Monitoring synaptic pathology in Alzheimer's disease through fluid and PET imaging biomarkers: a comprehensive review and future perspectives.

Alzheimer's disease (AD) is currently constrained by limited clinical treatment options. The initial pathophysiological event, which can be traced back to decades before the clinical symptoms become apparent, involves the excessive accumulation of amyloid-beta (Aß), a peptide comprised of 40-42 amino acids, in extraneuronal plaques within the brain. Biochemical and histological studies have shown that overaccumulation of Aß instigates an aberrant escalation in the phosphorylation and secretion of tau, a microtubule-binding axonal protein. The accumulation of hyperphosphorylated tau into intraneuronal neurofibrillary tangles is in turn correlated with microglial dysfunction and reactive astrocytosis, culminating in synaptic dysfunction and neurodegeneration. As neurodegeneration progresses, it gives rise to mild clinical symptoms of AD, which may eventually evolve into overt dementia. Synaptic loss in AD may develop even before tau alteration and in response to possible elevations in soluble oligomeric forms of Aß associated with early AD. These findings largely rely on post-mortem autopsy examinations, which typically involve a limited number of patients. Over the past decade, a range of fluid biomarkers such as neurogranin, α-synuclein, visinin-like protein 1 (VILIP-1), neuronal pentraxin 2, and ß-synuclein, along with positron emission tomography (PET) markers like synaptic vesicle glycoprotein 2A, have been developed. These advancements have facilitated the exploration of how synaptic markers in AD patients correlate with cognitive impairment. However, fluid biomarkers indicating synaptic loss have only been validated in cerebrospinal fluid (CSF), not in plasma, with the exception of VILIP-1. The most promising PET radiotracer, [11C]UCB-J, currently faces significant challenges hindering its widespread clinical use, primarily due to the necessity of a cyclotron. As such, additional research geared toward the exploration of synaptic pathology biomarkers is crucial. This will not only enable their extensive clinical application, but also refine the optimization process of AD pharmacological trials.

Evidence for reduced anti-inflammatory microglial phagocytic response in late-life major depression.

Major depressive disorder (MDD) is associated with Alzheimer's disease (AD) but the precise mechanisms underlying this relationship are not understood. While it is well established that cerebrospinal fluid (CSF) soluble levels of triggering receptor expressed on myeloid cells 2 (sTREM2) increase during early stages of AD, how sTREM2 levels behave in subjects with MDD is not known. In a longitudinal study, we measured CSF sTREM2 levels in 27 elderly cognitively intact individuals with late-life major depression (LLMD) and in 19 healthy controls. We tested the hypothesis that, similarly to what happens in early stages of AD, CSF sTREM2 would be elevated in MDD. In addition, we compared the associations of CSF sTREM2, pro- and anti- inflammatory, and AD biomarkers in LLMD and control subjects. Surprisingly, we found that mean CSF sTREM2 levels were significantly reduced in LLMD compared to controls. This reduction was no longer significant at the 3-year follow-up visit when depression severity improved. In addition, we found that CSF sTREM2 was associated with AD biomarkers and proinflammatory cytokines in controls but not in LLMD. These findings suggest that impaired microglia phagocytic response to AD pathology may be a novel link between MDD and AD.

Role of monomeric amyloid-ß in cognitive performance in Alzheimer's disease: Insights from clinical trials with secretase inhibitors and monoclonal antibodies.

