Safety, Tolerability, and Pharmacokinetics of Single and Multiple Ascending Intravenous Infusions of PF-07304814 (Lufotrelvir) in Participants Hospitalized With COVID-19.

Background: An urgent need remains for antiviral therapies to treat patients hospitalized with COVID-19. PF-07304814-the prodrug (lufotrelvir) and its active moiety (PF-00835231)-is a potent inhibitor of the SARS-CoV-2 3CL protease. Method: Eligible participants were 18 to 79 years old and hospitalized with confirmed COVID-19. This first-in-human phase 1b study was designed with 2 groups: single ascending dose (SAD) and multiple ascending dose (MAD). Participants could receive local standard-of-care therapy. In SAD, participants were randomized to receive a 24-hour infusion of lufotrelvir/placebo. In MAD, participants were randomized to receive a 120-hour infusion of lufotrelvir/placebo. The primary endpoint was to assess the safety and tolerability of lufotrelvir. The secondary endpoint was to evaluate the pharmacokinetics of lufotrelvir and PF-00835231. Results: In SAD, participants were randomized to receive 250 mg lufotrelvir (n = 2), 500 mg lufotrelvir (n = 2), or placebo (n = 4) by continuous 24-hour infusion. In MAD, participants were randomized to receive 250 mg lufotrelvir (n = 7), 500 mg lufotrelvir (n = 6), or placebo (n = 4) by continuous 120-hour infusion. No adverse events or serious adverse events were considered related to lufotrelvir. At doses of 250 and 500 mg, concentrations for the prodrug lufotrelvir and active moiety PF-00835231 increased in a dose-related manner. Unbound concentrations of the lufotrelvir active metabolite reached steady state approximately 2- and 4-fold that of in vitro EC90 following 250- and 500-mg doses, respectively. Conclusions: These safety and pharmacokinetic findings support the continued evaluation of lufotrelvir in clinical studies. Clinical Trials Registration. ClinicalTrials.gov NCT04535167.

Ensuring diversity in clinical trials: The role of clinical pharmacology.

Increasing the diversity of participants in clinical trials is important as it allows further examination of drug effects in all subgroups of patients who will be prescribed an approved medicine. It also gives patients more confidence in the medicine when they know that individuals similar to themselves have participated in pivotal efficacy and safety trials. Pfizer recently committed to ensuring that its clinical trials reflect racial and ethnic demographics of the patient populations in the countries and communities in which the trials are conducted. This paper furthers Pfizer's commitment by declaring what Clinical Pharmacology (CP) can do to advance this goal and expand patient populations to include other groups such as pediatrics, elderly, and those with organ impairment. This includes steps such as: Pfizer Clinical Pharmacology commits to these actions, which create a framework for the CP Community to enable increased diversity among participants in clinical trials and improved dosing recommendations for all patient subgroups.

Innovative Randomized Phase I Study and Dosing Regimen Selection to Accelerate and Inform Pivotal COVID-19 Trial of Nirmatrelvir.

Coronavirus disease 2019 (COVID-19) is a continued leading cause of hospitalization and death. Safe, efficacious COVID-19 antivirals are needed urgently. Nirmatrelvir (PF-07321332), the first orally bioavailable, severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) Mpro inhibitor against the coronaviridae family, has demonstrated potent preclinical antiviral activity and benign safety profile. We report safety, tolerability, and pharmacokinetic data of nirmatrelvir with and without ritonavir as a pharmacokinetic enhancer, from an accelerated randomized, double-blind, placebo-controlled, phase I study. Two interleaving single-ascending dose (SAD) cohorts were evaluated in a three-period crossover. Multiple-ascending dose (MAD) with nirmatrelvir/ritonavir twice daily (b.i.d.) dosing was evaluated over 10 days in five parallel cohorts. Safety was assessed, including in a supratherapeutic exposure cohort. Dose and dosing regimen for clinical efficacy evaluation in phase II/III clinical trials were supported by integrating modeling and simulations of SAD/MAD data with nonclinical data and a quantitative systems pharmacology model (QSP). In SAD, MAD, and supratherapeutic exposure cohorts, nirmatrelvir/ritonavir was safe and well-tolerated. Nirmatrelvir exposure and half-life were considerably increased by ritonavir, enabling selection of nirmatrelvir/ritonavir dose and regimen for phase II/III trials (300/100 mg b.i.d.), to achieve concentrations continuously above those required for 90% inhibition of viral replication in vitro. The QSP model suggested that a 5-day regimen would significantly decrease viral load in SARS-CoV-2-infected patients which may prevent development of severe disease, hospitalization, and death. In conclusion, an innovative and seamless trial design expedited establishment of phase I safety and pharmacokinetics of nirmatrelvir/ritonavir, enabling high confidence in phase II/III dose selection and accelerated pivotal trials' initiation (NCT04756531).

