To address the stated objectives, we prepared a research program composed of 2 WP. For the implementation of the WP1, I prepared several bioorthogonal prodrugs of the HDAC inhibitor vorinostat. One of these derivatives proved to be highly bioorthogonal and was rapidly uncaged in the presence of Pd-functionalised resins both in vitro and cancer cell culture. The deprotection proceeds via a tandem mechanism triggered by the Pd-catalysed depropargylation of a phenolic ether group and followed by 1,6-elimination of a 4-hydroxybenzyl group directly attached to the OH of the drug’s hydroxamic acid group; a previously unreported process that takes place at physiological pH. These results derived in a scientific publication: Rubio-Ruiz, B. et al. J Med Chem. 2016, 59, 9974-9980.
Connected with the 1st research objective, over the course of the project we investigated new avenues for the activation of our prodrugs: (i) firstly, we explored Pd-nanoparticles in order to perform bioorthogonal organometallic (BOOM) catalysis inside the cancer cells. Although these nanodevices showed a high capacity to activate Pd-labile pro-dyes in PBS, their catalytic activity in PBS supplemented with FBS was significantly lower indicating that these nanoparticles are not suitable to perform intracellular BOOM catalysis. Since these nanomaterials displayed an exceptional biocompatibility and high photothermal conversion capacity, they were used to tag cancer cells and induce photothermal ablation upon short exposure to NIR light. This research was published in ACS Applied Materials and Interfaces (Rubio-Ruiz, B. et al. ACS Appl Mater Interfaces 2018, 10, 3341-3348); (ii) secondly, aiming to expand the scope of locally-controlled BOOM chemistry in biomedicine, we explored metallic gold to catalyse the activation of our prodrugs. To this end, a solid supported gold catalysts was prepared by in situ generation of Au-nanoparticles (Au-NP) within a PEG-grafted low-crosslinked polystyrene matrix. Embedding these Au-NP in a solid support, we protected the metal nanostructures from large thiol-rich biomolecules, while allowing the free entry of alkyne-functionalized small molecules to undergo gold-mediated chemistries in biological systems. The new devices were fully biocompatible and able to catalyse the activation of our previously synthesised vorinostat prodrugs in cancer cells. These results gave rise a scientific publication (Pérez-López, A.M.; Rubio-Ruiz, B. et al. Angewandte Chemie International Edition 2017, 56, 12548-12552). The validation of this Pd/Au-activatable prodrug generated valuable intellectual property (IP) that was protected (Rubio-Ruiz, B. et al. International patent application PCT/GB2017/051379).
Finally, for the implementation of the WP2, we designed and synthesised a novel Pd-labile codrug. Upon the presence of our biocompatible Pd-devices, the propargyl moiety is cleaved causing the self-fragmentation of the linking moiety and releasing of 2 different anticancer drugs in vitro. The validation of this novel codrug in cancer cell culture is still in progress.
