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Most read from mAbs, October 2019

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The Antibody Society is pleased to be affiliated with mAbs, a multi-disciplinary journal dedicated to advancing the art and science of antibody research and development. We hope you enjoy these summaries based on the abstracts of the most read papers published in a recent issue.

All the articles are open access; PDFs can be freely downloaded by following the links below.

 

 

Issue 11.7 (Oct 2019)

Glycoform-resolved FcɣRIIIa affinity chromatography–mass spectrometry

Lippold et al. describe a method to determination the impact of individual antibody glycoforms on FcɣRIIIa affinity, and consequently antibody-dependent cell-mediated cytotoxicity (ADCC) without performing high purity glycoengineering. They hyphenated FcɣRIIIa affinity chromatography to mass spectrometry, which allowed direct affinity comparison of glycoforms of intact monoclonal antibodies. The approach enabled reproduction and refinement of known glycosylation effects, and insights on afucosylation pairing as well as on low-abundant, unstudied glycoforms. Their method greatly improves the understanding of individual glycoform structure–function relationships, and it is highly relevant for assessing Fc-glycosylation critical quality attributes related to ADCC.

Looking for therapeutic antibodies in next-generation sequencing repositories

It is now possible to query the great diversity of natural antibody repertoires using next-generation sequencing (NGS) using methods capable of producing millions of sequences in a single experiment. In this new article, Krawczyk et al. compare clinical-stage therapeutic antibodies to the ~1b sequences from 60 independent sequencing studies in the Observed Antibody Space database, which includes antibody sequences from NGS analysis of immunoglobulin gene repertoires. Of 242 post-Phase 1 antibodies, they found 16 with sequence identity matches of 95% or better for both heavy and light chains. There were also 54 perfect matches to therapeutic CDR-H3 regions in the NGS outputs, suggesting a nontrivial amount of convergence between naturally observed sequences and those developed artificially. The authors discuss the potential implications for both the legal protection of commercial antibodies and the discovery of antibody therapeutics.

Elucidating heavy/light chain pairing preferences to facilitate the assembly of bispecific IgG in single cells

Joshi et al. report that a high yield (>65%) of bispecific IgG1 (BsIgG1) without Fab engineering can be a surprisingly common occurrence, i.e., observed for 33 of the 99 different antibody pairs evaluated. Installing charge mutations at both CH1/CL interfaces was sufficient for near quantitative yield (>90%) of BsIgG1 for most (9 of 11) antibody pairs tested with this inherent cognate chain pairing preference. Mechanistically, they demonstrate that a strong cognate pairing preference in one Fab arm can be sufficient for high BsIgG1 yield. These observed chain pairing preferences are apparently driven by variable domain sequences and can result from a few specific residues in the complementarity-determining region (CDR) L3 and H3. Transfer of these CDR residues into other antibodies increased BsIgG1 yield in most cases. Mutational analysis revealed that the disulfide bond between heavy and light chains did not affect the yield of BsIgG1. This study provides some mechanistic understanding of factors contributing to antibody heavy/light chain pairing preference and subsequently contributes to the efficient production of BsIgG in single host cells.

Antibody Fc engineering for enhanced neonatal Fc receptor binding and prolonged circulation half-life

The neonatal Fc receptor (FcRn) promotes antibody recycling through rescue from normal lysosomal degradation. The binding interaction is pH-dependent with high affinity at low pH, but not under physiological pH conditions. In this new article, Mackness et al. describe how they combined rational design and saturation mutagenesis to generate novel antibody variants with prolonged half-life and acceptable development profiles. First, a panel of saturation point mutations was created at 11 key FcRn-interacting sites on the Fc region of an antibody. Multiple variants with slower FcRn dissociation kinetics than the wildtype (WT) antibody at pH 6.0 were successfully identified. The mutations were further combined and characterized for pH-dependent FcRn binding properties, thermal stability and the FcγRIIIa and rheumatoid factor binding. The most promising variants, YD (M252Y/T256D), DQ (T256D/T307Q) and DW (T256D/T307W), exhibited significantly improved binding to FcRn at pH 6.0 and retained similar binding properties as WT at pH 7.4. The pharmacokinetics in human FcRn transgenic mice and cynomolgus monkeys demonstrated that these properties translated to significantly prolonged plasma elimination half-life compared to the WT control. The novel variants exhibited thermal stability and binding to FcγRIIIa in the range comparable to clinically validated YTE and LS variants, and showed no enhanced binding to rheumatoid factor compared to the WT control. These engineered Fc mutants are promising new variants that are widely applicable to therapeutic antibodies, to extend their circulation half-life with obvious benefits of increased efficacy, and reduced dose and administration frequency.

