Blood Biomarkers from Research Use to Clinical Practice: What Must Be Done? A Report from the EU/US CTAD Task Force.

Timely and accurate diagnosis of Alzheimer's disease (AD) in clinical practice remains challenging. PET and CSF biomarkers are the most widely used biomarkers to aid diagnosis in clinical research but present limitations for clinical practice (i.e., cost, accessibility). Emerging blood-based markers have the potential to be accurate, cost-effective, and easily accessible for widespread clinical use, and could facilitate timely diagnosis. The EU/US CTAD Task Force met in May 2022 in a virtual meeting to discuss pathways to implementation of blood-based markers in clinical practice. Specifically, the CTAD Task Force assessed: the state-of-art for blood-based markers, the current use of blood-based markers in clinical trials, the potential use of blood-based markers in clinical practice, the current challenges with blood-based markers, and the next steps needed for broader adoption in clinical practice.

Cognitive and functional patterns of nondemented subjects with equivocal visual amyloid PET findings.

PURPOSE: Despite good to excellent inter-reader agreement in the evaluation of amyloid load on PET scans in subjects with Alzheimer's disease, some equivocal findings have been reported in the literature. We aimed to describe the clinical characteristics of subjects with equivocal PET images. METHODS: Nondemented subjects aged 70 years or more were enrolled from the MAPT trial. Cognitive and functional assessments were conducted at baseline, at 6 months, and annually for 3 years. During the follow-up period, 271 subjects had (18)F-AV45 PET scans. Images were visually assessed by three observers and classified as positive, negative or equivocal (if one observer disagreed). After debate, equivocal images were reclassified as positive (EP+) or negative (EP-). Scans were also classified by semiautomated quantitative analysis using mean amyloid uptake of cortical regions. We evaluated agreement among the observers, and between visual and quantitative assessments using kappa coefficients, and compared the clinical characteristics of the subjects according to their PET results. RESULTS: In 158 subjects (58.30 %) the PET scan was negative for amyloid, in 77 (28.41 %) the scan was positive and in 36 (13.28 %) the scan was equivocal. Agreement among the three observers was excellent (kappa 0.80). Subjects with equivocal images were more frequently men (58 % vs. 37 %) and exhibited intermediate scores on cognitive and functional scales between those of subjects with positive and negative scans. Amyloid load differed between the EP- and negative groups and between the EP+ and positive groups after reclassification. CONCLUSION: Equivocal amyloid PET images could represent a neuroimaging entity with intermediate amyloid load but without a specific neuropsychological pattern. Clinical follow-up to assess cognitive evolution in subjects with equivocal scans is needed.

[Effect of AChE and BuChE inhibition by rivastigmin in a group of old-old elderly patients with cerebrovascular impairment (SIVD type)]. / Effecto dell'inibizione AChE e BuChE tramite rivastigmina in un gruppo di soggetti geriatrici old-old affetti da demenza vascolare (SIVD-type).

AIM: Vascular dementia (VaD) is defined as a loss of cognitive function resulting from ischemic, hypoperfusive, or hemorrhagic brain lesions due to cerebrovascular disease or cardiovascular pathology. The main types of VaD are: Small Vessel Disease Dementia (sVAD), Large vessel disease dementia, hypoperfusive-ischemic dementia and hemorragic dementia. The sVAD is divided into two main categories: subcortical ischemic vascular dementia (SIVD) and cortical dementia. Currently, no drugs are approved for the treatment of VaD. This study aimed to determine whether rivastigmine, a second generation cholinesterase inhibitor with selectivity for the CNS, with capacity to inhibit both acetylcholinesterase (AChE) and butyryl-cholinesterase (BuChE), slows the rate of cognitive decline associated with VaD. METHODS: Study subjects were 27 male and 43 female outpatients aged 80.03±6.53 years, with Mini-Mental State Examination (MMSE) score ranging batween 22 and 12, affected by VaD. They were included in the study if they were undergoing pharmacological treatment with acetylsalicylic acid 100 mg for at least six months. Patients were divided into two groups: one group was treated with ASA 100 mg and rivastigmine patch 9.5 mg (Rivastigmine group), the other just with ASA 100 mg (ASA group). All patients were followed for 6 months, with a first evaluation (T0) and a second examination after six mounths of treatment (T1). RESULTS: Statistically data proved as the Rivastigmine group showed constant values at MMSE, compared with patients of the ASA group who experienced decline of their cognitive performances. The same result was found in CDR, ADL, GDS and NPI scales. It is remarkable to underline as Rivastigmine-treated patients had a mean improvement in GDS scales, in comparison with patients of the ASA group who showed a worsening of mood. CONCLUSION: Rivastigmine-therapy improves cognitive performance in elderly with SIVD.

