According to the amyloid cascade hypothesis, cerebral deposition of amyloid-β peptide (Aβ) is critical for Alzheimer's disease (AD) pathogenesis. Aβ generation is initiated when β-secretase (BACE1) ...cleaves the amyloid precursor protein. For more than a decade, BACE1 has been a prime target for designing drugs to prevent or treat AD. However, development of such agents has turned out to be extremely challenging, with major hurdles in cell penetration, oral bioavailability/metabolic clearance, and brain access. Using a fragment-based chemistry strategy, we have generated LY2811376 (S)-4-(2,4-difluoro-5-pyrimidin-5-yl-phenyl)-4-methyl-5,6-dihydro-4H-1,3thiazin-2-ylamine, the first orally available non-peptidic BACE1 inhibitor that produces profound Aβ-lowering effects in animals. The biomarker changes obtained in preclinical animal models translate into man at doses of LY2811376 that were safe and well tolerated in healthy volunteers. Prominent and long-lasting Aβ reductions in lumbar CSF were measured after oral dosing of 30 or 90 mg of LY2811376. This represents the first translation of BACE1-driven biomarker changes in CNS from preclinical animal models to man. Because of toxicology findings identified in longer-term preclinical studies, this compound is no longer progressing in clinical development. However, BACE1 remains a viable target because the adverse effects reported here were recapitulated in LY2811376-treated BACE1 KO mice and thus are unrelated to BACE1 inhibition. The magnitude and duration of central Aβ reduction obtainable with BACE1 inhibition positions this protease as a tractable small-molecule target through which to test the amyloid hypothesis in man.
BACE1 is a key protease controlling the formation of amyloid β, a peptide hypothesized to play a significant role in the pathogenesis of Alzheimer's disease (AD). Therefore, the development of potent ...and selective inhibitors of BACE1 has been a focus of many drug discovery efforts in academia and industry. Herein, we report the nonclinical and early clinical development of LY2886721, a BACE1 active site inhibitor that reached phase 2 clinical trials in AD. LY2886721 has high selectivity against key off-target proteases, which efficiently translates in vitro activity into robust in vivo amyloid β lowering in nonclinical animal models. Similar potent and persistent amyloid β lowering was observed in plasma and lumbar CSF when single and multiple doses of LY2886721 were administered to healthy human subjects. Collectively, these data add support for BACE1 inhibition as an effective means of amyloid lowering and as an attractive target for potential disease modification therapy in AD.
Glycogen synthase kinase-3 (GSK3) is involved in signaling from the insulin receptor. Inhibitors of GSK3 are expected to effect lowering of plasma glucose similar to insulin, making GSK3 an ...attractive target for the treatment of type 2 diabetes. Herein we report the discovery of a series of potent and selective GSK3 inhibitors. Compounds 7 − 12 show oral activity in an in vivo model of type II diabetes, and 9 and 12 have desirable PK properties.
The melanocortin receptors have been implicated as potential targets for a number of important therapeutic indications, including inflammation, sexual dysfunction, and obesity. We identified compound ...1, an arylpiperazine attached to the dipeptide H-d-Tic-d-p-Cl-Phe-OH, as a novel melanocortin subtype-4 receptor (MC4R) agonist through iterative directed screening of nonpeptidyl G-protein-coupled receptor biased libraries. Structure−activity relationship (SAR) studies demonstrated that substitutions at the ortho position of the aryl ring improved binding and functional potency. For example, the o-isopropyl-substituted compound 29 (K i = 720 nM) possessed 9-fold better binding affinity compared to the unsubstituted aryl ring (K i = 6600 nM). Sulfonamide 39 (K i = 220 nM) fills this space with a polar substituent, resulting in a further 2-fold improvement in binding affinity. The most potent compounds such as the diethylamine 44 (K i = 60 nM) contain a basic group at this position. Basic heterocycles such as the imidazole 50 (K i = 110 nM) were similarly effective. We also demonstrated good oral bioavailability for sulfonamide 39.
LY444711 is an orally active ghrelin agonist that binds with good affinity and is a potent activator of the growth hormone secretagogue receptor 1a (GHS-R1a) receptor. In rat models of feeding ...behavior and pharmacology, LY444711 creates a positive energy balance and induces adiposity by stimulating food consumption and sparing fat utilization.
2-(2-Amino-2-methyl-propionylamino)-5-phenyl-pentanoic acid {1-1-(4-methoxy-phenyl)-1-methyl-2-oxo-2-pyrrolidin-1-yl-ethyl-1
H-imidazol-4-yl}-amide (LY444711,
6) is an orally active ghrelin agonist that binds with high affinity to and is a potent activator of the growth hormone secretagogue receptor 1a (GHS-R1a) receptor. In rat models of feeding behavior and pharmacology,
6 creates a positive energy balance and induces adiposity by stimulating food consumption and sparing fat utilization. As an orally active ghrelin agonist,
6 represents a new pharmacological tool to investigate the orexigenic role of ghrelin in regulating energy homeostasis.
