Functional humanization of immunoglobulin heavy constant gamma 1 Fc domain human FCGRT transgenic mice

Effect of FcRn Binding on Monoclonal Antibody Disposition in the Brain

This study investigates the role of FcRn in brain disposition of monoclonal antibodies. Human FcRn (hFcRn) expressing mice and different FcRn binding variants of a non-target binding antibody trastuzumab (WT) were used for the investigation. The FcRn binding mutations were: YTE, YPY, YQAY, and IHH. YQAY and YPY mutants have enhanced FcRn binding at both neutral and acidic pH (7+/6+). YTE mutant has enhanced FcRn binding at only acidic pH (7-/6+), and IHH mutant has no FcRn binding (7-/6-). The pharmacokinetics (PK) of these mutants in plasma, brain interstitial fluid (ISF), and brain homogenate were measured following intravenous administration. The area under the concentration-time curve (AUC) for all PK profiles and ratios of brain and plasma AUCs were calculated for comparison. Results showed that WT antibody had brain:plasma AUC ratio of 0.70% and ISF:plasma AUC ratio of 0.59%. Among all mutants, YPY exhibited the highest AUC ratio for brain (3.86%) and ISF (3.49%). YQAY had relatively high AUC ratios of 1.49% in the brain and 0.81% in ISF. YTE showed a similar AUC ratio in the brain (0.60%) and ISF (0.62%) compared to WT, while IHH exhibited similar AUC ratio in the brain (0.52%) but higher AUC ratio in ISF (2.48%). The results suggest that binding to FcRn at neutral and acidic pH facilitates transcytosis of antibody into the brain. Just increasing the binding to FcRn at acidic pH does not impact the disposition of antibody in the brain. Complete removal of FcRn binding might lead to prolonged retention of antibody in ISF. Together, these data demonstrate that FcRn significantly affects brain disposition of antibody, and engineering of Fc domain to alter the binding of antibody to FcRn may be exploited to achieve better exposure of antibodies in the brain.

Application of humanized mice in the safety experiments of antibody drugs

Therapeutic antibodies are valued for their high specificity and selectivity in immunotherapy. However, the potential toxicity they may elicit underscores the necessity of assessing their preclinical efficacy and safety using suitable animal models. In this context, we review the various categories and applications of humanized mice, which have been engrafted with human cells or tissues to mimic the human immune system. These models are extensively utilized in the nonclinical assessment and development of various antibody drugs, acting as a conduit to clinical research. However, several challenges remain, including the limited lifespan of humanized mice, inadequate engraftment of human cells, and the rudimentary nature of the immune environment in these models. The development of humanized immune system models in mice presents both opportunities and challenges, potentially leading to new insights into the evolution and application of antibody therapeutics.

Pre-exposure antibody prophylaxis protects macaques from severe influenza

Influenza virus pandemics and seasonal epidemics have claimed countless lives. Recurrent zoonotic spillovers of influenza viruses with pandemic potential underscore the need for effective countermeasures. In this study, we show that pre-exposure prophylaxis with broadly neutralizing antibody (bnAb) MEDI8852 is highly effective in protecting cynomolgus macaques from severe disease caused by aerosolized highly pathogenic avian influenza H5N1 virus infection. Protection was antibody dose-dependent yet independent of Fc-mediated effector functions at the dose tested. Macaques receiving MEDI8852 at 10 milligrams per kilogram or higher had negligible impairment of respiratory function after infection, whereas control animals were not protected from severe disease and fatality. Given the breadth of MEDI8852 and other bnAbs, we anticipate that protection from unforeseen pandemic influenza A viruses is achievable.

A humanized monoclonal antibody targeting an ectonucleotidase rescues cardiac metabolism and heart function after myocardial infarction

Myocardial infarction (MI) results in aberrant cardiac metabolism, but no therapeutics have been designed to target cardiac metabolism to enhance heart repair. We engineer a humanized monoclonal antibody against the ectonucleotidase ENPP1 (hENPP1mAb) that targets metabolic crosstalk in the infarcted heart. In mice expressing human ENPP1, systemic administration of hENPP1mAb metabolically reprograms myocytes and non-myocytes and leads to a significant rescue of post-MI heart dysfunction. Using metabolomics, single-nuclear transcriptomics, and cellular respiration studies, we show that the administration of the hENPP1mAb induces organ-wide metabolic and transcriptional reprogramming of the heart that enhances myocyte cellular respiration and decreases cell death and fibrosis in the infarcted heart. Biodistribution and safety studies showed specific organ-wide distribution with the antibody being well tolerated. In humanized animals, with drug clearance kinetics similar to humans, we demonstrate that a single "shot" of the hENPP1mAb after MI is sufficient to rescue cardiac dysfunction.

