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Tag: Dennis Kyle

Characterization of β-Carboline Derivatives Reveals a High Barrier to Resistance and Potent Activity against Ring-Stage and DHA-Induced Dormant Plasmodium falciparum

Donna Huber on October 17, 2025

graphical abstract

Malaria, caused by Plasmodium falciparum, remains a major global health challenge, with an estimated 263 million new infections and 597,000 deaths annually. Increasing resistance to current antimalarial drugs underscores the urgent need for new therapeutics that target novel pathways in the parasite. We previously reported a novel class of β-carboline antimalarials, exemplified by PRC1584, which demonstrated a favorable oral pharmacokinetic profile, in vivo efficacy in Plasmodium berghei-infected mice, and no cross-resistance with other antimalarials in various P. falciparum strains. In this study, we demonstrate that PRC1584 exhibits a high resistance barrier and retains potent activity against fresh Ugandan P. falciparum isolates. PRC1584, along with its more potent analog PRC1697, demonstrated strong in vitro potency against both actively proliferating ring stages and dihydroartemisinin-induced dormant stages. Additionally, our study demonstrated that PfKelch13-C580Y mutation was associated with an increased susceptibility to PRC1584, whereas PfKelch13-R549T and Pfcoronin-R100 K-E107V mutations were not associated with this effect. These findings underscore the therapeutic potential of this new “irresistible” compound class, support a possible novel mechanism of action, and suggest the future development of novel ACTs active against resistant parasites by targeting DHA dormancy, an essential survival mechanism of P. falciparum.

Reagan S Haney, Joshua H Butler, Lyric A Wardlaw, Emilio F Merino, Victoria Mendiola, Caitlin A Cooper, Jopaul Mathew, Patrick K Tumwebaze, Philip J Rosenthal, Roland A Cooper, Dennis E Kyle, Zaira Rizopoulos, Delphine Baud, Stephen Brand, Maxim Totrov, Paul R Carlier, Maria Belen Cassera. ACS Infect Dis. 2025 Oct 17. doi: 10.1021/acsinfecdis.5c00714.

Discovery and optimization of a novel carboxamide scaffold with selective antimalarial activity

Donna Huber on March 28, 2025

graphical abstract

Artemisinin combination therapies (ACTs) are critical components of malaria control worldwide. Alarmingly, ACTs have begun to fail, owing to the rise in artemisinin resistance. Thus, there is an urgent need for an expanded set of novel antimalarials to generate new combination therapies. Herein, we have identified a 1,2,4-triazole-containing carboxamide scaffold that, through scaffold hopping efforts, resulted in a nanomolar potent deuterated picolinamide (110). The lead compound of this class (110) displays moderate aqueous solubility (13.4 μM) and metabolic stability (CLintapp HLM 17.3 μL/min/mg) in vitro, as well as moderate oral bioavailability (%F 16.2) in invivo pharmacokinetic studies. Compound 110 also displayed activity against various P. falciparum isolates with different genetic backgrounds and a slow-to-moderate rate of killing (average parasite reduction ratio 2.4), making the series appealing for further development.

Alicia Wagner, Roger Trombley, Maris Podgurski, Anthony A Ruberto, Meng Cui, Caitlin A Cooper, William E Long, Gia-Bao Nguyen, Adriana A Marin, Sarah Lee Mai, Franco Lombardo, Steven P Maher, Dennis E Kyle, Roman Manetsch.Eur J Med Chem. 2025 Mar 28:291:117572. doi: 10.1016/j.ejmech.2025.117572.

