**Open Label Study to Evaluate BL-M07D1 in HER2 Expressing Malignant Solid Tumors** This study is testing a new medicine called **BL-M07D1** for patients with advanced cancers that show **HER2** proteins. HER2 is a protein that can help cancer grow faster. The study aims to see if the medicine is safe and if it works well for these cancers. The study happens in three parts: finding out the right dose, adjusting the dose, and then testing the best dose in more people. Participants will get the medicine every 21 days. To join, you must be at least 18 years old, have a certain type of cancer, and have tried other treatments that didn't work. You also need to be healthy enough to participate and agree to provide a sample of your tumor. **Key Points:** - **Length and Visits:** The study involves a 21-day cycle for treatment. - **Eligibility:** Must have specific HER2 cancers and be healthy enough to participate. - **Exclusions:** Recent heart problems or certain other health issues may disqualify you. If you think you might qualify and are interested, speak to your doctor to learn more.