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Recent mouse knockout studies identified adapter protein-2-associated kinase 1 (AAK1) as a viable target for treating neuropathic pain. BMS-986176/LX-9211 (

Adaptor protein 2-associated kinase 1 (AAK1) is a serine/threonine kinase that was identified as a therapeutic target for the potential treatment of neuropathic pain. Inhibition of AAK1 in the central nervous system, particularly within the spinal cord, was found to be the relevant site for achieving an antinociceptive effect. We previously reported that compound

Recent mouse knockout studies identified adapter protein-2 associated kinase 1 (AAK1) as a viable target for treating neuropathic pain. Potent small-molecule inhibitors of AAK1 have been identified and show efficacy in various rodent pain models. (

Effective treatment of chronic pain, in particular neuropathic pain, without the side effects that often accompany currently available treatment options is an area of significant unmet medical need. A phenotypic screen of mouse gene knockouts led to the discovery that adaptor protein 2-associated kinase 1 (AAK1) is a potential therapeutic target for neuropathic pain. The synthesis and optimization of structure-activity relationships of a series of aryl amide-based AAK1 inhibitors led to the identification of 59, a brain penetrant, AAK1-selective inhibitor that proved to be a valuable tool compound. Compound 59 was evaluated in mice for the inhibition of μ2 phosphorylation. Studies conducted with 59 in pain models demonstrated that this compound was efficacious in the phase II formalin model for persistent pain and the chronic-constriction-injury-induced model for neuropathic pain in rats. These results suggest that AAK1 inhibition is a promising approach for the treatment of neuropathic pain.

This letter describes the first account of the chemical optimization (SAR and DMPK profiling) of a new series of mGlu4 positive allosteric modulators (PAMs), leading to the identification of VU0652957 (VU2957, Valiglurax), a compound profiled as a preclinical development candidate. Here, we detail the challenges faced in allosteric modulator programs (e.g., steep SAR, as well as subtle structural changes affecting overall physiochemical/DMPK properties and CNS penetration).

[Image: see text] Herein, we report the discovery of a novel potent, selective, CNS penetrant, and orally bioavailable mGlu(4) PAM, VU0652957 (VU2957, Valiglurax). VU2957 possessed attractive in vitro and in vivo pharmacological and DMPK properties across species. To advance toward the clinic, a spray-dried dispersion (SDD) formulation of VU2957 was developed to support IND-enabling toxicology studies. Based on its overall profile, VU2957 was evaluated as a preclinical development candidate for the treatment of Parkinson’s disease.

Previous reports from our laboratory disclosed the structure and activity of a novel 1H-pyrazolo[4,3-b]pyridine-3-amine scaffold (VU8506) which showed excellent potency, selectivity and in vivo efficacy in preclinical rodent models of Parkinson’s disease. Unfortunately, this compound suffered from significant CYP1A2 induction as measured through upstream AhR activation (125-fold) and thus was precluded from further advancement in chronic studies. Herein, we report a new scaffold developed recently which was systematically studied in order to mitigate the CYP1A2 liabilities presented in the earlier scaffolds. We have identified a novel structure that maintains the potency and selectivity of other mGlu4 PAMs, leading to 9i (hmGlu4 EC50 = 43 nM; AhR activation = 2.3-fold).

Since zwitterionic benzenesulfonamide Nav1.7 inhibitors suffer from poor membrane permeability, we sought to eliminate this characteristic by replacing the basic moiety with non-basic bicyclic acetals and monocyclic ethers. These efforts led to the discovery of the non-zwitterionic aryl sulfonamide 49 as a selective Nav1.7 inhibitor with improved membrane permeability. Despite its moderate cellular activity, 49 exhibited robust efficacy in mouse models of neuropathic and inflammatory pain and modulated translational electromyogram measures associated with activation of nociceptive neurons.

(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.

