Preclinical, randomized phase 1, and compassionate use evaluation of REGN4461, a leptin receptor agonist antibody for leptin deficiency.

Deficiency in the adipose-derived hormone leptin or leptin receptor signaling causes class 3 obesity in individuals with genetic loss-of-function mutations in leptin or its receptor LEPR and metabolic and liver disease in individuals with hypoleptinemia secondary to lipoatrophy such as in individuals with generalized lipodystrophy. Therapies that restore leptin-LEPR signaling may resolve these metabolic sequelae. We developed a fully human monoclonal antibody (mAb), REGN4461 (mibavademab), that activates the human LEPR in the absence or presence of leptin. In obese leptin knockout mice, REGN4461 normalized body weight, food intake, blood glucose, and insulin sensitivity. In a mouse model of generalized lipodystrophy, REGN4461 alleviated hyperphagia, hyperglycemia, insulin resistance, dyslipidemia, and hepatic steatosis. In a phase 1, randomized, double-blind, placebo-controlled two-part study, REGN4461 was well tolerated with an acceptable safety profile. Treatment of individuals with overweight or obesity with REGN4461 decreased body weight over 12 weeks in those with low circulating leptin concentrations (<8 ng/ml) but had no effect on body weight in individuals with higher baseline leptin. Furthermore, compassionate-use treatment of a single patient with atypical partial lipodystrophy and a history of undetectable leptin concentrations associated with neutralizing antibodies to metreleptin was associated with noteable improvements in circulating triglycerides and hepatic steatosis. Collectively, these translational data unveil an agonist LEPR mAb that may provide clinical benefit in disorders associated with relatively low leptin concentrations.

Alpaca single B cell interrogation and heavy-chain-only antibody discovery on an optofluidic platform.

In vivo VHH discovery approaches have been limited by the lack of methodologies for camelid B cell interrogation. Here, we report a novel application of the Beacon® optofluidic platform to the discovery of heavy-chain-only antibodies by screening alpaca B cells. Methods for alpaca B cell enrichment, culture, IgG2/3 detection, and sequencing were developed and used to discover target-specific VHH from an alpaca immunized with prostate-specific membrane antigen (PSMA) or a second target. PSMA-specific hits were expressed as VHH-Fc and characterized using label-free techniques. Anti-PSMA IgG2/3 titer plateaued on day 153, when on-Beacon IgG2/3 secretion and target binding rates peaked. Of 13 recombinantly expressed VHH-Fc, all but one bound with nanomolar affinity, and five were successfully humanized. Repertoire sequencing uncovered additional variants within the clonal lineages of the validated hits. The establishment of this workflow extends the powerful Beacon technology to enable rapid VHH discovery directly from natural camelid immune repertoires.

Blocking common γ chain cytokine signaling ameliorates T cell-mediated pathogenesis in disease models.

The common γ chain (γc; IL-2RG) is a subunit of the interleukin (IL) receptors for the γc cytokines IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. The lack of appropriate neutralizing antibodies recognizing IL-2RG has made it difficult to thoroughly interrogate the role of γc cytokines in inflammatory and autoimmune disease settings. Here, we generated a γc cytokine receptor antibody, REGN7257, to determine whether γc cytokines might be targeted for T cell-mediated disease prevention and treatment. Biochemical, structural, and in vitro analysis showed that REGN7257 binds with high affinity to IL-2RG and potently blocks signaling of all γc cytokines. In nonhuman primates, REGN7257 efficiently suppressed T cells without affecting granulocytes, platelets, or red blood cells. Using REGN7257, we showed that γc cytokines drive T cell-mediated disease in mouse models of graft-versus-host disease (GVHD) and multiple sclerosis by affecting multiple aspects of the pathogenic response. We found that our xenogeneic GVHD mouse model recapitulates hallmarks of acute and chronic GVHD, with T cell expansion/infiltration into tissues and liver fibrosis, as well as hallmarks of immune aplastic anemia, with bone marrow aplasia and peripheral cytopenia. Our findings indicate that γc cytokines contribute to GVHD and aplastic anemia pathology by promoting these characteristic features. By demonstrating that broad inhibition of γc cytokine signaling with REGN7257 protects from immune-mediated disorders, our data provide evidence of γc cytokines as key drivers of pathogenic T cell responses, offering a potential strategy for the management of T cell-mediated diseases.

