AL002c‐mediated reduction in amyloid β pathology is reflected by changes in plasma Alzheimer’s disease biomarkers in 5XFAD mice

Abstract

AbstractBackgroundThe R47H variant of the triggering receptor expressed on myeloid cells‐2 (TREM2) gene increases the risk for late‐onset Alzheimer’s disease (LOAD) and reduces TREM2 ligand binding in vitro, suggesting that enhancing TREM2 signaling has therapeutic potential in AD. AL002 is a novel humanized monoclonal Immunoglobulin G1 (IgG1) antibody that targets TREM2 and is currently being tested in a phase 2 trial in patients with early AD. Previously, AL002c, a variant of AL002, reduced filamentous amyloid β (Aβ) plaques and neurite dystrophy and increased inert plaques in a 5XFAD mouse model, while other Aβ pathology measures did not show treatment effects. Total Aβ42/40 ratio in plasma is inversely associated with amyloid burden independent of AD clinical diagnosis2 and is being used as a biomarker in AD clinical trials.3 To further evaluate the impact of AL002c on Aβ pathology, the present study assessed plasma AD biomarkers, including Aβ42/40 ratio, in residual samples from these 5XFAD mice.MethodFive‐month‐old 5XFAD mice (N = 32, n = 6‐13 per group) expressing either common variant (CV) or R47H variant human TREM2 (hTREM2), but lacking endogenous mouse Trem2, were injected intraperitoneally with 30 mg/kg AL002c or control mouse IgG1 weekly for 12 weeks (Figure 1). Levels of plasma Aβ42, Aβ40, and total tau (t‐tau) were quantified using Simoa® assay (Quanterix).ResultAL002c‐treated CV‐5XFAD and R47‐5XFAD mice had a higher plasma Aβ42/40 ratio (CV‐5XFAD p <0.001; R47‐5XFAD p<0.05; pooled CV and R47‐5XFAD p < 0.01) and lower plasma t‐tau (CV‐5XFAD p <0.05; R47‐5XFAD p<0.001; pooled CV and R47‐5XFAD p < 0.01) compared with their IgG1‐treated genotype counterparts (Figure 2). No differences were observed between R47H and CV genotypes in plasma Aβ42/40 ratio or t‐tau.ConclusionAL002c‐associated changes in plasma Aβ42/40 and tau were consistent with a concomitant reduction in filamentous plaques and neurite dystrophy.1 These results lend further support to the clinical utility of plasma Aβ42/40 as a marker for the reduction of neurotoxic amyloid plaques in clinical trials with AL002.