Current drug strategies for the treatment and control of schistosomiasis

INTRODUCTION

Schistosomiasis, one of the current Neglected Tropical Diseases (NTDs) affects over 230 million people globally, with nearly 700 million at risk in more than 74 countries. Praziquantel (PZQ) has served as the primary treatment for the past four decades; however, its effectiveness is limited as it solely eliminates adult worms. In regions where infections are frequent, PZQ exhibits only temporary efficacy and has restricted potential to disrupt the prolonged transmission of the disease.

AREAS COVERED

A comprehensive exploration using the PubMed database was conducted to review current pharmacotherapy approaches for schistosomiasis. This review also encompasses recent research findings related to potential novel therapeutics and the repurposing of existing drugs.

EXPERT OPINION

Current schistosoma treatment strategies, primarily relying on PZQ, face challenges like temporary effectiveness and limited impact on disease transmission. Drug repurposing, due to economic constraints, is decisive for NTDs. Despite PZQ's efficacy, its failure to prevent reinfection highlights the need for complementary strategies, especially in regions with persistent environmental foci. Integrating therapies against diverse schistosome stages boosts efficacy and impedes resistance. Uncovering novel agents is essential to address resistance concerns in tackling this neglected tropical disease. Integrated strategies present a comprehensive approach to navigate the complex challenges.

Small change, big difference: A promising praziquantel derivative designated P96 with broad-spectrum antischistosomal activity for chemotherapy of schistosomiasis japonica

BACKGROUND

Praziquantel (PZQ) has been the first line antischistosomal drug for all species of Schistosoma, and the only available drug for schistosomiasis japonica, without any alternative drugs since the 1980s. However, PZQ cannot prevent reinfection, and cannot cure schistosomiasis thoroughly because of its poor activity against juvenile schistosomes. In addition, reliance on a single drug is extremely dangerous, the development and spread of resistance to PZQ is becoming a great concern. Therefore, development of novel drug candidates for treatment and control of schistosomiasis is urgently needed.

METHODOLOGYS/PRINCIPAL FINDINGS

One of the PZQ derivative christened P96 with the substitution of cyclohexyl by cyclopentyl was synthesized by School of Pharmaceutical Sciences of Shandong University. We investigated the in vitro and in vivo activities of P96 against different developmental stages of S. japonicum. Parasitological studies and scanning electron microscopy were used to study the primary action characteristics of P96 in vitro. Both mouse and rabbit models were employed to evaluate schistosomicidal efficacy of P96 in vivo. Besides calculation of worm reduction rate and egg reduction rate, quantitative real-time PCR was used to evaluate the in vivo antischistosomal activity of P96 at molecular level. In vitro, after 24h exposure, P96 demonstrated the highest activities against both juvenile and adult worm of S. japonicum in comparison to PZQ. The antischistosomal efficacy was concentration-dependent, with P96 at 50μM demonstrating the most evident schistosomicidal effect. Scanning electron microscopy demonstrated that P96 caused more severe damages to schistosomula and adult worm tegument compared to PZQ. In vivo, our results showed that P96 was effective against S. japonicum at all developmental stages. Notably, its efficacy against young stage worms was significantly improved compared to PZQ. Moreover, P96 retained the high activity comparable to PZQ against the adult worm of S. japonicum.

CONCLUSIONS

P96 is a promising drug candidate for chemotherapy of schistosomiasis japonica, which has broad spectrum of action against various developmental stage, potentially addressing the deficiency of PZQ. It might be promoted as a drug candidate for use either alone or in combination with PZQ for the treatment of schistosomiasis.

