A Study to Learn About the Safety of BIIB080 and Whether it Can Improve Symptoms of Participants With Mild Cognitive Impairment Due to Alzheimer's Disease (AD) or Mild AD Dementia Between 50 to 80 Years of Age

Study Overview
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Brief Summary
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In this study, researchers will learn more about a study drug called BIIB080. The study will focus on participants with mild cognitive impairment or mild dementia due to AD. The main question researchers are trying to answer is if BIIB080 can slow the worsening of AD more than placebo. It will focus on what dose of BIIB080 slows worsening of AD the most. To help answer this question, researchers will use the Clinical Dementia Rating-Sum of Boxes, also known as the CDR-SB. Clinicians use the CDR-SB to measure several categories of dementia symptoms. The results for each category are added together for a total score. Lower scores are better. Researchers will also learn more about the safety of BIIB080. The study will be split into 2 parts. The 1st part is the Placebo-Controlled Period. The 2nd part is the Long-Term Extension Period. The 2nd part of the study will help researchers learn about the long-term safety of BIIB080, and how it affects the participant's daily life, thinking, and memory abilities in the longer term. A description of how the study will be done is given below. After screening, participants will first receive either a low dose or high dose of BIIB080, or a placebo, as an injection into the fluid around the spinal cord (cerebrospinal fluid). A placebo looks like the study drug but contains no real medicine. Participants will receive BIIB080 or placebo once every 12 weeks or 24 weeks. After 76 weeks of treatment in the Placebo-Controlled Period, eligible participants will move onto the Extension Treatment period, which will last 96 weeks. In the extension period, participants who received placebo will be switched to high dose BIIB080 every 12 or 24 weeks. Participants may be in the study for up to 201 weeks, or about 4 years. This includes the screening and follow-up periods. Participants can continue to take certain medications for AD. Participants must be on the same dose of medication for at least 8 weeks before the screening period. After the screening period, most participants will visit the clinic every 6 weeks.

Detailed Description
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BIIB080 is an investigational antisense therapy designed to target microtubule-associated protein tau (MAPT) mRNA and prevent production of tau protein.

Official Title
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A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study to Assess the Efficacy, Safety, and Tolerability of BIIB080 in Subjects With Mild Cognitive Impairment Due to Alzheimer's Disease or Mild Alzheimer's Disease Dementia

Conditions
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Mild Cognitive Impairment Due to Alzheimer's Disease, Alzheimer's Disease Dementia

Intervention / Treatment
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* Drug: BIIB080
* Drug: BIIB080-matching placebo


