The overall objective of this study is to compare the overall pattern of [18F]APN-1607 uptake in subjects with MCI, subjects with AD dementia, and healthy subjects.

Inclusion Criteria:

Inclusion Criteria for All Subjects:

• Written informed consent must be obtained before any assessment is performed.
• Female subjects must be documented by medical records or physician's note to be either surgically sterile (by means of hysterectomy, bilateral oophorectomy, or tubal ligation) or post-menopausal for at least 1 year (ie, 12 consecutive months with no menses without an alternative medical cause) or, if they are of childbearing potential, must commit to use a barrier contraception method or to abstinence for the duration of the study and must have negative serum and urine pregnancy tests.
• Male subjects and their partners of childbearing potential must commit to the use of two methods of contraception, one of which is a barrier method (ie, condom), or to abstinence for the study duration.
• Male subjects must not donate sperm for the study duration.
• Willing and able to participate in all study procedures.

Inclusion Criteria for Healthy Subjects:

• Medically healthy with no clinically relevant finding on physical examination, laboratory profiles, VS, or ECG at screening and upon reporting for the [18F]APN-1607 Imaging Visit.
• No cognitive impairment based on neuropsychological battery and as judged by the Investigator.
• No first-degree family history of early-onset AD or other neurological disease associated with dementia (prior to age 65).

Inclusion Criteria for Subjects with MCI:

• Written informed consent must be obtained before any assessment is performed.
• Must meet all of the clinical criteria for MCI according to NIA-AA criteria, including lack of functional impairment sufficient to warrant a diagnosis of dementia.

Inclusion Criteria for Subjects with AD:

• Has a diagnosis of AD dementia according to NIA-AA criteria, including significant impairment of activities of daily living.
• Medications taken for symptomatic treatment of AD must have been stable for 30 days prior to screening and through completion of the neuropsychological battery.

Exclusion Criteria:

Exclusion Criteria for All Subjects:

• Current or prior history (within the last 10 years) of alcohol or drug abuse.
• Known hypersensitivity to [18F]APN-1607 or its excipients.
• Clinically significant active or unstable medical illness or planned surgical procedures during the study period. History of cancer (other than nonmelanoma skin cancers or stable, local prostate cancer), unless without evidence of active disease within the last 3 years and without ongoing medical or surgical therapy.
• Laboratory tests with clinically significant abnormalities or a history or evidence of clinically significant unstable medical illness.
• Prior participation in other research protocols or clinical care in the last year in addition to the radiation exposure expected from participation in this clinical study, such that radiation exposure exceeds local guidelines.
• Pregnant, lactating or breastfeeding.
• Unsuitable veins for repeated venipuncture.
• Implants, or history of claustrophobia in MRI.