Tuning of Cr-Cr Magnetic Exchange through Chalcogenide Linkers in Cr2 Molecular Dimers

A set of three Cr-dimer compounds, Cr₂Q₂(en)₄X₂ (Q: S, Se; X: Br, Cl; en: ethylenediamine), with monoatomic chalcogenide bridges have been synthesized via a single-step solvothermal route. Chalcogenide linkers mediate magnetic exchange between Cr³⁺ centers, while bidentate ethylenediamine ligands complete the distorted octahedral coordination of Cr centers. Unlike the compounds previously reported, none of the chalcogenide atoms are connected to extra ligands. Magnetic susceptibility studies indicate antiferromagnetic coupling between Cr³⁺ centers, which are moderate in Cr₂Se₂(en)₄X₂ and stronger in Cr₂S₂(en)₄Cl₂. Fitting the magnetic data requires a biquadratic exchange term. High-frequency EPR spectra showing characteristic signals due to coupled S = 1 spin states could be interpreted in terms of the "giant spin" Hamiltonian. A fourth compound, Cr₂Se₈(en)₄, has a single diatomic Se bridge connecting the two Cr³⁺ centers and shows weak ferromagnetic exchange interactions. This work demonstrates the tunability in strength and type of exchange interactions between metal centers by manipulating the interatomic distances and number of bridging chalcogenide linkers.

Synthesis, structural insights, and biological screening of DNA targeted Ru(ii)(η6-p-cymene) complexes containing bioactive amino-benzothiazole ligand scaffolds

Two new drug candidates [Ru(p-cymene)(C7H4ClN2S)Cl2] and [Ru(p-cymene)(C7H5FN2S)Cl2] were synthesized and characterised. The in vitro cytotoxic activity of the complexes was assessed against five human cancer cell lines and anthelmintic activity was also investigated.

Rational approaches towards inorganic and organometallic antibacterials

The occurrence of drug-resistant bacteria is drastically rising and new and effective antibiotic classes are urgently needed. However, most of the compounds in development are minor modifications of previously used drugs to which bacteria can easily develop resistance. The investigation of inorganic and organometallic compounds as antibiotics is an alternative approach that holds great promises due to the ability of such molecules to trigger metal-specific mechanisms of action, which results in lethal consequences for pathogens. In this review, a selection of concepts to rationally design inorganic and organometallic antibiotics is discussed, highlighting their advantages by comparing them to classical drug discovery programmes. The review concludes with a short perspective for the future of antibiotic drug development and the role metal-based compounds will play in the field.

Synthesis, characterization and antiparasitic activity of organometallic derivatives of the anthelmintic drug albendazole

Helminthiases, a group of neglected tropical diseases, affect more than one billion people mainly in tropical and subtropical regions. Moreover, major intestinal protozoa have a significant impact on global public health. Albendazole (ABZ) is a broad-spectrum anthelmintic recommended by the World Health Organisation (WHO). However, drug resistance is emerging due to its widespread use. In order to tackle this problem, taking into account the spectacular results obtained with ferroquine, an organometallic derivatization of the antimalarial drug chloroquine, we have prepared, in this study, a series of new ferrocenyl and ruthenocenyl derivatives of the organic drug ABZ and assessed their activity against different helminths and protozoans, namely Trichuris muris, Heligmosomoides polygygrus, Schistosoma mansoni, Giardia lamblia, Haemonchus contortus and Toxoplasma gondii. The ferrocene-containing ABZ analogue 2d exhibited over 70% activity against T. muris adults in vitro at 200 μM and no toxicity to mammalian cells (IC50 >100 μM). H. polygyrus adults were not affected by any of the derivatives tested. Against T. gondii, the ferrocene-containing ABZ analogues 1a and 2d showed better in vitro activity than ABZ and low toxicity to the host cells. The activity of the analogous ruthenocenyl compound 2b against S. mansoni and T. gondii in vitro might be attributed to its toxicity towards the host cells rather than a specific antiparasitic activity. These results demonstrate that the derivatives show a species specific in vitro activity and the choice of the organometallic moieties attached to the organic drug is playing a very important role. Two of our organometallic compounds, namely 1b and 2d, were tested in T. muris infected mice. At a 400 mg kg-1 dose, the compounds showed moderate worm burden reductions but low worm expulsion rates. Overall, this work, which is one of the first studies reporting the potential of organometallic compounds on a very broad range of parasitic helminths and protozoan, is a clear confirmation of the potential of organometallic complexes against parasites of medical and veterinary importance.

