A 76-Week 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. Participants will receive study treatment via Intrathecal (IT) Injection every 12 weeks. Relevant Inclusion Criteria:

• Age 50-80
• Meets clinical criteria for Mild Cognitive Impairment (MCI) due to AD or mild AD dementia
• Evidence of amyloid pathology as measured by PET or CSF sampling
• MMSE 22-30
• CDR 0.5-1
• Have a reliable study partner who will attend designated study visits

Relevant Exclusion Criteria:

• TIA, stroke, or unexplained loss of consciousness within 1 year of screening
• History of seizures or epileptic syndrome within 10 years of screening
• History of, or ongoing, malignant disease
• History of bleeding disorder
• Uncontrolled diabetes
• Presence of clinically significant and/or unstable psychiatric illness
• Significant findings on brain MRI and/or abnormal lab values
• Presence of infection
• Any major surgery within 12 weeks of screening
• Use of any of the following medications within 30 days or 5 half-lives of the drug prior to the first dose and for the duration of the study:
  • Sensitive substrates for major CYP450 enzymes.
  • Strong inhibitors of major drug transporters.
  • Sensitive substrates of major drug transporters.

Contact the study coordinator for more information.