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Novel antimalarial compounds targeting both the pathogenic and transmissible stages of the human malaria parasite, Plasmodium falciparum, would greatly benefit malaria elimination strategies. However, most compounds affecting asexual blood stage parasites show severely reduced activity against gametocytes. The impact of this activity loss on a compound's transmission-blocking activity is unclear. Here, we report the systematic evaluation of the activity loss against gametocytes and investigate the confounding factors contributing to this. A threshold for acceptable activity loss between asexual blood stage parasites and gametocytes was defined, with near-equipotent compounds required to prevent continued gametocyte maturation and onward transmission. Target abundance is not predictive of gametocytocidal activity, but instead, lipoidal uptake is the main barrier of dual activity and is influenced by distinct physicochemical properties. This study provides guidelines for the required profiles of potential dual-active antimalarial agents and facilitates the development of effective transmission-blocking compounds., Competing Interests: Competing interests D.L. is a senior director in drug discovery at the Medicines for Malaria Venture (M.M.V.). M.M.V. funded part of this study. The other authors declare no competing interest., (© 2024. The Author(s).)

UCT594 is a 2-aminopyrazine carboxylic acid Plasmodium phosphatidylinositol 4-kinase inhibitor with potent asexual blood-stage activity, the potential for interrupting transmission, as well as liver-stage activities. Herein, we investigated pharmacokinetic/pharmacodynamic (PK/PD) relationships relative to blood-stage activity toward predicting the human dose. Dose-fractionation studies were conducted in the Plasmodium falciparum NSG mouse model to determine the PK/PD indices of UCT594, using the in vivo minimum parasiticidal concentration as a threshold. UCT594 demonstrated concentration-dependent killing in the P. falciparum -infected NSG mouse model. Using this data and the preclinical pharmacokinetic data led to a low predicted human dose of <50 mg. This makes UCT594 an attractive potential antimalarial drug., Competing Interests: The authors declare no conflict of interest.

Toward repositioning the antitubercular clinical candidate SQ109 as an antimalarial, analogs were investigated for structure-activity relationships for activity against asexual blood stages of the human malaria parasite Plasmodium falciparum pathogenic forms, as well as transmissible, sexual stage gametocytes. We show that equipotent activity (IC 50 ) in the 100-300 nM range could be attained for both asexual and sexual stages, with the activity of most compounds retained against a multidrug-resistant strain. The multistage activity profile relies on high lipophilicity ascribed to the adamantane headgroup, and antiplasmodial activity is critically dependent on the diamine linker. Frontrunner compounds showed conserved activity against genetically diverse southern African clinical isolates. We additionally validated that this series could block transmission to mosquitoes, marking these compounds as novel chemotypes with multistage antiplasmodial activity.

Gyrase and topoisomerase IV are the cellular targets for fluoroquinolones, a critically important class of antibacterial agents used to treat a broad spectrum of human infections. Unfortunately, the clinical efficacy of the fluoroquinolones has been curtailed by the emergence of target-mediated resistance. This is especially true for Neisseria gonorrhoeae , the causative pathogen of the sexually transmitted infection gonorrhea. Spiropyrimidinetriones (SPTs), a new class of antibacterials, were developed to combat the growing antibacterial resistance crisis. Zoliflodacin is the most clinically advanced SPT and displays efficacy against uncomplicated urogenital gonorrhea in human trials. Like fluoroquinolones, the primary target of zoliflodacin in N. gonorrhoeae is gyrase, and topoisomerase IV is a secondary target. Because unbalanced gyrase/topoisomerase IV targeting has facilitated the evolution of fluoroquinolone-resistant bacteria, it is important to understand the underlying basis for the differential targeting of zoliflodacin in N. gonorrhoeae . Therefore, we assessed the effects of this SPT on the catalytic and DNA cleavage activities of N. gonorrhoeae gyrase and topoisomerase IV. In all reactions examined, zoliflodacin displayed higher potency against gyrase than topoisomerase IV. Moreover, zoliflodacin generated more DNA cleavage and formed more stable enzyme-cleaved DNA-SPT complexes with gyrase. The SPT also maintained higher activity against fluoroquinolone-resistant gyrase than topoisomerase IV. Finally, when compared to zoliflodacin, the novel SPT H3D-005722 induced more balanced double-stranded DNA cleavage with gyrase and topoisomerase IV from N. gonorrhoeae , Escherichia coli , and Bacillus anthracis . This finding suggests that further development of the SPT class could yield compounds with a more balanced targeting against clinically important bacterial infections.

