In June 2011, Dr. Willmar Schwabe Pharmaceuticals sponsored a two-day expert meeting in Amsterdam, The Netherlands. The meeting brought together 19 dementia experts from a range of disciplines and countries to review preclinical and clinical data on Ginkgo biloba special extract EGb 761® in the context of recent developments in the diagnosis and treatment of age-related cognitive decline and Alzheimer's disease (AD). Ginkgo biloba special extract EGb 761® is formally approved and reimbursed for the symptomatic treatment of age-related cognitive decline or dementia by numerous authorities worldwide. The meeting therefore focused on relevant research questions and potential study designs with appropriate target populations to prove the efficacy of Ginkgo biloba special extract EGb 761® as a disease-modifying product in AD and to reveal further relevant modes of action.

Despite decades of research in the field of Alzheimer's disease (AD), a real understanding of its molecular pathophysiology and treatments relevant to the day-to-day lives of patients remain out of reach. Research has, with good reason, focused on certain key pathways and potential mechanisms, but sometimes this has been at the expense of work on other theories, which may be slowing down progress in this field. Interesting theories at present include oxidative stress and caloric restriction. Work on the Aβ cascade should continue but with a shift in focus to its intracellular effects and an awareness that additional pathogenetic factors and processes must be involved – most importantly, brain aging. Hyperphosphorylation of tau, for instance, provides another interesting pathway, with one old drug showing promise in this regard. Moreover, work in epigenetics and on protein homeostasis has produced interesting findings and both lines of investigation may reveal suitable targets for future intervention. Taken together, analysis of the biochemistry of aged neurons and the interplay with pathways of neurodegeneration may lead to a better understanding of AD and how to treat and prevent this condition.

The development of therapies for Alzheimer's disease (AD) presents numerous challenges for physicians, researchers, and the pharmaceutical industry, with many drug candidates showing promise at one stage of clinical research only to fall at the next hurdle. A great number of drugs with a variety of targets and clusters of mechanisms are currently in various stages of basic and clinical investigation. However, these hypothesis-derived agents may be tested much too late in the chronically progressive disease process to demonstrate meaningful effects or outcomes, mirroring the clinical syndromal scenario in which the underlying pathophysiological disease condition is frequently diagnosed extremely late. Moreover, the complexity of the disease calls for developments and improvements in study designs and methods modeled for different target populations and disease stages (e.g. asymptomatic to prodromal to syndromal). New integrated concepts and models of disease pathophysiology, use of validated and qualified biomarkers, outcomes and endpoints, particularly the development of a surrogate outcome, may allow targeting of characteristic mechanism-derived therapies of specifically affected biological systems at different time-points in the disease process, providing increasing opportunities for early and preventative intervention. A core set of feasible diagnostic and predictive biomarkers is already validated and in the process of standardization; however, continued and intensified research efforts will likely reveal a variety of novel biomarkers that grasp the complexity of the underlying disease process. In the future, trials of drugs to modify and prevent AD may embrace enrichment strategies and maybe be stratified by disease stage, genetic factors as well as by disease endophenotypes.

Oxidative stress and mitochondrial failure promote altered protein degradation, reduced neurotransmission, synapse loss and tau/hyperphosphorylation, which are early stages in the development of Alzheimer's disease (AD). A growing volume of data confirms that Ginkgo biloba extract (GBE) reduces oxidative stress and improves mitochondrial respiration and thus may be useful in preventing or slowing down the progression of AD. Treatment of Caenorhabditis elegans with GBE- extract reduces oxidative stress and extends median lifespan compared with controls. Levels of reactive oxygen species, including the superoxide anion radical, were reduced in brains from GBE-treated mice compared with controls. In older mice, GBE resulted in a protective effect by increasing production of adenosine triphosphate in neurons. A respiratory experiment indicated that GBE was able to rescue Aβ-induced defects in energy metabolism, with results suggesting long-term regulatory effects on mitochondria. GBE also had a selective effect on the activities of mitochondrial enzymes that assemble the electron transport system. The flavonoids, bilobalide and some of the ginkgolides (B and J) had a high protective capacity, indicating that a combination of several compounds within standardized Gingko biloba extracts contribute disproportionately for these protective effects.

Neuroplasticity, the ability of synapses to undergo structural adaptations in response to functional demand or dysfunctions is increasingly impaired in aging and Alzheimer's disease. EGb761® has been shown in several preclinical reports to increase nearly all aspects of impaired neuroplasticity (long-term potentiation, spine density, neuritogenesis, neurogenesis). While all three fractions of constituents (ginkgolides, flavonoids, bilobalide) seem to be active, the flavonoids and specifically the aglycone isorhamnetin seem to be most relevant.

Experimental and clinical data suggest that the Ginkgo biloba standardized extract EGb 761® exerts beneficial effects in conditions which are associated with impaired cognitive function. However, the neurochemical correlates of these memory enhancing effects are not yet fully clarified. The aim of this study was to examine the effect of repeated oral administration of EGb 761® and some of its characteristic constituents on extracellular levels of dopamine (DA), noradrenaline (NA), serotonin (5-HT), acetylcholine (ACh) and the metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the medial prefrontal cortex (mPFC) of awake rats by use of in vivo microdialysis technique.

