Robust Pharmacodynamic Effect of LY3202626, a Central Nervous System Penetrant, Low Dose BACE1 Inhibitor, in Humans and Nonclinical Species.

BACKGROUND: The development of beta-site amyloid-beta precursor protein cleaving enzyme (BACE) 1 inhibitors for the treatment of Alzheimer's disease requires optimization of inhibitor potency, selectivity, and brain penetration. Moreover, there is a need for low-dose compounds since liver toxicity was found with some BACE inhibitors. OBJECTIVE: To determine whether the high in vitro potency and robust pharmacodynamic effect of the BACE inhibitor LY3202626 observed in nonclinical species translated to humans. METHODS: The effect of LY3202626 versus vehicle on amyloid-ß (Aß) levels was evaluated in a series of in vitro assays, as well as in in vivo and multi-part clinical pharmacology studies. Aß levels were measured using analytical biochemistry assays in brain, plasma, and cerebrospinal fluid (CSF) of mice, dogs and humans. Nonclinical data were analyzed using an ANOVA followed by Tukey's post hoc test and clinical data used summary statistics. RESULTS: LY3202626 exhibited significant human BACE1 inhibition, with an IC50 of 0.615±0.101 nM in a fluorescence resonance energy transfer assay and an EC50 of 0.275±0.176 nM for lowering Aß1-40 and 0.228±0.244 nM for Aß1-42 in PDAPP neuronal cultures. In dogs, CSF Aß1hboxx concentrations were significantly reduced by ∼80% at 9 hours following a 1.5 mg/kg dose. In humans, CSF Aß1-42 was reduced by 73.1±7.96 % following administration of 6 mg QD. LY3202626 was found to freely cross the blood-brain barrier in dogs and humans. CONCLUSION: LY3202626 is a potent BACE1 inhibitor with high blood-brain barrier permeability. The favorable safety and pharmacokinetic/pharmacodynamic profile of LY3202626 supports further clinical development.

A Randomized, Double-Blind, Placebo- and Active-Controlled, Escalating Single-Dose Study to Evaluate the Safety, Tolerability, Pharmacokinetic, and Pharmacodynamic Profiles of Subcutaneous Eflapegrastim in Healthy Japanese and Caucasian Subjects.

BACKGROUND: Eflapegrastim (Rolontis®) is a novel long-acting pegylated recombinant human granulocyte colony-stimulating factor (G-CSF). Eflapegrastim has been developed to reduce the duration and incidence of chemotherapy-induced neutropenia in cancer patients using patient-friendly, less-frequent administration. OBJECTIVE: This phase I study aimed to evaluate the safety, tolerability, pharmacokinetic (PK), pharmacodynamic (PD), and immunogenicity of eflapegrastim following a single subcutaneous administration to healthy Japanese and Caucasian subjects. METHODS: A randomized, double-blind, placebo- and active-controlled, dose-escalation study was conducted in healthy Japanese and Caucasian subjects. Eligible subjects randomly received a single subcutaneous administration of eflapegrastim (1.1, 3.3, 10, 45, 135, and 270 µg/kg), pegfilgrastim 6 mg, or placebo in a ratio of 6:2:2 (Cohorts 1-2, Caucasian subjects only) or 12:2:2 (Cohorts 3-6, Japanese and Caucasian subjects). Safety and tolerability were assessed throughout the study. Serial blood samples were collected predose and up to day 22 postdose for PK and PD analyses. PK assessments were performed in the 45, 135, and 270 µg/kg dose groups. Antidrug antibodies to eflapegrastim were determined at baseline up to day 42 after the first dose for immunogenicity. RESULTS: A total of 84 subjects (42 males and 42 females) were enrolled, and 78 (31 Japanese and 47 Caucasian subjects) completed the study as planned. Japanese and Caucasian subjects showed similar PK and PD profiles. In the 45, 135, and 270 µg/kg dose groups, the maximum serum concentration (Cmax) of eflapegrastim exhibited a dose-proportional increase, whereas its exposure increased greater than dose proportional in both ethnic groups. The mean area under the effect-time curve (AUEClast) and maximum serum concentration of both absolute neutrophil count (ANCmax) and CD34+ cell count (CD34+max) increased in a dose-dependent manner. There were no significant adverse events attributable to eflapegrastim or pegfilgrastim in both Japanese and Caucasian subjects. No neutralizing antibodies against G-CSF were detected. CONCLUSIONS: Eflapegrastim was safe and well tolerated at doses up to 270 µg/kg in healthy Japanese and Caucasian subjects. In both ethnic groups, eflapegrastim showed dose-dependent PK and the exposure to eflapegrastim was positively correlated with ANC and CD34+ cell count. The comparable PK and PD profiles of eflapegrastim in Japanese and Caucasian subjects may indicate the same dosage regimen is acceptable. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: NCT01037543 (23 December 2009).