Florbetapir F 18 amyloid PET and 36-month cognitive decline: a prospective multicenter study.

This study was designed to evaluate whether subjects with amyloid beta (Aß) pathology, detected using florbetapir positron emission tomorgraphy (PET), demonstrated greater cognitive decline than subjects without Aß pathology. Sixty-nine cognitively normal (CN) controls, 52 with recently diagnosed mild cognitive impairment (MCI) and 31 with probable Alzheimer's disease (AD) dementia were included in the study. PET images obtained in these subjects were visually rated as positive (Aß+) or negative (Aß-), blind to diagnosis. Fourteen percent (10/69) of CN, 37% (19/52) of MCI and 68% (21/31) of AD were Aß+. The primary outcome was change in ADAS-Cog score in MCI subjects after 36 months; however, additional outcomes included change on measures of cognition, function and diagnostic status. Aß+ MCI subjects demonstrated greater worsening compared with Aß- subjects on the ADAS-Cog over 36 months (5.66 ± 1.47 vs -0.71 ± 1.09, P = 0.0014) as well as on the mini-mental state exam (MMSE), digit symbol substitution (DSS) test, and a verbal fluency test (P < 0.05). Similar to MCI subjects, Aß+ CN subjects showed greater decline on the ADAS-Cog, digit-symbol-substitution test and verbal fluency (P<0.05), whereas Aß+ AD patients showed greater declines in verbal fluency and the MMSE (P < 0.05). Aß+ subjects in all diagnostic groups also showed greater decline on the CDR-SB (P<0.04), a global clinical assessment. Aß+ subjects did not show significantly greater declines on the ADCS-ADL or Wechsler Memory Scale. Overall, these findings suggest that in CN, MCI and AD subjects, florbetapir PET Aß+ subjects show greater cognitive and global deterioration over a 3-year follow-up than Aß- subjects do.

Amyloid PET imaging in Alzheimer's disease: a comparison of three radiotracers.

PURPOSE: The increasing use of amyloid PET in Alzheimer's disease research and clinical trials has motivated efforts to standardize methodology. We compared retention of the (11)C radiotracer Pittsburgh Compound B (PiB) and that of two (18)F amyloid radiotracers (florbetapir and flutemetamol) using two study populations. We also examined the feasibility of converting between tracer-specific measures, using PiB as the common link between the two (18)F tracers. METHODS: One group of 40 subjects underwent PiB and flutemetamol imaging sessions and a separate group of 32 subjects underwent PiB and florbetapir imaging sessions. We compared cortical and white matter retention for each (18)F tracer relative to that of PiB, as well as retention in several reference regions and image analysis methods. Correlations between tracer pairs were used to convert tracer-specific threshold values for amyloid positivity between tracers. RESULTS: Cortical retention for each pair of tracers was strongly correlated regardless of reference region (PiB-flutemetamol, ρ = 0.84-0.99; PiB-florbetapir, ρ = 0.83-0.97) and analysis method (ρ = 0.90-0.99). Compared to PiB, flutemetamol had higher white matter retention, while florbetapir had lower cortical retention. Two previously established independent thresholds for amyloid positivity were highly consistent when values were converted between tracer pairs. CONCLUSION: Despite differing white and grey matter retention characteristics, cortical retention for each (18)F tracer was highly correlated with that of PiB, enabling conversion of thresholds across tracer measurement scales with a high level of internal consistency. Standardization of analysis methods and measurement scales may facilitate the comparison of amyloid PET data obtained using different tracers.