Adaptor-associated kinase 1 (AAK1), a member of the Ark1/Prk1 family of serine/threonine kinases, plays a role in modulating clatherin coated endocytosis of specific surface receptors. We have demonstrated that AAK1 inhibitors are efficacious in rodent models of neuropathic pain (Kostich et al., 2016). Here we have characterized the binding properties and distribution pattern of the tritiated AAK1 radioligand, [3H]BMT-046091, in rodents and cynomolgus monkeys, and used the radioligand to measure the brain target occupancy following systemic administration of AAK1 inhibitors. We have found that [3H]BMT-046091 is potent and selective AAK1 inhibitor. It inhibits AAK1 phosphorylation of a peptide derived from a physiologic substrate, the μ2 subunit of the adaptor protein complex, with an IC50 value of 2.8 nM, and is inactive at >5 μM in a panel of functional or binding assays for receptors, transporters and enzymes. [3H]BMT-046091 binding in the brain is absent in the AAK1 knockout mouse, and is displaceable with a high concentration of AAK1 inhibitors in wild type mice. Specific [3H]BMT-046091 binding is widespread in the brain and spinal cord with the highest density in the cortex, hippocampus, amygdala, striatum and thalamus. In the spinal cord, [3H]BMT-046091 binding appears enriched in the dorsal horn superficial layers. Oral administration of LP-935509, an AAK1 inhibitor, results in a dose-dependent occupation of AAK1 binding sites in the brain and spinal cord. The increase in AAK1 binding site occupancy by LP-935509 correlates with the decrease in antinociceptive responses in the rat chronic constriction injury model of neuropathic pain.

A series of phosphate and ester-based prodrugs of anilinopyrazinone 1 (BMS-665053) containing either a methylene or an (acyloxy)alkoxy linker was prepared and evaluated in rat pharmacokinetic studies with the goal of improving the oral bioavailability of the parent (1). The prodrugs, in general, had improved aqueous solubility and oral bioavailability compared to 1. Prodrug 12, which contains an (acyloxy)alkoxy linker, showed the greatest improvement in the oral bioavailability relative to the parent (1), with a seven-fold increase (from 5% to 36%) in rat pharmacokinetic studies.

Triazolopyridine ethers with mGlu2 positive allosteric modulator (PAM) activity are disclosed. The synthesis, in vitro activity, and metabolic stability data for a series of analogs is provided. The effort resulted in the discovery of a potent, selective, and brain penetrant lead molecule BMT-133218 ((+)-7m). After oral administration at 10mg/kg, BMT-133218 demonstrated full reversal of PCP-stimulated locomotor activity and prevented MK-801-induced working memory deficits in separate mouse models. Also, reversal of impairments in executive function were observed in rat set-shifting studies at 3 and 10mg/kg (p.o.). Extensive plasma protein binding as the result of high lipophilicity likely limited activity at lower doses. Optimized triazolopyridine ethers offer utility as mGlu2 PAMs for the treatment of schizophrenia and merit further preclinical investigation.

Schizophrenia is a serious illness that affects millions of patients and has been associated with N-methyl-d-aspartate receptor (NMDAR) hypofunction. It has been demonstrated that activation of metabotropic glutamate receptor 5 (mGluR5) enhances NMDA receptor function, suggesting the potential utility of mGluR5 positive allosteric modulators (PAMs) in the treatment of schizophrenia. Herein we describe the optimization of an mGluR5 PAM by replacement of a phenyl with aliphatic heterocycles and carbocycles as a strategy to reduce bioactivation in a biaryl acetylene chemotype. Replacement with a difluorocyclobutane followed by further optimization culminated in the identification of compound 32, a low fold shift PAM with reduced bioactivation potential. Compound 32 demonstrated favorable brain uptake and robust efficacy in mouse novel object recognition (NOR) at low doses.

