Proteasome inhibitors: The next generation of antimalarial drugs?

Among promising targets for new antimalarials is the Plasmodium falciparum proteasome. Multiple inhibitors have demonstrated potent antimalarial activity and synergy with artemisinins. Potent irreversible peptide vinyl sulfones offer synergy, minimal resistance selection, and lack of cross-resistance. These and other proteasome inhibitors have promise as components of new combination antimalarial regimens.

Enhanced anti-cancer effect of artemisinin- and curcumin-loaded niosomal nanoparticles against human colon cancer cells.

Colorectal cancer (CRC) is the third broadly identified cancer in the world. The ineffectiveness of colorectal cancer treatment is redundantly reported. Natural bioactive compounds have gained popularity in reducing the drawback of conventional anti-cancer agents. Curcumin (Cur) and Artemisinin (Art) are materials of a natural source that have been utilized to treat numerous kinds of cancers. Although the benefits of bioactive materials, their utilization is limited because of poor solubility, bioavailability, and low dispersion rate in aqueous media. Nano delivery system such as niosome can improve the bioavailability and stability of bioactive compounds within the drug. In current work, we used Cur-Art co-loaded niosomal nanoparticles (Cur-Art NioNPs) as an anti-tumor factor versus colorectal cancer cell line. The synthesized formulations were characterized using dynamic light scattering, scanning electron microscopy, and FTIR. The proliferation ability of the cells and expression of apoptosis-associated gene were MTT assay and qRT-PCR, respectively. Cur-Art NioNPs exhibited well distributed with an encapsulation efficiency of 80.27% and 85.5% for Cur and Art. The NioNPs had good release and degradation properties, and had no negative effect on the survival and proliferation ability of SW480 cells. Importantly, nanoformulation form of Cur and Art significantly displayed higher toxicity effect against SW480 cells. Furthermore, Cur-Art NioNPs increased Bax, Fas, and p53 gene expressions and suppressed Bcl2, Rb, and Cyclin D 1 gene expressions. In summary, these results display the niosome NPs as a first report of nano-combinational application of the natural herbal substances with a one-step fabricated co-delivery system for effective colorectal cancer.

Medicinal and mechanistic overview of artemisinin in the treatment of human diseases.

Artemisinin (ART) is a bioactive compound isolated from the plant Artemisia annua and has been traditionally used to treat conditions such as malaria, cancer, viral infections, bacterial infections, and some cardiovascular diseases, especially in Asia, North America, Europe and other parts of the world. This comprehensive review aims to update the biomedical potential of ART and its derivatives for treating human diseases highlighting its pharmacokinetic and pharmacological properties based on the results of experimental pharmacological studies in vitro and in vivo. Cellular and molecular mechanisms of action, tested doses and toxic effects of artemisinin were also described. The analysis of data based on an up-to-date literature search showed that ART and its derivatives display anticancer effects along with a wide range of pharmacological activities such as antibacterial, antiviral, antimalarial, antioxidant and cardioprotective effects. These compounds have great potential for discovering new drugs used as adjunctive therapies in cancer and various other diseases. Detailed translational and experimental studies are however needed to fully understand the pharmacological effects of these compounds.

Ex vivo RSA and pfkelch13 targeted-amplicon deep sequencing reveal parasites susceptibility to artemisinin in Senegal, 2017.

BACKGROUND: Malaria control is highly dependent on the effectiveness of artemisinin-based combination therapy (ACT), the current frontline malaria curative treatment. Unfortunately, the emergence and spread of parasites resistant to artemisinin (ART) derivatives in Southeast Asia and South America, and more recently in Rwanda and Uganda (East Africa), compromise their long-term use in sub-Saharan Africa, where most malaria deaths occur. METHODS: Here, ex vivo susceptibility to dihydroartemisinin (DHA) was evaluated from 38 Plasmodium falciparum isolates collected in 2017 in Thiès (Senegal) expressed in the Ring-stage Survival Assay (RSA). Both major and minor variants were explored in the three conserved-encoding domains of the pfkelch13 gene, the main determinant of ART resistance using a targeted-amplicon deep sequencing (TADS) approach. RESULTS: All samples tested in the ex vivo RSA were found to be susceptible to DHA (parasite survival rate < 1%). The non-synonymous mutations K189T and K248R in pfkelch13 were observed each in one isolate, as major (99%) or minor (5%) variants, respectively. CONCLUSION: The results suggest that ART is still fully effective in the Thiès region of Senegal in 2017. Investigations combining ex vivo RSA and TADS are a useful approach for monitoring ART resistance in Africa.