According to the ß-amyloid (Aß) hypothesis of Alzheimer's disease (AD), brain Aß accumulation is the primary cascade event leading to cognitive deficit and dementia. Numerous anti-Aß drugs either inhibiting production or aggregation of Aß or stimulating its clearance have failed to show clinical benefit in large scale AD trials, with ß- and γ-secretase inhibitors consistently worsening cognitive and clinical decline. In June 2021, the FDA approved aducanumab, an anti-Aß monoclonal antibody for early AD based on its ability to reduce brain amyloid plaques, while two other amyloid-clearing antibodies (lecanemab and donanemab) have recently produced encouraging cognitive and clinical results. We reviewed AD trials using PubMed, meeting abstracts and ClinicalTrials.gov and evaluated the effects of such drugs on cerebrospinal fluid (CSF) Aß levels, correlating them with cognitive effects. We found that ß-secretase and γ-secretase inhibitors produce detrimental cognitive effects by significantly reducing CSF Aß levels. We speculate that monoclonal antibodies targeting Aß protofibrils, fibrils or plaques may improve cognitive performance in early AD by increasing soluble Aß levels through Aß aggregate disassembly and/or stabilization of existing Aß monomers.These findings suggest that the real culprit in AD may be decreased levels of soluble monomeric Aß due to sequestration into brain Aß aggregates and plaques.

Plasma ATN(I) classification and precision pharmacology in Alzheimer's disease.

Evaluating potential therapies for Alzheimer's disease (AD) depends on use of biomarkers for appropriate subject selection and monitoring disease progression. Biomarkers that predict onset of clinical symptoms are particularly important for AD because they enable intervention before irreversible neurodegeneration occurs. The amyloid-ß-tau-neurodegeneration (ATN) classification system is currently used as a biological staging model for AD and is based on three classes of biomarkers evaluating amyloid-ß (Aß), tau pathology and neurodegeneration or neuronal injury. Promising blood-based biomarkers for each of these categories have been identified (Aß42/Aß40 ratio, phosphorylated tau, neurofilament light chain), and this matrix is now being expanded toward an ATN(I) system, where "I" represents a neuroinflammatory biomarker. The plasma ATN(I) system, together with APOE genotyping, offers a basis for individualized evaluation and a move away from the classic "one size fits all" approach toward a biomarker-driven individualisation of therapy for patients with AD.

A critical appraisal of tau-targeting therapies for primary and secondary tauopathies.

INTRODUCTION: Primary tauopathies are neurological disorders in which tau protein deposition is the predominant pathological feature. Alzheimer's disease is a secondary tauopathy with tau forming hyperphosphorylated insoluble aggregates. Tau pathology can propagate from region to region in the brain, while alterations in tau processing may impair tau physiological functions. METHODS: We reviewed literature on tau biology and anti-tau drugs using PubMed, meeting abstracts, and ClnicalTrials.gov. RESULTS: The past 15 years have seen >30 drugs interfering with tau aggregation, processing, and accumulation reaching the clinic. Initial results with tau aggregation inhibitors and anti-tau monoclonal antibodies have not shown clinical efficacy. DISCUSSION: The reasons for these clinical failures are unclear but could be linked to the clearing of physiological forms of tau by non-specific drugs. Research is now concentrating efforts on developing reliable translational animal models and selective compounds targeting specific tau epitopes, neurotoxic tau aggregates, and post-translational tau modifications.

Amyloid-ß immunotherapy for alzheimer disease: Is it now a long shot?

The amyloid-ß (Aß) cascade hypothesis of Alzheimer disease (AD) holds that brain accumulation of Aß initiates the disease process. Accordingly, drug research has targeted Aß production, clearance, and deposition as therapeutic strategies. Unfortunately, candidate drugs have failed to show clinical benefit in established, early, or prodromal disease, or in those with high AD risk. Currently, monoclonal antibodies specifically directed against the most neurotoxic Aß forms are undergoing large-scale trials to confirm initially encouraging results. However, recent findings on the normal physiology of Aß suggest that accumulation may be compensatory rather than the pathological initiator. If this is true, alternative strategies will be needed to defeat this devastating disease. ANN NEUROL 2019;85:303-315.

Time to test antibacterial therapy in Alzheimer's disease.

