The Alzheimer’s Prevention Initiative (API) Generation Study 1 (NCT0256551) evaluated CAD106, an active immunotherapy against Aβ, in delaying the clinical onset of Alzheimer’s disease in a cohort of cognitively unimpaired APOE4 homozygotes. Effect of CAD106 on brain amyloid burden after 2 years was measured by amyloid PET. Previous studies in mild AD showed that doses up to 450μg CAD106 induced sustained Aβ‐antibody response with no major safety concerns (Vandenberghe, 2017).

AbstractBackgroundAPI Generation Program evaluated the effectiveness of the BACE1 inhibitor umibecestat and the active immunotherapy CAD106 in delaying the onset of AD symptoms in APOE4 carriers. Data from imaging (vMRI and PET scans), and fluid biomarkers (blood and CSF) were collected during the 12‐week Screening phase. In this presentation, we will summarize results across the two studies and investigate the relationships between the various biomarkers and key baseline characteristics.MethodAmyloid levels were assessed via CSF and/or Amyloid PET scan in both studies for the APOE4 carriers. Generation Study 2 enrolled heterozygotes based on the following elevated amyloid inclusion criteria: Roche Elecsys® CSF p‐Tau/Abeta42 ratio > 0.024 and/or PET scans with any of the 3 amyloid F18 tracers (florbetapir, flutemetamol or florbetaben). If the centralized visual read of PET scan was negative, the SUVr was calculated (cortical composite in reference to whole cerebellum) for the three tracers in order to assess borderline cases. Thresholds for amyloid positivity equivalent to SUVR of 1.1 with florbetapir were used for the final decision on inclusion.ResultAcross both studies, over 500 lumbar punctures, 2700 amyloid PET scans and about 150 tau PET scans (conducted using flortaucipir) were performed. In Generation Study 1, over 200 FDG PET scans were also performed. Participants underwent amyloid testing during screening, blood sampling (plasma and serum) and underwent MRI scans for safety and to measure brain volumes. All baseline biomarker data will be presented, including available concentrations from CSF Tau/p‐Tau/Aβ42/Aβ40 along with the eligibility ratio for pTau/ab42. In about 150 participants, concordance between elevated/non elevated amyloid status by CSF and PET (using centiloids) will be shown. Baseline brain volume (whole brain and hippocampus) will be summarized for the different co‐variates (age, sex, cognition, genotype and amyloid status). Correlations among the various fluid biomarkers and imaging will be discussed.ConclusionThese data describe the biomarker signature of the world’s largest cohort of cognitively unimpaired APOE4 carriers with and without elevated amyloid. The anonymized study data, biomarker samples as well as images collected will be shared with the scientific community after study completion and reporting. ELECSYS is a registered trademark of Roche.

In addition to early mild non‐progressive cognitive worsening, BACE inhibitors have been associated with early non‐progressive reductions in hippocampal and whole brain volume in trial participants with elevated amyloid (A+, Egan et al, 2019). We have begun to evaluate the effects of umibecestat treatment and discontinuation on cognitively unimpaired amyloid‐positive (A+) and A‐ APOE4 homozygotes and A+ heterozygotes, testing the hypotheses that BACE inhibitor‐related hippocampal and whole brain shrinkage is apparent soon after treatment initiation, non‐progressive, limited to A+ participants, and reversible following discontinuation.