Achieving end-to-end success in the clinic: Pfizer's learnings on R&D productivity.

Over the past decade, Pfizer has focused efforts to improve its research and development (R&D) productivity. By the end of 2020, Pfizer had achieved an industry-leading clinical success rate of 21%, a tenfold increase from 2% in 2010 and well above the industry benchmark of ∼11%. The company had also maintained the quality of innovation, because 75% of its approvals between 2016 and 2020 had at least one expedited regulatory designation (e.g., Breakthrough Therapy). Pfizer's Signs of Clinical Activity (SOCA) paradigm enabled better decision-making and, along with other drivers (biology and modality), contributed to this productivity improvement. These laid a strong foundation for the rapid and effective development of the Coronavirus 2019 (COVID-19) vaccine with BioNTech, as well as the antiviral candidate Paxlovid™, under the company's 'lightspeed' paradigm.

End-to-end application of model-informed drug development for ertugliflozin, a novel sodium-glucose cotransporter 2 inhibitor.

Model-informed drug development (MIDD) is critical in all stages of the drug-development process and almost all regulatory submissions for new agents incorporate some form of modeling and simulation. This review describes the MIDD approaches used in the end-to-end development of ertugliflozin, a sodium-glucose cotransporter 2 inhibitor approved for the treatment of adults with type 2 diabetes mellitus. Approaches included (1) quantitative systems pharmacology modeling to predict dose-response relationships, (2) dose-response modeling and model-based meta-analysis for dose selection and efficacy comparisons, (3) population pharmacokinetics (PKs) modeling to characterize PKs and quantify population variability in PK parameters, (4) regression modeling to evaluate ertugliflozin dose-proportionality and the impact of uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A9 genotype on ertugliflozin PKs, and (5) physiologically-based PK modeling to assess the risk of UGT-mediated drug-drug interactions. These end-to-end MIDD approaches for ertugliflozin facilitated decision making, resulted in time/cost savings, and supported registration and labeling.

Pharmacokinetics and Pharmacodynamics of Ertugliflozin in Healthy Japanese and Western Subjects.

Ertugliflozin, a sodium-glucose cotransporter 2 inhibitor, is approved for treatment of type 2 diabetes. This randomized, double-blind (sponsor-open) study in healthy Japanese subjects and open-label study in Western subjects assessed ertugliflozin pharmacokinetics and pharmacodynamics. Cohort A received 3 ascending single doses of ertugliflozin (1, 5, and 25 mg; n = 6 Japanese, n = 6 Western) or placebo (n = 3 Japanese) under fasted conditions. Cohort B received multiple once-daily doses of ertugliflozin 25 mg (n = 6 Japanese) or placebo (n = 3 Japanese) for 7 days under fed conditions. For Japanese subjects in Cohort A, maximum plasma concentrations (Cmax ) were observed 1 to 1.5 hours after dosing, and apparent mean terminal half-life was 12.4 to 13.6 hours. The ratios of the geometric means (Japanese/Western) for ertugliflozin 1-, 5-, and 25-mg single doses were 95.94%, 99.66%, and 90.32%, respectively, for area under the plasma concentration-time curve and 107.59%, 97.47%, and 80.04%, respectively, for Cmax . Area under the plasma concentration-time curve and Cmax increased in a dose-proportional manner. For Cohort B, Cmax was observed 2.5 hours after dosing (days 1 and 7), and steady state was reached by day 4. The 24-hour urinary glucose excretion was dose dependent. Ertugliflozin was generally well tolerated. There were no meaningful differences in exposure, urinary glucose excretion, and safety between Japanese and Western subjects.