A first-in-human study to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of KM-819 (FAS-associated factor 1 inhibitor), a drug for Parkinson's disease, in healthy volunteers.

BACKGROUND: KM-819 is a novel FAS-associated factor 1 (FAF1) inhibitor, and a neuroprotective agent, under clinical development for the treatment of Parkinson's disease as a disease-modifying drug. METHODS: This first-in-human, single and multiple ascending dose study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of KM-819 in healthy volunteers. Additionally, the effect of age on safety and pharmacokinetics were assessed. The starting dose was determined considering the no observed adverse effect level based on preclinical studies, and the dose escalations in subsequent cohorts were decided based on safety, tolerability, and pharmacokinetic data from previous dose cohorts. RESULTS: After a single dose, the KM-819 plasma exposure showed a less than dose-proportional increase across a dose range of 10-400 mg. After repeated dosing, KM-819 plasma exposure increased in an approximately dose-proportional manner across the evaluated dose range (30-400 mg once daily for 7 days). The mean elimination half-life was 1.8 to 4.8 h with the lower KM-819 doses (≤30 mg), which increased to around 9 h with the higher doses (100-400 mg). When administered to the elderly population, KM-819 plasma exposure increased to 102% after a 200 mg once-daily dosing for 7 days. No clear treatment-related effects on the estimated pharmacodynamic variables were observed. Single or multiple doses of KM-819 were generally well tolerated. CONCLUSION: The data from this study can be used to guide rational drug dosing and choose therapeutic regimens in subsequent clinical studies.

Evaluation of the single-dose pharmacokinetics and pharmacodynamics of apixaban in healthy Japanese and Caucasian subjects.

PURPOSE: This double-blind, placebo-controlled, intra-subject, dose-escalation study assessed single-dose safety, pharmacokinetics, and pharmacodynamics of apixaban in healthy Japanese and Caucasian subjects. SUBJECTS AND METHODS: Sixteen healthy male Japanese and sixteen healthy male Caucasian subjects, matched for age, weight, and smoking status were randomized to receive four sequential single oral doses of either apixaban (2.5, 10, 25, and 50 mg) or matched placebo. Doses were separated by a ≥5-day washout. Blood samples were collected for the determination of apixaban plasma concentration, clotting times (international normalized ratio [INR], activated partial thromboplastin time, and modified prothrombin time [mPT]), and ex vivo thrombin generation (TG). Urine samples were collected for the analysis of apixaban concentration. RESULTS: Ascending single doses of apixaban 2.5-50 mg were safe and well tolerated by all subjects. Apixaban exposure increased the dose proportionally up to 10 mg. Apixaban reached maximum concentrations (C max) 3-4 h postdose, with mean C max ranging from 52.5-485.0 to 44.8-494.3 ng/mL in Japanese and Caucasian subjects. The mean half-life was ~8 and ~13 h and the renal clearance was 1.1 and 0.8 L/h in Japanese and Caucasian subjects, respectively. Pharmacodynamic assessments were similar between ethnic groups, with comparable dose-related prolongation of INR and mPT and inhibition of TG. CONCLUSION: Ascending single doses of apixaban over a 20-fold dose range were safe and well tolerated in Japanese and Caucasian subjects in this study. The consistency between pharmacokinetic and pharmacodynamic measures in Japanese and Caucasian subjects indicates that apixaban may be administered as a fixed dose with no need for adjustment in Japanese patients.