Alzheimer's disease is associated with cerebral accumulation of amyloid-ß peptide and hyperphosphorylated tau. In the past 28 years, huge efforts have been made in attempting to treat the disease by reducing brain accumulation of amyloid-ß in patients with Alzheimer's disease, with no success. While anti-amyloid-ß therapies continue to be tested in prodromal patients with Alzheimer's disease and in subjects at risk of developing Alzheimer's disease, there is an urgent need to provide therapeutic support to patients with established Alzheimer's disease for whom current symptomatic treatment (acetylcholinesterase inhibitors and N-methyl d-aspartate antagonist) provide limited help. The possibility of an infectious aetiology for Alzheimer's disease has been repeatedly postulated over the past three decades. Infiltration of the brain by pathogens may act as a trigger or co-factor for Alzheimer's disease, with Herpes simplex virus type 1, Chlamydia pneumoniae, and Porphyromonas gingivalis being most frequently implicated. These pathogens may directly cross a weakened blood-brain barrier, reach the CNS and cause neurological damage by eliciting neuroinflammation. Alternatively, pathogens may cross a weakened intestinal barrier, reach vascular circulation and then cross blood-brain barrier or cause low grade chronic inflammation and subsequent neuroinflammation from the periphery. The gut microbiota comprises a complex community of microorganisms. Increased permeability of the gut and blood-brain barrier induced by microbiota dysbiosis may impact Alzheimer's disease pathogenesis. Inflammatory microorganisms in gut microbiota are associated with peripheral inflammation and brain amyloid-ß deposition in subjects with cognitive impairment. Oral microbiota may also influence Alzheimer's disease risk through circulatory or neural access to the brain. At least two possibilities can be envisaged to explain the association of suspected pathogens and Alzheimer's disease. One is that patients with Alzheimer's disease are particularly prone to microbial infections. The other is that microbial infection is a contributing cause of Alzheimer's disease. Therapeutic trials with antivirals and/or antibacterials could resolve this dilemma. Indeed, antiviral agents are being tested in patients with Alzheimer's disease in double-blind placebo-controlled studies. Although combined antibiotic therapy was found to be effective in animal models of Alzheimer's disease, antibacterial drugs are not being widely investigated in patients with Alzheimer's disease. This is because it is not clear which bacterial populations in the gut of patients with Alzheimer's disease are overexpressed and if safe, selective antibacterials are available for them. On the other hand, a bacterial protease inhibitor targeting P. gingivalis toxins is now being tested in patients with Alzheimer's disease. Clinical studies are needed to test if countering bacterial infection may be beneficial in patients with established Alzheimer's disease.

Structure-activity relationships of flurbiprofen analogues as stabilizers of the amyloidogenic protein transthyretin.

The inherent amyloidogenic potentialof wild type transthyretin (TTR) is enhanced by a large number of point mutations, which destabilize the TTR tetramer, thereby promoting its disassembly and pathological aggregation responsible for TTR-related amyloidosis. TTR stabilizers are able to interact with the thyroxine-binding sites of TTR, stabilizing its tetrameric native state and inhibiting amyloidogenesis. Herein, we report on in vitro, ex vivo, and X-ray analyses to assess the TTR structural stabilization by analogues of flurbiprofen, a non-steroidal anti-inflammatory drug (NSAID). Overall, considering together binding selectivity and protective effects on TTR native structure by flurbiprofen analogues in the presence of plasma proteins, as determined by Western Blot,the aforementioned properties of analyzed compounds appear to be better (CHF5075 and CHF4802) or similar (CHF4795) or worse (CHF5074, also known as CSP-1103) as compared to those of diflunisal, used as a reference TTR stabilizer. Molecular details of the determinants affecting the interactionsof CHF5075, CHF4802, and CHF4795 with wild type TTRand of CHF5074 withtheamyloidogenic A25TTTR variant havebeen elucidated by X-ray analysis. Distinct interactions with TTR appear to characterize flurbiprofen analogues and the NSAID diflunisal and its analogues as TTR stabilizers. Relationships between stabilizing effect on TTR by flurbiprofen analogues determined experimentally and molecular details of their interactions with TTR have been established, providing the rationale for their protective effects on the native protein structure.

Amyloid deposition in a mouse model humanized at the transthyretin and retinol-binding protein 4 loci.

