A multicenter, randomized, placebo controlled, multiple-dose, safety and pharmacokinetic study of AIT-082 (Neotrofin) in mild Alzheimer's disease patients

Current biomarkers and treatment strategies in Alzheimer disease: An overview and future perspectives

Alzheimer's disease (AD), a progressive degenerative disorder first identified by Alois Alzheimer in 1907, poses a significant public health challenge. Despite its prevalence and impact, there is currently no definitive ante mortem diagnosis for AD pathogenesis. By 2050, the United States may face a staggering 13.8 million AD patients. This review provides a concise summary of current AD biomarkers, available treatments, and potential future therapeutic approaches. The review begins by outlining existing drug targets and mechanisms in AD, along with a discussion of current treatment options. We explore various approaches targeting Amyloid β (Aβ), Tau Protein aggregation, Tau Kinases, Glycogen Synthase kinase-3β, CDK-5 inhibitors, Heat Shock Proteins (HSP), oxidative stress, inflammation, metals, Apolipoprotein E (ApoE) modulators, and Notch signaling. Additionally, we examine the historical use of Estradiol (E2) as an AD therapy, as well as the outcomes of Randomized Controlled Trials (RCTs) that evaluated antioxidants (e.g., vitamin E) and omega-3 polyunsaturated fatty acids as alternative treatment options. Notably, positive effects of docosahexaenoic acid nutriment in older adults with cognitive impairment or AD are highlighted. Furthermore, this review offers insights into ongoing clinical trials and potential therapies, shedding light on the dynamic research landscape in AD treatment.

Identification of Novel Positive Allosteric Modulators of Neurotrophin Receptors for the Treatment of Cognitive Dysfunction

Alzheimer's disease (AD) is the most common neurodegenerative disorder and results in severe neurodegeneration and progressive cognitive decline. Neurotrophins are growth factors involved in the development and survival of neurons, but also in underlying mechanisms for memory formation such as hippocampal long-term potentiation. Our aim was to identify small molecules with stimulatory effects on the signaling of two neurotrophins, the nerve growth factor (NGF) and the brain derived neurotrophic factor (BDNF). To identify molecules that could potentiate neurotrophin signaling, 25,000 molecules were screened, which led to the identification of the triazinetrione derivatives ACD855 (Ponazuril) and later on ACD856, as positive allosteric modulators of tropomyosin related kinase (Trk) receptors. ACD855 or ACD856 potentiated the cellular signaling of the neurotrophin receptors with EC50 values of 1.9 and 3.2 or 0.38 and 0.30 µM, respectively, for TrkA or TrkB. ACD855 increased acetylcholine levels in the hippocampus by 40% and facilitated long term potentiation in rat brain slices. The compounds acted as cognitive enhancers in a TrkB-dependent manner in several different behavioral models. Finally, the age-induced cognitive dysfunction in 18-month-old mice could be restored to the same level as found in 2-month-old mice after a single treatment of ACD856. We have identified a novel mechanism to modulate the activity of the Trk-receptors. The identification of the positive allosteric modulators of the Trk-receptors might have implications for the treatment of Alzheimer's diseases and other diseases characterized by cognitive impairment.

Improving Alzheimer's disease phase II clinical trials

Over the past 30 years, many drugs have been studied as possible treatments for Alzheimer's disease, but only four have demonstrated sufficient efficacy to be approved as treatments, of which three are in the same class. This lack of success has raised questions both in the pharmaceutical industry and academia about the future of Alzheimer's disease therapy. The high cost and low success rate of drug development across many disease areas can be attributed, in large part, to late-stage clinical failures (Schachter and Ramoni, Nat Rev Drug Discov 2007;6:107-8). Thus, identifying in phase II, or preferably phase I, drugs that are likely to fail would have a dramatic impact on the costs associated with developing new drugs. With this in mind, the Alzheimer's Association convened a Research Roundtable on June 23 and 24, 2011, in Washington, DC, bringing together scientists from academia, industry, and government regulatory agencies to discuss strategies for improving the probability of phase II trial results predicting success when considering the go/no-go decision-making process leading to the initiation of phase III.

