Final Report Summary - NOXYCANCERSTARV (Synthesis of N-hydroxyheterocycles as starvation agents against highly invasive hypoxic solid tumours)
The purpose of this research project was the development of preclinical anti-cancer drug candidates able to fight hypoxic solid tumours, which are normally resistant to chemotherapy and radiotherapy. Highly invasive tumour cells are characterised by a metabolic switch, known as the Warburg effect, from 'normal' oxidative phosphorylation to an increased anaerobic glycolysis. This ensures a sufficient energy supply from glucose, even in hypoxic environments. One of the key human enzymes involved in anaerobic glycolysis, the muscle isoform of lactate dehydrogenase (hLDH5), has been recently shown to be overexpressed by metastatic cancer cells, and has been linked to the vitality of tumours in hypoxia. This enzyme may be considered as a valid target for new anticancer agents, since its inhibition would lead to a cut in cancer energy supply, thus reducing its metastatic and invasive potential. A validation of hLDH5 as a safe target derives from the observation that in humans, hereditary hLDH5 deficiency causes a certain level of myopathy only after intense anaerobic exercise, whereas it does not provoke any symptoms under ordinary circumstances. This project has supported a qualified international researcher, Dr Sarabindu Roy, in the management of a research line including molecular design and synthesis of a series of new compounds, as well as in the participation in the biological evaluation of their properties. Each step of his formation was adequately followed by additional specialised trainers: Dr Tiziano Tuccinardi for the molecular modelling; Prof. Gino Giannaccini, for the enzyme inhibition bioassays; Dr Valeria Di Bussolo, for the synthesis of gluco-conjugates. The project benefited from some preliminary results previously obtained at the host institution, where the scientist in charge had already identified a suitable structural scaffold, based on N-hydroxyheterocycles, which had furnished some first examples of exploratory hLDH5 inhibitors, endowed of moderate inhibitory potencies. In particular, it was found that the N-hydroxyindole-2-carboxylate (NHI) fragment gave some consistent inhibition of hLDH5. Therefore, this scaffold constituted the basis for the development of a larger series of analogues by the researcher during this project.
At the end of the project, our research group has produced over 100 molecules that were tested as hLDH5 inhibitors. A large proportion (over 30 %) of this focused collection of compounds afforded inhibitors showing appreciable levels of inhibition (Ki lower than 60 micromole). In particular, some of these NHI-based derivatives represent the most potent and selective inhibitors of hLDH5 thus far reported in the scientific literature, to the best of our knowledge, with Ki values as low as 1.5 micromole. Proliferation assays of the most potent hLDH5 inhibitors proved that these compounds possess potent anti-proliferative activities against invasive cancer cells.
Furthermore, exploratory studies devoted to the preparation of glyco-conjugates of the most potent NHI-based hLDH5 inhibitors demonstrated that these compounds can be efficiently prepared on a multi-gram scale by following our synthetic methodology, and some preliminary results showed that they behave as prodrugs of their parent non-conjugated derivatives, which benefit from a higher cellular uptake.
In conclusion, this research produced some suitable pre-clinical candidates to be further investigated as potential new anti-cancer drugs, which exploit an innovative and potentially safe mechanism of action.
At the end of the project, our research group has produced over 100 molecules that were tested as hLDH5 inhibitors. A large proportion (over 30 %) of this focused collection of compounds afforded inhibitors showing appreciable levels of inhibition (Ki lower than 60 micromole). In particular, some of these NHI-based derivatives represent the most potent and selective inhibitors of hLDH5 thus far reported in the scientific literature, to the best of our knowledge, with Ki values as low as 1.5 micromole. Proliferation assays of the most potent hLDH5 inhibitors proved that these compounds possess potent anti-proliferative activities against invasive cancer cells.
Furthermore, exploratory studies devoted to the preparation of glyco-conjugates of the most potent NHI-based hLDH5 inhibitors demonstrated that these compounds can be efficiently prepared on a multi-gram scale by following our synthetic methodology, and some preliminary results showed that they behave as prodrugs of their parent non-conjugated derivatives, which benefit from a higher cellular uptake.
In conclusion, this research produced some suitable pre-clinical candidates to be further investigated as potential new anti-cancer drugs, which exploit an innovative and potentially safe mechanism of action.
