The study medicine GSK4527226 is being studied in participants with Alzheimer's Disease (AD) in study 219867 (the parent study, NCT06079190). This new study is an extension of that parent study called an open-label extension (OLE). An OLE is a clinical trial where all participants receive the same study medicine. Participants must already be in study 219867 to be able to take part in this study. This study will assess the long-term safety and efficacy of GSK4527226 in participants with early AD (including mild cognitive impairment [MCI] and mild dementia due to AD) who have completed the parent study.

Inclusion Criteria:

• Completion of the Treatment Period in the parent study (NCT06079190).
• Participants may have missed doses during the Treatment Period or may be on a temporary dose suspension but must not have been permanently discontinued early from study intervention or withdrawn from the parent study.
• Willing and able to give informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF).
• Availability of an adult person who has frequent and sufficient contact with the participant, is able to provide accurate information regarding the participant's cognitive and functional abilities, agrees to provide information at clinic visits, and signs the study partner ICF.
• A female participant is eligible to participate if she is not pregnant or breastfeeding, and if of childbearing potential follows contraception requirements outlined in the protocol.
• A male participant is eligible to participate if he follows contraception requirements outlined in the protocol.

Exclusion Criteria:

• QT interval corrected (QTc) assessment at Day 1 that meets the stopping criteria described in the protocol.
• Participant is taking or will be starting a prohibited medication described in the protocol.
• Evidence of any Amyloid related imaging abnormalities (ARIA) or cerebral macrohemorrhage that meets the permanent discontinuation criteria described in the protocol.
• Other newly identified intracranial hemorrhage aneurysm, vascular malformation, infective lesion, space occupying lesion or brain tumor, or other Magnetic resonance imaging (MRI) findings contraindicating participation in the study.
• Newly identified infection(s) that may affect the Central nervous system (CNS).
• New diagnosis of moderate to severe alcohol and/or substance use disorder.
• Change in participant's ability to tolerate MRI procedures, contraindication to MRI, or any other clinical history or examination finding that would pose a potential hazard in combination with MRI.
• Newly diagnosed cancer.
• Newly identified severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric, human, or humanized antibodies or fusion proteins.
• Newly identified genetic predisposition for clotting disorder or hemorrhagic disease.
• Any other clinically significant change in health status (which, in the opinion of the investigator, would make the participant unsuitable for participation in the OLE study.

Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/About\_GSK\_Patient\_Level\_Data\_Sharing\_Final\_13July2023.pdf

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or asset(s) with development terminated across all indications.

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months, but an extension may be granted, when justified, for up to 6 months.

This is an open-label study.