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TerminatedPhase 3Results posted

221AD301 Phase 3 Study of Aducanumab (BIIB037) in Early Alzheimer's Disease

A Phase 3 Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study to Evaluate the Efficacy and Safety of Aducanumab (BIIB037) in Subjects With Early Alzheimer's Disease

Lead sponsor

Biogen

Asset

Aducanumab

Listed sites

181

Recruiting sites

Enrollment

1,653

actual

Study population

Alzheimer’s disease

Key I/E criteria

•MCI due to AD•Amyloid biomarker required (PET)•MMSE 24-30•Study partner/caregiver required•MRI contraindications excluded

Primary endpoint

•Clinical Dementia Rating-Sum of Boxes (CDR-SB)

Footprint

Where this trial recruits

Site locations as reported to ClinicalTrials.gov. Site count is not enrollment count; per-site enrollment is not available from source.

Identifiers

Registered as

Eudract number2015-000966-72

Org study ID221AD301

NCT IDNCT02477800

Timeline

Milestones

Study first posted2015-06-23estimated

Study start2015-08-13actual

Primary completion2019-08-08actual

Study completion2019-08-08actual

Last update posted2021-09-02actual

Results first posted2021-09-02actual

Assets

Drug assets

Aducanumab

Study populations

Who this study enrolls

Alzheimer’s disease

Eligibility

Who can enroll

Minimum age50 Years

Maximum age85 Years

SexAll

Healthy volunteersNot accepted

Inclusion criteria

Key Inclusion Criteria:

•Must meet all of the following clinical criteria for MCI due to AD or mild AD and must have:

•A Clinical Dementia Rating (CDR)-Global Score of 0.5.

•Objective evidence of cognitive impairment at screening

•An MMSE score between 24 and 30 (inclusive)

•Must have a positive amyloid Positron Emission Tomography (PET) scan

•Must consent to apolipoprotein E (ApoE) genotyping

•If using drugs to treat symptoms related to AD, doses must be stable for at least 8 weeks prior to screening visit 1

•Must have a reliable informant or caregiver

Exclusion criteria

•Any medical or neurological condition (other than Alzheimer's Disease) that might be a contributing cause of the subject's cognitive impairment

•Have had a stroke or Transient Ischemic Attack (TIA) or unexplained loss of consciousness in the past 1 year

•Clinically significant unstable psychiatric illness in past 6 months

•History of unstable angina, myocardial infarction, advanced chronic heart failure, or clinically significant conduction abnormalities within 1 year prior to Screening

•Indication of impaired renal or liver function

•Have human immunodeficiency virus (HIV) infection

•Have a significant systematic illness or infection in past 30 days

•Relevant brain hemorrhage, bleeding disorder and cerebrovascular abnormalities

•Any contraindications to brain magnetic resonance imaging (MRI) or PET scans

•Alcohol or substance abuse in past 1 year

•Taking blood thinners (except for aspirin at a prophylactic dose or less)

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply

Endpoints (8)

What's being measured

Protocol endpoints and posted registry outcome measures, grouped into outcome categories. Composite endpoints show their component event types. Standard codes (LOINC, SNOMED CT) are shown where available.

Coverage by outcome category

Global cognition

Function / daily living

Global cognition

6 endpoints

Primary/protocol endpoint

Change From Baseline in Clinical Dementia Rating Sum of Boxes (CDR-SB) Score at Week 78

Time frame:Baseline, Week 78

Clinical Dementia Rating-Sum of Boxes (CDR-SB)

change from baseline, improvement

Primary/registry result

Change From Baseline in Clinical Dementia Rating Sum of Boxes (CDR-SB) Score at Week 78

Time frame:Baseline, Week 78

Clinical Dementia Rating-Sum of Boxes (CDR-SB)

change from baseline, improvement

Posted result

Group	Value (mean), score on a scale	Standard error
Placebo (PC Period)n=333 Participants	1.56	0.108
BIIB037 Low Dose (PC Period)n=331 Participants	1.38	0.108
BIIB037 High Dose (PC Period)n=295 Participants	1.59	0.111

