CSB-321 Ph 1 in Immunotherapy for the Treatment of Cancer

Inclusion Criteria: 1. Participants 18 years of age and older. 2. Participants with either proven metastatic cancer that are going to be treated with one or more checkpoint inhibitors or immunotherapy under the licensed indications for the cancer type. Checkpoint inhibitors include PD-1, PD-L1, CTLA-4 and LAG-3 inhibitors OR Participants with unresectable or metastatic uveal melanoma planned to be treated with tebentafusp-tebn 3. Participants must have at least one lesion ≥ 15 mm in diameter or with two lesions both ≥ 15mm in diameter, when an optional biopsy is planned from one of the lesions. Lesion measurements are taken from a diagnostic quality computerized tomography (CT) or Magnetic Resonance Imaging (MRI). 4. ECOG performance status ≤ 2 (Karnofsky ≤ 60%). 5. Life expectancy of greater than 6 months. 6. If female, not of childbearing potential or must have a negative pregnancy test prior to each radiotracer injection. 7. Willing and able to undergo all study procedures. 8. Need archival lesion tissue ideally available within 90 days of enrollment either from biopsy or surgery without intervening therapy. Exclusion Criteria: 1. Participants for whom adverse events due to agents administered more than 4 weeks earlier have not resolved to Grade 1 or less, except for immune checkpoint inhibitor related endocrinopathies except for immune checkpoint inhibitor related endocrinopathies or deemed unlikely to be clinically significant by the investigator. 2. Participants in cohort 2 (ipilimumab with nivolumab) who have received or are expected to receive an investigational compound within 90 days prior to \[18F\]CSB-321 PET imaging. This includes immunotherapies that are not approved by the US FDA for the indications in this protocol. 3. Participants who have received a prior checkpoint inhibitor in the last year except for participants in cohort 3 (Prior checkpoint inhibitors are allowed for this cohort). 4. Participants who have received chemotherapy in the prior 6 months or are anticipated to receive chemotherapy in the 6 months following the initial \[18F\]CSB-321 injection for cohorts 2 and 3. 5. Any acute or chronic inflammatory disease or medical conditions that in the investigator's opinion may interfere with the study procedures or the interpretation of the study results such as infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia. 6. History of allergic reactions to compounds of similar chemical or biologic composition to \[18F\]CSB-321. 7. Current treatment with systemic steroids, or immunosuppressive agents. Participants with a condition requiring systemic treatment with either corticosteroids (\< 10 mg daily prednisone equivalent) inhaled or topical steroids, and adrenal replacement steroid doses \> 10 mg daily prednisone equivalent, are permitted in the absence of active autoimmune disease. 8. Participants who are unwilling or unable to have a CT scan. 9. Males and females unwilling to use adequate contraception prior to study and during study participation. 10. If female, nursing. 11. Unwilling and/or unable to sign a written informed consent document. 12. Laboratory values 1. Leukocytes \< 2000/mcL (CTCAE grade 3) 2. Absolute neutrophil count \< 1000 mcL (CTCAE grade 3) 3. Platelets \< 75,000 mcL (CTCAE grade 2) 4. Total bilirubin \> 1.5 x ULN, unless participant has Gilbert' disease. 5. AST/ALT \> 5 x ULN (CTCAE grade 3) 6. Albumin \< 2 g/dL 7. Alkaline phosphatase \> 5 ULN (CTCAE grade 3) 8. eGFR \< 45 mL/min/1.73 m2 Participants who are stable but have values outside the specified ranges may be included with approval of the study medical monitor. 13. Participants with a QTcF of greater than 470 ms as measured by 12-lead ECG.