• Voluntary participation in this clinical study; full understanding of the study and voluntary signing the informed consent form; willing to follow and abling to complete all trial procedures;

• Age ≥18 years but ≤75 years;

• Histologically or cytologically confirmed SCLC;

• Advanced SCLC that has progressed or replased after first-line platinum-containing chemotherapy (extensive-stage patients must have received immune checkpoint inhibitors);

• Having adequate organ functions;

• The Eastern Cancer Cooperative Group (ECOG) performance score of 0 or 1;

• Life expectancy of 12 weeks or more;

• Having at least one measurable tumor lesion according to RECIST v1.1;