Favorable Preclinical Pharmacological Profile of a Novel Antimalarial Pyrrolizidinylmethyl Derivative of 4-amino-7-chloroquinoline with Potent In Vitro and In Vivo Activities.

The 4-aminoquinoline drugs, such as chloroquine (CQ), amodiaquine or piperaquine, are still commonly used for malaria treatment, either alone (CQ) or in combination with artemisinin derivatives. We previously described the excellent in vitro activity of a novel pyrrolizidinylmethyl derivative of 4-amino-7-chloroquinoline, named MG3, against P. falciparum drug-resistant parasites. Here, we report the optimized and safer synthesis of MG3, now suitable for a scale-up, and its additional in vitro and in vivo characterization. MG3 is active against a panel of P. vivax and P. falciparum field isolates, either alone or in combination with artemisinin derivatives. In vivo MG3 is orally active in the P. berghei, P. chabaudi, and P. yoelii models of rodent malaria with efficacy comparable, or better, than that of CQ and of other quinolines under development. The in vivo and in vitro ADME-Tox studies indicate that MG3 possesses a very good pre-clinical developability profile associated with an excellent oral bioavailability, and low toxicity in non-formal preclinical studies on rats, dogs, and non-human primates (NHP). In conclusion, the pharmacological profile of MG3 is in line with those obtained with CQ or the other quinolines in use and seems to possess all the requirements for a developmental candidate.

Analgesic Effects of Fisetin, Peimine, Astaxanthin, Artemisinin, Bardoxolone Methyl and 740 Y-P and Their Influence on Opioid Analgesia in a Mouse Model of Neuropathic Pain.

Treatment of neuropathic pain remains a challenge for modern medicine due to the insufficiently understood molecular mechanisms of its development and maintenance. One of the most important cascades that modulate the nociceptive response is the family of mitogen-activated protein (MAP) kinases and phosphatidylinositol-3-kinase (PI3K), as well as nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this study was to determine the effect of nonselective modulators of MAP kinases-fisetin (ERK1/2 and NFκB inhibitor, PI3K activator), peimine (MAPK inhibitor), astaxanthin (MAPK inhibitor, Nrf2 activator) and artemisinin (MAPK inhibitor, NFκB activator), as well as bardoxolone methyl (selective activator of Nrf2) and 740 Y-P (selective activator of PI3K)-in mice with peripheral neuropathy and to compare their antinociceptive potency and examine their effect on analgesia induced by opioids. The study was performed using albino Swiss male mice that were exposed to chronic constriction injury of the sciatic nerve (CCI model). Tactile and thermal hypersensitivity was measured using von Frey and cold plate tests, respectively. Single doses of substances were administered intrathecally on day 7 after CCI. Among the tested substances, fisetin, peimine, and astaxanthin effectively diminished tactile and thermal hypersensitivity in mice after CCI, while artemisinin did not exhibit analgesic potency in this model of neuropathic pain. Additionally, both of the activators tested, bardoxolone methyl and 740 Y-P, also showed analgesic effects after intrathecal administration in mice exposed to CCI. In the case of astaxanthin and bardoxolone methyl, an increase in analgesia after combined administration with morphine, buprenorphine, and/or oxycodone was observed. Fisetin and peimine induced a similar effect on tactile hypersensitivity, where analgesia was enhanced after administration of morphine or oxycodone. In the case of 740 Y-P, the effects of combined administration with each opioid were observed only in the case of thermal hypersensitivity. The results of our research clearly indicate that substances that inhibit all three MAPKs provide pain relief and improve opioid effectiveness, especially if they additionally block NF-κB, such as peimine, inhibit NF-κB and activate PI3K, such as fisetin, or activate Nrf2, such as astaxanthin. In light of our research, Nrf2 activation appears to be particularly beneficial. The abovementioned substances bring promising results, and further research on them will broaden our knowledge regarding the mechanisms of neuropathy and perhaps contribute to the development of more effective therapy in the future.

