18F-LY3950321 (also known as 18F-MNI-1256) is a radiolabeled positron emission tomography (PET) tracer targeting granzyme B. The overall goal of this protocol is to evaluate the safety, tolerability, and radiation dosimetry of 18F-LY3950321.

Inclusion Criteria:

• Healthy with no clinically relevant finding on physical examination at Screening and upon reporting to the clinic for the Imaging Visit.
• Female subjects must not be of childbearing potential, or if they are of childbearing potential to agree to use contraception and not donate eggs.
• Male subjects with their partners of childbearing potential must commit to the use of 2 methods of contraception, 1 of which is a barrier method for male subjects for the study duration and 90 days after study completion.
• Male subjects must not donate sperm for the study duration and for 90 days after study completion.

Exclusion Criteria:

• Current or prior history of any alcohol or drug abuse in the past 2 years.
• Currently exposed to nicotine products or had regular nicotine exposure within a six-month period, to be verified by urine cotinine screening.
• ECG or Laboratory tests with clinically significant abnormalities and/or clinically significant unstable medical illness.
• Known history of hypersensitivity, including hypersensitivity to the active substances used for 18F-LY3950321 or derivatives, or to any of the associated excipients.
• Subject has received an investigational drug within 30 days or five half-lives prior to Day 1, whichever is longer.
• Prior participation in other research protocols or clinical care during the past year that would result in radiation exposure to an effective radiation dose exceeding the acceptable annual limit established by the US Federal Guidelines (effective dose of 50 milliSieverts, including the procedures in this clinical protocol).
• Pregnant, lactating or breastfeeding.
• Evidence of clinically significant gastrointestinal, cardiovascular, hepatic, renal, hematological, neoplastic, endocrine, alternative neurological, immunodeficiency, pulmonary, or other disorder or disease.
• Unsuitable veins for repeated venipuncture.
• Use of any prescription drugs (except approved forms of birth control) or herbal supplements, within 4 weeks prior to Day 1.
• Use of any over-the-counter (OTC) medication or dietary supplements (vitamins included) within 2 weeks prior to Day 1.
• Subject is, in the opinion of the Investigator, unsuitable in any other way to participate in this study.