Mechanism of Action and Clinical Application of Tafamidis in Hereditary Transthyretin Amyloidosis.

Transthyretin (TTR) transports the retinol-binding protein-vitamin A complex and is a minor transporter of thyroxine in blood. Its tetrameric structure undergoes rate-limiting dissociation and monomer misfolding, enabling TTR to aggregate or to become amyloidogenic. Mutations in the TTR gene generally destabilize the tetramer and/or accelerate tetramer dissociation, promoting amyloidogenesis. TTR-related amyloidoses are rare, fatal, protein-misfolding disorders, characterized by formation of soluble aggregates of variable structure and tissue deposition of amyloid. The TTR amyloidoses present with a spectrum of manifestations, encompassing progressive neuropathy and/or cardiomyopathy. Until recently, the only accepted treatment to halt progression of hereditary TTR amyloidosis was liver transplantation, which replaces the hepatic source of mutant TTR with the less amyloidogenic wild-type TTR. Tafamidis meglumine is a rationally designed, non-NSAID benzoxazole derivative that binds with high affinity and selectivity to TTR and kinetically stabilizes the tetramer, slowing monomer formation, misfolding, and amyloidogenesis. Tafamidis is the first pharmacotherapy approved to slow the progression of peripheral neurologic impairment in TTR familial amyloid polyneuropathy. Here we describe the mechanism of action of tafamidis and review the clinical data, demonstrating that tafamidis treatment slows neurologic deterioration and preserves nutritional status, as well as quality of life in patients with early-stage Val30Met amyloidosis.

Report on ISCTM Consensus Meeting on Clinical Assessment of Response to Treatment of Cognitive Impairment in Schizophrenia.

If treatments for cognitive impairment are to be utilized successfully, clinicians must be able to determine whether they are effective and which patients should receive them. In order to develop consensus on these issues, the International Society for CNS Clinical Trials and Methodology (ISCTM) held a meeting of experts on March 20, 2014, in Washington, DC. Consensus was reached on several important issues. Cognitive impairment and functional disability were viewed as equally important treatment targets. The group supported the notion that sufficient data are not available to exclude patients from available treatments on the basis of age, severity of cognitive impairment, severity of positive symptoms, or the potential to benefit functionally from treatment. The group reached consensus that cognitive remediation is likely to provide substantial benefits in combination with procognitive medications, although a substantial minority believed that medications can be administered without nonpharmacological therapy. There was little consensus on the best methods for assessing cognitive change in clinical practice. Some participants supported the view that performance-based measures are essential for measurement of cognitive change; others pointed to their cost and time requirements as evidence of impracticality. Interview-based measures of cognitive and functional change were viewed as more practical, but lacking validity without informant involvement or frequent contact from clinicians. The lack of consensus on assessment methods was viewed as attributable to differences in experience and education among key stakeholders and significant gaps in available empirical data. Research on the reliability, validity, sensitivity, and practicality of competing methods will facilitate consensus.

Randomized, Double-Blind, Placebo-Controlled Study of Encenicline, an α7 Nicotinic Acetylcholine Receptor Agonist, as a Treatment for Cognitive Impairment in Schizophrenia.

Encenicline is a novel, selective α7 nicotinic acetylcholine receptor agonist in development for treating cognitive impairment in schizophrenia and Alzheimer's disease. A phase 2, double-blind, randomized, placebo-controlled, parallel-design, multinational study was conducted. Patients with schizophrenia on chronic stable atypical antipsychotics were randomized to encenicline 0.27 or 0.9 mg once daily or placebo for 12 weeks. The primary efficacy end point was the Overall Cognition Index (OCI) score from the CogState computerized battery. Secondary end points include MATRICS Consensus Cognitive Battery (MCCB) (in US patients), the Schizophrenia Cognition Rating Scale (SCoRS) total score, SCoRS global rating, and Positive and Negative Syndrome Scale (PANSS) total and subscale and cognition factor scores. Of 319 randomized patients, 317 were included in the safety population, and 307 were included in the intent-to-treat population. Notable trends in improvement were demonstrated across all cognition scales. For the OCI score, the LS mean difference for encenicline 0.27 mg vs placebo was significant (Cohen's d=0.257; P=0.034). Mean SCoRS total scores decreased showing improvement in function over time, and the difference was significant for encenicline 0.9 mg vs placebo (P=0.011). Furthermore, the difference between encenicline 0.9 mg and placebo was significant for the PANSS Cognition Impairment Domain (P=0.0098, Cohen's d=0.40) and for the PANSS Negative scale (P=0.028, Cohen's d=0.33). Treatment-emergent adverse events were reported at similar frequencies across all treatment groups (39.0% with placebo, 23.4% with encenicline 0.27 mg, and 33.3% with encenicline 0.9 mg). Overall, encenicline was generally well tolerated and demonstrated clinically meaningful improvements in cognition and function in patients with schizophrenia.

