Structural basis for treating tumor necrosis factor α (TNFα)-associated diseases with the therapeutic antibody infliximab

Thermostability and binding properties of single-chained Fv fragments derived from therapeutic antibodies

Small antibody fragments have recently been used as alternatives to full-length monoclonal antibodies in therapeutic applications. One of the most popular fragment antibodies is single-chain fragment variables (scFvs), consisting of variable heavy (VH) and variable light (VL) domains linked by a flexible peptide linker. scFvs have small molecular sizes, which enables good tissue penetration and low immunogenicity. Despite these advantages, the use of scFvs, especially for therapeutic purpose, is still limited because of the difficulty to regulate the binding activity and conformational stability. In this study, we constructed and analyzed 10 scFv fragments derived from 10 representatives of FDA-approved mAbs to evaluate their physicochemical properties. Differential scanning calorimetry analysis showed that scFvs exhibited relatively high but varied thermostability, from 50 to 70°C of melting temperatures, and different unfolding cooperativity. Surface plasmon resonance analysis revealed that scFvs fragments that exhibit high stability and cooperative unfolding likely tend to maintain antigen binding. This study demonstrated the comprehensive physicochemical properties of scFvs derived from FDA-approved antibodies, providing insights into antibody design and development.

Infliximab Limits Injury in Myocardial Infarction

BACKGROUND

The purpose of this study was to investigate a therapeutic approach targeting the inflammatory response and consequent remodeling from ischemic myocardial injury.

METHODS AND RESULTS

Coronary thrombus aspirates were collected from patients at the time of ST-segment-elevation myocardial infarction and subjected to array-based proteome analysis. Clinically indistinguishable at myocardial infarction (MI), patients were stratified into vulnerable and resilient on the basis of 1-year left ventricular ejection fraction and death. Network analysis from coronary aspirates revealed prioritization of tumor necrosis factor-α signaling in patients with worse clinical outcomes. Infliximab, a tumor necrosis factor-α inhibitor, was infused intravenously at reperfusion in a porcine MI model to assess whether infliximab-mediated immune modulation impacts post-MI injury. At 3 days after MI (n=7), infliximab infusion increased proregenerative M2 macrophages in the myocardial border zone as quantified by immunofluorescence (24.1%±23.3% in infliximab versus 9.29%±8.7% in sham; P<0.01). Concomitantly, immunoassays of coronary sinus samples quantified lower troponin I levels (41.72±7.34 pg/mL versus 58.11±10.75 pg/mL; P<0.05) and secreted protein analysis revealed upregulation of injury-modifying interleukin-2, -4, -10, -12, and -18 cytokines in the infliximab-treated cohort. At 4 weeks (n=12), infliximab treatment resulted in significant protective influence, improving left ventricular ejection fraction (53.9%±5.4% versus 36.2%±5.3%; P<0.001) and reducing scar size (8.31%±10.9% versus 17.41%±12.5%; P<0.05).

CONCLUSIONS

Profiling of coronary thrombus aspirates in patients with ST-segment-elevation MI revealed highest association for tumor necrosis factor-α in injury risk. Infliximab-mediated immune modulation offers an actionable pathway to alter MI-induced inflammatory response, preserving contractility and limiting adverse structural remodeling.

Leveraging Cross-Linking Mass Spectrometry for Modeling Antibody-Antigen Complexes

Elucidating antibody-antigen complexes at the atomic level is of utmost interest for understanding immune responses and designing better therapies. Cross-linking mass spectrometry (XL-MS) has emerged as a powerful tool for mapping protein-protein interactions, suggesting valuable structural insights. However, the use of XL-MS studies to enable epitope/paratope mapping of antibody-antigen complexes is still limited up to now. XL-MS data can be used to drive integrative modeling of antibody-antigen complexes, where cross-links information serves as distance restraints for the precise determination of binding interfaces. In this approach, XL-MS data are employed to identify connections between binding interfaces of the antibody and the antigen, thus informing molecular modeling. Current literature provides minimal input about the impact of XL-MS data on the integrative modeling of antibody-antigen complexes. Here, we applied XL-MS to retrieve information about binding interfaces of three antibody-antigen complexes. We leveraged XL-MS data to perform integrative modeling using HADDOCK (active-passive residues and distance restraints strategies) and AlphaLink2. We then compared these three approaches with initial predictions of investigated antibody-antigen complexes by AlphaFold Multimer. This work emphasizes the importance of cross-linking data in resolving conformational dynamics of antibody-antigen complexes, ultimately enhancing the design of better protein therapeutics and vaccines.

Enhancing affinity purification of monoclonal antibodies from human serum for subsequent CZE-MS analysis

Due to the separation technique employed, capillary electrophoresis coupled to mass spectrometry (CE-MS) analysis performances are significantly influenced by the chemical composition and the complexity of the sample. In various applications, that impact has prevented the use of CE-MS for the characterization and quantification of proteins in biological samples. Here we present the development and evaluation and a sample preparation procedure, based on affinity purification, for the specific extraction of the monoclonal antibody (mAbs) infliximab from human serum in order to perform subsequent proteolytic digestion and CE-MS/MS analysis. Three distinctive sample preparation strategies were envisaged. In each case, the different steps composing the protocol were thoroughly optimized and evaluated in order to provide a sample preparation addressing the important complexity of serums samples while providing an optimal compatibility with CE-MS/MS analysis. The different sample preparation strategies were assessed concerning the possibility to achieve an appropriate absolute quantification of the mAbs using CE-MS/MS for samples mimicking patient serum samples. Also, the possibility to perform the characterization of several types of post-translational modifications (PTMs) was evaluated. The sample preparation protocols allowed the quantification of the mAbs in serums samples for concentration as low as 0.2 µg·mL-1 (2.03 nM) using CE-MS/MS analysis, also the possibility to characterize and estimate the modification level of PTMs hotspots in a consistent manner. Results allowed to attribute the effect on the electrophoretic separation of the different steps composing sample preparation. Finally, they demonstrated that sample preparation for CE-MS/MS analysis could benefit greatly for the extended applicability of this type of analysis for complex biological matrices.

Structure-based development of a canine TNF-α-specific antibody using adalimumab as a template

The canine anti-tumor necrosis factor-alpha (TNF-α) monoclonal antibody is a potential therapeutic option for treating canine arthritis. The current treatments for arthritis in dogs have limitations due to side effects, emphasizing the need for safer and more effective therapies. The crystal structure of canine TNF-α (cTNF-α) was successfully determined at a resolution of 1.85 Å, and the protein was shown to assemble as a trimer, with high similarity to the functional quaternary structure of human TNF-α (hTNF-α). Adalimumab (Humira), a known TNF-α inhibitor, effectively targets and neutralizes TNF-α to reduce inflammation and has been used to manage autoimmune conditions such as rheumatoid arthritis. By comparing the structure of cTNF-α with the complex structure of hTNF-α and adalimumab-Fab, the epitope of adalimumab on cTNF-α was identified. The significant structural similarities of epitopes in cTNF-α and hTNF-α indicate the potential of using adalimumab to target cTNF-α. Therefore, a canine/human chimeric antibody, Humivet-R1, was created by grafting the variable domain of adalimumab onto a canine antibody framework derived from ranevetmab. Humivet-R1 exhibits potent neutralizing ability (IC50  = 0.05 nM) and high binding affinity (EC50  = 0.416 nM) to cTNF-α, comparable to that of adalimumab for both hTNF-α and cTNF-α. These results strongly suggest that Humivet-R1 has the potential to provide effective treatment for canine arthritis with reduced side effects. Here, we propose a structure-guided antibody design for the use of a chimeric antibody to treat canine inflammatory disease. Our successful development strategy can speed up therapeutic antibody discovery for animals and has the potential to revolutionize veterinary medicine.