Structure-activity relationship studies of 2,8-disubstituted-1,5-naphthyridines, previously reported as potent inhibitors of Plasmodium falciparum ( Pf ) phosphatidylinositol-4-kinase β (PI4K), identified 1,5-naphthyridines with basic groups at 8-position, which retained Plasmodium PI4K inhibitory activity but switched primary mode of action to the host hemoglobin degradation pathway through inhibition of hemozoin formation. These compounds showed minimal off-target inhibitory activity against the human phosphoinositide kinases and MINK1 and MAP4K kinases, which were associated with the teratogenicity and testicular toxicity observed in rats for the Pf PI4K inhibitor clinical candidate MMV390048. A representative compound from the series retained activity against field isolates and lab-raised drug-resistant strains of Pf . It was efficacious in the humanized NSG mouse malaria infection model at a single oral dose of 32 mg/kg. This compound was nonteratogenic in the zebrafish embryo model of teratogenicity and has a low predicted human dose, indicating that this series has the potential to deliver a preclinical candidate for malaria.

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 hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, 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 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., Competing Interests: The authors declare no conflict of interest.

Artificial intelligence (AI) and machine learning (ML) are anticipated to accelerate drug discovery programs. Following our development of an end-to-end virtual screening cascade at the University of Cape Town (UCT) Holistic Drug Discovery and Development (H3D) Center, we report the ongoing implementation of open-source AI/ML tools for use in resource-constrained settings., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Toward addressing the cardiotoxicity liability associated with the antimalarial drug astemizole (AST, hERG IC 50 = 0.0042 μM) and its derivatives, we designed and synthesized analogues based on compound 1 ( Pf NF54 IC 50 = 0.012 μM; hERG IC 50 = 0.63 μM), our previously identified 3-trifluoromethyl-1,2,4-oxadiazole AST analogue. Compound 11 retained in vitro multistage antiplasmodium activity (ABS Pf NF54 IC 50 = 0.017 μM; gametocytes Pf iGc/ Pf LGc IC 50 = 1.24/1.39 μM, and liver-stage Pb HepG2 IC 50 = 2.30 μM), good microsomal metabolic stability (MLM CL int < 11 μL·min -1 ·mg -1 , E H < 0.33), and solubility (150 μM). It shows a ∼6-fold and >6000-fold higher selectivity against human ether-á-go-go-related gene higher selectively potential over hERG relative to 1 and AST, respectively. Despite the excellent in vitro antiplasmodium activity profile, in vivo efficacy in the Plasmodium berghei mouse infection model was diminished, attributable to suboptimal oral bioavailability ( F = 14.9%) at 10 mg·kg -1 resulting from poor permeability (log  D 7.4 = -0.82). No cross-resistance was observed against 44 common Pf mutant lines, suggesting activity via a novel mechanism of action., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Zoonotic and related infections pose an enormous health threat to the world's second-most populous continent. Despite the challenges faced by drug discovery scientists in Africa, recent progress toward identifying potential medicines across diverse disease areas is a cause for optimism and an indicator of progress in African-led scientific initiatives.

Recent antimalarial drug discovery has been a race to produce new medicines that overcome emerging drug resistance, whilst considering safety and improving dosing convenience. Discovery efforts have yielded a variety of new molecules, many with novel modes of action, and the most advanced are in late-stage clinical development. These discoveries have led to a deeper understanding of how antimalarial drugs act, the identification of a new generation of drug targets, and multiple structure-based chemistry initiatives. The limited pool of funding means it is vital to prioritize new drug candidates. They should exhibit high potency, a low propensity for resistance, a pharmacokinetic profile that favours infrequent dosing, low cost, preclinical results that demonstrate safety and tolerability in women and infants, and preferably the ability to block Plasmodium transmission to Anopheles mosquito vectors. In this Review, we describe the approaches that have been successful, progress in preclinical and clinical development, and existing challenges. We illustrate how antimalarial drug discovery can serve as a model for drug discovery in diseases of poverty., (© 2023. Springer Nature Limited.)

