RESUMEN
Focussed studies on imidazopyridine inhibitors of Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG) have significantly advanced the series towards desirable in vitro property space. LLE-based approaches towards combining improvements in cell potency, key physicochemical parameters and structural novelty are described, and a structure-based design hypothesis relating to substituent regiochemistry has directed efforts towards key examples with well-balanced potency, ADME and kinase selectivity profiles.
Asunto(s)
Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Imidazoles/química , Malaria/tratamiento farmacológico , Plasmodium falciparum/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Piridinas/química , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Humanos , Malaria/enzimología , Malaria/parasitología , Modelos Moleculares , Simulación del Acoplamiento Molecular , Plasmodium falciparum/enzimología , Conformación Proteica , Inhibidores de Proteínas Quinasas/químicaRESUMEN
Development of a class of bicyclic inhibitors of the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG), starting from known compounds with activity against a related parasite PKG orthologue, is reported. Examination of key sub-structural elements led to new compounds with good levels of inhibitory activity against the recombinant kinase and in vitro activity against the parasite. Key examples were shown to possess encouraging in vitro ADME properties, and computational analysis provided valuable insight into the origins of the observed activity profiles.
Asunto(s)
Antimaláricos/farmacología , Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Imidazoles/farmacología , Plasmodium falciparum/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Piridinas/farmacología , Antimaláricos/síntesis química , Antimaláricos/química , Proteínas Quinasas Dependientes de GMP Cíclico/metabolismo , Relación Dosis-Respuesta a Droga , Imidazoles/síntesis química , Imidazoles/química , Ligandos , Estructura Molecular , Pruebas de Sensibilidad Parasitaria , Plasmodium falciparum/enzimología , Inhibidores de Proteínas Quinasas/síntesis química , Inhibidores de Proteínas Quinasas/química , Piridinas/síntesis química , Piridinas/química , Relación Estructura-ActividadRESUMEN
A series of trisubstituted thiazoles have been identified as potent inhibitors of Plasmodium falciparum (Pf) cGMP-dependent protein kinase (PfPKG) through template hopping from known Eimeria PKG (EtPKG) inhibitors. The thiazole series has yielded compounds with improved potency, kinase selectivity and good in vitro ADME properties. These compounds could be useful tools in the development of new anti-malarial drugs in the fight against drug resistant malaria.
Asunto(s)
Antimaláricos/farmacología , Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Plasmodium falciparum/enzimología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Protozoarias/antagonistas & inhibidores , Tiazoles/farmacología , Alquilación , Antimaláricos/química , Humanos , Oxidación-Reducción , Inhibidores de Proteínas Quinasas/química , Relación Estructura-Actividad , Tiazoles/químicaRESUMEN
Autophagy is a cell-protective and degradative process that recycles damaged and long-lived cellular components. Cancer cells are thought to take advantage of autophagy to help them to cope with the stress of tumorigenesis; thus targeting autophagy is an attractive therapeutic approach. However, there are currently no specific inhibitors of autophagy. ULK1, a serine/threonine protein kinase, is essential for the initial stages of autophagy, and here we report that two compounds, MRT67307 and MRT68921, potently inhibit ULK1 and ULK2 in vitro and block autophagy in cells. Using a drug-resistant ULK1 mutant, we show that the autophagy-inhibiting capacity of the compounds is specifically through ULK1. ULK1 inhibition results in accumulation of stalled early autophagosomal structures, indicating a role for ULK1 in the maturation of autophagosomes as well as initiation.
