Fc Portion Research Articles

Abstract 2287: Bispecific anti-PD1 checkpoint inhibitors antibodies (BiCKI), an optimized platform designed to tackle anti-PD-(L)1 primary and secondary resistance mechanisms

Abstract Although Anti PD(L)1 therapy lead to impressive therapeutic responses by reinvigorating T cells, primary and secondary resistances occur de novo or during treatment impeding the full efficacy of the drug. To tackle this resistance mechanisms and reduced the immunotoxicity of combination therapy, we designed a 2nd generation of anti-PD1 antibody by fusing immune protein to the Fc portion of the antibody, named BiCKI®. The anti PD1 will more selectively drive the immune active drug on antigen-experienced (PD1+) T cells, through cis-targeting mechanism. These bifunctional molecules were designed with an optimized anti-PD1 backbone for bispecific format, fused to an active protein domain to the C-ter of heavy and/or light chains. Different protein candidate were successfully fused to the optimized anti-PD1, such as cytokines, costimulatory molecules, or dominant negative receptors with PD1/PDL1 full antagonistic activity. In contrast to combination, BiCKI® antibodies enable the simultaneous dual-binding specificity in a single drug allowing a synergistic activation. Each BiCKI® is selected on its synergistic capacity to re-activate of anti-tumor T cell responses or TCR signaling in cell-based assays. Bispecific antibody development in clinic has been hampered by difficult manufacturing process, reduced pharmacokinetic (PK) and drug exposure. Both anti PD-1 CDRs and VH/VL framework sequences were carefully selected and optimized for bioproductivity and biostability of the molecule. A 2 to 15-fold increased productivity in mammalian cells was observed versus the non-optimized anti-PD1 antibody or other anti-PD-1 bispecific backbones as Pembrolizumab or Nivolumab. We also evaluated the impact of the Fc isotype,linker flexibility and affinity of the fused compound on the PK profile of different bispecifics fused to costimulatory molecules or cytokines. The IgG isotype with reduced FcgR binding property, of the anti-PD-1 backbone was associated with a better PK profile with some exceptions for cytokine. The presence or length of a linker between Fc domain and the fused protein has a small impact the PK and drug efficacy. More importantly, the affinity of the fused compound has an impact the PK profile of BiCKI® For example, the anti-PD-1 fused to wild-type IL-7 cytokine possesses a high affinity for the CD127/CD132 receptors but display a reduced drug exposure both in mouse and cynomolgus. This potential difficulty was solved with further improved products including IL-7 mutants having reduced affinity for CD127 and/or CD132. While significant correlation between IL7 affinity and PK has been observed, increased PK and drug exposure could be achieved using optimized combination of Fc isotype a linker length design and BiCKI-IL7 mutants retaining significant IL7R signaling. Conclusion: Our BICKI® platform was designed to overcome major hurdles of bispecific antibody development, we improved its manufacturability and drug exposure by selectively designing the structure of bispecific antibodies. By fusing costimulatory molecule, cytokines or dominant negative receptor to the anti PD-1 blocking antibody, we can generate and select various efficient bispecific molecules acting in synergy to counteract primary and secondary resistance mechanisms of anti-PD(L)1 therapies. Citation Format: Caroline Mary, Aurore Morello, Virginie Thepenier, Géraldine Teppaz, Justine Durand, Nicolas Poirier. Bispecific anti-PD1 checkpoint inhibitors antibodies (BiCKI), an optimized platform designed to tackle anti-PD-(L)1 primary and secondary resistance mechanisms [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2287.

Abstract 910: A novel bifunctional anti-PD-1 IL-7 fusion protein to reinvigorate exhausted T cell and disarms Treg suppressive activity

