Pharmacotherapy for artemisinin-resistant malaria

Drug Property Optimization: Design, Synthesis, and Characterization of Novel Pharmaceutical Salts and Cocrystal-Salt of Lumefantrine

Lumefantrine (LMF) is a low-solubility antimalarial drug that cures acute, uncomplicated malaria. It exerts its pharmacological effects against erythrocytic stages of Plasmodium spp. and prevents malaria pathogens from producing nucleic acid and protein, thereby eliminating the parasites. Modifying the structure of a drug through the formation of a pharmaceutical cocrystal or salt presents an avenue through which its physicochemical properties can be optimized. In this work, we report the design/synthesis and solid-state characterization of four new salts and cocrystal-salt forms of LMF; an LMF-ADP salt, monoclinic space group P21/n; an LMF-FUM cocrystal-salt, monoclinic space group P21/c; an LMF-TAR solvate salt, monoclinic space group P21/n; and an LMF-SUC salt, triclinic, space group P1̅ (ADP, dianion of adipic acid; FUM, monoanion of fumaric acid; TAR, dianion of tartaric acid; SUC, dianion of succinic acid). These salts can be obtained by solution as well as by mechanochemical cocrystallization methods. The multicomponent systems gain their stability from hydrogen and partial ionic bonding interactions (N-H···O, O-H···O, N+-H···O-, and O-H+···O-) originating from both the dibutyl ammonium (N+-H) site and the alcohol hydroxyl (-OH) site of LMF toward the carboxylate (-C(O-)═O) functional groups of the coformer anions. SCXRD indicates for LMF-ADP, LMF-TAR, and LMF-SUC complete transfer of all carboxylic acid protons (H+) toward the LMF nitrogen, while for LMF-FUM, one of the protons is transferred (leaving a hydrofumarate monoanion). Using salicylic and acetylsalicylic acids as coformers yielded coamorphous solids. Solid-state characterization using powder X-ray diffraction (XRD) and thermal techniques (DSC and TGA) support and confirm the structures obtained from single-crystal XRD. LMF-ADP and LMF-FUM present superior stability under standard conditions (40 ± 2 °C, 75 ± 5% RH, and 3 months) compared to the amorphous samples and the other two salts. LMF-SUC showed poor thermal stability by DSC/TGA, and powder XRD patterns for LMF-TAR showed substantial change after the 3-month stability test. Finally, the calculated equilibrium solubilities for the cocrystal salts indicate an increase of more than twofold compared to LMF's solubility.

Identification of Malaria-Selective Proteasome β5 Inhibitors Through Pharmacophore Modeling, Molecular Docking, and Molecular Dynamics Simulation

Malaria remains a global health challenge, with increasing resistance to frontline antimalarial treatments such as artemisinin (ART) threatening the efficacy of current therapies. In this study, we investigated the potential of FDA-approved drugs to selectively inhibit the malarial proteasome, a novel target for antimalarial drug development. By leveraging pharmacophore modeling, molecular docking, molecular dynamics (MD) simulations, and binding free-energy calculations, we screened a library of compounds to identify inhibitors selective for the Plasmodium proteasome over the human proteasome. Our results highlighted Argatroban, LM-3632, Atazanavir Sulfate, and Pemetrexed Hydrate as promising candidates, with Argatroban and Pemetrexed Hydrate showing the highest binding affinity and selectivity toward the malarial proteasome. MD simulation and gmx_MMPBSA analysis confirmed the compounds' ability to remain within the active site of the malarial proteasome, while some exited or exhibited reduced stability within the human proteasome. This study underscores the potential of proteasome-targeting drugs for overcoming malarial drug resistance and paves the way for the further optimization of these compounds.

PHARE: a bioinformatics pipeline for compositional profiling of multiclonal Plasmodium falciparum infections from long-read Nanopore sequencing data

BACKGROUND

The emergence of drug-resistant clones of Plasmodium falciparum is a major public health concern, and the ability to detect and track the spread of these clones is crucial for effective malaria control and treatment. However, in endemic settings, malaria infected people often carry multiple P. falciparum clones simultaneously making it likely to miss drug-resistant clones using traditional molecular typing methods.

OBJECTIVES

Our goal was to develop a bioinformatics pipeline for compositional profiling in multiclonal P. falciparum samples, sequenced using the Oxford Nanopore Technologies MinION platform.

METHODS

We developed the 'Finding P. falciparum haplotypes with resistance mutations in polyclonal infections' (PHARE) pipeline using existing bioinformatics tools and custom scripts written in python. PHARE was validated on three control datasets containing P. falciparum DNA of four laboratory strains at varying mixing ratios. Additionally, the pipeline was tested on clinical samples from children admitted to a paediatric hospital in the Central African Republic.

RESULTS

The PHARE pipeline achieved high recall and accuracy rates in all control datasets. The pipeline can be used on any gene and was tested with amplicons of the P. falciparum drug resistance marker genes pfdhps, pfdhfr and pfK13.

