RESUMEN
DNMT1 maintains the parental DNA methylation pattern on newly replicated hemimethylated DNA. The failure of this maintenance process causes aberrant DNA methylation that affects transcription and contributes to the development and progression of cancers such as acute myeloid leukemia. Here, we structurally characterized a set of newly discovered DNMT1-selective, reversible, non-nucleoside inhibitors that bear a core 3,5-dicyanopyridine moiety, as exemplified by GSK3735967, to better understand their mechanism of inhibition. All of the dicyanopydridine-containing inhibitors examined intercalate into the hemimethylated DNA between two CpG base pairs through the DNA minor groove, resulting in conformational movement of the DNMT1 active-site loop. In addition, GSK3735967 introduces two new binding sites, where it interacts with and stabilizes the displaced DNMT1 active-site loop and it occupies an open aromatic cage in which trimethylated histone H4 lysine 20 is expected to bind. Our work represents a substantial step in generating potent, selective, and non-nucleoside inhibitors of DNMT1.
Asunto(s)
ADN (Citosina-5-)-Metiltransferasas , Metilación de ADN , Sitios de Unión , Dominio Catalítico , ADN/metabolismo , ADN (Citosina-5-)-Metiltransferasas/química , ADN (Citosina-5-)-Metiltransferasas/genética , ADN (Citosina-5-)-Metiltransferasas/metabolismoRESUMEN
Elevated expression of the c-MYC oncogene is one of the most common abnormalities in human cancers. Unfortunately, efforts to identify pharmacological inhibitors that directly target MYC have not yet yielded a drug-like molecule due to the lack of any known small molecule binding pocket in the protein, which could be exploited to disrupt MYC function. We have recently described a strategy to target MYC indirectly, where a screening effort designed to identify compounds that can rapidly decrease endogenous c-MYC protein levels in a MYC-amplified cell line led to the discovery of a compound series that phenocopies c-MYC knockdown by siRNA. Herein, we describe our medicinal chemistry program that led to the discovery of potent, orally bioavailable c-MYC-reducing compounds. The development of a minimum pharmacophore model based on empirical structure activity relationship as well as the property-based approach used to modulate pharmacokinetics properties will be highlighted.
Asunto(s)
Descubrimiento de Drogas , Proteínas Proto-Oncogénicas c-myc/metabolismo , Bibliotecas de Moléculas Pequeñas/farmacología , Animales , Área Bajo la Curva , Línea Celular Tumoral , Semivida , Humanos , Proteínas Proto-Oncogénicas c-myc/genética , Ratas , Bibliotecas de Moléculas Pequeñas/farmacocinética , Relación Estructura-Actividad , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
We report herein the discovery of isoxazole amides as potent and selective SET and MYND Domain-Containing Protein 3 (SMYD3) inhibitors. Elucidation of the structure-activity relationship of the high-throughput screening (HTS) lead compound 1 provided potent and selective SMYD3 inhibitors. The SAR optimization, cocrystal structures of small molecules with SMYD3, and mode of inhibition (MOI) characterization of compounds are described. The synthesis and biological and pharmacokinetic profiles of compounds are also presented.