Tafamidis in transthyretin amyloid cardiomyopathy: effects on transthyretin stabilization and clinical outcomes.

BACKGROUND: Transthyretin (TTR) amyloidosis is a progressive systemic disorder caused by misfolded TTR monomers that cumulatively deposit in the heart and systemically as amyloid. METHODS AND RESULTS: This phase 2 open-label trial evaluated the stabilization of TTR tetramers using 20 mg of tafamidis daily at week 6 (primary end point), month 6, and month 12, as well as safety of tafamidis treatment and efficacy with respect to progression of TTR amyloid cardiomyopathy. Thirty-one wild-type patients (median age, 76.7 years; 93.5% men) with a median disease duration of 55.6 months and mild to moderate heart failure (96.8%; New York Heart Association, classes I-II) were enrolled. Thirty of 31 patients (96.8%) achieved TTR stabilization after 6 weeks and 25 of 28 patients (89.3%) after 12 months. After 12 months of treatment, 3 patients discontinued prematurely, 2 patients died, 7 patients were hospitalized because of cardiovascular events, 20 of 28 patients demonstrated preserved New York Heart Association classification status, but 15 of 31 (48.4%) patients had clinical progression (eg, admission for cardiac failure, atrial fibrillation, and syncope). N-terminal prohormone brain natriuretic peptide levels did not increase significantly over time, troponin I and troponin T increased moderately, and no consistent clinically relevant changes were seen in echocardiographic cardiac assessments. Tafamidis treatment was generally well tolerated although 7 of 31 patients had bouts of diarrhea. CONCLUSIONS: Tafamidis treatment effectively achieved and maintained TTR stabilization and was well tolerated. The absence of significant changes in most biochemical and echocardiographic parameters suggests that further evaluation of tafamidis in TTR amyloid cardiomyopathy is warranted. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00694161.

Two 6-week, randomized, double-blind, placebo-controlled studies of ziprasidone in outpatients with bipolar I depression: did baseline characteristics impact trial outcome?

Two randomized, double-blind, placebo-controlled, 6-week studies comparing ziprasidone versus placebo for treatment of bipolar depression (BPD) failed to meet their primary study objectives, indicating that either ziprasidone is ineffective in the treatment of BPD or the study failed. Adult outpatients with bipolar I depression with 17-item Hamilton Rating Scale for Depression total score more than 20 at screening and baseline received either ziprasidone 40 to 80 mg/d, 120 to 160 mg/d, or placebo (study 1), or ziprasidone 40 to 160 mg/d or placebo (study 2). Primary efficacy measure in both studies was change from baseline in Montgomery-Åsberg Depression Rating Scale total scores at week 6 (end of the study). Mixed-model repeated-measures methodology was used to analyze the primary efficacy measure in both studies. Secondary efficacy measures in both studies included Hamilton Rating Scale for Depression total score and Clinical Global Impression-Improvement score. Post hoc analyses were conducted for both studies to examine potential reasons for study failure. In both, ziprasidone treatment groups failed to separate statistically from placebo for change from baseline Montgomery-Åsberg Depression Rating Scale score at week 6. Response rates were 49%, 53%, and 46% for placebo, ziprasidone 40 to 80 mg/d, and ziprasidone 120 to 160 mg/d, respectively (study 1), and 51% and 53% for placebo and ziprasidone 40 to 160 mg/d, respectively (study 2). Ziprasidone 40 to 160 mg/d did not show superiority over placebo at week 6 in the treatment of BPD. Post hoc analyses revealed serious inconsistencies in subject rating that may have limited the ability to detect a difference between drug and placebo response. Rating reliability warrants further investigation to improve clinical trial methodology in psychiatry.

