Making Sense of the Matrix: A Qualitative Assessment and Commentary on Connecting Psychiatric Symptom Scale Items to the Research Domain Criteria (RDoC)

The Research Domain Criteria (RDoC) initiative aims to organize research according to domains of brain function. Dysfunction within these domains leads to psychopathology that is classically measured with rating scales. Examining the correspondence between the specific measures assessed within rating scales and RDoC domains is necessary to assess the needs for new RDoC-focused scales. Such RDoC-focused scales have the potential of allowing translation of this work into the clinical domain of measuring psychopathology and designing treatment. Here, we describe an initial qualitative assessment by a group of 10 clinician-scientists of the alignment between RDoC domains and the items within five commonly used rating scales. In this commentary, we report limited correspondence and make recommendations for future work needed to address these limitations.

An Integrated Pharmacokinetic-Pharmacodynamic-Pharmacoeconomic Modeling Method to Evaluate Treatments for Adults with Schizophrenia

INTRODUCTION

Schizophrenia is a chronic mental disorder that worsens with each relapse. Long-acting injectable (LAI) antipsychotics may prevent the exacerbation of symptoms and occurrence of relapses through improved continuity of care. Different dose regimens are available for the LAIs aripiprazole monohydrate (AM) and aripiprazole lauroxil (AL), but their cost effectiveness is unclear.

OBJECTIVES

The study aim was to compare costs and effects (relapses) of the different aripiprazole LAI dose regimens to inform clinical and US payer decisions.

METHODS

A state-transition model calculated the outcomes of eight LAI dose regimens based on their relapse rates. As effectiveness data from randomized controlled trials were unavailable, relapse rates were modeled using pharmacokinetic and pharmacodynamic evidence. These described blood plasma levels of aripiprazole as a function of AM and AL dose regimens and described the probability of relapse as a function of aripiprazole blood plasma levels. The analysis had a time horizon of 1 year and took the US healthcare payer perspective. The incremental cost per relapse avoided and the probability of cost effectiveness were calculated in deterministic and probabilistic analyses. Scenario analyses explored the model's main assumptions, and results were validated against external data and other cost-effectiveness analyses.

RESULTS

Monthly administration of AM 400 mg consistently yielded the lowest predicted number of relapses across deterministic, probabilistic, and scenario analyses. The costs of treatment and relapses were projected to be the lowest with a monthly administration of AL 441 mg. The incremental cost per relapse avoided with AM 400 mg ranged from AM 400 mg being dominant to $US83,300. From willingness-to-pay thresholds of $US30,000 per relapse avoided, the probability of cost effectiveness was highest for AM 400 mg. The validation showed alignment with external data.

CONCLUSION

The analysis highlighted the robustness of the novel framework based on pharmacokinetic and pharmacodynamic evidence and demonstrated an application in a postmarketing setting.

Real-World Treatment Patterns and Characteristics Among Patients with Agitation and Dementia in the United States: Findings from a Large, Observational, Retrospective Chart Review

BACKGROUND

Few studies have examined patient characteristics and treatment patterns among patients with dementia and agitation in the United States (US).

OBJECTIVE

To examine real-world treatment patterns and characteristics of patients with agitation related to dementia who were treated with antipsychotics in US residential care and community-based settings.

METHODS

This retrospective chart review collected US physician-level data from patients 55 to 90 years old initiated on an antipsychotic medication for the treatment of agitation related to dementia from January 2018 to May 2018. Clinical characteristics and treatment patterns were assessed overall and stratified by residential care and community-based settings.

RESULTS

A total of 313 participating physicians, 59.5% of whom were primary care physicians, abstracted 801 patient charts (residential care: n = 312; community-based: n = 489). Of patients with agitation who were initiated on an antipsychotic, most patients (74.5%) were initiated within 3 months of the onset of their studied agitation episode, and 62.8% experienced multiple agitation episodes before initiation. While non-pharmacological therapies are recommended first-line approach for agitation in dementia, use of non-pharmacological therapy before initiation of antipsychotics was reported for only 37.8% of patients in residential care and 21.3% in community-based settings.

CONCLUSION

Most patients were initiated on an antipsychotic treatment after multiple episodes of agitation and largely without initial non-pharmacological therapy, suggesting that current treatment guideline recommendations for first-line non-pharmacological intervention may not be adequately followed in clinical practice. Understanding the clinical burden and treatment patterns among dementia patients with agitation is imperative for effective disease management.

Association of the US Food and Drug Administration Antipsychotic Drug Boxed Warning With Medication Use and Health Outcomes in Elderly Patients With Dementia

IMPORTANCE

Atypical antipsychotics (AAPs) are often used off-label to manage dementia-associated neuropsychiatric symptoms. In 2005, the US Food and Drug Administration (FDA) issued a boxed warning for the use of AAPs in elderly patients. The long-term association of this warning with health outcomes is unknown to date.

OBJECTIVE

To assess the long-term association of the 2005 FDA boxed warning on AAPs with psychiatric medication and opioid use, health events, and quality of life among elderly individuals with dementia.

