IgG Fc engineering to modulate antibody effector functions

Pharmacokinetics, Pharmacodynamics, and Safety of Nipocalimab in Healthy Chinese Volunteers: A Single-Dose, Phase I Study

INTRODUCTION

Nipocalimab is a high-affinity, fully human, immunoglobulin G (IgG) 1 monoclonal antibody that inhibits the neonatal Fc receptor. Nipocalimab is under development for the treatment of various IgG autoantibody- and alloantibody-mediated diseases. This study assessed the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of a single dose of nipocalimab in healthy Chinese volunteers.

METHODS

In this phase I, open-label study, healthy volunteers received single doses of intravenous (IV) nipocalimab at 15, 30, or 45 mg/kg. The primary objective was to assess the PK following a single administration of nipocalimab. Secondary objectives included the PD effects of nipocalimab on change from baseline in total serum IgG levels, safety, and tolerability.

RESULTS

A total of 30 healthy Chinese volunteers (mean age 31.0 years, 93.3% men) received single doses of IV nipocalimab. Following a single infusion of nipocalimab, mean exposure increased as the dose of nipocalimab increased. Maximum serum nipocalimab concentrations increased proportionally with doses, whereas the area under the concentration-time curve increased by greater than a dose-proportional manner. Nipocalimab led to dose-dependent reductions in serum IgG levels from baseline; this decrease was sustained over a longer period of time with higher dose levels. Nipocalimab was generally well tolerated, with an acceptable safety profile, across all three doses; most of the treatment-emergent adverse events (TEAEs) were mild. Higher doses of nipocalimab were not associated with increased frequency of TEAEs.

CONCLUSION

Our findings add to the evidence on the safety, tolerability, and PD of nipocalimab in the Chinese population, and support for the treatment of pathogenic IgG-mediated diseases in this population.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05151692.

Design of an Fc Mutation to Abrogate Fcγ Receptor Binding Based on Residue Interaction Network Analysis

Immunoglobulins mediate their immune responses through interactions with Fc γ-receptors (FcγRs) on immune cells, triggering crucial responses such as antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). While enhancing these interactions can be beneficial, in certain therapeutic scenarios, such as cytokine or receptor blockade therapies, it is critical to reduce FcγR binding to avoid adverse immune reactions. This study aims to design negative mutations in the Fc region to reduce Fcγ receptor binding based on the residue interaction network analysis. The mutation sites of Fc were targeted through betweenness centrality analysis, and mutations were designed by focusing on hydrophobic to hydrophilic residue changes. The negative effect of the designed mutants on binding affinity was verified by previous reports and binding experiments. From this study, we identified a new Fc variant candidate (V263(B)D) that lacks a binding affinity for Fcγ receptors. This research highlights a strategic approach for designing Fc mutations that effectively reduce immune activation, which may be valuable in therapeutic contexts, where immune response moderation is crucial.

Integrating Biochemical and Computational Approaches Reveal Structural Insights in Trastuzumab scFv-Fc Antibody Engineering

Antibody-based agents have become a preferred treatment for various diseases, including cancer, due to significant advances in antibody engineering. The use of single-chain Fv-Fcs (scFv-Fcs) has been a promising engineering approach for therapeutic design. The concept is that the Fc provides increased stability and target binding and ultimately improves performance. However, the structural and dynamic relationship between the variable and Fc domains, which are fused in close proximity, and the impact on stability and target binding are not well understood. This study evaluated trastuzumab-derived scFv-Fc antibodies, focusing on the impact of their design on important biopharmaceutical parameters. Computational modelling and molecular dynamics, alongside experimental studies, were used to ascertain their dynamics, expression and purification, stabilities, and binding potencies. The results showed that the scFv subunits exhibited stochastic interplays that lead to diverse shapes and were associated with functional performance. This new understanding of scFv-Fc antibodies and their structural and functional nuances provides important details to further guide the design of more effective and less toxic therapeutics.

Cadonilimab plus chemotherapy as first-line treatment for persistent, recurrent, or metastatic cervical cancer: a cost-effectiveness analysis

Background

Immunotherapy has made significant advancements in cervical cancer (CC) treatment; however, its efficacy remains limited in programmed death ligand 1 (PD-L1)-negative patients. Cadonilimab, the first bispecific antibody targeting both programmed death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), demonstrated superior efficacy and manageable safety as a first-line treatment for persistent, recurrent, or metastatic CC (p/r/m CC) in the phase III COMPASSION-16 trial. Notably, it showed significant survival benefits in PD-L1-negative patients. This study aimed to evaluate its cost-effectiveness from the perspective of the Chinese healthcare system.

Methods

A partitioned survival model was developed based on data derived from the COMPASSION-16 trial. The model utilized a 3-week cycle length and a 10-year time horizon. The primary outcomes included costs, quality-adjusted life-years (QALYs), incremental cost-effectiveness ratio (ICER), incremental net monetary benefit (INMB), and incremental net health benefit (INHB). Additionally, sensitivity analyses, scenario analyses, and subgroup analyses were performed.

Results

The cadonilimab plus chemotherapy regimen provided an additional 0.61 QALYs compared to chemotherapy alone, at an incremental cost of $42,486.54. This yielded an ICER of $70,220.88/QALY, exceeding the willingness-to-pay threshold of $38,042/QALY. The corresponding INMB and INHB were -$19,469.55 and -0.51 QALYs, respectively. Consequently, cadonilimab plus chemotherapy was not deemed to be cost-effective. Sensitivity analyses showed that the results remained consistent when each parameter varied within the predetermined range, indicating the model's robustness. Subgroup analyses demonstrated no significant positive correlation between economic outcomes and PD-L1 expression levels. Notably, in the subgroup of patients who did not receive bevacizumab, cadonilimab plus chemotherapy emerged as a cost-effective alternative.

Conclusion

In China, cadonilimab plus chemotherapy is not considered cost-effective compared to standard chemotherapy as a first-line treatment for the general p/r/m CC population. However, it represents a cost-effective option for patients ineligible for bevacizumab therapy.

Mapping affinity and allostery in human IgG antibody Fc region-Fc γ receptor interactions

IgG antibodies, required for a functional immune system, recognize antigens and neutralize pathogens using their Fab regions, while signaling to the immune system by binding to host Fc γ receptors (FcγRs) through their Fc regions. These FcγR interactions initiate and modulate antibody-mediated effector functions that are essential for host immunity, therapeutic monoclonal antibody effectiveness and IgG-mediated pathologies. FcγRs include both activating and inhibitory receptors and the relative binding affinities of the IgG Fc region to FcγRs that generate opposing signals is a key determinant of the immune response. Substantial research effort has been devoted to understanding and manipulating FcγR interactions to decipher their fundamental biological activities and to develop therapeutic monoclonal antibodies with tailored effector functions. However, a common Fc-FcγR binding interface, the high sequence identity of FcγRs, and the inherent conformational dynamics of the IgG Fc region, have prohibited a full understanding of these interactions, even when employing state-of-the-art biophysical and biological methods. Here, we used site-saturation libraries of the human IgG1 Fc region to determine the effective affinities of more than 98% of all possible single-site amino acid substitutions in the Fc to all human FcγRs, as well as the most common FcγR polymorphisms. We provide a comprehensive analysis of Fc amino acid variations that determine Fc stability, orthosteric control of FcγR binding, and short- and long-range allosteric control of FcγR binding. We also predict the relative activating versus inhibitory effector function capacity of nearly every possible single-site Fc mutation.

Immune inhibitory receptor agonist therapeutics

The immune system maintains the health of an organism through complex sensing and communication mechanisms. Receptors on the surface of immune cells respond to stimuli resulting in activity described at its most basic as inhibitory or stimulatory. Significant progress in therapeutic intervention has occurred by modulating these pathways, yet much remains to be accomplished. Therapeutics that antagonize, or block, immune inhibitory receptor (IIR) pathways, such as checkpoint inhibitors in cancer are a key example. Antagonism of immune stimulatory receptors (ISRs) for dysregulated inflammation and autoimmunity have received significant attention. An alternative strategy is to agonize, or induce signaling, in immune pathways to treat disease. Agonism of ISRs has been employed with some success in disease settings, but agonist therapeutics of IIRs have great, untapped potential. This review discusses and highlights recent advances in pre-clinical and clinical therapeutics designed to agonize IIR pathways to treat diseases. In addition, an understanding of IIR agonists based on activity at a cellular level as either agonist suppression of stimulatory cells (SuSt), or a new concept, agonist suppression of suppressive cells (SuSu) is proposed.

