Anthelmintic activity of artesunate against Fasciola hepatica in naturally infected sheep

Advancement in Diagnosis, Treatment, and Vaccines against Fasciola hepatica: A Comprehensive Review

In this review article, we aim to provide an overview of fasciolosis in ruminants. Diagnosis through new coprological methods (such as Flukefinder®, FLOTAC®, and Mini-FLOTAC®) remains the most suitable approach for farms. Regarding treatment, there is a scarcity of available drugs, and resistance to them has prompted new approaches (including drug combinations, enhanced metabolism, or the use of natural compounds) to address this issue. Additionally, several researchers have developed vaccines to control the disease, but their efficacy varies, and none are currently sufficient for commercial use. Further studies are needed to better understand all aspects discussed in this manuscript, with the goal of improving diagnosis, treatment, and disease control. It is important to note that this manuscript does not delve into in-depth knowledge of the discussed aspects; rather, it provides an overview of the different methodologies related to these three aspects of parasitic disease.

Inverse α-Effect as the Ariadne's Thread on the Way to Tricyclic Aminoperoxides: Avoiding Thermodynamic Traps in the Labyrinth of Possibilities

Stable tricyclic aminoperoxides can be selectively assembled via a catalyst-free three-component condensation of β,δ'-triketones, H₂O₂, and an NH-group source such as aqueous ammonia or ammonium salts. This procedure is scalable and can produce gram quantities of tricyclic heterocycles, containing peroxide, nitrogen, and oxygen cycles in one molecule. Amazingly, such complex tricyclic molecules are selectively formed despite the multitude of alternative reaction routes, via equilibration of peroxide, hemiaminal, monoperoxyacetal, and peroxyhemiaminal functionalities! The reaction is initiated by the "stereoelectronic frustration" of H₂O₂ and combines elements of thermodynamic and kinetic control with a variety of mono-, bi-, and tricyclic structures evolving under the conditions of thermodynamic control until they reach a kinetic wall created by the inverse α-effect, that is, the stereoelectronic penalty for the formation of peroxycarbenium ions and related transition states. Under these conditions, the reaction stops before reaching the most thermodynamically stable products at a stage where three different heterocycles are assembled and fused at the acyclic precursor frame.

Development of Biodegradable Delivery Systems Containing Novel 1,2,4-Trioxolane Based on Bacterial Polyhydroxyalkanoates

In this work, delivery systems in the form of microparticles and films containing 1,2,4-trioxolane (ozonide, OZ) based on polyhydroxyalkanoates (PHAs) were developed. Main systems’ characteristics were investigated: the particle yield, average diameter, zeta potential, surface morphology, loading capacity, and drug release profile of microparticles, as well as surface morphology and release profiles of OZ-containing films. PHA-based OZ-loaded microparticles have been found to have satisfactory size, zeta potential, and ozonide loading-release behavior. It was noted that OZ content influenced the surface morphology of obtained systems.

Marriage of Peroxides and Nitrogen Heterocycles: Selective Three-Component Assembly, Peroxide-Preserving Rearrangement, and Stereoelectronic Source of Unusual Stability of Bridged Azaozonides

Stable bridged azaozonides can be selectively assembled via a catalyst-free three-component condensation of 1,5-diketones, hydrogen peroxide, and an NH-group source such as aqueous ammonia or ammonium salts. This procedure is scalable and can produce gram quantities of bicyclic stereochemically rich heterocycles. The new azaozonides are thermally stable and can be stored at room temperature for several months without decomposition and for at least 1 year at -10 °C. The chemical stability of azaozonides was explored for their subsequent selective transformations including the first example of an aminoperoxide rearrangement that preserves the peroxide group. The amino group in aminoperoxides has remarkably low nucleophilicity and does not participate in the usual amine alkylation and acylation reactions. These observations and the 15 pK_a units decrease in basicity in comparison with a typical dialkyl amine are attributed to the strong hyperconjugative n_N→σ*_C-O interaction with the two antiperiplanar C-O bonds. Due to the weakness of the complementary n_O→σ*_C-N donation from the peroxide oxygens (a consequence of "inverse α-effect"), this interaction depletes electron density from the NH moiety, protects it from oxidation, and makes it similar in properties to an amide.