DESIGN, SETTING, AND PARTICIPANTS

For this cross-sectional study, data were analyzed from the household component of the Medical Expenditure Panel Survey (MEPS), the National Ambulatory Medical Care Survey (NAMCS), and the National Hospital Ambulatory Medical Care Survey (NHAMCS) fielded between January 1, 1996, and December 31, 2014. This interrupted time-series analysis applied to 3-year moving means derived from the 1996-2014 MEPS, NAMCS, and NHAMCS. All survey respondents included in this analysis were 65 years or older and had dementia. Data analysis was performed from December 1, 2017, to March 15, 2018.

EXPOSURES

The 2005 FDA boxed warning on AAPs.

MAIN OUTCOMES AND MEASURES

Use of psychiatric medications and opioids, prevalence of cerebrovascular and cardiovascular events, prevalence of falls and/or fractures, 2-year mortality, and health-related quality of life assessed by the Medical Outcomes Study 12-Item Short-Form Health Survey scores.

RESULTS

A total of 2430 (MEPS) and 5490 (NAMCS and NHAMCS) respondents were identified, corresponding to weighted populations of 22 996 526 (MEPS) and 65 502 344 (NAMCS and NHAMCS) noninstitutionalized elderly individuals with dementia (mean [SD] age, 81.06 [1.13] years; 63.1% female). In the MEPS sample, compared with before 2005, AAP use (from an annual slope of 0.99 to -0.18 percentage points), cerebrovascular events (0.75 to -0.50 percentage points), and falls and/or fractures (-1.72 to -0.40 percentage points) decreased and opioid use (0.04 to 1.29 percentage points), antiepileptic use (-0.42 to 1.21 percentage points), cardiovascular events (-0.13 to 1.30 percentage points), and 2-year mortality risk (-0.68 to 0.18 percentage points) increased. Health-related quality of life remained relatively unchanged. The NAMCS and NHAMCS sample yielded similar findings.

CONCLUSIONS AND RELEVANCE

These data suggest that the 2005 FDA boxed warning was associated with some unintended negative patient outcomes.

The Role of Norepinephrine and Its α-Adrenergic Receptors in the Pathophysiology and Treatment of Major Depressive Disorder and Schizophrenia: A Systematic Review

Norepinephrine (NE) is recognized as having a key role in the pathophysiology of major depressive disorder (MDD) and schizophrenia, although its distinct actions via α-adrenergic receptors (α-ARs) are not well defined. We performed a systematic review examining the roles of NE and α-ARs in MDD and schizophrenia. PubMed and ProQuest database searches were performed to identify English language papers published between 2008 and 2015. In total, 2,427 publications (PubMed, n = 669; ProQuest, n = 1,758) were identified. Duplicates, articles deemed not relevant, case studies, reviews, meta-analyses, preclinical reports, or articles on non-target indications were excluded. To limit the review to the most recent data representative of the literature, the review further focused on publications from 2010 to 2015, which were screened independently by all authors. A total of 16 research reports were identified: six clinical trial reports, six genetic studies, two biomarker studies, and two receptor studies. Overall, the studies provided indirect evidence that α-AR activity may play an important role in aberrant regulation of cognition, arousal, and valence systems associated with MDD and schizophrenia. Characterization of the NE pathway in patients may provide clinicians with information for more personalized therapy of these heterogeneous diseases. Current clinical studies do not provide direct evidence to support the role of NE α-ARs in the pathophysiology of MDD and schizophrenia and in the treatment response of patients with these diseases, in particular with relation to specific valence systems. Clinical studies that attempt to define associations between specific receptor binding profiles of psychotropics and particular clinical outcomes are needed.

Hospital Readmission Rates Among Patients With Schizophrenia Treated With Long-Acting Injectables or Oral Antipsychotics

OBJECTIVE

This study analyzed hospital readmission rates of patients with schizophrenia who were treated with long-acting injectable antipsychotics (LAIs) or with oral antipsychotics after being discharged from a hospitalization.

METHODS

Medical claims of patients with schizophrenia who were ages 18-64 and had a first hospitalization for a serious mental illness (index hospitalization, October 2007 through September 2012) and at least one prescription for a first- or second-generation antipsychotic were analyzed from the Truven Health MarketScan Multi-State Medicaid Database. Analyses were conducted for patients with a sole diagnosis of schizophrenia (N=1,450) and for all patients with schizophrenia (N=15,556), which added patients with a codiagnosis of bipolar disorder or major depressive disorder. Probability of rehospitalization for any cause at 30 and 60 days after the initial hospitalization was assessed with multivariate logistic regression and propensity score matching (PSM) methods. The PSM model matched age, preindex use of LAIs or short-acting injectables, and select comorbidities between the LAI and the oral antipsychotics groups.

RESULTS

LAIs were associated with significantly lower probability of rehospitalization compared with oral antipsychotics at 60 days for schizophrenia-only patients (adjusted odds ratio [AOR]=.60, 95% confidence interval [CI]=.41-.90) and for all patients (AOR=.70, CI=.52-.95). The absolute difference in probability of rehospitalization for all patients was significantly lower by 5.0% at 60 days in the LAI group compared with the oral antipsychotics group.

