Complexation of histone deacetylase inhibitor belinostat to Cu(II) prevents premature metabolic inactivation in vitro and demonstrates potent anti-cancer activity in vitro and ex vivo in colon cancer.

PURPOSE: The histone deacetylase inhibitor (HDACi), belinostat, has had limited therapeutic impact in solid tumors, such as colon cancer, due to its poor metabolic stability. Here we evaluated a novel belinostat prodrug, copper-bis-belinostat (Cubisbel), in vitro and ex vivo, designed to overcome the pharmacokinetic challenges of belinostat. METHODS: The in vitro metabolism of each HDACi was evaluated in human liver microsomes (HLMs) using mass spectrometry. Next, the effect of belinostat and Cubisbel on cell growth, HDAC activity, apoptosis and cell cycle was assessed in three colon cancer cell lines. Gene expression alterations induced by both HDACis were determined using RNA-Seq, followed by in silico analysis to identify master regulators (MRs) of differentially expressed genes (DEGs). The effect of both HDACis on the viability of colon cancer patient-derived tumor organoids (PDTOs) was also examined. RESULTS: Belinostat and Cubisbel significantly reduced colon cancer cell growth mediated through HDAC inhibition and apoptosis induction. Interestingly, the in vitro half-life of Cubisbel was significantly longer than belinostat. Belinostat and its Cu derivative commonly dysregulated numerous signalling and metabolic pathways while genes downregulated by Cubisbel were potentially controlled by VEGFA, ERBB2 and DUSP2 MRs. Treatment of colon cancer PDTOs with the HDACis resulted in a significant reduction in cell viability and downregulation of stem cell and proliferation markers. CONCLUSIONS: Complexation of belinostat to Cu(II) does not alter the HDAC activity of belinostat, but instead significantly enhances its metabolic stability in vitro and targets anti-cancer pathways by perturbing key MRs in colon cancer. Complexation of HDACis to a metal ion might improve the efficacy of clinically used HDACis in patients with colon cancer.

Multi-targeted metallo-ciprofloxacin derivatives rationally designed and developed to overcome antimicrobial resistance.

Antimicrobial resistance is a major global threat to human health due to the rise, spread and persistence of multi-drug-resistant bacteria or 'superbugs'. There is an urgent need to develop novel chemotherapeutics to overcome this overarching challenge. The authors derivatized a clinically used fluoroquinolone antibiotic ciprofloxacin (Cip), and complexed it to a copper phenanthrene framework. This resulted in the development of two novel metallo-antibiotics of general formula [Cu(N,N)(CipHA)]NO3 where N,N represents a phenanthrene ligand and CipHA represents a hydroxamic acid of Cip derivative. Comprehensive studies, including a detailed proteomic study in which Staphylococcus aureus cells were exposed to the complexes, were undertaken to gain an insight into their mode of action. These new complexes possess potent antibacterial activity against S. aureus and methicillin-resistant S. aureus. In addition, they were found to be well tolerated in vivo in Galleria mellonella larvae, which has both functional and structural similarities to the innate immune system of mammals. These findings suggest that proteins involved in virulence, pathogenesis, and the synthesis of nucleotides and DNA repair mechanisms are most affected. In addition, both complexes affected similar cell pathways when compared with clinically used Cip, including cationic antimicrobial peptide resistance. The Cu-DPPZ-CipHA (DPPZ = dipyrido[3,2-a:2',3'-c]phenazine) analogue also induces cell leakage, which leads to an altered proteome indicative of reduced virulence and increased stress.

Vorinostat and Belinostat, hydroxamate-based anti-cancer agents, are nitric oxide donors.

Vorinostat (suberoylanilide hydroxamic acid; SAHA) and Belinostat are two hydroxamate-based histone deacetylase inhibitors that are used clinically as potent anti-cancer agents. Their metabolic breakdown into inactive metabolites such as carboxylic acid and glucuronic derivatives results in them having short half-lives, which can negatively impact their pharmacokinetic profiles. Herein we report the potential of both Vorinostat and Belinostat to also act as nitric oxide donors under both chemical and biological ex vivo experimental conditions. More specifically, using ruthenium(III) as an effective NO scavenger, we were able to establish, in the first instance, that both Vorinostat and Belinostat had the capacity to release NO under chemical conditions. Both Vorinostat and Belinostat were then shown to cause vascular relaxation of rat aorta via NO-mediated activation of the haem-containing guanylate cyclase enzyme. A summary of our findings is reported herein.

A new class of prophylactic metallo-antibiotic possessing potent anti-cancer and anti-microbial properties.