Familial amyloidotic polyneuropathy is an autosomal dominant disorder caused by a point mutation in the transthyretin (TTR) gene. The process of TTR amyloidogenesis begins with rate-limiting dissociation of the TTR tetramer. Thus, the TTR stabilizers, such as Tafamidis and Diflunisal, are now in clinical trials. Mouse models will be useful to testing the efficacy of these drugs. Although several mouse models have been generated, they all express mouse Rbp4. Thus, human TTR associates with mouse RBP4, resulting in different kinetic and thermodynamic stability profiles of TTR tetramers. To overcome this problem, we previously produced humanized mouse strains at both the TTR and Rbp4 loci (Ttr hTTRVal30 , Ttr hTTRMet30 , and Rbp4 hRBP4 ). By mating these mice, we produced double-humanized mouse strains, Ttr hTTRVal30/hTTRVal30 :Rbp4 hRBP4/hRBP4 and Ttr hTTRVal30/Met30 :Rbp4 hRBP4/hRBP4 . We used conventional transgenic mouse strains on a wild-type (Ttr +/+ :Tg[6.0hTTRMet30]) or knockout Ttr background (Ttr-/-:Tg[6.0hTTRMet30]) as reference strains. The double-humanized mouse showed 1/25 of serum hTTR and 1/40 of serum hRBP4 levels. However, amyloid deposition was more pronounced in Ttr hTTRVal30/Met30 :Rbp4 hRBP4/hRBP4 than in conventional transgenic mouse strains. In addition, a similar amount of amyloid deposition was also observed in Ttr hTTRVal30/ hTTRVal30 :Rbp4 hRBP4/ hRBP4 mice that carried the wild-type human TTR gene. Furthermore, amyloid deposition was first observed in the sciatic nerve without any additional genetic change. In all strains, anti-TTR antibody-positive deposits were found in earlier age and at higher percentage than amyloid fibril deposition. In double-humanized mice, gel filtration analysis of serum revealed that most hTTR was free of hRBP4, suggesting importance of free TTR for amyloid deposition.

Emerging drugs to reduce abnormal ß-amyloid protein in Alzheimer's disease patients.

INTRODUCTION: Currently available drugs against Alzheimer's disease (AD) target cholinergic and glutamatergic neurotransmissions without affecting the underlying disease process. Putative disease-modifying drugs are in development and target ß-amyloid (Aß) peptide and tau protein, the principal neurophatological hallmarks of the disease. Areas covered: Phase III clinical studies of emerging anti-Aß drugs for the treatment of AD were searched in US and EU clinical trial registries and in the medical literature until May 2016. Expert opinion: Drugs in Phase III clinical development for AD include one inhibitor of the ß-secretase cleaving enzyme (BACE) (verubecestat), three anti-Aß monoclonal antibodies (solanezumab, gantenerumab, and aducanumab), an inhibitor of receptor for advanced glycation end products (RAGE) (azeliragon) and the combination of cromolyn sodium and ibuprofen (ALZT-OP1). These drugs are mainly being tested in subjects during early phases of AD or in subjects at preclinical stage of familial AD or even in asymptomatic subjects at high risk of developing AD. The hope is to intervene in the disease process when it is not too late. However, previous clinical failures with anti-Aß drugs and the lack of fully understanding of the pathophysiological role of Aß in the development of AD, put the new drugs at substantial risk of failure.

Recalibrating the Risk-Benefit Profiles of Lecanemab and Donanemab: Scales, Immunoreactivity, and Changes in Amyloid-ß42.

Three recent anti-amyloid-ß antibody trials for Alzheimer's disease reported similar effect sizes, used non-reactive saline as placebo, and showed large numbers of adverse events including imaging anomalies (ARIA) that correlate with cognitive changes. Conversely, all previous antibody trials were less reactive and pronounced ineffective. We argue that these observations point to unblinding bias, inflating apparent efficacy and thus altering the risk-benefit balance. Further, we highlight data demonstrating that beyond reducing amyloid, monoclonal antibodies increase monomeric amyloid-ß42 in cerebrospinal fluid, which may explain potential benefits. We should recalibrate the efficacy of these antibodies and devote more resources into strategies beyond removing amyloid.

