol^-1 (CD3 × HER2) and 5.2 kcal·mol^-1 (CD3 × EGFR). The BsAbs generated by "BAPTS" technology not only had the similar post-translation modifications to the parental antibodies, but also demonstrated excellent in vitro and in vivo bioactivity. The kinetics parameters and activation energy of the reaction illustrate feasible for high-throughput screening and industrial applications using the "BAPTS" approach. KEY POINTS: • The trans-splicing reaction of Npu DnaE intein in "BAPTS" platform is a rapid process with low reaction activation and high rate. • The BsAb generated by "BAPTS" remained effective in tumor cell killing. • The kinetics parameters and activation energy of the reaction illustrate feasible for high-throughput screening and industrial applications using the "BAPTS" approach.

Systematic workflow for studying domain contributions of bispecific antibodies to selectivity in multimodal chromatography

In this article, a systematic workflow was formulated and implemented to understand selectivity differences and preferred binding patches for bispecific monoclonal antibodies (mAbs) and their parental mAbs on three multimodal cation exchange resin systems. This workflow incorporates chromatographic screening of the parent mAbs and their fragments at various pH followed by surface property mapping and protein footprinting using covalent labeling followed by liquid chromatography-mass spectrometry analysis. The chromatography screens on multimodal resins with the intact mAbs indicated enhanced selectivity as compared to single-mode interaction systems. While the bispecific antibody (bsAb) eluted between the two parental mAbs on most of the resins, the retention of the bispecific transitioned from co-eluting with one parental mAb to the other parental mAb on Capto MMC. To investigate the contribution of different domains, mAb fragments were evaluated and the results indicated that the interactions were likely dominated by the Fab domain at higher pH. Protein surface property maps were then employed to hypothesize the potential preferred binding patches in the solvent-exposed regions of the parental Fabs. Finally, protein footprinting was carried out with the parental mAbs and the bsAb in the bound and unbound states at pH 7.5 to identify the preferred binding patches. Results with the intact mAb analysis supported the hypothesis that interactions with the resins were primarily driven by the residues in the Fab fragments and not the Fc. Furthermore, peptide mapping data indicated that the light chain may be playing a more important role in the higher binding of Parent A as compared with Parent B in these resin systems. Finally, results with the bsAb indicated that both halves of the molecule contributed to binding with the resins, albeit with subtle differences as compared to the parental mAbs. The workflow presented in this paper lays the foundation to systematically study the chromatographic selectivity of large multidomain molecules which can provide insights into improved biomanufacturability and expedited downstream bioprocess development.

A new approach to produce IgG4-like bispecific antibodies

While achieving rapid developments in recent years, bispecific antibodies are still difficult to design and manufacture, due to mispair of both heavy and light chains. Here we report a novel technology to make bispecific molecules. The knob-into-hole method was used to pair two distinct heavy chains as a heterodimer. IgG₄ S228P CH1-CL interface was then partially replaced by T-cell receptor α/β constant domain to increase the efficiency of cognate heavy and light chain pairing. Following expression and purification, the bispecific antibody interface exchange was confirmed by Western blotting and LC–MS/MS. To ensure its validity, we combined a monovalent bispecific antibody against PD-1 (sequence from Pembrolizumab) and LAG3 (sequence from Relatlimab). The results showed that the molecule could be assembled correctly at a ratio of 95% in cells. In vitro functional assay demonstrated that the purified bispecific antibody exhibits an enhanced agonist activity compared to that of the parental antibodies. Low immunogenicity was predicted by an open-access software and ADA test.