Cognition and amyloid load in Alzheimer disease imaged with florbetapir F 18(AV-45) positron emission tomography.

OBJECTIVE: To examine the association between regional brain uptake of a novel amyloid positron emission tomography (PET) tracer florbetapir F 18 ([(18)F]-AV-45) and cognitive performance in a pilot study. DESIGN: Cross-sectional comparison of [(18)F]-AV-45 in AD patients versus controls. SETTING: Three specialty memory clinics. PARTICIPANTS: Eleven participants with probable Alzheimer disease (AD) by NINDS/ADRDA criteria and 15 healthy comparison (HC) participants. MEASUREMENTS: Participants underwent PET imaging following a 370 MBq (10 mCi) intravenous administration of [(18)F]-AV-45. Regional/cerebellar standardized uptake value ratios (SUVRs) were calculated. Cognition was assessed using Mini-Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Wechsler Logical Memory IA (immediate recall) test (LMIA), and verbal category fluency. RESULTS: Greater [(18)F]-AV-45 SUVR was associated with poorer performance on all cognitive tests. In the HC group, occipital, parietal, precuneus, temporal, and cortical average SUVR was associated with greater ADAS-Cog, and greater anterior cingulate SUVR was associated with lower LMIA. Two HC participants had [(18)F]-AV-45 cortical/cerebellar SUVR greater than 1.5, one of whom had deficits in episodic recall and on follow-up met criteria for amnestic mild cognitive impairment. CONCLUSION: [(18)F]-AV-45 SUVR in several brain regions was associated with worse global cognitive performance particularly in HC, suggesting its potential as a marker of preclinical AD.

The use of the exploratory IND in the evaluation and development of 18F-PET radiopharmaceuticals for amyloid imaging in the brain: a review of one company's experience.

AIM AND METHODS: The regulatory mechanism of exploratory INDs established in 2006 by the US Food and Drug Administration (FDA) is useful for the evaluation of tracer dose radiopharmaceutical agents, and especially valuable for development of amyloid imaging agents because of the absence of appropriate animal models. The authors employed exploratory INDs to study four related novel 18F-labeled positron emission tomography (PET) amyloid imaging agents, 18F-AV-19, 18F-AV-45, 18F-AV-138 and 18F-AV-144. These exploratory INDs contained preclinical data on the mechanism of action, secondary pharmacology, biodistribution, pharmacokinetics and dosimetry and results from a single dose, extended acute toxicology study. Each compound was then tested in a human PET study in up to 15 healthy elderly controls (HC) and 15 patients with AD. Compared to HC, patients with AD showed accumulation of tracer in cortical areas expected to be high in amyloid deposition with all four tracer compounds, and no serious adverse events were observed for any of the tracers. RESULTS: .18F-AV-45 showed the best imaging characteristics and was chosen for further development under a traditional IND. CONCLUSIONS: In summary the exploratory IND pathway was very useful for comparing four related agents with respect to efficacy (amyloid plaque binding), kinetics and dosimetry.

Outcome measures for the study of activities of daily living in vascular dementia.

Decline in functional abilities is a major component of the dementia syndrome. The definition of dementia in the International Classification of Diseases (10th rev.) requires a cognitive impairment sufficient to impair personal activities of daily living (ADL). The Diagnostic and Statistical Manual of Mental Disorders (4th ed.) also requires cognitive deficits sufficiently severe to cause impairment in occupational or social functioning and must represent a decline from a higher level of functioning. However, the term disability is more appropriate than impairment to describe a loss in activities, as opposed to a loss of elementary functions, and is consistent with World Health Organization definitions of impairment, disability, and handicap. There is no doubt that ADL outcomes are required in therapeutic drug studies on vascular dementia, and there is a good rationale and some evidence for the use of ADL scales developed for therapeutic research in Alzheimer disease, favoring scales devoid of items sensitive to physical disabilities. Similarly, ADL-related clinical milestones could be used for longer-term studies aiming predominantly at slowing progression of disease in both early and later stages of dementia. Slower decline in ADL and delay in reaching ADL-related clinical milestones should be considered as valid outcomes by regulatory bodies in the process of dementia drug approval.