CONCLUSIONS

Compared with use of oral antipsychotics, use of LAIs was associated with fewer readmissions of Medicaid patients with schizophrenia within 60 days after an index hospitalization.

Discovery of Novel Indoline Cholesterol Ester Transfer Protein Inhibitors (CETP) through a Structure-Guided Approach

Using the collective body of known (CETP) inhibitors as inspiration for design, a structurally novel series of tetrahydroquinoxaline CETP inhibitors were discovered. An exemplar from this series, compound 5, displayed potent in vitro CETP inhibition and was efficacious in a transgenic cynomologus-CETP mouse HDL PD (pharmacodynamic) assay. However, an undesirable metabolic profile and chemical instability hampered further development of the series. A three-dimensional structure of tetrahydroquinoxaline inhibitor 6 was proposed from (1)H NMR structural studies, and this model was then used in silico for the design of a new class of compounds based upon an indoline scaffold. This work resulted in the discovery of compound 7, which displayed potent in vitro CETP inhibition, a favorable PK-PD profile relative to tetrahydroquinoxaline 5, and dose-dependent efficacy in the transgenic cynomologus-CETP mouse HDL PD assay.

Long-term outcomes of antipsychotic treatment in patients with first-episode schizophrenia: a systematic review

BACKGROUND

Treatment during first-episode psychosis (FEP) or early schizophrenia may affect the rates of relapse and remission, as well as cognitive functioning, over time. Prolonged duration of psychosis is associated with a poor prognosis, but the effects of treatment in patients with FEP or early schizophrenia on the long-term outcomes are not well defined.

OBJECTIVE

To understand the long-term effects of treatment with antipsychotic agents on remission, relapse, and cognition in patients with FEP or early schizophrenia.

METHODS

Using PubMed and Scopus databases, a systematic review was undertaken of articles published between January 1, 2000, and May 20, 2015, that reported randomized and nonrandomized prospective clinical trials on the long-term effects of oral or long-acting injectable antipsychotics on measures of relapse, remission, or cognition in patients with FEP or early schizophrenia. For comparative purposes, trials reporting the effects of later intervention with antipsychotics in patients with longer disease history were also evaluated. Titles, abstracts, and full-text articles were independently screened for eligibility by all the authors based on the predefined criteria.

RESULTS

Nineteen studies met inclusion criteria: 13 reported long-term outcomes of relapse, remission, or cognition following antipsychotic treatment in patients with FEP and six reported on patients with a longer disease history. Antipsychotic treatment in patients with FEP produced high rates of remission in the year following treatment initiation, and untreated FEP reduced the odds of later achieving remission. Maintenance therapy was more effective than treatment discontinuation or intermittent/guided discontinuation in preventing relapse. Initiating antipsychotic treatment in patients with FEP also produced sustained cognitive improvement for up to 2 years. Antipsychotic therapy also reduced the risk or rate of relapse in patients with a longer disease history, with outcomes in one study favoring a long-acting injectable formulation over an oral antipsychotic.

CONCLUSION

Treatment of patients with FEP is associated with benefits in the long-term outcomes of remission, relapse, and cognition. More long-term studies of treatment in patients with FEP are needed to confirm these findings.

Identification of novel cannabinoid CB1 receptor antagonists by using virtual screening with a pharmacophore model

CB1 receptor antagonists have proven to be clinically effective in treating obesity and related disorders. We report here the identification of a novel class of azetidinone CB1 antagonists by using virtual screening methods. For this purpose, we developed a pharmacophore model based on known representative CB1 antagonists and employed it to screen a database of about a half million Schering-Plough compounds. We applied a stepwise filtering protocol based on molecular weight, compound availability, and a modified rule-of-five to reduce the number of hits. We then combined Bayesian modeling and clustering techniques to select a final set of 420 compounds for in vitro testing. Five compounds were found to have >50% inhibition at 100 nM in a CB1 competitive binding assay and were further characterized by using both CB1 and CB2 assays. The most potent compound has a CB1 K i of 53 nM and >5-fold selectivity against the CB2 receptor.

Cyclobutane derivatives as potent NK1 selective antagonists

A series of novel cyclobutane derivatives as potent and selective NK1 receptor antagonists is described. Several compounds in this series exhibited high in vitro binding affinity (Ki <or=1 nM), and potent inhibition of central NK1 receptor following oral administration. Syntheses of these compounds are also described herein.

Cyclic urea derivatives as potent NK1 selective antagonists. Part II: Effects of fluoro and benzylic methyl substitutions

A series of novel five-membered urea derivatives as potent NK1 receptor antagonists is described. The effects of substitution of a 4-fluoro group at the phenyl ring and the introduction of an alpha-methyl group at the benzylic position to improve potency and duration of in vivo activity are discussed. Several compounds with high affinity and sustained in vivo activity were identified.

Cyclic urea derivatives as potent NK1 selective antagonists

A series of novel five- and six-membered ring urea derivatives have been described as potent and selective NK1 receptor antagonists. Several compounds in this series exhibited good oral activity and brain penetration. Syntheses of these compounds are also described herein.