Design of a fragment crystallizable-engineered tetravalent bispecific antibody targeting programmed cell death-1 and vascular endothelial growth factor with cooperative biological effects

Clinical studies have shown that combination therapy of PD-1 and VEGF antibodies significantly improves clinical benefit over PD-1 antibody alone in certain settings. Ivonescimab, an on-market tetravalent anti-PD-1/VEGF bispecific antibody, was designed to improve efficacy and safety over combo therapy. In this study, the mechanism of action is investigated. In the presence of VEGF, ivonescimab forms soluble complexes with VEGF dimers, leading to the enhanced binding avidity of ivonescimab to PD-1 therefore promoting its increased potency on PD-1/PD-L1-signaling blockade. Likewise, PD-1 binding enhanced ivonescimab binding to VEGF, therefore enhancing VEGF-signaling blockade. Furthermore, ivonescimab treatment demonstrated statistically significant anti-tumor response in vivo. Moreover, ivonescimab contains Fc-silencing mutations abrogating FcγRI/IIIa binding and showed significantly reduced effector function in vitro which is consistent with the better safety profile of ivonescimab in monkeys and humans. Briefly, ivonescimab displays unique cooperative binding and promotes the increased in vitro functional bioactivities with a favorable safety profile.

Optimization of Adcitmer, a Monomethyl-Auristatin E bearing antibody-drug conjugate for the treatment of CD56-expressing cancers

The cell adhesion protein CD56 has been identified as a potential therapeutic target in several solid tumors and hematological malignancies. Recently, we developed a CD56-directed antibody-drug conjugate (ADC), called Adcitmer and demonstrated its antitumor properties in preclinical models of the rare and aggressive skin cancer Merkel cell carcinoma (MCC).The present study aims to further optimize Adcitmer to overcome the therapeutic limitations observed with previously evaluated CD56-targeting ADCs, which were partially related to toxic effects on leukocytes. To this end, we aimed to avoid interaction of Adcitmer with immune cells via Fc gamma receptor (FcγR) binding. Since glycosylation is essential for FcγR binding, an aglycosylated form of Adcitmer was generated and evaluated on human leukocytes and MCC cell lines using cell death (annexin V/7-aminoactinomycine D) and proliferation (2,3-Bis-(2-methoxy-4Nitro-5-sulfophenyl)-2H-tetrazolium-5carboxanilide) assays. Finally, the therapeutic performance of Adcitmer and its aglycosylated form was assessed in an MCC xenograft mouse model.Investigating the Adcitmer interaction with immune cells demonstrated that it is mostly mediated by Fc recognition. Accordingly, Adcitmer aglycosylation led to reduced immune cell toxicity and strikingly also to improved therapeutic performance even in an MCC xenograft model using immunodeficient mice.Our study suggests that aglycosylated Adcitmer should be considered as a therapeutic option in patients with advanced MCC or other CD56-positive tumors.

Biomembrane structure at the molecular level and its application in precision medicine

Biomembranes are fundamental to our understanding of the cell, the basic building block of all life. They form important barriers between the cytoplasm and the microenvironment of the cell and separate organelles within cells. Despite substantial advances in the study of cell membrane structure models, they are still in the stage of model hypothesis due to the high complexity of the components, structures, and functions of membranes. In this review, we summarized the progresses on membrane structure, properties, and functions at the molecular level using newly developed technologies and discussed some challenges and future directions in biomembrane research from our perspective. Moreover, we demonstrated the dynamic functions of membrane proteins and their role in achieving early detection, precise diagnosis, and the development of personalized treatment strategies at the molecular level. Overall, this review aims to engage researchers in related fields and multidisciplinary readers to understand and explore biomembranes for the accurate and effective development of membrane-targeting therapeutic agents.

Whole-canine neutralizing antibodies generated by single B cell antibody technology elicit therapeutic protection against canine distemper virus infection

Canine distemper virus (CDV) causes a highly contagious and fatal disease in domestic and wild carnivores. Currently, vaccination is the primary method for preventing canine distemper. However, incidents of vaccine immunization failures continue to be reported. There are no specific and effective treatment agents available for canine distemper infection. Neutralizing antibodies offer a potential approach for the treatment of viral diseases. In this study, single B cell antibody technology was applied to obtain whole-canine antibodies against CDV. 7 monoclonal antibodies were screened and showed high binding affinity to CDV hemagglutinin (H) protein, with D16 and F53 exhibited high specificity and neutralizing activity against CDV. Furthermore, D16 exhibited effective therapeutic potential in dogs subjected to lethal dose CDV attacks in vivo. In conclusion, our study offers an alternative approach for acquiring neutralizing antibody and provides a promising new strategy for the treatment of CDV infection.

CD22 modulation alleviates amyloid β-induced neuroinflammation

Neuroinflammation is a crucial driver of multiple neurodegenerative diseases, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Yet, therapeutic targets for neurodegenerative diseases based on neuroinflammation still warrant investigation. CD22 has been implicated in neuroinflammatory diseases, namely AD. Specifically, plasma soluble CD22 (sCD22) level is upregulated in patients with AD. Direct experimental evidence for the role of CD22 in neuroinflammation is needed, as is a better understanding of its impact on microglia activation and therapeutic potential. Here we reported that sCD22 promotes neuroinflammation both in vivo and in vitro. sCD22 activated microglia via both p38 and ERK1/2 signaling pathway for the secretion of TNFα, IL-6 and CCL3. Moreover, sCD22 activated microglia via sialic acid binding domain and 2,6 linked sialic acid glycan on sCD22. The pivotal therapeutic potential of targeting CD22 was demonstrated in Amyloid β (Aβ) induced-neuroinflammation in hCD22 transgenic mice. Suciraslimab improved working memory and resolved neuroinflammation in vivo. Further, membrane CD22 inhibited Amyloid β (Aβ) induced-NFκB signaling pathway and mechanistic study delineated that suciraslimab suppressed Aβ-induced IL-1β secretion in human microglia and PBMC. Suciraslimab also suppressed IL-12 and IL-23 secretion in human PBMC. Moreover, suciraslimab reduced the surface expression of α4 integrin on B cells. Intriguingly, we discovered that CD22 interact with Aβ and suciraslimab enhanced internalization of CD22-Aβ complex in microglia. Our data highlights the importance of sCD22 in driving neuroinflammation and the dual mechanism of targeting CD22 to resolve Aβ-induced inflammation and promote Aβ phagocytosis.

Safety and efficacy of nipocalimab in adults with generalised myasthenia gravis (Vivacity-MG3): a phase 3, randomised, double-blind, placebo-controlled study

BACKGROUND

Given burdensome side-effects and long latency for efficacy with conventional agents, there is a continued need for generalised myasthenia gravis treatments that are safe and provide consistently sustained, long-term disease control. Nipocalimab, a neonatal Fc receptor blocker, was associated with dose-dependent reductions in total IgG and anti-acetylcholine receptor (AChR) antibodies and clinically meaningful improvements in the Myasthenia Gravis Activities of Daily Living (MG-ADL) scale in patients with generalised myasthenia gravis in a phase 2 study. We aimed to assess the safety and efficacy of nipocalimab in a phase 3 study.

METHODS

Vivacity-MG3 was a phase 3, randomised, double-blind, placebo-controlled, phase 3 study conducted at 81 outpatient centres with expertise in myasthenia gravis in 17 countries in Asia-Pacific, Europe, and North America. Adults (aged ≥18 years) with generalised myasthenia gravis inadequately controlled with standard-of-care therapy (MG-ADL score ≥6) were randomly assigned (1:1) to either nipocalimab (30 mg/kg loading dose then 15 mg/kg every 2 weeks for maintenance dosing) or placebo infusions every 2 weeks, added to standard-of-care therapy in both groups, for 24 weeks. Randomisation was stratified by antibody status, day 1 MG-ADL total score, and region. The sponsor, investigators, clinical raters, and participants were masked to treatment assignment. The primary endpoint was the difference between nipocalimab and placebo based on least-squares mean change from baseline in MG-ADL total score averaged over weeks 22, 23, and 24 in the intention-to-treat population of patients who were antibody-positive (for AChR, anti-muscle-specific tyrosine kinase [MuSK], or anti-low-density lipoprotein receptor-related protein 4 [LRP4]). Adverse events were assessed in patients who received at least one dose of study drug. This study is registered at ClinicalTrials.gov, NCT04951622; the double-blind phase is completed and an open-label extension phase is ongoing.

FINDINGS

Between July 15, 2021, and Nov 17, 2023, 199 patients were enrolled, and 196 patients received study drug (98 in the nipocalimab group and 98 in the placebo group); of these, 153 (77 in the nipocalimab group and 76 in the placebo group) were antibody-positive. The least-squares mean change in MG-ADL score from baseline to weeks 22, 23, and 24 was -4·70 (SE 0·329) in the nipocalimab group versus -3·25 (0·335) in the placebo group (difference -1·45 [95% CI -2·38 to -0·52]; p=0·0024). The incidence of adverse events was similar between groups (82 [84%] of 98 in both the nipocalimab and placebo groups), including infections (42 [43%] of 98 in the nipocalimab group and placebo group) and headache (14 [14%] of 98 in the nipocalimab group and 17 [17%] of 98 in the placebo group). Serious adverse events were reported for nine (9%) of 98 patients in the nipocalimab group and 14 (14%) of 98 patients in the placebo group, three of which had a fatal outcome (nipocalimab: myasthenic crisis; placebo: cardiac arrest and myocardial infarction).

