The purpose of this study is to evaluate the binding of a novel tracer, [11C]TASP0410699, using Positron Emission Tomography (PET) scans with or without dosing of TS-121

Inclusion Criteria:

1. Healthy males 18 - 55 years of age (at time of initial informed consent)
2. Body weight ≥ 50 kg
3. Body Mass Index (BMI) 18 - 30 kg/m2
4. Male subjects with partners of childbearing potential must agree to use appropriate and effective measures of contraception for 90 days following drug administration

Exclusion Criteria:

1. Prescription, over-the-counter or herbal medications, supplements, within 14 days before the study.
2. Clinically significant abnormal electrocardiogram, physical examination, or hematology, biochemistry, hormone, or urinalysis values at screening & baseline.
3. Significant history &/or presence of hepatic, renal, cardiovascular, hemodynamic, pulmonary, gastrointestinal, hematological, CNS, immunologic, ophthalmologic, metabolic, endocrine, or oncological disease or condition within last 5 years.
4. Current use of tobacco or tobacco-containing products, recent history of alcohol or drug abuse OR positive urine screen for alcohol or controlled substances at screening or baseline.
5. History &/or current evidence of serologic positive results for hepatitis B or C, or HIV.
6. Donation or acute loss of 450 milliliters or more of blood or plasma, within 60 days of the study.
7. Any subject who has received treatment with a non-FDA approved drug within 30 days of study screening.
8. Subjects who suffer from claustrophobia.
9. Current, past, or anticipated exposure to radiation in the workplace or participation in other research studies involving ionizing radiation that would exceed the yearly dose limits for normal subjects.