The Alzheimer's Association appropriate use recommendations for blood biomarkers in Alzheimer's disease.

Blood-based markers (BBMs) have recently shown promise to revolutionize the diagnostic and prognostic work-up of Alzheimer's disease (AD), as well as to improve the design of interventional trials. Here we discuss in detail further research needed to be performed before widespread use of BBMs. We already now recommend use of BBMs as (pre-)screeners to identify individuals likely to have AD pathological changes for inclusion in trials evaluating disease-modifying therapies, provided the AD status is confirmed with positron emission tomography (PET) or cerebrospinal fluid (CSF) testing. We also encourage studying longitudinal BBM changes in ongoing as well as future interventional trials. However, BBMs should not yet be used as primary endpoints in pivotal trials. Further, we recommend to cautiously start using BBMs in specialized memory clinics as part of the diagnostic work-up of patients with cognitive symptoms and the results should be confirmed whenever possible with CSF or PET. Additional data are needed before use of BBMs as stand-alone diagnostic AD markers, or before considering use in primary care.

Putting participants and study partners FIRST when clinical trials end early.

Between 2018 and 2019, multiple clinical trials ended earlier than planned, resulting in calls to improve communication with and support for participants and their study partners ("dyads"). The multidisciplinary Participant Follow-Up Improvement in Research Studies and Trials (Participant FIRST) Work Group met throughout 2021. Its goals were to identify best practices for communicating with and supporting dyads affected by early trial stoppage. The Participant FIRST Work Group identified 17 key recommendations spanning the pre-trial, mid-trial, and post-trial periods. These focus on prospectively allocating sufficient resources for orderly closeout; developing dyad-centered communication plans; helping dyads build and maintain support networks; and, if a trial stops, informing dyads rapidly. Participants and study partners invest time, effort, and hope in their research participation. The research community should take intentional steps toward better communicating with and supporting participants when clinical trials end early. The Participant FIRST recommendations are a practical guide for embarking on that journey.

Characterization of pre-analytical sample handling effects on a panel of Alzheimer's disease-related blood-based biomarkers: Results from the Standardization of Alzheimer's Blood Biomarkers (SABB) working group.

INTRODUCTION: Pre-analytical sample handling might affect the results of Alzheimer's disease blood-based biomarkers. We empirically tested variations of common blood collection and handling procedures. METHODS: We created sample sets that address the effect of blood collection tube type, and of ethylene diamine tetraacetic acid plasma delayed centrifugation, centrifugation temperature, aliquot volume, delayed storage, and freeze-thawing. We measured amyloid beta (Aß)42 and 40 peptides with six assays, and Aß oligomerization-tendency (OAß), amyloid precursor protein (APP)699-711 , glial fibrillary acidic protein (GFAP), neurofilament light (NfL), total tau (t-tau), and phosphorylated tau181. RESULTS: Collection tube type resulted in different values of all assessed markers. Delayed plasma centrifugation and storage affected Aß and t-tau; t-tau was additionally affected by centrifugation temperature. The other markers were resistant to handling variations. DISCUSSION: We constructed a standardized operating procedure for plasma handling, to facilitate introduction of blood-based biomarkers into the research and clinical settings.

Comparative analytical performance of multiple plasma Aß42 and Aß40 assays and their ability to predict positron emission tomography amyloid positivity.

INTRODUCTION: This report details the approach taken to providing a dataset allowing for analyses on the performance of recently developed assays of amyloid beta (Aß) peptides in plasma and the extent to which they improve the prediction of amyloid positivity. METHODS: Alzheimer's Disease Neuroimaging Initiative plasma samples with corresponding amyloid positron emission tomography (PET) data were run on six plasma Aß assays. Statistical tests were performed to determine whether the plasma Aß measures significantly improved the area under the receiver operating characteristic curve for predicting amyloid PET status compared to age and apolipoprotein E (APOE) genotype. RESULTS: The age and APOE genotype model predicted amyloid status with an area under the curve (AUC) of 0.75. Three assays improved AUCs to 0.81, 0.81, and 0.84 (P < .05, uncorrected for multiple comparisons). DISCUSSION: Measurement of Aß in plasma contributes to addressing the amyloid component of the ATN (amyloid/tau/neurodegeneration) framework and could be a first step before or in place of a PET or cerebrospinal fluid screening study. HIGHLIGHTS: The Foundation of the National Institutes of Health Biomarkers Consortium evaluated six plasma amyloid beta (Aß) assays using Alzheimer's Disease Neuroimaging Initiative samples. Three assays improved prediction of amyloid status over age and apolipoprotein E (APOE) genotype. Plasma Aß42/40 predicted amyloid positron emission tomography status better than Aß42 or Aß40 alone.

