Skip to main content
NCBI home page
ACS Medicinal Chemistry Letters logoLink to ACS Medicinal Chemistry Letters
. 2022 Jun 21;13(7):1068–1076. doi: 10.1021/acsmedchemlett.2c00078

Synthesis, Anti-Plasmodial Activities, and Mechanistic Insights of 4-Aminoquinoline-Triazolopyrimidine Hybrids

Shefali Chowdhary †, Shalini †, Joel Mosnier ‡,§,∥,⊥, Isabelle Fonta ‡,§,∥,⊥, Bruno Pradines ‡,§,∥,⊥, Nosipho Cele #, Pule Seboletswe #, Parvesh Singh #, Vipan Kumar †,*
PMCID: PMC9290004  PMID: 35859870

Abstract

graphic file with name ml2c00078_0008.jpg

In the search of new antiplasmodial agents, a multitargeted approach was used in the synthesis of triazolopyrimidine- and 4-aminoquinolines-based hybrids. In vitro antiplasmodial evaluation on chloroquine-sensitive (3D7) and -resistant (W2) P. falciparum strains identified triazolopyrimidine-4-aminoquinoline hybrids to be the most potent in the series, outperforming bis-triazolopyrimidines. The active compounds were subjected to mechanistic studies with the plausible and expected targets including heme, PfCRT, and PfDHODH, that eventually validated the biological data. The active compound surpassed the antimalarial drug CQ by inhibiting the parasite’s cellular process (hemozoin formation) and parasitic enzymes (PfCRT and PfDHODH), as confirmed by UV–vis and molecular modeling studies.

Keywords: Triazolopyrimidine, 4-aminoquinoline, antiplasmodial, heme inhibition, PfCRT, PfDHODH

Malaria remains the most endemic global infectious disease caused by female Anopheles mosquito. Over 241 million cases and 627 000 deaths due to malaria were estimated globally in 2020 with children under the age of five and pregnant women being the most susceptible.1 Among various parasitic species, Plasmodium falciparum, P. vivax, and P. ovale cause the majority of human malaria cases.2 For many decades, quinoline-containing compounds, including chloroquine (CQ), amodiaquine, and quinine have been commissioned in the treatment of malaria. However, in the late 1950s, CQ-resistant P. falciparum malaria emerged independently in Southeast Asia and in South America, and have expanded gradually throughout India and Africa.3,4 The World Health Organization (WHO) now recommends artemisinin-based combination therapy (ACT) that includes artemisinin- and quinoline-based drugs.5 However, artemisinin-resistant P. falciparum parasites have also spread in different regions during the past decade.6,7

CQ resistance has been linked to specific mutations in the polymorphism of P. falciparum chloroquine resistance transporter (PfCRT) gene.8 Nonetheless, despite the development of resistance, CQ remains a compelling pharmacophore for chemical modification because of its excellent clinical efficacy; low host toxicity; and convenient, simple, and cost-effective synthesis.9,10 The antimalarial activity of the 7-chloro-4-aminoquinoline core is due to its ability to inhibit hemozoin formation (parasite’s defense mechanism).11 Resistance to CQ can be reversed or avoided by making specific changes around the quinoline nucleus. These moieties are designed to prevent drug efflux from the parasite’s digestive vacuole by interfering with the function of PfCRT.12 The failure of existing therapies, however, has prompted the search for newer P. falciparum targets that interfere with the nucleotide biosynthesis pathway. The Plasmodium species lack pyrimidine salvaging enzymes and rely solely on the de novo pyrimidine synthesis pathway in their DNA and RNA synthesis. Since pyrimidine biosynthesis requires the catalytic enzyme P. falciparum dihydroorotate dehydrogenase (PfDHODH), it has emerged as a viable target for antiplasmodial drug development.13

Triazolopyrimidines (TPs), a fused biaryl scaffold, is a subtype of the purine analogue. It possesses antimicrobial,14,15 antifungal,16 antibacterial,17 and antitumor18 activities and can act as a carbonic anhydrase inhibitor,19 an anti-Alzheimer agent,20 and a selective ATP site directed inhibitor of the EGF receptor protein tyrosine kinase,21 making it riveting pharmacologically. Essramycin, (I; Figure 1), the first natural TP, was recently isolated and reported to possess antibacterial activity.22 The triazolopyrimidine scaffold has proven to be a highly effective chemical class for the identification of potent and species-specific PfDHODH inhibitors, leading to the discovery of a clinical development candidate. DSM265 (II; Figure 1), a triazolopyrimidine series compound, is currently in phase I human clinical trials for the treatment of malaria and is the first PfDHODH inhibitor to reach this stage of development.23 However, point mutations (C276Y, C276F, and G181S) in PfDHODH have interfered with DSM265 binding, thus thwarting its clinical success and therefore precipitating the need for new PfDHODH inhibitors.24 A derivative of [1,2,4]-triazolo[1,5-a]pyrimidine, DSM1 (III; Figure 1) discovered by Phillips and co-workers, has also advanced to clinical trials.25

Figure 1.

Figure 1

Open in a new tab

Structures of triazolopyrimidine based bioactive compounds.

The current scenario has focused researchers’ attention on exploring new drug discovery alternatives, such as the design and synthesis of “antimalarial hybrids”.26 It is a rational approach to drug design that is known as “covalent bitherapy”. This method entails synthesizing a single entity by joining two different moieties with distinct intrinsic properties, resulting in dual activity in a single hybrid molecule.27 On this backdrop, and in continuation,28−31 the current manuscript comprises the synthesis of bis-triazolopyrimidines and 7-chloro-4-aminoquinoline-triazolopyrimidine hybrids along with their antiplasmodial evaluation on CQ-susceptible and CQ-resistant strains of P. falciparum. UV–vis spectroscopy and docking studies of the most promising scaffolds were carried out in order to decipher their antiplasmodial mechanism.

