**A Phase 1 Study of IM-1021 in Advanced Cancer** This study tests a new drug, IM-1021, on adults with advanced cancer to see if it's safe and works well. IM-1021 is a special medicine called an *antibody-drug conjugate (ADC)*, designed to target cancer cells. This study has two parts. In **Part A**, doctors will find the right dose by gradually increasing it while checking for any side effects. In **Part B**, they will test the best dose on more people to ensure safety and effectiveness. Participants must be at least 18, have certain types of cancer, and have tried other treatments before. Some types of cancer in the study include: B-cell lymphomas, pancreatic cancer, and breast cancer. Participants must be healthy enough, not pregnant, and willing to practice safe birth control. **Key Points:** - **Study Length**: Participation involves multiple visits over time for treatment and check-ups. - **Safety**: Doctors will closely monitor for side effects or reactions to the drug. - **Eligibility**: Must have specific cancers and have tried at least one other treatment. To qualify, you should not have certain medical conditions or have had specific treatments before.