Weighing the benefits of new Alzheimer's treatments

Memantine for dementia

BACKGROUND

Memantine is a moderate affinity uncompetitive antagonist of glutamate NMDA receptors. It is licensed for use in moderate and severe Alzheimer's disease (AD); in the USA, it is also widely used off-label for mild AD.

OBJECTIVES

To determine efficacy and safety of memantine for people with dementia. To assess whether memantine adds benefit for people already taking cholinesterase inhibitors (ChEIs).

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's register of trials (http://www.medicine.ox.ac.uk/alois/) up to 25 March 2018. We examined clinical trials registries, press releases and posters of memantine manufacturers; and the web sites of the FDA, EMEA and NICE. We contacted authors and companies for missing information.

SELECTION CRITERIA

Double-blind, parallel group, placebo-controlled, randomised trials of memantine in people with dementia.

DATA COLLECTION AND ANALYSIS

We pooled and analysed data from four clinical domains across different aetiologies and severities of dementia and for AD with agitation. We assessed the impact of study duration, severity and concomitant use of ChEIs. Consequently, we restricted analyses to the licensed dose (20 mg/day or 28 mg extended release) and data at six to seven months duration of follow-up, and analysed separately results for mild and moderate-to-severe AD.We transformed results for efficacy outcomes into the difference in points on particular outcome scales.

MAIN RESULTS

Across all types of dementia, data were available from almost 10,000 participants in 44 included trials, most of which were at low or unclear risk of bias. For nearly half the studies, relevant data were obtained from unpublished sources. The majority of trials (29 in 7885 participants) were conducted in people with AD.1. Moderate-to-severe AD (with or without concomitant ChEIs). High-certainty evidence from up to 14 studies in around 3700 participants consistently shows a small clinical benefit for memantine versus placebo: clinical global rating (CGR): 0.21 CIBIC+ points (95% confidence interval (CI) 0.14 to 0.30); cognitive function (CF): 3.11 Severe Impairment Battery (SIB) points (95% CI 2.42 to 3.92); performance on activities of daily living (ADL): 1.09 ADL19 points (95% CI 0.62 to 1.64); and behaviour and mood (BM): 1.84 Neuropsychiatric Inventory (NPI) points (95% CI 1.05 to 2.76). There may be no difference in the number of people discontinuing memantine compared to placebo: risk ratio (RR) 0.93 (95% CI 0.83 to 1.04) corresponding to 13 fewer people per 1000 (95% CI 31 fewer to 7 more). Although there is moderate-certainty evidence that fewer people taking memantine experience agitation as an adverse event: RR 0.81 (95% CI 0.66 to 0.99) (25 fewer people per 1000, 95% CI 1 to 44 fewer), there is also moderate-certainty evidence, from three additional studies, suggesting that memantine is not beneficial as a treatment for agitation (e.g. Cohen Mansfield Agitation Inventory: clinical benefit of 0.50 CMAI points, 95% CI -3.71 to 4.71) .The presence of concomitant ChEI does not impact on the difference between memantine and placebo, with the possible exceptions of the BM outcome (larger effect in people taking ChEIs) and the CF outcome (smaller effect).2. Mild AD (Mini Mental State Examination (MMSE) 20 to 23): mainly moderate-certainty evidence based on post-hoc subgroups from up to four studies in around 600 participants suggests there is probably no difference between memantine and placebo for CF: 0.21 ADAS-Cog points (95% CI -0.95 to 1.38); performance on ADL: -0.07 ADL 23 points (95% CI -1.80 to 1.66); and BM: -0.29 NPI points (95% CI -2.16 to 1.58). There is less certainty in the CGR evidence, which also suggests there may be no difference: 0.09 CIBIC+ points (95% CI -0.12 to 0.30). Memantine (compared with placebo) may increase the numbers of people discontinuing treatment because of adverse events (RR 2.12, 95% CI 1.03 to 4.39).3. Mild-to-moderate vascular dementia. Moderate- and low-certainty evidence from two studies in around 750 participants indicates there is probably a small clinical benefit for CF: 2.15 ADAS-Cog points (95% CI 1.05 to 3.25); there may be a small clinical benefit for BM: 0.47 NOSGER disturbing behaviour points (95% CI 0.07 to 0.87); there is probably no difference in CGR: 0.03 CIBIC+ points (95% CI -0.28 to 0.34); and there may be no difference in ADL: 0.11 NOSGER II self-care subscale points (95% CI -0.35 to 0.54) or in the numbers of people discontinuing treatment: RR 1.05 (95% CI 0.83 to 1.34).There is limited, mainly low- or very low-certainty efficacy evidence for other types of dementia (Parkinson's disease and dementia Lewy bodies (for which CGR may show a small clinical benefit; four studies in 319 people); frontotemporal dementia (two studies in 133 people); and AIDS-related Dementia Complex (one study in 140 people)).There is high-certainty evidence showing no difference between memantine and placebo in the proportion experiencing at least one adverse event: RR 1.03 (95% CI 1.00 to 1.06); the RR does not differ between aetiologies or severities of dementia. Combining available data from all trials, there is moderate-certainty evidence that memantine is 1.6 times more likely than placebo to result in dizziness (6.1% versus 3.9%), low-certainty evidence of a 1.3-fold increased risk of headache (5.5% versus 4.3%), but high-certainty evidence of no difference in falls.