The synthetic pathways employed are depicted in Schemes 1-2. The synthesis of 7-chloro-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine (4) was achieved via an initial refluxing of ethyl acetoacetate 1 with 1H-1,2,4-triazol-5-amine 2 through intermediate 3, as represented in Scheme 1.32 The preparation of 4-aminoquinoline-based compounds (6a–f) was carried out by refluxing 4,7-dichloroquinoline with subsequent amines (diaminoalkanes and piperazine) in the presence of triethylamine, Scheme 1. Scheme 2i illustrates the microwave-assisted approach used for the preparation of bis-triazolopyrimidines, 7a–e, by heating the precursor 4 with different diamines in ethanol. The nucleophilic substitution reaction of precursors 6a–f on 4 afforded the targeted triazolopyrimidine-4-aminoquinoline hybrids, 8a–f in 48–81% yield, Scheme 2ii.

Scheme 1. Synthesis of Precursors 4 and 6a–f.

Scheme 1

Open in a new tab

Scheme 2. Synthesis of Target Compounds (i) 7a–e; and (ii) 8a–f.

Scheme 2

Open in a new tab

The structures of the synthesized compounds were determined using analytical and spectroscopic techniques. For example, the compound 8a, showed a peak at m/z 354.1172 [M + H]+ in its HRMS-ESI. Its 1H NMR spectrum showed the characteristic doublets at δ 8.39 (J = 5.4 Hz), 8.17 (J = 9.12 Hz), and 6.61 (J = 5.4 Hz) corresponding to quinoline ring protons along with singlets at δ 8.41 and 6.81 assigned to triazolopyrimidine protons. The absorptions peaks at δ 25.30 and δ 156.63 corresponding to methyl and triazolopyrimidine carbons along with aliphatic carbons at δ 69.01, 41.47 in 13C NMR spectrum further attested the assigned structure.

The synthesized compounds were assayed for their in vitro antiplasmodial activities on both CQ-susceptible (3D7) and CQ-resistant (W2) strains of P. falciparum and the results are enlisted in Table 1. Among the synthesized triazolopyrimidines dimers, the compounds exhibited low antiplasmodial activities, IC50s ranging from 11.3 to 53.8 μM on the CQ-resistant strain and 11.6–52.2 μM on the CQ-susceptible strain, respectively. The structure–activity-relationship (SAR) studies among the dimers revealed poor activities at shorter (n = 1, 2) and longer (n = 7) alkyl chain lengths, while mild activities were observed at butyl and hexyl chain length as evident from 7c and 7d. The inclusion of quinoline core among these hybrids resulted in substantial enhancement in antiplasmodial activities, both on CQ-susceptible and CQ-resistant strains. The compound 8a with an ethyl linker displayed poor activity on both the tested strains. Increasing the spacer length substantially improved the activity as evidenced by hybrids 8b–e. The hybrid 8e with an octyl chain as spacer proved to be the most potent of synthesized series displaying IC50s of 0.17 and 0.20 μM on strains, respectively. In particular, compound 8e proved to be 3-fold more active than the standard drug CQ on the CQ-resistant strain. The compound 8f having non flexible piperazine linker displayed minor activity, 12.9 μM. In addition to this, active compounds 8b–e were also tested on Vero cell lines to evaluate cytotoxicity. The tested compounds were well tolerated on the normal cell and thus displayed good selectivity indices (SI), Table 1. The synthesized compounds 7a–e and 8a–f also exhibited resistance index (RI) ranging from 0.79 to 1.20 and thus were considered to have a little cross-resistance with CQ. The graphical representation of SAR is provided in Figure 2.

Table 1. In vitro Antiplasmodial Activities of the Synthesized Compounds on CQ-Susceptible (3D7) and CQ-Resistant (W2) Strains of P. falciparuma.

    mean IC50 ± SDb in μM (no.)c
   SIe
  
s no. codes 3D7 W2 IC50d (μM) 3D7 W2 RIf
1 7a 52.2 ± 5.1 (6) 53.8 ± 10.3 (6) - - - 1.03
2 7b 47.3 ± 4.0 (6) 49.1 ± 5.6 (6) - - - 1.03
3 7c 12.5 ± 3.2 (6) 11.8 ± 1.8 (6) - - - 0.94
4 7d 11.6 ± 1.5 (6) 11.3 ± 1.9 (6) - - - 0.97
5 7e 45.8 ± 4.3 (6) 49.4 ± 7.0 (6) - - - 1.08
6 8a 9.0 ± 1.6 (8) 10.8 ± 2.3 (8) - - - 1.20
7 8b 0.62 ± 0.23 (9) 0.49 ± 0.14 (8) 180.691 291.43 368.75 0.79
8 8c 0.27 ± 0.07 (6) 0.42 ± 0.15 (8) 250.412 927.45 596.21 1.56
9 8d 0.30 ± 0.11 (9) 0.28 ± 0.10 (8) 310.734 1035.78 1109.76 0.93
10 8e 0.17 ± 0.05 (7) 0.20 ± 0.06 (6) 350.896 2064.09 1754.48 1.18
11 8f 12.6 ± 2.3 (6) 12.9 ± 2.1 (6) - - - 1.02
12 CQ 0.023 ± 0.006 (6) 0.53 ± 0.13 (6) - - - 23.04
Open in a new tab
a

Mean and standard deviation of 6 to 9 independent experiments.

b

Antiplasmodial activities on P. falciparum strains.

c

no = number of independent experiments.

d

Cytotoxicity on Vero cells.

e

Selectivity index: SI = IC50 (cytotoxicity)/IC50 (antiplasmodial activity).

f

Resistance index: RI = IC50 (W2)/IC50 (3D7).

