A Double-blind Dual Study Assessing Safety and Efficacy of Buntanetap in Participants With Early AD

The goal of this clinical trial is to learn if buntanetap/Posiphen works to treat early Alzheimer's disease in adults aged 55-85. It will also learn about the safety of buntanetap/Posiphen. The main questions it aims to answer are: * Does buntanetap/Posiphen improve cognition as measured by ADAS-Cog13? * Does buntanetap/Posiphen improve function as measured by ADCS-iADL? * What medical issues do participants have, if any, when taking buntanetap/Posiphen? Researchers will compare buntanetap/Posiphen to a placebo (a look-alike substance that contains no drug) to see if buntanetap/Posiphen works to treat early Alzheimer's disease. Participants will: * Take buntanetap/Posiphen or a placebo every day for 18 months * Visit the clinic periodically for checkups, tests, and questionnaires (screening visits, enrollment, month 1, month 3, month 6, month 9, month 12, month 15, month 18), including a volumetric MRI at month 6 and month 18 * Complete pre- and post-clinic visit phone calls