Dual-pharmacophore artezomibs hijack the Plasmodium ubiquitin-proteasome system to kill malaria parasites while overcoming drug resistance.

Artemisinins (ART) are critical anti-malarials and despite their use in combination therapy, ART-resistant Plasmodium falciparum is spreading globally. To counter ART resistance, we designed artezomibs (ATZs), molecules that link an ART with a proteasome inhibitor (PI) via a non-labile amide bond and hijack parasite's own ubiquitin-proteasome system to create novel anti-malarials in situ. Upon activation of the ART moiety, ATZs covalently attach to and damage multiple parasite proteins, marking them for proteasomal degradation. When damaged proteins enter the proteasome, their attached PIs inhibit protease function, potentiating the parasiticidal action of ART and overcoming ART resistance. Binding of the PI moiety to the proteasome active site is enhanced by distal interactions of the extended attached peptides, providing a mechanism to overcome PI resistance. ATZs have an extra mode of action beyond that of each component, thereby overcoming resistance to both components, while avoiding transient monotherapy seen when individual agents have disparate pharmacokinetic profiles.

Modified Plasmodium falciparum Ring-Stage Survival Assay with ML10 Kinase Inhibitor.

The ring-stage survival assay is the reference assay to measure in vitro Plasmodium falciparum artemisinin partial resistance. The main challenge of the standard protocol is to generate 0-to-3-h postinvasion ring stages (the stage least susceptible to artemisinin) from schizonts obtained by sorbitol treatment and Percoll gradient. We report here a modified protocol facilitating the production of synchronized schizonts when multiple strains are tested simultaneously, by using ML10, a protein kinase inhibitor, that reversibly blocks merozoite egress.

Evolution of Plasmodium falciparum antimalarial drug resistance markers post-adoption of artemisinin-based combination therapies in Yaounde, Cameroon.

OBJECTIVES: This study aimed to investigate the evolution of Plasmodium falciparum antimalarial drug resistance markers by comparing the pre- and post-adoption of artemisinin-based combination therapies (ACTs) in Yaounde, Cameroon. METHODS: The molecular characterization of known antimalarial drug resistance markers (Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and Pfk13) in P. falciparum-positive samples collected in 2014 and 2019-2020 was achieved using nested polymerase chain reaction, followed by targeted amplicon deep sequencing on the Illumina MiSeq platform. Data derived were compared with those published during the pre-ACT adoption period from 2004 to 2006. RESULTS: A high prevalence of Pfmdr1 184F, Pfdhfr 51I/59R/108N, and Pfdhps 437G mutant alleles was observed during the post-ACT adoption period. The Pfcrt 76T and Pfmdr1 86Y mutant alleles significantly declined between 2004 and 2020 (P <0.0001). Conversely, the resistance markers to antifolates, Pfdhfr 51I/59R/108N and Pfdhps 437G, significantly increased during the same study period (P <0.0001). We identified nine mutations in the propeller domains of Pfk13; although they were all present in single parasite isolates, none of them are known to confer artemisinin resistance. CONCLUSION: This study documented a near-complete reversion to sensitive parasites for markers conferring resistance to the 4-aminoquinolines and arylamino alcohols in Yaounde. In contrast, the Pfdhfr mutations associated with pyrimethamine resistance are moving toward saturation.

Artemisinin derivatives induce oxidative stress leading to DNA damage and caspase-mediated apoptosis in Theileria annulata-transformed cells.

