RESUMEN
Inhibiting Arginase 1 (ARG1), a metalloenzyme that hydrolyzes l-arginine in the urea cycle, has been demonstrated as a promising therapeutic avenue in immuno-oncology through the restoration of suppressed immune response in several types of cancers. Most of the currently reported small molecule inhibitors are boronic acid based. Herein, we report the discovery of non-boronic acid ARG1 inhibitors through virtual screening. Biophysical and biochemical methods were used to experimentally profile the hits while X-ray crystallography confirmed a class of trisubstituted pyrrolidine derivatives as optimizable alternatives for the development of novel classes of immuno-oncology agents targeting this enzyme.
Asunto(s)
Arginasa , Neoplasias , Humanos , Modelos Moleculares , Arginasa/química , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/química , Ácidos Borónicos/farmacología , Ácidos Borónicos/química , Arginina/químicaRESUMEN
A multiplexed system based on inductive nanoelectrospray mass spectrometry (nESI-MS) has been developed for high-throughput screening (HTS) bioassays. This system combines inductive nESI and field amplification micro-electrophoresis to achieve a "dip-and-go" sample loading and purification strategy that enables nESI-MS based HTS assays in 96-well microtiter plates. The combination of inductive nESI and micro-electrophoresis makes it possible to perform efficient in situ separations and clean-up of biological samples. The sensitivity of the system is such that quantitative analysis of peptides from 1-10 000â nm can be performed in a biological matrix. A prototype of the automation system has been developed to handle 12 samples (one row of a microtiter plate) at a time. The sample loading and electrophoretic clean-up of biosamples can be done in parallel within 20â s followed by MS analysis at a rate of 1.3 to 3.5â s per sample. The system was used successfully for the quantitative analysis of BACE1-catalyzed peptide hydrolysis, a prototypical HTS assay of relevance to drug discovery. IC50 values for this system were in agreement with LC-MS but recorded in times more than an order of magnitude shorter.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/química , Ensayos Analíticos de Alto Rendimiento , Péptidos/análisis , Cromatografía Líquida de Alta Presión , Ensayos Analíticos de Alto Rendimiento/instrumentación , Ensayos Analíticos de Alto Rendimiento/métodos , Hidrólisis , Cinética , Límite de Detección , Nanoestructuras/química , Oligopéptidos/química , Espectrometría de Masa por Ionización de Electrospray/instrumentación , Espectrometría de Masa por Ionización de Electrospray/métodosRESUMEN
The synthesis of a series of iminoheterocycles and their structure-activity relationships (SAR) as inhibitors of the aspartyl protease BACE1 will be detailed. An effort to access the S3 subsite directly from the S1 subsite initially yielded compounds with sub-micromolar potency. A subset of compounds from this effort unexpectedly occupied a different binding site and displayed excellent BACE1 affinities. Select compounds from this subset acutely lowered Aß40 levels upon subcutaneous and oral administration to rats.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Secretasas de la Proteína Precursora del Amiloide/uso terapéutico , Ácido Aspártico Endopeptidasas/uso terapéutico , Secretasas de la Proteína Precursora del Amiloide/genética , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Animales , Ácido Aspártico Endopeptidasas/genética , Ácido Aspártico Endopeptidasas/metabolismo , Diseño de Fármacos , Descubrimiento de Drogas , Modelos Moleculares , Estructura Molecular , Ratas , Relación Estructura-ActividadRESUMEN
