1. Participant is < 21 years of age 2. Parent/ Legal Guardian/ Adult Participant can understand the consent process and is willing to provide informed consent/HIPAA: 3. (a) Participant is receiving one or more of the study drugs of interest at the time of enrollment or (b) Participant is NOT receiving one or more of the study drugs of interest but is SARS-COV-2 positive within 60 days prior to enrollment 1. Participant has a known pregnancy Below exclusion criteria apply only to participants receiving one or more of the study drugs of interest at the time of enrollment, 2. Has had intermittent dialysis within previous 24 hours 3. Has had a kidney transplant within previous 30 days 4. Has had a liver transplant within previous 1 year 5. Has had a stem cell transplant within previous 1 year 6. Has had therapeutic hypothermia within previous 24 hours 7. Has had plasmapheresis within the previous 24 hours 8. Has a Ventricular Assist Device 9. Has any condition which would make the participant, in the opinion of the investigator, unsuitable for the study

• Completed Study WN29922 or WN39658, either its double-blind part or OLE part, and did not discontinue study drug early
• The participant should be capable of completing assessments either alone or with the help of the caregiver
• Availability of a person (referred to as the "caregiver")
• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception methods with a failure rate of <1% per year (bilateral tubal ligation, male sterilization, hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterine devices) during the treatment period and for at least 16 weeks after the final dose of gantenerumab
• Agreement not to donate blood or blood products for transfusion for the duration of the study and for 1 year after final dose of study drug
• Pregnant or breastfeeding, or intending to become pregnant during the study or within at least 16 weeks after the final dose of study drug
• Prematurely discontinued from Study WN29922 or WN39658
• Any medical condition that may jeopardize the participant's safety if he or she continues to receive study treatment
• Received any investigational treatment other than gantenerumab during or since completion of Study WN29922 or WN39658, either its double-blind or OLE part
• Evidence of disseminated leptomeningeal hemosiderosis
• Evidence of intracerebral macrohemorrhage
• Use of prohibited medication
• Evidence of ARIA-E on the last MRI scan report in Study WN29922 or WN39658, either its double-blind or OLE part

• Age 21 to 65 years at screening
• Medically healthy (does not meet criteria for an exclusionary medical condition)
• No current DSM-5 psychiatric diagnosis
• No current use of psychotropic medications
• Ability/willingness to complete all study activities
• Use of acceptable contraceptive methods (sexually active males and women of childbearing potential)
• Speaks and reads English
• No use of psychedelic drugs within prior 3 months of dosing visit
• Able to swallow oral medications
• Pregnancy
• Current exclusionary medical illness
• Current DSM-5 psychiatric diagnosis and/or suicidal thoughts/behavior within prior 12 months
• Clinically significant safety lab abnormalities (i.e., Complete Blood Count with Differential, Comprehensive Metabolic Panel, and urinalysis)
• Clinically significant electrocardiogram (ECG)
• Hypertension or tachycardia
• First degree relative(s) with a history of schizophrenia, schizophreniform disorder, bipolar I disorder, bipolar II disorder, major depressive disorder with psychotic features