Dive Insight:

The scientific debate over the cause of Alzheimer’s has raged for decades, with many researchers pointing to tau and amyloid beta, two proteins that build up and twist together in patients’ brains. Most late-stage projects have targeted amyloid beta, as Aduhelm does, but all failed until Biogen claimed positive results in one of two studies that tested Aduhelm.

Those setbacks have prompted researchers to look more closely at tau, and a number of projects have reached mid- and even late-stage research. Results to date, however, have been disappointing. Gosuranemab’s failure follows those of LMTX of TauRx Therapeutics in a Phase 3 trial and semorinemab from AC Immune and Roche.

Together, the findings casts some doubt on whether a tau-blocking antibody from Eli Lilly can help patients. Lilly is due to deliver results later this year.

Biogen gained access gosuranemab from Bristol Myers Squibb for $300 million upfront as part of a licensing deal in 2017. Bristol Myers acquired the drug when it bought iPerian in a deal that included $175 million in cash to the target’s shareholders, and up to $610 million in milestones and royalties. Responsibility for milestone fees and royalties fell to Biogen when it licensed the drug.

The Phase 2 trial that Biogen reported Wednesday enrolled 654 patients with mild cognitive impairment from Alzheimer’s disease, who were infused with either gosuranemab or a placebo once every four weeks. After 78 weeks, researchers evaluated the patients on five different scales and found no difference between patients given gosuranemab or placebo.

“This is additional bad news for the anti-tau hypothesis,” Leerink analyst Marc Goodman wrote in a June 16 note to clients.

Due to doubts over tau targeting, analysts and investors didn’t have high expectations that this drug would succeed. The company’s shares were largely unmoved in Thursday morning trading, likely because reimbursement and uptake for Aduhelm are now much more important to the company’s success.

Biogen has a second tau-focused drug in Phase 1 testing that, like gosuranemab, is a synthetic antibody which binds to the protein. In partnership with Ionis Pharmaceuticals, the biotech company is developing another drug in Phase 1 that blocks production of tau.

Biogen’s Phase 3 pipeline also includes a second anti-amyloid drug called lecanemab, or BAN2401, that it’s developing with Eisai.