• Provide written informed consent, signed, and dated by the participant and study partner, or by the participant's legally authorized representative if applicable, according to local regulations for the ICF and, if applicable, country specific ICFs.

• Participant is at least 18 years old.

• People of childbearing potential

∙ Must have a negative serum pregnancy test at screening (V1)

‣ Must agree not to try to become pregnant during the study until 5 half-lives after the last dose of any study drug.

‣ Must agree not to breastfeed from the time of signed ICF until 5 half-lives after the last dose of any study drug.

‣ If partner is not sterilized, must agree to use highly effective contraceptive measures from screening (V1) until 5 half lives after last dose of any study drug

• Mutation Status:

∙ Participant is a carrier of a mutation in an APP, PSEN1, or PSEN2 gene that is associated with DIAD or does not know their mutation status and there is a mutation in their family pedigree that puts them at a direct risk of inheriting the known mutation;

‣ Participant is -25 to -11 years from predicted age of cognitive symptom onset based on their mutation type or family pedigree Note: If the at-risk parent is deemed a non-carrier through confirmed genetic testing at any time during the study, the participant will be withdrawn.

• Cognitive status of participant is normal (CDR-SB 0).

• Fluency in DIAN-TU trial approved language and evidence of adequate premorbid intellectual functioning. Participants must be fluent in languages for which cognitive and clinical measures have been translated and validated for use in the DIAN-TU. Fluency is generally defined as daily or frequent functional use of a language generally from birth or a young age. In cultures where multiple languages are spoken or for participants who are multilingual, determination as to whether a participant's level of fluency in languages for which clinical and cognitive measures are available meets qualification for the study should be made by the site PI.

• Participant has adequate visual and auditory abilities to perform all aspects of the cognitive and clinical assessments.

• Participant is receiving stable doses of medication(s) for the treatment of non-excluded medical condition(s) for at least 30 days prior to baseline visit (V2) except for medications taken for episodic conditions (e.g., migraine abortive therapy, antibiotics, and other medications for upper respiratory and gastrointestinal ailments).

• Participant has a study partner who in the PI's judgment can provide accurate information as to the participant's cognitive and functional abilities, who agrees to provide information at the study visits that require study partner input for scale completion, and who signs the necessary ICF, if applicable.

⁃ The participant agrees not to donate blood or blood products for transfusion from the time of Screening (V1) for a study drug arm, for the duration of the study, and for 5 half lives after the final dose of study drug.

⁃ In the opinion of the PI, the participant will be compliant and have a high probability of completing the study.

⁃ The participant is able and willing to complete all study-related testing, evaluations, and procedures.