An end-to-end automated platform process for high-throughput engineering of next-generation multi-specific antibody therapeutics

Next-generation multi-specific antibody therapeutics (MSATs) are engineered to combine several functional activities into one molecule to provide higher efficacy compared to conventional, mono-specific antibody therapeutics. However, highly engineered MSATs frequently display poor yields and less favorable drug-like properties (DLPs), which can adversely affect their development. Systematic screening of a large panel of MSAT variants in very high throughput (HT) is thus critical to identify potent molecule candidates with good yield and DLPs early in the discovery process. Here we report on the establishment of a novel, format-agnostic platform process for the fast generation and multiparametric screening of tens of thousands of MSAT variants. To this end, we have introduced full automation across the entire value chain for MSAT engineering. Specifically, we have automated the in-silico design of very large MSAT panels such that it reflects precisely the wet-lab processes for MSAT DNA library generation. This includes mass saturation mutagenesis or bulk modular cloning technologies while, concomitantly, enabling library deconvolution approaches using HT Sanger DNA sequencing. These DNA workflows are tightly linked to fully automated downstream processes for compartmentalized mammalian cell transfection expression, and screening of multiple parameters. All sub-processes are seamlessly integrated with tailored workflow supporting bioinformatics. As described here, we used this platform to perform multifactor optimization of a next-generation bispecific, cross-over dual variable domain-Ig (CODV-Ig). Screening of more than 25,000 individual protein variants in mono- and bispecific format led to the identification of CODV-Ig variants with over 1,000-fold increased potency and significantly optimized production titers, demonstrating the power and versatility of the platform.

An integrated approach for characterizing immunogenic responses toward a bispecific antibody

Bispecific antibodies (bsAbs) recognize and bind two different targets or two epitopes of the same antigen, making them an attractive diagnostic and treatment modality. Compared to the production of conventional bivalent monospecific antibodies, bsAbs require greater engineering and manufacturing. Therefore, bsAbs are more likely to differ from endogenous immunoglobulins and contain new epitopes that can increase immunogenic risk. Anti-A/B is a bsAb designed using a ‘knobs-into-holes’ (KIH) format. Anti-A/B exhibited an unexpectedly high immunogenicity in both preclinical and clinical studies, resulting in early termination of clinical development. Here, we used an integrated approach that combined in silico analysis, in vitro assays, and an in vivo study in non-human primates to characterize anti-A/B immunogenicity. Our findings indicated that the immunogenicity is associated with epitopes in the anti-B arm and not with mutations engineered through the KIH process. Our results showed the value of this integrated approach for performing immunogenicity risk assessment during clinical candidate selection to effectively mitigate risks during bsAb development.

Principles and Current Clinical Landscape of Multispecific Antibodies against Cancer

Building upon the resounding therapeutic success of monoclonal antibodies, and supported by accelerating progress in engineering methods, the field of multispecific therapeutic antibodies is growing rapidly. Over 140 different molecules are currently in clinical testing, with excellent results in recent phase 1-3 clinical trials for several of them. Multivalent bispecific IgG-modified formats predominate today, with a clear tendency for more target antigens and further increased valency in newer constructs. The strategies to augment anticancer efficacy are currently equally divided between disruption of multiple surface antigens, and additional redirection of cytotoxic T or NK lymphocytes against the tumor. Both effects complement other modern modalities, such as tyrosine kinase inhibitors and adoptive cell therapies, with which multispecifics are increasingly applied in combination or merged, for example, in the form of antibody producing CAR-T cells and oncolytics. While mainly focused on B-cell malignancies early on, the contemporary multispecific antibody sector accommodates twice as many trials against solid compared to hematologic cancers. An exciting emerging prospect is the targeting of intracellular neoantigens using T-cell receptor (TCR) fusion proteins or TCR-mimic antibody fragments. Considering the fact that introduction of PD-(L)1 inhibitors only a few years ago has already facilitated 5-year survival rates of 30-50% for per se highly lethal neoplasms, such as metastatic melanoma and non-small-cell lung carcinoma, the upcoming enforcement of current treatments with "next-generation" immunotherapeutics, offers a justified hope for the cure of some advanced cancers in the near future.