Impact of geographical and cultural factors on clinical trials in acute mania: lessons from a ziprasidone and haloperidol placebo-controlled study.

Clinical trials today are conducted in multiple countries to enhance patient recruitment and improve efficiency of trials. However, the demographic and cultural diversity may contribute to variations in study outcomes. Here we conducted post-hoc analyses for a placebo-controlled study with ziprasidone and haloperidol for the treatment of acute mania to address the demographic, dosing, and outcome disparities in India, Russia and the USA. We compared the baseline characteristics, outcomes and discontinuations in patients and explored the relationship between the outcome measures across these countries. We found substantial differences in baseline characteristics of subjects, administered dosage and disease severity in India compared to the USA and Russia. Conversely, US subjects had a higher placebo response compared to subjects in Russia and India. These results are probably due to demographic differences in patient populations and psychiatric clinical practice across countries. While we offer initial ideas to address the disparities identified in this analysis, it is clear that further research to improve our understanding of geographical differences is essential to ensure globally applicable results for clinical trials in psychiatry.

Measurement of the serotonin 1A receptor availability in patients with schizophrenia during treatment with the antipsychotic medication ziprasidone.

The aim of this study was to compare 5-HT(1A) availability in vivo in individuals with schizophrenia before and during treatment with the atypical antipsychotic ziprasidone. Six individuals with schizophrenia underwent two PET scans with [(11)C]WAY 100635; the first while medication-free (baseline) and the second while taking the atypical antipsychotic ziprasidone (on-medication). Regional volumes of distribution (V(T), mL g(-1)) were derived using a two-tissue compartment kinetic model. Outcome measures included binding potential relative to the plasma (BP(P), mL g(-1)) and the binding potential relative to the nonspecific distribution volume (BP(ND), unitless). No significant differences were observed in regional BP(P) or BP(ND) with ziprasidone treatment. A significant correlation was noted between BP(P) measured in the orbitofrontal cortex during the on-medication condition and degree of improvement in negative symptoms with treatment (r = 0.96, p = 0.004). Consistent with the published literature of changes in 5-HT(1A) binding during treatment with 5-HT(1A) receptor agonists, this study did not detect a significant reduction in 5-HT(1A) binding with ziprasidone. The finding of a relationship between 5-HT(1A) binding and the degree of improvement in negative symptoms provides further support for the role of the 5-HT(1A) receptor in the pathophysiology and treatment of this symptom domain.

Findings of a U.S. national cardiometabolic screening program among 10,084 psychiatric outpatients.

OBJECTIVE: A national cardiometabolic screening program for patients in a variety of public mental health facilities, group practices, and community behavioral health clinics was funded by Pfizer Inc. between 2005 and 2008. METHODS: A one-day, voluntary metabolic health fair in the United States offered patients attending public mental health clinics free cardiometabolic screening and same-day feedback to physicians from a biometrics testing third party that was compliant with the Health Insurance Portability and Accountability Act. RESULTS: This analysis included 10,084 patients at 219 sites; 2,739 patients (27%) reported having fasted for over eight hours. Schizophrenia or bipolar disorder was self-reported by 6,233 (62%) study participants. In the overall sample, the mean waist circumference was 41.1 inches for men and 40.4 inches for women; 27% were overweight (body mass index [BMI] 25.0-29.9 kg/m(2)), 52% were obese (BMI >or=30.0 kg/m(2)), 51% had elevated triglycerides (>or=150 mg/dl), and 51% were hypertensive (>or=130/85 mm Hg). In the fasting sample, 52% had metabolic syndrome, 35% had elevated total cholesterol (>or=200 mg/dl), 59% had low levels of high-density lipoprotein cholesterol (<40 mg/dl for men or <50 mg/dl for women), 45% had elevated triglycerides (>or=150 mg/dl), and 33% had elevated fasting glucose (>or=100 mg/dl). Among the 1,359 fasting patients with metabolic syndrome, 60% were not receiving any treatment. Among fasting patients who reported treatment for specific metabolic syndrome components, 33%, 65%, 71%, and 69% continued to have elevated total cholesterol, low levels of high-density lipoprotein, high blood pressure, and elevated glucose levels, respectively. CONCLUSIONS: The prevalence of metabolic syndrome and cardiometabolic risk factors, such as overweight, hypertension, dyslipidemia, and glucose abnormalities, was substantial and frequently untreated in this U.S. national mental health clinic screening program.