Novel insights for the treatment of Alzheimer's disease

The development of treatments for Alzheimer's disease (AD) is currently shifting away from the correction of neurotransmitter abnormalities and from attempts to remove the pathognomonic protein deposits. Drug discovery is heading towards novel types of pharmacological interventions which are aimed at more central and upstream pathophysiological events. The large number of upcoming treatment targets can be grouped into two major categories. The first category consists of antecedents of beta amyloid peptide (Aβ) and TAU deposition including Aβ production, degradation and clearance, TAU hyperphosphorylation and aggregation. The second consists of protectors against neuronal dysfunction and premature death such as mitochondrial functioning, nerve growth and regeneration, and neuronal membrane integrity. It is hoped that some of these strategies will not only have larger symptomatic effects than the currently available drugs but also an impact on the underlying neurodegeneration. Since the novel treatments will be typically administered over years they must meet high standards of safety, drug-drug compatibility, and tolerability. Probably the most important target groups for novel treatments are carriers of mutations causing AD, and individuals with minor cognitive impairment representing a pre-dementia stage of the disease. To minimise incorrect case identifications, drug development must be paralleled by improved diagnostic techniques. Novel pharmacological strategies may be cost-effective if disability and need of full-time care can be postponed or prevented without prolonging time lived with dementia or extending survival. We are uncertain whether the advent of novel disease-retarding strategies will revolutionise the management of AD. Symptomatic treatments will continue to be needed, and psychosocial approaches will retain an essential role in supporting affected individuals and their families.

Progress in the development of new drugs in Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease with a global prevalence estimated at 26.55 million in 2006. During the past decades, several agents have been approved that enhance cognition of AD patients. However, the effectiveness of these treatments are limited or controversial and they do not modify disease progression. Recent advances in understanding AD pathogenesis have led to the development of numerous compounds that might modify the disease process. AD is mainly characterized neuropathologically by the presence of two kinds of protein aggregates: extracellular plaques of Abeta-peptide and intracellular neurofibrillary tangles. Abeta and tau could interfere in an original way contributing to a cascade of events leading to neuronal death and transmitter deficits. Investigation for novel therapeutic approaches targeting the presumed underlying pathogenic mechanisms is major focus of research. Antiamyloid agents targeting production, accumulation, clearance, or toxicity associated with Abeta peptide, are some approaches under investigation to limit extracellular plaques of Abeta-peptide accumulation. We can state as an example: Abeta passive and active immunization, secretases modulation, Abeta degradation enhancement, or antiaggregation and antifibrillization agents. Tau-related therapies are also under clinical investigation but few compounds are available. Another alternative approach under development is neuroprotective agents such as antioxidants, anti-inflammatory drugs, compounds acting against glutamate mediated neurotoxicity. Neurorestorative approaches through neurotrophin or cell therapy also represent a minor avenue in AD research. Finally, statins, receptor for advanced glycation end products inhibitors, thiazolidinediones, insulin, and hormonal therapies are some other ways of research for a therapeutic approach of Alzheimer's disease. Taking into account AD complexity, it becomes clear that polypharmacology with drugs targeting different sites could be the future treatment approach and a majority of the recent drugs under evaluation seems to act on multiple targets. This article exposes general classes of disease-modifying therapies under investigation.

Present and prospective clinical therapeutic regimens for Alzheimer's disease

Alzheimer's disease (AD) is an incurable neurodegenerative disorder that produces cognitive impairments that increase in severity as the disease progresses. The clinical symptoms are related to the presence of neuritic plaques and neurofibrillary tangles in the cerebral cortex which represent the pathophysiological hallmarks of AD. The debilitating nature of the disease can result in clinical burden for the patient, emotional strain for those that care for patients with Alzheimer's, and significant financial burden to society. The goals of current treatments, such as cholinesterase inhibitors and N-methyl-D-aspartate receptor antagonist, are to reduce the severity or slow the progression of cognitive symptoms. Although these treatments have demonstrated modest clinical benefit, they are unable to prevent, prohibit, or reverse the underlying pathophysiology of AD. Considerable progress has been made toward the development of disease-modifying treatments. Treatments currently under development mainly target the production, aggregation, and removal of existing amyloid beta-peptide aggregates which are believed to instigate the overall development of the neuropathology. Additional strategies that target tau pathology are being studied to promote neural protection against AD pathology. The current research has continued to expand our knowledge toward the development of disease modifying Alzheimer's therapies; however, no specific treatment strategy capable of demonstrating empirical efficacy and safety has yet to emerge.

