Mgmt Breakfast: Tau Data by YE:26 Could Inform Phase III Alzheimer’s Strategy

Research evidence excerpt

Mgmt Breakfast: Tau Data by YE:26 Could Inform Phase III Alzheimer’s Strategy

Biogen Inc. (BIIB)

Equity Research

July 16, 2026

patients with the highest tau levels. Their broader hypothesis is that nearly all symptomatic, amyloid-

positive Alzheimer's disease patients already possess clinically relevant tau pathology. As such, Phase

III will unlikely restrict patients by low, medium, or high baseline tau.

Mgmt also questioned whether tau PET imaging fully captures the biology they are targeting. They

noted that tau PET may fail to detect earlier stages of pathological tau accumulation, meaning patients

categorized as low tau may nonetheless have clinically meaningful disease biology. As a result, they

do not want tau PET thresholds to become a barrier to identifying appropriate patients for treatment.

Confusional State Adverse Events and Mechanistic Investigations

The most detailed safety discussion centered on confusional state, which emerged as one of the

more noticeable adverse events across dose groups. Mgmt noted that the most common adverse

events overall were procedural in nature and generally consistent with intrathecal administration.

These included lumbar puncture site discomfort, post-lumbar puncture syndromes, and other

expected procedure-related effects.

Confusional state represented the next most notable event of interest. Mgmt acknowledged that

there appeared to be a dose relationship, with higher doses associated with greater incidence.

However, they emphasized that the majority of events were mild-to-moderate, typically occurred within

approximately seven days of dosing, and generally resolved during the subsequent week. Importantly,

these events rarely led to treatment discontinuation. One aspect mgmt found particularly interesting