INTERPRETATION

Results from the completed double-blind phase of Vivacity-MG3 support the role of nipocalimab, added to standard-of-care therapies, as a safe treatment for sustained disease control over 6 months for a broad population of patients with generalised myasthenia gravis who are antibody-positive. The ongoing open-label extension phase should provide longer term sustained safety and efficacy data with nipocalimab.

FUNDING

Janssen Research & Development, LLC, a Johnson & Johnson company.

A Novel Tetravalent CD95/Fas Fusion Protein With Superior CD95L/FasL Antagonism

Inhibition of CD95/Fas activation is currently under clinical investigation as a therapy for glioblastoma multiforme and preclinical studies suggest that disruption of the CD95-CD95L interaction could also be a strategy to treat inflammatory and neurodegenerative disorders. Besides neutralizing anti-CD95L/FasL antibodies, mainly CD95ed-Fc, a dimeric Fc fusion protein of the extracellular domain of CD95 (CD95ed), is used to prevent CD95 activation. In view of the fact that full CD95 activation requires CD95L-induced CD95 trimerization and clustering of the resulting liganded CD95 trimers, we investigated whether fusion proteins of the extracellular domain of CD95 with a higher valency than CD95ed-Fc have an improved CD95L-neutralization capacity. We evaluated an IgG1(N297A)-based tetravalent CD95ed fusion protein which was obtained by replacing the variable domains of IgG1(N297A) with CD95ed (CD95ed-IgG1(N297A)) and a hexavalent variant obtained by fusion of CD95ed with a TNC-Fc(DANA) scaffold (CD95ed-TNC-Fc(DANA)) promoting hexamerization. The established N297A and DANA mutations were used to minimize FcγR binding of the constructs under maintenance of neonatal Fc receptor (FcRn) binding. Size exclusion high-performance liquid chromatography indicated effective assembly of CD95ed-IgG1(N297A). More important, CD95ed-IgG1(N297A) was much more efficient than CD95ed-Fc in protecting cells from cell death induction by human and murine CD95L. Surprisingly, despite its hexavalent structure, CD95ed-TNC-Fc(DANA) displayed an at best minor improvement of the capacity to neutralize CD95L suggesting that besides valency, other factors, such as spatial organization and agility of the CD95ed domains, play also a role in neutralization of CD95L trimers by CD95ed fusion proteins. More studies are now required to evaluate the superior CD95L-neutralizing capacity of CD95ed-IgG1(N297A) in vivo.

Simple endoglycosidase-assisted peptide mapping workflow for characterizing non-consensus n-glycosylation in therapeutic monoclonal antibodies

N-linked glycosylation, an extensively studied protein post-translational modification, was conventionally understood to occur at asparagine (Asn or N) sites with the consensus motif NXS/T, where X can be any amino acid residue except for proline, followed by serine or threonine. However, with advancements in characterization techniques and bioinformatic tools, increasing evidence indicates that Asn residues that are not located in the NXS/T consensus motif can also undergo N-glycosylation, which is also known as non-consensus or noncanonical N-glycosylation. Characterizing non-consensus N-glycosylation remains challenging because of the unpredictable sequon and its relatively low abundance. Here, we report an endoglycosidase-assisted peptide mapping workflow for mass spectrometry (MS) characterization of non-consensus N-glycosylation in monoclonal antibodies (mAbs). The feasibility of the workflow was demonstrated by a challenging case study, in which an atypical glycosite located within an NPNNXN sequence in a 25-residue tryptic peptide was identified in the fragment antigen-binding (Fab) region of a mAb. With the aids of endoglycosidase treatment, the resulting truncated glycan structures improved peptide ionization efficiency in MS and hence facilitated reliable quantitation of glycosite occupancy. Meanwhile, the remaining mono-/di-saccharides served as a large mass tag enabling differentiation between the glycopeptide and deamidated peptide, thus allowing for database searching for glycosite localization and semi-automation of the data processing workflow. This workflow offers a simple solution for characterizing non-consensus N-glycosylation for the development of therapeutic mAbs.

Transferrin receptor targeting chimeras for membrane protein degradation

Cancer cells require high levels of iron for rapid proliferation, leading to significant upregulation of cell-surface transferrin receptor 1 (TfR1), which mediates iron uptake by binding to the iron-carrying protein transferrin1-3. Leveraging this phenomenon and the fast endocytosis rate of TfR1 (refs. 4,5), we developed transferrin receptor targeting chimeras (TransTACs), a heterobispecific antibody modality for membrane protein degradation. TransTACs are engineered to drive rapid co-internalization of a target protein of interest and TfR1 from the cell surface, and to enable target protein entry into the lysosomal degradation pathway. We show that TransTACs can efficiently degrade a diverse range of single-pass, multi-pass, native or synthetic membrane proteins, including epidermal growth factor receptor, programmed cell death 1 ligand 1, cluster of differentiation 20 and chimeric antigen receptor. In example applications, TransTACs enabled the reversible control of human primary chimeric antigen receptor T cells and the targeting of drug-resistant epidermal growth factor receptor-driven lung cancer with the exon 19 deletion/T790M/C797S mutations in a mouse xenograft model. TransTACs represent a promising new family of bifunctional antibodies for precise manipulation of membrane proteins and targeted cancer therapy.

FcγRIIB (CD32B) antibodies enhance immune responses through activating FcγRs

Fc receptors (FcR) play a key role in coordinating responses from both the innate and adaptive immune system. The inhibitory Fc gamma receptor (FcγRIIB/CD32B; referred to as FcγRII/CD32 in mice) restrains the immune response, specifically through regulating immunoglobulin G (IgG) effector functions. FcγRII-deficient mice demonstrate elevated incidence and severity of autoimmunity and increased responses to immunization and infections. To explore the potential of FcγRIIB as a target for augmenting vaccines, we tested the ability of monoclonal antibodies (mAb) against mouse FcγRII and human FcγRIIB to enhance humoral responses in preclinical models. We used wild-type (WT), FcγR-deficient, and human FcγRIIB transgenic (Tg) mice with either a functional intracellular domain (hFcγRIIB Tg) or lacking immunoreceptor tyrosine-based inhibitory motif (ITIM) signalling capacity (NoTIM). Targeting mouse FcγRII and human FcγRIIB with antibodies significantly augmented humoral immune responses against experimental antigens and enhanced tumour clearance in vivo. Surprisingly, mAbs without a functional Fc (N297Q; referred to as Fc-null) lacked efficacy. Similarly, blocking FcγRII in mice lacking activating FcγRs failed to enhance immune responses. Conversely, blocking both signalling-competent and signalling-defective (NoTIM) FcγRIIB in Tg mice with a WT, but not Fc-null, FcγRIIB mAb equally enhanced immunity. These data indicate the redundancy of inhibitory signalling in potentiating immune responses in vivo. Collectively, our data suggest that mAb-targeting of FcγRIIB stabilizes mAb Fc and enhances immune responses via Fc-mediated crosslinking of activating FcγRs, irrespective of the inhibitory function of FcγRIIB. These findings support a strategy to boost immune responses in immunization protocols.

In Situ Self-Assembly of Antibody-Rhamnose Complex as a Pre-Targeting Strategy for Enhanced Cancer Immunotherapy

Enhancing the Fc effector functions of monoclonal antibodies (mAbs) is a proven strategy for improving cancer immunotherapy. In this study, we present a novel pre-targeting approach that integrates host-guest chemistry with an antibody-recruiting concept to create mAbs with superior effector functions. Using rituximab (RTX), a clinically approved anti-CD20 mAb, as our model, we modified RTX by conjugating it with adamantane (Ada) derivatives and various polyethylene glycol (PEG) linkers to produce RTX-Ada conjugates. These conjugates effectively formed RTX-rhamnose (Rha) complexes in situ through self-assembly, driven by host-guest interactions with Rha-modified β-cyclodextrin. This mechanism successfully redirected endogenous anti-Rha antibodies to target cells, enhancing the availability of Fc domains for improved effector functions, including complement-dependent cytotoxicity (CDC). A structure-activity relationship study indicated that the potency of these in situ complexes was significantly influenced by the length of the PEG linker used; shorter PEG linkers correlated with higher CDC activity. Given the variability in endogenous antibody levels among individuals, this strategy presents a flexible and promising platform for enhancing the efficacy of mAb-based cancer immunotherapy.