RESUMEN
Activation of the inositol-requiring enzyme-1 alpha (IRE1α) protein caused by endoplasmic reticulum stress results in the homodimerization of the N-terminal endoplasmic reticulum luminal domains, autophosphorylation of the cytoplasmic kinase domains, and conformational changes to the cytoplasmic endoribonuclease (RNase) domains, which render them functional and can lead to the splicing of X-box binding protein 1 (XBP 1) mRNA. Herein, we report the first crystal structures of the cytoplasmic portion of a human phosphorylated IRE1α dimer in complex with (R)-2-(3,4-dichlorobenzyl)-N-(4-methylbenzyl)-2,7-diazaspiro(4.5)decane-7-carboxamide, a novel, IRE1α-selective kinase inhibitor, and staurosporine, a broad spectrum kinase inhibitor. (R)-2-(3,4-dichlorobenzyl)-N-(4-methylbenzyl)-2,7-diazaspiro(4.5)decane-7-carboxamide inhibits both the kinase and RNase activities of IRE1α. The inhibitor interacts with the catalytic residues Lys599 and Glu612 and displaces the kinase activation loop to the DFG-out conformation. Inactivation of IRE1α RNase activity appears to be caused by a conformational change, whereby the αC helix is displaced, resulting in the rearrangement of the kinase domain-dimer interface and a rotation of the RNase domains away from each other. In contrast, staurosporine binds at the ATP-binding site of IRE1α, resulting in a dimer consistent with RNase active yeast Ire1 dimers. Activation of IRE1α RNase activity appears to be promoted by a network of hydrogen bond interactions between highly conserved residues across the RNase dimer interface that place key catalytic residues poised for reaction. These data implicate that the intermolecular interactions between conserved residues in the RNase domain are required for activity, and that the disruption of these interactions can be achieved pharmacologically by small molecule kinase domain inhibitors.
Asunto(s)
Endorribonucleasas/antagonistas & inhibidores , Endorribonucleasas/metabolismo , Inhibidores de Proteínas Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/metabolismo , Línea Celular Tumoral , Cristalización , Endorribonucleasas/química , Activación Enzimática/efectos de los fármacos , Activación Enzimática/fisiología , Humanos , Conformación Proteica/efectos de los fármacos , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/química , Estructura Secundaria de Proteína , Estructura Terciaria de ProteínaRESUMEN
Tumor cells upregulate many cell signaling pathways, with AKT being one of the key kinases to be activated in a variety of malignancies. GSK2110183 and GSK2141795 are orally bioavailable, potent inhibitors of the AKT kinases that have progressed to human clinical studies. Both compounds are selective, ATP-competitive inhibitors of AKT 1, 2 and 3. Cells treated with either compound show decreased phosphorylation of several substrates downstream of AKT. Both compounds have desirable pharmaceutical properties and daily oral dosing results in a sustained inhibition of AKT activity as well as inhibition of tumor growth in several mouse tumor models of various histologic origins. Improved kinase selectivity was associated with reduced effects on glucose homeostasis as compared to previously reported ATP-competitive AKT kinase inhibitors. In a diverse cell line proliferation screen, AKT inhibitors showed increased potency in cell lines with an activated AKT pathway (via PI3K/PTEN mutation or loss) while cell lines with activating mutations in the MAPK pathway (KRAS/BRAF) were less sensitive to AKT inhibition. Further investigation in mouse models of KRAS driven pancreatic cancer confirmed that combining the AKT inhibitor, GSK2141795 with a MEK inhibitor (GSK2110212; trametinib) resulted in an enhanced anti-tumor effect accompanied with greater reduction in phospho-S6 levels. Taken together these results support clinical evaluation of the AKT inhibitors in cancer, especially in combination with MEK inhibitor.
