Enhancement of the click chemistry for the inverse Diels Alder technology by functionalization of amide-based monomers.

In the near future personalized medicine with nucleic acids will play a key role in molecular diagnostics and therapy, which require new properties of the nucleic acids, like stability against enzymatic degradation. Here we demonstrate that the replacement of nucleobases with PNA by functional molecules harbouring either a dienophile or a diene reactivity is feasible and confers all new options for functionalization. These newly developed derivatives allow independent multi-ligations of multi-faceted components by use of the inverse Diels Alder technology. The high chemical stability and the ease of synthesis qualify these polyamide building blocks as favourites for intracellular delivery and targeting applications. This allows local drug concentrations sufficient for imaging and therapy and simultaneously a reduction of the application doses. It is important to point out that this technology is not restricted to ligation of medicament material; it is also a candidate to develop new and highly efficient active compounds for a "sustainable pharmacy".

A cyclic-RGD-BioShuttle functionalized with TMZ by DARinv "Click Chemistry" targeted to αvß3 integrin for therapy.

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 α(v)ß(3) [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 α(v)ß(3) 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 α(v)ß(3) integrin-ligand, ligated to the cytotoxic drug TMZ. The ligation was carried out by the Diels Alder Reaction with inverse electron demand (DAR(inv)).

Extension of the PNA world by functionalized PNA monomers eligible candidates for inverse Diels Alder Click Chemistry.

Progress in genome research led to new perspectives in diagnostic applications and to new promising therapies. On account of their specificity and sensitivity, nucleic acids (DNA/RNA) increasingly are in the focus of the scientific interest. While nucleic acids were a target of therapeutic interventions up to now, they could serve as excellent tools in the future, being highly sequence-specific in molecular diagnostics. Examples for imaging modalities are the representation of metabolic processes (Molecular Imaging) and customized therapeutic approaches ("Targeted Therapy"). In the individualized medicine nucleic acids could play a key role; this requires new properties of the nucleic acids, such as stability. Due to evolutionary reasons natural nucleic acids are substrates for nucleases and therefore suitable only to a limited extent as a drug. To use DNA as an excellent drug, modifications are required leading e.g. to a peptide nucleic acid (PNA). Here we show that an easy substitution of nucleobases by functional molecules with different reactivity like the Reppe anhydride and pentenoic acid derivatives is feasible. These derivatives allow an independent multi-ligation of functionalized compounds, e.g. pharmacologically active ones together with imaging components, leading to local concentrations sufficient for therapy and diagnostics at the same time. The high chemical stability and ease of synthesis could enhance nucleic chemistry applications and qualify PNA as a favourite for delivery. This system is not restricted to medicament material, but appropriate for the development of new and highly efficient drugs for a sustainable pharmacy.