An antibody cocktail targeting two different CD73 epitopes enhances enzyme inhibition and tumor control

CD73, an ectoenzyme responsible for adenosine production, is often elevated in immuno-suppressive tumor environments. Inhibition of CD73 activity holds great promise as a therapeutic strategy for CD73-expressing cancers. In this study, we have developed a therapeutic anti-human CD73 antibody cocktail, HB0045. HB0045 is a 1:1 mixture of two humanized monoclonal IgG1 antibodies (mAbs), HB0038 and HB0039. The cocktail not only harnesses the advantages of its parental mAbs in enzyme inhibition but also shows a significantly greater capability of promoting T cell proliferation in vitro. Structural analyses show that HB0045 effectively locks the CD73 dimer in a "partially open" non-active conformation through a double lock mechanism. In various animal models of syngeneic and xenograft tumors, HB0045 inhibits tumor growth more potently than the single mAbs. Collectively, our findings provide functional and structural insights into the mechanism of a CD73-targeting antibody cocktail.

Genetically engineered IgG1 and nanobody oligomers acquire strong intrinsic CD40 agonism

Most anti-CD40 antibodies show robust agonism only upon binding to FcγR+ cells, such as B cells, macrophages, or DCs, but a few anti-CD40 antibodies display also strong intrinsic agonism dependent on the recognized epitope and/or isotype. It is worth mentioning, however, that also the anti-CD40 antibodies with intrinsic agonism can show a further increase in agonistic activity when bound by FcγR-expressing cells. Thus, conventional antibodies appear not to be sufficient to trigger the maximum possible CD40 activation independent from FcγR-binding. We proved here the hypothesis that oligomeric and oligovalent anti-CD40 antibody variants generated by genetic engineering display high intrinsic, thus FcγR-independent, agonistic activity. We generated tetra-, hexa- and dodecavalent variants of six anti-CD40 antibodies and a CD40-specific nanobody. All these oligovalent variants, even when derived of bivalent antagonistic anti-CD40 antibodies, showed strongly enhanced CD40 agonism compared to their conventional counterparts. In most cases, the CD40 agonism reached the maximum response induced by FcγR-bound anti-CD40 antibodies or membrane CD40L, the natural engager of CD40. In sum, our data show that increasing the valency of anti-CD40 antibody constructs by genetic engineering regularly results in molecules with high intrinsic agonism and level out the specific limitations of the parental antibodies.

Efficacy and safety of asfotase alfa in patients with hypophosphatasia: A systematic review

BACKGROUND

Hypophosphatasia (HPP) is a rare genetic disorder characterized by defective bone mineralization, leading to skeletal abnormalities and systemic complications. Asfotase alfa, a recombinant human tissue-nonspecific alkaline phosphatase (TNSALP) enzyme replacement therapy, has emerged as a promising treatment for HPP. However, a comprehensive evaluation of its efficacy and safety is warranted to guide clinical practice effectively.

METHODS

The study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in Prospective Register of Systematic Reviews (PROSPERO). A search strategy across databases found studies on asfotase alfa for HPP. Two researchers independently extracted and assessed data. This systematic review examined how the drug impacted clinical outcomes such as survival rates, musculoskeletal symptoms, respiratory function, growth measurements, dental health, quality of life, and laboratory results.

RESULTS

This systematic review included 15 articles with a total of 455 HPP patients. Asfotase alfa was predominantly administered at a dose of 6 mg per kg per week among the reviewed studies. Notable findings included enhanced survival rates, relief from musculoskeletal pain, improvements in respiratory outcomes, growth parameters, dental health, and quality of life. Changes in laboratory variables indicated positive responses to treatment, including changes such as increase in alkaline phosphatase (ALP), decline in pyridoxal 5'-phosphate (PLP) and inorganic pyrophosphate (PPi) levels.

CONCLUSION

Asfotase alfa demonstrates efficacy in improving clinical outcomes and safety in patients with HPP. Its therapeutic benefits extend across various domains. However, Larger, age-stratified comparative studies are needed to further investigate the drug's effects in HPP patients.

Stellabody: A novel hexamer-promoting mutation for improved IgG potency

Advances in antibody engineering are being directed at the development of next generation immunotherapeutics with improved potency. Hexamerisation of IgG is a normal physiological aspect of IgG biology and recently described mutations that facilitate this process have a substantial impact upon monoclonal antibody behavior resulting in the elicitation of dramatically enhanced complement-dependent cytotoxicity, Fc receptor function, and enhanced antigen binding effects, such as targeted receptor agonism or microbe neutralization. Whereas the discovery of IgG hexamerisation enhancing mutations has largely focused on residues with exposure at the surface of the Fc-Fc and CH2-CH3 interfaces, our unique approach is the engineering of the mostly buried residue H429 in the CH3 domain. Selective substitution at position 429 forms the basis of Stellabody technology, where the choice of amino acid results in distinct hexamerisation outcomes. H429F results in monomeric IgG that hexamerises after target binding, so called "on-target" hexamerisation, while the H429Y mutant forms pH-sensitive hexamers in-solution prior to antigen binding. Moreover, Stellabody technologies are broadly applicable across the family of antibody-based biologic therapeutics, including conventional mAbs, bispecific mAbs, and Ig-like biologics such as Fc-fusions, with applications in diverse diseases.

A new silicon phthalocyanine dye induces pyroptosis in prostate cancer cells during photoimmunotherapy

Photoimmunotherapy (PIT) combines the specificity of antibodies with the cytotoxicity of light activatable photosensitizers (PS) and is a promising new cancer therapy. We designed and synthesized, in a highly convergent manner, the silicon phthalocyanine dye WB692-CB2, which is novel for being the first light-activatable PS that can be directly conjugated via a maleimide linker to cysteines. In the present study we conjugated WB692-CB2 to a humanized antibody with engineered cysteines in the heavy chains that specifically targets the prostate-specific membrane antigen (PSMA). The resulting antibody dye conjugate revealed high affinity and specificity towards PSMA-expressing prostate cancer cells and induced cell death after irradiation with red light. Treated cells exhibited morphological characteristics associated with pyroptosis. Mechanistic studies revealed the generation of reactive oxygen species, triggering a cascade of intracellular events involving lipid peroxidation, caspase-1 activation, gasdermin D cleavage and membrane rupture followed by release of pro-inflammatory cellular contents. In first in vivo experiments, PIT with our antibody dye conjugate led to a significant reduction of tumor growth and enhanced overall survival in mice bearing subcutaneous prostate tumor xenografts. Our study highlights the future potential of the new phthalocyanine dye WB692-CB2 as PS for the fluorescence-based detection and PIT of cancer, including local prostate tumor lesions, and systemic activation of anti-tumor immune responses by the induction of pyroptosis.

Using IMGT unique numbering for IG allotypes and Fc-engineered variants of effector properties and half-life of therapeutic antibodies

Therapeutic monoclonal antibodies (mAb) are usually of the IgG1, IgG2, and IgG4 classes, and their heavy chains may be modified by amino acid (aa) changes involved in antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), and/or half-life. Allotypes and Fc-engineered variants are classified using IMGT/HGNC gene nomenclature (e.g., Homo sapiens IGHG1). Allotype names follow the WHO/IMGT nomenclature. IMGT-engineered variant names use the IMGT nomenclature (e.g., Homsap G1v1), which comprises species and gene name (both abbreviated) followed by the letter v (for variant) and a number. Both allotypes and engineered variants are defined by their aa changes and positions, based on the IMGT unique numbering for C domain, identified in sequence motifs, referred to as IMGT topological motifs, as their limits and length are standardized and correspond to a structural feature (e.g., strand or loop). One hundred twenty-six variants are displayed with their type, IMGT numbering, Eu-IMGT positions, motifs before and after changes, and their property and function (effector and half-life). Three motifs characterize effector variants, CH2 1.6-3, 23-BC-41, and the FG loop, whereas three different motifs characterize half-life variants, two on CH2 13-AB-18 and 89-96 with H93, and one on CH3 the FG loop with H115.

Clinical Progresses and Challenges of Bispecific Antibodies for the Treatment of Solid Tumors

In recent years, bispecific antibodies (BsAbs) have emerged as a promising therapeutic strategy against tumors. BsAbs can recruit and activate immune cells, block multiple signaling pathways, and deliver therapeutic payloads directly to tumor sites. This review provides a comprehensive overview of the recent advances in the development and clinical application of BsAbs for the treatment of solid tumors. We discuss the different formats, the unique mechanisms of action, and the clinical outcomes of the most advanced BsAbs in solid tumor therapy. Several studies have also analyzed the clinical progress of bispecific antibodies. However, this review distinguishes itself by exploring the challenges associated with bispecific antibodies and proposing potential solutions. As the field progresses, BsAbs hold promise to redefine cancer treatment paradigms and offer new hope to patients with solid tumors.

Cadonilimab (PD-1/CTLA-4) in combination with lenvatinib in unresectable hepatocellular carcinoma (uHCC): A retrospective real-world study

Background

Previous research has shown that combining tyrosine kinase inhibitors (TKIs) with immunotherapy results in synergistic clinical efficacy. Cadonilimab, the first approved bi-specific antibody targeting PD-1 and CTLA-4, was studied to evaluate its efficacy and safety in combination with Lenvatinib as a first-line treatment for patients with unresectable hepatocellular carcinoma (uHCC).