Understanding the relationship between baseline BMI and subsequent weight change in antipsychotic trials: effect modification or regression to the mean?

The purpose of this study was to examine whether prior evidence of an inverse relationship between initial body weight and subsequent antipsychotic-induced weight change represents true effect modification or a statistical artifact, regression to the mean (RTM). We conducted a post-hoc analysis after pooling seven randomized, placebo- or active-controlled trials of ziprasidone and other antipsychotic agents. ANCOVA was applied to evaluate treatment-by-baseline body mass index (BMI) range interaction effect on weight change. Regression analysis was applied to estimate the potential bias due to RTM. Statistical interaction tests between baseline BMI ranges and treatment assignments (haloperidol, olanzapine, risperidone, or ziprasidone, versus placebo) were not significant within studies or across studies. Correlation between baseline and follow-up measurements of body weight in placebo-treated subjects was less than perfect (r=0.87, 6-month cohort), leading to RTM. Consistent with predictions based on RTM, the greatest weight change, on average, was observed in subgroups with baseline weights differing the most from the population mean. Our findings suggest that the previously observed correlation between baseline BMI and weight change subsequent to antipsychotic treatment reflects in part RTM, and not effect modification. This class of drugs appears to cause similar weight gain in both high and low baseline BMI groups.

Reduction of functional disability with atypical antipsychotic treatment: a randomized long term comparison of ziprasidone and haloperidol.

BACKGROUND: Recent interest has focused on the definition and measurement of clinical remission in people with schizophrenia. This study examined the process of development of "functional remission" in a long-term comparative double-blind study of haloperidol and the atypical antipsychotic medication ziprasidone. METHODS: Community dwelling patients with schizophrenia were randomized to treatment with haloperidol (n=47) or ziprasidone dosed either once or twice daily (n=139). They were re-examined at follow-up intervals that ranged up to 196 weeks. Their community functioning was examined with the Heinrichs-Carpenter Quality of Life Scale (QLS). Total scores for occupational and interpersonal functioning and achievement of improvement milestones across the individual items were both analyzed. RESULTS: Mixed model repeated measures analyses detected a significant (p<.05) treatment effect over time favoring ziprasidone for interpersonal functioning. While the mixed model was not significant for role functioning, the mean change at endpoint was significantly greater than 0 for the ziprasidone group but not the haloperidol group. Analyses of the distributions of change scores across the items showed that the number of items where endpoint scores were 5 or 6 (reflecting minimal to no impairment) was significantly higher in ziprasidone treated patients, (p=.03). IMPLICATIONS: Long term treatment with ziprasidone was associated with greater functional gains than treatment with haloperidol, even when the time course of dropout was controlled. Both treatment retention and functional gains favored the atypical treatment in this long-term study. Future long-term studies will be needed to clarify the determinants of these functional changes.

Metabolic risk status and second-generation antipsychotic drug selection: a retrospective study of commercially insured patients.