Combination studies of neurokinin 1 (NK1) receptor antagonists and serotonin-selective reuptake inhibitors (SSRIs) have shown promise in preclinical models of depression. Such a combination may offer important advantages over the current standard of care. Herein we describe the discovery and optimization of an indazole-based chemotype to provide a series of potent dual NK1 receptor antagonists/serotonin transporter (SERT) inhibitors to overcome issues of ion channel blockade. This effort culminated in the identification of compound 9, an analogue that demonstrated favorable oral bioavailability, excellent brain uptake, and robust in vivo efficacy in a validated depression model. Over the course of this work, a novel heterocycle-directed asymmetric hydrogenation was developed to facilitate installation of the key stereogenic center.

The metabotropic glutamate receptor 5 (mGluR5) is an attractive target for the treatment of schizophrenia due to its role in regulating glutamatergic signaling in association with the N-methyl-d-aspartate receptor (NMDAR). We describe the synthesis of 1H-pyrazolo[3,4-b]pyridines and their utility as mGluR5 positive allosteric modulators (PAMs) without inherent agonist activity. A facile and convergent synthetic route provided access to a structurally diverse set of analogues that contain neither the aryl-acetylene-aryl nor aryl-methyleneoxy-aryl elements, the predominant structural motifs described in the literature. Binding studies suggest that members of our new chemotype do not engage the receptor at the MPEP and CPPHA mGluR5 allosteric sites. SAR studies culminated in the first non-MPEP site PAM, 1H-pyrazolo[3,4-b]pyridine 31 (BMT-145027), to improve cognition in a preclinical rodent model of learning and memory.

To identify novel targets for neuropathic pain, 3097 mouse knockout lines were tested in acute and persistent pain behavior assays. One of the lines from this screen, which contained a null allele of the adapter protein-2 associated kinase 1 (AAK1) gene, had a normal response in acute pain assays (hot plate, phase I formalin), but a markedly reduced response to persistent pain in phase II formalin. AAK1 knockout mice also failed to develop tactile allodynia following the Chung procedure of spinal nerve ligation (SNL). Based on these findings, potent, small-molecule inhibitors of AAK1 were identified. Studies in mice showed that one such inhibitor, LP-935509, caused a reduced pain response in phase II formalin and reversed fully established pain behavior following the SNL procedure. Further studies showed that the inhibitor also reduced evoked pain responses in the rat chronic constriction injury (CCI) model and the rat streptozotocin model of diabetic peripheral neuropathy. Using a nonbrain-penetrant AAK1 inhibitor and local administration of an AAK1 inhibitor, the relevant pool of AAK1 for antineuropathic action was found to be in the spinal cord. Consistent with these results, AAK1 inhibitors dose-dependently reduced the increased spontaneous neural activity in the spinal cord caused by CCI and blocked the development of windup induced by repeated electrical stimulation of the paw. The mechanism of AAK1 antinociception was further investigated with inhibitors of α2 adrenergic and opioid receptors. These studies showed that α2 adrenergic receptor inhibitors, but not opioid receptor inhibitors, not only prevented AAK1 inhibitor antineuropathic action in behavioral assays, but also blocked the AAK1 inhibitor-induced reduction in spinal neural activity in the rat CCI model. Hence, AAK1 inhibitors are a novel therapeutic approach to neuropathic pain with activity in animal models that is mechanistically linked (behaviorally and electrophysiologically) to α2 adrenergic signaling, a pathway known to be antinociceptive in humans.

A series of pyrazinone-based compounds incorporating either carbamate or aryl ether groups was synthesized and evaluated as corticotropin-releasing factor-1 (CRF1) receptor antagonists. Structure-activity relationship studies led to the identification of highly potent CRF1 receptor antagonists 14a (IC50=0.74 nM) and 14b (IC50=1.9 nM). The synthesis, structure-activity relationships and in vitro metabolic stability properties of compounds in this series will be described.

