This study is exploring a new drug, RYZ401, for people with certain types of solid tumors. These tumors have something called SSTRs, which are special protein markers found in some cancers. The main goal is to find the best dose and see how safe it is, as well as how well it works.

Eligibility: To join, you must be at least 18 years old and have certain advanced cancers. These include neuroendocrine tumors (NETs) from places like the stomach, pancreas, lungs, and more. There are two groups in this study: Dose Escalation and Dose Expansion. To qualify, your tumor must be SSTR-positive, which means it shows up on a special scan.

Exclusion: You cannot participate if you've had certain treatments before, like some radiation therapies, organ transplants, or have serious health issues like severe heart disease or uncontrolled diabetes.

• The study involves finding the best dose and checking safety.
• Participants must be over 18 and have specific advanced tumors.
• Can't join if you've had certain past treatments or have major health concerns.