Participants will first receive the study drug and be closely monitored for safety. In the second part, participants will be randomly assigned to receive either the study drug by injection or the standard treatment by IV. Treatment is given in 28 day cycles and may continue for up to 24 cycles.

This study is for people with a type of skin cancer that has spread or cannot be removed with surgery and who have a weakened immune system.

Participants may be able to join if they are adults with this type of skin cancer. They cannot have received certain similar cancer treatments in the past year, had a lung transplant, or had a lung complication called graft versus host disease. People with cancer that spread to the brain may be eligible if it has not worsened after treatment.

This study is testing whether a study drug works better than a standard treatment at slowing or stopping advanced skin cancer in people with weakened immune systems. Researchers will also see if either treatment can help shrink the cancer.