Phosphodiesterase 10A (PDE10A) inhibitors increase the functionality of striatal medium spiny neurons and produce antipsychotic-like effects in rodents by blocking PDE10A mediated hydrolysis of cAMP and/or cGMP. In the current study, we characterized a radiolabeled PDE10A inhibitor, [(3)H]BMS-843496, and developed an ex vivo PDE10 binding autoradiographic assay to explore the relationship between PDE10 binding site occupancy and the observed biochemical and behavioral effects of PDE10 inhibitors in mice. [(3)H]BMS-843496 is a potent PDE10A inhibitor with a binding affinity (KD) of 0.15 nM and a functional selectivity of >100-fold over other PDE subtypes tested. Specific [(3)H]BMS-843496 binding sites were dominant in the basal ganglia, especially the striatum, with low to moderate binding in the cortical and hippocampal areas, of the mouse and monkey brain. Systemic administration of PDE10 inhibitors produced a dose- and plasma/brain concentration-dependent increase in PDE10A occupancy measured in the striatum. PDE10A occupancy was positively correlated with striatal pCREB expression levels. PDE10A occupancy was also correlated with antipsychotic-like effects measured using the conditioned avoidance response model; a minimum of ∼40% occupancy was typically required to achieve efficacy. In contrast, a clear relationship between PDE10A occupancy and catalepsy scores, a potential extrapyramidal symptom readout in rodent, was not evident.

This letter describes the first account of the chemical optimization (SAR and DMPK profiling) of a new series of mGlu

Previous reports from our laboratory disclosed the structure and activity of a novel 1H-pyrazolo[4,3-b]pyridine-3-amine scaffold (VU8506) which showed excellent potency, selectivity and in vivo efficacy in preclinical rodent models of Parkinson's disease. Unfortunately, this compound suffered from significant CYP1A2 induction as measured through upstream AhR activation (125-fold) and thus was precluded from further advancement in chronic studies. Herein, we report a new scaffold developed recently which was systematically studied in order to mitigate the CYP1A2 liabilities presented in the earlier scaffolds. We have identified a novel structure that maintains the potency and selectivity of other mGlu

[Image: see text] There is a significant unmet medical need for more efficacious and rapidly acting antidepressants. Toward this end, negative allosteric modulators of the N-methyl-d-aspartate receptor subtype GluN2B have demonstrated encouraging therapeutic potential. We report herein the discovery and preclinical profile of a water-soluble intravenous prodrug BMS-986163 (6) and its active parent molecule BMS-986169 (5), which demonstrated high binding affinity for the GluN2B allosteric site (K(i) = 4.0 nM) and selective inhibition of GluN2B receptor function (IC(50) = 24 nM) in cells. The conversion of prodrug 6 to parent 5 was rapid in vitro and in vivo across preclinical species. After intravenous administration, compounds 5 and 6 have exhibited robust levels of ex vivo GluN2B target engagement in rodents and antidepressant-like activity in mice. No significant off-target activity was observed for 5, 6, or the major circulating metabolites met-1 and met-2. The prodrug BMS-986163 (6) has demonstrated an acceptable safety and toxicology profile and was selected as a preclinical candidate for further evaluation in major depressive disorder.

Depression is a serious illness that affects millions of patients. Current treatments are associated with a number of undesirable side effects. Neurokinin 1 receptor (NK1R) antagonists have recently been shown to potentiate the antidepressant effects of serotonin-selective reuptake inhibitors (SSRIs) in a number of animal models. Herein we describe the optimization of a biaryl chemotype to provide a series of potent dual NK1R antagonists/serotonin transporter (SERT) inhibitors. Through the choice of appropriate substituents, the SERT/NK1R ratio could be tuned to afford a range of target selectivity profiles. This effort culminated in the identification of an analog that demonstrated oral bioavailability, favorable brain uptake, and efficacy in the gerbil foot tap model. Ex vivo occupancy studies with compound 58 demonstrated the ability to maintain NK1 receptor saturation (>88% occupancy) while titrating the desired level of SERT occupancy (11-84%) via dose selection.

Small molecule modulators of GPR88 activity (agonists, antagonists, or modulators) are of interest as potential agents for the treatment of a variety of psychiatric disorders including schizophrenia. A series of phenylglycinol and phenylamine analogs have been prepared and evaluated for their GPR88 agonist activity and pharmacokinetic (PK) properties.

