Safety of ADU-1604 in Adults With Metastatic Melanoma

Inclusion Criteria: 1. Male or female aged ≥18 years 2. Histologically-confirmed metastatic or unresectable melanoma 3. Progression of disease following at least one prior therapy, and is not a candidate for, or is intolerant to, established therapy known to provide clinical benefit (i.e. available treatment options have been exhausted). Subjects must have BRAF mutation status confirmed; if a subject is BRAF V600E/K positive, they must have received a BRAF- targeted regimen prior to entering the study, unless the patient was deemed ineligible for such treatment 4. Measurable disease according to RECIST (v1.1) \[NOT required during Dose Escalation\] 5. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 Exclusion Criteria: 1. Prior diagnosis of uveal or mucosal melanoma 2. Prior treatment with CTLA-4-directed therapy in the metastatic setting. Use of CTLA- 4-directed treatment in the adjuvant or neoadjuvant setting is acceptable provided the last dose was \>6 months before the first dose of ADU-1604 and there was no discontinuation of treatment due to a treatment-related toxicity.