Overview of the Clinical Pharmacology of Ertugliflozin, a Novel Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitor.

Ertugliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), is approved in the US, EU, and other regions for the treatment of adults with type 2 diabetes mellitus (T2DM). This review summarizes the ertugliflozin pharmacokinetic (PK) and pharmacodynamic data obtained during phase I clinical development, which supported the registration and labeling of this drug. The PK of ertugliflozin was similar in healthy subjects and patients with T2DM. Oral absorption was rapid, with time to peak plasma concentrations (Tmax) occurring at 1 h (fasted) and 2 h (fed) postdose. The terminal phase half-life ranged from 11 to 18 h and steady-state concentrations were achieved by 6 days after initiating once-daily dosing. Ertugliflozin exposure increased in a dose-proportional manner over the tested dose range of 0.5-300 mg. Ertugliflozin is categorized as a Biopharmaceutical Classification System Class I drug with an absolute bioavailability of ~ 100% under fasted conditions. Administration of the ertugliflozin 15 mg commercial tablet with food resulted in no meaningful effect on ertugliflozin area under the plasma concentration-time curve (AUC), but decreased peak concentrations (Cmax) by 29%. The effect on Cmax is not clinically relevant and ertugliflozin can be administered without regard to food. Mild, moderate, and severe renal impairment were associated with a ≤ 70% increase in ertugliflozin exposure relative to subjects with normal renal function, and no dose adjustment in renal impairment patients is needed based on PK results. Consistent with the mechanism of action of SGLT2 inhibitors, 24-h urinary glucose excretion decreased with worsening renal function. In subjects with moderate hepatic impairment, a decrease in AUC (13%) relative to subjects with normal hepatic function was observed and not considered clinically relevant. Concomitant administration of metformin, sitagliptin, glimepiride, or simvastatin with ertugliflozin did not have clinically meaningful effects on the PK of ertugliflozin or the coadministered medications. Coadministration of rifampin decreased ertugliflozin AUC and Cmax by 39% and 15%, respectively, and is not expected to affect efficacy in a clinically meaningful manner. This comprehensive evaluation supports administration to patients with T2DM without regard to prandial status and with no dose adjustments for coadministration with commonly prescribed drugs, or in patients with renal impairment or mild-to-moderate hepatic impairment based on ertugliflozin PK.

Pharmacokinetics, metabolism, and excretion of the antidiabetic agent ertugliflozin (PF-04971729) in healthy male subjects.

The disposition of ertugliflozin (PF-04971729), an orally active selective inhibitor of the sodium-dependent glucose cotransporter 2, was studied after a single 25-mg oral dose of [(14)C]-ertugliflozin to healthy human subjects. Mass balance was achieved with approximately 91% of the administered dose recovered in urine and feces. The total administered radioactivity excreted in feces and urine was 40.9% and 50.2%, respectively. The absorption of ertugliflozin in humans was rapid with a T(max) at ∼1.0 hour. Of the total radioactivity excreted in feces and urine, unchanged ertugliflozin collectively accounted for ∼35.3% of the dose, suggestive of moderate metabolic elimination in humans. The principal biotransformation pathway involved glucuronidation of the glycoside hydroxyl groups to yield three regioisomeric metabolites, M4a, M4b, and M4c (∼39.3% of the dose in urine), of which M4c was the major regioisomer (∼31.7% of the dose). The structure of M4a and M4c were confirmed to be ertugliflozin -4-O-ß- and -3-O-ß-glucuronide, respectively, via comparison of the HPLC retention time and mass spectra with authentic standards. A minor metabolic fate involved oxidation by cytochrome P450 to yield monohydroxylated metabolites M1 and M3 and des-ethyl ertugliflozin (M2), which accounted for ∼5.2% of the dose in excreta. In plasma, unchanged ertugliflozin and the corresponding 4-O-ß- (M4a) and 3-O-ß- (M4c) glucuronides were the principal components, which accounted for 49.9, 12.2, and 24.1% of the circulating radioactivity. Overall, these data suggest that ertugliflozin is well absorbed in humans, and eliminated largely via glucuronidation.

