This study looks at TST001, a new medicine for serious tumors, like stomach and pancreatic cancer. TST001 is a special type of medicine called a monoclonal antibody, which helps the immune system find and attack cancer cells. The study has two parts: Part A checks how much TST001 is safe to give, while Part B tests different combinations of TST001 with other cancer drugs.

There are three groups in Part B:

• Cohort A: For patients with untreated stomach cancer. They get TST001, another drug called nivolumab, and a chemo mix called mFOLFOX6.
• Cohort B: For patients whose stomach cancer got worse after past treatments. They receive TST001 and nivolumab.
• Cohort C: For patients with untreated pancreatic cancer. They get TST001, along with chemo drugs called gemcitabine and paclitaxel.

Key Points:

• The study involves getting treatments every 2-3 weeks.
• Participants must be adults (18+ years) with certain types of cancer.
• There are risks like side effects and the need for frequent hospital visits.