Dihydroartemisinin-Bile Acid Hybridization as an Effective Approach to Enhance Dihydroartemisinin Anticancer Activity

Dihydroartemisinin-Ursodeoxycholic Bile Acid Hybrids in the Fight against SARS-CoV-2

Here, we propose the molecular hybridization of dihydroartemisinin (DHA) and ursodeoxycholic bile acid (UDCA), approved drugs, for the preparation of antiviral agents against SARS-CoV-2. DHA and UDCA were selected on the basis of their recently demonstrated in vitro activity against SARS-CoV-2. A selection of DHA-UDCA-based hybrids obtained by varying the nature of the linkage and the bile acid conjugation point as well as unconjugated DHA and UDCA were tested in vitro for cytotoxicity and anti-SARS-CoV-2 activity on Vero E6 and Calu-3 human lung cells. The hybrid DHA-t-UDCMe, obtained by conjugation via click chemistry on a gram scale, was identified as a potential candidate for SARS-CoV-2 infection treatment due to significant reduction of viral replication, possibly involving ACE2 downregulation, no cytotoxicity, and chemical stability.

Synthesis of modified bile acids via palladium-catalyzed C(sp3)-H (hetero)arylation

A Pd(II)-catalyzed strategy for the diastereo- and regioselective (hetero)arylation of unactivated C(sp3)-H bonds in bile acids is accomplished with aryl and heteroaryl iodides under solvent-free conditions using the 8-aminoquinoline auxiliary as a directing group. This methodology demonstrated excellent functional group tolerance with respect to aryl/heteroaryl iodides on O-protected N-(quinolin-8-yl)cholyl/deoxycholyl amides to afford β-C(sp3)-H (hetero)arylated products in good-to-excellent yields. Moreover, the 8-aminoquinoline (AQ) auxiliary can easily be removed to obtain modified bile acids.

Molecular Hybridization as a Strategy for Developing Artemisinin-Derived Anticancer Candidates

Artemisinin is a natural compound extracted from Artemisia species belonging to the Asteraceae family. Currently, artemisinin and its derivatives are considered among the most significant small-molecule antimalarial drugs. Artemisinin and its derivatives have also been shown to possess selective anticancer properties, however, there are several limitations and gaps in knowledge that retard their repurposing as effective anticancer agents. Hybridization resulting from a covalent combination of artemisinin with one or more active pharmacophores has emerged as a promising approach to overcome several issues. The variety of hybridization partners allows improvement in artemisinin activity by tuning the ability of conjugated artemisinin to interact with various molecule targets involved in multiple biological pathways. This review highlights the current scenario of artemisinin-derived hybrids with potential anticancer activity. The synthetic approaches to achieve the corresponding hybrids and the structure-activity relationships are discussed to facilitate further rational design of more effective candidates.

Anticancer Activity and Molecular Mechanisms of an Ursodeoxycholic Acid Methyl Ester-Dihydroartemisinin Hybrid via a Triazole Linkage in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma is the third most common cause of cancer-related death according to the International Agency for Research on Cancer. Dihydroartemisinin (DHA), an antimalarial drug, has been reported to exhibit anticancer activity but with a short half-life. We synthesized a series of bile acid-dihydroartemisinin hybrids to improve its stability and anticancer activity and demonstrated that an ursodeoxycholic-DHA (UDC-DHA) hybrid was 10-fold more potent than DHA against HepG2 hepatocellular carcinoma cells. The objectives of this study were to evaluate the anticancer activity and investigate the molecular mechanisms of UDCMe-Z-DHA, a hybrid of ursodeoxycholic acid methyl ester and DHA via a triazole linkage. We found that UDCMe-Z-DHA was even more potent than UDC-DHA in HepG2 cells with IC₅₀ of 1 μM. Time course experiments and stability in medium determined by cell viability assay as well as HPLC-MS/MS analysis revealed that UDCMe-Z-DHA was more stable than DHA, which in part accounted for the increased anticancer activity. Mechanistic studies revealed that UDCMe-Z-DHA caused G0/G1 arrest and induced reactive oxygen species (ROS), mitochondrial membrane potential loss and autophagy, which may in turn lead to apoptosis. Compared to DHA, UDCMe-Z-DHA displayed much lower cytotoxicity toward normal cells. Thus, UDCMe-Z-DHA may be a potential drug candidate for hepatocellular carcinoma.

