A novel class of AMPA receptor allosteric modulators. Part 1: design, synthesis, and SAR of 3-aryl-4-cyano-5-substituted-heteroaryl-2-carboxylic acid derivatives.

The synthesis and initial SAR studies of novel, highly potent positive allosteric modulators of AMPA receptors based on 3-(4-tert-butylphenyl)-4-cyano-5-methylsulfanyl-thiophene-2-carboxylic acid (6a) are described. SAR studies at the thioether moiety indicated that substitution at this position was mandatory and better potency was achieved with small groups.

A novel class of positive allosteric modulators of AMPA receptors: design, synthesis, and structure-activity relationships of 3-biphenyl-4-yl-4-cyano-5-ethyl-1-methyl-1H-pyrrole-2-carboxylic acid, LY2059346.

The synthesis and structure-activity relationship (SAR) of novel and highly potent positive allosteric modulators of AMPA receptors, 3-biphenyl-4-yl-4-cyano-5-ethyl-1-methyl-1H-pyrrole-2-carboxylic acid, are described. These studies indicated that higher potency was achieved with ortho substitution of the distal (D) phenyl of the 3-biphenyl ring and resulted in the discovery of a potent pyrrole LY2059346 (23q), that was selected for further evaluation in in vitro native tissue assays and in vivo experiments.

AMPA receptor potentiators for the treatment of CNS disorders.

Glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors mediate most of the excitatory neurotransmission in the mammalian central nervous system and also participate in forms of synaptic plasticity thought to underlie memory and learning, and the formation of neural networks during development. Molecular cloning techniques have shown that the AMPA receptor family is composed of four different subunits named GluR1-4 or GluRA-D (newly termed as Glu(A1)-Glu(A4)) and native AMPA receptors are most likely tetramers generated by the assembly of one or more of these subunits, yielding homomeric or heteromeric receptors. Additional complexity among AMPA receptors is conferred by alternative splicing of RNA for each subunit giving rise to flip and flop variants. Clinical and experimental data have suggested that positive modulation of AMPA receptors may be therapeutically effective in the treatment of cognitive deficits. Several classes of AMPA receptor potentiators have been reported, including pyrroliddones (piracetam, aniracetam), benzothiazides (cyclothiazide), benzylpiperidines (CX-516, CX-546) and more recently biarylpropylsulfonamides (LY392098, LY404187 and LY503430). These molecules enhance cognitive function in rodents, which appears to correlate with increased hippocampal activity. In addition, clinical studies have suggested that AMPA receptor modulators enhance cognitive function in elderly subjects, as well as patients suffering from neurological and psychiatric disorders. Several independent studies have suggested that AMPA receptors can increase BDNF expression by both calcium-dependent and independent pathways. For example, recent studies have shown that AMPA receptors interact with the protein tyrosine kinase, Lyn. Activation of Lyn can recruit the mitogen-activated protein kinase (MAPK) signalling pathway and increase the expression of BDNF. Therefore, in addition to directly enhancing glutamatergic synaptic transmission, AMPA receptor activation can increase the expression of BDNF in vitro and in vivo. This may account for activity of AMPA receptor potentiators in rodent models predictive of antidepressant activity (forced swim and tail suspension tests). The increase in neurotrophin expression also may contribute to the functional, neuroprotective and neurotrophic actions of LY404187 and LY503430 after infusion of 6-OHDA into the substantia nigra. In conclusion, several potent, selective and systemically active AMPA receptor potentiators have been reported. Data indicate that these molecules modulate glutamatergic transmission, enhance synaptic transmission, long-term potentiation (LTP) and increase neurotrophin expression. Therefore, these AMPA receptor potentiators offer an exciting new class of drugs with potential for treating (1) cognitive impairment associated with Alzheimer's disease and schizophrenia, (2) depression, (3) slowing the progression and potentially enhancing recovery from Parkinson's disease.

Importance of phenolic address groups in opioid kappa receptor selective antagonists.

In vitro characterization and comparison of JDTic, its dehydroxy analogue and nor-BNI, and its dehydroxy analogue demonstrates that the N-substituted 3,4-dimethyl-(3-hydroxyphenyl)piperidine-derived antagonist, JDTic, relies more heavily on its phenol address group for affinity and antagonist activity relative to the corresponding naltrexone derived antagonists, nor-BNI. The structural flexibility of the former class of compound relative to the latter is postulated to underlie the difference.

Discovery of the first N-substituted 4beta-methyl-5-(3-hydroxyphenyl)morphan to possess highly potent and selective opioid delta receptor antagonist activity.

