Randomized, double-blind, placebo-controlled, multicenter study to evaluate the safety and tolerability of metrifonate in patients with probable Alzheimer disease. The Metrifonate Study Group. Double-blind, placebo-controlled study of metrifonate, an acetylcholinesterase inhibitor, for Alzheimer disease. A multicentre, randomized, double-blind, placebo-controlled study to evaluate the efficacy, tolerability and safety of two doses of metrifonate in patients with mild-to-moderate Alzheimer's disease: the MALT study. Rivastigmine and donepezil treatment in moderate to moderately-severe Alzheimer's disease over a 2-year period. Efficacy and safety of a loading-dose regimen versus a no-loading-dose regimen of metrifonate in the symptomatic treatment of Alzheimer's disease: a randomized, double-masked, placebo-controlled trial. Metrifonate Study Group.
A randomized, double-blind, placebo-controlled, parallel-group study was undertaken to evaluate the safety and tolerability of a once-daily oral administration of metrifonate in patients with probable mild to moderate Alzheimer disease. Metrifonate was given as a loading dose of 125-225 mg based on weight (2.5 mg/kg) for 2 weeks, followed by a maintenance dose of 50-90 mg based on weight (1.0 mg/kg) for 4 weeks. Twenty-nine patients received metrifonate, and 10 patients received placebo. Metrifonate produced a mean erythrocyte acetylcholinesterase inhibition at the end of treatment of 86.3%. The proportion of patients who experienced at least one adverse event was comparable between the metrifonate (76%) and placebo (80%) groups. Selected adverse events in disfavor of metrifonate (defined as those for which the incidence in the metrifonate and placebo groups differed by at least 10%) were diarrhea, nausea, leg cramps, and accidental injury. Adverse events were predominantly mild in intensity and transient. No severe adverse events were experienced by any patient. The most notable hemodynamic change observed during metrifonate treatment was a clinically insignificant mean decrease in the heart rate (by electrocardiogram) of approximately 9 beats/min, compared with an approximate 3-beats/min decrease for the placebo group. No muscle weakness was observed in this study. No clinically relevant laboratory abnormalities, such as liver toxicity, or changes in exercise tolerance or pulmonary function tests were found with metrifonate treatment. This metrifonate dose provided a high level of acetylcholinesterase inhibition, which was associated in these patients with a favorable safety and tolerability profile. Indeed, the magnitude of the peripheral acetylcholinesterase inhibition is the highest tolerable inhibition level yet observed. Fifty patients with probable Alzheimer disease (AD) completed a 3-month double-blind study to compare metrifonate to placebo. We dosed metrifonate to achieve a 40-60% inhibition of red blood cell acetylcholinesterase activity. The Alzheimer Disease Assessment Scale cognitive subscale score (ADAS-C) served as the primary outcome measure. At the completion of 3 months of treatment, the metrifonate group ADAS-C score differed significantly from the placebo group score by 2.6 points (p < 0.01). A 0.75-point trend toward improvement occurred during treatment in the ADAS cognitive performance of the metrifonate group (p = 0.15), and a 1.10-point deterioration in cognitive performance was found in the placebo group (p < 0.02). On the Global Improvement Scale (GIS), the two groups differed significantly on their changes from baseline to treatment phase (p < 0.02). Significant deterioration occurred in GIS scores (p < 0.01) and in Mini Mental State Examination (MMSE) scores (p < 0.03) in the placebo-treated group. Adverse effects were uncommon and did not require adjustment of the dose of metrifonate or discontinuation of treatment. We achieved a mean of 52.3% decrease in red blood cell acetylcholinesterase activity. During up to 18 months of subsequent open metrifonate treatment of patients, we found a deterioration of 1.68 points per year in MMSE performance. These findings support further study of the effects of metrifonate on deterioration rate in AD. Metrifonate is a long-lasting acetylcholinesterase inhibitor being developed for the symptomatic treatment of Alzheimer's disease (AD).
                This study compared the efficacy, tolerability and safety of two doses of metrifonate in patients with mild-to-moderate AD, over a 26-week treatment period.
                Six hundred and five patients were randomized to placebo (n=208), a 40/50 mg dose (40 or 50 mg by weight; n=200) or a 60/80 mg dose (60 or 80 mg by weight; n=197) metrifonate. Patients randomized to receive metrifonate were administered a once-daily loading dose of 80 or 120 mg based on weight for 2 weeks, followed by the relevant maintenance dose for 24 weeks. Four main clinical domains of AD were assessed: cognition (ADAS-cog and MMSE), psychiatric and behavioural symptoms (ADAS-noncog and NPI), instrumental and basic activities of daily living (DAD) and global functioning (CIBIC-plus, CIBIS-plus and GDS).
                ADAS-cog performance was significantly improved in the 60/80 mg and 40/50 mg dose groups, compared with placebo, in the intention-to-treat (ITT) population. In addition, statistically significant treatment differences were demonstrated between the 60/80 mg dose group and placebo on MMSE, ADAS-noncog, the NPI subitems of hallucinations and apathy, DAD, CIBIC-plus, CIBIS-plus and the GDS. The performance of the 40/50 mg dose group was also significantly superior to placebo on the CIBIS-plus and the NPI subitem aberrant motor behaviour.