Anti-ACVR1 antibodies exacerbate heterotopic ossification in fibrodysplasia ossificans progressiva (FOP) by activating FOP-mutant ACVR1.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder whose most debilitating pathology is progressive and cumulative heterotopic ossification (HO) of skeletal muscles, ligaments, tendons, and fascia. FOP is caused by mutations in the type I BMP receptor gene ACVR1, which enable ACVR1 to utilize its natural antagonist, activin A, as an agonistic ligand. The physiological relevance of this property is underscored by the fact that HO in FOP is exquisitely dependent on activation of FOP-mutant ACVR1 by activin A, an effect countered by inhibition of anti-activin A via monoclonal antibody treatment. Hence, we surmised that anti-ACVR1 antibodies that block activation of ACVR1 by ligands should also inhibit HO in FOP and provide an additional therapeutic option for this condition. Therefore, we generated anti-ACVR1 monoclonal antibodies that block ACVR1's activation by its ligands. Surprisingly, in vivo, these anti-ACVR1 antibodies stimulated HO and activated signaling of FOP-mutant ACVR1. This property was restricted to FOP-mutant ACVR1 and resulted from anti-ACVR1 antibody-mediated dimerization of ACVR1. Conversely, wild-type ACVR1 was inhibited by anti-ACVR1 antibodies. These results uncover an additional property of FOP-mutant ACVR1 and indicate that anti-ACVR1 antibodies should not be considered as therapeutics for FOP.

High affinity human Fc specific monoclonal antibodies for capture kinetic analyses of antibody-antigen interactions.

We recently demonstrated that capturing human monoclonal antibodies (hmAbs) using high affinity anti-human Fc (AHC) antibodies allows reliable characterization of antibody-antigen interactions. Here, we characterized six human Fc specific mouse monoclonal antibodies (mAbs) and compared their binding profiles with three previously characterized goat AHC polyclonal antibodies (pAbs), exhibiting properties of a good capture reagent. All six mouse AHC mAbs specifically bound with high affinity to the Fc region of hIgG1, hIgG2, hIgG4 and to 43 different hIgG variants, containing substitutions and/or mutations in the hinge and/or Fc region, that have been reported to exhibit modified antibody effector function and/or pharmacokinetics. Biacore sensor surfaces individually derivatized with mouse AHC mAbs exhibited >2.5-fold higher hIgG binding capacity compared to the three goat AHC pAb surfaces and reproducibly captured hIgG over 300 capture-regeneration cycles. The results of the capture kinetic analyses performed on 31 antibody-antigen interactions using surfaces derivatized with either of the two highest affinity AHC mAbs (REGN7942 or REGN7943) were in concordance with those performed using goat AHC pAb surfaces. Our data demonstrate that AHC mAbs such as REGN7942 and REGN7943 that have properties superior than the three goat AHC pAbs are highly valuable research reagents, especially to perform capture kinetic analyses of antibody-antigen interactions on optical biosensors.

Targeting immunodominant Bet v 1 epitopes with monoclonal antibodies prevents the birch allergic response.