The orexin antagonist SB-649868 promotes and maintains sleep in men with primary insomnia.

STUDY OBJECTIVES: To assess the acute effects of SB-649868 in male subjects with Primary Insomnia with regard to (1) objective and subjective sleep parameters, (2) safety and tolerability, (3) next-day residual effects. DESIGN: Multicenter, randomized, double-blind, placebo-controlled crossover study using a complete set of Williams orthogonal Latin Squares SETTING: 9 sleep centers in Germany PATIENTS: 52 male subjects with a diagnosis of primary insomnia (difficulty in sleep initiation and maintenance) confirmed by polysomnography INTERVENTIONS: SB-649868 (10, 30, 60 mg) and placebo administered after dinner 90 minutes before bedtime MEASUREMENTS AND RESULTS: Sleep effects assessed by polysomnography during 2 consecutive nights and by sleep questionnaires completed by subjects after each night at the sleep laboratory. Safety and tolerability were assessed by adverse events collection, electrocardiogram (ECG), vital signs, laboratory tests. Next-day residual effects were assessed by Digit Symbol Substitution Test, and modified Verbal Learning Memory Test administered at "lights on" after night 2. SB-649868 significantly reduced latency to persistent sleep, wake after sleep onset (WASO), and increased total sleep time (TST) compared to placebo. A dose-dependent effect was observed. A dose-dependent increase in absolute and percent REM sleep and reduction in REM sleep latency was observed mainly at the 60-mg dose. SB-649868 was well tolerated with inconsistent next day residual effects. SB-649868 sleep effects were correlated with SB-649868 circulating levels. CONCLUSION: The data demonstrate the sleep-promoting properties of the orexin antagonist SB-649868 in male patients with insomnia.

Phase I studies on the safety, tolerability, pharmacokinetics and pharmacodynamics of SB-649868, a novel dual orexin receptor antagonist.

The orexin system plays a major role in the integration of metabolic and circadian influences that drive wakefulness. This paper describes initial Phase I trials of a novel dual orexin receptor antagonist SB-649868 that has demonstrated preclinical potential for treatment of sleep disorders. The trial designs included a single ascending dose escalation study (dose range: 10-80 mg in the fed and fasted states) and a multiple repeat dose study (dose range: 5-30 mg in the fed state) enrolling a total of 103 male volunteer subjects. SB-649868 was well tolerated at all doses in this study population, with mechanism-related adverse events (e.g. somnolence and fatigue) observed in a majority of subjects after 60 and 80 mg single doses. Although total drug exposure was similar in the fed and fasted states, the rate, but not the extent, of absorption increased in the fed state, resulting in an increased C(max). The typical estimated half-life of SB-649868 was 3-6 h - comparable with currently used hypnotic agents. Repeated administration of SB-649868 dose-dependently increased exposure to simvastatin (10 mg), suggesting CYP3A4 inhibition ranging from very mild (5 mg) to strong (30 mg). Evening dosing resulted in significant dose-dependent improvement in latency to persistent sleep, total sleep time and wake after sleep onset as measured by polysomnography. Next-morning testing did not detect evidence of residual cognitive effects. Results of these trials support further investigation of SB-649868 and other dual orexin receptor antagonists as potentially effective and well-tolerated treatments for patients with sleep disorders.

Contribution of SPECT measurements of D2 and 5-HT2A occupancy to the clinical development of the antipsychotic SB-773812.