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Most read from mAbs, May-June 2019

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The Antibody Society is pleased  to be affiliated with mAbs, a multi-disciplinary journal dedicated to advancing the art and science of antibody research and development. We hope you enjoy these summaries based on the abstracts of the most read papers published in a recent issue.

All the articles are open access; PDFs can be freely downloaded by following the links below.

Issue 11.4 (May-June 2019)

Combining the best of two worlds: highly flexible chimeric antigen receptor adaptor molecules (CAR-adaptors) for the recruitment of chimeric antigen receptor T cells.

In this review, Darowski et al. summarize emerging approaches that aim to further evolve CAR-T cell therapy based on combinations of so-called universal or modular CAR-(modCAR-)T cells, and their respective adaptor molecules (CAR-adaptors), which mediate the crosslinking between target and effector cells. The activity of such modCAR-T cells is entirely dependent on binding of the respective CAR-adaptor to both a tumor antigen and to the CAR-expressing T cell. Contrary to conventional CAR-T cells, where the immunological synapse is established by direct interaction of CAR and membrane-bound target, modCAR-T cells provide a highly flexible and customizable development of the CAR-T cell concept and offer an additional possibility to control T cell activity.

Efficient tumor killing and minimal cytokine release with novel T-cell agonist bispecific antibodies.

Using a sequence-based discovery platform, Trinklein et al. identified new anti-CD3 antibodies from humanized rats that bind to multiple epitopes and elicit varying levels of T-cell activation. In T-BsAb format, 12 different anti-CD3 arms induce equivalent levels of tumor cell lysis by primary T-cells, but potency varies by a thousand-fold. The lead CD3-targeting arm stimulates very low levels of cytokine release, but drives robust tumor antigen-specific killing in vitro and in a mouse xenograft model. This new CD3-targeting antibody underpins a next-generation T-BsAb platform in which potent cytotoxicity is uncoupled from high levels of cytokine release, which may lead to a wider therapeutic window in the clinic.

Sym021, a promising anti-PD1 clinical candidate antibody derived from a new chicken antibody discovery platform.

In this study by Gjetting et al., the Symplex antibody discovery platform was adapted to chicken immunoglobulin genes and combined with high-throughput humanization of antibody frameworks by “mass complementarity-determining region grafting”. Wild type chickens were immunized with an immune checkpoint inhibitor programmed cell death 1 (PD1) antigen, and a repertoire of 144 antibodies was generated. The PD1 antibody repertoire was successfully humanized, and the authors found that most humanized antibodies retained affinity largely similar to that of the parental chicken antibodies. The lead antibody Sym021 blocked PD-L1 and PD-L2 ligand binding, resulting in elevated T-cell cytokine production in vitro. Detailed epitope mapping showed that the epitope recognized by Sym021 was unique compared to the clinically approved PD1 antibodies pembrolizumab and nivolumab. Moreover, Sym021 bound human PD1 with a stronger affinity (30 pM) compared to nivolumab and pembrolizumab, while also cross-reacting with cynomolgus and mouse PD1. This enabled direct testing of Sym021 in the syngeneic mouse in vivo cancer models and evaluation of preclinical toxicology in cynomolgus monkeys. Preclinical in vivo evaluation in various murine and human tumor models demonstrated a pronounced anti-tumor effect of Sym021, supporting its current evaluation in a Phase 1 clinical trial.