The BACE1 inhibitor verubecestat (MK-8931) reduces CNS ß-amyloid in animal models and in Alzheimer's disease patients.

ß-Amyloid (Aß) peptides are thought to be critically involved in the etiology of Alzheimer's disease (AD). The aspartyl protease ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) is required for the production of Aß, and BACE1 inhibition is thus an attractive target for the treatment of AD. We show that verubecestat (MK-8931) is a potent, selective, structurally unique BACE1 inhibitor that reduced plasma, cerebrospinal fluid (CSF), and brain concentrations of Aß40, Aß42, and sAPPß (a direct product of BACE1 enzymatic activity) after acute and chronic administration to rats and monkeys. Chronic treatment of rats and monkeys with verubecestat achieved exposures >40-fold higher than those being tested in clinical trials in AD patients yet did not elicit many of the adverse effects previously attributed to BACE inhibition, such as reduced nerve myelination, neurodegeneration, altered glucose homeostasis, or hepatotoxicity. Fur hypopigmentation was observed in rabbits and mice but not in monkeys. Single and multiple doses were generally well tolerated and produced reductions in Aß40, Aß42, and sAPPß in the CSF of both healthy human subjects and AD patients. The human data were fit to an amyloid pathway model that provided insight into the Aß pools affected by BACE1 inhibition and guided the choice of doses for subsequent clinical trials.

Effects of the glycine reuptake inhibitors bitopertin and RG7118 on glycine in cerebrospinal fluid: results of two proofs of mechanism studies in healthy volunteers.

RATIONALE: Hypofunction of NMDA receptors has been implicated in neuropsychiatric disorders including schizophrenia. NMDA receptor neurotransmission can be enhanced through inhibition of glycine reuptake by the glycine transporter type 1 (GlyT1). OBJECTIVES: The primary objective of these studies was to explore the relationship between plasma exposure and glycine cerebrospinal fluid (CSF) concentrations following administration of bitopertin and RG7118 in healthy volunteers. METHODS: The bitopertin study comprised four dose levels (3, 10, 30 and 60 mg) administered once daily for 10 days. In the RG7118 study, placebo, 15 or 30 mg RG7118 was administered once daily for 28 days. CSF samples were taken on day -2 and day 10, and day -1 and day 26 for bitopertin and RG7118, respectively. RESULTS: Twenty-two and 24 subjects participated in the bitopertin and RG7118 study, respectively. In the bitopertin study, CSF glycine concentrations showed a dose-dependent increase from baseline to day 10. The geometric mean ratios (coefficient of variation) of AUC0-12 h on day 10 over baseline were 1.3 (17 %), 1.3 (49 %), 1.7 (18 %) and 2.3 (14 %) after 3, 10, 30 and 60 mg, respectively. In the RG7118 study, the geometric mean ratio of glycine concentration (CV) on day 26 at 6 h post-dose over time-matched baseline was approx. 1.9 (24 and 15 %) for 15 and 30 mg. CONCLUSIONS: The mechanism of action of bitopertin and RG7118, i.e. inhibition of glycine reuptake in the brain, was confirmed. The maximal increase observed in healthy volunteers was similar to the one observed in animals showing the good translatability of this biomarker.

The effect of LCZ696 (sacubitril/valsartan) on amyloid-ß concentrations in cerebrospinal fluid in healthy subjects.

