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Structure-Activity Relationship Studies Reveal New Astemizole Analogues Active against Plasmodium falciparum In Vitro.

ABSTRACT: In the context of drug repositioning and expanding the existing structure-activity relationship around astemizole (AST), a new series of analogues were designed, synthesized, and evaluated for their antiplasmodium activity. Among 46 analogues tested, compounds 21, 30, and 33 displayed high activities against asexual blood stage parasites (PfNF54 IC₅₀ = 0.025-0.043 μM), whereas amide compound 46 additionally showed activity against late-stage gametocytes (stage IV/V; PfLG IC₅₀ = 0.6 ± 0.1 μM) and 860-fold higher selectivity over hERG (46, SI = 43) compared to AST. Several analogues displaying high solubility (Sol > 100 μM) and low cytoxicity in the Chinese hamster ovary (SI > 148) cell line have also been identified.

SUBMITTER: Mambwe D

PROVIDER: S-EPMC8366009 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Structure-Activity Relationship Studies Reveal New Astemizole Analogues Active against Plasmodium falciparum In Vitro.

Mambwe Dickson D Kumar Malkeet M Ferger Richard R Taylor Dale D Njoroge Mathew M Coertzen Dina D Reader Janette J van der Watt Mariëtte M Birkholtz Lyn-Marie LM Chibale Kelly K

ACS medicinal chemistry letters 20210802 8

In the context of drug repositioning and expanding the existing structure-activity relationship around astemizole (AST), a new series of analogues were designed, synthesized, and evaluated for their antiplasmodium activity. Among 46 analogues tested, compounds 21, 30, and 33 displayed high activities against asexual blood stage parasites (PfNF54 IC50 = 0.025-0.043 μM), whereas amide compound 46 additionally showed activity against late-stage gametocy ...[more]

PMID: 34413963

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Project description:BackgroundNew anti-malarial drugs are needed urgently to address the increasing challenges of drug-resistant falciparum malaria. Two rhinacanthin analogues containing a naphthoquinone moiety resembling atovaquone showed promising in-vitro activity against a P. falciparum laboratory reference strain (K1). The anti-malarial activity of these 2 compounds was further evaluated for P. falciparum field isolates from an area of multi-drug resistance in Northeast Thailand.MethodsUsing a pLDH enzyme-linked immunosorbent assay, four P. falciparum isolates from Northeast Thailand in 2018 were tested for in vitro sensitivity to the two synthetic rhinacanthin analogues 1 and 2 as well as established anti-malarials. Mutations in the P. falciparum cytochrome b gene, a marker for atovaquone (ATQ) resistance, were genotyped in all four field isolates as well as 100 other clinical isolates from the same area using PCR-artificial Restriction Fragment Length Polymorphisms. Pfkelch13 mutations, a marker for artemisinin (ART) resistance, were also examined in all isolates.ResultsThe 50% inhibitory concentrations (IC50) of P. falciparum field isolates for rhinacanthin analogue 1 was 321.9-791.1 nM (median = 403.1 nM). Parasites were more sensitive to analogue 2: IC50 48.6-63.3 nM (median = 52.2 nM). Similar results were obtained against P. falciparum reference laboratory strains 3D7 and W2. The ART-resistant IPC-5202 laboratory strain was more sensitive to these compounds with a median IC50 45.9 and 3.3 nM for rhinacanthin analogues 1 and 2, respectively. The ATQ-resistant C2B laboratory strain showed high-grade resistance towards both compounds (IC50 > 15,000 nM), and there was a strong positive correlation between the IC50 values for these compounds and ATQ (r = 0.83-0.97, P < 0.001). There were no P. falciparum cytochrome b mutations observed in the field isolates, indicating that P. falciparum isolates from this area remained ATQ-sensitive. Pfkelch13 mutations and the ring-stage survival assay confirmed that most isolates were resistant to ART.ConclusionsTwo rhinacanthin analogues showed parasiticidal activity against multi-drug resistant P. falciparum isolates, although less potent than ATQ. Rhinacanthin analogue 2 was more potent than analogue 1, and can be a lead compound for further optimization as an anti-malarial in areas with multidrug resistance.

Dataset Information

Structure-Activity Relationship Studies Reveal New Astemizole Analogues Active against Plasmodium falciparum In Vitro.

Publications

Structure-Activity Relationship Studies Reveal New Astemizole Analogues Active against <i>Plasmodium falciparum</i> In Vitro.

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