Preclinical Characterization of (R)-3-((3S,4S)-3-fluoro-4-(4-hydroxyphenyl)piperidin-1-yl)-1-(4-methylbenzyl)pyrrolidin-2-one (BMS-986169), a Novel, Intravenous, Glutamate N-Methyl-d-Aspartate 2B Receptor Negative Allosteric Modulator with Potential in Major Depressive Disorder.

(R)-3-((3S,4S)-3-fluoro-4-(4-hydroxyphenyl)piperidin-1-yl)-1-(4-methylbenzyl)pyrrolidin-2-one (BMS-986169) and the phosphate prodrug 4-((3S,4S)-3-fluoro-1-((R)-1-(4-methylbenzyl)-2-oxopyrrolidin-3-yl)piperidin-4-yl)phenyl dihydrogen phosphate (BMS-986163) were identified from a drug discovery effort focused on the development of novel, intravenous glutamate N-methyl-d-aspartate 2B receptor (GluN2B) negative allosteric modulators (NAMs) for treatment-resistant depression (TRD). BMS-986169 showed high binding affinity for the GluN2B subunit allosteric modulatory site (Ki = 4.03-6.3 nM) and selectively inhibited GluN2B receptor function in Xenopus oocytes expressing human N-methyl-d-aspartate receptor subtypes (IC50 = 24.1 nM). BMS-986169 weakly inhibited human ether-a-go-go-related gene channel activity (IC50 = 28.4 µM) and had negligible activity in an assay panel containing 40 additional pharmacological targets. Intravenous administration of BMS-986169 or BMS-986163 dose-dependently increased GluN2B receptor occupancy and inhibited in vivo [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine ([3H]MK-801) binding, confirming target engagement and effective cleavage of the prodrug. BMS-986169 reduced immobility in the mouse forced swim test, an effect similar to intravenous ketamine treatment. Decreased novelty suppressed feeding latency, and increased ex vivo hippocampal long-term potentiation was also seen 24 hours after acute BMS-986163 or BMS-986169 administration. BMS-986169 did not produce ketamine-like hyperlocomotion or abnormal behaviors in mice or cynomolgus monkeys but did produce a transient working memory impairment in monkeys that was closely related to plasma exposure. Finally, BMS-986163 produced robust changes in the quantitative electroencephalogram power band distribution, a translational measure that can be used to assess pharmacodynamic activity in healthy humans. Due to the poor aqueous solubility of BMS-986169, BMS-986163 was selected as the lead GluN2B NAM candidate for further evaluation as a novel intravenous agent for TRD.

The γ-Secretase Modulator, BMS-932481, Modulates Aß Peptides in the Plasma and Cerebrospinal Fluid of Healthy Volunteers.

The pharmacokinetics, pharmacodynamics, safety, and tolerability of BMS-932481, a γ-secretase modulator (GSM), were tested in healthy young and elderly volunteers after single and multiple doses. BMS-932481 was orally absorbed, showed dose proportionality after a single dose administration, and had approximately 3-fold accumulation after multiple dosing. High-fat/caloric meals doubled the Cmax and area under the curve and prolonged Tmax by 1.5 hours. Consistent with the preclinical pharmacology of GSMs, BMS-932481 decreased cerebrospinal fluid (CSF) Aß39, Aß40, and Aß42 while increasing Aß37 and Aß38, thereby providing evidence of γ-secretase enzyme modulation rather than inhibition. In plasma, reductions in Aß40 and Aß42 were observed with no change in total Aß; in CSF, modest decreases in total Aß were observed at higher dose levels. Increases in liver enzymes were observed at exposures associated with greater than 70% CSF Aß42 lowering after multiple dosing. Although further development was halted due to an insufficient safety margin to test the hypothesis for efficacy of Aß lowering in Alzheimer's disease, this study demonstrates that γ-secretase modulation is achievable in healthy human volunteers and supports further efforts to discover well tolerated GSMs for testing in Alzheimer's disease and other indications.

Robust Translation of γ-Secretase Modulator Pharmacology across Preclinical Species and Human Subjects.

The amyloid-ß peptide (Aß)-in particular, the 42-amino acid form, Aß1-42-is thought to play a key role in the pathogenesis of Alzheimer's disease (AD). Thus, several therapeutic modalities aiming to inhibit Aß synthesis or increase the clearance of Aß have entered clinical trials, including γ-secretase inhibitors, anti-Aß antibodies, and amyloid-ß precursor protein cleaving enzyme inhibitors. A unique class of small molecules, γ-secretase modulators (GSMs), selectively reduce Aß1-42 production, and may also decrease Aß1-40 while simultaneously increasing one or more shorter Aß peptides, such as Aß1-38 and Aß1-37. GSMs are particularly attractive because they do not alter the total amount of Aß peptides produced by γ-secretase activity; they spare the processing of other γ-secretase substrates, such as Notch; and they do not cause accumulation of the potentially toxic processing intermediate, ß-C-terminal fragment. This report describes the translation of pharmacological activity across species for two novel GSMs, (S)-7-(4-fluorophenyl)-N2-(3-methoxy-4-(3-methyl-1H-1,2,4-triazol-1-yl)phenyl)-N4-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidine-2,4-diamine (BMS-932481) and (S,Z)-17-(4-chloro-2-fluorophenyl)-34-(3-methyl-1H-1,2,4-triazol-1-yl)-16,17-dihydro-15H-4-oxa-2,9-diaza-1(2,4)-cyclopenta[d]pyrimidina-3(1,3)-benzenacyclononaphan-6-ene (BMS-986133). These GSMs are highly potent in vitro, exhibit dose- and time-dependent activity in vivo, and have consistent levels of pharmacological effect across rats, dogs, monkeys, and human subjects. In rats, the two GSMs exhibit similar pharmacokinetics/pharmacodynamics between the brain and cerebrospinal fluid. In all species, GSM treatment decreased Aß1-42 and Aß1-40 levels while increasing Aß1-38 and Aß1-37 by a corresponding amount. Thus, the GSM mechanism and central activity translate across preclinical species and humans, thereby validating this therapeutic modality for potential utility in AD.

Tau overexpression impacts a neuroinflammation gene expression network perturbed in Alzheimer's disease.

Filamentous inclusions of the microtubule-associated protein, tau, define a variety of neurodegenerative diseases known as tauopathies, including Alzheimer's disease (AD). To better understand the role of tau-mediated effects on pathophysiology and global central nervous system function, we extensively characterized gene expression, pathology and behavior of the rTg4510 mouse model, which overexpresses a mutant form of human tau that causes Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). We found that the most predominantly altered gene expression pathways in rTg4510 mice were in inflammatory processes. These results closely matched the causal immune function and microglial gene-regulatory network recently identified in AD. We identified additional gene expression changes by laser microdissecting specific regions of the hippocampus, which highlighted alterations in neuronal network activity. Expression of inflammatory genes and markers of neuronal activity changed as a function of age in rTg4510 mice and coincided with behavioral deficits. Inflammatory changes were tau-dependent, as they were reversed by suppression of the tau transgene. Our results suggest that the alterations in microglial phenotypes that appear to contribute to the pathogenesis of Alzheimer's disease may be driven by tau dysfunction, in addition to the direct effects of beta-amyloid.