AIMS: LCZ696 (angiotensin receptor neprilysin inhibitor) is a novel drug developed for the treatment of heart failure with reduced ejection fraction. Neprilysin is one of multiple enzymes degrading amyloid-ß (Aß). Its inhibition may increase Aß levels. The potential exists that treatment of LCZ696, through the inhibition of neprilysin by LBQ657 (an LCZ696 metabolite), may result in accumulation of Aß. The aim of this study was to assess the blood-brain-barrier penetration of LBQ657 and the potential effects of LCZ696 on cerebrospinal fluid (CSF) concentrations of Aß isoforms in healthy human volunteers. METHODS: In a double-blind, randomized, parallel group, placebo-controlled study, healthy subjects received once daily LCZ696 (400 mg, n = 21) or placebo (n = 22) for 14 days. RESULTS: LCZ696 had no significant effect on CSF AUEC(0,36 h) of the aggregable Aß species 1-42 or 1-40 compared with placebo (estimated treatment ratios 0.98 [95% CI 0.73, 1.34; P = 0.919] and 1.05 [95% CI 0.82, 1.34; P = 0.702], respectively). A 42% increase in CSF AUEC(0,36 h) of soluble Aß 1-38 was observed (estimated treatment ratio 1.42 [95% CI 1.05, 1.91; P = 0.023]). CSF levels of LBQ657 and CSF Aß 1-42, 1-40, and 1-38 concentrations were not related (r(2) values 0.022, 0.010, and 0.008, respectively). CONCLUSIONS: LCZ696 did not cause changes in CSF levels of aggregable Aß isoforms (1-42 and 1-40) compared with placebo, despite achieving CSF concentrations of LBQ657 sufficient to inhibit neprilysin. The clinical relevance of the increase in soluble CSF Aß 1-38 is currently unknown.

The potent BACE1 inhibitor LY2886721 elicits robust central Aß pharmacodynamic responses in mice, dogs, and humans.

BACE1 is a key protease controlling the formation of amyloid ß, a peptide hypothesized to play a significant role in the pathogenesis of Alzheimer's disease (AD). Therefore, the development of potent and selective inhibitors of BACE1 has been a focus of many drug discovery efforts in academia and industry. Herein, we report the nonclinical and early clinical development of LY2886721, a BACE1 active site inhibitor that reached phase 2 clinical trials in AD. LY2886721 has high selectivity against key off-target proteases, which efficiently translates in vitro activity into robust in vivo amyloid ß lowering in nonclinical animal models. Similar potent and persistent amyloid ß lowering was observed in plasma and lumbar CSF when single and multiple doses of LY2886721 were administered to healthy human subjects. Collectively, these data add support for BACE1 inhibition as an effective means of amyloid lowering and as an attractive target for potential disease modification therapy in AD.

Pharmacokinetic Profile of Orally Administered Scyllo-Inositol (Elnd005) in Plasma, Cerebrospinal Fluid and Brain, and Corresponding Effect on Amyloid-Beta in Healthy Subjects.

ELND005 (scyllo-inositol), an endogenous inositol stereoisomer, is being investigated as an oral treatment for Alzheimer's disease (AD). Pharmacokinetics of ELND005 in plasma, cerebrospinal fluid (CSF), and brain was characterized in healthy young subjects. Eight men received 2000 mg ELND005 every 12 hours for 10 days. Plasma and CSF samples were collected at predetermined time points; ELND005 and amyloid-beta (Aß) fragments were measured by validated bioanalytical methods. Brain ELND005 levels, estimated by (1) H Magnetic Resonance Spectroscopy (MRS) scans were obtained from gray/white matter voxels at baseline and Day 8. ELND005 was well-tolerated during the study. During the apparent steady state, ELND005 plasma levels rapidly peaked at 39.8 µg/mL and decreased to an average trough concentration of 10.6 µg/mL at the end of the 12-hour dosing regimen. In contrast, CSF drug levels slowly peaked at 13.7 µg/mL and remained near the same level with average trough concentrations of 12.4 µg/mL. At Day 8, Brain ELND005 concentrations increased by 58-76% compared to baseline levels. The CSF concentrations achieved in this study were similar to those associated with efficacy in transgenic models of AD. No changes were detected in plasma and CSF levels of Aß fragments.

