Aims

Tissue loss happens in aging and neurodegenerative conditions, such as frontotemporal dementia (FTD), with specific patterns related to the symptomatology. Tissue degeneration is hypothesized to be a consequence of synaptic loss. Our goal is to assess synaptic density in vivo using novel radiotracer [¹⁸F]SDM8 in aging and FTD.

Methods

Cognitively unimpaired young (CUY) [21-22yoa], cognitively unimpaired elderlies (CUE) [60-81yoa] and FTD [47-72yoa] participants from TRIAD cohort underwent an MRI, neuropsychological evaluation, and 90-minutes dynamic [¹⁸F]SDM8 PET-scan (synaptic density). We calculated the standardized uptake value ratio from 40-90 minutes and used the centrum semiovale as reference region. Voxel-wise analyses were conducted to assess synaptic density differences between CUY, CUE and FTD. Analyses were corrected for sex; when including only CUE and FTD, we also corrected for age.

Results

CUY present high [¹⁸F]SDM8 binding as compared to CUE, in the precuneus, and frontal and temporal lobes (Figure1A). Moreover, when comparing CUE and FTD, we observed greater [¹⁸F]SDM8 binding in the medial frontal lobe and the frontal pole (Figure1B).

Conclusions

Synaptic loss seems to increase with age, and with dementia onset. CUE show less synaptic density as compared to CUY, in regions vulnerable to neurodegenerative conditions’ development. Moreover, we observed a strong difference between CUE and FTD, in brain regions related to the disease symptomatology, i.e. frontal lobe. Frontal synaptic loss seems to appear in aging around the orbitofrontal cortex. Conversely, in FTD, it is located towards the dorsomedial prefrontal cortex. We hypothesize that synaptic loss is a process appearing in aging, possibly potentiated in FTD.

Aims

Intronic G₄C₂ hexanucleotide repeat expansions of C9orf72 are the most common cause of familial variants of frontotemporal dementia / amyotrophic lateral sclerosis (FTD/ALS). Neuroinflammation is hypothesized to be a driving factor in the disease course; microglia activation is present prior to symptom onset and persists throughout the disease.

Methods

Here, we establish the contributions of NLRP3 and NLRC4 inflammasomes in the pathogenesis of FTD/ALS, resulting from a stress-induced neuronal-microglial crosstalk feedforward loop. In a mouse model of c9FTD/ALS, inflammasome-mediated inflammation was increased with microglial and caspase-1 activation.

Results

Here, we report that treatment with a microbiome-derived phenolic metabolite, 3-hydroxybenzoic acid (3-HBA), attenuated inflammasome-dependent inflammation, behavioral deficits, and neurodegeneration by targeting NLRP3 and NLRC4 inflammasome responses. Furthermore, genetic ablation of Nlrp3attenuated behavioral deficits and prevented neurodegeneration, ultimately improving survival.

Conclusions

These findings establish the integral role inflammasome-mediated innate immunity in c9FTD/ALS pathogenesis, and identify a novel treatment strategy with a diet-derived phenolic metabolite to rescue pathologies associated with FTD/ALS.

Aims

Tauopathies display distinct filament folds of abnormal tau protein of 3R and 4R isoforms. While AD expresses both 4R and 3R isoforms, CBD and PSP express mainly the 4R form. AD and CBD Tau fibrils structures have been determined and cryoEM analyses enabled to determine the theoretical binding sites of different Tau PET tracers on these various tau fibrils, whereas PSP tau fibrils remain undescribed. Objectives: The aim of this study was to characterize and better understand the differences in tau pathology between CBD, PSP and AD using the tau PET tracer 3H-PI2620.

Methods

On AD, CBD, PSP and control postmortem human brain tissue, we performed saturation and competition binding assays on frontal cortex. Regional distribution was also carried out on human brain homogenates of AD, PSP, CBD and control cases. We compared immunostaining and 3H-PI2620 autoradiography on frozen adjacent sections of frontal cortex and putamen.

Results

3H-PI2620 displayed two binding sites for AD and CBD but only one for PSP. Bmax values were higher in AD compared to CBD and PSP respectively. However 3H-PI2620 bound with similar high affinities in the three tauopathies. In AD and CBD unlabelled PI2620 competed with 3H-PI2620 for two binding sites but only for one in PSP.

Conclusions

In this study we observed differences in 3H-PI2620 binding properties between the tauopathies and ongoing studies will further unravel the interactions between the different hallmarks inducing the complexity of these tauopathies

Aims

GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function.

Methods

We utilized targeted lipidomic profiling to characterize changes in lysosomal lipids in the brain of Grn-/- mouse as well as in GRN-FTD patient CSF and plasma samples. Further, we investigated a protein replacement strategy by engineering protein transport vehicle (PTV):PGRN—a recombinant protein linking PGRN to a modified Fc domain that binds human transferrin receptor for enhanced CNS biodistribution.

Results

Here, we found that Grn–/– mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn–/– brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine. PTV:PGRN rescued various Grn–/– phenotypes in primary murine macrophages and hu- man iPSC-derived microglia, including oxidative stress, lysosomal dysfunction, and endomembrane damage. Peripherally delivered PTV:PGRN corrected levels of BMP, glucosylsphingosine, and disease pathology in Grn–/– CNS, including microgliosis, lipofuscinosis, and neuronal damage.

Conclusions

PTV:PGRN thus represents a potential biotherapeutic for GRN-FTD.