Bispecific T cell engagers: an emerging therapy for management of hematologic malignancies

Harnessing the power of immune cells, especially T cells, to enhance anti-tumor activities has become a promising strategy in clinical management of hematologic malignancies. The emerging bispecific antibodies (BsAbs), which recruit T cells to tumor cells, exemplified by bispecific T cell engagers (BiTEs), have facilitated the development of tumor immunotherapy. Here we discussed the advances and challenges in BiTE therapy developed for the treatment of hematologic malignancies. Blinatumomab, the first BiTE approved for the treatment of acute lymphocytic leukemia (ALL), is appreciated for its high efficacy and safety. Recent studies have focused on improving the efficacy of BiTEs by optimizing treatment regimens and refining the molecular structures of BiTEs. A considerable number of bispecific T cell-recruiting antibodies which are potentially effective in hematologic malignancies have been derived from BiTEs. The elucidation of mechanisms of BiTE action and neonatal techniques used for the construction of BsAbs can improve the treatment of hematological malignancies. This review summarized the features of bispecific T cell-recruiting antibodies for the treatment of hematologic malignancies with special focus on preclinical experiments and clinical studies.

Dissecting the molecular basis of high viscosity of monospecific and bispecific IgG antibodies

Some antibodies exhibit elevated viscosity at high concentrations, making them poorly suited for therapeutic applications requiring administration by injection such as subcutaneous or ocular delivery. Here we studied an anti-IL-13/IL-17 bispecific IgG₄ antibody, which has anomalously high viscosity compared to its parent monospecific antibodies. The viscosity of the bispecific IgG₄ in solution was decreased by only ~30% in the presence of NaCl, suggesting electrostatic interactions are insufficient to fully explain the drivers of viscosity. Intriguingly, addition of arginine-HCl reduced the viscosity of the bispecific IgG₄ by ~50% to its parent IgG level. These data suggest that beyond electrostatics, additional types of interactions such as cation-π and/or π-π may contribute to high viscosity more significantly than previously understood. Molecular dynamics simulations of antibody fragments in the mixed solution of free arginine and explicit water were conducted to identify hotspots involved in self-interactions. Exposed surface aromatic amino acids displayed an increased number of contacts with arginine. Mutagenesis of the majority of aromatic residues pinpointed by molecular dynamics simulations effectively decreased the solution's viscosity when tested experimentally. This mutational method to reduce the viscosity of a bispecific antibody was extended to a monospecific anti-GCGR IgG₁ antibody with elevated viscosity. In all cases, point mutants were readily identified that both reduced viscosity and retained antigen-binding affinity. These studies demonstrate a new approach to mitigate high viscosity of some antibodies by mutagenesis of surface-exposed aromatic residues on complementarity-determining regions that may facilitate some clinical applications.

Ten years in the making: application of CrossMab technology for the development of therapeutic bispecific antibodies and antibody fusion proteins

Bispecific antibodies have recently attracted intense interest. CrossMab technology was described in 2011 as novel approach enabling correct antibody light-chain association with their respective heavy chain in bispecific antibodies, together with methods enabling correct heavy-chain association using existing pairs of antibodies. Since the original description, CrossMab technology has evolved in the past decade into one of the most mature, versatile, and broadly applied technologies in the field, and nearly 20 bispecific antibodies based on CrossMab technology developed by Roche and others have entered clinical trials. The most advanced of these are the Ang-2/VEGF bispecific antibody faricimab, currently undergoing regulatory review, and the CD20/CD3 T cell bispecific antibody glofitamab, currently in pivotal Phase 3 trials. In this review, we introduce the principles of CrossMab technology, including its application for the generation of bi-/multispecific antibodies with different geometries and mechanisms of action, and provide an overview of CrossMab-based therapeutics in clinical trials.

