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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, April 2019

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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 freely downloaded by following the links below.

Issue 11.3 (April 2019)

CH2 domain orientation of human immunoglobulin G in solution: Structural comparison of glycosylated and aglycosylated Fc regions using small-angle X-ray scattering

Yageta et al examined the small-angle X-ray scattering (SAXS) profile of the glycosylated Fc region (gFc) and aglycosylated Fc region (aFc) in solution to determine if removal of the N-linked glycan alters the CH2 domain orientation in the Fc region. For both gFc and aFc, the best-fitted SAXS profiles corresponded to ones calculated based on the crystal structure of gFc that formed a “semi-closed” CH2 domain orientation. Collectively, the data indicated that the removal of the N-linked glycan only negligibly affected the CH2 domain orientation in solution. Their findings will guide the development of methodology for the production of highly refined functional Fc variants.

Charge variants characterization and release assay development for co-formulated antibodies as a combination therapy

Characterization of co-formulated biologics can be challenging due to the high degree of similarity in the physicochemical properties of co-formulated proteins, especially at different concentrations of individual components. In this new report, Cao et al present the results of a deamidation study of one monoclonal antibody component (mAb-B) in co-formulated combination antibodies (referred to as COMBO) that contain various ratios of mAb-A and mAb-B. A single deamidation site in the complementarity-determining region of mAb-B was identified as a critical quality attribute (CQA) due to its impact on biological activity. A conventional charge-based method of monitoring mAb-B deamidation presented specificity and robustness challenges, especially when mAb-B was a minor component in the COMBO, making it unsuitable for lot release and stability testing. The authors developed and qualified a new, quality-control-friendly, single quadrupole Dalton mass detector (QDa)–based method to monitor site-specific deamidation. Their approach can be also used as a multi-attribute method for monitoring other quality attributes in COMBO. This analytical paradigm is applicable to the identification of CQAs in combination therapeutic molecules, and to the subsequent development of a highly specific, highly sensitive, and sufficiently robust method for routine monitoring CQAs for lot release test and during stability studies.

Capture and display of antibodies secreted by hybridoma cells enables fluorescent on-cell screening

Puligedda et. al describe a system in which hybridomas specifically capture and display the mAbs they secrete. Using On-Cell mAb Screening (OCMS™), monoclonal antibodies (mAbs) displayed on the cell surface can be rapidly assayed for expression level and binding specificity using fluorescent antigens with high-content (image-based) methods or flow cytometry. OCMS™ demonstrated specific mAb binding to poliovirus and rabies virus by forming a cell surface IgG “cap”, as a universal assay for anti-viral mAbs. The authors produced and characterized OCMS™-enabled hybridomas secreting mAbs that neutralize poliovirus and used fluorescence microscopy to identify and clone a human mAb specific for the human N-methyl-D-aspartate receptor. They also used OCMS™ to assess expression and antigen binding of a recombinant mAb produced in 293T cells.

Physicochemical and functional assessments demonstrating analytical similarity between rituximab biosimilar HLX01 and the MabThera®

As discussed by Xu et al, development of bio-therapeutics has exhibited exponential growth in China over the past decade. However, no biosimilar drug has been approved in China (CN) due to the lack of a national biosimilar regulatory guidance. HLX01, a rituximab biosimilar developed in China under European Medicines Agency biosimilar guidelines and requirements, was the first such drug submitted for regulatory review in China, and it is expected to receive approval there as a biosimilar product. To demonstrate the analytical similarities of HLX01, CN-rituximab (sourced in China but manufactured in Europe) and EU-rituximab (sourced and manufactured in Europe), an extensive 3-way physicochemical and functional similarity assessment using a series of orthogonal and state-of-the-art techniques was conducted, following the similarity requirement guidelines recently published by China’s Center for Drug Evaluation. The results of the similarity study showed an identical protein amino acid sequence and highly similar primary structures between HLX01 and the reference product (RP) MabThera®, along with high similarities in higher order structures, potency, integrity, purity and impurity profiles, biological and immunological binding functions, as well as degradation behaviors under stress conditions. In addition, HLX01 presented slightly lower aggregates and better photostability compared with the RP. Despite slight changes in relative abundance of glycan moieties and heavy chain C-terminal lysine modification, no differences in biological activities and immunological properties were observed between the RP and HLX01. In conclusion, HLX01 is highly similar to CN- and EU-sourced RP in terms of physicochemical properties and biological activities, suggesting similar product quality, efficacy, and safety. The regulatory requirements interpreted and applied towards the HLX01 marketing application sets a precedent for analytical similarity assessment of biosimilar products in China.

