Fine Tuning Antibody Conjugation Methods using SNAP-tag Technology

Background: Targeted imaging and therapy (theranostics) is a promising approach for the simultaneous improvement of cancer diagnosis, prognosis and management. Therapeutic and imaging reagents are coupled to tumor-targeting molecules such as antibodies, providing a basis for truly personalized medicine. However, the development of antibody–drug conjugates with acceptable pharmaceutical properties is a complex process and several parameters must be optimized, such as the controlled conjugation method and the drug-to-antibody ratio. Objective: The major aim of this work is to address fundamental key challenges for the development of versatile technology platform for generating homogenous immunotheranostic reagent. Method: We conjugated the theranostics reagent IRDye700dx to a recombinant antibody fusion protein containing a self-labeling protein (SNAP-tag) which provides a unique reaction site. Results: The resulting conjugate was suitable for the imaging of cancer cells expressing the epidermal growth factor receptor and demonstrated potent phototherapeutic and imaging activities against them. Conclusion: Here, we describe a simple, rapid and robust site-directed labeling method that can be used to generate homogeneous immunoconjugate with defined pharmacological properties.