Ring-Contracted Artemisinin Derivatives as Novel CDK 4/6 Inhibitors: Synthesis and Anti-Breast Cancer Evaluation.

The endoperoxide group of artemisinins is universally accepted an essential group for their anti-cancer effects. In this study, a series of D-ring-contracted artemisinin derivatives were constructed by combining ring-contracted artemisinin core with fragments of functional heterocyclic molecules or classical CDK4/6 inhibitors to identify more efficacious breast cancer treatment agents. Twenty-six novel hybridized molecules were synthesized and characterized by HRMS, IR, 1H-NMR and 13C NMR. In antiproliferative activities and kinase inhibitory effects assays, we found that the antiproliferative effects of B01 were close to those of the positive control Palbociclib, with GI50 values of 4.87±0.23 µM and 9.97±1.44 µM towards T47D cells and MDA-MB-436 cells respectively. In addition, the results showed that B01 was the most potent compound against CDK6/cyclin D3 kinase, with an IC50 value of 0.135±0.041 µM, and its activity was approximately 1/3 of the positive control Palbociclib.

Artemisinin and Derivatives-Based Hybrid Compounds: Promising Therapeutics for the Treatment of Cancer and Malaria.

Cancer and malaria are major health conditions around the world despite many strategies and therapeutics available for their treatment. The most used strategy for the treatment of these diseases is the administration of therapeutic drugs, which suffer from several shortcomings. Some of the pharmacological limitations associated with these drugs are multi-drug resistance, drug toxicity, poor biocompatibility and bioavailability, and poor water solubility. The currently ongoing preclinical studies have demonstrated that combination therapy is a potent approach that can overcome some of the aforementioned limitations. Artemisinin and its derivatives have been reported to exhibit potent efficacy as anticancer and antimalarial agents. This review reports hybrid compounds containing artemisinin scaffolds and their derivatives with promising therapeutic effects for the treatment of cancer and malaria.

Chemical hybridization of sulfasalazine and dihydroartemisinin promotes brain tumor cell death.

Gliomas are primary brain tumors with still poor prognosis for the patients despite a combination of cytoreduction via surgery followed by a radio-chemotherapy. One strategy to find effective treatment is to combine two different compounds in one hybrid molecule via linker to add to or at best potentiate their impact on malignant cells. Here, we report on the effects of a newly synthesized hybrid of sulfasalazine (SAS) and dihydroartemisinin (DHA), called AC254. In previous studies, both SAS and DHA have already proved to have anti-tumor properties themselves and to have sensitizing respectively potentiating effects on other treatments against malignant tumors. We investigated the impact of individual drugs SAS and DHA, their 1:1 combination and a novel SAS-DHA hybrid compound (AC254) on rodent and human glioma cells. In our study SAS alone showed no or only a mild effect on glioma, whereas DHA led to a significant reduction of cell viability in a dose-dependent manner. Next we compared the efficacy of the hybrid AC254 to the combinational treatment of its parent compounds SAS and DHA. The hybrid was highly efficient in combating glioma cells compared to single treatment strategies regarding cell viability and cell death. Interestingly, AC254 showed a remarkable advantage over the combinational treatment with both parent compounds in most used concentrations. In addition to its reduction of tumor cell viability and induction of cell death, the hybrid AC254 displayed changes in cell cycle and reduction of cell migration. Taken together, these results demonstrate that clinically established compounds such as SAS and DHA can be potentiated in their anti-cancer effects by chemical hybridization. Thus, this concept provides the opportunity to devise new effective chemotherapeutic agents.

Biological Activity of Selected Natural and Synthetic Terpenoid Lactones.