Potential therapeutic targets for neurokinin-1 receptor antagonists

The peptide substance P and its tachykinin receptor, neurokinin-1 (NK1), have been the focus of considerable research for their role in a variety of both central and peripheral diseases. Recent preclinical data, as well as relevant clinical findings, support the potential therapeutic value of NK1 receptor antagonists in centrally mediated disease states, including anxiety and depression. In addition, a separate body of literature supports the use of NK1 receptor antagonists as inhibitors of centrally mediated emetic and cough responses. The role of NK1 receptor antagonists as analgesic agents with potential to treat migraine headache has also been investigated. NK1 receptors are also found in a number of peripheral regions, including the bladder, gastrointestinal tract and bone marrow. Preclinical models have been employed to address the potential therapeutic uses for NK1 receptor antagonists in diseases associated with inflammatory responses, including asthma, irritable bowel syndrome and cystitis of the bladder. Finally, other more recent publications suggest a role for NK1 receptor antagonists as tumour suppressants and haematopoietic agents. These applications for NK1 receptor antagonists are discussed in this review.

Identification of single-nucleotide polymorphisms of the human neurokinin 1 receptor gene and pharmacological characterization of a Y192H variant

Neurokinin receptors in the central nervous system are involved in the neural circuitry of anxiety, depression and emesis. This has led to the development of nonpeptidic NK1 receptor antagonists as therapeutic agents. Clinical trials have shown that NK1 receptor antagonists have efficacy in chemotherapy-induced emesis and depression. Sequence polymorphisms can potentially influence the efficacy of drugs in patient populations and are an important consideration in the drug development process. To identify DNA sequence variants in the NK1 receptor, comparative DNA sequencing was performed on a population of 93 individuals. In total, 19 single-nucleotide polymorphisms (SNPs) were identified with one SNP (g.78351T>C) resulting in a tyrosine to histidine substitution at residue 192 (Y192H). The Y192H variant was expressed using site-directed mutagenesis and was characterized with respect to affinity, receptor kinetics, functional calcium response and receptor internalization. In all cases the Y192H variant was found to display properties similar to those of the wild-type receptor.

Isopropyl amide derivatives of potent and selective muscarinic M2 receptor antagonists

Low molecular weight amide derivatives were synthesized and evaluated as M(2) receptor antagonists for the treatment of Alzheimer's disease. Isopropyl amides 19 and 31 are highly potent, selective and low molecular weight M(2) receptor antagonists with structural features different from our clinical candidate 1.

Muscarinic M2 antagonists: anthranilamide derivatives with exceptional selectivity and in vivo activity

Anthranilamide analogues such as 23 are potent and highly selective muscarinic M2 antagonists that also show good oral bioavailability and in vivo activity.

Centrally administered hemokinin-1 (HK-1), a neurokinin NK1 receptor agonist, produces substance P-like behavioral effects in mice and gerbils

Hemokinin-1 (HK-1) is a recently described mouse tachykinin peptide whose biological functions are not fully understood. To date, a unique receptor for HK-1 has not been identified. Recent studies suggest HK-1 may have a role in immunological functions, but there has been little characterization of HK-1's effects in the central nervous system (CNS). In the present studies, we confirm that HK-1 is an endogenous agonist at all of the known tachykinin receptors, and is selective for the NK1 receptor over the NK2 and NK3 subtypes. CHO cells transfected with the human NK1 receptor released intracellular calcium in response to HK-1. In addition, HK-1 competed with substance P (SP) for binding to mouse NK1 and human NK1 receptors. In vivo central administration of HK-1 to gerbils and mice induced foot-tapping and scratching behaviors, respectively, similar to those observed following central administration of SP or the NK1 receptor agonist, GR-73632. Furthermore, these behavioral effects were blocked by the selective NK1 receptor antagonist, MK-869. Finally, a comprehensive expression analysis of HK-1 demonstrated that HK-1 mRNA is much more broadly expressed than previously reported with expression observed in many brain regions. Together these data demonstrate that HK-1 is a functional agonist at NK1 receptors and suggest that HK-1 may function both centrally and peripherally.

Improving the oral efficacy of CNS drug candidates: discovery of highly orally efficacious piperidinyl piperidine M2 muscarinic receptor antagonists

In search of a backup M(2) muscarinic receptor antagonist to the previously reported compound 1, we discovered compound (+)-14, which showed superior oral efficacy in animal models. The improvement of oral efficacy was achieved by modulating both the molecular weight and lipophilicity of the lead compounds.

Enhancement of pharmacokinetic properties and in vivo efficacy of benzylidene ketal M(2) muscarinic receptor antagonists via benzamide modification

We previously reported the initial discovery of a novel class of stabilized benzylidene ketal M(2) receptor antagonists. This paper discusses new analogues consisting of benzamide modifications which not only improved M(2) receptor affinity and selectivity, but also enhanced the pharmacokinetic properties of the series. These changes led to the discovery of a highly potent and selective M(2) antagonist, which demonstrated in vivo efficacy and had good bioavailability in multiple species.