Further developments in the measurement of working memory in rodents.

This article reviews automated test procedures that can be used to study memory for discrete/trial-unique events in rodents and other animals. A distinction is made between delayed response tasks, i.e. those tasks for which all information necessary to determine the correct response is available prior to the retention interval, and delayed comparison tasks, i.e. tasks in which the subject must compare stimuli presented prior to and after the retention interval in order to determine the correct response. Delayed comparison procedures potentially provide a purer estimate of the subject's memory capacities, but have also been more difficult for rodents to acquire. Suggestions are offered for potential directions for improved delayed comparison tasks.

Effects of the selective sigma receptor ligand, 6-[6-(4-hydroxypiperidinyl)hexyloxy]-3-methylflavone (NPC 16377), on behavioral and toxic effects of cocaine.

Certain sigma receptor ligands have been shown to block locomotor stimulation produced by cocaine at doses that do not have significant behavioral activity when given alone. Using a potent and selective ligand of sigma binding sites, 6-[6-(4-hydroxypiperidinyl)hexyloxy]-3-methylflavone (NPC 16377), we further investigated the influence of sigma ligands on additional behavioral and toxic effects of cocaine in mice. A behaviorally inactive dose of NPC 16377 shifted the dose-effect function for the locomotor stimulant effects of cocaine to the right by a factor of 2.5. A higher dose of NPC 16377 produced an insurmountable blockade of this stimulant effect of cocaine. Prior exposure to cocaine enhances the locomotor stimulant effects of cocaine (sensitization). NPC 16377 prevented the development of cocaine sensitization without producing behavioral effects of its own. However, NPC 16377 was unable to block the expression of sensitization in mice previously exposed to cocaine. NPC 16377 also did not consistently alter the discriminative stimulus effects of cocaine or methamphetamine in rats discriminating either 3 or 10 mg/kg of cocaine, or 1 mg/kg of methamphetamine from saline. The potential phencyclidine-like behavioral effects of NPC 16377 were also evaluated. Unlike the NMDA channel ligand, dizocilpine, NPC 16377 did not increase responding under a fixed-interval schedule of food presentation in rats nor did it substitute for the discriminative stimulus effects of either 1.5 mg/kg of phencyclidine or 0.2 mg/kg of dizocilpine in rats discriminating these drugs from saline. NPC 16377 displayed limited but significant anticonvulsant activity against diazepam-sensitive cocaine convulsions. The lethal effects of higher doses of cocaine were neither significantly blocked nor enhanced in rats or mice with NPC 16377. These findings extend earlier observations on the cocaine-blocking effects of sigma ligands to a novel structure with exceptional selectivity for sigma sites. These data indicate that some sigma ligands may be capable of altering certain behavioral and toxic actions of cocaine without notable behavioral side effects as evidenced in preclinical tests. As such, these compounds may ultimately be useful in the treatment of cocaine abuse.

NPC 16377, a potent and selective sigma-ligand. II. Behavioral and neuroprotective profile.

6-[6-(4-Hydroxypiperidinyl)hexyloxy]-3-methylflavone HCI, (NPC 16377), a potent and highly selective sigma-site ligand, was evaluated in tests predictive of antipsychotic and neuroprotective potential and for toxicity. Like haloperidol, clozapine and remoxipride, and the sigma-ligands BMY 14802, ifenprodil and rimcazole, NPC 16377 reversed amphetamine-induced hyperactivity and apomorphine-induced climbing in mice. Additional evidence for antipsychotic activity was obtained in rats with NPC 16377, clozapine, BMY 14802, ifenprodil, haloperidol and rimcazole, all of which reduced conditioned avoidance responses at doses that did not reduce escape behavior. NPC 16377 did not induce catalepsy in mice, suggesting a decreased liability for producing extrapyramidal side effects. NPC 16377 extended survival time for mice exposed to a hypoxic environment. In a model of global ischemia using conscious gerbils, NPC 16377 prevented damage to hippocampal CA1 neurons after either intraperitoneal or oral administration. NPC 16377 did not disrupt prepulse inhibition or block the disruption of prepulse inhibition induced by the phencyclidine site-selective ligand (+)MK-801. In rats trained to discriminate phencyclidine from saline, NPC 16377 did not substitute for the psychotomimetic. These data are consistent with the notion that selective sigma-agents may possess antipsychotic and neuroprotective activities. Moreover, the results from prepulse inhibition and drug discrimination experiments suggest that NPC 16377 is devoid of phencyclidine-like effects.