Terpenoids with lactone moieties have been indicated to possess high bioactivity. Certain terpenoid lactones exist in nature, in plants and animals, but they can also be obtained by chemical synthesis. Terpenoids possessing lactone moieties are known for their cytotoxic, anti-inflammatory, antimicrobial, anticancer, and antimalarial activities. Moreover, one terpenoid lactone, artemisinin, is used as a drug against malaria. Because of these abilities, there is constant interest in new terpenoid lactones that are both isolated and synthesized, and their biological activities have been verified. In some cases, the activity of the terpenoid lactone is specifically connected to the lactone moiety. Recent works have revealed that new terpenoid lactones can demonstrate such functions and are thus considered to be potential active agents against many diseases.

Combating multi-drug resistant malaria parasite by inhibiting falcipain-2 and heme-polymerization: Artemisinin-peptidyl vinyl phosphonate hybrid molecules as new antimalarials.

Artemisinin-based combination therapies (ACTs) have been able to reduce the clinical and pathological malaria cases in endemic areas around the globe. However, recent reports have shown a progressive decline in malaria parasite clearance in South-east Asia after ACT treatment, thus envisaging a need for new artemisinin (ART) derivatives and combinations. To address the emergence of drug resistance to current antimalarials, here we report the synthesis of artemisinin-peptidyl vinyl phosphonate hybrid molecules that show superior efficacy than artemisinin alone against chloroquine-resistant as well as multidrug-resistant Plasmodium falciparum strains with EC50 in pico-molar ranges. Further, the compounds effectively inhibited the survival of ring-stage parasite for laboratory-adapted artemisinin-resistant parasite lines as compared to artemisinin. These hybrid molecules showed complete parasite clearance in vivo using P. berghei mouse malaria model in comparison to artemisinin alone. Studies on the mode of action of hybrid molecules suggested that these artemisinin-peptidyl vinyl phosphonate hybrid molecules possessed dual activities: inhibited falcipain-2 (FP-2) activity, a P. falciparum cysteine protease involved in hemoglobin degradation, and also blocked the hemozoin formation in the food-vacuole, a step earlier shown to be blocked by artemisinin. Since these hybrid molecules blocked multiple steps of a pathway and showed synergistic efficacies, we believe that these lead compounds can be developed as effective antimalarials to prevent the spread of resistance to current antimalarials.

Stereoselective Access to Antimelanoma Agents by Hybridization and Dimerization of Dihydroartemisinin and Artesunic acid.

A library of five hybrids and six dimers of dihydroartemisinin and artesunic acid has been synthetized in a stereo-controlled manner and evaluated for the anticancer activity against metastatic melanoma cell line (RPMI7951). Among novel derivatives, three artesunic acid dimers showed antimelanoma activity and cancer selectivity, being not toxic on normal human fibroblast (C3PV) cell line. Among the three dimers, the one bearing 4-hydroxybenzyl alcohol as a spacer showed no cytotoxic effect (CC50 >300 µM) and high antimelanoma activity (IC50 =0.05 µM), which was two orders of magnitude higher than that of parent artesunic acid, and of the same order of commercial drug paclitaxel. In addition, this dimer showed cancer-type selectivity towards melanoma compared to prostate (PC3) and breast (MDA-MB-231) tumors. The occurrence of a radical mechanism was hypothesized by DFO and EPR analyses. Qualitative structure activity relationships highlighted the role of artesunic acid scaffold in the control of toxicity and antimelanoma activity.

Synthesis and biological activities of novel mitochondria-targeted artemisinin ester derivatives.

A series of novel artemisinin ester derivatives were designed and synthesized for targeting mitochondria. Cytotoxicity against SMMC-7721, HepG2, OVCAR3, A549 and J82 cancer cell lines was evaluated. Compound 2c (IC50 = 3.0 µM) was the most potent anti-proliferative molecule against the OVCAR3 cells with low cytotoxicity in normal HUVEC cells. The mechanism of action of compound 2c was further investigated by analyzing cell apoptosis, mitochondrial membrane potential (Δψm) and intracellular ROS generation. The results indicated that compound 2c targeted mitochondria and induced cell apoptosis. ROS and heme attributed to the cytotoxicity and cell apoptosis of compound 2c. These promising findings indicated the compound 2c could serve as a great candidate against ovarian cancer for further investigation.

