Inclusion criteria Part 1: Safety run-in

   - Histologically confirmed, unresectable or metastatic melanoma with BRAF V600 mutation

   - Aspartate transaminase (AST) < 2.5× ULN and Alanine transaminase (ALT) < 2.5× ULN

   - Measurable disease according to RECIST 1.1

   - ECOG performance status ≤ 1

Part 2: Biomarker cohort

   - Histologically confirmed, unresectable or metastatic melanoma with BRAF V600 mutation

   - At least two cutaneous or subcutaneous or nodal lesions for tumor sample collection

   - Measurable disease according to RECIST 1.1

   - ECOG performance status ≤ 2

Part 3: Double-blind, randomized, placebo-controlled part

   - Histologically confirmed, unresectable or metastatic melanoma with BRAF V600 mutation

   - ECOG performance status ≤ 2

   - Measurable disease according to RECIST 1.1

Exclusion Criteria:

Part 1: Safety run-in

   - Subjects with uveal or mucosal melanoma

   - Any history of CNS metastases

   - Prior systemic anti-cancer treatment for unresectable or metastatic melanoma

   - Neoadjuvant and/or adjuvant therapy for melanoma completed less than 6 months prior to
   enrollmen

   - Radiation therapy within 4 weeks prior to start of study treatment

   - Active autoimmune disease, and/or history of autoimmune disease(s) that required
   treatment

Parts 2 & 3: Biomarker cohort & double-blind, randomized, placebo-controlled part

   - Subjects with uveal or mucosal melanoma

   - Prior systemic anti-cancer treatment for unresectable or metastatic melanoma

   - Neoadjuvant and/or adjuvant therapy for melanoma completed less than 6 months prior to
   enrollment

   - Radiation therapy within 4 weeks prior to start of study treatment

   - Clinically active cerebral melanoma metastasis.

   - Active autoimmune disease, and/or history of autoimmune disease(s) that required
   treatment

Other protocol-defined Inclusion/Exclusion may apply.