A critical appraisal of blood-based biomarkers for Alzheimer's disease.

Biomarkers that predict the clinical onset of Alzheimer's disease (AD) enable the identification of individuals in the early, preclinical stages of the disease. Detecting AD at this point may allow for more effective therapeutic interventions and optimized enrollment for clinical trials of novel drugs. The current biological diagnosis of AD is based on the AT(N) classification system with the measurement of brain deposition of amyloid-ß (Aß) ("A"), tau pathology ("T"), and neurodegeneration ("N"). Diagnostic cut-offs for Aß1-42, the Aß1-42/Aß1-40 ratio, tau and hyperphosphorylated-tau concentrations in cerebrospinal fluid have been defined and may support AD clinical diagnosis. Blood-based biomarkers of the AT(N) categories have been described in the AD continuum. Cross-sectional and longitudinal studies have shown that the combination of blood biomarkers tracking neuroaxonal injury (neurofilament light chain) and neuroinflammatory pathways (glial fibrillary acidic protein) enhance sensitivity and specificity of AD clinical diagnosis and improve the prediction of AD onset. However, no international accepted cut-offs have been identified for these blood biomarkers. A kit for blood Aß1-42/Aß1-40 is commercially available in the U.S.; however, it does not provide a diagnosis, but simply estimates the risk of developing AD. Although blood-based AD biomarkers have a great potential in the diagnostic work-up of AD, they are not ready for the routine clinical use.

Receptor for advanced glycation end products contributes to postnatal pulmonary development and adult lung maintenance program in mice.

The role of the receptor for advanced glycation end products (RAGE) in promoting the inflammatory response through activation of NF-κB pathway is well established. Recent findings indicate that RAGE may also have a regulative function in apoptosis, as well as in cellular proliferation, differentiation, and adhesion. Unlike other organs, lung tissue in adulthood and during organ development shows relatively high levels of RAGE expression. Thus a role for the receptor in lung organogenesis and homeostasis may be proposed. To evaluate the role of RAGE in lung development and adult lung homeostasis, we generated hemizygous and homozygous transgenic mice overexpressing human RAGE, and analyzed their lungs from the fourth postnatal day to adulthood. Moderate RAGE hyperexpression during lung development influenced secondary septation, resulting in an impairment of alveolar morphogenesis and leading to significant changes in morphometric parameters such as airspace number and the size of alveolar ducts. An increase in alveolar cell apoptosis and a decrease in cell proliferation were demonstrated by the terminal deoxy-nucleotidyltransferase-mediated dUTP nick end labeling reaction, active caspase-3, and Ki-67 immunohistochemistry. Alterations in elastin organization and deposition and in TGF-ß expression were observed. In homozygous mice, the hyperexpression of RAGE resulted in histological changes resembling those changes characterizing human bronchopulmonary dysplasia (BPD). RAGE hyperexpression in the adult lung is associated with an increase of the alveolar destructive index and persistent inflammatory status leading to "destructive" emphysema. These results suggest an important role for RAGE in both alveolar development and lung homeostasis, and open new doors to working hypotheses on the pathogenesis of BPD and chronic obstructive pulmonary disease.

CHF5074 restores visual memory ability and pre-synaptic cortical acetylcholine release in pre-plaque Tg2576 mice.

