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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.

Treatment of cancer using standard chemotherapy still offers a poor prognosis combined with severe side effects. Novel antibody-based therapies have been shown to overcome low efficiency and lack of selectivity by targeting cancer-associated antigens, such as aminopeptidase CD13. We isolated a high-affinity CD13-specific single-chain fragment variable (scFv13) from a phage display library of V-genes from mice immunized with soluble antigen. An immunotoxin comprising the scFv13 and a truncated version of the exotoxin A of Pseudomonas aeruginosa (ETA′, scFv13–ETA′) and a bispecific scFv targeting CD13 and CD16 simultaneously (bsscFv[13xds16]) was generated and investigated for their therapeutic potential. Both fusion proteins bound specifically to target cells with high affinity. Furthermore, scFv13–ETA′ inhibited the proliferation of human cancer cell lines efficiently at low concentrations (IC50 values of 408 pM–7 nM) and induced apoptosis (40–85% of target cells). The bsscFv triggered dose-dependent antibody-dependent cell-mediated cytotoxicity, resulting in the lysis of up to 23.9% A2058 cells, 18.0% MDA-MB-468 cells and 19.1% HL-60 cells. The provided data demonstrate potent therapeutic activity of the scFv13–ETA′ and the bsscFv[13xds16]. The CD13-specific scFv is therefore suitable for the direct and specific delivery of both cytotoxic agents and effector cells to cancer-derived cells, making it ideal for further therapeutic evaluation.

OncoTarget 7(41), 67166-67174 (2016). doi:10.18632/oncotarget.11568, Published by Impact Journals LLC, [S.l.]