Synthesis and antiplasmodial activity of regioisomers and epimers of second-generation dual acting ivermectin hybrids

Antiplasmodial and Insecticidal Activities of Third-Generation Ivermectin Hybrids

Preclinical and/or clinical studies have demonstrated the potential of Ivermectin (IVM) for malaria control. In order to improve its antiplasmodial activity and build on previous knowledge, we have designed a third generation of hybrid molecules in which selected pharmacophores were appended to the IVM macrolide, while retaining one or both sugar moieties at the C-13 position. Moreover, we synthesized IVM hybrids that contain structural features of potent IVM metabolites. The evaluation of the in vitro antiplasmodial activity of these compounds against Plasmodium berghei pre-erythrocytic stages and Plasmodium falciparum erythrocytic stages identified molecules that displayed enhanced activity against the latter when compared to IVM. Additionally, two IVM intermediates and one IVM hybrid retained the insecticidal activity of the parental molecule, clarifying the contribution of the sugar moieties to this feature. Altogether, these results provide key structure-activity relationships to guide the rational design of new generations of IVM hybrids.

Ovicidal activity of diaryl dichalcogenides and ivermectin on Fasciola hepatica: A novel candidate for a blending-based therapeutic strategy

Fasciolosis is a food and waterborne disease caused by Fasciola spp., representing a global health burden to various hosts, including humans and other animals. This study investigates the in vitro activity of tellurium- and selenium-containing diaryl dichalcogenides: diacetal ditelluride (LQ07), diacetal diselenide (LQ62), and diacetyl diselenide (LQ68) alone and in combination with ivermectin (IVM) against eggs of Fasciola hepatica. The eggs were exposed for 12 h with each organochalcogen (OC) (0.1 - 2 mmol l-1) and IVM (0.01 - 2 mmol l-1) following an incubation of 15 days, allowing embryonation. The inhibitory concentration of 50 % (IC50) of each OC or IVM was tested with the IC10, IC30, and IC50 of IVM or each OC, respectively. LQ07, LQ62, and LQ68, as well as IVM, demonstrated a concentration-dependent ovicidal activity. The peak ovicidal activity of 99.74 % was achieved when IVM was tested at 2.0 mmol l-1. LQ62 and LQ68 demonstrated greater ovicidal activity, having an IC50 < 0.32 mmol l-1 being 6.25-fold more toxic than IVM alone. The percentage of dead eggs was significantly higher in the IVM group (early mortality), as Se-containing OCs led to the (miracidia) embryonation of the eggs with no hatching (late mortality). Blending Se-containing OCs and IVM showed an additive effect of up to 27 % against F. hepatica eggs. The present data contribute to the potential use of blending-based therapeutic strategies to combat F. hepatica infections in eradication programs worldwide. The combinations may also act against multidrug-resistant strains, reinstating drug-based parasite control.

Structure-activity relationship of anticancer and antiplasmodial gold bis(dithiolene) complexes

Monoanionic gold bis(dithiolene) complexes were recently shown to display activity against ovarian cancer cells, Gram-positive bacteria, Candida strains and the rodent malaria parasite, P. berghei. To date, only monoanionic gold(III) bis(dithiolene) complexes with a thiazoline backbone substituted with small alkyl chains have been evaluated for biomedical applications. We now analyzed the influence of the length and the hydrophobicity vs. hydrophilicity of these complexes' alkyl chain on their anticancer and antiplasmodial properties. Isomer analogues of these monoanionic gold(III) bis(dithiolene) complexes, this time with a thiazole backbone, were also investigated in order to assess the influence of the nature of the heterocyclic ligand on their overall chemical and biological properties. In this report we present the total synthesis of four novel monoanionic gold(III) bis(dithiolene) complexes with a long alkyl chain and a polyoxygenated (PEG) chain aiming to improve their solubility and biological properties. Our results showed that the complexes with a PEG chain showed promising anticancer and antiplasmodial activities beside improved solubility, a key parameter in drug discovery and development.

