RESUMEN
Hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase (RdRp) plays a central role in virus replication. NS5B has no functional equivalent in mammalian cells, and as a consequence is an attractive target for selective inhibition. This paper describes the discovery of a novel family of HCV NS5B non-nucleoside inhibitors inspired by the bioisosterism between sulfonamide and phosphonamide. Systematic structural optimization in this new series led to the identification of IDX375, a potent non-nucleoside inhibitor that is selective for genotypes 1a and 1b. The structure and binding domain of IDX375 were confirmed by X-ray co-crystalisation study.
Asunto(s)
Antivirales/química , Hepacivirus/enzimología , Lactamas/química , Compuestos Organofosforados/química , Proteínas no Estructurales Virales/antagonistas & inhibidores , Regulación Alostérica , Animales , Antivirales/síntesis química , Antivirales/metabolismo , Antivirales/farmacología , Sitios de Unión , Cristalografía por Rayos X , Genotipo , Semivida , Haplorrinos , Hepacivirus/genética , Hepacivirus/fisiología , Humanos , Lactamas/farmacología , Ratones , Simulación de Dinámica Molecular , Compuestos Organofosforados/farmacología , Estructura Terciaria de Proteína , Ratas , Relación Estructura-Actividad , Sulfonamidas/química , Proteínas no Estructurales Virales/metabolismo , Replicación Viral/efectos de los fármacosRESUMEN
The hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase (RdRp) plays a central role in virus replication. NS5B has no functional equivalent in mammalian cells and, as a consequence, is an attractive target for selective inhibition. This Letter describes the discovery of a new family of HCV NS5B non-nucleoside inhibitors, based on the bioisosterism between amide and phosphonamidate functions. As part of this program, SAR in this new series led to the identification of IDX17119, a potent non-nucleoside inhibitor, active on the genotypes 1b, 2a, 3a and 4a. The structure and binding domain of IDX17119 were confirmed by X-ray co-crystallization study.
Asunto(s)
Antivirales/farmacología , Genotipo , Hepacivirus/efectos de los fármacos , Proteínas no Estructurales Virales/antagonistas & inhibidores , Sitio Alostérico , Antivirales/química , Antivirales/metabolismo , Cristalografía por Rayos X , Relación Estructura-Actividad , Proteínas no Estructurales Virales/metabolismoRESUMEN
We disclose here the synthesis of a series of macrocyclic HCV protease inhibitors, where the homoserine linked together the quinoline P2' motif and the macrocyclic moiety. These compounds exhibit potent inhibitory activity against HCV NS3/4A protease and replicon cell based assay. Their enzymatic and antiviral activities are modulated by substitutions on the quinoline P2' at position 8 by methyl and halogens and by small heterocycles at position 2. The in vitro structure activity relationship (SAR) studies and in vivo pharmacokinetic (PK) evaluations of selected compounds are described herein.
Asunto(s)
Antivirales/síntesis química , Antivirales/farmacología , Hepacivirus/efectos de los fármacos , Homoserina/farmacología , Inhibidores de Serina Proteinasa/síntesis química , Inhibidores de Serina Proteinasa/farmacología , Proteínas no Estructurales Virales/antagonistas & inhibidores , Antivirales/química , Relación Dosis-Respuesta a Droga , Hepacivirus/enzimología , Homoserina/síntesis química , Homoserina/química , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Inhibidores de Serina Proteinasa/química , Relación Estructura-Actividad , Proteínas no Estructurales Virales/metabolismoRESUMEN
Exploration of the P2 region by mimicking the proline motif found in BILN2061 resulted in the discovery of two series of potent HCV NS3/4A protease inhibitors. X-ray crystal structure of the ligand in contact with the NS3/4A protein and modulation of the quinoline heterocyclic region by structure based design and modeling allowed for the optimization of enzyme potency and cellular activity. This research led to the selection of clinical candidate IDX320 having good genotype coverage and pharmacokinetic properties in various species.
