Abstract 2720: Engineering sweeping antibodies for the clearance of tumor-derived, pro-tumorigenic cytokines
Authors: Baker Jillian M. , Singh Nevil J. , Luetkens Tim 
Published: March 2024

Abstract
Soluble, tumor-derived, pro-tumorigenic (STP) cytokines have been shown to contribute to cancer cell proliferation and drug resistance. But therapeutic targeting of STP cytokines by monoclonal antibodies is limited by high concentrations and persistent production of antigen. We hypothesize that the ability of sweeping antibodies (swAbs) to actively clear soluble antigens will overcome these limitations. SwAbs differ from conventional antibodies via (1) pH-dependent binding of antigen, and (2) increased binding to the neonatal Fc receptor (FcRn). SwAbs facilitate clearance of soluble antigens by releasing antigen in the low pH environment of FcRn-expressing cells. SwAbs are then recycled via FcRn for repeated clearance of antigen.We are developing swAbs against four STP cytokines contributing to cancer cell proliferation, survival, migration or intra-tumoral angiogenesis: hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β) and interleukin 16 (IL-16). We selected four existing neutralizing antibodies against these cytokines with available crystal structures and generated a second antibody targeting interleukin 16 with high affinity (clone 3B6; KD = 13 nM) de novo using phage display. We are using bio-layer interferometry and custom recycling/clearance assays for antibody characterization and pre-clinical validation. To introduce pH dependency into the four antibodies with crystal structures, we performed targeted histidine mutagenesis of residues at the interface with the respective target antigens. For the de novo-generated interleukin-16 antibody, we performed an unbiased histidine scanning approach by mutating residues across all six complementarity-determining regions (CDRs), which resulted in slight increases in pH sensitivity. We then performed a second round of mutagenesis of the most pH-sensitive 3B6 variants by replacing additional residues considered developability liabilities with histidine residues. We found that this approach significantly increased expression and affinity at pH 7 of the resulting 3B6 variants but only modestly increased pH sensitivity. In contrast, replacing a single residue in the heavy CDR1 in clone 14.1, a pre-clinical anti-IL-16 antibody, resulted in substantially increased pH sensitivity (KD(pH=7) = 2 nM; KD(pH&lt;6) = n.b.). We are currently performing pH-sensitivity screenings for the three additional STP-specific antibodies. Our findings indicate that the ability to introduce pH sensitivity is largely dependent on the parental antibody and that some antibodies may not be amenable to this process. In addition, we show that histidine mutagenesis can be an effective approach to enhance expressibility and binding, while also increasing pH sensitivity. This project will answer the question whether anti-STP cytokine swAbs are an effective approach to treat patients with cancer.
Citation Format: Jillian M. Baker, Nevil J. Singh, Tim Luetkens. Engineering sweeping antibodies for the clearance of tumor-derived, pro-tumorigenic cytokines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2720.