A real-time antibody-dependent cellular phagocytosis assay by live cell imaging.

Antibody-dependent cellular phagocytosis (ADCP) is a cellular process by which antibody-opsonized targets (pathogens or cells) activate the Fc receptors on the surface of phagocytes to induce phagocytosis, resulting in internalization and degradation of pathogens or target cells through phagosome acidification. Besides NK cells-mediated antibody-dependent cellular cytotoxicity (ADCC), tumor-infiltrated monocytes and macrophages can directly kill tumor cells in the presence of tumor antigen-specific antibodies through ADCP, representing another attractive strategy for cancer immunotherapy. Even though several methods have been developed to measure ADCP, an automated and high-throughput quantitative assay should offer highly desirable advantages for drug discovery.

Preclinical and translational pharmacology of afucosylated anti-CCR8 antibody for depletion of tumour-infiltrating regulatory T cells.

Background And Purpose: RO7502175 is an afucosylated antibody designed to eliminate C-C motif chemokine receptor 8 (CCR8) Treg cells in the tumour microenvironment through enhanced antibody-dependent cellular cytotoxicity (ADCC).

Experimental Approach: We report findings from preclinical studies characterizing pharmacology, pharmacokinetics (PK)/pharmacodynamics (PD) and safety profile of RO7502175 and discuss the translational PK/PD approach used to inform first-in-human (FiH) dosing strategy and clinical development in solid tumour indications.

Key Results: RO7502175 demonstrated selective ADCC against human CCR8 Treg cells from dissociated tumours in vitro.

Application of N-Terminal Site-Specific Biotin and Digoxigenin Conjugates to Clinical Anti-drug Antibody Assay Development.

Biotin- and digoxigenin (DIG)-conjugated therapeutic drugs are critical reagents used for the development of anti-drug antibody (ADA) assays for the assessment of immunogenicity. The current practice of generating biotin and DIG conjugates is to label a therapeutic antibody with biotin or DIG via primary amine groups on lysine or N-terminal residues. This approach modifies lysine residues nonselectively, which can impact the ability of an ADA assay to detect those ADAs that recognize epitopes located at or near the modified lysine residue(s).

Structural basis of antibody inhibition and chemokine activation of the human CC chemokine receptor 8.

The C-C motif chemokine receptor 8 (CCR8) is a class A G-protein coupled receptor that has emerged as a promising therapeutic target in cancer. Targeting CCR8 with an antibody has appeared to be an attractive therapeutic approach, but the molecular basis for chemokine-mediated activation and antibody-mediated inhibition of CCR8 are not fully elucidated. Here, we obtain an antagonist antibody against human CCR8 and determine structures of CCR8 in complex with either the antibody or the endogenous agonist ligand CCL1.

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.

A novel, label-free, pre-equilibrium assay to determine the association and dissociation rate constants of therapeutic antibodies on living cells.

Background And Purpose: Monoclonal antibodies (Ab) represent the fastest growing drug class. Knowledge of the biophysical parameters (k, k and K) that dictate Ab:receptor interaction is critical during the drug discovery process. However, with the increasing complexity of Ab formats and their targets, it became apparent that existing technologies present limitations and are not always suitable to determine these parameters.

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.

Dual antibody inhibition of KLK5 and KLK7 for Netherton syndrome and atopic dermatitis.

The epidermis is a barrier that prevents water loss while keeping harmful substances from penetrating the host. The impermeable cornified layer of the stratum corneum is maintained by balancing continuous turnover driven by epidermal basal cell proliferation, suprabasal cell differentiation, and corneal shedding. The epidermal desquamation process is tightly regulated by balance of the activities of serine proteases of the Kallikrein-related peptidases (KLK) family and their cognate inhibitor lymphoepithelial Kazal type-related inhibitor (LEKTI), which is encoded by the serine peptidase inhibitor Kazal type 5 gene.

Systematic pharmacological analysis of agonistic and antagonistic fibroblast growth factor receptor 1 MAbs reveals a similar unique mode of action.