Streamlined data-driven drug discovery remains challenging, especially in resource-limited settings. We present ZairaChem, an artificial intelligence (AI)- and machine learning (ML)-based tool for quantitative structure-activity/property relationship (QSAR/QSPR) modelling. ZairaChem is fully automated, requires low computational resources and works across a broad spectrum of datasets. We describe an end-to-end implementation at the H3D Centre, the leading integrated drug discovery unit in Africa, at which no prior AI/ML capabilities were available. By leveraging in-house data collected over a decade, we have developed a virtual screening cascade for malaria and tuberculosis drug discovery comprising 15 models for key decision-making assays ranging from whole-cell phenotypic screening and cytotoxicity to aqueous solubility, permeability, microsomal metabolic stability, cytochrome inhibition, and cardiotoxicity. We show how computational profiling of compounds, prior to synthesis and testing, can inform progression of frontrunner compounds at H3D. This project is a first-of-its-kind deployment at scale of AI/ML tools in a research centre operating in a low-resource setting., (© 2023. Springer Nature Limited.)

Highly druggable and essential to almost all aspects of cellular life, the protein and phosphoinositide kinase gene families offer a wealth of potential targets for pharmacological modulation for both noncommunicable and infectious diseases. Despite the success of kinase inhibitors in oncology and other disease indications, targeting kinases comes with significant challenges. Key hurdles for kinase drug discovery include selectivity and acquired resistance. The phosphatidylinositol 4-kinase beta inhibitor MMV390048 showed good efficacy in Phase 2a clinical trials, demonstrating the potential of kinase inhibitors for malaria treatment. Here we argue that the potential benefits of Plasmodium kinase inhibitors outweigh the risks, and we highlight the opportunity for designed polypharmacology to reduce the risk of resistance., Competing Interests: Declaration of interests The authors declare no competing financial interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This viewpoint outlines the case for developing new chemical entities (NCEs) as racemates in infectious diseases and where both enantiomers and racemate retain similar on- and off-target activities as well as similar PK profiles. There are not major regulatory impediments for the development of a racemic drug, and minimizing the manufacturing costs becomes a particularly important objective when bringing an anti-infective therapeutic to the marketplace in the endemic settings of infectious diseases., Competing Interests: The authors declare the following competing financial interest(s): T.S. is an employee of Ares Trading SA, an affiliate of Merck KGaA, Darmstadt, Germany., (© 2023 The Authors. Published by American Chemical Society.)

The translation of a preclinical antimalarial drug development candidate to the clinical phases should be supported by rational human dose selection. A model-informed strategy based on preclinical data, which incorporates pharmacokinetic-pharmacodynamic (PK-PD) properties with physiologically based pharmacokinetic (PBPK) modeling, is proposed to optimally predict an efficacious human dose and dosage regimen for the treatment of Plasmodium falciparum malaria. The viability of this approach was explored using chloroquine, which has an extensive clinical history for malaria treatment. First, the PK-PD parameters and the PK-PD driver of efficacy for chloroquine were determined through a dose fractionation study in the P. falciparum-infected humanized mouse model. A PBPK model for chloroquine was then developed for predicting the drug's PK profiles in a human population, from which the human PK parameters were determined. Lastly, the PK-PD parameters estimated in the P. falciparum-infected mouse model and the human PK parameters derived from the PBPK model were integrated to simulate the human dose-response relationships against P. falciparum, which subsequently allowed the determination of an optimized treatment. The predicted efficacious human dose and dosage regimen for chloroquine were comparable to those recommended clinically for the treatment of uncomplicated, drug-sensitive malaria, which provided supportive evidence for the proposed model-based approach to antimalarial human dose predictions., Competing Interests: The authors declare no conflict of interest.

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 partially 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 modest 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., (Copyright © 2021 Omollo et al.)