Converting bile acids into mitocans

Cholic acid (1, CD), deoxycholic (3, DCA), chenodeoxycholic acid (5, CDCA), ursodeoxycholic acid (7, UDCA), and lithocholic acid (9, LCA) were acetylated and converted into their piperazinyl spacered rhodamine B conjugates 16-20. While the parent bile acids showed almost no cytotoxic effects for several human tumor cell lines, the piperazinyl amides were cytostatic but an even superior effect was observed for the rhodamine B conjugates. Extra staining experiments showed these compounds as mitocans; they led to a cell arrest in the G1 phase.

Synthesis and Biological Investigation of Bile Acid-Paclitaxel Hybrids

Chenodeoxycholic acid and ursodeoxycholic acid (CDCA and UDCA, respectively) have been conjugated with paclitaxel (PTX) anticancer drugs through a high-yield condensation reaction. Bile acid-PTX hybrids (BA-PTX) have been investigated for their pro-apoptotic activity towards a selection of cancer cell lines as well as healthy fibroblast cells. Chenodeoxycholic-PTX hybrid (CDC-PTX) displayed cytotoxicity and cytoselectivity similar to PTX, whereas ursodeoxycholic-PTX hybrid (UDC-PTX) displayed some anticancer activity only towards HCT116 colon carcinoma cells. Pacific Blue (PB) conjugated derivatives of CDC-PTX and UDC-PTX (CDC-PTX-PB and UDC-PTX-PB, respectively) were also prepared via a multistep synthesis for evaluating their ability to enter tumor cells. CDC-PTX-PB and UDC-PTX-PB flow cytometry clearly showed that both CDCA and UDCA conjugation to PTX improved its incoming into HCT116 cells, allowing the derivatives to enter the cells up to 99.9%, respect to 35% in the case of PTX. Mean fluorescence intensity analysis of cell populations treated with CDC-PTX-PB and UDC-PTX-PB also suggested that CDC-PTX-PB could have a greater ability to pass the plasmatic membrane than UDC-PTX-PB. Both hybrids showed significant lower toxicity with respect to PTX on the NIH-3T3 cell line.

Synthesis and Exon-Skipping Properties of a 3'-Ursodeoxycholic Acid-Conjugated Oligonucleotide Targeting DMD Pre-mRNA: Pre-Synthetic versus Post-Synthetic Approach

Steric blocking antisense oligonucleotides (ASO) are promising tools for splice modulation such as exon-skipping, although their therapeutic effect may be compromised by insufficient delivery. To address this issue, we investigated the synthesis of a 20-mer 2'-OMe PS oligonucleotide conjugated at 3'-end with ursodeoxycholic acid (UDCA) involved in the targeting of human DMD exon 51, by exploiting both a pre-synthetic and a solution phase approach. The two approaches have been compared. Both strategies successfully provided the desired ASO 51 3'-UDC in good yield and purity. It should be pointed out that the pre-synthetic approach insured better yields and proved to be more cost-effective. The exon skipping efficiency of the conjugated oligonucleotide was evaluated in myogenic cell lines and compared to that of unconjugated one: a better performance was determined for ASO 51 3'-UDC with an average 9.5-fold increase with respect to ASO 51.

Bile-Acid-Appended Triazolyl Aryl Ketones: Design, Synthesis, In Vitro Anticancer Activity and Pharmacokinetics in Rats

