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.