Design, synthesis, and antiprotozoal evaluation of new 2,4-bis[(substituted-aminomethyl)phenyl]quinoline, 1,3-bis[(substituted-aminomethyl)phenyl]isoquinoline and 2,4-bis[(substituted-aminomethyl)phenyl]quinazoline derivatives.

A series of new 2,4-bis[(substituted-aminomethyl)phenyl]quinoline, 1,3-bis[(substituted-aminomethyl)phenyl]isoquinoline, and 2,4-bis[(substituted-aminomethyl)phenyl]quinazoline derivatives was designed, synthesised, and evaluated in vitro against three protozoan parasites (Plasmodium falciparum, Leishmania donovani, and Trypanosoma brucei brucei). Biological results showed antiprotozoal activity with IC50 values in the µM range. In addition, the in vitro cytotoxicity of these original molecules was assessed with human HepG2 cells. The quinoline 1c was identified as the most potent antimalarial candidate with a ratio of cytotoxic to antiparasitic activities of 97 against the P. falciparum CQ-sensitive strain 3D7. The quinazoline 3h was also identified as the most potent trypanosomal candidate with a selectivity index (SI) of 43 on T. brucei brucei strain. Moreover, as the telomeres of the parasites P. falciparum and Trypanosoma are possible targets of this kind of nitrogen heterocyclic compounds, we have also investigated stabilisation of the Plasmodium and Trypanosoma telomeric G-quadruplexes by our best compounds through FRET melting assays.

Synthesis and Antiplasmodial Evaluation of 4-Carboxamido- and 4-Alkoxy-2-Trichloromethyl Quinazolines.

From three previously identified antiplasmodial hit compounds (A-C) and inactive series (D), all based on a 2-trichloromethylquinazoline scaffold, we conducted a structure-activity relationship (SAR) study at position four of the quinazoline ring by synthesizing 42 novel derivatives bearing either a carboxamido- or an alkoxy-group, to identify antiplasmodial compounds and to enrich the knowledge about the 2-trichloromethylquinazoline antiplasmodial pharmacophore. All compounds were evaluated in vitro for their cytotoxicity towards the HepG2 cell line and their activity against the multiresistant K1 P. falciparum strain, using doxorubicin, chloroquine and doxycycline as reference drugs. Four hit-compounds (EC50 K1 P. falciparum ≤ 2 µM and SI ≥ 20) were identified among 4-carboxamido derivatives (2, 9, 16, and 24) and two among 4-alkoxy derivatives (41 and 44). Regarding the two most potent molecules (16 and 41), five derivatives without a 2-CCl3 group were prepared, evaluated, and appeared totally inactive (EC50 > 50 µM), showing that the 2-trichloromethyl group was mandatory for the antiplasmodial activity.

Design, synthesis and antimalarial activity of novel bis{N-[(pyrrolo[1,2-a]quinoxalin-4-yl)benzyl]-3-aminopropyl}amine derivatives.

Novel series of bis- and tris-pyrrolo[1,2-a]quinoxaline derivatives 1 were synthesized and tested for in vitro activity upon the intraerythrocytic stage of W2 and 3D7 Plasmodium falciparum strains. Biological results showed good antimalarial activity with IC50 in the µM range. In attempting to investigate the large broad-spectrum antiprotozoal activities of these new derivatives, their properties toward Leishmania donovani were also investigated and revealed their selective antiplasmodial profile. In parallel, the in vitro cytotoxicity of these molecules was assessed on the human HepG2 cell line. Structure-activity relationships of these new synthetic compounds are discussed here. The bis-pyrrolo[1,2-a]quinoxalines 1n and 1p were identified as the most potent antimalarial candidates with selectivity index (SI) of 40.6 on W2 strain, and 39.25 on 3D7 strain, respectively. As the telomeres of the parasite could constitute an attractive target, we investigated the possibility of targeting Plasmodium telomeres by stabilizing the Plasmodium telomeric G-quadruplexes through a FRET melting assay by our new compounds.

Simultaneous detection of the protozoan parasites Toxoplasma, Cryptosporidium and Giardia in food matrices and their persistence on basil leaves.

