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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

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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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Antibody-based innovations in the tumor microenvironment

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Please join us at the Society’s annual meeting, Antibody Engineering & Therapeutics on December 11-15, 2017 at the Manchester Grand Hyatt, San Diego, CA!

Clinical successes of the checkpoint modulators have revived the ambition to cure cancer by manipulation of the tumor microenvironment, or by unleashing or even priming (novel) adaptive immune responses. Hence, understanding the tumor microenvironment is an increasingly vital theme in the field of antibody-based therapeutics. This theme is excitingly addressed during two sessions “Antibody-based innovations in the tumor microenvironment 1 & 2”, jointly chaired by Kerry Chester and Janine Schuurman, which will be held on Thursday December 14, 2017. The sessions’ antibody-focused complementary topics are intended to expand knowledge at the cutting edge of the tumor microenvironment field, and are anticipated to boost lively discussions and stimulate new lines of thinking.

Antibody-based innovations in the tumor microenvironment (I, morning session)

Chairwomen: Kerry Chester, Professor of Molecular Medicine, UCL Cancer Institute, University College London, United Kingdom, and Janine Schuurman, Vice President Research, Genmab, Utrecht, The Netherlands

The sessions will open with a presentation by John Anderson (UCL) who will examine current thinking on immune evasion as a hallmark of cancer and why the solid tumor microenvironment is particularly hostile to immunotherapeutic function of effector cells. He will explain that, unlike adult cancers, pediatric cancers generally arise with few mutations and tend to be insensitive to existing immune modulators. Treatment approaches designed to target cell surface antigens in combination with agents to reverse immune evasion are likely to be required for this special group of patients.  New data will be presented in support of this hypothesis.

Syd Johnson (MacroGenics) will then share data on how to achieve co-stimulation of immune cells specifically within the tumor microenvironment using bispecific Dual-Affinity Re-Targeting (DART) and TRIDENT antibodies that bind both tumor-specific antigens and T-cell costimulatory molecules. Importantly, tumor binding is required to trigger costimulation. The talk will be illustrated with a case study showing how to achieve optimal tumor dependent T cell engagement by varying the relative position and valence of each antibody binding site in the molecule; manufacturability, stability and PK will also be addressed.

Natalia Arenas Ramirez (University Hospital Zurich) will then present an elegant antibody-based solution to problems associated with IL-2 immunotherapy.  IL2 binding to the IL-2 receptor α (CD25) subunit leads to unwanted side effects, including stimulation of immunosuppressive Tregs.  The talk will describe development of NARA1, an anti-IL-2 monoclonal antibody that acts as a high-affinity CD25 mimic, preferentially stimulating CD8+ cells while keeping the Tregs low.  Potent antitumor responses are achieved.

After the Networking Break, Volker Schellenberger (Amunix) will present an interesting approach to achieving activation in the tumor environment using bispecific T-cell engagers based on the ProTIA (Protease Triggered Immune Activator) platform. ProTIA combines tumor binding, proteolytic activation and polymer targeting due to an attached XTEN. Amunix’ lead molecule, AMX-168, is expected to enter clinical development in 2018.

Next, Shautong Song (Icell Kealex Therapeutics) will showcase an innovative way to focus treatment within the tumor microenvironment via bi-specific T-cell engager-armed oncolytic vaccinia virus. The treatment has several modes of action: vaccinia virus can directly lyse tumor cells and bi-specific T-cell engagement directs T-cells to kill both tumor and by-stander cells. In addition, T-cell engagement promotes T-cell infiltration into tumors and the cytokines released upon activation create a pro-inflammatory microenvironment that inhibits tumor growth. The strategy provides a sophisticated means of reducing systemic side effects associated with bi-specific T-cell engagers.

To complete the morning session, Dane Wittrup (Massachusetts Institute of Technology) will explore how classical monoclonal anti-tumor antibodies, such as anti-HER2 or anti-CD20, synergize with immune oncology antibodies, such as anti-PD-1. This is achieved not only by delivery of  tumor debris to antigen presenting cells for cross presentation, but also by creating a more inflammatory state and a localized cytokine storm in the tumor microenvironment.

Antibody-based innovations in the tumor microenvironment (II, afternoon session)

Chairwomen: Janine Schuurman, Vice President Research, Genmab, Utrecht, The Netherlands and Kerry Chester, Professor of Molecular Medicine, UCL Cancer Institute, University College London, United Kingdom

The afternoon session opens with a presentation centering on adaptive immune responses boosted by therapeutic cancer vaccines using RNA. Sebastian Kreiter (BioNTech) will focus on preclinical and clinical efforts to use personalized neoepitope vaccines in combination with immunomodulatory antibodies.

Edward Roberts (UCSF) will follow with a complementary line of thinking harnessing long term anti-tumor therapeutic effects. He will share data, including imaging data, to give us insights in the requirements for effective tumor antigen trafficking to the lymph nodes by the dendritic cells. These understandings may stimulate ideas for effective T cell priming approaches.

The TNFR super family (TNFR-SF) is a highly represented target class in the immunomodulatory targets space. Clustering is an important prerequisite for agonistic effects of antibodies against these targets. Nick Wilson (Agenus) will share emerging data on the role of antibody Fc and Fc-receptor biology to optimize the agonistic properties of antibodies against this target class.

Daratumumab, an anti-CD38 antibody that is approved for the treatment of relapsed / refractory myeloma, has multiple mechanisms of actions. Apart from rapid tumor cell reduction and direct anti-tumor effects, daratumumab significantly reduces CD38+ immune suppressive cells in the tumor microenvironment. Kate Sasser (Genmab) will focus on the immune modulatory activity of this antibody substantiated with data from in vitro evaluations and clinical studies.

Bispecific antibodies directed against both CD3and a tumor target can engage non-tumor-specific T cells, resulting in effective tumor-specific cell killing. Dirk Hose (Heidelberg University) will share data on a bispecific IgG-based molecule that targets CD3 and the B-cell maturation antigen (BCMA), which has been implicated in multiple myeloma. This presentation will cover the generation of this molecule and include early stage clinical learnings.

Anti-CD3 bispecifics can have severe toxicity profiles related to the expression profile of the tumor antigen. The last speaker of this full-day session on the tumor microenvironment will share data on the improvement of the therapeutic index of an anti-CD3 bispecific antibody also directed against a widely expressed antigen, epidermal growth factor receptor (EGFR). In this case study, Leila Boustany, (CytomX) will present the localization of the activity to the tumor microenvironment, which is accomplished by an engineering approach, i.e., a protease activatable EGFRxCD3 bispecific exploiting the protease activity present in the tumor microenvironment.

We anticipate that these complementary scientific insights focusing around antibody-based innovations in the tumor microenvironment will excite us all and inspire our forward-looking capabilities.

Interested in attending the meeting? Learn more from this PDF, which includes all session summaries written by the chairpersons.

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Membership is free for students and employees of the Society’s corporate sponsors.