Most read from mAbs

by

The Antibody Society is pleased and proud to be affiliated with mAbs, a multi-disciplinary journal dedicated to advancing the art and science of antibody research and development. We hope you enjoy these summaries based on the abstracts of the most read papers published in a recent issue. All the articles are open access; PDFs can be downloaded by following the links below.

Issue 10.8 (November/December 2018)

Rapid, automated characterization of disulfide bond scrambling and IgG2 isoform determination. In this new report, Resemann et al. discuss a rapid LC-MALDI-TOF/TOF workflow that can both identify the IgG2 disulfide linkages and provide a semi-quantitative assessment of the distribution of the disulfide isoforms. They established signature disulfide-bonded IgG2 hinge peptides that correspond to the A, A/B, and B disulfide isoforms, and can be applied to the fast classification of IgG2 isoforms in heterogeneous mixtures.

Charge variant native mass spectrometry benefits mass precision and dynamic range of monoclonal antibody intact mass analysis. Bailey et al. describe charge variant native mass spectrometry (CVMS), an integrated native ion exchange mass spectrometry-based charge variant analytical approach that delivers detailed molecular information in a single, semi-automated analysis. They used pure volatile salt mobile phases over a pH gradient that effectively separated variants based on minimal differences in isoelectric point. Characterization of variants such as deamidation, which are traditionally unattainable by intact mass due to their minimal molecular weight differences, were measured unambiguously by mass and retention time to allow confident MS1 identification. The authors demonstrated that efficient chromatographic separation allows introduction of the purified forms of the charge variant isoforms into the Orbitrap mass spectrometer. Based on their results, they conclude that the CVMS method allows confident assignment of intact monoclonal antibody isoforms of similar mass and relative abundance measurements across three orders of magnitude dynamic range.

A systematic approach for analysis and characterization of mispairing in bispecific antibodies with asymmetric architecture. In this new report, Wang et al. discuss a systematic approach for analysis and characterization of mispairing in asymmetric bispecific antibodies. This approach consists of three orthogonal components, the first of which is a liquid chromatography (LC)-mass spectrometry (MS)–based method to measure the mass of intact antibodies. This method is used for fast analysis of mispairing and requires minimal method development, which makes it an ideal choice for early-stage development. The second component is a hydrophobic interaction chromatography (HIC)–based mispairing method that is suitable for lot release testing. The HIC method is robust and quality control friendly, and offers great linearity, precision, and accuracy. The third component is a two-dimensional LC-MS method for on-line chromatographic peak identification, which not only expedites this task but also reduces the risk of undesirable modifications during conventional fraction collection. These three methods dovetail to form the foundation of a complementary toolbox for analysis and characterization of mispairing in asymmetric bispecific antibodies and provide guidance and support for process development throughout the drug development life cycle.

Characterization and analysis of scFv-IgG bispecific antibody size variants. Cao et al. report size variants that were observed for an appended scFv-IgG bispecific antibody. Structural characterization studies showed that the size variants resulted from the engineered disulfide bond on the scFv, whereby the engineered disulfide was found to be either open or unable to form an intrachain disulfide bond due to cysteinylation or glutathionylation of the cysteines. Furthermore, the scFv engineered cysteines also formed intermolecular disulfide bonds, leading to the formation of highly stable dimers and aggregates. Because both the monomer variants and dimers showed lower bioactivity, they were considered to be product-related impurities that must be monitored and controlled. To this end, the authors developed and optimized a robust, precise, and accurate high-resolution size-exclusion chromatographic method, using a statistical design-of-experiments methodology.

