RESUMO
Conventional antibody-drug conjugates (ADCs) are heterogeneous mixtures of chemically distinct molecules that vary in both drugs/antibody (DAR) and conjugation sites. Suboptimal properties of heterogeneous ADCs have led to new site-specific conjugation methods for improving ADC homogeneity. Most site-specific methods require extensive antibody engineering to identify optimal conjugation sites and introduce unique functional groups for conjugation with appropriately modified linkers. Alternative nonrecombinant methods have emerged in which bifunctional linkers are utilized to cross-link antibody interchain cysteines and afford ADCs containing four drugs/antibody. Although these methods have been shown to improve ADC homogeneity and stability in vitro, their effect on the pharmacological properties of ADCs in vivo is unknown. In order to determine the relative impact of interchain cysteine cross-linking on the therapeutic window and other properties of ADCs in vivo, we synthesized a derivative of the known ADC payload, MC-MMAF, that contains a bifunctional dibromomaleimide (DBM) linker instead of a conventional maleimide (MC) linker. The DBM-MMAF derivative was conjugated to trastuzumab and a novel anti-CD98 antibody to afford ADCs containing predominantly four drugs/antibody. The pharmacological properties of the resulting cross-linked ADCs were compared with analogous heterogeneous ADCs derived from conventional linkers. The results demonstrate that DBM linkers can be applied directly to native antibodies, without antibody engineering, to yield highly homogeneous ADCs via cysteine cross-linking. The resulting ADCs demonstrate improved pharmacokinetics, superior efficacy, and reduced toxicity in vivo compared to analogous conventional heterogeneous ADCs.
Assuntos
Anticorpos Monoclonais/farmacologia , Antineoplásicos/farmacologia , Cisteína/química , Imunoconjugados/farmacologia , Neoplasias Pulmonares/tratamento farmacológico , Trastuzumab/farmacologia , Animais , Anticorpos Monoclonais/química , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Western Blotting , Proliferação de Células/efeitos dos fármacos , Reagentes de Ligações Cruzadas , Feminino , Citometria de Fluxo , Imunofluorescência , Proteína-1 Reguladora de Fusão/imunologia , Humanos , Imunoconjugados/química , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Masculino , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Ratos , Ratos Sprague-Dawley , Receptor ErbB-2/antagonistas & inibidores , Trastuzumab/química , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Alzheimer's disease (AD) is a devastating neurodegenerative disease affecting millions of people. ß-Secretase-1 (BACE-1), an enzyme involved in the processing of the amyloid precursor protein (APP) to form Aß, is a well validated target for AD. Herein, the authors characterize 10 randomly selected hydroxyethylamine (HEA) BACE-1 inhibitors in terms of their association and dissociation rate constants and thermodynamics of binding using surface plasmon resonance (SPR). Rate constants of association (ka) measured at 25 °C ranged from a low of 2.42×10(4) M(-1) s(-1) to the highest value of 8.3×10(5) M(-1) s(-1). Rate constants of dissociation (kd) ranged from 1.09×10(-4) s(-1) (corresponding to a residence time of close to three hours), to the fastest of 0.028 s(-1). Three compounds were selected for further thermodynamic analysis where it was shown that equilibrium binding was enthalpy driven while unfavorable entropy of binding was observed. Structural analysis revealed that upon ligand binding, the BACE-1flap folds down over the bound ligand causing an induced fit. The maximal difference between alpha carbon positions in the open and closed conformations of the flap was over 5 Å. Thus the negative entropy of binding determined using SPR analysis was consistent with an induced fit observed by structural analysis.
Assuntos
Doença de Alzheimer/enzimologia , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Etanolaminas , Inibidores de Proteases/farmacologia , Secretases da Proteína Precursora do Amiloide/química , Ácido Aspártico Endopeptidases/química , Ácido Aspártico Proteases/antagonistas & inibidores , Ácido Aspártico Proteases/química , Enzimas Imobilizadas/antagonistas & inibidores , Enzimas Imobilizadas/química , Humanos , Cinética , Inibidores de Proteases/química , Conformação Proteica , TermodinâmicaRESUMO
Leucine-rich repeat kinase 2 (LRRK2) has been implicated in the pathogenesis of Parkinson's disease (PD). Inhibition of LRRK2 kinase activity is a therapeutic approach that may lead to new treatments for PD. Herein we report the discovery of a series of [1,2,4]triazolo[4,3-b]pyridazines that are potent against both wild-type and mutant LRRK2 kinase activity in biochemical assays and show an unprecedented selectivity towards the G2019S mutant. A structural rational for the observed selectivity is proposed.