BACKGROUND: Blocking the major cat allergen, Fel d 1, with mAbs was effective in preventing an acute cat allergic response. OBJECTIVES: This study sought to extend the allergen-specific antibody approach and demonstrate that a combination of mAbs targeting Bet v 1, the immunodominant and most abundant allergenic protein in birch pollen, can prevent the birch allergic response. METHODS: Bet v 1-specific mAbs, REGN5713, REGN5714, and REGN5715, were isolated using the VelocImmune platform. Surface plasmon resonance, x-ray crystallography, and cryo-electron microscopy determined binding kinetics and structural data. Inhibition of IgE-binding, basophil activation, and mast cell degranulation were assessed via blocking ELISA, flow cytometry, and the passive cutaneous anaphylaxis mouse model. RESULTS: REGN5713, REGN5714, and REGN5715 bind with high affinity and noncompetitively to Bet v 1. A cocktail of all 3 antibodies, REGN5713/14/15, blocks IgE binding to Bet v 1 and inhibits Bet v 1- and birch pollen extract-induced basophil activation ex vivo and mast cell degranulation in vivo. Crystal structures of the complex of Bet v 1 with immunoglobulin antigen-binding fragments of REGN5713 or REGN5715 show distinct interaction sites on Bet v 1. Cryo-electron microscopy reveals a planar and roughly symmetrical complex formed by REGN5713/14/15 bound to Bet v 1. CONCLUSIONS: These data confirm the immunodominance of Bet v 1 in birch allergy and demonstrate blockade of the birch allergic response with REGN5713/14/15. Structural analyses show simultaneous binding of REGN5713, REGN5714, and REGN5715 with substantial areas of Bet v 1 exposed, suggesting that targeting specific epitopes is sufficient to block the allergic response.

Novel antibody cocktail targeting Bet v 1 rapidly and sustainably treats birch allergy symptoms in a phase 1 study.

BACKGROUND: The efficacy of an allergen-specific IgG cocktail to treat cat allergy suggests that allergen-specific IgG may be a major protective mechanism elicited by allergen immunotherapy. OBJECTIVES: Extending these findings, we tested a Bet v 1-specific antibody cocktail in birch-allergic subjects. METHODS: This was a phase 1, randomized, double-blind, study with 2 parts. Part A administered ascending doses of the Bet v 1-specific antibody cocktail REGN5713/14/15 (150-900 mg) in 32 healthy adults. Part B administered a single subcutaneous 900-mg dose or placebo in 64 birch-allergic subjects. Total nasal symptom score response to titrated birch extract nasal allergen challenge and skin prick test (SPT) with birch and alder allergen were assessed at screening and days 8, 29, 57, and 113 (SPT only); basophil activation tests (n = 26) were conducted. RESULTS: Single-dose REGN5713/14/15 significantly reduced total nasal symptom score following birch nasal allergen challenge relative to baseline. Differences in total nasal symptom score areas under the curve (0-1 hour) for subjects treated with REGN5713/14/15 versus those given placebo (day 8: -1.17, P = .001; day 29: -1.18, P = .001; day 57: -0.85, P = .024) and titration SPT with birch difference in area under the curve of mean wheal diameters for subjects treated with REGN5713/14/15 versus placebo (all P < .001) were sustained for ≥2 months; similar results were observed with alder SPT. REGN5713/14/15 was well tolerated. Basophil responsiveness to birch-related allergens was significantly decreased in subjects treated with REGN5713/14/15 versus those given placebo on days 8, 57, and 113 (all P < .01). CONCLUSIONS: Single-dose REGN5713/14/15 was well tolerated and provided a rapid (1 week) and durable (2 months) reduction in allergic symptoms after birch allergen nasal allergen challenge, potentially offering a new paradigm for the treatment of birch allergy symptoms.

Tumor-targeted CD28 bispecific antibodies enhance the antitumor efficacy of PD-1 immunotherapy.

Monoclonal antibodies that block the programmed cell death 1 (PD-1) checkpoint have revolutionized cancer immunotherapy. However, many major tumor types remain unresponsive to anti-PD-1 therapy, and even among responsive tumor types, most of the patients do not develop durable antitumor immunity. It has been shown that bispecific antibodies activate T cells by cross-linking the TCR/CD3 complex with a tumor-specific antigen (TSA). The class of TSAxCD3 bispecific antibodies have generated exciting results in early clinical trials. We have recently described another class of "costimulatory bispecifics" that cross-link a TSA to CD28 (TSAxCD28) and cooperate with TSAxCD3 bispecifics. Here, we demonstrate that these TSAxCD28 bispecifics (one specific for prostate cancer and the other for epithelial tumors) can also synergize with the broader anti-PD-1 approach and endow responsiveness-as well as long-term immune memory-against tumors that otherwise do not respond to anti-PD-1 alone. Unlike CD28 superagonists, which broadly activate T cells and induce cytokine storm, TSAxCD28 bispecifics display little or no toxicity when used alone or in combination with a PD-1 blocker in genetically humanized immunocompetent mouse models or in primates and thus may provide a well-tolerated and "off the shelf" combination approach with PD-1 immunotherapy that can markedly enhance antitumor efficacy.

