1. German Cancer Research Center, Dept. of Imaging and Radiooncology, INF 280, D-69120 Heidelberg, Germany
2. German Cancer Research Center, Central Peptide Synthesis Unit, INF 580, D-69120 Heidelberg, Germany
3. University of Heidelberg, Institute of Pathology, INF 220, D-69120 Heidelberg, Germany
4. German Cancer Research Center, Division of Biophysics of Macromolecules, INF 580, D-69120 Heidelberg, Germany
* The authors contributed equally to this work
Clinical experiences often document, that a successful tumor control requires high doses of drug applications. It is widely believed that unavoidable adverse reactions could be minimized by using gene-therapeutic strategies protecting the tumor-surrounding healthy tissue as well as the bone-marrow. One new approach in this direction is the use of “Targeted Therapies” realizing a selective drug targeting to gain effectual amounts at the target site, even with drastically reduced application doses. MCF-7 breast cancer cells expressing the αvβ3 [alpha(v)beta(3)] integrin receptor are considered as appropriate candidates for such a targeted therapy. The modularly composed BioShuttle carrier consisting of different units designed to facilitate the passage across the cell membranes and for subcellular addressing of diagnostic and/or therapeutic molecules could be considered as an eligible delivery platform. Here we used the cyclic RGD-BioShuttle as a carrier for temozolomide (TMZ) at the αvβ3 integrin receptor realizing local TMZ concentrations sufficient for cell killing. The IC50 values are 12 µMol/L in the case of cRGD-BioShuttle-TMZ and 100 µMol/L for underivatized TMZ, which confirms the advantage of TMZ reformulation to realize local concentrations sufficient for cell killing.
Our paper focuses on the design, synthesis and application of the cRGD-BioShuttle conjugate composed of the cyclic RGD, a αvβ3 integrin-ligand, ligated to the cytotoxic drug TMZ. The ligation was carried out by the Diels Alder Reaction with inverse electron demand (DARinv).
Keywords: Click-Chemistry, Cycloaddition, BioShuttle, Ligation chemistry, Linker Systems, Adaptor Systems, inverse Diels Alder Reaction, RGD, Tetrazines, targeted Therapy, Temozolomide