Assuntos
Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Piridazinas/farmacologia , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Modelos Moleculares , Estrutura Molecular , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/química , Proteínas Serina-Treonina Quinases/metabolismo , Piridazinas/síntese química , Piridazinas/química , Relação Estrutura-AtividadeRESUMO
Leucine rich repeat kinase 2 (LRRK2) has been implicated in the pathogenesis of Parkinson's disease (PD). Inhibition of LRRK2 kinase activity is a therapeutic approach that may lead to new treatments for PD. Herein we report the discovery of a series of cinnoline-3-carboxamides that are potent against both wild-type and mutant LRRK2 kinase activity in biochemical assays. These compounds are also shown to be potent inhibitors in a cellular assay and to have good to excellent CNS penetration.
Assuntos
Compostos Heterocíclicos com 2 Anéis/química , Inibidores de Proteínas Quinases/química , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Amidas/síntese química , Amidas/química , Amidas/metabolismo , Animais , Sítios de Ligação , Células HEK293 , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Camundongos , Simulação de Acoplamento Molecular , Mutação , Ligação Proteica , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Estrutura Terciária de Proteína , TransfecçãoRESUMO
Mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with familial Parkinson's disease (PD). The kinase activity of this complex protein is increased by pathogenic mutations. Inhibition of LRRK2 kinase activity has therefore emerged as a promising approach for the treatment of PD. Herein we report our findings on a series of 4-alkylamino-7-aryl-3-cyanoquinolines that exhibit kinase inhibitory activity against both wild type and G2019S mutant LRRK2. Activity was determined in both biochemical and cellular assays. Compound 14 was further evaluated in an in vivo pharmacodynamic study and found to significantly inhibit Ser935 phosphorylation after oral dosing.
Assuntos
Descoberta de Drogas , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Quinolinas/farmacologia , Animais , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Modelos Moleculares , Estrutura Molecular , Mutação , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/química , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Quinolinas/síntese química , Quinolinas/química , Relação Estrutura-AtividadeRESUMO
The structure-activity relationship of a series of dihydroisoquinoline BACE-1 inhibitors is described. Application of structure-based design to screening hit 1 yielded sub-micromolar inhibitors. Replacement of the carboxylic acid of 1 was guided by X-ray crystallography, which allowed the replacement of a key water-mediated hydrogen bond. This work culminated in compounds such as 31, which possess good BACE-1 potency, excellent permeability and a low P-gp efflux ratio.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Ácido Aspártico/química , Desenho de Fármacos , Isoquinolinas/farmacologia , Inibidores de Proteases/farmacologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Ácido Aspártico Endopeptidases/metabolismo , Catálise , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Humanos , Isoquinolinas/síntese química , Isoquinolinas/química , Modelos Moleculares , Estrutura Molecular , Inibidores de Proteases/síntese química , Inibidores de Proteases/química , Relação Estrutura-AtividadeRESUMO
The structure activity relationship of the prime region of conformationally restricted hydroxyethylamine (HEA) BACE inhibitors is described. Variation of the P1' region provided selectivity over Cat-D with a series of 2,2-dioxo-isothiochromanes and optimization of the P2' substituent of chromane-HEA(s) with polar substituents provided improvements in the compound's in vitro permeability. Significant potency gains were observed with small aliphatic substituents such as methyl, n-propyl, and cyclopropyl when placed at the C-2 position of the chromane.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Cromanos/química , Desenho de Fármacos , Inibidores Enzimáticos/síntese química , Sítios de Ligação , Células Cultivadas , Etilaminas/síntese química , Etilaminas/química , Etilaminas/farmacologia , Concentração Inibidora 50 , Modelos Moleculares , Relação Estrutura-AtividadeRESUMO
