SYNTHESIS OF INTEGRIN-TARGETING PRO-DRUGS FOR THE SELECTIVE RELEASE OF ANTI-TUMOR AGENTS

In this PhD work, a variety of new SMDCs were designed and synthesized featuring different types of linkers and cytotoxic payloads. All of them were characterized and conjugated to peptidomimetic ligands bearing the RGD sequence (namely, the cyclo[DKP-RGD] and cyclo[RDGfK] compounds) aimed at targeting αVβ3 integrin receptor, which is overexpressed in many human cancers. Firstly, six new conjugates containing peptide linkers prone to cleavage in intracellular vesicles (such as the lysosomes) were synthesized and evaluated in vitro. The loss of potency generally displayed by these SMDCs in antiproliferative assays prompted us to the design of new conjugates bearing peptide linkers susceptible to proteolysis in the extracellular environment. This strategy has got credits from literature data and it has been proposed as a promising alternative to internalizing conjugates. Based on this, two new conjugates containing aminoacid sequences recognized and cleaved by MMP-2 were synthesized. The conjugates’ binding ability was studied by competitive binding assays on the integrin αVβ3 receptor was studied, and the effective cleavage of the peptide linker in the presence of recombinant human MMP-2 was observed. Finally, two new conjugates that may be activated both in intracellular compartments and in extracellular milieu, by means of the ubiquitous tumor-associated enzyme β-glucuronidase, were synthesized and evaluated by their ability of inhibit biotinylated vitronectin (binding assays). Further evaluation of the efficient drug release from these non-internalizing prodrugs, brought at the diseased site by the RGD affinity for tumor-expressed integrins, will potentially support the clinical investigation of this anticancer devices.