BackgroundS-adenosyl methionine (SAMe) is a pivotal metabolite in multiple pathways required for neuronal homeostasis, several of which are compromised in Alzheimer’s disease (AD). Correction of the SAMe deficiency that is characteristic of the AD brain may attenuate or prevent pathological processes driving AD-associated neurodegeneration including aberrant tau hyperphosphorylation and DNA hypomethylation.ObjectivesThe primary aim is to test the hypothesis that daily treatment with 400 mg oral SAMe for 180 days will lead to a greater reduction from baseline in plasma levels of p-tau181 compared to placebo in patients with mild cognitive impairment or dementia due to AD.Design, Setting, ParticipantsThis is a phase II, randomized, multi-center, double-blind, placebo-controlled trial among 60 participants with mild cognitive impairment or dementia due to AD. Participants will be randomized in a 1:1 ratio to receive either SAMe or matching placebo, to be taken as an adjunct to their AD standard of care.Measurements and ResultsThe primary outcome is change in plasma p-tau181 concentration between baseline and following 180 days of treatment, which will be compared between the active and placebo group. Secondary outcomes are the safety of SAMe administration (incidence of serious adverse events), change from baseline in cognitive performance (as measured by the Repeatable Battery for the Assessment of Neuropsychological Status), and epigenetic changes in DNA methylation.ConclusionDemonstration of effective and safe lowering of plasma p-tau181 with SAMe in this phase II trial would pave the way for an exciting field of translational research and a larger phase III trial.Electronic Supplementary MaterialSupplementary material is available in the online version of this article at 10.14283/jpad.2023.55.