Biogen’s tau-lowering antisense oligonucleotide diranersen (BIIB-080) cleared another hurdle at Alzheimer’s Association International Conference after new published analysis of Phase II “Celia” data. In the update, Catherine Mummery of University College London’s Dementia Research Centre said the trial provides proof-of-concept support for moving into Phase III. The program missed its primary endpoint—establishing a dose-response relationship—but still showed clinical signals across multiple measures. Patients receiving diranersen exhibited slowed cognitive and functional decline versus placebo, with tau reductions confirmed by biomarker readouts including PET assessments highlighted by conference discussants. The Phase II findings are being framed by Biogen as consistent with previously approved symptomatic therapies’ effect size, even as analysts and academic clinicians wait for larger confirmatory data. Biogen’s next decision point will hinge on whether Phase III replicates the magnitude and durability of the cognitive slowing while clarifying dose selection and endpoint sensitivity. For the Alzheimer’s pipeline, the Celia readout increases attention on tau-targeting oligonucleotide approaches as the field broadens beyond amyloid-only mechanisms and tests whether tau lowering can translate into clinically meaningful progression effects.