A 24-Month Study to Evaluate the Efficacy and Safety of Elenbecestat (E2609) in Participants With Early Alzheimer's Disease

Study Overview
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Brief Summary
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The name of this trial is MissionAD1. This phase 3 study consists of a Core and Open Label Extension (OLE) Phase in participants with Early Alzheimer's Disease (EAD), and will be conducted to evaluate the efficacy and safety of E2609. The Core is a 24-month treatment, multicenter, double blind, placebo controlled parallel group study. The OLE is a 24-month treatment, one group study. The data for the studies E2609-G000-301 (NCT02956486, MissionAD1) and E2609-G000-302 (NCT03036280, MissionAD2) will be pooled.

Official Title
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A Placebo-Controlled, Double-Blind, Parallel-Group, 24 Month Study With an Open-Label Extension Phase to Evaluate the Efficacy and Safety of Elenbecestat (E2609) in Subjects With Early Alzheimer's Disease

Conditions
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Alzheimer's Disease

Intervention / Treatment
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* Drug: Elenbecestat
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Core Study Mild cognitive impairment due to Alzheimer's disease (AD) or mild AD dementia including Mini Mental State Examination score equal to or greater than 24 Clinical Dementia Rating (CDR) global score of 0.5 CDR Memory Box score of 0.5 or greater Impaired episodic memory confirmed by a list learning task Positive biomarker for brain amyloid pathology as indicated by either amyloid positron emission tomography or cerebrospinal fluid AD assessment or both Extension Phase • Participants who complete the Core Study Exclusion Criteria: Core Study Females who are breastfeeding or pregnant at Screening or Baseline. Females of child-bearing potential must use a highly effective method of contraception throughout the entire study period and for 28 days after study drug discontinuation Any condition that may be contributing to cognitive impairment above and beyond that caused by the participant's AD Participants with a history of seizures within 5 years of Screening History of transient ischemic attacks or stroke within 12 months of Screening Psychiatric diagnosis or symptoms (example, hallucinations, major depression, delusions etc.) Suicidal ideation or any suicidal behavior within 6 months before Screening or has been hospitalized or treated for suicidal behavior in the past 5 years Have any contraindications to magnetic resonance imaging (MRI) scanning or Have lesions that could indicate a dementia diagnosis other than AD on brain MRI Exhibit other significant pathological findings on brain MRI. Participants who have a history of moderate to severe hepatic impairment (example, Child-Pugh Class B or C) Results of laboratory tests conducted during Screening that are outside the following limits: Absolute lymphocyte count below the lower limit of normal (LLN) Thyroid stimulating hormone above normal range Abnormally low Vitamin B12 levels Participants at increased risk of infection Have received any live vaccine/live attenuated vaccine in the 3 months before randomization Any chronic inflammatory disease that is not adequately controlled or that requires systemic immunosuppressive or immunomodulatory therapy Any other clinically significant abnormalities Severe visual or hearing impairment A prolonged corrected QT (QTc) interval (QT interval with Fridericia's correction [QTcF] greater than 450 milliseconds [ms]) Malignant neoplasms within 5 years of Screening Known or suspected history of drug or alcohol abuse Taking prohibited medications, which must be reviewed with the Investigator Have participated in a recent clinical study Note: Other protocol-defined Inclusion/Exclusion Criteria may apply.

