A Study to Investigate the Safety and Effectiveness of SAR448851 in Participants With Early Alzheimer's Disease

Inclusion Criteria:

* Participant must be 55 to 85 years (inclusive) of age, at the time of signing the informed consent.
* Diagnosis of mild cognitive impairment (MCI) due to Alzheimer's disease (AD) (National Institute on Aging-Alzheimer's Association \[NIA-AA\] Stage 3) or mild AD dementia (NIA-AA Stage 4).
* Have a global Clinical Dementia Rating (CDR) score 0.5 to 1.0 and a CDR-Memory Box score ≥ 0.5 at screening.
* Have a study partner who must provide separate written informed consent at screening. Study partner should be \>18 years of age, have known participant for at least 1 year, and have a minimum of 8 hours per week contact with participant.
* The participant has evidence of cerebral amyloid pathology confirmed by positive visual read on amyloid positron emission tomography (PET) at screening.

Exclusion Criteria:

* The participant has any history of significant neurological disease including but not limited to, frontotemporal dementia, Lewy body dementia, Huntington's disease, serious infection of the brain, Parkinson's disease, multiple concussions, multiple sclerosis, or epilepsy or recurrent seizures (except febrile childhood seizures).
* The participant has evidence of more than 4 microhemorrhages (\<10 mm in diameter) or superficial siderosis.
* The participant carries two copies of the apolipoprotein-E epsilon 4 (APOE4) allele (APOE4/4).
* The participant is currently receiving or has previously received any anti-amyloid immunotherapy (including, but not limited to, aducanumab, lecanemab, or donanemab) or triggering receptor expressed on myeloid cells 2 (TREM-2) targeting therapy.
* The participant is currently receiving anticoagulant therapies.
* The participant has had malignancy in the 3 years prior to Screening, excluding basal cell carcinoma, squamous cell carcinoma of the skin, melanoma in situ, Stage 1 or 2 prostate cancer, fully resected renal cell cancers, or cervical carcinoma in situ that has been successfully treated.

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.