Drug resistance in liver flukes

Liver flukes include Fasciola hepatica, Fasciola gigantica, Clonorchis sinensis, Opisthorchis spp., Fascioloides magna, Gigantocotyle explanatum and Dicrocoelium spp. The two main species, F. hepatica and F. gigantica, are major parasites of livestock and infections result in huge economic losses. As with C. sinensis, Opisthorchis spp. and Dicrocoelium spp., they affect millions of people worldwide, causing severe health problems. Collectively, the group is referred to as the Food-Borne Trematodes and their true significance is now being more widely recognised. However, reports of resistance to triclabendazole (TCBZ), the most widely used anti-Fasciola drug, and to other current drugs are increasing. This is a worrying scenario. In this review, progress in understanding the mechanism(s) of resistance to TCBZ is discussed, focusing on tubulin mutations, altered drug uptake and changes in drug metabolism. There is much interest in the development of new drugs and drug combinations, the re-purposing of non-flukicidal drugs, and the development of new drug formulations and delivery systems; all this work will be reviewed. Sound farm management practices also need to be put in place, with effective treatment programmes, so that drugs can be used wisely and their efficacy conserved as much as is possible. This depends on reliable advice being given by veterinarians and other advisors. Accurate diagnosis and identification of drug-resistant fluke populations is central to effective control: to determine the actual extent of the problem and to determine how well or otherwise a treatment has worked; for research on establishing the mechanism of resistance (and identifying molecular markers of resistance); for informing treatment options; and for testing the efficacy of new drug candidates. Several diagnostic methods are available, but there are no recommended guidelines or standardised protocols in place and this is an issue that needs to be addressed.

Catalyst Development for the Synthesis of Ozonides and Tetraoxanes Under Heterogeneous Conditions: Disclosure of an Unprecedented Class of Fungicides for Agricultural Application

The catalyst H_3+x PMo_12-x ⁺⁶ Mo_x ⁺⁵ O₄₀ supported on SiO₂ was developed for peroxidation of 1,3- and 1,5-diketones with hydrogen peroxide with the formation of bridged 1,2,4,5-tetraoxanes and bridged 1,2,4-trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5-tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim-methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.

Exogenous Iron Increases Fasciocidal Activity and Hepatocellular Toxicity of the Synthetic Endoperoxides OZ78 and MT04

The synthetic peroxides OZ78 and MT04 recently emerged as fasciocidal drug candidates. However, the effect of iron on fasciocidal activity and hepatocellular toxicity of these compounds is unknown. We investigated the in vitro fasciocidal activity and hepatocellular toxicity of OZ78 and MT04 in absence and presence of Fe(II)chloride and hemin, and conducted a toxicological study in mice. Studies were performed in comparison with the antimalarial artesunate (AS), a semisynthetic peroxide. Fasciocidal effects of OZ78 and MT04 were confirmed and enhanced by Fe²⁺ or hemin. In HepG2 cells, AS reduced cellular ATP and impaired membrane integrity concentration-dependently. In comparison, OZ78 or MT04 were not toxic at 100 µM and reduced the cellular ATP by 13% and 19%, respectively, but were not membrane-toxic at 500 µM. The addition of Fe²⁺ or hemin increased the toxicity of OZ78 and MT04 significantly. AS inhibited complex I, II, and IV of the mitochondrial electron transport chain, and MT04 impaired complex I and II, whereas OZ78 was not toxic. All three compounds increased cellular reactive oxygen species (ROS) concentration-dependently, with a further increase by Fe²⁺ or hemin. Mice treated orally with up to 800 mg OZ78, or MT04 showed no relevant hepatotoxicity. In conclusion, we confirmed fasciocidal activity of OZ78 and MT04, which was increased by Fe²⁺ or hemin. OZ78 and MT04 were toxic to HepG2 cells, which was explained by mitochondrial damage associated with ROS generation in the presence of iron. No relevant hepatotoxicity was observed in mice in vivo, possibly due to limited exposure and/or high antioxidative hepatic capacity.