Figure 2.

Figure 2

Open in a new tab

Graphical representation of SAR of synthesized series.

The parasite of malaria grows by degrading hemoglobin, which produces free heme in large quantities. Monomeric heme is toxic to the parasite, and in its defensive mechanism, the parasite polymerizes it into a nontoxic crystalline material called hemozoin.33 4-Aminoquinolines, as aforesaid, is believed to inhibit the formation of hemozoin by forming a complex with the free heme through π–π stacking between the quinoline ring and the porphyrin ring of free heme. The UV–vis spectrum of aqueous hematin can be studied to acknowledge this complexation between heme and CQ.34,35 Thus, in order to comprehend this primary mode of action of the synthesized hybrids, we carried out the heme binding studies of the most potent scaffold (8e). The titrations of 8e with monomeric heme in 40% DMSO:water solutions of hemin (12 μM) were carried out at pH 7.4 (0.02 M HEPES buffer, physiological pH) and pH 5.6 (0.02 M MES buffer, digestive vacuole of parasites), respectively. A band at 401 nm was observed corresponding to monomeric heme, and a significant decrease in intensity of absorption band with addition of 2 μM aliquots of 8e was observed, which represents an eloquent compound-heme binding (Figure 3). Using HypSpec (a nonlinear least-squares fitting program) to analyze the titration curves, the binding of 8e with heme was determined via logK values at both physiological and acidic pH conditions. As evident from Table 2, the binding of 8e with heme was marginally better than CQ at both tested pH.

Figure 3.

Figure 3

Open in a new tab

Titration of monomeric heme (12 μM) at (A) pH 7.4 and (B) pH 5.6, with addition of 2 μM aliquots of 8e (0–20 μM) along with the linear dependence of absorption at 401 nm on heme-8e complex.

Table 2. Binding Constant (Log K Values) for 8e and CQ.

entry pH 5.6 (MES buffer) pH 7.4 (HEPES buffer)
8e 6.38 6.79
CQ 5.18 5.10
Open in a new tab

To further elucidate the mode of action for the antiplasmodial efficacy of potent compounds 8c, 8d, and 8e, molecular docking studies were conducted using two antiplasmodial drug targets (i.e., PfCRT and PfDHODH). Crystal structures of PfCRT and PfDHODH targets were downloaded from Protein Data Bank with PDB ID: 6UKJ and 4RX0, respectively.36,37 All the calculations were performed using the Schrödinger molecular modeling suite (release 2021-2) and OPLS-2005 force field. PfCRT was chosen because the compounds were more active on the drug-resistant strain, which is a common feature of PfCRT inhibitors. Mutations in this protein are known to affect the parasite’s sensitivity to a wide range of antimalarials. The principal mechanism of these mutations confer drug resistance is by allowing the drug to efflux far from its primary site of action.38

A PfCRT inhibitor that binds to the central cavity of drug transport-competent isoforms and restores chloroquine sensitivity may aid in the therapeutic restoration of this potent and low-cost antimalarial in multidrug-resistant areas. This hypothesis is analogous to a previously proposed population biology trap for P. falciparum dihydroorotate dehydrogenase inhibitors.40

The induced-fit docking (IFD) protocol which allows for the receptor’s structural flexibility upon ligand binding, was used to examine the binding interactions of potent compounds 8c, 8d, and 8e responsible for their antiplasmodial properties. IFD combines Glide docking and Prime conformational refinement to predict the best ligand binding modes accurately. The protocol varies ligand-induced structural changes in the receptor to arrive at a low-energy pose of the receptor–ligand complexes.41

The biological studies indicated that compound 8e is a more potent antiplasmodial agent than compounds 8d and 8c, which is supported by 8e’s higher binding free energy (ΔG bind = −127.24 kcal·mol–1) and docking score of −7.854 (Table 3). The higher docking score of 8e indicates that it fits well into PfCRT’s binding pocket, resulting in the most stable interactions. The ligand’s lowest glide emodel and glide energy reflect this strong binding. (Table 3). The longer aminoalkyl chain length of compound 8e may have influenced its tight binding, favoring both hydrophobic interactions with the binding site residues for stable PfCRT complexation and the molecule’s lipophilicity. Furthermore, the lower IC50 values of compounds 8c and 8d compared with 8e, which are also replicated in their docking scores and MM-GBSA (ΔG bind energy), indicate that a decrease in the spacer chain length is detrimental to antiplasmodial potency.

