To Evaluate the Efficacy of Durvalumab + Anlotinib in Terms of OS and PFS.

This is an open-label, randomised, multicenter, Phase II study. This study is planned to enroll 90 eligible patients to receive durvalumab combined with up to 4 cycles of etoposide and platinum-based chemotherapy (EP). And approximately 64 patients who complete the 4 cycles of durvalumab + EP treatment and don\'t have progressive diseases (Non-PD patients) will be randomized in a 1:1 ratio to receive maintenance treatment durvalumab + anlotinib (Arm 1) or durvalumab (Arm 2) until confirmed progressive disease. Prophylactic cranial irradiation (PCI) is allowed at the investigators\' discretion as per SoC guidance for ES-SCLC. Patients will attend a safety follow up visit 90 days after last dose of durvalumab. Tumor assessments will be performed at Screening with follow-up at Week 6 ±1 week and Week 12 ±1 week from the date of the first cycle treatment, and then every 8 weeks ±1 week until confirmed objective disease progression.