Cerebrospinal fluid (CSF) p-tau181 (tau phosphorylated at threonine 181) is an established biomarker of Alzheimer's disease (AD), reflecting abnormal tau metabolism in the brain. Here we investigate ...the performance of CSF p-tau217 as a biomarker of AD in comparison to p-tau181. In the Swedish BioFINDER cohort (n = 194), p-tau217 shows stronger correlations with the tau positron emission tomography (PET) tracer
Fflortaucipir, and more accurately identifies individuals with abnormally increased
Fflortaucipir retention. Furthermore, longitudinal increases in p-tau217 are higher compared to p-tau181 and better correlate with
Fflortaucipir uptake. P-tau217 correlates better than p-tau181 with CSF and PET measures of neocortical amyloid-β burden and more accurately distinguishes AD dementia from non-AD neurodegenerative disorders. Higher correlations between p-tau217 and
Fflortaucipir are corroborated in an independent EXPEDITION3 trial cohort (n = 32). The main results are validated using a different p-tau217 immunoassay. These findings suggest that p-tau217 might be more useful than p-tau181 in the diagnostic work up of AD.
Introduction
This study explored the safety and tolerability features of donanemab (LY3002813) in patients with mild cognitive impairment due to Alzheimer's disease (AD) or mild to moderate AD ...dementia.
Methods
Patients with AD were enrolled into the single‐ascending dose phase and were administered a single, intravenous (IV) dose of donanemab (five dosing cohorts from 0.1 to 10 mg/kg) or placebo followed by a 12‐week follow‐up period for each dose level. After the follow‐up period, the same patients proceeded into the multiple‐ascending dose (MAD) phase (five cohorts) and were administered IV doses of donanemab (0.3 to 10 mg/kg) or placebo approximately once per month for up to four doses depending on the initial doses (only cohort 1 went from 0.1 mg/kg to a higher dose of 0.3 mg/kg during the MAD phase). This phase concluded with a 12‐week follow‐up period. The relative exposure assessment of an unblinded, single, subcutaneous 3‐mg/kg dose of donanemab in patients with AD was also performed, followed by a 12‐week follow‐up period. One cohort of healthy subjects received an unblinded, single, IV 1‐mg/kg dose of donanemab. These two cohorts did not continue to the MAD phase.
Results
Donanemab was generally well tolerated up to 10 mg/kg. After single‐dose administration from 0.1 to 3.0 mg/kg, the mean terminal elimination half‐life was ≈4 days, increasing to ≈10 days at 10 mg/kg. Only the 10‐mg/kg dose showed changes in amyloid positron emission tomography. Amyloid reduction of 40% to 50% was achieved. Approximately 90% of subjects developed anti‐drug antibodies at 3 months after a single intravenous dose.
Discussion
Intravenous donanemab 10 mg/kg can reduce amyloid deposits in AD despite having a shorter than expected half‐life.
Tau-PET is a prognostic marker for cognitive decline in Alzheimer's disease, and the heterogeneity of tau-PET patterns matches cognitive symptom heterogeneity. Thus, tau-PET may allow ...precision-medicine prediction of individual tau-related cognitive trajectories, which can be important for determining patient-specific cognitive endpoints in clinical trials. Here, we aimed to examine whether tau-PET in cognitive-domain-specific brain regions, identified via fMRI meta-analyses, allows the prediction of domain-specific cognitive decline. Further, we aimed to determine whether tau-PET-informed personalized cognitive composites capture patient-specific cognitive trajectories more sensitively than conventional cognitive measures.
We included Alzheimer's Disease Neuroimaging Initiative (ADNI) participants classified as controls (i.e., amyloid-negative, cognitively normal, n = 121) or Alzheimer's disease-spectrum (i.e., amyloid-positive, cognitively normal to dementia, n = 140), plus 111 AVID-1451-A05 participants for independent validation (controls/Alzheimer's disease-spectrum=46/65). All participants underwent baseline
F-flortaucipir tau-PET, amyloid-PET, and longitudinal cognitive testing to assess annual cognitive changes (i.e., episodic memory, language, executive functioning, visuospatial). Cognitive changes were calculated using linear mixed models. Independent meta-analytical task-fMRI activation maps for each included cognitive domain were obtained from the Neurosynth database and applied to tau-PET to determine tau-PET signal in cognitive-domain-specific brain regions. In bootstrapped linear regression, we assessed the strength of the relationship (i.e., partial R
) between cognitive-domain-specific tau-PET vs. global or temporal-lobe tau-PET and cognitive changes. Further, we used tau-PET-based prediction of domain-specific decline to compose personalized cognitive composites that were tailored to capture patient-specific cognitive decline.