Type I interferons induce guanylate-binding proteins and lysosomal defense in hepatocytes to control malaria

Donna Huber on March 25, 2025

graphical abstractPlasmodium parasites undergo development and replication within hepatocytes before infecting erythrocytes and initiating clinical malaria. Although type I interferons (IFNs) are known to hinder Plasmodium infection within the liver, the underlying mechanisms remain unclear. Here, we describe two IFN-I-driven hepatocyte antimicrobial programs controlling liver-stage malaria. First, oxidative defense by NADPH oxidases 2 and 4 triggers a pathway of lysosomal fusion with the parasitophorous vacuole (PV) to help clear Plasmodium. Second, guanylate-binding protein (GBP) 1-mediated disruption of the PV activates the caspase-1 inflammasome, inducing pyroptosis to remove infected host cells. Remarkably, both human and mouse hepatocytes enlist these cell-autonomous immune programs to eliminate Plasmodium, with their pharmacologic or genetic inhibition leading to profound malarial susceptibility in vivo. In addition to identifying IFN-I-mediated cell-autonomous immune circuits controlling Plasmodium infection in the hepatocytes, our study also extends the understanding of how non-immune cells are integral to protective immunity against malaria.

Camila Marques-da-Silva, Clyde Schmidt-Silva, Carson Bowers, Nana Appiah Essel Charles-Chess, Cristina Samuel, Justine C Shiau, Eui-Soon Park, Zhongyu Yuan, Bae-Hoon Kim, Dennis E Kyle, John T Harty, John D MacMicking, Samarchith P Kurup. Cell Host Microbe. 2025 Mar 25:S1931-3128(25)00091-5. doi: 10.1016/j.chom.2025.03.008.

Screening the Global Health Priority Box against Plasmodium berghei liver stage parasites using an inexpensive luciferase detection protocol

Donna Huber on November 23, 2024

Optimization of conditions for a luciferase endpoint with in-house reagents (FLAR).

Background: Malaria, a disease caused by parasites of the genus Plasmodium, continues to impact many regions globally. The rise in resistance to artemisinin-based anti-malarial drugs highlights the need for new treatments. Ideally, new anti-malarials will kill the asymptomatic liver stages as well as the symptomatic blood stages. While blood stage screening assays are routine and efficient, liver stage screening assays are more complex and costly. To decrease the cost of liver stage screening, a previously reported luciferase detection protocol requiring only common laboratory reagents was adapted for testing against luciferase-expressing Plasmodium berghei liver stage parasites.

Methods: After optimizing cell lysis conditions, the concentration of reagents, and the density of host hepatocytes (HepG2), the protocol was validated with 28 legacy anti-malarials to show this simple protocol produces a stable signal useful for obtaining quality small molecule potency data similar to that obtained from a high content imaging endpoint. The protocol was then used to screen the Global Health Priority Box (GHPB) and confirm the potency of hits in dose-response assays. Selectivity was determined using a galactose-based, 72 h HepG2 assay to avoid missing mitochondrial-toxic compounds due to the Crabtree effect. Receiver-operator characteristic plots were used to retroactively characterize the screens’ predictive value.

Results: Optimal luciferase signal was achieved using a lower HepG2 seed density (5 × 103 cells/well of a 384-well microtitre plate) compared to many previously reported luciferase-based screens. While producing lower signal compared to a commercial alternative, this luciferase detection method was found much more stable, with a > 3 h half-life, and robust enough for producing dose-response plots with as few as 500 sporozoites/well. A screen of the GHPB resulted in 9 hits with selective activity against P. berghei liver schizonts, including MMV674132 which exhibited 30.2 nM potency. Retrospective analyses show excellent predictive value for both anti-malarial activity and cytotoxicity.

Conclusions: This method is suitable for high-throughput screening at a cost nearly 20-fold less than using commercial luciferase detection kits, thereby enabling larger liver stage anti-malarial screens and hit optimization make-test cycles. Further optimization of the hits detected using this protocol is ongoing.

Gia-Bao Nguyen, Caitlin A Cooper, Olivia McWhorter, Ritu Sharma, Anne Elliot, Anthony Ruberto, Rafael Freitas, Ashutosh K Pathak, Dennis E Kyle, Steven P Maher. Malar J. 2024 Nov 23;23(1):357. doi: 10.1186/s12936-024-05155-y.