CHF5074, a new microglial modulator, attenuates memory deficit in Alzheimer's disease transgenic mice. In this study, the effect of an acute or subacute CHF5074 treatment on in vivo novel object recognition test and on [³H]Acetylcholine (ACh) and GABA release in pre-plaque (7-month-old) Tg2576 mice have been compared with those induced by the γ-secretase inhibitor LY450139 (semagacestat). Vehicle-treated Tg2576 mice displayed an impairment of recognition memory compared with wild-type animals. This impairment was recovered in transgenic animals acutely treated with CHF5074 (30 mg/kg), while LY450139 (1, 3, 10 mg/kg) was ineffective. In frontal cortex synaptosomes from vehicle-treated Tg2576 mice, K⁺-evoked [³H]ACh release was lower than that measured in wild-type mice. This reduction was absent in transgenic animals subacutely treated with CHF5074 (30 mg/kg daily for 8 days), while it was slightly, not significantly, amplified by LY450139 (3 mg/kg daily for 8 days). There were no differences between the groups on spontaneous [³H]ACh release as well as spontaneous and K⁺-evoked GABA release. These results suggest that CHF5074 has beneficial effects on visual memory and cortical cholinergic dysfunctions in pre-plaque Tg2576 mice. Together with previous findings, these data suggest that CHF5074 could be a possible candidate for early Alzheimer's disease therapeutic regimens.

Multi-target action of the novel anti-Alzheimer compound CHF5074: in vivo study of long term treatment in Tg2576 mice.

BACKGROUND: Alzheimer disease is a multifactorial disorder characterized by the progressive deterioration of neuronal networks. The pathological hallmarks includes extracellular amyloid plaques and intraneuronal neurofibrillary tangles, but the primary cause is only partially understood. Thus, there is growing interest in developing agents that might target multiple mechanisms leading to neuronal degeneration. CHF5074 is a nonsteroidal anti-inflammatory derivative that has been shown to behave as a γ-secretase modulator in vitro and to inhibit plaque deposition and to reverse memory deficit in vivo in transgenic mouse models of Alzheimer's disease (AD). In the present study, the effects of a long-term (13-month) treatment with CHF5074 on indicators of brain functionality and neurodegeneration in transgenic AD mice (Tg2576) have been assessed and compared with those induced by a prototypical γ-secretase inhibitor (DAPT). RESULTS: To this end, plaque-free, 6-month-old Tg2576 mice and wild-type littermates were fed with a diet containing CHF5074 (125 and 375 ppm/day), DAPT (375 ppm/day) or vehicle for 13 months. The measured indicators included object recognition memory, amyloid burden, brain oligomeric and plasma Aß levels, intraneuronal Aß, dendritic spine density/morphology, neuronal cyclin A positivity and activated microglia. Tg2576 mice fed with standard diet displayed an impairment of recognition memory. This deficit was completely reverted by the higher dose of CHF5074, while no effects were observed in DAPT-treated mice. Similarly, amyloid plaque burden, microglia activation and aberrant cell cycle events were significantly affected by CHF5074, but not DAPT, treatment. Both CHF5074 and DAPT reduced intraneuronal Aß content, also increasing Aß40 and Aß42 plasma levels. CONCLUSIONS: This comparative analysis revealed a profoundly diverse range of clinically relevant effects differentiating the multifunctional anti-inflammatory derivative CHF5074 from the γ-secretase inhibitor DAPT and highlighted unique mechanisms and potential targets that may be crucial for neuroprotection in mouse models of AD.

Pharmacokinetics and pharmacodynamics of CHF5074 after short-term administration in healthy subjects.

CHF5074 has been shown to inhibit brain ß-amyloid deposition and attenuate memory deficits in different transgenic mice models of Alzheimer disease. We evaluated the safety, pharmacokinetics, and pharmacodynamics of 3 ascending dose regimens of CHF5074 (200, 400, and 600 mg/d for 14 d) in a double-blind, placebo-controlled, parallel group study involving 48 healthy subjects. Plasma, urine, and cerebrospinal fluid (CSF) samples were collected for measuring drug and main metabolite concentrations and potential biomarkers of pharmacodynamic activity (ß-amyloid1-40, ß-amyloid1-42, soluble CD40 ligand, and tumor necrosis factor-α). All subjects completed the study, and no serious or severe adverse events were reported. The maximum tolerated dose was close to 600 mg/d with mild diarrhea being the most frequent adverse event at this dose. CHF5074 reached peak plasma levels 2 to 3 hours after drug administration and then was slowly eliminated (t(1/2z)=30 h) in the urine as glucoronide. Systemic exposure to the drug appeared to be dose-proportional with a 2-fold accumulation ratio at steady state. Metabolite plasma levels peaked at 4 to 5 hours and accounted for about 25% of the parent compound. Drug levels in the CSF were dose-proportional. The drug dose-dependently lowered the levels of the soluble CD40 ligand, a marker of microglia activation, in both plasma and CSF samples.