In both amyloid-positive cohorts (ADNI age = 75.99±7.69 and A05 age = 74.03±9.03), cognitive-domain-specific tau-PET outperformed global and temporal-lobe tau-PET for predicting future cognitive decline in episodic memory, language, executive functioning, and visuospatial abilities. Further, a tau-PET-informed personalized cognitive composite across cognitive domains enhanced the sensitivity to assess cognitive decline in amyloid-positive subjects, yielding lower sample sizes required for detecting simulated intervention effects compared to conventional cognitive endpoints (i.e., memory composite, global cognitive composite). However, the latter effect was less strong in A05 compared to the ADNI cohort.
Combining tau-PET with task-fMRI-derived maps of major cognitive domains facilitates the prediction of domain-specific cognitive decline. This approach may help to increase the sensitivity to detect Alzheimer's disease-related cognitive decline and to determine personalized cognitive endpoints in clinical trials.
Background
Previous studies found that
18
FLSN3316612 was a promising positron emission tomography (PET) radioligand for imaging
O
-GlcNAcase in nonhuman primates and human volunteers. This study ...sought to further evaluate the suitability of
18
FLSN3316612 for human clinical research.
Methods
Kinetic evaluation of
18
FLSN3316612 was conducted in a combined set of baseline brain scans from 17 healthy human volunteers and test-retest imaging was conducted in 10 of these volunteers; another 6 volunteers had whole-body scans to measure radiation exposure to body organs. Total distribution volume (
V
T
) estimates were compared for the one- and two-tissue compartment models with the arterial input function. Test-retest variability and reliability were evaluated via mean difference and intraclass correlation coefficient (ICC). The time stability of
V
T
was assessed down to a 30-min scan time. An alternative quantification method for
18
FLSN3316612 binding without blood was also investigated to assess the possibility of eliminating arterial sampling.
Results
Brain uptake was generally high and could be quantified as
V
T
with excellent identifiability using the two-tissue compartment model.
18
FLSN3316612 exhibited good absolute test-retest variability (12.5%), but the arithmetic test-retest variability was far from 0 (11.3%), reflecting a near-uniform increase of
V
T
on the retest scan in nine of 10 volunteers.
V
T
values were stable after 110 min in all brain regions, suggesting that no radiometabolites accumulated in the brain. Measurements obtained using only brain activity (i.e., area under the curve (AUC) from 150–180 min) correlated strongly with regional
V
T
values during test-retest conditions (
R
2
= 0.84), exhibiting similar reliability to
V
T
(ICC = 0.68 vs. 0.64). Estimated radiation exposure for
18
FLSN3316612 PET was 20.5 ± 2.1 μSv/MBq, comparable to other
18
F-labeled radioligands for brain imaging.
Conclusions
18
FLSN3316612 is an excellent PET radioligand for imaging
O
-GlcNAcase in the human brain. Alternative quantification without blood is possible, at least for within-subject repeat studies. However, the unexplained increase of
V
T
under retest conditions requires further investigation.
Rabies is a fatal disease of mammals that poses a high zoonotic risk to humans as well. The distribution of rabies is mainly driven by host animal migration and human-mediated dispersion. To ...contribute to the global understanding of the rabies virus (RABV) molecular epidemiology, 94 RABV field isolates collected from animals in 13 European Russian regions were phylogenetically characterized using the nearly full-size N gene nucleotide sequences. According to phylogenetic inferences, all isolates belonged to one of the two established phylogenetic groups, either group C (n = 54) or group D (n = 40), which are part of the clade Cosmopolitan of RABVs. Some representatives of group C collected from regions located far apart from each other had a remarkably high level of nucleotide identity. The possibility of the contribution of local bat species to the distribution of RABVs was discussed. Interestingly, over the years, the fraction of group D isolates has been constantly decreasing compared with that of group C isolates. The phylogenetic insights generated herein might have an important contribution to the control and surveillance of animal rabies epidemiology in the region.