Clinically significant psychotropic drug-drug interactions in the primary care setting.

In recent years, the growing numbers of patients seeking care for a wide range of psychiatric illnesses in the primary care setting has resulted in an increase in the number of psychotropic medications prescribed. Along with the increased utilization of psychotropic medications, considerable variability is noted in the prescribing patterns of primary care providers and psychiatrists. Because psychiatric patients also suffer from a number of additional medical comorbidities, the increased utilization of psychotropic medications presents an elevated risk of clinically significant drug interactions in these patients. While life-threatening drug interactions are rare, clinically significant drug interactions impacting drug response or appearance of serious adverse drug reactions have been documented and can impact long-term outcomes. Additionally, the impact of genetic variability on the psychotropic drug's pharmacodynamics and/or pharmacokinetics may further complicate drug therapy. Increased awareness of clinically relevant psychotropic drug interactions can aid clinicians to achieve optimal therapeutic outcomes in patients in the primary care setting.

Effect of human cerebrospinal fluid sampling frequency on amyloid-ß levels.

BACKGROUND: ß-amyloid peptide (Aß) is associated with neurodegeneration in Alzheimer's disease. Emerging evidence indicates that Aß levels in cerebrospinal fluid (CSF) may serve as an early clinical biomarker for evaluating pharmacological activity of new drug candidates targeting Aß production or Aß clearance. Therefore, it is critical to understand whether intrasubject levels of CSF Aß are consistent between sampling intervals to determine whether Aß can be used as a pharmacodynamic biomarker for drug candidates. Previous studies have produced seemingly conflicting observations for the intrasubject stability of CSF Aß levels; we attempt to reconcile these conflicting observations. METHODS: The current study examined the Aß levels in CSF collected with various sampling frequencies from three clinical studies conducted in healthy young or elderly subjects at the same investigative site for the purpose of designing future studies. RESULTS: The results suggest that CSF sampling frequency and/or sampling volume contributes to intrasubject variability in CSF Aß levels, and that lowering the CSF sampling frequency may help minimize this effect. CONCLUSION: These results will help guide clinical trial design for Alzheimer's disease therapy.

Robust central reduction of amyloid-ß in humans with an orally available, non-peptidic ß-secretase inhibitor.

According to the amyloid cascade hypothesis, cerebral deposition of amyloid-ß peptide (Aß) is critical for Alzheimer's disease (AD) pathogenesis. Aß generation is initiated when ß-secretase (BACE1) cleaves the amyloid precursor protein. For more than a decade, BACE1 has been a prime target for designing drugs to prevent or treat AD. However, development of such agents has turned out to be extremely challenging, with major hurdles in cell penetration, oral bioavailability/metabolic clearance, and brain access. Using a fragment-based chemistry strategy, we have generated LY2811376 [(S)-4-(2,4-difluoro-5-pyrimidin-5-yl-phenyl)-4-methyl-5,6-dihydro-4H-[1,3]thiazin-2-ylamine], the first orally available non-peptidic BACE1 inhibitor that produces profound Aß-lowering effects in animals. The biomarker changes obtained in preclinical animal models translate into man at doses of LY2811376 that were safe and well tolerated in healthy volunteers. Prominent and long-lasting Aß reductions in lumbar CSF were measured after oral dosing of 30 or 90 mg of LY2811376. This represents the first translation of BACE1-driven biomarker changes in CNS from preclinical animal models to man. Because of toxicology findings identified in longer-term preclinical studies, this compound is no longer progressing in clinical development. However, BACE1 remains a viable target because the adverse effects reported here were recapitulated in LY2811376-treated BACE1 KO mice and thus are unrelated to BACE1 inhibition. The magnitude and duration of central Aß reduction obtainable with BACE1 inhibition positions this protease as a tractable small-molecule target through which to test the amyloid hypothesis in man.

