Sandrine Cojean’s research while affiliated with University of Paris-Saclay and other places

Leishmaniasis chemotherapy faces significant challenges, including high costs, severe side effects, and the emergence of drug-resistant parasites, demanding global efforts to identify novel antileishmanial agents. Pentavalent antimony (SbV), the primary treatment for over 78 years, suffers from reduced efficacy and high toxicity, underscoring the urgent need for alternatives. We have synthesized metalloporphyrins with potent antileishmanial properties, including the SbV-porphyrin complex (SbVT4MPP). SbVT4MPP exhibited high potency against both Sb-sensitive and Sb-resistant Leishmania spp. with IC50 as low as 0.05 and 0.12 µM, respectively, for amastigotes and promastigotes; 170-fold more effective than SbV and with a 28–37-fold selectivity index, highlighting the importance of host cells on drug activity. Sterol profiling of L. infantum revealed that SbVT4MPP ablated ergosterol production while accumulating cholestane-based sterols (e.g., cholesta-5,7,22-trien-3β-ol). Additional sterols appeared exclusively under SbVT4MPP treatment, accompanied by upregulated erg6, encoding sterol-C-24 methyltransferase (SMT), a key enzyme in sterol biosynthesis. Overexpression of ERG6 reduced SbVT4MPP potency, increasing the IC50 by 2.5-fold, confirming ERG6's role in its mode of action. Disruption of ergosterol biosynthesis was indirectly confirmed through hypoosmotic shock assays, which indicated increased membrane fluidity in SbVT4MPP-treated Leishmania. In vivo studies revealed a 96 % reduction in parasite load, highlighting SbVT4MPP’s efficacy in visceral leishmaniasis model. Since ERG6 is absent in mammals, it represents a selective and promising pharmacological target. Our findings position SbVT4MPP as a novel chemical entity with potent in vitro and in vivo antileishmanial efficacy, providing mechanistic insights and warranting further preclinical investigation as a promising drug candidate for leishmaniasis treatment.

Our research group previously discovered CTN1122, an imidazo[1,2‐a]pyrazine compound with promising antileishmanial activity against intramacrophage amastigotes of Leishmania major and L. donovani strains. CTN1122 effectively targets Leishmania casein kinase 1 (L–CK1.2) and exhibits a favorable safety profile. To further explore its chemical space, we developed a convergent strategy to modify the C2 position of the imidazo[1,2‐a]pyrazine core using Suzuki‐Miyaura coupling of the corresponding triflate intermediate. Among 15 newly synthesized analogs, seven derivatives featuring variously substituted phenyl rings at C2 demonstrated L–CK1.2 inhibition within micromolar to submicromolar ranges and antileishmanial activity in vitro with low cytotoxicity in macrophages. Compounds 7 d and 7 l were particularly potent, with IC50 values of 1.25 μM and 0.92 μM against L. major, and 1.44 μM and 2.34 μM against L. donovani, respectively. They showed IC50 L–CK1.2=0.30 μM and 0.57 μM with enhanced selectivity indices (SI=3.8 and 1.6) over the human CK1ϵ ortholog. Additionally, four C2 analogs and two C5 isomers exhibited notable antiparasitic effects without strongly inhibiting L–CK1.2, indicating a possible alternative mechanism of action. Compound 7 k displayed the highest general activity, with IC50 values of 0.31 μM on L. major and 0.27 μM on L. donovani, coupled with favorable selectivity indexes.

Visceral leishmaniasis, the most severe form of the disease, is caused by L. donovani and L. infantum parasites; cutaneous leishmaniasis is the most common endemic form of leishmaniasis and mainly caused by L. tropica and L. major. We have previously described a series of thiazolopyrimidine derivatives and reported their antipromastigote activities against various parasites. In this study, we also investigated their activities against L. donovani and L. major axenic amastigotes, intramacrophage amastigotes and cytotoxicity on macrophages to assess selectivity. As a result, five of the compounds tested showed no cytotoxicity on the macrophage cell line; their anti-amastigote activity was close to the positive control, miltefosine. These results confirm the antileishmanial activity of the thiazolopyrimidine scaffold and demonstrate that this may be a starting point for the generation of new lead compounds for treating visceral leishmaniasis and cutaneous leishmaniasis. To elucidate the mechanism of action, we also performed several ligand- and structure-based in silico studies.