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Core Study: Elenbecestat 50 mg<br>Participants will receive one 50 milligram (mg) elenbecestat tablet, orally, once a day in the morning. The core study will be double blinded. | Drug: Elenbecestat<br>* Oral tablet.<br>* Other names: E2609;|
| Placebo Comparator: Core Study: Placebo<br>Participants will receive one matching placebo tablet, orally, once a day in the morning. The core study will be double blinded. | Drug: Placebo<br>* Oral tablet.<br>|
| Experimental: Open-label Extension Phase: Elenbecestat 50 mg<br>Participants completing the core study will receive one 50 mg elenbecestat tablet, orally, once a day in the morning. | Drug: Elenbecestat<br>* Oral tablet.<br>* Other names: E2609;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Core Phase: Change From Baseline up to Month 24 in the Clinical Dementia Rating-sum of Boxes (CDR-SB) Score | The clinical dementia rating (CDR) scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The CDR-SB is a sum of the individual domain scores and ranges from 0 to 18. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Extension Phase: Number of Participants Reporting One or More Treatment-emergent Adverse Events (TEAEs) | A TEAE is defined as an adverse event that emerged during treatment or within 28 days following the last dose of study drug, having been absent at pretreatment (Baseline) or reemerged during treatment, having been present at pretreatment (Baseline) but stopped before treatment, or worsened in severity during treatment relative to the pretreatment state, when the adverse event was continuous. Number of participants with TEAEs (serious and non-serious adverse events) were reported based on their safety assessments of laboratory tests, suicidal ideation and suicidal behavior, drug abuse potential, physical examination, neurological examination, regular measurement of vital signs, magnetic resonance imaging and electrocardiogram parameter values. | From first dose of study drug up to approximately 6 months (including 1 month follow up) for the extension phase | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Core Phase: Change From Baseline up to Month 24 in Alzheimer's Disease Composite Score (ADCOMS) | ADCOMS is a weighted linear combination of 12 items from three existing clinical scales: the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog), the Mini Mental State Examination (MMSE), and the CDR. Four items are from the ADAS-cog (A4 [Delayed Word Recall], A7 [Orientation], A8 [Word Recognition], A11 [Word Finding]); 2 items are from the MMSE (M1 [Orientation Time], M7 [Drawing]); 6 items are from the CDR (C1 [Personal Care], C2 [Community Affairs], C3 [Home and Hobbies], C4 [Judgment and Problem Solving], C5 [Memory], C6 [Orientation]). Composite score is derived from the variables from the 12 items, and ranges from 0 to 1.97, where higher score indicates worse performance. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in Amyloid Positron Emission Tomography (PET) Standardized Uptake Value Ratio (SUVR) | Amyloid PET scan assesses cerebral amyloid load using 3 tracers (florbetapir, florbetaben and flutemetamol) which is standardized into centiloids for evaluation of AD. Centiloid values on centiloid scale is based on mean composite SUVR in cingulate, frontal, parietal and temporal cortexes using whole cerebellum as reference region. SUVR is ratio of tracer uptake in each of cingulate, frontal, parietal and temporal cortexes relative to cerebellum. The centiloid scale anchor points are 0 and 100, where 0 represents a high-certainty amyloid negative scan and 100 represents the amount of global amyloid deposition found in a typical AD scans. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the ADCOMS for Participants Enriched by Baseline Amyloid PET SUVR Between 1.2 and 1.6 | ADCOMS is a weighted linear combination of 12 items from three existing clinical scales: the ADAS-cog, the MMSE, and the CDR. Four items are from the ADAS-cog (A4 [Delayed Word Recall], A7 [Orientation], A8 [Word Recognition], A11 [Word Finding]); 2 items are from the MMSE (M1 [Orientation Time], M7 [Drawing]); 6 items are from the CDR (C1 [Personal Care], C2 [Community Affairs], C3 [Home and Hobbies], C4 [Judgment and Problem Solving], C5 [Memory], C6 [Orientation]). Composite score is derived from the variables from the 12 items, and ranges from 0 to 1.97, where higher score indicates worse performance. Amyloid PET scans allow in vivo assessment of cerebral amyloid load. SUVR indicates the ratio of tracer uptake in the frontal cortex relative to the cerebellum or the ratio of tracer uptake in the whole brain relative to the cerebellum. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change Per Year (Mean Slope) in CDR-SB Score up to Month 24 | The CDR scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The CDR-SB is a sum of the individual domain scores and ranges from 0 to 18. Higher score indicates more impairment. In this outcome measure, change per year (mean slope) in CDR-SB score was calculated up to month 24, where higher change indicated more impairment and lower change indicated less impairment. | Up to Month 24 of the core phase | 
