2022 White Paper on Recent Issues in Bioanalysis: Enzyme Assay Validation, BAV for Primary End Points, Vaccine Functional Assays, Cytometry in Tissue, LBA in Rare Matrices, Complex NAb Assays, Spectral Cytometry, Endogenous Analytes, Extracellular Vesicles Part 2 - Recommendations on Biomarkers/CDx, Flow Cytometry, Ligand-Binding Assays Development & Validation; Emerging Technologies; Critical Reagents Deep Characterization

The 16th Workshop on Recent Issues in Bioanalysis (16th WRIB) took place in Atlanta, GA, USA on September 26-30, 2022. Over 1000 professionals representing pharma/biotech companies, CROs, and multiple regulatory agencies convened to actively discuss the most current topics of interest in bioanalysis. The 16th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on ICH M10 BMV final guideline (focused on this guideline training, interpretation, adoption and transition); mass spectrometry innovation (focused on novel technologies, novel modalities, and novel challenges); and flow cytometry bioanalysis (rising of the 3rd most common/important technology in bioanalytical labs) were the special features of the 16th edition. As in previous years, WRIB continued to gather a wide diversity of international, industry opinion leaders and regulatory authority experts working on both small and large molecules as well as gene, cell therapies and vaccines to facilitate sharing and discussions focused on improving quality, increasing regulatory compliance, and achieving scientific excellence on bioanalytical issues. This 2022 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2022 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on LBA, Biomarkers/CDx and Cytometry. Part 1 (Mass Spectrometry and ICH M10) and Part 3 (Gene Therapy, Cell therapy, Vaccines and Biotherapeutics Immunogenicity) are published in volume 15 of Bioanalysis, issues 16 and 14 (2023), respectively.

Abstract 4327: A novel protease resistant antibody platform with selectable cell killing functions

Invasive cancers express matrix metalloproteases, such as MMP-3 and MMP-7, which have the ability to cleave human antibodies in the lower hinge region. The human IgG lower hinge region contains two heavy chains, and cleavage occurs in a two-step process. First, one heavy chain is cleaved, resulting in a singly-cleaved intermediate. Cleavage of the second heavy chain liberates the Fc region from the antigen-binding region, resulting in an Fc fragment and a F(ab’)2 fragment. Previous work has demonstrated that the singly-cleaved intermediate accumulates on the surface of IgG1-opsonzied tumor cells in the presence of MMPs. The singly-cleaved intermediate is indistinguishable from the intact IgG counterpart when assessed by analytical techniques under native conditions and maintains normal antigen binding. However, the singly-cleaved intermediate displays a profound loss of Fc-mediated cell-killing functions both in vitro (e.g. ADCC and CDC) and with in vivo cell clearance, presumably because the lower hinge contains key recognition points for both FcγRs and the C1q component of complement. Singly-cleaved IgGs are of particular concern with regards to human IgG1 monoclonal therapeutic antibodies, because the proposed mechanisms of action for several anti-tumor mAbs in the clinic may be partially dependent on Fc effector functions, such as ADCC and CDC. For this reason, our group and others have proposed that cleavage and the subsequent inactivation of Fc-effector functions of human IgG antibodies may function as an immune evasion mechanism. To overcome the loss-of-function associated with human IgG1 cleavage, we aimed to develop a protease-resistant IgG1 platform which would still maintain Fc-mediated cell-killing functions. Mutation of the lower hinge of IgG1 provided protease-resistance, but also resulted in a loss of Fc-effector functions. Through specific mutations of amino acids in the CH2 region to enhance complement or Fcγ receptor binding, we were able restore or even enhance cell-killing functions selectively while maintaining protease-resistance. Therefore, we were able to generate protease-resistant antibodies with the ability to mediate either complement-dependent and/or antibody-dependent cellular cytotoxicity, which were also significantly resistant to inactivation by proteases associated with many invasive cancers.

Citation Format: Michelle Kinder, Katharine Grugan, Keri Soring, William Strohl, Robert Jordan, Randall Brezski. A novel protease resistant antibody platform with selectable cell killing functions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4327. doi:10.1158/1538-7445.AM2013-4327