Immunocompromised cancer patients are often at high risk of developing infections. Standard infection control measures are required to prevent the onset of infection but, under some circumstances, antimicrobial prophylaxis is necessary. We have developed a family of innovative metallo-antibiotics of general formula [Cu(N,N)(CipA)Cl] where N,N represents a phenanthrene ligand and CipA stands for a derivative of the clinically used fluoroquinolone antibiotic ciprofloxacin. The X-ray crystal structure of one member from this family, [Cu(phen)(CipA)Cl] (where phen is 1,10-phenanthroline), is also reported. These complexes combine into one drug entity a Cu-N,N-framework with DNA binding and DNA oxidant properties and an antibiotic derivative with known anti-proliferative and anti-microbial activities. The complexes were all found to exhibit excellent DNA recognition with binding affinity of lead agents in the order of ∼107 M(bp)-1. Biophysical studies involving calf thymus DNA indicate the complexes intercalate or semi-intercalate DNA via the minor groove. All complexes exhibited excellent nuclease activity with DNA strand scission being mediated predominantly via superoxide and hydroxyl radicals. The complexes were found to have promising anti-proliferative effects against a human breast adenocarcinoma cell line (MCF-7) and a human prostate carcinoma cell line (DU145) with low micromolar and, in some cases, nanomolar cytotoxicities observed. Selective targeting of Gram positive bacteria was also identified by this complex class with one lead compound having an order of magnitude greater potency against Methicillin-resistant S. aureus (MRSA) as compared to the CipA ligand. Importantly, from a clinical stand point, these complexes were also found to be well tolerated in an in vivo Galleria mellonella larvae model, which has both functional and structural similarities to that of the innate immune system of mammals.

Exploiting developments in nanotechnology for the preferential delivery of platinum-based anti-cancer agents to tumours: targeting some of the hallmarks of cancer.

Platinum drugs as anti-cancer therapeutics are held in extremely high regard. Despite their success, there are drawbacks associated with their use; their dose-limiting toxicity, their limited activity against an array of common cancers and patient resistance to Pt-based therapeutic regimes. Current investigations in medicinal inorganic chemistry strive to offset these shortcomings through selective targeting of Pt drugs and/or the development of Pt drugs with new or multiple modes of action. A comprehensive overview showcasing how liposomes, nanocapsules, polymers, dendrimers, nanoparticles and nanotubes may be employed as vehicles to selectively deliver cytotoxic Pt payloads to tumour cells is provided.

A novel dual-functioning ruthenium(II)-arene complex of an anti-microbial ciprofloxacin derivative - Anti-proliferative and anti-microbial activity.

7-(4-(Decanoyl)piperazin-1-yl)-ciprofloxacin, CipA, (1) which is an analogue of the antibiotic ciprofloxacin, and its ruthenium(II) complex [Ru(η(6)-p-cymene)(CipA-H)Cl], (2) have been synthesised and the x-ray crystal structures of 1·1.3H2O·0.6CH3OH and 2·CH3OH·0.5H2O determined. The complex adopts a typical pseudo-octahedral 'piano-stool' geometry, with Ru(II) π-bonded to the p-cymene ring and σ-bonded to a chloride and two oxygen atoms of the chelated fluoroquinolone ligand. The complex is highly cytotoxic in the low µM range and is as potent as the clinical drug cisplatin against the human cancer cell lines A2780, A549, HCT116, and PC3. It is also highly cytotoxic against cisplatin- and oxaliplatin-resistant cell lines suggesting a different mechanism of action. The complex also retained low µM cytotoxicity against the human colon cancer cell line HCT116p53 in which the tumour suppressor p53 had been knocked out, suggesting that the potent anti-proliferative properties associated with this complex are independent of the status of p53 (in contrast to cisplatin). The complex also retained moderate anti-bacterial activity in two Escherichia coli, a laboratory strain and a clinical isolate resistant to first, second and third generation ß-lactam antibiotics.

Pyrithione-based ruthenium complexes as inhibitors of aldo-keto reductase 1C enzymes and anticancer agents.

Four ruthenium complexes of clinically used zinc ionophore pyrithione and its oxygen analog 2-hydroxypyridine N-oxide were prepared and evaluated as inhibitors of enzymes of the aldo-keto reductase subfamily 1C (AKR1C). A kinetic study assisted with docking simulations showed a mixed type of inhibition consisting of a fast reversible and a slow irreversible step in the case of both organometallic compounds 1A and 1B. Both compounds also showed a remarkable selectivity towards AKR1C1 and AKR1C3 which are targets for breast cancer drug design. The organoruthenium complex of ligand pyrithione as well as pyrithione itself also displayed toxicity on the hormone-dependent MCF-7 breast cancer cell line with EC50 values in the low micromolar range.