Evaluate the Safety and Efficacy of BGT007H Cell Therapy in Patients With Relapsed/Refractory Pancreatic Cancer

This study is a single-arm, open-label, modified "3+3" dose-escalation exploratory study. The BGT007H cell therapy group will be evaluated at 5 dose levels, which are (3.0×10\^7, 1.0×10\^8, 2.0×10\^8, 3.0×10\^8, 4.0×10\^8) BGT007H cells. If a lower adverse reaction and preliminary benefit (SD or PR) are observed, the same dose will be repeated 1-2 times after a 1-month interval. Each subject will be observed for at least 4 weeks after cell infusion (DLT observation period). The first two dose groups (3.0×10\^7, 1.0×10\^8 cells) will each include 1 subject, and the remaining 3 dose groups will follow the conventional "3+3" dose-escalation method. If a DLT occurs in the first subject at the first dose level, an additional 5 subjects will be included. If no DLT occurs in the expanded subjects, the study will proceed to the next higher dose group. If another subject experiences a DLT, enrollment will be halted and the study protocol will be revised. The next subject can only be enrolled if it is confirmed that the previous subject did not experience grade 3 or higher adverse events related to the study drug (CTCAE 5.0) during the DLT observation period. If no DLT occurs in a dose group, the study will proceed to the next higher dose group. In a group of 3 subjects, if one experiences a DLT, an additional 3 subjects will be included in the next higher dose group. If one out of three subjects experiences a DLT, 3 more subjects will be included in the dose group. If only one out of the expanded 6 subjects experiences a DLT, then the study will proceed to include 3 more subjects at the next higher dose. If 2 or more out of the expanded 6 subjects experience a DLT, then the dose is considered to be higher than the MTD (MTD is defined as the highest dose at which ≤1/6 or ≤2/9 subjects experience a DLT). New subjects will be enrolled at the previous lower dose (tolerated dose) group until 6 or 9 subjects are reached in the lower dose group. If ≤1/6 or ≤2/9 subjects, this lower dose group is defined as the MTD or the optimal effective dose. During the study, the investigators may consider the safety and preliminary efficacy data of the enrolled subjects, with the safety of the subjects and the maximum benefit of the disease as the premise, and conduct the study treatment at the maximum tolerated dose or other doses determined by the investigators.