AUTHORS' CONCLUSIONS

We found important differences in the efficacy of memantine in mild AD compared to that in moderate-to-severe AD. There is a small clinical benefit of memantine in people with moderate-to-severe AD, which occurs irrespective of whether they are also taking a ChEI, but no benefit in people with mild AD.Clinical heterogeneity in AD makes it unlikely that any single drug will have a large effect size, and means that the optimal drug treatment may involve multiple drugs, each having an effect size that may be less than the minimum clinically important difference.A definitive long-duration trial in mild AD is needed to establish whether starting memantine earlier would be beneficial over the long term and safe: at present the evidence is against this, despite it being common practice. A long-duration trial in moderate-to-severe AD is needed to establish whether the benefit persists beyond six months.

Memantine for dementia

BACKGROUND

Memantine, a low affinity antagonist to glutamate NMDA receptors, may prevent excitatory neurotoxicity in dementia.

OBJECTIVES

To determine efficacy and safety of memantine for people with Alzheimer's disease (AD), vascular (VD) and mixed dementia.

SEARCH STRATEGY

The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group was searched on 8th February 2006. This register contains references from all major healthcare databases and many ongoing trial databases and is updated regularly. In addition, the search engines Copernic and Google were used to identify unpublished trials through inspection of the websites of licensing bodies like the FDA , EMEA and NICE and of companies' websites (Lundbeck, Merz, Forest, Suntori etc) and clinical trials registries.

SELECTION CRITERIA

Double-blind, parallel group, placebo-controlled, randomized trials of memantine in people with dementia.

DATA COLLECTION AND ANALYSIS

Data were pooled where possible. Intention-to-treat (ITT) and observed case (OC) analyses are reported.

MAIN RESULTS

1. Moderate to severe AD. Two out of three six month studies show a small beneficial effect of memantine. Pooled data indicate a beneficial effect at six months on cognition (2.97 points on the 100 point SIB, 95% CI 1.68 to 4.26, P < 0.00001), activities of daily living (1.27 points on the 54 point ADCS-ADLsev, 95% CI 0.44 to 2.09, P = 0.003) and behaviour (2.76 points on the 144 point NPI, 95% CI 0.88 to 4.63, P=0.004), supported by clinical impression of change (0.28 points on the 7 point CIBIC+, 95% CI 0.15 to 0.41, P < 0.0001).2. Mild to moderate AD. Pooled data from three unpublished studies indicate a marginal beneficial effect at six months on ITT cognition (0.99 points on the 70 point ADAS-Cog, 95% CI 0.21 to 1.78, P = 0.01) which was barely detectable clinically (0.13 CIBIC+ points, 95% CI 0.01 to 0.25, P = 0.03) but no effect on behaviour, activities of daily living or OC analysis of cognition.3. Mild to moderate vascular dementia. Pooled data from two six month studies indicated a small beneficial effect of memantine on cognition (1.85 ADAS-Cog points, 95% CI 0.88 to 2.83, P = 0.0002), and behaviour (0.84 95% CI 0.06 to 0.91, P = 0.03) but this was not supported by clinical global measures.4. Patients taking memantine were slightly less likely to develop agitation (134/1739, 7.7% versus 175/1873, 9.3% OR 0.78, 95% CI 0.61 to 0.99, P = 0.04). This effect was slightly larger, but still small, in moderate to severe AD (58/506 [12%] vs 88/499 [18%]; OR = 0.6, 95% CI 0.42 to 0.86, P = 0.005). There is no evidence either way about whether it has an effect on agitation which is already present.5. Memantine is well tolerated.

AUTHORS' CONCLUSIONS

Memantine has a small beneficial effect at six months in moderate to severe AD. In patients with mild to moderate dementia, the small beneficial effect on cognition was not clinically detectable in those with vascular dementia and was detectable in those with AD. Memantine is well tolerated.

