Biomarker treatment effects in two phase 3 trials of gantenerumab.

INTRODUCTION: We report biomarker treatment effects in the GRADUATE I and II phase 3 studies of gantenerumab in early Alzheimer's disease (AD).

METHODS: Amyloid and tau positron emission tomography (PET), volumetric magnetic resonance imaging (vMRI), cerebrospinal fluid (CSF), and plasma biomarkers used to assess gantenerumab treatment related changes on neuropathology, neurodegeneration, and neuroinflammation over 116 weeks.

RESULTS: Gantenerumab reduced amyloid PET load, CSF biomarkers of amyloid beta (Aβ)40, total tau (t-tau), phosphorylated tau 181 (p-tau181), neurogranin, S100 calcium-binding protein B (S100B), neurofilament light (NfL), alpha-synuclein (α-syn), neuronal pentraxin-2 (NPTX2), and plasma biomarkers of t-tau, p-tau181, p-tau217, and glial fibrillary acidic protein (GFAP) while increasing plasma Aβ40, Aβ42. vMRI showed increased reduction in whole brain volume and increased ventricular expansion, while hippocampal volume was unaffected. Tau PET showed no treatment effect.

DISCUSSION: Robust treatment effects were observed for multiple biomarkers in GRADUATE I and II. Comparison across anti-amyloid antibodies indicates utility of p-tau and GFAP as biomarkers of amyloid plaque removal while NfL and tau PET seem unsuitable as consistent indicators of clinical efficacy. vMRI might be confounded by non-neurodegenerative brain volume changes. TRIAL REGISTRATION NUMBER (CLINICALTRIALS.GOV IDENTIFIER): NCT03444870 and NCT03443973.

HIGHLIGHTS: Gantenerumab significantly reduced brain amyloid load. Tau positron emission tomography showed no treatment effect in a small subset of participants. Volumetric magnetic resonance imaging showed increased whole brain volume reduction under treatment while hippocampal volume was unaffected. Robust treatment effects on cerebrospinal fluid and plasma biomarkers were found, despite lack of clinical efficacy.