Background: KHK6640 is a novel humanized anti-amyloid beta oligomer-specific antibody. Both KHK6640 and the mouse parent antibody E64 have demonstrated high potency and efficacy for cognitive improvement in several rodent Alzheimer's disease models, including an anti-amyloid beta injection mouse model and in age-matched double transgenic littermates. The favorable safety and pharmacokinetic profiles of KHK6640 reported in preclinical studies warrant clinical trials in Alzheimer's disease patients.


Objectives: We evaluated the safety, pharmacokinetics, and efficacy of intravenous and subcutaneous oligomer-specific antibody KHK6640 in treating patients with prodromal Alzheimer's disease or mild to moderate Alzheimer's disease.


Design: Phase I/2a, multicenter, randomized, double-blind, placebo-controlled trial.


Setting: Nine sites in Europe participated in this clinical trial.


Participants: 97 patients with prodromal Alzheimer's disease or mild to moderate Alzheimer's disease.


Intervention: Single and multiple ascending intravenous and subcutaneous doses of KHK6640 in doses ranging from 0.1 mg/kg to 20 mg/kg or placebo was administered to patients monthly for six months.


Measurements: Primary outcomes were safety including amyloid-related imaging abnormalities for edema and hemorrhage, assessed with magnetic resonance imaging. Plasma and cerebrospinal fluid samples were analyzed to investigate pharmacokinetics and KHK6640 effects on biomarkers. Cognition, brain glucose metabolism and amyloid load were exploratory outcomes.


Results: No amyloid-related imaging abnormalities for edema were observed. Amyloid-related imaging abnormalities for hemorrhage were comparable to that of placebo and population background. KHK6640 exposure was approximately dose-equivalent, with a serum terminal elimination half-life of approximately 19 days. KHK6640 pharmacokinetics in serum and cerebrospinal fluid, including cerebrospinal fluid oligomers trapped by the antibody were dose related. Positive trends seen in the positron emission tomography brain glucose metabolism and amyloid load, cerebrospinal tau but cognition assessments were inconclusive, due to low numbers.


Conclusions: KHK6640 was well-tolerated across all doses, without any amyloid-related imaging abnormalities for edema, and amyloid-related imaging abnormalities for hemorrhage was as population background. The demonstrated dose-response of specific target biomarkers provides dosing guidance on dose and administration method selection for further clinical development.