Directed Evolution of PD-L1-Targeted Affibodies by mRNA Display

• DOI: 10.1021/acschembio.2c00218
• Publication Date: 2022-05-25T11:50:14Z
• Authors: Brian J. Grindel; Brian J. Engel; Justin N. Ong; Anupallavi Sriniv...; Xiaowen Liang; Niki M. Zacharias; Robert C. Bast; Michael A. Curran; Terry T. Takahashi; Richard W. Roberts; Steven W. Millward
• Keywords: Protein Engineering

Therapeutic monoclonal antibodies directed against PD-L1 (e.g., atezolizumab) disrupt PD-L1:PD-1 signaling and reactivate exhausted cytotoxic T-cells in the tumor compartment. Although anti-PD-L1 are successful as immune checkpoint inhibitor (ICI) therapeutics, there is still a pressing need to develop high-affinity, low-molecular-weight ligands for molecular imaging diagnostic applications. Affibodies small polypeptides (∼60 amino acids) that provide stable scaffold from which evolve high-affinity ligands. Despite its proven utility development of probes, this has never been optimized use mRNA display, powerful vitro selection platform incorporating high library diversity, unnatural acids, chemical modification. In manuscript, we describe PD-L1-binding affibody by display. Following randomization 13 acids define binding interface well-described Her2 affibody, resulting was selected recombinant human (hPD-L1). After four rounds, enriched split either hPD-L1 or mouse ortholog (mPD-L1). The dual target resulted identification human/mouse cross-reactive (M1) with low nanomolar affinity both targets. M1 bound similar mPD-L1 expressed on cell surface inhibited through axis at micromolar concentrations cell-based functional assay. vivo optical M1-Cy5 an immune-competent model lymphoma revealed significant uptake relative Cy5-conjugated affibody.