Abstract Introduction AZD4635 is an A2A receptor antagonist currently being tested as monotherapy and in combination with durvalumab in patients with advanced solid cancers. High adenosine levels found in tumors are immune suppressive and therefore AZD4635 could potentiate immune checkpoint inhibitors such as durvalumab (anti-PDL1). Predictions of A2A receptor engagement in patients at different doses and at different time points may enable better interpretation of clinical biomarker data measuring effects on immune modulation. A quantitative assessment of the receptor occupancy in the brain of non-human primates was conducted for AZD4635 with PET imaging and the resulting PK/PD model was applied to predict occupancy in humans in tumors. Methods PET measurements of A2AR occupancy in brain was performed using the radioligand [18F]MNI-444 in three anesthetized cynomologus monkeys. PET data acquisition was performed for 120 min following IV-administration of [18F]MNI-444 at baseline and following pretreatment of AZD4635. Sampling for AZD4635 plasma exposure determination was performed. As part of PK/PD analysis of the occupancy data, a novel modification of the non Invasive-LOGAN data analysis of the PET data was performed to obtain a time course of occupancy for each dose. A bio-phase PK/PD mathematical model was then used to describe the relationship of occupancy with circulating concentrations of AZD4635. In parallel, a PK model for AZD4635 in humans was developed using data from cohort 1 (Clinical trial NCT02740985) after 125 mg and used for PK predictions for alternative doses of AZD4635 in the clinic. Results A clear Exposure-Effect relationship was observed for AZD4635-driven A2AR occupancy in cyno brain when dosed 30 min prior to PET measurement. The PK/PD analysis of cyno PET-determined receptor occupancy provided an Occ50 that is in line with the in vitro potency for the compound under physiological concentrations of adenosine in the brain. The resulting PK/PD model has then been applied to predict the level of occupancy in human tumours at other clinically relevant doses. Different simulations were done varying the amount of endogenous adenosine levels. Conclusions AZD4635 was shown to occupy A2AR in cyno brain in an exposure dependent manner. The resulting PK/PD model built using this dataset was used to run simulations of expected tumor receptor occupancy in man and aid clinical dose selection for AZD4635. Sensitivity analysis has shown that prediction of human occupancy in the tumour is highly dependent on adenosine concentrations in the tumour. Simulations with tumor adenosine concentrations of 1 μM indicate that AZD4635 is predicted to provide ~90% receptor occupancy over the whole dosing interval at a clinically relevant dose. Citation Format: Peter Johnström, Pablo Morentin Gutierrez, Katarina Varnäs, Magnus Schou, Akihiro Takano, Lorraine Jones, Ganesh Mugundu, Patricia McCoon, Paul Lyne, Jeffrey Infante, Gerald Falchook, Manish Patel, Janet Karlix, Melinda Merchant, James Clarke, Alan Cross, Nicholas Seneca, Lars Farde, Miles Congreve, Jon S. Mason, Fiona H. Marshall. AZD4635 A2A receptor occupancy in cynomolgus monkey using PET and its application to an oncology clinical development program [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2641. doi:10.1158/1538-7445.AM2017-2641

18F-AV-1451 is currently the most widely used of several experimental tau PET tracers. The objective of this study was to evaluate 18F-AV-1451 binding with full kinetic analysis using a metabolite-corrected arterial input function and to compare parameters derived from kinetic analysis with SUV ratio (SUVR) calculated over different imaging time intervals. Methods: 18F-AV-1451 PET brain imaging was completed in 16 subjects: 4 young healthy volunteers (YHV), 4 aged healthy volunteers (AHV), and 8 Alzheimer disease (AD) subjects. Subjects were imaged for 3.5 h, with arterial blood samples obtained throughout. PET data were analyzed using plasma and reference tissue–based methods to estimate the distribution volume, binding potential (BPND), and SUVR. BPND and SUVR were calculated using the cerebellar cortex as a reference region and were compared across the different methods and across the 3 groups (YHV, AHV, and AD). Results: AD demonstrated increased 18F-AV-1451 retention compared with YHV and AHV based on both invasive and noninvasive analyses in cortical regions in which paired helical filament tau accumulation is expected in AD. A correlation of R2 > 0.93 was found between BPND (130 min) and SUVR-1 at all time intervals. Cortical SUVR curves reached a relative plateau around 1.0–1.2 for YHV and AHV by approximately 50 min, but increased in AD by up to approximately 20% at 110–130 min and approximately 30% at 160–180 min relative to 80–100 min. Distribution volume (130 min) was lower by 30%–35% in the YHV than AHV. Conclusion: Our data suggest that although 18F-AV-1451 SUVR curves do not reach a plateau and are still increasing in AD, an SUVR calculated over an imaging window of 80–100 min (as currently used in clinical studies) provides estimates of paired helical filament tau burden in good correlation with BPND, whereas SUVR sensitivity to regional cerebral blood changes needs further investigation.