Synthesis of artemisinin-piperazine-furan ether hybrids and evaluation of in vitro cytotoxic activity.

For the first time, eight novel artemisinin-piperazine-furane ether hybrids (5a-h) were efficiently synthesized and investigated for their in vitro cytotoxic activity against some human cancer and benign cells. The absolute configuration of hybrid 5c was determined by X-ray crystallographic analysis. Hybrids 5a-h exhibited more pronounced growth-inhibiting action on hepatocarcinoma cell lines than their parent dihydroartemisinin (DHA) and the reference cytosine arabinoside (ARA). The hybrid 5a showed the best cytotoxic activity against human hepatocarcinoma cells SMMC-7721 (IC50 = 0.26 ± 0.03 µM) after 24 h. Furthermore, hybrid 5a also showed good cytotoxic activity against human breast cancer cells MCF-7 and low cytotoxicity against human breast benign cells MCF-10A in vitro. We found the cytotoxicity of hybrid 5a did not change when tumour cells absorb iron sulfate (FeSO4); thus, we conclude the anti-tumour mechanism induced by iron ions (Fe2+) is unclear.

Structural optimization and biological evaluation for novel artemisinin derivatives against liver and ovarian cancers.

An increasing number of artemisinin (ARS) and its derivatives have been reported for their potential therapeutic value of human cancer. However, their therapeutic potencies are limited owing to their poor pharmacokinetic profiles. Our previous studies showed that a lead compound ARS4 originated from incorporating the pharmacophore of the approved chemotherapeutic agent melphalan into the basic skeleton of artemisinin with a succinic linker exhibited an excellent toxicity to human ovarian cancer cells and low cytotoxicity to normal cells. The mechanism studies demonstrated that it inhibited the growth and proliferation of ovarian cancer cells and resulted in S-phase arrest, apoptosis and inhibition of migration. Meanwhile, it exhibited excellent antitumor activities in animal models. Herein, further structure optimization for this lead compound ARS4 was performed and nineteen novel derivatives were designed and synthesized. Among them, compounds 10-12, 15, 16, 18 and 19 demonstrated powerful cytotoxic effects against human liver cancer and ovarian cancer cell lines, with their IC50s below 0.86 µM against Hep3B and A2780 cell lines, which are superior to that of ARS4. Four compounds (11, 15, 16 and 18) were selected to further evaluate their antitumor activities in in vitro and in vivo ovarian and liver cancer models, the results indicated that compound 18 exhibited the best therapeutic effect, not only effectively inhibited the growth of 7404 xenograft and Huh7 xenograft, but also presented a good dose-dependent inhibition toward the growth of A2780 xenograft. Overall, based on these positive results, these novel chemical structures may provide a new inspiration for the discovery of novel antitumor agents originated from artemisinin scaffolds.

Novel artemisinin derivatives with potent anticancer activities and the anti-colorectal cancer effect by the mitochondria-mediated pathway.

Many artemisinin derivatives have good inhibitory effects on malignant tumors. In this work, a novel series of artemisinin derivatives containing piperazine and fluorine groups were designed and synthesized and their structures were confirmed by 1H NMR, 13C NMR and HRMS technologies. The in vitro cytotoxicity against various cancer cell lines was evaluated. Among the derivatives, compound 12h was found to exhibit not only the best activity against HCT-116 cells (IC50 = 0.12 ± 0.05 µM), but also low toxicity against normal cell line L02 (IC50 = 12.46 ± 0.10 µM). The mechanisms study revealed that compound 12h caused the cell cycle arrest in G1 phase, induced apoptosis in a concentration-dependent manner, significantly reduced mitochondrial membrane potential, increased intracellular ROS and Ca2+ levels, up-regulated the expression of Bax, cleaved caspase-9, cleaved caspase-3, and down-regulated the expression of Bcl-2 protein. A series of analyses confirmed that 12h can inhibit HCT-116 cells migration and induce apoptosis by a mechanism of the mitochondria-mediated pathway in the HCT-116 cell line. The present work indicates that compound 12h may merit further investigation as a potential therapeutic agent for colorectal cancer.