UNLABELLED: The aim of this study was to assess human striatal dopamine receptor 2 (D(2)) and cortical 5-hydroxytryptamine receptor 2A (5-HT(2A)) occupancy of SB-773812 to demonstrate brain penetration and binding to the target receptors and assess the pharmacokinetics-receptor occupancy relationship over time to aid dose selection and dosage regimen, in preparation for the phase II trials. METHODS: D(2) and 5-HT(2A) occupancy were measured over time (both at the time of maximum [T(max); 6 ± 2 h] and at the time of minimum [T(trough); 24 ± 4 h] plasma concentration after dosing) by means of (123)I-iodobenzamide and (123)I-4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]5-iodo-2-methoxybenzamide ((123)I-R91150) SPECT in 3 studies. Study A consisted of SB-773812 single doses in healthy volunteers-D(2) occupancy measured at 48 (n = 9) and 56 mg (n = 9) and 5-HT(2A) occupancy at 56 mg (n = 9); study B consisted of D(2) and 5-HT(2A) occupancy measured in 12 stabilized-schizophrenia patients on stable doses (16-18 d of 56 mg/d) after washout of previous medication; and study C included D(2) occupancy measured in a double-blind study of patients with acutely exacerbated schizophrenia (n = 10) on stable doses (18-21 d) of SB-773812 (100 mg/d; n = 7) or risperidone (6 mg/d; n = 3). RESULTS: Study A showed less than 30% D(2) occupancy at T(max), maintained at T(trough). 5-HT(2A) occupancy was 74%-97% and also maintained over time. Study B revealed that 8 of the 12 schizophrenia patients showed more than 40% D(2) occupancy. 5-HT(2A) occupancy ranged from 91% to 100%. In study C, SB-773812-induced D(2) occupancy was 60.3% ± 13.3% at T(max) and 55.1% ± 4.9% at T(trough). The pharmacokinetics-receptor occupancy relationship was assessed in each study and strengthened, combining all data to yield a concentration associated with 50% occupancy (EC(50)) of 92.7 ± 13.5 ng/mL for D(2) and 2.11 ± 0.50 ng/mL for 5-HT(2A). CONCLUSION: In all subjects, SB-773812 showed penetration into the brain, reaching its target receptors. In patients with schizophrenia, D(2) occupancy levels induced by a single dose were maintained over time, indicating that once-daily dosing regimens are appropriate. Pharmacokinetics-receptor occupancy analysis provided guidance for the selection of a clinically effective dose, supporting progression in phase II.

On-line monitoring of lung mechanics during spontaneous breathing: a physiological study.

BACKGROUND: Monitoring the mechanics of breathing in patients with advanced chronic obstructive lung diseases prior to lung transplantation is useful to characterize changes in the mechanical properties of the lungs. On-line methods of monitoring immediately process the data for clinical decisions. However, the few available methods are so far limited to monitor respiratory mechanics in ventilator-dependent patients. We investigated whether on-line monitoring of the lung mechanics, including intrinsic PEEP, was feasible in spontaneously breathing patients. METHODS: In 9 stable patients with chronic obstructive pulmonary disease (COPD) and 11 with cystic fibrosis (CF) undergoing the procedure for the lung transplantation waiting list, we applied 2 methods of on-line monitoring (modified recursive least squares, RLS and modified multiple linear regression methods, SLS) of intrinsic PEEP (P(0)), dynamic lung elastance (E(Ldyn)) and inspiratory resistance (R(Linsp)), and compared them with an off-line graphical analysis (GA), our reference technique. RESULTS: In CF patients, there was no difference between methods, while in COPD, the median values of E(Ldyn) and R(Linsp) were significantly different between GA/SLS and GA/RLS, respectively (Dunn's, p<0.05). However, the correlation was very high for all comparisons, particularly for E(Ldyn) (R>0.98) and R(Linsp) (R>0.93). Moreover, Bland-Altman plots showed that the mean differences were consistently low and the intervals of agreement reasonable. CONCLUSIONS: Our study suggests that on-line methods are reliable for monitoring lung mechanics in spontaneous breathing patients with severe lung diseases and could help clinicians in their decision-making process.

Within-subject comparison of striatal D2 receptor occupancy measurements using [123I]IBZM SPECT and [11C]Raclopride PET.

Antipsychotic-induced D2 receptor occupancy values tend to be lower when measured with [(123)I]IBZM SPECT than with [(11)C]Raclopride PET. To clarify this issue, D2 receptor occupancy was measured in the same subjects using both techniques. Twenty patients with schizophrenia on monotherapy with risperidone (n=7; 3-9 mg/d), olanzapine (n=5; 5-20 mg/d) or clozapine (n=8; 150-450 mg/d) at stable doses, and ten healthy volunteers (HV) underwent both a [(123)I]IBZM SPECT and a [(11)C]Raclopride PET examinations in random order on different days within a week. Patients with schizophrenia were scanned at a fixed interval after last dose administration. Quantification of receptor availability was performed using the most conventional methods from the literature: the tissue ratio derived specific uptake ratios (SUR) were used for SPECT, and simplified reference tissue model (SRTM) derived binding potentials (BP(ND)) for PET. Analysis was performed using both occipital cortex and cerebellum as reference regions for both modalities. Striatal D2 receptor occupancy was measured as the percentage reduction of [(123)I]IBZM SUR or [(11)C]Raclopride BP(ND) compared to the population average measured in HV using the same modality. Occupancy values measured by SPECT were lower than those measured with PET, by 12.4% and 13.8% when occipital cortex and cerebellum were used as reference regions. This difference should be taken in consideration when interpreting reported antipsychotic striatal D2 receptor occupancy values from the literature.