BACKGROUND: Bovine theileriosis caused by the eukaryotic parasite Theileria annulata is an economically important tick-borne disease. If it is not treated promptly, this lymphoproliferative disease has a significant fatality rate. Buparvaquone (BPQ) is the only chemotherapy-based treatment available right now. However, with the emergence of BPQ resistance on the rise and no backup therapy available, it is critical to identify imperative drugs and new targets against Theileria parasites. METHODS: Artemisinin and its derivatives artesunate (ARS), artemether (ARM), or dihydroartemisinin (DHART) are the primary defence line against malaria parasites. This study has analysed artemisinin and its derivatives for their anti-Theilerial activity and mechanism of action. RESULTS: ARS and DHART showed potent activity against the Theileria-infected cells. BPQ in combination with ARS or DHART showed a synergistic effect. The compounds act specifically on the parasitised cells and have minimal cytotoxicity against the uninfected host cells. Treatment with ARS or DHART induces ROS-mediated oxidative DNA damage leading to cell death. Further blocking intracellular ROS by its scavengers antagonised the anti-parasitic activity of the compounds. Increased ROS production induces oxidative stress and DNA damage causing p53 activation followed by caspase-dependent apoptosis in the Theileria-infected cells. CONCLUSIONS: Our findings give unique insights into the previously unknown molecular pathways underpinning the anti-Theilerial action of artemisinin derivatives, which may aid in formulating new therapies against this deadly parasite. Video abstract.

Characterization of Plasmodium falciparum prohibitins as novel targets to block infection in humans by impairing the growth and transmission of the parasite.

Prohibitins (PHBs) are highly conserved pleiotropic proteins as they have been shown to mediate key cellular functions. Here, we characterize PHBs encoding putative genes ofPlasmodium falciparum by exploiting different orthologous models. We demonstrated that PfPHB1 (PF3D7_0829200) and PfPHB2 (PF3D7_1014700) are expressed in asexual and sexual blood stages of the parasite. Immunostaining indicated hese proteins as mitochondrial residents as they were found to be localized as branched structures. We further validated PfPHBs as organellar proteins residing in Plasmodium mitochondria, where they interact with each other. Functional characterization was done in Saccharomyces cerevisiae orthologous model by expressing PfPHB1 and PfPHB2 in cells harboring respective mutants. The PfPHBs functionally complemented the yeast PHB1 and PHB2 mutants, where the proteins were found to be involved in stabilizing the mitochondrial DNA, retaining mitochondrial integrity and rescuing yeast cell growth. Further, Rocaglamide (Roc-A), a known inhibitor of PHBs and anti-cancerous agent, was tested against PfPHBs and as an antimalarial. Roc-A treatment retarded the growth of PHB1, PHB2, and ethidium bromide petite yeast mutants. Moreover, Roc-A inhibited growth of yeast PHBs mutants that were functionally complemented with PfPHBs, validating P. falciparum PHBs as one of the molecular targets for Roc-A. Roc-A treatment led to growth inhibition of artemisinin-sensitive (3D7), artemisinin-resistant (R539T) and chloroquine-resistant (RKL-9) parasites in nanomolar ranges. The compound was able to retard gametocyte and oocyst growth with significant morphological aberrations. Based on our findings, we propose the presence of functional mitochondrial PfPHB1 and PfPHB2 in P. falciparum and their druggability to block parasite growth.

B7-H3 but not PD-L1 is involved in the antitumor effects of Dihydroartemisinin in non-small cell lung cancer.

Dihydroartemisinin (DHA), an active antimalaria metabolite derived from artemisinin, has received increasing attention for its anticancer activities. However, little is known about the anticancer mechanisms of DHA, although the existing data define its antimalaria effects by producing excessive reactive oxygen species (ROS). In this study, we showed that DHA effectively suppresses in vitro and in vivo tumor growth of non-small cell lung cancer (NSCLC) without perceptible toxicity on heart, liver, spleen, lung, and kidney tissues. Of note, DHA inhibited the expression of B7-H3 rather than PD-L1, whereas overexpression of B7-H3 completely rescued DHA's inhibition on cell proliferation and migration of NSCLC A549 and HCC827 cells. B7-H3 overexpression also largely inhibited DHA's induction on the apoptosis of the two cell lines. Furthermore, DHA treatment led to increased infiltration of CD8+ T Lymphocytes in the xenografts as compared with that of negative controls. Taken together, our results suggest that B7-H3 but not PD-L1 is involved in the antitumor effects of DHA in NSCLC, which may be indicative of an effective B7-H3 blockade and further combination with anti-PD-L1/PD-1 immunotherapy.

