IgG sialylation occurs in B cells pre antibody secretion.

Sialic acids as terminal sugar residues on cell surface or secreted proteins have many functional roles. In particular, the presence or absence of α2,6-linked sialic acid residues at the immunoglobulin G (IgG) Fc fragment can switch IgG effector functions from pro- to anti-inflammatory activity. IgG glycosylation is considered to take place inside the plasma blast/plasma cell while the molecule travels through the endoplasmic reticulum and Golgi apparatus before being secreted. However, more recent studies have suggested that IgG sialylation may occur predominantly post-antibody secretion. To what extent this extracellular IgG sialylation process contributes to overall IgG sialylation remains unclear, however. By generating bone marrow chimeric mice with a B cell-specific deletion of ST6Gal1, the key enzyme required for IgG sialylation, we now show that sialylation of the IgG Fc fragment exclusively occurs within B cells pre-IgG secretion. We further demonstrate that B cells expressing ST6Gal1 have a developmental advantage over B cells lacking ST6Gal1 expression and thus dominate the plasma cell pool and the resulting serum IgG population in mouse models in which both ST6Gal1-sufficient and -deficient B cells are present.

Heterologous Ad26/Ad5 adenovirus-vectored vaccines elicited SARS-CoV-2-specific antibody responses with potent Fc activities.

Introduction: Antibodies against the SARS-CoV-2 spike protein are a critical immune determinant for protection against the virus. While virus neutralization is a key function of spike-specific antibodies, antibodies also mediate Fc-dependent activities that can play a role in protection or pathogenesis. Methods: This study characterized serum antibody responses elicited after two doses of heterologous adenovirus-vectored (Ad26/ Ad5) vaccines. Results: Vaccine-induced antibody binding titers and Fc-mediated functions decreased over six months, while neutralization titers remained stable. Comparison of antibody isotypes elicited after Ad26/Ad5 vs. LNP-mRNA vaccination and after infection showed that anti-spike IgG1 were dominant and produced to high levels in all groups. The Ad26/Ad5 vaccines also induced IgG4 but not IgG2 and IgG3, whereas the LNP-mRNA vaccines elicited a full Ig spectrum (IgM, IgG1-4, IgA1-2). Convalescent COVID-19 patients had mainly IgM and IgA1 alongside IgG1. Despite these differences, the neutralization potencies against early variants were similar. However, both vaccine groups had antibodies with greater Fc potencies of binding complement and Fcg receptors than the COVID-19 group. The Ad26/Ad5 group also displayed a greater potency of RBD-specific antibody-mediated cellular phagocytosis. Discussion: Antibodies with distinctive quality were induced by different vaccines and infection. The data imply the utility of different vaccine platforms to elicit antibody responses with fine-tuned Fc activities.

Gonadotropin elevation is ootoxic to ovulatory oocytes and inhibits oocyte maturation, and activin decoy receptor ActRIIB:Fc therapeutically restores maturation.