Artesunate-modified nano-graphene oxide for chemo-photothermal cancer therapy

Poor water-solubility of artesunate (ARS) hampers its clinical application. We here covalently linked ARS to PEGylated nanographene oxide (nGO-PEG) to obtain ARS-modified nGO-PEG (nGO-PEG-ARS) with excellent photothermal effect and dispersibility in physiological environment. nGO-PEG-ARS induced reactive oxygen species (ROS) and peroxynitrite (ONOO─) generations. Although nGO-PEG with near-infrared (NIR) irradiation did not induce cytotoxicity, the photothermal effect of nGO-PEG under NIR irradiation enhanced not only cell uptake but also ONOO─ generation of nGO-PEG-ARS, resulting in the synergistic chemo-photothermal effect of nGO-PEG-ARS in killing HepG2 cells. Pretreatment with Fe(III) 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato chloride (FeTTPS, a ONOO─ scavenger) instead of antioxidant N-Acetyle-Cysteine (NAC, an ROS scavenger) significantly blocked the cytotoxicity of nGO-PEG-ARS with or without NIR irradiation, demonstrating that ONOO─ instead of ROS dominated the synergistic chemo-photothermal anti-cancer action of nGO-PEG-ARS. nGO-PEG-ARS with NIR irradiation resulted in a complete tumor cure within 15 days earlier than other treatment groups, and did not induce apparent histological lesion for the mice treated with nGO-PEG-ARS with or without NIR irradiation for 30 days, further proving the synergistic chemo-photothermal anti-cancer effect of nGO-PEG-ARS. Collectively, nGO-PEG-ARS is a versatile nano-platform for multi-modal synergistic cancer therapy.

Transcriptome profiling of gene expression during immunisation trial against Fasciola hepatica: identification of genes and pathways involved in conferring immunoprotection in a murine model

BACKGROUND

Fasciolosis remains a significant food-borne trematode disease causing high morbidity around the world and affecting grazing animals and humans. A deeper understanding concerning the molecular mechanisms by which Fasciola hepatica infection occurs, as well as the molecular basis involved in acquiring protection is extremely important when designing and selecting new vaccine candidates. The present study provides a first report of microarray-based technology for describing changes in the splenic gene expression profile for mice immunised with a highly effective, protection-inducing, multi-epitope, subunit-based, chemically-synthesised vaccine candidate against F. hepatica.

METHODS

The mice were immunised with synthetic peptides containing B- and T-cell epitopes, which are derived from F. hepatica cathepsin B and amoebapore proteins, as novel vaccine candidates against F. hepatica formulated in an adjuvant adaptation vaccination system; they were experimentally challenged with F. hepatica metacercariae. Spleen RNA from mice immunised with the highest protection-inducing synthetic peptides was isolated, amplified and labelled using Affymetrix standardised protocols. Data was then background corrected, normalised and the expression signal was calculated. The Ingenuity Pathway Analysis tool was then used for analysing differentially expressed gene identifiers for annotating bio-functions and constructing and visualising molecular interaction networks.

RESULTS

Mice immunised with a combination of three peptides containing T-cell epitopes induced high protection against experimental challenge according to survival rates and hepatic damage scores. It also induced differential expression of 820 genes, 168 genes being up-regulated and 652 genes being down-regulated, p value <0.05, fold change ranging from -2.944 to 7.632. A functional study of these genes revealed changes in the pathways related to nitric oxide and reactive oxygen species production, Interleukin-12 signalling and production in macrophages and Interleukin-8 signalling with up-regulation of S100 calcium-binding protein A8, Matrix metallopeptidase 9 and CXC chemokine receptor 2 genes.

CONCLUSION

The data obtained in the present study provided us with a more comprehensive overview concerning the possible molecular pathways implied in inducing protection against F. hepatica in a murine model, which could be useful for evaluating future vaccine candidates.

Ultrastructural changes to the tegumental system and gastrodermal cells of adult Fasciola hepatica following treatment in vivo with a commercial preparation of myrrh (Mirazid)

An in vivo study in the laboratory rat model has been carried out to monitor changes to the tegument and gut of adult Fasciola hepatica following treatment with myrrh ('Mirazid'). Rats infected with the triclabendazole-resistant Dutch isolate were dosed orally with Mirazid at a concentration of 250 mg/kg and flukes recovered 2, 3 and 7 days post-treatment (pt). The flukes were processed for examination by scanning and transmission electron microscopy. A variety of changes to the external surface were observed, culminating in the sloughing of the tegumental syncytium. Internal changes to the syncytium and tegumental cell bodies were more severe and were evident from 2 days pt onwards. Swelling of the basal infolds (leading to flooding of the surface layer) and a decline in secretory body production were the major changes seen. The gastrodermal cells were less severely affected than the tegument, pointing to a trans-tegumental route of uptake for Mirazid by the fluke. Some loss of muscle fibres in the main somatic muscle layers was observed, which may be correlated with the decline in movement of flukes seen at recovery.