| Core Phase: Time to Worsening of CDR Score up to Month 24 | The CDR scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The global CDR score is computed via an algorithm and ranges from 0 to 3. Higher score indicates more impairment. In this outcome measure, time (in months) to worsening of CDR score (that is, an increase from baseline by at least 0.5 points on the global CDR scale on 2 consecutive scheduled visits) up to month 24 was calculated. | Up to Month 24 of the core phase | 
| Core Phase: Time to Conversion to Dementia for Participants Who Were Not Clinically Staged as Having Dementia at the Core Phase Baseline up to Month 24 | Time (in months) to conversion to dementia for participants who were not clinically staged as having dementia at the core phase baseline (that is time from randomization to conversion to dementia in clinical diagnosis). | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the CDR-SB Score for Participants Enriched by Baseline Amyloid PET SUVR Between 1.2 and 1.6 | The CDR scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The CDR-SB is a sum of the individual domain scores and ranges from 0 to 18. Higher score indicates more impairment. Amyloid PET scans allow in vivo assessment of cerebral amyloid load. SUVR indicates the ratio of tracer uptake in the frontal cortex relative to the cerebellum or the ratio of tracer uptake in the whole brain relative to the cerebellum. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the Alzheimer's Disease Assessment Scale-cognition14 (ADAS-Cog14) Score | ADAS-cog14 is a psychometric instrument that evaluates 14-items (Immediate Word-recall [0-10], Commands [0-5], Constructional Praxis [0-5], Delayed Word-recall [0-10], Naming Objects/Fingers [0-5], Ideational Praxis [0-5], Orientation[0-8], Word Recognition [0-12], Remembering Test Instructions [0-5], Comprehension[0-5], Word Finding Difficulty [0-5], Spoken Language Ability [0-5], Executive Function [0-5], and Number Cancellation [0-5] test). It is considered to be more sensitive for less impaired populations such as MCI/Prodromal and mild AD participants. The total score ranges from 0 to 90. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the MMSE Score | The MMSE is a cognitive instrument commonly used for screening purposes, for staging of disease severity and is often measured longitudinally in AD clinical studies to follow disease progression and treatment effects. MMSE is composed of 30 questions grouped into domains (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Naming [0-2], Repetition [0-1], Comprehension [0-3], Reading [0-1], Writing [0-1], Drawing [0-1]). For each of the MMSE domains, six items are computed (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Language: Naming, Repetition, Comprehension, Reading, Writing, and Drawing [0-9]). The MMSE Total Score is the sum of the six domains and ranges from 0 to 30. If any domain score was missing then the total score was missing. Higher score indicates better function. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the Functional Assessment Questionnaire (FAQ) Score | FAQ scores 10 items & measures activities of daily living (paying bills/balancing checkbook, assembling tax records, shopping alone for clothes or groceries, playing game of skill such as bridge or chess/working on a hobby, heating water & turning off stove, preparing balanced meal, keeping track of current events, paying attention & understanding television program, remembering appointments, driving or traveling out of neighborhood). Each item is rated as follows: 0=Normal, 1=Has difficulty but does by self, 2=Requires assistance, 3=Dependent, or 8=Not Applicable. The total score is the sum of all 10 items & ranges from 0 to 30. Higher score indicates more impairment. If any activity was missed, then the total score was missed. Activities rated as Not Applicable were not used in the computation of the total score. To account for Not Applicable activity, the total score was weighted as:Total Score=Total Score*30/(30 minus 3 times the number of activities markedNot Applicable). | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the ADAS-cog14 Word List (Immediate Recall and Delayed Recall) Score | The ADAS-cog14 Word List is a summation of two items: Immediate Word-recall and Delayed Word-recall. Immediate Word-recall test: Participants are asked to recall words and the number of No responses for each trial (total 3 trials) are summed. Subscore: sum of scores from 3 trials, divided by 3. Score ranges from 0 to 10. Delayed Word-recall: Participants used to recall words after a delay and the number of No responses are summed. Score ranges from 0 to 10. The Total Score ranges from 0 to 20. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Baseline up to Month 24 in the Alzheimer's Disease Assessment Scale-cognition11 (ADAS-Cog11) Score | ADAS-cog11 is a psychometric instrument that evaluates 11-items (Immediate Word-recall [0 to 10], Commands [0-5], Constructional Praxis [0-5], Naming Objects/Fingers [0-5], Ideational Praxis [0-5], Orientation[0-8], Word Recognition [0-12], Remembering Test Instructions [0-5], Comprehension[0-5], Word Finding Difficulty [0-5], Spoken Language Ability [0-5] test) and is considered more sensitive for less impaired populations such as MCI/Prodromal and mild AD participants. The Total score ranges from 0 to 70. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 24 of the core phase | 