Anti-Mitochondrial and Insecticidal Effects of Artemisinin against Drosophila melanogaster.

Artemisinin (ART) is an endoperoxide molecule derived from the medicinal plant Artemisia annua L. and is clinically used as an antimalarial drug. As a secondary metabolite, the benefit of ART production to the host plant and the possible associated mechanism are not understood. It has previously been reported that Artemisia annua L. extract or ART can inhibit both insect feeding behaviors and growth; however, it is not known whether these effects are independent of each other, i.e., if growth inhibition is a direct outcome of the drug's antifeeding activity. Using the lab model organism Drosophila melanogaster, we demonstrated that ART repels the feeding of larvae. Nevertheless, feeding inhibition was insufficient to explain its toxicity on fly larval growth. We revealed that ART provoked a strong and instant depolarization when applied to isolated mitochondria from Drosophila while exerting little effect on mitochondria isolated from mice tissues. Thus, ART benefits its host plant through two distinct activities on the insect: a feeding-repelling action and a potent anti-mitochondrial action which may underlie its insect inhibitory activities.

Artemisinin suppresses aerobic glycolysis in thyroid cancer cells by downregulating HIF-1a, which is increased by the XIST/miR-93/HIF-1a pathway.

The incidence of thyroid cancer (TC) continues to increase worldwide. Aerobic glycolysis, the prominent feature of glucose metabolism in cancer progression, is associated with TC. We first demonstrated that HIF-1a is highly expressed in TC tissues and is positively correlated with the level of XIST in the serum of patients with TC. Then, we proved that XIST regulates the expression of HIF-1a through the XIST/miR-93/HIF-1a pathway, thereby regulating the level of glycolysis in TC cells. Knockdown of XIST inhibits glycolysis, proliferation, the cell cycle and metastasis of TC cells. Finally, we verified that artemisinin could target the degradation of HIF-1a and inhibit glycolysis in TC cells. Collectively, XIST levels in serum may be used as a tumor marker for TC promoted by HIF-1a, which could be treated using artemisinin.

Plasmodium Iron-Sulfur [Fe-S] cluster assembly protein Dre2 as a plausible target of Artemisinin: Mechanistic insights derived in a prokaryotic heterologous system.

Iron-sulfur (Fe-S) cluster containing proteins have been assigned roles in various essential cellular processes, such as regulation of gene expression, electron transfer, sensing of oxygen and balancing free radical chemistry. However, their role as the drug target remains sparse. Recently the screening of protein alkylation targets for artemisinin in Plasmodium falciparum led to identification of Dre2, a protein involved in redox mechanism for the cytoplasmic Fe-S cluster assembly in different organisms. In the present study, to further explore the interaction between artemisinin and Dre2, we have expressed the Dre2 protein of both P. falciparum and P. vivax in E. coli. The opaque brown colour of the IPTG induced recombinant Plasmodium Dre2 bacterial pellet, suggested iron accumulation as confirmed by the ICP-OES analysis. In addition, overexpression of rPvDre2 in E. coli reduced its viability, growth and increased the ROS levels of bacterial cells, which in turn led to an increase in expression of stress response genes of E. coli such as recA, soxS, mazF. Moreover, the overexpression of rDre2 induced cell death could be rescued by treatment with Artemisinin derivatives suggesting their interaction. The interaction between DHA and PfDre2 was later demonstrated by CETSA and microscale thermophoresis. Overall, this study suggests that Dre2 is the probable target of Artemisinin and the antimalarial activity of DHA/Artemether could also be due to yet unidentified molecular mechanism altering the Dre2 activity in addition to inducing DNA and protein damage.