Therapeutic Antibodies in Medicine

Antibody engineering has developed into a wide-reaching field, impacting a multitude of industries, most notably healthcare and diagnostics. The seminal work on developing the first monoclonal antibody four decades ago has witnessed exponential growth in the last 10-15 years, where regulators have approved monoclonal antibodies as therapeutics and for several diagnostic applications, including the remarkable attention it garnered during the pandemic. In recent years, antibodies have become the fastest-growing class of biological drugs approved for the treatment of a wide range of diseases, from cancer to autoimmune conditions. This review discusses the field of therapeutic antibodies as it stands today. It summarizes and outlines the clinical relevance and application of therapeutic antibodies in treating a landscape of diseases in different disciplines of medicine. It discusses the nomenclature, various approaches to antibody therapies, and the evolution of antibody therapeutics. It also discusses the risk profile and adverse immune reactions associated with the antibodies and sheds light on future applications and perspectives in antibody drug discovery.

Synthetic Peptide Antibodies as TNF-α Inhibitors: Molecularly Imprinted Polymer Nanogels Neutralize the Inflammatory Activity of TNF-α in THP-1 Derived Macrophages

Tumor Necrosis Factor-α (TNF-α) is a cytokine that is normally produced by immune cells when fighting an infection. But, when too much TNF-α is produced as in autoimmune diseases, this leads to unwanted and persistent inflammation. Anti-TNF-α monoclonal antibodies have revolutionized the therapy of these disorders by blocking TNF-α and preventing its binding to TNF-α receptors, thus suppressing the inflammation. Herein, we propose an alternative in the form of molecularly imprinted polymer nanogels (MIP-NGs). MIP-NGs are synthetic antibodies obtained by nanomoulding the 3-dimensional shape and chemical functionalities of a desired target in a synthetic polymer. Using an in-house developed in silico rational approach, epitope peptides of TNF-α were generated and 'synthetic peptide antibodies' were prepared. The resultant MIP-NGs bind the template peptide and recombinant TNF-α with high affinity and selectivity, and can block the binding of TNF-α to its receptor. Consequently they were applied to neutralize pro-inflammatory TNF-α in the supernatant of human THP-1 macrophages, leading to a downregulation of the secretion of pro-inflammatory cytokines. Our results suggest that MIP-NGs, which are thermally and biochemically more stable and easier to manufacture than antibodies, and cost-effective, are very promising as next generation TNF-α inhibitors for the treatment of inflammatory diseases.

Simultaneous quantification and structural characterization of monoclonal antibodies after administration using capillary zone electrophoresis-tandem mass spectrometry

Monoclonal antibodies (mAbs) are demonstrating major success in various therapeutic areas such as oncology and the treatment of immune disorders. Over the past two decades, novel analytical methodologies allowed to address the challenges of mAbs characterization in the context of their production. However, after administration only their quantification is performed and insights regarding their structural evolution remain limited. For instance, clinical practice has recently highlighted significant inter-patient differences in mAb clearance and unexpected clinical responses, without providing alternative interpretations. Here, we report the development of a novel analytical strategy based on capillary zone electrophoresis coupled to tandem mass spectrometry (CE-MS/MS) for the simultaneous absolute quantification and structural characterization of infliximab (IFX) in human serum. CE-MS/MS quantification was validated over the range 0.4-25 µg·mL^-1 corresponding to the IFX therapeutic window and achieved a LOQ of 0.22 µg·mL^-1 (1.5 nM) while demonstrating outstanding specificity compared to the ELISA assay. CE-MS/MS allowed structural characterization and estimation of the relative abundance of the six major N-glycosylations expressed by IFX. In addition, the results allowed characterization and determination of the level of modification of post-translational modifications (PTMs) hotspots including deamidation of 4 asparagine and isomerization of 2 aspartate. Concerning N-glycosylation and PTMs, a new normalization strategy was developed to measure the variation of modification levels that occur strictly during the residence time of IFX in the patient's system, overcoming artefactual modifications induced by sample treatment and/or storage. The CE-MS/MS methodology was applied to the analysis of samples from patients with Crohn's disease. The data identified a gradual deamidation of a particular asparagine residue located in the complementary determining region that correlated with IFX residence time, while the evolution of IFX concentration showed significant variability among patients.

Membrane Protein Binding Interactions Studied in Live Cells via Diethylpyrocarbonate Covalent Labeling Mass Spectrometry

Membrane proteins are vital in the human proteome for their cellular functions and make up a majority of drug targets in the U.S. However, characterizing their higher-order structures and interactions remains challenging. Most often membrane proteins are studied in artificial membranes, but such artificial systems do not fully account for the diversity of components present in cell membranes. In this study, we demonstrate that diethylpyrocarbonate (DEPC) covalent labeling mass spectrometry can provide binding site information for membrane proteins in living cells using membrane-bound tumor necrosis factor α (mTNFα) as a model system. Using three therapeutic monoclonal antibodies that bind TNFα, our results show that residues that are buried in the epitope upon antibody binding generally decrease in DEPC labeling extent. Additionally, serine, threonine, and tyrosine residues on the periphery of the epitope increase in labeling upon antibody binding because of a more hydrophobic microenvironment that is created. We also observe changes in labeling away from the epitope, indicating changes to the packing of the mTNFα homotrimer, compaction of the mTNFα trimer against the cell membrane, and/or previously uncharacterized allosteric changes upon antibody binding. Overall, DEPC-based covalent labeling mass spectrometry offers an effective means of characterizing structure and interactions of membrane proteins in living cells.

Psoriatic arthritis: review of potential biomarkers predicting response to TNF inhibitors

Psoriatic arthritis (PsA) is a chronic and painful inflammatory immune-mediated disease. It affects up to 40% of people with psoriasis and it is associated with several comorbidities such as obesity, diabetes, metabolic syndrome, and hypertension. PsA is difficult to diagnose because of its diverse symptoms, namely axial and peripheral arthritis, enthesitis, dactylitis, skin changes, and nail dystrophy. Different drugs exist to treat the inflammation and pain. When patients do not respond to conventional drugs, they are treated with biologic drugs. Tumour necrosis factor inhibitors (TNFi's) are commonly given as the first biologic drug; beside being expensive, they also lack efficacy in 50% of patients. A biomarker predicting individual patient's response to TNFi would help treating them earlier with an appropriate biologic drug. This study aimed to review the literature to identify potential biomarkers that should be investigated for their predictive ability. Several such biomarkers were identified, namely transmembrane TNFα (tmTNF), human serum albumin (HSA) and its half-life receptor, the neonatal Fc receptor (FcRn) which is also involved in IgG lifespan; calprotectin, high mobility group protein B1 (HMGB1) and advanced glycation end products (AGEs) whose overexpression lead to excessive production of pro-inflammatory cytokines; lymphotoxin α (LTα) which induces inflammation by binding to TNF receptor (TNFR); and T helper 17 (Th17) cells which induce inflammation by IL-17A secretion.