In the news: Dennis Kyle

Donna Huber on July 8, 2024

Dennis Kyle
CTEGD Director Dennis Kyle (Photo by Andrew Davis Tucker/UGA)

 

Dennis Kyle is the Director of CTEGD and the GRA Eminent Scholar in Antiparasitic Drug Discovery in the Departments of Cellular Biology and Infectious Diseases.

Brain-eating amoeba: Will the warming climate bring more cases? (MSN)

Optimization of diastereomeric dihydropyridines as antimalarials

Donna Huber on June 18, 2024

graphical abstract

The increase in research funding for the development of antimalarials since 2000 has led to a surge of new chemotypes with potent antimalarial activity. High-throughput screens have delivered several thousand new active compounds in several hundred series, including the 4,7-diphenyl-1,4,5,6,7,8-hexahydroquinolines, hereafter termed dihydropyridines (DHPs). We optimized the DHPs for antimalarial activity. Structure-activity relationship studies focusing on the 2-, 3-, 4-, 6-, and 7-positions of the DHP core led to the identification of compounds potent (EC50 < 10 nM) against all strains of P. falciparum tested, including the drug-resistant parasite strains K1, W2, and TM90-C2B. Evaluation of efficacy of several compounds in vivo identified two compounds that reduced parasitemia by >75 % in mice 6 days post-exposure following a single 50 mg/kg oral dose. Resistance acquisition experiments with a selected dihydropyridine led to the identification of a single mutation conveying resistance in the gene encoding for Plasmodium falciparum multi-drug resistance protein 1 (PfMDR1). The same dihydropyridine possessed transmission blocking activity. The DHPs have the potential for the development of novel antimalarial drug candidates.

Kurt S Van Horn, Yingzhao Zhao, Prakash T Parvatkar, Julie Maier, Tina Mutka, Alexis Lacrue, Fabian Brockmeier, Daniel Ebert, Wesley Wu, Debora R Casandra, Niranjan Namelikonda, Jeanine Yacoub, Martina Sigal, Spencer Knapp, David Floyd, David Waterson, Jeremy N Burrows, James Duffy, Joseph L DeRisi, Dennis E Kyle, R Kiplin Guy, Roman Manetsch. Eur J Med Chem. 2024 Jun 18:275:116599. doi: 10.1016/j.ejmech.2024.116599.

A Drug Repurposing Approach Reveals Targetable Epigenetic Pathways in Plasmodium vivax Hypnozoites

Donna Huber on May 29, 2024

Hypnozonticidal hit detection and confirmation.
Hypnozonticidal hit detection and confirmation.

Radical cure of Plasmodium vivax malaria must include elimination of quiescent ‘hypnozoite’ forms in the liver; however, the only FDA-approved treatments are contraindicated in many vulnerable populations. To identify new drugs and drug targets for hypnozoites, we screened the Repurposing, Focused Rescue, and Accelerated Medchem (ReFRAME) library and a collection of epigenetic inhibitors against P. vivax liver stages. From both libraries, we identified inhibitors targeting epigenetics pathways as selectively active against P. vivax and P. cynomolgi hypnozoites. These include DNA methyltransferase (DNMT) inhibitors as well as several inhibitors targeting histone post-translational modifications. Immunofluorescence staining of Plasmodium liver forms showed strong nuclear 5-methylcystosine signal, indicating liver stage parasite DNA is methylated. Using bisulfite sequencing, we mapped genomic DNA methylation in sporozoites, revealing DNA methylation signals in most coding genes. We also demonstrated that methylation level in proximal promoter regions as well as in the first exon of the genes may affect, at least partially, gene expression in P. vivax. The importance of selective inhibitors targeting epigenetic features on hypnozoites was validated using MMV019721, an acetyl-CoA synthetase inhibitor that affects histone acetylation and was previously reported as active against P. falciparum blood stages. In summary, our data indicate that several epigenetic mechanisms are likely modulating hypnozoite formation or persistence and provide an avenue for the discovery and development of improved radical cure antimalarials.

