an-Sheng Li

Synthesis of the next-generation therapeutic antibodies that combine cell targeting and antibody-catalyzed prodrug activation

An obstacle in the utilization of catalytic Abs for selective prodrug activation in cancer therapy has been systemic tumor targeting. Here we report the generation of catalytic Abs that effectively target tumor cells with undiminished prodrug activation capability. Ab conjugates were prepared by covalent conjugation of an integrin αvβ3-targeting antagonist to catalytic Ab 38C2 through either sulfide groups of cysteine residues generated by reduction of the disulfide bridges in the hinge region or surface lysine residues not involved in the catalytic activity. Using flow cytometry, the Ab conjugates were shown to bind efficiently to integrin αvβ3-expressing human breast cancer cells. The Ab conjugates also retained the retro-aldol activity of their parental catalytic Ab 38C2, as measured by methodol and doxorubicin (dox) prodrug activation. Complementing these Ab conjugates, an evolved set of dox prodrugs was designed and synthesized. Dox prodrugs that showed higher stability and lower toxicity were evaluated both in the presence and absence of the integrin αvβ3-targeting 38C2 conjugates for cell-killing efficacy by using human breast cancer cells. Our study reveals that cell targeting and prodrug activation capabilities can be efficiently combined for selective chemotherapy with novel dox prodrugs.

Preparation of integrin α(v)β(3)-targeting Ab 38C2 constructs

This protocol describes the preparation of Ab constructs using agents that target cells expressing integrins αvβ3 and αvβ5, and the monoclonal aldolase Ab 38C2. The targeting agents are equipped with a diketone or vinylketone linker, and selectively react through the reactive Lys residues in the Ab binding sites to form 38C2 conjugates or chemically programmed 38C2 (i.e., cp38C2). The targeting agent possessing a diketone linker reacts with the Lys residues forming an enaminone derivative. By contrast, the vinylketone linker is used as the corresponding acetone adduct (i.e., a pro-vinylketone linker), and this pro-adapter undergoes a 38C2-catalyzed retro-aldol reaction to produce the vinylketone linker, which forms a Michael-type adduct with the Lys residues. The Ab construct formation is achieved in <1 h for the diketone compounds at ambient temperature, and in 2–16 h using the pro-vinylketone linker at 37 °C. The 38C2 constructs are retargeted to cells over-expressing integrins, and are potential candidates for immunotherapy.

Preparation of integrin |[alpha]|(v)|[beta]|(3)-targeting Ab 38C2 constructs

This protocol describes the preparation of Ab constructs using agents that target cells expressing integrins αvβ3 and αvβ5, and the monoclonal aldolase Ab 38C2. The targeting agents are equipped with a diketone or vinylketone linker, and selectively react through the reactive Lys residues in the Ab binding sites to form 38C2 conjugates or chemically programmed 38C2 (i.e., cp38C2). The targeting agent possessing a diketone linker reacts with the Lys residues forming an enaminone derivative. By contrast, the vinylketone linker is used as the corresponding acetone adduct (i.e., a pro-vinylketone linker), and this pro-adapter undergoes a 38C2-catalyzed retro-aldol reaction to produce the vinylketone linker, which forms a Michael-type adduct with the Lys residues. The Ab construct formation is achieved in <1 h for the diketone compounds at ambient temperature, and in 2–16 h using the pro-vinylketone linker at 37 °C. The 38C2 constructs are retargeted to cells over-expressing integrins, and are potential candidates for immunotherapy.