In Alzheimer’s disease (AD), increased metabolism of monoamines by monoamine oxidase type B (MAO-B) leads to the production of toxic reactive oxygen species (ROS), which are thought to contribute to disease pathogenesis. Inhibition of the MAO-B enzyme may restore brain levels of monoaminergic neurotransmitters, reduce the formation of toxic ROS and reduce neuroinflammation (reactive astrocytosis), potentially leading to neuroprotection. Sembragiline (also referred as RO4602522, RG1577 and EVT 302 in previous communications) is a potent, selective and reversible inhibitor of MAO-B developed as a potential treatment for AD.

Activated microglia play a key role in inflammatory demyelinating injury in multiple sclerosis (MS). Microglial activation can be measured in vivo using a positron emission tomography (PET) ligand 11C-PBR28. We evaluated the test-retest variability (TRV) and lesion detectability of 11C-PBR28 binding in MS subjects and healthy controls (HCs) with high-resolution PET.

OBJECTIVE: The mechanism of action of anti-B cell therapy in multiple sclerosis (MS) is not fully understood. Here we compared the effect of anti-CD20 therapy on focal rat models of pattern I (T cell and macrophage-mediated delayed-type hypersensitivity) [DTH-EAE]) and pattern II (antibody-mediated focal myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalitis [fMOG-EAE]) lesion formation. DESIGN/METHODS: DTH-EAE lesions were induced via an intrastriatal injection of heat-killed BCG, then a peripheral injection of complete Freud’s adjuvant supplemented with TB. The fMOG-EAE lesions were induced by a subcutaneous injection of recombinant rat MOG in incomplete adjuvant and then activated by the injection of cytokines into the striatum. Microglial activation was assessed in situ and vivo using the TSPO SPECT ligand [ 125 I]DPA-713 and by immunostaining for MHCII. The effects of treatment on demyelination and lymphocyte recruitment to the brain were also evaluated. RESULTS: Anti-CD20 therapy reduced extralesional microglial activation, and lesion formation in both patterns I and II EAE, with a greater effect in the former model. Immunohistochemistry for MHCII demonstrated a reduced volume of microglial activation in the brains of anti-CD20 treated DTH-EAE animals, which was accompanied by a reduction in T cell recruitment and demyelination. Ex vivo autoradiography with the TSPO ligand [ 125 I]DPA-713 following the administration of anti-CD20 reduced binding by ~53%. In vivo imaging of [ 123 I]DPA-713 using SPECT/CT showed an increased uptake of radioactivity in the ipsilateral area compared with the contralateral side. Anti-CD20-treated DTH-EAE rodents showed significant reduction of radioligand binding compared with untreated animals. CONCLUSIONS: The suppression of lesion development by anti-CD20 treatment in pattern I MS-like lesions, which were hitherto considered B cell independent, suggests that B cells play an important role in lesion development, independent of auto-antibody production. Thus, CD20-positive B cell depletion has the potential to be effective in MS, independent of the pathogenetic type of lesion formation. Study Supported by: F. Hoffmann-LaRoche, Ltd. Disclosure: Dr. Anthony has received personal compensation for activities with Genentech, Inc. Dr. Dickens has nothing to disclose. Dr. Seneca has received personal compensation for activities with Roche Diagnostics Corp. Dr. Campbell has nothing to disclose. Dr. Checa has nothing to disclose. Dr. Kersemans has nothing to disclose. Dr. Warren has nothing to disclose. Dr. Tredwell has nothing to disclose. Dr. Gouverneur has nothing to disclose. Dr. Leppert has received personal compensation for activities with Roche Diagnostics Corp. as an employee. Dr. Leppert holds stock and/or stock options in Roche Diagnostics Corp.

