Design, synthesis and biological evaluation of nucleoside phosphoramidates with potential anticancer activity

One in seven approved anticancer drugs in the UK are nucleoside analogues (NA). However, frequent development of resistances and unpredictable toxicity are crucial drawbacks of these compounds. Some of the main resistance mechanisms against NAs include limited cellular permeability and decreased initial phosphorylation of the NAs, thus limiting the concentration of active NAs inside the target cells. The ProTide approach is a pronucleotide technology that successfully overcomes these drawbacks by releasing the monophosphorylated NA into the cell and has led to multiple clinical candidate drugs. This work was focussed on the application of the ProTide approach to novel and known anticancer NAs with the aim of improving their performance and pharmacological properties. Herein, new synthesis and optimisation of selected pyridine and purine NA with modifications in the base and / or in the sugar moieties, along with different synthetic approaches to build the prodrugs are reported. The anticancer activity of the compounds was evaluated via cell viability assays, and the activation of the prodrugs and resistance to enzymatic degradation was proved via enzymatic assays involving Nuclear Magnetic Resonance (NMR) or spectrophotometric methods. Molecular modelling studies were performed in order to understand the interaction of the ProTides and their metabolites with the enzymes. Finally, the family with the best in vitro activity results was enlarged by developing novel ProTide-related nucleoside diamidate prodrugs, which aimed to further improve their bioavailability and stability characteristics