The goal of this clinical trial is to assess the safety and tolerability of AT1019 when used in combination with SBRT and PD-1 inhibitor, and determine the maximum tolerated dose (MTD) of AT1019 in the combination therapy of SBRT and PD-1 inhibitor in patients with advanced solid tumors. The main questions it aims to answer are:
Is the combination of AT1019, SBRT and PD-1 inhibitor safe and well-tolerated in patients with advanced solid tumors? What is the maximum tolerated dose (MTD) of AT1019 when combined with SBRT and PD-1 targeted immunotherapy?
Participants will:
* First receive PD-1 inhibitor treatment as scheduled.
* Undergo SBRT, which will be given in 3 to 5 fractions, with each fraction ranging from 6Gy to 18Gy, and the treatment will be administered once a week.
* Receive intratumoral injection of AT1019 within 1 to 2 days after each SBRT session.
* Undergo imaging examinations every 6 weeks (with a tolerance of ±1 week) to evaluate the treatment effect.