BACKGROUND: Elevated FSH often occurs in women of advanced maternal age (AMA, age ≥ 35) and in infertility patients undergoing controlled ovarian stimulation (COS). There is controversy on whether high endogenous FSH contributes to infertility and whether high exogenous FSH adversely impacts patient pregnancy rates. METHODS: The senescence-accelerated mouse-prone-8 (SAMP8) model of female reproductive aging was employed to assess the separate impacts of age and high FSH activity on the percentages (%) of viable and mature ovulated oocytes recovered after gonadotropin treatment. Young and midlife mice were treated with the FSH analog equine chorionic gonadotropin (eCG) to model both endogenous FSH elevation and exogenous FSH elevation. Previously we showed the activin inhibitor ActRIIB:Fc increases oocyte quality by preventing chromosome and spindle misalignments. Therefore, ActRIIB:Fc treatment was performed in an effort to increase % oocyte viability and % oocyte maturation. RESULTS: The high FSH activity of eCG is ootoxic to ovulatory oocytes, with greater decreases in % viable oocytes in midlife than young mice. High FSH activity of eCG potently inhibits oocyte maturation, decreasing the % of mature oocytes to similar degrees in young and midlife mice. ActRIIB:Fc treatment does not prevent eCG ootoxicity, but it restores most oocyte maturation impeded by eCG. CONCLUSIONS: FSH ootoxicity to ovulatory oocytes and FSH maturation inhibition pose a paradox given the well-known pro-growth and pro-maturation activities of FSH in the earlier stages of oocyte growth. We propose the FOOT Hypothesis ("FSH OoToxicity Hypothesis), that FSH ootoxicity to ovulatory oocytes comprises a new driver of infertility and low pregnancy success rates in DOR women attempting spontaneous pregnancy and in COS/IUI patients, especially AMA women. We speculate that endogenous FSH elevation also contributes to reduced fecundity in these DOR and COS/IUI patients. Restoration of oocyte maturation by ActRIB:Fc suggests that activin suppresses oocyte maturation in vivo. This contrasts with prior studies showing activin A promotes oocyte maturation in vitro. Improved oocyte maturation with agents that decrease endogenous activin activity with high specificity may have therapeutic benefit for COS/IVF patients, COS/IUI patients, and DOR patients attempting spontaneous pregnancies.

Dulaglutide restores endothelial progenitor cell levels in diabetic mice and mitigates high glucose-induced endothelial injury through SIRT1-mediated mitochondrial fission.

Type 2 diabetes mellitus (T2DM) significantly impairs the functionality and number of endothelial progenitor cells (EPCs) and resident endothelial cells, critical for vascular repair and regeneration, exacerbating the risk of vascular complications. GLP-1 receptor agonists, like dulaglutide, have emerged as promising therapeutic agents due to their multifaceted effects, including the enhancement of EPC activity and protection of endothelial cells. This study investigates dulaglutide's effects on peripheral blood levels of CD34+ and CD133+ cells in a mouse model of lower limb ischemia and its protective mechanisms against high-glucose-induced damage in endothelial cells. Results demonstrated that dulaglutide significantly improves blood flow, reduces tissue damage and inflammation in ischemic limbs, and enhances glycemic control. Furthermore, dulaglutide alleviated high-glucose-induced endothelial cell damage, evident from improved tube formation, reduced reactive oxygen species accumulation, and restored endothelial junction integrity. Mechanistically, dulaglutide mitigated mitochondrial fission in endothelial cells under high-glucose conditions, partly through maintaining SIRT1 expression, which is crucial for mitochondrial dynamics. This study reveals the potential of dulaglutide as a therapeutic option for vascular complications in T2DM patients, highlighting its role in improving endothelial function and mitochondrial integrity.

Multidimensional LC-MS with 1D multi-method option and parallel middle-up and bottom-up MS acquisition for in-depth characterization of antibodies.

Monoclonal antibodies (mAbs) are large and highly heterogeneous species typically characterized using a plethora of analytical methodologies. There is a trend within the biopharmaceutical industry to combine several of these methods in one analytical platform to simultaneously assess multiple structural attributes. Here, a protein analyzer for the fully automated middle-up and bottom-up liquid chromatography-mass spectrometry (LC-MS) analysis of charge, size and hydrophobic variants is described. The multidimensional set-up combines a multi-method option in the first dimension (1D) (choice between size exclusion - SEC, cation exchange - CEX or hydrophobic interaction chromatography - HIC) with second dimension (2D) on-column reversed-phase (RPLC) based desalting, denaturation and reduction prior to middle-up LC-MS analysis of collected 1D peaks and parallel on-column trypsin digestion of denatured and reduced peaks in the third dimension (3D) followed by bottom-up LC-MS analysis in the fourth dimension (4D). The versatile and comprehensive workflow is applied to the characterization of charge, hydrophobic and size heterogeneities associated with an engineered Fc fragment and is complemented with hydrogen-deuterium exchange (HDX) MS and FcRn affinity chromatography - native MS to explain observations in a structural/functional context.