Methods

A retrospective study was conducted on 29 uHCC patients diagnosed at Nanfang Hospital, Southern Medical University, between July 7, 2022, and March 3, 2023. Patients received Cadonilimab (10 mg/kg, IV, every 3 weeks) combined with Lenvatinib (8 mg, orally, daily). The primary endpoint was the objective response rate (ORR), with secondary endpoints including disease control rate (DCR), median progression-free survival (mPFS), median overall survival (mOS), median time to progression (mTTP), and safety.

Results

By April 2023, 29 patients had been enrolled in the study. The ORR was 37.9 %, DCR was 82.8 %, mPFS was 8.1 months, mTTP was 8.2 months, and mOS was not reached. A total of 93.1 % of patients experienced at least one treatment-related adverse event (TRAE). The most common adverse events were weight loss (51.7 %), increased aspartate aminotransferase (48.3 %), leukocytopenia (48.3 %), and neutropenia (48.3 %). TRAEs of grade 3 or higher occurred in 51.7 % of patients, with no grade 4 TRAEs observed.

Conclusion

This study demonstrated the efficacy and safety of this combination, potentially improving outcomes as a first-line therapy, and offering a novel therapeutic approach for advanced HCC.

Cutting-edge approaches to B-cell depletion in autoimmune diseases

B-cell depletion therapy (BCDT) has been employed to treat autoimmune disease for ~20 years. Immunoglobulin G1 (IgG1) monoclonal antibodies targeting CD20 and utilizing effector function (eg, antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis) to eliminate B cells have historically been the predominant therapeutic approaches. More recently, diverse BCDT approaches targeting a variety of B-cell surface antigens have been developed for use in hematologic malignancies, including effector-function-enhanced monoclonal antibodies, chimeric antigen receptor T-cell (CAR-T) treatment, and bispecific T-cell engagers (TCEs). The latter category of antibodies employs CD3 engagement to augment the killing of target cells. Given the improvement in B-cell depletion observed with CAR-T and TCEs compared with conventional monospecific antibodies for treatment of hematologic malignancies and the recent case reports demonstrating therapeutic benefit of CAR-T in autoimmune disease, there is potential for these mechanisms to be effective for B-cell-mediated autoimmune disease. In this review, we discuss the various BCDTs that are being developed in autoimmune diseases, describing the molecule designs, depletion mechanisms, and potential advantages and disadvantages of each approach as they pertain to safety, efficacy, and patient experience. Additionally, recent advances and strategies with TCEs are presented to help broaden understanding of the potential for bispecific antibodies to safely and effectively engage T cells for deep B-cell depletion in autoimmune diseases.

Therapeutic antibodies in oncology: an immunopharmacological overview

The biotechnological development of monoclonal antibodies and their immunotherapeutic use in oncology have grown exponentially in the last decade, becoming the first-line therapy for some types of cancer. Their mechanism of action is based on the ability to regulate the immune system or by interacting with targets that are either overexpressed in tumor cells, released into the extracellular milieu or involved in processes that favor tumor growth. In addition, the intrinsic characteristics of each subclass of antibodies provide specific effector functions against the tumor by activating antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, among other mechanisms. The rational design and engineering of monoclonal antibodies have improved their pharmacokinetic and pharmacodynamic features, thus optimizing the therapeutic regimens administered to cancer patients and improving their clinical outcomes. The selection of the immunoglobulin G subclass, modifications to its crystallizable region (Fc), and conjugation of radioactive substances or antineoplastic drugs may all improve the antitumor effects of therapeutic antibodies. This review aims to provide insights into the immunological and pharmacological aspects of therapeutic antibodies used in oncology, with a rational approach at molecular modifications that can be introduced into these biological tools, improving their efficacy in the treatment of cancer.

Peptibodies: Bridging the gap between peptides and antibodies

Peptides are a very critical class of pharmaceutical compounds that can control several signaling pathways and thereby affect many physiological and biochemical processes. Previous research suggests that both peptides and antibodies may serve as potent tools for research, diagnostics, vaccination, and therapeutics across diverse domains. The distinct attributes of peptides, like their profound tissue penetration, efficient cellular internalization, reduced immunogenicity, and adaptability to chemical modification, underscore their significance in biomedical applications. However, they also possess drawbacks such as lower affinity, poor absorption, low stability to proteolytic digestion, and rapid clearance. The advent of peptibodies is a significant advance that improves the limitations of both peptides and antibodies. Peptibodies, or Peptide-Fc fusions, represent a promising therapeutic modality comprising biologically active peptides fused to an Fc domain. The stability and efficacy of the peptide are enhanced by this fusion strategy, which overcomes some of the inherent limitations. Many peptibodies have been developed to treat conditions like cancer, diabetes, and lupus. Romiplostim and Dulaglutide are the only ones approved by the EMA and FDA, respectively. Given the growing significance of peptibodies in the pharmaceutical landscape, this investigation aims to explain key aspects encompassing the intrinsic properties of peptides, the intricacies of peptibody production, and their potential therapeutic applications.

Model acetylcholinesterase-Fc fusion glycoprotein biotechnology system for the manufacture of an organophosphorus toxicant bioscavenging countermeasure

Organophosphate (OP) toxicants remain an active threat to public health and to warfighters in the military. Current countermeasures require near immediate administration following OP exposure and are reported to have controversial efficacies. Acetylcholinesterase (AChE) fused to the human immunoglobulin 1 (IgG1) Fc domain (AChE-Fc) is a potential bioscavenger for OP toxicants, but a reproducible AChE-Fc biomanufacturing strategy remains elusive. This report is the first to establish a comprehensive laboratory-scale bioprocessing strategy that can reproducibly produce AChE-Fc and AChE(W86A)-Fc which is a mutated AChE protein with reduced enzymatic activity. Characterization studies revealed that AChE-Fc and AChE(W86A)-Fc are N-glycosylated dimeric fusion glycoproteins but only AChE-Fc had the capability to bind to paraoxon (a model OP). This AChE-Fc fusion glycoprotein bioprocessing strategy can be leveraged during industrial biomanufacturing development, while the research-grade AChE-Fc proteins can be used to determine the potential clinical relevance of the countermeasure against OP toxicants.

Tumor-Homing Antibody-Cytokine Fusions for Cancer Therapy

Recombinant cytokine products have emerged as a promising avenue in cancer therapy due to their capacity to modulate and enhance the immune response against tumors. However, their clinical application is significantly hindered by systemic toxicities already at low doses, thus preventing escalation to therapeutically active regimens. One promising approach to overcoming these limitations is using antibody-cytokine fusion proteins (also called immunocytokines). These biopharmaceuticals leverage the targeting specificity of antibodies to deliver cytokines directly to the tumor microenvironment, thereby reducing systemic exposure and enhancing the therapeutic index. This review comprehensively examines the development and potential of antibody-cytokine fusion proteins in cancer therapy. It explores the molecular characteristics that influence the performance of these fusion proteins, and it highlights key findings from preclinical and clinical studies, illustrating the potential of immunocytokines to improve treatment outcomes in cancer patients. Recent advancements in the field, such as novel engineering strategies and combination strategies to enhance the efficacy and safety of immunocytokines, are also discussed. These innovations offer new opportunities to optimize this class of biotherapeutics, making them a more viable and effective option for cancer treatment. As the field continues to evolve, understanding the critical factors that influence the performance of immunocytokines will be essential for successfully translating these therapies into clinical practice.

In silico evaluation of the role of Fab glycosylation in cetuximab antibody dynamics

Introduction

N-glycosylation is a post-translational modification that is highly important for the development of monoclonal antibodies (mAbs), as it regulates their biological activity, particularly in terms of immune effector functions. While typically added at the Fc level, approximately 15-25% of circulating antibodies exhibit glycosylation in the Fab domains as well. To the best of our knowledge, cetuximab (Erbitux®) is the only therapeutic antibody presenting Fab glycosylation approved world-wide targeting the epidermal growth factor receptor for the treatment of metastatic-colorectal and head and neck cancers. Additionally, it can trigger antibody-dependent cell cytotoxicity (ADCC), a response that typically is influenced by N-glycosylation at Fc level. However, the role of Fab glycosylation in cetuximab remains poorly understood. Hence, this study aims to investigate the structural role of Fab glycosylation on the conformational behavior of cetuximab.

Methods

The study was performed in silico via accelerated molecular dynamics simulations. The commercial cetuximab was compared to its form without Fab glycosylation and structural descriptors were evaluated to establish conformational differences.

Results

The results clearly show a correlation between the Fab glycosylation and structural descriptors that may modulate the conformational freedom of the antibody, potentially affecting Fc effector functions, and suggesting a negative role of Fab glycosylation on the interaction with FcγRIIIa.