Asunto(s)
Autofagia/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Serina-Treonina Quinasas TOR/metabolismo , Animales , Homólogo de la Proteína 1 Relacionada con la Autofagia , Línea Celular , Evaluación Preclínica de Medicamentos , RatonesRESUMEN
Imidazopyridazine compounds are potent, ATP-competitive inhibitors of calcium-dependent protein kinase 1 (CDPK1) and of Plasmodium falciparum parasite growth in vitro. Here, we show that these compounds can be divided into two classes depending on the nature of the aromatic linker between the core and the R2 substituent group. Class 1 compounds have a pyrimidine linker and inhibit parasite growth at late schizogony, whereas class 2 compounds have a nonpyrimidine linker and inhibit growth in the trophozoite stage, indicating different modes of action for the two classes. The compounds also inhibited cyclic GMP (cGMP)-dependent protein kinase (PKG), and their potency against this enzyme was greatly reduced by substitution of the enzyme's gatekeeper residue at the ATP binding site. The effectiveness of the class 1 compounds against a parasite line expressing the modified PKG was also substantially reduced, suggesting that these compounds kill the parasite primarily through inhibition of PKG rather than CDPK1. HSP90 was identified as a binding partner of class 2 compounds, and a representative compound bound to the ATP binding site in the N-terminal domain of HSP90. Reducing the size of the gatekeeper residue of CDPK1 enabled inhibition of the enzyme by bumped kinase inhibitors; however, a parasite line expressing the modified enzyme showed no change in sensitivity to these compounds. Taken together, these findings suggest that CDPK1 may not be a suitable target for further inhibitor development and that the primary mechanism through which the imidazopyridazines kill parasites is by inhibition of PKG or HSP90.
Asunto(s)
Antimaláricos/farmacología , Plasmodium falciparum/efectos de los fármacos , Proteínas Protozoarias/antagonistas & inhibidores , Antimaláricos/química , Línea Celular , Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Proteínas Quinasas Dependientes de GMP Cíclico/metabolismo , Proteínas HSP90 de Choque Térmico/antagonistas & inhibidores , Proteínas HSP90 de Choque Térmico/metabolismo , Humanos , Imidazoles/química , Imidazoles/farmacología , Simulación del Acoplamiento Molecular , Terapia Molecular Dirigida/métodos , Plasmodium falciparum/crecimiento & desarrollo , Plasmodium falciparum/metabolismo , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Quinasas/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Piridazinas/química , Piridazinas/farmacologíaRESUMEN
PfCDPK1 is a Plasmodium falciparum calcium-dependent protein kinase, which has been identified as a potential target for novel antimalarial chemotherapeutics. In order to further investigate the role of PfCDPK1, we established a high-throughput in vitro biochemical assay and used it to screen a library of over 35,000 small molecules. Five chemical series of inhibitors were initially identified from the screen, from which series 1 and 2 were selected for chemical optimization. Indicative of their mechanism of action, enzyme inhibition by these compounds was found to be sensitive to both the ATP concentration and substitution of the amino acid residue present at the "gatekeeper" position at the ATP-binding site of the enzyme. Medicinal chemistry efforts led to a series of PfCDPK1 inhibitors with 50% inhibitory concentrations (IC50s) below 10 nM against PfCDPK1 in a biochemical assay and 50% effective concentrations (EC50s) less than 100 nM for inhibition of parasite growth in vitro. Potent inhibition was combined with acceptable absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties and equipotent inhibition of Plasmodium vivax CDPK1. However, we were unable to correlate biochemical inhibition with parasite growth inhibition for this series overall. Inhibition of Plasmodium berghei CDPK1 correlated well with PfCDPK1 inhibition, enabling progression of a set of compounds to in vivo evaluation in the P. berghei rodent model for malaria. These chemical series have potential for further development as inhibitors of CDPK1.
Asunto(s)
Antimaláricos/farmacología , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/enzimología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Quinasas/metabolismo , Proteínas Protozoarias/metabolismo , Animales , Antimaláricos/uso terapéutico , Malaria/tratamiento farmacológico , Ratones , Plasmodium berghei/efectos de los fármacos , Plasmodium berghei/patogenicidad , Plasmodium falciparum/patogenicidad , Plasmodium vivax/efectos de los fármacos , Plasmodium vivax/patogenicidad , Inhibidores de Proteínas Quinasas/uso terapéutico , Proteínas Protozoarias/antagonistas & inhibidoresRESUMEN
The structural diversity and SAR in a series of imidazopyridazine inhibitors of Plasmodium falciparum calcium dependent protein kinase 1 (PfCDPK1) has been explored and extended. The opportunity to further improve key ADME parameters by means of lowering logD was identified, and this was achieved by replacement of a six-membered (hetero)aromatic linker with a pyrazole. A short SAR study has delivered key examples with useful in vitro activity and ADME profiles, good selectivity against a human kinase panel and improved levels of lipophilic ligand efficiency. These new analogues thus provide a credible additional route to further development of the series.