The Alzheimer's Association international guidelines for handling of cerebrospinal fluid for routine clinical measurements of amyloid ß and tau.

The core cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarkers amyloid beta (Aß42 and Aß40), total tau, and phosphorylated tau, have been extensively clinically validated, with very high diagnostic performance for AD, including the early phases of the disease. However, between-center differences in pre-analytical procedures may contribute to variability in measurements across laboratories. To resolve this issue, a workgroup was led by the Alzheimer's Association with experts from both academia and industry. The aim of the group was to develop a simplified and standardized pre-analytical protocol for CSF collection and handling before analysis for routine clinical use, and ultimately to ensure high diagnostic performance and minimize patient misclassification rates. Widespread application of the protocol would help minimize variability in measurements, which would facilitate the implementation of unified cut-off levels across laboratories, and foster the use of CSF biomarkers in AD diagnostics for the benefit of the patients.

Measures of resting state EEG rhythms for clinical trials in Alzheimer's disease: Recommendations of an expert panel.

The Electrophysiology Professional Interest Area (EPIA) and Global Brain Consortium endorsed recommendations on candidate electroencephalography (EEG) measures for Alzheimer's disease (AD) clinical trials. The Panel reviewed the field literature. As most consistent findings, AD patients with mild cognitive impairment and dementia showed abnormalities in peak frequency, power, and "interrelatedness" at posterior alpha (8-12 Hz) and widespread delta (< 4 Hz) and theta (4-8 Hz) rhythms in relation to disease progression and interventions. The following consensus statements were subscribed: (1) Standardization of instructions to patients, resting state EEG (rsEEG) recording methods, and selection of artifact-free rsEEG periods are needed; (2) power density and "interrelatedness" rsEEG measures (e.g., directed transfer function, phase lag index, linear lagged connectivity, etc.) at delta, theta, and alpha frequency bands may be use for stratification of AD patients and monitoring of disease progression and intervention; and (3) international multisectoral initiatives are mandatory for regulatory purposes.

Inhibition of Interleukin-23-Mediated Inflammation with a Novel Small Molecule Inverse Agonist of RORγt.

Blockade of interleukin (IL)-23 or IL-17 with biologics is clinically validated as a treatment of psoriasis. However, the clinical impact of targeting other nodes within the IL-23/IL-17 pathway, especially with small molecules, is less defined. We report on a novel small molecule inverse agonist of retinoid acid-related orphan receptor (ROR) γt and its efficacy in preclinical models of psoriasis and arthritis. 1-(2,4-Dichloro-3-((1,4-dimethyl-6-(trifluoromethyl)-1H-indol-2-yl)methyl)benzoyl)piperidine-4-carboxylic acid (A-9758) was optimized from material identified from a high-throughput screening campaign. A-9758 is selective for RORγt and exhibits robust potency against IL-17A release both in vitro and in vivo. In vivo, we also show that IL-23 is sufficient to drive the accumulation of RORγt+ cells, and inhibition of RORγt significantly attenuates IL-23-driven psoriasiform dermatitis. Therapeutic treatment with A-9758 (i.e., delivered during active disease) was also effective in blocking skin and joint inflammation. Finally, A-9758 exhibited efficacy in an ex vivo human whole blood assay, suggesting small molecule inverse agonists of RORγt could be efficacious in human IL-17-related diseases. SIGNIFICANCE STATEMENT: Using a novel small molecule inverse agonist, and preclinical assays, we show that RORγt is a viable target for the inhibition of RORγt/Th17-driven diseases such as psoriasis. Preclinical models of psoriasis show that inhibition of RORγt blocks both the accumulation and effector function of IL-17-producing T cells.

