Abstract
OBJECTIVE: Sabirnetug (ACU193) is a humanized monoclonal antibody selective for soluble amyloid beta oligomers (AβOs), synaptotoxins that are early and persistent triggers of Alzheimer's disease (AD). Sabirnetug pharmacodynamics were examined in the INTERCEPT-AD phase 1 study in mild cognitive impairment and mild dementia due to AD (NCT04931459) using biofluid biomarkers associated with Aβ and tau pathology, synaptic dysfunction, neuroinflammation, and neurodegeneration. METHODS: INTERCEPT-AD was a randomized, first-in-human study of sabirnetug versus placebo administered as a single (SAD; 2, 10, 25, 60 mg/kg) or multiple (MAD; three doses of 10 or 60 mg/kg every 4 weeks [Q4W] or 25 mg/kg Q2W) ascending doses. Biomarkers were measured pre-/post-dose in CSF and EDTA-plasma. Correlations of biomarker changes versus dose, exposure duration, and target engagement were determined. RESULTS: In MAD cohorts, CSF pTau181 decreased significantly (60 mg/kg Q4W, p = 0.049). VAMP2 decreased significantly at all doses (p ≤ 0.041); neurogranin decreased significantly at 60 mg/kg Q4W (p = 0.037). Aβ(1-42)/Aβ(1-40) trended upward with sabirnetug dose. Aβ(1-42)/Aβ(1-40) and neurogranin changes correlated with sabirnetug-AβO target engagement (p ≤ 0.01). Decreases in tTau, VAMP2, and neurogranin correlated with exposure duration (p ≤ 0.007). Plasma pTau181, pTau217, GFAP, and NfL trended lower. DISCUSSION: Following three sabirnetug doses, changes in CSF and plasma biomarkers were observed. The CSF biomarker response increased with increasing dose and exposure duration, consistent with previous reports that sabirnetug reaches the central compartment and engages its AβO target. The ongoing phase 2 ALTITUDE-AD study (NCT06335173) will test whether sabirnetug's pharmacodynamic effects can be substantiated with a larger sample size and longer treatment duration.