Asunto(s)
Descubrimiento de Drogas , Hepacivirus/efectos de los fármacos , Compuestos Macrocíclicos/química , Compuestos Macrocíclicos/farmacología , Proteínas no Estructurales Virales/antagonistas & inhibidores , Animales , Haplorrinos , Hepatocitos/enzimología , Humanos , Concentración 50 Inhibidora , Ratones , Microsomas Hepáticos/enzimología , Estructura Molecular , Ratas , Ratas Sprague-Dawley , Inhibidores de Serina Proteinasa/síntesis química , Inhibidores de Serina Proteinasa/química , Inhibidores de Serina Proteinasa/farmacología , Proteínas no Estructurales Virales/químicaRESUMEN
We identified a novel class of 2-((phenylsulfonyl)methyl)-thieno[3,2-d]pyrimidine compounds as potent HIV-1 replication inhibitors serendipitously during the process of evaluation of triazolothienopyrimidine (TTPM) compounds. Herein, we report synthesis and biological evaluation of 2-((phenylsulfonyl)methyl)-thieno[3,2-d]pyrimidine compounds using a cell-based full replication assay to identify thienopyrimidines 6 and 30, which could be further utilized as viable lead compounds.
Asunto(s)
VIH-1/efectos de los fármacos , Pirimidinas/química , Descubrimiento de Drogas , Humanos , Relación Estructura-ActividadRESUMEN
Structural homology between thrombin inhibitors and the early tetrapeptide HCV protease inhibitor led to the bioisosteric replacement of the P2 proline by a 2,4-disubstituted azetidine within the macrocyclic ß-strand mimic. Molecular modeling guided the design of the series. This approach was validated by the excellent activity and selectivity in biochemical and cell based assays of this novel series and confirmed by the co-crystal structure of the inhibitor with the NS3/4A protein (PDB code: 4TYD).
Asunto(s)
Azetidinas/farmacología , Diseño de Fármacos , Inhibidores de Serina Proteinasa/farmacología , Proteínas no Estructurales Virales/antagonistas & inhibidores , Azetidinas/síntesis química , Azetidinas/química , Cristalografía por Rayos X , Relación Dosis-Respuesta a Droga , Modelos Moleculares , Estructura Molecular , Inhibidores de Serina Proteinasa/síntesis química , Inhibidores de Serina Proteinasa/química , Relación Estructura-Actividad , Proteínas no Estructurales Virales/metabolismoRESUMEN
We identified a novel class of triazolothienopyrimidine (TTPM) compounds as potent HIV-1 replication inhibitors during a high-throughput screening campaign that evaluated more than 200,000 compounds using a cell-based full replication assay. Herein, we report the optimization of the antiviral activity in a cell-based assay system leading to the discovery of aryl-substituted TTPM derivatives (38, 44, and 45), which exhibited significant inhibition of HIV-1 replication with acceptable safety margins. These novel and potent TTPMs could serve as leads for further development.
Asunto(s)
Fármacos Anti-VIH/síntesis química , VIH-1/metabolismo , Pirimidinas/química , Triazoles/química , Fármacos Anti-VIH/química , Fármacos Anti-VIH/farmacología , Línea Celular , Evaluación Preclínica de Medicamentos , VIH-1/efectos de los fármacos , Ensayos Analíticos de Alto Rendimiento , Humanos , Pirimidinas/síntesis química , Pirimidinas/farmacología , Relación Estructura-Actividad , Replicación Viral/efectos de los fármacosRESUMEN
We describe a novel 7-aminopyrazolo[1,5-a]pyrimidine (7-APP) derivative as a potent hepatitis C virus (HCV) inhibitor. A series of 7-APPs was synthesized and evaluated for inhibitory activity against HCV in different cell culture systems. The synthesis and preliminary structure-activity relationship study of 7-APP are reported.
Asunto(s)
Antivirales/farmacología , Descubrimiento de Drogas , Hepacivirus/efectos de los fármacos , Pirazoles/farmacología , Pirimidinas/farmacología , Animales , Antivirales/química , Antivirales/metabolismo , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Estabilidad de Medicamentos , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Pirazoles/química , Pirazoles/metabolismo , Pirimidinas/química , Pirimidinas/metabolismo , Ratas , Relación Estructura-ActividadRESUMEN
Following the previous SAR of a novel dihydropyrimidinone scaffold as HIV-1 replication inhibitors a detailed study directed towards optimizing the metabolic stability of the ester functional group in the dihydropyrimidinone (DHPM) scaffold is described. Replacement of the ester moiety by thiazole ring significantly improved the metabolic stability while retaining antiviral activity against HIV-1 replication. These novel and potent DHPMs with bioisosteres could serve as advanced leads for further optimization.
