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.

Design and synthesis of a novel series of 4-heteroarylamino-1'-azaspiro[oxazole-5,3'-bicyclo[2.2.2]octanes as α7 nicotinic receptor agonists 2. Development of 4-heteroaryl SAR.

Quinuclidine-containing spirooxazolines, as described in the previous report in this series, were demonstrated to have utility as α7 nicotinic acetylcholine receptor (α7 nAChR) partial agonists. In this work, the SAR of this chemotype was expanded to include an array of diazine heterocyclic substitutions. Many of the heterocyclic analogs were potent partial agonists of the α7 receptor, selective against other nicotinic receptors and the serotinergic 5HT3A receptor. (1'S,3'R,4'S)-N-(6-phenylpyrimidin-4-yl)-4H-1'-azaspiro[oxazole-5,3'-bicyclo[2.2.2]octan]-2-amine, a potent and selective α7 nAChR partial agonist, was demonstrated to improve cognition in the mouse novel object recognition (NOR) model of episodic memory.

BMS-986163, a Negative Allosteric Modulator of GluN2B with Potential Utility in Major Depressive Disorder.

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 (Ki = 4.0 nM) and selective inhibition of GluN2B receptor function (IC50 = 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.

Nicotinic alpha 7 receptor agonists EVP-6124 and BMS-933043, attenuate scopolamine-induced deficits in visuo-spatial paired associates learning.

Agonists at the nicotinic acetylcholine alpha 7 receptor (nAChR α7) subtype have the potential to treat cognitive deficits in patients with Alzheimer's disease (AD) or schizophrenia. Visuo-spatial paired associates learning (vsPAL) is a task that has been shown to reliably predict conversion from mild cognitive impairment to AD in humans and can also be performed by nonhuman primates. Reversal of scopolamine-induced impairment of vsPAL performance may represent a translational approach for the development of nAChR α7 agonists. The present study investigated the effect of treatment with the acetylcholinesterase inhibitor, donepezil, or three nAChR α7 agonists, BMS-933043, EVP-6124 and RG3487, on vsPAL performance in scopolamine-treated cynomolgus monkeys. Scopolamine administration impaired vsPAL performance accuracy in a dose- and difficulty- dependent manner. The impairment of eventual accuracy, a measure of visuo-spatial learning during the task, was significantly ameliorated by treatment with donepezil (0.3 mg/kg, i.m.), EVP-6124 (0.01 mg/kg, i.m.) or BMS-933043 (0.03, 0.1 and 0.3 mg/kg, i.m.). Both nAChR α7 agonists showed inverted-U shaped dose-effect relationships with EVP-6124 effective at a single dose only whereas BMS-933043 was effective across at least a 10 fold dose/exposure range. RG3487 was not efficacious in this paradigm at the dose range examined (0.03-1 mg/kg, i.m.). These results are the first demonstration that the nAChR α7 agonists, EVP-6124 and BMS-933043, can ameliorate scopolamine-induced cognitive deficits in nonhuman primates performing the vsPAL task.

BMS-933043, a Selective α7 nAChR Partial Agonist for the Treatment of Cognitive Deficits Associated with Schizophrenia.

The therapeutic treatment of negative symptoms and cognitive dysfunction associated with schizophrenia is a significant unmet medical need. Preclinical literature indicates that α7 neuronal nicotinic acetylcholine (nACh) receptor agonists may provide an effective approach to treating cognitive dysfunction in schizophrenia. We report herein the discovery and evaluation of 1c (BMS-933043), a novel and potent α7 nACh receptor partial agonist with high selectivity against other nicotinic acetylcholine receptor subtypes (>100-fold) and the 5-HT3A receptor (>300-fold). In vivo activity was demonstrated in a preclinical model of cognitive impairment, mouse novel object recognition. BMS-933043 has completed Phase I clinical trials.

The qEEG Signature of Selective NMDA NR2B Negative Allosteric Modulators; A Potential Translational Biomarker for Drug Development.

The antidepressant activity of the N-methyl-D-aspartate (NMDA) receptor channel blocker, ketamine, has led to the investigation of negative allosteric modulators (NAMs) selective for the NR2B receptor subtype. The clinical development of NR2B NAMs would benefit from a translational pharmacodynamic biomarker that demonstrates brain penetration and functional inhibition of NR2B receptors in preclinical species and humans. Quantitative electroencephalography (qEEG) is a translational measure that can be used to demonstrate pharmacodynamic effects across species. NMDA receptor channel blockers, such as ketamine and phencyclidine, increase the EEG gamma power band, which has been used as a pharmacodynamic biomarker in the development of NMDA receptor antagonists. However, detailed qEEG studies with ketamine or NR2B NAMs are lacking in nonhuman primates. The aim of the present study was to determine the effects on the qEEG power spectra of the NR2B NAMs traxoprodil (CP-101,606) and BMT-108908 in nonhuman primates, and to compare them to the NMDA receptor channel blockers, ketamine and lanicemine. Cynomolgus monkeys were surgically implanted with EEG radio-telemetry transmitters, and qEEG was measured after vehicle or drug administration. The relative power for a number of frequency bands was determined. Ketamine and lanicemine increased relative gamma power, whereas the NR2B NAMs traxoprodil and BMT-108908 had no effect. Robust decreases in beta power were elicited by ketamine, traxoprodil and BMT-108908; and these agents also produced decreases in alpha power and increases in delta power at the doses tested. These results suggest that measurement of power spectra in the beta and delta bands may represent a translational pharmacodynamic biomarker to demonstrate functional effects of NR2B NAMs. The results of these studies may help guide the selection of qEEG measures that can be incorporated into early clinical evaluation of NR2B NAMs in healthy humans.