Table 3. Induced Fit Docking (IFD) and MM-GBSA (ΔG Bind) Calculations of Selected Compounds.

drug target ligand docking score glide emodel glide energy ΔG bind (kcal·mol–1)
PfCRT 8c –6.365 –64.355 –48.114 –104.86
8d –6.761 –69.445 –51.340 –114.68
8e –7.854 –78.585 –56.766 –127.24
CQ2+ –3.771 –40.737 –34.958 –69.67
PfDHODH 8c –7.569 –104.239 –67.713 –81.51
8d –8.290 –100.770 –64.736 –82.34
8e –8.884 –95.267 –61.258 –101.46
CQ2+ –9.022 –72.177 –48.755 –116.27
DSM42139 –10.057 –82.379 –46.154 –103.58
Open in a new tab

Furthermore, the PfCRT complexes of 8c, 8d, and 8e (Figure 4) revealed fundamental pharmacophore interactions that could explain the ligands’ decreased efflux. Overall, the spacer’s amino units appear to be critical for PfCRT solid interaction. This group formed hydrogen bonds with Leu160 and Asn330 in 8e, demonstrating the compound’s higher potency over 8c and 8d, which did not have the interaction. The protonated quinoline nitrogen in 8e also formed hydrogen bond interactions with Ser140, Leu217, and Ser220, a CQ drug-resistance residue. The pyrimidine nitrogen also interacted similarly with Gln253.

Figure 4.

Figure 4

Open in a new tab

3D representation of the PfCRT complexes of selected ligands.

Compound 8e formed a network of hydrophobic interactions with Gln156, Asp137, Ala138, Val224, and Try345, which conceivably stabilized the PfCRT complex. The absence of these interactions in 8c and 8d complexes rationalizes their lower antiplasmodial potencies compared with 8e.

In the PfDHODH-8e complex, the protonated quinoline nitrogen formed a hydrogen bond with Gly226 (Figure 5). The spacer amino units interacted similarly with Gly181 and Leu531, while the 7-Cl unit formed a water-mediated halogen bond with Asn230. The quinoline ring also interacted with the His185 imidazole ring via π–π stacking. Overall, 8e’s improved potency was highlighted by its superior ΔG bind energy (−101.46 kcal·mol–1) and docking score (−8.884) relative to 8c and 8d. The hydrogen bond interaction of quinoline nitrogen with Phe188, the π-cation interaction with Phe227 and His185, and the π–π stacking interaction of the pyridine ring with His185 are characteristics of the PfDHODH-8d complex. Akin to 8e, the spacer amino units of 8d showed hydrogen bond interactions with Leu531, Gly181, and His185.

Figure 5.

Figure 5

Open in a new tab

3D representation of the PfDHODH complexes of selected ligands.

The nitrogen of the triazolopyrimidine ring formed hydrogen bonds with Lys229 separately, whereas the triazolo ring formed π-cation interactions with Arg262. Despite the similar framework and binding profile of 8e and 8d, decreasing the spacer chain length significantly lowered 8d’s affinity for PfDHODH as evident from ΔG bind energy (−82.34 kcal·mol–1) and, consequently, the antiplasmodial potency. Likewise, the binding profile of the PfDHODH-8c complex justified its potency. The ligand exhibited the lowest docking score and MM-GBSA values of −7.569 and −81.51 kcal·mol–1, respectively. Although the ligand had similar hydrogen bond interactions of the spacer amino units with Gly181 and Leu531, the lower binding affinity was due to the absence of the π–π stacking interaction with His185 found in 8e and 8d. For comparison, docking simulations with PfCRT and PfDHODH were also done using CQ2+. As shown by the ΔG values, the complex formation between CQ2+ and PfCRT is less stable than 8e, whereas it is of comparable stability in the case of PfDHODH.

In conclusion, we synthesized bis-triazolopyrimidines and 4-aminoquinoline-triazolopyrimidine hybrids to assess their antiplasmodial potential in vitro against CQ-sensitive (3D7) and CQ-resistant (W2) P. falciparum strains. The SAR revealed that increasing the spacer length improved antiplasmodial activity in 4-aminoquinoline-triazolopyrimidine hybrids, whereas bis-triazolopyrimidines displayed poor activity profiles. The active hybrids outperformed CQ against resistant strains, with 8e emerging as the most promising among the series, with an IC50 of 0.20 μm. Following heme binding (UV–vis) and molecular modeling studies, the promising compound 8e was identified as a possible potent inhibitor of hemozoin formation, P. falciparum chloroquine resistance transporter (PfCRT), and P. falciparum dihydroorotate dehydrogenase (PfDHODH).

Acknowledgments

We are extremely thankful to Dr. Laurent Kremer and Dr. Matt D. Johansen (IRIM, France) for cytotoxic analysis of the synthesized compounds. P.S. would like to thank the Centre for High Performance Computing based in Cape Town for access to computational resources.

Glossary

ABBREVIATIONS

PfCRT

Plasmodium falciparum chloroquine resistance transporter

PfDHODH

Plasmodium falciparum dihydroorotate dehydrogenase

CQ

chloroquine

WHO

World Health Organization

ACT

artemisinin-based combination therapy

TPs

triazolopyrimidines

EGF

epidermal growth factor

HRMS-ESI

high-resolution mass spectrometry-electrospray ionization

NMR

nuclear magnetic resonance

IC50

half-maximal inhibitory concentration

μM

micromolar

SI

selectivity index

SAR

structure–activity relationship

RI

resistance index

DMSO

dimethyl sulfoxide

HEPES

4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid

MES

2-(N-morpholino)ethanesulfonic acid

nm

nanomolar

IFD

induced-fit docking

MM-GBSA

Molecular Mechanics/Generalized Born Surface Area

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsmedchemlett.2c00078.

  • Synthesis and spectral data of the synthesized hybrids (7a–e and 8a–e), materials and methods, molecular modeling studies, scanned copies of 1H and 13C NMR spectra of a few representative compounds including 7a, 7c, 8a, 8b, and 8e (PDF)

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

UGC (NFSC) has been acknowledged for providing a fellowship to S.C. (ref No. 1594/CSIR-UGC NET DEC 2018). V.K. thanks Council of Scientific and Industrial Research (CSIR) for providing financial support (grant no. 02(0400)/21/EMR-II). P.S. thanks NRF South Africa for a Competitive Grant for unrated Researchers (Grant No. 121276) and rated researcher funding (Grant No. 126963).