Structure-activity relationship (SAR) of a novel, potent and metabolically stable series of benzo [3.2.1] bicyclic sulfonamide-pyrazoles as γ-secretase inhibitors are described. Compounds that are efficacious in reducing the cortical Aßx-40 levels in FVB mice via oral dose, as well as those with high selectivity over Notch, are highlighted.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Pirazóis/farmacologia , Sulfonamidas/farmacologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/química , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Camundongos , Pirazóis/química , Relação Estrutura-Atividade , Sulfonamidas/químicaRESUMO
Extensive knowledge has been gained on the transcription network controlled by ERα, however, the mechanism underlying ESR1 (encoding ERα) expression is less understood. We recently discovered that the Hippo pathway is required for the proper expression of ESR1. YAP/TAZ are transcription coactivators that are phosphorylated and inhibited by the Hippo pathway kinase LATS. Here we delineated the molecular mechanisms underlying ESR1 transcription repression by the Hippo pathway. Mechanistically, YAP binds to TEAD to increase local chromatin accessibility to stimulate transcription of nearby genes. Among the YAP target genes, Vestigial-Like Protein 3 (VGLL3) competes with YAP/TAZ for binding to TEAD transcription factor and recruits the NCOR2/SMRT repressor to the super-enhancer of ESR1 gene, leading to epigenetic alteration and transcriptional silencing. We developed a potent LATS inhibitor VT02956. Targeting the Hippo pathway by VT02956 represses ESR1 expression and inhibits the growth of ER+ breast cancer cells as well as patient-derived tumour organoids. Moreover, histone deacetylase inhibitors, such as Entinostat, induce VGLL3 expression to inhibit ER+ breast cancer cells. Our study suggests LATS as unexpected cancer therapeutic targets, especially for endocrine-resistant breast cancers.
Assuntos
Neoplasias da Mama , Receptor alfa de Estrogênio , Via de Sinalização Hippo , Feminino , Humanos , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas de Sinalização YAP/metabolismoRESUMO
The SAR of a series of tri-substituted thiophene JNK3 inhibitors is described. By optimizing both the N-aryl acetamide region of the inhibitor and the 4-position of the thiophene we obtained single digit nanomolar compounds, such as 47, which demonstrated an in vivo effect on JNK activity when dosed orally in our kainic acid mouse model as measured by phospho-c-jun reduction.
Assuntos
Encéfalo/metabolismo , MAP Quinase Quinase 4/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacocinética , Administração Oral , Desenho de Fármacos , Ligação de Hidrogênio , Modelos Moleculares , Inibidores de Proteínas Quinases/síntese química , Relação Estrutura-AtividadeRESUMO
The structure-activity relationship (SAR) of a novel, potent and metabolically stable series of sulfonamide-pyrazoles that attenuate ß-amyloid peptide synthesis via γ-secretase inhibition is detailed herein. Sulfonamide-pyrazoles that are efficacious in reducing the cortical Aßx-40 levels in FVB mice via a single PO dose, as well as sulfonamide-pyrazoles that exhibit selectivity for inhibition of APP versus Notch processing by γ-secretase, are highlighted.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Precursor de Proteína beta-Amiloide/antagonistas & inibidores , Desenho de Fármacos , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacologia , Compostos Heterocíclicos com 3 Anéis/síntese química , Compostos Heterocíclicos com 3 Anéis/farmacologia , Sulfonamidas/síntese química , Sulfonamidas/farmacologia , Peptídeos beta-Amiloides/metabolismo , Animais , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/química , Compostos Heterocíclicos com 3 Anéis/química , Concentração Inibidora 50 , Camundongos , Camundongos Endogâmicos , Relação Estrutura-Atividade , Sulfonamidas/químicaRESUMO
In this Letter, we describe the discovery of selective JNK2 and JNK3 inhibitors, such as 10, that routinely exhibit >10-fold selectivity over JNK1 and >1000-fold selectivity over related MAPKs, p38α and ERK2. Substitution of the naphthalene ring affords an isoform selective JNK3 inhibitor, 30, with approximately 10-fold selectivity over both JNK1 and JNK2. A naphthalene ring penetrates deep into the selectivity pocket accounting for the differentiation amongst the kinases. Interestingly, the gatekeeper Met146 sulfide interacts with the naphthalene ring in a sulfur-π stacking interaction. Compound 38 ameliorates neurotoxicity induced by amyloid-ß in human cortical neurons. Lastly, we demonstrate how to install propitious in vitro CNS-like properties into these selective inhibitors.