Asunto(s)
Transcriptasa Inversa del VIH/antagonistas & inhibidores , VIH-1/efectos de los fármacos , Pirimidinonas/síntesis química , Inhibidores de la Transcriptasa Inversa/síntesis química , Replicación Viral/efectos de los fármacos , Animales , Línea Celular Tumoral , Estabilidad de Medicamentos , VIH-1/fisiología , Humanos , Microsomas Hepáticos/metabolismo , Modelos Moleculares , Nevirapina/farmacología , Pirimidinonas/farmacología , Ratas , Inhibidores de la Transcriptasa Inversa/farmacología , Relación Estructura-Actividad , Tiazoles/químicaRESUMEN
Herpes simplex virus infections are the cause of significant morbidity, and currently used therapeutics are largely based on modified nucleoside analogs that inhibit viral DNA polymerase function. To target this disease in a new way, we have identified and optimized selective thiazolylphenyl-containing inhibitors of the herpes simplex virus (HSV) helicase-primase enzyme. The most potent compounds inhibited the helicase, the primase and the DNA-dependent ATPase activities of the enzyme with IC50 (50% inhibitory concentration) values less than 100 nM. Inhibition of the enzymatic activities was through stabilization of the interaction between the helicase-primase and DNA substrates, preventing the progression through helicase or primase catalytic cycles. Helicase-primase inhibitors also prevented viral replication as demonstrated in viral growth assays. One compound, BILS 179 BS, displayed an EC50 (effective concentration inhibiting viral growth by 50%) of 27 nM against viral growth with a selectivity index greater than 2,000. Antiviral activity was also demonstrated for multiple strains of HSV, including strains resistant to nucleoside-based therapies. Most importantly, BILS 179 BS was orally active against HSV infections in murine models of HSV-1 and HSV-2 disease and more effective than acyclovir when the treatment frequency per day was reduced or when initiation of treatment was delayed up to 65 hours after infection. These studies validate the use of helicase-primase inhibitors for the treatment of acute herpesvirus infections and provide new lead compounds for optimization and design of superior anti-HSV agents.
Asunto(s)
Antivirales/uso terapéutico , ADN Helicasas/antagonistas & inhibidores , Inhibidores Enzimáticos/uso terapéutico , Herpes Simple/tratamiento farmacológico , Piridinas/uso terapéutico , Tiazoles/uso terapéutico , Animales , Antivirales/química , ADN Primasa , Modelos Animales de Enfermedad , Diseño de Fármacos , Inhibidores Enzimáticos/química , Femenino , Herpes Genital/tratamiento farmacológico , Herpes Genital/enzimología , Herpes Simple/enzimología , Herpesvirus Humano 1/enzimología , Herpesvirus Humano 2/enzimología , Humanos , Técnicas In Vitro , Ratones , Ratones Pelados , Proteínas ViralesRESUMEN
An SAR study that identified a series of thienopyridine-based potent IkappaB Kinase beta (IKKbeta) inhibitors is described. With focuses on the structural optimization at C4 and C6 of structure 1 (Fig. 1), the study reveals that small alkyl and certain aromatic groups are preferred at C4, whereas polar groups with proper orientation at C6 efficiently enhance compound potency. The most potent analogues inhibit IKKbeta with IC50s as low as 40 nM, suppress LPS-induced TNF-alpha production in vitro and in vivo, display good kinase selectivity profiles, and are active in a HeLa cell NF-kappaB reporter gene assay, demonstrating that they directly interfere with the NF-kappaB signaling pathway.
Asunto(s)
Quinasa I-kappa B/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/química , Piridinas/química , Animales , Descubrimiento de Drogas , Células HeLa , Humanos , Quinasa I-kappa B/metabolismo , Lipopolisacáridos/farmacología , Ratones , FN-kappa B/metabolismo , Inhibidores de Proteínas Quinasas/síntesis química , Inhibidores de Proteínas Quinasas/farmacología , Piridinas/síntesis química , Piridinas/farmacología , Transducción de Señal , Relación Estructura-Actividad , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
Several thieno[3,4-d]pyrimidine derivatives, including four hitherto unknown 2',3'-dideoxy- and 2',3'-dideoxy-2',3'-didehydro-C-nucleoside analogues of adenosine and inosine have been synthesized. When evaluated in cell culture experiments against human immunodeficiency virus, none of the tested compounds exhibited any significant antiviral effect, while two of them showed some cytotoxicity.