Model-based approaches to increase efficiency of drug development in schizophrenia: a can't miss opportunity.

BACKGROUND: Schizophrenia is a severe mental disorder characterized by definite specificities and complexities (heterogeneity of the disease symptoms, large between-subject variability in disease progression and response to therapeutic agents, placebo response, dropout, questionable preclinical models, importance of market differentiation, etc.) that make drug development in this field particularly difficult when compared to the other therapeutic areas. However, drug receptor binding (especially to D2, 5-HT2 and H1 receptors) can provide a useful quantitative framework that can be related to the downstream clinical (amelioration of disease-related scores) and unwanted (neurological effects and metabolic disregulation) effects. OBJECTIVE: This paper reviews the pharmacokinetic, pharmacodynamic and disease progression approaches applied to the development of new drugs for the treatment of schizophrenia. CONCLUSIONS: Only model-based methodologies, able to integrate the diverse characteristics of a compound, can provide a rational approach to increase efficiency in drug development in this area, through the development of pharmacokinetic-pharmacodynamics models able to integrate quantitative descriptions of pharmacokinetics, desired and unwanted effects. These holistic approaches can be used in clinical trial simulations for reliably predicting the outcome of future trials. Meta-analyses of the competitor environment are also essential to position the new drug into a crowded competitive landscape.

Muscle glucose transport and phosphorylation in type 2 diabetic, obese nondiabetic, and genetically predisposed individuals.

Our objectives were to quantitate insulin-stimulated inward glucose transport and glucose phosphorylation in forearm muscle in lean and obese nondiabetic subjects, in lean and obese type 2 diabetic (T2DM) subjects, and in normal glucose-tolerant, insulin-resistant offspring of two T2DM parents. Subjects received a euglycemic insulin (40 mU.m(-2).min(-1)) clamp with brachial artery/deep forearm vein catheterization. After 120 min of hyperinsulinemia, a bolus of d-mannitol/3-O-methyl-d-[(14)C]glucose/d-[3-(3)H]glucose (triple-tracer technique) was given into brachial artery and deep vein samples obtained every 12-30 s for 15 min. Insulin-stimulated forearm glucose uptake (FGU) and whole body glucose metabolism (M) were reduced by 40-50% in obese nondiabetic, lean T2DM, and obese T2DM subjects (all P < 0.01); in offspring, the reduction in FGU and M was approximately 30% (P < 0.05). Inward glucose transport and glucose phosphorylation were decreased by approximately 40-50% (P < 0.01) in obese nondiabetic and T2DM groups and closely paralleled the decrease in FGU. The intracellular glucose concentration in the space accessible to glucose was significantly greater in obese nondiabetic, lean T2DM, obese T2DM, and offspring compared with lean controls. We conclude that 1) obese nondiabetic, lean T2DM, and offspring manifest moderate-to-severe muscle insulin resistance (FGU and M) and decreased insulin-stimulated glucose transport and glucose phosphorylation in forearm muscle; these defects in insulin action are not further reduced by the combination of obesity plus T2DM; and 2) the increase in intracelullar glucose concentration under hyperinsulinemic euglycemic conditions in obese and T2DM groups suggests that the defect in glucose phosphorylation exceeds the defect in glucose transport.

Characterization of the SPECT 5-HT2A receptor ligand 123I-R91150 in healthy volunteers: part 2--ketanserin displacement.