Rearrangements of organic peroxides and related processes

This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O-O-bond cleavage. Detailed information about the Baeyer-Villiger, Criegee, Hock, Kornblum-DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.

Disruption of spermatogenesis in the liver fluke, Fasciola hepatica by two artemisinin derivatives, artemether and artesunate

An in vivo study in the laboratory rat model has been carried out to monitor changes to the spermatogenic cells in the testis tubules of adult Fasciola hepatica following treatment with the artemisinins, artemether and artesunate. Rats infected with the triclabendazole (TCBZ)-resistant Sligo isolate were dosed orally with artemether at a concentration of 200 mg/kg and flukes recovered at 24, 48 and 72 h post treatment (pt). Rats infected with the TCBZ-resistant Oberon isolate were dosed orally with artesunate at a concentration of 200 mg/kg and flukes recovered 24, 48, 72 and 96 h pt. The flukes were processed for histological and transmission electron microscope (TEM) examination. Changes to the spermatogenic cells were evident at 24 h pt with artemether. The spermatogonial and spermatocyte cells contained abnormal mitochondria, there were fewer spermatids and spermatozoa in the tubules than normal, and a number of cells showed signs of apoptosis. There was a further decline in cell numbers at 48 h pt and the organization of the spermatocyte and spermatid rosettes was atypical. Sperm formation had become abnormal and those spermatozoa present possessed only a single axoneme. By 72 h pt, the testis tubules were vacuolated and filled with abnormal cells and cell debris. Only spermatogonial cells could be identified and there was widespread evidence of apoptosis in the cells. Distinct cellular changes following artesunate treatment did not become apparent until 48 h pt. The changes seen were similar to those described for artemether, but were generally less severe at matching time-periods. The fine structural changes occurring in the spermatogenic cells were compared to those observed in other cell types and fluke tissues and the overall information was collated to identify the cellular targets for artemisinin action and to establish the time-line for drug action.

A comparative study on the impact of two artemisinin derivatives, artemether and artesunate, on the female reproductive system of Fasciola hepatica

An in vivo study in the laboratory rat model has been carried out to monitor changes to the female reproductive system in adult Fasciola hepatica following treatment with the artemisinins, artemether and artesunate. Rats infected with the triclabendazole (TCBZ)-resistant Sligo isolate were dosed orally with artemether at a concentration of 200mg/kg and flukes recovered at 24, 48 and 72 h post-treatment (pt). Rats infected with the TCBZ-resistant Oberon isolate were dosed orally with artesunate at a concentration of 200mg/kg and flukes recovered 24, 48, 72 and 96 h pt. The flukes were processed for histological and transmission electron microscope (TEM) examination of the uterus, Mehlis' gland, ovary and vitellaria. After treatment with artemether, egg production had become abnormal by 72 h pt, with free vitelline cells and masses of shell protein material within the uterus; spermatozoa were absent. The Mehlis' gland and ovary retained a normal morphology over the 3-day period. A change in the cell population in the vitelline follicles was seen at 48 h pt, with a decline in the number of immature cells. This became more marked by 72 h and the follicles became progressively vacuolated over the 3-day period. At the TEM level, there were changes in the immature vitelline cells at 24h pt, as evidenced by a decrease in shell protein production and the presence of lipid droplets and abnormal mitochondria. Spaces in the follicles separated the cells from each other. The changes became progressively more severe with time, so that, by 72 h pt, the follicles were very disrupted, containing cells in the advanced stages of apoptotic breakdown. In extreme cases, the follicles were scarcely recognisable and had become filled with cellular debris. Fine structural changes to the vitelline cells induced by artesunate treatment were similar to those described for artemether, but generally occurred more quickly and were greater; this was particularly true of the swelling of the ger cisternae. Overall, the results have shown that artemisinin treatment has a severe impact on egg production by TCBZ-resistant flukes, an effect that is mediated by disruption of the vitelline cells.

Manganese triacetate as an efficient catalyst for bisperoxidation of styrenes

Bisperoxidation of styrenes with tert-butyl hydroperoxide in the presence of a catalytic amount of Mn(OAc)₃.

Repurposing drugs for the treatment and control of helminth infections

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Drug repurposing continues to be the central drug discovery strategy for helminths.

