Supplementary Material for: Albumin-Bilirubin Grade Analyses of Atezolizumab Plus Bevacizumab vs Sorafenib in Patients With Unresectable Hepatocellular Carcinoma: A Post Hoc Analysis of the Phase III IMbrave150 Study

Introduction: Atezolizumab + bevacizumab showed survival benefit in patients with unresectable hepatocellular carcinoma (HCC) vs sorafenib in the Phase III IMbrave150 study. This exploratory analysis examined the prognostic impact of baseline albumin-bilirubin (ALBI) score. Methods: Patients with treatment-naïve unresectable HCC, ≥1 measurable untreated lesion and Child-Pugh Class A liver function were randomized 2:1 to receive atezolizumab 1200 mg + bevacizumab 15 mg/kg every 3 weeks or sorafenib 400 mg twice daily. Overall survival (OS) and progression-free survival (PFS) were assessed in the intention-to-treat population by ALBI/modified (m)ALBI grade. Time to deterioration (TTD; defined as time to 0.5-point increase from baseline ALBI score over 2 visits or death) of liver function and safety were investigated. Results: Of 501 enrolled patients, 336 were randomized to receive atezolizumab + bevacizumab (ALBI Grade (G) 1: n=191; G2: n=144 (mALBI G2a: n=72, G2b: n=72); missing ALBI Grade: n=1) and 165 to sorafenib (ALBI G1: n=87; G2: n=78 (mALBI G2a: n=37; G2b: n=41)). Median follow-up was 15.6 months. OS and PFS improved with atezolizumab + bevacizumab vs sorafenib in patients with ALBI G1 (OS HR, 0.50 (95% CI: 0.35, 0.72); PFS HR, 0.61 (95% CI: 0.45, 0.82)). In patients with ALBI G2 or mALBI G2a or G2b, PFS was numerically longer with atezolizumab + bevacizumab vs sorafenib but no OS benefit was seen. Median TTD in the intention-to-treat population was 10.2 months (95% CI: 8.0, 11.0) with atezolizumab + bevacizumab vs 8.6 months (95% CI: 6.2, 11.8) with sorafenib (HR, 0.82 (95% CI: 0.65, 1.03)). Safety profiles of atezolizumab and bevacizumab were consistent with previous analyses, regardless of ALBI grade. Discussion/Conclusion: ALBI grade appeared to be prognostic for outcomes with both atezolizumab + bevacizumab and sorafenib treatment in patients with HCC. Atezolizumab + bevacizumab preserved liver function for a numerically longer duration than sorafenib.