Asunto(s)
Antineoplásicos/farmacología , Diaminas/farmacología , Regulación Neoplásica de la Expresión Génica , Neoplasias Pancreáticas/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/farmacología , Pirazoles/farmacología , Carga Tumoral/efectos de los fármacos , Administración Oral , Animales , Antineoplásicos/síntesis química , Glucemia/metabolismo , Línea Celular Tumoral , Diaminas/síntesis química , Evaluación Preclínica de Medicamentos , Sinergismo Farmacológico , Femenino , Humanos , Quinasas Quinasa Quinasa PAM/antagonistas & inhibidores , Quinasas Quinasa Quinasa PAM/genética , Quinasas Quinasa Quinasa PAM/metabolismo , Ratones , Ratones SCID , Fosfohidrolasa PTEN/antagonistas & inhibidores , Fosfohidrolasa PTEN/genética , Fosfohidrolasa PTEN/metabolismo , Neoplasias Pancreáticas/enzimología , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patología , Fosfatidilinositol 3-Quinasas/genética , Fosfatidilinositol 3-Quinasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Inhibidores de Proteínas Quinasas/síntesis química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Pirazoles/síntesis química , Proteínas Quinasas S6 Ribosómicas/antagonistas & inhibidores , Proteínas Quinasas S6 Ribosómicas/genética , Proteínas Quinasas S6 Ribosómicas/metabolismo , Transducción de Señal , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Although therapeutic interventions of signal-transduction cascades with targeted kinase inhibitors are a well-established strategy, drug-discovery efforts to identify targeted phosphatase inhibitors have proven challenging. Herein we report a series of allosteric, small-molecule inhibitors of wild-type p53-induced phosphatase (Wip1), an oncogenic phosphatase common to multiple cancers. Compound binding to Wip1 is dependent on a 'flap' subdomain located near the Wip1 catalytic site that renders Wip1 structurally divergent from other members of the protein phosphatase 2C (PP2C) family and that thereby confers selectivity for Wip1 over other phosphatases. Treatment of tumor cells with the inhibitor GSK2830371 increases phosphorylation of Wip1 substrates and causes growth inhibition in both hematopoietic tumor cell lines and Wip1-amplified breast tumor cells harboring wild-type TP53. Oral administration of Wip1 inhibitors in mice results in expected pharmacodynamic effects and causes inhibition of lymphoma xenograft growth. To our knowledge, GSK2830371 is the first orally active, allosteric inhibitor of Wip1 phosphatase.
Asunto(s)
Aminopiridinas/química , Dipéptidos/química , Inhibidores Enzimáticos/farmacología , Fosfoproteínas Fosfatasas/antagonistas & inhibidores , Administración Oral , Regulación Alostérica , Secuencias de Aminoácidos , Aminopiridinas/farmacología , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Dominio Catalítico , Línea Celular Tumoral , Dipéptidos/farmacología , Modelos Animales de Enfermedad , Ensayos de Selección de Medicamentos Antitumorales , Activación Enzimática/efectos de los fármacos , Inhibidores Enzimáticos/química , Femenino , Xenoinjertos , Humanos , Ratones , Ratones SCID , Modelos Biológicos , Neoplasias , Proteína Fosfatasa 2CRESUMEN
We recently reported the discovery of GSK2606414 (1), a selective first in class inhibitor of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), which inhibited PERK activation in cells and demonstrated tumor growth inhibition in a human tumor xenograft in mice. In continuation of our drug discovery program, we applied a strategy to decrease inhibitor lipophilicity as a means to improve physical properties and pharmacokinetics. This report describes our medicinal chemistry optimization culminating in the discovery of the PERK inhibitor GSK2656157 (6), which was selected for advancement to preclinical development.
RESUMEN
Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) is activated in response to a variety of endoplasmic reticulum stresses implicated in numerous disease states. Evidence that PERK is implicated in tumorigenesis and cancer cell survival stimulated our search for small molecule inhibitors. Through screening and lead optimization using the human PERK crystal structure, we discovered compound 38 (GSK2606414), an orally available, potent, and selective PERK inhibitor. Compound 38 inhibits PERK activation in cells and inhibits the growth of a human tumor xenograft in mice.
Asunto(s)
Adenina/análogos & derivados , Antineoplásicos/síntesis química , Indoles/síntesis química , Pirimidinas/síntesis química , Pirroles/síntesis química , eIF-2 Quinasa/antagonistas & inhibidores , Adenina/síntesis química , Adenina/química , Adenina/farmacología , Administración Oral , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Disponibilidad Biológica , Línea Celular Tumoral , Cristalografía por Rayos X , Perros , Ensayos de Selección de Medicamentos Antitumorales , Femenino , Humanos , Indoles/química , Indoles/farmacología , Masculino , Ratones , Ratones Desnudos , Modelos Moleculares , Trasplante de Neoplasias , Fosforilación , Conformación Proteica , Pirimidinas/química , Pirimidinas/farmacología , Pirroles/química , Pirroles/farmacología , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , Trasplante HeterólogoRESUMEN
Fragment screening of phosphoinositide-dependent kinase-1 (PDK1) in a biochemical kinase assay afforded hits that were characterized and prioritized based on ligand efficiency and binding interactions with PDK1 as determined by NMR. Subsequent crystallography and follow-up screening led to the discovery of aminoindazole 19, a potent leadlike PDK1 inhibitor with high ligand efficiency. Well-defined structure-activity relationships and protein crystallography provide a basis for further elaboration and optimization of 19 as a PDK1 inhibitor.