IL-36 receptor antagonistic antibodies inhibit inflammatory responses in preclinical models of psoriasiform dermatitis.

Psoriasis vulgaris (PV) results from activation of IL-23/Th17 immune pathway and is further amplified by cytokines/chemokines from skin cells. Among skin-derived pro-inflammatory cytokines, IL-36 family members are highly upregulated in PV patients and play a critical role in general pustular psoriasis. However, there is limited data showing crosstalk between the IL-23 and IL-36 pathways in PV. Herein, potential attenuation of skin inflammation in the IL-23-induced mouse model of psoriasiform dermatitis by functional inhibition of IL-36 receptor (IL-36R) was interrogated. Anti-mouse IL-36R monoclonal antibodies (mAbs) were generated and validated in vitro by inhibiting IL-36α-induced secretion of CXCL1 from NIH 3T3 cells. Antibody target engagement was demonstrated by inhibition of CXCL1 production in a novel acute model of IL-36α systemic injection in mice. In addition, anti-IL-36R mAbs inhibited tissue inflammation and inflammatory gene expression in an IL-36α ear injection model of psoriasiform dermatitis demonstrating engagement of the target in the ear skin. To elucidate the possible role of IL-36 signalling in IL-23/Th17 pathway, the ability of anti-IL-36R mAbs to inhibit skin inflammation in an IL-23 ear injection model was assessed. Inhibiting the IL-36 pathway resulted in significant attenuation of skin thickening and psoriasis-relevant gene expression. Taken together, these data suggest a role for IL-36 signalling in the IL-23/Th17 signalling axis in PV.

pH-evoked dural afferent signaling is mediated by ASIC3 and is sensitized by mast cell mediators.

BACKGROUND: Prior studies have shown that decreased meningeal pH activates dural afferents via opening of acid-sensing ion channels (ASICs), suggesting one pathophysiological mechanism for the generation of headaches. The studies described here further examined the ASIC subtype mediating pH-induced dural-afferent activation and examined whether sensitization influences pH responses. OBJECTIVE: Given the potential importance of meningeal mast cells to headache, the goal of this study was to evaluate dural afferent responses to pH following sensitization with mast cell mediators. METHODS: Cutaneous allodynia was measured in rats following stimulation of the dura with decreased pH alone or in combination with mast cell mediators. Trigeminal ganglion neurons retrogradely labeled from the dura were stained with an ASIC3 antibody using immunohistochemistry. Current and action potentials evoked by changes in pH alone or in combination with mast cell mediators were measured in retrogradely labeled dural afferents using patch-clamp electrophysiology. RESULTS: pH-sensitive dural afferents generated currents in response to the ASIC3 activator 2-guanidine-4-methylquinazoline (GMQ), approximately 80% of these neurons express ASIC3 protein, and pH-evoked behavioral responses were inhibited by the ASIC3 blocker APETx2. Following exposure to mast cell mediators, dural afferents exhibited increased pH-evoked excitability, and cutaneous allodynia was observed at higher pH than with pH stimuli alone. CONCLUSIONS: These data indicate that the predominant ASIC subtype responding to decreased meningeal pH is ASIC3. Additionally, they demonstrate that in the presence of inflammation, dural afferents respond to even smaller decreases in pH providing further support for the ability of small pH changes within the meninges to initiate afferent input leading to headache.

Receptor specificity defines algogenic properties of propofol and fospropofol.

BACKGROUND: Propofol-evoked injection site pain is not observed with fospropofol. We hypothesized that unlike propofol, fospropofol does not activate the irritant receptor, transient receptor potential 1 (TRPA1). METHODS: We tested the hypothesis using electrophysiology and behavioral studies. RESULTS: Our data demonstrate that propofol (100 µM) evokes an inward current only in TRPA1-expressing neurons. However, fospropofol (100 µM and 1 mM) is unable to evoke depolarizing currents in either TRPA1-positive or TRPA1-negative neurons. Both propofol and fospropofol produced general anesthesia. CONCLUSIONS: The lack of algogenic activity in fospropofol is most likely the result of its inability to activate TRPA1 on nociceptors.