Participation Criteria
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Eligibility Criteria
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Key Inclusion Criteria for Placebo-controlled Period: Must meet all the clinical staging criteria for MCI due to AD (Stage 3) or mild AD dementia (Stage 4) according to the National Institute on Aging at National Institutes of Health and the Alzheimer's Association (NIA-AA) and must have the following at Screening Visit 1: Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) Delayed Memory Index score of ≤85, indicative of objective evidence of memory impairment. CDR global score of 0.5 for MCI due to AD or 0.5 or 1 for mild AD dementia MMSE score of 21 to 30 (inclusive). CDR Memory Box score of ≥0.5. Evidence of amyloid pathology as measured by positive emission tomography (PET) or cerebrospinal fluid (CSF) sampling. Must have 1 care partner who, in the Investigator's judgment, has frequent and sufficient contact with the participant (at least 10 hours/week) to be able to provide accurate information about the participant's cognitive and functional abilities. Key Inclusion Criteria for LTE Period Participants must have completed the placebo-controlled period of the study, including the Week 76 visit. Participants must have taken at least 5 doses of BIIB080 or placebo during the placebo-controlled period. MMSE score >10 at the Week 76 visit. Must have 1 care partner who, in the Investigator's judgment, has frequent and sufficient contact with the participant (at least 10 hours/week) to be able to provide accurate information about the participant's cognitive and functional abilities. Key Exclusion Criteria for Placebo-controlled Period: Known allergy to BIIB080 or a history of hypersensitivity to any of the inactive ingredients in the drug product. Previous participation in this study or previous studies with BIIB080. Use of non-disease-modifying AD medications (including but not limited to donepezil, rivastigmine, galantamine, tacrine, and memantine) at doses that have not been stable for at least 8 weeks prior to Screening Visit 1 and during the screening period up to Day 1. Use of any commercially available disease-modifying AD medications such as anti-amyloid monoclonal antibodies. Prior participation in any active or passive immunotherapy study targeting Aβ, unless documentation of receipt of placebo is available. Prior participation in any passive immunotherapy study targeting tau, unless the last administration occurred 6 months or 5 half-lives, whichever is sooner, prior to Screening or documentation of receipt of placebo is available. Prior participation in any study involving an investigational treatment targeting tau that is not a passive immunotherapy, unless documentation of receipt of placebo is available. Prior participation in a study of any other agent(s) not included in exclusion criteria 5, 6, and 7 with a purported disease-modifying effect in AD within 12 months, unless documentation of receipt of placebo is available. Prior participation in a study of any gene therapy with a purported disease-modifying effect in AD, unless documentation of receipt of placebo is available. Current use or previous use of medications with a purported disease-modifying effect in AD, outside of investigational studies. Any vaccination given within 10 days prior to Day -1. Coronavirus disease 2019 (COVID-19) vaccinations using RNA or deoxyribonucleic acid (DNA) technology are allowed during the study, as well as other types of immunization/vaccination/booster, except during the 10 days before and after clinic visits. Contraindications to having a brain magnetic resonance imaging (MRI) [e.g., MRI-incompatible pacemaker; MRI-incompatible aneurysm clips, artificial heart valves, or other metal foreign body; claustrophobia that cannot be medically managed]. If the MRI compatibility of implanted devices is unknown, the participant must be excluded from the study. Current enrollment or a plan to enroll in any interventional clinical study in which an investigational treatment or approved therapy for investigational use is administered within 52 weeks prior to the Baseline Visit. Key Exclusion Criteria for LTE Period Any medical or psychiatric contraindication or clinically significant abnormality that, in the opinion of the Investigator, will substantially increase the risk associated with the participant's enrollment in and completion of the study. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 80 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 |
| --- | --- |
| Placebo Comparator: Placebo Q12W<br>Participants will receive BIIB080-matching placebo, intrathecal (IT) injection, once on Day 1 and then once every 12 weeks (Q12W) for up to 72 weeks, during the placebo-controlled period. Eligible participants will enter the long-term extension (LTE) period, during which they will be randomized to receive BIIB080 high dose, IT injection, either Q12W or once every 24 weeks (Q24W) for an additional 96 weeks. | Drug: BIIB080<br>* Administered as specified in the treatment arm.<br>* Other names: ISIS 814907;Drug: BIIB080-matching placebo<br>* Administered as specified in the treatment arm.<br>|
| Experimental: BIIB080 Low Dose Q24W<br>Participants will receive a low dose of BIIB080, IT injection, Q24W from Week 1 up to 72 weeks and BIIB080-matching placebo, IT injection, once at Weeks 12, 36, and 60 during the placebo-controlled period. Eligible participants will enter the LTE period, during which they will continue to receive BIIB080 low dose, IT injection, Q24W for an additional 96 weeks. | Drug: BIIB080<br>* Administered as specified in the treatment arm.<br>* Other names: ISIS 814907;Drug: BIIB080-matching placebo<br>* Administered as specified in the treatment arm.<br>|
| Experimental: BIIB080 High Dose Q24W<br>Participants will receive a high dose of BIIB080, IT injection, Q24W from Week 1 up to 72 weeks and BIIB080-matching placebo, IT injection, once at Weeks 12, 36, and 60 during the placebo-controlled period. Eligible participants will enter the LTE period, during which they will continue to receive BIIB080 high dose, IT injection, Q24W for an additional 96 weeks. | Drug: BIIB080<br>* Administered as specified in the treatment arm.<br>* Other names: ISIS 814907;Drug: BIIB080-matching placebo<br>* Administered as specified in the treatment arm.<br>|