NPC 16377, a potent and selective sigma-ligand. I. Receptor binding, neurochemical and neuroendocrine profile.

6-[6-(4-Hydroxypiperidinyl)hexyloxy]-3-methylflavone HCI (NPC 16377), a structurally novel compound, was found to be a highly potent and selective ligand for sigma-sites. Although 5-fold less potent than haloperidol and 2-fold less potent than ifenprodil to inhibit 1,3-di-o-tolylguanidine binding, NPC 16377 (IC50 = 36 nM) was more potent than alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazinyl butanol (BMY 14802), rimcazole and the atypical antipsychotic, clozapine. A similar rank order of potency was observed when [3H](+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperdine was used as the radioligand. Like BMY, rimcazole and clozapine, NPC 16377 (IC50 = 2671 nM) had low affinity for dopamine type 2 receptors. Additionally, the compound was only weakly active in 35 additional receptor binding assays including those for serotonin2 and serotonin1C receptors. In vivo, NPC 16377 potently inhibited the binding of [3H]-(+)-N-allylnormetazocine to sigma sites after both intraperitoneal and oral administration. At doses 30-fold in excess of the ID50 to inhibit [3H](+)N-allylnormetazocine, NPC 16377 failed to displace [3H]raclopride from dopamine type 2 binding sites. Unlike haloperidol, BMY 14802, ifenprodil and clozapine, behaviorally effective doses of NPC 16377 did not increase dopamine turnover in the frontal cortex, nucleus accumbens or corpus striatum of rats. In contrast, each of these agents increased circulating levels of both adrenocorticotropin and corticosterone, but only NPC 16377 decreased circulating plasma levels of prolactin. The results of the current study are consistent with the notion that NPC 16377 is a potent, selective and orally active sigma site ligand. At behaviorally relevant doses the compound produces neuroendocrine effects both similar to, and different from, neuroleptics, other sigma-ligands and atypical antipsychotics, while having no effect on dopamine turnover. Given these data, NPC 16377 should prove to be a useful compound to explore further the physiological and functional significance of sigma-sites in brain.

Effects of strychnine-insensitive glycine receptor antagonists and sigma agents on working memory performance: comparison with dizocilpine and scopolamine.

The strychnine insensitive glycine receptor antagonists (+/-) HA 966 (2.5, 3.5, 4.25 and 5.0mg/kg) and 7 chlorokynurenic acid (5.0, 10.0, and 15.0mg/kg), the putative sigma agents NPC 16377 (5.0 and 8.0mg/kg), BMY 14802 (5.0, 7.5 and 10.0mg/kg), and ifenprodil (5.0 and 7.0mg/kg) and the reference agents scopolamine and dizocilpine [(+) MK 801] were evaluated in a nonspatial delayed matching to sample working memory task in rats. (+/-) HA 966 impaired accuracy at the longest retention interval and decreased response probability measures. 7-Chlorokynurenic acid was essentially without effect. The noncompetitive NMDA antagonist dizocilpine reduced accuracy at all retention intervals, decreased the probability of a choice response and increased the probability of an intertrial interval response. The anticholinergic agent scopolamine selectively reduced accuracy at the longest retention interval but did not affect other performance measures. Sigma agents decreased response probability measures but did not affect accuracy at any retention interval. The results support the notion that sigma agents, glycine antagonists and NMDA antagonists produce different effects in cognitive tasks including working memory performance.

