<h3>Introduction</h3> Many pharmaceutical companies are working to identify novel treatments to slow or stop the progression of Alzheimer's Disease (AD), which they test through use of multi-site clinical trials. The Geriatric Psychiatry Research Program at McLean Hospital has been a study site in 8 clinical trials over the past 10 years, enrolling over 30 participants and their caregivers, or study partners. During the monthly, multi-hour study visits, McLean study staff accompanied participants and study partners and thus became familiar with the patient's clinical care. Two of the disease-modifying clinical trials conducted at McLean between 2012 and 2019 were terminated by the sponsors after interim analyses revealed study endpoints were not being met. Participants at McLean were immediately discontinued and required to stop infusions of study drug (or placebo) in both placebo-controlled and long-term extension phases of the trials. This abrupt discontinuation broke the pattern of regular study visits and consistent care the participants and study partners had come to expect, especially for those who had been involved in the same study for over 6 years. This observational, qualitative study seeks to examine the effects of study termination on participants and study partners and to provide insight into potential benefits of regular interaction with a consistent research care team. The primary goals of this study are to identify and characterize the impact that sponsor-initiated Alzheimer's clinical trial termination had on participants and their caregivers at McLean Hospital. <h3>Methods</h3> Study aims were accomplished by collecting mood, memory, function, and study satisfaction surveys from participants or study partners who were enrolled in Eli Lilly's LZAO, Eli Lilly's LZAX, or Biogen's Emerge trials at McLean when discontinued. For this one-time study visit, 7 subject and 8 caregiver surveys were administered to eligible individuals. Participants were asked to reflect on their experiences and mood at the time of study termination, 4-weeks after termination, and at the time of this visit. We evaluated qualitative trends in reported changes in mood, memory, function, social support and overall study experience for former subjects and caregivers. <h3>Results</h3> There were 17 participants enrolled in the study - 12 caregivers and 5 subjects. Caregivers reported that the aspects of trial participation they valued most were social interactions with staff, sense of giving back by contributing to AD research, feelings of hope related to trial participation, access to medical knowledge and experts, consistent health monitoring and structure from scheduled visits, and the safe space created to talk about AD. Caregivers tended to disagree when asked if they had less social contact with others following study termination but were more likely to agree that their study partner had less social contact with others following termination. When asked what resources they hoped would be available but were not offered at study termination, 4 caregivers wished they had longitudinal information about testing, specifically the amyloid PET scan data. Multiple caregivers wished the sponsor had provided more information about the rationale for study termination and offered other trial options or support resources. The majority of caregivers would have appreciated more help getting enrolled in other trials. Participants valued the social interaction with and quality of staff, transparent communication, interaction with experts, feeling more connected to others, and the hope of potential benefit from the study medication. Like caregivers, participants desired more specific information about their results and brain amyloid status and wished there had been additional clinical support offered at trial termination, such as facilitated group discussions with other participants. Two caregivers and one participant mentioned that the relationship between the sponsor and site should be closer for a better flow of information. Subjects and caregivers expressed feelings of disappointment, frustration, anger, and sadness at the abrupt ending of the trial, and two caregivers said they would not enroll another family member in a placebo-controlled trial. <h3>Conclusions</h3> Termination of a clinical trial had a significant qualitative impact on both participants and caregivers who were enrolled. Two themes, empowerment and support, emerged regarding the meaning of trial participation to subjects and study partners. When trials were ended abruptly, participants and caregivers were left without a source for the sense of empowerment and support previously provided by study participation. Increased attention should be directed to services provided by both the sponsor and site at the time of termination. Sponsors and study sites should focus on providing resources for emotional support and information to participants and study partners to ease negative feelings that may arise with trial discontinuation. <h3>This research was funded by</h3> Unfunded.