Late-Stage C(sp2 )-H Arylation of Artemisinic Acid and Arteannuin B: Effect of Olefin Migration Towards Synthesis of C-13 Arylated Artemisinin Derivatives.

In recent years, C-H bond functionalization has emerged as a pivotal tool for late-stage functionalization of complex natural products for the synthesis of potent biologically active derivatives. Artemisinin and its C-12 functionalized semi-synthetic derivatives are well-known clinically used anti-malarial drugs due to the presence of the essential 1,2,4-trioxane pharmacophore. However, in the wake of parasite developing resistance against artemisinin-based drugs, we conceptualized the synthesis of C-13 functionalized artemisinin derivatives as new antimalarials. In this regard, we envisaged that artemisinic acid could be a suitable precursor for the synthesis of C-13 functionalized artemisinin derivatives. Herein, we report C-13 arylation of artemisinic acid, a sesquiterpene acid and our attempts towards synthesis of C-13 arylated artemisinin derivatives. However, all our efforts resulted in the formation of a novel ring-contracted rearranged product. Additionally, we have extended our developed protocol for C-13 arylation of arteannuin B, a sesquiterpene lactone epoxide considered to be the biogenetic precursor of artemisinic acid. Indeed, the synthesis of C-13 arylated arteannuin B renders our developed protocol to be effective in sesquiterpene lactone as well.

A Water-Soluble Polymer-Lumefantrine Conjugate for the Intravenous Treatment of Severe Malaria.

Uncomplicated malaria is effectively treated with oral artemisinin-based combination therapy (ACT). Yet, there is an unmet clinical need for the intravenous treatment of the more fatal severe malaria. There is no combination intravenous therapy for uncomplicated due to the nonavailability of a water-soluble partner drug for the artemisinin, artesunate. The currently available treatment is a two-part regimen split into an intravenous artesunate followed by the conventional oral ACT . In a novel application of polymer therapeutics, the aqueous insoluble antimalarial lumefantrine is conjugated to a carrier polymer to create a new water-soluble chemical entity suitable for intravenous administration in a clinically relevant formulation . The conjugate is characterized by spectroscopic and analytical techniques, and the aqueous solubility of lumefantrine is determined to have increased by three orders of magnitude. Pharmacokinetic studies in mice indicate that there is a significant plasma release of lumefantrine and production its metabolite desbutyl-lumefantrine (area under the curve of metabolite is ≈10% that of the parent). In a Plasmodium falciparum malaria mouse model, parasitemia clearance is 50% higher than that of reference unconjugated lumefantrine. The polymer-lumefantrine shows potential for entering the clinic to meet the need for a one-course combination treatment for severe malaria.

P53 Gene Expression and Nitric Oxide Levels after Artemisinin-Caffeine Treatment in Breast, Lungs and Liver of DMBA-Induced Tumorigenesis.

OBJECTIVE: With increasing incidence of cancers globally and limited resources in some affected countries, repurposing existing drugs for reducing tumorigenesis is highly important. Artemisinin and caffeine have potent anti-oxidative and anti-tumor properties but are therapies for other diseases. This study evaluated the biochemical and p53 gene modulatory effects of doses of artemisinin-caffeine combination on breast, lungs and liver tissues in rats induced with DMBA. METHODS: After due ethical approval, 30 animals were treated with 40mg/kg single dose of 7,12-dimethylbenzene anthracene (DMBA) as a model for DNA damage and induction of carcinogenesis. Five animals each received normal saline (normal), low dose artemisinin (Art; 4mg/kg), low dose caffeine (Caff; 25mg/kg), low dose combination of caff + art (25+4mg/kg), high dose combination of caff + art (50+8mg/kg) or no treatment (DMBA). All treatment doses were orally administered daily for two weeks post DMBA treatment. Nitric oxide levels and p53 relative gene expression was carried out using primer-specific RT-PCR, GAPDH was used as loading control and amplicons were resolved by gel electrophoresis. RESULTS: DMBA induced lesions in breast, liver, and lung tissues evident from histology analysis, compared to normal group. In all 3 tissues, caffeine (25mg/kg) and combination of caff + art (25+4mg/kg) significantly reduced p53 gene expression (p < 0.05), but there was significant increase in the group treated with low dose art (4mg/kg) and high dose caff + art, which were similar to DMBA group (p<0.05). In lungs, nitric oxide (NO) increased in all groups but not in caffeine, in the liver NO decreased with caffeine or its combination with art, compared to DMBA group. CONCLUSIONS: This study shows a dose-dependent synergistic anticancer effects of caffeine and artemisinin combination on p53 gene and nitric oxide regulation hence can mitigate tumor development.

