Core Insights - Eisai Co., Ltd. announced new data on the anti-tau antibody etalanetug (E2814) at the 18th Clinical Trials on Alzheimer's Disease (CTAD) Conference, highlighting its potential in reducing tau pathology in Alzheimer's disease [1][2]. Group 1: Study Findings - The Phase Ib/II study (E2814-103) involved 7 individuals with dominantly inherited Alzheimer's disease (DIAD), showing that tau PET signals were stabilized or trended toward decrease after etalanetug administration, indicating inhibition of tau propagation [2][5]. - Etalanetug demonstrated a reduction in cerebrospinal fluid (CSF) eMTBR-tau243 by 62% at 3 months and 89% at 9 months, while plasma eMTBR-tau243 was reduced by 78% at 3 months and over 90% at 9 months, supporting its mechanism of action [5][6]. Group 2: Biomarker Development - eMTBR-tau243 is a novel biomarker that reflects tau pathology progression, with strong correlations shown between tau PET and eMTBR-tau243 in both plasma and CSF, allowing for easier measurement of tau pathology changes through blood tests [3][4][8]. - The biomarker consists of tau fragments, including tau protein amino acid residue 243, and is thought to arise during the formation of neurofibrillary tangles, a key feature of Alzheimer's disease [4][8]. Group 3: Ongoing Clinical Trials - Etalanetug is currently being evaluated in two ongoing clinical studies: the Tau NexGen Phase II/III trial in DIAD and a Phase II Study 202 for early sporadic Alzheimer's disease, both assessing etalanetug in combination with the standard-of-care antibody lecanemab [6][10]. - In September 2025, etalanetug received Fast Track designation from the U.S. FDA, indicating its potential as a disease-modifying therapy for tauopathies [10].