From an initial lead 1, a structure-based design approach led to identification of a novel, high-affinity iminohydantoin BACE1 inhibitor that lowers CNS-derived Aß following oral administration to rats. Herein we report SAR development in the S3 and F' subsites of BACE1 for this series, the synthetic approaches employed in this effort, and in vivo data for the optimized compound.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Péptidos beta-Amiloides/antagonistas & inhibidores , Anticonvulsivantes/síntesis química , Ácido Aspártico Endopeptidasas/antagonistas & inhibidores , Inhibidores Enzimáticos/síntesis química , Hidantoínas/síntesis química , Administración Oral , Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/líquido cefalorraquídeo , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Péptidos beta-Amiloides/sangre , Péptidos beta-Amiloides/líquido cefalorraquídeo , Animales , Anticonvulsivantes/farmacología , Ácido Aspártico Endopeptidasas/metabolismo , Sitios de Unión , Simulación por Computador , Cristalografía por Rayos X , Modelos Animales de Enfermedad , Diseño de Fármacos , Inhibidores Enzimáticos/farmacología , Humanos , Hidantoínas/farmacología , Modelos Moleculares , Unión Proteica , Ratas , Ratas Sprague-DawleyRESUMEN
With collaboration between chemistry, X-ray crystallography, and molecular modeling, we designed and synthesized a series of novel piperazine sulfonamide BACE1 inhibitors. Iterative exploration of the non-prime side and S2' sub-pocket of the enzyme culminated in identification of an analog that potently lowers peripheral Abeta(40) in transgenic mice with a single subcutaneous dose.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Ácido Aspártico Endopeptidasas/antagonistas & inhibidores , Piperazinas/química , Inhibidores de Proteasas/síntesis química , Sulfonamidas/química , Enfermedad de Alzheimer/tratamiento farmacológico , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Péptidos beta-Amiloides/antagonistas & inhibidores , Péptidos beta-Amiloides/metabolismo , Animales , Ácido Aspártico Endopeptidasas/metabolismo , Sitios de Unión , Cristalografía por Rayos X , Diseño de Fármacos , Ratones , Ratones Transgénicos , Modelos Moleculares , Fragmentos de Péptidos/antagonistas & inhibidores , Fragmentos de Péptidos/metabolismo , Piperazina , Inhibidores de Proteasas/química , Inhibidores de Proteasas/uso terapéutico , Relación Estructura-Actividad , Sulfonamidas/síntesis química , Sulfonamidas/uso terapéuticoRESUMEN
Herein we describe structure-activity relationship (SAR) and metabolite identification (Met-ID) studies that provided insight into the origin of time-dependent inhibition (TDI) of cytochrome P450 3A4 (CYP3A4) by compound 1. Collectively, these efforts revealed that bioactivation of the fluoropyrimidine moiety of 1 led to reactive metabolite formation via oxidative defluorination and was responsible for the observed TDI. We discovered that substitution at both the 4- and 6-positions of the 5-fluoropyrimidine of 1 was necessary to ameliorate this TDI as exemplified by compound 19.
Asunto(s)
Inhibidores del Citocromo P-450 CYP3A/química , Inhibidores del Citocromo P-450 CYP3A/farmacología , Citocromo P-450 CYP3A/metabolismo , Pirimidinas/química , Pirimidinas/farmacología , Animales , Inhibidores del Citocromo P-450 CYP3A/farmacocinética , Humanos , Cinética , Pirimidinas/farmacocinética , Ratas , Relación Estructura-Actividad , Distribución TisularRESUMEN
Leucine-rich repeat kinase 2 (LRRK2) is a large, multidomain protein which contains a kinase domain and GTPase domain among other regions. Individuals possessing gain of function mutations in the kinase domain such as the most prevalent G2019S mutation have been associated with an increased risk for the development of Parkinson's disease (PD). Given this genetic validation for inhibition of LRRK2 kinase activity as a potential means of affecting disease progression, our team set out to develop LRRK2 inhibitors to test this hypothesis. A high throughput screen of our compound collection afforded a number of promising indazole leads which were truncated in order to identify a minimum pharmacophore. Further optimization of these indazoles led to the development of MLi-2 (1): a potent, highly selective, orally available, brain-penetrant inhibitor of LRRK2.
