Ruthenium Carbonyl Complexes with Azole Heterocycles – Synthesis, X‐ray Diffraction Structures, DFT Calculations, Solution Behavior, and Antiproliferative Activity

The Anticancer Activity of Indazole Compounds: A Mini Review

The incidence and mortality of cancer continue to grow since the current medical treatments often fail to produce a complete and durable tumor response and ultimately give rise to therapy resistance and tumor relapse. Heterocycles with potential therapeutic values are of great pharmacological importance, and among them, indazole moiety is a privileged structure in medicinal chemistry. Indazole compounds possess potential anticancer activity, and indazole-based agents such as, axitinib, lonidamine and pazopanib have already been employed for cancer therapy, demonstrating indazole compounds as useful templates for the development of novel anticancer agents. The aim of this review is to present the main aspects of exploring anticancer properties, such as the structural modifications, the structure-activity relationship and mechanisms of action, making an effort to highlight the importance and therapeutic potential of the indazole compounds in the present anticancer agents.

Synthesis and Characterization of trans-Dichlorotetrakis(imidazole)cobalt(III) Chloride: A New Cobalt(III) Coordination Complex with Potential Prodrug Properties

Numerous therapies for the treatment of cancer have been explored with increasing evidence that the use of metal-containing compounds could prove advantageous as anticancer therapeutics. Previous works on Ru(III) complexes suggest that structurally similar Co(III) complexes may provide good alternative, low-cost, effective prodrugs. Herein, a new complex, trans-[Co(imidazole)₄Cl₂]Cl (2), has been synthesized in high yields utilizing ligand exchange under refluxing conditions. The structure of 2 has been characterized by elemental analysis, ¹H and ¹³C·NMR, ESI-MS, CV, and UV-Vis. The ability of 2 to become reduced in the presence of ascorbic acid was probed demonstrating the likely reduction of the Co(III) metal center to Co(II). In addition, preliminary cell line testing on 2 shows a lack of cytotoxicity.

Recent Advances in the Development of Indazole-based Anticancer Agents

Cancer is one of the leading causes of human mortality globally; therefore, intensive efforts have been made to seek new active drugs with improved anticancer efficacy. Indazole-containing derivatives are endowed with a broad range of biological properties, including anti-inflammatory, antimicrobial, anti-HIV, antihypertensive, and anticancer activities. In recent years, the development of anticancer drugs has given rise to a wide range of indazole derivatives, some of which exhibit outstanding activity against various tumor types. The aim of this review is to outline recent developments concerning the anticancer activity of indazole derivatives, as well as to summarize the design strategies and structure-activity relationships of these compounds.

cis-Tetrachlorido-bis(indazole)osmium(iv) and its osmium(iii) analogues: paving the way towards the cis-isomer of the ruthenium anticancer drugs KP1019 and/or NKP1339

The relationship between cis-trans isomerism and anticancer activity has been mainly addressed for square-planar metal complexes, in particular, for platinum(ii), e.g., cis- and trans-[PtCl2(NH3)2], and a number of related compounds, of which, however, only cis-counterparts are in clinical use today. For octahedral metal complexes, this effect of geometrical isomerism on anticancer activity has not been investigated systematically, mainly because the relevant isomers are still unavailable. An example of such an octahedral complex is trans-[RuCl4(Hind)2]-, which is in clinical trials now as its indazolium (KP1019) or sodium salt (NKP1339), but the corresponding cis-isomers remain inaccessible. We report the synthesis of Na[cis-OsIIICl4(κN2-1H-ind)2]·(Na[1]) suggesting a route to the cis-isomer of NKP1339. The procedure involves heating (H2ind)[OsIVCl5(κN1-2H-ind)] in a high boiling point organic solvent resulting in an Anderson rearrangement with the formation of cis-[OsIVCl4(κN2-1H-ind)2] ([1]) in high yield. The transformation is accompanied by an indazole coordination mode switch from κN1 to κN2 and stabilization of the 1H-indazole tautomer. Fully reversible spectroelectrochemical reduction of [1] in acetonitrile at 0.46 V vs. NHE is accompanied by a change in electronic absorption bands indicating the formation of cis-[OsIIICl4(κN2-1H-ind)2]- ([1]-). Chemical reduction of [1] in methanol with NaBH4 followed by addition of nBu4NCl afforded the osmium(iii) complex nBu4N[cis-OsIIICl4(κN2-1H-ind)2] (nBu4N[1]). A metathesis reaction of nBu4N[1] with an ion exchange resin led to the isolation of the water-soluble salt Na[1]. The X-ray diffraction crystal structure of [1]·Me2CO was determined and compared with that of trans-[OsIVCl4(κN2-1H-ind)2]·2Me2SO (2·2Me2SO), also prepared in this work. EPR spectroscopy was performed on the OsIII complexes and the results were analyzed by ligand-field and quantum chemical theories. We furthermore assayed effects of [1] and Na[1] on cell viability and proliferation in comparison with trans-[OsIVCl4(κN1-2H-ind)2] [3] and cisplatin and found a strong reduction of cell viability at concentrations between 30 and 300 μM in different cancer cell lines (HT29, H446, 4T1 and HEK293). HT-29 cells are less sensitive to cisplatin than 4T1 cells, but more sensitive to [1] and Na[1], as shown by decreased proliferation and viability as well as an increased late apoptotic/necrotic cell population.