Effect of single-dose oral artemether and tribendimidine on the tegument of adult Clonorchis sinensis in rats

Molluscicidal and Larvicidal Potency of N-Heterocylic Analogs against Biomophalaria alexandrina Snails and Schistosoma mansoni Larval Stages

This work describes the synthesis of quinoline-based N--heterocyclic arenes and their biological evaluation as molluscicides against adult Biomophalaria alexandrina snails as well as larvicides against Schistosoma mansoni larvae (miracidia and cercariae). Molecular docking studies were demonstrated to investigate their affinity for cysteine protease protein as an interesting target for antiparasitics. Compound AEAN showed the best docking results followed by APAN in comparison to the co-crystallized ligand D1R reflected by their binding affinities and RMSD values. The egg production, hatchability of B. alexandrina snails and ultrastructural topography of S. mansoni cercariae using SEM were assessed. Biological evaluations (hatchability and egg-laying capacity) revealed that the quinoline hydrochloride salt CAAQ was the most effective compound against adult B. alexandrina snails, whereas the indolo-quinoline derivative APAN had the most efficiency against miracidia, and the acridinyl derivative AEAA was the most effective against cercariae and caused 100% mortality. CAAQ and AEAA were found to modulate the biological responses of B. alexandrina snails with/without S. mansoni infection and larval stages that will affect S. mansoni infection. AEAA caused deleterious morphological effects on cercariae. CAAQ caused inhibition in the number of eggs/snail/week and reduced reproductive rate to 43.8% in all the experimental groups. CAAQ and AEAA can be recommended as an effective molluscicide of plant origin for the control program of schistosomiasis.

From awareness to action: NIPD's engagement in the control of food-borne clonorchiasis

Clonorchiasis is caused by ingestion of raw freshwater fish containing infective larvae of Clonorchis sinensis. China harbours the largest number of people with C. sinensis infection. During the past three decades, the National Institute of Parasitic Diseases, affiliated to the Chinese Center for Disease Control and Prevention (NIPD) conducted many studies to facilitate the control on clonorchiasis. Three national surveys have shown the updated epidemiology of clonorchiasis in China. Recently, a national surveillance system has also been established, which will enable the production of high-resolution map. The evaluation of the disease burden has enhanced the awareness on clonorchiasis. Diverse diagnosis techniques including rapid screening by questionnaire, serological tests, faecal examination and a molecular method have been developed or evaluated. The NIPD also participated in the early evaluation of praziquantel against clonorchiasis, which enhanced its application in China. Also, the NIPD has verified the efficacy of tribendimidine against clonorchiasis. A new sustainable strategy is also being explored. However, more research is expected to further facilitate control of clonorchiasis in China, as well as international cooperation in fighting human liver fluke infections in Asia.

A study of tribendimidine effects in vitro and in vivo on the liver fluke Opisthorchis felineus

Background

The food-borne liver fluke Opisthorchis felineus is an epidemiologically important species and the causative agent of opisthorchiasis across an extensive territory of Eurasia. For decades, treatment of opisthorchiasis has been based on praziquantel. Tribendimidine could be an alternative drug that has been successfully tested for Opisthorchis viverrini and Clonorchis sinensis infections. We aimed to assess tribendimidine effects in comparison with praziquantel in vivo and in vitro against the liver fluke Opisthorchis felineus.

Results

In this study we (i) calculated half-maximal inhibitory concentrations (IC₅₀) by motility tests against O. felineus adults and newly excysted metacercarie after tribendimidine treatment in vitro; (ii) determined whether tribendimidine and PZQ effects on adult liver flukes are dependent on or mediated by white blood cells; and (iii) tested in vivo the anthelmintic activity of tribendimidine on juvenile and adult worms. We found that the efficiency of tribendimidine in vitro was similar (IC₅₀ = 0.23 μM for newly excysted metacercariae and 0.19 μM for adult worms) to that of praziquantel (IC₅₀ 0.98 μM for newly excysted metacercariae and 0.47 μM for adult worms). The treatment of adult worms in vivo with praziquantel or tribendimidine at 400 mg/kg resulted in a 76% and 77.2% reduction, respectively, in the worm burden during chronic infection.