Asunto(s)
Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Indazoles/química , Indazoles/farmacología , Proteína 2 Quinasa Serina-Treonina Rica en Repeticiones de Leucina/antagonistas & inhibidores , Animales , Encéfalo/metabolismo , Inhibidores Enzimáticos/administración & dosificación , Inhibidores Enzimáticos/farmacocinética , Humanos , Indazoles/administración & dosificación , Indazoles/farmacocinética , Proteína 2 Quinasa Serina-Treonina Rica en Repeticiones de Leucina/metabolismo , Masculino , Simulación del Acoplamiento Molecular , Enfermedad de Parkinson/tratamiento farmacológico , Enfermedad de Parkinson/enzimología , Ratas , Ratas WistarRESUMEN
ß-Amyloid (Aß) peptides are thought to be critically involved in the etiology of Alzheimer's disease (AD). The aspartyl protease ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) is required for the production of Aß, and BACE1 inhibition is thus an attractive target for the treatment of AD. We show that verubecestat (MK-8931) is a potent, selective, structurally unique BACE1 inhibitor that reduced plasma, cerebrospinal fluid (CSF), and brain concentrations of Aß40, Aß42, and sAPPß (a direct product of BACE1 enzymatic activity) after acute and chronic administration to rats and monkeys. Chronic treatment of rats and monkeys with verubecestat achieved exposures >40-fold higher than those being tested in clinical trials in AD patients yet did not elicit many of the adverse effects previously attributed to BACE inhibition, such as reduced nerve myelination, neurodegeneration, altered glucose homeostasis, or hepatotoxicity. Fur hypopigmentation was observed in rabbits and mice but not in monkeys. Single and multiple doses were generally well tolerated and produced reductions in Aß40, Aß42, and sAPPß in the CSF of both healthy human subjects and AD patients. The human data were fit to an amyloid pathway model that provided insight into the Aß pools affected by BACE1 inhibition and guided the choice of doses for subsequent clinical trials.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Péptidos beta-Amiloides/química , Ácido Aspártico Endopeptidasas/antagonistas & inhibidores , Sistema Nervioso Central/metabolismo , Óxidos S-Cíclicos/farmacología , Tiadiazinas/farmacología , Administración Oral , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Animales , Ácido Aspártico Endopeptidasas/metabolismo , Encéfalo/metabolismo , Dominio Catalítico , Cristalografía por Rayos X , Diseño de Fármacos , Femenino , Glucosa/metabolismo , Macaca fascicularis , Espectroscopía de Resonancia Magnética , Ratones , Vaina de Mielina/química , Péptidos/química , Conejos , RatasRESUMEN
The widespread emergence of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically eroded the efficacy of current ß-lactam antibiotics and created an urgent need for new treatment options. We report an S. aureus phenotypic screening strategy involving chemical suppression of the growth inhibitory consequences of depleting late-stage wall teichoic acid biosynthesis. This enabled us to identify early-stage pathway-specific inhibitors of wall teichoic acid biosynthesis predicted to be chemically synergistic with ß-lactams. We demonstrated by genetic and biochemical means that each of the new chemical series discovered, herein named tarocin A and tarocin B, inhibited the first step in wall teichoic acid biosynthesis (TarO). Tarocins do not have intrinsic bioactivity but rather demonstrated potent bactericidal synergy in combination with broad-spectrum ß-lactam antibiotics against diverse clinical isolates of methicillin-resistant staphylococci as well as robust efficacy in a murine infection model of MRSA. Tarocins and other inhibitors of wall teichoic acid biosynthesis may provide a rational strategy to develop Gram-positive bactericidal ß-lactam combination agents active against methicillin-resistant staphylococci.