Dihydroartemisinin loaded layered double hydroxide nanocomposites for tumor specific photothermal-chemodynamic therapy.

With the inspiration to develop new cancer nanotherapeutics by repurposing old drugs, in the current study, a novel two dimensional nanomedicine namely Mn doped, dihydroartemisinin (DHA) loaded layered double hydroxide (MnMgFe-LDH/DHA) with peroxide self-supplying properties for enhanced photothermal-chemodynamic therapy was proposed. Such nanostructures could be synthesized by a simple coprecipitation method, and the as-prepared MnMgFe-LDH/DHA exhibits excellent photothermal properties with a photothermal conversion efficiency up to 10.7%. Besides, the in situ reaction between the released DHA and Fe2+/Mn2+ produced by the degradation of LDH can lead to a burst of intracellular reactive oxygen species (ROS) by Fenton-like reactions. Furthermore, the in vivo experiments demonstrate that MnMgFe-LDH/DHA exhibits a remarkable chemodynamic/photothermal therapy (CDT/PTT) synergistic effect on tumor treatment with negligible damage to normal tissues. Finally, this research provides a smart strategy to construct a DHA repurposing nanomedicine for tumor specific treatment.

Artemisinin-derived hybrids and their anticancer activity.

The emergence of drug-resistance and the low specificity of anticancer agents are the major challenges in the treatment of cancer and can result in many side effects, creating an urgent demand to develop novel anticancer agents. Artemisinin-derived compounds, bearing a peroxide-containing sesquiterpene lactone moiety, could form free radicals with high reactivity and possess diverse pharmaceutical properties including in vitro and in vivo anticancer activity besides their typical antimalarial activity. Hybrid molecules have the potential to improve the specificity and overcome the drug resistance, therefore hybridization of artemisinin skeleton with other anticancer pharmacophores may provide novel anticancer candidates with high specificity and great potency against drug-resistant cancers. The review outlines the recent advances of artemisinin-derived hybrids as potential anticancer agents, and the structure-activity relationships are also discussed to provide an insight for rational designs of novel hybrids with high activity.

Artemisinin-derived dimers as potential anticancer agents: Current developments, action mechanisms, and structure-activity relationships.

Anticancer agents play a pivotal role in cancer treatment. However, most of the anticancer drugs currently used in the clinics have a severe anticancer scenario, as well as low specificity and fatal side effects. Thus, there is an urgent demand to develop novel drugs with great efficacy, high specificity, and low side effects. Artemisinin and its semisynthetic derivatives are mainstays of chemotherapy against malaria, and artemisinin-based compounds, especially artemisinin-derived dimers, also exhibit excellent in vitro and in vivo anticancer activity. The structure-activity relationship (SAR) demonstrated that the linker between the two artemisinin moieties influenced the anticancer activity significantly; so, the rational design of the linker may provide valuable therapeutic intervention for the treatment of cancer. This review outlines the potential anticancer activity of artemisinin-derived dimers tethered by different linkers. The SARs, as well as mechanisms of action, are discussed to provide insights for the rational design of more effective dimers.

Anti-Mycobacterial Peroxides: A New Class of Agents for Development Against Tuberculosis.

