In each portion of the study subjects will have a screening visit and, no more than 28 days later, those who are eligible for the study will receive MVT-2163. Each cohort will have 3-6 subjects. Subjects in cohort 1 will be administered MVT-2163 alone on day 1. Subjects in cohorts 2 and 3 will receive MVT-5873 on day 1, followed approximately 10 minutes later by MVT-2163. Subjects will return for visits to the clinic on days 2, 4, and 7 for additional imaging and safety assessments. A follow-up visit will occur on day 28.