Asunto(s)
Adenosina/análogos & derivados , Antivirales/síntesis química , Antivirales/farmacología , Inosina/análogos & derivados , Pirimidinas/síntesis química , Pirimidinas/farmacología , Antivirales/química , VIH/efectos de los fármacos , Espectroscopía de Resonancia Magnética , Pirimidinas/química , Espectrometría de Masa por Ionización de ElectrosprayRESUMEN
RNA viruses are the agents of numerous widespread and often severe diseases. Their unique RNA-dependent RNA polymerase (RDRP) is essential for replication and, thus, constitutes a valid target for the development of selective chemotherapeutic agents. In this regard, we have investigated sugar-modified ribonucleoside analogues as potential inhibitors of the RDRP. Title compounds retain 'natural' pyrimidine bases, but possess a beta-methyl substituent at the 2'-position of the D- or L-ribose moiety. Evaluation against a broad range of RNA viruses, either single-stranded positive (ssRNA+), single-stranded negative (ssRNA-) or double-stranded (dsRNA), revealed potent activities for D-2'-C-methyl-cytidine and -uridine against ssRNA+, and dsRNA viruses. None of the L-enantiomers were active. Moreover, the 5'-triphosphates of the active D-enantiomers were found to inhibit the bovine virus diarrhoea virus polymerase. Thus, the 2'-methyl branching of natural pyrimidine ribonucleosides transforms physiological molecules into potent, broad-spectrum antiviral agents that merit further development.
Asunto(s)
Antivirales/farmacología , Nucleósidos de Pirimidina/farmacología , Virus ARN/efectos de los fármacos , Virus ARN/fisiología , Replicación Viral/efectos de los fármacos , Animales , Antivirales/química , Línea Celular , Cricetinae , Perros , Haplorrinos , Humanos , Estructura Molecular , Nucleósidos de Pirimidina/química , Relación Estructura-ActividadRESUMEN
High-throughput screening is routinely employed as a method for the identification of novel hit structures. Large numbers of active compounds are typically procured in this way and must undergo a rigorous validation process. This process is described in detail for a collection of screening hits identified as inhibitors of IkappaB kinase-beta (IKKbeta), a key regulatory enzyme in the nuclear factor-kappaB (NF-kappaB) pathway. From these studies, a promising hit series was selected. Subsequent lead generation activities included the development of a pharmacophore hypothesis and structure-activity relationship (SAR) for the hit series. This led to the exploration of related scaffolds offering additional opportunities, and the various structural classes were comparatively evaluated for enzyme inhibition, selectivity, and drug-like properties. A novel lead series of thienopyridines was thereby established, and this series advanced into lead optimization for further development.
Asunto(s)
Quinasa I-kappa B/antagonistas & inhibidores , Quinasa I-kappa B/química , Modelos Moleculares , Piridinas/síntesis química , Oxazoles/síntesis química , Oxazoles/química , Piridinas/química , Relación Estructura-ActividadRESUMEN
RNA-dependent RNA polymerase from respiratory syncytial virus (RSV) is a multi-subunit ribonucleoprotein (RNP) complex that, in addition to synthesizing the full 15 222 nt viral genomic RNA, is able to synthesize all 10 viral mRNAs. We have prepared crude RNP from RSV-infected HEp-2 cells, based on a method previously used for Newcastle disease virus, and established a novel polyadenylation-dependent capture [poly(A) capture] assay to screen for potential inhibitors of RSV transcriptase activity. In this homogeneous assay, radiolabeled full-length polyadenylated mRNAs produced by the viral RNP are detected through capture on immobilized biotinylated oligo(dT) in a 96-well streptavidin-coated FlashPlate. Possible inhibitors identified with this assay could interfere at any step required for the production of complete RSV mRNAs, including transcription, polyadenylation and, potentially, co-transcriptional guanylylation. A specific inhibitor of RSV transcriptase with antiviral activity was identified through screening of this assay.