Conclusions

The differences between WBR values after PZQ and TBN treatment were not significant, thus tribendimidine was as effective as praziquantel against O. felineus liver flukes. Given the broad-spectrum activity of tribendimidine and efficacy against O. felineus, this drug may be a promising candidate for the treatment of opisthorchiasis felinea and other liver fluke infections.

Great efficacy of sulfachloropyrazine-sodium against acute murine toxoplasmosis

OBJECTIVE

To identify more effective and less toxic drugs to treat animal toxoplasmosis.

METHODS

Efficacy of seven kinds of sulfonamides against Toxoplasma gondii (T. gondii) in an acute murine model was evaluated. The mice used throughout the study were randomly assigned to many groups (10 mice each), which either remained uninfected or were infected intraperitoneally with tachyzoites of T. gondii (strains RH and CN). All groups were then treated with different sulfonamides and the optimal treatment protocol was determined candidates. Sulfadiazine-sodium (SD) was used for comparison.

RESULTS

The optimal therapy involved gavaging mice twice per day with 250 mg/kg bw of sulfachloropyrazine-sodium (SPZ) for five days. Using this protocol, the average survival time and the time-point of 50% fatalities were prolonged significantly compared with SD treatment. Treatment with SPZ protected 40% of mice from death, and the heart and kidney tissue of these animals was parasite-free, as determined by nested-PCR. SPZ showed excellent therapeutic effects in the treatment of T. gondii in an acute murine model and is therefore a promising drug candidate for the treatment and prevention of T. gondii in animals.

CONCLUSIONS

It can be concluded that the effective drug sulfachloropyrazine may be the new therapeutic options against animal toxoplasmosis.

Schistosomiasis chemotherapy

After malaria, schistosomiasis (or bilharzia) is the second most prevalent disease in Africa, and is occurring in over 70 countries in tropical and subtropical regions. It is estimated that 600 million people are at risk of infection, 200 million people are infected, and at least 200,000 deaths per year are associated with the disease. All schistosome species are transmitted through contact with fresh water that is infested with free-swimming forms of the parasite, which is known as cercariae and produced by snails. When located in the blood vessels of the host, larval and adult schistosomes digest red cells to acquire amino acids for growth and development. Vaccine candidates have been unsuccessful up to now. Against such devastating parasitic disease, the antischistosomal arsenal is currently limited to a single drug, praziquantel, which has been used for more than 35 years. Because the question of the reduction of the activity of praziquantel was raised recently, it is thus urgent to create new and safe antischistosomal drugs that should be combined with praziquantel to develop efficient bitherapies.

Advances with the Chinese anthelminthic drug tribendimidine in clinical trials and laboratory investigations