Abstract Despite the clinical success of anti-PD(L)1 therapy, the majority of patient remain unresponsive or fail to develop a durable response. We explored a second generation of PD-1 antibody by fusing IL-7 cytokine to the Fc portion, called BiCKI® IL-7. The high affinity of the anti PD-1 antibody will allow the concentration/retention of the drug into the tumor microenvironment and preferentially deliver IL-7 in cis-dependent manner to PD-1+ cells. IL-7 is an optimal target for immunotherapy to preferentially stimulate effector T-cell (Teff) functions over regulatory T-cells (Treg)due to the differential expression of IL-7R and poor capacity of IL-7 to stimulate Treg proliferation. Moreover, It has been published that PD-1 blockades increase IL-7R expression and improve IL-7 signaling in exhausted T-cells rationalizing our combinatorial approach. Results Our anti PD-1/IL-7 bispecific antibody efficiently blocks the PD-1/PD-L1 and PD-L2 interactions and the PD-1-mediated inhibitory signal (pSHP1) and in parallel activates IL-7R pSTAT5 signaling into T cells. Anti PD-1/IL-7 preferentially binds in cis to T cells coexpressing PD-1 and CD127 enabling a selective activation of primed antigen- experienced T cells over PD1-negative (e.g. naïve) cells. A high affinity/avidity of the molecule was observed using biosensor when both receptor CD127 and PD-1, supporting the cis-targeting activity of the drug. Using in vitro T cell activation bioassay, we observed that IL-7 portion fused to the anti-PD-1 synergizes to enhance TCR mediated signaling (NFAT) through activation of the non-canonical pathway while IL-7 in combination with anti-PD1 (two separates product) has no additive effect. Although IL-7R expression decrease over chronic stimulation of Teff cells, we demonstrated that IL-7 efficiently activates progenitor and some fully-exhausted human T-cells (pSTAT5) and maintain their proliferation and survival capacity. This IL-7R signaling activation was associated with a significant increased IFNγ secretion using ex-vivo fresh human tumor explant culture. A significant higher IFNγ production was obtained with anti PD-1/IL-7compared to anti PD-1 treatment alone, including in non-responder patients to anti-PD1, suggesting that the anti PD-1/IL-7 bispecific can reactivate TILs that are resistant to PD-1 therapy. Knowing that Tregs have a key suppressive function, we also explored the possibility that anti-PD-1/IL-7 affect Treg functions. In a human Treg/Teff coculture assay, anti PD-1/IL-7 abrogates the Treg capacity to inhibit proliferation and IFN-g secretion of CD8+ Teff. Moreover, IL-7 and anti-PD-1/IL-7 does not stimulate Treg proliferation, in contrast to IL-2 and IL-15. Conclusion Our data validate the therapeutic potential of providing IL-7 signals to overcome PD-1 resistance. The bifunctional anti-PD1/IL-7 favors the T-cell effector over T-regulatory immune balance by stimulating Teff cells and exhausted T-cell, while disarming Tregs suppressive functions. Citation Format: Aurore Morello, Justine Durand, Virginie Thepenier, Géraldine Teppaz, Margaux Seite, Sabrina Pengam, Caroline Mary, Nicolas Poirier. A novel bifunctional anti-PD-1 IL-7 fusion protein to reinvigorate exhausted T cell and disarms Treg suppressive activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 910.

An IgA mimicry of IgG that binds Polymeric Immunoglobulin Receptor for mucosa transcytosis.

Most pathogens establish infection through mucosa, where secretory immunoglobulin A (sIgA) plays an ‘immune exclusion’ role in humoral defense. Extravasation of intravenously (i.v.) administrated therapeutic immunoglobulin G (IgG) mainly relies on convection and/or neonatal Fc receptor-mediated transcytosis from circulation into interstitial space. Active transport of interstitial IgG further across epithelium into mucosa, like sIgA, is a much desired feature for the next generation of therapeutic antibodies, especially for anti-infection purposes. For the first time, we report the engineering of an IgA mimicry of IgG, with its Fc portion in fusion with the 18-aa tail piece (tp) of sIgA and the J chain, possessing sIgA’s full binding activity towards polymeric immunoglobulin receptor that mediates mucosa transcytosis. In a diphtheria toxin receptor (DTR) knockin mouse model, i.v. injected anti-diphtheria toxin (DT) IgG(tp)J protected DTR+ cells from deletion upon DT injection. The compact design of IgG(tp)J opens new revenues for more effective therapeutic IgG mimicking some of the important biological functions of IgA.

Porcine CLEC12B is expressed on alveolar macrophages and blood dendritic cells

CLEC12B is a C-type lectin-like receptor expressed on myeloid cells. In this study, we have characterized the porcine homologue of CLEC12B (poCLEC12B). To this end, we have generated constructs encoding a c-myc tagged version of the whole receptor, or its ectodomain fused to the Fc portion of human IgG1, from a cDNA clone obtained from an alveolar macrophage library, and raised monoclonal antibodies (mAb) against this molecule. Using these mAbs, poCLEC12B was found to be expressed on alveolar macrophages and, at lower levels, on blood conventional type 1 dendritic cells (cDC1) and plasmacytoid DCs. No binding was detected on monocytes, monocyte-derived macrophages or monocyte-derived DCs. Engagement of CLEC12B on alveolar macrophages with mAbs had no apparent effect on cytokine production (TNF-α, IL-8) induced by LPS. These results provide the basis for future investigations aimed to assess the role of poCLEC12B in different microbial infections and to evaluate its potential in vaccination strategies targeting DCs.