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A series of phosphate and ester-based prodrugs of anilinopyrazinone 1 (BMS-665053) containing either a methylene or an (acyloxy)alkoxy linker was prepared and evaluated in rat pharmacokinetic studies with the goal of improving the oral bioavailability of the parent (1). The prodrugs, in general, had improved aqueous solubility and oral bioavailability compared to 1. Prodrug 12, which contains an (acyloxy)alkoxy linker, showed the greatest improvement in the oral bioavailability relative to the parent (1), with a seven-fold increase (from 5% to 36%) in rat pharmacokinetic studies.

Introduction A radioligand for measuring the density of corticotropin-releasing factor subtype-1 receptors (CRF 1 receptors) in living animal and human brain with positron emission tomography (PET) would be a useful tool for neuropsychiatric investigations and the development of drugs intended to interact with this target. This study was aimed at discovery of such a radioligand from a group of CRF 1 receptor ligands based on a core 3-(phenylamino)‐pyrazin-2(1 H )-one scaffold. Methods CRF 1 receptor ligands were selected for development as possible PET radioligands based on their binding potency at CRF 1 receptors (displacement of [ 125 I]CRF from rat cortical membranes), measured lipophilicity, autoradiographic binding profile in rat and rhesus monkey brain sections, rat biodistribution, and suitability for radiolabeling with carbon-11 or fluorine-18. Two identified candidates (BMS-721313 and BMS-732098) were labeled with fluorine-18. A third candidate (BMS-709460) was labeled with carbon-11 and all three radioligands were evaluated in PET experiments in rhesus monkey. CRF 1 receptor density ( B max ) was assessed in rhesus brain cortical and cerebellum membranes with the CRF 1 receptor ligand, [ 3 H]BMS-728300. Results The three ligands selected for development showed high binding affinity ( IC 50 values, 0.3–8 nM) at CRF 1 receptors and moderate lipophilicity ( LogD , 2.8–4.4). [ 3 H]BMS-728300 and the two 18 F-labeled ligands showed region-specific binding in rat and rhesus monkey brain autoradiography, namely higher binding density in the frontal and limbic cortex, and cerebellum than in thalamus and brainstem. CRF 1 receptor B max in rhesus brain was found to be 50–120 fmol/mg protein across cortical regions and cerebellum. PET experiments in rhesus monkey showed that the radioligands [ 18 F]BMS-721313, [ 18 F]BMS-732098 and [ 11 C]BMS-709460 gave acceptably high brain radioactivity uptake but no indication of the specific binding as seen in vitro . Conclusions Candidate CRF 1 receptor PET radioligands were identified but none proved to be effective for imaging monkey brain CRF 1 receptors. Higher affinity radioligands are likely required for successful PET imaging of CRF 1 receptors.

The known interactions between the serotonergic and neurokinin systems suggest that serotonin reuptake inhibitor (SSRIs) efficacy may be improved by neurokinin-1 receptor (NK1R) antagonism. In the current studies combination of a subeffective dose of an SSRI (0.3 mg/kg fluoxetine or 0.03 mg/kg citalopram) with a subeffective dose of an NK1R antagonist (0.3 mg/kg aprepitant or 1 mg/kg CP-122,721) produced efficacy in the gerbil forced swim test (FST). Serotonin transporter (SERT) occupancy produced by 1 mg/kg fluoxetine (lowest efficacious dose) was 52 ± 5% and was reduced to 29 ± 4% at 0.3 mg/kg, a dose that was efficacious in combination with 0.3 mg/kg aprepitant or 1 mg/kg CP-122,721; the corresponding NK1R occupancies were 79 ± 4% and 61 ± 4% for aprepitant and CP-122,721, respectively. For citalopram, SERT occupancy at the lowest efficacious dose (0.1 mg/kg) was 50 ± 4% and was reduced to 20 ± 5% at 0.03 mg/kg, a dose that was efficacious when combined with aprepitant (0.3 mg/kg). Aprepitant (10 mg/kg) augmented the serotonin elevation produced by fluoxetine (1 or 10 mg/kg) in the gerbil prefrontal cortex; i.e. NK1R antagonism can modulate serotonin responses. A novel orally-available dual-acting NK1R antagonist/SERT inhibitor BMS-795176 is described; gerbil Ki = 1.4 and 1 nM at NK1R and SERT, respectively. BMS-795176 was efficacious in the gerbil FST; efficacy was observed with 35 ± 3% SERT occupancy and 73 ± 3% NK1R occupancy. The interaction between NK1R antagonism and SERT inhibition to lower the SERT occupancy required for antidepressant-like efficacy suggests that BMS-795176 has the potential to improve efficacy with a reduction in SSRI-associated side effects.