UNLABELLED: As part of the radioiodinated 4-amino-N-1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]5-iodo-2-methoxybenzamide ((123)I-R91150) characterization study, ketanserin challenges were performed on healthy volunteers with the aim of assessing the specificity of (123)I-R91150 binding to subtype 2A of the 5-hydroxytryptamine receptor (5-HT(2A)), the sensitivity of (123)I-R91150 SPECT in measuring ligand displacement, the relationship between ketanserin plasma concentrations and (123)I-R91150 displacement, and the suitability of the cerebellum as a reference region for quantification. METHODS: Dynamic SPECT was performed on 6 healthy men (mean age +/- SD, 21 +/- 0.89 y) from the time of (123)I-R91150 injection until 470 min afterward. Ketanserin was administered intravenously at 210 min after injection at 3 doses: 0.1 mg/kg (n = 2), 0.05 mg/kg (n = 2), and 0.015 mg/kg (n = 2). Blood samples for measurement of ketanserin plasma concentrations were drawn. MRI was performed on all subjects and coregistered to the SPECT data for region-of-interest drawing on cortical regions and cerebellum. The simplified reference tissue model (SRTM) was considered the gold standard for quantification, and results were compared with those obtained with the tissue ratio method (TR). The percentage (123)I-R91150 displacement was calculated with both methods as the percentage difference between baseline and postketanserin scans. RESULTS: Depending on the cerebral regions with the maximum ketanserin dose studied, SRTM and TR mean displacements were 57.1%-95.4% and 71.9%-101.2%, respectively, for the 0.1 mg/kg dose; 51.7%-91.4% and 56.7%-102.8%, respectively, for the 0.05 mg/kg dose; and 7.7%-54.5% and 13.8%-47.0%, respectively, for the lowest dose, 0.015 mg/kg. A good correlation was found between the 2 methods. No ketanserin-induced displacement was observed in the cerebellum time-activity curves, supporting the use of the cerebellum as a reference region. The relationship between displacement and ketanserin plasma concentration fit with a rectangular hyperbola, with a 5.6 ng/mL concentration associated with 50% of the maximum displacement (EC(50)). EC(50) values calculated using occupancies derived both with SRTM and with TR were in good agreement. CONCLUSION: (123)I-R91150 SPECT is sensitive enough to measure ketanserin dose-dependent displacement in cerebral regions rich in 5-HT(2A) receptors. These results support the selectivity of (123)I-R91150 for 5-HT(2A) receptors and its use as a SPECT ligand for measurements of drug-induced 5-HT(2A) receptor occupancy in humans.

Multiple dose pharmacokinetics of paroxetine in children and adolescents with major depressive disorder or obsessive-compulsive disorder.

The current study examined the pharmacokinetics (PK), safety, and tolerability of paroxetine after repeated multiple oral dosing in children and adolescents with major depressive or obsessive-compulsive disorder. In this 6-week, open-label, repeat dose, dose-rising study, 62 patients (27 children and 35 adolescents) were treated with paroxetine 10 mg/day for the first 2 weeks of the study, 20 mg/day for the next 2 weeks, and 30 mg/day for the final 2 weeks. Pharmacokinetic sampling and safety assessments occurred at baseline and subsequently on the final treatment day of each dosing level. Between-patient variability in PK was pronounced at the 10 mg dose level, but markedly reduced at higher doses. A supra-proportional increase in plasma concentrations with increasing dose was evident in both age groups. Data for C(max) and AUC(0-24) indicated that, at each dose level, paroxetine steady-state systemic exposure was higher in children than in adolescents. The differences between age groups, however, diminished with each increasing dose, and were virtually abolished when differences in weight among different age groups were considered. Stepwise regression analysis indicated that both oral clearance and volume of distribution were highly dependent on paroxetine dose, cytochrome P4502D6 genotype, and weight (p<0.0001), but not age or sex. Paroxetine was generally safe and well tolerated in both age groups, with the most frequently observed adverse events being largely consistent with those observed in prior paroxetine studies of adult psychiatric patients. Certain gastrointestinal and behavioral activation events (aggressive reaction and nervousness) were reported more frequently in the youngest age group.

Characterization of a 7% carbon dioxide (CO2) inhalation paradigm to evoke anxiety symptoms in healthy subjects.