Tazofelone is a new inflammatory bowel disease agent. The biotransformation of tazofelone in human livers and the cytochrome P450 responsible for the biotransformation has been studied. Two ...metabolites of tazofelone were formed in vitro. A sulfoxide metabolite was identified by cochromatography with authentic standards, and a quinol metabolite of tazofelone was identified by mass spectrometry and proton NMR. Sulfoxidation was catalyzed by a single enzyme system while formation of the quinol metabolite was catalyzed by a two enzyme system. The Km and Vmax values for sulfoxidation were 12.4 microM and 0.27 nmol/min/mg protein, respectively. The high affinity Km and Vmax values for the formation of the quinol metabolite were 7.5 microM and 0.17 nmol/min/mg protein, respectively. Tazofelone was incubated at 20 microM concentration with human microsomes to determine which of the cytochrome P450 isozyme(s) is involved in the oxidation of tazofelone. A strong correlation was found between the immunoquantified concentrations of CYP3A and the rates of formation of the sulfoxide and quinol metabolites of tazofelone. Similarly, significant correlations were observed between the formation of midazolam 1'-hydroxylation and the rates of formation of both metabolites of tazofelone. Inhibition studies have indicated that triacetyloleandomycin, a CYP3A specific inhibitor, almost completely inhibited the formation of both of these tazofelone metabolites. Incubations with specific cDNA expressed microsomes indicated that the formation of both the sulfoxide and quinol metabolites was highest with CYP3A4 containing microsomes. The correlation data was confirmed by inhibition studies and cDNA expressed cytochrome P450 systems demonstrating that the biotransformation of tazofelone to its metabolites is primarily mediated by CYP3A.
Disubstituted isoquinolones 2 and 3 have affinity for GPIIb-IIIa and represent leads for further structural evaluation. Structure−activity studies centered on the bicyclic β-turn mimic contained in ...these molecules indicated that this moiety could accommodate a variety of modifications. Specifically, monocyclic, 6,5-bicyclic, and 6,7-bicyclic structures provide compounds with affinity for GPIIb-IIIa. Within the 6,6-series, isoquinoline, tetralin, tetralone, and benzopyran nuclei yield potent antagonists that are specific for GPIIb-IIIa. Attachment of the arginine isostere (benzamidine) to the supporting nucleus can be accomplished with an ether or amide linkage, although the latter enhances activity. Several compounds in this series provided measurable blood levels after oral dosing. Conversion of the acid moiety in these molecules to an ester generally provided compounds which gave greater systemic exposure after oral administration. Absolute bioavailabilities in the rat for the ethyl ester prodrug derivatives of the tetralin, tetralone, and benzopyran analogues of 3 were 28%, 23%, and 24%, respectively.
6-4-Amidinobenzoylamino-tetralone-2-acetic acid is a potent antagonist of GPIIb-IIIa. Substitution in the meta position of the benzamidine, or replacement with a heteroaryl amidine was tolerated in ...this series. Use of an acyl-linked 4-alkyl piperidine as an arginine isostere also provided active compounds. Compounds from this series provided substantial systemic exposure in the rat following oral administration.
Previous studies in rats and humans demonstrated poor oral bioavailability of potent in vitro 2‐aminobenzimidazole inhibitors of rhinovirus replication due to significant first‐pass elimination and ...possibly also to poor aqueous solubility. Estimations of aqueous solubility, as well as measurements of caco‐2 permeability and NADPH dependent compound loss in rat liver microsomal incubations were employed alongside traditional in vivo experiments in rats to guide subsequent chemistry efforts. Retention of activity upon replacement of the metabolically labile vinyl oxime in the lead molecule with a vinyl carboxamide was a major breakthrough; however, oral bioavail‐ability among the latter compounds was variable. Based on the ability to independently measure solubility, permeability, and metabolic stability of new compounds, variable solubility across the series (ranging from approximately 1 to 10 µg/mL) was identified as the cause of the inconsistent performance. Subsequent efforts to improve solubility led to the discovery of highly soluble (>10 mg/mL) and potent dessulfonyl vinyl carboxamide benzimidazoles. Determination of the metabolic stability of these compounds as a surrogate of the extent of their first‐pass elimination supported a prediction of excellent oral bioavail‐ability. In comparison to the sulfonyl‐containing vinyl carboxamides, caco‐2 permeabilities were reduced 5 to 10‐fold; however, these were considered to be in the range of well‐absorbed compounds based on comparison to a series of reference compounds of known percentage absorption in humans. Subsequent experiments in the rat verified the oral bioavailability of these N‐alkyl compounds, with one compound (368177) having an absolute oral bioavailability of 89.4%. The application of solubility and caco‐2 permeability as surrogates for oral absorption potential, in conjunction with the use of microsomal incubations as a surrogate for first‐pass metabolism, was shown to augment a rational chemistry approach to discover orally bioavailable inhibitors of rhinovirus replication. Future expanded use of these surrogates is planned.
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