Study of SYSA1801 in the Treatment of Claudin( CLDN) 18.2 Positive Advanced Malignant Solid Tumor

This study includes two stages. The dose escalation and dose expansion part (Stage I) will determine the MTD and RP2D of SYSA1801 in subjects with advanced solid tumor for which there is no available standard likely to confer clinical benefit based on a modified 3+3 dose escalation design (an accelerated dose titration design followed by traditional 3+3 dose escalation design) The extension cohort (Stage II) will evaluate the preliminary efficacy and safety of SYSA1801 in subjects with Claudin 18.2 positive gastric cancer (GC), gastroesophageal junction (GEJ) cancer, pancreatic cancer, non-small cell lung cancer and other solid tumors who have relapsed and/or are refractory to approved therapies.