A Study of Carboplatin Plus Etoposide With or Without ZKAB001 (Anti-PD-L1 Antibody) in Patients With ES-SCLC

Patients will receive ZKAB001 5mg/kg administered by IV infusion every 21days，

Patients will receive placebo administered by IV infusion every 21days.

Carboplatin should be administered after completion of placebo/ZKAB001 by IV infusion over 30-60 minutes to achieve an initial target AUC of 5 mg/mL/min. Carboplatin and etoposide will be used for a total of 4 cycles， followed by placebo/ZKAB001 maintenance therapy.

"Etoposide (100 mg/m\^2) should be administered intravenously over 60 minutes following carboplatin administration. On Days 2 and 3 of each cycle, etoposide 100 mg/m2) should be administered intravenously over 60 minutes.~Carboplatin and etoposide will be used for a total of 4 cycles， followed by placebo/ZKAB001 maintenance therapy."