RESUMEN
A novel series of AKT inhibitors containing 2,3,5-trisubstituted pyridines with novel azaindazoles as hinge binding elements are described. Among these, the 4,7-diazaindazole compound 2c has improved drug-like properties and kinase selectivity than those of indazole 1, and displays greater than 80% inhibition of GSK3beta phosphorylation in a BT474 tumor xenograft model in mice.
Asunto(s)
Indazoles/química , Inhibidores de Proteínas Quinasas/química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Pirazinas/química , Piridinas/química , Animales , Línea Celular Tumoral , Glucógeno Sintasa Quinasa 3/antagonistas & inhibidores , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Humanos , Indazoles/síntesis química , Indazoles/farmacología , Ratones , Fosforilación , Inhibidores de Proteínas Quinasas/síntesis química , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Pirazinas/síntesis química , Pirazinas/farmacología , Piridinas/síntesis química , Piridinas/farmacología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
2,3,5-Trisubstituted pyridines have been designed as potent AKT inhibitors that are selective against ROCK1 based on the comparison between AKT and ROCK1 structures. Substitution at the 2-position of the core pyridine is the key element to provide selectivity against ROCK1. An X-ray co-crystal structure of 9p in PKA supports the proposed rationale of ROCK1 selectivity.
Asunto(s)
Inhibidores de Proteínas Quinasas/química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Piridinas/química , Quinasas Asociadas a rho/antagonistas & inhibidores , Sitios de Unión , Cristalografía por Rayos X , Humanos , Inhibidores de Proteínas Quinasas/síntesis química , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Piridinas/síntesis química , Piridinas/farmacología , Relación Estructura-Actividad , Quinasas Asociadas a rho/metabolismoRESUMEN
The synthesis and evaluation of tetrasubstituted aminopyridines, bearing novel azaindazole hinge binders, as potent AKT inhibitors are described. Compound 14c was identified as a potent AKT inhibitor that demonstrated reduced CYP450 inhibition and an improved developability profile compared to those of previously described trisubstituted pyridines. It also displayed dose-dependent inhibition of both phosphorylation of GSK3beta and tumor growth in a BT474 tumor xenograft model in mice.
Asunto(s)
Aminopiridinas/química , Sistema Enzimático del Citocromo P-450/metabolismo , Canales de Potasio Éter-A-Go-Go/metabolismo , Inhibidores de Proteínas Quinasas/química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Pirazinas/química , Piridinas/química , Aminopiridinas/síntesis química , Aminopiridinas/farmacocinética , Animales , Línea Celular Tumoral , Perros , Canal de Potasio ERG1 , Glucógeno Sintasa Quinasa 3/antagonistas & inhibidores , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Haplorrinos , Humanos , Ratones , Fosforilación , Inhibidores de Proteínas Quinasas/síntesis química , Inhibidores de Proteínas Quinasas/farmacocinética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Pirazinas/síntesis química , Pirazinas/farmacocinética , Ratas , Relación Estructura-Actividad , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
A pyrrolopyridinyl thiophene carboxamide 7 was discovered as a tractable starting point for a lead optimization effort in an AKT kinase inhibition program. SAR studies aided by a co-crystal structure of 7 in AKT2 led to the identification of AKT inhibitors with subnanomolar potency. Representative compounds showed antiproliferative activity as well as inhibition of phosphorylation of the downstream target GSK3beta.
