Baseline Tau Burden Linked to Reduced Amyloid Clearance With Gantenerumab in New GRADUATE Analysis

In a new post hoc analysis of the phase 3 GRADUATE program, adults with early Alzheimer disease (AD) who had greater baseline tau pathology experienced less amyloid removal following treatment with gantenerumab, suggesting that tau burden may influence the biologic response to antiamyloid therapy.¹

Presented at the 2026 Alzheimer's Association International Conference (AAIC), held July 12-15, in London, England, investigators reported that both regional and participant-level measures of baseline tau were independently associated with reduced amyloid clearance over 116 weeks of treatment. The findings add to growing evidence that underlying disease biology, including tau accumulation, may contribute to variability in treatment response among patients receiving amyloid-targeting monoclonal antibodies.

Post Hoc Analysis of the GRADUATE Program

Led by Matteo Tonietto, PhD, principal scientist of Roche's Pharma Research and Early Development division in Switzerland, the study analyzed imaging data from 38 participants randomized to active treatment in the phase 3 GRADUATE studies who underwent baseline tau PET imaging together with baseline and week-116 amyloid PET imaging.

Using linear mixed-effects modeling, investigators assessed whether baseline tau pathology independently influenced amyloid removal after adjusting for baseline amyloid burden, age, sex, and drug exposure. Regional amyloid burden was converted to Centiloid values, while tau PET measurements were standardized against an external cohort of cognitively unimpaired, amyloid-negative individuals.

The analysis showed that both regional and participant-level tau burden were significantly associated with reduced amyloid clearance. Regions with greater tau deposition demonstrated less amyloid removal, and participants with higher overall tau burden similarly experienced smaller reductions in amyloid. Investigators also observed a nonlinear relationship, suggesting tau may influence amyloid removal only after reaching a certain pathological threshold.

Potential Mechanisms and Clinical Implications

Although the study was not designed to determine mechanism, investigators proposed that advanced tau pathology may be associated with denser, more treatment-resistant amyloid plaques or with impaired microglial function that limits antibody-mediated plaque clearance. Additional studies will be needed to determine whether these observations are specific to gantenerumab or represent a broader characteristic of amyloid-targeting immunotherapies.¹

The findings build on previous reports suggesting that baseline patient characteristics, including age and amyloid burden, can influence treatment-associated amyloid removal. Together, these analyses suggest multiple aspects of disease biology may contribute to variability in biomarker response.

Building on Previous Gantenerumab Findings

In GRADUATE I and II, gantenerumab (Genentech/Roche), a fully human monoclonal IgG1 antibody targeting amyloid-β, did not meet the primary end point of slowing clinical decline in adults with early AD. Across both studies, treatment with gantenerumab failed to produce a statistically significant benefit on the Clinical Dementia Rating-Sum of Boxes (CDR-SB) compared with placebo after 116 weeks of treatment.²

In the trials, gantenerumab treatment was associated with an 8% relative reduction in clinical decline in GRADUATE 1 (–0.31 points on CDR-SB; P = .0954) and a 6% relative reduction in GRADUATE 2 (–0.19 points; P = .2998), although neither result reached statistical significance. The global phase 3 program enrolled nearly 2,000 participants aged 50 to 90 years with early AD and confirmed amyloid pathology, who received subcutaneous gantenerumab at a target dose of 1020 mg or placebo over 116 weeks using an optimized titration strategy designed to maximize drug exposure while minimizing treatment interruptions.

From a safety perspective, amyloid-related imaging abnormalities (ARIA) occurred in approximately 25% of participants receiving gantenerumab across the pooled studies, with most events reported as asymptomatic and few resulting in treatment discontinuation.

Although the current findings provide additional insight into the relationship between tau and amyloid clearance, the analysis included only 38 participants with complete longitudinal PET imaging and should be considered exploratory. Whether similar interactions between baseline tau pathology and amyloid removal occur with other antia-myloid therapies remains unknown and warrants further investigation.¹

REFERENCES
1. Tonietto M, Silvestri E, Belousov A, et al. Tau pathology Interferes With Amyloid Removal by Gantenerumab. Presented at: Alzheimer’s Association International Conference (AAIC); July 12-15, 2026; London England.
2. Genentech provides update on phase III GRADUATE program evaluating gantenerumab in early Alzheimer’s disease. November 13, 2022. Accessed November 14, 2022. https://www.gene.com/media/press-releases/14974/2022-11-13/genentech-provides-update-on-phase-iii-g