Nectin4 is a novel TIGIT ligand which combines checkpoint inhibition and tumor specificity

BackgroundThe use of checkpoint inhibitors has revolutionized cancer therapy. Unfortunately, these therapies often cause immune-related adverse effects, largely due to a lack of tumor specificity.MethodsWe stained human natural killer cells...

Assessment of Human Natural Killer Cell Events Driven by FcγRIIIa Engagement in the Presence of Therapeutic Antibodies.

One mechanism of action for clinical efficacy by therapeutic antibodies is the promotion of immune-related functions, such as cytokine secretion and cytotoxicity, driven by FcγRIIIa (CD16) expressed on natural killer (NK) cells. These observations have led to research focusing on methods to increase Fc receptor-mediated events, which include removal of a fucose moiety found on the Fc portion of the antibody. Further studies have elucidated the mechanistic changes in signaling, cellular processes, and cytotoxic characteristics that increase ADCC activity with afucosylated antibodies. Additionally, other studies have shown the potential benefits of these antibodies in combination with small molecule inhibitors. These experiments demonstrated the molecular and cellular mechanisms underlying the benefits of using afucosylated antibodies in combination settings. Many of these observations were based on an artificial in vitro activation assay in which the FcγRIIIa on human NK cells was activated by therapeutic antibodies. This assay provided the flexibility to study downstream effector NK cell functions, such as cytokine production and degranulation. In addition, this assay has been used to interrogate signaling pathways and identify molecules that can be modulated or used as biomarkers. Finally, other therapeutic molecules (i.e., small molecule inhibitors) have been added to the system to provide insights into the combination of these therapeutics with therapeutic antibodies, which is essential in the current clinical space. This manuscript aims to provide a technical foundation for performing this artificial human NK cell activation assay. The protocol demonstrates key steps for cell activation as well as potential downstream applications that range from functional readouts to more mechanistic observations.

CD32a receptor in health and disease

Low-affinity Fcγ-receptors that recognize the Fc portion of immunoglobulin (Ig) molecules, usually being in antigen-bound state, thus representing a link between innate and adaptive immunity. They play a significant role in inflammatory and infectious diseases. Among them, a separate FcγRII family (CD32) is discerned, which is characterized by transmission of intracellular signal independently of the common γ-chain, they have one α-chain containing two extracellular immunoglobulin-like domains. FcγRII receptors are present in almost all cells of the innate immune system: monocytes and macrophages, neutrophils, eosinophils, dendritic cells, as well as on B-lymphocytes and platelets. They perform two main functions: target recognition, facilitation of phagocytosis and destruction of antibody-opsonized cells by monocytes/ macrophages (including pathogenic cells). In parallel, the phagocytes are activated via the cytokine synthesis stimulation. The FcγRIIA (CD32a) and FcγRIIC (CD32c) activating receptors, like as FcγRIIB (CD32b) inhibiting receptors are present among the members of the FcγRII family. The low-affinity FcγRII receptors bind to IgG, with immune complexes being their natural ligands. High levels of immune complexes are usually found in both chronic viral infections and autoimmune diseases. There are shown polymorphic variants of the CD32a gene, which can affect the receptor function, and, thereby, causing susceptibility for different infections, influence the development of autoimmune diseases and primary immunodeficiencies. Activation of the CD32a receptor induces the production of pro-inflammatory cytokines, including TNFα and interferons, that are involved into inflammation in systemic lupus erythematosus, Kawasaki disease, Graves’ disease and rheumatoid arthritis. It has been shown that antibacterial activity of platelets is carried out via the CD32a receptor. The study of CD32a expression in people The CD32a receptor is considered a biomarker of cells that are a reservoir of HIV infection. At the present time, however, many questions remain regarding the mechanisms of CD32a expression of on HIV-infected cells and the role of CD32a in the formation of an HIV reservoir and/or development of appropriate resistance. In addition to HIV infection, the significance of FcγR receptors is shown in other infectious diseases, for example, with influenza and dengue virus infections. Better understanding of the CD32a structure and function will help to assess its role in immunopathogenesis of different conditions. This review focuses on the role of CD32a in development of the normal immune response in normal state and various diseases.

Assessment of FcgRIIIA single nucleotide polymorphisms (SNPs) on the efficacy of IgG1 monoclonal antibodies (mAbs) in PANGEA study patients (pts) with advanced gastroesophageal adenocarcinoma (aGEA).