Asunto(s)
Proteínas Bacterianas/metabolismo , Vías Biosintéticas/efectos de los fármacos , Pared Celular/metabolismo , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Ácidos Teicoicos/biosíntesis , beta-Lactamas/farmacología , Animales , Pared Celular/efectos de los fármacos , Dicloxacilina/farmacología , Dicloxacilina/uso terapéutico , Femenino , Ratones Endogámicos BALB C , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Fenotipo , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Resultado del TratamientoRESUMEN
We describe successful efforts to optimize the in vivo profile and address off-target liabilities of a series of BACE1 inhibitors represented by 6 that embodies the recently validated fused pyrrolidine iminopyrimidinone scaffold. Employing structure-based design, truncation of the cyanophenyl group of 6 that binds in the S3 pocket of BACE1 followed by modification of the thienyl group in S1 was pursued. Optimization of the pyrimidine substituent that binds in the S2'-S2â³ pocket of BACE1 remediated time-dependent CYP3A4 inhibition of earlier analogues in this series and imparted high BACE1 affinity. These efforts resulted in the discovery of difluorophenyl analogue 9 (MBi-4), which robustly lowered CSF and cortex Aß40 in both rats and cynomolgus monkeys following a single oral dose. Compound 9 represents a unique molecular shape among BACE inhibitors reported to potently lower central Aß in nonrodent preclinical species.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Diseño de Fármacos , Compuestos Heterocíclicos/química , Iminas/química , Péptidos beta-Amiloides/líquido cefalorraquídeo , Animales , Corteza Cerebral/metabolismo , Inhibidores Enzimáticos/farmacología , Macaca fascicularis , Estructura Molecular , Ratas , Relación Estructura-ActividadRESUMEN
Verubecestat 3 (MK-8931), a diaryl amide-substituted 3-imino-1,2,4-thiadiazinane 1,1-dioxide derivative, is a high-affinity ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitor currently undergoing Phase 3 clinical evaluation for the treatment of mild to moderate and prodromal Alzheimer's disease. Although not selective over the closely related aspartyl protease BACE2, verubecestat has high selectivity for BACE1 over other key aspartyl proteases, notably cathepsin D, and profoundly lowers CSF and brain Aß levels in rats and nonhuman primates and CSF Aß levels in humans. In this annotation, we describe the discovery of 3, including design, validation, and selected SAR around the novel iminothiadiazinane dioxide core as well as aspects of its preclinical and Phase 1 clinical characterization.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Precursor de Proteína beta-Amiloide/antagonistas & inhibidores , Óxidos S-Cíclicos/farmacología , Descubrimiento de Drogas , Tiadiazinas/farmacología , Enfermedad de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Óxidos S-Cíclicos/síntesis química , Óxidos S-Cíclicos/química , Perros , Relación Dosis-Respuesta a Droga , Humanos , Macaca fascicularis , Modelos Moleculares , Estructura Molecular , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , Tiadiazinas/síntesis química , Tiadiazinas/químicaRESUMEN
Among the three isoenzymes of neuraminidase (Neu) or sialidase, Neu-1 has been suggested to be induced by cell activation and to be involved in IL (interleukin)-4 biosynthesis in murine T-cells. In the present study, we found that antigen-induced airway eosinophilia, a typical response dependent on Th2 (T-helper cell type 2) cytokines, as well as mRNA expression of Th2 cytokines, including IL-4, are suppressed in Neu-1-deficient mice, thereby demonstrating the in vivo role of murine Neu-1 in regulation of Th2 cytokines. To elucidate the roles of various sialidases in human T-cell activation, we investigated their tissue distribution, gene induction and function. Neu-1 is the predominant isoenzyme at the mRNA level in most tissues and cells in both mice and humans, including T-cells. T-cells also have significant levels of Neu-3 mRNAs, albeit much lower than those of Neu-1, whereas the levels of Neu-2 mRNAs are minimal. In human T-cells, both Neu-1 and Neu-3 mRNAs are significantly induced by T-cell-receptor stimulation, as is sialidase activity against 4-methylumbelliferyl- N -acetylneuramic acid (a substrate for both Neu-1 and Neu-3) and the ganglioside G(D1a) [NeuAcalpha2-3Galbeta1-3GalNAcbeta1-4(NeuAcalpha2-3)Galbeta1-4Glcbeta1-cer] (a substrate for Neu-3, but not for Neu-1). The expression of the two sialidase genes may be under differential regulation. Western blot analysis and enzymic comparison with recombinant sialidases have revealed that Neu-3 is induced as a major isoform in activated cells. The induction of Neu-1 and Neu-3 in T-cells is unique. In human monocytes and neutrophils stimulated with various agents, the only observation of sialidase induction has been by IL-1 in neutrophils. Functionally, a major difference has been observed in Jurkat T-cell lines over-expressing Neu-1- and Neu-3. Upon T-cell receptor stimulation, IL-2, interferon-gamma, IL-4 and IL-13 are induced in the Neu-1 line, whereas in the Neu-3 line the same cytokines are induced, with the exception of IL-4. Taken together, these results suggest an important immunoregulatory role for both Neu-1 and Neu-3 in humans.