| Experimental: BIIB080 High Dose Q12W<br>Participants will receive a high dose of BIIB080, IT injection, once on Day 1 and then Q12W for up to 72 weeks during the placebo-controlled period. Eligible participants will enter the LTE period, during which they will continue to receive BIIB080 high dose, IT injection, Q12W for an additional 96 weeks. | Drug: BIIB080<br>* Administered as specified in the treatment arm.<br>* Other names: ISIS 814907;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dose-response in Change From Baseline to Week 76 on the CDR-SB | The Clinical Dementia Rating (CDR) scale is a clinician-rated dementia staging system that tracks the progression of cognitive impairment in 6 categories (memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care). Each category is scored on a 5-point scale in which None=0, Questionable=0.5, Mild=1, Moderate=2, and Severe=3. The global CDR score is established by clinical scoring rules and has values of 0 (no dementia), 0.5, (questionable dementia), 1 (mild dementia), 2 (moderate dementia), and 3 (severe dementia). The CDR-SB is obtained by adding the ratings in each of the 6 categories and ranges from 0 to 18 with higher scores indicative of greater impairment. | Baseline to Week 76 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change From Baseline to Week 76 on the CDR-SB | The CDR scale is a clinician-rated dementia staging system that tracks the progression of cognitive impairment in 6 categories (memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care). Each category is scored on a 5-point scale in which None=0, Questionable=0.5, Mild=1, Moderate=2, and Severe=3. The global CDR score is established by clinical scoring rules and has values of 0 (no dementia), 0.5, (questionable dementia), 1 (mild dementia), 2 (moderate dementia), and 3 (severe dementia). The CDR-SB is obtained by adding the ratings in each of the 6 categories and ranges from 0 to 18 with higher scores indicative of greater impairment. Positive change from baseline indicates clinical decline. | Baseline to Week 76 | 
| Change From Baseline to Week 76 on the Alzheimer's Disease Cooperative Study Activities of Daily Living for Mild Cognitive Impairment (ADCS-ADL-MCI) | The ADCS-ADL-MCI consists of 17 instrumental items (e.g., shopping, preparing meals, using household appliances) and 1 basic item (getting dressed). Ratings reflect caregiver observations about the participant's actual functioning and provide an assessment of change in the functional state of the participant over time. The total score ranges from 0 to 53, with lower values over time reflecting functional deterioration. Positive change from baseline indicates clinical improvement. | Baseline to Week 76 | 
| Change From Baseline to Week 76 on the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAS-Cog 13) | ADAS-Cog13 comprises both cognitive tasks and clinical ratings of cognitive performance. The scale items capture word recall, ability to follow commands, the ability to correctly copy or draw an image, naming, the ability to interact with everyday objects, orientation, word recognition, memory, comprehension of spoken language, word-finding, and language ability, with a measure for delayed word recall and concentration/distractibility. The total score ranges from 0 to 85. An increase in score over time indicates increasing cognitive impairment. Positive change from baseline indicates clinical decline. | Baseline to Week 76 | 
| Change From Baseline to Week 76 on the Mini Mental State Examination (MMSE) | The MMSE is a widely used performance-based test of global cognitive status. It consists of 11 tasks that assess orientation, word recall, attention and calculation, language abilities, and visuospatial functions. The scores from the 11 tests are combined to obtain the total score, which ranges from 0 to 30, with lower scores over time indicating increasing cognitive impairment. Positive change from baseline indicates clinical improvement. | Baseline to Week 76 | 
| Change From Baseline to Week 76 on the Modified Integrated Alzheimer's Disease Rating Scale (iADRS) | iADRS is a composite and is calculated as a linear combination of total scores of ADAS-Cog13 and Alzheimer's Disease Cooperative Study Instrumental Activities of Daily Living Inventory (ADCS-iADL) that measures cognition and daily function. ADCS-iADL is calculated from a subset of questions from ADCS-ADL. Range for ADCS-iADL is 0-59 and higher scores reflect better performance. ADAS-Cog13 comprises cognitive tasks and clinical ratings of cognitive performance. Scale items capture word recall, ability to follow commands, ability to correctly copy/draw, naming, ability to interact with everyday objects, orientation, word recognition, memory, spoken language comprehension, word-finding, and language ability, with a measure for delayed word recall and concentration/distractibility. Score ranges from 0 to 85 with higher scores reflecting cognitive impairment. iADRS score range is 0-144 and higher scores indicate greater impairment. Positive change from baseline indicates clinical decline. | Baseline to Week 76 | 
| Change From Baseline to Week 76 on the Alzheimer's Disease Composite Score (ADCOMS) | ADCOMS is a composite score comprised of ADAS-cog (4 items), MMSE (2 items) and CDR-SB (6 items). The total scores on the scale range from 0 to 1.97 with higher scores indicating greater impairment. Positive change from baseline indicates clinical decline. | Baseline to Week 76 | 
| Number of Participants With Treatment-Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs) | An AE is any untoward medical occurrence in a patient or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including abnormal laboratory finding), symptom, or disease temporally associated with use of a medicinal (investigational) product, whether or not related to medicinal (investigational) product. TEAE is any AE that started or worsened on or after the administration of the first dose of study drug through the end of follow-up period. SAE is any untoward medical occurrence that at any dose results in death, in the view of investigator, places the participant at immediate risk of death (life-threatening event), requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, results in congenital anomaly/birth defect or is medically important event. | From first dose of study drug up to end of study of placebo-controlled period (up to Week 96) |