Conclusion

Fab glycosylation of cetuximab is the most critical challenge for biosimilar development, but the differences highlighted in this work with respect to its aglycosylated form can improve the knowledge and represent also a great opportunity to develop novel strategies of biotherapeutics.

Precision engineering of antibodies: A review of modification and design in the Fab region

The binding of functional groups to antibodies is crucial for disease treatment, diagnosis, and basic scientific research. Traditionally, antibody modifications have focused on the Fc region to maintain antigen-antibody binding activity. However, such modifications may impact critical antibody functions, including immune cell surface receptor activation, cytokine release, and other immune responses. In recent years, modifications targeting the antigen-binding fragment (Fab) region have garnered increasing attention. Precise modifications of the Fab region not only maximize the retention of antigen-antibody binding capacity but also enhance numerous physicochemical properties of antibodies. This paper reviews the chemical, biological, biochemical, and computer-assisted methods for modifying the Fab region of antibodies, discussing their advantages, limitations, recent advances, and future trends.

Pharmacokinetics and Pharmacodynamics of Nipocalimab, a Neonatal Fc Receptor Blocker, in Healthy Japanese Volunteers

BACKGROUND AND OBJECTIVES

Nipocalimab is a high-affinity, fully human, effectorless immunoglobulin G1 monoclonal antibody targeting the neonatal Fc receptor and is currently under evaluation for the treatment of rare and prevalent immunoglobulin G autoantibody-mediated and alloantibody-mediated diseases. This phase I, randomized, double-blind, placebo-controlled, single-dose escalation study in healthy Japanese volunteers (N = 24) assessed the safety, pharmacokinetics, and effect on the serum immunoglobulin G level of single doses of nipocalimab.

METHODS

Volunteers were grouped into three cohorts and received intravenous nipocalimab at 10, 30, or 60 mg/kg or placebo. To complement the study, genetic variation in the Fcγ receptor and transporter subunit of the neonatal Fc receptor was analyzed in Japanese and diverse populations.

RESULTS

Nipocalimab was generally safe and well tolerated at all dose levels, with three (12.5% [3/24]) volunteers experiencing treatment-emergent adverse events across all nipocalimab doses. Mean serum immunoglobulin G levels decreased in a dose-dependent manner from baseline with nipocalimab treatment compared with placebo. Maximum serum nipocalimab concentrations demonstrated proportional increases with dose, while the area under the concentration-time curve was dose dependent and demonstrated non-linear increases with dose. Mean observed half-life was longer as the dose increased. Analysis of genetic variation in Fcγ receptor and transporter identified no unique Japanese variants or variants that alter amino acid sequences in or near the neonatal Fc receptor immunoglobulin G binding site targeted by nipocalimab.

CONCLUSIONS

The comparable pharmacokinetic/pharmacodynamic profiles and highly conserved neonatal Fc receptor structure among diverse populations further support the clinical development of nipocalimab for the treatment of various immunoglobulin G autoantibody-mediated and alloantibody-mediated diseases across global sites and populations, including the Japanese population.

Bispecific and multispecific antibodies in oncology: opportunities and challenges

Research into bispecific antibodies, which are designed to simultaneously bind two antigens or epitopes, has advanced enormously over the past two decades. Owing to advances in protein engineering technologies and considerable preclinical research efforts, bispecific antibodies are constantly being developed and optimized to improve their efficacy and to mitigate toxicity. To date, >200 of these agents, the majority of which are bispecific immune cell engagers, are in either preclinical or clinical evaluation. In this Review, we discuss the role of bispecific antibodies in patients with cancer, including history and development, as well as innovative targeting strategies, clinical applications, and adverse events. We also discuss novel alternative bispecific antibody constructs, such as those targeting two antigens expressed by tumour cells or cells located in the tumour microenvironment. Finally, we consider future research directions in this rapidly evolving field, including innovative antibody engineering strategies, which might enable more effective delivery, overcome resistance, and thus optimize clinical outcomes.

Fc engineering by monoclonal mammalian cell display for improved affinity and selectivity towards FcγRs

Fc optimization can significantly enhance therapeutic efficacy of monoclonal antibodies. However, existing Fc engineering approaches are sub-optimal with noted limitations, such as inappropriate glycosylation, polyclonal libraries, and utilizing fragment but not full-length IgG display. Applying cell cycle arrested recombinase-mediated cassette exchange, this study constructed high-quality monoclonal Fc libraries in CHO cells, displayed full-length IgG on cell surface, and preformed ratiometric fluorescence activated cell sorting (FACS) with the antigen and individual FcγRs. Identified Fc variants were quantitatively evaluated by flow cytometry, ELISA, kinetic and steady-state binding affinity measurements, and cytotoxicity assays. An error-prone Fc library focusing on the hinge-CH2 region was constructed in CHO cells with a functional diversity of 7.5 × 106. Panels of novel Fc variants with enhanced affinity and selectivity for FcγRs were isolated. Particularly, clone 2a-10 (G236E/K288R/K290W/K320M) showed increased binding strength towards FcγRIIa-131R and 131H allotypes with kinetic dissociation constants (KD-K) of 140 nM and 220 nM, respectively, while reduced binding strength towards FcγRIIb compared to WT Fc; clone 2b-1 (K222I/V302E/L328F/K334E) had KD-K of 180 nM towards FcγRIIb; clone 3a-2 (P247L/K248E/K334I) exhibited KD-K of 190 nM and 100 nM towards FcγRIIIa-176F and 176 V allotypes, respectively, and improved potency of 2.0 ng/ml in ADCC assays. Key mutation hotspots were identified, including P247 for FcγRIIIa, K290 for FcγRIIa, and K334 for FcγRIIb bindings. Discovery of Fc variants with enhanced affinity and selectivity towards individual FcγR and the identification of novel mutation hotspots provide valuable insights for further Fc optimization and serve as a foundation for advancing antibody therapeutics development.

New immune cell engagers for cancer immunotherapy

There have been major advances in the immunotherapy of cancer in recent years, including the development of T cell engagers - antibodies engineered to redirect T cells to recognize and kill cancer cells - for the treatment of haematological malignancies. However, the field still faces several challenges to develop agents that are consistently effective in a majority of patients and cancer types, such as optimizing drug dose, overcoming treatment resistance and improving efficacy in solid tumours. A new generation of T cell-targeted molecules was developed to tackle these issues that are potentially more effective and safer. In addition, agents designed to engage the antitumour activities of other immune cells, including natural killer cells and myeloid cells, are showing promise and have the potential to treat a broader range of cancers.

Cancer therapy with antibodies

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

A Perspective on the CD47-SIRPA Axis in High-Risk Neuroblastoma

Neuroblastoma is a pediatric cancer with significant clinical heterogeneity. Despite extensive efforts, it is still difficult to cure children with high-risk neuroblastoma. Immunotherapy is a promising approach to treat children with this devastating disease. We have previously reported that macrophages are important effector cells in high-risk neuroblastoma. In this perspective article, we discuss the potential function of the macrophage inhibitory receptor SIRPA in the homeostasis of tumor-associated macrophages in high-risk neuroblastoma. The ligand of SIRPA is CD47, known as a "don't eat me" signal, which is highly expressed on cancer cells compared to normal cells. CD47 is expressed on both tumor and stroma cells, whereas SIRPA expression is restricted to macrophages in high-risk neuroblastoma tissues. Notably, high SIRPA expression is associated with better disease outcome. According to the current paradigm, the interaction between CD47 on tumor cells and SIRPA on macrophages leads to the inhibition of tumor phagocytosis. However, data from recent clinical trials have called into question the use of anti-CD47 antibodies for the treatment of adult and pediatric cancers. The restricted expression of SIRPA on macrophages in many tissues argues for targeting SIRPA on macrophages rather than CD47 in CD47/SIRPA blockade therapy. Based on the data available to date, we propose that disruption of the CD47-SIRPA interaction by anti-CD47 antibody would shift the macrophage polarization status from M1 to M2, which is inferred from the 1998 study by Timms et al. In contrast, the anti-SIRPA F(ab')2 lacking Fc binds to SIRPA on the macrophage, mimics the CD47-SIRPA interaction, and thus maintains M1 polarization. Anti-SIRPA F(ab')2 also prevents the binding of CD47 to SIRPA, thereby blocking the "don't eat me" signal. The addition of tumor-opsonizing and macrophage-activating antibodies is expected to enhance active tumor phagocytosis.

Development of a highly effective combination monoclonal antibody therapy against Herpes simplex virus

BACKGROUND

Infections with Herpes simplex virus (HSV)-1 or -2 usually present as mild chronic recurrent disease, however in rare cases can result in life-threatening conditions with a large spectrum of pathology. Monoclonal antibody therapy has great potential especially to treat infections with virus resistant to standard therapies. HDIT101, a humanized IgG targeting HSV-1/2 gB was previously investigated in phase 2 clinical trials. The aim of this study was to develop a next-generation therapy by combining different antiviral monoclonal antibodies.