A series of substituted pyridines, ether linked to a phenylpiperidine core were optimized for dual NK(1)/SERT affinity. Optimization based on NK(1)/SERT binding affinities, and minimization of off-target ion channel activity lead to the discovery of compound 44. In vivo evaluation of 44 in the gerbil forced swim test (a depression model), and ex-vivo NK(1)/SERT receptor occupancy data support the potential of a dual acting compound for the treatment of depression.

Based on a favorable balance between CRF-R1 affinity, lipophilicity and metabolic stability, compound 10 was evaluated for potential development as PET radioligand. Compound [18F]10 was prepared with high radiochemical purity and showed promising binding properties in rat brain imaging experiments.

Triazolopyridine ethers with mGlu

Herein we describe the structure activity relationships uncovered in the pursuit of an mGluR5 positive allosteric modulator (PAM) for the treatment of schizophrenia. It was discovered that certain modifications of an oxazolidinone-based chemotype afforded predictable changes in the pharmacological profile to give analogs with a wide range of functional activities. The discovery of potent silent allosteric modulators (SAMs) allowed interrogation of the mechanism-based liabilities associated with mGluR5 activation and drove our medicinal chemistry effort toward the discovery of low efficacy (fold shift) PAMs devoid of agonist activity. This work resulted in the identification of dipyridyl 22 (BMS-952048), a compound with a favorable free fraction, efficacy in a rodent-based cognition model, and low potential for convulsions in mouse.

The efficacy of positive allosteric modulators (PAMs) of the metabotropic glutamate receptor 4 (mGlu4) in preclinical rodent models of Parkinson’s disease has been established by a number of groups. Here, we report an advanced preclinically characterized mGlu4 PAM, N-(3-chloro-4-fluorophenyl)-1H-pyrazolo[4,3-b]pyridin-3-amine (VU0418506). We detail the discovery of VU0418506 starting from a common picolinamide core scaffold and evaluation of a number of amide bioisosteres leading to the novel pyrazolo[4,3-b]pyridine head group. VU0418506 has been characterized as a potent and selective mGlu4 PAM with suitable in vivo pharmacokinetic properties in three preclinical safety species.

A series of pyrazinone-based compounds incorporating either carbamate or aryl ether groups was synthesized and evaluated as corticotropin-releasing factor-1 (CRF1) receptor antagonists. Structure-activity relationship studies led to the identification of highly potent CRF1 receptor antagonists 14a (IC50=0.74 nM) and 14b (IC50=1.9 nM). The synthesis, structure-activity relationships and in vitro metabolic stability properties of compounds in this series will be described.

Positive allosteric modulators (PAMs) of the metabotropic glutamate receptor subtype 5 (mGluR5) are of interest due to their potential therapeutic utility in schizophrenia and other cognitive disorders. Herein we describe the discovery and optimization of a novel oxazolidinone-based chemotype to identify BMS-955829 (4), a compound with high functional PAM potency, excellent mGluR5 binding affinity, low glutamate fold shift, and high selectivity for the mGluR5 subtype. The low fold shift and absence of agonist activity proved critical in the identification of a molecule with an acceptable preclinical safety profile. Despite its low fold shift, 4 retained efficacy in set shifting and novel object recognition models in rodents.