A structurally novel opioid delta receptor selective antagonist has been identified. This compound, (+)-5-(3-hydroxyphenyl)-4-methyl-2-(3-phenylpropyl)-2-azabicyclo[3.3.1]non-7-yl-(1-phenyl-1-cyclopentane)carboxamide [(+)-KF4, (+)-4], showed a K(e) value of 0.15 nM in the [(35)S]GTPgammaS functional assay. (+)-KF4 is also a delta inverse agonist with an IC(50) value of 1.8 nM. To our knowledge, this is the first potent and selective delta opioid receptor antagonist from the 5-phenylmorphan class of opioids.

Identification of (3R)-7-hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)- 3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro- 3-isoquinolinecarboxamide as a novel potent and selective opioid kappa receptor antagonist.

(3R)-7-Hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic) was identified as a potent and selective kappa opioid receptor antagonist. Structure-activity relationship (SAR) studies on JDTic analogues revealed that the 3R,4R stereochemistry of the 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine core structure, the 3R attachment of the 7-hydroxy-1,2,3,4-tetrahydroisoquinoline group, and the 1S configuration of the 2-methylpropyl (isopropyl) group were all important to its kappa potency and selectivity. The results suggest that, like other kappa opioid antagonists such as nor-BNI and GNTI, JDTic requires a second basic amino group to express potent and selective kappa antagonist activity in the [(35)S]GTPgammaS functional assay. However, unlike previously reported kappa antagonists, JDTic also requires a second phenol group in rigid proximity to this second basic amino group. The potent and selective kappa antagonist properties of JDTic can be rationalized using the "message-address" concept wherein the (3R,4R)-3,4-dimethyl-4-(hydroxyphenyl)piperidinyl group represents the message, and the basic amino and phenol group in the N substituent constitutes the address. It is interesting to note the structural commonality (an amino and phenol groups) in both the message and address components of JDTic. The unique structural features of JDTic will make this compound highly useful in further characterization of the kappa receptor.

LY503430, a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor potentiator with functional, neuroprotective and neurotrophic effects in rodent models of Parkinson's disease.

Glutamate is the major excitatory transmitter in the brain. Recent developments in the molecular biology and pharmacology of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) subtype of glutamate receptors have led to the discovery of selective, potent, and systemically active AMPA receptor potentiators. These molecules enhance synaptic transmission and play important roles in plasticity and cognitive processes. In the present study, we first characterized a novel AMPA receptor potentiator, (R)-4'-[1-fluoro-1-methyl-2-(propane-2-sulfonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430), on recombinant human GLUA1-4 and native preparations in vitro and then evaluated the potential neuroprotective effects of the molecule in rodent models of Parkinson's disease. Results indicated that submicromolar concentrations of LY503430 selectively enhanced glutamate-induced calcium influx into human embryonic kidney 293 cells transfected with human GLUA1, GLUA2, GLUA3, or GLUA4 AMPA receptors. The molecule also potentiated AMPA-mediated responses in native cortical, hippocampal, and substantia nigra neurons. We also report here that LY503430 provided dose-dependent functional and histological protection in animal models of Parkinson's disease. The neurotoxicity after unilateral infusion of 6-hydroxydopamine into either the substantia nigra or the striatum of rats and that after systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice were reduced. Interestingly, LY503430 also had neurotrophic actions on functional and histological outcomes when treatment was delayed until well after (6 or 14 days) the lesion was established. LY503430 also produced some increase in brain-derived neurotrophic factor in the substantia nigra and a dose-dependent increases in growth associated protein-43 (GAP-43) expression in the striatum. Therefore, we propose that AMPA receptor potentiators offer the potential of a new disease modifying therapy for Parkinson's disease.

Discovery of an opioid kappa receptor selective pure antagonist from a library of N-substituted 4beta-methyl-5-(3-hydroxyphenyl)morphans.

A library of compounds biased toward opioid receptor antagonist activity was prepared by incorporating N-phenylpropyl-4beta-methyl-5-(3-hydroxyphenyl)morphans as the core scaffold using simultaneous solution phase synthetic methodology. From this library, N-phenylpropyl-4beta-methyl-5-(3-hydroxyphenyl)-7alpha-[3-(1-piperidinyl)propanamido]morphan [(-)-3b] was identified as the first potent and selective kappa opioid receptor antagonist from the 5-phenylmorphan class of opioids.

Design and synthesis of a novel series of 1,2-disubstituted cyclopentanes as small, potent potentiators of 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid (AMPA) receptors.

2-Amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid (AMPA) potentiators are ligands that act as positive allosteric modulators at the AMPA receptors. We recently disclosed a novel series of 2-arylpropylsulfonamides that were potent potentiators of responses mediated through AMPA receptors. To further define the structural requirements for activity in this series, new ring-constrained analogues were prepared and a new stereocenter was introduced. The potentiating activity was highly dependent on the stereochemistry at the 2-position of the disubstituted cyclopentane and was independent of the relative stereochemistry at the 1-position. Compound (R,R)-10 represents a potent, novel potentiator of iGluR4 flip receptors (EC(50) = 22.6 nM).