Unexpected rearrangement of ivermectin in the synthesis of new derivatives with trypanocidal and antiplasmodial activities

Ivermectin is a sixteen-membered macrolactone "wonder drug" of Nobel prize-honored distinction that exhibits a wide range of antiparasitic activities. It has been used for almost four decades in the treatment of various parasitic diseases in humans and animals. In this paper, we describe the synthesis of the first-in-class ivermectin derivatives obtained via derivatization of the C13 position, along with the unexpected rearrangement of the oxahydrindene (hexahydrobenzofuran) unit of the macrolide ring. The structural investigation of the rearrangement has been performed using the single-crystal X-ray diffraction method. The antiparasitic and cytotoxic activities of the newly synthesized derivatives were determined in vitro with the bloodstream form of Trypanosoma brucei brucei, the hepatic stage of Plasmodium berghei, and human leukemia HL-60 cells. The compounds with the highest trypanocidal activity were the C13-epi-2-chloroacetamide analogs of native (6h) or rearranged (7h) ivermectin. Both 6h and 7h displayed trypanocidal activities within a similar mid-nanomolar concentration range as the commercially used trypanocides suramin and ethidium bromide. Furthermore, 6h and 7h exhibited a comparable cytotoxic to trypanocidal ratio as the reference drug ethidium bromide. The double-modified compound 7a (C13-epi-acetamide of rearranged ivermectin) exhibited the highest activity against P. berghei grown in human hepatoma cells, which was 2.5 times higher than that of ivermectin. The findings of this study suggest that C13-epi-amide derivatives of ivermectin are suitable leads in the rational development of new antiparasitic agents.

Antiparasitic activity of ivermectin: Four decades of research into a "wonder drug"

Parasitic diseases still pose a serious threat to human and animal health, particularly for millions of people and their livelihoods in low-income countries. Therefore, research into the development of effective antiparasitic drugs remains a priority. Ivermectin, a sixteen-membered macrocyclic lactone, exhibits a broad spectrum of antiparasitic activities, which, combined with its low toxicity, has allowed the drug to be widely used in the treatment of parasitic diseases affecting humans and animals. In addition to its licensed use against river blindness and strongyloidiasis in humans, and against roundworm and arthropod infestations in animals, ivermectin is also used "off-label" to treat many other worm-related parasitic diseases, particularly in domestic animals. In addition, several experimental studies indicate that ivermectin displays also potent activity against viruses, bacteria, protozoans, trematodes, and insects. This review article summarizes the last 40 years of research on the antiparasitic effects of ivermectin, and the use of the drug in the treatment of parasitic diseases in humans and animals.

Activity of Ivermectin and Its Metabolites against Asexual Blood Stage Plasmodium falciparum and Its Interactions with Antimalarial Drugs

Ivermectin is an endectocide used widely to treat a variety of internal and external parasites. Field trials of ivermectin mass drug administration for malaria transmission control have demonstrated a reduction of Anopheles mosquito survival and human malaria incidence. Ivermectin will mostly be deployed together with artemisinin-based combination therapies (ACT), the first-line treatment of falciparum malaria. It has not been well established if ivermectin has activity against asexual stage Plasmodium falciparum or if it interacts with the parasiticidal activity of other antimalarial drugs. This study evaluated antimalarial activity of ivermectin and its metabolites in artemisinin-sensitive and artemisinin-resistant P. falciparum isolates and assessed in vitro drug-drug interaction with artemisinins and its partner drugs. The concentration of ivermectin causing half of the maximum inhibitory activity (IC50) on parasite survival was 0.81 μM with no significant difference between artemisinin-sensitive and artemisinin-resistant isolates (P = 0.574). The ivermectin metabolites were 2-fold to 4-fold less active than the ivermectin parent compound (P < 0.001). Potential pharmacodynamic drug-drug interactions of ivermectin with artemisinins, ACT-partner drugs, and atovaquone were studied in vitro using mixture assays providing isobolograms and derived fractional inhibitory concentrations. There were no synergistic or antagonistic pharmacodynamic interactions when combining ivermectin and antimalarial drugs. In conclusion, ivermectin does not have clinically relevant activity against the asexual blood stages of P. falciparum. It also does not affect the in vitro antimalarial activity of artemisinins or ACT-partner drugs against asexual blood stages of P. falciparum.

Fluorene-Chloroquine Hybrids: Synthesis, in vitro Antiplasmodial Activity, and Inhibition of Heme Detoxification Machinery of Plasmodium falciparum

Fluorene-chloroquine hybrids have been identified as a new promising class of antiplasmodial agents. The most active compound 9d exhibited good in vitro antiplasmodial activity against a chloroquine-sensitive NF54 strain of the human malaria parasite Plasmodium falciparum with an IC50 value of 139 nM. UV-visible absorption, FTIR spectral and 1H NMR titration data corroborated the binding of 9d to monomeric and µ-oxodimeric heme as well as inhibition of β-hematin formation, which collectively supported the inhibition of heme detoxification machinery in P. falciparum. In silico docking studies revealed the binding interactions of the hybrids in the active site of the wild type as well as quadruple mutant of Pf-DHFR-TS dihydrofolate enzyme. Further, the ADMET parameters were predicted and were in good agreement with the expected values, suggesting the drug likeness of the synthesized hybrid molecules.Introduction.