Anticancer and antitrypanosomal activities of trinuclear ruthenium compounds with orthometalated phenazine ligands

Trinuclear ruthenium complexes with orthometalated phenazines of general formula [Ru3(μ3-O)(μ2-OAc)5(L)(py)2]PF6 (L = dppn, benzo[i]dipyrido[3,2-a:2',3'-c]phenazine, 1; dppz, dipyrido[3,2-a:2',3'-c]phenazine, 2; CH3-dppz, 7-methyldipyrido[3,2-a:2',3'-c]phenazine, 3; Cl-dppz, 7-chlorodipyrido[3,2-a:2',3'-c]phenazine, 4) were investigated for their cytotoxic activity toward the B16F10 murine melanoma and the L929 non-cancer cell lines and against Trypanosoma cruzi (2-4). This study also reports a multi-technique investigation into how complexes 1-4 interact with DNA and human serum albumin, HSA. At concentrations ranging from 2 to 50 μM, all the complexes reduced B16F10 murine melanoma cell viability by over 50%. Complex 4 had the highest cytotoxic effect in the series, diminishing B16F10 cell viability to 38% at 2 μM, with an overall order for anticancer activity of 4 > 2 > 3 > 1. Complexes 2-4 showed remarkable activity in inhibiting epimastigote and amastigote forms of T. cruzi. Complex 2 showed better antitrypanosomal activity than the reference drug (IC50 = 1.19 μM and IC50 = 0.25 μM for epimastigote and amastigotes forms, respectivily). Ethidium bromide (EB) displacement assays showed that DNA intercalation progressively increases with the extension of the π-conjugation of the cyclometalating ligand and the presence of substituents in the phenazinic portion (1 > 4-3 > 2), showing that complex 1 is a stronger intercalator than EB itself (Kapp > 107 M-1). Viscosity measurements followed the same trend. Cytotoxicity against cancer cells and antitrypanosomal activity follow the same order, which is different to the tendency of DNA intercalation, suggesting DNA is not the main target of these complexes. Compound 1-4 showed very high affinity with HSA (Kb ∼109 M-1). Circular dichroism results also showed that the complexes alter significantly the secondary structure of the HSA, lowering the α-helix % from 86.2 (pure protein) to less than 5% for compounds 1, 2 and 4 at 2.8 μM. These findings demonstrated the important role of phenazines for the biological activity of triruthenium compounds.

Novel multifunctional and multitarget homo- (Fe2) and heterobimetallic [(Fe,M) with M = Re or Mn] sulfonyl hydrazones

The synthesis and characterization of the novel ferrocenyl sulfonyl hydrazide [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-NH2}] (2) is reported. Additional studies on its reactivity using acetone or the ferrocenyl-, cyrhetrenyl- or cymantrenyl-aldehydes have allowed us to isolate and characterize [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CMe2}] (3), the bis(ferrocenyl) derivative [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]Fe(η5-C5H5)}] (4) and the heterodimetallic compounds [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]M(CO)3}] with M = Re (5a) or Mn (5b). The X-ray crystal structures of compounds 3, 5a and 5b are also reported. A comparative study of their electrochemical and spectroscopic properties is also described. Additional computational calculations based on the DFT methodology have allowed us to elucidate the effect produced by the replacement of the terminal -NH2 (in 2) by the -N[double bond, length as m-dash]CMe2 (in 3) and -N[double bond, length as m-dash]CHR (in 4, 5a and 5b) moieties on the electronic distribution and to explain the differences detected in their electrochemical properties and absorption spectra. In vitro cytotoxicity studies of compounds 2, 4, 5a and 5b on the HCT-116 (colon), MCF7 and MDA-MB231 (breast) cancer cell lines reveal that compound 2 has no significant activity (IC50 > 100 μM), while its derivatives 4, 5a and 5b proved to be active in the three cancer cell lines selected in this study. The growth inhibition potency of compounds 5a and 5b against the triple negative MDA-MB231 breast cancer cell line is similar (or slightly) greater than that of cisplatin. Moreover, compounds 2, 4, 5a and 5b are less toxic than cisplatin in the normal and non-tumoral BJ fibroblasts, and the heterodimetallic complexes 5a and 5b with selective index >2.1 show an outstanding selective toxicity towards the MDA-MB231 cancer cells.