Inflammatory bowel disease biomarkers

Inflammatory bowel disease (IBD) is characterized as chronic inflammation in the gastrointestinal tract, which includes two main subtypes, Crohn's disease and ulcerative colitis. Endoscopy combined with biopsy is the most effective way to establish IBD diagnosis and disease management. Imaging techniques have also been developed to monitor IBD. Although effective, the methods are expensive and invasive, which leads to pain and discomfort. Alternative noninvasive biomarkers are being explored as tools for IBD prognosis and disease management. This review focuses on novel biomarkers that have emerged in recent years. These serological biomarkers and microRNAs could potentially be used for disease management in IBD, thereby decreasing patient discomfort and morbidity.

Complementary Structural Information for Antibody-Antigen Complexes from Hydrogen-Deuterium Exchange and Covalent Labeling Mass Spectrometry

Characterizing antibody-antigen interactions is necessary for properly developing therapeutic antibodies, understanding their mechanisms of action, and patenting new drug molecules. Here, we demonstrate that hydrogen-deuterium exchange (HDX) mass spectrometry (MS) measurements together with diethylpyrocarbonate (DEPC) covalent labeling (CL) MS measurements provide higher order structural information about antibody-antigen interactions that is not available from either technique alone. Using the well-characterized model system of tumor necrosis factor α (TNFα) in complex with three different monoclonal antibodies (mAbs), we show that two techniques offer a more complete overall picture of TNFα's structural changes upon binding different mAbs, sometimes providing synergistic information about binding sites and changes in protein dynamics upon binding. Labeling decreases in CL generally occur near the TNFα epitope, whereas decreases in HDX can span the entire protein due to substantial stabilization that occurs when mAbs bind TNFα. Considering both data sets together clarifies the TNFα regions that undergo a decrease in solvent exposure due to mAb binding and that undergo a change in dynamics due to mAb binding. Moreover, the single-residue level resolution of DEPC-CL/MS can clarify HDX/MS data for long peptides. We feel that the two techniques should be used together when studying the mAb-antigen interactions because of the complementary information they provide.

Trimer-to-Monomer Disruption Mechanism for a Potent, Protease-Resistant Antagonist of Tumor Necrosis Factor-α Signaling

Aberrant tumor necrosis factor-α (TNFα) signaling is associated with many inflammatory diseases. The homotrimeric quaternary structure of TNFα is essential for receptor recognition and signal transduction. Previously, we described an engineered α/β-peptide inhibitor that potently suppresses TNFα activity and resists proteolysis. Here, we present structural evidence that both the α/β-peptide inhibitor and an all-α analogue bind to a monomeric form of TNFα. Calorimetry data support a 1:1 inhibitor/TNFα stoichiometry in solution. In contrast, previous cocrystal structures involving peptide or small-molecule inhibitors have shown the antagonists engaging a TNFα dimer. The structural data reveal why our inhibitors favor monomeric TNFα. Previous efforts to block TNFα-induced cell death with peptide inhibitors revealed that surfactant additives to the assay conditions cause a more rapid manifestation of inhibitory activity than is observed in the absence of additives. We attributed this effect to a loose surfactant TNFα association that lowers the barrier to trimer dissociation. Here, we used the new structural data to design peptide inhibitors bearing a surfactant-inspired appendage intended to facilitate TNFα trimer dissociation. The appendage modified the time course of protection from cell death.

A universal in silico V(D)J recombination strategy for developing humanized monoclonal antibodies

BACKGROUND

Humanization of mouse monoclonal antibodies (mAbs) is crucial for reducing their immunogenicity in humans. However, humanized mAbs often lose their binding affinities. Therefore, an in silico humanization method that can prevent the loss of the binding affinity of mAbs is needed.

METHODS

We developed an in silico V(D)J recombination platform in which we used V(D)J human germline gene sequences to design five humanized candidates of anti-tumor necrosis factor (TNF)-α mAbs (C1-C5) by using different human germline templates. The candidates were subjected to molecular dynamics simulation. In addition, the structural similarities of their complementarity-determining regions (CDRs) to those of original mouse mAbs were estimated to derive the weighted interatomic root mean squared deviation (wRMSDi) value. Subsequently, the correlation of the derived wRMSDi value with the half maximal effective concentration (EC50) and the binding affinity (KD) of the humanized anti-TNF-α candidates was examined. To confirm whether our in silico estimation method can be used for other humanized mAbs, we tested our method using the anti-epidermal growth factor receptor (EGFR) a4.6.1, anti-glypican-3 (GPC3) YP9.1 and anti-α4β1 integrin HP1/2L mAbs.

RESULTS

The R2 value for the correlation between the wRMSDi and log(EC50) of the recombinant Remicade and those of the humanized anti-TNF-α candidates was 0.901, and the R2 value for the correlation between wRMSDi and log(KD) was 0.9921. The results indicated that our in silico V(D)J recombination platform could predict the binding affinity of humanized candidates and successfully identify the high-affinity humanized anti-TNF-α antibody (Ab) C1 with a binding affinity similar to that of the parental chimeric mAb (5.13 × 10-10). For the anti-EGFR a4.6.1, anti-GPC3 YP9.1, and anti-α4β1 integrin HP1/2L mAbs, the wRMSDi and log(EC50) exhibited strong correlations (R2 = 0.9908, 0.9999, and 0.8907, respectively).

CONCLUSIONS

Our in silico V(D)J recombination platform can facilitate the development of humanized mAbs with low immunogenicity and high binding affinities. This platform can directly transform numerous mAbs with therapeutic potential to humanized or even human therapeutic Abs for clinical use.

Missense variants in the TNFA epitopes and their effects on interaction with therapeutic antibodies-in silico analysis

BACKGROUND

Tumor necrosis factor alpha (TNFA) is an important cytokine that influences multiple biological processes. It is one of the key mediators of acute and chronic systemic inflammatory reactions and plays a central role in several autoimmune diseases. A number of approved monoclonal antibodies (mAbs) are widely used to subside these autoimmune diseases. However, there is a high rate of non-responsiveness to treatments with these mAbs. Therefore, it is important to be able to predict responses of the patients in an individualistic manner to these therapeutic antibodies before administration. In the present study, we used in silico tools to explore the effects of missense variants in the respective epitopes of four therapeutic anti-TNFA mAbs-adalimumab (ADA), certolizumab pegol (CZP), golimumab (GLM), and infliximab (IFX)-on their interactions with TNFA.

RESULTS

The binding affinities of CZP and ADA to corresponding epitopes appear to be reduced by four (TNFAR131Q, TNFAE135G, TNFAR138Q, and TNFAR138W) and two (TNFAG66C and TNFAG66S) variants, respectively. The binding of GLM and IFX appears to be affected by TNFAR141S and TNFAR138W, respectively. TNFAG66C and TNFAG66S may be associated with autoimmune diseases, whereas TNFAE135G, TNFAR138W, and TNFAR141S may be pathogenic per se.

CONCLUSION

These variants may contribute to the observed inter-individual variability in response to anti-TNFA mAbs treatments and be used as markers to predict responses, and thus optimize therapeutic benefits to the patients.