Assuntos
Aminopiridinas/química , Proteína Quinase 10 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 9 Ativada por Mitógeno/antagonistas & inibidores , Doenças Neurodegenerativas/tratamento farmacológico , Fármacos Neuroprotetores/química , Inibidores de Proteínas Quinases/química , Triazinas/química , Aminopiridinas/farmacocinética , Aminopiridinas/uso terapêutico , Animais , Sítios de Ligação , Sistema Nervoso Central/metabolismo , Simulação por Computador , Humanos , Camundongos , Microssomos Hepáticos/metabolismo , Proteína Quinase 10 Ativada por Mitógeno/metabolismo , Proteína Quinase 9 Ativada por Mitógeno/metabolismo , Fármacos Neuroprotetores/farmacocinética , Fármacos Neuroprotetores/uso terapêutico , Inibidores de Proteínas Quinases/farmacocinética , Inibidores de Proteínas Quinases/uso terapêutico , Relação Estrutura-Atividade , Triazinas/farmacocinética , Triazinas/uso terapêuticoRESUMO
The SAR of a series of brain penetrant, trisubstituted thiophene based JNK inhibitors with improved pharmacokinetic properties is described. These compounds were designed based on information derived from metabolite identification studies which led to compounds such as 42 with lower clearance, greater brain exposure and longer half life compared to earlier analogs.
Assuntos
Encéfalo/metabolismo , Desenho de Fármacos , Degeneração Neural/prevenção & controle , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacologia , Tiofenos/farmacologia , Tiofenos/farmacocinética , Animais , Técnicas de Química Sintética , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Meia-Vida , Proteínas Quinases JNK Ativadas por Mitógeno/antagonistas & inibidores , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Camundongos , Modelos Moleculares , Estrutura Molecular , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacocinética , Estereoisomerismo , Relação Estrutura-Atividade , Tiofenos/síntese química , Tiofenos/químicaRESUMO
From high throughput screening, we discovered compound 1, the prototype for a series of disubstituted thiophene inhibitors of JNK which is selective towards closely related MAP kinases p38 and Erk2. Herein we describe the evolution of these compounds to a novel class of thiophene and thiazole JNK inhibitors that retain favorable solubility, permeability, and P-gp properties for development as CNS agents for treatment of neurodegeneration. Compound 61 demonstrated JNK3 IC(50)=77 nM and retained the excellent broad kinase selectivity observed for the series.
Assuntos
Proteínas Quinases JNK Ativadas por Mitógeno/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Quinolinas/síntese química , Tiazóis/química , Tiofenos/química , Animais , Desenho de Fármacos , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Camundongos , Microssomos Hepáticos/metabolismo , Proteína Quinase 10 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 10 Ativada por Mitógeno/metabolismo , Proteína Quinase 8 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 8 Ativada por Mitógeno/metabolismo , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/química , Quinolinas/farmacologia , Relação Estrutura-Atividade , Tiazóis/síntese química , Tiazóis/farmacologia , Tiofenos/síntese química , Tiofenos/farmacologiaRESUMO
In this Letter, we describe our efforts to design HEA BACE-1 inhibitors that are highly permeable coupled with negligible levels of permeability-glycoprotein activity. These efforts culminate in producing 16 which lowers Αß by 28% and 32% in the cortex and CSF, respectively, in the preclinical wild type Hartley guinea pig animal model when dosed orally at 30mpk BID for 2.5days.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Etilaminas/síntese química , Etilaminas/farmacologia , Inibidores de Proteases/síntese química , Inibidores de Proteases/farmacologia , Alquilação , Doença de Alzheimer , Animais , Encéfalo/metabolismo , Linhagem Celular , Cães , Desenho de Fármacos , Cobaias , Humanos , Indicadores e Reagentes , Inibidores de Proteases/farmacocinética , Ligação Proteica , Relação Estrutura-AtividadeRESUMO
The structure-activity relationship of the prime region of hydroxyethylamine BACE inhibitors is described. Variation in the aryl linker region with 5- and 6-membered heterocycles provided compounds such as 33 with improved permeability and reduced P-gp liability compared to benzyl amine analog 1.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Secretases da Proteína Precursora do Amiloide/metabolismo , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Ácido Aspártico Endopeptidases/metabolismo , Etilaminas/química , Etilaminas/farmacologia , Inibidores de Proteases/química , Inibidores de Proteases/farmacologia , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Doença de Alzheimer/tratamento farmacológico , Secretases da Proteína Precursora do Amiloide/química , Ácido Aspártico Endopeptidases/química , Cristalografia por Raios X , Etilaminas/síntese química , Humanos , Modelos Moleculares , Inibidores de Proteases/síntese química , Ligação Proteica , Relação Estrutura-AtividadeRESUMO
Herein we describe further evolution of hydroxyethylamine inhibitors of BACE-1 with enhanced permeability characteristics necessary for CNS penetration. Variation at the P2' position of the inhibitor with more polar substituents led to compounds 19 and 32, which retained the potency of more lipophilic analog 1 but with much higher observed passive permeability in MDCK cellular assay.