An efficient scale-up synthesis of (S)-5-chloro-1-(1-cyclopropylethyl)-3-(2,6-dichloro-4-(difluoromethoxy)phenylamino)-pyrazin-2(1H)-one, 1 (BMS-665053), is described. This new process features a one-step direct bis-ortho-chlorination of 4-(difluoromethoxy)aniline with HCl and H2O2, and a palladium-catalyzed coupling of 2,6-dichloro-4-(difluoromethoxy)aniline 2 and (S)-3,5-dichloro-1-(1-cyclopropylethyl)pyrazin-2(1H)-one 3. The process was applied to the preparation of batches of 1 for preclinical toxicology studies.

A series of N-fluoroalkyl-8-(6-methoxy-2-methylpyridin-3-yl)-2,7-dimethyl-N-alkylpyrazolo[1,5-a][1,3,5]triazin-4-amines were prepared and evaluated as potential CRF(1)R PET imaging agents. Optimization of their CRF(1)R binding potencies and octanol-phosphate buffer phase distribution coefficients resulted in discovery of analog 7e (IC(50)=6.5 nM, logD=3.5).

Pyrazinones bearing an N-1-alkyl chain with a chiral center have been reported as potent antagonists of the corticotropin-releasing factor-1 receptor (CRF1R). Separation of individual enantiomers for preclinical testing was an important aspect of lead optimization. To evaluate the applicability and efficiency of supercritical fluid chromatography (SFC) for enantiomeric resolution of this class of compounds, enantiomeric pairs of eight pyrazinones with different structural characteristics were tested under an array of SFC conditions. The results showed that pyrazinones with a 1-cyclopropyl-2-methoxyethyl substituent were readily separated with a Chiralpak AD-H or Chiralcel OD-H column with ethanol as the modifier. On the other hand, analogs with a less polar alkyl substituent were not amenable to the general method and required further optimization of the chromatographic conditions. In addition, structural variations on the pyrazinone core and aromatic moiety had an impact on the chiral resolution of this class of compounds. This investigation led to the development of efficient chiral SFC methods for separating all eight pyrazinone enantiomeric pairs encompassing an array of structural variations.

A series of 5-arylamino-1,2,4-triazin-6(1H)-ones was synthesized and evaluated as antagonists at the corticotropin releasing factor receptor. Formation of CYP-mediated oxidative reactive metabolites previously observed in a related N3-phenylpyrazinone structure was minimized by incorporation of the additional ring nitrogen found in the triazinones.

A series of N3-pyridylpyrazinones was investigated as corticotropin-releasing factor-1 receptor antagonists. It was observed that the binding affinity of analogues containing a pyridyl group was influenced not only by the substitution pattern on the pyridyl group, but also by the pKa of the pyridyl nitrogen. Analogues containing a novel 6-(difluoromethoxy)-2,5-dimethylpyridin-3-amine group were among the most potent N3-pyridylpyrazinones synthesized. The synthesis and SAR of N3-pyridylpyrazinones is described herein.

A series of pyrazinone-based heterocycles was identified as potent and orally active corticotropin-releasing factor-1 (CRF(1)) receptor antagonists. Selected compounds proved efficacious in an anxiety model in rats; however, pharmacokinetic properties were not optimal. In this article, we describe an in vitro intrinsic clearance-based approach to the optimization of pyrazinone-based CRF(1) receptor antagonists wherein sites of metabolism were identified by incubation with human liver microsomes. It was found that the rate of metabolism could be decreased by incorporation of appropriate substituents at the primary sites of metabolism. This led to the discovery of compound 12x, a highly potent (IC(50) = 1.0 nM) and selective CRF(1) receptor antagonist with good oral bioavailability (F = 52%) in rats and efficacy in the defensive withdrawal anxiety test in rats.