Comparative Analysis of the Anti-Inflammatory Effects of Liraglutide and Dulaglutide.

Inflammation plays a pathophysiological role in atherosclerosis and its clinical consequences. In addition to glycemic control, glucagon-like peptide-1 receptor agonists (GLP-1RAs) are of wide concern for cardioprotective effects. The structure, half-life, homology, and clinical efficacy of GLP-1RAs exhibit remarkable disparity. Several studies have compared the disparities in anti-inflammatory effects between daily and weekly GLP-1RAs. This study aimed to compare the similarities and differences between liraglutide and dulaglutide in terms of inhibiting atherosclerotic inflammation and improving co-cultured endothelial cell function. The expression of inflammation markers was examined by immunofluorescence, Western blotting, and real-time PCR. The tube-forming ability of endothelial cells was tested on Matrigel. The results verify that 10/50/100 nmol/L liraglutide and 100 nmol/L dulaglutide markedly suppressed the expression of inflammatory factors in LPS-induced atherosclerosis after 24 and 72 hours, respectively. Moreover, they promoted the polarization of M1 macrophages toward the M2 phenotype and improved the function of co-cultured endothelial cells. Both liraglutide and dulaglutide ameliorate atherosclerosis development. The difference between the two resided in the extended intervention duration required to observe the effect of dulaglutide, and liraglutide demonstrated a superior dose-dependent manner. We provide a potential strategy to understand the dynamics of drug action and possible timing administration.

CaptureSelect FcXP affinity medium exhibits strong aggregate separation capability.

Protein A affinity chromatography has been widely used for initial product capture in recombinant antibody/Fc-fusion purification. However, in general Protein A lacks the capability of separating aggregates (unless the aggregates are too large to enter the pores of resin beads or have their Protein A binding sites buried, in which case the aggregates do not bind). In the current work, we demonstrated that CaptureSelect FcXP affinity medium exhibited strong aggregate separation capability and effectively removed aggregates under pH or conductivity gradient elution in two bispecific antibody (bsAb) cases. For these two cases, aggregate contents were reduced from >16% and >22% (in the feed) to <1% and <5% (in the eluate) for the first and second bsAbs, respectively. While more case studies are required to further demonstrate FcXP's superiority in aggregate removal, findings from the current study suggest that FcXP can potentially be a better alternative than Protein A for product capture in cases where aggregate content is high.

Significant elevation of serum CA19-9 and CA242 levels induced by dulaglutide.

The use of dulaglutide, a common medication for managing type 2 diabetes, rarely causes elevated pancreatic tumour markers. Here, we report the case of a woman in her mid-60s with diabetes for over 10 years. The patient presented with markedly elevated serum CA19-9 and CA242 levels revealed during a routine health examination despite being asymptomatic. She had been receiving dulaglutide injections for 16 months. Imaging and interventional assessments did not reveal any hepatobiliary, gastrointestinal or pancreatic neoplasm. After excluding alternate diagnoses, the patient was determined to exhibit an adverse reaction to dulaglutide use. Management involved the discontinuation of dulaglutide, which resulted in normalisation of serum CA19-9 and CA242 levels within 6 weeks. This case underscores the importance of discontinuing dulaglutide and monitoring changes in the biomarker levels in asymptomatic patients receiving dulaglutide, rather than immediately resorting to imaging and endoscopic examinations.

Using atomistic solution scattering modelling to elucidate the role of the Fc glycans in human IgG4.