A longitudinal study regarding conversion from mild memory impairment to dementia in a Japanese community

OBJECTIVE

To estimate the rate that subjects with Mild Memory Impairment /Not Dementia (MMI/ND) shifted to dementia in a population-based cohort and to establish simple diagnostic methods for identification of high-risk persons for dementia.

METHODS

Subjects in a community-based elderly cohort of MMI/ND were followed longitudinally. Subjects were selected from the participants in the first Nakayama study. MMI/ND was defined as memory deficit with objective memory assessment, without dementia, impairment of general cognitive function, or disability in activities of daily living. The conversion rate was calculated using the person-year method.

RESULTS

At baseline, the sample consisted of 104 subjects (59 female; 45 male) selected from 1,162 community dwellers aged over 65 year. During the five-year follow-up, 14 subjects died, 13 moved to other communities, and six refused to participate further. Eleven (10.6%) subjects were diagnosed with Alzheimer's disease (AD), five (4.8%) were diagnosed with vascular dementia (VaD), and six (5.8%) were diagnosed with dementia of other etiology. The annual conversion rate that MMI/ND shifted to AD is calculated on 8.5% per 100 person-year, and shifted to dementia on 16.1% per 100 person-year in this survey.

CONCLUSIONS

The rate at which subjects with MMI/ND whose conditions shifted to dementia was the same as the rate that subjects with mild cognitive impairment (MCI) shifted to dementia in a previous report. It would be useful to identify groups of high-risk individuals for dementia by simple diagnostic methods.

Memantine for dementia

BACKGROUND

Memantine, a low affinity antagonist to glutamate NMDA receptors, may prevent excitatory neurotoxicity in dementia.

OBJECTIVES

To determine efficacy and safety of memantine for people with Alzheimer's disease (AD), vascular (VD) and mixed dementia.

SEARCH STRATEGY

The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group was searched on 20 May 2005. This register contains references from all major healthcare databases and many ongoing trial databases and is updated regularly. In addition the search engines Copernic and Google were used to identify unpublished trials through inspection of the websites of licensing bodies like the FDA , EMEA and NICE and of companies' websites (Lundbeck, Merz, Forest, Suntori etc) and clinical trials registries.

SELECTION CRITERIA

Double-blind, parallel group, placebo-controlled, randomized trials of memantine in people with dementia.

DATA COLLECTION AND ANALYSIS

Data were pooled where possible. Intention-to-treat (ITT) and observed case (OC) analyses are reported.

MAIN RESULTS

1. Moderate to severe AD. Two out of three six month studies show a small beneficial effect of memantine. Pooled data indicate a beneficial effect at six months on cognition (4.12 points on the 100 point SIB , 95% CI 2.14 to 5.74, P < 0.00001), activities of daily living (1.27 points on the 54 point ADCS-ADLsev, 95% CI 0.44 to 2.09, P = 0.003) and behaviour (2.76 points on the 144 NPI, 95% CI 0.88 to 4.63, P = 0.004), supported by clinical impression of change (0.28 points on the 7 point CIBIC+, 95% CI 0.15 to 0.41, P < 0.0001).2. Mild to moderate AD. In a single six month trial, memantine had a beneficial effect on ITT analysis of cognition, (1.9 ADAS-Cog points, 95% CI 0.35 to 3.45, P = 0.02) and behaviour (3.50 NPI points 95% CI 0.15 to 6.85, P = 0.04) supported by clinical global impression of change (0.30 CIBIC+ points, 95% CI 0.09 to 0.51, P = 0.005), but no effect on activities of daily living or OC analysis of cognition. The statistical significance of these benefits could be overturned by data from two unpublished studies which are known to show no significant effect. 3. Mild to moderate vascular dementia. In two six month studies, memantine improved cognition (1.85 ADAS-Cog points, 95% CI 0.88 to 2.83, P = 0.0002), and behaviour (0.84 95% CI 0.06 to 0.91, P = 0.03) but this was not supported by clinical global measures.4. Patients taking memantine appeared to be less likely to develop agitation (93/1167 [8%] versus 134/1141 [12%] (Peto odds ratio (OR): 0.65, 95% CI 0.49 to 0.86, P = 0.002). This was consistently seen in moderate to severe dementia. There were no data which suggested an effect on agitation which is already present.5. Memantine is well tolerated.

AUTHORS' CONCLUSIONS

Published data suggest a small beneficial effect of memantine at six months in moderate to severe AD. The beneficial effect on cognition in patients with mild to moderate vascular dementia was not detectable on global assessment at six months. Whether memantine has any effect in mild to moderate AD is unknown.