Targeted therapy of irritable bowel syndrome with anti-inflammatory cytokines

Irritable bowel syndrome (IBS) is a multifactorial disease of which infection, as well as inflammation, has recently been considered as an important cause. Inflammation works as a potential pathway for the pathogenesis of IBS. In this review, we have discussed the targeted therapy of IBS. We used the search term “inflammation in IBS” and “proinflammatory” and “antiinflammatory cytokines and IBS” using PubMed, MEDLINE, and Google Scholar. The literature search included only articles written in the English language. We have also reviewed currently available anti-inflammatory treatment and future perspectives. Cytokine imbalance in the systematic circulation and the intestinal mucosa may also characterize IBS presentation. Imbalances of pro-and anti-inflammatory cytokines and polymorphisms in cytokine genes have been reported in IBS. The story of targeted therapy of IBS with anti-inflammatory cytokines is far from complete and it seems that it has only just begun. This review describes the key issues related to pro-inflammatory cytokines associated with IBS, molecular regulation of immune response in IBS, inhibitors of pro-inflammatory cytokines in IBS, and clinical perspectives of pro- and anti-inflammatory cytokines in IBS.

A mechanistic perspective, clinical applications, and phage-display-assisted discovery of TNFα inhibitors

TNFα participates in a variety of physiological processes, but at supra-physiological concentrations it has been implicated in the pathology of inflammatory and autoimmune diseases. Therefore, much attention has been devoted to the development of strategies that overcome the effects of aberrant TNFα concentration. Promising strategies include drugs that destabilize the active (trimeric) form of TNFα and antagonists of TNFα receptor type I. Underpinning these strategies is the successful application of phage-display technology to identify anti-TNFα peptides and antibodies. Here, we review the development of inhibitors of the TNFα-TNF receptor system, with particular focus on the phage-display-assisted identification of molecules that interfere with this system by acting as inhibitors of TNFα or by sequestering TNFα away from its receptor.

Infliximab treatment of glycogenosis Ib with Crohn's-like enterocolitis: A case report

BACKGROUND

Glycogen storage disease type Ib (GSD-Ib) is a glycogen metabolism disorder that leads to the manifestations of inflammatory bowel disease (IBD), especially Crohn’s disease (CD)-like colitis. Although biological agents are effective for treating CD, their application in the treatment of GSD-Ib with CD-like colitis has been rarely reported.

CASE SUMMARY

A 13-year-old Han male was diagnosed with GSD-Ib with CD. The patient was treated with granulocyte colony-stimulating factor. When he had symptoms of CD-like colitis, he was continuously pumped with enteral nutrition and administered oral mesalazine for 2 wk; however, the symptoms did not improve significantly. Hence, infliximab (IFX) was administered. Hitherto, the patient has been followed up for 1 year, and no clinical manifestations have been observed. After 6 mo of treatment (fifth IFX treatment), the disease activity index and all inflammatory indexes decreased, and a review of the colonoscopy data showed that the ulcers appeared smooth.

CONCLUSION

In this study, the patient was successfully treated with IFX. In cases of GSD-Ib, IBD should be highly considered.

Homogeneous Immunoassay Using a Tri-Part Split-Luciferase for Rapid Quantification of Anti-TNF Therapeutic Antibodies

Anti-TNF therapeutics bind and sequester tumor necrosis factor (TNF) to prevent downstream signaling and are clinically important in the treatment of several autoimmune diseases. Effective treatment with these drugs requires frequent therapeutic drug monitoring (TDM). Current analytical methods, including reporter gene assay (RGA), enzyme-linked immunosorbent assay (ELISA), and mobility shift assay (MSA), can be technically rigorous, slow, and expensive. These qualities prevent the implementation of point-of-care testing and ultimately limit the frequency and utility of monitoring. An assay simple enough to be performed in the clinic would enable increased TDM frequency, more accurate dosing, and improved patient outcomes. Toward this end, we developed a homogeneous immunoassay based on a tri-part split-luciferase system for "add-and-read" detection of anti-TNF therapeutics. In our platform, two small fragments of the split-luciferase, called β9 and β10, are each fused to a different interacting protein. The binding of each of these proteins to anti-TNF antibodies forces the split-luciferase components into proximity where they reform the active luciferase. We identified the fusion proteins, β9-protein A (β9-A) and β10-TNF, as promising binding pairs. We systematically adjusted assay conditions to optimize the signal/background (S/B) ratio, limit of detection (LOD), and percent recovery. The assay has a large dynamic range (0.5-32 μg/mL) and is sensitive enough to monitor both subtherapeutic and supratherapeutic serum concentrations of anti-TNF antibodies, as demonstrated in clinical samples.

Current Status of Medical Therapy for Inflammatory Bowel Disease: The Wealth of Medications

Previously, the natural history of Crohn's disease and ulcerative colitis included significant morbidity due to limited treatment options that were not without serious side effects. Early treatment options included corticosteroids as well as mesalamine, thiopurines, and methotrexate. In 1998, monoclonal antibodies to a key inflammatory cytokine, TNFα, became available. Over the next 22 years, the field of gastroenterology has seen multiple new treatments emerging for inflammatory bowel disease (IBD) that target different aspects of the inflammatory cascade, significantly changing the therapeutic landscape. Additional monoclonal antibodies are available that target the integrins, which are adhesion proteins that traffic inflammatory leukocytes. Small molecule inhibitors block the inflammatory signals of several cytokines. New therapies that modulate lymphocyte escape from lymphoid tissue are promising. Lastly, stem cell technology has emerged as a platform to successfully treat perianal fistulizing disease. Our aim is to summarize the currently available therapies for IBD beyond steroids, mesalamine, and immune modulators. We highlight the most important clinical trials that have brought these treatments to clinical practice, and we discuss the ongoing clinical trials of novel therapies that have a high probability of eventual regulatory approval.

New insights on the interaction mechanism of rhTNFα with its antagonists Adalimumab and Etanercept

TNFα is a pro-inflammatory cytokine that is a therapeutic target for inflammatory autoimmune disorders. Thus, TNFα antagonists are successfully used for the treatment of these disorders. Here, new association patterns of rhTNFα and its antagonists Adalimumab and Etanercept are disclosed. Active rhTNFα was purified by IMAC from the soluble fraction of transformed Escherichia coli. Protein detection was assessed by SDS–PAGE and Western blot. The KD values for rhTNFα interactions with their antagonists were obtained by non-competitive ELISA and by microscale thermophoresis (MST). Molecular sizes of the complexes were evaluated by size-exclusion chromatography-high performance liquid chromatography (SEC-HPLC). Surprisingly, both antagonists recognized the monomeric form of rhTNFα under reducing and non-reducing conditions, indicating unexpected bindings of the antagonists to linear epitopes and to rhTNFα monomers. For the first time, the interactions of rhTNFα with Adalimumab and Etanercept were assessed by MST, which allows evaluating molecular interactions in solution with a wide range of concentrations. Biphasic binding curves with low and high KD values (&lt;10−9 M and &gt;10−8 M) were observed during thermophoresis experiments, suggesting the generation of complexes with different stoichiometry, which were confirmed by SEC-HPLC. Our results demonstrated the binding of TNFα-antagonists with rhTNFα monomers and linear epitopes. Also, complexes of high molecular mass were observed. This pioneer investigation constitutes valuable data for future approaches into the study of the interaction mechanism of TNFα and its antagonists.