Asunto(s)
Antimaláricos/química , Antimaláricos/farmacología , Plasmodium falciparum/enzimología , Proteínas Protozoarias/antagonistas & inhibidores , Piridazinas/química , Piridazinas/farmacología , Humanos , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Plasmodium falciparum/efectos de los fármacos , Proteínas Quinasas/metabolismo , Proteínas Protozoarias/metabolismoRESUMEN
A series of imidazopyridazines which are potent inhibitors of Plasmodium falciparum calcium-dependent protein kinase 1 (PfCDPK1) was identified from a high-throughput screen against the isolated enzyme. Subsequent exploration of the SAR and optimisation has yielded leading members which show promising in vitro anti-parasite activity along with good in vitro ADME and selectivity against human kinases. Initial in vivo testing has revealed good oral bioavailability in a mouse PK study and modest in vivo efficacy in a Plasmodium berghei mouse model of malaria.
Asunto(s)
Antimaláricos/farmacología , Malaria/tratamiento farmacológico , Plasmodium falciparum/enzimología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Protozoarias/antagonistas & inhibidores , Piridazinas/farmacología , Animales , Antimaláricos/administración & dosificación , Antimaláricos/química , Antimaláricos/uso terapéutico , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Ensayos Analíticos de Alto Rendimiento , Malaria/parasitología , Ratones , Modelos Moleculares , Estructura Molecular , Pruebas de Sensibilidad Parasitaria , Plasmodium falciparum/efectos de los fármacos , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/uso terapéutico , Proteínas Quinasas/metabolismo , Proteínas Protozoarias/metabolismo , Piridazinas/administración & dosificación , Piridazinas/química , Relación Estructura-ActividadRESUMEN
A high-throughput screen against PknB, an essential serine-threonine protein kinase present in Mycobacterium tuberculosis (M. tuberculosis), allowed the identification of an aminoquinazoline inhibitor which was used as a starting point for SAR investigations. Although a significant improvement in enzyme affinity was achieved, the aminoquinazolines showed little or no cellular activity against M. tuberculosis. However, switching to an aminopyrimidine core scaffold and the introduction of a basic amine side chain afforded compounds with nanomolar enzyme binding affinity and micromolar minimum inhibitory concentrations against M. tuberculosis. Replacement of the pyrazole head group with pyridine then allowed equipotent compounds with improved selectivity against a human kinase panel to be obtained.
Asunto(s)
Mycobacterium tuberculosis/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Pirimidinas/farmacología , Aminas , Humanos , Pruebas de Sensibilidad Microbiana , Quinazolinas , Relación Estructura-ActividadRESUMEN
Synthesis of a number of bicyclic five-membered ring derivatives of gabapentin led to the identification of two compounds, (-)-(11A) and (20A) which both had an excellent level of potency against alpha(2)delta and were profiled in an in vivo model of neuropathic pain.
Asunto(s)
Aminas/síntesis química , Aminoácidos/síntesis química , Compuestos Bicíclicos con Puentes/síntesis química , Ácidos Ciclohexanocarboxílicos/síntesis química , Ácido gamma-Aminobutírico/síntesis química , Aminas/química , Aminas/farmacocinética , Aminoácidos/química , Aminoácidos/farmacocinética , Animales , Barrera Hematoencefálica/metabolismo , Compuestos Bicíclicos con Puentes/química , Compuestos Bicíclicos con Puentes/farmacocinética , Células CHO , Cricetinae , Cricetulus , Ácidos Ciclohexanocarboxílicos/química , Ácidos Ciclohexanocarboxílicos/farmacocinética , Gabapentina , Neuralgia/tratamiento farmacológico , Dimensión del Dolor , Ratas , Estereoisomerismo , Relación Estructura-Actividad , Ácido gamma-Aminobutírico/química , Ácido gamma-Aminobutírico/farmacocinéticaRESUMEN
A range of 3-alkylated five-membered ring derivatives of Gabapentin were synthesized and several were found to have good levels of potency against the alpha2delta calcium subunit of a voltage-gated calcium channel. Two compounds were profiled in in vivo models of pain and anxiety.
