Open RoAD: Design and baseline characteristics of an open‐label rollover study evaluating long‐term safety and tolerability of subcutaneous gantenerumab in participants with early Alzheimer’s disease

Abstract Background Gantenerumab, a human monoclonal antibody targeting aggregated beta‐amyloid (Abeta), is a potential disease‐modifying treatment for early (prodromal‐to‐mild) Alzheimer’s disease (AD). SCarlet RoAD (SR) (NCT01224106) and Marguerite RoAD (MR) (NCT02051608) were two Phase III trials which assessed the efficacy and safety of subcutaneous (SC), low‐dose gantenerumab in participants with prodromal and mild AD, respectively, for up to 2 years. Following a gap period gantenerumab treatment was continued with uptitration to a dose of 1,200 mg monthly in open‐label extensions (OLE), which demonstrated substantial Abeta removal by positron emission tomography without new or unexpected safety findings. Here, we describe the study design, present baseline characteristics, and safety data from an additional open‐label, multicenter, rollover study, Open RoAD (OR) (NCT04339413), collecting long‐term safety and tolerability data for gantenerumab in participants who completed the SR OLE or MR OLE. Method Participants who completed either OLE study and were treated with doses up to 1,200 mg of gantenerumab for up to 5 years continue to receive the same dose of SC gantenerumab (every 4 weeks [q4w]) for 2 additional years in OR. The primary objective is to evaluate long‐term safety and tolerability by assessing adverse events, including amyloid‐related imaging abnormalities, and injection‐site reactions. Exploratory efficacy objectives include Mini‐Mental State Examination (MMSE) total score. The long‐term effect of gantenerumab on pharmacodynamic measures and biomarkers will also be explored. Result Baseline characteristics Fifty‐nine participants from SR OLE and 56 participants from MR OLE received at least one dose of gantenerumab in OR. The median participant age at baseline was 78 years, and the majority of the participants were female (61%). Sixty‐seven percent of participants were apolipoprotein‐E‐e4 (APOE e4) carriers. The median total MMSE score at baseline was 16. Safety data will be presented. Conclusion The RoAD studies are among the longest‐duration OLEs of an anti‐amyloid monoclonal antibody. Data from the OR study demonstrate that gantenerumab at doses of 1,200 mg administered SC q4w is well tolerated, with no new or unexpected safety findings in patients with early AD.