4526 Background: Targeted therapies (Ttx) have had limited efficacy in aGEA. The phase IIa PANGEA trial assessed the outcomes of pts treated with IgG1 mAbs targeting receptor tyrosine kinases (RTKs) or PD-1 based on predefined molecular groups. The fragment C (Fc) portion of mAbs binds to IgG receptors (FcgR) of immunologic effector cells such as natural killer (NK) cells, leading to antibody-dependent cell-mediated cytotoxicity (ADCC). The FcgR subclass, FcgRIIIA, has genetic variants with different Fc binding affinities. A single nucleotide polymorphism (SNP) in FcgRIIIA substitutes phenylalanine (F) with valine (V) at amino acid position 158, enhancing FcgR’s affinity for the IgG1 Fc domain. Pts with V/V or V/F FcgRIIIA allotypes have enhanced NK cell binding affinity compared to the homozygous F/F allotype. We evaluated the association of FcgRIIIA SNPs on Ttx outcomes amongst PANGEA pts and another cohort of aGEA pts treated with IgG1 mAbs. Methods: Whole-blood samples were identified from aGEA pts (N = 104), including 70/80 available PANGEA pts, who were treated with an IgG1 mAb (trastuzumab 24, anti-EGFR 21, anti-PD1 30, ramucirumab 48) in at least 1 Ttx line. After lymphocyte DNA extraction, FcgRIIIA genotyping was performed. The Cox proportional hazard model and log-rank tests, adjusted for pt age, were used to assess for an association of genotype with overall survival (OS). Results: Of 104 genotyped pts, the F/F, F/V & V/V genotypes were observed at a frequency of 32%, 51% and 17% respectively. There was no significant difference in median OS (mOS) between the F/F, F/V or V/V or comparing F/F vs V/F+V/V overall, nor in the PANGEA-only cohort. A trend of increased mOS was seen in 20 non-PANGEA pts harboring F/V or V/V compared to 14 F/F pts (mOS 43.4 vs 23.1 months, HR 0.41 [0.15-1.14] p = 0.09). However, 3-year OS rates trended higher in V/F+V/V pts (22%, 16/71) compared to F/F pts (7%, 2/33) (p = 0.09). At 3 years, 50% of V/V+V/F non-PANGEA pts were alive versus 13% of F/F pts (p = 0.04), while 13% of V/V+V/F PANGEA pts were alive versus 0% of F/F pts (p = 0.32). Conclusions: Amongst pts receiving IgG1 mAbs, the high affinity V FcgRIIIA SNP enriched for a subgroup of ‘extreme responders’ alive 3 years from diagnosis. Multivariate analyses accounting for baseline characteristics in a larger number of pts are ongoing to further elucidate the role of FcgRIIIA SNPs as predictive biomarkers. These findings may have implications on IgG1 mAb ADCC optimization.

Generation of Novel Diagnostic and Therapeutic Exosomes to Detect and Deplete Protumorigenic M2 Macrophages.

Given their protumorigenic function and prevalence in most malignant tumors with lower survival; early detection, and intervention of CD206-positive M2 macrophages may boost the clinical outcome. To determine in vivo distribution of M2 macrophages, 111In-oxine-based radiolabeling of the targeted exosomes is adopted. When these radiolabeled targeted exosomes are injected into breast tumor-bearing mice, exosomes accumulate at the periphery of the primary tumor, metastatic foci in the lungs, spleen, and liver. Ex vivo quantification of radioactivity also shows similar distribution. Injecting DiI dye-labeled exosomes into the same mice shows adherence of exosomes to the CD206-positive M2 macrophages on ex vivo fluorescent microscopy imaging. In addition, these engineered exosomes are utilized to carry the Fc portion of lgG2b with the intention of augmenting antibody-dependent cell-mediated cytotoxicity. It is demonstrated that M2 macrophage targeting therapeutic exosomes deplete M2 macrophages both in vitro and in vivo, and reduce tumor burden, increasing survival in a metastatic breast cancer model.

Targeting the IGF-Axis for Cancer Therapy: Development and Validation of an IGF-Trap as a Potential Drug.

