The addition of the PD-1 inhibitor serplulimab to chemotherapy significantly prolonged survival compared with chemotherapy alone as first-line treatment of patients with extensive-stage small cell lung cancer (ES-SCLC). Interim analysis of the phase 3 ASTRUM-005 study – comparing serplumimab plus chemotherapy to chemotherapy alone in 1st line extensive stage SCLC – showed a median OS of 15.4 months with serplulimab compared with 10.9 months with placebo. Patients who received serplulimab also had significantly longer median progression-free survival (PFS) 5.8 vs. 4.3 months respectively. The study included 585 patients with untreated extensive stage-SCLC, were randomized 2:1 to serplulimab (4.5 mg/kg) or placebo every 3 weeks. All patients received carboplatin and etoposide every 3 weeks for up to four cycles.