Structural features of bovine colostral immunoglobulin that confer proteolytic stability in a simulated intestinal fluid

Bovine colostral antibodies, purified from cow's milk produced immediately after calving, have enhanced resistance to degradation by intestinal proteases relative to antibodies from human or bovine serum, making them of particular interest as orally administered therapeutic agents. However, the basis of this resistance is not well defined. We evaluated the stability of AVX-470, a bovine colostral anti-tumor necrosis factor (TNF) polyclonal antibody used in early clinical studies for treatment of ulcerative colitis, using conditions that mimic the human small intestine. AVX-470 was degraded ∼3 times more slowly than human IgG antibodies or infliximab (a monoclonal mouse-human chimeric IgG). Bovine IgG1 antibodies, the primary component of AVX-470, were slowly cleaved to F(ab')2 fragments. In contrast, bovine IgG2 and human IgG1 antibodies were cleaved rapidly into Fab and smaller fragments, pointing to specific regions where additional stability might be gained. Infliximab was modified to incorporate the sequences from these regions, including the bovine IgG1 hinge region and a predicted disulfide bonding motif linking the upper hinge region, the CH1 domain, and the light chain. This infliximab-bovine IgG1 chimera (bovinized infliximab) retained the antigen binding and neutralization activity of the WT sequence but was degraded 9-fold more slowly than the unmodified infliximab. This remarkable increase in stability with as few as 18 amino acid substitutions suggests that this bovinization process is a means to enable oral delivery of proven therapeutic antibodies as well as novel antibodies to targets that have been previously inaccessible to therapies delivered by injection.

Fourteen small molecule and biological agents for psoriatic arthritis: A network meta-analysis of randomized controlled trials

BACKGROUND

The comparative efficacy and safety of small molecule and biological agents in the treatment of psoriatic arthritis (PsA) remain unknown.

OBJECTIVES

To compare the efficacy and safety of 14 small molecule and biological agents by network meta-analysis (NMA).

METHODS

Relevant randomized controlled trials involving biological treatments for PsA were identified by searching PubMed, Cochrane Library, EMBASE, Web of Science, and Clinicaltrials.gov and by manual retrieval, up to June 2018. NMA was conducted with Stata 14.0 based on the frequentist method. Effect measures were odds ratios (ORs) with 95% confidence intervals (CIs). Intervention efficacy and safety were ranked according to the surface under the cumulative ranking curve (SUCRA).

RESULTS

A total of 30 studies involving 10,191 adult subjects were included. According to NMA, ≥ 20% improvement in modifed American College of Rheumatology response criteria (ACR20) response, Psoriasis Area and Severity Index 75 (PASI75) response, and serious adverse events rate (SAEs) were observed. In direct comparisons, most of the biologics performed better than placebo in terms of ACR20 response rate and PASI75 response rate. Additionally, all medicines were comparable to placebo in terms of SAEs except secukinumab. In terms of mixed comparisons, with regard to the ACR20 response, etanercept (ETN) and infliximab (IFX) were more effective than golimumab (GOL), with ORs of 3.33 (95% CI: 1.17-9.48) and 1.24 (95% CI: 0.61-2.52), respectively. For PASI75 response, IFX was superior to certolizumab pegol (OR = 10.08, 95% CI: 1.54-75.48). In addition, these medicines were comparable to each other in terms of SAEs. ETN and IFX were shown to have the most favorable SUCRA for achieving improved ACR20 and PASI75 responses, respectively, while ABT-122 exhibited the best safety according to the SUCRA for SAEs. Considering both the efficacy (ACR20, PASI75) and safety (SAEs), GOL, ETN, and IFX are the top 3 treatments.

CONCLUSIONS AND IMPLICATIONS

Direct and indirect comparisons and integrated results suggested that the 3 anti- tumor necrosis factor -α biologics (GOL, ETN, and IFX) can be considered the best treatments for PsA after comprehensive consideration of efficacy and safety.

Structural insight into TNF-α inhibitors through combining pharmacophore-based virtual screening and molecular dynamic simulation

Tumor Necrosis Factor-alpha (TNF-α), a multifunctional cytokine responsible for providing resistance against infections, inflammation, and cancers. TNF-α has emerged as a promising drug target against several autoimmune and inflammatory disorders. Several synthetic antibodies (Infliximab, Etanercept, and Adalimumab) are available, but their potential to cause severe side effects has prompted them to develop alternative small molecules-based therapies for inhibition of TNF-α. In the present study, combined in silico approaches based on pharmacophore modeling, virtual screening, molecular docking, and molecular dynamics studies were employed to understand significant direct interactions between TNF-α protein and small molecule inhibitors. Initially, four different small molecule libraries (∼17.5 million molecules) were virtually screened against the selected pharmacophore model. The identified hits were further subjected to molecular docking studies. The three potent lead compounds (ZINC05848961, ZINC09402309, ZINC04502991) were further subjected to 100 ns molecular dynamic studies to examine their stability. Our docking and molecular dynamic analysis revealed that the selected lead compounds target the TNF receptor (TNFR) and efficiently block the production of TNF. Moreover, in silico ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) analysis revealed that all the predicted compounds have good pharmacokinetic properties with high gastrointestinal absorption and a decent bioavailability score. Furthermore, toxicity profiles further evidenced that these compounds have no risk of being mutagenic, tumorigenic, reproductive and irritant except ZINC11915498. In conclusion, the present study could serve as the starting point to develop new therapeutic regimens to treat various TNF- related diseases. Communicated by Ramaswamy H. Sarma.

The trimer to monomer transition of Tumor Necrosis Factor-Alpha is a dynamic process that is significantly altered by therapeutic antibodies

The cytokine tumor necrosis factor-alpha (TNF-α) readily forms homotrimers at sub-nM concentrations to promote inflammation. For the treatment of inflammatory diseases with upregulated levels of TNF-α, a number of therapeutic antibodies are currently used as scavengers to reduce the active TNF-α concentration in patients. Despite their clinical success, the mode-of-action of different antibody formats with regard to a stabilization of the trimeric state is not entirely understood. Here, we use a biosensor with dynamic nanolevers to analyze the monomeric and trimeric states of TNF-α together with the binding kinetics of therapeutic biologics. The intrinsic trimer-to-monomer decay rate k = 1.7 × 10⁻³ s⁻¹ could be measured directly using a microfluidic system, and antibody binding affinities were analyzed in the pM range. Trimer stabilization effects are quantified for Adalimumab, Infliximab, Etanercept, Certolizumab, Golimumab for bivalent and monovalent binding formats. Clear differences in trimer stabilization are observed, which may provide a deeper insight into the mode-of-action of TNF-α scavengers.

Structural Basis for How Biologic Medicines Bind their Targets in Psoriasis Therapy

As biologic therapies become first line treatments for many inflammatory disorders, it becomes increasingly important for the practicing physician to be familiar with how these drugs function at the molecular level. This information is useful in making therapeutic decisions and helping patients understand their treatment options. It is critical to patient safety and clinical response that the molecular differences between these drugs inform prescribing practices. To this end, we present and analyze the available structural biology information about the biologics used in the treatment of psoriasis including inhibitors of tumor necrosis factor alpha (TNFα), interleukin-17 (IL-17), and interleukin-23 (IL-23). We describe and analyze the molecular surface character of known binding epitopes for medications in these classes, showing that significant differences exist in epitope location, hydrophobicity, and charge. Some of these differences can be correlated with clinical data, but our analysis ultimately points to the need for more structural information to allow for a better understanding of the structure-function relationship of biologic therapies.

Protein-protein interactions: a structural view of inhibition strategies and the IL-23/IL-17 axis

Protein-protein interactions are central to biology and provide opportunities to modulate disease with small-molecule or protein therapeutics. Recent developments in the understanding of the tractability of protein-protein interactions are discussed with a focus on the ligandable nature of protein-protein interaction surfaces. General principles of inhibiting protein-protein interactions are illustrated with structural biology examples from six members of the IL-23/IL-17 signaling family (IL-1, IL-6, IL-17, IL-23 RORγT and TNFα). These examples illustrate the different approaches to discover protein-protein interaction inhibitors on a target-specific basis that has proven fruitful in terms of discovering both small molecule and biologic based protein-protein interaction inhibitors.