Drug metabolism is generally associated with liver enzymes. However, in the case of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), Mtb-mediated drug metabolism plays a significant role in treatment outcomes. Mtb is equipped with enzymes that catalyse biotransformation reactions on xenobiotics with consequences either in its favour or as a hindrance by deactivating or activating chemical entities, respectively. Considering the range of chemical reactions involved in the biosynthetic pathways of Mtb, information related to the biotransformation of antitubercular compounds would provide opportunities for the development of new chemical tools to study successful TB infections while also highlighting potential areas for drug discovery, host-directed therapy, dose optimization and elucidation of mechanisms of action. In this Review, we discuss Mtb-mediated biotransformations and propose a holistic approach to address drug metabolism in TB drug discovery and related areas., (© 2023. Springer Nature Limited.)

We previously identified a novel class of antimalarial benzimidazoles incorporating an intramolecular hydrogen bonding motif. The frontrunner of the series, analogue A , showed nanomolar activity against the chloroquine-sensitive NF54 and multi-drug-resistant K1 strains of Plasmodium falciparum ( Pf NF54 IC 50 = 0.079 μM; Pf K1 IC 50 = 0.335 μM). Here, we describe a cell-based medicinal chemistry structure-activity relationship study using compound A as a basis. This effort led to the identification of novel antimalarial imidazopyridines with activities of <1 μM, favorable cytotoxicity profiles, and good physicochemical properties. Analogue 14 ( Pf NF54 IC 50 = 0.08 μM; Pf K1 IC 50 = 0.10 μM) was identified as the frontrunner of the series. Preliminary mode of action studies employing molecular docking, live-cell confocal microscopy, and a cellular heme fractionation assay revealed that 14 does not directly inhibit the conversion of heme to hemozoin, although it could be involved in other processes in the parasite's digestive vacuole.

Structural modification of existing chemical scaffolds to afford new molecules able to circumvent drug resistance constitutes one of the rational approaches to antimalarial drug discovery. Previously synthesized compounds based on the 4-aminoquinoline core hybridized with a chemosensitizing dibenzylmethylamine side group showed in vivo efficacy in Plasmodium berghei -infected mice despite low microsomal metabolic stability, suggesting a contribution from their pharmacologically active metabolites. Here, we report on a series of these dibemequine (DBQ) metabolites with low resistance indices against chloroquine-resistant parasites and improved metabolic stability in liver microsomes. The metabolites also exhibit improved pharmacological properties including lower lipophilicity, cytotoxicity, and hERG channel inhibition. Using cellular heme fractionation experiments, we also demonstrate that these derivatives inhibit hemozoin formation by causing a buildup of toxic "free" heme in a similar manner to chloroquine. Finally, assessment of drug interactions also revealed synergy between these derivatives and several clinically relevant antimalarials, thus highlighting their potential interest for further development.

The rise in drug-resistant tuberculosis has necessitated the search for alternative antibacterial treatments. Spiropyrimidinetriones (SPTs) represent an important new class of compounds that work through gyrase, the cytotoxic target of fluoroquinolone antibacterials. The present study analyzed the effects of a novel series of SPTs on the DNA cleavage activity of Mycobacterium tuberculosis gyrase. H3D-005722 and related SPTs displayed high activity against gyrase and increased levels of enzyme-mediated double-stranded DNA breaks. The activities of these compounds were similar to those of the fluoroquinolones, moxifloxacin, and ciprofloxacin and greater than that of zoliflodacin, the most clinically advanced SPT. All the SPTs overcame the most common mutations in gyrase associated with fluoroquinolone resistance and, in most cases, were more active against the mutant enzymes than wild-type gyrase. Finally, the compounds displayed low activity against human topoisomerase IIα. These findings support the potential of novel SPT analogues as antitubercular drugs.

Iterative medicinal chemistry optimization of an ester-containing astemizole (AST) analogue 1 with an associated metabolic instability liability led to the identification of a highly potent 3-trifluoromethyl-1,2,4-oxadiazole analogue 23 ( Pf NF54 IC 50 = 0.012 μM; Pf K1 IC 50 = 0.040 μM) displaying high microsomal metabolic stability (HLM CL int < 11.6 μL·min -1 ·mg -1 ) and > 1000-fold higher selectivity over hERG compared to AST. In addition to asexual blood stage activity, the compound also shows activity against liver and gametocyte life cycle stages and demonstrates in vivo efficacy in Plasmodium berghei -infected mice at 4 × 50 mg·kg -1 oral dose. Preliminary interrogation of the mode of action using live-cell microscopy and cellular heme speciation revealed that 23 could be affecting multiple processes in the parasitic digestive vacuole, with the possibility of a novel target at play in the organelles associated with it.

