Clinical AD trials screen and exclude many potential participants who do not meet criteria relating to amyloid pathology. In the phase 1 INTERCEPT-AD study of sabirnetug (ACU193), 75% of screened participants were ineligible, largely due to negative amyloid positron emission tomography (PET). Elevated plasma concentrations of pTau217 strongly suggest AD pathology; conversely, lower pTau217 concentrations may identify individuals who are likely to be ineligible based on subsequent amyloid PET or cerebrospinal fluid (CSF) Ab₄₂/Ab₄₀ ratio assessment, sparing potential participants unnecessary radiation or lumbar punctures (LPs).

ALTITUDE-AD (NCT06335173) is an ongoing 80-week, global, randomized, double-blind, placebo-controlled phase 2 study of sabirnetug in individuals with early AD and evidence of amyloid pathology. Blood is analyzed using the Fujirebio plasma pTau217 assay, a Lumipulse platform-based, research-use-only assay analytically and clinically validated as a Lab-Developed Test. During screening, individuals with pTau217 concentrations ≥0.15 pg/mL qualify for amyloid pathology testing using either amyloid PET or CSF Aβ₄₂/Ab₄₀ ratio to determine study eligibility. The pTau217 ≥0.15 pg/mL cut-point was designed for enrichment purposes and is not intended as a diagnostic cut-point.