Synthesis, characterisation and in vitro antitumour potential of novel Pt(II) estrogen linked complexes

Advancements in steroidal Pt(II) & Pt(IV) derivatives for targeted chemotherapy (2000-2023)

One of the key strategies in chemotherapy involves crosslinking the DNA strands of cancer cells to impede their replication, with platinum (Pt) coordination compounds being a prominent class and cisplatin being its major representative. Steroidal ligands tethered to DNA interactive Pt core act as drug carriers for targeted therapy. While crosslinking of nuclear or mitochondrial DNA strands using coordination complexes has been studied for years, there remains a lack of comprehensive reviews addressing the advancements made in steroidal-Pt derivatives. This review specifically focuses on advancements made in steroid-tethered structural derivatives of Pt(II) or prodrug Pt(IV) for targeted chemotherapy, synthesized between 2000 and 2023. This period was deliberately chosen due to the widespread use of computational techniques for more accurate structure-based drug-design in last two decades. This review discusses the strategy behind tethering steroidal ligands such as testosterone, estrogen, bile acids, and cholesterol to the central DNA interactive Pt core through specific linker groups. The steroidal ligands function as drug delivery vehicles of DNA interactive Pt core and bind with their respective target receptors or proteins that are often overexpressed in cancer cells, thus enabling targeted delivery of Pt moiety to interact with DNA. We discussed structural features such as the location of the linker group on the steroid, the mono, bi, and tridentate configuration of the chelating arm in coordination with Pt, and the rigidity and flexibility of the linker group. The comparative in vitro, in vivo activities, and relative binding affinities of the designed compounds against standard Pt drugs are also discussed. We also provided a critique of observed trends and shortcomings. Our review will provide insights into future molecular designing of targeted DNA crosslinkers and their structural optimization to achieve desired drug properties. From this analysis, we proposed further research directions leading to the future of targeted chemotherapy.

State of art in the chemistry of nucleoside-based Pt(II) complexes

After the fortuitous discovery of the anticancer properties of cisplatin, many Pt(II) complexes have been synthesized, to obtain less toxic leads which could overcome the resistance phenomena. Given the importance of nucleosides and nucleotides as antimetabolites, studying their coordinating properties towards Pt(II) ions is challenging for bioorganic and medicinal chemistry. This review aims to describe the results achieved so far in the aforementioned field, paying particular attention to the synthetic aspects, the chemical-physical characterization, and the biological activities of the nucleoside-based Pt(II) complexes.

Recent advances on synthesis and biological activities of C-17 aza-heterocycle derived steroids

Steroids modification for improving their biological activities is one of the most efficient and fruitful methods to develop novel medicines. Steroids with aza-heterocycles attaching to the C-17 owing various biological activities have received great attentions and some of the compounds are developed successfully as drugs. In this review, the research of the syntheses and biological activities of steroids bearing various aza-heterocycles published in the last 8 years is assembled, and some important structure-activity relationships (SARs) of active compounds are presented. According to the analysis of the literatures and our experiences in this field, the potential of aza-heterocyclic steroids as medicinal drugs is proposed.

A Click Chemistry Approach to Targeted DNA Crosslinking with cis-Platinum(II)-Modified Triplex-Forming Oligonucleotides

Limitations of clinical platinum(II) therapeutics include systemic toxicity and inherent resistance. Modern approaches, therefore, seek new ways to deliver active platinum(II) to discrete nucleic acid targets. In the field of antigene therapy, triplex-forming oligonucleotides (TFOs) have attracted interest for their ability to specifically recognise extended duplex DNA targets. Here, we report a click chemistry based approach that combines alkyne-modified TFOs with azide-bearing cis-platinum(II) complexes-based on cisplatin, oxaliplatin, and carboplatin motifs-to generate a library of PtII -TFO hybrids. These constructs can be assembled modularly and enable directed platinum(II) crosslinking to purine nucleobases on the target sequence under the guidance of the TFO. By covalently incorporating modifications of thiazole orange-a known DNA-intercalating fluorophore-into PtII -TFOs constructs, enhanced target binding and discrimination between target and off-target sequences was achieved.

Recent Progresses in Conjugation with Bioactive Ligands to Improve the Anticancer Activity of Platinum Compounds

Platinum (Pt) drugs, including cisplatin, are widely used for the treatment of solid tumors. Despite the clinical success, side effects and occurrence of resistance represent major limitations to the use of clinically available Pt drugs. To overcome these problems, a variety of derivatives have been designed and synthetized. Here, we summarize the recent progress in the development of Pt(II) and Pt(IV) complexes with bioactive ligands. The development of Pt(II) and Pt(IV) complexes with targeting molecules, clinically available agents, and other bioactive molecules is an active field of research. Even if none of the reported Pt derivatives has been yet approved for clinical use, many of these compounds exhibit promising anticancer activities with an improved pharmacological profile. Thus, planning hybrid compounds can be considered as a promising approach to improve the available Pt-based anticancer agents and to obtain new molecular tools to deepen the knowledge of cancer progression and drug resistance mechanisms.

Probing the DNA Reactivity and the Anticancer Properties of a Novel Tubercidin-Pt(II) Complex

Herein, we reported on the synthesis of a novel Pt(II) neutral complex having as ligand the nucleoside tubercidin, a potent anti-tumor agent extracted from the bacterium Streptomyces Tubercidicus. In detail, the chelation of the metal by a diamine linker installed at C6 purine position of tubercidin assured the introduction of a cisplatin-like unit in the molecular scaffold. The behavior of the synthesized complex with a double-strand DNA model was monitored by CD spectroscopy and compared with that of cisplatin and tubercidin. In addition, the cell viability was evaluated against HeLa, A375 and WM266 human cancer cell lines using the MTT test. Lastly, the results of the apoptotic assay (FITC Annexin V) performed on the HeLa cancer cell line are also reported.

Exploiting azide-alkyne click chemistry in the synthesis, tracking and targeting of platinum anticancer complexes

Click chemistry is fundamentally important to medicinal chemistry and chemical biology. It represents a powerful and versatile tool, which can be exploited to develop novel Pt-based anticancer drugs and to better understand the biological effects of Pt-based anticancer drugs at a cellular level. Innovative azide-alkyne cycloaddition-based approaches are being used to functionalise Pt-based complexes with biomolecules to enhance tumour targeting. Valuable information in relation to the mechanisms of action and resistance of Pt-based drugs is also being revealed through click-based detection, isolation and tracking of Pt drug surrogates in biological and cellular environments. Although less well-explored, inorganic Pt-click reactions enable synthesis of novel (potentially multimetallic) Pt complexes and provide plausible routes to introduce functional groups and monitoring Pt-azido drug localisation.

Recent advances in platinum-based chemotherapeutics that exhibit inhibitory and targeted mechanisms of action

Current platinum-based drugs used in chemotherapy, like cisplatin and its derivatives, are greatly limited due to side-effects and drug resistance. This has inspired the search for novel platinum-based drugs that deviate from the conventional mechanism of action seen with current chemotherapeutics. This review highlights recent advances in platinum(II) and platinum(IV)-based complexes that have been developed within the past six years. The platinum compounds explored within this review are those that display a more targeted approach by incorporating ligands that act on selected cellular targets within cancer cells. This includes mitochondria, overexpressed receptors or proteins and enzymes that contribute to cancer cell proliferation. These types of platinum compounds have shown significant improvements in anticancer activity and as such, this review highlights the importance of pursuing these new designed platinum drugs for cancer therapy, with the potential of undergoing clinical trials.