Aims

Accumulation of pathological transactive response DNA binding protein 43 (TDP-43) into intracellular inclusions underlies frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), amyotrophic lateral sclerosis (ALS) as well as the newly defined limbic-predominant age-related TDP-43 encephalopathy (LATE). TDP-43 inclusions are also present as co-pathology in other neurodegenerative diseases including Alzheimer’s disease. However, no therapeutic interventions targeting TDP-43 pathology are in clinical development. Antibody-mediated clearance of misfolded TDP-43 by microglia and inhibition of cell-to-cell protein spreading represents an attractive strategy for therapeutic intervention.

Methods

Monoclonal antibodies (mAbs) were generated against various regions of TDP-43 using AC Immune’s proprietary SupraAntigen^TM platform and selected for evaluation in cell-based and mouse models of TDP-43 proteinopathies.

Results

From a panel of mAbs, ACI-5891 binding to the C-terminal domain of TDP-43 was identified to substantially reduce de novo and templated TDP-43 aggregation induced by FTLD-TDP brain extracts. In rNLS8 transgenic mouse model of ALS and FTLD-TDP, ACI-5891 significantly reduced the levels of phosphorylated TDP-43 (pTDP-43) and insoluble TDP-43 in the brain with a concomitant increase in hypertrophic microglia without induction of inflammation. These outcomes translated into a significant neuroprotective effect in a second mouse model induced by inoculation of FTLD-TDP brain extracts and correlated with significant increase of mAb-mediated TDP-43 aggregate uptake by microglia in vitro.

Conclusions

Our findings demonstrate for the first time that a mAb specific for the C-terminal region of TDP-43 enables clearance of misfolded TDP-43 in vivo through microglia engagement thus limiting pathology progression and conferring neuroprotection. These results support the clinical assessment of TDP-43 immunotherapy.

Aims

Across three main clinical syndromes of frontotemporal dementia (FTD), we used [¹¹C]PK11195 PET uptake as an index of regional inflammation, and assessed its predictive power for future cognitive decline. Negative associations between inflammation and cognitive decline were hypothesised.

Methods

We recruited 30 patients, with clinical diagnoses of behavioural variant of FTD (N=10), non-fluent variant (N=10) and semantic variants of primary progressive aphasia (N=10). All patients underwent structural MRI and dynamic [¹¹C]PK11195 PET at baseline, and cognitive assessment with the revised Addenbrooke's Cognitive Examination (ACE-R) every ~6 months up to 5 years. Regional [11C]PK11195 binding potentials were extracted, and averaged in 4 regions of interest: left and right frontal and temporal lobes. Linear mixed-effect models were used to estimate the annual rate of change (slope) in cognitive performance (Attention/Orientation ACE-R sub-scores) with regional inflammation as a predictor. Baseline cognitive performance, age and education were included as covariates.

Results

A negative predictive effect of [11C]PK11195 binding on cognitive performance over time was found for frontal regions (left: Estimate=-0.82, p=0.0009, p-FDR=0.0017; right: Estimate=-0.80, p=0.002, p-FDR=0.0212), also when diagnosis was included as a covariate. Bayesian correlations on cognitive slope and inflammation levels confirmed negative associations in left (r=-0.48, p=0.004, BF10=23.7) and right (r=-0.39, p=0.018, BF10=4.2) frontal regions. Adding grey-matter volumes to the models, inflammation in these regions provided additional information over atrophy (Estimate=-0.79, p=0.0006).

Conclusions

Inflammation PET in frontal regions provides useful information to predict cognitive decline in patients with FTD, across clinical syndromes. This result incentivises further exploration of immunomodulatory treatment strategies in FTD.

Aims

ALS has a complex underlying pathophysiology, indicating that a multi-factorial strategy is needed in order to target multiple pathways.

PrimeC is a novel formulation composed of unique doses of ciprofloxacin and celecoxib, aiming to synergistically inhibit the progression of ALS by addressing three key pathologies; microRNA dysregulation, iron accumulation and neuroinflammation.

Ciprofloxacin, a fluoroquinolone antibiotic, is an iron chelator, and a regulator of Dicer activity, a key enzyme in the microRNA processing pathway.

Celecoxib, an NSAID, regulates neuroinflammation mainly through COX-2 inhibition. Additionally, it has COX-2-independent anti-inflammatory activities.

The objective of the present study was to evaluate the safety and tolerability of PrimeC, and to examine its effects on ALS-related biomarkers

Methods

PrimeC was evaluated clinically in a 12-month, open-label, phase-IIa study in 15 patients with ALS.

Results

Results demonstrate that PrimeC was safe and tolerable in the ALS patient population. These findings were reinforced by encouraging clinical signals when utilizing numerous virtual control models (Origent-prediction-models, ENCALS-survival-prediction model, and PRO-ACT) as a novel approach to control arms in early phase, open-label studies. These results were accompanied by significant changes in ALS-related biomarkers of serum neuron-derived exosomes (NDEs) such as TDP-43 and LC3, indicating a positive biological activity.

Conclusions

The present study demonstrates that PrimeC is safe and well-tolerated. These findings in conjunction with the biological activity observed in biomarkers analysis set the stage for a larger, placebo-controlled study. Importantly, since the aforementioned pathologies are shared between neurodegenerative diseases, we hypothesize that PrimeC may serve as a therapeutic agent for indications, such as Parkinson’s and Alzheimer's.