Cerebrospinal fluid beta-amyloid and dynabridging in Alzheimer's disease drug development.

Cerebrospinal fluid (CSF) has become a matrix for biomarker discovery and development in recent years. A number of biomarkers for pathogenic processes in Alzheimer's disease have been identified. Studies have revealed the diagnostic potential of CSF amyloid-beta, tau and phosphorylated tau levels. California Clinical Trials has conducted a number of studies in collaboration with drug developers that demonstrate the importance of CSF amyloid-beta peptides as biomarkers for drug development. These studies also establish the utility of CSF sampling via continuous indwelling lumbar catheterization (dynabridging) for assessing pharmacokinetic and pharmacodynamic parameters in conjunction with biomarker analysis. Corroborative approaches using multiple biomarker methods including neuroimaging and CSF biomarkers will provide a complete picture of the Alzheimer's disease brain.

Identifying pharmacodynamic protein markers of centrally active drugs in humans: a pilot study in a novel clinical model.

Recognizing specific protein changes in response to drug administration in humans has the potential for significant utility in clinical research. In spite of this, many methodological and practical questions related to assessing such changes are unanswered. We conducted a series of clinical studies to assess the feasibility of measuring changes in proteins related to drug administration using a mass-spectrometry proteomics technique capable of quantifying hundreds of proteins simultaneously in cerebrospinal fluid (CSF) and plasma. Initially, the normal variability of proteins in these compartments was characterized in 16 healthy volunteers over a 2-week period. Drug-associated changes were subsequently assessed in the plasma and CSF proteomes of 11 subjects given atomoxetine, which served as a selective, centrally active probe to test the model. Protein levels in the CSF and plasma were unchanged between visits in the normal variability study. In contrast, statistically significant changes were detected in the CSF protein pattern after drug treatment. These studies suggest that identification of changes in the CSF proteome associated with the administration of centrally active drugs is feasible, and may be of value in the development of new drugs, as well as broader clinical research.

Antidepressant drug-drug interaction profile update.

Drug-drug interactions continue to be underappreciated and misunderstood by most clinicians. Although life-threatening drug interactions are rare, serious clinical consequences, including altered drug response, poor tolerability with reduced medication adherence, and increased costs for care tied to the increased complexity of therapy, are fairly commonplace. Drug interactions may be further complicated by genetic differences in metabolic capacity. Patients who routinely require long-term treatment for depression have an increased likelihood of experiencing a drug-drug interaction since they will take over-the-counter and prescription medications for intercurrent and/or co-morbid illness. Antidepressants can be the object of drug interactions when their metabolic pathways are affected by other substances, or they can precipitate interactions by inhibiting enzyme pathways. Clinicians can improve the short- and long-term outcomes of patients with a depressive disorder by considering the possibility of drug-drug interactions both before prescribing a specific antidepressant and while monitoring for response, adverse effects and patient compliance.

Delayed onset of oculogyric crisis and torticollis with intramuscular haloperidol.

OBJECTIVE: To report a case of delayed-onset dystonic reactions, oculogyric crisis (OGC), and torticollis after treatment with intramuscular haloperidol lactate injection. CASE SUMMARY: A 22-year-old Mexican American woman received intramuscular haloperidol lactate 7.5 mg followed 4 hours later by 10 mg. Twenty-six hours after the first injection, the patient reported that she was unable to lower her gaze and that her neck was stiff. She was immediately given intramuscular benztropine 2 mg; there was a nearly complete remission of symptoms within 15 minutes of treatment. An objective causality assessment revealed a probable relationship between the OGC/torticollis and haloperidol therapy. DISCUSSION: Dystonic reactions have been reported in 10-60% of patients treated with neuroleptic medication, most commonly when patients just start or increase the dose of the drug. The highest frequency of dystonic reactions has occurred in patients receiving high-potency neuroleptics. It has also been suggested that haloperidol-induced dystonic reactions are a result of the toxic metabolites of that agent. CONCLUSIONS: OGC and torticollis reactions may occur 12-24 hours after treatment with a high-potency neuroleptic, even in the absence of symptoms of extrapyramidal side effects (EPSEs). The delayed dystonic reaction may begin suddenly (no early EPSE symptomatology).