Asunto(s)
ADN Polimerasa Dirigida por ARN/metabolismo , Virus Sincitiales Respiratorios/enzimología , Inhibidores de la Transcriptasa Inversa/análisis , Línea Celular , Técnicas Genéticas , Humanos , Poliadenilación , ARN Mensajero/metabolismo , ADN Polimerasa Dirigida por ARN/aislamiento & purificación , Inhibidores de la Transcriptasa Inversa/química , Inhibidores de la Transcriptasa Inversa/farmacología , Transcripción GenéticaRESUMEN
Here, we describe the design, synthesis, biological evaluation, and identification of a clinical candidate non-nucleoside reverse transcriptase inhibitors (NNRTIs) with a novel aryl-phospho-indole (APhI) scaffold. NNRTIs are recommended components of highly active antiretroviral therapy (HAART) for the treatment of HIV-1. Since a major problem associated with NNRTI treatment is the emergence of drug resistant virus, this work focused on optimization of the APhI against clinically relevant HIV-1 Y181C and K103N mutants and the Y181C/K103N double mutant. Optimization of the phosphinate aryl substituent led to the discovery of the 3-Me,5-acrylonitrile-phenyl analogue RP-13s (IDX899) having an EC50 of 11 nM against the Y181C/K103N double mutant.
Asunto(s)
Fármacos Anti-VIH/farmacología , Descubrimiento de Drogas , Transcriptasa Inversa del VIH/antagonistas & inhibidores , VIH-1/efectos de los fármacos , VIH-1/enzimología , Indoles/farmacología , Ácidos Fosfínicos/farmacología , Inhibidores de la Transcriptasa Inversa/farmacología , Animales , Fármacos Anti-VIH/síntesis química , Fármacos Anti-VIH/química , Línea Celular , Cristalografía por Rayos X , Perros , Relación Dosis-Respuesta a Droga , Transcriptasa Inversa del VIH/metabolismo , Hepatocitos/química , Hepatocitos/metabolismo , Humanos , Indoles/síntesis química , Indoles/química , Macaca fascicularis , Masculino , Modelos Moleculares , Estructura Molecular , Ácidos Fosfínicos/síntesis química , Ácidos Fosfínicos/química , Ratas , Ratas Sprague-Dawley , Inhibidores de la Transcriptasa Inversa/síntesis química , Inhibidores de la Transcriptasa Inversa/química , Relación Estructura-ActividadRESUMEN
BACKGROUND: Ribonucleoside analogs possessing a ß-methyl substituent at the 2'-position of the d-ribose moiety have been previously discovered to be potent and selective inhibitors of hepatitis C virus (HCV) replication, their triphosphates acting as alternative substrate inhibitors of the HCV RdRp NS5B. Results/methodology: In this article, the authors detail the synthesis, anti-HCV evaluation in cell-based replicon assays and structure-activity relationships of several phosphoramidate diester derivatives of 2'-C-methylguanosine (2'-MeG). CONCLUSION: The most promising compound, namely the O-[S-(hydroxyl)pivaloyl-2-thioethyl]{abbreviated as O-[(HO)tBuSATE)]} N-benzylamine phosphoramidate diester derivative (IDX184), was selected for further in vivo studies, and was the first clinical pronucleotide evaluated for the treatment of chronic hepatitis C up to Phase II trials.
Asunto(s)
Antivirales/síntesis química , Antivirales/farmacología , Descubrimiento de Drogas , Guanosina Monofosfato/análogos & derivados , Hepacivirus/efectos de los fármacos , Hepatitis C/tratamiento farmacológico , Guanosina Monofosfato/síntesis química , Guanosina Monofosfato/farmacología , Humanos , Relación Estructura-ActividadRESUMEN
The aminothiazolylphenyl-containing compounds BILS 179 BS and BILS 45 BS are novel inhibitors of the herpes simplex virus helicase-primase with antiviral activity in vitro and in animal models of HSV disease. To verify the mechanism of antiviral action, resistant viruses were selected by serial passage or by single-step plaque selection of HSV-1 KOS in the presence of inhibitors. Three resistant isolates K138r3, K22r5, and K22r1 were found to be 38-, 316-, and 2500-fold resistant to BILS 22 BS, a potent analog of BILS 45 BS. All three viruses had growth properties in vitro similar to wild-type HSV-1 KOS but they were sensitive to acyclovir. Cutaneous and intra-cerebral inoculation of mice with K22r1 or K22r5 resulted in pathogenicity equivalent to that of HSV-1 KOS. Both isolates were fully competent for reactivation from latency following corneal inoculation. Helicase-primase purified from cells infected with resistant viruses showed decreased inhibition in an in vitro DNA-dependent ATPase assay that correlated well with antiviral resistance. Marker transfer experiments and DNA sequence analysis identified single base pair mutations clustered in the N-terminus of the UL5 gene that resulted in single amino acid changes in the UL5 protein. Taken together, the results indicate that helicase-primase inhibitors prevent HSV growth by inhibiting HSV helicase-primase through specific interaction with the UL5 protein.