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Antibodies new to the market, and exiting

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On February 23, 2018, Kyowa Hakko Kirin Co. Ltd and its partner Ultragenyx Pharmaceutical Inc. announced that a conditional marketing authorization had been granted in the European Union (EU) for burosumab (Crysvita) as a treatment for X-linked hypophosphatemia in children 1 year of age and older, and adolescents with growing skeletons. Burosumab is a human IgG1 monoclonal antibody that binds to and inhibits the activity of fibroblast growth factor 23, thereby reducing loss of phosphate from the kidney and other metabolic abnormalities, and ameliorating bone changes that are a hallmark of the disease. The marketing approval in the EU is the first for burosumab. A biologics license application is undergoing review by the US Food and Drug Administration (FDA), and an action on the application is expected by April 17, 2018.

On February 27, 2018, Roche announced that emicizumab (Hemlibra®) had been approved in the EU for routine prophylaxis of bleeding episodes in people with hemophilia A with factor VIII inhibitors. Emicizumab, a bispecific IgG4 mAb targeting Factors IXa and X that originated at Chugai Pharmaceutical Co. Ltd., was approved by the FDA on November 16, 2017.

On March 2, 2018, Biogen and AbbVie announced the voluntary worldwide withdrawal of marketing authorizations for ZINBRYTA® (daclizumab) for relapsing multiple sclerosis (MS). The withdrawal coincides with an urgent review by the European Medicines Agency (EMA) of inflammatory brain disorder in 8 patients, and follows a 2017 review by EMA of reports of liver injury. Due to the risk of serious liver damage, EMA limited use of Zinbryta to MS patients who had tried at least two other disease modifying treatments and could not be treated with any other such treatments. ZINBRYTA® had been marketed in the EU, US, Switzerland, Canada and Australia.

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Emicizumab granted FDA approval

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Emicizumab (Hemlibra, emicizumab-kxwh, ACE910, RO5534262), a bispecific IgG4 mAb targeting Factors IXa and X, was approved by the FDA on November 16, 2017. The drug, which is administered once a week, was approved to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients with hemophilia A who have developed Factor VIII inhibitors. The biologics license application was granted Priority Review and a Breakthrough Therapy designation. Hemlibra was also granted an orphan drug designation by the FDA.

Marketing applications for emicizumab are under review in the European Union and Japan; the European Medicines Agency is reviewing the marketing authorization application under accelerated assessment. Emicizumab was granted an orphan drug designation in Japan for the prevention and reduction of bleeding episodes in patients with congenital factor VIII deficiency with inhibitors. The drug was created by Chugai Pharmaceutical Co., Ltd. and co-developed by Chugai, Roche and Genentech.

The marketing applications for emicizumab include results from the Phase 3 HAVEN 1 (NCT02622321) study and interim analysis of the HAVEN 2 (NCT02795767) study. In the HAVEN 1 study, adult and adolescent patients (12 or older) who had previously received episodic treatment with bypassing agents were randomly assigned in a 2:1 ratio to emicizumab prophylaxis (group A) or no prophylaxis (group B). The primary end point of the study was the difference in bleeding rates between Group A and Group B. Emicizumab was administered subcutaneously at a dose of 3 milligrams per kilogram per week (mg/kg/week) for 4 weeks followed by 1.5 mg/kg/week up to the end of the study. The annualized bleeding rate in Group A was reduced by 87% compared to Group B (2.9 events vs 23.3 events, P<0.001). [1] The HAVEN 2 study is evaluating the efficacy, safety, and pharmacokinetics of subcutaneous administration of emicizumab in hemophilia A pediatric patients with inhibitors.

1. Oldenburg J, Mahlangu JN, Kim B, Schmitt C, Callaghan MU, Young G, Santagostino E, Kruse-Jarres R, Negrier C, Kessler C, et al. Emicizumab prophylaxis in hemophilia A with inhibitors. N Engl J Med. 2017;377(9):809-818. doi: 10.1056/NEJMoa1703068.

The Antibody Society maintains a comprehensive table of approved antibody therapeutics and those in regulatory review in the EU or US. As of November 16, 2017, a total of 10 mAbs have been granted first approvals in either the US or EU in 2017, and marketing applications for a total of 9 antibody therapeutics that have not yet been approved in either the EU or US are undergoing review in these regions.

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