Alternative mode-of-inhibition of clinically validated targets is an effective strategy for circumventing existing clinical drug resistance. Herein, we report 1,3-diarylpyrazolyl-acylsulfonamides as potent inhibitors of HadAB/BC, a 3-hydroxyl-ACP dehydratase complex required to iteratively elongate the meromycolate chain of mycolic acids in Mycobacterium tuberculosis ( Mtb ). Mutations in compound 1 -resistant Mtb mutants mapped to HadC (Rv0637; K157R), while chemoproteomics confirmed the compound's binding to HadA (Rv0635), HadB (Rv0636), and HadC. The compounds effectively inhibited the HadAB and HadBC enzyme activities and affected mycolic acid biosynthesis in Mtb , in a concentration-dependent manner. Unlike known 3-hydroxyl-ACP dehydratase complex inhibitors of clinical significance, isoxyl and thioacetazone, 1,3-diarylpyrazolyl-acylsulfonamides did not require activation by EthA and thus are not liable to EthA-mediated resistance. Further, the crystal structure of a key compound in a complex with Mtb HadAB revealed unique binding interactions within the active site of HadAB, providing a useful tool for further structure-based optimization of the series.

Compounds acting on multiple targets are critical to combating antimalarial drug resistance. Here, we report that the human "mammalian target of rapamycin" (mTOR) inhibitor sapanisertib has potent prophylactic liver stage activity, in vitro and in vivo asexual blood stage (ABS) activity, and transmission-blocking activity against the protozoan parasite Plasmodium spp. Chemoproteomics studies revealed multiple potential Plasmodium kinase targets, and potent inhibition of Plasmodium phosphatidylinositol 4-kinase type III beta (PI4Kβ) and cyclic guanosine monophosphate-dependent protein kinase (PKG) was confirmed in vitro. Conditional knockdown of PI4Kβ in ABS cultures modulated parasite sensitivity to sapanisertib, and laboratory-generated P. falciparum sapanisertib resistance was mediated by mutations in PI4Kβ. Parasite metabolomic perturbation profiles associated with sapanisertib and other known PI4Kβ and/or PKG inhibitors revealed similarities and differences between chemotypes, potentially caused by sapanisertib targeting multiple parasite kinases. The multistage activity of sapanisertib and its in vivo antimalarial efficacy, coupled with potent inhibition of at least two promising drug targets, provides an opportunity to reposition this pyrazolopyrimidine for malaria.

Fluorene-chloroquine hybrids have been identified as a new promising class of antiplasmodial agents. The most active compound 9 d exhibited good in vitro antiplasmodial activity against a chloroquine-sensitive NF54 strain of the human malaria parasite Plasmodium falciparum with an IC 50 value of 139 nM. UV-visible absorption, FTIR spectral and 1 H NMR titration data corroborated the binding of 9 d to monomeric and μ-oxodimeric heme as well as inhibition of β-hematin formation, which collectively supported the inhibition of heme detoxification machinery in P. falciparum. In silico docking studies revealed the binding interactions of the hybrids in the active site of the wild type as well as quadruple mutant of Pf-DHFR-TS dihydrofolate enzyme. Further, the ADMET parameters were predicted and were in good agreement with the expected values, suggesting the drug likeness of the synthesized hybrid molecules., (© 2022 Wiley-VCH GmbH.)

We have a long-term vision to develop drug discovery research capacity within Ghana, to tackle unmet medical needs in Ghana and the wider West African region. However, there are several issues and challenges that need to be overcome to enable this vision, including training, human resource, equipment, infrastructure, procurement, and logistics. We discuss these challenges from the context of Ghana in this review. An important development is the universities and research centres within Ghana working together to address some of these challenges. Therefore, while there is a long way to go to fully accomplish our vision, there are encouraging signs., Competing Interests: The authors have declared that no competing interests exist.