Inhibition of complement pathway activation with Pozelimab, a fully human antibody to complement component C5.

Complement is a key component of the innate immune system. Inappropriate complement activation underlies the pathophysiology of a variety of diseases. Complement component 5 (C5) is a validated therapeutic target for complement-mediated diseases, but the development of new therapeutics has been limited by a paucity of preclinical models to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) properties of candidate therapies. The present report describes a novel humanized C5 mouse and its utility in evaluating a panel of fully human anti-C5 antibodies. Surprisingly, humanized C5 mice revealed marked differences in clearance rates amongst a panel of anti-C5 antibodies. One antibody, pozelimab (REGN3918), bound C5 and C5 variants with high affinity and potently blocked complement-mediated hemolysis in vitro. In studies conducted in both humanized C5 mice and cynomolgus monkeys, pozelimab demonstrated prolonged PK and durable suppression of hemolytic activity ex vivo. In humanized C5 mice, a switch in dosing from in-house eculizumab to pozelimab was associated with normalization of serum C5 concentrations, sustained suppression of hemolytic activity ex vivo, and no overt toxicity. Our findings demonstrate the value of humanized C5 mice in identifying new therapeutic candidates and treatment options for complement-mediated diseases.

The impact of different human IgG capture molecules on the kinetics analysis of antibody-antigen interaction.

Surface plasmon resonance (SPR) is a well-established method to characterize biomolecular interactions and is widely used in drug discovery and development. Here, we demonstrate that capture surfaces profoundly impact the binding kinetics parameters that are measured for antibody-antigen interactions. Six unique antibody-antigen interactions were characterized using eight different anti-human IgG capture surfaces. The antigen binding affinities for six different human monoclonal antibodies (hmAbs) captured using three different goat anti-human Fc (AHC) polyclonal antibody (pAb) surfaces were in reasonable agreement (3-7-fold weaker) with those measured by kinetic exclusion assay (KinExA). In contrast, up to 81, 32, 489, 2826, and 219-fold weaker antigen binding affinities were measured using mouse AHC mAb, Protein G, Protein A, Protein A/G, and Protein L surfaces, respectively. Protein A, Protein A/G and Protein G interacted with the Fab of hmAbs, possibly affecting antigen binding to hmAbs captured over these surfaces. Additional studies revealed that mouse AHC mAb binds hmAbs with a weak affinity (5.5-36.3 nM) and t½ values of 1.4-3.3min, compared to the sub-nanomolar affinities of the goat AHC pAbs. These results emphasize the value of measuring binding kinetics of the capture molecule before immobilizing them onto the sensor surface to perform capture kinetics assays on label-free biosensors.

IL-33 blockade affects mediators of persistence and exacerbation in a model of chronic airway inflammation.

BACKGROUND: Severe inflammatory airway diseases are associated with inflammation that does not resolve, leading to structural changes and an overall environment primed for exacerbations. OBJECTIVE: We sought to identify and inhibit pathways that perpetuate this heightened inflammatory state because this could lead to therapies that allow for a more quiescent lung that is less predisposed to symptoms and exacerbations. METHODS: Using prolonged exposure to house dust mite in mice, we developed a mouse model of persistent and exacerbating airway disease characterized by a mixed inflammatory phenotype. RESULTS: We show that lung IL-33 drives inflammation and remodeling beyond the type 2 response classically associated with IL-33 signaling. IL-33 blockade with an IL-33 neutralizing antibody normalized established inflammation and improved remodeling of both the lung epithelium and lung parenchyma. Specifically, IL-33 blockade normalized persisting and exacerbating inflammatory end points, including eosinophilic, neutrophilic, and ST2+CD4+ T-cell infiltration. Importantly, we identified a key role for IL-33 in driving lung remodeling because anti-IL-33 also re-established the presence of ciliated cells over mucus-producing cells and decreased myofibroblast numbers, even in the context of continuous allergen exposure, resulting in improved lung function. CONCLUSION: Overall, this study shows that increased IL-33 levels drive a self-perpetuating amplification loop that maintains the lung in a state of lasting inflammation and remodeled tissue primed for exacerbations. Thus IL-33 blockade might ameliorate symptoms and prevent exacerbations by quelling persistent inflammation and airway remodeling.