Difference from Placebo0.11095% CI-0.469 - 0.403p0.2250MMRM Model

Difference from late start group0.0395% CI-0.262 - 0.326p0.8330MMRM Model

Secondary/protocol endpoint

Change From Baseline in Mini-Mental State Examination (MMSE) Score at Week 78

Time frame:Baseline, Week 78

Mini-Mental State Examination (MMSE)

change from baseline, improvement

Secondary/protocol endpoint

Change From Baseline in Alzheimer's Disease Assessment Scale-Cognitive Subscale (13 Items) (ADAS-Cog 13) Score at Week 78

Time frame:Baseline, Week 78

ADAS-Cog

change from baseline, improvement

Secondary/registry result

Change From Baseline in Mini-Mental State Examination (MMSE) Score at Week 78

Time frame:Baseline, Week 78

Mini-Mental State Examination (MMSE)

change from baseline, improvement

Posted result

Group	Value (mean), score on a scale	Standard error
Placebo (PC Period)n=332 Participants	-3.5	0.21
BIIB037 Low Dose (PC Period)n=334 Participants	-3.3	0.21
BIIB037 High Dose (PC Period)n=297 Participants	-3.6	0.21

Difference from Placebo0.295% CI-0.35 - 0.74p0.4795MMRM Model

Difference from Placebo-0.195% CI-0.62 - 0.49p0.8106MMRM Model

Secondary/registry result

Change From Baseline in Alzheimer's Disease Assessment Scale-Cognitive Subscale (13 Items) (ADAS-Cog 13) Score at Week 78

Time frame:Baseline, Week 78

ADAS-Cog

change from baseline, improvement

Posted result

Group	Value (mean), score on a scale	Standard error
Placebo (PC Period)n=331 Participants	5.140	0.3783
BIIB037 Low Dose (PC Period)n=332 Participants	4.558	0.3780
BIIB037 High Dose (PC Period)n=294 Participants	4.552	0.3872

Difference from Placebo-0.58395% CI-1.5835 - 0.4181p0.2536MMRM Model

Difference from Placebo-0.58895% CI-1.6067 - 0.4309p0.2578MMRM Model

Function / daily living

2 endpoints

Secondary/protocol endpoint

Change From Baseline in Alzheimer's Disease Cooperative Study-Activities of Daily Living Inventory (Mild Cognitive Impairment Version) (ADCS-ADL-MCI) Score at Week 78

Time frame:Baseline, Week 78

ADCS-Activities of Daily Living (ADCS-ADL)

change from baseline, improvement

Secondary/registry result

Change From Baseline in Alzheimer's Disease Cooperative Study-Activities of Daily Living Inventory (Mild Cognitive Impairment Version) (ADCS-ADL-MCI) Score at Week 78

Time frame:Baseline, Week 78

ADCS-Activities of Daily Living (ADCS-ADL)

change from baseline, improvement

Posted result

Group	Value (mean), score on a scale	Standard error
Placebo (PC Period)n=331 Participants	-3.8	0.35
BIIB037 Low Dose (PC Period)n=330 Participants	-3.1	0.35
BIIB037 High Dose (PC Period)n=298 Participants	-3.1	0.35

Difference from Placebo0.795% CI-0.19 - 1.64p0.1225MMRM Model

Difference from late start group0.795% CI-0.25 - 1.61p0.1506MMRM Model

Publications (3)

Bibliography

Records linked to this trial through ClinicalTrials.gov references, PubMed NCT search, and curated study seeds. 'Canonical' marks design/result papers; others are registry references or candidates.

Registry references + supporting bibliography

Provenance

Sources

Trial identity, design, statusClinicalTrials.gov API v2

Snapshot dateJuly 21, 2026

Endpoint classificationDelfa ADRD endpoint taxonomy

Results tableClinicalTrials.gov results section

Trial facts come from public ClinicalTrials.gov records. Endpoint categories are Delfa's classification of those records, not a ClinicalTrials.gov field. All figures reflect the July 21, 2026 snapshot.