Fibroblast growth factor receptor 1 (FGFR1) is a receptor tyrosine kinase that plays a major role in developmental processes and metabolism. The dysregulation of FGFR1 through genetic aberrations leads to skeletal and metabolic diseases as well as cancer. For this reason, FGFR1 is a promising therapeutic target, yet a very challenging one due to potential on-target toxicity.

Development of an F-labeled anti-human CD8 VHH for same-day immunoPET imaging.

Purpose: Cancer immunotherapies (CITs) have revolutionized the treatment of certain cancers, but many patients fail to respond or relapse from current therapies, prompting the need for new CIT agents. CD8 T cells play a central role in the activity of many CITs, and thus, the rapid imaging of CD8 cells could provide a critical biomarker for new CIT agents. However, existing Zr-labeled CD8 PET imaging reagents exhibit a long circulatory half-life and high radiation burden that limit potential applications such as same-day and longitudinal imaging.

Structure of the core human NADPH oxidase NOX2.

NOX2 is the prototypical member of the NADPH oxidase NOX superfamily and produces superoxide (O), a key reactive oxygen species (ROS) that is essential in innate and adaptive immunity. Mutations that lead to deficiency in NOX2 activity correlate with increased susceptibility to bacterial and fungal infections, resulting in chronic granulomatous disease. The core of NOX2 is formed by a heterodimeric transmembrane complex composed of NOX2 (formerly gp91) and p22, but a detailed description of its structural architecture is lacking.

Genome-wide association study identifies kallikrein 5 in type 2 inflammation-low asthma.

Background: Clinical studies of type 2 (T2) cytokine-related neutralizing antibodies in asthma have identified a substantial subset of patients with low levels of T2 inflammation who do not benefit from T2 cytokine neutralizing antibody treatment. Non-T2 mechanisms are poorly understood in asthma but represent a redefined unmet medical need.

Objective: We sought to gain a better understanding of genetic contributions to T2-low asthma.

Loss of the intracellular enzyme QPCTL limits chemokine function and reshapes myeloid infiltration to augment tumor immunity.

Tumor-associated macrophages are composed of distinct populations arising from monocytes or tissue macrophages, with a poorly understood link to disease pathogenesis. Here, we demonstrate that mouse monocyte migration was supported by glutaminyl-peptide cyclotransferase-like (QPCTL), an intracellular enzyme that mediates N-terminal modification of several substrates, including the monocyte chemoattractants CCL2 and CCL7, protecting them from proteolytic inactivation. Knockout of Qpctl disrupted monocyte homeostasis, attenuated tumor growth and reshaped myeloid cell infiltration, with loss of monocyte-derived populations with immunosuppressive and pro-angiogenic profiles.

Development of an SPR-based binding assay for characterization of anti-CD20 antibodies to CD20 expressed on extracellular vesicles.

Characterization of anti-CD20 antibody binding to CD20 is critical to development of anti-CD20 therapeutics. While SPR is widely used to characterize binding of therapeutics to their targets, its application to the characterization of anti-CD20 therapeutics has been limited by the challenges of obtaining recombinant or native full-length CD20 suitable for ligand binding assays. Extracellular vesicles (EVs) are nanoparticles naturally released from cells that provide a favorable microenvironment for membrane proteins such as CD20 to maintain proper conformation and activity.

Conformation-locking antibodies for the discovery and characterization of KRAS inhibitors.

Small molecules that stabilize inactive protein conformations are an underutilized strategy for drugging dynamic or otherwise intractable proteins. To facilitate the discovery and characterization of such inhibitors, we created a screening platform to identify conformation-locking antibodies for molecular probes (CLAMPs) that distinguish and induce rare protein conformational states. Applying the approach to KRAS, we discovered CLAMPs that recognize the open conformation of KRAS stabilized by covalent inhibitors.

Antibody toolkit reveals N-terminally ubiquitinated substrates of UBE2W.