Toxoplasma gondii, Cryptosporidium spp. and Giardia intestinalis are emerging pathogen parasites in the food domain. However, without standardized methods for their detection in food matrices, parasitic foodborne outbreaks remain neglected. In this study, a new immunomagnetic separation assay (IMS Toxo) targeting the oocyst's wall of T. gondii was developed using a specific purified monoclonal antibody. Performance of this IMS Toxo coupled to microscopic and qPCR analyses was evaluated in terms of limit of detection (LOD) and recovery rate (RR) on: i) simple matrix (LOD = 5 oocysts; RR between 5 and 56%); ii) raspberries and basil (LOD = 33 oocysts/g; RR between 0.2 and 35%). Finally, to simultaneously extract the three protozoa from these food matrices, T. gondii oocysts were directly concentrated (without IMS Toxo) from the supernatant of the IMS of Cryptosporidium and Giardia (oo)cysts. This strategy associated to qPCR detection led to LOD <1 to 3 (oo)cysts/g and RR between 2 and 35%. This procedure was coupled to RT-qPCR analyses and showed that the three protozoa persisted on the leaves of basil and remained viable following storage at 4 °C for 8 days. These data strengthen the need to consider these protozoa in food safety.

Mechanics of the Toxoplasma gondii oocyst wall.

The ability of microorganisms to survive under extreme conditions is closely related to the physicochemical properties of their wall. In the ubiquitous protozoan parasite Toxoplasma gondii, the oocyst stage possesses a bilayered wall that protects the dormant but potentially infective parasites from harsh environmental conditions until their ingestion by the host. None of the common disinfectants are effective in killing the parasite because the oocyst wall acts as a primary barrier to physical and chemical attacks. Here, we address the structure and chemistry of the wall of the T. gondii oocyst by combining wall surface treatments, fluorescence imaging, EM, and measurements of its mechanical characteristics by using atomic force microscopy. Elasticity and indentation measurements indicated that the oocyst wall resembles common plastic materials, based on the Young moduli, E, evaluated by atomic force microscopy. Our study demonstrates that the inner layer is as robust as the bilayered wall itself. Besides wall mechanics, our results suggest important differences regarding the nonspecific adhesive properties of each layer. All together, these findings suggest a key biological role for the oocyst wall mechanics in maintaining the integrity of the T. gondii oocysts in the environment or after exposure to disinfectants, and therefore their potential infectivity to humans and animals.

Antileishmanial pharmacomodulation in 8-nitroquinolin-2(1H)-one series.

An antileishmanial pharmacomodulation at position 4 of 8-nitroquinolin-2(1H)-one was conducted by using the Sonogashira and Suzuki-Miyaura coupling reactions. A series of 25 derivatives was tested in vitro on the promastigote stage of Leishmania donovani along with an in vitro cytotoxicity evaluation on the human HepG2 cell line. Only the derivatives bearing a phenyl moiety at position 4 of the quinoline ring displayed interesting biologic profile, when the phenyl moiety was substituted at the para position by a Br or Cl atom, or by a CF3 group. Among them, molecules 17 and 19 were the most selective and were then tested in vitro on the intracellular amastigote stage of both L. donovani and Leishmania infantum, in parallel with complementary in vitro cytotoxicity assays on the macrophage cell lines THP-1 and J774A.1. Molecule 19 showed no activity on the amastigote stages of the parasites and some cytotoxicity on the J774A.1 cell line while molecule 17, less cytotoxic than 19, showed anti-amastigote activity in L. infantum, being 3 times less active than miltefosine but more active and selective than pentamidine. Nevertheless, hit-molecule 17 did not appear as selective as the parent compound.

In vitro antiplasmodial activity of some medicinal plants of Burkina Faso.

Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum drug resistance. There is an urgent need to investigate new sources of antimalarial drugs which are more effective against Plasmodium falciparum. One of the potential sources of antimalarial drugs is traditional medicinal plants. In this work, we studied the in vitro antiplasmodial activity of chloromethylenic, methanolic, and MeOH/H2O (1/1) crude extracts and decoction obtained from eight medicinal plants collected in Burkina Faso and of total alkaloids for five plants. Extracts were evaluated in vitro for efficacy against Plasmodium falciparum strain K1, which is resistant to chloroquine, pyrimethamine and proguanil using the fluorescence-based SYBR Green I assay. The antiproliferative activity on human-derived hepatoma cell line HepG2 and Chinese hamster ovary (CHO) cells was evaluated using the 3-[4,5-dimethylthyazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test in order to determine the selectivity index. Among the plant extracts tested for in vitro antiplasmodial activity, 16 were considered to be inactive (with IC50 > 10 µg/ml), six showed a moderate activity (5 < IC50 ≤ 10 µg/ml), and six were found to have a good in vitro activity with IC50 value ≤ 5 µg/ml. The highest antiplasmodial activity was found for extracts from: the alkaloid leaf extract and the chloromethylenic extracts of Combretum fragrans (IC50 = 3 µg/ml, IC50 = 5 µg/ml), the total alkaloids and the chloromethylenic leaf extracts of Combretum collinum (IC50 = 4 µg/ml), the MeOH/H2O leaf extract of Terminalia avicennioides (IC50 = 3.5 µg/ml), and the alkaloid leaf extract of Pavetta crassipes (IC50 = 5 µg/ml). Three other extracts showed moderate antiplasmodial activity (5 < IC50 ≤ 10 µg/ml): Terminalia avicennioides and Combretum fragrans methanolic extracts and Acacia kirkii alkaloid leaf extract (IC50 = 6.5, 9 and 10 µg/ml respectively). The Terminalia avicennioides crude MeOH/H2O (80:20 v/v) extract of the leaves was submitted to a successive liquid/liquid extraction with ethylacetate and n-butanol respectively. The extracts were investigated for in vitro antiplasmodial activity and antioxidant properties using DPPH(·), ABTS(+) and FRAP methods. The ethylacetate extract showed the best antiplasmodial activity (7 µg/ml) and the active constituent was isolated as ellagic acid by bioguided fractionation with an IC50 = 0.2 µM on Plasmodium falciparum and SI = 152. Besides, Terminalia avicennioides leaf extract and ellagic acid showed a good antioxidant activity. Our finding confirms the importance of investigating the antimalarial activity of plant species used in traditional medicine. Overall, two plants belonging to the Combretaceae family, Combretum fragrans and Combretum collinum appeared to be the best candidates and will be further investigated for their antiplasmodial properties, in order to isolate the molecules responsible for the antiplasmodial activity.

Synthesis of Nitrostyrylthiazolidine-2,4-dione Derivatives Displaying Antileishmanial Potential.

A series of 61 thiazolidine-2,4-diones bearing a styryl group at position 5 was synthesized in 2-5 steps and their structure was proved by elemental and spectral analyses. The compounds obtained were evaluated in vitro against the promastigote stage of the kinetoplastid parasite Leishmania infantum and the human HepG2 cell line, to determine selectivity indices and to compare their activities with those of antileishmanial reference drugs. The study of structure-activity relationships indicated the potential of some derivatives bearing a nitro group on the phenyl ring, especially when located at the meta position. Thus, among the tested series, compound 14c appeared as a hit compound with good antileishmanial activity (EC50 = 7 µM) and low cytotoxicity against both the hepatic HepG2 and macrophage THP-1 human cell lines (CC50 = 101 and 121 µM, respectively), leading to good selectivity indices (respectively, 14 and 17), in comparison with the reference antileishmanial drug compound miltefosine (EC50 = 3.3 µM, CC50 = 85 and 30 µM, SI = 26 and 9). Regarding its mechanism of action, among several possibilities, it was demonstrated that compound 14c is a prodrug bioactivated, predominantly by L. donovani nitroreductase 1, likely leading to the formation of cytotoxic metabolites that form covalent adducts in the parasite. Finally, compound 14c is lipophilic (measured CHI LogD7.7 = 2.85) but remains soluble in water (measured PBS solubility at pH7.4 = 16 µM), highlighting the antileishmanial potential of the nitrostyrylthiazolidine-2,4-dione scaffold.

Targeting the human parasite Leishmania donovani: discovery of a new promising anti-infectious pharmacophore in 3-nitroimidazo[1,2-a]pyridine series.

We report herein the discovery of antileishmanial molecules based on the imidazo[1,2-a]pyridine ring. In vitro screenings of imidazopyridines belonging to our chemical library, toward the promastigotes stage of Leishmania donovani, J774A.1 murine and HepG2 human cells, permitted to identify three selective hit-compounds (12, 20 and 28). New derivatives were then synthesized to allow structure-activity and -toxicity relationships analyses, enabling to characterize a lead-compound (44) displaying both a high potency (IC50=1.8 µM) and a good selectivity index, in comparison with three antileishmanial reference drug-compounds (amphotericin B, miltefosine and pentamidine). Moreover, lead-compound 44 also exhibits good in vitro activity against the intracellular amastigote stage of L. donovani. Thus, the 6-halo-3-nitro-2-(phenylsulfonylmethyl)imidazo[1,2-a]pyridine scaffold appears as a new promising selective antileishmanial pharmacophore, especially when substituted at position 8 by a bromine atom.