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Antibody therapeutics in early-stage clinical studies

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The popular “Antibodies to watch” articles aim to update members of The Antibody Society, as well as the broader scientific community, on progress in the late-stage clinical development of innovative antibody therapeutics. Data for these molecules (60 as of March 22, 2019) are made available in the Members Only area of The Antibody Society’s website. We are pleased to announce that we are expanding our coverage of the commercial clinical pipeline to include data for antibody therapeutics that have recently entered clinical study. Two factors motivated us: 1) the remarkable increase in the number entering clinical study annually (to ~120 in 2018); and 2) the remarkable focus on antibodies developed for cancer (~80% of the total in 2018). Data for antibody therapeutics that entered clinical study recently, in Excel format, may be downloaded from the Members Only area.

The biopharmaceutical industry’s intense focus on the development of antibody therapeutics, and particularly those for cancer, is unabated in 2019, according to the data available by mid-March. We have identified 17 antibody therapeutics for which an application to start clinical study was filed or a Phase 1 study was started in 2019, and an additional 11 antibody therapeutics with clinical studies not yet recruiting patients, as listed on clinicaltrials.gov. The rate of clinical entry for antibody therapeutics so far in 2019 is thus similar to that observed in 2018 (~10 per month). The trend toward development of antibodies as treatments for cancer is also quite similar. Of the 2019 cohort so far identified, 22 of 28 (79%) are for cancer.

The commercial clinical pipeline of cancer therapies has become increasingly dominated by 3 categories of antibodies: 1) immune checkpoint modulators; 2) antibody-drug conjugates (ADCs); and 3) bispecific antibodies (see figure for details).

Our data so far suggests that this trend will continue in 2019, as nearly three-quarters of the antibody therapeutics currently in the 2019 cohort fit in one (or more) of the 3 categories. Examples of antibodies that fit more than 1 category include TG-1801 (TG Therapeutics, Inc., Novimmune SA), a bispecific antibody targeting the immune checkpoint CD47 as well as CD19, and  INBRX-105 (Inhibrx, Inc.), a bispecific antibody targeting the immune checkpoints PD-L1 and 4-1BB. TG-1801, a human IgG1 designed to target and deplete B-cells, is undergoing evaluation in a Phase 1 study (NCT03804996) of patients with B-cell lymphoma. INBRX-105 is undergoing evaluation as a treatment for hematological and solid tumors in a Phase 1 study (NCT03809624).

More to come! Throughout 2019, we will track and report on the development of all antibody therapeutics that enter clinical study during the year.

Attention members! Please log in to access our data for all antibody therapeutics that entered clinical study during 2018 or so far in 2019. After logging in, click on ‘Antibodies in early-stage studies’ in the Members Only dropdown menu. Data will be updated throughout 2019.

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Congratulations to George P. Smith, Nobel Laureate, Chemistry 2018, for the Invention of Phage Display

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The Antibody Society congratulates Prof. George P. Smith, who will receive a 2018 Nobel Prize in Chemistry this December for his invention of phage display, and pioneering work on phage-library technology.