The anthelminthic drug tribendimidine has been approved by Chinese authorities for human use in 2004, and a first comprehensive review was published in Acta Tropica in 2005. Here, we summarise further advances made through additional clinical trials and laboratory investigations. Two phase IV trials have been conducted in the People's Republic of China, the first one enrolling 1292 adolescents and adults aged 15-70 years and the second one conducted with 899 children aged 4-14 years who were infected with one or multiple species of soil-transmitted helminths. Oral tribendimidine (single 400mg enteric-coated tablet given to adolescents/adults and 200mg to children) showed high cure rates against Ascaris lumbricoides (90.1-95.0%) and moderate-to-high cure rates against hookworm (82.0-88.4%). Another trial done in school-aged children using a rigorous diagnostic approach found a cure rate against hookworm of 76.5%. A single oral dose of tribendimidine showed only low cure rates against Trichuris trichiura (23.9-36.8%) confirming previous results. Tribendimidine administered to children infected with Enterobius vermicularis (two doses of 200mg each on consecutive days) resulted in a high cure rate (97.1%). Importantly, a series of randomised, exploratory trials revealed that tribendimidine shows interesting activity against the liver flukes Opisthorchis viverrini and Clonorchis sinensis, the tapeworm Taenia spp. and the threadworm Strongyloides stercoralis with respective cure rates of 70.0%, 40.0%, 53.3% and 36.4%. Pharmacokinetic studies in healthy Chinese volunteers indicated that after oral administration of tribendimidine, no parent drug was detected in plasma, but its primary metabolite, p-(1-dimethylamino ethylimino) aniline (aminoamidine, deacylated amidantel) (dADT), was found in plasma. dADT is then further metabolised to acetylated dADT (AdADT). dADT exhibits activity against several species of hookworm and C. sinensis in experimental studies, similar to that of tribendimidine. First studies elucidating the mechanism of action suggested that tribendimidine is an L-type nicotinic acetylcholine receptor agonist. Additional experimental studies revealed that the anti-parasite spectrum of tribendimidine is very broad. Indeed, to date, activity has been documented against 20 different nematode, trematode and cestode species. Taken together, tribendimidine warrants further scientific inquiry, including more comprehensive toxicity appraisals, mechanism of action studies and clinical investigation as it holds promise as a broad spectrum anthelminthics.

Antischistosomal activity of trioxaquines: in vivo efficacy and mechanism of action on Schistosoma mansoni

Schistosomiasis is among the most neglected tropical diseases, since its mode of spreading tends to limit the contamination to people who are in contact with contaminated waters in endemic countries. Here we report the in vitro and in vivo anti-schistosomal activities of trioxaquines. These hybrid molecules are highly active on the larval forms of the worms and exhibit different modes of action, not only the alkylation of heme. The synergy observed with praziquantel on infected mice is in favor of the development of these trioxaquines as potential anti-schistosomal agents.

Schistosomiasis is a tropical disease affecting more than 200 million people throughout the sub-tropical and tropical world. The treatment and control of schistosomiasis rely on the use of a single drug, the praziquantel and no vaccine is available. However, schistosome species with low sensitivity or resistance to praziquantel have been identified in several countries. It is an urgent need to develop new drugs against this parasite. In this context, our study reports the activity the trioxaquine PA1259. PA1259 is an hybrid drug containing two pharmacophores within a single molecule: a trioxane and an aminoquinoline. Initially developed against malaria, the trioxaquines target the heme a disposal product resulting from the digestion of the hemoglobin. The first action of the trioxaquine is an alkylation of the heme with the trioxane entity, and the second action is stacking with the heme due to the aminoquinoline moiety. In this study we show that this new drug is active in vitro against all schistosome stages (cercariae, schistosomule and adult). The PA1259 is also active in vivo and shows synergistic action in association with praziquantel. This opens the route to an efficient bitherapy of a highly neglected disease.

The in vitro and in vivo effect of tribendimidine and its metabolites against Clonorchis sinensis

