Identification of novel anti-CD16a antibody clones for the development of effective natural killer cell engagers

Identification of novel anti-CD16a antibody clones for the development of effective natural killer cell engagers

ABSTRACT

Natural killer (NK) cells are key players in human innate immunity. Cell engager antibody formats that recruit and activate NK cells more effectively have emerged as a promising immunotherapy approach to target cancer cells through more effective antibody-dependent cell-mediated cytotoxicity (ADCC). Monoclonal antibody drugs with ADCC activity have shown clinical benefit and improved outcomes for patients with certain types of cancer. CD16a, a Fc gamma III receptor, is the major component that is responsible for the ADCC activity of NK cells. Screening AvantGen’s yeast displayed human antibody libraries led to the isolation of 2 antibody clones, #1A2 and #2-2A2, that selectively recognize both isoforms (F and V) of CD16a on primary NK cells with high affinity, yet minimally (#1A2) or do not (#2-2A2) cross-react with both allelotypes of CD16b (NA1 and NA2) expressed by neutrophils. Epitope mapping studies revealed that they bind to an epitope dependent on residue Y158 of CD16a, since mutation of Y158 to the corresponding CD16b residue H158 completely abolishes binding to CD16a. When formatted as bispecific antibodies targeting CD16a and a tumor-associated antigen (TAA, e.g. CD19), they exhibit specific binding to NK cells and induce potent NK cell activation upon encountering tumor cells, resulting in effective tumor cell killing. Notably, these bispecific antibody engagers stimulate NK cell cytokine release during co-culture with target cells, resulting in target cell cytotoxicity. These anti-CD16a antibody clones are promising candidates for combination with any TAA of interest, offering the potential for novel NK cell engager-based cancer therapeutics that are minimally affected by the high concentrations of human IgG in the circulation.

Full article is available here: https://www.tandfonline.com/doi/full/10.1080/19420862.2024.2381261

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  • Why Yeast?

    Yeast, or Saccharomyces cerevisiae aka brewer’s yeast to be exact, has the best of both worlds as a model organism for drug discovery. In selecting the right model, two opposing factors are: 1) finding an organism that can be used cost-effectively and ethically, and 2) being physiologically relevant by having it as similar as humans, the intended patients. This is where yeast has all the advantages: 1) it is unicellular, grows incredibly fast at a doubling rate of 90 minutes, and is easy and safe (non-pathogenic) to culture, meanwhile 2) as a eukaryote it can properly express, fold, and glycosylate proteins such as antibodies similar to mammals.

  • Yeast is “similar” but not the same as in humans with regards to post-translation modification (PTM) of proteins such as glycosylation?

    Correct, there are slight differences in the PTM profiles of proteins expressed in yeast versus mammals. However, we recombinantly express our lead antibodies in HEK293 or CHO cells and rarely observe a loss in activity. This is in stark contrast with E. coli-based systems like phage or cell-free, where bacteria lack protein glycosylation machinery.

  • Is affinity maturation required after using one of your platforms?

    Due to our large size rationally-designed Germliner™ library collection coupled with our rapid cell sorting based screening, we consistently obtain single-digit and subnM affinity antibodies with optimal developable characteristics. Interestingly, our popular AvantGeneer affinity maturation platform has been frequently used to optimize client antibodies that were originally discovered with hybridoma and human transgenic mouse platforms.

  • My target is a GPCR. Will your platform work?

    We have had success with multi-transmembrane proteins such as GPCRs, by using virus-like-particles (VLPs), nanodiscs, and client-designed variants with increased solubility.

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    We typically use various amounts of biotinylated, DyLight™ 650 conjugated, and unlabeled antigens for all projects. It’s important that both labeled and unlabeled antigens are QC’ed by provider, third party, and/or AvantGen. >0.5 mg/mL concentration, >80% monomer percentage, and >90% purity. Preferred buffer is PBS and no tris-based buffers please.

    Estimated Material Amounts*

    Application Stage Discovery Affinity Maturation Rabbit mAb
    All stages 1.5-2 mg biotinylated or 2-3 mg unlabeled 0.5 mg biotinylated or 1 mg unlabeled 2 mg unlabeled and 1 mg biotinylated
    FACS and screening 0.5-1 mg biotinylated or 1-2 mg unlabeled 0.2-0.5 mg biotinylated or 0.5-1 mg unlabeled 1 mg biotinylated and 0.2 mg unlabeled
    Screening only 0.2 mg biotinylated or 0.2-0.5 mg unlabeled 0.2 mg biotinylated or 0.2-0.5 mg unlabeled 0.2-0.5 mg unlabeled

    *Assuming 50 kDa antigen. AvantGen can bioconjugate and QC as needed.

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