Study Overview: This research is for people aged 18 or older with advanced cancer that is HER2-positive. HER2 is a protein found on some cancer cells. This study tests an investigational medication that targets HER2 and aims to understand its effects on cancer cells. The study will involve taking small samples of the tumor before and after treatment to see how the medication affects certain proteins and immune cells.

Key Criteria to Participate: Participants must have a confirmed HER2-positive cancer that has spread and cannot be treated with standard therapies anymore. They should be in good health aside from the cancer and willing to provide blood samples and undergo tumor biopsy procedures. People with certain lung diseases, recent heart problems, or ongoing infections cannot join.

• Time Commitment: The study involves receiving the investigational medication intravenously every 3 weeks in 21-day cycles.
• Duration: Participants will be in the study as long as they benefit from the treatment and are tolerating it well.
• Follow-Up: After the treatment ends, there will be a follow-up for 30 days.