This study investigates the use of chimeric antigen receptor (CAR)-T cells in treating carcinoembryonic antigen (CEA)-positive advanced malignant solid tumors. The purpose of this study is to evaluate the safety and tolerability of the investigational medication in patients with this condition.

The study focuses on assessing how well the investigational medication works and how safe it is for patients. It evaluates the medication's effects and determines the best dosage for further research.

• Who can participate: Adults aged 18 and older with advanced malignant tumors, including colorectal and lung cancer, may join. Participants must have failed at least second-line standard therapy and show CEA positivity.
• Study details: Participants will receive an investigational medication through an infusion. The study will monitor the effects of the medication, and some participants may receive a placebo, which is an inactive substance that looks like the investigational medicine but does not contain any medicine.