A library of bile-acid-appended triazolyl aryl ketones was synthesized and characterized by detailed spectroscopic techniques such as ¹H and ¹³C NMR, HRMS and HPLC. All the synthesized conjugates were evaluated for their cytotoxicity at 10 µM against MCF-7 (human breast adenocarcinoma) and 4T1 (mouse mammary carcinoma) cells. In vitro cytotoxicity studies on the synthesized conjugates against MCF-7 and 4T1 cells indicated one of the conjugate 6cf to be most active against both cancer cell lines, with IC₅₀ values of 5.71 µM and 8.71 µM, respectively, as compared to the reference drug docetaxel, possessing IC₅₀ values of 9.46 µM and 13.85 µM, respectively. Interestingly, another compound 6af (IC₅₀ = 2.61 µM) was found to possess pronounced anticancer activity as compared to the reference drug docetaxel (IC₅₀ = 9.46 µM) against MCF-7. In addition, the potent compounds (6cf and 6af) were found to be non-toxic to normal human embryonic kidney cell line (HEK 293), as evident from their cell viability of greater than 86%. Compound 6cf induces higher apoptosis in comparison to 6af (46.09% vs. 33.89%) in MCF-7 cells, while similar apoptotic potential was observed for 6cf and 6af in 4T1 cells. The pharmacokinetics of 6cf in Wistar rats showed an MRT of 8.47 h with a half-life of 5.63 h. Clearly, these results suggest 6cf to be a potential candidate for the development of anticancer agents.

Research progress in the application of bile acid-drug conjugates: A "trojan horse" strategy

Bile acid transporters are highly expressed in intestinal cells and hepatocytes, and they determine the uptake of drugs in cells by modulating cellular entry and exit. In order to improve the oral bioavailability of drugs and investigate the potential application prospects of drugs used to target cancer, numerous studies have adopted these transporters to identify prodrug strategies. Through the connection of covalent bonds between drugs and bile acids, the resulting bile acid-drug conjugates continue to be recognized as similar to natural unmodified bile acid and is translocated by the transporter. The present mini-review provides a brief summary of recent progress of the application of bile acid-drug conjugates based primarily on ASBT, NTCP, and OATP, with the hope of contributing to subsequent research.

Physiology and Physical Chemistry of Bile Acids

Bile acids (BAs) are facial amphiphiles synthesized in the body of all vertebrates. They undergo the enterohepatic circulation: they are produced in the liver, stored in the gallbladder, released in the intestine, taken into the bloodstream and lastly re-absorbed in the liver. During this pathway, BAs are modified in their molecular structure by the action of enzymes and bacteria. Such transformations allow them to acquire the chemical-physical properties needed for fulling several activities including metabolic regulation, antimicrobial functions and solubilization of lipids in digestion. The versatility of BAs in the physiological functions has inspired their use in many bio-applications, making them important tools for active molecule delivery, metabolic disease treatments and emulsification processes in food and drug industries. Moreover, moving over the borders of the biological field, BAs have been largely investigated as building blocks for the construction of supramolecular aggregates having peculiar structural, mechanical, chemical and optical properties. The review starts with a biological analysis of the BAs functions before progressively switching to a general overview of BAs in pharmacology and medicine applications. Lastly the focus moves to the BAs use in material science.

Enhancing the chemosensitivity of HepG2 cells towards cisplatin by organoselenium pseudopeptides

Despite all recent advances in the treatment of hepatocellular carcinoma (HCC), chemotherapy resistance still represents a major challenge in its successful clinical management. Chemo-sensitization offers an attractive strategy to counter drug resistance. Herein we report the identification of novel organoselenium-based pseudopeptides as promising highly effective chemo-sensitizers in treating HCC with cisplatin. A series of functionalized pseudopeptide- (5-9 and 17-19), peptidomimetic- (10-12 and 20-23), and tetrazole-based (13-16 and 24-27) organoselenium compounds were synthesized via isonitrile-based multicomponent reactions from two novel selenium-containing isocyanides. All compounds were evaluated for their cytotoxicity against HepG2 and the non-cytotoxic doses were used to restor the sensitivity of the cells to cisplatin. New organoselenium compounds (7, 9, 15, or 23) led to an effective chemo-sensitization of HepG2 cells towards cisplatin (up-to 27-fold). Cell cycle studies indicate that the most potent peptidomimetic diselenide 23 arrested cells at the S phase and induced apoptosis via ROS modulation.

Bile Acid Conjugates with Anticancer Activity: Most Recent Research

The advantages of a treatment modality that combines two or more therapeutic agents in cancer therapy encourages the study of hybrid functional compounds for pharmacological applications. In light of this, we reviewed recent works on hybrid molecules based on bile acids. Due to their biological properties, as well as their different chemical/biochemical reactive moieties, bile acids can be considered very interesting starting molecules for conjugation with natural or synthetic bioactive molecules.