Human IgG Fc-engineering for enhanced plasma half-life, mucosal distribution and killing of cancer cells and bacteria

Monoclonal IgG antibodies constitute the fastest growing class of therapeutics. Thus, there is an intense interest to design more potent antibody formats, where long plasma half-life is a commercially competitive differentiator affecting dosing, frequency of administration and thereby potentially patient compliance. Here, we report on an Fc-engineered variant with three amino acid substitutions Q311R/M428E/N434W (REW), that enhances plasma half-life and mucosal distribution, as well as allows for needle-free delivery across respiratory epithelial barriers in human FcRn transgenic mice. In addition, the Fc-engineered variant improves on-target complement-mediated killing of cancer cells as well as both gram-positive and gram-negative bacteria. Hence, this versatile Fc technology should be broadly applicable in antibody design aiming for long-acting prophylactic or therapeutic interventions.

Assessing developability early in the discovery process for novel biologics

Beyond potency, a good developability profile is a key attribute of a biological drug. Selecting and screening for such attributes early in the drug development process can save resources and avoid costly late-stage failures. Here, we review some of the most important developability properties that can be assessed early on for biologics. These include the influence of the source of the biologic, its biophysical and pharmacokinetic properties, and how well it can be expressed recombinantly. We furthermore present in silico, in vitro, and in vivo methods and techniques that can be exploited at different stages of the discovery process to identify molecules with liabilities and thereby facilitate the selection of the most optimal drug leads. Finally, we reflect on the most relevant developability parameters for injectable versus orally delivered biologics and provide an outlook toward what general trends are expected to rise in the development of biologics.

FSH-blocking therapeutic for osteoporosis

Pharmacological and genetic studies over the past decade have established the follicle-stimulating hormone (FSH) as an actionable target for diseases affecting millions, namely osteoporosis, obesity, and Alzheimer's disease. Blocking FSH action prevents bone loss, fat gain, and neurodegeneration in mice. We recently developed a first-in-class, humanized, epitope-specific FSH-blocking antibody, MS-Hu6, with a KD of 7.52 nM. Using a Good Laboratory Practice (GLP)-compliant platform, we now report the efficacy of MS-Hu6 in preventing and treating osteoporosis in mice and parameters of acute safety in monkeys. Biodistribution studies using 89Zr-labeled, biotinylated or unconjugated MS-Hu6 in mice and monkeys showed localization to bone and bone marrow. The MS-Hu6 displayed a β phase t½ of 7.5 days (180 hr) in humanized Tg32 mice. We tested 217 variations of excipients using the protein thermal shift assay to generate a final formulation that rendered MS-Hu6 stable in solution upon freeze-thaw and at different temperatures, with minimal aggregation, and without self-, cross-, or hydrophobic interactions or appreciable binding to relevant human antigens. The MS-Hu6 showed the same level of "humanness" as human IgG1 in silico and was non-immunogenic in ELISpot assays for IL-2 and IFN-γ in human peripheral blood mononuclear cell cultures. We conclude that MS-Hu6 is efficacious, durable, and manufacturable, and is therefore poised for future human testing.

Biophysical differences in IgG1 Fc-based therapeutics relate to their cellular handling, interaction with FcRn and plasma half-life

Antibody-based therapeutics (ABTs) are used to treat a range of diseases. Most ABTs are either full-length IgG1 antibodies or fusions between for instance antigen (Ag)-binding receptor domains and the IgG1 Fc fragment. Interestingly, their plasma half-life varies considerably, which may relate to how they engage the neonatal Fc receptor (FcRn). As such, there is a need for an in-depth understanding of how different features of ABTs affect FcRn-binding and transport behavior. Here, we report on how FcRn-engagement of the IgG1 Fc fragment compare to clinically relevant IgGs and receptor domain Fc fusions, binding to VEGF or TNF-α. The results reveal FcRn-dependent intracellular accumulation of the Fc, which is in line with shorter plasma half-life than that of full-length IgG1 in human FcRn-expressing mice. Receptor domain fusion to the Fc increases its half-life, but not to the extent of IgG1. This is mirrored by a reduced cellular recycling capacity of the Fc-fusions. In addition, binding of cognate Ag to ABTs show that complexes of similar size undergo cellular transport at different rates, which could be explained by the biophysical properties of each ABT. Thus, the study provides knowledge that should guide tailoring of ABTs regarding optimal cellular sorting and plasma half-life.

Analysis of clinically approved antibody-based therapeutics reveals different structural designs, such as full-length IgG1 or Fc-fusions, entail distinct biophysical properties that affect FcRn binding, intracellular transport and plasma half-life.

Next-Generation Sequencing analysis discloses genes implicated in equine endometrosis that may lead to tumorigenesis

Endometrosis is a periglandular fibrosis associated with dysfunction of affected glandular epithelial cells that is the most common cause of reduced fertility in mares, although it is not fully understood. The etiology of the disease is still partially unknown. This study focuses on understanding the genetic mechanisms potentially underlying endometrosis in mares using the Next Generation Sequencing (NGS) technique. Endometrial samples, used in the study, were obtained in the anestrus phase both from healthy mares and those diagnosed with endometrosis. The NGS data were analyzed for gene involvement in biological processes and pathways (e.g. STAR, KOBAS-I, STRING, and ClustVis software). Bioinformatic analysis revealed differential expression of 55 transcripts. In tissues with endometrosis, most genes displayed upregulated expression. The protein-protein interaction analysis disclosed a substantial transcript network including transcripts related to metabolism e.g. sulfur metabolism (SELENBP1), ovarian steroidogenesis, steroid hormone biosynthesis, and chemical carcinogenesis (CYP1B1), COXs (COX4I1, COX3, UQCRFS1) as well as transcripts related to immune response e.g. MMP7, JCHAIN, PIGR, CALR, B2M, FCGRT. Interestingly, the latter has been previously linked with various pathologies including cancers in the female reproductive system. In conclusion, this study evaluated genes that are not directly impacted by sex hormone feedback, but that create a metabolic and immune environment in tissues, thus influencing fertility and pregnancy in mares with endometrosis. Moreover, some of the identified genes may be implicated in tumorigenesis of endometrial lesions. These data may be useful as a starting point in further research, such as the development of targeted strategies for rapid diagnosis and/or prevention of this pathology based on gene and protein-protein interactions.