5,19-cyclo-9beta,10xi-androstane-3,17-dione promotes neurotrophic factor biosynthesis in 1321N1 human astrocytoma cells and improves passive avoidance learning impairment

Since neurotrophic factors are essential for neurons to form neuronal networks and maintain neuronal functions, neurotrophic factor-like substances or inducers of neurotrophic factors can be useful for the treatment of serious neuronal diseases such as Alzheimer's and Parkinson's diseases. In the present study, we examined an effect of 5,19-cyclo-9beta,10xi-androstane-3,17-dione (CAD) on neurotrophic factor synthesis in glial cells and scopolamine-induced impairment of learning in mice. 1321N1 human astrocytoma cells promoted secretion of certain neurotrophic factors in response to CAD with no cytotoxicity, which caused dramatic neurite outgrowth in rat pheochromocytoma (PC12) cells. In fact, CAD significantly enhanced nerve growth factor (NGF) secretion and its gene expression in 1321N1 cells, in a time and concentration-dependent manner. Because second messengers such as cAMP, inositol 1,4,5-trisphosphates and Ca(2+) induce NGF gene expression, we measured activities of adenylyl cyclase and phospholipase C and intracellular Ca(2+) concentration in 1321N1 cells. However, CAD changed neither second messenger levels. CAD enhanced the gene expression of proto-oncogene, c-fos that is one of the components of transcription factor (AP-1). In addition to those above, the in vivo effects of CAD were also examined. Although injection of muscarinic receptor antagonist scopolamine impaired passive avoidance learning in mice, pretreatment with CAD significantly reversed the adverse effect in a dose-dependent manner. Taking these results together, CAD has enormous therapeutic potential for serious neuronal diseases.

A novel cyathane diterpene, cyrneine A, induces neurite outgrowth in a Rac1-dependent mechanism in PC12 cells

We examined the effects of cyrneine A, a novel diterpene isolated from the mushroom Sarcodon cyrneus, on morphology of rat pheochromocytoma cells (PC12). In response to cyrneine A, PC12 cells extended their neurites, an effect partially blocked by the extracellular signal-regulated kinase (ERK) kinase inhibitor PD98059, but not by the protein kinase C inhibitor GF109203X, nor the phosphatidylinositol-3-kinase inhibitor wortmannin. Cyrneine A did not activate ERK at any of the time points tested (5-120 min), indicating that only the basal activity of ERK is required for cyrneine A-induced neurite outgrowth. As transcriptional regulation is required for neurite extension, the activity of three major transcription factors was determined. Cyrneine A enhanced activation of the transcription factors activator protein-1 (AP-1) and nuclear factor-kappaB, but not CREB, and this was accompanied by enhanced c-fos expression. Moreover, we determined the role of Rac1, a small GTPase protein of the Rho family that regulates actin dynamics, in cyrneine A-induced neurite outgrowth. Treatment with cyrneine A led to actin translocation and subsequently, to accumulation of F-actin at the tip of neurites. Rac1 activity was increased by cyrneine A and expression of a dominant-negative Rac1 mutant significantly inhibited the cyrneine A-induced extension of neurites. These results suggest that cyrneine A induces neurite outgrowth in a Rac1-dependent mechanism.