Asunto(s)
Descubrimiento de Drogas , Inhibidores de Proteínas Quinasas/síntesis química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Piridinas/síntesis química , Piridinas/farmacología , Tiofenos/química , Animales , Cristalografía por Rayos X , Descubrimiento de Drogas/métodos , Humanos , Ratones , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Tienopiridinas , Tiofenos/síntesis química , Tiofenos/farmacologíaRESUMEN
AKT inhibitors containing an imidazopyridine aminofurazan scaffold have been optimized. We have previously disclosed identification of the AKT inhibitor GSK690693, which has been evaluated in clinical trials in cancer patients. Herein we describe recent efforts focusing on investigating a distinct region of this scaffold that have afforded compounds (30 and 32) with comparable activity profiles to that of GSK690693.
Asunto(s)
Oxadiazoles/síntesis química , Inhibidores de Proteínas Quinasas/síntesis química , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Animales , Línea Celular , Línea Celular Tumoral , Cristalografía por Rayos X , Humanos , Oxadiazoles/química , Oxadiazoles/farmacología , Oxadiazoles/uso terapéutico , Inhibidores de Proteínas Quinasas/farmacología , Estructura Secundaria de Proteína/fisiología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Relación Estructura-ActividadRESUMEN
Overexpression of AKT has an antiapoptotic effect in many cell types, and expression of dominant negative AKT blocks the ability of a variety of growth factors to promote survival. Therefore, inhibitors of AKT kinase activity might be useful as monotherapy for the treatment of tumors with activated AKT. Herein, we describe our lead optimization studies culminating in the discovery of compound 3g (GSK690693). Compound 3g is a novel ATP competitive, pan-AKT kinase inhibitor with IC 50 values of 2, 13, and 9 nM against AKT1, 2, and 3, respectively. An X-ray cocrystal structure was solved with 3g and the kinase domain of AKT2, confirming that 3g bound in the ATP binding pocket. Compound 3g potently inhibits intracellular AKT activity as measured by the inhibition of the phosphorylation levels of GSK3beta. Intraperitoneal administration of 3g in immunocompromised mice results in the inhibition of GSK3beta phosphorylation and tumor growth in human breast carcinoma (BT474) xenografts.
Asunto(s)
Oxadiazoles/farmacología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Animales , Femenino , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Ratones , Ratones SCID , Modelos Moleculares , Oxadiazoles/química , Oxadiazoles/metabolismo , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Especificidad por SustratoRESUMEN
Akt kinases 1, 2, and 3 are important regulators of cell survival and have been shown to be constitutively active in a variety of human tumors. GSK690693 is a novel ATP-competitive, low-nanomolar pan-Akt kinase inhibitor. It is selective for the Akt isoforms versus the majority of kinases in other families; however, it does inhibit additional members of the AGC kinase family. It causes dose-dependent reductions in the phosphorylation state of multiple proteins downstream of Akt, including GSK3 beta, PRAS40, and Forkhead. GSK690693 inhibited proliferation and induced apoptosis in a subset of tumor cells with potency consistent with intracellular inhibition of Akt kinase activity. In immune-compromised mice implanted with human BT474 breast carcinoma xenografts, a single i.p. administration of GSK690693 inhibited GSK3 beta phosphorylation in a dose- and time-dependent manner. After a single dose of GSK690693, >3 micromol/L drug concentration in BT474 tumor xenografts correlated with a sustained decrease in GSK3 beta phosphorylation. Consistent with the role of Akt in insulin signaling, treatment with GSK690693 resulted in acute and transient increases in blood glucose level. Daily administration of GSK690693 produced significant antitumor activity in mice bearing established human SKOV-3 ovarian, LNCaP prostate, and BT474 and HCC-1954 breast carcinoma xenografts. Immunohistochemical analysis of tumor xenografts after repeat dosing with GSK690693 showed reductions in phosphorylated Akt substrates in vivo. These results support further evaluation of GSK690693 as an anticancer agent.