The authors declare no competing financial interest.

Supplementary Material

ml2c00078_si_001.pdf (852.2KB, pdf)

References

  1. World Health Organization (WHO). World Malaria Report; WHO: Geneva, Switzerland, 2021. See the following: https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2021).
  2. Cox-Singh J.; Davis T.M. E.; Lee K. S.; Shamsul S.S. G.; Matusop A.; Ratnam S.; Rahman H. A.; Conway D. J.; Singh B. Plasmodium knowlesi malaria in humans is widely distributed and potentially life threatening. Clin. Infect. Dis. 2008, 46 (2), 165–171. 10.1086/524888. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Wellems T. E.; Plowe C. V. Chloroquine-Resistant Malaria. J. Infect. Dis. 2001, 184 (6), 770–776. 10.1086/322858. [DOI] [PubMed] [Google Scholar]
  4. Uzo P. F. Alkaloids from Plants with Antimalarial Activity: A Review of Recent Studies, Evidence-Based Complement. Altern. Med. 2020, 2020, 8749083. 10.1155/2020/8749083. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Tougher S.; Ye Y.; Amuasi J. H.; Kourgueni I. A.; Thomson R.; Goodman C.; Mann A. G.; Ren R.; Willey B. A.; Adegoke C. A.; Amin A.; Ansong D.; Bruxvoort K.; Diallo D. A.; Diap G.; Festo C.; Johanes B.; Juma E.; Kalolella A.; Malam O.; Mberu B.; Ndiaye S.; Nguah S. B.; Seydou M.; Taylor M.; Rueda S. T.; Wamukoya M.; Arnold F.; Hanson K. Effect of the Affordable Medicines Facility - Malaria (AMFm) on the availability, price, and market share of quality-assured artemisinin-based combination therapies in seven countries: A before-and-after analysis of outlet survey data. Lancet. 2012, 380 (9857), 1916–1926. 10.1016/S0140-6736(12)61732-2. [DOI] [PubMed] [Google Scholar]
  6. Ashley E. A.; Dhorda M.; Fairhurst R. M.; Amaratunga C.; Lim P.; Suon S.; Sreng S.; Anderson J. M.; Mao S.; Sam B.; Sopha C.; Chuor C. M.; Nguon C.; Sovannaroth S.; Pukrittayakamee S.; Jittamala P.; Chotivanich K.; Chutasmit K.; Suchatsoonthorn C.; Runcharoen R.; Hien T. T.; Thuy-Nhien N. T.; Thanh N. V.; Phu N. H.; Htut Y.; Han K.-T.; Aye K. H.; Mokuolu O. A.; Olaosebikan R. R.; Folaranmi O. O.; Mayxay M.; Khanthavong M.; Hongvanthong B.; Newton P. N.; Onyamboko M. A.; Fanello C. I.; Tshefu A. K.; Mishra N.; Valecha N.; Phyo A. P.; Nosten F.; Yi P.; Tripura R.; Borrmann S.; Bashraheil M.; Peshu J.; Faiz M. A.; Ghose A.; Hossain M. A.; Samad R.; Rahman M. R.; Hasan M. M.; Islam A.; Miotto O.; Amato R.; MacInnis B.; Stalker J.; Kwiatkowski D. P.; Bozdech Z.; Jeeyapant A.; Cheah P. Y.; Sakulthaew T.; Chalk J.; Intharabut B.; Silamut K.; Lee S. J.; Vihokhern B.; Kunasol C.; Imwong M.; Tarning J.; Taylor W. J.; Yeung S.; Woodrow C. J.; Flegg J. A.; Das D.; Smith J.; Venkatesan M.; Plowe C. V.; Stepniewska K.; Guerin P. J.; Dondorp A. M.; Day N. P.; White N. J. Spread of Artemisinin Resistance in Plasmodium falciparum Malaria. N. Engl. J. Med. 2014, 371 (5), 411–423. 10.1056/NEJMoa1314981. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Ménard D.; Khim N.; Beghain J.; Adegnika A. A.; Shafiul-Alam M.; Amodu O.; Rahim-Awab G.; Barnadas C.; Berry A.; Boum Y.; Bustos M. D.; Cao J.; Chen J.-H.; Collet L.; Cui L.; Thakur G.-D.; Dieye A.; Djallé D.; Dorkenoo M. A.; Eboumbou-Moukoko C. E.; Espino F.-E.-C.J.; Fandeur T.; Ferreira-da-Cruz M.-F.; Fola A. A.; Fuehrer H.-P.; Hassan A. M.; Herrera S.; Hongvanthong B.; Houzé S.; Ibrahim M. L.; Jahirul-Karim M.; Jiang L.; Kano S.; Ali-Khan W.; Khanthavong M.; Kremsner P. G.; Lacerda M.; Leang R.; Leelawong M.; Li M.; Lin K.; Mazarati J.-B.; Ménard S.; Morlais I.; Muhindo-Mavoko H.; Musset L.; Na-Bangchang K.; Nambozi M.; Niaré K.; Noedl H.; Ouédraogo J.-B.; Pillai D. R.; Pradines B.; Quang-Phuc B.; Ramharter M.; Randrianarivelojosia M.; Sattabongkot J.; Sheikh-Omar A.; Silué K. D.; Sirima S. B.; Sutherland C.; Syafruddin D.; Tahar R.; Tang L.-H.; Touré O. A.; Tshibangu-wa-Tshibangu P.; Vigan-Womas I.; Warsame M.; Wini L.; Zakeri S.; Kim S.; Eam R.; Berne L.; Khean C.; Chy S.; Ken M.; Loch K.; Canier L.; Duru V.; Legrand E.; Barale J.-C.; Stokes B.; Straimer J.; Witkowski B.; Fidock D. A.; Rogier C.; Ringwald P.; Ariey F.; Mercereau-Puijalon O. A Worldwide Map of Plasmodium falciparum K13-Propeller Polymorphisms. N. Engl. J. Med. 2016, 374 (25), 2453–2464. 