Are there consistent abnormalities in event-related EEG oscillations in patients with Alzheimer's disease compared to other diseases belonging to dementia?

Cerebrospinal and structural-molecular neuroimaging in-vivo biomarkers are recommended for diagnostic purposes in Alzheimer's disease (AD) and other dementias; however, they do not explain the effects of AD neuropathology on neurophysiological mechanisms underpinning cognitive processes. Here, an Expert Panel from the Electrophysiology Professional Interest Area of the Alzheimer's Association reviewed the field literature and reached consensus on the event-related electroencephalographic oscillations (EROs) that show consistent abnormalities in patients with significant cognitive deficits due to Alzheimer's, Parkinson's (PD), Lewy body (LBD), and cerebrovascular diseases. Converging evidence from oddball paradigms showed that, as compared to cognitively unimpaired (CU) older adults, AD patients had lower amplitude in widespread delta (>4 Hz) and theta (4-7 Hz) phase-locked EROs as a function of disease severity. Similar effects were also observed in PD, LBD, and/or cerebrovascular cognitive impairment patients. Non-phase-locked alpha (8-12 Hz) and beta (13-30 Hz) oscillations were abnormally reduced (event-related desynchronization, ERD) in AD patients relative to CU. However, studies on patients with other dementias remain lacking. Delta and theta phase-locked EROs during oddball tasks may be useful neurophysiological biomarkers of cognitive systems at work in heuristic and intervention clinical trials performed in AD patients, but more research is needed regarding their potential role for other dementias.

Activation of TRPV4 on dural afferents produces headache-related behavior in a preclinical rat model.

BACKGROUND: The mechanisms contributing to the pain of migraine are poorly understood although activation of afferent nociceptors in the trigeminovascular system has been proposed as a key event. Prior studies have shown that dural-afferent nociceptors are sensitive to both osmotic and mechanical stimuli. Based on the sensitivity to these stimuli we hypothesized that dural afferents express the osmo/mechano-sensitive channel transient receptor-potential vanilloid 4 (TRPV4). METHODS: These studies used in vitro patch-clamp electrophysiology of trigeminal neurons retrogradely labeled from the dura to examine the functional expression of TRPV4. Additionally, we used a rat headache model in which facial/hind paw allodynia following dural stimulation is measured to determine whether activation of meningeal TRPV4 produces responses consistent with migraine. RESULTS: These studies found that 56% and 49% of identified dural afferents generate currents in response to hypotonic solutions and 4α-PDD, respectively. The response to these stimuli indicates that dural afferents express TRPV4. Activation of meningeal TPRV4 using hypotonic solution or 4α-PDD in vivo resulted in both facial and hind paw allodynia that was blocked by the TRPV4 antagonist RN1734. CONCLUSION: These data indicate that activation of TRPV4 within the meninges produces afferent nociceptive signaling from the head that may contribute to migraine headache.

Evaluation of cutaneous allodynia following induction of cortical spreading depression in freely moving rats.

BACKGROUND: Cortical spreading depression (CSD) is a wave of depolarization followed by depression of bioelectrical activity that slowly propagates through the cortex. CSD is believed to be the underlying mechanism of aura in migraine; however, whether CSD can elicit pain associated with migraine headache is unclear. METHODS: Awake, freely moving rats were monitored for both CSD events and behavioral responses resulting from dural-cortical pinprick and/or KCl injection to the occipital cortex. RESULTS: We observed tactile allodynia of the face and hindpaws, as well as enhanced Fos expression within the trigeminal nucleus caudalis (TNC) following CSD induced by KCl injection into the cortex, but not by pinprick. Application of KCl onto the dura elicited cutaneous allodynia and increased Fos staining in the TNC but did not elicit CSD events. CONCLUSIONS: These data suggest that sustained activation of trigeminal afferents that may be required to establish cutaneous allodynia may not occur following CSD events in normal animals.

EEG measures for clinical research in major vascular cognitive impairment: recommendations by an expert panel.