Human immunoglobulin G (IgG) exists as four subclasses IgG1-4, each of which has two Fab subunits joined by two hinges to a Fc subunit. IgG4 has the shortest hinge with 12 residues. The Fc subunit has two glycan chains, but the importance of glycosylation is not fully understood in IgG4. Here, to evaluate the stability and structure of non-glycosylated IgG4, we performed a multidisciplinary structural study of glycosylated and deglycosylated human IgG4 A33 for comparison with our similar study of human IgG1 A33. After deglycosylation, IgG4 was found to be monomeric by analytical ultracentrifugation; its sedimentation coefficient of 6.52 S was reduced by 0.27 S in reflection of its lower mass. X-ray and neutron solution scattering showed that the overall Guinier radius of gyration RG and its cross-sectional values after deglycosylation were almost unchanged. In the P(r) distance distribution curves, the two M1 and M2 peaks that monitor the two most common distances within IgG4 were unchanged following deglycosylation. Further insight from Monte Carlo simulations for glycosylated and deglycosylated IgG4 came from 111,382 and 117,135 possible structures respectively. Their comparison to the X-ray and neutron scattering curves identified several hundred best-fit models for both forms of IgG4. Principal component analyses showed that glycosylated and deglycosylated IgG4 exhibited different conformations from each other. Within the constraint of unchanged RG and M1-M2 values, the glycosylated IgG4 models showed more restricted Fc conformations compared to deglycosylated IgG4, but no other changes. Kratky plots supported this interpretation of greater disorder upon deglycosylation, also observed in IgG1. Overall, these more variable Fc conformations may demonstrate a generalisable impact of deglycosylation on Fc structures, but with no large conformational changes in IgG4 unlike those seen in IgG1.

Factor VIII moiety of recombinant Factor VIII Fc fusion protein impacts Fc effector function and CD16+ NK cell activation.

Recombinant Factor VIII-Fc fusion protein (rFVIIIFc) is an enhanced half-life therapeutic protein product used for the management of hemophilia A. Recent studies have demonstrated that rFVIIIFc interacts with Fc gamma receptors (FcγR) resulting in the activation or inhibition of various FcγR-expressing immune cells. We previously demonstrated that rFVIIIFc, unlike recombinant Factor IX-Fc (rFIXFc), activates natural killer (NK) cells via Fc-mediated interactions with FcγRIIIA (CD16). Additionally, we showed that rFVIIIFc activated CD16+ NK cells to lyse a FVIII-specific B cell clone. Here, we used human NK cell lines and primary NK cells enriched from peripheral blood leukocytes to study the role of the FVIII moiety in rFVIIIFc-mediated NK cell activation. Following overnight incubation of NK cells with rFVIIIFc, cellular activation was assessed by measuring secretion of the inflammatory cytokine IFNγ by ELISA or by cellular degranulation. We show that anti-FVIII, anti-Fc, and anti-CD16 all inhibited indicating that these molecules were involved in rFVIIIFc-mediated NK cell activation. To define which domains of FVIII were involved, we used antibodies that are FVIII domain-specific and demonstrated that blocking FVIII C1 or C2 domain-mediated membrane binding potently inhibited rFVIIIFc-mediated CD16+ NK cell activation, while targeting the FVIII heavy chain domains did not. We also show that rFVIIIFc binds CD16 with about five-fold higher affinity than rFIXFc. Based on our results we propose that FVIII light chain-mediated membrane binding results in tethering of the fusion protein to the cell surface, and this, together with increased binding affinity for CD16, allows for Fc-CD16 interactions to proceed, resulting in NK cellular activation. Our working model may explain our previous results where we observed that rFVIIIFc activated NK cells via CD16, whereas rFIXFc did not despite having identical IgG1 Fc domains.

A pharmacokinetic study comparing the biosimilar HEC14028 and Dulaglutide (Trulicity®) in healthy Chinese subjects.