Asunto(s)
Aminas/síntesis química , Aminoácidos/síntesis química , Ansiolíticos/síntesis química , Ácidos Ciclohexanocarboxílicos/síntesis química , Ciclopentanos/síntesis química , Ácido gamma-Aminobutírico/síntesis química , Aminas/química , Aminas/farmacología , Aminoácidos/química , Aminoácidos/farmacología , Animales , Ansiolíticos/química , Ansiolíticos/farmacología , Canales de Calcio/metabolismo , Carragenina/farmacología , Ácidos Ciclohexanocarboxílicos/química , Ácidos Ciclohexanocarboxílicos/farmacología , Ciclopentanos/química , Ciclopentanos/farmacología , Gabapentina , Hiperalgesia/inducido químicamente , Hiperalgesia/tratamiento farmacológico , Ratas , Estereoisomerismo , Ácido gamma-Aminobutírico/química , Ácido gamma-Aminobutírico/farmacologíaRESUMEN
A range of 3,4-alkylated five-membered ring derivatives of gabapentin were synthesised. One compound (21) had an excellent level of potency against alpha(2)delta and was profiled in in vivo models of pain and anxiety.
Asunto(s)
Aminas/química , Aminoácidos/síntesis química , Ansiolíticos/síntesis química , Ácidos Ciclohexanocarboxílicos/química , Ciclopentanos/síntesis química , Ácido gamma-Aminobutírico/química , Aminas/síntesis química , Aminas/farmacocinética , Aminoácidos/química , Aminoácidos/farmacología , Animales , Ansiolíticos/química , Ansiolíticos/farmacocinética , Ácidos Ciclohexanocarboxílicos/síntesis química , Ácidos Ciclohexanocarboxílicos/farmacocinética , Ciclopentanos/química , Ciclopentanos/farmacología , Modelos Animales de Enfermedad , Gabapentina , Hiperalgesia/inducido químicamente , Hiperalgesia/tratamiento farmacológico , Ratas , Ácido gamma-Aminobutírico/síntesis química , Ácido gamma-Aminobutírico/farmacocinéticaRESUMEN
The single-celled apicomplexan parasite Plasmodium falciparum is responsible for the majority of deaths due to malaria each year. The selection of drug resistance has been a recurring theme over the decades with each new drug that is developed. It is therefore crucial that future generations of drugs are explored to tackle this major public health problem. Cyclic GMP (cGMP) signaling is one of the biochemical pathways that is being explored as a potential target for new antimalarial drugs. It has been shown that this pathway is essential for all of the key developmental stages of the complex malaria parasite life cycle. This gives hope that targeting cGMP signaling might give rise to drugs that treat disease, block its transmission and even prevent the establishment of infection. Here we review previous work that has been carried out to develop and optimize inhibitors of the cGMP-dependent protein kinase (PKG) which is a critical regulator of the malaria parasite life cycle.
RESUMEN
The SAR of a series of novel pyrido[3,4-d]pyramid-4-ylamine mGluR1 antagonists is described. The multiple of the unbound K(i) in cerebrospinal fluid necessary to give morphine like analgesic effects in an electromyograph pinch model in rodents is determined and the effect of structure on CNS penetration examined.
