Study of Safety, Tolerability, Pharmacodynamics and Pharmacokinetics of NIO752 in Early Alzheimer's Disease Participants

Main Inclusion Criteria (placebo-controlled part): * Between 30 to 74 years old (both inclusive) at the time of informed consent. * A diagnosis of mild Alzheimer's Disease (AD) or mild cognitive impairment (MCI) due to AD at screening with at least a 6-month decline in cognitive function prior to screening documented in the medical record. Both participants with sporadic AD as well as Amyloid Precursor Protein (APP), Presenilin-1 (PSEN1) or Presenilin-2 (PSEN2) mutation carriers are eligible. * Participants must have a diagnosis of MCI due to AD or mild AD at screening as defined by a Clinical Dementia Rating Scale (CDR) Global Score of 0.5 or 1 and a Memory Score ≥ 0.5. * A history of CSF biomarkers supporting the diagnosis of AD obtained at any time point prior to screening, including CSF amyloid (amyloid-β 42 and/or 42/40 ratio) AND tau species (total tau and/or phosphorylated tau). All participants must have documented historical confirmation of both CSF biomarkers (amyloid-β and tau species) with results supporting a diagnosis of AD prior to screening. This criterion will be determined individually for each participant taking into consideration the biomarker assay used in each case. For participants (Cohorts 1 \& 2 only) with no historical CSF biomarker information, a LP for CSF collection must be performed at the screening visit. For CSF collected at screening, participants must have confirmed positivity of amyloid-β-42 ≤ 1000 pg/mL as well as positivity on, at least, …