Biogen’s tau-lowering program diranersen (BIIB-080, BIIB-080) drew fresh attention at AAIC 2026 after published Phase 2 data showed cognitive and biomarker signals that Biogen says support a Phase 3 move. In the Celia trial, each dose arm outperformed placebo on multiple clinical and biomarker measures at 18 months, with tau reductions seen across doses and the clearest cognitive effects reported in the 60-mg group. Independent reporting from the conference noted that Celia missed its primary dose-response endpoint, but multiple secondary endpoints favored diranersen, and PET and clinical results reinforced target engagement. The company is leaning on both clinical outcomes and the consistency of tau reductions to argue for continued development despite the formal mid-stage miss. The program places a second wave of anti-tau strategies in the spotlight alongside ongoing amyloid-focused standards, with AAIC attendees watching whether Celia’s effects can reproduce in a pivotal setting. For biotech observers, the decision highlights how mid-stage efficacy can be weighed when a program demonstrates both target suppression and clinically interpretable slowing of decline.