BACKGROUND: Routine metabolic screening and consideration of patient metabolic status in the choice of a second-generation antipsychotic (SGA) medication are recommended. This study evaluated the association between abnormal blood glucose and lipid values and SGA prescribing patterns. MATERIALS AND METHODS: A retrospective cohort study using administrative data from 2 managed care plans in the United States evaluated 7904 adults initiating SGA therapy between 2001 and 2004. Baseline serum glucose, total cholesterol, and triglyceride values were available for 989 patients (12.5%), and follow-up assessments were done in 699 patients (8.8%). Abnormal values were defined as the following: total cholesterol, 200 mg/dL or higher; triglycerides, 200 mg/dL or higher; and glucose, 126 mg/dL or higher. The likelihood of abnormal laboratory values being associated with selection of a lower metabolic risk SGA drug (aripiprazole or ziprasidone) and with switching decisions was assessed using multivariate logistic regression models. RESULTS: Thirteen percent of the patients had glucose and lipid tests within 6 months of starting SGA therapy. The likelihood of starting a patient on an SGA drug with lower metabolic risk (ziprasidone: odds ratio, 3.26; 95% confidence interval, 1.25-8.47; aripiprazole: odds ratio, 2.13; 95% confidence interval, 0.77-5.88) was higher if the patient had elevated glucose values but was not associated with elevated cholesterol or triglyceride values or if the patient had preexisting diabetes or dyslipidemia. Abnormal glucose and lipid values were not associated with switching SGA medications in the first 6 months of therapy. Among patients who did switch SGA medications, elevated glucose and lipid values were not associated with a greater likelihood of switching to aripiprazole or ziprasidone. CONCLUSIONS: Low rates of recommended monitoring were observed. Abnormal metabolic parameters among those who were tested were not consistently associated with the selection of an SGA drug with lower metabolic risk.

The impact of calories and fat content of meals on oral ziprasidone absorption: a randomized, open-label, crossover trial.

BACKGROUND: Food is known to increase the bioavailability of ziprasidone. Therefore, we evaluated the effects of meals of differing caloric and fat content on steady-state ziprasidone exposure in a stable, treated group of subjects with DSM-IV diagnoses of schizophrenia, schizoaffective disorder, bipolar disorder, or psychotic disorder (not otherwise specified) who were already receiving oral ziprasidone as their standard therapy. METHOD: Patients took ziprasidone under 6 meal conditions in randomized sequences (fasted, low calorie/low fat, low calorie/high fat, medium calorie/high fat, high calorie/low fat, and high calorie/high fat); each crossover period was separated by at least 3 days for washout of the previous meal condition. Serial blood samples were obtained over the 12 hours postdose. The study was conducted from July 27 to September 28 of 2006. RESULTS: Maximum ziprasidone exposures in this study were observed with high-calorie meals (1000 kcal), which were nearly twice those observed under fasting conditions. The medium-calorie meal (500 kcal) was associated with exposures similar to the high-calorie meals. Low-calorie meals (250 kcal) were associated with exposures that were approximately 60% to 90% lower than those of medium- and high-calorie meals, and approached exposures seen under fasting conditions. Fat content of the meal had no significant effect on ziprasidone absorption. The ziprasidone exposures observed with medium- and high-calorie meals had less variability than those with low-calorie meals and under fasting conditions. CONCLUSIONS: These results confirm that ziprasidone should be taken with food and that a meal equal to or greater than 500 kcal, irrespective of fat content, is required for optimal and reproducible bioavailability of the administered dose.

Ziprasidone for the treatment of acute manic or mixed episodes associated with bipolar disorder.

Ziprasidone, a benzisothiazolyl piperazine-type atypical antipsychotic agent, has a unique receptor-binding profile. A potent antagonist of serotonin 5-HT(2A) and dopamine D(2) receptors, ziprasidone has an affinity for 5-HT(2A) receptors >10-fold higher than its affinity for D(2) receptors. Ziprasidone has been shown to be effective in the treatment of bipolar disorder in patients experiencing manic or mixed episodes. It was significantly more effective than placebo in improving manic symptoms as early as day 2 of treatment in two 3-week placebo-controlled trials as monotherapy. In a 12-week, placebo-controlled trial of patients with acute mania, ziprasidone as monotherapy showed comparable efficacy with, and fewer movement-related adverse events than, haloperidol. It has demonstrated efficacy in two 1-year open-label extension trials, both as monotherapy and in combination with lithium. Ziprasidone has a generally favourable adverse effect profile. In short-term placebo-controlled trials, there were similar discontinuation rates in active treatment and placebo recipients. While twice as many patients treated with ziprasidone compared with placebo discontinued therapy because of adverse events, the number of events was small and adverse effects were generally mild or moderate. The favourable tolerability of ziprasidone has been confirmed in long-term extension studies and its use was not associated with weight gain or dyslipidaemia. Ziprasidone-related movement disorders occurred infrequently.

Serotonin 1A receptor availability in patients with schizophrenia and schizo-affective disorder: a positron emission tomography imaging study with [11C]WAY 100635.