10.1056/NEJMoa1513137. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Roux A.T.; Maharaj L.; Oyegoke O.; Akoniyon O.P.; Adeleke M.A.; Maharaj R.; Okpeku M. Chloroquine and Sulfadoxine-Pyrimethamine Resistance in Sub-Saharan Africa—A Review. Front. Genet. 2021, 12, 668574. 10.3389/fgene.2021.668574. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Hawley S. R.; Bray P. G.; Mungthin M.; Atkinson J. D.; O’Neill P. M.; Ward S. A. Relationship between antimalarial drug activity, accumulation, and inhibition of heme polymerization in Plasmodium falciparum in vitro. Antimicrob. Agents Chemother. 1998, 42 (3), 682–686. 10.1128/AAC.42.3.682. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Payne D. Spread of chloroquine resistance in Plasmodium falciparum. Parasitol. Today. 1987, 3 (8), 241–246. 10.1016/0169-4758(87)90147-5. [DOI] [PubMed] [Google Scholar]
  11. Dorn A.; Stoffel R.; Matile H.; Bubendorf A.; Ridley R. G. Malarial Haemozoin, Malarial haemozoin/P-haematin supports haem polymerization in the absence of protein. Nature. 1995, 374 (6519), 269. 10.1038/374269a0. [DOI] [PubMed] [Google Scholar]
  12. Peyton D. H. Reversed Chloroquine Molecules as a Strategy to Overcome Resistance in Malaria. Curr. Top. Med. Chem. 2012, 12 (5), 400–407. 10.2174/156802612799362968. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Baldwin J.; Michnoff C. H.; Malmquist N. A.; White J.; Roth M. G.; Rathod P. K.; Phillips M. A. High-throughput screening for potent and selective inhibitors of Plasmodium falciparum dihydroorotate dehydrogenase. J. Biol. Chem. 2005, 280 (23), 21847–21853. 10.1074/jbc.M501100200. [DOI] [PubMed] [Google Scholar]
  14. Ben Said A.; Rahmouni A.; Daami-Ramadi M.; Romdhane A.; Ben Janet H. Design and Synthesis of new antimicrobial [1,2,4]triazolo[1,5-c]pyrimidines. J. Tunis. Chem. Soc. 2017, 19, 94–104. 10.1007/s12272-001-1153-1. [DOI] [Google Scholar]
  15. Gami S. P.; Vilapara K. V.; Khunt H. R.; Babariya J. S.; Naliapara Y. T. Synthesis and Antimicrobal Activities of some Novel Triazolo[1,5-a]Pyrimidine Derivatives. Int. Lett. Chem. Phys. Astron. 2014, 30, 127–134. 10.18052/www.scipress.com/ILCPA.30.127. [DOI] [Google Scholar]
  16. Chen Q.; Zhu X. L.; Jiang L. L.; Liu Z. M.; Yang G. F. Synthesis, antifungal activity and CoMFA analysis of novel 1,2,4-triazolo[1,5-a]pyrimidine derivatives. Eur. J. Med. Chem. 2008, 43 (3), 595–603. 10.1016/j.ejmech.2007.04.021. [DOI] [PubMed] [Google Scholar]
  17. Wang H.; Lee M.; Peng Z.; Blázquez B.; Lastochkin E.; Kumarasiri M.; Bouley R.; Chang M.; Mobashery S. Synthesis and evaluation of 1,2,4-triazolo[1,5- a]pyrimidines as antibacterial agents against Enterococcus faecium. J. Med. Chem. 2015, 58 (10), 4194–4203. 10.1021/jm501831g. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Zhang N.; Ayral-Kaloustian S.; Nguyen T.; Afragola J.; Hernandez R.; Lucas J.; Gibbons J.; Beyer C. Synthesis and SAR of [1,2,4]triazolo[1,5-a]pyrimidines, a class of anticancer agents with a unique mechanism of tubulin inhibition. J. Med. Chem. 2007, 50 (2), 319–327. 10.1021/jm060717i. [DOI] [PubMed] [Google Scholar]
  19. Said M. A.; Eldehna W. M.; Nocentini A.; Bonardi A.; Fahim S. H.; Bua S.; Soliman D. H.; Abdel-Aziz H. A.; Gratteri P.; Abou-Seri S. M.; Supuran C. T. Synthesis, biological and molecular dynamics investigations with a series of triazolopyrimidine/triazole-based benzenesulfonamides as novel carbonic anhydrase inhibitors. Eur. J. Med. Chem. 2020, 185, 111843. 10.1016/j.ejmech.2019.111843. [DOI] [PubMed] [Google Scholar]
  20. Jameel E.; Meena P.; Maqbool M.; Kumar J.; Ahmed W.; Mumtazuddin S.; Tiwari M.; Hoda N.; Jayaram B. Rational design, synthesis and biological screening of triazine-triazolopyrimidine hybrids as multitarget anti-Alzheimer agents. Eur. J. Med. Chem. 2017, 136, 36–51. 10.1016/j.ejmech.2017.04.064. [DOI] [PubMed] [Google Scholar]
  21. Traxler P. M.; Furet P.; Mett H.; Buchdunger E.; Meyer T.; Lydon N. Inhibitors of the EGF-Receptor Protein Tyrosine Kinase. J. Med. Chem. 1996, 39 (12), 2285–2292. 10.1021/jm960118j. [DOI] [PubMed] [Google Scholar]