BACKGROUND: With few exceptions, existing tuberculosis drugs were developed many years ago and resistance profiles have emerged. This has created a need for new drugs with discrete modes of action. There is evidence that tuberculosis (like other bacteria) is susceptible to oxidative pressure and this has yet to be properly utilised as a therapeutic approach in a manner similar to that which has proven highly successful in malaria therapy. OBJECTIVE: To develop an alternative approach to the incorporation of bacterial siderophores that results in the creation of antitubercular peroxidic leads for subsequent development as novel agents against tuberculosis. METHODS: Eight novel peroxides were prepared and the antitubercular activity (H37Rv) was compared to existing artemisinin derivatives in vitro. The potential for toxicity was evaluated against the L6 rat skeletal myoblast and HeLa cervical cancer lines in vitro. RESULTS: The addition of a pyrimidinyl residue to an artemisinin or, preferably, a tetraoxane peroxidic structure results in antitubercular activity in vitro. The same effect is not observed in the absence of the pyrimidine or with other heteroaromatic substituents. CONCLUSION: The incorporation of a pyrimidinyl residue adjacent to the peroxidic function in an organic peroxide results in anti-tubercular activity in an otherwise inactive peroxidic compound. This will be a useful approach for creating oxidative drugs to target tuberculosis.

Design and synthesis of novel artemisinin derivatives with potent activities against colorectal cancer in vitro and in vivo.

A series of novel derivatives of artemisinin-4-(arylamino)quinazoline have been designed and synthesized, and most of them showing potent in vitro cytotoxic activity against HCT116 and WM-266-4 cell lines. Compound 32 was the most active derivative against HCT116 cell line with an IC50 of 110 nM, and significantly improved the antitumor activity of the parent compounds dihydroartemisinin (DHA) (IC50 = 2.85 µM) and Gefitinib (IC50 = 19.82 µM). In vivo HCT116 xenografts assay showed that compound 32 exhibited potent antitumor activity with obvious tumor growth delay and tumor shrunken after 18 days treatment on xenografted mice, and especially without loss of body weight. Our results indicate that compounds 32 may represent a safe, novel structural lead for developing new chemotherapy of colorectal cancer.

Synthesis of novel S-linked dihydroartemisinin derivatives and evaluation of their anticancer activity.

We report herein the synthesis and anticancer activity of a set of novel S-linked artemisinins bearing an aliphatic/aromatic/heterocyclic nucleus as a substituent on the sulfur. The compounds were prepared from artemisinin via its lactol-form by an acid-catalyzed condensation of the desired thiol with the lactol. Both the C-10-α- and ß-configured thiol ethers were synthesized with a view to making them available for the anticancer activity evaluation using a variety of cell lines. The results show that many of the synthetic derivatives studied possessed good potential as anticancer agents. In order to draw more information on the origin of the anticancer activity, one of the compounds (9a), that showed a broad-spectrum activity in terms of reducing the viability of most of the cell lines studied, in particular proven to be most effective against Prostate (PC-3) cells, was studied in detail to find the underlying mechanism of its action by MTT assay, immunoblotting, flow cytometry and microscopy. Pretreatment of the PC-3 cells with N-acetyl cysteine affected the efficacy of 9a, suggesting the role of reactive oxygen species in reducing their viability. Cell cycle analysis showed increase in G1 phase that was indicative of G1 cell cycle arrest. Wound healing assay revealed anti-migratory effect of 9a Quantitative PCR and western blot analysis showed changes in the gene expression of PCNA, E2F1, Pin1, cyclinD1, phospho-c-jun, c-Myc, eIF4E and other genes involved in proliferation and maintaining the transformed phenotype of prostate cancer cells. Here we report the anti-proliferative property of 9a with a vital and potent target(s) in prostate cancer cells with one of such targets being Pin1 belonging to the parvulin family of PPIases. The results suggest that 9a could be a promising agent in combating prostate cancer.

Design, Synthesis, and Mechanism of Dihydroartemisinin⁻Coumarin Hybrids as Potential Anti-Neuroinflammatory Agents.