The G51S purine nucleoside phosphorylase polymorphism is associated with cognitive decline in Alzheimer's disease patients

Alzheimer's disease (AD) is a polygenic and multifactorial complex disease, whose etiopathology is still unclear, however several genetic factors have shown to increase the risk of developing the disease. Purine nucleotides and nucleosides play an important role in the brain. Besides their role in neurotransmission and neuromodulation, they are involved in trophic factor release, apoptosis, and inflammatory responses. These mediators may also have a pivotal role in the control of neurodegenerative processes associated with AD. In this report the distribution of the exonic G/A single nucleotide polymorphism (SNP) in purine nucleoside phosphorylase (PNP) gene, resulting in the amino acid substitution serine to glycine at position 51 (G51S), was investigated in a large population of AD patients (n=321) and non-demented control (n=208). The PNP polymorphism distribution was not different between patients and controls. The polymorphism distribution was also analyzed in AD patients stratified according to differential progressive rate of cognitive decline during a 2-year follow-up. An increased representation of the PNP AA genotype was observed in AD patients with fast cognitive deterioration in comparison with that from patients with slow deterioration rate. Our findings suggest that the G51S PNP polymorphism is associated with a faster rate of cognitive decline in AD patients, highlighting the important role of purine metabolism in the progression of this neurodegenerative disorder.

Disease-modifying therapies in Alzheimer's disease: how far have we come?

Currently, there are no disease-modifying therapies available for Alzheimer's disease (AD). Acetylcholinesterase inhibitors and memantine are licensed for AD and have moderate symptomatic benefits. Epidemiological studies have suggested that NSAIDs, estrogen, HMG-CoA reductase inhibitors (statins) or tocopherol (vitamin E) can prevent AD. However, prospective, randomised studies have not convincingly been able to demonstrate clinical efficacy. Major progress in molecular medicine suggests further drug targets. The metabolism of the amyloid-precursor protein and the aggregation of its Abeta fragment are the focus of current studies. Abeta peptides are produced by the enzymes beta- and gamma-secretase. Inhibition of gamma-secretase has been shown to reduce Abeta production. However, gamma-secretase activity is also involved in other vital physiological pathways. Involvement of gamma-secretase in cell differentiation may preclude complete blockade of gamma-secretase for prolonged times in vivo. Inhibition of beta-secretase seems to be devoid of serious adverse effects according to studies with knockout animals. However, targeting beta-secretase is hampered by the lack of suitable inhibitors to date. Other approaches focus on enzymes that cut inside the Abeta sequence such as alpha-secretase and neprilysin. Stimulation of the expression or activity of alpha-secretase or neprilysin has been shown to enhance Abeta degradation. Furthermore, inhibitors of Abeta aggregation have been described and clinical trials have been initiated. Peroxisome proliferator activated receptor-gamma agonists and selected NSAIDs may be suitable to modulate both Abeta production and inflammatory activation. On the basis of autopsy reports, active immunisation against Abeta in humans seems to have proven its ability to clear amyloid deposits from the brain. However, a first clinical trial with active vaccination against the full length Abeta peptide has been halted because of adverse effects. Further trials with vaccination or passive transfer of antibodies are planned.

Neuroprotection and neurodegenerative diseases: from biology to clinical practice

Neurodegenerative diseases and, in particular, Alzheimer disease, are characterized by progressive neuronal loss correlated in time with the symptoms of the disease considered. Whereas the symptoms of those incapacitating diseases are beginning to be managed with a relative efficacy, the ultimate objective of therapy nonetheless remains preventing cell (neuronal and/or astrocytic) death in a neurocytoprotective approach. In biologic terms, in the light of progress at basic research level, three strategies may be envisaged: (1) antagonizing the cytotoxic causal events (excess intracellular calcium, accumulation of abnormal proteins, excitotoxic effects of amino acids, oxidative stress, processes related to inflammation, etc.); (2) stimulating the endogenous protective processes (anti-free radical or DNA repair systems, production of neurotrophic factors, potential cytoprotective action of steroids, etc.); (3) promoting damaged structure repair strategies (grafts) or deep brain or cortical neurostimulation with a view to triggering (beyond the symptomatic actions) potential 'protective' cell mechanisms. The clinical transition of the various strategies whose efficacy is being tested in animal and/or cell models, experimental analogs of the diseases, and thus the objective demonstration in humans of pharmacological and/or surgical neurocytoprotection, is currently the subject of considerable methodological debate (What are the right psychometric assessment criteria? What are the most pertinent laboratory or neuroradiological markers, etc.?). A number of clinical trials have been completed or are ongoing with drugs that are reputed to be neuroprotective. Thus, elements of the response are beginning to be generated with a view to determining whether it will soon be possible to effectively slow or even stop the neurodegenerative process whose etiology, in most cases, remains obscure.