Asunto(s)
Antivirales/farmacología , ADN Helicasas/antagonistas & inhibidores , Inhibidores Enzimáticos/farmacología , Herpesvirus Humano 1/efectos de los fármacos , Herpesvirus Humano 1/aislamiento & purificación , Tiazoles/química , Animales , ADN Primasa , Modelos Animales de Enfermedad , Farmacorresistencia Viral , Herpesvirus Humano 1/enzimología , Herpesvirus Humano 1/genética , Ratones , Ratones Endogámicos BALB C , Mutagénesis , Tiazoles/farmacología , Proteínas ViralesRESUMEN
Nefang, a polyherbal product composed of Mangifera indica (bark and leaf), Psidium guajava, Carica papaya, Cymbopogon citratus, Citrus sinensis, and Ocimum gratissimum (leaves), is a potential therapy against P. falciparum malaria. In vitro antiplasmodial activities of its constituent solvent extracts were analyzed on CQ-sensitive (3D7) and multidrug resistant (Dd2) P. falciparum strains. The interactions involving the differential solvent extracts were further analyzed using a variable potency ratio drug combination approach. Effective concentration 50 (EC50) values were determined by nonlinear regression curve-fitting of the dose-response data and used in calculating the fractional inhibitory concentration 50 (FIC50) and combination indices (CI) for each pair. The derived EC50 values (3D7/Dd2, µ g/mL) are Nefang-96.96/55.08, MiB-65.33/34.58, MiL-82.56/40.04, Pg-47.02/25.79, Cp-1188/317.5, Cc-723.3/141, Cs-184.4/105.1, and Og-778.5/118.9. Synergism was obtained with MiB/Pg (CI = 0.351), MiL/Pg (0.358), MiB/Cs (0.366), MiL/Cs (0.482), Pg/Cs (0.483), and Cs/Og (0.414) when analyzed at equipotency ratios. Cytotoxicity testing of Nefang and the solvent extracts on two human cell lines (Hep G2 and U2OS) revealed no significant toxicity relative to their antiplasmodial activities (SI > 20). Taken together, our data confirm the antimalarial activities of Nefang and its constituent plant extracts and identified extract pairs with promising synergistic interactions for exploitation towards a rational phytotherapeutic and evidence-based antimalarial drug discovery.
Asunto(s)
Antimaláricos , Malaria Falciparum/tratamiento farmacológico , Extractos Vegetales , Plasmodium falciparum , Solventes/química , Antimaláricos/química , Antimaláricos/farmacología , Evaluación Preclínica de Medicamentos , Células Hep G2 , Humanos , Extractos Vegetales/química , Extractos Vegetales/farmacologíaRESUMEN
New antimalarial agents that exhibit multistage activities against drug-resistant strains of malaria parasites represent good starting points for developing next-generation antimalarial therapies. To facilitate the progression of such agents into the development phase, we developed an image-based parasitological screening method for defining drug effects on different asexual life cycle stages of Plasmodium falciparum. High-throughput screening of a newly assembled diversity-oriented synthetic library using this approach led to the identification of carbohybrid-based 2-aminopyrimidine compounds with fast-acting growth inhibitory activities against three laboratory strains of multidrug-resistant P. falciparum. Our structure-activity relationship study led to the identification of two derivatives (8aA and 11aA) as the most promising antimalarial candidates (mean EC50 of 0.130 and 0.096 µM against all three P. falciparum strains, selectivity indices >600, microsomal stabilities >80%, and mouse malaria ED50 values of 0.32 and 0.12 mg/kg/day, respectively), targeting all major blood stages of multidrug-resistant P. falciparum parasites.