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Most repurposed drugs come from veterinary medicine and known drug classes.

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Only a handful of drugs have advanced clinically.

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More collaborations and funding are needed to advance discoveries to the market.

Helminth infections are responsible for a considerable public health burden, yet the current drug armamentarium is small. Given the high cost of drug discovery and development, the high failure rates and the long duration to develop novel treatments, drug repurposing circumvents these obstacles by finding new uses for compounds other than those they were initially intended to treat. In the present review, we summarize in vivo and clinical trial findings testing clinical candidates and marketed drugs against schistosomes, food-borne trematodes, soil-transmitted helminths, Strongyloides stercoralis, the major human filariases lymphatic filariasis and onchocerciasis, taeniasis, neurocysticercosis and echinococcosis. While expanding the applications of broad-spectrum or veterinary anthelmintics continues to fuel alternative treatment options, antimalarials, antibiotics, antiprotozoals and anticancer agents appear to be producing fruitful results as well. The trematodes and nematodes continue to be most investigated, while cestodal drug discovery will need to be accelerated. The most clinically advanced drug candidates include the artemisinins and mefloquine against schistosomiasis, tribendimidine against liver flukes, oxantel pamoate against trichuriasis, and doxycycline against filariasis. Preclinical studies indicate a handful of promising future candidates, and are beginning to elucidate the broad-spectrum activity of some currently used anthelmintics. Challenges and opportunities are further discussed.

Efficacy and safety of artemether in the treatment of chronic fascioliasis in Egypt: exploratory phase-2 trials

Background

Fascioliasis is an emerging zoonotic disease of considerable veterinary and public health importance. Triclabendazole is the only available drug for treatment. Laboratory studies have documented promising fasciocidal properties of the artemisinins (e.g., artemether).

Methodology

We carried out two exploratory phase-2 trials to assess the efficacy and safety of oral artemether administered at (i) 6×80 mg over 3 consecutive days, and (ii) 3×200 mg within 24 h in 36 Fasciola-infected individuals in Egypt. Efficacy was determined by cure rate (CR) and egg reduction rate (ERR) based on multiple Kato-Katz thick smears before and after drug administration. Patients who remained Fasciola-positive following artemether dosing were treated with single 10 mg/kg oral triclabendazole. In case of treatment failure, triclabendazole was re-administered at 20 mg/kg in two divided doses.

Principal Findings

CRs achieved with 6×80 mg and 3×200 mg artemether were 35% and 6%, respectively. The corresponding ERRs were 63% and nil, respectively. Artemether was well tolerated. A high efficacy was observed with triclabendazole administered at 10 mg/kg (16 patients; CR: 67%, ERR: 94%) and 20 mg/kg (4 patients; CR: 75%, ERR: 96%).

Conclusions/Significance

Artemether, administered at malaria treatment regimens, shows no or only little effect against fascioliasis, and hence does not represent an alternative to triclabendazole. The role of artemether and other artemisinin derivatives as partner drug in combination chemotherapy remains to be elucidated.

Fasciola hepatica and F. gigantica are two liver flukes that parasitize herbivorous large size mammals (e.g., sheep and cattle), as well as humans. A single drug is available to treat infections with Fasciola flukes, namely, triclabendazole. Recently, laboratory studies and clinical trials in sheep and humans suffering from acute fascioliasis have shown that artesunate and artemether (drugs that are widely used against malaria) also show activity against fascioliasis. Hence, we were motivated to assess the efficacy and safety of oral artemether in patients with chronic Fasciola infections. The study was carried out in Egypt and artemether administered according to two different malaria treatment regimens. Cure rates observed with 6×80 mg and 3×200 mg artemether were 35% and 6%, respectively. In addition, high efficacy was observed when triclabendazole, the current drug of choice against human fascioliasis, was administered to patients remaining Fasciola positive following artemether treatment. Concluding, monotherapy with artemether does not represent an alternative to triclabendazole against fascioliasis, but its role in combination chemotherapy regimen remains to be investigated.