Inhibiting translation presents a tantalizing strategy to tackle the most virulent human malaria parasite. Xie et al. disclose a compound that binds selectively to Plasmodium falciparum tyrosine aminoacyl-tRNA synthetase, preventing the incorporation of tyrosine into nascent proteins and paving the way for a new generation of safe, effective antimalarials., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Pyrido[1,2- a ]benzimidazoles (PBIs) are synthetic antiplasmodium agents with potent activity and are structurally differentiated from benchmark antimalarials. To study the cellular uptake of PBIs and understand the underlying phenotype of their antiplasmodium activity, their antiparasitic activities were examined in chloroquine (CQ)-susceptible and CQ-resistant Plasmodium falciparum in vitro . Moreover, drug uptake and heme detoxification suppression were examined in Plasmodium berghei -infected mice. The in vitro potency of PBIs is comparable to most 4-aminoquinolines. They have a speed of action in vitro that is superior to that of atovaquone and an ability to kill rings and trophozoites. The antiparasitic effects observed for the PBIs in cell culture and in infected mice are similar in terms of potency and efficacy and are comparable to CQ but with the added advantage of demonstrating equipotency against both CQ susceptible and resistant parasite strains. PBIs have a high rate of uptake by parasite cells and, conversely, a limited rate of uptake by host cells. The mechanism of cellular uptake of the PBIs differs from the ion-trap mechanism typically observed for 4-aminoquinolines, although they share key structural features. The high cellular uptake, attractive parasiticidal profile, and susceptibility of resistant strains to PBIs are desirable characteristics for new antimalarial agents.

The continuous, worldwide spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) endanger the World Health Organization's (WHO) goal to end the global TB pandemic by the year 2035. During the past 50 years, very few new drugs have been approved by medical agencies to treat drug-resistant TB. Therefore, the development of novel antimycobacterial drug candidates to combat the threat of drug-resistant TB is urgent. In this work, we developed and optimized a total synthesis of the antimycobacterial natural flavonoid chlorflavonin by selective ruthenium(II)-catalyzed ortho -C(sp 2 )-H-hydroxylation of a substituted 3'-methoxyflavonoid skeleton. We extended our methodology to synthesize a small compound library of 14 structural analogs. The new analogs were tested for their antimycobacterial in vitro activity against Mycobacterium tuberculosis ( Mtb ) and their cytotoxicity against various human cell lines. The most promising new analog bromflavonin exhibited improved antimycobacterial in vitro activity against the virulent H37Rv strain of Mtb (Minimal Inhibitory Concentrations (MIC 90 ) = 0.78 μm). In addition, we determined the chemical and metabolic stability as well as the p K a values of chlorflavonin and bromflavonin. Furthermore, we established a quantitative structure-activity relationship model using a thermodynamic integration approach. Our computations may be used for suggesting further structural changes to develop improved derivatives.

As the so-called "next frontier" in global economic terms, Africa's disease burden continues to choke and cripple economic growth across the continent. The highest burden is attributable to malaria and tuberculosis (TB), which also remain among the deadliest infectious diseases affecting mankind the world over (Malaria, 627,000 deaths; TB, 1.5 million deaths, in 2020). In achieving self-determination with respect to the health needs of all who live on the continent, Africa must align with global north efforts and be a source of health innovation. This will in part require the creation of an ecosystem of innovative pharmaceutical R&D and expanding it across the continent by scaling up through sustained performance and excellence. To this end, the Holistic Drug Discovery and Development (H3D) Centre at University of Cape Town in South Africa has risen to this challenge. Here, we highlight the innovation experiences gained at H3D, covering the advances made in our quest to contribute to a global pipeline of therapeutic interventions against malaria and TB. We discuss selected chemical series starting from their identification, structure-activity relationships, mode of action, safety, proof-of-concept studies, and lessons learned., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Widespread Plasmodium falciparum resistance to first-line antimalarials underscores the vital need to develop compounds with novel modes of action and identify new druggable targets. Here, we profile five compounds that potently inhibit P. falciparum asexual blood stages. Resistance selection studies with three carboxamide-containing compounds, confirmed by gene editing and conditional knockdowns, identify point mutations in the parasite transporter ABCI3 as the primary mediator of resistance. Selection studies with imidazopyridine or quinoline-carboxamide compounds also yield changes in ABCI3, this time through gene amplification. Imidazopyridine mode of action is attributed to inhibition of heme detoxification, as evidenced by cellular accumulation and heme fractionation assays. For the copy-number variation-selecting imidazopyridine and quinoline-carboxamide compounds, we find that resistance, manifesting as a biphasic concentration-response curve, can independently be mediated by mutations in the chloroquine resistance transporter PfCRT. These studies reveal the interconnectedness of P. falciparum transporters in overcoming drug pressure in different parasite strains., Competing Interests: Declaration of interests B.L. and M.D. are employees of MMV; M.G.G.-L. and F.-J.G. are employees of GSK., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

