Experimental Tau-Targeting Alzheimer's Drug Shows Modest Cognitive Benefits in Mid-Stage Trial

Biogen's experimental drug diranersen, which targets tau protein tangles in the brain, slowed cognitive decline in early-stage Alzheimer's patients during a mid-stage clinical trial. Results presented July 14 at the Alzheimer's Association International Conference in London showed a 26% slowing in the lowest-dose group (60 mg every six months), 14% in the middle-dose group (115 mg every six months), and 9% in the highest-dose group (115 mg every three months). The drug reduced tau levels in brain and spinal fluid by 50-65% across all treatment groups. However, the lack of a dose-dependent cognitive response and temporary confusion side effects in higher-dose recipients raised concerns. The trial involved over 400 patients tracked for 18 months. Biogen plans a late-phase study. The findings offer hope for targeting tau, a protein historically harder to address than amyloid, but experts caution about the small effect size and unexpected side effects. The FDA previously approved anti-amyloid drugs lecanemab (Leqembi) in 2023 and donanemab (Kisunla) in 2024.