S. P. Maher, M. A. Bakowski, A. Vantaux, E. L. Flannery, C. Andolina, M. Gupta, Y. Antonova-Koch, M. Argomaniz, M. Cabrera-Mora, B. Campo, A. T. Chao, A. K. Chatterjee, W. T. Cheng, E. Chuenchob, C. A. Cooper, K. Cottier, M. R. Galinski, A. Harupa-Chung, H. Ji, S. B. Joseph, T. Lenz, S. Lonardi, J. Matheson, S. A. Mikolajczak, T. Moeller, A. Orban, V. Padín-Irizarry, K. Pan, J. Péneau, J. Prudhomme, C. Roesch, A. A. Ruberto, S. S. Sabnis, C. L. Saney, J. Sattabongkot, S. Sereshki, S. Suriyakan, R. Ubalee, Y. Wang, P. Wasisakun, J. Yin, J. Popovici, C. W. McNamara, C. J. Joyner, F. Nosten, B. Witkowski, K. G. Le Roch, D. E. Kyle. 2024. eLife13:RP98221, https://doi.org/10.7554/eLife.98221.1

 

The influence of oviposition status on measures of transmission potential in malaria-infected mosquitoes depends on sugar availability

Donna Huber on May 23, 2024

graphical abstract

Background: Like other oviparous organisms, the gonotrophic cycle of mosquitoes is not complete until they have selected a suitable habitat to oviposit. In addition to the evolutionary constraints associated with selective oviposition behavior, the physiological demands relative to an organism’s oviposition status also influence their nutrient requirement from the environment. Yet, studies that measure transmission potential (vectorial capacity or competence) of mosquito-borne parasites rarely consider whether the rates of parasite replication and development could be influenced by these constraints resulting from whether mosquitoes have completed their gonotrophic cycle.

Methods: Anopheles stephensi mosquitoes were infected with Plasmodium berghei, the rodent analog of human malaria, and maintained on 1% or 10% dextrose and either provided oviposition sites (‘oviposited’ herein) to complete their gonotrophic cycle or forced to retain eggs (‘non-oviposited’). Transmission potential in the four groups was measured up to 27 days post-infection as the rates of (i) sporozoite appearance in the salivary glands (‘extrinsic incubation period’ or EIP), (ii) vector survival and (iii) sporozoite densities.

Results: In the two groups of oviposited mosquitoes, rates of sporozoite appearance and densities in the salivary glands were clearly dependent on sugar availability, with shorter EIP and higher sporozoite densities in mosquitoes fed 10% dextrose. In contrast, rates of appearance and densities in the salivary glands were independent of sugar concentrations in non-oviposited mosquitoes, although both measures were slightly lower than in oviposited mosquitoes fed 10% dextrose. Vector survival was higher in non-oviposited mosquitoes.

Conclusions: Costs to parasite fitness and vector survival were buffered against changes in nutritional availability from the environment in non-oviposited but not oviposited mosquitoes. Taken together, these results suggest vectorial capacity for malaria parasites may be dependent on nutrient availability and oviposition/gonotrophic status and, as such, argue for more careful consideration of this interaction when estimating transmission potential. More broadly, the complex patterns resulting from physiological (nutrition) and evolutionary (egg-retention) trade-offs described here, combined with the ubiquity of selective oviposition behavior, implies the fitness of vector-borne pathogens could be shaped by selection for these traits, with implications for disease transmission and management. For instance, while reducing availability of oviposition sites and environmental sources of nutrition are key components of integrated vector management strategies, their abundance and distribution are under strong selection pressure from the patterns associated with climate change.

Justine C Shiau, Nathan Garcia-Diaz, Dennis E Kyle, Ashutosh K Pathak. Parasit Vectors. 2024 May 23;17(1):236. doi: 10.1186/s13071-024-06317-2.