Biogen
Biogen
One-line summary: Neuroscience-focused biotech (NASDAQ: BIIB); tracked here for its diranersen intrathecal anti-tau ASO in Alzheimer's — a messy Ph2 (technically failed primary, inverted dose response) that it is nonetheless advancing to Ph3, which the panel reads as an ASO-tolerability problem rather than a tau-target failure.
What it is
Biogen is a large-cap biotech concentrated in CNS/neuroscience. With partner ionis it is developing diranersen, an intrathecally-administered antisense oligonucleotide (ASO) that lowers tau production — a disease-modifying approach to Alzheimer's distinct from the anti-amyloid antibodies (Leqembi, Kisunla).
Why it matters to stock-market
Biogen is the trigger for biogen-tau-failure-to-brain-shuttle-rerate: its confusing tau readout is the "is the target real at all" gate. If tau proof-of-concept survives, the panel argues most of the value accrues to IV brain-shuttle players (Denali, Arrowhead) plus alnylam's intrathecal program — because diranersen's own problem is delivery/tolerability, and it is intrathecal (a commercial handicap).
Key facts
- Diranersen Ph2 "technically failed" its primary but advances to Ph3. Randomized placebo/low/high dose; primary at 76 weeks was high-dose ADAS-cog/CDR-SB vs placebo — the high dose missed while the low dose looked better (an inverted dose response, consistent with Ph1b). Low dose showed tau-imaging reduction and a 0.54-point CDR-SB slowdown (FDA-meaningful; bogey 0.5). Biogen stock fell. From yaron-werber on 2026-07-17-podcast-biotech-hangout-episode-189-july-17-2026.
- Read as ASO tolerability, not target failure. john-maraganore in 2026-07-17-podcast-biotech-hangout-episode-189-july-17-2026: the inverted dose response "is due once again to the poor tolerability that one sees with ASOs" (the higher dose had more AEs) — "net... encouraged by this as it relates to Tau."
- Bear counter: efficacy achieved was "really no better than current anti-amyloid drugs like Leqembi and Kisunla," and buy-side was "nine to one negatively inclined" (from the prior week, 2026-07-10-podcast-biotech-hangout-episode-188-july-10-2026).
Open questions
- Does the Ph3 (run on the lower dose) reproduce the 0.54-point signal? See biogen-tau-failure-to-brain-shuttle-rerate.