OBJECTIVE:The mechanism of action of anti-B cell therapy in multiple sclerosis (MS) is not fully understood. Here, we compared the effect of anti-CD20 therapy on microglial activation in two distinct focal rat models of MS. METHODS:The effect of anti-CD20 therapy on lesion formation and extralesional microglial activation was evaluated in the fDTH-EAE (experimental allergic encephalomyelitis) model, which is a focal demyelinating type-IV delayed-type hypersensitivity lesion. For comparison, effects were also assessed in the focal humoral MOG model induced by intracerebral injection of cytokine in myelin oligodendrocyte glycoprotein immunized rats. Microglial activation was assessed in situ and in vivo using the TSPO SPECT ligand [(125)I]DPA-713, and by immunostaining for MHCII. The effect of treatment on demyelination and lymphocyte recruitment to the brain were evaluated. RESULTS:Anti-CD20 therapy reduced microglial activation, and lesion formation in the humoral model, but it was most effective in the antibody-independent fDTH-EAE. Immunohistochemistry for MHCII also demonstrated a reduced volume of microglial activation in the brains of anti-CD20-treated fDTH-EAE animals, which was accompanied by a reduction in T-cell recruitment and demyelination. The effect anti-CD20 therapy in the latter model was similarly strong as compared to the T-cell targeting MS compound FTY720. INTERPRETATION:The suppression of lesion development by anti-CD20 treatment in an antibody-independent model suggests that B-cells play an important role in lesion development, independent of auto-antibody production. Thus, CD20-positive B-cell depletion has the potential to be effective in a wider population of individuals with MS than might have been predicted from our knowledge of the underlying histopathology.

Objective: The mechanism of action of anti-B-cell therapy in multiple sclerosis (MS) is not fully understood. Here we compared the effect of anti-CD20 therapy on focal rat models of pattern I (T-cell and macrophage-mediated delayed-type hypersensitivity) [DTH-EAE]) and pattern II (antibody-mediated focal myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalitis [fMOG-EAE]) lesion formations.

Introduction: The aims of the present positron emission tomography (PET) study were to set up a system for C-11-cyanation labeling of the selective mGluR5-antagonist [C-11]AZD9272 and to perform the first in vivo characterization of [C-11]AZD9272 binding in cynomolgus monkeys.Methods: [C-11]AZD9272 was labeled using palladium mediated C-11-cyanation. Altogether seven PET measurements were performed in three cynomolgus monkeys including baseline and co-injection experiments with unlabelled AZD9272 (0.04 and 0.4 mg/kg). Radiometabolites in plasma were measured using HPLC.Results: [C-11]AZD9272 was prepared in over 50% incorporation yield from hydrogen [C-11]cyanide in a total synthesis time of 45-50 min. The radiochemical purity of the radioligand in its final formulation was high (>99%) and the mean specific radioactivity was 47 GBq/mu mol (1278 Ci/mmol, n=7) calculated at end of bombardment (EOB). In the baseline measurements 10% of the total injected radioactivity was present in monkey brain at five minutes after i.v. injection. The radioactivity concentration was high in the caudate, cingulate gyrus and thalamus whereas it was moderate in the temporal cortex and lower for the cerebellum. After co-injection with cold AZD9272 the binding of [C-11]AZD9272 was reduced in a dose-dependent fashion. Analysis of radiometabolites showed relatively slow metabolism and resulted only in hydrophilic radiometabolites.Conclusion: A fast and efficient method was developed to label AZD9272 with C-11. PET-examination in Cynomolgus monkeys showed that [C-11]AZD9272 entered the brain to a high extent, that binding was saturable and that the regional radioactivity pattern was in accordance with the known distribution of mGluR5. The results support further examination of [C-11]AZD9272 binding in human subjects. (C) 2013 Published by Elsevier Inc.