Protection of sensory function in diabetic rats by Neotrofin

We investigated the ability of Neotrofin, an agent that enhances endogenous nerve growth factor (NGF) levels, to prevent phenotypic, functional and structural changes that occur in the peripheral nerve of streptozotocin-diabetic rats. Eight weeks of Neotrofin treatment prevented depletion of NGF protein in plantar foot skin and sciatic nerve of diabetic rats and increased NGF protein in associated skeletal muscles. These effects were accompanied by maintenance of normal nerve levels of the neuropeptides substance P and calcitonin gene related peptide. Thermal hypoalgesia and conduction slowing of large sensory fibres in diabetic rats were ameliorated by Neotrofin treatment, whereas there was no effect on conduction slowing in large motor fibres or on reduced myelinated fibre axonal calibre. Enhancing endogenous production of neurotrophic factors using small molecules may be an alternative to either exogenous treatment with neurotrophic factors or gene therapy as a therapeutic approach to treating diabetic neuropathy.

Future directions in the treatment of Alzheimer’s disease

Alzheimer's disease (AD) remains the most common of the neurodegenerative disorders. In the elderly, it represents the most frequently occurring form of dementia, especially if considered alongside concomitant cerebrovascular disease. Current treatment involves the use of acetylcholinesterase inhibitors, which have shown symptomatic benefits in the recognised domains of cognition, function and behaviour. While they may have intrinsic disease-modifying activity, this is yet to be proven, and strategies to alter the fundamental neuropathological changes in AD continue to be sought. Much of the evidence suggests that the accumulation of amyloid-beta may play a pivotal role, therefore the bulk of current research is focused on possible intervention along the amyloid pathways. However, the abnormal phosphorylation of tau is also a reasonable target and as the molecular basis of AD is better delineated, more targeted treatment approaches are being proposed. This paper reports on the current data that is setting the future directions for research into AD.

Emerging drugs for sarcopenia: age-related muscle wasting

Sarcopenia is the term widely used to describe the progressive loss of muscle mass with advancing age. Even before significant muscle wasting becomes apparent, ageing is associated with a slowing of movement and a gradual decline in muscle strength, factors that increase the risk of injury from sudden falls and the reliance of the frail elderly on assistance in accomplishing even basic tasks of independent living. Sarcopenia is recognised as one of the major public health problems now facing industrialised nations, and its effects are expected to place increasing demands on public healthcare systems worldwide. Although the effects of ageing on skeletal muscle are unlikely to be halted or reversed, the underlying mechanisms responsible for these deleterious changes present numerous targets for drug discovery with potential opportunities to attenuate muscle wasting, improve muscle function, and preserve functional independence. Very few drugs have been developed with sarcopenia specifically in mind. However, because many of the effects of ageing on skeletal muscle resemble those indicated in many neuromuscular disorders, drugs that target neurodegenerative diseases may also have important relevance for treating age-related muscle wasting and weakness. This review describes a selection of the emerging drugs that have been developed during the period 1997 - 2004, relevant to sarcopenia.

Emerging therapeutics for Alzheimer's disease: an avenue of hope

Emerging therapies for Alzheimer's disease offer hope to patients and their caregivers. Future treatments will probably include combination approaches with agents that modify amyloid processing, deposition, and clearance. One example, the AD vaccine, reduced amyloid burden and changed behavior in animal models of AD, but the human trial was halted when several subjects developed brain inflammation. Anti-inflammatory agents have epidemiologic support, but clinical trials have been disappointing, possibly related to inadequate study with anti-inflammatory agents that modify amyloid processing. Agents that target known cardiovascular risk factors, such as hypercholesterolemia, hypertension, and insulin resistance, have epidemiologic, preclinical, and clinical evidence to warrant further investigation. Heavy metal chelators, antioxidants, neurotrophic factors, glutaminergic modulators, and agents that modify hyperphosphorylation of Tau are other approaches in research and development.