Development and validation of a liquid chromatography and ion spray tandem mass spectrometry method for the quantification of artesunate, artemether and their major metabolites dihydroartemisinin and dihydroartemisinin-glucuronide in sheep plasma

Recently, promising fasciocidal activities of artesunate and artemether were described in rats and sheep. Therefore, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to quantify artesunate, artemether and their metabolites dihydroartemisinin and dihydroartemisinin-glucuronide in sheep plasma. Protein precipitation with methanol was used for sample workup. Reversed-phase high-performance liquid chromatography (HPLC) was performed using an Atlantis C18 analytical column with a mobile phase gradient system of ammonium formate and acetonitrile. The analytes were detected by MS/MS using selected reaction monitoring (SRM) with electrospray ionisation in the positive mode (transition m/z 267.4 → 163.0). The analytical range for dihydroartemisinin, dihydroartemisinin-glucuronide and artesunate was 10-1000 ng/ml and for artemether 90-3000 ng/ml with a lower limit of quantification of 10 and 90 ng/ml, respectively. Inter- and intra-day accuracy and precision deviations were < 10%. Consistent relative recoveries (60-80%) were observed over the investigated calibration range for all analytes. All analytes were stable in the autosampler for at least 30 h (6 °C) and after three freeze and thaw cycles. The validation results demonstrated that the LC-MS/MS method is precise, accurate and selective and can be used for the determination of the artemisinins in sheep plasma. The method was applied successfully to determine the pharmacokinetic parameters of artesunate and its metabolites in plasma of intramuscularly treated sheep.

The drugs we have and the drugs we need against major helminth infections

Parasitic worms (helminths) have accompanied humans for thousands of years and, still today, they are pervasive where poverty persists, including large parts of Southeast Asia and the Western Pacific Region. The global strategy for the control of helminth infections is morbidity control and elimination as a public health problem. Regular administration of anthelminthic drugs to at-risk populations (e.g. school-aged children) serves as the backbone of interventions in areas where helminth infections are highly endemic. In this review, we focus on soil-transmitted helminthiasis (ascariasis, hookworm disease, strongyloidiasis and trichuriasis) and food-borne trematodiasis (clonorchiasis, fascioliasis, intestinal fluke infections, opisthorchiasis and paragonimiasis) and discuss the few drugs that are currently available for their treatment and control. Emphasis is placed on efficacy with new light shed on multiple dosing and combination therapy. We summarise recent advances made with anthelminthic drugs that might become the future armentarium for the control of major helminthiasis (e.g. artemisinins, cyclooctadepsipeptides, mefloquine, monepantel, nitazoxandide, synthetic peroxides and tribendimidine). Issuing from our review are current research gaps and the need for concerted efforts to discover, develop and deploy the next generation of anthelminthic drugs.

In vivo and in vitro sensitivity of Fasciola hepatica to triclabendazole combined with artesunate, artemether, or OZ78

Triclabendazole resistance is continually documented from livestock, and hence new treatment strategies for Fasciola hepatica infections are needed. We investigated the effect of triclabendazole combined with artesunate, artemether, or OZ78 compared to that of monotherapy against adult and juvenile F. hepatica in rats. In vitro experiments with triclabendazole and its sulfoxide and sulfone metabolites, each in combination with the peroxides, complemented our study. F. hepatica-infected rats were subjected to single drugs or drug combinations 3 to 4 weeks (juvenile flukes) and >8 weeks (adult flukes) postinfection. Negative binomial regressions of worm and egg counts were used to analyze dose-response relationships and whether the effects of drug combinations were synergistic or antagonistic. The in vitro assays were evaluated by means of viability scales based on fluke motility. Fifty percent effective dose values of 113.0, 77.7, 22.9, and 2.7 mg/kg of body weight were calculated for monotherapy with artesunate, artemether, OZ78, and triclabendazole, respectively, against adult F. hepatica. Likelihood ratio tests revealed synergistic interactions (P < 0.05) of combinations of triclabendazole (2.5 mg/kg) plus artesunate or artemether on adult worm burden. Antagonistic effects on the adult burden and egg output were observed when a lower triclabendazole dose (1.25 mg/kg) was combined with the artemisinins. No significant interactions (P = 0.07) were observed for OZ78 and triclabendazole combinations and between the triclabendazole effect and the effects of the other partner drugs on juvenile worms. Our in vitro studies of adult worms agreed with the in vivo results, while the in vitro analysis of juvenile worms revealed greater interactions than observed in vivo. In conclusion, single-agent triclabendazole demonstrated a more potent in vivo and in vitro fasciocidal activity than the experimental drugs artesunate, artemether, and OZ78. When combined, synergistic but also antagonistic effects depending on the doses administered were observed, which should be elucidated in more detail in future studies.