Inflammatory bowel disease and targeted oral anti-TNFα therapy

Antibodies have provided invaluable treatment options for many diseases, with immunotherapy revolutionising the treatment of several inflammatory disorders including inflammatory bowel disease (IBD). Accumulating evidence suggests that IBD results from an inappropriate response to intestinal microbes and environmental factors in genetically susceptible individuals, with overactivity of the pro-inflammatory pathways. On a pathophysiological level, IBD is a complex disease with intestinal fibrosis, stenosis and an increased incidence of cancer observed in those whose disease is inadequately controlled over time. Regulating the actions of the pro-inflammatory cytokine human tumor necrosis factor-alpha (hTNFα) through the use of anti-TNFα monoclonal antibodies (e.g. infliximab, certolizumab, adalimumab and golimumab) has proven an effective intervention for IBD with their increased use a testament of their effectiveness. These agents are administered systemically thereby causing their distribution throughout the body in a condition that is localised to the gastrointestinal (GI) tract. Immunogenicity, the induction of anti-drug antibodies (ADAs), serum sickness and other undesirable side effects limit their use, whilst up to 50% of patients do not respond to initial therapy. Diseases confined to the GI tract are ideal for targeting by oral therapy which mitigates side effects and allows for lower doses to be administered. Several oral anti-TNFα agents have been investigated with success but are not yet in general clinical use. This partially reflects the fact that the oral administration of antibodies has many barriers including the harsh environment of the GI tract and the presence of enzymes including pepsin, trypsin and chymotrypsin in the intestine which provide significant challenges to targeted oral therapy.

The impact of thioredoxin reduction of allosteric disulfide bonds on the therapeutic potential of monoclonal antibodies

Therapeutic mAbs are used to manage a wide range of cancers and autoimmune disorders. However, mAb-based treatments are not always successful, highlighting the need for a better understanding of the factors influencing mAb efficacy. Increased levels of oxidative stress associated with several diseases are counteracted by the activities of various oxidoreductase enzymes, such as thioredoxin (Trx), which also reduces allosteric disulfide bonds in proteins, including mAbs. Here, using an array of in vitro assays, we explored the functional effects of Trx-mediated reduction on the mechanisms of action of six therapeutic mAbs. We found that Trx reduces the interchain disulfide bonds of the mAbs, after which they remain intact but have altered function. In general, this reduction increased antigen-binding capacity, resulting in, for example, enhanced tumor necrosis factor (TNF) neutralization by two anti-TNF mAbs. Conversely, Trx reduction decreased the antiproliferative activity of an anti-tyrosine kinase-type cell-surface receptor HER2 mAb. In all of the mAbs, Fc receptor binding was abrogated by Trx activity, with significant loss in both complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) activity of the mAbs tested. We also confirmed that without alkylation, Trx-reduced interchain disulfide bonds reoxidize, and ADCC activity is restored. In summary, Trx-mediated reduction has a substantial impact on the functional effects of an mAb, including variable effects on antigen binding and Fc function, with the potential to significantly impact mAb efficacy in vivo.

Crystal Structures of PF-06438179/GP1111, an Infliximab Biosimilar

BACKGROUND

Higher-order structure (HOS) assessment is an important component of biosimilarity evaluations. While established spectroscopic methods are routinely used to characterize structure and evaluate similarity, the addition of X-ray crystallographic analysis to these biophysical methods enables orthogonal elucidation of HOS at higher resolution.

METHODS

Crystal structures of the infliximab biosimilar PF-06438179/GP1111 and the reference product Remicade^®, sourced from US and European Union markets, were determined and compared to evaluate HOS similarity. Analytical ultracentrifugation studies were conducted to understand reversible self-association.

RESULTS

In contrast to more routine spectroscopic methods, the crystal structures enable three-dimensional assessment of complementarity-determining regions and other local regions at near-atomic resolution. The biosimilar structures are highly similar to those of the reference product, as demonstrated visually and though all-atom root-mean-squared deviation measurements.

CONCLUSION

The structures provide new insights into the physicochemical properties of the proposed biosimilar and the reference product, further strengthening the 'totality of evidence' in the evaluation of similarity.

Development and Characterization of a Potent Tumor Necrosis Factor-Alpha-Blocking Agent

Tumor necrosis factor-α (TNFα), one of the major proinflammatory cytokines, plays a key role in an effective immune response. However, the chronic presence of TNFα can lead to several inflammatory disorders, such as rheumatoid arthritis, psoriasis, Crohn's disease, etc. Inhibition of TNFα by pharmacological inhibitors or antibodies has proven to be effective in palliative treatment to some extent. The aim of this study was to develop an anti-TNFα antibody, which may be used as a therapeutic option to inhibit TNFα-mediated cytotoxicity. We characterized several hybridoma clones secreting monoclonal antibodies (mAbs) to human-TNFα. Four mAbs rescued L929 fibroblast cells from TNFα-triggered cell death and one of these, namely C8, was found to have the highest affinity. To gain insights into the mechanism by which mAb C8 inhibits human TNFα-mediated toxicity, the epitope corresponding to the mAb was delineated. The antigenic determinant was found to comprise of the stretch of amino acids 99-120, of which, 102-104 (glutamine, arginine, glutamic acid) form the core epitope. The observation was supported by bioinformatics analyses of an antigen/antibody complex model. In addition, the binding affinity of mAb C8 to TNFα was found to be comparable with that of infliximab, which is a commercially available anti-TNFα mAb.

Toll-like receptor-induced cytokines as immunotherapeutic targets in cancers and autoimmune diseases

Immune cells of the myeloid and lymphoid lineages express Toll-like receptors (TLRs) to recognize pathogenic components or cellular debris and activate the immune system through the secretion of cytokines. Cytokines are signaling molecules that are structurally and functionally distinct from one another, although their secretion profiles and signaling cascades often overlap. This situation gives rise to pleiotropic cell-to-cell communication pathways essential for protection from infections as well as cancers. Nonetheless, deregulated signaling can have detrimental effects on the host, in the form of inflammatory or autoimmune diseases. Because cytokines are associated with numerous autoimmune and cancerous conditions, therapeutic strategies to modulate these molecules or their biological responses have been immensely beneficial over the years. There are still challenges in the regulation of cytokine function in patients, even in those who take approved biological therapeutics. In this review, our purpose is to discuss the differential expression patterns of TLR-regulated cytokines and their cell type specificity that is associated with cancers and immune-system-related diseases. In addition, we highlight key structural features and molecular recognition of cytokines by receptors; these data have facilitated the development and approval of several biologics for the treatment of autoimmune diseases and cancers.

Assessing the Extended In-Use Stability of the Infliximab Biosimilar PF-06438179/GP1111 Following Preparation for Intravenous Infusion

Objective

PF-06438179/GP1111 (PF-SZ-IFX) is an infliximab biosimilar. We evaluated the extended in-use physicochemical and biological stability of PF-SZ-IFX upon preparation for intravenous infusion.

