Periodic Reporting for period 1 - ChemoBOOM (Development of Palladium-Labile Prodrugs for Bioorthogonally-Activated Chemotherapy)
Reporting period: 2016-02-01 to 2018-01-31
The research program was divided into two specific research objectives:
Objective 1: Development of novel O-Propargylated Pd-labile prodrugs of cytotoxic agents. In recent years several transition metal-mediated bioorthogonal deprotection reactions have been reported, however they can be grouped in 2 classes: the deprotection of carbamate-masked primary amino groups and the N-depropargylation of endocyclic nitrogen atoms with lactam-lactim tautomerism. As the cytotoxicity of many therapeutic agents is modulated by other chemical functionalities, the 1st specific objective of the project was to extend the scope of functional groups amenable to activation by Pd chemistry in order to increase the diversity of bioorthogonally-activated prodrugs. This is, for example, the case of hydroxamic acid-based drugs such as HDAC inhibitor vorinostat whose pharmacological activity is endowed by the metal-chelating capacity of the hydroxamic acid group. During the course of this project, we have developed a novel strategy that enabled -for the first time- to devise a completely inactive precursor of vorinostat that is rapidly uncaged by biocompatible Pd-resins in cell culture models of glioma and lung cancer. To expand the scope of the locally-controlled bioorthogonal organometallic chemistry in biomedicine, we successfully extended this strategy beyond Pd and demonstrated the bioorthogonal activation of this prodrug by a heterogenous Au catalysts.
Objective 2. Development of precursors of combination therapy activated by Pd chemistry. One of the most promising approaches to address cancer heterogeneity is the use of combination therapy, which is based on the simultaneous use of drugs with different mode of actions and synergistic effect. Accordingly, the 2nd research objective of the project was to create an unprecedented class of bioorthogonal prodrug that consists in 2 chemotherapeutic drugs connected by a Pd-labile bioorthogonal promoiety that upon Pd-mediated cleavage release the active forms of each drug. Based on the uncaging chemistry validated in objective 1, we developed a novel anticancer codrug that combined 2 approved drugs into a single molecular entity and we have proved its in vitro activation via Pd-functionalized resins.
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.