The gerbil elevated plus-maze II: anxiolytic-like effects of selective neurokinin NK1 receptor antagonists

Neurokinin NK1 receptor antagonists may have therapeutic potential in the treatment of anxiety and depression. Species variants in the NK1 receptor result in reduced affinity of NK1 receptor antagonists at rat and mouse NK1 receptors, making it difficult to test NK1 antagonists in traditional preclinical models of anxiety and depression. Gerbil NK1 receptors are similar in homology to the human NK1 receptor. In a companion article, we described the anxiety-like behavioral profile of gerbils on an adapted elevated plus-maze, and the ability of anxiolytic drugs to produce anti-anxiety effects in the gerbil elevated plus-maze. The aim of the present study was to determine whether oral (p.o.) administration of the NK1 receptor antagonists MK-869, L-742,694, L-733,060, CP-99,994, and CP-122,721 produced anxiolytic-like effects in the gerbil elevated plus-maze. Upon testing, all five NK1 antagonists produced anxiolytic-like effects. MK-869 (0.01-3 mg/kg) was the most potent NK1 antagonist, producing anxiolytic-like effects on percentage of open arm time, percentage of open arm entries, stretch-attend postures, and head dips at 0.03-0.3 mg/kg doses. L-742,694 (1-30 mg/kg) and L-733,060 (1-10 mg/kg) produced anxiolytic-like effects on percentage of open arm time and stretch-attend postures at 3-10 mg/kg doses. CP-99,994 (3-30 mg/kg) only produced an anxiolytic-like effect on stretch-attend postures. CP-122,721 (3-30 mg/kg) produced an anxiolytic-like effect on percentage of open arm time at 30 mg/kg. The order of potency of the NK1 antagonists to increase percentage of open arm time was very similar to their potency to block NK1 agonist-induced foot-tapping. These studies demonstrate that neurokinin NK1 receptor antagonists produce anxiolytic-like effects in a novel gerbil elevated plus-maze, and suggest that this is an appropriate model to test NK1 antagonists for preclinical anxiolytic activity.

Correlation of neurokinin (NK) 1 receptor occupancy in gerbil striatum with behavioral effects of NK1 antagonists

Interest in central neurokinin (NK) 1 receptors has increased based on reports of the therapeutic potential for NK1 antagonists in anxiety and depression. In these studies, an ex vivo binding procedure was used to correlate NK1 receptor occupancy in striatum by NK1 antagonists with their potency to inhibit NK1 agonist-induced foot tapping in gerbils (GFT). The following compounds were administered orally: CP-99,994 [(+)-cis-n-[(2-methoxyphenyl)methyl]-2-phenyl-3-piperidinamine), L-742,694 [5-[[2(S)-[[3,5-bis(trifluoromethyl)phenyl]methoxy]-3(S)-phenyl-4-morpholinyl]methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one]), MK-869 [5-[[2(R)-[1(R)-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3(S)-(4-fluorophenyl)-4-morpholinyl]methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one], CP-122,721 [cis-n-[[2-methoxy-5-(trifluoromethoxy)phenyl]methyl]-2-phenyl-3-piperidinamine], L-760,735-F [4-[[2(R)-[1(R)-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3(S)-(4-fluorophenyl)-4-morpholinyl]methyl]-N,N-dimethyl-1H-1,2,3-triazole-5- methanamine], GR205171 [N-[[2-methoxy-5-[5-(trifluoromethyl)-1H-tetrazol-1-yl]phenyl]methy]-2(S)-phenyl-3(S)-piperidinamine], L-733,060 [(2S,3S)3-([3,5-bis(trifluoro methyl)phenyl]methoxy)-2-phenylpiperidine], and L-733,061 [(2R,3R)-3-([3,5-bis(trifluoromethyl)phenyl]methoxy)-2-phenylpiperidine]. Two hours later, gerbils received the NK1 agonist GR73632 [H(2)N-(CH(2))(4)-CO-Phe-Pro-NMe-Leu-Met-NH(2)] i.c.v. and foot tapping was measured for 5 min. The same procedure was used for ex vivo binding studies except that saline, rather than agonist, was administered i.c.v. before dissection of the striatum. The tissue homogenate was then used in an equilibrium radioligand binding assay. When IC(50) values for inhibition of ex vivo (125)I-substance P binding by NK1 antagonists were compared with the corresponding EC(50) values for inhibition of GFT, a significant positive correlation was observed (r(2) = 0.97, p < 0.001). This result indicates that increased NK1 receptor occupancy in striatum by NK1 antagonists parallels the inhibition of agonist-mediated GFT. For all compounds, the dose that produced the maximum inhibition of GFT resulted in less than 100% ex vivo receptor occupancy in striatum. When gerbils did not receive the i.c.v. saline injection before ex vivo binding, thereby leaving the blood-brain barrier (BBB) intact, the IC(50) values for antagonists were unchanged, suggesting that potential damage to the BBB caused by the i.c.v. injection did not affect determinations of antagonist potency in the GFT model.

