Inclusion Criteria:

          1. Male or female patients at least 18 years of age at the time of signing the ICF.

          2. Histologically confirmed diagnosis of unresectable stage IIIB D, or unresectable stage
             IV malignant melanoma.

          3. Eligible for combination treatment with nivolumab and ipilimumab.

          4. An ECOG performance status of 0 or 1.

          5. Adequate organ function as indicated by the following laboratory values:

             Hematological

               1. Absolute neutrophil count ≥1,500/µL

               2. Platelet count ≥100 x 103/µL

               3. Hemoglobin ≥9 g/dL or ≥5.6 mmol/L Renal

               4. Creatinine ≤1.5 x upper limit of normal (ULN) Hepatic

               5. Total bilirubin ≤1.5 x ULN or direct bilirubin ≤ ULN for patients with total
                  bilirubin levels >1.5 ULN

               6. Aspartate aminotransferase/serum glutamic oxaloacetic transaminase and alanine
                  aminotransferase/serum glutamic pyruvic transaminase ≤2.5 x ULN for patients
                  without liver metastasis or ≤5 x ULN for patients with liver metastasis.

          6. Male patients who are sexually active with a female of childbearing potential must
             agree to use an adequate method of contraception.

          7. Women of childbearing potential (WOCBP) must have a negative urine or serum/plasma
             pregnancy test.

          8. WOCBP must use adequate contraception.

        Exclusion Criteria:

          1. Previous non melanoma malignancies unless curatively treated and complete remission
             was achieved at least 2 years prior to randomization. Patients with prior curatively
             treated basal or squamous cell carcinoma of the skin, carcinoma in situ of the cervix,
             or carcinoma in situ of the breast, or other in situ cancers are allowed irrespective
             of time passed since curative treatment. Patients with prior completely resected
             malignant melanoma are also allowed.

          2. Known brain metastases or leptomeningeal metastases. If a patient experiences
             neurological symptoms indicative of brain metastases, a brain MRI should be performed.

          3. Diagnosis of uveal or ocular melanoma.

          4. Known history or any evidence of active, non-infectious pneumonitis.

          5. History of New York Heart Association class 3-4 congestive heart failure or history of
             myocardial infarction within 6 months of starting induction therapy.

          6. Active infection requiring systemic treatment.

          7. Diagnosis of immunodeficiency.

          8. Known history of severe hypersensitivity reactions to nivolumab, ipilimumab,
             sargramostim, or their excipients.

          9. Known history of human immunodeficiency virus (HIV) (HIV 1/2 antibodies).

         10. History of or active hepatitis B (hepatitis B surface antigen reactive) or active
             hepatitis C (hepatitis C virus antibody).

         11. Women who are breastfeeding.

         12. Prior systemic treatment for unresectable stage IIIB D or unresectable stage IV
             malignant melanoma.

         13. Systemic corticosteroid treatment (doses exceeding 10 mg daily of prednisone or
             equivalent) or any other form of immunosuppressive treatment within 7 days prior to
             the first dose of induction therapy.

         14. Receipt of a live vaccine within 30 days prior to start of induction therapy.

         15. Receipt of any other investigational treatment within 4 weeks of the first dose of
             induction therapy.