Assuntos
Acetamidas/química , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Ácido Aspártico Endopeptidases/antagonistas & inibidores , Butanóis/química , Cicloexilaminas/química , Inibidores de Proteases/química , Acetamidas/síntese química , Acetamidas/farmacocinética , Secretases da Proteína Precursora do Amiloide/metabolismo , Ácido Aspártico Endopeptidases/metabolismo , Sítios de Ligação , Butanóis/síntese química , Butanóis/farmacocinética , Permeabilidade da Membrana Celular/efeitos dos fármacos , Cristalografia por Raios X , Cicloexilaminas/síntese química , Cicloexilaminas/farmacocinética , Humanos , Inibidores de Proteases/síntese química , Inibidores de Proteases/farmacocinética , Relação Estrutura-AtividadeRESUMO
The structural modification of a series of [3.3.1] bicyclic sulfonamide based gamma-secretase inhibitors is described. Appropriate substitution on the bicyclic scaffold provides a significant increase in the metabolic stability of the compounds resulting in an improved in vivo metabolic profile.
Assuntos
Doença de Alzheimer/enzimologia , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Compostos Bicíclicos com Pontes/química , Inibidores de Proteases/química , Sulfonamidas/química , Doença de Alzheimer/tratamento farmacológico , Compostos Bicíclicos com Pontes/farmacologia , Compostos Bicíclicos com Pontes/uso terapêutico , Humanos , Inibidores de Proteases/farmacologia , Inibidores de Proteases/uso terapêutico , Relação Estrutura-Atividade , Sulfonamidas/farmacologia , Sulfonamidas/uso terapêuticoRESUMO
Systematic SAR studies of in vitro factor Xa inhibitory activity around compound 1 were performed by modifying each of the three phenyl rings. A class of highly potent, selective, efficacious and orally bioavailable direct factor Xa inhibitors was discovered. These compounds were screened in hERG binding assays to examine the effects of substitution groups on the hERG channel affinity. From the leading compounds, betrixaban (compound 11, PRT054021) has been selected as the clinical candidate for development.
Assuntos
Anticoagulantes/síntese química , Anticoagulantes/farmacologia , Benzamidas/síntese química , Benzamidas/farmacologia , Descoberta de Drogas/métodos , Inibidores do Fator Xa , Piridinas/síntese química , Piridinas/farmacologia , Administração Oral , Animais , Anticoagulantes/administração & dosagem , Benzamidas/administração & dosagem , Domínio Catalítico/efeitos dos fármacos , Linhagem Celular , Cães , Relação Dose-Resposta a Droga , Canal de Potássio ERG1 , Canais de Potássio Éter-A-Go-Go/genética , Fator Xa/metabolismo , Humanos , Macaca fascicularis , Piridinas/administração & dosagem , Coelhos , RatosRESUMO
Using structure-guided design, hydroxyethylamine BACE-1 inhibitors were optimized to nanomolar Abeta cellular inhibition with selectivity against cathepsin-D. X-ray crystallography illuminated the S1' residues critical to this effort, which culminated in compounds 56 and 57 that exhibited potency and selectivity but poor permeability and high P-gp efflux.