A Study of SYS6040 for Injection in Patients With Advanced Solid Tumors

This study is testing SYS6040 — a new injectable drug — in people with advanced solid tumors or small cell lung cancer (SCLC) that have not responded to standard treatments, to find out how safe it is, how much to give, and whether it shows signs of working. **You may be eligible if...** - You are 18 or older with a solid tumor confirmed by biopsy that has progressed despite standard treatments - For the expanded cohort: you have small cell lung cancer (SCLC) that has failed at least one platinum-based chemotherapy regimen - You are in generally good health with acceptable organ function - You have measurable or evaluable disease on imaging **You may NOT be eligible if...** - You have received certain prior treatments or are within a required washout period from your last therapy - You have uncontrolled brain metastases - You have severe organ failure, uncontrolled infections, or active autoimmune disease - You are pregnant or breastfeeding - You have known allergy to components of the study drug Talk to your doctor to see if this trial is right for you.