Evaluation of the Anticancer Activity of a Bile Acid-Dihydroartemisinin Hybrid Ursodeoxycholic-Dihydroartemisinin in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy in adults and accounts for 85-90% of all primary liver cancer. Based on the estimation by the International Agency for Research on Cancer in 2018, liver cancer is the fourth leading cause of cancer death globally. Dihydroartemisinin (DHA), the main active metabolite of artemisinin derivatives, is a well-known drug for the treatment of malaria. Previous studies have demonstrated that DHA exhibits antitumor effects toward a variety of human cancers and has a potential for repurposing as an anticancer drug. However, its short half-life is a concern and may limit the application in cancer therapy. We have reported that UDC-DHA, a hybrid of bile acid ursodeoxycholic acid (UDCA) and DHA, is ∼12 times more potent than DHA against a HCC cell line HepG2. In this study, we found that UDC-DHA was also effective against another HCC cell line Huh-7 with an IC₅₀ of 2.16 μM, which was 18.5-fold better than DHA with an IC₅₀ of 39.96 μM. UDC-DHA was much more potent than the combination of DHA and UDCA at 1:1 molar ratio, suggesting that the covalent linkage rather than a synergism between UDCA and DHA is critical for enhancing DHA potency in HepG2 cells. Importantly, UDC-DHA was much less toxic to normal cells than DHA. UDC-DHA induced G0/G1 arrest and apoptosis. Both DHA and UDC-DHA significantly elevated cellular reactive oxygen species generation but with different magnitude and timing in HepG2 cells; whereas only DHA but not UDC-DHA induced reactive oxygen species in Huh-7 cells. Depolarization of mitochondrial membrane potential was detected in both HepG2 and Huh-7 cells and may contribute to the anticancer effect of DHA and UDC-DHA. Furthermore, UDC-DHA was much more stable than DHA based on activity assays and high performance liquid chromatography-MS/MS analysis. In conclusion, UDC-DHA and DHA may exert anticancer actions via similar mechanisms but a much lower concentration of UDC-DHA was required, which could be attributed to a better stability of UDC-DHA. Thus, UDC-DHA could be a better drug candidate than DHA against HCC and further investigation is warranted.

Artemisinins as Anticancer Drugs: Novel Therapeutic Approaches, Molecular Mechanisms, and Clinical Trials

Artemisinin and its derivatives have shown broad-spectrum antitumor activities in vitro and in vivo. Furthermore, outcomes from a limited number of clinical trials provide encouraging evidence for their excellent antitumor activities. However, some problems such as poor solubility, toxicity and controversial mechanisms of action hamper their use as effective antitumor agents in the clinic. In order to accelerate the use of ARTs in the clinic, researchers have recently developed novel therapeutic approaches including developing novel derivatives, manufacturing novel nano-formulations, and combining ARTs with other drugs for cancer therapy. The related mechanisms of action were explored. This review describes ARTs used to induce non-apoptotic cell death containing oncosis, autophagy, and ferroptosis. Moreover, it highlights the ARTs-caused effects on cancer metabolism, immunosuppression and cancer stem cells and discusses clinical trials of ARTs used to treat cancer. The review provides additional insight into the molecular mechanism of action of ARTs and their considerable clinical potential.

Cancer stem cells and nanomedicine: new opportunities to combat multidrug resistance?

'Multidrug resistance' (MDR) is a difficult challenge for cancer treatment. The combined role of cytochrome P450 enzymes (CYPs) and active efflux transporters (AETs) in cancer cells appears relevant in inducing MDR. Chemotherapeutic drugs can be substrates of both CYPs and AETs and CYP inducers or inhibitors can produce the same effects on AETs. In addition, a small subpopulation of cancer stem-like cells (CSCs) appears to survive conventional chemotherapy, leading to recurrent disease. Natural products appear efficacious against CSCs; their combinational treatments with standard chemotherapy are promising for cancer eradication, in particular when supported by nanotechnologies.