A patient with primary biliary cirrhosis and multiple sclerosis.

A 48-year-old woman with primary biliary cirrhosis (PBC) and multiple sclerosis (MS) is reported. She presented with a visual deficit in 1975. In the course of a diagnostic evaluation, she was found to have PBC. In 1986, the diagnosis of MS was made. The patient's liver function deteriorated and liver transplantation was performed in May 1988. This is the third known case of this association.

N-methyl-D-aspartate antagonists and working memory performance: comparison with the effects of scopolamine, propranolol, diazepam, and phenylisopropyladenosine.

The effects of the competitive N-methyl-D-aspartate (NMDA) antagonists CPP (5 & 10 mg/kg) and NPC 12626 (25 & 40 mg/kg) and the noncompetitive NMDA antagonists phencyclidine (1, 3, & 6.25 mg/kg) and MK 801 (0.1 & 0.2 mg/kg) on performance of rats on a nonspatial delayed matching-to-sample working memory task were evaluated. At the highest dose, each NMDA antagonist reduced choice accuracy at all retention intervals. In contrast, the reference anticholinergic agent scopolamine selectively reduced accuracy at long retention intervals, suggesting that scopolamine but not the NMDA antagonists directly interfered with time-dependent working memory retention. Propranolol, diazepam, and phenylisopropyladenosine had little or no effect on choice accuracy, suggesting that noradrenergic, gamma-aminobutyric acid-diazepam, and adenosine receptors may be relatively unimportant for working memory performance as assessed in this task. The NMDA antagonists also differed from scopolamine in that doses of NMDA antagonists that reduced response accuracy also reduced response probability, altered bias (competitive antagonists only), and increased intertrial interval responding (noncompetitive antagonists only). It was concluded that NMDA antagonists disrupt cognitive functions including, but not limited to, those required for accurate working memory performance.

Photochemically induced thrombosis of the precentral cortex impairs operant variable-interval spatial delayed alternation performance by rats.

A variable-interval spatial delayed alternation memory task was used to quantify the behavioral effects of photochemically induced thrombic infarction of the precentral (frontal) cortex. Upon achieving criterion on the behavioral task, rats received thrombicischemic lesions, predominantly limited to the medial precentral cortex, induced by injection of the fluorescein dye Rose Bengal and illumination of the skull above the target area. Beginning six days after surgery, rats were retested on the memory task. Compared to Sham-operated controls (n = 5), rats with precentral cortex lesions (n = 5) demonstrated a retention interval-dependent accuracy deficit (impaired at the longest retention interval only) and slower reaction time (increased response latency). These effects were significant only during the first week of postoperative testing. Rats with lesions also demonstrated a greater probability of a choice response throughout the three postoperative test weeks. The results suggest that photochemical thrombosis in the precentral cortex produces functional, behavioral consequences in rats which can be reliably and objectively measured.

Possible cerebroprotective and in vivo NMDA antagonist activities of sigma agents.

The recent finding that ifenprodil binds with high affinity to sigma sites suggests that other sigma agents may have ifenprodil-like cerebroprotectant and functional N-methyl-D-aspartate (NMDA) antagonist effects. The present study, compared the in vivo effects of ifenprodil and the sigma agents, BMY 14802, caramiphen and haloperidol, in three tests sensitive to NMDA antagonists and purported cerebroprotectant drugs. When administered at or below the rotorod TD50 dose, all four compounds significantly increased survival time in an hypoxic environment (4% O2 in nitrogen). Caramiphen and ifenprodil (ED50 = 52 and 61 mg/kg, respectively) also blocked maximal electroshock-induced seizures, whereas BMY 14802 and haloperidol were ineffective. Finally, caramiphen (ED50 = 95 mg/kg) antagonized seizures and lethality induced by administration of NMDA (250 mg/kg, IP). BMY 14802, haloperidol and ifenprodil only partially antagonized NMDA-induced seizures, but did enhance the anticonvulsant potency of the noncompetitive NMDA antagonist, MK-801. Together, these findings suggest that sigma agents may have cerebroprotective effects.