ABBY: A phase 2 randomized trial of crenezumab in mild to moderate Alzheimer disease

Abstract

Objective: To evaluate the safety and efficacy of crenezumab in patients with mild to moderate Alzheimer disease (AD).

Methods: In this phase 2 trial, 431 patients with mild to moderate AD 50 to 80 years of age were randomized 2:1 (crenezumab:placebo). Patients received low-dose subcutaneous crenezumab 300 mg or placebo every 2 weeks (n = 184) or high-dose intravenous crenezumab 15 mg/kg or placebo every 4 weeks (n = 247) for 68 weeks. Primary outcome measures were change in Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog12) and Clinical Dementia Rating-Sum of Boxes scores from baseline to week 73.

Results: The primary and secondary endpoints were not met. In an exploratory post hoc analysis, a reduction in decline on the ADAS-Cog12 was observed in the high-dose group. Separation from the placebo group on the ADAS-Cog12 was greatest in the milder subsets of AD patients and reached statistical significance in the group with Mini-Mental State Examination scores of 22 to 26. In both groups, there was a significant increase in CSF β-amyloid_1-42 levels that correlated with crenezumab CSF levels. The overall rate of adverse events was balanced between groups. One case of amyloid-related imaging abnormalities indicative of vasogenic edema or effusions was reported.

Conclusions: Although prespecified criteria for testing treatment effects were not met, these data suggest a potential treatment effect in patients with mild AD treated with high-dose crenezumab. Together with the safety profile for crenezumab, these data support the exploration of crenezumab treatment at even higher doses in patients with early AD.

Clinicaltrialsgov identifier: NCT 01343966.

Classification of evidence: This study provides Class II evidence that, for people with AD, crenezumab does not significantly improve cognition or function at 18 months. The study is rated Class II because <80% of enrolled patients completed the study.

Figure 1. ADAS-Cog12 scores

Mean change from baseline to week 73 in (A and D) mild to moderate (MMSE score 18–26), (B and E) mild (MMSE score 20–26), and (C and F) milder (MMSE score 22–26) populations. (A–C) Low-dose 300 mg SC cohort. (D–F) High-dose 15 mg/kg IV cohort. Error bars show SE of the least-squares mean. AD = Alzheimer disease; ADAS-Cog12 = 12-point Alzheimer's Disease Assessment Scale–Cognitive Subscale; BL = baseline; Cr = crenezumab; Diff = difference; MMSE = Mini-Mental State Examination; %Red = percentage reduction; Pl = placebo; SC = subcutaneous; SE = standard error.

Figure 2. CSF Aβ_1-42 and crenezumab correlation analysis

Correlation analysis of change in CSF Aβ_1-42 from baseline and crenezumab concentrations in patients receiving low-dose 300 mg SC (circles) and those receiving high-dose 15 mg/kg IV (triangles). Aβ = β-amyloid.