Frailty syndrome and the risk of vascular dementia: the Italian Longitudinal Study on Aging.

BACKGROUND: Frailty is a clinical syndrome generally associated with a greater risk for adverse outcomes such as falls, disability, institutionalization, and death. Cognition and dementia have already been considered as components of frailty, but the role of frailty as a possible determinant of dementia, Alzheimer's disease (AD), and vascular dementia (VaD) has been poorly investigated. We estimated the predictive role of frailty syndrome on incident dementia and its subtypes in a nondemented, Italian, older population. METHODS: We evaluated 2581 individuals recruited from the Italian Longitudinal Study on Aging sample population consisting of 5632 subjects aged 65 to 84 years and with a 3.9-year median follow-up. A phenotype of frailty according to a modified measurement of Cardiovascular Health Study criteria was operationalized. Dementia, AD, and VaD were classified using current published criteria. RESULTS: Over a 3.5-year follow-up, 65 of 2581 (2.5%) older subjects, 16 among 252 frail individuals (6.3%), of which 9 were affected by VaD (3.6%), developed overall dementia. In a proportional hazards model, frailty syndrome was associated with a significantly increased risk of overall dementia (adjusted hazard ratio: 1.85; 95% confidence interval: 1.01-3.40) and, in particular, VaD (adjusted hazard ratio: 2.68; 95% confidence interval: 1.16-7.17). The risk of AD or other types of dementia did not significantly change in frail individuals in comparison with subjects without frailty syndrome. CONCLUSION: In our large population-based sample, frailty syndrome was a short-term predictor of overall dementia and VaD.

Investigational treatments for neurodegenerative diseases caused by inheritance of gene mutations: lessons from recent clinical trials.

We reviewed recent major clinical trials with investigational drugs for the treatment of subjects with neurodegenerative diseases caused by inheritance of gene mutations or associated with genetic risk factors. Specifically, we discussed randomized clinical trials in subjects with Alzheimer's disease, Huntington's disease and amyotrophic lateral sclerosis bearing pathogenic gene mutations, and glucocerebrosidase-associated Parkinson's disease. Learning potential lessons to improve future therapeutic approaches is the aim of this review. Two long-term, controlled trials on three anti-ß-amyloid monoclonal antibodies (solanezumab, gantenerumab and crenezumab) in subjects carrying Alzheimer's disease-linked mutated genes encoding for amyloid precursor protein or presenilin 1 or presenilin 2 failed to show cognitive or functional benefits. A major trial on tominersen, an antisense oligonucleotide designed to reduce the production of the huntingtin protein in subjects with Huntington's disease, was prematurely interrupted because the drug failed to show higher efficacy than placebo and, at highest doses, led to worsened outcomes. A 28-week trial of tofersen, an antisense oligonucleotide for superoxide dismutase 1 in patients with amyotrophic lateral sclerosis with superoxide dismutase 1 gene mutations failed to show significant beneficial effects but the 1-year open label extension of this study indicated better clinical and functional outcomes in the group with early tofersen therapy. A trial of venglustat, a potent and brain-penetrant glucosylceramide synthase inhibitor, in Parkinson's disease subjects with heterozygous glucocerebrosidase gene mutations revealed worsened clinical and cognitive performance of patients on the enzyme inhibitor compared to placebo. We concluded that clinical trials in neurodegenerative diseases with a genetic basis should test monoclonal antibodies, antisense oligonucleotides or gene editing directed against the mutated enzyme or the mutated substrate without dramatically affecting physiological wild-type variants.