The insulin-like growth factor (IGF)-axis was implicated in cancer progression and identified as a clinically important therapeutic target. Several IGF-I receptor (IGF-IR) targeting drugs including humanized monoclonal antibodies have advanced to phase II/III clinical trials, but to date, have not progressed to clinical use, due, at least in part, to interference with insulin receptor signaling and compensatory signaling by the insulin receptor (IR) isoform A that can bind IGF-II and initiate mitogenic signaling. Here we briefly review the current state of IGF-targeting biologicals, discuss some factors that may be responsible for their poor performance in the clinic and outline the stepwise bioengineering and validation of an IGF-Trap—a novel anti-cancer therapeutic that could bypass these limitations. The IGF-Trap is a heterotetramer, consisting of the entire extracellular domain of the IGF-IR fused to the Fc portion of human IgG1. It binds human IGF-I and IGF-II with a three-log higher affinity than insulin and could inhibit IGF-IR driven cellular functions such as survival, proliferation and invasion in multiple carcinoma cell models in vitro. In vivo, the IGF-Trap has favorable pharmacokinetic properties and could markedly reduce metastatic outgrowth of colon and lung carcinoma cells in the liver, outperforming IGF-IR and ligand-binding monoclonal antibodies. Moreover, IGF-Trap dose-response profiles correlate with their bio-availability profiles, as measured by the IGF kinase receptor-activation (KIRA) assay, providing a novel, surrogate biomarker for drug efficacy. Our studies identify the IGF-Trap as a potent, safe, anti-cancer therapeutic that could overcome some of the obstacles encountered by IGF-targeting biologicals that have already been evaluated in clinical settings.

Fc-modified HIT-like monoclonal antibody as a novel treatment for sepsis

AbstractSepsis is characterized by multiorgan system dysfunction that occurs because of infection. It is associated with high morbidity and mortality and is in need of improved therapeutic interventions. Neutrophils play a crucial role in sepsis, releasing neutrophil extracellular traps (NETs) composed of DNA complexed with histones and toxic antimicrobial proteins that ensnare pathogens, but also damage host tissues. At presentation, patients often have a significant NET burden contributing to the multiorgan damage. Therefore, interventions that inhibit NET release would likely be ineffective at preventing NET-based injury. Treatments that enhance NET degradation may liberate captured bacteria and toxic NET degradation products (NDPs) and likely be of limited therapeutic benefit as well. We propose that interventions that stabilize NETs and sequester NDPs may be protective in sepsis. We showed that platelet factor 4 (PF4), a platelet-associated chemokine, binds and compacts NETs, increasing their resistance to DNase I. We now show that PF4 increases NET-mediated bacterial capture, reduces the release of NDPs, and improves outcome in murine models of sepsis. A monoclonal antibody KKO which binds to PF4-NET complexes, further enhances DNase resistance. However, the Fc portion of this antibody activates the immune response and increases thrombotic risk, negating any protective effects in sepsis. Therefore, we developed an Fc-modified KKO that does not induce these negative outcomes. Treatment with this antibody augmented the effects of PF4, decreasing NDP release and bacterial dissemination and increasing survival in murine sepsis models, supporting a novel NET-targeting approach to improve outcomes in sepsis.

The Diverse Functions of the Ubiquitous Fcγ Receptors and Their Unique Constituent, FcRγ Subunit.

Fc gamma receptors (FcγRs) are widely expressed on a variety of immune cells and play a myriad of regulatory roles in the immune system because of their structural diversity. Apart from their indispensable role in specific binding to the Fc portion of antibody subsets, FcγRs manifest diverse biological functions upon binding to their putative ligands. Examples of such manifestation include phagocytosis, presentation of antigens, mediation of antibody-dependent cellular cytotoxicity, anaphylactic reactions, and the promotion of apoptosis of T cells and natural killer cells. Functionally, the equilibrium between activating and inhibiting FcγR maintains the balance between afferent and efferent immunity. The γ subunit of the immunoglobulin Fc receptor (FcRγ) is a key component of discrete immune receptors and Fc receptors including the FcγR family. Furthermore, FcγRs exert a key role in terms of crosslinking the innate and adaptive workhorses of immunity. Ablation of one of these receptors might positively or negatively influence the immune response. Very recently, we discovered that FcRγ derived from natural cytotoxicity triggering receptor 1 (NCR1) curtails CD8+ T cell expansion and thereby turns an acute viral infection into a chronic one. Such a finding opens a new avenue for targeting the FcγRs as one of the therapeutic regimens to boost the immune response. This review highlights the structural heterogeneity and functional diversity of the ubiquitous FcγRs along with their featured subunit, FcRγ.

IgG-Fc glycosylation before and after rituximab treatment in immune thrombocytopenia