Asunto(s)
Antineoplásicos/farmacología , Oxadiazoles/farmacología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Animales , Antineoplásicos/farmacocinética , Femenino , Humanos , Ratones , Ratones Desnudos , Ratones SCID , Neoplasias/tratamiento farmacológico , Neoplasias/metabolismo , Oxadiazoles/farmacocinética , Inhibidores de Proteínas Quinasas/farmacocinética , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
A novel benzimidazole series of small-molecule thrombopoietin receptor agonists has been discovered. Herein, we discuss the preliminary exploration of structure-activity relationships within this chemotype.
Asunto(s)
Bencimidazoles/química , Bencimidazoles/farmacología , Receptores de Citocinas/agonistas , Receptores de Citocinas/metabolismo , Trombopoyetina/metabolismo , Ácidos/química , Bencimidazoles/síntesis química , Estructura Molecular , Naftoles/química , Relación Estructura-ActividadRESUMEN
A novel benzylidenethiazolidinedione has been discovered with antimicrobial activity. Here, we present the results of a structure-activity study on this compound with respect to its antimicrobial activity.
Asunto(s)
Antibacterianos/síntesis química , Antibacterianos/farmacología , Compuestos de Bencilo/síntesis química , Compuestos de Bencilo/farmacología , Tiazolidinedionas/síntesis química , Tiazolidinedionas/farmacología , Enterococcus faecalis/efectos de los fármacos , Bacterias Gramnegativas/efectos de los fármacos , Indicadores y Reactivos , Pruebas de Sensibilidad Microbiana , Staphylococcus aureus/efectos de los fármacos , Streptococcus pneumoniae/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
In our continuing efforts to identify small molecule vitronectin receptor antagonists, we have discovered a series of phenylbutyrate derivatives, exemplified by 16, which have good potency and excellent oral bioavailability (approximately 100% in rats). This new series is derived conceptually from opening of the seven-membered ring of SB-265123.
Asunto(s)
Integrina alfaVbeta3/antagonistas & inhibidores , Fenilbutiratos/farmacología , Fenilbutiratos/farmacocinética , Acetatos/química , Administración Oral , Aminopiridinas/química , Animales , Disponibilidad Biológica , Adhesión Celular/efectos de los fármacos , Línea Celular , Semivida , Humanos , Fenilbutiratos/química , RatasRESUMEN
Bacterial enoyl-acyl carrier protein (ACP) reductase (FabI) catalyzes the final step in each elongation cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. High-throughput screening of the Staphylococcus aureus FabI enzyme identified a novel, weak inhibitor with no detectable antibacterial activity against S. aureus. Iterative medicinal chemistry and X-ray crystal structure-based design led to the identification of compound 4 [(E)-N-methyl-N-(2-methyl-1H-indol-3-ylmethyl)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylamide], which is 350-fold more potent than the original lead compound obtained by high-throughput screening in the FabI inhibition assay. Compound 4 has exquisite antistaphylococci activity, achieving MICs at which 90% of isolates are inhibited more than 500 times lower than those of nine currently available antibiotics against a panel of multidrug-resistant strains of S. aureus and Staphylococcus epidermidis. Furthermore, compound 4 exhibits excellent in vivo efficacy in an S. aureus infection model in rats. Biochemical and genetic approaches have confirmed that the mode of antibacterial action of compound 4 and related compounds is via inhibition of FabI. Compound 4 also exhibits weak FabK inhibitory activity, which may explain its antibacterial activity against Streptococcus pneumoniae and Enterococcus faecalis, which depend on FabK and both FabK and FabI, respectively, for their enoyl-ACP reductase function. These results show that compound 4 is representative of a new, totally synthetic series of antibacterial agents that has the potential to provide novel alternatives for the treatment of S. aureus infections that are resistant to our present armory of antibiotics.