ACU193, a Monoclonal Antibody that Selectively Binds Soluble Aß Oligomers: Development Rationale, Phase 1 Trial Design, and Clinical Development Plan.

Alzheimer's disease is a large and growing unmet medical need. Clinical trial designs need to assess disease-related outcomes earlier to accelerate the development of better treatments for Alzheimer's disease. ACU193 is a monoclonal antibody that selectively targets amyloid β oligomers, thought to be the most toxic species of Aβ that accumulates early in AD and contributes to downstream pathological effects. Nonclinical data indicate that ACU193 can reduce the toxic effects of amyloid β oligomers. ACU193 is currently being investigated in a phase 1 clinical trial designed with the properties described in this report. This phase 1 trial is designed to provide data to enable a go/no-go decision regarding the initiation of a subsequent phase 2/3 study. To design a phase 1 study that assesses target engagement and incorporates novel measures to support more rapid development of a potential disease-modifying treatment for Alzheimer's disease. The INTERCEPT-AD trial for ACU193 is an ongoing randomized, placebo-controlled phase 1a/b study that assesses safety, tolerability, pharmacokinetics, target engagement, clinical measures, and several Alzheimer's disease biomarkers, including novel digital and imaging biomarkers. For INTERCEPT-AD, brief inpatient stays for patients in the single ascending dose portion of the study, with the remainder of the evaluations being performed as outpatients at multiple clinical trial sites in the U.S. Patients with early Alzheimer's disease (mild cognitive impairment or mild dementia with a positive florbetapir positron emission tomography scan). ACU193 administered intravenously at doses of 2- 60 mg/kg. Safety assessments including magnetic resonance imaging for the presence of amyloid-related imaging abnormalities, clinical assessments for Alzheimer's disease including the Alzheimer's Disease Rating Scale-cognition and Clinical Dementia Rating scale, pharmacokinetics, a measure of target engagement, and digital and imaging biomarkers, including a computerized cognitive test battery and a measure of cerebral blood flow using arterial spin labelling magnetic resonance imaging. A phase 1 study design was developed for ACU193 that allows collection of data that will enable a go/no-go decision for initiation of a subsequent adaptive phase 2/3 study. A phase 1a/b trial and an overall clinical development plan for an Alzheimer's disease treatment can be designed that maintains patient safety, allows informed decision-making, and achieves an accelerated timeline by using novel biomarkers and adaptive study designs.

Eric Siemers, Janice Hitchcock, Karen Sundell, Robert Dean, Jasna Jerecic, Erika Cline, Kent Iverson, Jerome Moore, and Russell Barton are employees or consultants for Acumen Pharmaceuticals, Inc. Chris Edgar is an employee of Cogstate Ltd. Richard Manber, Niccolo Fuin, and Tanya Poppe are employees of Ixico Plc.