The interactions of antibodies with myeloid Fcγ receptors and the complement system are regulated by an Asn297-linked glycan in the Fc portion of IgG. Alterations of serum IgG-Fc glycosylation have been reported in various autoimmune diseases, and correlate with treatment response and disease activity. We hypothesized that IgG-Fc glycosylation is altered in immune thrombocytopenia (ITP) and associates with response to anti-CD20 monoclonal antibody treatment (rituximab). IgG-Fc glycosylation was analyzed by liquid chromatography-mass spectrometry. We found that IgG-Fc glycosylation was identical between refractory ITP patients (HOVON64 trial; N = 108) and healthy controls (N = 120). Two months after rituximab treatment, we observed a shift in Fc glycosylation, with a mean 1.7% reduction in galactosylation for IgG1 and IgG4 and a mean 1.5% increase for bisection in IgG1, IgG2/3 and IgG4 (adjusted p < 1.7 × 10−3 and p < 2 × 10−4, respectively). Neither baseline nor longitudinal changes in IgG-Fc glycosylation after rituximab were associated with clinical treatment response. We conclude that IgG-Fc glycosylation in refractory ITP is similar to healthy controls and does not predict treatment responses to rituximab. The observed changes two months after treatment suggest that rituximab may influence total serum IgG-Fc glycosylation. Overall, our study suggests that the pathophysiology of refractory ITP may differ from other autoimmune diseases.

The Proteolytic Cleavage of Therapeutic Monoclonal Antibody Hinge Region: More Than a Matter of Subclass.

The hinge region of immunoglobulin G (IgG) is involved in C1q and FcγRIIIA-expressing natural killer (NK) cell recruitment. Both heavy chains (HCs) of the hinge region can be cleaved sequentially by several proteases of the tumor/inflammatory/infectious microenvironment, including matrix metalloproteinase 12 (MMP12), or immunoglobulin-degrading enzyme from Streptococcus pyogenes (IdeS), impairing Fc-mediated functions. The cleavage of therapeutic monoclonal antibodies (TmAbs), which are based on a human IgG1, IgG2 or IgG4 structure, has been poorly investigated, although it may represent an escape mechanism to these treatments. Therefore, we used non-reducing SDS-PAGE to compare the cleavage kinetics of five IgG1 TmAbs (trastuzumab, rituximab, cetuximab, infliximab, ipilimumab), one IgG2 TmAb (panitumumab), and two IgG4 TmAbs (nivolumab and pembrolizumab) by MMP12 and IdeS, which were found to cleave the first and second HCs with different kinetics. Panitumumab was more protease-resistant than IgG1 and IgG4 TmAbs. The latter were usually more protease-sensitive, whereas IgG1 TmAbs were usually cleaved with intermediate kinetics. However, we observed intra-subclass variability among IgG4 and IgG1 TmAbs. Nivolumab and pembrolizumab were cleaved similarly by MMP12, whereas pembrolizumab was more IdeS-resistant. Ipilimumab was more IdeS-sensitive and MMP12-resistant than the other IgG1 TmAbs, regardless of G1m allotype. In addition the Fc fragment of IgG1 TmAbs were highly resistant to cleavage by MMP12, whereas their cleavage kinetic by IdeS was very similar to that observed with the intact forms (excluding ipilimumab). Importantly, the cleavage kinetic of ipilimumab Fc fragment by IdeS was superimposable to that of trastuzumab, cetuximab and infliximab Fc fragment, showing that the variability observed for intact ipilimumab is unrelated to its Fc portion. We propose that the variability in the cleavage sensitivity/resistance balance among TmAbs of IgG1 and IgG4 subclasses results partially, from TmAb characteristics related to and/or located in the Fab region. Finally, with ELISA and flow cytometry, we observed that a single cleavage of IgG1 TmAbs greatly decreased their affinity for FcγRIIIA and C1q and their ability to induce FcγRIIIA-dependent functional responses of NK cells. Overall, our results indicate that the cleavage of the hinge region should be considered with TmAbs treatment and in the development of new molecules.

P420 A randomised, observer-blinded phase Ib multiple, ascending dose study of UTTR1147A, an IL-22Fc fusion protein, in healthy volunteers and ulcerative colitis patients