Asunto(s)
Antagonistas de Aminoácidos Excitadores/síntesis química , Receptores de Glutamato Metabotrópico/antagonistas & inhibidores , Animales , Electromiografía/métodos , Antagonistas de Aminoácidos Excitadores/química , Antagonistas de Aminoácidos Excitadores/farmacología , Dimensión del Dolor/efectos de los fármacos , Dimensión del Dolor/métodos , Ratas , Receptores de Glutamato Metabotrópico/fisiología , Relación Estructura-ActividadRESUMEN
One of the attractive properties of artemisinins is their extremely fast-killing capability, quickly relieving malaria symptoms. Nevertheless, the unique benefits of these medicines are now compromised by the prolonged parasite clearance times and the increasing frequency of treatment failures, attributed to the increased tolerance of Plasmodium falciparum to artemisinin. This emerging artemisinin resistance threatens to undermine the effectiveness of antimalarial combination therapies. Herein, we describe the medicinal chemistry efforts focused on a cGMP-dependent protein kinase (PKG) inhibitor scaffold, leading to the identification of novel chemical entities with very potent, similar to artemisinins, fast-killing potency against asexual blood stages that cause disease, and activity against gametocyte activation that is required for transmission. Furthermore, we confirm that selective PKG inhibitors have a slow speed of kill, while chemoproteomic analysis suggests for the first time serine/arginine protein kinase 2 (SRPK2) targeting as a novel strategy for developing antimalarial compounds with extremely fast-killing properties.
Asunto(s)
Antimaláricos/farmacología , Artemisininas/química , Plasmodium falciparum/efectos de los fármacos , Antimaláricos/química , Antimaláricos/metabolismo , Artemisininas/metabolismo , Artemisininas/farmacología , Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Proteínas Quinasas Dependientes de GMP Cíclico/genética , Proteínas Quinasas Dependientes de GMP Cíclico/metabolismo , Canal de Potasio ERG1/antagonistas & inhibidores , Canal de Potasio ERG1/metabolismo , Humanos , Concentración 50 Inhibidora , Mutagénesis Sitio-Dirigida , Plasmodium falciparum/crecimiento & desarrollo , Proteínas Protozoarias/antagonistas & inhibidores , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Solubilidad , Relación Estructura-Actividad , Tiazoles/químicaRESUMEN
To combat drug resistance, new chemical entities are urgently required for use in next generation anti-malarial combinations. We report here the results of a medicinal chemistry programme focused on an imidazopyridine series targeting the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG). The most potent compound (ML10) has an IC50 of 160 pM in a PfPKG kinase assay and inhibits P. falciparum blood stage proliferation in vitro with an EC50 of 2.1 nM. Oral dosing renders blood stage parasitaemia undetectable in vivo using a P. falciparum SCID mouse model. The series targets both merozoite egress and erythrocyte invasion, but crucially, also blocks transmission of mature P. falciparum gametocytes to Anopheles stephensi mosquitoes. A co-crystal structure of PvPKG bound to ML10, reveals intimate molecular contacts that explain the high levels of potency and selectivity we have measured. The properties of this series warrant consideration for further development to produce an antimalarial drug.Protein kinases are promising drug targets for treatment of malaria. Here, starting with a medicinal chemistry approach, Baker et al. generate an imidazopyridine that selectively targets Plasmodium falciparum PKG, inhibits blood stage parasite growth in vitro and in mice and blocks transmission to mosquitoes.
Asunto(s)
Proteínas Quinasas Dependientes de GMP Cíclico/antagonistas & inhibidores , Imidazoles/uso terapéutico , Malaria/enzimología , Malaria/transmisión , Piridinas/uso terapéutico , Animales , Línea Celular , Cristalografía por Rayos X , Culicidae , Proteínas Quinasas Dependientes de GMP Cíclico/química , Proteínas Quinasas Dependientes de GMP Cíclico/metabolismo , Modelos Animales de Enfermedad , Femenino , Humanos , Imidazoles/farmacología , Estadios del Ciclo de Vida/efectos de los fármacos , Malaria/tratamiento farmacológico , Ratones Endogámicos BALB C , Modelos Moleculares , Plasmodium chabaudi/efectos de los fármacos , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/crecimiento & desarrollo , Inhibidores de Proteínas Quinasas/farmacología , Inhibidores de Proteínas Quinasas/uso terapéutico , Piridinas/farmacología , Resultado del TratamientoRESUMEN
A structure-guided design approach using a homology model of Plasmodium falciparum calcium-dependent protein kinase 1 (PfCDPK1) was used to improve the potency of a series of imidazopyridazine inhibitors as potential antimalarial agents. This resulted in high affinity compounds with PfCDPK1 enzyme IC50 values less than 10 nM and in vitro P. falciparum antiparasite EC50 values down to 12 nM, although these compounds did not have suitable ADME properties to show in vivo efficacy in a mouse model. Structural modifications designed to address the ADME issues, in particular permeability, were initially accompanied by losses in antiparasite potency, but further optimization allowed a good balance in the compound profile to be achieved. Upon testing in vivo in a murine model of efficacy against malaria, high levels of compound exposure relative to their in vitro activities were achieved, and the modest efficacy that resulted raises questions about the level of effect that is achievable through the targeting of PfCDPK1.
