A Study to Investigate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of RO7812653 in Participants With Early Symptomatic Alzheimer's Disease (eAD)

Inclusion Criteria: * Probable AD dementia (consistent with National Institute on Aging and Alzheimer's Association (NIA-AA) core clinical criteria for probable AD dementia) \[McKhann et al 2011\] or Mild Cognitive Impairment (MCI) due to AD (consistent with the NIA-AA core clinical criteria for mild cognitive impairment due to AD) \[Albert et al 2011\]). * Willingness and ability to complete all aspects of the study. The participant should be capable of completing assessments either alone or with the help of the study partner. * Fluency in the language of the tests used at the study site. * Adequate visual and auditory acuity, in the investigator's judgment, sufficient to perform the neuropsychological testing (eyewear and hearing aids are permitted). * If the participant is receiving symptomatic AD medications, a stable dosing regimen for at least 8 weeks prior to screening and until randomization is required. * Agreement not to participate in other research studies for the duration of this study. Exclusion Criteria: * Any medical history or evidence of a condition other than AD that may affect cognition. * Presence of any significant cerebral abnormalities that would contraindicate lumbar puncture, as assessed on MRI * Any other significant cerebral abnormalities that the Investigator considers clinically significant * History of schizophrenia, schizoaffective disorder, major depression or bipolar disorder.' * Presence of cardiovascular, respiratory, hepatic, renal, gas…