Subacute (14 days, once daily), but not acute, oral treatment with EGb 761® (100 and 300 mg/kg) or the flavonoid fraction, which represents about 24% of the whole extract caused a significant and dose-dependent increase in extracellular DA levels in the mPFC. Repeated administration of EGb 761® also caused a modest but significant increase in the NA levels, whereas the concentrations of 5-HT and those of the metabolites DOPAC, HVA and 5-HIAA were not affected. The same treatment regimen was used in a subsequent study with the aim of investigating the effects of two Ginkgo-specific acylated flavonols, 3-O-(2’’-O-(6’’’-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)quercetin (Q-ag) and 3-O-(2’’-O-(6’’’-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)kaempferol (K-ag). Both compounds together represent about 4.5% of the whole extract. Repeated oral treatment with Q-ag (10 mg/kg) for 14 days caused a significant increase in extracellular DA levels of 159% and extracellular acetylcholine (ACh) levels of 151% compared to controls. Similarly, administration of K-ag (10 mg/kg) induced a significant rise of DA levels to 142% and ACh levels to 165% of controls, whereas treatment with isorhamnetin, an O-methylated aglycon component of EGb 761® flavonol glycosides had no effect. None of the tested flavonoids had a significant effect on extracellular DOPAC and HVA levels.

The present findings provide evidence that the subacute treatment with EGb 761® and its flavonol constituents increases DA and ACh release in the rat mPFC, and suggest that the two Ginkgo-specific acylated flavonol glycosides Q-ag and K-ag are active constituents contributing to these effects. As seen for isorhamnetin, the effect on neurotransmitter levels seems not to be a general effect of flavonols but rather to be a specific action of acylated flavonol glycosides which are present in EGb 761®. The direct involvement of these two flavonol derivatives in the increase of dopaminergic and cholinergic neurotransmission in the prefrontal cortex may be one of the underlying mechanisms behind the reported effects of EGb 761® on the improvement of cognitive function.

Research into Gingko biloba extract EGb 761® has been ongoing for many years. Early studies showed that the extract was superior to placebo in improving symptoms of dementia, and this has been confirmed by more recent research. The GINDEM-NP, GOTADAY and GOT-IT! studies showed that 240 mg/day EGb 761® improved cognitive function, neuropsychiatric symptoms, activities of daily living, and quality of life in patients with mild to moderate dementia compared with placebo, with results reproducible in independent trials. The strength of the effect in terms of improvements in neurosensory symptoms associated with old age and dementia was strong enough to be detected by caregivers and independent clinicians. A combination of 240 mg/day EGb 761® and 10 mg/day (initially 5 mg/day) donepezil was also more effective than either drug alone. Regarding the improvement of neuropsychiatric symptoms, a cross-comparison of studies with different antidementia agents suggests that EGb 761® is at least as effective as memantine, galantamine, and donepezil. Safety data revealed no important safety concerns with EGb 761®.

Research into early intervention for Alzheimer's disease (AD) and dementia has involved cohort data from large epidemiological studies and data from specifically designed intervention trials. Cohort data indicate that use of nootropics and Ginkgo biloba extract may be associated with a reduced incidence of dementia and death. Data from large trials have often been inconclusive due to issues with poor medication adherence. However, such trials do indicate potential benefits with Gingko biloba extract in terms of reduced incidence of dementia of the AD type, vascular dementia and mixed pathology, reduced progression in terms of the clinical dementia rating and improvements in attention and memory. Furthermore, Gingko biloba extract EGb 761® is a useful option for long-term intervention on the basis of decades of previous experience and an excellent safety record. However, benefits can be expected only with sufficient medication adherence and treatment duration, so clear evidence of a disease-modifying benefit of this extract is needed from adequately designed trials using modern methods to ensure high levels of adherence.

In June 2011 a two-day expert meeting “The Ageing Brain” took place in Amsterdam, The Netherlands. The main aim was to discuss the available preclinical and clinical data on Ginkgo biloba special extract EGb 761® in the context of current developments in the diagnosis and treatment of age-related cognitive decline and Alzheimer's disease. 19 dementia experts covering the disciplines bio- and neurochemistry, gerontology, neurology, pharmacology, and psychiatry from Australia, Asia, Europe and North America reviewed available preclinical and clinical data for EGb 761® and identified core topics for future research. Based on a wide range of preclinical effects demonstrated for Ginkgo biloba, EGb 761® can be conceptualized as a multi-target compound with activity on distinct pathophysiological pathways in Alzheimer's disease (AD) and age-related cognitive decline. While symptomatic efficacy in dementia and mild cognitive impairment (MCI) has been demonstrated, interpretation of data from dementia prevention trials is complicated by important methodological issues. Bridging pre-clinical research and clinical research as well as deciding on suitable study designs for future trials with EGb 761® remain important questions. The participants of the “Ageing Brain” meeting on Ginkgo biloba special extract EGb 761® concluded that there is plenty of promising data, both pre-clinical and clinical, to consider future research with the compound targeting cognitive impairment in old age as a worthwhile activity.