Methods

Two batches of PF-SZ-IFX were reconstituted to a concentration of 10 mg/mL and subsequently diluted to 0.4 and 4.0 mg/mL, representing the clinically relevant range for intravenous infusion. Dilution was performed in polyethylene saline infusion bags, which are commonly used in clinical practice. To simulate product handling under worst-case conditions, reconstituted solutions were stored for up to 30 days at 5 ± 3 °C and up to 14 days at 25 ± 2 °C (60 ± 5% relative humidity); diluted solutions were stored for up to 30 days under the same sets of conditions. Physicochemical and biological stability were evaluated according to pH, osmolality, appearance, particulate content, protein concentration, proportions of molecular weight variants and charge variants and potency. Standard and state-of-the-art analytical techniques were employed, including imaged isoelectric focusing, size exclusion chromatography, reducing sodium dodecyl sulphate capillary electrophoresis and functional cell-based bioassay.

Results

Across batches and concentrations of PF-SZ-IFX, all parameters resided within the predefined acceptance criteria, including pH, osmolality, particulate content, clarity, protein concentration, molecular weight variants, charge variants and potency, for up to 30 days under both storage conditions tested (up to 14 days for reconstituted samples stored at 25 ± 2 °C).

Conclusions

Physicochemical and biological analyses demonstrated that the infliximab biosimilar PF-SZ-IFX was not affected by extended storage of the diluted preparations used for intravenous infusion.

Synthetic antibody protein mimics of infliximab by molecular scaffolding on novel CycloTriVeratrilene (CTV) derivatives

Syntheses of novel semi-orthogonally protected CycloTriVeratrilene (CTV) analogues with enhanced water solubility, that is 3 and 4, derived from the previously described CTV scaffold derivative 2 are described here. These scaffolds 2-4 enabled a sequential introduction of three different complementarity determining region (CDR) mimics via Cu(i)-catalysed azide-alkyne cycloaddition towards medium-sized protein mimics denoted as "synthetic antibodies". The highly optimised sequential introduction enabled selective attachment of three different CDR mimics in a one-pot fashion. This approach of obtaining synthetic antibodies, demonstrated by the synthesis of paratope mimics of monoclonal antibody infliximab (Remicade®), provided a facile access to a range of (highly) pre-organised molecules bearing three different (cyclic) peptide segments and may find a wide range of applications in the field of protein-protein interaction disruptors as well as in the development of synthetic vaccines or lectin mimics. The prepared synthetic antibodies were tested for their affinity towards tumour necrosis factor alpha using surface plasmon resonance and synthetic antibodies with micromolar affinities were uncovered.

MAbTope: A Method for Improved Epitope Mapping

Abs are very efficient drugs, ∼70 of them are already approved for medical use, over 500 are in clinical development, and many more are in preclinical development. One important step in the characterization and protection of a therapeutic Ab is the determination of its cognate epitope. The gold standard is the three-dimensional structure of the Ab/Ag complex by crystallography or nuclear magnetic resonance spectroscopy. However, it remains a tedious task, and its outcome is uncertain. We have developed MAbTope, a docking-based prediction method of the epitope associated with straightforward experimental validation procedures. We show that MAbTope predicts the correct epitope for each of 129 tested examples of Ab/Ag complexes of known structure. We further validated this method through the successful determination, and experimental validation (using human embryonic kidney cells 293), of the epitopes recognized by two therapeutic Abs targeting TNF-α: certolizumab and golimumab.

Assessment of the higher order structure of Humira®, Remicade®, Avastin®, Rituxan®, Herceptin®, and Enbrel® by 2D-NMR fingerprinting

The advent of monoclonal antibody biosimilar products has stimulated the development of analytical methods that can better characterize an important quality attribute, namely the higher order structure (HOS). Here, we propose a simple approach based on heteronuclear 2D NMR techniques at natural abundance for generating spectral fingerprints of the HOS at high resolution. We show that the proposed method can assess the HOS of six therapeutic products, adalimumab (Humira®), bevacizumab (Avastin®), infliximab (Remicade®), rituximab (Rituxan®), trastuzumab (Herceptin®), and Etanercept (Enbrel®). After treatment with immobilized papain, the purified fragments (Fab and Fc) were analyzed by 2D proton-nitrogen and proton-carbon NMR correlations. All Fab and Fc fragments produced high-resolution 2D-NMR spectra from which assessment of their higher order structure can be performed in the context of comparability studies. In particular, the two different sequences of Fc fragments could be unambiguously distinguished. The results show that it is possible to obtain structurally dependent information at amino acid resolution of these important therapeutic agents.

Structure Based Prediction of Asparagine Deamidation Propensity in Monoclonal Antibodies

Identification of asparagine (Asn) sites that are prone to deamidation is critical for the development of therapeutic monoclonal antibodies (mAbs). Despite a common chemical degradation pathway, the rates of Asn deamidation can vary dramatically among different sites, and prediction of the sensitive deamidation sites is still challenging. In this study, characterization of Asn deamidation for five IgG1 and five IgG4 mAbs under both normal and stressed conditions revealed dramatic differences in the Asn deamidation rates. A comprehensive analysis of the deamidation sites indicated that the deamidation rate differences could be explained by differences in the local structure conformation, structure flexibility and solvent accessibility. A decision tree was developed to predict the deamidation propensity for all Asn sites in IgG mAbs based on the analysis of these three structural parameters. This decision tree will allow potential Asn deamidation hot spots to be identified early in development.

Role of biologics and biosimilars in inflammatory bowel disease: current trends and future perspectives

Inflammatory bowel disease (IBD) is an idiopathic chronic inflammatory disease of the gastrointestinal system. The spectrum is of predominantly two types, namely, ulcerative colitis and Crohn’s disease. The incidence of IBD has been increasing steadily since 1990, and so the number of agents used in their treatment. Biologics that are derived partly or completely from living biological sources such as animals and humans have become widely available, which provide therapeutic benefits to the IBD patients. Currently, monoclonal antibodies against tumor necrosis factor-alpha (infliximab, adalimumab, certolizumab, and golimumab), integrins (vedolizumab and natalizumab), and interleukin (IL)-12 and IL-23 antagonists (ustekinumab) are approved for use in IBD. Biosimilars of infliximab and adalimumab are also available for the treatment of IBD. This review summarizes the clinical pharmacology, studies leading to their approval, overall indications and their use in IBD, usage in pregnancy and lactation, and the adverse effects of these agents. This review also summarizes the recent advances and future perspectives specific to biologics and biosimilars in IBD.

Structural basis for tumor necrosis factor blockade with the therapeutic antibody golimumab

Tumor necrosis factor α (TNFα) is a proinflammatory cytokine, and elevated levels of TNFα in serum are associated with various autoimmune diseases, including rheumatoid arthritis (RA), ankylosing spondylitis (AS), Crohn's disease (CD), psoriasis, and systemic lupus erythaematosus. TNFα performs its pleiotropic functions by binding to two structurally distinct transmembrane receptors, TNF receptor (TNFR) 1 and TNFR2. Antibody-based therapeutic strategies that block excessive TNFα signaling have been shown to be effective in suppressing such harmful inflammatory conditions. Golimumab (Simponi®) is an FDA-approved fully human monoclonal antibody targeting TNFα that has been widely used for the treatment of RA, AS, and CD. However, the structural basis underlying the inhibitory action of golimumab remains unclear. Here, we report the crystal structure of the Fv fragment of golimumab in complex with TNFα at a resolution of 2.73 Å. The resolved structure reveals that golimumab binds to a distinct epitope on TNFα that does not overlap with the binding residues of TNFR2. Golimumab exerts its inhibitory effect by preventing binding of TNFR1 and TNFR2 to TNFα by steric hindrance. Golimumab does not induce conformational changes in TNFα that could affect receptor binding. This mode of action is specific to golimumab among the four anti-TNFα therapeutic antibodies currently approved for clinical use.