BACKGROUND: Postmortem and positron emission tomography (PET) studies have reported several alterations in serotonin 1A receptor (5-HT(1A)) binding parameters in patients with schizophrenia. This study examines 5-HT(1A) availability in vivo in individuals with schizophrenia and schizo-affective disorder. MATERIALS AND METHODS: Twenty-two medication-free individuals with schizophrenia or schizo-affective disorder and 18 healthy subjects underwent PET scans with [(11)C]WAY 100635. Regional distribution volumes (V(T), in milliliters per gram) were derived using a two-tissue compartment kinetic model. Outcome measures for 5-HT(1A) availability included binding potential (BP) and the specific to nonspecific equilibrium partition coefficient (V(3)''). Eleven brain regions with high density of 5-HT(1A) were included in the analysis. RESULTS: No significant differences were observed in regional BP or V(3)'' between patients and controls. No significant relationships were observed between regional 5-HT(1A) availability and symptom severity. CONCLUSION: The postmortem literature reports increased 5-HT(1A) binding in the prefrontal cortex in schizophrenia. This study did not detect differences in 5-HT(1A) binding. Whereas in two recently published PET studies, one reports increased binding in the temporal lobe while the other reports decreased binding in the amygdala. These inconsistencies suggest that the alterations demonstrated in postmortem studies cannot be reliably detected at the resolution achieved with PET. This raises the question as to whether major changes in the level of expression of the 5-HT(1A) receptor play a role in the pathophysiology of schizophrenia.

Serotonin transporter availability in patients with schizophrenia: a positron emission tomography imaging study with [11C]DASB.

BACKGROUND: Postmortem studies have reported several alterations in serotonin transporter (SERT) binding parameters in patients with schizophrenia. The aim of this study was to compare SERT availability in vivo in patients with schizophrenia and matched control subjects. METHODS: Ten medication-free patients with schizophrenia and 10 healthy subjects underwent positron emission tomography (PET) scans for 90 min after 11C-3-amino-4-(2-dimethylaminomethylphenylthio)benzonitrile ([11C]DASB) injection. Metabolite-corrected arterial input function was measured. Regional distribution volumes (mL/g) were derived with a two tissue compartment kinetic model. Outcome measures for SERT availability included binding potential (BP) and the specific-to-nonspecific equilibrium partition coefficient (V3''). Ten brain regions with high density of SERT and where SERT availability can be reliably quantified with [11C]DASB were included in the analysis. RESULTS: No significant differences were observed in regional BP or V3'' between patients and control subjects. No significant relationships were observed between regional SERT availability and severity of positive, negative, and depressive symptoms. CONCLUSIONS: This study failed to detect alterations of SERT availability in patients with schizophrenia; however, this study does not rule out the possibility that schizophrenia might be associated with alterations of SERT density in the cortical regions, where the [11C]DASB-specific binding signal is too low for reliable quantification of SERT.

Brain serotonin transporter distribution in subjects with impulsive aggressivity: a positron emission study with [11C]McN 5652.

OBJECTIVE: The serotonin system is believed to play a role in modulating impulsivity and violence. Previous imaging studies have implicated the anterior cingulate and orbitofrontal cortex in impulsive aggression. This study evaluated regional serotonin transporter distribution in the brain of individuals with impulsive aggression by using positron emission tomography (PET) with the serotonin transporter PET radiotracer [(11)C]McN 5652. METHOD: Ten individuals with impulsive aggression and 10 age- and sex-matched healthy comparison subjects underwent [(11)C]McN 5652 PET. All individuals were medication free at the time of scanning. Regional total distribution volumes were derived by using a one-tissue compartment kinetic model with arterial input function. Outcome measures of serotonin transporter availability included the binding potential and the specific-to-nonspecific partition coefficient (V(3)''). RESULTS: Serotonin transporter availability was significantly reduced in the anterior cingulate cortex of individuals with impulsive aggression compared with healthy subjects, as noted by differences in both binding potential (mean=3.1 ml/g [SD=1.9] versus 5.0 ml/g [SD=2.0], respectively) and V(3)'' (mean=0.15 [SD=0.09] versus 0.26 [SD=0.09]). In other regions examined, serotonin transporter density was nonsignificantly lower in individuals with impulsive aggression compared with healthy subjects. CONCLUSIONS: Pathological impulsive aggressivity might be associated with lower serotonergic innervation in the anterior cingulate cortex, a region that plays an important role in affective regulation.