A novel mouse strain optimized for chronic human antibody administration

Species differences in IgG Fc–Fcγ receptor (FcγR) interactions have made humanized mouse models an attractive strategy to evaluate the efficacy and toxicity of human antibodies. We previously published a humanized FcγR mouse model that fully recapitulates the expression and function of these receptors in vivo. However, the immunogenicity of exogenous human IgG has made long-term assessment of antibody function challenging, since endogenous mouse anti-human IgG responses limit the duration and success of these studies. Here, we present a mouse strain that expresses human IgG1 and FcγRs, thereby conferring tolerance to chronic administration of human IgG and enabling functional assessment of antibodies. Because this strain is appropriate for chronic disease models, we expect that researchers will benefit from its use.

Therapeutic human IgG antibodies are routinely tested in mouse models of oncologic, infectious, and autoimmune diseases. However, assessing the efficacy and safety of long-term administration of these agents has been limited by endogenous anti-human IgG immune responses that act to clear human IgG from serum and relevant tissues, thereby reducing their efficacy and contributing to immune complex–mediated pathologies, confounding evaluation of potential toxicity. For this reason, human antibody treatment in mice is generally limited in duration and dosing, thus failing to recapitulate the potential clinical applications of these therapeutics. Here, we report the development of a mouse model that is tolerant of chronic human antibody administration. This model combines both a human IgG1 heavy chain knock-in and a full recapitulation of human Fc receptor (FcγR) expression, providing a unique platform for in vivo testing of human monoclonal antibodies with relevant receptors beyond the short term. Compared to controls, hIgG1 knock-in mice mount minimal anti-human IgG responses, allowing for the persistence of therapeutically active circulating human IgG even in the late stages of treatment in chronic models of immune thrombocytopenic purpura and metastatic melanoma.

Prevention of diabetes-associated fibrosis: Strategies in FcRn-targeted nanosystems for oral drug delivery

Diabetes mellitus is a chronic disease with an elevated risk of micro- and macrovascular complications, such as fibrosis. To prevent diabetes-associated fibrosis, the symptomatology of diabetes must be controlled, which is commonly done by subcutaneous injection of antidiabetic peptides. To minimize the pain and distress associated with such injections, there is an urgent need for non-invasive oral transmucosal drug delivery strategies. However, orally administered peptide-based drugs are exposed to harsh conditions in the gastrointestinal tract and poorly cross the selective intestinal epithelium. Thus, targeting of drugs to receptors expressed in epithelial cells, such as the neonatal Fc receptor (FcRn), may therefore enhance uptake and transport through mucosal barriers. This review compiles how in-depth studies of FcRn biology and engineering of receptor-binding molecules may pave the way for design of new classes of FcRn-targeted nanosystems. Tailored strategies may open new avenues for oral drug delivery and provide better treatment options for diabetes and, consequently, fibrosis prevention.

Perspective: Quality Versus Quantity; Is It Important to Assess the Role of Enhancers in Complex Disease from an In Vivo Perspective?

Sequencing of the human genome has permitted the development of genome-wide association studies (GWAS) to analyze the genetics of a number of complex disorders such as depression, anxiety and substance abuse. Thanks to their ability to analyze huge cohort sizes, these studies have successfully identified thousands of loci associated with a broad spectrum of complex diseases. Disconcertingly, the majority of these GWAS hits occur in non-coding regions of the genome, much of which controls the cell-type-specific expression of genes essential to health. In contrast to gene coding sequences, it is a challenge to understand the function of this non-coding regulatory genome using conventional biochemical techniques in cell lines. The current commentary scrutinizes the field of complex genetics from the standpoint of the large-scale whole-genome functional analysis of the promoters and cis-regulatory elements using chromatin markers. We contrast these large scale quantitative techniques against comparative genomics and in vivo analyses including CRISPR/CAS9 genome editing to determine the functional characteristics of these elements and to understand how polymorphic variation and epigenetic changes within these elements might contribute to complex disease and drug response. Most importantly, we suggest that, although the role of chromatin markers will continue to be important in identifying and characterizing enhancers, more emphasis must be placed on their analysis in relevant in-vivo models that take account of the appropriate cell-type-specific roles of these elements. It is hoped that offering these insights might refocus progress in analyzing the data tsunami of non-coding GWAS and whole-genome sequencing "hits" that threatens to overwhelm progress in the field.