Browsing by Author "Chung, Anna"

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    Synthesis of precision antibody conjugates using proximity-induced chemistry
    (Ivyspring, 2021) Cao, Yu J.; Yu, Chenfei; Wu, Kuan-Lin; Wang, Xuechun; Liu, Dong; Tian, Zeru; Zhao, Lijun; Qi, Xuexiu; Loredo, Axel; Chung, Anna; Xiao, Han; Bioengineering; Biosciences; Chemistry
    Rationale: Therapeutic antibody conjugates allow for the specific delivery of cytotoxic agents or immune cells to tumors, thus enhancing the antitumor activity of these agents and minimizing adverse systemic effects. Most current antibody conjugates are prepared by nonspecific modification of antibody cysteine or lysine residues, inevitably resulting in the generation of heterogeneous conjugates with limited therapeutic efficacies. Traditional strategies to prepare homogeneous antibody conjugates require antibody engineering or chemical/enzymatic treatments, processes that often affect antibody folding and stability, as well as yield and cost. Developing a simple and cost-effective way to precisely couple functional payloads to native antibodies is of great importance. Methods: We describe a simple proximity-induced antibody conjugation method (pClick) that enables the synthesis of homogeneous antibody conjugates from native antibodies without requiring additional antibody engineering or post-synthesis treatments. A proximity-activated crosslinker is introduced into a chemically synthesized affinity peptide modified with a bioorthogonal handle. Upon binding to a specific antibody site, the affinity peptide covalently attaches to the antibody via spontaneous crosslinking, yielding an antibody molecule ready for bioorthogonal conjugation with payloads. Results: We have prepared well-defined antibody-drug conjugates and bispecific small molecule-antibody conjugates using pClick technology. The resulting conjugates exhibit excellent in vitro cytotoxic activity against cancer cells and, in the case of bispecific conjugates, superb antitumor activity in mouse xenograft models. Conclusions: Our pClick technology enables efficient, simple, and site-specific conjugation of various moieties to the existing native antibodies. This technology does not require antibody engineering or additional UV/chemical/enzymatic treatments, therefore providing a general, convenient strategy for developing novel antibody conjugates.
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    Unleashing the potential of noncanonical amino acid biosynthesis to create cells with precision tyrosine sulfation
    (Springer Nature, 2022) Chen, Yuda; Jin, Shikai; Zhang, Mengxi; Hu, Yu; Wu, Kuan-Lin; Chung, Anna; Wang, Shichao; Tian, Zeru; Wang, Yixian; Wolynes, Peter G.; Xiao, Han; Bioengineering; Biosciences; Chemistry; Physics and Astronomy; Center for Theoretical Biological Physics
    Despite the great promise of genetic code expansion technology to modulate structures and functions of proteins, external addition of ncAAs is required in most cases and it often limits the utility of genetic code expansion technology, especially to noncanonical amino acids (ncAAs) with poor membrane internalization. Here, we report the creation of autonomous cells, both prokaryotic and eukaryotic, with the ability to biosynthesize and genetically encode sulfotyrosine (sTyr), an important protein post-translational modification with low membrane permeability. These engineered cells can produce site-specifically sulfated proteins at a higher yield than cells fed exogenously with the highest level of sTyr reported in the literature. We use these autonomous cells to prepare highly potent thrombin inhibitors with site-specific sulfation. By enhancing ncAA incorporation efficiency, this added ability of cells to biosynthesize ncAAs and genetically incorporate them into proteins greatly extends the utility of genetic code expansion methods.