Negative Allosteric Modulators Selective for The NR2B Subtype of The NMDA Receptor Impair Cognition in Multiple Domains.

Antidepressant activity of N-methyl-D-aspartate (NMDA) receptor antagonists and negative allosteric modulators (NAMs) has led to increased investigation of their behavioral pharmacology. NMDA antagonists, such as ketamine, impair cognition in multiple species and in multiple cognitive domains. However, studies with NR2B subtype-selective NAMs have reported mixed results in rodents including increased impulsivity, no effect on cognition, impairment or even improvement of some cognitive tasks. To date, the effects of NR2B-selective NAMs on cognitive tests have not been reported in nonhuman primates. The current study evaluated two selective NR2B NAMs, CP101,606 and BMT-108908, along with the nonselective NMDA antagonists, ketamine and AZD6765, in the nonhuman primate Cambridge Neuropsychological Test Automated Battery (CANTAB) list-based delayed match to sample (list-DMS) task. Ketamine and the two NMDA NR2B NAMs produced selective impairments in memory in the list-DMS task. AZD6765 impaired performance in a non-specific manner. In a separate cohort, CP101,606 impaired performance of the nonhuman primate CANTAB visuo-spatial Paired Associates Learning (vsPAL) task with a selective impairment at more difficult conditions. The results of these studies clearly show that systemic administration of a selective NR2B NAM can cause transient cognitive impairment in multiple cognitive domains.

The Novel, Nicotinic Alpha7 Receptor Partial Agonist, BMS-933043, Improves Cognition and Sensory Processing in Preclinical Models of Schizophrenia.

The development of alpha7 nicotinic acetylcholine receptor agonists is considered a promising approach for the treatment of cognitive symptoms in schizophrenia patients. In the present studies we characterized the novel agent, (2R)-N-(6-(1H-imidazol-1-yl)-4-pyrimidinyl)-4'H-spiro[4-azabicyclo[2.2.2]octane-2,5'-[1,3]oxazol]-2'-amine (BMS-933043), in vitro and in rodent models of schizophrenia-like deficits in cognition and sensory processing. BMS-933043 showed potent binding affinity to native rat (Ki = 3.3 nM) and recombinant human alpha7 nicotinic acetylcholine receptors (Ki = 8.1 nM) and agonist activity in a calcium fluorescence assay (EC50 = 23.4 nM) and whole cell voltage clamp electrophysiology (EC50 = 0.14 micromolar (rat) and 0.29 micromolar (human)). BMS-933043 exhibited a partial agonist profile relative to acetylcholine; the relative efficacy for net charge crossing the cell membrane was 67% and 78% at rat and human alpha7 nicotinic acetylcholine receptors respectively. BMS-933043 showed no agonist or antagonist activity at other nicotinic acetylcholine receptor subtypes and was at least 300 fold weaker at binding to and antagonizing human 5-HT3A receptors (Ki = 2,451 nM; IC50 = 8,066 nM). BMS-933043 treatment i) improved 24 hour novel object recognition memory in mice (0.1-10 mg/kg, sc), ii) reversed MK-801-induced deficits in Y maze performance in mice (1-10 mg/kg, sc) and set shift performance in rats (1-10 mg/kg, po) and iii) reduced the number of trials required to complete the extradimensional shift discrimination in neonatal PCP treated rats performing the intra-dimensional/extradimensional set shifting task (0.1-3 mg/kg, po). BMS-933043 also improved auditory gating (0.56-3 mg/kg, sc) and mismatch negativity (0.03-3 mg/kg, sc) in rats treated with S(+)ketamine or neonatal phencyclidine respectively. Given this favorable preclinical profile BMS-933043 was selected for further development to support clinical evaluation in humans.

Design and Synthesis of a New Series of 4-Heteroarylamino-1'-azaspiro[oxazole-5,3'-bicyclo[2.2.2]octanes as α7 Nicotinic Receptor Agonists. 1. Development of Pharmacophore and Early Structure-Activity Relationship.

The design and synthesis of a series of quinuclidine-containing spirooxazolidines ("spiroimidates") and their utility as α7 nicotinic acetylcholine receptor partial agonists are described. Selected members of the series demonstrated excellent selectivity for α7 over the highly homologous 5-HT3A receptor. Modification of the N-spiroimidate heterocycle substituent led to (1S,2R,4S)-N-isoquinolin-3-yl)-4'H-4-azaspiro[bicyclo[2.2.2]octane-2,5'oxazol]-2'-amine (BMS-902483), a potent α7 partial agonist, which improved cognition in preclinical rodent models.

Design and synthesis of 4-heteroaryl 1,2,3,4-tetrahydroisoquinolines as triple reuptake inhibitors.

A series of 4-bicyclic heteroaryl 1,2,3,4-tetrahydroisoquinoline inhibitors of the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT) was discovered. The synthesis and structure-activity relationship (SAR) of these triple reuptake inhibitors (TRIs) will be discussed. Compound 10i (AMR-2), a very potent inhibitor of SERT, NET, and DAT, showed efficacy in the rat forced-swim and mouse tail suspension models with minimum effective doses of 0.3 and 1 mg/kg (po), respectively. At efficacious doses in these assays, 10i exhibited substantial occupancy levels at the three transporters in both rat and mouse brain. The study of the metabolism of 10i revealed the formation of a significant active metabolite, compound 13.

Synthesis of water-soluble prodrugs of BMS-191011: a maxi-K channel opener targeted for post-stroke neuroprotection.

A variety of water-soluble prodrugs of BMS-191011 was synthesized and evaluated for solution state stability and rate of conversion to BMS-191011 in rat and human plasma. The deoxycarnitine ester prodrug (11c) was selected for clinical evaluation based on its superior chemical stability, crystallinity and cleavage to BMS-191011 in human plasma.