HPLC analysis of Stephania rotunda extracts and correlation with antiplasmodial activity.

Stephania rotunda (Menispermaceae), a creeper commonly found in the mountainous areas of Cambodia, has been mainly used for the treatment of fever and malaria. Thus, the aim of this study is to investigate the chemical composition and antiplasmodial activity of different samples of S. rotunda and compare their antiplasmodial activity with their alkaloid content. Sixteen samples from different parts (roots, stem, and tuber) of S. rotunda were collected from four regions of Cambodia (Battambang, Pailin, Siem Reap, and Kampot). Reversed-phase HPLC was used to determine the content of three bioactive alkaloids (cepharanthine, tetrahydropalmatine, and xylopinine). These three alkaloids have been found in all samples from Battambang and Pailin (samples I-IX), whereas only tetrahydropalmatine was present in samples from Siem Reap and Kampot (samples X-XVI). The analyzed extracts were evaluated for their antiplasmodial activity on W2 strain of Plasmodium falciparum. Among them, 13 extracts were significantly active with inhibitory concentration 50 (IC(50) ) from 1.2 to 3.7 µg/mL and 2 extracts were moderately active (IC(50) = 6.1 and 10 µg/mL, respectively), whereas sample XI was not active (IC(50) = 19.6 µg/mL). A comparison between antiplasmodial activity and concentration of the three bioactive alkaloids in S. rotunda extracts has been realized.

New antiplasmodial 4-amino-thieno[3,2-d]pyrimidines with improved intestinal permeability and microsomal stability.

The increasing number of Plasmodium falciparum strains resistant to current treatments justifies the urgent need to discover new compounds active on several stages of the parasite development. Based on the structure of Gamhepathiopine, a 2-tert-butylaminothieno[3,2-d]pyrimidin-4(3H)-one previously identified for its dual activity against the sexual and asexual stages of P. falciparum, 25 new 4-amino-substituted analogues were synthesized and evaluated on the erythrocytic and hepatic stages of Plasmodium. A promising compound, N2-(tert-butyl)-N [4]-(3-(dimethylamino)propyl)-6-(p-tolyl)thieno[3,2-d]pyrimidine-2,4-diamine, showed improved physicochemical properties, intestinal permeability (PAMPA model) and microsomal stability compared to Gamhepathiopine, while maintaining a good antiplasmodial activity on the erythrocytic stage of P. falciparum and on the hepatic stage of P. berghei.

Novel thienopyrimidones targeting hepatic and erythrocytic stages of Plasmodium parasites with increased microsomal stability.

Based on the structure of a previously identified hit, Gamhepathiopine 1, which showed promising antiplasmodial activity, but poor microsomal stability, several strategies were investigated to improve the metabolic stability of the compounds. This included the introduction of fluorine or deuterium atoms, as well as carbocyclic groups. Among the new compounds, the 2-aminocyclobutyl derivative 5g demonstrated enhanced microsomal stability compared to compound 1, while retaining antiplasmodial activity against erythrocytic and hepatic stages of Plasmodium, without significant cytotoxicity against primary hepatocytes.

Interaction forces drive the environmental transmission of pathogenic protozoa.

The protozoan parasites Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (Giardia) and oocysts (Cryptosporidium and Toxoplasma), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites' surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano- to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano- to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution.

Synthesis and promising in vitro antiproliferative activity of sulfones of a 5-nitrothiazole series.

 The synthesis in water of new sulfone derivatives under microwave irradiation is described. This eco-friendly process leads to the expected products in good yields by reaction of various substituted sulfinates (commercially available or obtained by reduction of the corresponding sulfonyl chlorides) with 4-chloromethyl-2-methyl-5-nitro-1,3-thiazole. In order to evaluate the antiproliferative effect of these compounds, several sulfone derivatives are also dichlorinated on the Cα next to the sulfonyl group. An evaluation on different cancer cell lines reveals promising selective in vitro antiproliferative activity toward HepG2 human cell lines by dihydrogenated sulfones, suggesting further research should be to explore their anticancer potential in the treatment of liver cancer.

A new synthetic route to original sulfonamide derivatives in 2-trichloromethylquinazoline series: a structure-activity relationship study of antiplasmodial activity.