Abstract Background Inflammatory bowel disease (IBD) is characterised by gut dysbiosis, weakened epithelial barrier, and a dysregulated immune system. Interleukin-22 (IL-22), an IL-10 family cytokine, has demonstrated efficacy in animal IBD models by promoting intestinal epithelial repair, increasing antimicrobial peptide production, and increasing mucin production via goblet cells1. UTTR1147A is a fusion protein in which IL-22 is linked with the Fc portion of IgG4 to improve the pharmacokinetic (PK) characteristics. Methods A phase I study (NCT02749630) was conducted to evaluate the safety, tolerability, PK, and pharmacodynamics (PD) of repeat IV dosing of UTTR1147A in healthy volunteers (HV) and UC patients with centrally read Mayo endoscopic score ≥ 2. 38 HVs and 24 UC patients were given UTTR1147A or placebo at doses ranging from 30 to 90 µg/kg either biweekly or monthly (6:2 UTTR1147A: placebo per cohort). PK and serum PD (REG3A and CRP) were studied across multiple time points and the Mayo Clinic Score was evaluated at baseline, day 30 and day 85. Results Overall, UTTR1147A was safe and adequately tolerated in HV and UC patients. The most common adverse events were on-target dermatological effects (dry skin, erythema, and pruritus) that were manageable, monitorable and reversible. Dose-limiting non-serious dermatological toxicities (severe dry skin, erythema, exfoliation, and discomfort) were seen in two HVs and 1 UC patient dosed with 90ug/kg Q2wk. There were 2 unrelated serious adverse events (ankle fracture and cytomegalovirus infection) that eventually resolved. PK analyses showed that UTTR1147A exposures were, in general, dose proportional within HVs and within UC patients, with a mean elimination half-life of ~16 days and ~12 days, respectively. At the same dose level, UC patients showed relatively lower drug exposures than HVs, possibly due to faster drug clearance. Consistent with the Phase Ia2, UTTR1147A directly induced production of serum PD biomarkers REG3A and CRP at all dose cohorts tested compared with placebo. Notably, UC patients appear to have attenuated serum PD responses compared with HV. Clinical response was observed in 7/18 patients, and clinical remission in 5/18 patients treated with UTTR1147A compared with 1/6 and 0/6 placebo patients, respectively. Conclusion UTTR1147A demonstrated adequate safety and PK profile in healthy volunteers and UC patients. PD biomarker data demonstrated pharmacological activity of UTTR1147A providing evidence of IL-22R pathway activation. Together with the preliminary signals of efficacy, these data support further investigation of this potential, novel non-immunosuppressive therapy in IBD.

Inhibitori faktora nekroze tumora-a i mehanizmi njihovog dejstva

Tumor necrosis factor (TNF)-a is a proinflammatory cytokine with a role in immunity to pathogens, as well as in the pathogenesis of several autoimmune/inflammatory diseases. Biological drugs targeting this cytokine and inhibiting its effects are designed. Until today, five TNF-a inhibitors are approved: infliximab, adalimumab, golimumab (monoclonal antibodies), certolizumab pegol (pegylated antigen-binding fragment of immunoglobulin), and etanercept [TNF receptor type 2-fragment crystallizable (Fc) of immunoglobulin fusion protein]. Their approved biosimilars are on the market, too. They are mainly used for the treatment of rheumatoid arthritis, inflammatory bowel disease, and psoriasis. Although TNF-a inhibitors are present in clinical practice for more than two decades and are established as an efficacious therapeutics, researchers are still occupied by revealing the complex mechanisms of their action. Namely, in addition to binding and neutralisation of soluble TNF-a, these drugs also bind/block transmembrane form of TNF-a (tmTNF-a), trigger diverse intracellular signals in tmTNF-a positive cells (a process named "reverse signalling") or, if they have an Fc fragment, mediate killing of tmTNF-a-expressing cells by other immune cells or the complement system. Also, TNF-a inhibitors that contain Fc portion of the IgG antibody may affect Fc receptor-expressing cells and have an effector function quite independent of their TNF-a neutralisation capacity.

Both IgM and IgG Antibodies Against Polyethylene Glycol Can Alter the Biological Activity of Methoxy Polyethylene Glycol-Epoetin Beta in Mice.

Pre-existing antibodies that bind polyethylene glycol are present in about 40% of healthy individuals. It is currently unknown if pre-existing anti-polyethylene glycol (PEG) antibodies can alter the bioactivity of pegylated drugs with a single long PEG chain, which represents the majority of newly developed pegylated medicines. Methoxy polyethylene glycol-epoetin beta (PEG-EPO) contains a single 30 kDa PEG chain and is used to treat patients suffering from anemia. We find that the pre-existing human anti-PEG IgM and IgG antibodies from normal donors can bind to PEG-EPO. The prevalence and concentrations of anti-PEG IgM and IgG antibodies were also higher in patients that responded poorly to PEG-EPO. Monoclonal anti-PEG IgM and IgG antibodies at concentrations found in normal donors blocked the biological activity of PEG-EPO to stimulate the production of new erythrocytes in mice and accelerated the clearance of 125I-PEG-EPO, resulting in PEG-EPO accumulation primarily in the liver and spleen. Accelerated clearance by the anti-PEG IgG antibody was mediated by the Fc portion of the antibody. Importantly, infusing higher doses of PEG-EPO could compensate for the inhibitory effects of anti-PEG antibodies, suggesting that pre-existing anti-PEG antibodies can be “dosed through.” Our study indicates that the bioactivity and therapeutic activity of PEG-EPO may be reduced in patients with elevated levels of pre-existing anti-PEG antibodies. New pegylated medicines with a single long PEG chain may also be affected in patients with high levels of anti-PEG antibodies.