This study aimed to evaluate the pharmacokinetics (PKs), safety, and immunogenicity of the biosimilar HEC14028 compared to reference Trulicity® (dulaglutide) in healthy male Chinese subjects. This study was a single-center, randomized, open, single-dose, parallel-controlled comparative Phase I clinical trial, including a screening period of up to 14 days, a 17-day observation period after administration, and a 7-day safety follow-up period. A total of 68 healthy male subjects were randomly assigned (1:1) to the test group (HEC14028) and the reference group (dulaglutide) (single 0.75 mg abdominal subcutaneous dose). The primary objective was to evaluate the pharmacokinetic characteristics of HEC14028 and compare the pharmacokinetic similarities between HEC14028 and dulaglutide. The primary PK endpoints were maximum plasma concentration (Cmax) and area under the blood concentration-time curve from zero time to the estimated infinite time (AUC0-∞). The study results showed that HEC14028 and dulaglutide were pharmacokinetically equivalent: 90% confidence interval (CI) of Cmax and AUC0-∞ geometric mean ratios were 102.9%-122.0% and 97.1%-116.9%, respectively, which were both within the range of 80.00%-125.00%. No grade 3 or above treatment emergent adverse events (TEAEs), serious adverse events (SAEs), TEAEs leading to withdrawal from the trial, or TEAEs leading to death were reported in this study. Both HEC14028 and dulaglutide showed good and similar safety profiles, and no incremental immunogenicity was observed in subjects receiving HEC14028 and dulaglutide.

Cost-Effectiveness of Recombinant Factor IX Fc Prophylaxis and Recombinant Factor IX On-Demand Treatment in Patients with Haemophilia B Without Inhibitors.

INTRODUCTION: Recombinant factor IX (rFIX) and recombinant FIX Fc fusion protein (rFIXFc) are standard half-life and extended half-life FIX replacement therapies, respectively, and represent established treatment options indicated for adults and children with haemophilia B. These FIX replacement therapies can be administered as prophylaxis (to prevent bleeding) or 'on-demand' (to stop bleeding). This analysis aimed to estimate the cost-effectiveness of once-weekly prophylaxis with rFIXFc versus on-demand treatment with rFIX in patients with haemophilia B without inhibitors in the Italian healthcare setting. METHODS: A Markov model was developed to assess a hypothetical cohort of adolescent or adult male patients (≥ 12 years) with haemophilia B (FIX level of ≤ 2 IU/dL) without inhibitors. Model inputs were derived from the pivotal phase 3 clinical studies for rFIXFc and rFIX, published literature and assumptions when published data were unavailable. The model employed a lifelong time horizon with 6-monthly transitions between health states, and it estimated total costs, total quality-adjusted life years (QALYs), number of bleeds, number of surgeries and incremental cost-effectiveness ratio. RESULTS: rFIXFc prophylaxis was associated with lower total costs per patient (€5,308,625 versus €6,564,510) and greater total QALYs per patient (15.936 versus 11.943) compared with rFIX on-demand; rFIXFc prophylaxis was therefore the dominant treatment strategy. The model also demonstrated that rFIXFc prophylaxis was associated with fewer incremental bleeds (- 682.29) and surgeries (- 0.39) compared with rFIX on-demand. CONCLUSIONS: rFIXFc prophylaxis provides improved health outcomes and lower costs, and represents a cost-effective treatment option compared with rFIX on-demand for adolescent and adult male patients with haemophilia B. This comparative assessment of cost-effectiveness should help to inform both clinicians and healthcare policy makers when making treatment decisions for patients with haemophilia B.

Research progress in Fc-effector functions against SARS-CoV-2.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused more than 676 million cases in the global human population with approximately 7 million deaths and vaccination has been proved as the most effective countermeasure in reducing clinical complications and mortality rate of SARS-CoV-2 infection in people. However, the protective elements and correlation of protection induced by vaccination are still not completely understood. Various antibodies with multiple protective mechanisms can be induced simultaneously by vaccination in vivo, thereby complicating the identification and characterization of individual correlate of protection. Recently, an increasing body of observations suggests that antibody-induced Fc-effector functions play a crucial role in combating SARS-CoV-2 infections, including neutralizing antibodies-escaping variants. Here, we review the recent progress in understanding the impact of Fc-effector functions in broadly disarming SARS-CoV-2 infectivity and discuss various efforts in harnessing this conserved antibody function to develop an effective SARS-CoV-2 vaccine that can protect humans against infections by SARS-CoV-2 virus and its variants of concern.