β-Diketonate versus β-Ketoiminate: The Importance of a Ferrocenyl Moiety in Improving the Anticancer Potency

Herein we present a library of fully characterized β-diketonate and β-ketoiminate compounds that are functionalized with a ferrocenyl moiety. Their cytotoxic potential has been determined by screening against human breast adenocarcinomas (MCF-7 and MDA-MB-231), human colorectal carcinoma p53 wild type (HCT116 p53+/+ ) and normal human prostate (PNT2) cell lines. The ferrocenyl β-diketonate compounds are more than 18 times more cytotoxic than the ferrocenyl β-ketoiminate analogues. Against MCF-7, compounds functionalized at the meta position are up to nine times more cytotoxic than when functionalized at the para position. The ferrocenyl β-diketonate compounds have increased selectivity towards MCF-7 and MDA-MB-231, with several complexes having selectivity index (SI) values that are more than nine times (MCF-7) and more than six times (MDA-MB-231) that of carboplatin. The stability of these compounds in dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) has been assessed by NMR spectroscopy and mass spectrometry studies, and the compounds show no oxidation of the iron center from FeII to FeIII . Cytotoxicity screening was performed in both DMSO and DMF, with no significant differences observedin their potency.

Targeting of the mitochondrion by dinuclear thiolato-bridged arene ruthenium complexes in cancer cells and in the apicomplexan parasite Neospora caninum

A library of 18 dinuclear-thiolato bridged arene ruthenium complexes, some of which with demonstrated activity against cancer cells, was screened for activity against a transgenic Neospora caninum strain that constitutively expresses beta-galactosidase. Initial assessments were done at concentrations of 2500, 250, 25 and 2.5 nM, and 5 compounds were further evaluated with regard to their half maximal proliferation-inhibiting concentration (IC50). Among those, [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-CH3)3]Cl (1), [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-But)3]Cl (2) and [(η6-p-MeC6H4Pri)2Ru2(μ2-SCH2C6H4-p-But)2(μ2-SC6H4-p-OH)]BF4 (9) inhibited N. caninum proliferation with low C50 values of 15, 5 and 1 nM, respectively, while [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-OH)3]Cl (3) and [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-mco)3]Cl (5, mco = 4-methylcoumarinyl) were less active (IC50 = 280 and 108 nM, respectively). These compounds did not affect human foreskin fibroblast (HFF) host cells at dosages of 5 μM and above, but impaired proliferation of the human ovarian carcinoma cell line A2780 (IC50 values of 130 nM (1), 30 nM (2), 530 nM (3), 7730 nM (5), 130 nM (9)). A2780 cancer cells were treated with complexes 1, 2, and 5, and biodistribution analysis using inductively coupled plasma mass spectrometry (ICP-MS) showed that most of the drugs accumulated in the mitochondrial fractions. Transmission electron microscopy showed that the parasite mitochondrion is the primary target also in N. caninum tachyzoites, but these compounds, when applied at 200 nM for 15 days in vitro, did not act parasiticidal. Complexes 1, 2 and 9 applied orally at 2 and 10 mg kg-1 day-1 during 5 days in a neosporosis mouse model did not reduce parasite load and did not limit parasite dissemination to the central nervous system. In accordance with these results, ICP-MS carried out on different organs of mice orally administrated with complexes 1 and 9, demonstrated that the drugs were readily absorbed, and after 3 and 48 h, were mainly detected in liver and kidney, but were largely absent from the brain. Thus, dinuclear thiolato-bridged arene ruthenium complexes exhibit interesting activities against N. caninum in vitro, but further modifications of these promising molecules are required to improve their bioavailability and pharmacokinetic properties in order to exert a pronounced and selective effect against N. caninum in vivo.