136 Objectives Activated microglia play a key role in inflammatory demyelinating injury in multiple sclerosis (MS). [11C]PBR28 is a PET ligand quantifying microglial activation in vivo. We evaluated the test-retest (T-RT) variability of [11C]PBR28 binding in MS patients and healthy controls (HC) with a high resolution PET. Methods Four MS patients (relapsing-remitting type in inactive phase, age: 41±7, 2M/2F) and 4 HC (age: 42±8, 2M/2F), matched for translocator protein genotype (2 C/C and 2 C/T in each group), were studied. Dynamic data were acquired over 120 min after injection of 628±102 MBq [11C]PBR28. Subjects were scanned twice, one to three weeks apart. Brain MRIs were collected for registration, regions-of-interest analysis, partial volume correction (PVC), and MS lesion evaluation. Volume of distribution (VT) derived from MA1 modeling (t*=30 min, using arterial input data), normalized by plasma free fraction (fP) was the main outcome measure (VT/fP). PVC VT/fP was calculated in grey matter (GM). T-RT variability was evaluated. Correlation of VT/fP and clinical parameters were assessed. Results T-RT results showed a mean absolute variation of 12±10% across GM and white matter (WM). HC VT/fP values (ml/cm3) were 258±139 in GM and 231±116 in WM; MS values were 267±76 in GM, 248±67 in WM, and 254±80 in MS lesions. No significant difference was found between lesions and normal-appearing WM of MS. VT/fP values of GM and WM in HC were higher in C/C genotype than in C/T, although it was not significant. PVC increased VT/fP by ~ 16%, with a slightly larger correction in MS. Clinical disease activity (Expanded disease status scale) was not correlated with VT/fP. Conclusions [11C]PBR28 PET has good T-RT reproducibility for quantifying activated microglia in the human brain. Larger studies, including MS subjects from heterogeneous disease activity status, are needed to evaluate the sensitivity of this ligand.

Expression of monoamine oxidase type B (MAO-B) in brain increases with aging, and is further increased in Alzheimer's disease (AD). This up-regulation of MAO-B has been suggested to contribute to neurodegenerative processes by increasing oxidative stress, prompting development of MAO-B inhibitors (MAO-Bi) in treatment of AD. Evidence of clinical efficacy comes from unpublished data on lazabemide, a selective MAO-Bi previously developed by Roche that significantly improved cognition and functionality in AD patients. RO4602522 is a potent and selective MAO-Bi which is currently tested in a phase 2 AD patient study (“MAyflOwer RoAD”). Simulations based on earlier PK/MAO-B inhibition data from young healthy subjects predicted that maximal enzyme inhibition in hippocampus (median of 84%) would be approached in AD patients at 1mg (median of 80%), assuming no relevant effect of age and disease on PK/PD relationship. This PET study is undertaken to confirm high level MAO-B occupancy at the doses tested in “MAyflOwer RoAD” study, and to characterize the PK/MAO-B inhibition relationship in AD patients. Results of 1mg and 0.2mg groups are presented. After signing informed consent, 6 AD patients and 6 elderly controls (ECs) were administered 1mg RO4602522 for 2 weeks, or a 5mg dose followed by 0.2mg doses for 6 days. PET scans for MAO-B occupancy were performed at baseline and 24h postdose at steady-state, using [11 C]-L-deprenyl-D2 tracer. Five AD patients (2 at 1mg, 3 at 0.2mg), MMSE 17–26 and 6 ECs (3 at 1mg, 3 at 0.2mg) underwent pre and postdose PET scans. At 1mg doses, MAO-B occupancy ranged from 71%-88%, across subjects and brain regions of interest, with a trend for higher occupancy in subcortical regions. Occupancies in 0.2mg group ranged from 37–83%, and were very sensitive to plasma concentrations. Plots of MAO-B occupancy vs concentration showed a sharp increase at low concentrations, to a plateau in MAO-B occupancy (Figure 1), as predicted from the model in young subjects. Data in AD patients and ECs were well predicted by the model generated with enzyme occupancy data from young subjects, and showed that near-maximal inhibition of brain MAO-B was achieved with 1mg RO4606522 daily, regardless of the population. Relationship between plasma concentration and MAO-B inhibition in hippocampus of AD patients and elderly controls in steady-state conditions at 0.2mg and 1mg RO4602522 (note: MAO-B inhibition in hippocampus (81.1%) for third AD patient at 0.2 mg not reflected in this plot as corresponding plasma concentration was not available)