Estimation of the absolute bioavailability of rivastigmine in patients with mild to moderate dementia of the Alzheimer's type.

OBJECTIVE: To investigate the bioavailability of rivastigmine, an approved therapy for patients with mild to moderate dementia of the Alzheimer's type, at the highest approved single dose of 6 mg. DESIGN AND SETTING: Randomised, two-period crossover, single-centre, non-blinded, inpatient study. PATIENTS AND PARTICIPANTS: Eleven patients (five females and six males) with mean age 69.5 years. METHODS: The 6 mg oral dose was compared with a 2 mg intravenous dose of rivastigmine infused over a 1-hour period. Plasma concentrations of rivastigmine and its metabolite NAP 226-90 were measured with a gas chromatographic/mass spectrometric method. RESULTS: Following oral administration of a single 6 mg capsule, rivastigmine is rapidly absorbed with an average time to peak plasma concentration of about 1 hour and an average peak concentration of about 25.6 g/L. By a noncompartmental approach, the absolute bioavailability of the 6 mg oral dose of rivastigmine was 71.7% when compared with a 2mg intravenous infusion normalised for dose. By using a population pharmacokinetic model with Michaelis-Menten elimination, absolute bioavailability was estimated at 60.2%. The average terminal elimination half-life of rivastigmine ranged from 1.4 to 1.7 hours for both treatments. Plasma concentrations of the major metabolite, NAP 226-90, formed by the hydrolysis of rivastigmine by cholinesterase are lower than those of the parent compound following oral and intravenous administration. CONCLUSION: A noncompartmental approach and a compartmental approach based on a population pharmacokinetic model with Michaelis-Menten elimination yielded comparable values, 71.7% and 60.2% respectively, for the absolute bioavailability of a single 6 mg oral dose of rivastigmine. Comparison with previous studies confirmed that the oral form of the drug exhibits increased bioavailability with increasing dose, consistent with its nonlinear pharmacokinetics..

Brasofensine treatment for Parkinson's disease in combination with levodopa/carbidopa.

OBJECTIVE: To investigate the safety, tolerability, pharmacokinetic, and pharmacodynamic properties of the dopamine transporter antagonist brasofensine (BMS-204756) in patients with Parkinson's disease receiving levodopa/carbidopa treatment. METHODS: A 4-period crossover study was performed in 8 men (mean age 66 y) with moderate Parkinson's disease (Hoehn-Yahr stage II-IV). A dose escalation study was used in which each patient was given a single oral dose of brasofensine 0.5, 1, 2, or 4 mg, which was coadministered with the patient's usual dose of levodopa/carbidopa. RESULTS: The maximum concentration (Cmax) values of brasofensine observed in plasma after oral administration were 0.35, 0.82, 2.14, and 3.27 ng/mL for the 0.5-, 1-, 2-, and 4-mg doses, respectively; these concentrations occurred 4 hours (time to Cmax) after administration in all cases. Exposure to brasofensine (based on AUC0-infinity) increased at a rate greater than proportional to dose. Based on the motor performance subscale of the Unified Parkinson's Disease Rating Scale, no change in patient disability was observed at any dose level. CONCLUSIONS: Brasofensine was safe and well tolerated in the patient cohort studied at daily doses of up to 4 mg. Adverse events were generally mild in intensity, and included headache, insomnia, phlebitis, dizziness, ecchymosis, and vomiting.