Vascular contribution to cognitive impairment (VCI) and dementia is related to etiologies that may affect the neurophysiological mechanisms regulating brain arousal and generating electroencephalographic (EEG) activity. A multidisciplinary expert panel reviewed the clinical literature and reached consensus about the EEG measures consistently found as abnormal in VCI patients with dementia. As compared to cognitively unimpaired individuals, those VCI patients showed (1) smaller amplitude of resting state alpha (8-12 Hz) rhythms dominant in posterior regions; (2) widespread increases in amplitude of delta (< 4 Hz) and theta (4-8 Hz) rhythms; and (3) delayed N200/P300 peak latencies in averaged event-related potentials, especially during the detection of auditory rare target stimuli requiring participants' responses in "oddball" paradigms. The expert panel formulated the following recommendations: (1) the above EEG measures are not specific for VCI and should not be used for its diagnosis; (2) they may be considered as "neural synchronization" biomarkers to enlighten the relationships between features of the VCI-related cerebrovascular lesions and abnormalities in neurophysiological brain mechanisms; and (3) they may be tested in future clinical trials as prognostic biomarkers and endpoints of interventions aimed at normalizing background brain excitability and vigilance in wakefulness.

Medullary pain facilitating neurons mediate allodynia in headache-related pain.

OBJECTIVE: To develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches. To explore neural mechanisms underlying cephalic and extracephalic allodynia. METHODS: Inflammatory mediators (IM) were applied to the dura of unanesthetized rats via previously implanted cannulas, and sensory thresholds of the face and hind-paws were characterized. RESULTS: IM elicited robust facial and hind-paw allodynia, which peaked within 3 hours. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in the treatment of migraine, including sumatriptan, naproxen, and a calcitonin gene-related peptide antagonist. Consistent with clinical observations, the allodynia was unaffected by a neurokinin-1 antagonist. Having established facial and hind-paw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes in the rostral ventromedial medulla (RVM) interfered with its expression. Bupivacaine, destruction of putative pain-facilitating neurons, or block of cholecystokinin receptors prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating RVM "on" cells and transient suppression of RVM "off" cells after IM. INTERPRETATION: Facial and hind-paw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for development of novel therapeutic strategies for headache pain. The data also demonstrate the requirement for activation of descending facilitation from the RVM for the expression of cranial and extracranial cutaneous allodynia, and are consistent with a brainstem generator of allodynia associated with headache disorders.

Translational animal models for Alzheimer's disease: An Alzheimer's Association Business Consortium Think Tank.

Over 5 million Americans and 50 million individuals worldwide are living with Alzheimer's disease (AD). The progressive dementia associated with AD currently has no cure. Although clinical trials in patients are ultimately required to find safe and effective drugs, animal models of AD permit the integration of brain pathologies with learning and memory deficits that are the first step in developing these new drugs. The purpose of the Alzheimer's Association Business Consortium Think Tank meeting was to address the unmet need to improve the discovery and successful development of Alzheimer's therapies. We hypothesize that positive responses to new therapies observed in validated models of AD will provide predictive evidence for positive responses to these same therapies in AD patients. To achieve this goal, we convened a meeting of experts to explore the current state of AD animal models, identify knowledge gaps, and recommend actions for development of next-generation models with better predictability. Among our findings, we all recognize that models reflecting only single aspects of AD pathogenesis do not mimic AD. Models or combinations of new models are needed that incorporate genetics with environmental interactions, timing of disease development, heterogeneous mechanisms and pathways, comorbidities, and other pathologies that lead to AD and related dementias. Selection of the best models requires us to address the following: (1) which animal species, strains, and genetic backgrounds are most appropriate; (2) which models permit efficient use throughout the drug development pipeline; (3) the translatability of behavioral-cognitive assays from animals to patients; and (4) how to match potential AD therapeutics with particular models. Best practice guidelines to improve reproducibility also need to be developed for consistent use of these models in different research settings. To enhance translational predictability, we discuss a multi-model evaluation strategy to de-risk the successful transition of pre-clinical drug assets to the clinic.

Persistence of Inflammatory Phenotype in Residual Psoriatic Plaques in Patients on Effective Biologic Therapy.