Sulfide analogues as potent and selective M(2) muscarinic receptor antagonists

We have discovered highly potent, selective sulfide M(2) receptor antagonists with low molecular weight and different structural features compared with our phase I clinical candidate Sch 211803. Analogue 30 showed superior M(2) receptor selectivity profile over Sch 211803. More importantly, this study provided new leads for the discovery of M(2) receptor antagonists as potential drug candidates.

Substituted 2-(R)-methyl piperazines as muscarinic M(2) selective ligands

A novel series of 2-(R)-methyl-substituted piperazines (e.g., 2) is described. They are potent M(2) selective ligands that have >100-fold selectivity versus the M(1) receptor. In the rat microdialysis assay, compound 14 showed significantly enchanced levels of acetylcholine after oral administration.

Synthesis and structure-activity relationships of M(2)-selective muscarinic receptor ligands in the 1-[4-(4-arylsulfonyl)-phenylmethyl]-4-(4-piperidinyl)-piperazine family

The synthesis and muscarinic binding properties of compounds based on the 1-[4-(4-arylsulfonyl)phenylmethyl]-4-(1-aroyl-4-piperidinyl)-piperazine skeleton are described. For compounds, substituted with appropriately configured methyl groups at the benzylic center and at the piperazine 2-position, high levels of selective, M(2) subtype affinity could be obtained, particularly when the terminal N-aroyl residue was ortho-substituted.

Metabolic stabilization of benzylidene ketal M(2) muscarinic receptor antagonists via halonaphthoic acid substitution

The potential toxicological liabilities of the M(2) muscarinic antagonist 1 were addressed by replacing the methylenedioxyphenyl moiety with a p-methoxyphenyl group, resulting in M(2) selective compounds such as 3. Several halogenated naphthamide derivatives of 3 were studied in order to improve the pharmacokinetic profile via blockage of oxidative metabolism. Compound 4 demonstrated excellent M(2) affinity and selectivity, human microsomal stability, and oral bioavailability in rodents and primates.

Facilitation of acetylcholine release and improvement in cognition by a selective M2 muscarinic antagonist, SCH 72788

Current treatment of Alzheimer's Disease (AD) requires acetylcholinesterase inhibition to increase acetylcholine (ACh) concentrations in the synaptic cleft. Another mechanism by which ACh levels can be increased is blockade of presynaptic M2 muscarinic autoreceptors that regulate ACh release. An antagonist designed for this purpose must be highly selective for M2 receptors to avoid blocking postsynaptic M1 receptors, which mediate the cognitive effects of ACh. Structure-activity studies of substituted methylpiperadines led to the synthesis of 4-[4-[1(S)-[4-[(1,3-benzodioxol-5-yl)sulfonyl]phenyl]ethyl]-3(R)-methyl-1-piperazinyl]-4-methyl-1-(propylsulfonyl)piperidine. This compound, SCH 72788, binds to cloned human M2 receptors expressed in CHO cells with an affinity of 0.5 nM, and its affinity at M1 receptors is 84-fold lower. SCH 72788 is a functional M2 antagonist that competitively inhibits the ability of the agonist oxotremorine-M to inhibit adenylyl cyclase activity. In an in vivo microdialysis paradigm, SCH 72788 increases ACh release from the striatum of conscious rats. The compound is also active in a rodent model of cognition, the young rat passive avoidance response paradigm. The effects of SCH 72788 suggest that M2 receptor antagonists may be useful for treating the cognitive decline observed in AD and other dementias.

Design and synthesis of ether analogues as potent and selective M2 muscarinic receptor antagonists

Novel, selective M2 muscarinic antagonists, which replace the metabolically labile styrenyl moiety of the prototypical M2 antagonist 1 with an ether linkage, were synthesized. A detailed SAR study in this class of compounds has yielded highly active compounds that showed M2 Ki values of < 1.0 nM and >100-fold selectivity against M1, M3, and M5 receptors.

Benzylidene ketal derivatives as M2 muscarinic receptor antagonists

Benzylidene ketal derivatives were investigated as selective M2 receptor antagonists for the treatment of Alzheimer's disease. Compound 10 was discovered to have subnanomolar M2 receptor affinity and 100-fold selectivity against other muscarinic receptors. Also, 10 demonstrated in vivo efficacy in rodent models of muscarinic activity and cognition.

Diphenyl sulfoxides as selective antagonists of the muscarinic M2 receptor

Structure activity studies on [4-(phenylsulfonyl)phenyl]methylpiperazine led to the discovery of 4-cyclohexyl-alpha-[4-[[4-methoxyphenyl(S)-sufinyl]phenyl]-1-pi perazineacetonitrile, 1, an M2 selective muscarinic antagonist. Affinity at the cloned human M2 receptor was 2.7 nM; the M1/M2 selectivity is 40-fold.

Design and synthesis of piperidinyl piperidine analogues as potent and selective M2 muscarinic receptor antagonists

Identification of a number of highly potent M2 receptor antagonists with >100-fold selectivity against the M1 and M3 receptor subtypes is described. In the rat microdialysis assay, this series of compounds showed pronounced enhancement of brain acetylcholine release after oral administration.