We report herein a simple and efficient two-step synthetic approach to new 2-trichloromethylquinazolines possessing a variously substituted sulfonamide group at position 4 used to prepare new quinazolines with antiparasitic properties. Thus, an original series of 20 derivatives was synthesized, which proved to be less-toxic than previously synthesized hits on the human HepG2 cell line, but did not display significant antiplasmodial activity. A brief Structure-Activity Relationship (SAR) evaluation shows that a more restricted conformational freedom is probably necessary for providing antiplasmodial activity.

4-Substituted Thieno[3,2-d]pyrimidines as Dual-Stage Antiplasmodial Derivatives.

Malaria remains one of the major health problems worldwide. The increasing resistance of Plasmodium to approved antimalarial drugs requires the development of novel antiplasmodial agents that can effectively prevent and/or treat this disease. Based on the structure of Gamhepathiopine, a 2-tert-butylaminothieno[3,2-d]pyrimidin-4(3H)-one hit, active on the sexual and asexual stages of the parasite and thanked for the introduction of various substituents at position 4 of the thienopyrimidine core by nucleophilic aromatic substitution and pallado-catalyzed coupling reactions, a series of 4-substituted thieno[3,2-d]pyrimidines were identified as displaying in vitro activities against both the erythrocytic stage of P. falciparum and the hepatic stage of P. berghei. Among the 28 compounds evaluated, the chloro analogue of Gamhepathiopine showed good activity against the erythrocytic stage of P. falciparum, moderate toxicity on HepG2, and better activity against hepatic P. berghei parasites, compared to Gamhepathiopine.

Pd-catalyzed C-C and C-N cross-coupling reactions in 2-aminothieno[3,2-d]pyrimidin-4(3H)-one series for antiplasmodial pharmacomodulation.

In 2015, we identified gamhepathiopine (M1), a 2-tert-butylaminothieno[3,2-d]pyrimidin-4(3H)-one antiplasmodial hit targeting all development stages of the human malarial parasite P. falciparum. However, this hit compound suffers from sensitivity to hepatic oxidative metabolism. Herein, we describe the synthesis of 33 new compounds in the 2-aminothieno[3,2-d]pyrimidin-4(3H)-one series modulated at position 6 of this scaffold. The modulations were performed using three palladium-catalyzed cross coupling reactions, namely Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig. For the latter, we developed the reaction conditions. Then, we evaluated the synthesized compounds for their antiplasmodial activity on the K1 P. falciparum strain and their cytotoxicity on the human HepG2 cell line. Although we did not obtain a compound better than M1 in terms of the antiplasmodial activity, we identified compound 1g bearing a piperidine at position 6 of the thieno[3,2-d]pyrimidin-4(3H)-one ring with an improved cytotoxicity and metabolic stability. 1g is an interesting new starting point for further pharmacomodulation studies. This study also provides valuable antiplasmodial SAR data regarding the nature of the ring at position 6, the possible substituent on this ring, and the introduction of a spacer between this ring and the thienopyrimidinone moiety.

Treating leishmaniasis in Amazonia, part 2: Multi-target evaluation of widely used plants to understand medicinal practices.