                Metrifonate significantly improved a wide range of symptoms across all four clinical domains of AD in a dose-dependent manner, and was safe and well tolerated at both doses studied.
                Copyright 1999 John Wiley & Sons, Ltd. Randomised controlled trials that directly compare cholinesterase inhibitors for the treatment of Alzheimer's disease have been characterised by significant methodological limitations. As a consequence, they have failed to establish whether there are differences between agents in this class. To help address this question, a double-blind, randomised, controlled, multicentre trial was designed to evaluate the efficacy and tolerability of cholinesterase inhibitor treatment in patients with moderate to moderately-severe Alzheimer's disease over a 2-year period.
                Patients were randomly assigned to rivastigmine 3-12 mg/day or donepezil 5-10 mg/day. Efficacy measures comprised assessments of cognition, activities of daily living, global functioning and behavioural symptoms. Safety and tolerability assessments included adverse events and measurement of vital signs.
                In total, 994 patients received cholinesterase inhibitor treatment (rivastigmine, n = 495; donepezil, n = 499), and 57.9% of patients completed the study. The most frequent reason for premature discontinuation in both treatment groups was adverse events, primarily gastrointestinal. Adverse events were more frequent in the rivastigmine group during the titration phase, but similar in the maintenance phase. Serious adverse events were reported by 31.7% of rivastigmine- and 32.5% of donepezil-treated patients, respectively. Rivastigmine and donepezil had similar effects on measures of cognition and behaviour, but rivastigmine showed a statistically significant advantage on measures of activities of daily living and global functioning in the ITT-LOCF population. However, this was not maintained in the non-ITT-LOCF populations. In secondary subgroup analyses, AD patients who had genotypes that encoded for full expression of the butyrylcholinesterase enzyme (BuChE wt/wt; n = 226/340), who were < 75 years of age (n = 362/994) or who had symptoms suggestive of concomitant Lewy body disease (n = 49/994) showed significantly greater benefits from rivastigmine treatment.
                Cholinesterase inhibitor treatment may offer continued therapeutic benefit for up to 2 years in patients with moderate AD. Although both drugs performed similarly on cognition and behaviour, rivastigmine may provide greater benefit in activities of daily living and global functioning. This prospective, randomized, double-masked, placebo-controlled, parallel-group study assessed the safety and efficacy of 2 dosage regimens of once-daily metrifonate in patients with probable Alzheimer's disease (AD) of mild-to-moderate severity. A total of 395 patients were randomized to receive placebo (n = 134) or metrifonate in 1 of 2 regimens. The loading-dose group (n = 133) received a daily loading dose of metrifonate 100 mg or 150 mg (by weight) for 2 weeks, followed by a daily maintenance dose of metrifonate 50 mg for 4 weeks; the no-loading-dose group (n = 128) received the daily maintenance dose of metrifonate 50 mg for 6 weeks. The primary measure of efficacy was the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog); secondary measures of efficacy included the Mini-Mental State Examination (MMSE), the Clinician's Interview Based Impression of Change with Caregiver Input (CIBIC-Plus), the Clinician's Interview Based Impression of Severity with Caregiver Input (CIBIS-Plus), and the ADAS-Noncognitive Subscale (ADAS-Noncog). Safety was assessed by the prevalence of premature study termination and treatment-emergent adverse events, as well as by changes in vital signs, findings on electrocardiographic and neurologic examinations, and abnormalities on laboratory tests. At 4 weeks of treatment, defined by the protocol as the target efficacy determination, the mean ADAS-Cog scores of the intent-to-treat population (last observation carried forward) favored the loading-dose group versus the placebo group, but the difference was not statistically significant. However, at week 6, the difference in mean ADAS-Cog scores was statistically significant compared with placebo. At neither week 4 nor week 6 was there a statistically significant difference in the mean ADAS-Cog scores of the no-loading-dose and placebo groups. For the CIBIC-Plus, the treatment difference between the placebo and loading-dose groups significantly favored metrifonate at week 6 but not at week 4, whereas the treatment difference between the placebo and no-loading-dose groups was statistically significant at both time points. For the MMSE, CIBIS-Plus, and ADAS-Noncog, treatment differences for both groups versus placebo did not reach statistical significance at either week 4 or 6. Assessment of the frequency of adverse events in metrifonate-treated patients revealed that the no-loading-dose regimen was better tolerated than the loading-dose regimen. Given the overall similar efficacy and more favorable safety profile associated with the no-loading-dose regimen versus the loading-dose regimen observed in this study, the no-loading-dose regimen appears to be the better strategy for initiating metrifonate treatment in patients with probable AD of mild-to-moderate severity.
Metrifonate given once per day appears to be related to clinical response in cognition, global improvement, and activities of daily living in patients with mild to moderate Alzheimer's disease.Tolerability is good with adverse events as expected from a cholinesterase inhibitor, but with a low incidence of neuromuscular dysfunction and respiratory failure, too low to be detected in this review. It has been withdrawn from further development.