A Study of INCMGA00012 in Metastatic Merkel Cell Carcinoma (POD1UM-201)

Inclusion Criteria:

* Signed informed consent.
* Diagnosis of MCC with distant metastatic disease or recurrent, advanced locoregional disease not amenable to surgery or radiation
* Eastern Cooperative Oncology Group performance status of 0 to 1.
* Measurable disease according to RECIST v1.1.
* Availability of tumor tissue (fresh or archival) for central pathology review.
* Willingness to avoid pregnancy or fathering children based on protocol-defined criteria.

Exclusion Criteria:

* Prior systemic therapy for MCC, including chemotherapy and prior PD-1 or PD-L1-directed therapy.
* Treatment with anticancer drugs or participation in another interventional clinical study within 21 days before the first administration of study drug.
* Has not recovered to ≤ Grade 1 or baseline from toxic effects of prior therapy (with the exceptions for anemia not requiring transfusion support and any grade of alopecia) and/or complications from prior surgical intervention within 7 days before starting study treatment.
* Radiation therapy administered within 2 weeks of first dose of study treatment or radiation therapy to the thoracic region that is \> 30 Gy within 6 months of the first dose of study treatment.
* Known central nervous system (CNS) metastases and/or carcinomatous meningitis.
* History of second malignancy within 3 years (with exceptions).
* Laboratory values outside the protocol-defined range at screening.
* Clinically significant pulmonary, cardiac, gastrointestinal or autoimmune disorders.
* Active bacterial, fungal, or viral infections, including hepatitis A, B, and C.
* Receipt of a live vaccine within 28 days of planned start of study therapy.
* Current use of protocol-defined prohibited medication.
* Known hypersensitivity to another monoclonal antibody that cannot be controlled with standard measures (eg, antihistamines and corticosteroids).
* Inability or unlikely, in the opinion of the investigator, to comply with the Protocol requirements.
* Participant who is pregnant or breastfeeding.