ETHNOPHARMACOLOGICAL RELEVANCE: Leishmaniasis are widely distributed among tropical and subtropical countries, and remains a crucial health issue in Amazonia. Indigenous groups across Amazonia have developed abundant knowledge about medicinal plants related to this pathology. AIM OF THE STUDY: We intent to explore the weight of different pharmacological activities driving taxa selection for medicinal use in Amazonian communities. Our hypothesis is that specific activity against Leishmania parasites is only one factor along other (anti-inflammatory, wound healing, immunomodulating, antimicrobial) activities. MATERIALS AND METHODS: The twelve most widespread plant species used against leishmaniasis in Amazonia, according to their cultural and biogeographical importance determined through a wide bibliographical survey (475 use reports), were selected for this study. Plant extracts were prepared to mimic their traditional preparations. Antiparasitic activity was evaluated against promastigotes of reference and clinical New-World strains of Leishmania (L. guyanensis, L. braziliensis and L. amazonensis) and L. amazonensis intracellular amastigotes. We concurrently assessed the extracts immunomodulatory properties on PHA-stimulated human PBMCs and RAW264.7 cells, and on L. guyanensis antigens-stimulated PBMCs obtained from Leishmania-infected patients, as well as antifungal activity and wound healing properties (human keratinocyte migration assay) of the selected extracts. The cytotoxicity of the extracts against various cell lines (HFF1, THP-1, HepG2, PBMCs, RAW264.7 and HaCaT cells) was also considered. The biological activity pattern of the extracts was represented through PCA analysis, and a correlation matrix was calculated. RESULTS: Spondias mombin L. bark and Anacardium occidentale L. stem and leaves extracts displayed high anti-promatigotes activity, with IC50 ≤ 32 µg/mL against L. guyanensis promastigotes for S. mombin and IC50 of 67 and 47 µg/mL against L. braziliensis and L. guyanensis promastigotes, respectively, for A. occidentale. In addition to the antiparasitic effect, antifungal activity measured against C. albicans and T. rubrum (MIC in the 16-64 µg/mL range) was observed. However, in the case of Leishmania amastigotes, the most active species were Bixa orellana L. (seeds), Chelonantus alatus (Aubl.) Pulle (leaves), Jacaranda copaia (Aubl.) D. Don. (leaves) and Plantago major L. (leaves) with IC50 < 20 µg/mL and infection rates of 14-25% compared to the control. Concerning immunomodulatory activity, P. major and B. orellana were highlighted as the most potent species for the wider range of cytokines in all tested conditions despite overall contrasting results depending on the model. Most of the species led to moderate to low cytotoxic extracts except for C. alatus, which exhibited strong cytotoxic activity in almost all models. None of the tested extracts displayed wound healing properties. CONCLUSIONS: We highlighted pharmacologically active extracts either on the parasite or on associated pathophysiological aspects, thus supporting the hypothesis that antiparasitic activities are not the only biological factor useful for antileishmanial evaluation. This result should however be supplemented by in vivo studies, and attracts once again the attention on the importance of the choice of biological models for an ethnophamacologically consistent study. Moreover, plant cultural importance, ecological status and availability were discussed in relation with biological results, thus contributing to link ethnobotany, medical anthropology and biology.

Improving Aqueous Solubility and In Vitro Pharmacokinetic Properties of the 3-Nitroimidazo[1,2-a]pyridine Antileishmanial Pharmacophore.

An antileishmanial structure−activity relationship (SAR) study focused on positions 2 and 8 of the imidazo[1,2-a]pyridine ring was conducted through the synthesis of 22 new derivatives. After being screened on the promatigote and axenic amastigote stages of Leishmania donovani and L. infantum, the best compounds were tested against the intracellular amastigote stage of L. infantum and evaluated regarding their in vitro physicochemical and pharmacokinetic properties, leading to the discovery of a new antileishmanial6-chloro-3-nitro-8-(pyridin-4-yl)-2-[(3,3,3-trifluoropropylsulfonyl)methyl]imidazo[1,2-a]pyridine hit. It displayed low cytotoxicities on both HepG2 and THP1 cell lines (CC50 > 100 µM) associated with a good activity against the intracellular amastigote stage of L. infantum (EC50 = 3.7 µM versus 0.4 and 15.9 µM for miltefosine and fexinidazole, used as antileishmanial drug references). Moreover, in comparison with previously reported derivatives in the studied series, this compound displayed greatly improved aqueous solubility, good mouse microsomal stability (T1/2 > 40 min) and high gastrointestinal permeability in a PAMPA model, making it an ideal candidate for further in vivo studies on an infectious mouse model.

Synthesis of antiplasmodial 2-aminothieno[3,2-d]pyrimidin-4(3H)-one analogues using the scaffold hopping strategy.

Gamhepathiopine (also known as M1), is a multi-stage acting antiplasmodial 2-tert-butylaminothieno[3,2-d]pyrimidin-4(3H)-one hydrochloride that was first described in 2015. The development of this compound is limited by poor microsomal stability, insufficient aqueous solubility and low intestinal permeability. In order to obtain new optimized derivatives, we conducted a scaffold hopping strategy from compound M1, resulting in the synthesis of 20 new compounds belonging to six chemical series. All the compounds were tested on the K1 multi-resistant strain of Plasmodium falciparum and the human HepG2 cell-line, to evaluate their antiplasmodial activity and their cytotoxicity. Analogues' biological results also highlighted the mandatory presence of a heteroatom at position 5 of the thieno[3,2-d]pyrimidin-4(3H)-one moeity for the antiplasmodial activity. However, modifications at position 7 were detrimental for the antiplasmodial activity. We identified furane bioisostere 3j as a promising candidate, showing good blood stage antiplasmodial activity, better water solubility and highly improved intestinal permeability in the PAMPA assay.