BAFF-neutralizing interaction of belimumab related to its therapeutic efficacy for treating systemic lupus erythematosus

BAFF, a member of the TNF superfamily, has been recognized as a good target for autoimmune diseases. Belimumab, an anti-BAFF monoclonal antibody, was approved by the FDA for use in treating systemic lupus erythematosus. However, the molecular basis of BAFF neutralization by belimumab remains unclear. Here our crystal structure of the BAFF-belimumab Fab complex shows the precise epitope and the BAFF-neutralizing mechanism of belimumab, and demonstrates that the therapeutic activity of belimumab involves not only antagonizing the BAFF-receptor interaction, but also disrupting the formation of the more active BAFF 60-mer to favor the induction of the less active BAFF trimer through interaction with the flap region of BAFF. In addition, the belimumab HCDR3 loop mimics the DxL(V/L) motif of BAFF receptors, thereby binding to BAFF in a similar manner as endogenous BAFF receptors. Our data thus provides insights for the design of new drugs targeting BAFF for the treatment of autoimmune diseases.

Structural Biology of the TNFα Antagonists Used in the Treatment of Rheumatoid Arthritis

The binding of the tumor necrosis factor α (TNFα) to its cognate receptor initiates many immune and inflammatory processes. The drugs, etanercept (Enbrel^®), infliximab (Remicade^®), adalimumab (Humira^®), certolizumab-pegol (Cimzia^®), and golimumab (Simponi^®), are anti-TNFα agents. These drugs block TNFα from interacting with its receptors and have enabled the development of breakthrough therapies for the treatment of several autoimmune inflammatory diseases, including rheumatoid arthritis, Crohn's disease, and psoriatic arthritis. In this review, we describe the latest works on the structural characterization of TNFα-TNFα antagonist interactions related to their therapeutic efficacy at the atomic level. A comprehensive comparison of the interactions of the TNFα blockers would provide a better understanding of the molecular mechanisms by which they neutralize TNFα. In addition, an enhanced understanding of the higher order complex structures and quinary structures of the TNFα antagonists can support the development of better biologics with the improved pharmacokinetic properties. Accumulation of these structural studies can provide a basis for the improvement of therapeutic agents against TNFα for the treatment of rheumatoid arthritis and other autoimmune inflammatory diseases in which TNFα plays an important role in pathogenesis.

Higher order structures of Adalimumab, Infliximab and their complexes with TNFα revealed by electron microscopy

Adalimumab and Infliximab are recombinant IgG1 monoclonal antibodies (mAbs) that bind and neutralize human tumor necrosis factor alpha (TNFα). TNFα forms a stable homotrimer with unique surface-exposed sites for Adalimumab, Infliximab, and TNF receptor binding. Here, we report the structures of Adalimumab-TNFα and Infliximab-TNFα complexes modeled from negative stain EM and cryo-EM images. EM images reveal complex structures consisting of 1:1, 1:2, 2:2, and 3:2 complexes of Adalimumab-TNFα and Infliximab-TNFα. The 2:2 complex structures of Adalimumab-TNFα and Infliximab-TNFα show diamond-shaped profiles and the 2D class averages reveal distinct orientations of the Fab domains, indicating different binding modes by Adalimumab and Infliximab to TNFα. After separation by size exclusion chromatography and analysis by negative stain EM, the 3:2 complexes of Adalimumab-TNFα or Infliximab-TNFα complexes are more complicated but retain features recognized in the 2:2 complexes. Preliminary cryo-EM analysis of 3:2 Adalimumab-TNFα complex generated a low-resolution density consistent with a TNFα trimer bound with three Fab domains from three individual antibody molecules, while each antibody molecule binds to two molecules of TNFα trimer. The Fc domains are not visible in the reconstruction. These results show the two mAbs form structurally distinct complexes with TNFα.

Glycan and Peptide IgE Epitopes of the TNF-alpha Blockers Infliximab and Adalimumab - Precision Diagnostics by Cross-Reactivity Immune Profiling of Patient Sera

Biological drugs like therapeutic antibodies are widely used for the treatment of various diseases like inflammatory disorders and cancer. A drawback of these novel treatments is the substantial proportion of patients experiencing adverse reactions such as loss-of-drug effect or hypersensitivity reactions. These reactions are associated with pre-existing and/or developing anti-drug antibodies. Especially IgE development is a risk factor for life-threatening systemic anaphylaxis.

Methods: In order to characterize the individual drug-specific serum IgE, an IgE cross-reactivity immune profiling (ICRIP) assay was developed. Individual IgG epitopes of anti-drug antibodies against adalimumab were identified by epitope mapping via peptide microarray.

Results: ICRIP analyses of sera from patients treated with the therapeutic antibodies adalimumab (ADL) and infliximab (IFX) reveal individual, distinct IgE binding patterns. IgG epitopes were identified mostly located in the variable region of ADL.

Conclusions: Using ICRIP and peptide microarrays for pharmacovigilance of the TNF-α blockers IFX and ADL, risk factors and biomarkers before and during therapy shall be identified. These diagnostic systems provide the basis for a safe and efficacious therapy decision for each patient in cases of adverse drug reactions mediated by different types of anti-drug antibodies.

Natural Conformational Sampling of Human TNFα Visualized by Double Electron-Electron Resonance

Double electron-electron resonance in conjunction with site-directed spin labeling has been used to probe natural conformational sampling of the human tumor necrosis factor α trimer. We suggest a previously unreported, predeoligomerization conformation of the trimer that has been shown to be sampled at low frequency. A model of this trimeric state has been constructed based on crystal structures using the double-electron-electron-resonance distances. The model shows one of the protomers to be rotated and tilted outward at the tip end, leading to a breaking of the trimerous symmetry and distortion at a receptor-binding interface. The new structure offers opportunities to modulate the biological activity of tumor necrosis factor α through stabilization of the distorted trimer with small molecules.

Anti-TNFα therapy in inflammatory lung diseases

Increased levels of tumor necrosis factor (TNF) α have been linked to a number of pulmonary inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), sarcoidosis, and interstitial pulmonary fibrosis (IPF). TNFα plays multiple roles in disease pathology by inducing an accumulation of inflammatory cells, stimulating the generation of inflammatory mediators, and causing oxidative and nitrosative stress, airway hyperresponsiveness and tissue remodeling. TNFα-targeting biologics, therefore, present a potentially highly efficacious treatment option. This review summarizes current knowledge on the role of TNFα in pulmonary disease pathologies, with a focus on the therapeutic potential of TNFα-targeting agents in treating inflammatory lung diseases.

An orthogonally protected CycloTriVeratrylene (CTV) as a highly pre-organized molecular scaffold for subsequent ligation of different cyclic peptides towards protein mimics

The synthesis of a semi-orthogonally protected CycloTriVeratrilene (CTV) scaffold derivative as well as the sequential introduction of three different peptide loops onto this molecular scaffold via Cu(I)-catalyzed azide alkyne cycloaddition towards a medium-sized protein mimic is described. This approach for the construction of medium-sized protein mimics is illustrated by the synthesis of a paratope mimic of the monoclonal antibody Infliximab (Remicade®) and provides access to a range of highly pre-organized molecular constructs bearing three different peptide segments. This approach may find wide applications for development of protein-protein interaction disruptors as well as synthetic vaccines.