New antibiotics with either a novel mode of action or novel mode of inhibition are urgently needed to overcome the threat of drug-resistant tuberculosis (TB). The present study profiles new spiropyrimidinetriones (SPTs), DNA gyrase inhibitors having activity against drug-resistant Mycobacterium tuberculosis ( Mtb ), the causative agent of TB. While the clinical candidate zoliflodacin has progressed to phase 3 trials for the treatment of gonorrhea, compounds herein demonstrated higher inhibitory potency against Mtb DNA gyrase (e.g., compound 42 with IC 50 = 2.0) and lower Mtb minimum inhibitor concentrations (0.49 μM for 42 ). Notably, 42 and analogues showed selective Mtb activity relative to representative Gram-positive and Gram-negative bacteria. DNA gyrase inhibition was shown to involve stabilization of double-cleaved DNA, while on-target activity was supported by hypersensitivity against a gyrA hypomorph. Finally, a docking model for SPTs with Mtb DNA gyrase was developed, and a structural hypothesis was built for structure-activity relationship expansion.

Described here is a series of spiropyrimidinetrione (SPT) compounds with activity against Mycobacterium tuberculosis through inhibition of DNA gyrase. The SPT class operates via a novel mode of inhibition, which involves Mg 2+ -independent stabilization of the DNA cleavage complex with DNA gyrase and is thereby not cross-resistant with other DNA gyrase-inhibiting antibacterials, including fluoroquinolones. Compound 22 from the series was profiled broadly and showed in vitro cidality as well as intracellular activity against M. tuberculosis in macrophages. Evidence for the DNA gyrase mode of action was supported by inhibition of the target in a DNA supercoiling assay and elicitation of an SOS response seen in a recA reporter strain of M. tuberculosis. Pharmacokinetic properties of 22 supported evaluation of efficacy in an acute model of M. tuberculosis infection, where modest reduction in CFU numbers was seen. This work offers promise for deriving a novel drug class of tuberculosis agent without preexisting clinical resistance.

Breast cancer is the most common malignancy in women worldwide and it remains a global health burden, in part, due to poor response and tolerance to current therapeutics. Drug repurposing, which seeks to identify new indications for existing and investigational drugs, has become an exciting strategy to address these challenges. Here we describe the anti-breast cancer activity of a diaryl-imidazopyridazine compound, MMV652103, which was previously identified for its anti-plasmodial activity. We demonstrate that MMV652103 potently inhibits the oncogenic PI4KB and PIK3C2G lipid kinases, is selectively cytotoxic to MCF7 and T47D estrogen receptor positive breast cancer cells and inhibits their ability to survive and migrate. The underlying mechanisms involved included the induction of reactive oxygen species and activation of the DNA damage and p38 MAPK stress signaling pathways. This was associated with a G1 cell cycle arrest and an increase in levels of the cyclin-dependent kinase inhibitor p21 and activation of apoptotic and autophagic cell death pathways. Lastly, MMV652103 significantly reduced the weight and metastases of MCF7 induced tumors in an in vivo chick embryo model and displayed a favorable safety profile. These findings position MMV652103 as a promising chemotherapeutic in the treatment of oestrogen receptor positive breast cancers., (Copyright © 2022 Neumann-Mufweba et al.)