The ABL kinase inhibitor imatinib causes phenotypic changes and lethality in adult Schistosoma japonicum

Schistosomiasis caused by different species of schistosome parasites is one of the most debilitating helminthic diseases of humans worldwide. For decades, chemotherapy is the main method of controlling schistosomiasis. However, the fear of drug resistance has motivated the search for alternatives. It has been demonstrated that the ABL kinase inhibitor imatinib affected the development and survival of Schistosoma mansoni in vitro; however, there is still lack of information on whether imatinib also affects other schistosome species such as Schistosoma japonicum. In the present study, the anti-schistosomal potency of imatinib on adult S. japonicum was investigated in vitro, and the results showed that imatinib had a significant impact on various physiological processes of S. japonicum adult worms. Besides its negative effects on worm motility, pairing stability, and gonad development, imatinib caused pathological changes in the gastrodermis as well as the death of the parasite. Our findings suggest that imatinib is an intriguing candidate for further development as an option to fight S. japonicum.

Assessment of tegumental damage to Schistosoma mansoni and S. haematobium after in vitro exposure to ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine using scanning electron microscopy

Background

Schistosomiasis is one of the most harmful parasitic diseases worldwide, praziquantel being the only drug in widespread use to treat it. We recently demonstrated that ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine (Fc-OXA, Rc-OXA and Bn-OXA) are promising antischistosomal drug candidates.

Methods

In this study we assessed the tegumental damage of these three derivatives of oxamniquine using scanning electron microscopy. Adult Schistosoma mansoni and S. haematobium were exposed to a concentration of 100 μM of each drug and incubated for 4–120 h, according to their onset of action and activity.

Results

While on S. mansoni the fastest acting compound was Fc-OXA, which revealed high activity after 4 h of incubation, on S. haematobium, Rc-OXA revealed the quickest onset, being lethal on all males within 24 h. In both species studied, the three derivatives showed the same patterns of tegumental damage consisting of blebs, sloughing and tegument rupturing all over the body. Additionally, on S. mansoni distinct patterns of tegumental damage were observed for each of the compounds: tissue ruptures in the gynaecophoric canal for Fc-OXA, loss of spines for Rc-OXA and oral sucker rupture for Bn-OXA.

Conclusions

Our study confirmed that Fc-OXA, Rc-OXA and Bn-OXA are promising broad spectrum antischistosomal drug candidates. All derivatives show fast in vitro activity against S. mansoni and S. haematobium while validating the previous finding that the parent drug oxamniquine is less active in vitro under the conditions described. This work sets the base for further studies on the identification of a lead oxamniquine derivative, with the aim of identifying a molecule with the potential to become a new drug for human use.

Synthesis, characterization and biological activity of organometallic derivatives of the antimalarial drug mefloquine as new antischistosomal drug candidates

We present the design, synthesis, characterization and biological evaluation of new ferrocenyl and ruthenocenyl derivatives of the organic antimalarial mefloquine, a drug also known for its antischistosomal activity. The two metallocenyl derivatives prepared (3 and 4) demonstrated comparable activity to mefloquine against adult-stage Schistosoma mansoni in vitro. Importantly, both compounds were found to have lower toxicity in all cell lines than mefloquine itself. Administration of a 200 mg kg-1 oral dose of 3 and 4 to S. mansoni-infected mice did not significantly reduce worm burden, contrary to mefloquine.

Schistosomiasis

Schistosomiasis (bilharzia) is a neglected tropical disease caused by parasitic flatworms (blood flukes) of the genus Schistosoma, with considerable morbidity in parts of the Middle East, South America, Southeast Asia and, particularly, in sub-Saharan Africa. Infective larvae grow in an intermediate host (fresh-water snails) before penetrating the skin of the definitive human host. Mature adult worms reside in the mesenteric (Schistosoma mansoni and Schistosoma japonicum) or pelvic (Schistosoma haematobium) veins, where female worms lay eggs, which are secreted in stool or urine. Eggs trapped in the surrounding tissues and organs, such as the liver and bladder, cause inflammatory immune responses (including granulomas) that result in intestinal, hepato-splenic or urogenital disease. Diagnosis requires the detection of eggs in excreta or worm antigens in the serum, and sensitive, rapid, point-of-care tests for populations living in endemic areas are needed. The anti-schistosomal drug praziquantel is safe and efficacious against adult worms of all the six Schistosoma spp. infecting humans; however, it does not prevent reinfection and the emergence of drug resistance is a concern. Schistosomiasis elimination will require a multifaceted approach, including: treatment; snail control; information, education and communication; improved water, sanitation and hygiene; accurate diagnostics; and surveillance-response systems that are readily tailored to social-ecological settings.

