Biology subjects

Chibale, K.

Publications and source records attributed to Chibale, K..

7 recordsLinked to original sources

bioRxiv2025

The Human Chk1 Inhibitor CHIR-124 Shows Multistage Activity Against Plasmodium falciparum via Dual Inhibition of PfArk1 and Hemozoin Formation

The high burden of malaria and growing resistance to frontline antimalarials demand new drug target combinations with reduced propensities for conferring parasite resistance. An attractive approach for circumventing antimalarial drug resistance is target repurposing in which known drugs that act through protein targets of human origin that are also active against the human malaria parasite Plasmodium falciparum are exploited to identify novel antimalarial drug targets. Here we show that the human checkpoint kinase 1 (Chk1) inhibitor CHIR-124 is active in vitro against both drug-sensitive and drug-resistant asexual blood stage parasites and competitively binds to several Plasmodium kinases. The compound also shows moderate activity against both the liver and gametocyte forms of the parasite. Further target investigation of CHIR-124 via conditional knockdown experiments confirmed that P. falciparum Aurora-related kinase 1 (PfArk1) is implicated in its parasiticidal activity. Notably, CHIR-124 also inhibits {beta}-hematin (synthetic hemozoin) formation and causes a dose-dependent increase in free heme that correlates with inhibition of parasite growth. These findings suggest that polypharmacology is involved in the activity of CHIR-124 against P. falciparum via the dual inhibition of Plasmodium PfArk1 and hemozoin formation, both essential for parasite proliferation. This is further supported by in vitro drug combination experiments, morphological studies and resistance generation attempts. This study validates the feasibility of dual Plasmodium kinase/hemozoin formation inhibitors active against resistant strains with decreased resistance risks in the fight against malaria.

microbiology↗

bioRxiv2025

Targeting Aurora kinases as essential cell cycle regulators to deliver multi-stage antimalarials against Plasmodium falciparum

Kinases that play critical roles in the development and adaptation of Plasmodium falciparum present novel opportunities for chemotherapeutic intervention. Of particular interest are mitotic kinases that regulate the proliferation of the parasites by controlling nuclear division, segregation and cytokinesis. We evaluated the potential of human Aurora kinase (Aur) inhibitors to inhibit P. falciparum development by targeting members of the Aurora-related kinase (Ark) family in this parasite. Several human AurB inhibitors exhibited multistage potency (<250 nM) against all proliferative stages of parasite development, including asexual blood stages, liver schizonts and male gametes. Among the most potent compounds, hesperadin and AT83 exhibit >1000x selectivity towards the parasite without concerns about mammalian cell toxicity. Importantly, we identified PfArk1 as the principal vulnerable Ark family member, with specific inhibition of PfArk1 as the primary target for hesperadin and the human anaplastic lymphoma kinase (ALK) inhibitor TAE684. Hesperadins whole-cell and protein activity validates it as a unique PfArk1 tool compound. Inhibition of PfArk1 results in the parasites inability to complete mitotic processes, presenting with unsegregated, multi-lobed nuclei caused by aberrant microtubule organization. This suggests that PfArk1 is the main Aur mitotic kinase in proliferative stages of Plasmodium, characterized by bifunctional AurA and B activity. This paves the way for drug discovery campaigns based on hesperadin targeting PfArk1.

molecular biology↗

bioRxiv2024

Characterization of antimalarial activity of artemisinin-based hybrid drugs

In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed and their activity profile was characterized against drug-sensitive and drug-resistant Plasmodium falciparum parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in the hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide and in inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed some limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/577447v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@6ea6b6org.highwire.dtl.DTLVardef@831dedorg.highwire.dtl.DTLVardef@21ee5dorg.highwire.dtl.DTLVardef@1a842b7_HPS_FORMAT_FIGEXP M_FIG C_FIG Hepatic and cell-host-mediated metabolism are responsible for short plasma half-lives of antimalarial artemisinins (ARTs), illustrated here by dihydroartemisinin (DHA). ART-based hybrid drugs that overcome rapid degradation can facilitate activity against ART-resistant parasites, as illustrated by hybrid 1.

microbiology↗

bioRxiv2023

Fusidic acid-based drug combinations exhibit enhanced activity against Mycobacterium tuberculosis

Tuberculosis (TB) imposes a major burden on global public health which is exacerbated by the escalating number of multidrug-resistant (MDR)-TB cases. There is consequently an urgent need for new anti-TB drugs and combination regimens. We have investigated the natural product antibiotic fusidic acid (FA) for repurposing against Mycobacterium tuberculosis, the causative agent of TB. Here, we report the results of synergy screens combining FA with a panel of approved anti-TB agents. Checkerboard and time-kill kinetics assays identified seven compounds from different chemical classes that synergized with FA in inhibiting the growth of M. tuberculosis in vitro: rifampicin (RIF), a rifamycin and frontline anti-TB drug; the macrolides, erythromycin (ERY), clarithromycin (CLR), and roxythromycin (ROX); the oxazolidinone, linezolid (LZD); the aminoglycoside, streptomycin (STR); and the aminocyclitol, spectinomycin (SPC). Among these, the strongest synergies were observed where FA was combined with SPC and ERY. Moreover, the FA-RIF combination was cidal, while all other FA combinations were bacteriostatic. These results provide in vitro evidence of the potential utility of FA-containing combinations against M. tuberculosis.