CONCLUSIONS

The PHARE pipeline helps to provide a more complete picture of drug resistance in the circulating P. falciparum population and can help to guide treatment recommendations. PHARE is freely available under the GNU Lesser General Public License v.3.0 on GitHub: https://github.com/Fippu/PHARE.

Design, synthesis and antiplasmodial evaluation of new amide-, carbamate-, and ureido-type harmicines

Malaria, one of the oldest parasitic diseases, remains a global health threat, and the increasing resistance of the malaria parasite to current antimalarials is forcing the discovery of new, effective drugs. Harmicines, hybrid compounds in which harmine/β-carboline alkaloids and cinnamic acid derivatives are linked via an amide bond or a triazole ring, represent new antiplasmodial agents. In this work, we used a multiple linear regression technique to build a linear quantitative structure-activity relationship (QSAR) model, based on a group of 40 previously prepared amide-type (AT) harmicines and their antiplasmodial activities against erythrocytic stage of chloroquine-sensitive strain of P. falciparum (Pf3D7). After analysing the QSAR model, new harmicines were designed and synthesized: six amide-type, eleven carbamate-type and two ureido-type harmicines at the N-9 position of the β-carboline core. Subsequently, we evaluated the antiplasmodial activity of the new harmicines against the erythrocytic and hepatic stages of the Plasmodium life cycle in vitro and their antiproliferative activity against HepG2 cells. UT harmicine (E)-1-(2-(7-methoxy-1-methyl-9H-pyrido[3,4-b]indol-9-yl)ethyl)-3-(3-(3-(trifluoromethyl)phenyl)allyl)urea at the N-9 position of the β-carboline ring exhibited pronounced antiplasmodial activity against both the erythrocytic and the hepatic stages of the Plasmodium life cycle, accompanied by good selectivity towards Plasmodium.

Synergistic antimalarial treatment of Plasmodium berghei infection in mice with dihydroartemisinin and Gymnema inodorum leaf extract

BACKGROUND

Chemotherapy is crucial in the fight against malaria. The rise of resistance to most antimalarial medicines has been a serious hurdle to effective treatment. Artemisinin-based combination therapies (ACTs) are currently the most effective antimalarial medication. Malaria parasites are growing more resistant to ACTs, particularly in Southeast Asia. As a result, effective alternative antimalarials are in high demand. The leaf extract of Gymnema inodorum (GIE) has previously shown promise as an effective antimalarial. Therefore, this study evaluated the antimalarial potential of combination dihydroartemisinin (DHA) and GIE therapy against Plasmodium berghei in a mouse model.

METHODS

The medications were evaluated using the standard 4-day test for determining the 50% effective dosage (ED₅₀) of DHA and GIE on P. berghei ANKA (PbANKA). DHA and GIE were combined using a fixed-ratio approach, with DHA/GIE ED_50s of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100, respectively.

RESULTS

The ED₅₀ against PbANKA was determined to be 2 mg/kg of DHA and 100 mg/kg of GIE. The 60/40 (DHA/GIE) ratio demonstrated significantly higher antimalarial activity than the other ratios (p < 0.001) against PbANKA, with 88.95% inhibition, suggesting synergistic efficacy (combination index (CI) = 0.68695). Furthermore, this ratio protected PbANKA-infected mice against loss of body weight and packed cell volume decline, leading to a longer survival time over 30 days.

CONCLUSION

Our results suggest that GIE could be an effective adjuvant to DHA that can enhance the antimalarial effects in the treatment of PbANKA-infected mice.

Effect of Allicin and Artesunate Combination Treatment on Experimental Mice Infected with Plasmodium berghei

Malaria is still a significant health problem in endemic countries and increases Plasmodium resistance to the available antimalarial drugs. Hence, this study aimed to investigate the antimalarial activity of allicin and its combination with artesunate (ART) against rodent malaria Plasmodium berghei ANKA (PbANKA) infected mice. Allicin was prepared in 20% Tween-80. Balb/c mice were inoculated intraperitoneally with 1×10⁷ PbANKA-infected erythrocytes and orally given by gavage with the chosen doses of 1, 10, 50, and 100 mg/kg of allicin and 1, 5, 10, and 20 mg/kg of ART once a day for 4 consecutive days. Effective dose 50 (ED₅₀) of allicin and ART was subsequently investigated. Moreover, the combination (1 : 1) of allicin and ART at the doses of their respective ED₅₀, ED₅₀ 1/2, ED₅₀ 1/4, and ED₅₀ 1/8 was also carried out. The untreated control was given 20% Tween-80. The results showed that allicin presented a dose-dependent antimalarial activity with significance (p < 0.05). The ED₅₀ values of allicin and ART were about 14 and 5 mg/kg, respectively. For combination, allicin and ART showed a synergistic effect at the combination doses of ED₅₀, ED₅₀ 1/2, and ED₅₀ 1/4 with significantly (p < 0.01) prevented reduction of packed cell volume, bodyweight loss, rapid dropping of rectal temperature, and markedly prolonged mean survival time, compared with the untreated control and single treatment. It can be concluded that allicin exerted potential antimalarial activity in single and its combination with ART.