Diphenylsulfone muscarinic antagonists: piperidine derivatives with high M2 selectivity and improved potency

Piperidine analogues of our previously described piperazine muscarinic antagonists are described. Piperidine analogues show a distinct structure-activity relationship (SAR) that differs from comparable piperazines. Compounds with high selectivity and improved potency for the M2 receptor have been identified. The lead compound, 12b, increases acetylcholine release in vivo. Compounds of this class may be useful for the treatment of cognitive disorders such as Alzheimer's disease (AD).

In vivo autoradiography of [3H]SCH 39166 in rat brain: selective displacement by D1/D5 antagonists

The purpose of this study was to examine the receptor occupancy of D1/D5 antagonists for D1-like dopamine receptors in rat brain using [3H]SCH 39166, a highly selective D1/D5 antagonist with low affinity for 5HT2 receptors. A single concentration of triated SCH 39166 was administered to rats, with or without competing doses of the Dl/D5 antagonist SCH 23390 and unlabeled SCH 39166. the D2-like antagonists haloperidol or the 5-HT, antagonist ketanserin. The bound radioactivity in the cortex, striatum, nucleus accumbens and olfactory tubercle was then quantified using an in vivo autoradiographic procedure. The results indicated that [3H]SCH 39166 was dose dependently displaced by the Dl/D5 antagonists in regions associated with both the nigro-striatal pathway and the mesolimbic dopamine pathway, particularly the nucleus accumbens. Neither haloperidol nor ketanserin displaced [3H]SCH 39166 in any of the regions examined. The data were compared with previously published data examining the in vivo binding of [3H]SCH 39166 in rat brain homogenates. The relative values obtained were comparable to values detected in rat brain homogenates after in vivo binding of [3H]SCH 39166.

SCH 57790: a novel M2 receptor selective antagonist

As a decrease in cholinergic neurons has been observed in Alzheimer's Disease (AD), therapeutic approaches to AD include inhibition of acetylcholinesterase to increase acetylcholine levels. Evidence suggests that acetylcholine release in the CNS is modulated by negative feedback via presynaptic M2 receptors, blockade of which should provide another means of increasing acetylcholine release. Structure-activity studies of [4-(phenylsulfonyl)phenyl]methylpiperazines led to the synthesis of 4-cyclohexyl-alpha-[4-[[4-methoxyphenyl]sulfinyl]-phenyl]-1-piperazin eacetonitrile. This compound, SCH 57790, binds to cloned human M2 receptors expressed in CHO cells with an affinity of 2.78 nM; the affinity at M1 receptors is 40-fold lower. SCH 57790 is an antagonist at M2 receptors expressed in CHO cells, as the compound blocks the inhibition of adenylyl cyclase activity mediated by the muscarinic agonist oxotremorine. This compound should be useful in assessing the potential of M2 receptor blockade for enhancement of cognition.

Characterization of the binding of SCH 39166 to the five cloned dopamine receptor subtypes

Characterization studies were conducted on the five cloned dopamine receptor subtypes (D1-D5) using the novel D1-selective antagonist, SCH 39166, as well as other related benzazepines and dopaminergic agents. The results demonstrate that SCH 39166 exhibits saturable, high-affinity binding to the D1 and D5 receptors, but binds with low affinity to the D2, D3, and D4 receptors. In contrast, the D2 antagonist haloperidol showed low affinity for the "D1-like" receptors and high affinity for the "D2-like" receptors. A series of agonists was also evaluated and the D5 receptor subtype displayed a two-site fit for the endogenous agonist dopamine, as well as for the agonist apomorphine. Differences in agonist binding among the D1-like receptors reflect the importance of the nonconserved amino acid substitutions.

In vivo binding to dopamine receptors: a correlate of potential antipsychotic activity

Antagonists of dopamine receptors (especially those of the D2 subtype) have long been recognized as effective antipsychotics. SCH 39166, a dopamine D1 selective antagonist, is now also being evaluated for its clinical antipsychotic properties. The studies described herein determine the binding affinity of a variety of dopamine receptor antagonists (both dopamine D1 and D2 selective compounds) for the dopamine D1 and D2 receptors, in vivo, and correlate this affinity with their behavioral activity in the rat conditioned avoidance response (CAR) test. The in vivo binding affinities of the D1 selective compounds at the dopamine D1 site exhibited a high correlation (r = 0.97) with their activities in the rat CAR test. Likewise, D2 selective compounds' inhibition of in vivo binding to dopamine D2 receptors correlated with their behavioral potencies (r = 0.98). Conversely, any binding of selective agents to their non-targeted receptor did not correlate with their behavioral activity. These data suggest that in vivo binding to either dopamine D1 and/or D2 receptors is predictive of potential antipsychotic efficacy.

