Latrepirdine for Alzheimer's disease

Sarah Chau, Nathan Herrmann, Myuri T Ruthirakuhan, Jinghan Jenny Chen, Krista L Lanctôt

Current treatments for Alzheimer's disease (AD) provide modest symptomatic relief but do not slow the progression of the disease. Latrepirdine may modulate several targets involved in AD pathology, including lipid peroxidation, mitochondrial permeability, voltage-gated calcium ion channels as well as neurotransmitter receptor activity, and thus potentially represents both a symptomatic and disease-modifying intervention. Several randomized, placebo-controlled trials have sought to evaluate the effect of latrepirdine on cognition, function and behaviour in patients with AD. To evaluate the efficacy and safety of latrepirdine for the treatment of AD. We searched the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 4 June 2014 using the terms: latrepirdine OR dimebon OR dimebolin OR 2,3,4,5-tetrahydro-2,8-dimethyl-5- (2-(6-methyl-3-pyridyl)ethyl)-1H-pyrido(4,3-b)indole. We included all randomized, double-blind, placebo-controlled trials where latrepirdine was administered to patients with mild, moderate or severe AD. We assessed the quality of studies and two authors extracted data. We calculated mean difference (MD), risk ratio (RR) and 95% confidence interval (CI) on an intention-to-treat (ITT) basis for all relevant outcome measures. Seven trials involving a total of 1697 participants were found and six were included in the quantitative analyses. No data were available from the seventh trial. Three trials involving 1243 patients were included in analyses of efficacy outcomes, and four trials involving 1034 patients were included in analyses of safety and tolerability outcomes. We judged five trials to be at high risk of bias due to selective outcome reporting and three to be at high risk of attrition bias. There was low quality evidence favouring latrepirdine on the Clinician's Interview - Based Impression of Change Plus Caregiver Input after 26 weeks (CIBIC-Plus) (MD -0.60, 95% CI -0.89 to -0.31, 1 study, P < 0.001). Due to imprecision in the results, it was not possible to determine whether latrepirdine had any effect on cognition measured with the Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-Cog) (MD -1.49, 95% CI -3.47 to 0.49, 3 studies, P = 0.14) or the Mini-Mental State Examination (MMSE) (MD 0.59, 95% CI -0.94 to 2.11, 3 studies, P = 0.45), or on function measured with the Alzheimer's Disease Co-operative Study - Activities of Daily Living scale (ADCS-ADL) (MD 1.00, 95% CI -1.15 to 3.15, 3 studies, P = 0.36) at study endpoint (26 or 52 weeks). We considered the evidence provided on these outcomes to be of overall low quality. However, there was some high quality evidence showing a very small benefit of latrepirdine on the Neuropsychiatric Inventory (NPI) (MD -1.77, 95% CI -3.09 to -0.45, 3 studies, P = 0.009) at study endpoint (26 or 52 weeks). Additionally, moderate quality evidence suggested that latrepirdine and placebo were comparable in adverse events (RR 1.03, 95% CI 0.93 to 1.14, P = 0.51), serious adverse events (RR 0.86, 95% CI 0.55 to 1.35, P = 0.52), dropouts (RR 0.91, 95% CI 0.65 to 1.27, P = 0.57) and dropouts due to adverse events (RR 0.98, 95% CI 0.57 to 1.67, P = 0.93). Our meta-analysis is limited by the small number of studies, imprecision, inconsistencies between studies and likelihood of bias. Nevertheless, the evidence to date suggests that while not associated with an increased risk of adverse events compared with placebo, there is no effect of latrepirdine on cognition and function in mild-to-moderate AD patients, though there appears to be a modest benefit for behaviour. Further studies should investigate the potential benefit of latrepirdine on neuropsychiatric symptoms in AD.