Designing binding kinetic assay on the bio-layer interferometry (BLI) biosensor to characterize antibody-antigen interactions.

The Octet biosensors provide a high-throughput alternative to the well-established surface plasmon resonance (SPR) and SPR imaging (SPRi) biosensors to characterize antibody-antigen interactions. However, the utility of the Octet biosensors for accurate and reproducible measurement of binding rate constants of monoclonal antibodies (mAbs) is limited due to challenges such as analyte rebinding, and mass transport limitation (MTL). This study focuses on addressing these challenges and provides experimental conditions to reliably measure kinetics of mAb-antigen interactions. The mAb capture density of less than 0.6 nm was found to be optimal to measure a wide range of binding affinities on Octet HTX biosensor. The titration kinetic and single cycle kinetic assays performed on Octet HTX generated reproducible binding kinetic parameters and correlated with the values measured on Biacore 4000 and MASS-1. Kinetic assays performed on 0.1 nm density mAb surfaces significantly reduced MTL and enabled characterization of picomolar affinity mAbs. Finally, kinetic analysis performed on 150 antibodies to 10 antigens with molecular weights ranging from 21kD to 105kD showed concordance between Octet HTX, Biacore 4000 and MASS-1 (R2 > 0.90). The data presented in this study suggest that under optimal experimental conditions, Octet biosensor is capable of generating kinetic values comparable to SPR/SPRi biosensors.

Extending the throughput of Biacore 4000 biosensor to accelerate kinetic analysis of antibody-antigen interaction.

The surface plasmon resonance (SPR) biosensors are being routinely used in different stages of drug discovery and development. However, the lack of high throughput SPR biosensors continues to be a primary bottleneck for the rapid kinetic screening of large panels of monoclonal antibodies (mAbs). To further increase the throughput of the Biacore 4000 biosensor, we have developed three kinetic screening assays to characterize mAb-antigen interactions - (i) 16-mAb capture kinetic, (ii) single cycle kinetic (SCK), and (iii) parallel kinetic (PK). The performance of all three kinetic assays was evaluated by characterizing the binding of kinetically diverse human mAbs to four antigens with molecular weights of 14kD, 29kD, 38kD, and 48kD and binding affinities ranging from 130pM to 200 nM. The binding rate constants measured using all three kinetic assays were reproducible across multiple experiments and correlated with the values generated using the conventional 8-mAb capture kinetic assay on the Biacore 4000 (R2 > 0.94). Moreover, the 16-mAb capture assay decreased experiment time and analyte consumption by 35% and 50%, respectively. This work illustrates the significance of the 16-mAb capture kinetic, SCK, and PK assays to increase the throughput of Biacore 4000 and to support rapid kinetic screening of mAbs.

ANGPTL8 Blockade With a Monoclonal Antibody Promotes Triglyceride Clearance, Energy Expenditure, and Weight Loss in Mice.

Angiopoietin-like protein (ANGPTL)8 is a negative regulator of lipoprotein lipase-mediated plasma triglyceride (TG) clearance. In this study, we describe a fully human monoclonal antibody (REGN3776) that binds monkey and human ANGPTL8 with high affinity. Inhibition of ANGPTL8 with REGN3776 in humanized ANGPTL8 mice decreased plasma TGs and increased lipoprotein lipase activity. Additionally, REGN3776 reduced body weight and fat content. The reduction in body weight was secondary to increased energy expenditure. Finally, single administration of REGN3776 normalized plasma TGs in dyslipidemic cynomolgus monkeys. In conclusion, we show that blockade of ANGPTL8 with monoclonal antibody strongly reduced plasma TGs in mice and monkeys. These data suggest that inhibition of ANGPTL8 may provide a new therapeutic avenue for the treatment of dyslipidemia with beneficial effects on body weight.