Selective up-regulation of D-1 dopamine receptors following chronic administration of SCH 39166 in primates

Caudate, putamen and frontal cortex tissues were obtained from rhesus monkeys that had taken part in a toxicology study required by the Food and Drug Administration. These monkeys had received daily oral treatments of SCH 39166 at three different doses (3, 12 and 48 mg/kg) for three consecutive months. Plasma membranes from the caudate and putamen were analyzed for changes in D-1 and D-2 receptor affinity and number using saturation analyses of 3H-SCH 23390 and 3H-spiperone binding, respectively. Saturation studies were performed on membranes from the frontal cortex using 3H-ketanserin to determine if 5HT2 receptor number or affinity were affected by chronic treatment with SCH 39166. Results indicate a significant, dose-dependent up-regulation of D-1 receptor number in both caudate and putamen, with no changes in either D-2 receptors in the striatal regions or 5HT2 receptors in the frontal cortex. These data, therefore, indicate that SCH 39166 is a selective antagonist at D-1 receptors in the CNS of nonhuman primates.

[3H]SCH 39166, a new D1-selective radioligand: in vitro and in vivo binding analyses

SCH 39166 [(-)-trans-6,7,7a,8,9, 13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H-benzo-[d]naphtho[2, 1b]azepine] has recently been described as a selective D1 antagonist and has entered clinical trials for the treatment of schizophrenia. The tritiated analogue of this compound, [3H]SCH 39166, has now been synthesized and characterized for its in vitro and in vivo binding profiles. [3H]SCH 39166 binds to D1 receptors in a saturable, high-affinity fashion, with a KD of 0.79 nM. In competition studies, D1-selective antagonists like SCH 23390 displaced the binding of [3H]SCH 39166 with nanomolar affinities, whereas antagonists of other receptors exhibited poor affinity. In vivo, [3H]SCH 39166 bound to receptors in rat striatum in a fashion suggestive of D1 selectivity. Further, when the time course for the binding of [3H]SCH 39166 was compared with the behavioral time course of the unlabeled compound, the two durations of action were virtually indistinguishable. Similar studies were performed for SCH 23390 and its tritiated analogue, but the in vivo binding of this radioligand exhibited a duration of action far greater than the behavioral activity of the unlabeled drug. In concert, these data demonstrate that [3H]SCH 39166 selectively labels D1 receptors in vitro and in vivo, and that this drug is superior for in vivo imaging of the D1 receptor.

In vivo binding of SCH 39166: a D-1 selective antagonist

SCH 39166 [(-)-trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxy-N-methyl- 5H-benzo[d]naphtho-[2,1b]-azepine] has been identified previously as a potent and selective D-1 antagonist. These studies demonstrated that SCH 39166 binds to the D-1 receptor in vitro and inhibits the rat conditioned avoidance response, a test predictive of antipsychotic activity. The current study demonstrates that SCH 39166 inhibits the in vivo binding of [125I]SCH 38840 to D-1 receptors in rat striatal tissue with an ED50 of 11.67 nmol/animal or 0.016 mg/kg s.c. SCH 39166 did not inhibit the in vivo binding of [125I]SCH 38840 to rat frontal cortex, suggesting that, unlike other D-1 antagonists, SCH 39166 was not binding to 5-hydroxytryptamine (5-HT)2 receptors in vivo. The in vivo binding of SCH 39166 to D-2 receptors was studied using [3H]raclopride and demonstrated that SCH 39166 did not bind to D-2 receptors up to doses of 100 mumol/animal or approximately 150 mg/kg s.c. Further studies to determine the in vivo selectivity of SCH 39166 utilized N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) to inactivate selected neurotransmitter receptors. Preadministration of SCH 39166, at doses as low as 0.01 mg/kg s.c., produced a statistically significant protection of D-1 receptors from EEDQ inactivation. SCH 39166 produced a similar protection of 5-HT2 receptors only at the highest dose tested, 10 mg/kg s.c., whereas there was no protection of D-2 sites even at this high dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Serotonergic component of SCH 23390: in vitro and in vivo binding analyses

A series of benzazepines related to SCH 23390 were tested for binding to the 5HT-2 receptor. The compounds tested inhibited the binding of 3H-ketanserin with KI values generally greater than those observed for the D-1 receptor, but less than those for the D-2 receptor. When this serotonergic activity was correlated to the D-1 activity, the resulting coefficient was 0.84, indicating a strong correlation between the two activities. Conversely, the 5HT-2 activity did not show a good correlation with the D-2 activity. To further test the significance of the 5HT-2 binding of the SCH 23390, in vivo binding studies were performed using 125I-SCH 38840 in the frontal cortex, an area containing both D-1 and 5HT-2 receptors. The in vivo binding of 125I-SCH 38840 to frontal cortex exhibited peak levels one hour following subcutaneous administration, similar to the time course previously observed in striatum. The binding was both D-1 and tissue specific. Competition studies with selected standards demonstrated that inhibition of the binding to frontal cortex, in contrast to the inhibition observed in the striatum, exhibited a Hill coefficient less than unity, implying interaction at more than one receptor subtype. When SCH 23390 and ketanserin were administered simultaneously, the inhibition of the in vivo binding of 125I-SCH 38840 to striatum was not different than that observed with SCH 23390, alone. However, the inhibition of binding to frontal cortex was significantly greater than that demonstrated with either SCH 23390 or ketanserin, alone, suggesting that 125I-SCH 38840 was binding to both D-1 and 5HT-2 receptors, in vivo.