**Study Overview**: This research is looking at a new treatment called **CRN09682** for people with certain types of tumors called **SST2-expressing NENs** (neuroendocrine neoplasms) and other solid tumors. The study will check if the treatment is safe and how well it works. It will take place in different medical centers. **Key Points**: - **Study Phases**: The study has two parts. The first part will find the right dose of the medicine. The second part will test the medicine more thoroughly. - **Eligibility**: To join, participants must have a specific type of tumor that the study is targeting. They should not have had certain treatments or surgeries recently. - **Safety and Tests**: Participants should expect to have regular tests to monitor their health and how their tumor responds to the treatment. **Medical Terms Explained**: - **SST2-expressing NENs**: This refers to tumors that show a specific protein called SST2. - **MTD and DLTs**: These terms are used to find the safest dose of the new treatment without side effects. - **PK**: This stands for pharmacokinetics, meaning how the treatment moves through the body. Participants will need to consider their eligibility, the safety measures, and the study's potential benefits and risks before joining.