The purpose of the study was to understand the in vitro and in vivo effect of tribendimidine (TBD) and its metabolites of p-(1-dimethylamino ethylimino)aniline (aminoamidine, deacylated amidantel, BAY d 9216, dADT), acetylated dADT (AdADT), terephthalaldehyde (TPAL), and terephthalic acid (TPAC) against adult Clonorchis sinensis. In in vitro test, the adults of C. sinensis were placed to each of the 24 wells of a Falcon plate and maintained in Hanks' balanced salt solution-20% calf serum. Besides observation on the direct in vitro effect of TBD and its metabolites, the worms exposed to TBD and its metabolites for 1-24 h were transferred to the medium without drug and incubated continually for another 72 h. The reversible effect of TBD and its metabolites was assessed by the recovery of worm motor activity and parasite survival. In in vivo test, 235 rats were divided into five batches for oral infection of each rat with 50 C. sinensis metacercariae. Five to 6 weeks post-infection, groups of rats were treated orally or intramuscularly with a single dose of TBD or its metabolites, while untreated but infected rats served as control. All treated rats were killed 2 weeks post-treatment for assessment of efficacy. When adult C. sinensis were exposed to TBD or dADT 0.5 microg/mL, they were paralyzed rapidly accompanied by dilatation of the gut. The in vitro effect of AdADT decreased significantly, which was at least lower than 20- to 40-fold compared with TBD and dADT. TPAL and TPAC at a high concentration of 100 microg/mL exhibited no effect against adult C. sinensis. In the worms exposed to TBD or dADT 1 microg/mL for 1 h, well recovery of the worm motor activity from paralysis was seen in the medium without drug. If exposure time extended to 4-24 h before transferred to the medium without drug, few worms were dead and most worms showed very poor recovery of their activity. When the worms exposed to TBD or dADT 10 microg/mL for 1, 4, and 24 h were transferred to the drug-free medium, recovery of poor motor activity of worms or worm death was seen. In the worms exposed to AdADT 20 and 40 microg/mL for 1-24 h, more worms recovered poor motor activity in the medium without drug. In rats infected with C. sinensis and treated orally with TBD or dADT, the ED(50) and ED(95) were 20.318 and 195.358 mg/kg or 18.969 and 268.882 mg/kg. Under the equal dosages used in the treatment of rats infected with C sinensis, the effects between TBD and dADT or TBD and AdADT were similar. Intramuscular TBD or dADT at a single dose of 12.5-75 mg/kg showed effect against adult C. sinensis harbored in rats. TPAL and TPAC exhibit no effect against C sinensis harbored in rats treated orally with a higher dose of 1 g/kg. The results indicate that TBD and dADT exhibit a strong in vitro effect to paralyze the adult C. sinensis, but less in vitro effect was seen in AdADT. TBD, dADT, and AdADT exhibit similar therapeutic effect in oral treatment of rats infected with C. sinensis, and intramuscular TBD and dADT also show promising effect against C. sinensis in rats. TPAL and TPAC are ineffective metabolites of TBD.

Combination chemotherapy against Clonorchis sinensis: experiments with artemether, artesunate, OZ78, praziquantel, and tribendimidine in a rat model

Caused by the Chinese liver fluke Clonorchis sinensis, clonorchiasis is of growing public health importance. Treatment and control of the disease rely on a single drug, praziquantel, and little information regarding combination chemotherapy is available. Here, we evaluated the in vivo efficacy of praziquantel combined with artemether, artesunate, OZ78, and tribendimidine, as well as an artesunate-tribendimidine combination against C. sinensis, in a rat model. Data from previous experiments were included, and negative binomial regression analyses were carried out to determine dose-response relationships and to study the effect of drug combination. All drugs given in monotherapy were efficacious in killing the worms; doses of 16 and 70 mg/kg of body weight of artesunate, for example, reduced worm burden by 50% and 95%, respectively. Artemether and OZ78 (12.5 to 50 mg/kg) showed dose-dependent killing of worms but no significant drug interactions when given with 150 mg/kg praziquantel, suggesting independent additive effects. In contrast, artesunate and tribendimidine (12.5 to 50 mg/kg) showed synergistic interactions with 150 mg/kg praziquantel. When low doses of 3.1 and 6.25 mg/kg OZ78 and artemether, respectively, were combined with praziquantel (150 mg/kg) an increased worm survival, above the level observed with praziquantel monotherapy, was noted. A similar antagonism was seen when praziquantel (75 mg/kg) was combined with several of the companion drugs at various doses. In conclusion, in vivo efficacy of praziquantel, the artemisinins, OZ78, and tribendimidine against C. sinensis is confirmed, and combination chemotherapy with praziquantel produces synergistic and antagonistic effects depending on the doses administered. Further preclinical investigations are warranted.