METHODS

A lymph-node derived phage display library (LYNDAL) was screened against recombinant gB from Herpes simplex virus (HSV) -1 and HDIT102 scFv was selected for its binding characteristics using bio-layer interferometry. HDIT102 was further developed as fully human IgG and tested alone or in combination with HDIT101, a clinically tested humanized anti-HSV IgG, in vitro and in vivo. T-cell stimulating activities by antigen-presenting cells treated with IgG-HSV immune complexes were analyzed using primary human cells. To determine the epitopes, the cryo-EM structures of HDIT101 or HDIT102 Fab bound to HSV-1F as well as HSV-2G gB protein were solved at resolutions < 3.5 Å.

RESULTS

HDIT102 Fab showed strong binding to HSV-1F gB with Kd of 8.95 × 10-11 M and to HSV-2G gB with Kd of 3.29 × 10-11 M. Neutralization of cell-free virus and inhibition of cell-to-cell spread were comparable between HDIT101 and HDIT102. Both antibodies induced internalization of gB from the cell surface into acidic endosomes by binding distinct epitopes in domain I of gB and compete for binding. CryoEM analyses revealed the ability to form heterogenic immune complexes consisting of two HDIT102 and one HDIT101 Fab bound to one gB trimeric molecule. Both antibodies mediated antibody-dependent phagocytosis by antigen presenting cells which stimulated autologous T-cell activation. In vivo, the combination of HDIT101 and HDIT102 demonstrated synergistic effects on survival and clinical outcome in immunocompetent BALB/cOlaHsd mice.

CONCLUSION

This biochemical and immunological study showcases the potential of an effective combination therapy with two monoclonal anti-gB IgGs for the treatment of HSV-1/2 induced disease conditions.

Development of pharmacological immunoregulatory anti-cancer therapeutics: current mechanistic studies and clinical opportunities

Immunotherapy represented by anti-PD-(L)1 and anti-CTLA-4 inhibitors has revolutionized cancer treatment, but challenges related to resistance and toxicity still remain. Due to the advancement of immuno-oncology, an increasing number of novel immunoregulatory targets and mechanisms are being revealed, with relevant therapies promising to improve clinical immunotherapy in the foreseeable future. Therefore, comprehending the larger picture is important. In this review, we analyze and summarize the current landscape of preclinical and translational mechanistic research, drug development, and clinical trials that brought about next-generation pharmacological immunoregulatory anti-cancer agents and drug candidates beyond classical immune checkpoint inhibitors. Along with further clarification of cancer immunobiology and advances in antibody engineering, agents targeting additional inhibitory immune checkpoints, including LAG-3, TIM-3, TIGIT, CD47, and B7 family members are becoming an important part of cancer immunotherapy research and discovery, as are structurally and functionally optimized novel anti-PD-(L)1 and anti-CTLA-4 agents and agonists of co-stimulatory molecules of T cells. Exemplified by bispecific T cell engagers, newly emerging bi-specific and multi-specific antibodies targeting immunoregulatory molecules can provide considerable clinical benefits. Next-generation agents also include immune epigenetic drugs and cytokine-based therapeutics. Cell therapies, cancer vaccines, and oncolytic viruses are not covered in this review. This comprehensive review might aid in further development and the fastest possible clinical adoption of effective immuno-oncology modalities for the benefit of patients.

ATG-101 Is a Tetravalent PD-L1×4-1BB Bispecific Antibody That Stimulates Antitumor Immunity through PD-L1 Blockade and PD-L1-Directed 4-1BB Activation

Immune checkpoint inhibitors (ICI) have transformed cancer treatment. However, only a minority of patients achieve a profound response. Many patients are innately resistant while others acquire resistance to ICIs. Furthermore, hepatotoxicity and suboptimal efficacy have hampered the clinical development of agonists of 4-1BB, a promising immune-stimulating target. To effectively target 4-1BB and treat diseases resistant to ICIs, we engineered ATG-101, a tetravalent "2+2″ PD-L1×4-1BB bispecific antibody. ATG-101 bound PD-L1 and 4-1BB concurrently, with a greater affinity for PD-L1, and potently activated 4-1BB+ T cells when cross-linked with PD-L1-positive cells. ATG-101 activated exhausted T cells upon PD-L1 binding, indicating a possible role in reversing T-cell dysfunction. ATG-101 displayed potent antitumor activity in numerous in vivo tumor models, including those resistant or refractory to ICIs. ATG-101 greatly increased the proliferation of CD8+ T cells, the infiltration of effector memory T cells, and the ratio of CD8+ T/regulatory T cells in the tumor microenvironment (TME), rendering an immunologically "cold" tumor "hot." Comprehensive characterization of the TME after ATG-101 treatment using single-cell RNA sequencing further revealed an altered immune landscape that reflected increased antitumor immunity. ATG-101 was well tolerated and did not induce hepatotoxicity in non-human primates. According to computational semimechanistic pharmacology modeling, 4-1BB/ATG-101/PD-L1 trimer formation and PD-L1 receptor occupancy were both maximized at around 2 mg/kg of ATG-101, providing guidance regarding the optimal biological dose for clinical trials. In summary, by localizing to PD-L1-rich microenvironments and activating 4-1BB+ immune cells in a PD-L1 cross-linking-dependent manner, ATG-101 safely inhibits growth of ICI resistant and refractory tumors.

SIGNIFICANCE

The tetravalent PD-L1×4-1BB bispecific antibody ATG-101 activates 4-1BB+ T cells in a PD-L1 cross-linking-dependent manner, minimizing the hepatotoxicity of existing 4-1BB agonists and suppressing growth of ICI-resistant tumors. See related commentary by Ha et al., p. 1546.

Striking the Balance with a PD-L1×4-1BB Bispecific Antibody

Antibody-based immune checkpoint blockade therapy has revolutionized the field of cancer immunotherapy, yet its efficacy remains limited in immunologically cold tumors. Combining checkpoint inhibitors with costimulatory agonists improves tumoricidal activity of T cells but also can lead to off-target hepatotoxicity. Although bispecific antibodies confer tumor selectivity to alleviate undesirable adverse effects, toxicity concerns persist with increased dosing. In this issue of Cancer Research, Yuwen and colleagues introduce ATG-101, a tetravalent PD-L1×4-1BB bispecific antibody with high programmed death ligand 1 (PD-L1) affinity and low 4-1BB affinity, aiming to mitigate hepatotoxicity. ATG-101 demonstrates PD-L1-dependent 4-1BB activation, leading to selective T-cell activation within the tumor microenvironment. ATG-101 exhibits potent antitumor activity, even in large, immunologically cold, and monotherapy-resistant tumor models. Single-cell RNA sequencing reveals significant shifts of immune cell populations in the tumor microenvironment from protumor to antitumor phenotypes following ATG-101 treatment. In cynomolgus monkeys, no serious cytokine storm and hepatotoxicity are observed after ATG-101 treatment, indicating a broad therapeutic window for ATG-101 in cancer treatment. This study highlights the potential of tetravalent bispecific antibodies in cancer immunotherapy, with implications for various antibody-based treatment modalities across different fields. See related article by Yuwen et al., p. 1680.

Receptor transfer between immune cells by autoantibody-enhanced, CD32-driven trogocytosis is hijacked by HIV-1 to infect resting CD4 T cells

Immune cell phenotyping frequently detects lineage-unrelated receptors. Here, we report that surface receptors can be transferred from primary macrophages to CD4 T cells and identify the Fcγ receptor CD32 as driver and cargo of this trogocytotic transfer. Filamentous CD32+ nanoprotrusions deposit distinct plasma membrane patches onto target T cells. Transferred receptors confer cell migration and adhesion properties, and macrophage-derived membrane patches render resting CD4 T cells susceptible to infection by serving as hotspots for HIV-1 binding. Antibodies that recognize T cell epitopes enhance CD32-mediated trogocytosis. Such autoreactive anti-HIV-1 envelope antibodies can be found in the blood of HIV-1 patients and, consistently, the percentage of CD32+ CD4 T cells is increased in their blood. This CD32-mediated, antigen-independent cell communication mode transiently expands the receptor repertoire and functionality of immune cells. HIV-1 hijacks this mechanism by triggering the generation of trogocytosis-promoting autoantibodies to gain access to immune cells critical to its persistence.

Enhanced therapeutic potential of antibody fragment via IEDDA-mediated site-specific albumin conjugation

BACKGROUND

The use of single-chain variable fragments (scFvs) for treating human diseases, such as cancer and immune system disorders, has attracted significant attention. However, a critical drawback of scFv is its extremely short serum half-life, which limits its therapeutic potential. Thus, there is a critical need to prolong the serum half-life of the scFv for clinical applications. One promising serum half-life extender for therapeutic proteins is human serum albumin (HSA), which is the most abundant protein in human serum, known to have an exceptionally long serum half-life. However, conjugating a macromolecular half-life extender to a small protein, such as scFv, often results in a significant loss of its critical properties.