  22. El-Gendy M.M. A.; Shaaban M.; Shaaban K. A.; El-Bondkly A. M.; Laatsch H. Essramycin: A first triazolopyrimidine antibiotic isolated from nature. J. Antibiot. (Tokyo). 2008, 61 (3), 149–157. 10.1038/ja.2008.124. [DOI] [PubMed] [Google Scholar]
  23. Phillips M. A.; Lotharius J.; Marsh K.; White J.; Dayan A.; White K. L.; Njoroge J. W.; El Mazouni F.; Lao Y.; Kokkonda S.; Tomchick D. R.; Deng X.; Laird T.; Bhatia S. N.; March S.; Ng C. L.; Fidock D. A.; Wittlin S.; Lafuente-Monasterio M.; Benito F. J. G.; Alonso L. M. S.; Martinez M. S.; Jimenez-Diaz M. B.; Bazaga S. F.; Angulo-Barturen I.; Haselden J. N.; Louttit J.; Cui Y.; Sridhar A.; Zeeman A.-M.; Kocken C.; Sauerwein R.; Dechering K.; Avery V. M.; Duffy S.; Delves M.; Sinden R.; Ruecker A.; Wickham K. S.; Rochford R.; Gahagen J.; Iyer L.; Riccio E.; Mirsalis J.; Bathhurst I.; Rueckle T.; Ding X.; Campo B.; Leroy D.; Rogers M. J.; Rathod P. K.; Burrows J. N.; Charman S. A. A long-duration dihydroorotate dehydrogenase inhibitor (DSM265) for prevention and treatment of malaria. Science Translational Medicine. 2015, 7 (296), 296ra111–296ra111. 10.1126/scitranslmed.aaa6645. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. White J.; Dhingra S. K.; Deng X.; El Mazouni F.; Lee M. C. S.; Afanador G. A.; Lawong A.; Tomchick D. R.; Ng C. L.; Bath J.; Rathod P. K.; Fidock D. A.; Phillips M. A. Identification and Mechanistic Understanding of Dihydroorotate Dehydrogenase Point Mutations in Plasmodium falciparum that Confer in Vitro Resistance to the Clinical Candidate DSM265. ACS Infectious Diseases. 2019, 5 (1), 90–101. 10.1021/acsinfecdis.8b00211. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Phillips M. A.; Gujjar R.; Malmquist N. A.; White J.; El Mazouni F.; Baldwin J.; Rathod P. K. Triazolopyrimidine-Based Dihydroorotate Dehydrogenase Inhibitors with Potent and Selective Activity against the Malaria Parasite Plasmodium falciparum. J. Med. Chem. 2008, 51 (12), 3649–3653. 10.1021/jm8001026. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Agarwal D.; Gupta R. D.; Awasthi S. K. Are antimalarial hybrid molecules a close reality or a distant dream?. Antimicrob. Agents Chemother. 2017, 61 (5), e00249-17 10.1128/AAC.00249-17. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Muregi F. W.; Ishih A. Next-generation antimalarial drugs: Hybrid molecules as a new strategy in drug design. Drug Dev.Res. 2010, 71 (1), 20–32. 10.1002/ddr.20345. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Shalini J.; Legac; Adeniyi A. A.; Kisten P.; Rosenthal P. J.; Singh P.; Kumar V. Functionalized Naphthalimide-4-aminoquinoline Conjugates as Promising Antiplasmodials, with Mechanistic Insights. ACS Med. Chem. Lett. 2020, 11 (2), 154–161. 10.1021/acsmedchemlett.9b00521. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Shalini S.; Kumar; Gendrot M.; Fonta I.; Mosnier J.; Cele N.; Awolade P.; Singh P.; Pradines B.; Kumar V. Amide Tethered 4-Aminoquinoline-naphthalimide Hybrids: A New Class of Possible Dual Function Antiplasmodials. ACS Med. Chem. Lett. 2020, 11 (12), 2544–2552. 10.1021/acsmedchemlett.0c00536. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Saini A.; Kumar S.; Raj R.; Chowdhary S.; Gendrot M.; Mosnier J.; Fonta I.; Pradines B.; Kumar V. Synthesis and antiplasmodial evaluation of 1H-1,2,3-triazole grafted 4-aminoquinoline-benzoxaborole hybrids and benzoxaborole analogues. Bioorg. Chem. 2021, 109, 104733. 10.1016/j.bioorg.2021.104733. [DOI] [PubMed] [Google Scholar]
  31. Rani A.; Sharma A.; Legac J.; Rosenthal P. J.; Singh P.; Kumar V. A trio of quinoline-isoniazid-phthalimide with promising antiplasmodial potential: Synthesis, in-vitro evaluation and heme-polymerization inhibition studies. Bioorg. Med. Chem. 2021, 39, 116159. 10.1016/j.bmc.2021.116159. [DOI] [PubMed] [Google Scholar]
  32. Gujjar R.; Marwaha A.; El Mazouni F.; White J.; White K. L.; Creason S.; Shackleford D. M.; Baldwin J.; Charman W. N.; Buckner F. S.; Charman S.; Rathod P. K.; Phillips M. A. Identification of a metabolically stable triazolopyrimidine-based dihydroorotate dehydrogenase inhibitor with antimalarial activity in mice. J. Med. Chem. 2009, 52 (7), 1864–1872. 10.1021/jm801343r. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Egan T. J. Recent advances in understanding the mechanism of hemozoin (malaria pigment) formation. J. Inorg. Biochem. 2008, 102 (5–6), 1288–1299. 10.1016/j.jinorgbio.2007.12.004. [DOI] [PubMed] [Google Scholar]
