IMbrave150: Updated overall survival (OS) data from a global, randomized, open-label phase III study of atezolizumab (atezo) + bevacizumab (bev) versus sorafenib (sor) in patients (pts) with unresectable hepatocellular carcinoma (HCC).

267 Background: Atezo + bev has been approved globally for pts with unresectable HCC who have not received prior systemic therapy, based on results from IMbrave150 (NCT03434379). At a median of 8.6 mo follow-up, both coprimary endpoints were met, with statistically significant and clinically meaningful improvements observed with atezo + bev vs sor for OS (HR, 0.58 [95% CI, 0.42, 0.79]; P<0.001) and independently-assessed progression-free survival (PFS; per RECIST 1.1; HR, 0.59 [95% CI, 0.47, 0.76]; P<0.001) (Finn, et al. N Engl J Med 2020). Here, we report an updated OS analysis for IMbrave150. Methods: The global, multicenter, randomized, open-label, Phase III study IMbrave150 enrolled 501 systemic treatment–naive pts with unresectable HCC, ≥1 measurable untreated lesion (RECIST 1.1), Child-Pugh class A liver function and ECOG PS 0/1. Pts were randomized 2:1 to receive either atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w or sor 400 mg bid until unacceptable toxicity or loss of clinical benefit per investigator. This post hoc, descriptive OS analysis was conducted with 12 mo of additional follow up from the primary analysis. Results: 501 pts were enrolled, including 336 to atezo + bev and 165 to sor. At the clinical cut-off date of Aug 31, 2020, median follow-up was 15.6 mo and 280 OS events were observed. Median OS was 19.2 mo with atezo + bev vs 13.4 mo with sor (HR, 0.66 [95% CI, 0.52, 0.85]; P=0.0009). Survival at 18 mo was 52% with atezo + bev and 40% with sor. Survival benefit with atezo + bev over sor was generally consistent across subgroups and with the primary analysis. The updated objective response rate (ORR; 29.8% per RECIST 1.1) with atezo + bev was in line with the primary analysis, with more pts achieving complete response (CR; 7.7%) than previously reported. Additional response data are in Table. Safety was aligned with the primary analysis, with no new signals identified. Conclusions: IMbrave150 showed consistent clinically meaningful treatment benefit and safety with 12 mo of additional follow-up. The combination provides the longest survival seen in a front-line Phase III study in advanced HCC, confirming atezo + bev as a standard of care for previously untreated, unresectable HCC. Clinical trial information: NCT03434379. [Table: see text]