RESULTS

In this study, we conjugated the HSA to a permissive site of scFv to improve pharmacokinetic profiles. To ensure minimal damage to the antigen-binding capacity of scFv upon HSA conjugation, we employed a site-specific conjugation approach using a heterobifunctional crosslinker that facilitates thiol-maleimide reaction and inverse electron-demand Diels-Alder reaction (IEDDA). As a model protein, we selected 4D5scFv, derived from trastuzumab, a therapeutic antibody used in human epithermal growth factor 2 (HER2)-positive breast cancer treatment. We introduced a phenylalanine analog containing a very reactive tetrazine group (frTet) at conjugation site candidates predicted by computational methods. Using the linker TCO-PEG4-MAL, a single HSA molecule was site-specifically conjugated to the 4D5scFv (4D5scFv-HSA). The 4D5scFv-HSA conjugate exhibited HER2 binding affinity comparable to that of unmodified 4D5scFv. Furthermore, in pharmacokinetic profile in mice, the serum half-life of 4D5scFv-HSA was approximately 12 h, which is 85 times longer than that of 4D5scFv.

CONCLUSIONS

The antigen binding results and pharmacokinetic profile of 4D5scFv-HSA demonstrate that the site-specifically albumin-conjugated scFv retained its binding affinity with a prolonged serum half-life. In conclusion, we developed an effective strategy to prepare site-specifically albumin-conjugated 4D5scFv, which can have versatile clinical applications with improved efficacy.

A Dual-domain Engineered Antibody for Efficient HBV Suppression and Immune Responses Restoration

Chronic hepatitis B (CHB) remains a major public health concern because of the inefficiency of currently approved therapies in clearing the hepatitis B surface antigen (HBsAg). Antibody-based regimens have demonstrated potency regarding virus neutralization and HBsAg clearance. However, high dosages or frequent dosing are required for virologic control. In this study, a dual-domain-engineered anti-hepatitis B virus (HBV) therapeutic antibody 73-DY is developed that exhibits significantly improved efficacy regarding both serum and intrahepatic viral clearance. In HBV-tolerant mice, administration of a single dose of 73-DY at 2 mg kg-1 is sufficient to reduce serum HBsAg by over 3 log10 IU mL-1 and suppress HBsAg to < 100 IU mL-1 for two weeks, demonstrating a dose-lowering advantage of at least tenfold. Furthermore, 10 mg kg-1 of 73-DY sustainably suppressed serum viral levels to undetectable levels for ≈ 2 weeks. Molecular analyses indicate that the improved efficacy exhibited by 73-DY is attributable to the synergy between fragment antigen binding (Fab) and fragment crystallizable (Fc) engineering, which conferred sustained viral suppression and robust viral eradication, respectively. Long-term immunotherapy with reverse chimeric 73-DY facilitated the restoration of anti-HBV immune responses. This study provides a foundation for the development of next-generation antibody-based CHB therapies.

New, Old, and Shared Antibody Specificities in Autoimmune Diseases

Autoantibodies represent a primary characteristic of many systemic autoimmune diseases [...].

Effector functions are required for broad and potent protection of neonatal mice with antibodies targeting HSV glycoprotein D

Multiple failed herpes simplex virus (HSV) vaccine candidates induce robust neutralizing antibody (Ab) responses in clinical trials, raising the hypothesis that Fc-domain-dependent effector functions may be critical for protection. While neonatal HSV (nHSV) infection results in mortality and lifelong neurological morbidity in humans, it is uncommon among neonates with a seropositive birthing parent, supporting the hypothesis that Ab-based therapeutics could protect neonates from HSV. We therefore investigated the mechanisms of monoclonal Ab (mAb)-mediated protection in a mouse model of nHSV infection. For a panel of glycoprotein D (gD)-specific mAbs, neutralization and effector functions contributed to nHSV-1 protection. In contrast, effector functions alone were sufficient to protect against nHSV-2, exposing a functional dichotomy between virus types consistent with vaccine trial results. Effector functions are therefore crucial for protection by these gD-specific mAbs, informing effective Ab and vaccine design and demonstrating the potential of polyfunctional Abs as therapeutics for nHSV infections.

Development and characterization of DIA 12.3, a fully human intact anti-CEACAM1 monoclonal antibody

Carcinoembryonic antigen cell adhesion molecule-1 (CEACAM1), a homotypic cell adhesion molecule glycoprotein with apical expression on normal epithelial cells and activated lymphocytes, is overexpressed on many tumors and acts as an inhibitory receptor on NK cells, preventing their killing of CEACAM1 positive tumors. Production of humanized anti-CEACAM1 antibodies to block the inhibitory activity of CEACAM1 for immunotherapy and immunoimaging. Starting from a scFv, a fully human intact anti-CEACAM1 (DIA 12.3) that recognizes the N-terminal domain of CEACAM1 was developed and shown to bind CEACAM1 positive tumor cells and enhanced NK cell killing of CEACAM1 positive targets. DIA 12.3 bound to human neutrophils without activation, indicating they would be safe for human use. DIA 12.3 exhibited some cross-reactivity to CEACAM5, a tumor marker with high sequence homology to the N-terminal domain of CEACAM1. CEACAM1 PET imaging with 64Cu-COTA-DIA 12.3 showed excellent imaging of CEACAM1 positive tumors with reduced binding to CEACAM5 tumors. Based on its immunoinhibitory an immunoimaging activities, DIA 12.3 shows promise for therapeutic studies in man.

Protocol of a first-in-human clinical trial to evaluate the safety, tolerability, and preliminary efficacy of the bispecific CD276xCD3 antibody CC-3 in patients with colorectal cancer (CoRe_CC-3)

Introduction

Colorectal cancer (CRC) is the third most common cancer worldwide in men and women. In the metastasized stage, treatment options and prognosis are limited. To address the high medical need of this patient population, we generated a CD276xCD3 bispecific antibody termed CC-3. CD276 is expressed on CRC cells and on tumor vessels, thereby allowing for a "dual" anticancer effect.

Methods and analysis

This first-in-human clinical study is planned as a prospective multicenter trial, enrolling patients with metastatic CRC after three lines of therapy. During the dose-escalation part, initially, an accelerated titration design with single-patient cohorts is employed. Here, each patient will receive a fixed dose level (starting with 50 µg for the first patient); however, between patients, dose level may be increased by up to 100%, depending on the decision of a safety review committee. Upon occurrence of any adverse events (AEs) grade ≥2, dose-limiting toxicity (DLT), or reaching a dose level of ≥800 µg, the escalation will switch to a standard 3 + 3 dose design. After maximum tolerated dose (MTD) has been determined, defined as no more than one of the six patients experiencing DLT, an additional 14 patients receive CC-3 at the MTD level in the dose-expansion phase. Primary endpoints are incidence and severity of AEs, as well as the best objective response to the treatment according to response evaluation criteria in solid tumors (RECIST) 1.1. Secondary endpoints include overall safety, efficacy, survival, quality of life, and pharmacokinetic investigations.

Ethics and dissemination

The CD276xCD3 study was approved by the Ethics Committee of the Medical Faculty of the Heinrich Heine University Düsseldorf and the Paul-Ehrlich-Institut (P00702). Clinical trial results will be published in peer-reviewed journals. Trial registration numbers: ClinicalTrials.cov Registry (NCT05999396) and EU ClinicalTrials Registry (EU trial number 2022-503084-15-00).

High-Throughput Glycan Profiling of Human Serum IgG Subclasses Using Parallel Reaction Monitoring Peptide Bond Fragmentation of Glycopeptides and Microflow LC-MS

LC-MS-based N-glycosylation profiling in four human serum IgG subclasses (IgG1, IgG2, IgG3, and IgG4) often requires additional affinity-based enrichment of specific IgG subclasses, owing to the high amino acid sequence similarity of Fc glycopeptides among subclasses. Notably, for IgG4 and the major allotype of IgG3, the glycopeptide precursors share identical retention time and mass and therefore cannot be distinguished based on precursor or glycan fragmentation. Here, we developed a parallel reaction monitoring (PRM)-based method for quantifying Fc glycopeptides through combined transitions generated from both glycosidic and peptide bond fragmentation. The latter enables the subpopulation of IgG3 and IgG4 to be directly distinguished according to mass differences without requiring further enrichment of specific IgG subclasses. In addition, a multinozzle electrospray emitter coupled to a capillary flow liquid chromatograph was used to increase the robustness and detection sensitivity of the method for low-yield peptide backbone fragment ions. The gradient was optimized to decrease the overall run time and make the method compatible with high-throughput analysis. We demonstrated that this method can be used to effectively monitor the relative levels of 13 representative glycoforms, with a good limit of detection for individual IgG subclasses.