Background: Given the altered responses to both artemisinins and lumefantrine in Eastern Africa, monitoring antimalarial drug resistance in all African countries is paramount. Methods: We measured the susceptibility to six antimalarials using ex vivo growth inhibition assays (IC50) for a total of 805 Plasmodium falciparum isolates obtained from travelers returning to France (2016-2023), mainly from West and Central Africa. Isolates were sequenced using molecular inversion probes (MIPs) targeting fourteen drug resistance genes across the parasite genome. Findings: Ex vivo susceptibility to several drugs has significantly decreased in 2019-2023 versus 2016-2018 parasite samples: lumefantrine (median IC50: 23·0 nM [IQR: 14·4-35·1] in 2019-2023 versus 13·9 nM [8·42-21·7] in 2016-2018, p<0·0001), monodesethylamodiaquine (35·4 [21·2-51·1] versus 20·3 nM [15·4-33·1], p<0·0001), and marginally piperaquine (20·5 [16·5-26·2] versus 18.0 [14·2-22·4] nM, p<0·0001). Only four isolates carried a validated pfkelch13 mutation. Multiple mutations in pfcrt and one in pfmdr1 (N86Y) were significantly associated with altered susceptibility to multiple drugs. The susceptibility to lumefantrine was altered by pfcrt and pfmdr1 mutations in an additive manner, with the wild-type haplotype (pfcrt K76-pfmdr1 N86) exhibiting the least susceptibility. Interpretation: Our study on P. falciparum isolates from West and Central Africa indicates a low prevalence of molecular markers of artemisinin resistance but a significant decrease in susceptibility to the partner drugs that have been the most widely used since a decade -lumefantrine and amodiaquine. These phenotypic changes likely mark parasite adaptation to sustained drug pressure and call for intensifying the monitoring of antimalarial drug resistance in Africa.

Background: Given the altered responses to both artemisinins and lumefantrine in Eastern Africa, monitoring antimalarial drug resistance in all African countries is paramount. Methods: We measured the susceptibility to six antimalarials using ex vivo growth inhibition assays (IC50) for a total of 805 Plasmodium falciparum isolates obtained from travelers returning to France (2016-2023), mainly from West and Central Africa. Isolates were sequenced using molecular inversion probes (MIPs) targeting fourteen drug resistance genes across the parasite genome. Findings: Ex vivo susceptibility to several drugs has significantly decreased in 2019-2023 versus 2016-2018 parasite samples: lumefantrine (median IC50: 23.0 nM [IQR: 14.4-35.1] in 2019-2023 versus 13.9 nM [8.42-21.7] in 2016-2018, p<0.0001), monodesethylamodiaquine (35.4 [21.2-51.1] versus 20.3 nM [15.4-33.1], p<0.0001), and marginally piperaquine (20.5 [16.5-26.2] versus 18.0 [14.2-22.4] nM, p<0.0001). Only four isolates carried a validated pfkelch13 mutation. Multiple mutations in pfcrt and one in pfmdr1 (N86Y) were significantly associated with altered susceptibility to multiple drugs. The susceptibility to lumefantrine was altered by pfcrt and pfmdr1 mutations in an additive manner, with the wild-type haplotype (pfcrt K76-pfmdr1 N86) exhibiting the least susceptibility. Interpretation: Our study on P. falciparum isolates from West and Central Africa indicates a low prevalence of molecular markers of artemisinin resistance but a significant decrease in susceptibility to the partner drugs that have been the most widely used since a decade -lumefantrine and amodiaquine. These phenotypic changes likely mark parasite adaptation to sustained drug pressure and call for intensifying the monitoring of antimalarial drug resistance in Africa.

Leishmania major is responsible for zoonotic cutaneous leishmaniasis. Therapy is mainly based on the use of antimony-based drugs; however, treatment failures and illness relapses were reported. Although studies were developed to understand mechanisms of drug resistance, the interactions of resistant parasites with their reservoir hosts and vectors remain poorly understood. Here we compared the development of two L. major MON-25 trivalent antimony-resistant lines, selected by a stepwise in vitro Sb(III)-drug pressure, to their wild-type parent line in the natural vector Phlebotomus papatasi. The intensity of infection, parasite location and morphological forms were compared by microscopy. Parasite growth curves and IC50 values have been determined before and after the passage in Ph. papatasi. qPCR was used to assess the amplification rates of some antimony-resistance gene markers. In the digestive tract of sand flies, Sb(III)-resistant lines developed similar infection rates as the wild-type lines during the early-stage infections, but significant differences were observed during the late-stage of the infections. Thus, on day 7 p. i., resistant lines showed lower representation of heavy infections with colonization of the stomodeal valve and lower percentage of metacyclic promastigote forms in comparison to wild-type strains. Observed differences between both resistant lines suggest that the level of Sb(III)-resistance negatively correlates with the quality of the development in the vector. Nevertheless, both resistant lines developed mature infections with the presence of infective metacyclic forms in almost half of infected sandflies. The passage of parasites through the sand fly guts does not significantly influence their capacity to multiply in vitro. The IC50 values and molecular analysis of antimony-resistance genes showed that the resistant phenotype of Sb(III)-resistant parasites is maintained after passage through the sand fly. Sb(III)-resistant lines of L. major MON-25 were able to produce mature infections in Ph. papatasi suggesting a possible circulation in the field using this vector.