The hinge-engineered IgG1-IgG3 hybrid subclass IgGh47 potently enhances Fc-mediated function of anti-streptococcal and SARS-CoV-2 antibodies.

Streptococcus pyogenes can cause invasive disease with high mortality despite adequate antibiotic treatments. To address this unmet need, we have previously generated an opsonic IgG1 monoclonal antibody, Ab25, targeting the bacterial M protein. Here, we engineer the IgG2-4 subclasses of Ab25. Despite having reduced binding, the IgG3 version promotes stronger phagocytosis of bacteria. Using atomic simulations, we show that IgG3's Fc tail has extensive movement in 3D space due to its extended hinge region, possibly facilitating interactions with immune cells. We replaced the hinge of IgG1 with four different IgG3-hinge segment subclasses, IgGhxx. Hinge-engineering does not diminish binding as with IgG3 but enhances opsonic function, where a 47 amino acid hinge is comparable to IgG3 in function. IgGh47 shows improved protection against S. pyogenes in a systemic infection mouse model, suggesting that IgGh47 has promise as a preclinical therapeutic candidate. Importantly, the enhanced opsonic function of IgGh47 is generalizable to diverse S. pyogenes strains from clinical isolates. We generated IgGh47 versions of anti-SARS-CoV-2 mAbs to broaden the biological applicability, and these also exhibit strongly enhanced opsonic function compared to the IgG1 subclass. The improved function of the IgGh47 subclass in two distant biological systems provides new insights into antibody function.

The IgG-specific endoglycosidases EndoS and EndoS2 are distinguished by conformation and antibody recognition.

The IgG-specific endoglycosidases EndoS and EndoS2 from Streptococcus pyogenes can remove conserved N-linked glycans present on the Fc region of host antibodies to inhibit Fc-mediated effector functions. These enzymes are therefore being investigated as therapeutics for suppressing unwanted immune activation, and have additional application as tools for antibody glycan remodeling. EndoS and EndoS2 differ in Fc glycan substrate specificity due to structural differences within their catalytic glycosyl hydrolase domains. However, a chimeric EndoS enzyme with a substituted glycosyl hydrolase from EndoS2 loses catalytic activity, despite high structural homology between the two enzymes, indicating either mechanistic divergence of EndoS and EndoS2, or improperly-formed domain interfaces in the chimeric enzyme. Here, we present the crystal structure of the EndoS2-IgG1 Fc complex determined to 3.0 Å resolution. Comparison of complexed and unliganded EndoS2 reveals relative reorientation of the glycosyl hydrolase, leucine-rich repeat and hybrid immunoglobulin domains. The conformation of the complexed EndoS2 enzyme is also different when compared to the earlier EndoS-IgG1 Fc complex, and results in distinct contact surfaces between the two enzymes and their Fc substrate. These findings indicate mechanistic divergence of EndoS2 and EndoS. It will be important to consider these differences in the design of IgG-specific enzymes, developed to enable customizable antibody glycosylation.

Cross-sectional, case-control and longitudinal associations between exposure to glucagon-like peptide-1 receptor agonists and the dispensing of antidepressants.