MRSA screening and spa gene detection in isolates from healthcare workers at ophthalmology hospital in Egypt

BackgroundStaphylococcus aureus has a major role in different types of eye infections as conjunctivitis, keratitis, and endophthalmitis. Methicillin-resistant Staphylococcus aureus (MRSA) was almost restricted to hospitals, but its prevalence has been increased in people outside hospitals. The cell wall of Staphylococcus aureus has protein A which can bind to the Fc portion of IgG. This ptnA is encoded by surface protein A of Staphylococcus aureus (spa) gene that contains a highly polymorphic sequence which is composed of repeats of 24-bp. Sequence typing of the spa gene repeat region is used to study the epidemiology of MRSA. The purpose of this study was screening of MRSA strains among healthcare workers (HCWs) in the Hospital of the Research Institute of Ophthalmology (RIO), Giza, Egypt, and detecting spa gene in their DNAs by PCR.ResultsIn the present study, 81 samples from healthcare providers in the hospital of the Research Institute of Ophthalmology, Egypt, were screened for MRSA. Out of these 81 samples, 41 isolates (50.6%) were identified as coagulase-positive Staphylococcus aureus. Twelve staphylococcal isolates were resistant to both oxacillin and cefoxitin, and those were identified as MRSA with a percentage of 14.8% (12/81). Conventional PCR could detect spa gene in 10 out of 12 DNA MRSA with a percentage of 83.3% (10/12).ConclusionIn the present study, the prevalence of MRSA in HCWs was 14.8%. Since amplification of spa gene by PCR is a necessary preliminary step for spa typing of MRSA and since using different primers for spa gene amplification might affect PCR results, then proper selection of the primers and thermal cycling reaction conditions are recommended for PCR performance and spa typing.

Fc\u03b3RIIIa receptor polymorphism influences NK cell mediated ADCC activity against HIV

BackgroundHIV-specific Antibody Dependent Cell Cytotoxicity (ADCC) has shown to be important in HIV control and resistance. The ADCC is mediated primarily by natural killer cell activated through the binding of FcγRIIIa receptor to the Fc portion of antibody bound to the antigen expressed on the infected cells. However, no data is available on the influence of the polymorphism in FcγRIIIa receptor on HIV-specific ADCC response.MethodsThe Sanger’s method of sequencing was used to sequence the exon of FcγRIIIa receptor while the ADCC activity was determined using NK cell activation assay. The polymorphism in FcγRIIIa receptor was assessed in HIV-infected Indian individuals with or without HIV-specific ADCC antibodies and its influence on the magnitude of HIV-specific ADCC responses was analyzed.ResultsTwo polymorphisms: V176F (rs396991) and Y158H (rs396716) were observed. The Y158H polymorphism is reported for the first time in Indian population. Both, V176F (V/V genotype) (p = 0.004) and Y158H (Y/H genotype) (p = 0.032) were found to be significantly associated with higher magnitude of HIV-specific ADCC response.ConclusionThe study underscores the role of polymorphism in the FcγRIIIa receptor on HIV-specific ADCC response and suggests that the screening of the individuals for FcγRIIIa-V176F and Y158H polymorphisms could be useful for prediction of efficient treatment in monoclonal antibody-based therapies aimed at ADCC in HIV infection.

Paper-Based Radial Chromatographic Immunoassay for the Detection of Pathogenic Bacteria in Milk.

Here, a paper-based radial flow chromatographic immunoassay (RFCI) employing gold nanoparticles (AuNPs) as chromatic agents was developed for the detection of Escherichia coli O157:H7 in whole milk. A 4-repeated gold-binding peptide-tagged (4GBP) streptococcal protein G (SPG) fusion protein was constructed as a bifunctional linker to immobilize antibodies on the surface of AuNPs with a well-oriented form based on the specific affinity of GBP and SPG to the gold and Fc portion of the antibody, respectively. 4GS@AuNPs prepared with the bifunctional linker protein exhibited excellent colloidal stability even at high salt concentrations of up to 500 mM, which is a critical requirement for its application to a broad range of biological and food samples. The enhanced colloidal stability and excellent binding capability of the immuno-4GS@AuNPs toward target bacteria lowered the detection limit of RFCI for target pathogenic bacteria in whole milk as low as 103 CFU/mL, which is by an order of magnitude lower than that of conventional immuno-AuNPs prepared with physical adsorption of antibodies. The RFCI pattern could also be converted into a grayscale value by simple image processing for quantitative determination of target pathogenic bacteria. This paper-based detection system would provide an effective means of monitoring the presence of food-borne pathogens in real food samples with naked eyes.