A Study to Evaluate the Efficacy and Safety of Autogene Cevumeran (RO7198457) in Combination With Pembrolizumab Versus Pembrolizumab Alone in Participants With Previously Untreated Advanced Melanoma.

Prior treatment

• Previous splenectomy;
• Prior allogeneic bone marrow transplantation or prior solid organ transplantation;

Other illness

• Any anti-cancer therapy with the exceptions as specified in the protocol;
• History of autoimmune disease;
• Positive test for Human Immunodeficiency Virus (HIV) infection;
• Active hepatitis B or C or tuberculosis;
• Significant cardiovascular disease;
• Known clinically significant liver disease.

Other

• Ocular/uveal melanoma;
• Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases;

• Histologically confirmed metastatic (recurrent or de novo Stage IV) or unresectable locally advanced (Stage IIIC or IIID) cutaneous, acral, or mucosal melanoma;
• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1;
• Life expectancy \>/= 12 weeks;
• Adequate hematologic and end-organ function;
• Naive to prior systemic anti-cancer therapy for advanced melanoma with some exceptions;
• Tumor specimen availability;
• Measurable disease per RECIST v1.1.