Format chain exchange (FORCE) for high-throughput generation of bispecific antibodies in combinatorial binder-format matrices

Generation of bispecific antibodies (bsAbs) requires a combination of compatible binders in formats that support desired functionalities. Here, we report that bsAb-matrices can be generated by Format Chain Exchange (FORCE), enabling screening of combinatorial binder/format spaces. Input molecules for generation of bi/multi-valent bsAbs are monospecific entities similar to knob-into-hole half-antibodies, yet with complementary CH3-interface-modulated and affinity-tagged dummy-chains. These contain mutations that lead to limited interface repulsions without compromising expression or biophysical properties of educts. Mild reduction of combinations of educts triggers spontaneous chain-exchange reactions driven by partially flawed CH3-educt interfaces resolving to perfect complementarity. This generates large bsAb matrices harboring different binders in multiple formats. Benign biophysical properties and good expression yields of educts, combined with simplicity of purification enables process automation. Examples that demonstrate the relevance of screening binder/format combinations are provided as a matrix of bsAbs that simultaneously bind Her1/Her2 and DR5 without encountering binder or format-inflicted interferences.

Bispecific antibodies have been generated in many different formats and it is becoming clear that rational design alone cannot create optimal functionalities. Here the authors introduce the high throughput methodology, Format Chain Exchange (FORCE), to enable combinatorial generation of bispecific antibodies.

Mitigating the risk of cytokine release syndrome in a Phase I trial of CD20/CD3 bispecific antibody mosunetuzumab in NHL: impact of translational system modeling

Mosunetuzumab, a T-cell dependent bispecific antibody that binds CD3 and CD20 to drive T-cell mediated B-cell killing, is currently being tested in non-Hodgkin lymphoma. However, potent immune stimulation with T-cell directed therapies poses the risk of cytokine release syndrome, potentially limiting dose and utility. To understand mechanisms behind safety and efficacy and explore safety mitigation strategies, we developed a novel mechanistic model of immune and antitumor responses to the T-cell bispecifics (mosunetuzumab and blinatumomab), including the dynamics of B- and T-lymphocytes in circulation, lymphoid tissues, and tumor. The model was developed and validated using mosunetuzumab nonclinical and blinatumomab clinical data. Simulations delineated mechanisms contributing to observed cell and cytokine (IL6) dynamics and predicted that initial step-fractionated dosing limits systemic T-cell activation and cytokine release without compromising tumor response. These results supported a change to a step-fractionated treatment schedule of mosunetuzumab in the ongoing Phase I clinical trial, enabling safer administration of higher doses.

A single mutation increases heavy-chain heterodimer assembly of bispecific antibodies by inducing structural disorder in one homodimer species

We previously reported efficient heavy-chain assembly of heterodimeric bispecific antibodies by exchanging the interdomain protein interface of the human IgG1 CH3 dimer with the protein interface of the constant α and β domains of the human T-cell receptor, a technology known as bispecific engagement by antibodies based on the T-cell receptor (BEAT). Efficient heterodimerization in mammalian cell transient transfections was observed, but levels were influenced by the nature of the binding arms, particularly in the Fab-scFv-Fc format. In this study, we report a single amino acid change that significantly and consistently improved the heterodimerization rate of this format (≥95%) by inducing partial disorder in one homodimer species without affecting the heterodimer. Correct folding and assembly of the heterodimer were confirmed by the high-resolution (1.88-1.98 Å) crystal structure presented here. Thermal stability and 1-anilinonaphthalene-8-sulfonic acid-binding experiments, comparing original BEAT, mutated BEAT, and "knobs-into-holes" interfaces, suggested a cooperative assembly process of heavy chains in heterodimers. The observed gain in stability of the interfaces could be classified in the following rank order: mutated BEAT > original BEAT > knobs-into-holes. We therefore propose that the superior cooperativity found in BEAT interfaces is the key driver of their greater performance. Furthermore, we show how the mutated BEAT interface can be exploited for the routine preparation of drug candidates, with minimal risk of homodimer contamination using a single Protein A chromatography step.

sRNA-Based Screening Chromosomal Gene Targets and Modular Designing Escherichia coli for High-Titer Production of Aglycosylated Immunoglobulin G