Prediction of improved antimalarial chemotherapy of artesunate-mefloquine in combination with mefloquine sensitive and resistant Plasmodium falciparum malaria.

BACKGROUND: Declining in susceptibility of Plasmodium falciparum to mefloquine is reported in South-East Asia. A revisiting on mefloquine pharmacokinetics-pharmacodynamics (PK/PD) could assist in finding new appropriate dosage regimens in combination with artesunate as a three-day course treatment. OBJECTIVE: This study aimed to investigate promising alternative artesunate-mefloquine combination regimens that are effective for the treatment of patients with mefloquine-sensitive and resistant P. falciparum malaria. METHODS: Data collected during 2008-2009 from 124 patients with uncomplicated P. falciparum malaria were included in the analysis, 90 and 34 patients with sensitive and recrudescence response, respectively. All patients were treated with a three-day combination of artesunate-mefloquine. Population PK-PD models were developed. The developed models were validated with clinically observed data. Simulations of clinical efficacy of alternative mefloquine regimens were performed based on mefloquine sensitivity, patients' adherence and parasite biomass. RESULTS: The developed PK/PD models well described with clinically observed data. For mefloquine-resistant P. falciparum, a three-day standard regimen of artesunate-mefloquine is suitable (>50% efficacy) only when the level of parasite sensitivity was < 1.5-fold of the cut-off level (IC50 < 36 nM). For mefloquine-sensitive parasite with IC50 < 23.19 nM (0.96-fold), all regimens provided satisfactory efficacy. In the isolates with IC50 of 24 nM, regimen-I is recommended. Curative treatment criteria for mefloquine and artesunate were C336h (>408 ng.mL-1) or Cmax/IC50 (>130.1 g.m/M), and Cmax/IC50 (>381.2 g.m/M), respectively. CONCLUSIONS: Clinical use of a three-day standard artesunate-mefloquine is suitable only when the IC50 of P. falciparum isolates is lower than 36 nM. Otherwise, other ACT regimens should be replaced. For mefloquine-sensitive parasite, a dose reduction is recommended with the IC50 is lower than 23.19 nM.

Design, Synthesis, and Biological Evaluation of Novel Amyl Ester Tethered Dihydroartemisinin-Isatin Hybrids as Potent Anti-Breast Cancer Agents.

A series of novel amyl ester tethered dihydroartemisinin-isatin hybrids 4a-d and 5a-h were designed, synthesized, and evaluated as anti-breast cancer agents. The synthesized hybrids were preliminarily screened against estrogen receptor-positive (MCF-7 and MCF-7/ADR) and triple-negative (MDA-MB-231 and) breast cancer cell lines. Three hybrids 4a,d and 5e not only were more potent than artemisinin and adriamycin against drug-resistant MCF-7/ADR and MDA-MB-231/ADR breast cancer cell lines, but also displayed non-cytotoxicity towards normal MCF-10 A breast cells, and the SI values were >4.15, indicating their excellent selectivity and safety profiles. Thus, hybrids 4a,d and 5e could act as potential anti-breast cancer candidates and were worthy of further preclinical evaluations. Moreover, the structure-activity relationships which may facilitate further rational design of more effective candidates were also enriched.