BackgroundSchistosomiasis 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.MethodsIn 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.ResultsWhile 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.ConclusionsOur 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.

Strongyloides stercoralis is a soil-transmitted helminth affecting an estimated 30−100 million people. Since the infection may be severe and life-threatening, accessible and effective treatment is pivotal. Currently, ivermectin is the drug of choice but has limitations. Moxidectin, a veterinary anthelminthic approved for use in human onchocerciasis, is a promising drug alternative against strongyloidiasis. In this study, we evaluated the in vitro activity of moxidectin on Strongyloides ratti larvae (L 3 ) and adult females and the activity as well as the pharmacokinetics of moxidectin in S. ratti infected rats. In vitro, moxidectin had an activity that was similar to that of ivermectin, with median lethal concentration values for L 3 and adults in the range of 0.08− 1.44 μM, after 72 h of exposure. In vivo, doses of 250, 500, and 750 μg/kg of moxidectin resulted in a reduction of the worm burden ranging from 48.5 to 75%. At the highest dose (750 μg/kg) we observed a maximal blood concentration of 50.3 ng/mL and an area under the curve of 895.2 ng × h/mL. The half-life in rats was 9 h, and moxidectin was cleared to undetectable blood levels within 7 d (<10 ng/mL). No exposure-response relationship was observed. This work contributes to the characterization of moxidectin in the treatment of S. ratti as a model of Strongyloides spp. and, as such, supports moving moxidectin further along the drug development pipeline in the treatment of human strongyloidiasis.

Background Schistosomiasis affects over 200 million people worldwide but only praziquantel is available for treatment and control. Drug discovery is often based on phenotypic drug screening, involving different parasite stages retrieved from infected mice. Aiming to reduce animal use, we validated an in vitro growth method for juvenile Schistosoma mansoni for the purpose of drug sensitivity assays. Methodology/Principal findings We compared inter–batch variability of serum, worm size and organ development, gender distribution, and drug sensitivity between in vitro and in vivo grown worms over different life stages. In vitro developed S. mansoni in Hybridoma medium supplemented with 20% human serum were similar in size as in vivo worms until 28 days of incubation (males 1.4 ± 0.2 mm, females 1.1 ± 0.5 mm long). qPCR analysis revealed similar gender distribution both on newly transformed schistosomula and worms grown for 21 days. Worms developed in vitro and in vivo were similarly sensitive to praziquantel from 7 to 35 days of development with the exception of 21 days of development, where a slightly lower activity was observed for the in vitro grown worms (IC50: 0.54 μM in vitro, 0.14 μM in vivo 72 hours post-incubation). The evaluation of five additional drugs revealed a similar sensitivity at the 72 hours evaluation time point, with the exception of mefloquine, where we observed a 10-fold lower sensitivity on in vitro developed schistosomes when compared to in vivo grown (IC50: 4.43 μM in vitro, 0.48 μM in vivo). Conclusion A large number of juvenile S. mansoni worms can be grown in vitro, which show similar drug sensitivity, gender distribution, size and morphology as the worms recovered from rodents, supporting the use of this method in drug screening efforts.

Schistosomiasis is ad iseaseo fp overty affecting millionso fp eople. Praziquantel (PZQ),w ith its strengths and weaknesses, is the only treatment available. We previously reported findings on three lead compounds derivedfrom oxamniquine (OXA), an old antischistosomald rug:f errocene-containing (Fc-CH 2-OXA),r uthenocene-containing (Rc-CH 2-OXA) and benzene-containing (Ph-CH 2-OXA) OXA derivatives. These derivatives showed excellent in vitro activity againstb oth Schistosoma mansoni larvae and adult worms and S. haematobium adult worms, and were also active in vivo against adult S. mansoni. Encouraged by these promising results, we conducteda dditional in-depthp reclinical studiesa nd report in this investigation on metabolic stability studies, in vivos tudies on S. haematobium and juvenile S. mansoni,c omputational simulations,a nd formulation development. Molecular dynamicss imulations supportedt he in vitro results on the target protein. Though all three compounds were poorly stable within an acidic environment, they were only slightly cleared in the in vitro liver model. This is likely the reasonw hy the promising in vitro activity did not translate into in vivo activityo nS. haematobium. This limitation could not be overcome by the formulation of lipid nanocapsules as aw ay to improve the in vivo activity. Further studies should focus on increasing the compound's bioavailability,t or each an active concentration in the microenvironment of the parasite.

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<div>Schistosomiasis is a disease of poverty affecting millions of people. Praziquantel (PZQ), with its </div><div>strengths and weaknesses, is the only treatment available. We previously reported 3 lead </div><div>compounds derived from oxamniquine (OXA), an old antischistosomal drug: ferrocene‐containing </div><div>(Fc‐CH2‐OXA), ruthenocene‐containing (Rc‐CH2‐OXA) and benzene‐containing (Ph‐CH2‐OXA). </div><div>These derivatives showed excellent in vitro activity against both Schistosoma mansoni and S. </div><div>haematobium larvae and adult worms, and in vivo against S. mansoni. Encouraged by these </div><div>promising results, we followed a guided drug discovery process and report in this investigation on </div><div>metabolic stability studies, in vivo studies, computational simulations, and formulation studies. </div><div>Molecular dynamics simulations supported the in vitro results on the target protein. Though all </div><div>three compounds were poorly stable within an acidic environment, they were only slightly cleared </div><div>in the in vitro liver model. This is likely the reason as to why the promising in vitro activity did not </div><div>translate to in vivo activity. This limitation could not be saved by the formulation of lipid </div><div>nanocapsules as an intent to improve the in vivo activity. Further studies should focus on increasing </div><div>the compound’s bioavailability, in order to reach an active concentration in the parasite’s </div><div>microenvironment. </div>