Study on PD-1 Blockade Before Surgery for Treatable Merkel Cell Carcinoma

Inclusion Criteria

• Must have treatable stage I-III Merkel cell carcinoma.
• Must have enough tumor tissue for research biopsies before surgery.
• Must have enough remaining tumor tissue after initial biopsies for further research collection during surgery.
• Must agree to undergo two tumor biopsy procedures for research purposes.
• Male participants must use contraception during treatment and for 120 days after the last dose, and must not donate sperm during this time.
• Female participants must not be pregnant or breastfeeding and must agree to use contraception during treatment and for 120 days after the last dose, unless they are not of childbearing potential.
• Must provide a tumor tissue sample that has not been previously treated with radiation.
• Must have a performance status score of 0 to 1, indicating good overall health.
• Must have adequate organ function.
• Participants with Hepatitis B can join if they have been on antiviral therapy for at least 4 weeks and have an undetectable viral load.
• Participants with a history of Hepatitis C can join if their viral load is undetectable and they completed antiviral therapy at least 4 weeks before joining the study.

Exclusion Criteria

• Cannot have cancer that cannot be completely removed by surgery.
• Must have recovered from any major surgery before starting the study treatment.
• Women of childbearing potential cannot have a positive pregnancy test before starting the study.
• Cannot have received previous treatment with certain immune therapies.
• Cannot have had other cancer treatments within 4 weeks before starting the study.
• Cannot have had radiation therapy within 2 weeks before starting the study.
• Cannot have received a live vaccine within 30 days before starting the study.
• Cannot be participating in another study or using an investigational device within 4 weeks before starting the study.
• Cannot have an immune deficiency or be on high-dose steroids or other immune-suppressing drugs.
• Cannot have another active cancer that required treatment in the past 3 years, except for certain skin cancers.
• Cannot have active cancer spread to the brain or spinal cord unless stable and not requiring steroids.
• Cannot have severe allergies to pembrolizumab or its ingredients.
• Cannot have an active autoimmune disease needing treatment in the past 2 years.
• Cannot have a history of lung inflammation needing steroids.
• Cannot have an active infection needing treatment.
• Cannot have HIV infection.
• Cannot have active Hepatitis B and C infections.
• Cannot have any condition or treatment that might interfere with the study.
• Cannot have psychiatric or substance abuse issues that would affect participation.
• Cannot be pregnant, breastfeeding, or planning to have children during the study and for 120 days after.
• Cannot have had a tissue or organ transplant.