Antischistosomal agents: state of art and perspectives

Praziquantel has remained the drug of choice for schistosomiasis chemotherapy for almost 40 years. The pressing need to develop a new antischistosomal drug may necessitate exploring and filtering chemotherapeutic history to search for the most promising ones. In this context, this review attempts to summarize all progress made in schistosomiasis chemotherapy from the early 20th century (mid-1910s) to 2016. We gathered almost 100 compounds providing information on therapeutic action, specifically covering at least first in vivo studies in animal model and in vitro. Pharmacokinetic and toxicity profiles of antischistosomal agents were also described. Preclinical studies indicate a handful of promising future candidates.

Characterization of the Activities of Dinuclear Thiolato-Bridged Arene Ruthenium Complexes against Toxoplasma gondii

The in vitro effects of 18 dinuclear thiolato-bridged arene ruthenium complexes (1 monohiolato compound, 4 dithiolato compounds, and 13 trithiolato compounds), originally designed as anticancer agents, on the apicomplexan parasite Toxoplasma gondii grown in human foreskin fibroblast (HFF) host cells were studied. Some trithiolato compounds exhibited antiparasitic efficacy at concentrations of 250 nM and below. Among those, complex 1 and complex 2 inhibited T. gondii proliferation with 50% inhibitory concentrations (IC₅₀s) of 34 and 62 nM, respectively, and they did not affect HFFs at dosages of 200 μM or above, resulting in selectivity indices of >23,000. The IC₅₀s of complex 9 were 1.2 nM for T. gondii and above 5 μM for HFFs. Transmission electron microscopy detected ultrastructural alterations in the matrix of the parasite mitochondria at the early stages of treatment, followed by a more pronounced destruction of tachyzoites. However, none of the three compounds applied at 250 nM for 15 days was parasiticidal. By affinity chromatography using complex 9 coupled to epoxy-activated Sepharose followed by mass spectrometry, T. gondii translation elongation factor 1α and two ribosomal proteins, RPS18 and RPL27, were identified to be potential binding proteins. In conclusion, organometallic ruthenium complexes exhibit promising activities against Toxoplasma, and the potential mechanisms of action of these compounds as well as their prospective applications for the treatment of toxoplasmosis are discussed.

Inhibition of the Ras/Raf interaction and repression of renal cancer xenografts in vivo by an enantiomeric iridium(iii) metal-based compound

Targeting protein-protein interactions (PPIs) offers tantalizing opportunities for therapeutic intervention for the treatment of human diseases. Modulating PPI interfaces with organic small molecules has been found to be exceptionally challenging, and few candidates have been successfully developed into clinical drugs. Meanwhile, the striking array of distinctive properties exhibited by metal compounds renders them attractive scaffolds for the development of bioactive leads. Here, we report the identification of iridium(iii) compounds as inhibitors of the H-Ras/Raf-1 PPI. The lead iridium(iii) compound 1 exhibited potent inhibitory activity against the H-Ras/Raf-1 interaction and its signaling pathway in vitro and in vivo, and also directly engaged both H-Ras and Raf-1-RBD in cell lysates. Moreover, 1 repressed tumor growth in a mouse renal xenograft tumor model. Intriguingly, the Δ-enantiomer of 1 showed superior potency in the biological assays compared to Λ-1 or racemic 1. These compounds could potentially be used as starting scaffolds for the development of more potent Ras/Raf PPI inhibitors for the treatment of kidney cancer or other proliferative diseases.

