This study looks at a new drug called **CTO1681** to help prevent or lessen side effects from a treatment known as **CAR T-cell therapy** in patients with **DLBCL**, a type of blood cancer. **CAR T-cell therapy** is a treatment that uses special immune cells to fight cancer, but it can cause side effects like **cytokine release syndrome (CRS)**, which is when the body releases too many proteins that can make you feel sick.

In this study, participants will take CTO1681 three times a day for 15 days, starting just before they receive CAR T-cell therapy. They will have regular check-ups and tests, including blood and urine samples, scans, and heart tests, to see if the drug helps with side effects. The study will last a total of 43 days, with additional follow-up for 6 months to monitor safety and cancer response.

• **Participation Requirements:** Must be 18+ with DLBCL, having certain health conditions.
• **Study Length:** Initial phase 43 days, with follow-up up to 6 months.
• **Tests and Procedures:** Includes blood tests, heart tests, and scans.