The overall goal of this protocol is to evaluate the biodistribution of [18F]MNI-958 also known as APN-0000455 or PM-PBB3, as a tau targeted radiopharmaceutical.

The overall goal of this protocol is to evaluate the biodistribution of [18F]MNI-958 also known as APN-0000455 or PM-PBB3, as a tau targeted radiopharmaceutical. The specific objectives are:

• To determine the radiation dosimetry of [18F]MNI-958
• To assess the safety and tolerability of a single dose of [18F]MNI-958

Inclusion Criteria:

• The participant is 18 to 55 years old.
• 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 or, if they are of child-bearing potential, must commit to use a barrier contraception method for the duration of the study.
• 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 for male subjects for the study duration.
• Male subjects must not donate sperm for the study duration.
• Willing and able to cooperate with study procedures.

Exclusion Criteria:

• The subject has a clinically significant abnormal laboratory value and/or clinically significant unstable medical or psychiatric illness.
• The subject is a currently exposed to nicotine products or had regular nicotine exposure within a six month period, to be verified by urine cotinine screening.
• History of drug or alcohol abuse within 12 months prior to screening, or evidence of such abuse as indicated by the laboratory assays conducted during the screening visit.
• The subject has evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, neurological, immunodeficiency, pulmonary, or other disorder or disease.
• The subject has any disorder that may interfere with drug absorption, distribution, metabolism, or excretion.
• 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 does not exceed the effective dose of 50 mSv, equivalent with the acceptable annual limits established by the US Federal Guidelines.
• Pregnancy or women who are breastfeeding, lactating or nursing.
• Unsuitable veins for repeated venipuncture.
• History of immunodeficiency diseases, including a positive HIV test result.
• A positive Hepatitis B surface antigen (HBsAg) or Hepatitis C antibody test result.