  34. Egan T. J.; Hunter R.; Kaschula C. H.; Marques H. M.; Misplon A.; Walden J. Structure-function relationships in aminoquinolines: Effect of amino and chloro groups on quinoline-hematin complex formation, inhibition of β- hematin formation, and antiplasmodial activity. J. Med. Chem. 2000, 43 (2), 283–291. 10.1021/jm990437l. [DOI] [PubMed] [Google Scholar]
  35. Dascombe M. J.; Drew M.G. B.; Morris H.; Wilairat P.; Auparakkitanon S.; Moule W. A.; Alizadeh-Shekalgourabi S.; Evans P. G.; Lloyd M.; Dyas A. M.; Carr P.; Ismail F.M. D. Mapping antimalarial pharmacophores as a useful tool for the rapid discovery of drugs effective in vivo: Design, construction, characterization, and pharmacology of metaquine. J. Med. Chem. 2005, 48 (17), 5423–5436. 10.1021/jm0408013. [DOI] [PubMed] [Google Scholar]
  36. Kim J.; Tan Y. Z.; Wicht K. J.; Erramilli S. K.; Dhingra S. K.; Okombo J.; Vendome J.; Hagenah L. M.; Giacometti S. I.; Warren A. L.; Nosol K.; Roepe P. D.; Potter C. S.; Carragher B.; Kossiakoff A. A.; Quick M.; Fidock D. A.; Mancia F. Structure and drug resistance of the Plasmodium falciparum transporter PfCRT. Nature 2019, 576 (7786), 315–320. 10.1038/s41586-019-1795-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Phillips M. A.; Lotharius J.; Marsh K.; White J.; Dayan A.; White K. L.; Njoroge J. W.; Mazouni F. E.; Lao Y.; Kokkonda S.; Tomchick D. R.; Deng X.; Laird T.; Bhatia S. N.; March S.; Ng C. L.; Fidock D. A.; Wittlin S.; Lafuente-Monasterio M.; Benito F. J. G.; Alonso L. M. S.; Martinez M. S.; Jimenez-Diaz M. B.; Bazaga S. F.; Angulo-Barturen I.; Haselden J. N.; Louttit J.; Cui Y.; Sridhar A.; Zeeman A.-M.; Kocken C.; Sauerwein R.; Dechering K.; Avery V. M.; Duffy S.; Delves M.; Sinden R.; Ruecker A.; Wickham K. S.; Rochford R.; Gahagen J.; Iyer L.; Riccio E.; Mirsalis J.; Bathhurst I.; Rueckle T.; Ding X.; Campo B.; Leroy D.; Rogers M. J.; Rathod P. K.; Burrows J. N.; Charman S. A. A long-duration dihydroorotate dehydrogenase inhibitor (DSM265) for prevention and treatment of malaria. Sci. Transl. Med. 2015, 7 (296), 296ra111–296ra111. 10.1126/scitranslmed.aaa6645. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Shafik S. H.; Cobbold S. A.; Barkat K.; Richards S. N.; Lancaster N. S.; Llinas M.; Hogg S. J.; Summers R. L.; McConville M. J.; Martin R. E. ″The natural function of the malaria parasite’s chloroquine resistance transporter.″. Nature communications. 2020, 11 (1), 3922. 10.1038/s41467-020-17781-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Phillips M. A.; White K. L.; Kokkonda S.; Deng X.; White J.; El Mazouni F.; Marsh K.; Tomchick D. R.; Manjalanagara K.; Rudra K. R.; Wirjanata G.; Noviyanti R.; Price R. N.; Marfurt J.; Shackleford D. M.; Chiu F. C. K.; Campbell M.; Jimenez-Diaz M. B.; Bazaga S. F.; Angulo-Barturen I.; Martinez M. S.; Lafuente-Monasterio M.; Kaminsky W.; Silue K.; Zeeman A.-M.; Kocken C.; Leroy D.; Blasco B.; Rossignol E.; Rueckle T.; Matthews D.; Burrows J. N.; Waterson D.; Palmer M. J.; Rathod P. K.; Charman S. A. A Triazolopyrimidine-Based Dihydroorotate Dehydrogenase Inhibitor with Improved Drug-like Properties for Treatment and Prevention of Malaria. ACS Infectious Diseases 2016, 2 (12), 945–957. 10.1021/acsinfecdis.6b00144. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Small-Saunders J. L.; Hagenah L. M.; Fidock D. A. “Turning the tide: targeting PfCRT to combat drug-resistant P. falciparum?”. Nature Reviews Microbiology 2020, 18 (5), 261–262. 10.1038/s41579-020-0353-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Schrödinger Release 2020-3: Induced Fit Docking protocol, Glid. P.; Schrödinger, LLC: New York, NY, 2016. [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ml2c00078_si_001.pdf (852.2KB, pdf)

Articles from ACS Medicinal Chemistry Letters are provided here courtesy of American Chemical Society

RESOURCES