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Descrizione del progetto

This research project aims at the synthesis and the study of new molecules with cytotoxic activity that: a) are able to coordinate Cu(I)/Cu(II) ions, and b) effectively inhibit the activity of protein disulfide isomerase (PDI), which has emerged in recent decades as an interesting target in the treatment of some types of cancer (in particular ovarian, breast and brain cancer). Recently, we (Carcelli et al., 2020) and prof. Keppler’s research group (Hager et al., 2018) have synthesized some thiosemicarbazones (TSCs) with nanomolar cytotoxic activity that effectively inhibit the activity of PDI. TSCs have been long studied for their anticancer activity: 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine) was tested in numerous phase I and phase II studies, but the severe side effects blocked further developments. Between 2015 and 2016 there was a decisive turning point, with the identification of two new TSCs with nanomolar activity, COTI-2 (developed by Critical Outcome Technologies Inc.) and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC, developed by Oncochel Therapeutics), both in phase I clinical development. The activity of these two new TSCs does not seem attributable to the traditionally invoked molecular mechanisms, i.e. chelation of iron ions and production of ROS or inhibition of the enzyme ribonucleotide reductase, but, within a multifactorial framework, both chelation of Cu(II) ions (and probably also zinc), and proteins such as p53 and PDI emerged as alternative molecular targets. In this project we intend to introduce modifications in the structure of 3-methoxy-2-hydroxybenzaldehyde thiosemicarbazone (3M2HT), whose nanomolar cytotoxicity in complex with Cu(II) we have already demonstrated, in order to increase solubility and significantly vary lipophilicity, looking for structure/activity correlations. The poor solubility of TSCs and of the related metal complexes has always been a problem in the application of these compounds, in particular as concerns their in vivo experimentation. It is well-known that lipophilicity is a crucial parameter in this context: for instance, it has been demonstrated that the complete methylation of Triapine not only brings the cytotoxic activity in the nanomolar range but makes the per-methylated derivative an effective PDI inhibitor (Hager et al., 2018). The new TSCs will be studied as ligands towards Cu(II) ions, trying to characterize their behaviour in solution and to isolate and characterise the Cu(II) complexes also in the solid state. Their cytotoxic activity will be evaluated by Prof. Gandin’s group at the University of Padova, and also investigations on the action mechanisms will be conducted.