Immobilization of microbial transglutaminase for the production of homogeneous immunotherapeutic antibody–drug conjugates

Antibody–drug conjugates (ADCs) have revolutionized chemotherapy, allowing it to shift from systemic cytotoxic chemotherapy to specific targeting of cells expressing tumor antigens. ADCs thus offer increased therapeutic efficacy and lower toxicity compared to conventional chemotherapy. Bioconjugation of a highly active therapeutic agent to an antibody is one of the key steps in producing ADCs. The most advanced ADC technologies are based on the production of stoichiometrically homogeneous bioconjugates. Enzymatic modification of antibodies using microbial transglutaminase (mTGase) enables the production of biopharmaceuticals with standardized pharmacokinetic, physicochemical, and therapeutic properties. However, side reactions catalyzed by free mTGase in solution reduce the yield and purity of ADCs. In this study, we evaluated the efficiency of various approaches to mTGase immobilization: streptavidin–biotin interaction, the use of an epoxy-activated polymer, and self-immobilization of mTGase. The highest bioconjugation activity was observed when using streptavidin-modified magnetic particles and biotinylated mTGase. However, mTGase self-immobilization on AH-Sepharose 4B or immobilization using epoxy-activated agarose ensures comparable efficiency in enzymatic antibody modification and is the most rational route from the perspective of process scalability. We believe that the proposed approaches are of high practical significance, opening up avenues for optimizing enzymatic bioconjugation and scaling up the production of stoichiometric ADCs for targeted cancer immunotherapy.