Tuberculosis remains a global health threat that is being exacerbated by the increase in infections attributed to drug resistant Mycobacterium tuberculosis . To combat this, there has been a surge in drug discovery programs to develop new, potent compounds and identify promising drug targets in the pathogen. Two areas of M. tuberculosis biology that have emerged as rich sources of potential novel drug targets are cell wall biosynthesis and energy metabolism. Both processes are important for survival of M. tuberculosis under replicating and nonreplicating conditions. However, both processes are also inherently adaptable under different conditions. Furthermore, cell wall biosynthesis is energy intensive and, thus, reliant on an efficiently functioning energy production system. This Perspective focuses on the interplay between cell wall biosynthesis and energy metabolism in M. tuberculosis , how adaptations in one pathway may affect the other, and what consequences this could have for drug discovery and development and the identification of novel drug targets.

Selective inhibition of the angiotensin-converting enzyme C-domain (cACE) and neprilysin (NEP), leaving the ACE N-domain (nACE) free to degrade bradykinin and other peptides, has the potential to provide the potent antihypertensive and cardioprotective benefits observed for nonselective dual ACE/NEP inhibitors, such as omapatrilat, without the increased risk of adverse effects. We have synthesized three 1-carboxy-3-phenylpropyl dipeptide inhibitors with nanomolar potency based on the previously reported C-domain selective ACE inhibitor lisinopril-tryptophan (LisW) to probe the structural requirements for potent dual cACE/NEP inhibition. Here we report the synthesis, enzyme kinetic data, and high-resolution crystal structures of these inhibitors bound to nACE and cACE, providing valuable insight into the factors driving potency and selectivity. Overall, these results highlight the importance of the interplay between the S 1 ' and S 2 ' subsites for ACE domain selectivity, providing guidance for future chemistry efforts toward the development of dual cACE/NEP inhibitors.

A series of indolyl-3-methyleneamines incorporating lipophilic side chains were designed through a structural rigidification approach and synthesized for investigation as new chemical entities against Mycobacterium tuberculosis (Mtb). The screening led to the identification of a 6-chloroindole analogue 7j bearing an N -octyl chain and a cycloheptyl moiety, which displayed potent in vitro activity against laboratory and clinical Mtb strains, including a pre-extensively drug-resistant (pre-XDR) isolate. 7j also demonstrated a marked ability to restrict the intracellular growth of Mtb in murine macrophages. Further assays geared toward mechanism of action elucidation have thus far ruled out the involvement of various known promiscuous targets, thereby suggesting that the new indole 7j may inhibit Mtb via a unique mechanism., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

Kinase-focused inhibitors previously revealed compounds with differential activity against different stages of Plasmodium falciparum gametocytes. MMV666810, a 2-aminopyrazine, is more active on late-stage gametocytes, while a pyrazolopyridine, MMV674850, preferentially targets early-stage gametocytes. Here, we probe the biological mechanisms underpinning this differential stage-specific killing using in-depth transcriptome fingerprinting. Compound-specific chemogenomic profiles were observed with MMV674850 treatment associated with biological processes shared between asexual blood stage parasites and early-stage gametocytes but not late-stage gametocytes. MMV666810 has a distinct profile with clustered gene sets associated primarily with late-stage gametocyte development, including Ca 2+ -dependent protein kinases (CDPK1 and 5) and serine/threonine protein kinases (FIKK). Chemogenomic profiling therefore highlights essential processes in late-stage gametocytes, on a transcriptional level. This information is important to prioritize compounds that preferentially compromise late-stage gametocytes for further development as transmission-blocking antimalarials.

Phenotypic whole cell high-throughput screening of a ∼150,000 diverse set of compounds against Mycobacterium tuberculosis (Mtb) in cholesterol-containing media identified 1,3-diarylpyrazolyl-acylsulfonamide 1 as a moderately active hit. Structure-activity relationship (SAR) studies demonstrated a clear scope to improve whole cell potency to MIC values of <0.5 μM, and a plausible pharmacophore model was developed to describe the chemical space of active compounds. Compounds are bactericidal in vitro against replicating Mtb and retained activity against multidrug-resistant clinical isolates. Initial biology triage assays indicated cell wall biosynthesis as a plausible mode-of-action for the series. However, no cross-resistance with known cell wall targets such as MmpL3, DprE1, InhA, and EthA was detected, suggesting a potentially novel mode-of-action or inhibition. The in vitro and in vivo drug metabolism and pharmacokinetics profiles of several active compounds from the series were established leading to the identification of a compound for in vivo efficacy proof-of-concept studies.