microbiology↗

bioRxiv2022

First fully-automated AI/ML virtual screening cascade implemented at a drug discovery centre in Africa

We present ZairaChem, an artificial intelligence (AI)- and machine learning (ML)-based tool to train small-molecule activity prediction models. ZairaChem is fully automated, requires low computational resources and works across a broad spectrum of datasets, ranging from whole-cell growth inhibition assays to drug metabolism properties. The tool has been implemented end-to-end at the Holistic Drug Discovery and Development (H3D) Centre, the leading integrated drug discovery unit in Africa, at which no prior AI/ML capabilities were available. We have exploited in-house data collected from over a decade of drug discovery research in malaria and tuberculosis and built models to predict the outcomes of 15 key checkpoint assays. We subsequently deployed these models as a virtual screening cascade at an organisational scale to increase the hit rate of current experimental assays. We show how computational profiling of compounds, prior to synthesis and experimental testing, can increase the rate of progression by up to 40%. Moreover, we demonstrate that the approach can be applied to prioritise small molecules within a chemical series and to assess the likelihood of success of novel chemotypes, promoting efficient usage of limited experimental resources. This project is part of a first-of-its-kind collaboration between the H3D Centre, a research centre operating in a low-resource setting, and the Ersilia Open Source Initiative, a young tech non-profit devoted to building data science capacity in the Global South.

bioinformatics↗

bioRxiv2020

Multistage and transmission-blocking targeted antimalarials discovered from the open-source MMV Pandemic Response Box

New chemical matter is needed to target the divergent biology associated with the different life cycle stages of Plasmodium. Here, we report the parallel screening of the Medicines for Malaria Venture Pandemic Response Box to identify multistage-active and stage-specific compounds against various life cycle stages of Plasmodium parasites (asexual parasites, stage IV/V gametocytes, gametes, oocysts and liver stages) and for endectocidal activity. Hits displayed unique chemotypes and included two multistage-active compounds, 16 asexual-targeted, six with prophylactic potential and ten gametocyte-targeted compounds. Notably, four structurally diverse gametocyte-targeted compounds with potent transmission-blocking activity were identified: the JmjC inhibitor ML324, two azole antifungals including eberconazole, and the antitubercular clinical candidate SQ109. Besides ML324, none of these have previously attributed antiplasmodial activity, emphasizing the success of de novo parallel screening against different Plasmodium stages to deliver leads with novel modes-of-action. Importantly, the discovery of such transmission-blocking targeted compounds covers a previously unexplored base for delivery of compounds required for malaria elimination strategies.

microbiology↗

bioRxiv2019

Developing synergistic drug combinations to restore antibiotic sensitivity in drug-resistant Mycobacterium tuberculosis

Tuberculosis (TB) is a leading global cause of mortality owing to an infectious agent, accounting for almost one-third of antimicrobial resistance (AMR) deaths annually. We aimed to identify synergistic anti-TB drug combinations with the capacity to restore therapeutic efficacy against drug-resistant mutants of the causative agent, Mycobacterium tuberculosis. We investigated combinations containing the known translational inhibitors, spectinomycin (SPT) and fusidic acid (FA), or the phenothiazine, chlorpromazine (CPZ), which disrupts mycobacterial energy metabolism. Potentiation of whole-cell drug efficacy was observed in SPT-CPZ combinations. This effect was lost against an M. tuberculosis mutant lacking the major facilitator superfamily (MFS) efflux pump, Rv1258c. Notably, the SPT-CPZ combination restored SPT efficacy against an SPT-resistant mutant carrying a g1379t point mutation in rrs, encoding the mycobacterial 16S ribosomal RNA. Combinations of SPT with FA, which targets the mycobacterial elongation factor G, exhibited potentiating activity against wild-type M. tuberculosis. Moreover, this combination produced a marginal potentiating effect against both FA-monoresistant and SPT-monoresistant mutants. Finally, combining SPT with the frontline anti-TB agents, rifampicin (RIF) and isoniazid, resulted in enhanced activity in vitro and ex vivo against both drug-susceptible M. tuberculosis and a RIF-monoresistant rpoB S531L mutant.These results support the utility of novel potentiating drug combinations in restoring antibiotic susceptibility of M. tuberculosis strains carrying genetic resistance to any one of the partner compounds.

microbiology↗