Topological Scaffold-Based Trispecific Recombinant Protein-Drug Conjugates for Solid Tumor Eradication

Topology structure of proteins plays vital roles on their bioactivity and property. However, the understanding of how the biological effect of active targeting groups varies with different spatial positions in the recombinant protein scaffold is poor. Here a three trispecific recombinant heterotrimeric proteins and their drug conjugates are reported with a star and linear topology structure prepared by genetically encoded fusion and SpyTag-SpyCatcher technology, which can simultaneously bind the human epidermal growth factor receptor 1 and 2 as well as integrin α_vβ₃ on the surface of cancer cells. The biological difference of heterotrimeric proteins with different topologic structures is evaluated. Given the unique topological structure and superior biologic effects, star-shaped trispecific recombinant proteins can specifically deliver the covalently linked payload, 7-ethyl-10-hydroxycamptothecin, into HeLa tumor, leading to complete tumor eradication, while linear structural ones can only control tumor growth to some extent. The remarkable antitumor activity of the designed recombinant protein-drug conjugate with star-shaped structure in both small and large tumor models can be attributed not only to the triple targeting against EGFR, HER2, and integrin α_vβ₃, but also to the "site effect" of targeting elements in heterotrimeric fusion proteins brought by the unique topological structure. The results suggest that trispecific heterotrimeric recombinant proteins with a star-shaped topological structure is a promising drug conjugate platform.