Sample size
AD, MCI
SECONDARY
No formal sample size calculation was performed for the primary safety endpoint. Sample size calculation was based on the multiple comparison procedure—modeling approach. A sample size of 528 participants was planned to provide approximately 80% power to detect a dose–response relationship in the change from the baseline CDR-SB score (secondary objective) at 78 weeks, assuming a maximal 40% reduction with the highest gosuranemab dose compared to placebo and an estimated 20% dropout rate at 18 months (week 78) in this study. This calculation assumed an estimated mean change of 1.99 from the baseline CDR-SB score at 78 weeks in the placebo group and a common s.d. of 2.38, based on available data from Alzheimer’s Disease Neuroimaging Initiative (ADNI1, ADNI2 and ADNI GO) studies (amyloid positive from amyloid PET or CSF testing, MMSE score of ≥22, CDR global score of 0.5 for MCI and 0.5 or 1 for mild AD). All analyses were two-sided at a 5% significance level.