| Core Phase: Change From Last Dose in the CDR-SB Score | The CDR scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The CDR-SB is a sum of the individual domain scores and ranges from 0 to 18. Higher score indicates more impairment. | From last dose in the core phase (up to Month 24) up to 3 months follow up (up to Month 27) | 
| Core Phase: Change From Last Dose in the ADCOMS | ADCOMS is a weighted linear combination of 12 items from three existing clinical scales: the ADAS-cog, the MMSE, and the CDR. Four items are from the ADAS-cog (A4 [Delayed Word Recall], A7 [Orientation], A8 [Word Recognition], A11 [Word Finding]); 2 items are from the MMSE (M1 [Orientation Time], M7 [Drawing]); 6 items are from the CDR (C1 [Personal Care], C2 [Community Affairs], C3 [Home and Hobbies], C4 [Judgment and Problem Solving], C5 [Memory], C6 [Orientation]). Composite score is derived from the variables from the 12 items, and ranges from 0 to 1.97, where higher score indicates worse performance. | From last dose in the core phase (up to Month 24) up to 3 months follow-up (up to Month 27) | 
| Core Phase: Change From Last Dose in the ADAS-cog11 Score | ADAS-cog11 is a psychometric instrument that evaluates 11-items (Immediate Word-recall [0 to 10], Commands [0-5], Constructional Praxis [0-5], Naming Objects/Fingers [0-5], Ideational Praxis [0-5], Orientation[0-8], Word Recognition [0-12], Remembering Test Instructions [0-5], Comprehension[0-5], Word Finding Difficulty [0-5], Spoken Language Ability [0-5] test) and is considered more sensitive for less impaired populations such as MCI/Prodromal and mild AD participants. The Total score ranges from 0 to 70. Higher score indicates more impairment. | From last dose in the core phase (up to Month 24) up to 3 months follow-up (up to Month 27) | 
| Core Phase: Change From Last Dose in the ADAS-cog14 Score | ADAS-cog14 is a psychometric instrument that evaluates 14-items (Immediate Word-recall [0 to 10], Commands [0-5], Constructional Praxis [0-5], Delayed Word-recall [0-10], Naming Objects/Fingers [0-5], Ideational Praxis [0-5], Orientation[0-8], Word Recognition [0-12], Remembering Test Instructions [0-5], Comprehension[0-5], Word Finding Difficulty [0-5], Spoken Language Ability [0-5], Executive Function [0-5], and Number Cancellation [0-5] test). It is considered to be more sensitive for less impaired populations such as MCI/Prodromal and mild AD participants. The Total Score ranges from 0 to 90. Higher score indicates more impairment. | From last dose in the core phase (up to Month 24) up to 3 months follow-up (up to Month 27) | 
| Core Phase: Change From Last Dose in the MMSE Score | The MMSE is a cognitive instrument commonly used for screening purposes, for staging of disease severity and is often measured longitudinally in AD clinical studies to follow disease progression and treatment effects. MMSE is composed of 30 questions grouped into domains (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Naming [0-2], Repetition [0-1], Comprehension [0-3], Reading [0-1], Writing [0-1], Drawing [0-1]). For each of the MMSE domains, six items are computed (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Language: Naming, Repetition, Comprehension, Reading, Writing, and Drawing [0-9]). The MMSE Total Score is the sum of the six domains and ranges from 0 to 30. If any domain score was missing then the total score was missing. Higher score indicates better function. | From last dose in the core phase (up to Month 24) up to 3 months follow-up (up to Month 27) | 
| Core Phase: Change From Last Dose in the ADAS-cog14 Word List (Immediate Recall and Delayed Recall) Score | The ADAS-cog14 Word List is a summation of two items: Immediate Word-recall and Delayed Word-recall. Immediate Word-recall test: Participants are asked to recall words and the number of No responses for each trial (total 3 trials) are summed. Subscore: sum of scores from 3 trials, divided by 3. Score ranges from 0 to 10. Delayed Word-recall: Participants used to recall words after a delay and the number of No responses are summed. Score ranges from 0 to 10. The Total Score ranges from 0 to 20. Higher score indicates more impairment. | From last dose in the core phase (up to Month 24) up to 3 months follow-up (up to Month 27) | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in CDR-SB Score | The CDR scale is a clinical global rating scale that requires interviewing both the participant and an informant who knows and has contact with the participant. The CDR scale is a clinician directed assessment of both cognition and function, and is intended to capture the state and therefore the disease stage of the participant. The CDR scale assesses 6 domains of participant function (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment=0, questionable impairment=0.5, mild impairment=1, moderate impairment=2 and severe impairment=3. The CDR-SB is a sum of the individual domain scores and ranges from 0 to 18. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in ADCOMS | ADCOMS is a weighted linear combination of 12 items from three existing clinical scales: the ADAS-cog, the MMSE, and the CDR. Four items are from the ADAS-cog (A4 [Delayed Word Recall], A7 [Orientation], A8 [Word Recognition], A11 [Word Finding]); 2 items are from the MMSE (M1 [Orientation Time], M7 [Drawing]); 6 items are from the CDR (C1 [Personal Care], C2 [Community Affairs], C3 [Home and Hobbies], C4 [Judgment and Problem Solving], C5 [Memory], C6 [Orientation]). Composite score is derived from the variables from the 12 items, and ranges from 0 to 1.97, where higher score indicates worse performance. | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in MMSE Score | The MMSE is a cognitive instrument commonly used for screening purposes, for staging of disease severity and is often measured longitudinally in AD clinical studies to follow disease progression and treatment effects. MMSE is composed of 30 questions grouped into domains (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Naming [0-2], Repetition [0-1], Comprehension [0-3], Reading [0-1], Writing [0-1], Drawing [0-1]). For each of the MMSE domains, six items are computed (Orientation to Time [0-5], Orientation to Place [0-5], Registration [0-3], Attention and Calculation [0-5], Recall [0-3], Language: Naming, Repetition, Comprehension, Reading, Writing, and Drawing [0-9]). The MMSE Total Score is the sum of the six domains and ranges from 0 to 30. If any domain score is missing then the total score is missing. Higher score indicates better function. | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in FAQ Score | FAQ scores 10 items & measures activities of daily living (paying bills/balancing checkbook, assembling tax records, shopping alone for clothes or groceries, playing game of skill such as bridge or chess/working on a hobby, heating water & turning off stove, preparing balanced meal, keeping track of current events, paying attention & understanding television program, remembering appointments, driving or traveling out of neighborhood). Each item is rated as follows: 0=Normal, 1=Has difficulty but does by self, 2=Requires assistance, 3=Dependent, or 8=Not Applicable. The total score is the sum of all 10 items & ranges from 0 to 30. Higher score indicates more impairment. If any activity was missed, then the total score was missed. Activities rated as Not Applicable were not used in the computation of the total score. To account for Not Applicable activity, the total score was weighted as:Total Score=Total Score*30/(30 minus 3 times the number of activities markedNot Applicable). | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in ADAS-cog14 Score | ADAS-cog14 is a psychometric instrument that evaluates 14-items (Immediate Word-recall [0 to 10], Commands [0-5], Constructional Praxis [0-5], Delayed Word-recall [0-10], Naming Objects/Fingers [0-5], Ideational Praxis [0-5], Orientation[0-8], Word Recognition [0-12], Remembering Test Instructions [0-5], Comprehension[0-5], Word Finding Difficulty [0-5], Spoken Language Ability [0-5], Executive Function [0-5], and Number Cancellation [0-5] test). It is considered to be more sensitive for less impaired populations such as MCI/Prodromal and mild AD participants. The total score ranges from 0 to 90. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Change From Core Phase Baseline up to Month 12 of the Extension Phase in ADAS-cog14 Word List (Immediate Recall and Delayed Recall) Score | The ADAS-cog14 Word List is a summation of two items: Immediate Word-recall and Delayed Word-recall. Immediate Word-recall test: Participants are asked to recall words and the number of No responses for each trial (total 3 trials) are summed. Subscore: sum of scores from 3 trials, divided by 3. Score ranges from 0 to 10. Delayed Word-recall: Participants used to recall words after a delay and the number of No responses are summed. Score ranges from 0 to 10. The Total Score ranges from 0 to 20. Higher score indicates more impairment. | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 
| Extension Phase: Time to Conversion to Dementia for Participants Who Were Not Clinically Staged as Having Dementia at the Core Phase Baseline up to Month 12 of the Extension Phase | Time (in months) to conversion to dementia for participants who were not clinically staged as having dementia at the core phase baseline (that is time from randomization to conversion to dementia in clinical diagnosis). | Baseline (Day 1: before first dose in the core phase) up to Month 12 of the extension phase | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Elenbecestat, E2609, Alzheimer's Disease, Early Alzheimer's Disease, Prodromal Alzheimer's Disease, Dementia, Dementia, Alzheimer's type, Mild Cognitive Impairment, MissionAD1