New data show greater tau reduction at higher doses but strongest clinical signal at lowest dose, raising key questions about optimal dosing in further trials, says the ADDF
NEW YORK, July 14, 2026 /PRNewswire/ — Today at the Alzheimer’s Association International Conference (AAIC), Biogen presented results from the phase 2 CELIA study of diranersen (BIIB080), an investigational therapy designed to target tau in people with early Alzheimer’s disease. While the study failed to meet its primary endpoint of demonstrating dose response-related effects on change in Clinical Dementia Rating-Sum of Boxes (CDR-SB), the new data showed strong biomarker effects, including reductions in CSF tau and tau PET, as well as clinical effects at lower doses, raising important questions about the optimal dose and design of future trials.
“These are the first data from a randomized trial to show a tau-targeting drug producing both a robust biomarker effect and a signal of clinical benefit,” said Laura Nisenbaum, PhD, Interim Chief Science Officer at the Alzheimer’s Drug Discovery Foundation (ADDF). “Tau is one of the two defining pathologies of Alzheimer’s disease and has long been difficult to target, which makes these results all the more notable. But the dose-response discordance between the biomarker and clinical endpoints raises important questions about the optimal level of tau reduction and the right dose of diranersen to test in subsequent studies. Those questions will be central to designing the strongest possible phase 3 program.”
The central unanswered question from the study is the discordance between the biomarker and clinical findings. Higher doses led to greater tau reduction, while the lowest dose showed the strongest clinical signal. Biogen has said these results support advancing diranersen into further trials as it continues to analyze the full data to understand why the biomarker and clinical effects diverged and what that means for future trial design.
With disease-modifying anti-amyloid therapies now available, tau represents an important opportunity to expand Alzheimer’s treatment options beyond a single target. The Alzheimer’s therapeutic pipeline continues to broaden, with 75% of current clinical trials aimed at pathways beyond amyloid and tau, including inflammation, neurotransmitters, and metabolic dysfunction. This growing range of potential therapeutic approaches is essential to the future of Alzheimer’s care, as the field moves toward treatments that can be individualized and combined based on each person’s underlying disease biology.
“Alzheimer’s is a complex disease, and these results are another signal that drug development is moving in the right direction: beyond a single target and toward a broader arsenal of therapies that address the full pathobiology,” said Isobel Coleman, Chief Executive Officer of the ADDF. “Tau is one of the core pathologies we will need to tackle if we are going to make combination therapy a reality. There is still more to learn, but progress like this helps move the field closer to the precision medicine future the ADDF has championed for decades.”
About The Alzheimer’s Drug Discovery Foundation (ADDF)
Founded in 1998 by Leonard A. and Ronald S. Lauder, the Alzheimer’s Drug Discovery Foundation is dedicated to rapidly accelerating the development of drugs to prevent, treat, and cure Alzheimer’s disease. The ADDF is the only public charity solely focused on funding the development of drugs for Alzheimer’s, employing a venture philanthropy model to support research in academia and the biotech industry. The ADDF’s leadership and contributions to the field have played a pivotal role in bringing the first Alzheimer’s PET scan (Amyvid®) and blood test (PrecivityAD®) to market, as well as fueling the current robust and diverse drug pipeline. Through the generosity of its donors, the ADDF has awarded nearly $400 million to fund 792 Alzheimer’s drug development, biomarker, and prevention programs in 21 countries. To learn more, please visit: http://www.alzdiscovery.org/.
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SOURCE Alzheimer’s Drug Discovery Foundation