The amyloid-beta (Abeta) peptide, which likely plays a key role in Alzheimer disease, is derived from the amyloid-beta precursor protein (APP) through consecutive proteolytic cleavages by beta-site APP-cleaving enzyme and gamma-secretase. Unexpectedly gamma-secretase inhibitors can increase the secretion of Abeta peptides under some circumstances. This "Abeta rise" phenomenon, the same inhibitor causing an increase in Abeta at low concentrations but inhibition at higher concentrations, has been widely observed. Here we show that the Abeta rise depends on the beta-secretase-derived C-terminal fragment of APP (betaCTF) or C99 levels with low levels causing rises. In contrast, the N-terminally truncated form of Abeta, known as "p3," formed by alpha-secretase cleavage, did not exhibit a rise. In addition to the Abeta rise, low betaCTF or C99 expression decreased gamma-secretase inhibitor potency. This "potency shift" may be explained by the relatively high enzyme to substrate ratio under conditions of low substrate because increased concentrations of inhibitor would be necessary to affect substrate turnover. Consistent with this hypothesis, gamma-secretase inhibitor radioligand occupancy studies showed that a high level of occupancy was correlated with inhibition of Abeta under conditions of low substrate expression. The Abeta rise was also observed in rat brain after dosing with the gamma-secretase inhibitor BMS-299897. The Abeta rise and potency shift are therefore relevant factors in the development of gamma-secretase inhibitors and can be evaluated using appropriate choices of animal and cell culture models. Hypothetical mechanisms for the Abeta rise, including the "incomplete processing" and endocytic models, are discussed.

A series of N-alkylbenzenesulfonamides were developed from a high throughput screening hit. Classic and parallel synthesis strategies were employed to produce compounds with good in vitro and in vivo gamma-secretase activity.

The present studies represent the first published report of a dopamine D1 positive allosteric modulator (PAM). D1 receptors have been proposed as a therapeutic target for the treatment of cognitive deficits associated with schizophrenia. However, the clinical utility of orthosteric agonist compounds is limited by cardiovascular side effects, poor pharmacokinetics, lack of D1 selectivity, and an inverted dose response. A number of these challenges may be overcome by utilization of a selective D1 PAM. The current studies describe two chemically distinct D1 PAMs: Compound A [1-((rel-1S,3R,6R)-6-(benzo[d][1,3]dioxol-5-yl)bicyclo[4.1.0]heptan-3-yl)-4-(2-bromo-5-chlorobenzyl)piperazine] and Compound B [rel-(9R,10R,12S)-N-(2,6-dichloro-3-methylphenyl)-12-methyl-9,10-dihydro-9,10-ethanoanthracene-12-carboxamide]. Compound A shows pure PAM activity, with an EC50 of 230 nM and agonist activity at the D2 receptor in D2-expressing human embryonic kidney cells. Compound B shows superior potency (EC50 of 43 nM) and selectivity for D1 versus D2 dopamine receptors. Unlike Compound A, Compound B is selective for human and nonhuman primate D1 receptors, but lacks activity at the rodent (rat and mouse) D1 receptors. Using molecular biology techniques, a single amino acid was identified at position 130, which mediates the species selectivity of Compound B. These data represent the first described D1-selective PAMs and define critical amino acids that regulate species selectivity.

Stereoselective reduction of dehydroalanine double bond in nocathiacin I afforded the primary amide 2. Enzymatic hydrolysis of the amide 2 provided the carboxylic acid 3, which upon coupling with a variety of amines furnished amides 4-32. Some of these semi-synthetic derivatives have retained very good antibacterial activity and have improved aqueous solubility.

The synthesis and antibacterial activity of oxazolidinones containing dihydro-1,2-oxazine and 2-pyrazoline ring systems are described. Linezolid analogs utilizing dihydro-1,2-oxazines as morpholine mimics were prepared utilizing a nitrosoamine/diene 4+2 cycloaddition strategy. Pyrazolidine, hexahydro-pyridazine, and 2-pyrazoline analogs more closely related to eperezolid were also prepared. The most active of these new oxazolidinones were the dihydro-1,2-oxazine 6 and the 2-pyrazoline 20 both of which had potency similar to linezolid against a panel of Gram-positive bacteria.