Cardiac blood pool imaging is currently performed almost exclusively with 99mTc-based compounds and SPECT/CT imaging. Using a generator-based PET radioisotope has a few advantages, including not ...needing nuclear reactors to produce it, obtaining better resolution in humans, and potentially reducing the radiation dose to the patient. When the shortlived radioisotope 68Ga is used, it can be applied repeatedly on the same day—for example, for the detection of bleeding. Our objective was to prepare and evaluate a long-circulating polymer functionalized with gallium for its biodistribution, toxicity, and dosimetric properties. A 500 kDa hyperbranched polyglycerol was conjugated to the chelator NOTA and radiolabeled rapidly at room temperature with 68Ga. It was then injected intravenously into a rat, and gated imaging allowed us to easily observe wall motion and cardiac contractility, confirming the suitability of this radiopharmaceutical for cardiac blood pool imaging. Internal radiation dose calculations showed that the radiation doses that patients would receive from the PET agent would be 2.5× lower than those from the 99mTc agent. A complete 14-day toxicology study in rats concluded that there were no gross pathology findings, changes in body or organ weights, or histopathological events. This radioactive-metal-functionalized polymer might be a suitable non-toxic agent to advance for clinical application.
INTRODUCTION
Donanemab is an amyloid‐targeting therapy that specifically targets brain amyloid plaques. The objective of these analyses was to characterize the relationship of donanemab exposure with ...plasma biomarkers and clinical efficacy through modeling.
METHODS
Data for the analyses were from participants with Alzheimer's disease from the phase 1 and TRAILBLAZER‐ALZ studies. Indirect‐response models were used to fit plasma phosphorylated tau 217 (p‐tau217) and plasma glial fibrillated acidic protein (GFAP) data over time. Disease‐progression models were developed using pharmacokinetic/pharmacodynamic modeling.
RESULTS
The plasma p‐tau217 and plasma GFAP models adequately predicted the change over time, with donanemab resulting in decreased plasma p‐tau217 and plasma GFAP concentrations. The disease‐progression models confirmed that donanemab significantly reduced the rate of clinical decline. Simulations revealed that donanemab slowed disease progression irrespective of baseline tau positron emission tomography (PET) level within the evaluated population.
DISCUSSION
The disease‐progression models show a clear treatment effect of donanemab on clinical efficacy regardless of baseline disease severity.
It has been proposed that the signal distribution on tau positron emission tomography (PET) images could be used to define pathologic stages similar to those seen in neuropathology.
Three topographic ...staging schemes for tau PET, two sampling the temporal and occipital subregions only and one sampling cortical gray matter across the major brain lobes, were evaluated on flortaucipir F 18 PET images in a test-retest scenario and from Alzheimer's Disease Neuroimaging Initiative 2.
All three schemes estimated stages that were significantly associated with amyloid status and when dichotomized to tau positive or negative were 90% to 94% concordant in the populations identified. However, the schemes with fewer regions and simpler decision rules yielded more robust performance in terms of fewer unclassified scans and increased test-retest reproducibility of assigned stage.
Tau PET staging schemes could be useful tools to concisely index the regional involvement of tau pathology in living subjects. Simpler schemes may be more robust.
Alpha-solenoids are flexible protein structural domains formed by ensembles of alpha-helical repeats (Armadillo and HEAT repeats among others). While homology can be used to detect many of these ...repeats, some alpha-solenoids have very little sequence homology to proteins of known structure and we expect that many remain undetected. We previously developed a method for detection of alpha-helical repeats based on a neural network trained on a dataset of protein structures. Here we improved the detection algorithm and updated the training dataset using recently solved structures of alpha-solenoids. Unexpectedly, we identified occurrences of alpha-solenoids in solved protein structures that escaped attention, for example within the core of the catalytic subunit of PI3KC. Our results expand the current set of known alpha-solenoids. Application of our tool to the protein universe allowed us to detect their significant enrichment in proteins interacting with many proteins, confirming that alpha-solenoids are generally involved in protein-protein interactions. We then studied the taxonomic distribution of alpha-solenoids to discuss an evolutionary scenario for the emergence of this type of domain, speculating that alpha-solenoids have emerged in multiple taxa in independent events by convergent evolution. We observe a higher rate of alpha-solenoids in eukaryotic genomes and in some prokaryotic families, such as Cyanobacteria and Planctomycetes, which could be associated to increased cellular complexity. The method is available at http://cbdm.mdc-berlin.de/~ard2/.
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