Read the 3 papers that started the field:

-Invention of phage display (Smith GP. Filamentous fusion phage: novel expression vectors that display cloned antigens on the virion surface. Science 1985)

– Improving phage display and affinity selection (Parmley SF, Smith GP. Antibody-selectable filamentous fd phage vectors: affinity purification of target genes. Gene 1988)

– Proof of concept for phage-displayed peptide libraries (Scott JK, Smith GP. Searching for peptide ligands with an epitope library. Science 1990)

As a postdoc with Prof. Smith, The Antibody Society Board Member Dr. Jamie K. Scott helped produce the proof of concept for phage-displayed peptide libraries.

Most read from mAbs issue 10.7

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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.

MAbs Issue 10.7 (October 2018)

Platform development for expression and purification of stable isotope labeled monoclonal antibodies in Escherichia coli.  In this report, Reddy et al. present the expression and purification of a stable isotope labeled mAb from a genetically engineered E. coli strain capable of forming disulfide bonds in its cytoplasm. Using 2D NMR spectral fingerprinting, they show that the unlabeled mAb and the mAb singly or triply labeled with 13C, 15N, 2H are well folded, with only minor structural differences relative to the mammalian cell-produced mAb that are attributed to the lack of glycosylation in the Fc domain.

Massive parallel screening of phage libraries for the generation of repertoires of human immunomodulatory monoclonal antibodies. Sasso et al discuss a novel approach for the generation of several novel human immunomodulatory antibodies capable of binding their targets in their native conformation and useful for therapeutic applications. They performed a massive parallel screening of phage libraries by using activated human lymphocytes to generate large collections of scFvs against 10 immune checkpoints: LAG-3, PD-L1, PD-1, TIM3, BTLA, TIGIT, OX40, 4-1BB, CD27 and ICOS. By next-generation sequencing and bioinformatics analysis, they ranked individual scFvs in each collection and identified those with the highest level of enrichment. Human IgGs from three of these collections (i.e., PD-1, PD-L1 and LAG-3) were generated and shown to have comparable or better binding affinity and biological activity than clinically validated mAbs. The repertoires generated in this work represent a convenient source of agonistic or antagonistic antibodies against the ‘Checkpoint Immunome’ for preclinical screening and clinical implementation of optimized treatments.

High-throughput screening of antibody variants for chemical stability: identification of deamidation-resistant mutants. In this report, DiCara et al describe a high-throughput method for antibody stability screening during the early stages of antibody discovery and highlight the value of broad searches of antibody sequence space. They developed a high-throughput assay to characterize asparagine deamidation and used it to identify a mutation that unexpectedly stabilizes a critical asparagine. Ninety antibody variants were incubated under thermal stress in order to induce deamidation and screened for both affinity and total binding capacity. Surprisingly, a mutation five residues downstream from the unstable asparagine greatly reduced deamidation.

Extending human IgG half-life using structure-guided design. Booth et al. report on the development of a structure- and network-based framework to interrogate the engagement of IgG with multiple Fc receptors (FcRn, C1q, TRIM21, FcγRI, FcγRIIa/b, FcγRIIIa) simultaneously. They identified features that govern Fc-FcRn interactions and identified multiple distinct pathways for enhancing FcRn binding in a pH-specific manner. Network analysis provided a novel lens to study the allosteric impact of half-life-enhancing Fc mutations on FcγR engagement, which occurs distal to the FcRn binding site. Applying these principles, they engineered a panel of unique Fc variants that enhance FcRn binding while maintaining robust biophysical properties and wild type-like binding to activating receptors.

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We encourage you to join the Society to take advantage of the substantial benefits of membership, including discounts on fees for selected KNect365, CHI, and Hanson Wade meetings, discounted subscriptions to Society-affiliated journals PEDS and mAbs (special subscription rate of US $84 online only access for Antibody Society members)  and access to information in the Members Only section of the website. In particular, we encourage members to take advantage of the discount on registration for Antibody Engineering & Therapeutics, which is the annual meeting of The Antibody Society traditionally held in San Diego in December. Membership is free for students, post-docs and employees of our corporate sponsors!