Exploring sensitivity & throughput of a parallel flow SPRi biosensor for characterization of antibody-antigen interaction.

Rapid growth in the field of biotherapeutics has led to an increased demand for high-throughput, label-free biosensors exhibiting high sensitivity. To support the current needs, Sierra Sensors introduced a surface plasmon resonance imaging (SPRi) based biosensor, Molecular Affinity Screening System (MASS-1). We assessed the potential utility of MASS-1 to support Regeneron's therapeutic antibody discovery. A large panel of antibody-antigen interactions was characterized using MASS-1 and the kinetic data were compared with the Biacore 4000 biosensor. Less than 10% deviation in the binding rate constants measured across eight flow channels of MASS-1 was observed. The single injection cycle kinetic assay allowed rapid measurement of binding rate constants for antibody-antigen interactions. MASS-1 sensitivity was independent of protein immobilization level and kinetic analysis performed using ultra-low density mAb surfaces allowed characterization of picomolar affinity interactions without mass transport limitation. High-throughput characterization of a panel of 189 monoclonal antibodies to 13 different antigens with molecular weights ranging from 14kD to 105kD revealed that binding kinetic parameters measured on MASS-1 were comparable to those measured on Biacore 4000. Our data demonstrate that MASS-1 measures reliable binding kinetic parameters and has an appropriate combination of throughput and sensitivity to support discovery and development of therapeutic antibodies.

Pre- and postexposure efficacy of fully human antibodies against Spike protein in a novel humanized mouse model of MERS-CoV infection.

Traditional approaches to antimicrobial drug development are poorly suited to combatting the emergence of novel pathogens. Additionally, the lack of small animal models for these infections hinders the in vivo testing of potential therapeutics. Here we demonstrate the use of the VelocImmune technology (a mouse that expresses human antibody-variable heavy chains and κ light chains) alongside the VelociGene technology (which allows for rapid engineering of the mouse genome) to quickly develop and evaluate antibodies against an emerging viral disease. Specifically, we show the rapid generation of fully human neutralizing antibodies against the recently emerged Middle East Respiratory Syndrome coronavirus (MERS-CoV) and development of a humanized mouse model for MERS-CoV infection, which was used to demonstrate the therapeutic efficacy of the isolated antibodies. The VelocImmune and VelociGene technologies are powerful platforms that can be used to rapidly respond to emerging epidemics.

Enhanced EGFR inhibition and distinct epitope recognition by EGFR antagonistic mAbs C225 and 425.

Monoclonal antibodies (mAbs) that inhibit activation of the epidermal growth factor receptor (EGFR) have shown therapeutic potential in select malignancies including breast cancer. Here, we describe that combined use of two such mAbs, C225 (Cetuximab) and 425 (EMD55900), reduced growth and survival of EGFR overexpressing MDA-MB-468 breast cancer cells more effectively than either antibody alone. Similarly, the C225/425 antibody combination more effectively inhibited AKT and MAPK phosphorylation in MDA-MB-468 cells. Surface plasmon resonance, size exclusion chromatography and analytical ultracentrifugation demonstrated that mAbs C225 and 425 simultaneously bind to distinct antigenic epitopes on domain III of the soluble wild-type EGFR. Furthermore, neither mAb competed with the other for binding to cells expressing either wild-type EGFR or a mutant EGFR (EGFRvIII) associated with neoplasia. Mutagenesis experiments revealed that residues S460/G461 in EGFR domain III are essential components of the 425 epitope and clearly distinguish it from the EGF/ TGFalpha binding site and the C225 interaction interface. Collectively, these results support the conclusion that therapeutic EGFR blockade in cancer patients by combined use of mAbs C225 and 425 could provide advantages over the use of the two antibodies as single agents.