The ubiquitin conjugating enzyme UBE2W catalyzes non-canonical ubiquitination on the N-termini of proteins, although its substrate repertoire remains unclear. To identify endogenous N-terminally-ubiquitinated substrates, we discover four monoclonal antibodies that selectively recognize tryptic peptides with an N-terminal diglycine remnant, corresponding to sites of N-terminal ubiquitination. Importantly, these antibodies do not recognize isopeptide-linked diglycine (ubiquitin) modifications on lysine.

Imaging Reveals Importance of Shape and Flexibility for Glomerular Filtration of Biologics.

Advances in antibody engineering have enabled the construction of novel molecular formats in diverse shapes and sizes, providing new opportunities for cancer immunotherapeutic drug discovery while also revealing limitations in knowledge of structure-activity relationships. The current understanding of renal filtration originates largely from data reported for dextrans, IgG, albumin, and selected globular proteins. For a one-armed IgG-based T-cell imaging agent, we observed higher renal signal than typically observed for bivalent IgGs, prompting us to explore the factors governing renal filtration of biologics.

Discovery of a caspase cleavage motif antibody reveals insights into noncanonical inflammasome function.

Inflammasomes sense a number of pathogen and host damage signals to initiate a signaling cascade that triggers inflammatory cell death, termed pyroptosis. The inflammatory caspases (1/4/5/11) are the key effectors of this process through cleavage and activation of the pore-forming protein gasdermin D. Caspase-1 also activates proinflammatory interleukins, IL-1β and IL-18, via proteolysis.

Preclinical optimization of Ly6E-targeted ADCs for increased durability and efficacy of anti-tumor response.

Early success with brentuximab vedotin in treating classical Hodgkin lymphoma spurred an influx of at least 20 monomethyl auristatin E (MMAE) antibody-drug conjugates (ADCs) into clinical trials. While three MMAE-ADCs have been approved, most of these conjugates are no longer being investigated in clinical trials. Some auristatin conjugates show limited or no efficacy at tolerated doses, but even for drugs driving initial remissions, tumor regrowth and metastasis often rapidly occur.

Bivalent antibody pliers inhibit β-tryptase by an allosteric mechanism dependent on the IgG hinge.

Human β-tryptase, a tetrameric trypsin-like serine protease, is an important mediator of allergic inflammatory responses in asthma. Antibodies generally inhibit proteases by blocking substrate access by binding to active sites or exosites or by allosteric modulation. The bivalency of IgG antibodies can increase potency via avidity, but has never been described as essential for activity.

Development of a specific immunoassay to selectively measure active tryptase in airway samples.

Tryptase is a tetrameric trypsin-like serine protease contained within the secretory granules of mast cells and is an important mediator of allergic inflammatory responses in respiratory diseases. Detection of active tryptase in the airway may provide important information about asthma and other respiratory diseases. An activity based probe has been incorported within an immunoassay to allow for measurement of active tryptase in human tissues.

Structure of CD20 in complex with the therapeutic monoclonal antibody rituximab.

Cluster of differentiation 20 (CD20) is a B cell membrane protein that is targeted by monoclonal antibodies for the treatment of malignancies and autoimmune disorders but whose structure and function are unknown. Rituximab (RTX) has been in clinical use for two decades, but how it activates complement to kill B cells remains poorly understood. We obtained a structure of CD20 in complex with RTX, revealing CD20 as a compact double-barrel dimer bound by two RTX antigen-binding fragments (Fabs), each of which engages a composite epitope and an extensive homotypic Fab:Fab interface.

Effect of Modulating FcRn Binding on Direct and Pretargeted Tumor Uptake of Full-length Antibodies.

Full-length antibodies lack ideal pharmacokinetic properties for rapid targeted imaging, prompting the pursuit of smaller peptides and fragments. Nevertheless, studying the disposition properties of antibody-based imaging agents can provide critical insight into the pharmacology of their therapeutic counterparts, particularly for those coupled with potent payloads. Here, we evaluate modulation of binding to the neonatal Fc receptor (FcRn) as a protein engineering-based pharmacologic strategy to minimize the overall blood pool background with directly labeled antibodies and undesirable systemic click reaction of radiolabeled tetrazine with circulating pretargeted -cyclooctene (TCO)-modified antibodies.