Many psoriasis patients treated with biologics do not achieve total skin clearance. These patients possess residual plaques despite ongoing biologic treatment. To elucidate mechanisms of plaque persistence despite overall good drug response, we studied 50 subjects: psoriasis patients with residual plaques treated with one of three different biologics, untreated patients, and healthy controls. Skin biopsies from all subjects were characterized using three methods: mRNA expression, histology, and FACS of hematopoietic skin cells. Although all three methods provided evidence of drug effect, gene expression analysis revealed the persistence of key psoriasis pathways in treated plaques, including granulocyte adhesion and diapedesis, T helper type17 activation pathway, and interferon signaling with no novel pathways emerging. Focal decreases in parakeratosis and keratinocyte proliferation and differential reduction in IL-17 producing CD103- T cells, but no change in CD103+ tissue-resident memory T cells were observed. Of note, antitumor necrosis factor increased the interferon signaling pathway already present. Interestingly mast cells were the dominant source of IL-22 in all psoriasis subjects. These data suggest that while subtle differences can be observed in drug-treated plaques, underlying biologic mechanisms are similar to those present in untreated psoriatic lesions.

Monocytes/Macrophages play a pathogenic role in IL-23 mediated psoriasis-like skin inflammation.

Psoriasis is an immune-mediated inflammatory skin disease that affects millions worldwide. Studying immune cells involved in psoriasis pathogenesis is essential to identify effective and safe therapeutics for the disease. Using human psoriasis skin, activated macrophages were observed in both lesional and non-lesional skin, but were elevated in lesional skin. Activation of the IL-23/IL-17 pathway is integral to the development of psoriasis. To further characterize the monocyte/macrophage (Mon/Mac) population when the IL-23 pathway is activated, a murine model of intradermal injection of IL-23 was used. Flow cytometry revealed that Mon/Mac cells were the dominant immune population, particularly late in the model, highlighted by strong presence of Ly6ChiMHC IIhi cells. The Mon/Mac cells were also shown to have high expression for TNFα but not IL-17A. Prophylactic dosing of a CSF-1R inhibitor to deplete Mon/Mac cells significantly reduced several inflammatory mediators from the skin tissue suggesting a pathogenic role for Mon/Mac. Treatment dosing of the inhibitor produced a less robust effect. Mon/Mac cells were also differentiated by levels of Ki67 and TNFα expression. These data point to an important contribution of Mon/Mac cells in IL-23 related skin inflammation and suggest that these cells are a significant player in the underlying pathophysiology of psoriasis.

Characterization of psoriasiform dermatitis induced by systemic injection of interleukin-23 minicircles in mice.

The interleukin (IL)-23/IL-17 axis plays a central role in the pathogenesis of psoriasis and is elevated in lesional psoriatic skin. Different murine models have been developed to mimic this pathophysiology each carrying specific merits and limitations. In an attempt to address some of these limitations, B10.RIII mice received a single hydrodynamic injection of IL-23 minicircles (MC) to induce hepatic transcription and the endogenous production of IL-23. Plasma and ear IL-23 levels were dose-dependently (0.3-3 µg) increased in MC injected mice and were sustained over the 14-day study duration. Beginning on day 7 post-injection, mice developed dose-related ear inflammation, histologically confirmed increases in epidermal and dermal area, as well as enhanced neutrophil and macrophage content. Flow cytometry demonstrated increased levels of granulocytes, T cells and monocytes/macrophages in the ear skin, with T cells identified as the main cellular source of IL-17A. Evaluation of mRNA and protein showed time-dependent, increased levels of the IL-23/IL-17 pathway and inflammatory/microbial cytokines/chemokines in the ear which differed kinetically from circulating levels. An anti-IL-23p40 antibody was assessed following both prophylactic administration and administration once the disease was established. Prophylactic dosing completely prevented the development of the ear phenotype across endpoints. Treatment administration showed a dose-related response, with a maximum inhibition of 64-94%, depending on endpoint. These data demonstrate that the IL-23 MC model is a useful approach to study IL-23/IL-17-driven skin inflammation and may facilitate preclinical assessment of novel therapies.