Antischistosomal Activity of Pyrido[1,2-a]benzimidazole Derivatives and Correlation with Inhibition of β-Hematin Formation

The extensive use of praziquantel against schistosomiasis raises concerns about drug resistance. New therapeutic alternatives targeting critical pathways within the parasite are therefore urgently needed. Hemozoin formation in Schistosoma presents one such target. We assessed the in vitro antischistosomal activity of pyrido[1,2-a]benzimidazoles (PBIs) and investigated correlations with their ability to inhibit β-hematin formation. We further evaluated the in vivo efficacy of representative compounds in experimental mice and conducted pharmacokinetic analysis on the most potent. At 10 μM, 48/57 compounds resulted in >70% mortality of newly transformed schistosomula, whereas 37 of these maintained >60% mortality of adult S. mansoni. No correlations were observed between β-hematin inhibitory and antischistosomal activities against both larval and adult parasites, suggesting possible presence of other target(s) or a mode of inhibition of crystal formation that is not adequately modeled by the assay. The most active compound in vivo showed 58.7 and 61.3% total and female worm burden reduction, respectively. Pharmacokinetic analysis suggested solubility-limited absorption and high hepatic clearance as possible contributors to the modest efficacy despite good in vitro activity. The PBIs evaluated in this report thus merit further optimization to improve their efficacy and to elucidate their possible mode of action.

Sesquiterpenes evaluation on Schistosoma mansoni: Survival, excretory system and membrane integrity

The main challenge in schistosomiasis control has been the emergence of drug-resistant parasites. Since the 1970's, praziquantel (PZQ) is the single drug for treatment. This fact highlights the importance to research news chemotherapeutic agents. In the last years, S. mansoni excretory system and tegument have been major targets for drug development. The purpose of this study was to evaluate the effect of sesquiterpenes, alpha-humulene and trans-caryophyllene on S. mansoni survival, excretory system and membrane integrity, after in vitro exposure. The in vitro studies, showed that sesquiterpenes reduced egg production and motor activity of worms at sublethal concentrations, and caused death in a concentration-dependent manner (100 and 200μg/mL). Tegumental analysis by Scanning Electron Microscopy (SEM), showed tegument damage. Additionally, it was possible to observe lesions, evidenced by intense marking trough Hoechst probe, in the tegument and suckers of worms exposed to 200μg/mL. In this study, we also showed that resorufin is only capable of identifying the interaction of sesquiterpenes in males excretory system, Pgp expression and inferring that females are more tolerant to treatments. Thus, the present study results contribute to an understanding of alpha-humulene and trans-caryophyllene effect over these targets, contributing for the development of schistosomicidal drugs.

New iminodibenzyl derivatives with anti-leishmanial activity

Leishmaniasis is an infection caused by protozoa of the genus Leishmania and transmitted by sandflies. Current treatments are expensive and time-consuming, involving Sb(V)-based compounds, lipossomal amphotericin B and miltefosine. Recent studies suggest that inhibition of trypanothione reductase (TR) could be a specific target in the development of new drugs because it is essential and exclusive to trypanosomatids. This work presents the synthesis and characterization of new iminodibenzyl derivatives (dado) with ethylenediamine (ea), ethanolamine (en) and diethylenetriamine (dien) and their copper(II) complexes. Computational methods indicated that the complexes were highly lipophilic. Pro-oxidant activity assays by oxidation of the dihydrorhodamine (DHR) fluorimetric probe showed that [Cu(dado-ea)]²⁺ has the highest rate of oxidation, independent of H₂O₂ concentration. The toxicity to L. amazonensis promastigotes and RAW 264,7 macrophages was assessed, showing that dado-en was the most active new compound. Complexation to copper did not have an appreciable effect on the toxicity of the compounds.

Sedaxicenes: potential new antifungal ferrocene-based agents?

Novel bifunctional organometallic antifungal agents has been designed from an active organic core and added with a metallocene moiety. Their synthesis and promising mycotoxicity has been presented.