The production of the aglycosylated immunoglobulin G (IgG) in Escherichia coli has received wide interest for its analytical and therapeutic applications. To enhance the production titer of IgG, we first used synthetic sRNAs to perform a systematical analysis of the gene expression in the translational level in the glycolytic pathway (module 1) and the tricarboxylic acid (TCA) cycle (module 2) to reveal the critical genes for the efficient IgG production. Second, to provide sufficient amino acid precursors for the protein biosynthesis, amino acid biosynthesis pathways (module 3) were enhanced to facilitate the IgG production. Upon integrated engineering of these genes in the three modules (module 1, aceF; module 2, gltA and acnA; module 3, serB) and optimization of fermentation conditions, the recombinant E. coli enabled a titer of the full-assembled IgG of 4.5 ± 0.6 mg/L in flask cultures and 184 ± 9.2 mg/L in the 5 L high cell density fed-batch fermenter, which is, as far as we know, the highest reported titer of IgG production in recombinant E. coli.

Development of bispecific antibodies in China: overview and prospects

A bispecific antibody (bsAb) can simultaneously bind two different epitopes or antigens, allowing for multiple mechanistic functions with synergistic effects. BsAbs have attracted significant scientific attentions and efforts towards their development as drugs for cancers. There are 21 bsAbs currently undergoing clinical trials in China. Here, we review their platform technologies, expression and production, and biological activities and bioassay of these bsAbs, and summarize their structural formats and mechanisms of actions. T-cell redirection and checkpoint inhibition are two main mechanisms of the bsAbs that we discuss in detail. Furthermore, we provide our perspective on the future of bsAb development in China, including CD3-bsAbs for solid tumors and related cytokine release syndromes, expression and chemistry, manufacturing and controls, clinical development, and immunogenicity.

Synthetic sRNA-Based Engineering of Escherichia coli for Enhanced Production of Full-Length Immunoglobulin G

Production of monoclonal antibodies (mAbs) receives considerable attention in the pharmaceutical industry. There has been an increasing interest in the expression of mAbs in Escherichia coli for analytical and therapeutic applications in recent years. Here, a modular synthetic biology approach is developed to rationally engineer E. coli by designing three functional modules to facilitate high-titer production of immunoglobulin G (IgG). First, a bicistronic expression system is constructed and the expression of the key genes in the pyruvate metabolism is tuned by the technologies of synthetic sRNA translational repression and gene overexpression, thus enhancing the cellular material and energy metabolism of E. coli for IgG biosynthesis (module 1). Second, to prevent the IgG biodegradation by proteases, the expression of a number of key proteases is identified and inhibited via synthetic sRNAs (module 2). Third, molecular chaperones are co-expressed to promote the secretion and folding of IgG (module 3). Synergistic integration of the three modules into the resulting recombinant E. coli results in a yield of the full-length IgG ≈150 mg L^-1 in a 5L fed-batch bioreactor. The modular synthetic biology approach could be of general use in the production of recombinant mAbs.

Avidity-based binding to HER2 results in selective killing of HER2-overexpressing cells by anti-HER2/CD3

A primary barrier to the success of T cell-recruiting bispecific antibodies in the treatment of solid tumors is the lack of tumor-specific targets, resulting in on-target off-tumor adverse effects from T cell autoreactivity to target-expressing organs. To overcome this, we developed an anti-HER2/CD3 T cell-dependent bispecific (TDB) antibody that selectively targets HER2-overexpressing tumor cells with high potency, while sparing cells that express low amounts of HER2 found in normal human tissues. Selectivity is based on the avidity of two low-affinity anti-HER2 Fab arms to high target density on HER2-overexpressing cells. The increased selectivity to HER2-overexpressing cells is expected to mitigate the risk of adverse effects and increase the therapeutic index. Results included in this manuscript not only support the clinical development of anti-HER2/CD3 1Fab-immunoglobulin G TDB but also introduce a potentially widely applicable strategy for other T cell-directed therapies. The potential of this discovery has broad applications to further enable consideration of solid tumor targets that were previously limited by on-target, but off-tumor, autoimmunity.