Asunto(s)
Membrana Celular/enzimología , Lisosomas/enzimología , Neuraminidasa/biosíntesis , Receptores de Antígenos de Linfocitos T/fisiología , Linfocitos T/enzimología , Animales , Antígenos CD28/farmacología , Complejo CD3/farmacología , Linfocitos T CD4-Positivos/enzimología , Línea Celular , Línea Celular Tumoral , Células Cultivadas , Citocinas/antagonistas & inhibidores , Citocinas/biosíntesis , Inducción Enzimática/efectos de los fármacos , Inducción Enzimática/fisiología , Eosinofilia/etiología , Eosinofilia/patología , Regulación Enzimológica de la Expresión Génica/fisiología , Humanos , Insectos/citología , Isoenzimas/biosíntesis , Isoenzimas/fisiología , Células Jurkat/enzimología , Recuento de Leucocitos , Pulmón/efectos de los fármacos , Pulmón/patología , Activación de Linfocitos/fisiología , Ratones , Ratones Endogámicos DBA , Ratones Endogámicos , Neuraminidasa/deficiencia , Neuraminidasa/fisiología , Especificidad de Órganos/fisiología , ARN Mensajero/metabolismo , Receptores de Antígenos de Linfocitos T/metabolismo , Subgrupos de Linfocitos T/enzimología , Linfocitos T/efectos de los fármacos , Linfocitos T/metabolismo , Activación TranscripcionalRESUMEN
Human photoreceptor cGMP-phosphodiesterases (PDE6s) are important reagents in PDE inhibitor discovery. However, recombinant human PDE6s have not been expressed, and isolation of native human PDE6s is highly difficult. In this study, the catalytic subunit(s) of human rod and cone PDE6s (PDE6alphabeta and PDE6alpha', respectively) were co-expressed or expressed separately as catalytically active enzymes. Sildenafil inhibited both the recombinant PDE6s in a dose-dependent manner with Ki values of 94 and 98 nM, respectively. These Ki values were four-fold higher than that (25 nM) of a human native PDE6 preparation. Similarly, 3-isobutyl-1-methylxanthine (IBMX)'s Ki values for the recombinant PDE6s were five- to eight-fold higher than that of the native enzyme. However, E4021 and zaprinast exhibited much (30-80-fold) lower potencies for the recombinant PDE6s than for the native enzyme. Additional PDE5 inhibitors representing other structural classes and possessing different selectivity against native PDE6 also showed different potencies against the recombinant and native PDE6s. In particular, one class of xanthine analogues exhibited significantly (5-15-fold) higher potencies for the recombinant PDE6s than for the native enzyme. Our data demonstrates that the recombinant and native PDE6s exhibit differential sensitivity to inhibitors, and cautions the use of recombinant catalytic subunits of PDE6 in drug discovery or in structural/functional studies.
