BackgroundGantenerumab is a fully human monoclonal antibody that binds aggregated amyloid-β (Aβ) and removes Aβ plaques by Fc receptor-mediated phagocytosis. In the SCarlet RoAD trial, we assessed the efficacy and safety of gantenerumab in prodromal Alzheimer’s disease (AD).MethodsIn this randomized, double-blind, placebo-controlled phase III study, we investigated gantenerumab over 2 years. Patients were randomized to gantenerumab 105 mg or 225 mg or placebo every 4 weeks by subcutaneous injection. The primary endpoint was the change from baseline to week 104 in Clinical Dementia Rating Sum of Boxes (CDR-SB) score. We evaluated treatment effects on cerebrospinal fluid biomarkers (all patients) and amyloid positron emission tomography (substudy). A futility analysis was performed once 50% of patients completed 2 years of treatment. Safety was assessed in patients who received at least one dose.ResultsOf the 3089 patients screened, 797 were randomized. The study was halted early for futility; dosing was discontinued; and the study was unblinded. No differences between groups in the primary (least squares mean [95% CI] CDR-SB change from baseline 1.60 [1.28, 1.91], 1.69 [1.37, 2.01], and 1.73 [1.42, 2.04] for placebo, gantenerumab 105 mg, and gantenerumab 225 mg, respectively) or secondary clinical endpoints were observed. The incidence of generally asymptomatic amyloid-related imaging abnormalities increased in a dose- and APOE ε4 genotype-dependent manner. Exploratory analyses suggested a dose-dependent drug effect on clinical and biomarker endpoints.ConclusionsThe study was stopped early for futility, but dose-dependent effects observed in exploratory analyses on select clinical and biomarker endpoints suggest that higher dosing with gantenerumab may be necessary to achieve clinical efficacy.Trial registrationClinicalTrials.gov, NCT01224106. Registered on October 14, 2010.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-017-0318-y) contains supplementary material, which is available to authorized users.
Although dyskinesia is a frequent and important problem in Parkinson's disease (PD), a reliable assessment measure has not been thoroughly developed and tested. We modified the Obeso dyskinesia scale to create an objective rating scale for dyskinesia assessment during activities of daily living. Thirteen physicians and 15 study coordinators involved in a clinical trial independently reviewed videotape segments of PD patients performing three tasks: walking, putting on a coat, and lifting a cup to the lips for drinking. Raters evaluated the severity of worst dyskinesia seen, the types of all dyskinesias seen, and the type of dyskinesia most associated with motoric disability. For all assessments, the total group showed statistically significant inter- and intrarater reliability. Physicians had a higher consistency than did coordinators, but for most measures the difference was not statistically significant. Physicians and coordinators found the scale easy to use and especially practical for rating dyskinesia severity and for identifying the most disabling dyskinesia. Dyskinesias can be assessed in clinical trials and warrant regular documentation.
IMPORTANCE In schizophrenia, the severity of negative symptoms is a key predictor of long-term disability. Deficient signaling through the N-methyl-D-aspartate receptor is hypothesized to underlie many signs and symptoms associated with schizophrenia in particular negative symptoms. Glycine acts as an N-methyl-D-aspartate receptor coagonist. Blockade of the glycine transporter type 1 to inhibit glycine reuptake and elevate synaptic glycine concentrations represents an effective strategy to enhance N-methyl-D-aspartate receptor transmission. OBJECTIVE To determine the efficacy and safety of bitopertin (RG1678), a glycine reuptake inhibitor, in patients with schizophrenia and predominant negative symptoms who were stable while taking an antipsychotic treatment. DESIGN, SETTING, AND PARTICIPANTS This randomized, double-blind, placebo-controlled, phase 2 proof-of-concept trial involved 323 patients with schizophrenia and predominant negative symptoms across 66 sites worldwide. INTERVENTIONS Bitopertin (10, 30, or 60 mg/d) or placebo added to standard antipsychotic therapy for a treatment duration of 8 weeks. MAIN OUTCOMES AND MEASURES Change from baseline in the Positive and Negative Syndrome Scale negative factor score. RESULTS In the per-protocol population, 8 weeks of treatment with bitopertin was associated with a significant reduction of negative symptoms in the 10-mg/d (mean [SE] reduction in negative symptoms score, −25% [2%]; P = .049) and 30-mg/d (mean [SE], −25% [2%]; P = .03) bitopertin groups, a significantly higher response rate and a trend toward improved functioning in the 10-mg/d group when compared with placebo (mean [SE], −19% [2%]). Results reached trend-level significance in the intent-to-treat population. Estimates of bitopertin binding to glycine transporter type 1 showed that low to medium levels of occupancy yielded optimal efficacy in patients, consistent with findings in preclinical assays. CONCLUSIONS AND RELEVANCE Bitopertin-mediated glycine reuptake inhibition may represent a novel treatment option for schizophrenia, with the potential to address negative symptoms.
Tolcapone is a potent catechol-O-methyltransferase inhibitor that prolongs the plasma half-life of levodopa. This multicenter, double-blind, placebo-controlled study used two 10-hour clinical evaluations to compare the efficacy and safety of three doses of tolcapone (50, 200, and 400 mg tid) with placebo in patients with Parkinson's disease (PD) experiencing motor fluctuations from levodopa/carbidopa. One hundred fifty-one patients completed the study. Clinical evaluations lasting 10 hours were performed on day -1 and day 42 using United Parkinson's Disease Rating Scale motor subscale and "on/off" and dyskinesia assessments every 30 minutes. Tolcapone significantly reduced "off" time an average of 40% and increased total "on" time by about 25% at all dose levels, as compared to placebo treatment. Levodopa/carbidopa dosage and frequency were significantly reduced. Tolcapone was well tolerated, with patients experiencing typical dopaminergic side effects that could be reduced or eliminated by lowering levodopa/carbidopa dosages. Tolcapone was effective at prolonging the clinical benefit of levodopa and reducing total levodopa requirements in PD patients with motor fluctuations.
L-Deprenyl (Selegeline) is an enzyme-activated irreversible inhibitor of monoamine oxidase B (MAO B; EC 1.4.3.4). It is used to treat Parkinson's disease at a dose of 5 mg twice a day. Since enzyme inhibition is irreversible, the recovery of functional enzyme activity after withdrawal from L-deprenyl requires the synthesis of new enzyme. We have measured a 40 day half-time for brain MAO B synthesis in Parkinson's disease and in normal subjects after withdrawal from L-deprenyl. This is the first measurement of the synthesis rate of a specific protein in the living human brain. L-Deprenyl is currently used by 50,000 patients with Parkinson's disease in the United States and its use is expected to increase with reports that it may be beneficial in Alzheimer's disease. The slow turnover of brain MAO B suggests that the current clinical dose of L-deprenyl may be excessive and that the clinical efficacy of reduced dosing should be evaluated. Such an evaluation may have mechanistic importance as well as an impact on reducing the side effects and the costs arising from excessive drug use.
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