AIM: To determine if the dispensing of glucagon-like peptide (GLP)-1 receptor agonists is associated with increased dispensing of antidepressants. MATERIALS AND METHODS: We used cross-sectional, case-control and retrospective cohort study designs to examine the association between dispensed GLP-1 receptor agonists and antidepressants between 2012 and 2022 in the 10% random sample of the Australian Pharmaceutical Benefits Scheme (PBS) data. PBS-listed GLP-1 receptor agonists, exenatide, dulaglutide and semaglutide were the exposures. Outcomes were the odds ratio [ORs; 99% confidence interval (CI)] and hazard ratio (99% CI) of being dispensed any antidepressant. Analyses were adjusted for demographic measures and the dispensing of medicines to manage cardiovascular diseases or anxiety/insomnia. Statistical tests were two-sided at the 1% level of significance. RESULTS: In total, 358 075 of 1 746 391 individuals were dispensed antidepressants, and 8495 of the 24 783 dispensed a GLP-1 receptor agonist were also dispensed an antidepressant in 2022 (OR 1.44; 99% CI 1.38-1.50); 24 103 of the 1 746 391 participants had been dispensed a GLP-1 receptor agonist between 2012 and 2021, and of these 8083 were dispensed antidepressants in 2022 (OR 1.52; 99% CI 1.46-1.59). The 2012 cohort included 1 213 316 individuals who had not been dispensed antidepressants that year. The hazard ratio of being dispensed an antidepressant between 2013 and 2022 following the dispensing of a GLP-1 receptor agonist was 1.19 (99% CI 1.12-1.27). Additional analyses restricting the time of exposure confirmed these associations for all PBS-listed GLP-1 receptor agonists. CONCLUSIONS: Individuals exposed to GLP-1 receptor agonists are at greater risk of being dispensed antidepressants. The possible impact of GLP-1 receptor agonists on the mood of consumers requires ongoing vigilance and further research.

A Novel Dual-Fc Bispecific Antibody with Enhanced Fc Effector Function.

Bispecific antibodies (BsAbs) are undergoing continued development for applications in oncology and autoimmune diseases. While increasing activity by having more than one targeting arm, most BsAb engineering employs single Fc engagement as monoclonal antibodies. Here, we designed a novel immunoglobulin gamma-1 (IgG1)-derived dual-Fc BsAb containing two Fc regions and two distinct asymmetric antigen binding arms comprising a Fab arm and another VHH domain. In conjunction with the knob-into-hole technology, dual-Fc BsAbs could be produced with a high yield and good stability. We explore how Fc engineering effects on dual-Fc constructs could boost the desired therapeutic efficacy. This new format enabled simultaneous bispecific binding to corresponding antigens. Furthermore, compared to the one-Fc control molecules, dual-Fc BsAbs were shown to increase the avidity-based binding to FcγRs to result in higher ADCC and ADCP activities by potent avidity via binding to two antigens and Fc receptors. Overall, this novel BsAb format with enhanced effector functionalities provides a new option for antibody-based immunotherapy.

Development of a platform method for rapid detection and characterization of domain-specific post-translational modifications in bispecific antibodies.

Charge heterogeneity is inherent to all therapeutic antibodies and arises from post-translational modifications (PTMs) and/or protein degradation events that may occur during manufacturing. Among therapeutic antibodies, the bispecific antibody (bsAb) containing two unique Fab arms directed against two different targets presents an additional layer of complexity to the charge profile. In the context of a bsAb, a single domain-specific PTM within one of the Fab domains may be sufficient to compromise target binding and could potentially impact the stability, safety, potency, and efficacy of the drug product. Therefore, characterization and routine monitoring of domain-specific modifications is critical to ensure the quality of therapeutic bispecific antibody products. We developed a Digestion-assisted imaged Capillary isoElectric focusing (DiCE) method to detect and quantitate domain-specific charge variants of therapeutic bispecific antibodies (bsAbs). The method involves enzymatic digestion using immunoglobulin G (IgG)-degrading enzyme of S. pyogenes (IdeS) to generate F(ab)2 and Fc fragments, followed by imaged capillary isoelectric focusing (icIEF) under reduced, denaturing conditions to separate the light chains (LCs) from the Fd domains. Our results suggest that DiCE is a highly sensitive method that is capable of quantitating domain-specific PTMs of a bsAb. In one case study, DiCE was used to quantitate unprocessed C-terminal lysine and site-specific glycation of Lys98 in the complementarity-determining region (CDR) of a bsAb that could not be accurately quantitated using conventional, platform-based charge variant analysis, such as intact icIEF. Quantitation of these PTMs by DiCE was comparable to results from peptide mapping, demonstrating that DiCE is a valuable orthogonal method for ensuring product quality. This method may also have potential applications for characterizing fusion proteins, antibody-drug conjugates, and co-formulated antibody cocktails.