Asunto(s)
3',5'-GMP Cíclico Fosfodiesterasas/antagonistas & inhibidores , Inhibidores de Fosfodiesterasa/farmacología , Células Fotorreceptoras/metabolismo , Piperazinas/farmacología , Proteínas Recombinantes/antagonistas & inhibidores , 3',5'-GMP Cíclico Fosfodiesterasas/genética , Animales , Células Cultivadas , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 6 , Humanos , Insectos/citología , Hidrolasas Diéster Fosfóricas/genética , Hidrolasas Diéster Fosfóricas/metabolismo , Purinas , Citrato de Sildenafil , Sulfonas , TransfecciónRESUMEN
Inhibition of BACE1 to prevent brain Aß peptide formation is a potential disease-modifying approach to the treatment of Alzheimer's disease. Despite over a decade of drug discovery efforts, the identification of brain-penetrant BACE1 inhibitors that substantially lower CNS Aß levels following systemic administration remains challenging. In this report we describe structure-based optimization of a series of brain-penetrant BACE1 inhibitors derived from an iminopyrimidinone scaffold. Application of structure-based design in tandem with control of physicochemical properties culminated in the discovery of compound 16, which potently reduced cortex and CSF Aß40 levels when administered orally to rats.
RESUMEN
On the basis of our observation that the biaryl substituent of iminopyrimidinone 7 must be in a pseudoaxial conformation to occupy the contiguous S1-S3 subsites of BACE1, we have designed a novel fused bicyclic iminopyrimidinone scaffold intended to favor this bioactive conformation. Strategic incorporation of a nitrogen atom in the new constrained ring allowed us to develop SAR around the S2' binding pocket and ultimately resulted in analogues with low nanomolar potency for BACE1. In particular, optimization of the prime side substituent led to major improvements in potency by displacement of two conserved water molecules from a region near S2'. Further optimization of the pharmacokinetic properties of this fused pyrrolidine series, in conjunction with facile access to a rat pharmacodynamic model, led to identification of compound 43, which is an orally active, brain penetrant inhibitor that reduces Aß(40) in the plasma, CSF, and cortex of rats in a dose-dependent manner.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/antagonistas & inhibidores , Ácido Aspártico Endopeptidasas/antagonistas & inhibidores , Compuestos Bicíclicos Heterocíclicos con Puentes/síntesis química , Nitrilos/síntesis química , Pirimidinas/síntesis química , Pirimidinonas/síntesis química , Tiofenos/síntesis química , Administración Oral , Secretasas de la Proteína Precursora del Amiloide/química , Péptidos beta-Amiloides/metabolismo , Animales , Ácido Aspártico Endopeptidasas/química , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacocinética , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Corteza Cerebral/metabolismo , Cristalografía por Rayos X , Células HEK293 , Humanos , Macaca fascicularis , Modelos Moleculares , Conformación Molecular , Nitrilos/farmacocinética , Nitrilos/farmacología , Fragmentos de Péptidos/metabolismo , Permeabilidad , Pirimidinas/farmacocinética , Pirimidinas/farmacología , Pirimidinonas/farmacocinética , Pirimidinonas/farmacología , Teoría Cuántica , Ratas , Estereoisomerismo , Relación Estructura-Actividad , Termodinámica , Tiofenos/farmacocinética , Tiofenos/farmacologíaRESUMEN
A number of novel amidine containing heterocycles were designed to reproduce the unique interaction pattern, revealed by X-ray crystallography, between the BACE-1 catalytic diad and a weak NMR screening hit (3), with special attention paid to maintaining the appropriate basicity and limiting the number of H-bonding donors of these scaffolds. The iminohydantoin cores (10 and 23) were examined first and found to interact with the catalytic diad in one of two binding modes (A and B), each with the iminohydantoin core flipped 180 degrees in relation to the other. The amidine structural motif within each core forms a bidentate interaction with a different aspartic acid of the catalytic diad. Both modes reproduced a highly conserved interaction pattern between the inhibitors and the catalytic aspartates, as revealed by 3. Potent iminohydantoin BACE-1 inhibitors have been obtained, validating the molecular design as aspartyl protease catalytic site inhibitors. Brain penetrant small molecule BACE inhibitors with high ligand efficiencies have been discovered, enabling multiple strategies for further development of these inhibitors into highly potent, selective and in vivo efficacious BACE inhibitors.