84P Adebrelimab plus chemotherapy (chemo) as first-line treatment for extensive-stage small-cell lung cancer (ES-SCLC): 3-year update of the phase III CAPSTONE-1 study

In the phase 3 CAPSTONE-1 study, adebrelimab, a humanized IgG4 anti-PD-L1 monoclonal antibody, plus chemo as first-line treatment for ES-SCLC significantly improved overall survival (OS) vs placebo plus chemo. Here we reported updated outcomes ∼3 years after the enrollment of the last patient. 462 patients with systemically untreated ES-SCLC were randomized 1:1 to receive 4-6 cycles of adebrelimab (20 mg/kg, iv, d1, q3w) or placebo, with carboplatin (AUC 5, d1, q3w) plus etoposide (100 mg/m2, d1, d2, d3, q3w), followed by maintenance therapy with adebrelimab or placebo. The primary endpoint was OS. As of data cutoff of Aug. 11, 2023, median follow-up was 15.1 mo for all patients in the adebrelimab group and 12.8 mo in the placebo group; median follow-up for censored patients was 45.8 mo and 42.5 mo, respectively. OS events were recorded in 188 (81.7%) patients in the adebrelimab group and 212 (91.4%) in the placebo group. Median OS was 15.3 mo (95% CI 13.2-17.3) with adebrelimab plus chemo vs 12.8 mo (95% CI 11.3-13.9) with placebo plus chemo (HR 0.73, 95% CI 0.60-0.89; one-sided p=0.0008). Over 10% improvement in OS rate was seen at 12, 24 and 36 mo in the adebrelimab group vs placebo group (Table 1). The OS benefits with adebrelimab were generally consistent across clinically relevant subgroups. No new safety signals were observed.Table: 84POS outcomesAdebrelimab + chemo (N=230)Placebo + chemo (N=232)Median OS*, mo (95% CI)15.3 (13.2-17.3)12.8 (11.3-13.9)HR† (95% CI); p-value‡0.73 (0.60-0.89); p=0.0008OS rate*, % (95% CI)12 mo62.9 (56.3-68.8)52.0 (45.4-58.2)24 mo30.9 (25.0-37.0)17.8 (13.1-23.0)36 mo21.1 (16.1-26.7)10.5 (6.9-14.9)* Kaplan-Meier method. † Stratified Cox proportional-hazards model stratified by liver metastases (yes/no), brain metastases (yes/no), and lactate dehydrogenase concentration (normal/elevated) at baseline. ‡ One-sided p-value was calculated based on stratified log-rank test. Open table in a new tab * Kaplan-Meier method. † Stratified Cox proportional-hazards model stratified by liver metastases (yes/no), brain metastases (yes/no), and lactate dehydrogenase concentration (normal/elevated) at baseline. ‡ One-sided p-value was calculated based on stratified log-rank test. After prolonged follow-up, the addition of adebrelimab to chemo continued to demonstrate OS benefits with manageable toxicities, further supporting this regimen as a new first-line treatment option for ES-SCLC.