Serotonin transporters in obsessive-compulsive disorder: a positron emission tomography study with [(11)C]McN 5652.

BACKGROUND: Serotonergic abnormalities have been hypothesized to contribute to obsessive-compulsive disorder (OCD). This study examined whether brain serotonin transporter (SERT) availability is altered in OCD using positron emission tomography (PET) and the SERT PET radiotracer [(11)C]McN 5652. METHODS: Eleven OCD subjects, free of psychiatric medications and comorbid depression, and 11 matched healthy control subjects underwent PET scans following injection of [(11)C]McN 5652 and magnetic resonance imaging (MRI) scans. Total distribution volumes (V(T)) were derived by kinetic analysis (one tissue compartment model) using the arterial input function. Two measures of SERT availability were computed: binding potential (BP) and specific to nonspecific partition coefficient (V(3)"). Groups were compared using region of interest (ROI) analysis and voxelwise analysis of spatially normalized parametric maps; ROIs were selected based on their relatively high SERT density and included subcortical (dorsal caudate, dorsal putamen, ventral striatum, midbrain, thalamus) and limbic (hippocampus, amygdala, anterior cingulate cortex) regions. RESULTS: No significant group differences were observed in [(11)C]McN 5652 BP or V(3)" in the ROIs. No significant group differences were detected in the voxelwise analysis of BP or V(3)" maps. CONCLUSIONS: OCD without comorbid depression, may not be associated with major changes in SERT availability in subcortical and limbic regions.

Occupancy of brain serotonin transporters during treatment with paroxetine in patients with social phobia: a positron emission tomography study with 11C McN 5652.

RATIONALE: Although selective serotonin reuptake inhibitors (SSRIs) are widely used in the treatment of anxiety and depressive disorders, the occupancy of the serotonin reuptake transporter (SERT) achieved in humans at typical clinical doses by these agents remains poorly characterized. OBJECTIVE: The purpose of this study was to determine the occupancy of the SERT achieved in vivo by the SSRI paroxetine in social phobia patients at typical antianxiety doses. METHODS: Measures of SERT availability were obtained with positron emission tomography and the SERT radiotracer [(11)C](+)-McN 5652 in five patients with social phobia before and during treatment with paroxetine at usual therapeutic doses (20-40 mg per day). RESULTS: Occupancy of the SERT by paroxetine was high in all subjects and in all regions measured after 3-6 months of continuous treatment. CONCLUSIONS: The results of this study in an anxiety disorder sample are consistent with previously reported results in a depressed sample and suggest that paroxetine at therapeutic doses achieves very high occupancy levels of the SERT.

Prefrontal dopamine D1 receptors and working memory in schizophrenia.

Studies in nonhuman primates documented that appropriate stimulation of dopamine (DA) D1 receptors in the dorsolateral prefrontal cortex (DLPFC) is critical for working memory processing. The defective ability of patients with schizophrenia at working memory tasks is a core feature of this illness. It has been postulated that this impairment relates to a deficiency in mesocortical DA function. In this study, D1 receptor availability was measured with positron emission tomography and the selective D1 receptor antagonist [11C]NNC 112 in 16 patients with schizophrenia (seven drug-naive and nine drug-free patients) and 16 matched healthy controls. [11C]NNC 112 binding potential (BP) was significantly elevated in the DLPFC of patients with schizophrenia (1.63 +/- 0.39 ml/gm) compared with control subjects (1.27 +/- 0.44 ml/gm; p = 0.02). In patients with schizophrenia, increased DLPFC [11C]NNC 112 BP was a strong predictor of poor performance at the n-back task, a test of working memory. These findings confirm that alteration of DLPFC D1 receptor transmission is involved in working memory deficits presented by patients with schizophrenia. Increased D1 receptor availability observed in patients with schizophrenia might represent a compensatory (but ineffective) upregulation secondary to sustained deficiency in mesocortical DA function.