Asunto(s)
Antimaláricos/síntesis química , Plasmodium falciparum/efectos de los fármacos , Inhibidores de Proteínas Quinasas/síntesis química , Proteínas Protozoarias/antagonistas & inhibidores , Piridazinas/síntesis química , Animales , Antimaláricos/farmacología , Ratones , Plasmodium falciparum/enzimología , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Quinasas/química , Proteínas Protozoarias/química , Piridazinas/farmacología , Relación Estructura-ActividadRESUMEN
PknB is an essential serine/threonine kinase of Mycobacterium tuberculosis with possible roles in a number of signalling pathways involved in cell division and metabolism. We screened a library of >50,000 compounds for inhibitors of the in vitro phosphorylation of GarA (Rv1827) by PknB and identified a number of inhibitors. A program of synthetic medicinal chemistry was subsequently conducted around one class of inhibitors and was successful in generating ATP competitive inhibitors with potency in the nanomolar range. Compounds in this class showed cross-reactivity with the related M. tuberculosis kinase, PknF, but not with PknG in an in vitro autophosphorylation assay. These synthesised inhibitors were able to prevent the growth of M. tuberculosis in an Alamar blue assay and in an intracellular model of infection, but only in the micromolar range. We attempted to determine if cell wall permeability was an explanation for the discrepancy between the potent in vitro compared with relatively poor in vivo activity, but found no evidence that the activity of the inhibitors could be improved by weakening the cell wall. Despite a number of drug discovery efforts attempting to develop inhibitors against PknB, it is yet to be reported that any such inhibitors prevent mycobacterial growth at submicromolar concentrations.
Asunto(s)
Antibacterianos/farmacología , Macrófagos/efectos de los fármacos , Mycobacterium tuberculosis/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Tuberculosis/tratamiento farmacológico , Antibacterianos/metabolismo , División Celular , Células Cultivadas , Descubrimiento de Drogas , Humanos , Mycobacterium tuberculosis/crecimiento & desarrollo , Mycobacterium tuberculosis/metabolismo , Transducción de Señal/efectos de los fármacos , Tuberculosis/metabolismoRESUMEN
Mycobacterium tuberculosis has an on-going impact on global public health and new therapeutics to treat tuberculosis are urgently required. The emergence of drug resistant tuberculosis poses a serious threat to the control of this pathogen, and the development of drugs that are active against the resistant strains is vital. A medium-throughput assay using the Alamar Blue reagent was set-up to identify novel inhibitors of M. tuberculosis from a library of known drugs, for which there has already been extensive research investigating their suitability and safety as human therapeutics. Of the 1514 compounds screened, 53 were demonstrated to possess inhibitory properties against M. tuberculosis at a concentration of 5microM or below. Of these, 17 were novel inhibitors while 36 were known tuberculosis drugs or had been previously described as possessing anti-tuberculosis activity. Five compounds were selected as those which represent the most promising starting points for new anti-tuberculosis agents. It was demonstrated that all five were active against intracellular M. tuberculosis in a macrophage model of infection. The anti-tuberculosis agents identified in this screen represent promising new scaffolds on which future drug development efforts can be focused.