Current drugs and future hopes in the treatment of Alzheimer's disease

In spite of several years of experience with the use of cholinesterase inhibitors for treatment of symptoms of Alzheimer's disease their influence on disease progression remains still unclear. New cholinesterase inhibitors should provide an additional neuroprotective activity, because only substances which stop neuronal death can influence disease progression. New treatment strategies are focusing on amyloid processing, preventing the occurrence of toxic A beta(1-42) peptide. These procedures include the vaccination trials, but their clinical usefulness has to be proven. Also strategies focussing on neurofibrillary pathologies should be explored in detail. Drug development for Alzheimer's disease should include all pathological events associated with neurodegeneration, like oxidative stress, neuroinflammation or disturbances in growth factor signaling. Abnormal protein aggregation as a common feature of different neurodegenerative diseases might also be a promising drug target. Beside beta sheet breakers directed against beta-amyloid deposition the endogenous protein beta-synuclein or derivatives of it might be able to counteract aggregation of alpha-synuclein as well as of amyloid beta protein. Interaction with alpha-synuclein deserves special attention because it might be an early step of synaptic degeneration. Due to the complexity of the disease combination of different drugs might be the most promising way to go. The parallel development of early biological markers should enable intervention in pre-symptomatic disease stages.

Neuroprotective effect of memantine in different retinal injury models in rats

PURPOSE

To evaluate the neuroprotective effect of memantine, an NMDA receptor channel blocker, in two retinal ganglion cell (RGC) injury models in rats.

METHODS

Neuroprotective effect of memantine was tested in partial optic nerve injury and chronic ocular hypertensive models. In the optic nerve injury model, memantine (0.1 - 30 mg/kg) was injected intraperitoneally immediately after injury. Two weeks later, optic nerve function was determined by measuring compound action potential and surviving RGC was determined by retrograde labeling with dextran tetramethyl rhodamine. Chronic ocular hypertension was attained by laser photocoagulation of episcleral and limbal veins. Memantine (5 or 10 mg/kg) was administered continuously each day with an osmotic pump, either immediately after or 10 days after first laser photocoagulation, for 3 weeks, after which RGC survival was determined.

RESULTS

Two weeks after partial optic nerve injury, there was approximately 80% reduction in RGC number. Memantine (5 mg/kg) caused a twofold increase in compound action potential amplitude and a 1.7-fold increase in survival of RGCs, respectively. In the chronic ocular hypertension model there was 37% decrease in RGCs after 3 weeks of elevated intraocular pressure. Memantine (10 mg/kg daily) reduced ganglion cell loss to 12% when applied immediately after first laser photocoagulation, and prevented any further loss when applied 10 days after first laser photocoagulation.

CONCLUSION

The protective effect of memantine suggests that excessive stimulation of NMDA receptors by glutamate is involved in causing cell damage in these RGC injury models.

Screening for mild cognitive impairment (MCI) utilizing combined mini-mental-cognitive capacity examinations for identifying dementia prodromes

OBJECTIVE

To test correctness of results when combining Mini-Mental State Examination (MMSE) and Cognitive Capacity Screening Examination (CCSE) for identifying mild cognitive impairment (MCI) among non-demented elderly subjects at risk for developing dementia.

METHODS

A retrospective study was conducted among consecutively referred volunteers with memory complaints to a research out-patient clinic. Two cognitive screening tests (MMSE and CCSE) were performed according to established protocol. Resulting combined screening test (termed by acronym as CMC) combined the non-overlapping test items derived from both MMSE and CCSE. Conversion to dementia at follow-up served as the 'gold-standard' for evaluating correctness of CMC for identifying MCI.

RESULTS

Of 351 subjects completing cognitive assessments and meeting requirements for study protocol, 84 (23.9%) developed dementia of different types within 3-6 years (3.89 +/- 2.17) of follow-up. Among these, 47 met criteria for probable Alzheimer disease (AD), 22 for probable vascular dementia (VaD), 12 for mixed AD/VaD and three for probable frontotemporal dementia. When final diagnosis of AD was used as the 'gold standard' for testing correctness of MCI identified by cognitive screening tests, sensitivities of MMSE, CCSE and CMC for identifying MCI were relatively 61.0%, 74.3% and 83.1% with minimum specificity set at 80%. When diagnosis of all types of dementia was used as the standard for testing predictive correctness of MCI, CCSE emerged as an optimal MCI screening test.

CONCLUSION

Combining the CCSE and MMSE screening tests resulted in higher sensitivity than was achieved by MMSE alone and maintained specificity at comparable levels for identifying MCI. The results confirmed that CMC has optimal correctness and utility as a brief cognitive test for screening MCI as a prodrome for dementia among non-demented elderly populations.