The present study is aimed at characterizing the carbon dioxide (CO2) procedure in healthy subjects to achieve reliable provocation of anxiety symptoms. Thirty healthy subjects inhaled in single-blind both compressed air and 7% CO2 mixture. Panic Symptom List (PSLIII-R), Visual Analogue Scale-Anxiety (VAS-A), State Anxiety Inventory (STAI-Y/1), respiratory parameters and skin conductance were measured. 'Responders' were classified depending on PSLIII-R scores after CO2. Twelve out of the 21 'responders' performed a second test to assess test-retest repeatability. In 21 subjects Delta%VAS-A (45.4 +/- 32.1) and PSLIII-R (pre-test 2.3 +/-2.1, post-test 17.5 +/- 8.2) but not STAI-Y/1, significantly increased during CO2 inhalation. Respiratory Rate, Minute Volume, end-Tidal CO2 and skin conductance rose in 'responders'. Repeatability was studied with Bland-Altman plots, revealing mean difference between tests close to 0 for both Delta%VAS-A and PSLIII-R. Among physiologic parameters, end-Tidal CO2 and Respiratory Rate showed good repeatability, with a within-subject CV of 9.2% and 6%, respectively. The challenge produced measurable response in healthy subjects. Good test-retest repeatability was observed in 'responders'. These data indicate that the test can be suitable for testing putative anti-panic or anxiolytic drugs in clinical studies using a within subject, crossover design.

Design, methods, and evaluation directions of a multi-access service for the management of diabetes mellitus patients.

Recent advances in information and communication technology allow the design and testing of new models of diabetes management, which are able to provide assistance to patients regardless of their distance from the health care providers. The M2DM project, funded by the European Commission, has the specific aim to investigate the potential of novel telemedicine services in diabetes management. A multi-access system based on the integration of Web access, telephone access through interactive voice response systems, and the use of palmtops and smart modems for data downloading has been implemented. The system is based on a technological platform that allows a tight integration between the access modalities through a middle layer called the multi-access organizer. Particular attention has been devoted to the design of the evaluation scheme for the system: A randomized controlled study has been defined, with clinical, organizational, economic, usability, and users' satisfaction outcomes. The evaluation of the system started in January 2002. The system is currently used by 67 patients and seven health care providers in five medical centers across Europe. After 6 months of usage of the system no major technical problems have been encountered, and the majority of patients are using the Web and data downloading modalities with a satisfactory frequency. From a clinical viewpoint, the hemoglobin A1c (HbA1c) of both active patients and controls decreased, and the variance of HbA1c in active patients is significantly lower than the control ones. The M2DM system allows for the implementation of an easy-to-use, user-tailored telemedicine system for diabetes management. The first clinical results are encouraging and seem to substantiate the hypothesis of its clinical effectiveness.

Modeling airflow-related shear stress during heterogeneous constriction and mechanical ventilation.

Ventilator-induced lung injury has been proposed as being caused by overdistention and closure and reopening of small airways and alveoli. Here we investigate the possibility that heterogeneous constriction increases airflow-related shear stress to a dangerously high level that may be sufficient to cause injury to the epithelial cells during mechanical ventilation. We employed an anatomically consistent model of the respiratory system, based on Horsfield morphometric data, and solved for the time evolution of pressure and flow along the airway tree during mechanical ventilation. We simulated constant-flow ventilation with passive expiration in two different conditions: baseline and highly heterogeneous constriction. The constriction was applied with two strategies: establishing a simple diameter reduction or adding also a length shortening. The shear stress distribution on airway walls was analyzed for airways ranging from the trachea to the acini. Our results indicate that 1). heterogeneous constriction can amplify the maximal values of shear stress up to 50-fold, with peak values higher than 0.6 cmH2O; 2). the highest shear stress is found in pathways constricted by 60-80%; 3). simultaneous diameter reduction and shortening amplifies the shear stresses by three- to fourfold, with shear stresses reaching 2 cmH2O; and 4). there is a range of airways (diameters from 0.6 to 0.3 mm at baseline) that appear to be at risk of very high stresses. We conclude that elevated airflow-related shear stress on the epithelial cell layer can occur during heterogeneous constriction and conjecture that this may constitute a mechanism contributing to ventilator-induced lung injury.