Cancer patients frequently suffer from cancer-related fatigue (CRF), which is a complex syndrome associated with weakness and depressed mood. Neuroinflammation is one of the major inducers of CRF. The aim of this study is to find a potential agent not only on the treatment of cancer, but also for reducing CRF level of cancer patients. In this study, total-thirty new Dihydroartemisinin-Coumarin hybrids (DCH) were designed and synthesized. The in vitro cytotoxicity against cancer cell lines (HT-29, MDA-MB-231, HCT-116, and A549) was evaluated. Simultaneously, we also tested the anti-neuroinflammatory activity of DCH. DCH could inhibit the activated microglia N9 release of NO, TNF-α, and IL-6. The docking analysis was shown that MD-2, the coreceptor of TLR4, might be one of the targets of DCH.

Hyaluronic acid - dihydroartemisinin conjugate: Synthesis, characterization and in vitro evaluation in lung cancer cells.

In recent years, a great deal of attention has been given towards re-purposing and re-innovating the potential drugs. In this regard, dihydroartemisinin (DHA) has been reported to demonstrate anti-proliferative effects on various cancerous cells viz. breast, liver and lung. However, it is associated with some limitations, such as low bioavailability which is hampered by its poor aqueous solubility and its rapid metabolism in systemic circulation. Therefore, in order to overcome these limitations, we synthesized a novel hyaluronic acid-dihydroartemisinin conjugate in which the hydroxyl group of DHA was covalently linked to carboxylic group of hyaluronic acid (HA). The conjugate was successfully characterized using 1H NMR, Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The synthesized conjugate self-assembled into nanoparticles in aqueous solution. The developed nanoparticles were characterized for their average size, zeta potential, Transmission Electron Microscopy (TEM), X-ray Powder Diffraction (XRD) and loading efficiency. The nanoparticles were cytotoxic to lung cancer (A549) cell line which was determined using CCK-8 cell viability assay. This was further supported by Annexin-V-FITC-Propidium iodide apoptosis assay, reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) loss. Conclusively, present findings demonstrate hyaluronic acid conjugates can be used to improve the therapeutic outcomes of anticancer drugs.

Artemisinin-indole and artemisinin-imidazole hybrids: Synthesis, cytotoxic evaluation and reversal effects on multidrug resistance in MCF-7/ADR cells.

A series of artemisinin derivatives with MDR reversal activity were designed and synthesized. All hybrids were screened to anticancer activities against four human cancer cell lines (A549, MCF-7, HepG-2, MDA-MB-231) and normal human hepatic cell (L02) in vitro. Most of the new compounds showed higher anticancer activities than artemisinin, among which compounds 11a and 11c displayed superior potency with IC50 6.78 µM and 5.25 µM against MCF-7, respectively. The further research indicated that the most potent 11c induced cell cycle arrest at G2 phase in MCF-7. Additionally, compound 11c showed remarkable MDR reversal activity which reversed adriamycin against MCF-7/ADR cells with IC50 0.76 µM.

Novel dihydroartemisinin derivative DHA-37 induces autophagic cell death through upregulation of HMGB1 in A549 cells.

Dihydroartemisinin (DHA) and its analogs are reported to possess selective anticancer activity. Here, we reported a novel DHA derivative DHA-37 that exhibited more potent anticancer activity on the cells tested. Distinct from DHA-induced apoptosis, DHA-37 triggered excessive autophagic cell death, and became the main contributor to DHA-37-induced A549 cell death. Incubation of the cells with DHA-37 but not DHA produced increased dots distribution of GFP-LC3 and expression ratio of LC3-II/LC3-I, and enhanced the formation of autophagic vacuoles as revealed by TEM. Treatment with the autophagy inhibitor 3-MA, LY294002, or chloroquine could reverse DHA-37-induced cell death. In addition, DHA-37-induced cell death was associated significantly with the increased expression of HMGB1, and knockdown of HMGB1 could reverse DHA-37-induced cell death. More importantly, the elevated HMGB1 expression induced autophagy through the activation of the MAPK signal but not PI3K-AKT-mTOR pathway. In addition, DHA-37 also showed a wonderful performance in A549 xenograft mice model. These findings suggest that HMGB1 as a target candidate for apoptosis-resistant cancer treatment and artemisinin-based drugs could be used in inducing autophagic cell death.